Doxorubicin-induced cardiac injury remains a major clinical challenge in oncology. The drug generates reactive oxygen species, disrupts mitochondrial function and triggers programmed cell death in cardiomyocytes, the contractile cells of the heart, eventually leading to arrhythmias and heart failure that can appear within days of a high dose or years after treatment ends. Until now, the only widely accepted preventive strategy has been dexrazoxane, an iron-chelating agent that offers partial protection but does not eliminate the risk. Because the cardiomyocyte has been treated as the primary victim and the primary subject of investigation, the role of the cardiac fibroblast in chemotherapy cardiotoxicity has remained, in the authors’ words, incompletely defined. The new study set out to test whether GNL3, a GTP-binding protein better known for its roles in tumor biology and cell proliferation, might matter in this setting.

The experimental design was unusually rigorous for a mechanistic cardiology study. The team created two lines of genetically engineered mice: one in which GNL3 was specifically deleted from cardiac fibroblasts, and another in which the protein was specifically overproduced in those same cells. They then subjected both lines to a single intraperitoneal injection of doxorubicin at 15 milligrams per kilogram, a standard acute injury model that reproduces the kind of cardiac stress seen clinically after high-dose chemotherapy. Using echocardiography to measure heart function in living animals, along with western blotting, quantitative PCR, immunofluorescence, co-immunoprecipitation and chromatin immunoprecipitation to dissect molecular events, the researchers tracked both the injury and the signaling pathways underlying it.

The results were striking. GNL3 expression rose sharply in the hearts of doxorubicin-treated mice, and the increase was concentrated in the fibroblast fraction of the tissue. When the researchers deleted GNL3 from cardiac fibroblasts, the mice fared markedly better: myocardial injury was reduced, oxidative stress declined, cardiomyocyte apoptosis decreased, and systolic function — the heart’s ability to pump blood — was better preserved. Conversely, mice engineered to overexpress GNL3 in their fibroblasts suffered worse outcomes across all of these measures, and their survival was reduced after doxorubicin exposure. In a critical control experiment, deleting GNL3 from cardiomyocytes themselves produced no obvious protective effect, a result that argues strongly against the idea that the protein matters mainly inside the muscle cells and instead points the finger squarely at the fibroblast.

To understand how a protein made in fibroblasts could damage neighboring cardiomyocytes, the team turned to conditioned medium assays, a technique in which cardiomyocytes are grown in a bath of liquid previously occupied by doxorubicin-treated fibroblasts. When the culture medium came from fibroblasts with high GNL3 levels, the exposed cardiomyocytes showed more injury-associated damage; when GNL3 was removed from the fibroblasts, the medium was less harmful. This established that GNL3 acts, at least in part, through secreted factors — a paracrine mechanism in which one cell type changes the chemical environment of another. The central suspect in that chemical conversation turned out to be Fas ligand, or FasL, a death receptor ligand famous in immunology for its role in instructing cells to undergo apoptosis.

The molecular trail leading to FasL ran through a well-characterized signaling pathway known as calcineurin/NFATc1, or CaN/NFATc1. Calcineurin is a calcium-dependent phosphatase, and NFATc1 is a transcription factor that it activates; when active, NFATc1 moves into the nucleus and binds to promoter regions of target genes to switch them on. Using chromatin immunoprecipitation, the researchers demonstrated that GNL3 was functionally linked to this axis and that increased NFATc1 occupancy at the Fasl promoter occurred in cardiac fibroblasts — in other words, GNL3 upregulation drives the transcription factor to dock onto the gene for FasL and crank up its production. Fibroblasts loaded with GNL3 consequently secreted more FasL, which then traveled to neighboring cardiomyocytes and pushed them toward apoptosis, oxidative stress and functional decline.

This fibroblast-to-cardiomyocyte death signal is what the authors describe as FasL-linked crosstalk, and it reframes the architecture of chemotherapy cardiotoxicity. Rather than a single cell type succumbing to a toxic drug, the heart’s response to doxorubicin emerges as a coordinated collapse involving multiple cell populations: the drug induces GNL3 in fibroblasts, GNL3 activates calcineurin and NFATc1, NFATc1 amplifies Fasl transcription, and secreted FasL delivers a lethal message to the contractile cells. It is a chain reaction in which the supporting cast of the heart becomes a transmitter of damage, and interrupting any link in the chain — as the knockout mice demonstrated — materially protects the organ.

The clinical implications are immediate and tantalizing. If the same pathway operates in human patients, GNL3 or its downstream product FasL could serve as biomarkers for identifying oncology patients at elevated risk of anthracycline cardiotoxicity before symptoms appear, allowing oncologists and cardiologists to tailor dosing, monitoring and cardioprotective therapy. More ambitiously, the pathway itself becomes a drug target. Inhibiting the CaN/NFATc1 axis in cardiac fibroblasts, blocking FasL signaling, or even targeting GNL3 directly could, in principle, shield the heart without compromising doxorubicin’s ability to kill tumor cells — a long-sought goal, since the very mechanism that makes anthracyclines lethal to cancer cells also makes them dangerous to cardiac tissue. The authors are careful to frame these findings as nominating CF-derived GNL3 as a candidate pathway for further investigation rather than as an established therapeutic target, and the work was conducted in mice, so translation to patients will require additional validation.

The study also carries a broader scientific lesson about where to look for answers in cardiovascular medicine. Cardiac fibroblasts were long dismissed as passive scaffolding, but research over the past two decades has progressively revealed them as active participants in nearly every form of heart disease, from fibrosis after myocardial infarction to inflammation in myocarditis. This study extends that re-evaluation into the realm of acute drug toxicity, showing that a stromal cell can dictate whether a chemotherapeutic challenge becomes a survivable insult or a catastrophic one. It also highlights GNL3 itself as a protein whose portfolio is expanding: previously studied mainly in nucleolar biology and cancer, it now appears to function as a stress-responsive regulator in the heart’s supporting cells, wired into one of the most conserved death-signaling pathways in biology.

For the millions of patients who receive anthracycline chemotherapy each year, the promise of this work lies in the possibility of decoupling cancer treatment from cardiovascular harm. The Wuhan team, led by corresponding author Wanli Jiang, has laid out a complete mechanistic arc — from drug exposure to protein upregulation to transcription factor activation to intercellular death signaling to measurable cardiac dysfunction — and each step of that arc is now a potential point of intervention. The research was supported by the Natural Science Foundation for Young Scientists of Hubei Province and the Guiding Program of Natural Science Foundation of Hubei Province, China, and is available open access. As follow-up studies test whether GNL3 behaves the same way in chronic injury models and in human tissue, one conclusion already stands: the heart’s fibroblasts are not bystanders in chemotherapy cardiotoxicity, and silencing the wrong conversation between cells may cost patients their hearts even when the cancer is cured.

Subject of Research: Fibroblast-derived GNL3 signaling in acute doxorubicin-induced cardiac injury

Article Title: Cardiac fibroblast-derived GNL3 aggravates acute doxorubicin-induced cardiac injury via FasL-linked fibroblast–cardiomyocyte crosstalk

Article References: Lu, X., Yang, J., Zhang, H., Zhang, Z., Xing, X., Wan, S., Lai, W., Zhang, Y., & Jiang, W. (2026). Cardiac fibroblast-derived GNL3 aggravates acute doxorubicin-induced cardiac injury via FasL-linked fibroblast–cardiomyocyte crosstalk. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06450-4

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06450-4

Keywords: doxorubicin, cardiotoxicity, GNL3, cardiac fibroblasts, FasL, NFATc1, apoptosis, oxidative stress, paracrine signaling, anthracyclines, heart failure, calcineurin

Fusarium oxysporum f. sp. lycopersici, abbreviated Fol, is one of the most economically destructive soil-borne pathogens in tomato production worldwide. The fungus enters through the roots, colonizes the vascular tissue, and produces the signature symptoms of chlorosis, leaf wilting, and browning of the stem vasculature that ultimately kill the entire plant. Part of what makes Fol so difficult to manage is its chlamydospores, thick-walled dormant spores that persist in infested soil for years, waiting for a susceptible host. Despite cultural, biological, chemical, and resistance-based control strategies, disease management remains an uphill battle, particularly as new pathogenic races continue to emerge.

To invade a living plant, a fungus must contend with a hostile environment. As Fol grows through host tissue, it encounters reactive oxygen species unleashed by the plant immune system, along with nutrient limitation and other stresses. Surviving this barrage requires extensive transcriptional reprogramming, a process orchestrated by transcription factors that coordinate fungal development, stress adaptation, and virulence. Although many virulence-promoting transcription factors have been identified in F. oxysporum, far less is known about those that support disease indirectly, by safeguarding the basic cellular machinery of the pathogen itself.

The research team, led by Ching-Yu Chen and Ying-Lien Chen of National Taiwan University, began their investigation in the well-studied calcineurin signaling pathway, a conserved calcium- and calmodulin-activated phosphatase cascade that governs growth, morphogenesis, ion homeostasis, stress responses, and virulence in fungal pathogens. Their earlier work had shown that calcineurin controls hyphal growth, conidiation, chlamydospore formation, and virulence in Fol. The best-known calcineurin substrate in fungi is Crz1, a zinc finger transcription factor that, once dephosphorylated, moves into the nucleus and switches on genes involved in growth, stress tolerance, drug resistance, and pathogenicity. Yet across many fungi, deletion of crz1 produces far milder defects than deletion of calcineurin itself, hinting that other, poorly characterized substrates must carry out critical downstream functions.

Using protein similarity searches against the Fol 4287 genome, the researchers identified two candidate Crz1 homologs, encoded by the genes FOXG_00040 and FOXG_05246. Sequence and phylogenetic analyses told two very different stories. FOXG_00040, which they named FolCrz1, clustered tightly with canonical Crz1 orthologs from filamentous fungi and retained the hallmark architecture, including two C2H2 zinc finger motifs and the conserved PxIxIT and LxVP short linear motifs that calcineurin uses to recognize its substrates. FOXG_05246 was another matter entirely. Although it shares some structural features with Crz1, its overall sequence identity is low, it lacks the conserved PxIxIT motif at the corresponding position, and its closest homologs outside the genus Fusarium show only about 40 percent identity. The protein appears to be a Fusarium-specific invention, a regulatory pathway that evolved within this genus and nowhere else. The team designated it FolSrz1, short for stress resistance zinc finger 1.

Deleting each gene revealed sharply divergent roles. Mutants lacking FolCrz1 grew normally on standard medium and responded to calcium in a manner consistent with a conserved calcineurin-Crz1 pathway; the protein, tagged with green fluorescent protein, rushed into the nucleus within minutes of calcium treatment, and this movement was abolished by the calcineurin inhibitor cyclosporin A. Deleting FolSrz1, by contrast, slowed vegetative growth, thinned aerial mycelia, produced a pink colony appearance, and made the fungus hypersensitive to hydrogen peroxide and menadione, two oxidative stress-inducing agents. FolSrz1 mutants were also unusually sensitive to sodium dodecyl sulfate, pointing to a role in membrane integrity. Notably, FolSrz1-GFP sat mostly in the cytoplasm with only partial nuclear presence, and neither oxidative stress nor cyclosporin A changed this pattern, suggesting that its localization is governed by something other than canonical calcineurin-dependent translocation.

Both transcription factors proved important for producing chlamydospores, the fungus’s primary survival structures and field inoculum. Wild-type cultures generated roughly 1.28 billion chlamydospores per gram of dried mycelium, while the FolCrz1 and FolSrz1 mutants produced about 397 million and 77.5 million respectively, reductions that left spore morphology and lipid content unchanged. This indicates that both proteins participate in the induction of chlamydospore formation rather than in the structural development of the spores themselves. The FolCrz1 mutant additionally showed heightened sensitivity to tebuconazole, a widely used triazole fungicide, echoing findings in other Fusarium species and suggesting a conserved role for Crz1 in azole tolerance.

The most dramatic result emerged from tomato infection assays. Three-week-old seedlings dipped in spore suspensions developed severe wilting when inoculated with the wild type or the FolCrz1 mutant, with disease severity indices of 73 and 75 percent respectively at 28 days post-inoculation. Seedlings inoculated with the FolSrz1 mutant remained largely healthy, showing only mild yellowing of lower leaves, and the disease severity index plummeted to 22 percent. Vascular browning confirmed that the mutant could still invade the host; it simply could not do much damage once inside. FolCrz1, despite its conserved biochemistry, turned out to be dispensable for virulence in this pathosystem, reinforcing the idea that calcineurin must act through other substrates to support disease.

To uncover what FolSrz1 actually controls, the team compared gene expression between the wild type and the mutant using RNA sequencing, identifying 1,249 differentially expressed genes, 616 upregulated and 633 downregulated. The enriched pathways were strikingly mundane in the best sense: double-strand break repair, ubiquitin-mediated proteolysis, autophagy, nucleocytoplasmic transport, steroid biosynthesis, and copper ion transport. Crucially, genes encoding antioxidant enzymes, secreted effectors, cell wall-degrading enzymes, and mycotoxin biosynthesis proteins showed no significant differential expression. Quantitative PCR validation confirmed that FolSrz1’s influence was strongest under basal conditions; when the fungus was hit with hydrogen peroxide, expression differences between the strains largely dissolved, and the FolSRZ1 transcript itself was not induced by stress.

This pattern led the researchers to a counterintuitive conclusion. FolSrz1 is not a classic oxidative stress-responsive regulator that switches on detoxification genes when danger strikes. Rather, it maintains the steady-state machinery that keeps the cell functional: the ubiquitin-proteasome system and autophagy that clear damaged proteins and organelles, the non-homologous end-joining pathway that repairs broken DNA, and, importantly, the copper transporters Ctr1a and Ctr1b, orthologs of the yeast high-affinity copper importer Ctr1, which were significantly downregulated in the mutant. Copper is an essential cofactor for copper/zinc superoxide dismutase, so reduced copper uptake could impair superoxide detoxification, helping explain the mutant’s sensitivity to menadione, though not fully its sensitivity to hydrogen peroxide, which is detoxified primarily by catalases and peroxidases.

Measurements in infected tomato roots tied the molecular picture to disease. Hydrogen peroxide accumulation in roots at 24 hours post-inoculation was indistinguishable between wild-type and mutant infections, confirming that the mutant does not trigger an altered oxidative burst. Yet quantitative PCR at five days post-inoculation showed that the FolSrz1 mutant had achieved only about 51 percent of the wild-type fungal biomass in root tissue. The attenuated virulence, in other words, stems not from a failure to detoxify host reactive oxygen but from a general loss of fitness during colonization, a fitness that depends on intact genome maintenance, proteostasis, and copper homeostasis. This mechanism echoes recent work showing that copper acquisition, governed by the transcription factor Mac1, is itself essential for Fol to colonize tomato plants.

The study thus adds a new layer to the calcineurin story and offers a fresh conceptual angle on fungal virulence: a pathogen can be disarmed not only by stripping away its weapons but by sabotaging the cellular housekeeping that keeps those weapons functioning. Because FolSrz1 exists only within Fusarium, it also represents a potentially selective target for control strategies aimed at this genus without disrupting beneficial or unrelated soil microbes. As Fusarium wilt continues to spread through tomato-growing regions and chlamydospores stubbornly persist in field soils, understanding how a Fusarium-specific transcription factor quietly sustains the pathogen’s inner life may prove as important as cataloging the offensive arsenal it supports.

Subject of Research: Role of the Crz1-like transcription factor FolSrz1 in oxidative stress resistance and virulence of the tomato wilt fungus Fusarium oxysporum f. sp. lycopersici

Article Title: The Crz1-like protein FolSrz1 contributes to oxidative stress resistance and virulence through maintenance of cellular homeostasis in Fusarium oxysporum f. sp. lycopersici

Article References: Chen, C.-Y., Hsieh, Y.-J., Lin, C.-H., Hsu, L.-H., & Chen, Y.-L. (2026). The Crz1-like protein FolSrz1 contributes to oxidative stress resistance and virulence through maintenance of cellular homeostasis in Fusarium oxysporum f. sp. lycopersici. Journal of Agriculture and Food Research, 31, Article 103300. https://doi.org/10.1016/j.jafr.2026.103300

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103300

Keywords: Fusarium oxysporum, FolSrz1, transcription factor, calcineurin, oxidative stress, Fusarium wilt, tomato, virulence, chlamydospores, copper homeostasis, cellular homeostasis, plant pathology