Hydrogen sulfide improves endothelial barrier function by modulating the ubiquitination degradation of KLF4 through TRAF7 S-sulfhydration in diabetic aorta.

Anomalous vascular endothelium significantly contributes to various cardiovascular diseases. VE-cadherin plays a vital role in governing the endothelial barrier. Krüppel-like factor 4(KLF4), as a transcription factor, which binds the VE-cadherin promoter and enhances its transcription. Tumor necrosis factor receptor-associated factor 7 (TRAF7) is an E3 ubiquitin ligase that has been shown to modulate the degradation of KLF4. H2S can covalently modify cysteine residues on proteins through S-sulfhydration, thereby influencing the structure and functionality of the target protein. However, the role of S-sulfhydration on endothelial barrier integrity remains to be comprehensively elucidated. This study aims to investigate whether protein S-sulfhydration in the endothelium regulates endothelial integrity and its underlying mechanism. In this study, we observed that protein S-sulfhydration was reduced in the endothelium during diabetes and TRAF7 was the main target. Overexpression of TRAF7-Cys327 mutant could mitigate the endothelial barrier damage by weakening TRAF7 interaction with KLF4 and reducing ubiquitination degradation of KLF4. In conclusion, our research demonstrates that H2S plays a pivotal role in regulating S-sulfhydration of TRAF7 at Cys327. This regulation effectively inhibits the ubiquitin-mediated degradation of KLF4, resulting in an upregulation of VE-cadherin levels. This molecular mechanism contributes to the prevention of endothelial barrier damage.

Aptamer-bivalent-cholesterol-mediated proximity entropy-driven exosomal protein reporter for tumor diagnosis.

Exosomal proteins from the parental cells are considered to be promising biomarker sets for precise tumor diagnostics and monitoring. However, the accurate quantitative analysis of low-abundance exosomal proteins remains challenging due to the heterogeneity of clinical samples. Here, we standardized the exosomal concentration with a fluorogenic membrane probe and developed an aptamer-bivalent-cholesterol-mediated Proximity Entropy-driven Exosomal Protein Reporter (PEEPR). The proposed PEEPR enables the in-situ analysis of multiple exosomal proteins by integrating bivalent cholesterol anchor (exosomal lipid bilayer) and aptamer (exosomal proteins) with a proximity entropy-driven circuit. Based on this strategy, we successfully achieved detection limits of 3.9 pg/mL exosomal GPC-3 and 3.4 pg/mL exosomal PD-L1. Notably, the standardization of exosome concentrations is designed to avoid errors due to biological heterogeneity. The results showed that evaluating the levels of exosomal GPC-3 and PD-L1 in clinical samples via this strategy could accurately differentiate healthy individuals, hepatitis B patients, and hepatocellular carcinoma patients. In summary, PEEPR is a promising clinical diagnostic strategy for the quantitative analysis of a variety of tumor-associated exosomal proteins for the precise diagnosis and personalized treatment monitoring of tumors.

Exogenous H2 S promotes ubiquitin-mediated degradation of SREBP1 to alleviate diabetic cardiomyopathy via SYVN1 S-sulfhydration.

BACKGROUND: Diabetic cardiomyopathy, a distinctive complication of diabetes mellitus, has been correlated with the presence of intracellular lipid deposits. However, the intricate molecular mechanisms governing the aberrant accumulation of lipid droplets within cardiomyocytes remain to be comprehensively elucidated. METHODS: Both obese diabetic (db/db) mice and HL-1 cells treated with 200 µmol/L palmitate and 200 µmol/L oleate were used to simulate type 2 diabetes conditions. Transmission electron microscopy is employed to assess the size and quantity of lipid droplets in the mouse hearts. Transcriptomics analysis was utilized to interrogate mRNA levels. Lipidomics and ubiquitinomics were employed to explore the lipid composition alterations and proteins participating in ubiquitin-mediated degradation in mice. Clinical data were collected from patients with diabetes-associated cardiomyopathy and healthy controls. Western blot analysis was conducted to assess the levels of proteins linked to lipid metabolism, and the biotin-switch assay was employed to quantify protein cysteine S-sulfhydration levels. RESULTS: The administration of H2 S donor, NaHS, effectively restored hydrogen sulfide levels in both the cardiac tissue and plasma of db/db mice (+7%, P < 0.001; +5%, P < 0.001). Both db/db mice (+210%, P < 0.001) and diabetic patients (+83%, P = 0.22, n = 5) exhibit elevated plasma triglyceride levels. Treatment with GYY4137 effectively lowers triglyceride levels in db/db mice (-43%, P = 0.007). The expression of cystathionine gamma-lyase and HMG-CoA reductase degradation protein 1 (SYVN1) was decreased in db/db mice compared with the wild-type mice (cystathionine gamma-lyase: -31%, P = 0.0240; SYVN1: -35%, P = 0.01), and NaHS-treated mice (SYVN1: -31%, P = 0.03). Conversely, the expression of sterol regulatory element-binding protein 1 (SREBP1) was elevated (+91%, P = 0.007; +51%, P = 0.03 compared with control and NaHS-treated mice, respectively), along with diacylglycerol O-acyltransferase 1 (DGAT1) (+95%, P = 0.001; +35%, P = 0.02) and 1-acylglycerol-3-phosphate O-acyltransferase 3 (AGPAT3) (+88%, P = 0.01; +22%, P = 0.32). Exogenous H2 S led to a reduction in lipid droplet formation (-48%, P < 0.001), restoration of SYVN1 expression, modification of SYVN1's S-sulfhydration status and enhancement of SREBP1 ubiquitination. Overexpression of SYVN1 mutated at Cys115 decreased SREBP1 ubiquitination and increased the number of lipid droplets. CONCLUSIONS: Exogenous H2 S enhances ubiquitin-proteasome degradation of SREBP1 and reduces its nuclear translocation by modulating SYVN1's cysteine S-sulfhydration. This pathway limits lipid droplet buildup in cardiac myocytes, ameliorating diabetic cardiomyopathy.

Exogenous H2S initiating Nrf2/GPx4/GSH pathway through promoting Syvn1-Keap1 interaction in diabetic hearts.

Excessive ROS accumulation contributes to cardiac injury in type 2 diabetes mellitus. Hydrogen sulfide (H2S) is a vital endogenous gasotransmitter to alleviate cardiac damage in diabetic cardiomyopathy (DCM). However, the underlying mechanisms remain unclear. In this study, we investigated the effects of NaHS administration in db/db mice via intraperitoneal injection for 20 weeks and the treatment of high glucose (HG), palmitate (PA) and NaHS in HL-1 cardiomyocytes for 48 h, respectively. H2S levels were decreased in hearts of db/db mice and HL-1 cardiomyocytes exposed to HG and PA, which were restored by NaHS. Exogenous H2S activated the nuclear factor erythroid 2-related factor 2 (Nrf2)/glutathione peroxidase 4 (GPx4)/glutathione (GSH) pathway, suppressed ferroptosis and mitigated mitochondrial apoptosis in db/db mice. However, these effects were abrogated after Nrf2 knockdown. NaHS treatment elevated the ubiquitination level of Kelch-like ECH-associated protein (Keap1) by preserving its E3 ligase synoviolin (Syvn1), resulting in Nrf2 nuclear translocation. H2S facilitated the sulfhydration of Syvn1-cys115 site, a post-translational modification. Transfecting Syvn1 C115A in cardiomyocytes exposed to HG and PA partially attenuated the effects of NaHS on Nrf2 and cell death. Our findings suggest that exogenous H2S regulates Nrf2/GPx4/GSH pathway by promoting the Syvn1-Keap1 interaction to reduce ferroptosis and mitochondrial apoptosis in DCM.

Hydrogen sulfide regulates SERCA2a SUMOylation by S-Sulfhydration of SENP1 to ameliorate cardiac systole-diastole function in diabetic cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus that eventually progresses to heart failure. The sarco(endo)plasmic reticulum calcium ATPase 2a (SERCA2a), an important calcium pump in cardiomyocytes, is closely related to myocardial systolic-diastolic function. In mammalian cells, hydrogen sulfide (H2S), as a second messenger, antioxidant, and sulfurizing agent, is involved in diverse biological processes. Despite the importance of H2S for protection against DCM, the mechanisms remain poorly understood. The aim of the present study was to determine whether H2S regulates intracellular calcium homeostasis by acting on SERCA2a to reduce cardiomyocyte apoptosis during DCM. Db/db mice were injected with NaHS for 18 weeks. Neonatal rat cardiomyocytes (NRCMs) were treated with high glucose, palmitate, oleate, and NaHS for 48 h. Compared to the NaHS-treated groups, in vivo and in vitro type 2 diabetic models both showed reduced intracellular H2S content, reduced cystathionine γ-lyase (CSE) expression, impaired cardiac function, decreased SERCA2a expression and decreased SERCA2a activity, reduced SUMOylation of SERCA2a, increased sentrin-specific protease 1 (SENP1) expression, and disruption of calcium homeostasis leading to activation of the mitochondrial apoptosis pathway. Compared to the NaHS-treated type 2 diabetes cellular model, overexpression of SENP1 C683A reduced the S-sulfhydration of SENP1, reduced the SUMOylation of SERCA2a, reduced the increased expression and activity of SERCA2a, and induced mitochondrial apoptosis in cardiomyocytes. These results suggested that exogenous H2S elevates SENP1 S-sulfhydration to increase SERCA2a SUMOylation, improve myocardial systolic-diastolic function, and decrease cardiomyocyte apoptosis in DCM.

Hydrogen Sulfide Regulates SERCA2a Ubiquitylation via Muscle RING Finger-1 S-Sulfhydration to Affect Cardiac Contractility in db/db Mice.

Hydrogen sulfide (H2S), as a gasotransmitter, is involved in various pathophysiological processes. Diabetic cardiomyopathy (DCM) is a major complication of diabetes mellitus (DM), which leads to structural and functional abnormalities of the myocardium and eventually causes heart failure (HF). Systolic and diastolic dysfunction are fundamental features of heart failure. SERCA2a, as a key enzyme for calcium transport in the endoplasmic reticulum (ER), affects the process of myocardial relaxation and contraction. H2S can protect the cardiac function against diabetic hearts, however, its mechanisms are unclear. This study found that exogenous H2S affects cellular calcium transport by regulating the H2S/MuRF1/SERCA2a/cardiac contractile pathway. Our results showed that, compared with the db/db mice, exogenous H2S restored the protein expression levels of CSE and SERCA2a, and the activity of SERCA2a, while reducing cytosolic calcium concentrations and MuRF1 expression. We demonstrated that MuRF1 could interact with SERCA2a via co-immunoprecipitation. Using LC-MS/MS protein ubiquitylation analysis, we identified 147 proteins with increased ubiquitination levels, including SERCA2a, in the cardiac tissues of the db/db mice compared with NaHS-treated db/db mice. Our studies further revealed that NaHS administration modified MuRF1 S-sulfhydration and enhanced the activity and expression of SERCA2a. Under hyperglycemia and hyperlipidemia, overexpression of the MuRF1-Cys44 mutant plasmid reduced the S-sulfhydration level of MuRF1 and decreased the ubiquitination level of SERCA2a and the intracellular Ca2+ concentration. These findings suggested that H2S modulates SERCA2a ubiquitination through MuRF1 S-sulfhydration of Cys44 to prevent decreased myocardial contractility due to increased cytosolic calcium.

Investigating the potential clinical significance of long non-coding RNA 00092 in patients with breast cancer.

Background: Aberrant promoter methylation and its resultant aberrant gene expression are important epigenetic mechanisms that promote the development of breast cancer (BC). However, the prognostic value of this type of methylation-driven gene in BC is unknown. Methods: To identify DNA methylation-driven long non-coding RNAs (lncRNAs), a comprehensive analysis of RNA-sequencing and DNA methylation data of 1,200 clinical samples was performed. Differentially expressed lncRNAs (DELs) and survival-related lncRNAs in BC were identified using the R package. The function of the lncRNA was evaluated using Kaplan-Meier and receiver operating characteristic (ROC) curve analyses. The expression of the key lncRNA in tissues and cells was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Biological functions of the key lncRNA were analyzed using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. The Connectivity Map (CMap) was used to search for small-molecule targeted drugs for the key lncRNA. The functions of the key lncRNA in BC progression were investigated using cell proliferation and cell cycle assays. Results: A total of 14 methylation-driven lncRNAs, 526 DELs, and 93 survival-associated lncRNAs were identified. The above data were intersected, and a unique lncRNA, LINC00092, was obtained. LINC00092 was hypermethylated and hypoexpressed in both BC tissues and cell lines. LINC00092 was found to be a diagnostic marker for BC, with its low expression being associated with poor prognosis (P=0.013). LINC00092 overexpression inhibited the proliferation and cell cycle of BC cells in vitro. Nimesulide and sulpiride were screened out as potential targeted therapeutic drugs for LINC00092 in BC, and sulpiride was observed to partially reverse the proliferative effect of (small interfer) si-LINC00092 on BC cells. Conclusions: LINC00092 is a methylation-driven lncRNA in BC and could be a potential therapeutic target for this disease.

Hydrogen sulphide reduced the accumulation of lipid droplets in cardiac tissues of db/db mice via Hrd1 S-sulfhydration.

Accumulation of lipid droplets (LDs) induces cardiac dysfunctions in type 2 diabetes patients. Recent studies have shown that hydrogen sulphide (H2 S) ameliorates cardiac functions in db/db mice, but its regulation on the formation of LDs in cardiac tissues is unclear. Db/db mice were injected with NaHS (40 µmol·kg-1 ) for twelve weeks. H9c2 cells were treated with high glucose (40 mmol/L), oleate (200 µmol/L), palmitate (200 µmol/L) and NaHS (100 µmol/L) for 48 hours. Plasmids for the overexpression of wild-type Hrd1 and Hrd1 mutated at Cys115 were constructed. The interaction between Hrd1 and DGAT1 and DGAT2, the ubiquitylation level of DGAT1 and 2, the S-sulfhydration of Hrd1 were measured. Exogenous H2 S ameliorated the cardiac functions, decreased ER stress and reduced the number of LDs in db/db mice. Exogenous H2 S could elevate the ubiquitination level of DGAT 1 and 2 and increased the expression of Hrd1 in cardiac tissues of db/db mice. The S-sulfhydration of Hrd1 by NaHS enhanced the interaction between Hrd1 and DGAT1 and 2 to inhibit the formation of LD. Our findings suggested that H2 S modified Hrd1 S-sulfhydration at Cys115 to reduce the accumulation of LDs in cardiac tissues of db/db mice.

Exogenous H2 S prevents the nuclear translocation of PDC-E1 and inhibits vascular smooth muscle cell proliferation in the diabetic state.

Hydrogen sulphide (H2 S) inhibits vascular smooth muscle cell (VSMC) proliferation induced by hyperglycaemia and hyperlipidaemia; however, the mechanisms are unclear. Here, we observed lower H2 S levels and higher expression of the proliferation-related proteins PCNA and cyclin D1 in db/db mouse aortae and vascular smooth muscle cells treated with 40 mmol/L glucose and 500 µmol/L palmitate, whereas exogenous H2 S decreased PCNA and cyclin D1 expression. The nuclear translocation of mitochondrial pyruvate dehydrogenase complex-E1 (PDC-E1) was significantly increased in VSMCs treated with high glucose and palmitate, and it increased the level of acetyl-CoA and histone acetylation (H3K9Ac). Exogenous H2 S inhibited PDC-E1 translocation from the mitochondria to the nucleus because PDC-E1 was modified by S-sulfhydration. In addition, PDC-E1 was mutated at Cys101. Overexpression of PDC-E1 mutated at Cys101 increased histone acetylation (H3K9Ac) and VSMC proliferation. Based on these findings, H2 S regulated PDC-E1 S-sulfhydration at Cys101 to prevent its translocation from the mitochondria to the nucleus and to inhibit VSMC proliferation under diabetic conditions.

5-FU@DHA-UIO-66-NH2 potentiates chemotherapy sensitivity of breast cancer cells through a microRNA let-7a-dependent mechanism.

BACKGROUND: Drug delivery systems with magnetization facilitate the accumulation of drug at the target site. This study aimed to explore the mechanism by which docosahexaenoic acid (DHA)-modified porous metal-organic framework (MOF) UIO-66-NH2 loads chemotherapeutic drug 5-fluorouracil (5-FU) and reduces the chemotherapy resistance of breast cancer (BC) cells. METHODS: UIO-66-NH2 was synthesized and DHA with carboxyl end was used to modify the surface of UIO-66-NH2. 5-FU was incorporated to UIO-66-NH2 or DHA-UIO-66-NH2 by a post-synthesis method. The loading and release of 5-FU by @DHA-UIO-66-NH2 was investigated with ultraviolet (UV) spectroscopy. RT-qPCR was conducted to detect the expression of let-7a in cells. The uptake of DHA-UIO-66-NH2 by MCF-7 BC cells was observed by confocal laser scanning microscope (CLSM). Cell counting kit-8 (CCK-8), flow cytometry, and live/dead cell staining were applied to investigate the effects of 5-FU@DHA-UIO-66-NH2 on BC cells, and a BC mouse model was established to explore its effects on tumorigenesis. HE staining and routine blood index analysis were applied for determination of the biological safety of 5-FU@DHA-UIO-66-NH2. RESULTS: 5-FU@DHA-UIO-66-NH2 was successfully constructed and characterized. The loading amount of DHA-UIO-NH2 for 5-FU reached 30.31%. DHA-UIO-66-NH2 was effectively taken up by MCF-7 cells. Further, 5-FU@DHA-UIO-66-NH2 exhibited stronger inhibitory effects on MCF-7 cell viability in vitro as well as tumorigenesis in vivo than 5-FU and 5-FU@UIO-66-NH2. DHA up-regulated let-7a to reduce the resistance of MCF-7 cells to 5-FU. Moreover, the biosafety of 5-FU@DHA-UIO-66-NH2 was identified. CONCLUSIONS: 5-FU@DHA-UIO-66-NH2 increased the level of let-7a in BC cells, repressed cell viability and augmented apoptosis, and thus reduced the chemotherapy resistance of BC cells.

Hydrogen sulphide ameliorating skeletal muscle atrophy in db/db mice via Muscle RING finger 1 S-sulfhydration.

Muscle atrophy occurs in many pathological states, including cancer, diabetes and sepsis, whose results primarily from accelerated protein degradation and activation of the ubiquitin-proteasome pathway. Expression of Muscle RING finger 1 (MuRF1), an E3 ubiquitin ligase, was increased to induce the loss of muscle mass in diabetic condition. However, hydrogen sulphide (H2 S) plays a crucial role in the variety of physiological functions, including antihypertension, antiproliferation and antioxidant. In this study, db/db mice and C2C12 myoblasts treated by high glucose and palmitate and oleate were chose as animal and cellular models. We explored how exogenous H2 S attenuated the degradation of skeletal muscle via the modification of MuRF1 S-sulfhydration in db/db mice. Our results show cystathionine-r-lyase expression, and H2 S level in skeletal muscle of db/db mice was reduced. Simultaneously, exogenous H2 S could alleviate ROS production and reverse expression of ER stress protein markers. Exogenous H2 S could decrease the ubiquitination level of MYOM1 and MYH4 in db/db mice. In addition, exogenous H2 S reduced the interaction between MuRF1 with MYOM1 and MYH4 via MuRF1 S-sulfhydration. Based on these results, we establish that H2 S prevented the degradation of skeletal muscle via MuRF1 S-sulfhydration at the site of Cys44 in db/db mice.

Exogenous H2S Promoted USP8 Sulfhydration to Regulate Mitophagy in the Hearts of db/db Mice.

Hydrogen sulfide (H2S), an important gasotransmitter, regulates cardiovascular functions. Mitochondrial damage induced by the overproduction of reactive oxygen species (ROS) results in myocardial injury with a diabetic state. The purpose of this study was to investigate the effects of exogenous H2S on mitophagy formation in diabetic cardiomyopathy. In this study, we found that exogenous H2S could improve cardiac functions, reduce mitochondrial fragments and ROS levels, enhance mitochondrial respiration chain activities and inhibit mitochondrial apoptosis in the hearts of db/db mice. Our results showed that exogenous H2S facilitated parkin translocation into mitochondria and promoted mitophagy formation in the hearts of db/db mice. Our studies further revealed that the ubiquitination level of cytosolic parkin was increased and the expression of USP8, a deubiquitinating enzyme, was decreased in db/db cardiac tissues. S-sulfhydration is a novel posttranslational modification of specific cysteine residues on target proteins by H2S. Our results showed that the S-sulfhydration level of USP8 was obviously decreased in vivo and in vitro under hyperglycemia and hyperlipidemia, however, exogenous H2S could reverse this effect and promote USP8/parkin interaction. Dithiothreitol, a reducing agent that reverses sulfhydration-mediated covalent modification, increased the ubiquitylation level of parkin, abolished the effects of exogenous H2S on USP8 deubiquitylation and suppressed the interaction of USP8 with parkin in neonatal rat cardiomyocytes treated with high glucose, oleate and palmitate. Our findings suggested that H2S promoted mitophagy formation by increasing S-sulfhydration of USP8, which enhanced deubiquitination of parkin through the recruitment of parkin in mitochondria.

Exogenous H2S Induces Hrd1 S-sulfhydration and Prevents CD36 Translocation via VAMP3 Ubiquitylation in Diabetic Hearts.

Hydrogen sulfide (H2S) plays physiological roles in vascular tone regulation, cytoprotection, and ATP synthesis. HMG-CoA reductase degradation protein (Hrd1), an E3 ubiquitin ligase, is involved in protein trafficking. H2S may play a role in controlling fatty acid uptake in diabetic cardiomyopathy (DCM) in a manner correlated with modulation of Hrd1 S-sulfhydration; however, this role remains to be elucidated. The aim of the present study was to examine whether H2S can attenuate lipid accumulation and to explain the possible mechanisms involved in the regulation of the H2S-Hrd1/VAMP3 pathway. Db/db mice and neonatal rat cardiomyocytes treated with high glucose, palmitate and oleate were used as animal and cellular models of type 2 diabetes, respectively. The expression of cystathionine-γ-lyase (CSE), Hrd1, CD36 and VAMP3 was detected by Western blot analysis. In addition, Hrd1 was mutated at Cys115, and Hrd1 S-sulfhydration was examined using an S-sulfhydration assay. VAMP3 ubiquitylation was investigated by immunoprecipitation. Lipid droplet formation was tested by TEM, BODIPY 493/503 staining and oil red O staining. The expression of CSE and Hrd1 was decreased in db/db mice compared to control mice, whereas CD36 and VAMP3 expression was increased. NaHS administration reduced droplet formation, and exogenous H2S restored Hrd1 expression, modified S-sulfhydration, and decreased VAMP3 expression in the plasma membrane. Using LC-MS/MS analysis, we identified 85 proteins with decreased ubiquitylation, including 3 vesicle-associated membrane proteins, in the cardiac tissues of model db/db mice compared with NaHS-treated db/db mice. Overexpression of Hrd1 mutated at Cys115 diminished VAMP3 ubiquitylation, whereas it increased CD36 and VAMP3 expression and droplet formation. siRNA-mediated Hrd1 deletion increased the expression of CD36 in the cell membrane. These findings suggested that H2S regulates VAMP3 ubiquitylation via Hrd1 S-sulfhydration at Cys115 to prevent CD36 translocation in diabetes.

Hydrogen sulfide regulates muscle RING finger-1 protein S-sulfhydration at Cys44 to prevent cardiac structural damage in diabetic cardiomyopathy.

BACKGROUND AND PURPOSE: Hydrogen sulfide (H2 S) plays important roles as a gasotransmitter in pathologies. Increased expression of the E3 ubiquitin ligase, muscle RING finger-1 (MuRF1), may be involved in diabetic cardiomyopathy. Here we have investigated whether and how exogenous H2 S alleviates cardiac muscle degradation through modifications of MuRF1 S-sulfhydration in db/db mice. EXPERIMENTAL APPROACH: Neonatal rat cardiomyocytes were treated with high glucose (40 mM), oleate (100 µM), palmitate (400 µM), and NaHS (100 µM) for 72 hr. MuRF1 was silenced with siRNA technology and mutation at Cys44 . Endoplasmic reticulum stress markers, MuRF1 expression, and ubiquitination level were measured. db/db mice were injected with NaHS (39 µmol·kg-1 ) for 20 weeks. Echocardiography, cardiac ultrastructure, cystathionine-γ-lyase, cardiac structure proteins expression, and S-sulfhydration production were measured. KEY RESULTS: H2 S levels and cystathionine-γ-lyase protein expression in myocardium were decreased in db/db mice. Exogenous H2 S reversed endoplasmic reticulum stress, including impairment of the function of cardiomyocytes and structural damage in db/db mice. Exogenous H2 S could suppress the levels of myosin heavy chain 6 and myosin light chain 2 ubiquitination in cardiac tissues of db/db mice, and MuRF1 was modified by S-sulfhydration, following treatment with exogenous H2 S, to reduce the interaction between MuRF1 and myosin heavy chain 6 and myosin light chain 2. CONCLUSIONS AND IMPLICATIONS: Our findings suggest that H2 S regulates MuRF1 S-sulfhydration at Cys44 to prevent myocardial degradation in the cardiac tissues of db/db mice. LINKED ARTICLES: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

CaSR activates PKCδ to induce cardiomyocyte apoptosis via ER stress­associated apoptotic pathways during ischemia/reperfusion.

Endoplasmic reticulum (ER) stress can be activated by ischemia/reperfusion (I/R) injury in cardiomyocytes. Persistent ER stress, with an increase in intracellular Ca2+ ([Ca2+]i) concentration, leads to apoptosis. Protein kinase C (PKC) has a key role in myocardial damage by elevation of [Ca2+]i. The calcium­sensing receptor (CaSR), a G protein­coupled receptor, can increase the release of [Ca2+]i from the ER through the inositol triphosphate receptor (IP3R). Intracellular calcium overload has been demonstrated to cause cardiac myocyte apoptosis during I/R. However, the associations between PKC, CaSR and ER stress are not clear. The present study examined the hypothesis that activation of PKCδ by CaSR participates in ER stress­associated apoptotic pathways within myocardial I/R. Rat hearts were subjected to 30 min of ischemia in vivo, followed by reperfusion for 120 min. GdCl3 (a CaSR activator) was used to elevate the intracellular Ca2+ concentration, but the Ca2+ concentration in the ER was significantly decreased during I/R. Following exposure to GdCl3, expression levels of CaSR, glucose­regulated protein 78 (GRP78), Caspase­12, phosphorylated JNK and Caspase­3 were increased, and the ratios of apoptotic myocardial cells were significantly increased. By contrast, following exposure to rottlerin, a PKCδ inhibitor, the expression levels of these proteins and the ratio of apoptotic myocardial cells were significantly reduced. The present study also demonstrated that PKCδ translocated into the ER to induce an ER stress response and participate in the ER stress­related apoptosis pathway. These results confirmed that CaSR activated PKCδ to induce cardiomyocyte apoptosis through ER stress­associated apoptotic pathways during I/R in vivo.

Exogenous H2S reduces the acetylation levels of mitochondrial respiratory enzymes via regulating the NAD+-SIRT3 pathway in cardiac tissues of db/db mice.

Hydrogen sulfide (H2S), a gaseous molecule, is involved in modulating multiple physiological functions, such as antioxidant, antihypertension, and the production of polysulfide cysteine. H2S may inhibit reactive oxygen species generation and ATP production through modulating respiratory chain enzyme activities; however, the mechanism of this effect remains unclear. In this study, db/db mice, neonatal rat cardiomyocytes, and H9c2 cells treated with high glucose, oleate, and palmitate were used as animal and cellular models of type 2 diabetes. The mitochondrial respiratory rate, respiratory chain complex activities, and ATP production were decreased in db/db mice compared with those in db/db mice treated with exogenous H2S. Liquid chromatography with tandem mass spectrometry analysis showed that the acetylation level of proteins involved in the mitochondrial respiratory chain were increased in the db/db mice hearts compared with those with sodium hydrosulfide (NaHS) treatment. Exogenous H2S restored the ratio of NAD+/NADH, enhanced the expression and activity of sirtuin 3 (SIRT3) and decreased mitochondrial acetylation level in cardiomyocytes under hyperglycemia and hyperlipidemia. As a result of SIRT3 activation, acetylation of the respiratory complexe enzymes NADH dehydrogenase 1 (ND1), ubiquinol cytochrome c reductase core protein 1, and ATP synthase mitochondrial F1 complex assembly factor 1 was reduced, which enhanced the activities of the mitochondrial respiratory chain activity and ATP production. We conclude that exogenous H2S plays a critical role in improving cardiac mitochondrial function in diabetes by upregulating SIRT3.

Exogenous H2S switches cardiac energy substrate metabolism by regulating SIRT3 expression in db/db mice.

Hydrogen sulfide (H2S) is involved in diverse physiological functions, such as anti-hypertension, anti-proliferation, regulating ATP synthesis, and reactive oxygen species production. Sirtuin 3 (SIRT3) is a NAD + -dependent deacetylase that regulates mitochondrial energy metabolism. The role of H2S in energy metabolism in diabetic cardiomyopathy (DCM) may be related to regulate SIRT3 expression; however, this role remains to be elucidated. We hypothesized that exogenous H2S could switch cardiac energy metabolic substrate preference by lysine acetylation through promoting the expression of SIRT3 in cardiac tissue of db/db mice. Db/db mice, neonatal rat cardiomyocytes, and H9c2 cell line with the treatment of high glucose, oleate, and palmitate were used as animal and cellular models of type 2 diabetes. Using LC-MS/MS, we identified 76 proteins that increased acetylation, including 8 enzymes related to fatty acid ß-oxidation and 7 enzymes of the tricarboxylic acid (TCA) cycle in the db/db mice hearts compared to those with the treatment of NaHS. Exogenous H2S restored the expression of NAMPT and the ratio of NAD+/NADH enhanced the expression and activity of SIRT3. As a result of activation of SIRT3, the acetylation level and activity of fatty acid ß-oxidation enzyme LCAD and the acetylation of glucose oxidation enzymes PDH, IDH2, and CS were reduced which resulted in activation of PDH, IDH2, and CS. Our finding suggested that H2S induced a switch in cardiac energy substrate utilization from fatty acid ß-oxidation to glucose oxidation in DCM through regulating SIRT3 pathway. KEY MESSAGES: H2S regulated the acetylation level and activities of enzymes in fatty acid oxidation and glucose oxidation in cardiac tissues of db/db mice. Exogenous H2S decreased mitochondrial acetylation level through upregulating the expression and activity of SIRT3 in vivo and in vitro. H2S induced a switch in cardiac energy substrate utilization from fatty acid oxidation to glucose.

Exogenous H2S Protects Against Diabetic Cardiomyopathy by Activating Autophagy via the AMPK/mTOR Pathway.

BACKGROUND/AIM: Autophagy plays an important role in cellular homeostasis through the disposal and recycling of cellular components. Hydrogen sulphide (H2S) is the third endogenous gas that has been shown to confer cardiac protective effects. Given the regulation of autophagy in cardioprotection, this study aimed to investigate the protective effects of H2S via autophagy during high glucose treatment. METHODS: This study investigated the content of H2S in the plasma as well as myocardial, ultrastructural changes in mitochondria and autophagosomes. This study also investigated the apoptotic rate using Hoechst/PI as well as expression of autophagy-associated proteins and mitochondrial apoptotic proteins in H9C2 cells treated with or without GYY4137. Mitochondria of cardiac tissues were isolated and RCR and ADP/O were also detected. AMPK knockdown was performed with siRNA transfection. RESULTS: In a STZ-induced diabetic model, NaHS treatment not only increased the expression of p-AMPK in diabetic group but further activated cell autophagy. Following 48h high glucose, autophagosomes and cell viability were reduced. The present results showed that autophagy could be induced by H2S, which was verified by autophagic ultrastructural observation and LC3-I/LC3-II conversion. In addition, the mitochondrial membrane potential (MMP) was significantly decreased. The expressions levels of autophagic-related proteins were significantly elevated. Moreover, H2S activated the AMPK/rapamycin (mTOR) signalling pathway. CONCLUSIONS: Our findings demonstrated that H2S decreases oxidative stress and protects against mitochondria injury, activates autophagy, and eventually leads to cardiac protection via the AMPK/mTOR pathway.

Exogenous H2S facilitating ubiquitin aggregates clearance via autophagy attenuates type 2 diabetes-induced cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes. Hydrogen sulphide (H2S), a newly found gaseous signalling molecule, has an important role in many regulatory functions. The purpose of this study is to investigate the effects of exogenous H2S on autophagy and its possible mechanism in DCM induced by type II diabetes (T2DCM). In this study, we found that sodium hydrosulphide (NaHS) attenuated the augment in left ventricular (LV) mass and increased LV volume, decreased reactive oxygen species (ROS) production and ameliorated H2S production in the hearts of db/db mice. NaHS facilitated autophagosome content degradation, reduced the expression of P62 (a known substrate of autophagy) and increased the expression of microtubule-associated protein 1 light chain 3 II. It also increased the expression of autophagy-related protein 7 (ATG7) and Beclin1 in db/db mouse hearts. NaHS increased the expression of Kelch-like ECH-associated protein 1 (Keap-1) and reduced the ubiquitylation level in the hearts of db/db mice. 1,4-Dithiothreitol, an inhibitor of disulphide bonds, increased the ubiquitylation level of Keap-1, suppressed the expression of Keap-1 and abolished the effects of NaHS on ubiquitin aggregate clearance and ROS production in H9C2 cells treated with high glucose and palmitate. Overall, we concluded that exogenous H2S promoted ubiquitin aggregate clearance via autophagy, which might exert its antioxidative effect in db/db mouse myocardia. Moreover, exogenous H2S increased Keap-1 expression by suppressing its ubiquitylation, which might have an important role in ubiquitin aggregate clearance via autophagy. Our findings provide new insight into the mechanisms responsible for the antioxidative effects of H2S in the context of T2DCM.

Hydrogen Sulphide modulating mitochondrial morphology to promote mitophagy in endothelial cells under high-glucose and high-palmitate.

Endothelial cell dysfunction is one of the main reasons for type II diabetes vascular complications. Hydrogen sulphide (H2 S) has antioxidative effect, but its regulation on mitochondrial dynamics and mitophagy in aortic endothelial cells under hyperglycaemia and hyperlipidaemia is unclear. Rat aortic endothelial cells (RAECs) were treated with 40 mM glucose and 200 µM palmitate to imitate endothelium under hyperglycaemia and hyperlipidaemia, and 100 µM NaHS was used as an exogenous H2 S donor. Firstly, we demonstrated that high glucose and palmitate decreased H2 S production and CSE expression in RAECs. Then, the antioxidative effect of H2 S was proved in RAECs under high glucose and palmitate to reduce mitochondrial ROS level. We also showed that exogenous H2 S inhibited mitochondrial apoptosis in RAECs under high glucose and palmitate. Using Mito Tracker and transmission electron microscopy assay, we revealed that exogenous H2 S decreased mitochondrial fragments and significantly reduced the expression of p-Drp-1/Drp-1 and Fis1 compared to high-glucose and high-palmitate group, whereas it increased mitophagy by transmission electron microscopy assay. We demonstrated that exogenous H2 S facilitated Parkin recruited by PINK1 by immunoprecipitation and immunostaining assays and then ubiquitylated mitofusin 2 (Mfn2), which illuminated the mechanism of exogenous H2 S on mitophagy. Parkin siRNA suppressed the expression of Mfn2, Nix and LC3B, which revealed that it eliminated mitophagy. In summary, exogenous H2 S could protect RAECs against apoptosis under high glucose and palmitate by suppressing oxidative stress, decreasing mitochondrial fragments and promoting mitophagy. Based on these results, we proposed a new mechanism of H2 S on protecting endothelium, which might provide a new strategy for type II diabetes vascular complication.