The study, led by researchers from Xiamen University in China, investigates the protective effects of hydrogen sulfide, a gasotransmitter that has long been recognized for its antioxidant and anti-inflammatory properties. In the context of diabetes, vascular smooth muscle cells undergo a pathological phenotypic switch, becoming more proliferative and migratory, which contributes to the thickening and stiffening of arterial walls. The researchers sought to understand how hydrogen sulfide might counteract these abnormal cellular behaviors, aiming to identify specific molecular targets that could serve as therapeutic interventions for diabetic vascular complications.

Using a combination of in vivo and in vivo models, the team utilized type 2 diabetes mellitus mice and mouse aortic vascular smooth muscle cells cultured under high-glucose and high-fat conditions to mimic the metabolic environment of diabetic patients. Their initial observations revealed a critical deficiency in the diabetic state: a marked decrease in the expression of cystathionine gamma-lyase, the primary enzyme responsible for synthesizing hydrogen sulfide in the body. This reduction in endogenous hydrogen sulfide production was directly correlated with increased oxidative stress and the activation of the NLRP3 inflammasome, a complex protein structure that plays a key role in initiating inflammation.

The activation of the NLRP3 inflammasome is a central event in the pathogenesis of diabetic vasculopathy, as it triggers the release of pro-inflammatory cytokines that exacerbate tissue damage. The researchers found that when hydrogen sulfide levels were low, vascular smooth muscle cells exhibited heightened proliferative and migratory activity, further contributing to vascular remodeling. To test the hypothesis that hydrogen sulfide could reverse these pathological changes, the team administered sodium hydrosulfide, a stable hydrogen sulfide donor, to the experimental models. The results were striking: the introduction of hydrogen sulfide effectively reversed the elevated oxidative stress and suppressed the activation of the NLRP3 inflammasome, thereby reducing the abnormal proliferation and migration of vascular smooth muscle cells.

However, the study went beyond confirming the protective effects of hydrogen sulfide to elucidate the specific molecular mechanism behind these benefits. The researchers focused on a post-translational modification known as S-sulfhydration, a process where hydrogen sulfide adds a sulfane sulfur group to cysteine residues of proteins. Through detailed protein analysis, they identified that hydrogen sulfide promotes the S-sulfhydration of thioredoxin reductase 1, a key enzyme in the cellular redox system. This modification occurs specifically at the Cys611 residue of thioredoxin reductase 1, a site that is crucial for the enzyme’s catalytic activity and its interaction with other redox-regulating proteins.

The S-sulfhydration of thioredoxin reductase 1 at Cys611 has profound downstream effects on the thioredoxin 1-thioredoxin-interacting protein-NLRP3 signaling axis. Thioredoxin 1 is a major intracellular antioxidant that binds to and inhibits thioredoxin-interacting protein, which is a known activator of the NLRP3 inflammasome. By enhancing the activity of thioredoxin reductase 1 through S-sulfhydration, hydrogen sulfide ensures that thioredoxin 1 remains in its active, reduced state. This active thioredoxin 1 effectively sequesters thioredoxin-interacting protein, preventing it from activating the NLRP3 inflammasome. Consequently, the entire inflammatory cascade is dampened, leading to a reduction in the production of inflammatory mediators that drive vascular damage.

To validate this mechanism, the researchers employed pharmacological inhibition and rescue experiments. They used specific inhibitors to block the S-sulfhydration of thioredoxin reductase 1 and observed that the protective effects of hydrogen sulfide were significantly diminished. Conversely, when they restored the S-sulfhydration status of thioredoxin reductase 1, the anti-inflammatory and anti-proliferative effects were reinstated. These experiments provided strong evidence that the S-sulfhydration of thioredoxin reductase 1 at Cys611 is not merely a byproduct of hydrogen sulfide exposure but is a critical regulatory step in the pathway that leads to vascular protection. This finding underscores the importance of specific post-translational modifications in mediating the biological effects of gasotransmitters.

The implications of this study extend beyond the immediate understanding of diabetic vasculopathy. By identifying the thioredoxin reductase 1 S-sulfhydration pathway as a key mediator of hydrogen sulfide’s protective effects, the researchers have highlighted a promising therapeutic target for the treatment of diabetic vascular complications. Drugs that can enhance the S-sulfhydration of thioredoxin reductase 1 or stabilize hydrogen sulfide levels could potentially offer new avenues for preventing or slowing the progression of vascular damage in diabetic patients. This approach could complement existing therapies that focus on glucose control and blood pressure management, providing a more comprehensive strategy for managing the complications of type 2 diabetes.

Furthermore, the study contributes to the growing body of evidence supporting the role of hydrogen sulfide in various physiological and pathological processes. While hydrogen sulfide has been studied in the context of cardiovascular protection, this research provides a detailed mechanistic insight into how it specifically targets the inflammatory pathways involved in diabetic vascular remodeling. The identification of the Cys611 residue as a critical site for S-sulfhydration offers a precise molecular target for future drug development. Understanding the intricate balance between oxidative stress, inflammation, and cellular redox regulation is essential for developing effective treatments for chronic diseases like diabetes, and this study makes a significant contribution to that understanding.

In conclusion, this research from Xiamen University provides a comprehensive mechanistic explanation for how hydrogen sulfide attenuates diabetic vascular remodeling. By demonstrating that hydrogen sulfide promotes the S-sulfhydration of thioredoxin reductase 1 at Cys611, thereby inhibiting the thioredoxin 1-thioredoxin-interacting protein-NLRP3 axis, the study reveals a novel pathway for vascular protection. These findings not only enhance our understanding of the molecular pathogenesis of diabetic vasculopathy but also open new possibilities for therapeutic interventions. As the global burden of type 2 diabetes continues to rise, identifying and targeting such specific molecular mechanisms will be crucial for improving patient outcomes and reducing the severity of its vascular complications.

Subject of Research: Mechanism of hydrogen sulfide-mediated protection against diabetic vascular remodeling via TrxR1 S-sulfhydration

Article Title: Hydrogen sulfide promotes S-sulfhydration of TrxR1 and attenuates diabetic vascular remodeling

Article References: Wei, Z., Wu, R., Ruan, J., Yang, J., Fu, X., Li, Y., Jiao, L., Xiang, L., Yu, D., Yan, G., Zhang, L., & Li, H. (2026). Hydrogen sulfide promotes S-sulfhydration of TrxR1 and attenuates diabetic vascular remodeling. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03297-3

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03297-3

Keywords: Hydrogen Sulfide, Diabetic Vasculopathy, TrxR1, S-sulfhydration, NLRP3 Inflammasome, Vascular Smooth Muscle Cells, Type 2 Diabetes, Oxidative Stress, Cell Death Discovery, Xiamen University, Hydrogen, sulfide

The research, led by Hongliang Cui, Jiaxin Li, Yangbo Fu, and Feiteng Sun, with corresponding authors Lei He, Zhiran Li, Fei Sun, and Jun Yu, focuses on the Drosophila testis, one of the most powerful and best-understood model systems for studying adult stem cell biology. Within this organ, germline stem cells sit alongside another population known as cyst stem cells, or CySCs. The CySCs are somatic cells, meaning they do not make sperm themselves. Instead, they envelop the germline cells, provide essential structural and biochemical support, and help orchestrate the step-by-step process by which a stem cell ultimately becomes a mature sperm cell. The balance between keeping CySCs in their stem cell state and allowing them to differentiate is delicate, and the mechanisms that maintain this balance have remained incompletely understood.

The team set out to determine what happens when a single gene in the CySC lineage is manipulated. Through targeted genetic experiments that raised or lowered the levels of Mppa specifically in these somatic support cells, the researchers uncovered two distinct problems. First, the maintenance of the cyst stem cells themselves was disrupted, meaning the population of supporting cells that anchors the niche began to falter. Second, and perhaps more strikingly, the differentiation of the neighboring germ cells was impaired. This second effect is what scientists call a nonautonomous function: Mppa acts in one cell type, the CySCs, but its consequences ripple outward to affect a completely different cell type, the germline.

Nonautonomous regulation is a recurring theme in stem cell biology, but the specific mechanism uncovered here adds an unexpected twist. When the researchers dug into what Mppa actually does at the molecular level, they found that it is a conserved mitochondrial protein with a central role in maintaining ATP homeostasis. ATP, or adenosine triphosphate, is the universal energy currency of the cell, and mitochondria are the organelles that generate most of it. In other words, the failure of germ cells to differentiate properly in these experiments was not caused by a signaling molecule or a transcription factor acting directly on the germline. It was caused, at least in part, by an energy supply problem in the supporting cells.

To understand how a mitochondrial defect in CySCs could translate into a developmental failure, the team turned to transcriptomics, the systematic measurement of gene expression across the genome. The transcriptomic analysis revealed that Mppa’s influence converged on mitochondrial function, with particular involvement of pathways related to cytochrome P450 enzymes. Cytochrome P450 proteins are best known for their roles in metabolism and detoxification, but in this context they emerged as part of the regulatory landscape through which Mppa shapes mitochondrial performance. The finding suggests that the energy state of the niche cells is monitored and managed through a coordinated transcriptional program, and that Mppa sits near the top of that program.

The researchers did not stop at gene expression. To identify the physical partners of Mppa, they performed a proteomic screen using liquid chromatography coupled with tandem mass spectrometry, or LC–MS/MS, a technique that can catalog the proteins that associate with a molecule of interest inside cells. The results painted a picture of Mppa as deeply embedded in the cell’s energy machinery. Its binding partners were enriched for proteins involved in diverse energy metabolism processes, oxidation–reduction reactions, and the maintenance of cellular redox balance, the equilibrium between oxidizing and reducing agents that cells must constantly manage to avoid damage.

Among the many associations detected in the mass spectrometry screen, the team went on to validate specific interactions experimentally. One confirmed binding partner was UQCR-C1, a component of the ubiquinol–cytochrome c reductase complex, better known as Complex III of the mitochondrial electron transport chain. This complex is a critical relay in the series of molecular steps that transfer electrons derived from food and ultimately drive the production of ATP. The physical association between Mppa and a core component of the respiratory chain provides a concrete biochemical link between the protein and the energy homeostasis it helps to regulate, grounding the genetic and transcriptomic observations in a defined molecular interaction.

Taken together, the study proposes a model in which Mppa functions as a kind of metabolic custodian for the testicular stem cell niche. By sustaining ATP levels and supporting mitochondrial and redox homeostasis in CySCs, Mppa enables those cells to remain stem cells and to perform their supportive duties toward the germline. When Mppa is lost or reduced, the energy balance of the niche falters, the CySC population becomes unstable, and the germ cells that depend on them fail to progress through their differentiation program. The germline defect, in this view, is a downstream consequence of a metabolic failure in a neighboring cell type, a striking illustration of how deeply interdependent the cells of a tissue niche really are.

The choice of the Drosophila testis as the experimental system is significant. The fly testis has long served as a paradigm for studying how stem cells are maintained and how niche signals control fate decisions, and many principles discovered there have proven relevant to stem cell biology across species. Because the germline and its somatic support cells can be manipulated independently with genetic tools, the system is uniquely suited to dissecting nonautonomous interactions of exactly the kind described here. The fact that Mppa is described as a conserved mitochondrial protein raises the possibility that similar energy-dependent mechanisms operate in other stem cell niches, including those of mammals.

The clinical resonance of the work lies in male fertility. Spermatogenesis disorders linked to disrupted germ cell differentiation are a recognized cause of male infertility, and the mechanisms behind many such disorders remain poorly defined. By showing that the energy equilibrium of somatic niche cells can govern germ cell differentiation nonautonomously, the study opens a new conceptual avenue for understanding and potentially investigating infertility: rather than looking only at the germ cells themselves, researchers and clinicians may need to consider the metabolic health of the supporting cells that surround them. The work was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Nantong Natural Science Foundation, and the Qinglan Project of Jiangsu Province, and all experiments were conducted on Drosophila melanogaster, requiring no ethical approval for human or animal subjects. As with any fly genetics study, translating these findings to human biology will require further work, but the study offers a compelling demonstration that the road to healthy sperm runs through the mitochondria of the cells next door.

Subject of Research: Nonautonomous mitochondrial regulation of cyst stem cell maintenance and germ cell differentiation in the Drosophila testis

Article Title: Mppa sustains cyst stem cell maintenance and orchestrates germ cell differentiation through nonautonomous regulation of mitochondrial homeostasis in Drosophila testes

Article References: Cui, H., Li, J., Fu, Y., Sun, F., Wang, X., Chen, X., Wu, J., Chu, Y., Wang, C., Dong, J., He, L., Li, Z., Sun, F., & Yu, J. (2026). Mppa sustains cyst stem cell maintenance and orchestrates germ cell differentiation through nonautonomous regulation of mitochondrial homeostasis in Drosophila testes. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03397-0

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03397-0

Keywords: Drosophila, spermatogenesis, cyst stem cells, stem cell niche, mitochondria, ATP homeostasis, germ cell differentiation, cytochrome P450, UQCR-C1, redox balance, male fertility, Cell Death Discovery

The chemistry at the heart of the discovery is well established. During clot formation, fibrin and associated proteins are cross-linked via Nε-(γ-glutamyl)lysine bonds, covalent bridges between glutamine and lysine residues that provide clot rigidity and reduce the rate of fibrinolysis, the enzymatic dismantling of the clot. This cross-linking also incorporates fibrinolytic inhibitors into the clot matrix, further protecting it from premature dissolution. To date, this function has been attributed exclusively to Factor XIIIa, also known as plasma transglutaminase, one of eight transglutaminases identified in mammals. The new report demonstrates that TG2, a second member of the family, contributes to the same stabilizing chemistry in vivo.

The experimental logic behind the claim is straightforward but compelling. The researchers isolated whole thrombi from TG2-deficient mice and from wild-type controls and observed clear differences between the two groups, indicating that the absence of TG2 alters the structural integrity of the clots that form in living animals. In parallel experiments with human thrombi, the team found that clots were more stable in the presence of active TG2 than when TG2 activity was specifically inhibited. That pharmacological loss-of-function result is particularly significant, because it shows that the effect is not merely a developmental compensation in genetically modified mice but a direct, acute dependence on the enzyme’s catalytic activity.

TG2 is no stranger to cell biologists. It is a ubiquitous enzyme, expressed in many tissues and cell types, and it is abundantly present in erythrocytes, the red blood cells that are themselves structural components of any thrombus. Red cells constitute a large fraction of clot volume, and their membranes and cytoskeletal proteins are potential substrates for transglutaminase-mediated cross-linking. The new findings suggest that TG2 released or active within the erythrocyte-rich environment of a thrombus can forge the same Nε-(γ-glutamyl)lysine bonds that Factor XIIIa creates, effectively providing a second, redundant cross-linking engine embedded within the clot itself.

The implications for fibrinolysis deserve particular attention. The resistance of a mature clot to plasmin-mediated degradation depends not only on the rigidity of the fibrin mesh but also on the incorporation of fibrinolytic inhibitors such as alpha-2-antiplasmin into the clot structure. If TG2 contributes to this incorporation, then inhibiting TG2 could, in principle, render clots more susceptible to lysis, a property that might be exploited therapeutically in settings where pathological clot persistence is the problem, such as ischemic stroke or myocardial infarction. Conversely, situations in which excessive clot fragility or premature fibrinolysis causes bleeding might benefit from strategies that support TG2-dependent cross-linking.

The study also reframes the evolutionary and physiological logic of hemostasis. Factor XIIIa circulates in plasma as the zymogen Factor XIII and is activated by thrombin during the coagulation cascade, a highly regulated, feed-forward system. TG2, by contrast, is not a classical coagulation factor; it is a multifunctional enzyme implicated in cell death programs, extracellular matrix assembly and signal transduction. Its presence in erythrocytes means that every thrombus, by virtue of the red cells it traps, carries its own reservoir of cross-linking potential. The authors therefore propose TG2 as an additional factor involved in blood coagulation, a formal elevation of the enzyme into the coagulation hierarchy that textbooks will need to accommodate.

Methodologically, the work spans genetically defined animal models and human material. The mouse experiments compared whole thrombi isolated from TG2-deficient and wild-type animals, an approach that captures the net effect of the enzyme in a physiological setting rather than in simplified reconstituted systems. The human experiments used specific inhibition of TG2 activity, a strategy that isolates the enzyme’s catalytic contribution from its possible non-catalytic scaffolding roles. The convergence of genetic and pharmacological evidence on the same conclusion, that clots lacking TG2 activity are measurably less stable, strengthens the causal interpretation and rules out the most obvious alternative explanations, such as differences in clot formation independent of stabilization.

The clinical horizon is speculative but real. Drugs that inhibit TG2 are under development for other indications, including fibrosis and cancer, and the new findings raise the question of whether such agents could affect hemostasis in patients. The observation that human thrombi are less stable when TG2 is inhibited suggests a potential bleeding liability that would need to be evaluated in clinical trials. On the other side of the ledger, the enzyme’s role in stabilizing clots and incorporating fibrinolytic inhibitors suggests that TG2 activity could be a determinant of thrombus persistence, and modulating it might one day complement existing fibrinolytic therapies. Any such applications would require careful dose-finding and safety work, but the study provides the mechanistic foundation for that translational conversation.

There are also broader lessons for the coagulation field. The cross-linking of fibrin via Nε-(γ-glutamyl)lysine bonds has been studied almost exclusively through the lens of Factor XIIIa since its function was established, and the assumption of exclusivity has shaped experimental design, drug discovery and diagnostic thinking. The demonstration that a second transglutaminase contributes to the same process in both mouse and human clots is a reminder that biological systems often maintain redundancy in critical hemodynamic mechanisms, and that a single-enzyme paradigm can obscure parallel pathways. The authors’ finding that TG2 is abundantly present in erythrocytes, cells that are present in every clot but usually treated as passive structural filler, is a vivid example of how a familiar cell type can harbor an unexpected biochemical function.

The study, published open access in Cell Death Discovery on 17 October 2026, was led by Mauro Piacentini, Nicola J. Mutch, Eleonora Candi, Zhuo Wang, Martin Griffin and Gerry Melino, with contributions from Alessandro Mauriello, Manuel Scimeca, Mara Mancini, Valerio Da Ros, Francesco Barilla and Yufang Shi. The work was supported in part by the Italian NextGenerationEU programme through the Heal Italia project, by the Italian Association for Cancer Research and by the Italian Ministry of Health. The authors declare no competing interests. As the field digests the result, the central message is clear: the blood clotting cascade has at least two transglutaminase contributors, not one, and the second has been hiding in plain sight inside our red blood cells all along.

Subject of Research: Role of transglutaminase 2 in blood clot stabilization and coagulation

Article Title: Transglutaminase 2 contributes to the blood clotting cascade

Article References: Piacentini, M., Mutch, N. J., Mauriello, A., Scimeca, M., Mancini, M., Da Ros, V., Barilla’, F., Shi, Y., Candi, E., Wang, Z., Griffin, M., & Melino, G. (2026). Transglutaminase 2 contributes to the blood clotting cascade. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03388-1

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03388-1

Keywords: transglutaminase 2, blood clotting, coagulation, fibrin, Factor XIIIa, hemostasis, fibrinolysis, clot stability, erythrocytes, thrombus, Cell Death Discovery, enzyme cross-linking

The research focuses on IKKβ, the inhibitor of NF-κB kinase subunit β, a catalytic engine of the NF-κB transcription factor pathway that governs inflammatory gene expression throughout the body. Earlier work had shown that ablating microglial IKKβ suppresses inflammatory activation and beta-amyloid accumulation in Alzheimer’s models, but the mechanism controlling IKKβ itself remained obscure. The Nanchang team found that in Alzheimer’s disease mouse models, IKKβ expression was significantly upregulated while its ubiquitination level was markedly reduced—a biochemical signature suggesting that something was actively protecting the kinase from degradation.

That something, the researchers discovered, is CYLD, the cylindromatosis protein, a deubiquitinase already famous in cancer biology for its tumor-suppressive role. Ubiquitination is the process by which cells tag proteins with chains of the small protein ubiquitin, directing them either to the proteasome for destruction or to new signaling roles. K48-linked chains conventionally mark proteins for degradation, while K63-linked chains serve as signaling scaffolds. Remarkably, the study identified CYLD as a deubiquitinase capable of removing both K48- and K63-linked polyubiquitin chains from IKKβ—meaning CYLD simultaneously stabilizes the kinase and enables its signaling activity.

The experimental logic of the study followed a clear arc. When the researchers knocked down CYLD, IKKβ expression dropped, pro-inflammatory cytokine secretion was dampened, and neuronal apoptosis was attenuated. Ultimately, these changes led to improved cognitive function in Alzheimer’s disease mice. The finding is striking because it suggests that a single enzymatic target in microglia can cascade outward to protect neurons and preserve memory-related behavior.

Mechanistically, CYLD ablation enhanced IKKβ ubiquitination, weakened NF-κB signaling, and pushed microglia toward a tissue-repair-associated polarization state. This is critical because microglia are not uniformly harmful or helpful; depending on the microenvironment, activated microglia can adopt either a pro-inflammatory or an anti-inflammatory phenotype. By removing CYLD’s protective grip on IKKβ, researchers effectively nudged microglia away from the destructive pro-inflammatory state and toward a reparative one.

The team then took a complementary approach: direct microglial knockout of IKKβ. This genetic intervention repressed activation of the NLRP3 inflammasome—a multiprotein innate immune complex that drives maturation of interleukin-1β and other pyrogenic signals—and suppressed pro-inflammatory cytokine production. In turn, these changes restrained neuronal pyroptosis, a form of inflammatory programmed cell death characterized by membrane rupture and release of damage-associated molecular patterns. Pyroptosis has emerged as a key mechanism by which neuroinflammation kills neurons in neurodegenerative disease.

What makes this study particularly compelling is the way it links microglia-neuron crosstalk to a specific ubiquitin-editing event. The researchers establish that microglial IKKβ plays an essential role in neuroinflammation during Alzheimer’s disease progression, and suggest that targeting IKKβ deubiquitination in microglia may represent a novel therapeutic strategy. Rather than broadly suppressing NF-κB throughout the body—which would carry significant immunological risk—the approach would specifically modulate how microglial IKKβ is tagged and processed by ubiquitin chains.

The dual specificity of CYLD is what gives this circuit its power. By removing both K48- and K63-linked chains from IKKβ, CYLD simultaneously prevents the kinase from being degraded and keeps it available for signaling. This is a rare biochemical arrangement; most deubiquitinases specialize in one chain type. The dual action means CYLD acts as both a stabilizer and an enabler of IKKβ, effectively amplifying the kinase’s inflammatory output in microglia.

Therapeutically, the implications are significant. Current Alzheimer’s disease treatments offer limited options, and anti-amyloid therapies have shown only modest clinical benefit. If CYLD-mediated IKKβ stabilization is a central driver of microglial neuroinflammation, then inhibiting CYLD—or disrupting its interaction with IKKβ—could offer a way to calm the brain’s immune storm without globally immunosuppressing patients. The study’s demonstration that CYLD knockdown improved cognitive function in disease mice provides proof of concept that this pathway is behaviorally relevant, not just biochemically interesting.

Of course, translating these findings from mouse models to human patients will require substantial additional work. Alzheimer’s disease in humans involves decades of accumulated pathology, and microglial states in human brains may differ from those in laboratory animals. Nevertheless, the identification of a specific deubiquitinase-kinase axis that links microglial inflammatory polarization to neuronal death offers a concrete molecular target in a field that has long struggled to find one. The Nanchang University team’s work suggests that the next generation of Alzheimer’s therapeutics may not target plaques or tangles directly, but rather the ubiquitin-editing enzymes that determine whether the brain’s immune cells fight the disease or feed it.

Subject of Research: CYLD-mediated IKKβ deubiquitination in microglia-neuron crosstalk in Alzheimer's disease

Article Title: Modulation of IKKβ deubiquitination dynamics by CYLD links microglia-neuron crosstalk to be involved in Alzheimer’s disease

Article References: Luo, Q., Wang, W., Gu, X., Wu, Z., Qiao, Y., Li, Y., Gong, L., Tang, Z., & Liu, X. (2026). Modulation of IKKβ deubiquitination dynamics by CYLD links microglia-neuron crosstalk to be involved in Alzheimer’s disease. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03358-7

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03358-7

Keywords: Alzheimer's disease, microglia, CYLD, IKKβ, NF-κB, NLRP3 inflammasome, pyroptosis, neuroinflammation, deubiquitinase, Cell Death Discovery, Modulation, deubiquitination

The research team approached the problem from a perspective that has been reshaping the field for the past decade. Diabetic retinopathy is increasingly understood not simply as a plumbing failure of tiny blood vessels, but as a neurovascular degenerative disease in which early neuronal dysfunction, chronic metabolic stress and progressive microvascular damage reinforce one another. Within that framework, the metabolic state of endothelial cells, the thin layer of cells lining the interior of blood vessels, becomes a central question. Growing new vessels is an energetically expensive enterprise, and endothelial cells must ramp up their metabolism to proliferate, migrate and remodel tissue.

Lipocalin-2, often abbreviated LCN2, entered the picture because clinical studies had already reported elevated levels of the protein in patients with diabetic retinopathy. Elevated levels of a molecule in a disease state, however, do not by themselves prove that the molecule causes the disease; it could be a bystander, a marker of tissue stress, or even a protective response. What remained poorly defined, as the authors note in their abstract, was the functional role of LCN2 in diabetic retinal vascular pathology. Answering that question required more than correlation, and the team turned to a pair of genetically engineered mouse models designed to manipulate LCN2 with precision.

The first model was an LCN2 overexpressing mouse, designated LCN2-Tg, in which the animals carry extra copies of the gene and produce abnormally high amounts of the protein throughout life. The second was the opposite experiment: an endothelium-specific LCN2 knockout, written Lcn2-fl/fl; Cdh5-CreERT2, in which the gene is deleted selectively in endothelial cells. The Cdh5-CreERT2 system uses the cadherin-5 promoter, active almost exclusively in vascular endothelium, to drive an inducible form of the Cre recombinase enzyme, allowing researchers to remove Lcn2 from blood vessel lining cells in adult animals. This specificity matters, because LCN2 is produced by many cell types, including immune cells and epithelial tissue, and a whole-body knockout would make it impossible to attribute any vascular effect to the endothelium itself.

With these tools in hand, the researchers examined how LCN2 influences retinal vascular remodeling and endothelial function under both physiological and pathological conditions. The results were striking. Loss of LCN2 in endothelial cells suppressed both the normal, developmental expansion of retinal vessels and the pathological vessel growth that mimics what happens in diabetic retinopathy. Crucially, however, the deficiency did this while preserving vascular stability. That distinction is important from a therapeutic standpoint: an ideal treatment for retinal neovascularization would prune away the destructive, leaky vessels that characterize the disease without destabilizing the healthy vasculature that the retina depends on for oxygen and nutrients.

The mechanistic heart of the paper lies in energy metabolism. When the team looked at animals and cells with elevated LCN2, they found enhanced endothelial cell energy metabolism, and this metabolic boost went hand in hand with exacerbated pathological neovascularization. In other words, LCN2 appears to act as a metabolic enabler for endothelial cells, revving up their bioenergetic machinery so they can sustain the high demands of proliferation and migration. Sprouting new capillaries requires cells to divide rapidly, crawl through surrounding tissue, and reorganize their cytoskeletons, all of which consume large quantities of ATP and biosynthetic intermediates. By amplifying metabolic capacity, LCN2 gives pathological vessels the fuel they need to advance.

The converse experiment confirmed the logic. When LCN2 was downregulated, endothelial cells showed suppressed proliferation and migration, accompanied by a restricted metabolic capacity. The cells simply lacked the energetic headroom to mount an angiogenic response. This coupling of behavior to metabolism is consistent with a broader theme in vascular biology: endothelial cells are not passive tubes but metabolically dynamic cells whose glycolytic flux, mitochondrial activity and nutrient handling directly govern whether vessels sprout, stabilize or regress. The new study places LCN2 squarely within that regulatory circuitry, identifying it as a regulator of what the authors call endothelial metabolic competence in the diabetic retina.

Why does this matter for patients? Current treatments for proliferative diabetic retinopathy rely heavily on blocking vascular endothelial growth factor, or VEGF, either through injections of anti-VEGF antibodies into the eye or through laser photocoagulation that destroys peripheral retinal tissue to reduce oxygen demand. These approaches have transformed outcomes, but they have limitations. Anti-VEGF therapy requires repeated injections, some patients respond incompletely, and there are lingering concerns about the long-term effects of suppressing a factor that also supports neuronal and vascular health in the retina. A target that operates through a different axis, in this case cellular energy metabolism rather than growth factor signaling, could complement existing therapies or offer an alternative for patients who do not respond well to VEGF blockade.

The authors are careful about the translational implications, and appropriately so. Their conclusion is that pathological upregulation of LCN2 contributes to retinal microvascular dysfunction, and that targeting LCN2-dependent metabolic regulation may therefore represent a potential therapeutic strategy for diabetic retinopathy. That is a long road from a mouse study. Human diabetic retinopathy unfolds over years in a metabolic environment shaped by hyperglycemia, inflammation and oxidative stress, and interventions that work in genetically defined animals do not always translate. Any future therapy would need a safe way to inhibit LCN2 in the eye, whether through antibodies, small molecules or gene-based approaches, and would need to avoid interfering with the protein’s beneficial roles in innate immunity and tissue repair elsewhere in the body.

Even so, the study adds a compelling new character to the cast of molecules implicated in diabetic eye disease, and it does so with an unusually clean experimental design that combines gain-of-function and cell-type-specific loss-of-function genetics. It also reinforces a conceptual shift with implications well beyond ophthalmology: pathological angiogenesis is not just a signaling problem but a metabolic one, and the vessels that ravage the diabetic retina can be weakened by cutting their fuel supply. For the hundreds of millions of people living with diabetes worldwide, and for the growing fraction of them who will develop retinopathy as the disease progresses, a new metabolic handle on the process is a development worth watching closely.

Subject of Research: The role of lipocalin-2 in endothelial energy metabolism and pathological angiogenesis in diabetic retinopathy

Article Title: Knockdown of lipocalin 2 alleviates ocular angiogenesis in diabetic retinopathy by lowering endothelial cell energy metabolism

Article References: Mei, T., Yang, H., Zuo, H., Wu, J., Liu, K., Zhao, M., Wu, K., Song, H., Zhang, Z., Luo, S., Lai, Y., Luo, J., Zhang, F., Zuo, C., & Zhao, L. (2026). Knockdown of lipocalin 2 alleviates ocular angiogenesis in diabetic retinopathy by lowering endothelial cell energy metabolism. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03378-3

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03378-3

Keywords: diabetic retinopathy, lipocalin-2, angiogenesis, endothelial cells, energy metabolism, retinal vascular disease, knockout mouse models, neovascularization, metabolic regulation, ophthalmology, vascular biology, Cell Death Discovery

Secondary lymphedema typically develops after cancer surgery, particularly when lymph nodes are removed or irradiated as part of treatment for breast cancer, melanoma, or gynecological malignancies. Yet clinicians have long observed something puzzling: the condition often appears months or even years after the operation, long after the surgical wound has healed. This delayed onset has led researchers to suspect that the surgery alone cannot explain the full picture, and that cancer treatments themselves, particularly chemotherapy, may quietly undermine the lymphatic vessels that drain fluid from tissues. When those vessels fail, protein-rich fluid accumulates in the limbs, causing swelling, thickening of the skin, recurrent infections, and a lasting reduction in quality of life.

The Toulouse team, led by Barbara Garmy-Susini, focused on 5-fluorouracil, or 5-FU, a first-line chemotherapeutic used against colorectal, breast, and many other cancers. In laboratory experiments, they found that 5-FU inflicts measurable damage on lymphatic endothelial cells, the specialized cells that line the inside of lymphatic vessels and coordinate their growth, maintenance, and pumping function. The drug disrupted the expression of master transcription factors that keep lymphatic vessels healthy, including GATA2, FOXC2, and SOX18, a trio of genetic regulators that act as the operational blueprint of the lymphatic system. When these genes are silenced or diminished, lymphatic vessels lose their structural integrity and their capacity to transport fluid, setting the stage for lymphedema.

The mechanism behind this damage turned out to be mitochondrial. 5-FU impaired the power plants of lymphatic endothelial cells, reducing their maximal respiration, depleting their ATP production, and eroding their spare respiratory capacity, which is the reserve a cell can call upon under stress. At the same time, mitochondria in the treated cells accumulated superoxide, a highly reactive and destructive oxygen radical. The result was a double blow: less energy to power the vessel’s contractile and barrier functions, and more oxidative stress to corrode cellular components. The researchers also observed an increase in mitochondrial mass, a compensatory response that in this context appears maladaptive, adding more dysfunctional machinery rather than repairing the existing network.

Enter metformin. Although best known as a first-line treatment for type 2 diabetes, metformin has attracted intense scientific interest in recent years for its effects on metabolism, aging, and cancer. At the molecular level, it acts as an inhibitor of complex I of the mitochondrial electron transport chain, subtly modulating how cells generate energy. That same property, the researchers discovered, is precisely what makes it protective for lymphatic vessels under chemotherapy attack. When lymphatic endothelial cells were treated with metformin alongside 5-FU, the mitochondrial damage was largely prevented: maximal respiration, ATP production, and spare respiratory capacity were restored, superoxide accumulation was blocked, and the pathological expansion of mitochondrial mass was curtailed.

The protective effect extended beyond cellular energetics to the genetic identity of the vessels themselves. Metformin restored the expression of GATA2, FOXC2, and SOX18 in cells exposed to 5-FU, effectively preserving the molecular program that defines functional lymphatic endothelium. Notably, the team found that the antioxidant effect of metformin depends on the GATA2 pathway, linking the drug’s metabolic action to the transcriptional machinery that safeguards lymphatic vessel integrity. This mechanistic connection is significant because it suggests that metformin is not merely mopping up free radicals generically, but is reinforcing a master regulatory circuit that lymphatic cells rely on to survive metabolic stress.

To test whether these cellular findings translated into living organisms, the researchers turned to mouse models. When animals received 5-FU, their lymphatic vessels collapsed, a structural failure that would be expected to impair drainage. In mice that also received metformin, this vessel collapse was not observed. The team then used a murine model of lymphedema to ask the more clinically relevant question: could metformin treat established chemotherapy-associated lymphatic damage? The answer was encouraging. Metformin reduced the limb swelling caused by 5-FU treatment, markedly decreased the reflux of lymph back into tissues, lessened the abnormal thickening of the skin, and corrected the disorganized proliferation of lymphatic vessels that characterizes the disease.

These results carry considerable weight because metformin brings an unusually favorable profile to the table. It has been used in clinical practice for decades, has a well-characterized safety record, is inexpensive, and is already taken by a large share of cancer patients who have coexisting diabetes or insulin resistance. A preventive or therapeutic strategy for lymphedema that could be delivered with an existing, orally available drug would represent a major departure from current care, which relies mainly on compression garments, manual lymphatic drainage, and, in select cases, surgical procedures such as lymphovenous anastomosis or vascularized lymph node transfer. None of these approaches reverse the underlying cellular dysfunction; they manage symptoms or reroute fluid around damaged vessels.

The study also reframes how the field thinks about lymphedema risk. If chemotherapy agents such as 5-FU can compromise lymphatic mitochondria and transcriptional programs, then the timing of interventions could shift. Rather than waiting for swelling to appear, oncologists might one day identify patients at risk and protect their lymphatic system during treatment itself. The work was supported by the European Union’s Horizon 2020 programme through the Theralymph project and by the French National Cancer Institute, reflecting a coordinated effort to bring lymphatic protection into mainstream cancer care. The researchers caution, as with any preclinical study, that mouse models do not perfectly recapitulate human disease, and clinical trials in cancer patients will be needed to establish the right dosing, timing, and patient selection before metformin can be recommended for lymphedema prevention.

Even so, the convergence of evidence is striking. A drug that inhibits complex I, restores mitochondrial respiration, suppresses superoxide, preserves GATA2-dependent gene expression, prevents vessel collapse, and reduces limb volume in vivo offers a coherent mechanistic story from molecule to organ. For the millions of cancer survivors who live with or fear lymphedema, the prospect that a decades-old diabetes pill could protect the vessels that surgery and chemotherapy put at risk is a compelling one. The Toulouse findings now provide the biological rationale to test that prospect in the clinic, and they underscore a broader lesson of modern pharmacology: some of the most valuable new applications may come from old drugs whose full range of actions we are only beginning to understand.

Subject of Research: Metformin's reversal of chemotherapy-induced lymphatic mitochondrial dysfunction and secondary lymphedema

Article Title: Metformin reverses lymphatic mitochondrial dysfunction induced by 5-FU chemotherapy

Article References: Loi, H., Draia-Nicolau, T., Balzan, E., Morfoisse, F., Lacazette, E., Prats, A.-C., & Garmy-Susini, B. (2026). Metformin reverses lymphatic mitochondrial dysfunction induced by 5-FU chemotherapy. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03403-5

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03403-5

Keywords: metformin, lymphedema, 5-fluorouracil, chemotherapy, lymphatic endothelial cells, mitochondria, GATA2, superoxide, lymphatic vessels, drug repurposing, cancer survivors, Cell Death Discovery

The research, led by Shujie Zeng, Leyan Cao, Wenxuan Dong, Leping Li, Zihao Zhang and Peng Jin at institutions including Shandong Provincial Hospital, Shandong Cancer Hospital and Institute, and Zhongshan Hospital of Fudan University, focuses on a protein called semaphorin 4D, abbreviated SEMA4D. Semaphorins were originally discovered as guidance cues that steer growing nerve fibers to their correct destinations, but over the past two decades they have been recognized as versatile signaling molecules in the immune system and in cancer. SEMA4D in particular has attracted attention because high levels of the protein in tumor cells are associated with an immunosuppressive tumor microenvironment, meaning a milieu in which immune cells are present but rendered ineffective, or excluded from the tumor altogether.

What has remained poorly understood is how the conversation between tumor cells and macrophages regulates SEMA4D and, crucially, how the soluble, freely circulating form of the protein is generated inside living tumors. The new work addresses this gap by combining laboratory co-culture experiments with genetically engineered mouse models, allowing the researchers to trace the entire regulatory axis from tumor-derived SEMA4D to macrophage behavior to T cell function, and finally to tumor growth itself.

The team’s in vitro experiments used co-culture systems in which tumor cells and macrophages were grown together, alongside models in which SEMA4D production was either increased or shut down. These experiments revealed that tumor-derived SEMA4D pushes tumor-associated macrophages, the macrophages that populate tumors, toward the M2 phenotype. Macrophage polarization is a central concept in tumor immunology. M1 macrophages are classically activated, inflammatory cells that present antigens, produce pro-inflammatory signals and support anti-tumor immunity. M2 macrophages, by contrast, are associated with tissue repair, wound healing and, in the context of cancer, immunosuppression. A tumor microenvironment dominated by M2 macrophages is one in which cytotoxic CD8-positive T cells, the immune system’s primary tumor-killing weapons, are inhibited in both their infiltration into the tumor and their effector function once they arrive.

The study found precisely this pattern: tumor-derived SEMA4D drove M2 polarization of tumor-associated macrophages and suppressed the infiltration and function of CD8-positive T cells. But the most consequential finding concerned the mechanism by which SEMA4D becomes soluble. SEMA4D normally sits on the cell surface as a membrane-bound protein. For it to diffuse through the tumor microenvironment and act at a distance, it must be cleaved from the cell surface, and the identity of the molecular scissors responsible in tumors has been a key open question.

The answer, according to the new research, is matrix metalloproteinase 14, or MMP14, an enzyme produced by the tumor-associated macrophages themselves. MMP14 is a membrane-anchored member of the matrix metalloproteinase family, enzymes best known for remodeling the extracellular matrix, the protein scaffold that gives tissues their structure. The study demonstrates that TAM-derived MMP14 promotes the generation of soluble SEMA4D, thereby converting a membrane-bound tumor protein into a diffusible immunosuppressive signal. In other words, the macrophages recruited into the tumor are not passive bystanders; they are equipped with the enzymatic machinery that activates the tumor’s immune-evasion program.

To establish this mechanism in living animals rather than in culture dishes, the researchers used a macrophage-specific conditional knockout mouse model, in which the gene encoding MMP14 was deleted only in macrophages, leaving the enzyme intact in other cell types. This genetic precision matters, because MMP14 is expressed in many tissues and a global knockout would produce broad developmental and physiological effects that would obscure the specific role of the macrophage-derived enzyme in tumor immunity. With MMP14 removed from macrophages, the levels of soluble SEMA4D in the tumor microenvironment dropped significantly.

The consequences of that reduction were dramatic. Genetic ablation of MMP14 in tumor-associated macrophages reversed the M2 polarization of macrophages and promoted robust infiltration of both M1 macrophages and CD8-positive T cells into the tumor core, the innermost and most immunologically hostile region of the tumor. Immune exclusion, the physical barrier that keeps cytotoxic T cells at the tumor periphery, is one of the major reasons why immunotherapies such as immune checkpoint inhibitors fail in many patients. By dissolving this barrier at its enzymatic source, the MMP14 knockout effectively opened the tumor to immune attack, and the mice showed tumor regression as a result.

Perhaps the most convincing element of the study is the rescue experiment. To demonstrate that soluble SEMA4D is not merely correlated with the observed immune changes but is causally responsible for them, the researchers supplemented the MMP14 knockout mice with recombinant soluble SEMA4D, the purified protein produced in the laboratory. The result was unambiguous: exogenous soluble SEMA4D fully abrogated the anti-tumor benefits of MMP14 deletion, re-establishing the immunosuppressive tumor microenvironment despite the absence of the macrophage enzyme. This kind of loss-of-function and rescue design is the gold standard for establishing causal mechanisms in vivo, and it strongly supports the conclusion that the macrophage-MMP14-SEMA4D axis is a genuine driver of immune exclusion rather than a secondary correlate of tumor biology.

The therapeutic implications are considerable. Current immunotherapies, including checkpoint inhibitors targeting PD-1 and PD-L1, depend on the presence of functional T cells within the tumor. Patients whose tumors are immunologically cold, lacking T cell infiltration, rarely respond. The new findings suggest that targeting the macrophage-MMP14-SEMA4D regulatory axis could convert cold tumors into hot ones by removing the soluble signal that keeps T cells out, potentially sensitizing tumors to existing immunotherapies. SEMA4D-targeting agents are already being explored in clinical development for other indications, and the study provides a mechanistic rationale for combining such approaches with strategies that modulate macrophage behavior. The authors note that targeting this axis represents a promising therapeutic strategy for enhancing antitumor immunity. As with all preclinical mouse studies, translation to human cancers will require further validation, but the identification of a specific, druggable enzyme acting as the gatekeeper of an immunosuppressive signal offers a concrete molecular target in the ongoing effort to make immunotherapy work for more patients.

Subject of Research: The role of macrophage-derived MMP14 in generating soluble semaphorin 4D and shaping immunosuppression in the tumor microenvironment

Article Title: Macrophage-derived MMP14 fosters immunosuppressive tumor microenvironment by regulating soluble semaphorin 4D

Article References: Zeng, S., Cao, L., Dong, W., Li, L., Zhang, Z., & Jin, P. (2026). Macrophage-derived MMP14 fosters immunosuppressive tumor microenvironment by regulating soluble semaphorin 4D. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03393-4

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03393-4

Keywords: macrophages, MMP14, semaphorin 4D, tumor microenvironment, immunosuppression, CD8-positive T cells, M2 polarization, immune exclusion, cancer immunotherapy, tumor-associated macrophages, Cell Death Discovery, conditional knockout

The protein at the center of the study is adenine nucleotide translocase 3, or ANT3, a transporter embedded in the inner mitochondrial membrane that normally shuttles ATP out of the mitochondrial matrix in exchange for ADP from the cytosol. Beyond its day job as an exchange factor, ANT3 has long been implicated as a core constituent of the mitochondrial permeability transition pore, or mPTP, a high-conductance channel whose opening dissipates the proton gradient that powers ATP synthesis, swells the mitochondria, and can launch cell death. Disruption of ANT3 protein homeostasis, or conformational changes in the protein itself, are sufficient to trigger this catastrophic opening. What has remained murky is how the cell regulates ANT3’s abundance and shape in the first place, and that is precisely the question the Chongqing group set out to answer.

The researchers’ starting point was prolonged starvation, a physiological stress that cells in metabolically demanding tissues experience during nutrient deprivation. They found that extended starvation drives SIRT2, a NAD+-dependent deacetylase that typically resides in the cytoplasm and nucleus, to translocate into the mitochondria. This relocation matters because it places SIRT2 in the same compartment as ANT3, allowing the two proteins to bind directly. Once docked onto ANT3, SIRT2 performs its signature reaction: it removes an acetyl group from lysine 96, a specific residue on the ANT3 protein. Acetylation at lysine residues is a widespread post-translational modification that can alter a protein’s charge, structure, interactions, and stability, and the new work shows that the acetyl state of this one lysine carries enormous consequences for ANT3 behavior.

The consequences unfold along two parallel tracks. First, deacetylation of ANT3 at K96 promotes conformational changes in the protein, shifting it into a state that favors the formation of a complex with VDAC1, the voltage-dependent anion channel that sits in the outer mitochondrial membrane. The ANT3-VDAC1 pairing spans the contact sites between the inner and outer membranes and is considered a plausible architecture for the permeability transition pore, so enhancing this complex effectively assembles more of the death apparatus at the mitochondrial boundary. Second, and perhaps more surprisingly, deacetylated ANT3 binds more strongly to USP15, a deubiquitinating enzyme that removes ubiquitin tags from its substrates. Strengthened binding to USP15 enhances ANT3 deubiquitination, which stabilizes the ANT3 protein and raises its steady-state levels inside the mitochondria.

The logic of this dual mechanism is elegant and somewhat ruthless. By simultaneously reshaping ANT3 and protecting it from degradation, SIRT2 ensures that more of the transporter is present and more of it is locked into the pore-forming conformation with VDAC1. The result is an accelerated assembly of the permeability transition pore complex and, ultimately, an accelerated onset of cell death. In other words, starvation does not merely weaken the cell passively; it actively recruits a deacetylase to the mitochondria, which then stabilizes and reconfigures the very channel that will destroy the organelle. The study’s authors describe this as a rarely reported molecular mechanism in which SIRT2-mediated acetylation-dependent regulation governs programmed cell death.

Technically, the work illustrates how a single deacetylation event can be amplified into a systems-level outcome through feed-forward loops. The K96 deacetylation does not act alone; it recruits USP15, whose deubiquitinating activity further increases ANT3 abundance, which in turn increases the pool of ANT3 available to pair with VDAC1. This kind of positive feedback is characteristic of switch-like biological decisions, where a graded stress signal, in this case the duration of starvation, must be converted into a binary outcome: live or die. SIRT2’s dependence on NAD+ also ties the pathway directly to cellular metabolism, since NAD+ availability fluctuates with nutrient status and redox state. A starving cell, with its altered NAD+/NADH balance, thus provides both the signal and the enzymatic cofactor for the death-promoting modification.

The findings carry weight for a field that has struggled for decades with the molecular identity of the permeability transition pore. Genetic ablation of individual candidate components, including the ANT isoforms, has produced confusing and sometimes contradictory results, and the pore’s exact composition remains contested. By focusing on post-translational regulation rather than mere presence or absence of the protein, the new study offers a way to reconcile some of that ambiguity: ANT3 may be innocuous in one acetylation state and lethal in another. Conformational state, protein stability, and partner binding, all governed here by K96 acetylation, could explain why simply deleting a pore component does not always abolish permeability transition, since compensatory mechanisms and residual complexes may fill the gap.

There are also broader implications for human disease. Excessive mPTP opening is a hallmark of ischemia-reperfusion injury, where restored blood flow after a heart attack or stroke paradoxically kills cells that survived the initial insult, and it contributes to neurodegeneration, muscle wasting, and liver injury. Conversely, blocking pore opening can allow damaged cells to evade death, a trait exploited by some cancers. A pathway in which SIRT2, USP15, ANT3, and VDAC1 cooperate provides multiple potential intervention points. Small molecules that modulate SIRT2 activity are already under investigation in oncology and neurology, and deubiquitinase inhibitors are an active area of drug development. The Chongqing study does not test therapeutic compounds, but it maps the wiring that such compounds would need to respect.

The research, led by corresponding authors Liangbo Sun, Jiqin Lian, Mingzhen Yang, and Haojun Xiong, with Dong Liu, Meng He, and Jiahong Liu contributing equally as first authors, was supported by the National Natural Science Foundation of China and the Chongqing Natural Science Foundation. Animal experiments were conducted under the guidelines of the Army Medical University Laboratory Animal Center with ethics committee approval, and the authors declare no competing interests. The article was published open access on 29 September 2026, with raw western blotting data and supplementary materials made available alongside the paper, a transparency practice that allows independent researchers to scrutinize the key biochemical evidence.

What makes the study resonate beyond its immediate findings is the picture it paints of cellular death as an actively regulated, enzymatically driven process rather than a passive collapse. A starving cell does not merely run out of fuel; it deploys SIRT2 to the mitochondria, strips an acetyl group from ANT3 at lysine 96, stabilizes the protein through USP15-mediated deubiquitination, and assembles the ANT3-VDAC1 complex that breaches the mitochondrial barrier. Each step is reversible in principle, which means each step is a potential checkpoint at which the cell, or a clinician, could intervene. As researchers continue to dissect the permeability transition pore and the acetylation networks that tune it, the K96 switch on ANT3 stands out as a vivid example of how the smallest chemical changes can command the largest cellular decisions.

Subject of Research: SIRT2-mediated deacetylation of the mitochondrial protein ANT3 and its role in regulating programmed cell death during starvation

Article Title: SIRT2-mediated deacetylation of ANT3 at Lys96 promotes cell death

Article References: Liu, D., He, M., Liu, J., Shan, M., Ma, X., lu, L., Bi, X., Xiong, H., Yang, M., Lian, J., & Sun, L. (2026). SIRT2-mediated deacetylation of ANT3 at Lys96 promotes cell death. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03330-5

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03330-5

Keywords: SIRT2, ANT3, VDAC1, USP15, mitochondrial permeability transition pore, deacetylation, lysine 96, starvation, programmed cell death, deubiquitination, mitochondria, cell death discovery

The study, conducted in a mouse model of glaucoma, demonstrates that administration of rhNGF protects retinal ganglion cells from degeneration and preserves visual function. Crucially, the investigators did not stop at showing that the treatment worked; they dissected the mechanisms underlying the benefit, revealing that rhNGF counteracts two intertwined drivers of glaucomatous damage—oxidative stress and neuroinflammation. This dual action positions nerve growth factor not merely as a survival signal for ailing neurons, but as a molecular shield against the hostile retinal environment that develops as the disease progresses.

Nerve growth factor was the first neurotrophin ever discovered, identified more than seventy years ago by Rita Levi-Montalcini and Stanley Cohen, work that earned the Nobel Prize in Physiology or Medicine in 1986. NGF is best known for its role in the development and maintenance of sympathetic and sensory neurons, but it also acts on the central nervous system, including the retina, where its receptors—TrkA and p75NTR—are expressed by retinal ganglion cells and by glial cells such as Müller cells and astrocytes. Over the years, evidence has accumulated that NGF signaling can promote neuronal survival, yet translating that biology into a practical therapy has been difficult, in part because delivering protein drugs to target tissues is challenging and because earlier clinical efforts were hampered by formulation and delivery limitations.

In the glaucoma model used in the study, elevated intraocular pressure triggers a cascade of degenerative events in the retina. Pressure insult compromises axonal transport at the optic nerve head, deprives ganglion cells of trophic support, and sets off a vicious cycle in which stressed neurons release damage signals that activate glial cells. Activated microglia and macroglia, in turn, release pro-inflammatory cytokines such as TNF-alpha and interleukin-1 beta and generate reactive oxygen species, further injuring neurons and perpetuating the inflammatory loop. The result is progressive loss of retinal ganglion cells, thinning of the nerve fiber layer, and deterioration of the visual responses that these cells convey to the brain.

When the researchers administered rhNGF to the glaucomatous mice, they observed a marked preservation of retinal structure and function compared with untreated animals. Histological analysis revealed significantly higher survival of retinal ganglion cells, and functional assessments of the visual pathway confirmed that the anatomical protection translated into preserved vision-related output. The magnitude of the effect indicates that rhNGF does not merely delay degeneration marginally but provides substantive neuroprotection in this experimental setting.

The mechanistic findings are arguably the most significant contribution of the work. Molecular analyses of treated retinas showed a pronounced reduction in markers of oxidative stress. Levels of reactive oxygen species and lipid peroxidation products fell, while endogenous antioxidant defenses were bolstered. This matters because oxidative damage is now recognized as a central pillar of glaucoma pathobiology: the retina is one of the most oxygen-demanding tissues in the body, its ganglion cell mitochondria are exceptionally vulnerable, and oxidative modifications to proteins, lipids, and DNA accumulate early in the disease and correlate with neuronal loss. By damping oxidative injury, rhNGF appears to interrupt one of the key upstream triggers of the degenerative cascade.

Equally important was the effect on neuroinflammation. In untreated glaucomatous retinas, the researchers documented robust activation of microglia—the resident immune cells of the retina and optic nerve—along with elevated expression of inflammatory cytokines. In rhNGF-treated animals, microglial activation was substantially attenuated and the inflammatory signature was blunted. This anti-inflammatory action is notable because it suggests that NGF signaling, in addition to its classical trophic role, actively reprograms the glial response to injury. The TrkA receptor, when engaged by NGF, can activate survival pathways such as PI3K-Akt and MAPK signaling in neurons, while modulating the reactivity of glial cells that would otherwise amplify tissue damage. The study’s data indicate that both dimensions of NGF biology—direct neuronal support and immunomodulation—contribute to the observed protection.

The interplay between oxidative stress and inflammation is what makes these findings particularly compelling. These two processes are not independent; reactive oxygen species can activate inflammatory signaling pathways, including the NF-kappaB and inflammasome pathways, and inflammatory cells are themselves major producers of free radicals. In glaucoma, this creates a self-reinforcing spiral in which each process feeds the other. A therapy that targets only one arm of the spiral may achieve limited benefit, whereas an intervention that simultaneously reduces oxidative damage and suppresses neuroinflammation can potentially break the cycle. The rhNGF results suggest that the molecule does precisely that, which may explain why the neuroprotection achieved in the mouse model was so robust.

The therapeutic implications extend beyond the laboratory. Recombinant human NGF has already navigated part of the translational path: a topical ocular formulation of rhNGF has been approved in Europe for the treatment of neurotrophic keratitis, a disease of corneal nerve degeneration, providing clinical precedent for the safety and feasibility of delivering this protein to the eye. The new findings raise the prospect of repurposing or reformulating rhNGF for glaucoma, potentially as an adjunct to pressure-lowering therapy. Such a combination would address both sides of the disease: intraocular pressure as the major modifiable risk factor, and the downstream neurodegenerative processes that pressure control alone cannot fully halt. For the millions of patients who continue to progress despite adequate pressure management, a neuroprotective add-on would represent a genuine paradigm shift.

Significant work remains before rhNGF can be considered a glaucoma therapy. The current evidence comes from an animal model, and mouse glaucoma models, while informative, do not capture every feature of the human disease, which unfolds over decades rather than weeks. Questions of dosing, delivery route, treatment timing, and long-term safety will need to be answered, and results will need to be replicated in additional models and ultimately in clinical trials. Nevertheless, the study provides a rigorous mechanistic foundation for the idea that nerve growth factor can protect the optic nerve in glaucoma, and it identifies oxidative stress and neuroinflammation as tractable, druggable targets. If the neuroprotective efficacy observed in mice can be reproduced in patients, rhNGF could become one of the first treatments in ophthalmology to preserve vision not by lowering pressure, but by directly defending the neurons that make sight possible.

Subject of Research: Neuroprotective efficacy of recombinant human nerve growth factor in a mouse model of glaucoma

Article Title: rhNGF shows neuroprotective efficacy by counteracting oxidative stress and neuroinflammation in a glaucoma mouse model

Article References: Vecchiotti, D., Di Vito Nolfi, M., Compagnoni, C., Miscione, M. S., Verzella, D., D’Andrea, D., Flati, I., Galli, F., d’Angelo, M., Angelucci, A., Cattani, F., Cimini, A., Tessitore, A., Capece, D., Alesse, E., Allegretti, M., & Zazzeroni, F. (2026). rhNGF shows neuroprotective efficacy by counteracting oxidative stress and neuroinflammation in a glaucoma mouse model. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03345-y

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03345-y

Keywords: glaucoma, rhNGF, nerve growth factor, neuroprotection, oxidative stress, neuroinflammation, retinal ganglion cells, intraocular pressure, microglia, optic nerve, TrkA receptor, Cell Death Discovery

The findings carry broad implications for male reproductive biology, inflammatory infertility research, and the fundamental question of how a highly specialized cell reprograms or discards the standard machinery of programmed cell death. Spermatozoa are transcriptionally silent cells. Once released from the testis and matured in the epididymis, they can no longer produce new proteins, synthesize DNA, or regulate their own gene expression. This limitation makes them an exceptional model for understanding which components of the apoptotic apparatus survive in a cell that has essentially frozen its molecular inventory.

To investigate how sperm respond to inflammatory conditions, the researchers exposed mature human sperm samples to TNF-α under controlled laboratory conditions and then assessed hallmarks of apoptosis, including phosphatidylserine externalization, mitochondrial membrane potential, caspase activation, and DNA fragmentation. In most somatic cells, binding of TNF-α to TNFR1 initiates a cascade: the receptor trimerizes, recruits the adaptor protein TRADD, and assembles a multiprotein complex known as Complex I. From there, signaling branches toward survival via NF-κB activation or toward death through Complex II and caspase-8, which in turn activates the executioner caspases-3 and -7.

In the sperm cells, however, this cascade appeared to stall at a very early stage. The study found that although TNFR1 is present on the sperm surface and can bind TNF-α, the downstream signaling that normally follows receptor engagement is functionally incomplete. The adaptor proteins required to transmit the death signal are either absent, sequestered, or otherwise nonfunctional in the mature gamete. Without a competent signalosome, the receptor behaves largely as a passive binding site rather than an active trigger of apoptosis.

The authors describe this phenomenon as TNFR1-associated apoptotic resistance. In essence, the receptor’s presence creates a misleading impression: the cell appears equipped to respond to TNF-α, but the molecular wiring behind the receptor has been dismantled during spermiogenesis. This is a biologically coherent outcome. During the dramatic remodeling that converts a round spermatid into a streamlined sperm cell, most of the cytoplasm is discarded, along with the organelles and protein pools that somatic cells rely upon for signaling. What remains is a compact, highly specialized cell optimized for delivery of the paternal genome, not for orchestrating complex signaling conversations with its environment.

Importantly, the resistance was not absolute or indiscriminate. The researchers found that sperm could still undergo forms of cell death, but these appeared to proceed through pathways that do not depend on the canonical TNFR1-driven route. Mitochondrial dysfunction, oxidative stress, and membrane damage can all compromise sperm function and viability, and these stressors operate independently of the receptor pathway. The distinction matters clinically: it suggests that inflammatory conditions rich in TNF-α, such as those seen in male reproductive tract infections, may impair fertility through mechanisms other than classic apoptosis, for example by damaging membranes, disrupting the acrosome, or generating reactive oxygen species.

The implications extend to assisted reproduction as well. Semen processing techniques, sperm selection methods, and culture conditions all expose gametes to variable inflammatory and oxidative environments. Understanding that mature sperm are intrinsically resistant to TNF-α-mediated apoptosis clarifies why simply bathing sperm in inflammatory cytokines does not selectively eliminate damaged cells through this route, a consideration that could inform future sperm selection strategies designed to enrich for the healthiest subpopulations. If TNFR1 signaling is inert, then therapeutic or diagnostic approaches that assume its functionality in sperm need to be reconsidered.

From an evolutionary perspective, apoptotic resistance in the mature gamete raises fascinating questions. On one hand, insensitivity to inflammatory death signals could protect sperm during their transit through tissues that are sometimes inflamed, allowing them to reach the oocyte even under hostile conditions. On the other hand, some scientists have argued that apoptosis-like changes in sperm serve as a quality control mechanism, marking defective cells for removal. The new findings suggest that this quality control, if it exists in mature sperm, does not operate through the TNFR1 axis, pointing instead to other regulators that remain to be fully characterized.

The study also adds to a growing literature on death receptor signaling in germ cells. Earlier work established that immature germ cells express functional death receptors and can respond to Fas ligand and TNF family cytokines, and that this responsiveness diminishes as cells mature. The present work sharpens that picture by demonstrating, with modern flow cytometric, biochemical, and functional assays, that the block in mature sperm occurs at the level of receptor-proximal complex assembly rather than at the death execution machinery itself. In other words, some executioner components persist in the gamete, but the ignition switch that would engage them has been disconnected.

Looking ahead, the researchers suggest several directions for follow-up work. Characterizing exactly which adaptor proteins are lost or inactivated during spermiogenesis, determining whether any residual TNFR1 signaling influences sperm motility or fertilization capacity through non-apoptotic routes, and testing whether similar resistance mechanisms operate in sperm of other species are all natural next steps. There is also therapeutic potential: if the mechanisms that confer apoptotic resistance can be understood in molecular detail, they might inspire strategies to protect somatic cells from inflammatory death in conditions such as sepsis or neurodegeneration, or conversely, to sensitize unwanted cells to TNF-α. For now, the study stands as an elegant demonstration that even the most fundamental programs of cell biology are not universal, and that the human spermatozoon, in its stripped-down simplicity, has rewritten the rules of the death receptor pathway to suit its singular purpose.

Subject of Research: TNFR1-mediated apoptotic resistance in mature human spermatozoa exposed to TNF-α

Article Title: TNFR1-associated apoptotic resistance in mature human spermatozoa under TNF-α exposure

Article References: Barbonetti, A., Tonni, C., Donatelli, V., Castellini, C., Moretto, C., Tienforti, D., Augello, F. R., Cinque, B., & Palumbo, P. (2026). TNFR1-associated apoptotic resistance in mature human spermatozoa under TNF-α exposure. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03355-w

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03355-w

Keywords: TNFR1, TNF-α, apoptosis, human spermatozoa, male fertility, Cell Death Discovery, death receptor signaling, sperm selection, inflammatory cytokines, spermiogenesis, caspases, assisted reproduction