Yasu-Taka Azuma

Supersulfides are emerging sulfur-containing signaling molecules involved in redox regulation, mitochondrial function, and protein S-sulfhydration. However, their dynamic behavior in living mammalian systems remains poorly understood because existing analytical methods require destructive sample preparation or lack sufficient intracellular applicability. Here, we developed a genetically encoded supersulfide-dependent translocation reporter (SuTR) for mammalian cells and in vivo imaging. Although the previously reported probe psGFP failed to respond to supersulfides in mammalian cells, fusion of psGFP with the sulfide-responsive transcriptional repressor (SqrR) generated SuTR, a novel reporter that exhibited supersulfide-dependent translocation from the nucleus to the cytoplasm. Na₂S₂ and Na₂S₃ induced dose-dependent cytosolic translocation of SuTR, whereas Na₂S showed no effect. Fluorescence recovery after photobleaching (FRAP) analysis revealed accelerated fluorescence recovery shortly after supersulfide stimulation, and overexpression of the endogenous supersulfide-producing enzyme Cysteinyl-tRNA Synthetase 2 (CARS2) similarly altered reporter dynamics. Mutational analyses demonstrated that reporter responsiveness depends on the DNA-binding activity of SqrR. Furthermore, SuTR successfully detected supersulfide induction in mouse liver in vivo following Na₂S₃ administration. These findings establish SuTR as a genetically encoded reporter for monitoring supersulfide dynamics in mammalian cells and tissues.

Dominant-negative inhibition of ATP synthase provides a useful model to investigate the limits of cellular bioenergetic adaptation. Here, we expressed a truncated form of ATP synthase inhibitory factor 1 (DN-IF1, aa 1–60) in keratinocytes and stratified cells based on GFP intensity to generate graded levels of mitochondrial constraint. DN-IF1 expression induced a GFP-dependent reduction in ATP levels and cell proliferation, with the highest expressing cells exhibiting approximately 50% ATP depletion. These cells displayed altered morphology and markedly reduced MitoTracker fluorescence intensity, indicating impaired mitochondrial integrity. Notably, the GFPHigh population was unstable and progressively lost over time, suggesting that severely constrained bioenergetic states are not maintained at the population level. Collectively, these findings demonstrate that excessive inhibition of ATP synthase induces heterogeneous and unstable bioenergetic states, leading to selective loss of energetically compromised cells.

Chronic pancreatitis (CP) is a progressive inflammatory disorder characterized by pancreatic fibrosis and loss of exocrine function. Interleukin-19 (IL-19) is an anti-inflammatory cytokine, but its role in the pathogenesis of CP remains unclear. This study aimed to investigate the protective function of IL-19 using an ethanol/lipopolysaccharide (LPS)-induced murine CP. CP was induced in wild-type (WT) and IL-19 knockout (KO) mice by administration of ethanol in drinking water combined with repeated intraperitoneal injections of LPS (3 mg/kg) for 10 weeks. Pancreatic injury, inflammation, and fibrosis were assessed histologically and molecularly. IL-19 KO mice developed markedly more severe pancreatitis than WT mice, as evidenced by elevated serum amylase levels, extensive fibrosis, acinar cell necrosis, loss of pancreatic architecture, and prominent inflammatory infiltration. In contrast, WT mice exhibited only mild pancreatic injury with largely preserved acinar structure. mRNA expression levels of tumor necrosis factor-α and transforming growth factor-β in the pancreas were significantly higher in IL-19 KO mice, consistent with enhanced inflammatory and fibrotic responses. Notably, pancreatic IL-19 mRNA expression was significantly upregulated in CP, suggesting an endogenous compensatory mechanism. IL-19 deficiency worsens ethanol/LPS-induced chronic pancreatitis, indicating that endogenous IL-19 protects against inflammation and fibrosis and may serve as a therapeutic target.

Lipid droplet (LD) accumulation in hepatocytes is one of the major symptoms associated with fatty liver disease. Mitochondria play a key role in catabolizing fatty acids for energy production through β-oxidation. The interplay between mitochondria and LD assumes a crucial role in lipid metabolism, while it is obscure how mitochondrial morphology affects systemic lipid metabolism in the liver. We previously reported that cilnidipine, an already existing anti-hypertensive drug, can prevent pathological mitochondrial fission by inhibiting protein–protein interaction between dynamin-related protein 1 (Drp1) and filamin, an actin-binding protein. Here, we found that cilnidipine and its new dihydropyridine (DHP) derivative, 1,4-DHP, which lacks Ca²⁺ channel-blocking action of cilnidipine, prevent the palmitic acid-induced Drp1–filamin interaction, LD accumulation and cytotoxicity of human hepatic HepG2 cells. Cilnidipine and 1,4-DHP also suppressed the LD accumulation accompanied by reducing mitochondrial contact with LD in obese model and high-fat diet-fed mouse livers. These results propose that targeting the Drp1–filamin interaction become a new strategy for the prevention or treatment of fatty liver disease.

Lipid droplet (LD) accumulation in hepatocytes is one of the major symptoms associated with fatty liver disease. Mitochondria play a key role in catabolizing fatty acids for energy production through β-oxidation. The interplay between mitochondria and LD assumes a crucial role in lipid metabolism, while it is obscure how mitochondrial morphology affects systemic lipid metabolism in the liver. We previously reported that cilnidipine, an already existing anti-hypertensive drug, has potency to prevent pathological mitochondrial fission by inhibiting protein-protein interaction between dynamin-related protein 1 (Drp1) and filamin, an actin-binding protein. Here, we found that cilnidipine and its new dihydropyridine (DHP) derivative, 1,4-DHP, which lacks Ca2+ channel blocking action of cilnidipine, prevent the palmitic ac-id-induced Drp1-filamin interaction, LD accumulation and cytotoxicity of human hepatic HepG2 cells. Cilnidipine and 1,4-DHP also suppressed the LD accumulation accompanied by reducing mitochondrial contact with LD in obese model and high fat diet-fed mouse livers. These results propose that targeting Drp1-filimin interaction becomes a new strategy for the prevention or treatment of fatty liver disease.

We recently reported that transient receptor potential canonical (TRPC) 6 channel activity contributes to intracellular Zn²⁺ homeostasis in the heart. Zn²⁺ has also been implicated in the regulation of intestinal redox and microbial homeostasis. This study aims to investigate the role of TRPC6-mediated Zn²⁺ influx in the stress resistance of the intestine. The expression profile of TRPC1-C7 mRNAs in the actively inflamed mucosa from inflammatory bowel disease (IBD) patients was analyzed using the GEO database. Systemic TRPC3 knockout (KO) and TRPC6 KO mice were treated with dextran sulfate sodium (DSS) to induce colitis. The Zn²⁺ concentration and the mRNA expression levels of oxidative/inflammatory markers in colon tissues were quantitatively analyzed, and gut microbiota profiles were compared. TRPC6 mRNA expression level was increased in IBD patients and DSS-treated mouse colon tissues. DSS-treated TRPC6 KO mice, but not TRPC3 KO mice, showed severe weight loss and increased disease activity index compared with DSS-treated WT mice. The mRNA abundances of antioxidant proteins were basically increased in the TRPC6 KO colon, with changes in gut microbiota profiles. Treatment with TRPC6 activator prevented the DSS-induced colitis progression accompanied by increasing Zn²⁺ concentration. We suggest that TRPC6-mediated Zn²⁺ influx activity plays a key role in stress resistance against IBD, providing a new strategy for treating colitis.

Zn2+ has been implicated in the regulation of intestinal redox and microbial homeostasis, and we recently reported that transient receptor potential canonical (TRPC) 6 channel activity contributes to intracellular Zn2+ homeostasis in mammalian cells. This study aims to investigate the role of TRPC6-mediated Zn2+ influx in stress resistance of intestine. Expression profile of TRPC1-C7 mRNAs in the actively inflamed mucosa from inflammatory bowel disease (IBD) patients was analyzed using GEO database. Systemic TRPC3-knockout (KO) and TRPC6-KO mice were treated with dextran sulphate sodium (DSS) to induce colitis. The Zn2+ concentration and the mRNA expression levels of oxidative/inflammatory markers in colon tissues were quantitatively analyzed, and gut microbiota profiles were compared. TRPC6 mRNA expression level was increased in IBD patients and DSS-treated mouse colon tissues. DSS-treated TRPC6-KO mice, but not TRPC3-KO mice, showed severe weight loss and increased disease activity index compared with DSS-treated WT mice. The mRNA abundances of antioxidant proteins were basically increased in TRPC6-KO colon, with changes in gut microbiota profiles. Treatment with TRPC6 activator prevented the DSS-induced colitis progression accompanied by increasing Zn2+ concentration. We suggest that TRPC6-mediated Zn2+ influx activity plays a key role in stress resistance against IBD, providing a new strategy for treating colitis.

IL-19 is a member of IL-10 family and is mainly produced by macrophages. Acute pancreatitis (AP) is an inflammatory disease characterized by acinar cell injury and necrosis. In the present study, the role of IL-19 in AP and AP-associated lung injury in mice was explored using L-arginine-induced pancreatitis. Experimental pancreatitis was induced by intraperitoneal injection of L-arginine in wild-type (WT) and IL-19 gene deficient (IL-19 KO) mice. In L-arginine treated mice, the serum amylase level was significantly increased in IL-19 KO mice, and interstitial edema, analyzed using hematoxylin and eosin (H&E)-stained sections, was aggravated mildly in IL-19 KO mice compared to WT mice. Compared to WT mice treated with L-arginine, mRNA expression of tumor necrosis factor (TNF)-α was significantly upregulated in IL-19 KO mice treated with L-arginine. In WT mice, IL-19 mRNA was equally expressed in the pancreas of both control and L-arginine treated mice. The condition of lung alveoli in WT and IL-19 KO mice treated with L-arginine was then evaluated. In mice with L-arginine-induced pancreatitis, alveolar area was remarkedly decreased, and expression of lung myeloperoxidase was significantly increased in IL-19 KO mice compared to WT mice. In the lungs, mRNA expressions of IL-6 and inducible nitric oxide synthase were significantly increased in IL-19 KO mice compared to WT mice. In summary, IL-19 was proposed to alleviate L-arginine-induced pancreatitis by regulating TNF-α production and to protect against AP-related lung injury by inhibiting neutrophil migration.