Cystathionine gamma-lyase deficiency exaggerates diethylnitrosamine-induced liver damage in mice.

Cystathionine gamma-lyase (CSE) is a key enzyme in reverse transsulfuration pathway and contributes to the majority of H2S generation in liver tissues via cysteine metabolism. Dysfunction of the CSE/H2S system is linked to both chronic and acute liver damage. This study investigated the regulatory role of CSE deficiency on diethylnitrosamine (DEN)-induced liver damage in mice. A single injection of DEN was administered into 4-week-old male CSE knockout (CSE-KO) mice and wild-type (WT) littermates, and the mice were sacrificed at 28 weeks of age. Compared to age-matched WT mice, CSE-KO mice spontaneously developed steatosis with increased oxidative stress and higher expressions of inflammation and fibrosis-related genes at 28-weeks of age. Following DEN injection, CSE-KO mice experienced more severe liver damage in comparison with the WT group as reflected by elevated levels of lipid accumulation, increased activities of alanine aminotransferase and aspartate aminotransferase, higher oxidative stress and fibrosis development, and increased expressions of inflammation and fibrosis-related genes. No visible tumors were observed in both types of mice with DEN treatment. In addition, the expression levels of the three H2S-generating proteins (CSE, cystathionine beta-synthase, and 3-mercaptopyruvate sulfurtransferase) and the H2S production rate in liver tissues were unaffected by DEN. Taken together, our study demonstrates that CSE provides a significant hepatoprotective effect and deficiency of CSE exaggerates DEN-induced liver damage in mice. Based on these findings, it can be suggested that targeting the CSE/H2S signaling pathway could be a potential therapeutic target for the treatment of liver diseases.

H2S Protects from Rotenone-Induced Ferroptosis by Stabilizing Fe-S Clusters in Rat Cardiac Cells.

Hydrogen sulfide (H2S) has been recently recognized as an important gasotransmitter with cardioprotections, and iron is vital for various cellular activities. This study explored the regulatory role of H2S on iron metabolism and mitochondrial functions in cultured rat cardiac cells. Rotenone, a mitochondrial complex I inhibitor, was used for establishing an in vitro model of ischemic cell damage. It was first found that rotenone induced oxidative stress and lipid peroxidation and decreased mitochondrial membrane potential and ATP generation, eventually causing cell death. The supplement of H2S at a physiologically relevant concentration protected from rotenone-induced ferroptotic cell death by reducing oxidative stress and mitochondrial damage, maintaining GPx4 expression and intracellular iron level. Deferiprone, an iron chelator, would also protect from rotenone-induced ferroptosis. Further studies demonstrated that H2S inhibited ABCB8-mediated iron efflux from mitochondria to cytosol and promoted NFS1-mediated Fe-S cluster biogenesis. It is also found that rotenone stimulated iron-dependent H2S generation. These results indicate that H2S would protect cardiac cells from ischemic damage through preserving mitochondrial functions and intracellular Fe-S cluster homeostasis.

The Antioxidant Properties of Glucosinolates in Cardiac Cells Are Independent of H2S Signaling.

The organic sulfur-containing compounds glucosinolates (GSLs) and the novel gasotransmitter H2S are known to have cardioprotective effects. This study investigated the antioxidant effects and H2S-releasing potential of three GSLs ((3E)-4-(methylsulfanyl)but-3-enyl GSL or glucoraphasatin, 4-hydroxybenzyl GSL or glucosinalbin, and (RS)-6-(methylsulfinyl)hexyl GSL or glucohesperin) in rat cardiac cells. It was found that all three GSLs had no effect on cardiac cell viability but were able to protect against H2O2-induced oxidative stress and cell death. NaHS, a H2S donor, also protected the cells from H2O2-stimulated oxidative stress and cell death. The GSLs alone or mixed with cysteine, N-acetylcysteine, glutathione, H2O2, iron and pyridoxal-5'-phosphate, or mouse liver lysates did not induce H2S release. The addition of GSLs also did not alter endogenous H2S levels in cardiac cells. H2O2 significantly induced cysteine oxidation in the cystathionine gamma-lyase (CSE) protein and inhibited the H2S production rate. In conclusion, this study found that the three tested GSLs protect cardiomyocytes from oxidative stress and cell death but independently of H2S signaling.

Preparation of acid-driven magnetically imprinted micromotors and selective loading of phycocyanin.

Phycocyanin, a macromolecular protein known for its robust fluorescence, proves to be highly suitable for verifying the successful deposition of imprinted layers. In this study, an acid-propelled magnetic micromotor was successfully fabricated by utilizing surface imprinting and self-propelled nanomotor technology to achieve selective loading and capture of targets such as phycocyanin for future applications in environmental monitoring and precision drug delivery in vivo. This micromotor features a distinct recognition layer achieved through a template electrodeposition method. The outermost imprint layer of the micromotor was meticulously crafted using poly(3,4-ethylenedioxythiophene)/poly(sodium-4-styrenesulfonate) in the presence of a template, while the Pt layer serves as the supportive foundation, the Ni layer acts as the magnetic guidance component, and the innermost layer consists of metal Zn. In acidic environments, the Zn reacts to generate bubbles, which propels the micromotor's motion. The micromotor was comprehensively characterized using techniques such as scanning electron microscopy. Findings highlight the exceptional self-propulsion of the Zn-based micromotor, which is a fusion of molecular imprinting and micromotor technologies. This innovative design achieves an impressive maximum velocity of approximately 100 µm s-1, as well as commendable magnetic steering performance. Furthermore, the micromotor demonstrates the ability to imprint target protein through the imprint layer, enabling selective recognition and capture for transport of specific phycocyanin. In vitro cytotoxicity tests have also demonstrated that the micromotors are non-toxic to cells. This breakthrough concept offers a novel avenue for realizing targeted capture and transport of specific nutrients within the human gastric environment.

Targeting selective E3 ligase for healing cardiac fibrosis.

Protein quality control is often disrupted in heart diseases. In this issue of Cell Chemical Biology, Yang et al.1 describe the selective E3 ligase SPOP as a pro-fibrotic factor for inducing cardiac fibrosis through RACK1 degradation-mediated Smad3 activation.

H2S regulation of iron homeostasis by IRP1 improves vascular smooth muscle cell functions.

Either H2S or iron is essential for cellular processes. Abnormal metabolism of H2S and iron has increased risk for cardiovascular diseases. The aim of the present study is to examine the mutual interplay of iron and H2S signals in regulation of vascular smooth muscle cell (SMC) functions. Here we found that deficiency of cystathionine gamma-lyase (CSE, a major H2S-producing enzyme in vascular system) induced but NaHS (a H2S donor) administration attenuated iron accumulation in aortic tissues from angiotensin II-infused mice. In vitro, iron overload induced labile iron levels, promoted cell proliferation, disrupted F-actin filaments, and inhibited protein expressions of SMC-specific markers (αSMA and calponin) more significantly in SMCs from CSE knockout mice (KO-SMCs) than the cells from wild-type mice (WT-SMCs), which could be reversed by exogenously applied NaHS. In contrast, KO-SMCs were more vulnerable to iron starvation-induced cell death. Either iron overload or NaHS did not affect elastin level and gelatinolytic activity. We further found that H2S induced more aconitase activity of iron regulatory protein 1 (IRP1) but inhibited its RNA binding activity accompanied with increased protein levels of ferritin and ferriportin, which would contribute to the lower level of labile iron level inside the cells. In addition, iron was able to suppress CSE-derived H2S generation, while iron also non-enzymatically induced H2S release from cysteine. This study reveals the mutual interaction between iron and H2S signals in regulating SMC phenotypes and functions; CSE/H2S system would be a target for preventing iron metabolic disorder-related vascular diseases.

Deficiency of cystathionine gamma-lyase promotes aortic elastolysis and medial degeneration in aged mice.

Enzymatic degradation of elastin by matrix metalloproteinases (MMPs) leads to the permanent dilation of aortic wall and constitutes the most prominent characters of aortic aneurysm and aging-related medial degeneration. Hydrogen sulfide (H2S) as a gasotransmitter exhibits a wide variety of cardio-protective functions through its anti-inflammatory and anti-oxidative actions. Cystathionine gamma-lyase (CSE) is a main H2S-generating enzyme in cardiovascular system. The regulatory roles of CSE/H2S system on elastin homeostasis and blood vessel degeneration have not yet been explored. Here we found that aged CSE knockout mice had severe aortic dilation and elastic degradation in abdominal aorta and were more sensitive to angiotensin II-induced aortic elastolysis and medial degeneration. Administration of NaHS would protect the mice from angiotensin II-induced inflammation, gelatinolytic activity, elastin fragmentation, and aortic dilation. In addition, human aortic aneurysm samples had higher inflammatory infiltration and lower expression of CSE. In cultured smooth muscle cells (SMCs), TNFα-induced MMP2/9 hyperactivity and elastolysis could be attenuated by exogenously applied NaHS or CSE overexpression while further deteriorated by complete knockout of CSE. It was further found that H2S inhibited MMP2 transcription by posttranslational modification of Sp1 via S-sulfhydration. H2S also directly suppressed MMP hyperactivity by S-sulfhydrating the cysteine switch motif. Taken together, this study revealed the involvement of CSE/H2S system in the pathogenesis of aortic elastolysis and medial degeneration by maintaining the inactive form of MMPs, suggesting that CSE/H2S system can be a target for the prevention of age-related medial degeneration and treatment of aortic aneurysm.

Hydrogen sulfide and metal interaction: the pathophysiological implications.

Hydrogen sulfide (H2S), previously recognized as a toxic gas, has emerged as an important gaseous signaling molecule along with nitric oxide, carbon monoxide and also hydrogen. H2S can be endogenously produced in the mammalian body at a very low level for various pathophysiological processes. Notably, H2S can interact with several essential metals in the body such as iron, copper, nickel, and zinc to carry out specific functions. The interactions of H2S with metal-binding proteins have been shown to aid in its signal transduction and cellular metabolism. In addition, H2S is capable of providing a cytoprotective role against metal toxicity. As the research in the field of H2S signaling in biology and medicine increases, much progresses have been developed for detecting H2S via interaction with metals. In this review, the interaction of H2S with metals, specifically in regard to metal-driven metabolism of H2S, the protection against metal toxicity by H2S and the detection of H2S using metals will be discussed. Discovering the interactions of this gasotransmitter with metals is important for determining the mechanisms underlying the cellular functions of H2S as well as developing novel therapeutic avenues.

H2S protects from oxidative stress-driven ACE2 expression and cardiac aging.

Cystathionine gamma-lyase (CSE)-derived hydrogen sulfide (H2S) plays an essential role in preserving cardiac functions. Angiotensin-converting enzyme 2 (ACE2) acts as the negative regulator of the renin-angiotensin system, exerting anti-oxidative stress and anti-inflammatory properties within the body. The interplays of CSE/H2S signaling and ACE2 in cardiac aging are unclear. In this study, the regulatory roles of H2S on ACE2 expression in mouse heart tissue and rat cardiomyocytes under different stress conditions were investigated. It was found that ACE2 protein level was lower in heart tissues from old mice (56-week-old) than young mice (8-week-old), and the knockout of CSE (CSE KO) induced moderate oxidative stress and further inhibited ACE2 protein level in mouse hearts at both young and old age. Incubation of rat cardiac cells (H9C2) with a low dose of H2O2 (50 µM) suppressed ACE2 protein level and induced cellular senescence, which was completely reversed by co-incubation with 30 µM NaHS (a H2S donor). Prolonged nutrient excess is an increased risk of heart disorders by causing metabolic dysfunction and cardiac remodeling. We further found high-fat diet feeding stimulated ACE2 expression and induced severe oxidative stress in CSE KO heart in comparison with wild-type heart. Lipid overload in H9C2 cells to mimic a status of nutrient excess also enhanced the expression of ACE2 protein and induced severe oxidative stress and cell senescence, which were significantly attenuated by the supplementation of exogenous H2S. Furthermore, the manipulation of ACE2 expression partially abolished the protective role of H2S against cellular senescence. These results demonstrate the dynamic roles of H2S in the maintenance of ACE2 levels under different levels of oxidative stress, pointing to the potential implications in targeting the CSE/H2S system for the interruption of aging and diabetes-related heart disorders.

Effect of hydrogen sulfide on glycolysis-based energy production in mouse erythrocytes.

Hydrogen sulfide (H2 S) is a gasotransmitter that regulates both physiological and pathophysiological processes in mammalian cells. Recent studies have demonstrated that H2 S promotes aerobic energy production in the mitochondria in response to hypoxia, but its effect on anaerobic energy production has yet to be established. Glycolysis is the anaerobic process by which ATP is produced through the metabolism of glucose. Mammalian red blood cells (RBCs) extrude mitochondria and nucleus during erythropoiesis. These cells would serve as a unique model to observe the effect of H2 S on glycolysis-mediated energy production. The purpose of this study was to determine the effect of H2 S on glycolysis-mediated energy production in mitochondria-free mouse RBCs. Western blot analysis showed that the only H2 S-generating enzyme expressed in mouse RBCs is 3-mercaptopyruvate sulfurtransferase (MST). Supplement of the substrate for MST stimulated, but the inhibition of the same suppressed, the endogenous production of H2 S. Both exogenously administered H2 S salt and MST-derived endogenous H2 S stimulated glycolysis-mediated ATP production. The effect of NaHS on ATP levels was not affected by oxygenation status. On the contrary, hypoxia increased intracellular H2 S levels and MST activity in mouse RBCs. The mitochondria-targeted H2 S donor, AP39, did not affect ATP levels of mouse RBCs. NaHS at low concentrations (3-100 µM) increased ATP levels and decreased cell viability after 3 days of incubation in vitro. Higher NaHS concentrations (300-1000 µM) lowered ATP levels, but prolonged cell viability. H2 S may offer a cytoprotective effect in mammalian RBCs to maintain oxygen-independent energy production.

H2S-mediated blockage of protein acetylation and oxidative stress attenuates lipid overload-induced cardiac senescence.

Hydrogen sulphide (H2S), a newly identified gasotransmitter, can be endogenously produced by cystathionine gamma-lyase (CSE) in the cardiovascular system. This study investigated the role of the CSE/H2S system on lipid overload-induced lipotoxicity and cardiac senescence. Lipid overload in rat cardiomyocyte cells (H9C2) promoted intracellular accumulation of lipid, oxidative stress, mitochondrial dysfunctions, lipid peroxidation and inhibited cell viability, all of which could be reversed by exogenously applied H2S. Further data revealed that H2S protected H9C2 cells from lipid overload-induced senescence by altering the expressions of lipid metabolism-related genes and inhibiting cellular acetyl-CoA and global protein acetylation. Enhancement of protein acetylation abolished the protective role of H2S on cardiac senescence. In vivo, knockout of the CSE gene strengthened cardiac lipid accumulation, protein acetylation, and cellular ageing in high fat diet-fed mice. Taken together, the CSE/H2S system is capable of maintaining lipid homeostasis and cellular senescence in heart cells under lipid overload.

H2S signaling and extracellular matrix remodeling in cardiovascular diseases: A tale of tense relationship.

Extracellular matrix (ECM) is a non-cellular three-dimensional macromolecular network that not only provides mechanical support but also transduces essential molecular signals in organ functions. ECM is constantly remodeled to control tissue homeostasis, responsible for cell adhesion, cell migration, cell-to-cell communication, and cell differentiation, etc. The dysregulation of ECM components contributes to various diseases, including cardiovascular diseases, fibrosis, cancer, and neurodegenerative diseases, etc. Aberrant ECM remodeling is initiated by various stress, such as oxidative stress, inflammation, ischemia, and mechanical stress, etc. Hydrogen sulfide (H2S) is a gasotransmitter that exhibits a wide variety of cytoprotective and physiological functions through its anti-oxidative and anti-inflammatory actions. Amounting research shows that H2S can attenuate aberrant ECM remodeling. In this review, we discussed the implications and mechanisms of H2S in the regulation of ECM remodeling in cardiovascular diseases, and highlighted the potential of H2S in the prevention and treatment of cardiovascular diseases through attenuating adverse ECM remodeling.

The interaction of disulfiram and H2S metabolism in inhibition of aldehyde dehydrogenase activity and liver cancer cell growth.

Disulfiram (DSF), a sulfur-containing compound, has been used to treat chronic alcoholism and cancer for decades by inactivating aldehyde dehydrogenase (ALDH). Hydrogen sulfide (H2S) is a new gasotransmitter and regulates various cellular functions by S-sulfhydrating cysteine in the target proteins. H2S exhibits similar properties to DSF in the sensitization of cancer cells. The interaction of DSF and H2S on ALDH activity and liver cancer cell survival are not clear. Here it was demonstrated that DSF facilitated H2S release from thiol-containing compounds, and DSF and H2S were both capable of regulating ALDH through inhibition of gene expression and enzymatic activity. The supplement of H2S sensitized human liver cancer cells (HepG2) to DSF-inhibited cell viability. The expression of cystathionine gamma-lyase (a major H2S-generating enzyme) was lower but ALDH was higher in mouse liver cancer stem cells (Dt81Hepa1-6) in comparison with their parental cells (Hepa1-6), and H2S was able to inhibit liver cancer stem cell adhesion. In conclusion, these data point to the potential of combining DSF and H2S for inhibition of cancer cell growth and tumor development by targeting ALDH.

An evolutionary perspective on the interplays between hydrogen sulfide and oxygen in cellular functions.

The physiological effects of the endogenously generated hydrogen sulfide (H2S) have been extensively studied in recent years. This review summarized the role of H2S in the origin of life and H2S metabolism in organisms from bacteria to vertebrates, examined the relationship between H2S and oxygen from an evolutionary perspective and emphasized the oxygen-dependent manner of H2S signaling in various physiological and pathological processes. H2S and oxygen are inextricably linked in various cellular functions. H2S is involved in aerobic respiration and stimulates oxidative phosphorylation and ATP production within the cell. Besides, H2S has protective effects on ischemia and reperfusion injury in several organs by acting as an oxygen sensor. Also, emerging evidence suggests the role of H2S is in an oxygen-dependent manner. All these findings indicate the subtle relationship between H2S and oxygen and further explain why H2S, a toxic molecule thriving in an anoxia environment several billion years ago, still affects homeostasis today despite the very low content in the body.

Cystathionine gamma-lyase/H2 S signaling facilitates myogenesis under aging and injury condition.

Hydrogen sulfide (H2 S) can be endogenously produced and belongs to the class of signaling molecules known as gasotransmitters. Cystathionine gamma-lyase (CSE)-derived H2 S is implicated in the regulation of cell differentiation and the aging process, but the involvements of the CSE/H2 S system in myogenesis upon aging and injury have not been explored. In this study, we demonstrated that CSE acts as a major H2 S-generating enzyme in skeletal muscles and is significantly down-regulated in aged skeletal muscles in mice. CSE deficiency exacerbated the age-dependent sarcopenia and cardiotoxin-induced injury/regeneration in mouse skeletal muscle, possibly attributed to inefficient myogenesis. In contrast, supplement of NaHS (an H2 S donor) induced the expressions of myogenic genes and promoted muscle regeneration in mice. In vitro, incubation of myoblast cells (C2C12) with H2 S promoted myogenesis, as evidenced by the inhibition of cell cycle progression and migration, altered expressions of myogenic markers, elongation of myoblasts, and formation of multinucleated myotubes. Myogenesis was also found to upregulate CSE expression, while blockage of CSE/H2 S signaling resulted in a suppression of myogenesis. Mechanically, H2 S significantly induced the heterodimer formation between MEF2c and MRF4 and promoted the binding of MEF2c/MRF4 to myogenin promoter. MEF2c was S-sulfhydrated at both cysteine 361 and 420 in the C-terminal transactivation domain, and blockage of MEF2c S-sulfhydration abolished the stimulatory role of H2 S on MEF2c/MRF4 heterodimer formation. These findings support an essential role for H2 S in maintaining myogenesis, presenting it as a potential candidate for the prevention of age-related sarcopenia and treatment of muscle injury.

H2S Persulfidated and Increased Kinase Activity of MPK4 to Response Cold Stress in Arabidopsis.

Hydrogen sulfide (H2S) is a gasotransmitter along with nitric oxide and carbon oxide, which is involved in plant growth and development as well as biotic and abiotic stress resistance. In a previous study, we reported that mitogen-activated protein kinases, especially MPK4, are important downstream components of H2S involved in alleviating cold stress; however the underlying mechanism is unclear. In this study, we determined that the ability of H2S to alleviate cold stress is impaired in mpk4 mutants, but not in the upstream mek2 and crlk1 mutants. MPK4 was basically persulfidated, and NaHS (H2S donor) further increased the persulfidation level of MPK4. MEK2 was not persulfidated by H2S. NaHS treatments increased the MPK4 activity level nearly tenfold. The persulfidation signal of MPK4 did not disappear after eight cystein residues in MPK4 were site-mutated, respectively. Above all, our results suggested that H2S alleviates cold stress directly by persulfidating MPK4 and increasing the MPK4 kinase activity.

Disrupted H2S Signaling by Cigarette Smoking and Alcohol Drinking: Evidence from Cellular, Animal, and Clinical Studies.

The role of endogenous hydrogen sulfide (H2S) as an antioxidant regulator has sparked interest in its function within inflammatory diseases. Cigarette and alcohol use are major causes of premature death, resulting from chronic oxidative stress and subsequent tissue damage. The activation of the Nrf2 antioxidant response by H2S suggests that this novel gasotransmitter may function to prevent or potentially reverse disease progression caused by cigarette smoking or alcohol use. The purpose of this study is to review the interrelationship between H2S signaling and cigarette smoking or alcohol drinking. Based on the databases of cellular, animal, and clinical studies from Pubmed using the keywords of H2S, smoking, and/or alcohol, this review article provides a comprehensive insight into disrupted H2S signaling by alcohol drinking and cigarette smoking-caused disorders. Major signaling and metabolic pathways involved in H2S-derived antioxidant and anti-inflammatory responses are further reviewed. H2S supplementation may prove to be an invaluable asset in treating or preventing diseases in those suffering from cigarette or alcohol addiction.

Interaction among estrogen, IGF-1, and H2S on smooth muscle cell proliferation.

Both estrogen and hydrogen sulfide (H2S) inhibit the proliferation of vascular smooth muscle cells (SMCs) and development of atherosclerosis. In the absence of endogenous H2S as occurred in CSE-knockout (KO) mouse, however, estrogen stimulates the proliferation of vascular SMCs. The underlying mechanisms for this seemingly controversial vascular effect of estrogen are unclear. In the present study, we demonstrated that the stimulatory effect of estrogen on the proliferation of CSE-KO SMCs was suppressed by the inhibitor of insulin-like growth factor-1 receptor (IGF-1R) or knockdown of IGF-1R protein expression. Estrogen downregulated the expression of insulin-like growth factor-1 (IGF-1) and IGF-1R in aortic tissues or aortic SMCs isolated from WT and CSE-KO mice. Furthermore, endogenous H2S downregulated IGF-1R, but upregulated estrogen receptor (ER)-α, in aortic tissues or SMCs. ER-α and IGF-1R were co-located in SMCs and co-immunoprecipitated, which was decreased by H2S. Finally, both endogenous and exogenous H2S induced the S-sulfhydration of IGF-1R, but not ER-α, in WT-SMCs and CSE-KO SMCs, which underlies the decreased formation of IGF-1R/ER-α hybrid in the presence of H2S. Thus, the absence of H2S favors the interaction of estrogen with IGF-1R/ER-α hybrid to stimulate SMCs proliferation. The appreciation of a critical role of H2S in preventing estrogen-induced SMCs proliferation will help better understand the regulation of complex vascular effects of estrogen and sex-related cardiovascular diseases.

Spermine Protects Cardiomyocytes from High Glucose-Induced Energy Disturbance by Targeting the CaSR-gp78-Ubiquitin Proteasome System.

PURPOSE: To determine the mediation of spermine on energy metabolism disorder and diabetic cardiomyopathy (DCM) development as well as the underlying mechanisms. METHODS: An in vitro model of DCM was established by incubating primary cultured neonatal rat cardiomyocytes with high glucose (HG). Spermine content was assessed by RP-HPLC. The protein levels were detected by western blot. Mitochondrial functions were analyzed using the respiratory chain complex assay kit and immunofluorescence staining. RESULTS: The endogenous content of spermine was decreased in the HG group, and the protein levels of ornithine decarboxylase, respiratory chain complex (I-V), mitochondrial fusion-related protein (Mfn1, Mfn2), Cx43, N-cadherin, CaSR, and ß-catenin (in cytomembrane) were also down-regulated by HG. In contrast, the protein levels of spermine-N1-acetyltransferase, gp78, Fis1, Drp1, and ß-catenin were up-regulated by HG. Meanwhile, we observed that HG increased ubiquitination levels of Mfn1, Mfn2, and Cx43, decreased membrane potential (ΔΨm), and the opening of mitochondrial permeability transport pore (mPTP) followed by intracellular ATP leakage. The supplement of spermine or siRNA-mediated knockdown of gp78 significantly alleviated the detrimental effects of HG, while downregulation of CaSR aggravated the development of DCM. We further confirmed that the lower level of spermine by HG activates the gp78-ubiquitin-proteasome pathway via downregulation of CaSR protein level, which in turn damages mitochondrial gap junction intercellular communication and leads to reduced ATP level. CONCLUSION: The protective role of spermine on energy metabolism disorder is based on higher CaSR protein level and lower gp78 activation, pointing to the possibility that spermine can be a target for the prevention and treatment of DCM.

Hydrogen sulfide guards myoblasts from ferroptosis by inhibiting ALOX12 acetylation.

Recognized as a novel and important gasotransmitter, hydrogen sulfide (H2S) is widely present in various tissues and organs. Cystathionine gamma-lyase (CSE)-derived H2S has been shown to regulate oxidative stress and lipid metabolism. The aim of the present study is to examine the role of H2S in ferroptosis and lipid peroxidation in mouse myoblasts and skeletal muscles. Ferroptosis agonist RSL3 inhibited the expressions of Gpx4 and reduced CSE/H2S signaling, which lead to increased oxidative stress, lipid peroxidation, and ferroptotic cell death. In addition, ferroptosis antagonist ferrostatin-1 (Fer-1) up-regulated the expression of CSE, scavenged the generation of reactive oxygen species (ROS) and lipid peroxidation, and improved cell viability. Exogenously applied NaHS was also able to block RSL3-induced ferroptotic cell death. Neither RSL3 nor H2S affected cell apoptosis. Furthermore, H2S reversed RSL3-induced Drp1 expression and mitochondrial damage, which lead to abnormal lipid metabolism as evidenced by altered expressions of ACSL4, FAS, ACC and CPT1 as well as higher acetyl-CoA contents in both cytoplasm and mitochondria. RSL3 promoted the protein expression and acetylation of ALOX12, a key protein in initiating membrane phospholipid oxidation, while the addition of NaHS attenuated ALOX12 acetylation and protected from membrane lipid peroxidation. Moreover, we observed that CSE deficiency alters the expressions of ferroptosis and lipid peroxidation-related proteins and enhances global protein acetylation in mouse skeletal muscles under aging or injury conditions. These results indicate that downregulation of CSE/H2S signaling would contribute to mitochondrial damage, abnormal lipid metabolism, membrane lipid peroxidation, and ferroptotic cell death. CSE/H2S system can be a target for preventing ferroptosis in skeletal muscle.