Objective:To investigate the effects of exogenous hydrogen sulfide on myocardial fibrosis and apoptosis in rats after myocardial infarction and the underlying mechanisms.Methods:Forty-three Sprague Dawley(SD)rats were divided into 4 groups according to the random number table method: a control group(n=12), a myocardial infarction group(MI group, n=13), an hydrogen sulfide(H 2S)group(n=6)and an MI+ H 2S group(n=12). The rat model of acute myocardial infarction was established by intraperitoneal injections of isoproterenol(50 mg/kg, once a day, for 2 days). Electrocardiogram and troponin changes were recorded 48 h after the last drug administration to determine whether the rat model was successfully constructed.After successful establishment of the model, rats in the MI group and the MI+ H 2S group were intraperitoneally injected with sodium hydrosulfide(56 μmol/kg, once a day, for 6 weeks).6 weeks later, echocardiogram and Masson's trichrome staining were performed to assess changes in cardiac function and collagen volume fraction in each group.Terminal deoxynucleotidyl transferase(TdT)dUTP nick end labeling(TUNEL)was used to detect the myocardial apoptosis rate in each group, and Western-blot was used to detect protein expression of Yes-related protein 1(YAP1), WW domain containing transcriptional regulator1(TAZ), mammalian Ste20-like kinase 2(MST2), Bcl-2-associated X protein(Bax), cysteine protease 3(caspase-3), the ratio of matrix metalloproteinase 3(MMP3)/matrix metalloproteinase inhibitor 2(TIMP2), and B-cell lymphoma factor(Bcl-2). Results:Compared with the control group, myocardial collagen volume fraction was increased( P<0.05), the myocardial cell apoptosis rate was increased( P<0.05), and myocardial YAP1, TAZ, MST2, Bax, caspase-3 protein expression and MMP3/TIMP2 ratio were increased in the MI group(all P<0.05), while the expression of Bcl-2 protein was decreased( P<0.05). Compared with the MI group, collagen volume fraction and the cardiomyocyte apoptosis rate were significantly decreased in the MI+ H 2S group( P<0.05). Also, protein expression of YAP1(2.406±0.024 vs.2.830±0.063), TAZ(0.964±0.090 vs.1.329±0.018), MST2(0.780±0.082 vs.1.788±0.097), Bax(1.500±0.008 vs.0.613±0.003)and caspase-3(0.620±0.024 vs.0.780±0.012)and the MMP3/TIMP2 ratio were decreased(all P<0.05), while protein expression of Bcl-2 was increased( P<0.05)in myocardial tissue. Conclusions:H 2S can mitigate myocardial fibrosis after myocardial infarction, through inhibiting the activation of the YAP1/TAZ signaling pathway, thus reducing apoptosis of cardiomyocytes.

Myocardial fibrosis is a key link in the occurrence and development of diabetic cardiomyopathy. Its etiology is complex, and the effect of drugs is not good.Cardiomyocyte apoptosis is an important cause of myocardial fibrosis. The purpose of this study was to investigate the effect of gaseous signal molecule sulfur dioxide (SO2 ) on diabetic myocardial fibrosis and its internal regulatory mechanism. Masson and TUNEL staining, Western-blot, transmission electron microscopy, RT-qPCR, immunofluorescence staining, and flow cytometry were used in the study, and the interstitial collagen deposition, autophagy, apoptosis, and changes in phosphatidylinositol 3-kinase (PI3K)/AKT pathways were evaluated from in vivo and in vitro experiments. The results showed that diabetic myocardial fibrosis was accompanied by cardiomyocyte apoptosis and down-regulation of endogenous SO2 -producing enzyme aspartate aminotransferase (AAT)1/2 . However, exogenous SO2 donors could up-regulate AAT1/2 , reduce apoptosis of cardiomyocytes induced by diabetic rats or high glucose, inhibit phosphorylation of PI3K/AKT protein, up-regulate autophagy, and reduce interstitial collagen deposition. In conclusion, the results of this study suggest that the gaseous signal molecule SO2 can inhibit the PI3K/AKT pathway to promote cytoprotective autophagy and inhibit cardiomyocyte apoptosis to improve myocardial fibrosis in diabetic rats. The results of this study are expected to provide new targets and intervention strategies for the prevention and treatment of diabetic cardiomyopathy.

Hypothyroidism alone can lead to myocardial fibrosis and result in heart failure, but traditional hormone replacement therapy does not improve the fibrotic situation. Hydrogen sulfide (H 2 S), a new gas signaling molecule, possesses antiinflammatory, antioxidant, and anti-fibrotic capabilities. Whether H 2 S could improve hypothyroidism-induced myocardial fibrosis are not yet studied. In our study, H 2 S could decrease collagen deposition in the myocardial tissue of rats caused by hypothyroidism. Furthermore, in hypothyroidism-induced rats, we found that H 2 S could enhance cystathionine-gamma-lyase (CSE), not cystathionine β-synthase (CBS), protein expressions. Finally, we noticed that H 2 S could elevate autophagy levels and inhibit the transforming growth factor-β1 (TGF-β1) signal transduction pathway. In conclusion, our experiments not only suggest that H 2 S could alleviate hypothyroidism-induced myocardial fibrosis by activating autophagy and suppressing TGF-β1/ SMAD family member 2 (Smad 2) signal transduction pathway, but also show that it can be used as a complementary treatment to conventional hormone therapy.

Sulfur dioxide (SO2), a novel endogenous gas signaling molecule, is involved in the regulation of cardiac function. Exerting a key role in progression of hyperthyroidism-induced cardiomyopathy (HTC), myocardial fibrosis is mainly caused by myocardial apoptosis, leading to poor treatment outcomes and prognoses. This study aimed to investigate the effect of SO2 on the hyperthyroidism-induced myocardial fibrosis and the underlying regulatory mechanisms. Elisa, Masson staining, Western-Blot, transmission electron microscope, and immunofluorescence were employed to evaluate the myocardial interstitial collagen deposition, endoplasmic reticulum stress (ERS), apoptosis, changes in endogenous SO2 , and Hippo pathways from in vitro and in vivo experiments. The study results indicated that the hyperthyroidism-induced myocardial fibrosis was accompanied by decreased cardiac function, and down-regulated ERS, apoptosis, and endogenous SO2 -producing enzyme aspartate aminotransferase (AAT)1/2 in cardiac myocytes. In contrast, exogenous SO2 donors improved cardiac function, reduced myocardial interstitial collagen deposition, up-regulated AAT1/2, antagonized ERS and apoptosis, and inhibited excessive activation of Hippo pathway in hyperthyroid rats. In conclusion, the results herein suggested that SO2 inhibited the overactivation of the Hippo pathway, antagonized ERS and apoptosis, and alleviated myocardial fibrosis in hyperthyroid rats. Therefore, this study was expected to identify intervention targets and new strategies for prevention and treatment of HTC.