The starting point for 6SA was nature itself. Ginger root has long been known to reduce neuroinflammation and modulate neurotransmitters, and among its pungent bioactive compounds, 6-shogaol has shown promise against neuroinflammation in neurodegenerative disease models, even alleviating depressive-like behaviors in mice with Parkinson’s disease or traumatic brain injury. Chemically, 6-shogaol resembles the vanilloid moiety of capsaicin, the fiery component of hot peppers, and both compounds activate TRPV1, a non-selective calcium-permeable cation channel implicated in pain, inflammation, and mood disorders. TRPV1 agonists such as capsaicin and palvanil have displayed antidepressant-like effects in rats, but their pungency and side effects have hindered clinical translation. Meanwhile, 6-shogaol itself suffers from poor water solubility, limited oral bioavailability, and appreciable cytotoxicity. The researchers’ strategy was to merge the chemical advantages of 6-shogaol and capsaicin into a single biomimicry analog, 6SA, retaining the alpha,beta-unsaturated carbonyl group of the former and the vanilloid head of the latter.

The synthesis itself is strikingly economical. The team directly coupled two inexpensive starting materials, (E)-oct-2-enoic acid and vanillylamine, using methyltrimethoxysilane-mediated amidation in toluene under reflux, followed by silica gel chromatography purification, to yield 6SA, chemically identified as (E)-N-(4-hydroxy-3-methoxybenzyl)oct-2-enamide, in 61.1 percent yield. According to the authors, this route reduces synthetic cost by roughly 99 percent compared with sourcing the parent natural product. Characterization by ultra-performance liquid chromatography, liquid chromatography-mass spectrometry, and nuclear magnetic resonance confirmed the molecular formula C16H23NO3 and a molecular weight of 277.364. Critically, the structural reshuffling paid off in drug-like properties: the octanol-water partition coefficient of 6SA was logP 1.63, lower than 6-shogaol’s 2.33, indicating better water solubility and a profile consistent with Lipinski’s guidance for both oral absorption and central nervous system penetration.

Safety testing also favored the new analog. In BV2 murine microglial cells, 6-shogaol reduced viability in a concentration-dependent manner starting at 5 micromolar, disrupted the G0/G1 cell cycle phase, and triggered measurable apoptosis. 6SA, by contrast, showed virtually no cytotoxicity up to 40 micromolar and left the cell cycle and apoptosis undisturbed. In vivo, mice given oral 6SA at 20 milligrams per kilogram daily for 21 days showed no histopathological changes in heart, liver, spleen, lung, or kidney, and serum markers of liver and kidney injury, including ALT, AST, blood urea nitrogen, and creatinine, remained normal. The parent 6-shogaol, at the same dose, caused mild hepatocyte swelling. Pharmacokinetic analysis by UPLC-MS/MS further demonstrated that 6SA achieved higher plasma and brain concentrations, a longer half-life, longer mean residence time, larger area under the curve, and higher maximum concentration than 6-shogaol, confirming improved oral bioavailability and blood-brain barrier distribution.

With safety and druggability established, the team turned to efficacy. They induced depressive-like behavior in male C57BL/6J mice by daily subcutaneous corticosterone injection for 21 days, a model that mimics chronic stress-driven hypercortisolemia. Mice receiving oral 6SA alongside the corticosterone showed markedly reduced immobility in the tail suspension test and forced swim test, and increased travel distance in the open field test, reversing the tendency of stressed mice to hug the arena periphery. 6SA also prevented the body weight loss caused by corticosterone, an effect seen with the antidepressant citalopram but not with 6-shogaol. Nissl staining of brain sections revealed that corticosterone produced dark, shrunken, damaged neurons in the prefrontal cortex, and 6SA outperformed both 6-shogaol and citalopram in protecting neurons from this damage. The treatment suppressed corticosterone-elevated IL-1beta and TNF-alpha mRNA in the prefrontal cortex, mirrored by anti-inflammatory effects in lipopolysaccharide-stimulated BV2 cells, and restored serum serotonin, or 5-HT, levels that corticosterone had driven down, returning them to those of untreated controls.

To pin down the molecular target, the researchers examined TRPV1 directly. In BV2 cells, 6SA, 6-shogaol, and the TRPV1 agonist nonivamide each raised intracellular calcium, an effect abolished by the TRPV1 antagonist capsazepine. Two orthogonal target-engagement assays supported direct binding: in the drug affinity responsive target stability assay, 6SA partially protected TRPV1 from protease digestion, and in the cellular thermal shift assay it increased the thermal stability of the channel. Molecular docking against the TRPV1 crystal structure showed that 6SA bound with affinities and in regions comparable to capsaicin and nonivamide. Most persuasively, when mice receiving 6SA and corticosterone were co-treated with capsazepine, the antidepressant effects of 6SA on tail suspension, forced swim, and open field behavior were largely blocked, indicating that TRPV1 activation is essential to the compound’s action in vivo.

The deeper mechanism emerged from single-cell RNA sequencing of prefrontal cortex tissue. The analysis identified eleven major brain cell populations and, within microglia, pinpointed the glutamine synthetase gene Glul and the long non-coding RNA Gm57375 as the key differentially expressed genes responding to 6SA. Gene set enrichment analysis showed that 6SA restored several depression-related pathways, including glutamatergic synapse, serotonergic synapse, long-term depression, and circadian rhythm signaling. Glul encodes the enzyme that converts toxic glutamate into harmless glutamine in the glutamate-glutamine cycle, and its expression is known to be decreased in the prefrontal cortex of patients with major depressive disorder; corticosterone downregulates Glul in mice, exacerbating neuroinflammation and excitotoxicity. Gm57375, by contrast, is a poorly characterized lncRNA, though many lncRNAs regulate gene expression and some are implicated in depression. Pseudotime analysis added a temporal dimension: corticosterone shifted microglia toward later, more dysregulated states along the differentiation trajectory, while 6SA held the cells in healthier earlier states, reversing the downregulation of Glul and Gm57375 in specific microglial subclusters.

Validation experiments connected the dots into a coherent signaling axis. Fluorescence in situ hybridization and immunofluorescence showed that Gm57375 colocalizes with nuclear DNA and with Glul, suggesting the lncRNA may act as a transcriptional or epigenetic regulator in the nucleus. Corticosterone reduced these colocalizations in BV2 cells, and 6SA restored both the expression and nuclear localization of Gm57375 while rescuing Glul protein and mRNA levels. In mouse prefrontal cortex, corticosterone decreased Glul and Gm57375 signals in Iba1-positive microglia, and 6SA restored them. In every case, co-treatment with the TRPV1 antagonist capsazepine abolished the restorative effects of 6SA, establishing that the compound acts through a TRPV1-Glul-Gm57375 axis in microglia. This finding is conceptually significant because the role of TRPV1 in depression has appeared contradictory, with both activation and inhibition reported to produce antidepressant-like effects; the new data suggest that the outcome depends on pathological state, treatment duration, and downstream circuitry, and that in a corticosterone-driven inflammatory context, TRPV1 agonism in microglia is protective.

The authors conclude that 6SA is a safe, druggable, cost-effective biomimicry compound with potent antidepressant activity, operating not through the classical monoamine systems alone but by reprogramming stress-injured microglia to restore glutamate detoxification and lncRNA-mediated gene regulation. Given that inflammation-linked depression represents a substantial subgroup of patients who respond poorly to standard therapy, a TRPV1-targeting anti-neuroinflammatory agent derived from ginger chemistry could open a genuinely new therapeutic avenue. Much work remains before clinical translation, including optimization, toxicology, and human studies, but the study demonstrates how bio-inspired structural redesign, rigorous pharmacokinetic engineering, and single-cell transcriptomics can converge to convert a pungent kitchen spice constituent into a rational drug candidate for one of the world’s most burdensome diseases.

Subject of Research: Development of the biomimicry TRPV1 agonist 6SA as an antidepressant targeting Glul-Gm57375 signaling in microglia.

Article Title: Biomimicry TRPV1 agonist 6SA attenuates corticosterone-induced depression via targeting Glul-Gm57375 signaling in microglia

Article References: Sun, Y., Liao, W., SZE, S. C. W., Feng, Y., Rong, J., & Zhao, J. (2026). Biomimicry TRPV1 agonist 6SA attenuates corticosterone-induced depression via targeting Glul-Gm57375 signaling in microglia. Journal of Advanced Research. https://doi.org/10.1016/j.jare.2026.09.001

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.09.001

Keywords: depression, 6SA, 6-shogaol, TRPV1, microglia, neuroinflammation, Glul, Gm57375, corticosterone, ginger, single-cell RNA sequencing, drug discovery

MASLD, previously known as non-alcoholic fatty liver disease, has become the most prevalent chronic liver condition globally, with an estimated worldwide prevalence of approximately 38 percent based on recent systematic reviews. It ranges from simple fat accumulation to inflammation and fibrosis and can progress to cirrhosis and hepatocellular carcinoma. There are few approved pharmacological treatments, and understanding the underlying molecular drivers is a priority for researchers. Mitochondrial dysfunction has long been recognized as a central feature of MASLD. Mitochondria are the energy factories of the hepatocyte, and when they fail, fatty acids accumulate inside the cell and inflammatory damage follows. Mitophagy — the selective autophagic degradation of damaged mitochondria — is the cell’s quality control system for keeping its mitochondrial network healthy. Earlier work from other groups has shown that restoring mitophagy, for instance with quercetin or cyanidin-3-O-glucoside, can improve fatty liver disease in animal models, and that impaired mitophagy is a mechanistic biomarker in patients with the disease. But the regulatory circuits that shut mitophagy down during MASLD development have remained incompletely mapped.

The new study, led by Mei Long of the Department of Rheumatology and Immunology at the First Affiliated Hospital of Hengyang Medical School, University of South China, together with Kewei Tan of the No. 922 Hospital of the People’s Liberation Army Joint Logistics Support Force and Yujie Dong of the Department of Ultrasound Medicine at the same institution, set out to fill that gap. The researchers first profiled ZNF143, a zinc finger transcription factor that binds specific GC-rich DNA motifs and acts both as an activator and repressor of transcription. ZNF143 is best studied in cancer biology, where it promotes glioma growth through KPNA2-mediated Hippo signalling and supports breast cancer cell survival through the NQO1–p53–Beclin1 axis under metabolic stress. Prior work by the same team had already implicated ZNF143 in fatty liver disease, showing that it inhibits hepatocyte mitophagy by upregulating the long non-coding RNA NEAT1 and activating the ROCK2 pathway. The current study extends that work by identifying an entirely separate, protein-level arm of the same transcription factor’s suppressive effect on mitochondrial quality control.

To test their hypothesis, the researchers used two complementary models of MASLD. The first was an in vivo model in which C57BL/6J mice were fed a high-fat diet for 16 weeks to induce hepatic steatosis and metabolic stress. The second was an in vitro model in which Huh-7 human hepatoma cells, a standard hepatic cell line, were exposed to free fatty acids to mimic lipid overload. Histological changes were assessed by hematoxylin and eosin staining, lipid accumulation was quantified by Oil Red O staining, and mitochondrial damage was assessed with JC-1 staining to monitor mitochondrial membrane potential and transmission electron microscopy to visualize mitochondrial ultrastructure. Serum and tissue markers of liver injury, including alanine aminotransferase, aspartate aminotransferase, total cholesterol and triglycerides, were measured to gauge the severity of hepatic dysfunction.

When the team examined the high-fat-diet-fed mice and the free-fatty-acid-treated Huh-7 cells, they found that ZNF143 was significantly upregulated in both settings, consistent with a role for this transcription factor in disease progression rather than simply a bystander effect. When the researchers knocked down ZNF143 using RNA interference, the consequences were striking: lipid accumulation in the liver decreased, mitochondrial damage was reduced, and liver injury markers fell. The mechanism behind this improvement was traced to a restoration of hepatocyte mitophagy, confirming that ZNF143 acts as a brake on mitochondrial quality control during MASLD.

The next step was to identify the transcriptional target through which ZNF143 exerts its effect. Using chromatin immunoprecipitation, the researchers demonstrated that ZNF143 binds directly to the promoter region of SMURF1, a HECT-type E3 ubiquitin ligase known for its role in ubiquitinating and degrading diverse substrate proteins in cancer, vascular remodeling and inflammatory signalling. Dual-luciferase reporter assays confirmed that this binding functionally activates SMURF1 transcription. In other words, ZNF143 does not merely correlate with MASLD; it actively turns up the expression of a ubiquitin ligase that then acts downstream.

SMURF1 has a complicated history in liver biology. Previous studies have shown that deleting Smurf1 attenuates liver steatosis in mice by stabilizing p53, and that Smurf1 aggravates fatty liver disease by stabilizing SREBP-1c, a master regulator of lipid synthesis, in an E3-activity-independent manner. Conversely, another study reported that SMAD-specific E3 ubiquitin protein ligase 1 can be protective in alcoholic steatohepatitis. The current study adds a new substrate to SMURF1’s growing portfolio in hepatic disease and clarifies how this E3 ligase suppresses mitochondrial quality control. Using co-immunoprecipitation, the team showed that SMURF1 physically interacts with TRPV1, the transient receptor potential vanilloid type 1 ion channel, and that SMURF1 ubiquitinates TRPV1, leading to its proteasomal degradation. TRPV1, the receptor activated by capsaicin, the pungent compound in chili peppers, has long been linked to metabolic health. Activation of TRPV1 by dietary capsaicin improves visceral fat remodelling through calcium influx, and TRPV1 activation prevents fatty liver disease in mice through upregulation of the mitochondrial uncoupling protein UCP2. By degrading TRPV1, SMURF1 removes a protective channel that supports mitochondrial and metabolic homeostasis in the hepatocyte.

The researchers then performed epistasis experiments to confirm the hierarchy of the pathway. When they knocked down TRPV1 in free-fatty-acid-treated Huh-7 cells that had already had ZNF143 depleted, the beneficial effect of ZNF143 knockdown on mitophagy was reversed. Similarly, overexpressing SMURF1 in ZNF143-depleted cells abolished the improvement in mitochondrial clearance. These results established that ZNF143 acts upstream of SMURF1 and TRPV1 in the same linear pathway: ZNF143 turns on SMURF1 transcription, SMURF1 ubiquitinates TRPV1 and targets it for degradation, and loss of TRPV1 suppresses mitophagy, leading to mitochondrial dysfunction and fat accumulation.

The significance of the finding is twofold. First, it adds to the emerging view that MASLD is fundamentally a disorder of impaired mitochondrial turnover, not simply one of excessive lipid synthesis. Multiple groups have shown that PINK1/Parkin-mediated mitophagy relieves fatty liver disease and that reversing Parkin-related mitophagy attenuates the condition. The current work identifies ZNF143 as a transcriptional switch that turns this quality control system off, providing a mechanistic explanation for why mitophagy declines during disease progression. Second, the study places TRPV1 — a channel best known from pain biology and dietary capsaicin research — at the centre of hepatic mitochondrial homeostasis. Recent work has implicated TRPV1 in mitophagy regulation in other contexts as well, including a 2025 report showing that TRPV1 inhibits both ferroptosis and mitophagy in heart failure through SFXN2, and a 2020 study showing that blocking TRPV1 promotes terminal mitophagy in multiple myeloma. The context-dependent role of TRPV1 in mitophagy across different tissues remains an open question, but the current study firmly establishes it as a downstream effector of ZNF143 in hepatocytes.

Therapeutically, the pathway offers several potential points of intervention. Small-molecule inhibitors of ZNF143 activity have already been developed for cancer applications, including YPC-21661 and YPC-22026, which were shown to inhibit ZNF143 activity both in vitro and in vivo. Inhibitors of SMURF1 have been designed for pulmonary arterial hypertension, suggesting that pharmacological tools against this E3 ligase could be repurposed for metabolic liver disease. Alternatively, TRPV1 agonists such as capsaicin or its analogues could theoretically compensate for the loss of TRPV1 protein caused by SMURF1-mediated degradation, consistent with epidemiological and experimental data suggesting that capsaicin may promote vascular and metabolic health. The authors note that the study’s findings, generated in mice and in a human hepatoma cell line, will need to be validated in human tissue samples and in additional model systems before any clinical translation.

The research was performed in accordance with guidelines approved by the Medical Ethics Committee of the First Affiliated Hospital of University of South China, and all authors declare no conflict of interest. The datasets generated and analysed during the study are available within the published article. As global rates of MASLD continue to climb in parallel with obesity and type 2 diabetes, identifying transcription factors such as ZNF143 that govern mitochondrial quality control provides a mechanistic framework for understanding disease progression and offers a roadmap for developing targeted therapies that restore the hepatocyte’s ability to clear its damaged mitochondria before steatosis spirals into inflammation, fibrosis and cancer.