Protein S-sulfhydration: Unraveling the prospective of hydrogen sulfide in the brain, vasculature and neurological manifestations

Shexiang Tongxin Dropping Pills attenuate ischemic microvascular dysfunction via suppressing P66Shc-mediated mitochondrial respiration deficits

ETHNOPHARMACOLOGICAL RELEVANCE

Ischemic stroke (IS) disrupts mitochondrial energy metabolism, leading to cerebral microvascular dysfunction (CMD). Shexiang Tongxin Dropping Pills (STDP) is a traditional Chinese medicinal formulation that has been clinically used for treating microcirculatory dysfunction. We have previously reported its ability to improve cerebral microcirculatory abnormalities. Nevertheless, the protective effects of STDP on cerebral microvascular mitochondria in the context of energy metabolism repair remain underinvestigated.

AIM OF THE STUDY

This study aims to investigate the potential mechanisms by which STDP ameliorates IS-induced CMD through the restoration of mitochondrial function.

MATERIALS AND METHODS

An ischemic stroke/reperfusion model was established by occluding and subsequently reperfusing the middle cerebral artery (MCAO/R) in C57BL/6 J mice. Laser speckle contrast imaging, Y-maze, rotarod tests and TTC staining were employed to evaluate the anti-ischemic stroke effects of STDP. Histological examination of cell adhesion proteins (ICAM 1, VCAM 1) and tight junction proteins (VE-cadherin, occludin) was conducted to assess the effects of STDP on the cerebral microvascular endothelium. In vitro, a bEnd.3 cell model was established through oxygen-glucose deprivation followed by reoxygenation (OGD/R). The cytoprotective capability of STDP was assessed by quantifying endothelial permeability, reactive oxygen species (ROS) levels, and cell viability. Mendelian randomization (MR) analysis and bioinformatic studies were performed to elucidate the causal associations between mitochondrial biological function and IS. Mitochondrial membrane potential (MMP) was assessed using a tetramethylrhodamine ethyl ester perchlorate fluorescent probe, while ATP production was quantified using a commercially available assay kit. Mitochondrial respiration was evaluated by measuring the oxygen consumption rate (OCR). Finally, the verification of important targets in mouse brain slices and bEnd.3 cells was conducted through immunoblotting and immunofluorescence.

RESULTS

STDP significantly restored cerebral blood flow and neurological function, and reduced infarct volume in MCAO/R mice. Furthermore, STDP markedly alleviated inflammation and hyperpermeability of the cerebral microvascular endothelium in MCAO/R mice, as evidenced by the suppression of ICAM-1 and VCAM-1 expression, along with the upregulation of VE-cadherin and occludin protein levels. Moreover, STDP not only mitigated hyperpermeability and excessive production of ROS induced by OGD/R in bEnd.3 cells but also enhanced the protective effects of the ROS scavenger N-acetylcysteine on bEnd.3 cells. Results of MR analysis and bioinformation studies demonstrated that the disruption of mitochondrial respiration is a critical pathogenic factor in IS-induced CMD. Our data confirmed that STDP effectively restored MMP and ATP production in OGD/R-treated bEnd.3 cells. Furthermore, STDP significantly enhanced basal respiration, maximal OCR, and spare respiratory capacity in bEnd.3 cells compared to the OGD/R group. Mechanistically, STDP markedly increased endothelial cystathionine γ-lyase (CSE)-mediated hydrogen sulfide (H2S) production and S-sulfhydration of P66shc, resulting in reduced protein expression and phosphorylation levels of P66Shc. This inhibition prevented its translocation into mitochondria, thereby restoring mitochondrial respiration.

CONCLUSION

STDP facilitated CSE expression and promoted H2S production, contributing to the inactivation of P66shc by suppressing its expression and increasing its sulfhydration. This process impeded P66Shc translocation to mitochondria, subsequently restoring mitochondrial respiration and alleviating IS-induced cerebral microvascular endothelial dysfunction.

Wuwei Shaji powder alleviates OVA-induced allergic asthma by protecting bronchial epithelial cells from ferroptosis via the S-sulfhydration of Keap1

ETHNOPHARMACOLOGICAL RELEVANCE

Asthma is a chronic inflammatory airway disease. Current treatments have limited efficacy and often cause severe side effects. Wuwei Shaji Powder (WSP), a traditional Mongolian remedy, is used for treating chronic pulmonary diseases, but its efficacy against asthma and underlying mechanisms are still unclear.

AIM OF THE STUDY

To investigate the therapeutic effect of WSP on asthma and elucidate its molecular mechanisms.

MATERIALS AND METHODS

An ovalbumin (OVA)-induced allergic asthma model was established in rats. Ferroptosis or apoptosis was induced in BEAS-2B cells using Erastin or CdCl2. Various techniques including histopathological staining, ELISA, Western blot, flow cytometry, and transmission electron microscopy were employed to assess WSP's effects and mechanisms.

RESULTS

WSP alleviated OVA-induced allergic asthma in rats without the immunosuppressive side effects observed with dexamethasone. WSP suppressed ferroptosis in bronchial epithelial cells both in vivo and in vitro. It reduced thiol- and sulfonic-based oxidative stress through Keap1 S-sulfhydration, disrupted the Keap1-Nrf2 interaction, and promoted Nrf2 nuclear translocation. Notably, we discovered that CdCl2 can induce ferroptosis in BEAS-2B cells, and WSP prevented both ferroptosis and apoptosis in these cells.

CONCLUSION

WSP alleviates OVA-induced allergic asthma by protecting bronchial epithelial cells from ferroptosis via S-sulfhydration of Keap1, providing new insights for its clinical application.

Sulfhydrated albumin transmits H2S signaling and ameliorates DOX-induced multiorgan injuries

Hydrogen sulfide (H2S) is a vital signaling molecule involved in various physiological processes; however, the mechanisms underlying its systemic signaling remain poorly understood. We hypothesized that albumin, the predominant plasma protein and a vital sulfhydryl carrier, mediated systemic H2S signaling, which could potentially treat H2S-deficient diseases. This study aimed to investigate this hypothesis. Our results showed the presence of sulfhydrated proteins in normal mouse serum, with albumin being particularly enriched. The level of sulfhydration was influenced by H2S availability and the redox environment. In vitro incubation of albumin with NaHS resulted in an increased number of sulfhydrated groups. Under reductive conditions, this sulfhydrated albumin (-SSH-Alb) released substantial amounts of H2S. When -SSH-Alb was added to cultured endothelial cells, it activated the cAMP signaling pathway, upregulated cystathionine γ-lyase (CSE) expression, and enhanced intracellular H2S levels. In an in vitro inflammatory model involving macrophages and endothelial cells, -SSH-Alb inhibited macrophage adhesion, reduced LPS-induced expression of adhesion molecules, and suppressed cytokine production and inflammasome activation. These effects correlated with improved cellular redox status. Furthermore, in vivo administration of -SSH-Alb protected mice from doxorubicin (DOX)-induced cardiotoxicity and intestinal damage. It improved mouse mortality, and alleviated ferroptotic cardiac injury and gut barrier dysfunction. These therapeutic benefits were associated with rebalanced local and systemic redox status. In summary, our study reveals that -SSH-Alb reserves, transmits, and amplifies H2S signals and exhibits significant anti-inflammatory and antioxidant properties. This characteristic of -SSH-Alb holds promise for preventing and treating a wide range of diseases.

Diallyl Trisulfide Attenuates Ischemia-Reperfusion-Induced ER Stress and Kidney Dysfunction in Aged Female Mice

Ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) in the aging population. Gender studies show that aging is associated with loss of protection from AKI in the female population. While ER stress contributes to IRI-induced AKI in the young, ER regulation during IR in the aged kidney is unclear. Because current evidence suggests hydrogen sulfide (H2S) modulates ER stress, we investigated whether exogenous supplementation of diallyl trisulfide (DATS), an H2S donor, mitigates AKI in aged female kidneys. Wild-type (WT, C57BL/6J) mice aged 75-78 weeks were treated with or without DATS before and after renal IRI. IRI increased ER stress proteins, inflammation, and fibrosis markers in the IRI kidney compared to the control. DATS mitigated ER stress, and reduced inflammation and fibrosis markers in the IRI kidney. Further, IRI kidneys demonstrated reduced blood flow, vascularity, angiogenesis, increased resistive index (RI), and reduced function. DATS treatment upregulated PI3K, AKT, p-mTOR, and pMAPK signaling to stimulate angiogenesis, which improved vascular density, blood flow, and renal function. Together, our results suggest that DATS rescues the aged female kidney IRI by modulating ER stress and upregulation of angiogenesis.

Sul-BertGRU: an ensemble deep learning method integrating information entropy-enhanced BERT and directional multi-GRU for S-sulfhydration sites prediction

MOTIVATION

S-sulfhydration, a crucial post-translational protein modification, is pivotal in cellular recognition, signaling processes, and the development and progression of cardiovascular and neurological disorders, so identifying S-sulfhydration sites is crucial for studies in cell biology. Deep learning shows high efficiency and accuracy in identifying protein sites compared to traditional methods that often lack sensitivity and specificity in accurately locating nonsulfhydration sites. Therefore, we employ deep learning methods to tackle the challenge of pinpointing S-sulfhydration sites.

RESULTS

In this work, we introduce a deep learning approach called Sul-BertGRU, designed specifically for predicting S-sulfhydration sites in proteins, which integrates multi-directional gated recurrent unit (GRU) and BERT. First, Sul-BertGRU proposes an information entropy-enhanced BERT (IE-BERT) to preprocess protein sequences and extract initial features. Subsequently, confidence learning is employed to eliminate potential S-sulfhydration samples from the nonsulfhydration samples and select reliable negative samples. Then, considering the directional nature of the modification process, protein sequences are categorized into left, right, and full sequences centered on cysteines. We build a multi-directional GRU to enhance the extraction of directional sequence features and model the details of the enzymatic reaction involved in S-sulfhydration. Ultimately, we apply a parallel multi-head self-attention mechanism alongside a convolutional neural network to deeply analyze sequence features that might be missed at a local level. Sul-BertGRU achieves sensitivity, specificity, precision, accuracy, Matthews correlation coefficient, and area under the curve scores of 85.82%, 68.24%, 74.80%, 77.44%, 55.13%, and 77.03%, respectively. Sul-BertGRU demonstrates exceptional performance and proves to be a reliable method for predicting protein S-sulfhydration sites.

AVAILABILITY AND IMPLEMENTATION

The source code and data are available at https://github.com/Severus0902/Sul-BertGRU/.

Hydrogen Sulfide Alleviates Schizophrenia-Like Behavior Through Regulating Apoptosis by S-Sulfhydrylation Modification

BACKGROUND

We initiated an exploration of the relationship between hydrogen sulfide (H2S) and Schizophrenia (SZ) as well as its mechanism at the three levels of population study, cellular investigation, and animal model.

MATERIALS AND METHODS

Clinical data and peripheral blood samples from 78 patients with SZ and 83 healthy controls (HC) were collected for the detection of H2S levels (ChiCTR (Chinese Clinical Trial Registry) 900026776). MK801 (Dizocilpine) was used to establish SZ models in cells and rats, with sodium hydrosulfide (NaHS) serving as an exogenous H2S donor. H2S levels in plasma and hippocampal tissue of rats were measured using Enzyme Linked Immunosorbent Assay (ELISA). Terminal dUTP Nick End Labeling (TUNEL) staining was employed to detect apoptosis, enzyme activity was determined to assess apoptotic protease activity, neuron damage was identified by Nissl staining, and the protein S-sulfhydrylation test was utilized to evaluate alterations in apoptosis-associated protein S-sulfhydrylation.

RESULTS

H2S content significantly decreased in the plasma of SZ patients and in the plasma and hippocampal tissue of SZ model rats. NaHS pretreatment reduced MK801-induced apoptosis in SH-SY5Y cells. SZ model rats exhibited increased behavioral abnormalities, hippocampal apoptosis, and reduced S-sulfhydrylation of an apoptosis-related protein, both restored after NaHS pretreatment.

CONCLUSIONS

H2S content is significantly reduced in SZ, and supplementation of H2S can alleviate SZ-like behavior by inducing S-sulfhydration of apoptotic proteins.

ASB1 engages with ELOB to facilitate SQOR ubiquitination and H2S homeostasis during spermiogenesis

Male infertility, frequently driven by oxidative stress, impacts half of infertile couples globally. Despite its significance, the precise mechanisms governing this process remain elusive. In this study, we demonstrate that ASB1, the substrate recognition subunit of a ubiquitin ligase, is highly expressed in the mouse testis. Mice lacking the Asb1 gene exhibit severe fertility impairment, characterized by oligoasthenoteratozoospermia. Subsequent investigations unveiled that Asb1 knockout (Asb1-KO) mice encountered excessive oxidative stress and decreased hydrogen sulfide (H2S) levels in their testes, and severe sperm DNA damage. Notably, the compromised fertility and sperm quality in Asb1-KO mice was significantly ameliorated by administering NaHS, a H2S donor. Mechanistically, ASB1 interacts with ELOB to induce the instability of sulfide-quinone oxidoreductase (SQOR) by enhancing its K48-linked ubiquitination on residues K207 and K344, consequently triggering proteasomal degradation. This process is crucial for preserving H2S homeostasis and redox balance. Overall, our findings offer valuable insights into the role of ASB1 during spermiogenesis and propose H2S supplementation as a promising therapeutic approach for oxidative stress-related male infertility.

Impaired Iron-Sulfur Cluster Synthesis Induces Mitochondrial PARthanatos in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM), a severe complication of diabetes, is characterized by mitochondrial dysfunction, oxidative stress, and DNA damage. Despite its severity, the intrinsic factors governing cardiomyocyte damage in DCM remain unclear. It is hypothesized that impaired iron-sulfur (Fe-S) cluster synthesis plays a crucial role in the pathogenesis of DCM. Reduced S-sulfhydration of cysteine desulfurase (NFS1) is a novel mechanism that contributes to mitochondrial dysfunction and PARthanatos in DCM. Mechanistically, hydrogen sulfide (H2S) supplementation restores NFS1 S-sulfhydration at cysteine 383 residue, thereby enhancing Fe-S cluster synthesis, improving mitochondrial function, increasing cardiomyocyte viability, and alleviating cardiac damage. This study provides novel insights into the interplay between Fe-S clusters, mitochondrial dysfunction, and PARthanatos, highlighting a promising therapeutic target for DCM and paving the way for potential clinical interventions to improve patient outcomes.

Insufficient S-sulfhydration of serum and glucocorticoid-regulated kinase 1 participates in hyperhomocysteinemia-induced liver injury

BACKGROUND & AIMS

Previous studies have established that hyperhomocysteinemia (HHcy) significantly contributes to the development of non-alcoholic steatohepatitis (NASH). Conversely, hydrogen sulfide (H2S) has shown potential in mitigating NASH. Despite these findings, it remains uncertain whether H2S can serve as a therapeutic agent against HHcy-induced liver damage.

METHODS

Mice were fed a high-methionine diet to induce HHcy and HepG2 cells were exposed to homocysteine (Hcy). In both models, we assessed liver injury, H2S concentration, and autophagy levels. For rescue, sodium hydrosulfide (NaHS), an H2S donor, was used to test its potential in reversing hepatic pathological features induced by HHcy.

RESULTS

1) Hcy accumulation led to liver damage and increased autophagy. This was linked to insufficient S-sulfhydration of serum and glucocorticoid-regulated kinase 1 (SGK1) at Cys244 and Cys282, a crucial autophagy regulator. The deficiency in S-sulfhydration was resulted from downregulation of cystathionine-γ-lyase (CSE) and subsequent H2S decrease, leading to SGK1 inactivation. 2) Administration of NaHS reduced the liver damage caused by high Hcy levels and restored H2S levels, promoting the S-sulfhydration and activation of SGK1. 3) Pharmacological inhibition of SGK1 induced autosis, a specific type of cell death caused by overactivation of autophagy. Conversely, a constitutively active mutant of SGK1 (SGK1S422D) significantly decreased autophagy and improved cell viability.

CONCLUSIONS

NaHS supplementation mitigates HHcy-induced liver injury by downregulating hepatic autophagy through the S-sulfhydration and activation of SGK1. This post-translational modification by H2S holds promise as a therapeutic approach for HHcy-induced liver injury.

Biophysical characterization of hydrogen sulfide: A fundamental exploration in understanding significance in cell signaling

Hydrogen sulfide (H₂S) has emerged as a significant signaling molecule involved in various physiological processes, including vasodilation, neurotransmission, and cytoprotection. Its interactions with biomolecules are critical to understand its roles in health and disease. Recent advances in biophysical characterization techniques have shed light on the complex interactions of H₂S with proteins, nucleic acids, and lipids. Proteins are primary targets for H₂S, which can modify cysteine residues through S-sulfhydration, impacting protein function and signaling pathways. Advanced spectroscopic techniques, such as mass spectrometry and NMR, have enabled the identification of specific sulfhydrated sites and provided insights into the structural and functional consequences of these modifications. Nucleic acids also interact with H₂S, although this area is less explored compared to proteins. Recent studies have demonstrated that H₂S can induce modifications in nucleic acids, affecting gene expression and stability. Techniques like gel electrophoresis and fluorescence spectroscopy have been utilized to investigate these interactions, revealing that H₂S can protect DNA from oxidative damage and modulate RNA stability and function. Lipids, being integral components of cell membranes, interact with H₂S, influencing membrane fluidity and signaling. Biophysical techniques such as electron paramagnetic resonance (EPR) and fluorescence microscopy have elucidated the effects of H₂S on lipid membranes. These studies have shown that H₂S can alter lipid packing and dynamics, which may impact membrane-associated signaling pathways and cellular responses to stress. In the current work we have integrated this with key scientific explainations to provide a comprehensive review.

Hydrogen sulfide inhibits skeletal muscle ageing by up-regulating autophagy through promoting deubiquitination of adenosine 5'-monophosphate (AMP)-activated protein kinase α1 via ubiquitin specific peptidase 5

BACKGROUND

Hydrogen sulfide (H2S), the third gasotransmitter discovered, regulates a variety of physiological functions. Whether H2S alleviates skeletal muscle ageing by regulating autophagy has not been reported.

METHODS

Mice were administered 150 mg/kg/day of D-galactose (D-gal), and C2C12 myotubes were cultured in 20 g/L D-gal to induce ageing. Sodium hydrosulfide (NaHS) was employed as an exogenous donor in the treatment group. The intracellular concentration of H2S was quantified by the 7-azido-4-methylcoumarin fluorescence probe. The proteins involved in the ubiquitin-mediated degradation of AMPKα1 were detected by liquid chromatography tandem mass spectrometry (LC-MS/MS) and co-immunoprecipitation (Co-IP). S-sulfhydration of USP5 was tested by a biotin-switch assay. Associated proteins were analysed by western blot.

RESULTS

NaHS was found to effectively restore the H2S content in both ageing gastrocnemius (+91.89%, P < 0.001) and C2C12 myotubes (+27.55%, P < 0.001). In comparison to the D-gal group, NaHS was observed to increase the mean cross-sectional area of muscle fibres (+44.91%, P < 0.001), to decrease the collagen volume fraction of gastrocnemius (-81.32%, P = 0.001) and to reduce the β-galactosidase-positive area of C2C12 myotubes (-28.74%, P < 0.001). NaHS was also found to reverse the expression of muscle atrophy F box protein (MAFbx), muscle-specific RING finger protein 1 (MuRF1), Cyclin D1 and p21 in the ageing gastrocnemius tissue (MAFbx: -31.73%, P = 0.008; MuRF1: -32.37%, P = 0.003; Cyclin D1: +45.34%, P = 0.010; p21: -25.53%, P = 0.022) and C2C12 myotubes (MAFbx: -16.38%, P < 0.001; MuRF1: -16.45%, P = 0.003; Cyclin D1: +40.23%, P < 0.001; p21: -35.85%, P = 0.026). The AMPKα1-ULK1 pathway was activated and autophagy was up-regulated in NaHS-treated gastrocnemius tissue (p-AMPKα1: +61.61%, P = 0.018; AMPKα1: +30.64%, P = 0.010; p-ULK1/ULK1: +85.87%, P = 0.005; p62: -29.07%, P < 0.001; Beclin1: +24.75%, P = 0.007; light chain 3 II/I [LC3 II/I]: +55.78%, P = 0.004) and C2C12 myotubes (p-AMPKα1: +77.49%, P = 0.018; AMPKα1: +26.18%, P = 0.022; p-ULK1/ULK1: +38.34%, P = 0.012; p62: -9.02%, P = 0.014; Beclin1: +13.36%, P < 0.001; LC3 II/I: +79.38%, P = 0.017; autophagy flux: +24.88%, P = 0.034) compared with the D-gal group. The effects of NaHS on autophagy were comparable to those of acadesine and LYN-1604, and chloroquine could reverse its effects on ageing. LC-MS/MS and Co-IP experiments demonstrated that USP5 is a deubiquitinating enzyme of AMPKα1. Following the knockdown of USP5, the activation of AMPKα1 was decreased (p-AMPKα1: -42.10%, P < 0.001; AMPKα1: -43.93%, P < 0.001), autophagy was inhibited (p-ULK1/ULK1: -27.51, P = 0.001; p62: +36.00, P < 0.001; Beclin1: -22.15%, P < 0.001) and NaHS lost its ability to up-regulate autophagy. NaHS was observed to restore the expression (gastrocnemius: +62.17%, P < 0.001; C2C12 myotubes: +37.51%, P = 0.003) and S-sulfhydration (+53.07%, P = 0.009) of USP5 and reduce the ubiquitination of AMPKα1.

CONCLUSIONS

H2S promotes the deubiquitination of AMPKα1 by increasing the expression and S-sulfhydration of USP5, thereby up-regulating autophagy and alleviating skeletal muscle ageing.

Hydrogel in the Treatment of Traumatic Brain Injury

The high prevalence of traumatic brain injury (TBI) poses an important global public health challenge. Current treatment modalities for TBI primarily involve pharmaceutical interventions and surgical procedures; however, the efficacy of these approaches remains limited. In the field of regenerative medicine, hydrogels have garnered significant attention and research efforts. This review provides an overview of the existing landscape and pathological manifestations of TBI, with a specific emphasis on delineating the therapeutic potential of hydrogels incorporated with various bioactive agents for TBI management. Particularly, the review delves into the utilization and efficacy of hydrogels based on extracellular matrix (ECM), stem cell-loaded, drug-loaded, self-assembled peptide structures or conductive in the context of TBI treatment. These applications are shown to yield favorable outcomes such as tissue damage mitigation, anti-inflammatory effects, attenuation of oxidative stress, anti-apoptotic properties, promotion of neurogenesis, and facilitation of angiogenesis. Lastly, a comprehensive analysis of the merits and constraints associated with hydrogel utilization in TBI treatment is presented, aiming to steer and advance future research endeavors in this domain.

Sodium thiosulfate: A donor or carrier signaling molecule for hydrogen sulfide?

Sodium thiosulfate has been used for decades in the treatment of calciphylaxis and cyanide detoxification, and has recently shown initial therapeutic promise in critical diseases such as neuronal ischemia, diabetes mellitus, heart failure and acute lung injury. However, the precise mechanism of sodium thiosulfate remains incompletely defined and sometimes contradictory. Although sodium thiosulfate has been widely accepted as a donor of hydrogen sulfide (H2S), emerging findings suggest that it is the executive signaling molecule for H2S and that its effects may not be dependent on H2S. This article presents an overview of the current understanding of sodium thiosulfate, including its synthesis, biological characteristics, and clinical applications of sodium thiosulfate, as well as the underlying mechanisms in vivo. We also discussed the interplay of sodium thiosulfate and H2S. Our review highlights sodium thiosulfate as a key player in sulfide signaling with the broad clinical potential for the future.

Diesel exhaust particulate matter induces GC-1 spg cells oxidative stress by KEAP1-NRF2 pathway and inhibition of ATP5α1 S-sulfhydration

Diesel exhaust particle (DEP) exposure induces a variety of toxicological effects through oxidative stress and inflammation responses. This research investigated the mechanisms underlying DEP-induced GC-1spg cells oxidative stress by examining ROS accumulation, antioxidant defense systems activation, mitochondrial dysfunction, and the Nrf2/Keap1/HO-1 pathway response. Subsequently, we further evaluated the ATP levels, ATP5α synthase activity and ATP5α synthase S-sulfhydrated modification in DEP-exposed GC-1 spg cells. The results showed that DEP exposure significantly inhibited cell proliferation and viability, increased intracellular ROS production, decreased MMP, down-regulated antioxidant capacity, activated the Nrf2/Keap1/HO-1 pathway. However, DEP-induced oxidative stress was partially alleviated by GSH and exogenous H2S. In addition, DEP exposure induced ATP depletion and ATP5α synthase inactivity in GC-1 spg cells, accompanied by ATP5α synthase S-sulfhydrated modification. In conclusion, our research showed that DEP may incapacitate mitochondria through oxidative stress injury, leading to GC-1 spg cells oxidative stress. This process may be associated with the reduction of ATP5α1 S-sulfhydrated modification. It provides a new perspective for the research of the mechanism related to male reproductive toxicity due to air pollution.

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Hydrogen sulfide protects cardiomyocytes from doxorubicin-induced ferroptosis through the SLC7A11/GSH/GPx4 pathway by Keap1 S-sulfhydration and Nrf2 activation

Recent studies have demonstrated that ferroptosis, a novel form of nonapoptotic regulated cell death plays an important role in doxorubicin (DOX)-induced cardiotoxicity (DoIC). Hydrogen sulfide (H2S) is emerging as the third important gaseous mediator in cardiovascular system. However, whether H2S has an effect on DOX-induced ferroptosis remains unknown. Here, we found that DOX not only triggered cardiomyocyte ferroptosis but also significantly inhibited the synthesis of endogenous H2S in the murine model of chronic DoIC. Application of NaHS, an H2S donor obviously activated the SLC7A11/GSH/GPx4 antioxidant pathway and thus alleviated DOX-induced ferroptosis and cardiac injury in mice. In contrast, cardiac-specific knockout of cystathionine γ-lyase gene (Cse) in mice (Csef/f/Cre+) to abolish the cardiac synthesis of endogenous H2S evidently exacerbated DOX-induced ferroptosis and cardiac dysfunction. A further suppression of SLC7A11/GSH/GPx4 pathway was obtained in Csef/f/Cre+ mice with DoIC, as compared to Csef/f/Cre- mice with DoIC. The aggravation caused by cardiac-specific Cse deficiency was remarkably rescued by exogenous supplementation of NaHS. Moreover, in DOX-stimulated H9c2 cardiomyocytes, pretreatment with NaHS dose-dependently enhanced the activity of SLC7A11/GSH/GPx4 pathway and subsequently mitigated ferroptosis and mitochondrial impairment. On the contrary, transfection with Cse siRNA in DOX-stimulated H9c2 cardiomyocytes markedly inhibited SLC7A11/GSH/GPx4 pathway, thus leading to aggravated ferroptosis and more damage to mitochondrial structure and function. In addition, the protective effect of NaHS on DOX-induced ferroptosis was closely related to the S-sulfhydrated Keap1, which in turn promoted nuclear translocation of Nrf2 and the transcription of SLC7A11 and GPx4. In conclusion, our findings suggest that H2S may exert protective effect on DoIC by inhibiting DOX-induced ferroptosis via Keap1/Nrf2-dependent SLC7A11/GSH/GPx4 antioxidant pathway.

The role of deubiquitinases in cardiac disease

Deubiquitinases are a group of proteins that identify and digest monoubiquitin chains or polyubiquitin chains attached to substrate proteins, preventing the substrate protein from being degraded by the ubiquitin-proteasome system. Deubiquitinases regulate cellular autophagy, metabolism and oxidative stress by acting on different substrate proteins. Recent studies have revealed that deubiquitinases act as a critical regulator in various cardiac diseases, and control the onset and progression of cardiac disease through a board range of mechanism. This review summarizes the function of different deubiquitinases in cardiac disease, including cardiac hypertrophy, myocardial infarction and diabetes mellitus-related cardiac disease. Besides, this review briefly recapitulates the role of deubiquitinases modulators in cardiac disease, providing the potential therapeutic targets in the future.

Investigating the impact of protein S-sulfhydration modification on vascular diseases: A comprehensive review

The post-translational modification of cysteine through redox reactions, especially S-sulfhydration, plays a critical role in regulating protein activity, interactions, and spatial arrangement. This review focuses on the impact of protein S-sulfhydration on vascular function and its implications in vascular diseases. Dysregulated S-sulfhydration has been linked to the development of vascular pathologies, including aortic aneurysms and dissections, atherosclerosis, and thrombotic diseases. The H2S signaling pathway and the enzyme cystathionine γ-lyase (CSE), which is responsible for H2S generation, are identified as key regulators of vascular function. Additionally, potential therapeutic targets for the treatment of vascular diseases, such as the H2S donor GYY4137 and the HDAC inhibitor entinostat, are discussed. The review also emphasizes the antithrombotic effects of H2S in regulating platelet aggregation and thrombosis. The aim of this review is to enhance our understanding of the function and mechanism of protein S-sulfhydration modification in vascular diseases, and to provide new insights into the clinical application of this modification.

AChE activity self-breathing control mechanisms regulated by H2Sn and GSH: Persulfidation and glutathionylation on sulfhydryl after disulfide bonds cleavage

Hydrogen sulfide (H2S), or dihydrogen sulfane (H2Sn), acts as a signal molecule through the beneficial mechanism of persulfidation, known as the post-translational transformation of cysteine residues to persulfides. We previously reported that Glutathione (GSH) could regulate enzyme activity through S-desulfurization or glutathionylation of residues to generate protein-SG or protein-SSG, releasing H2S. However, little is known about the mechanisms by which H2Sn and GSH affect the disulfide bonds. In this study, we provide direct evidences that H2Sn and GSH modify the sulfhydryl group on Cys272, which forms disulfide bonds in acetylcholinesterase (AChE), to generate Cys-SSH and Cys-SSG, respectively. Glutathionylation of disulfide is a two-step reaction based on nucleophilic substitution, in which the first CS bond is broken, then the SS bond is broken to release H2S. H2Sn and GSH controlled self-breathing motion in enzyme catalysis by disconnecting specific disulfide bonds and modifying cysteine residues, thereby regulating AChE activity. Here, we elucidated H2Sn and GSH mechanisms on disulfide in the AChE system and proposed a self-breathing control theory induced by H2Sn and GSH. These theoretical findings shed light on the biological functions of H2Sn and GSH on sulfhydryl and disulfide bonds and enrich the theory of enzyme activity regulation.

Hydrogen sulfide attenuates atherosclerosis induced by low shear stress by sulfhydrylating endothelium NFIL3 to restrain MEST mediated endothelial mesenchymal transformation

BACKGROUND

Endothelial-mesenchymal transition (EndMT) induced by low shear stress plays an important role in the development of atherosclerosis. However, little is known about the correlation between hydrogen sulfide (H2S), a protective gaseous mediator in atherosclerosis and the process of EndMT.

METHODS

We constructed a stable low-shear-stress-induced(2 dyn/cm2) EndMT model, acombined with the pretreatment method of hydrogen sulfide slow release agent(GYY4137). The level of MEST was detected in the common carotid artery of ApoE-/- mice with local carotid artery ligation. The effect of MEST on atherosclerosis development in vivo was verified using ApoE-/- mice were given tail-vein injection of endothelial-specific overexpressed and knock-down MEST adeno-associated virus (AAV).

RESULTS

These findings confirmed that MEST is up-regulated in low-shear-stress-induced EndMT and atherosclerosis. In vivo experiments showed that MEST gene overexpression significantly promoted EndMT and aggravated the development of atherosclerotic plaques and MEST gene knockdown significantly inhibited EndMT and delayed the process of atherosclerosis. In vitro, H2S inhibits the expression of MEST and EndMT induced by low shear stress and inhibits EndMT induced by MEST overexpression. Knockdown of NFIL3 inhibit the up regulation of MEST and EndMT induced by low shear stress in HUVECs. CHIP-qPCR assay and Luciferase Reporter assay confirmed that NFIL3 binds to MEST DNA, increases its transcription and H2S inhibits the binding of NFIL3 and MEST DNA, weakening NFIL3's transcriptional promotion of MEST. Mechanistically, H2S increased the sulfhydrylation level of NFIL3, an important upstream transcription factors of MEST. In part, transcription factor NFIL3 restrain its binding to MEST DNA by sulfhydration.

CONCLUSIONS

H2S negatively regulate the expression of MEST by sulfhydrylation of NFIL3, thereby inhibiting low-shear-stress-induced EndMT and atherosclerosis.

A critical role for host-derived cystathionine-β-synthase in Staphylococcus aureus-induced udder infection

Cystathionine-β-synthase (CBS) catalyzes the first step of the transsulfuration pathway. The role of host-derived CBS in Staphylococcus aureus (S. aureus)-induced udder infection remains elusive. Herein, we report that S. aureus infection enhances the expression of CBS in mammary epithelial cells in vitro and in vivo. A negative correlation is present between the expression of CBS and inflammation after employing a pharmacological inhibitor/agonist of CBS. In addition, CBS achieves a fine balance between eliciting sufficient protective innate immunity and preventing excessive damage to cells and tissues preserving the integrity of the blood-milk barrier (BMB). CBS/H2S reduces bacterial load by promoting the generation of antibacterial substances (ROS, RNS) and inhibiting apoptosis, as opposed to relying solely on intense inflammatory reactions. Conversely, H2S donor alleviate inflammation via S-sulfhydrating HuR. Finally, CBS/H2S promotes the expression of Abcb1b, which in turn strengthens the integrity of the BMB. The study described herein demonstrates the importance of CBS in regulating the mammary immune response to S. aureus. Increased CBS in udder tissue modulates excessive inflammation, which suggests a novel target for drug development in the battle against S. aureus and other infections.

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.

The Role of Hydrogen Sulfide in the Localization and Expression of p53 and Cell Death in the Nervous Tissue in Traumatic Brain Injury and Axotomy

Traumatic brain injury (TBI) is one of the leading causes of disability and death worldwide. It is characterized by various molecular-cellular events, with the main ones being apoptosis and damage to axons. To date, there are no clinically effective neuroprotective drugs. In this study, we examined the role of hydrogen sulfide (H2S) in the localization and expression of the key pro-apoptotic protein p53, as well as cell death in the nervous tissue in TBI and axotomy. We used a fast donor (sodium sulphide, Na2S) H2S and a classic inhibitor (aminooxyacetic acid, AOAA) of cystathionine β-synthase (CBS), which is a key enzyme in H2S synthesis. These studies were carried out on three models of neurotrauma in vertebrates and invertebrates. As a result, it was found that Na2S exhibits a pronounced neuroprotective effect that reduces the number of TUNEL-positive neurons and glial cells in TBI and apoptotic glia in axotomy. This effect could be realized through the Na2S-dependent decrease in the level of p53 in the cells of the nervous tissue of vertebrates and invertebrates, which we observed in our study. We also observed the opposite effect when using AOAA, which indicates the important role of CBS in the regulation of p53 expression and death of neurons and glial cells in TBI and axotomy.

Modulating miR-146a Expression by Hydrogen Sulfide Ameliorates Motor Dysfunction and Axonal Demyelination in Cuprizone-Induced Multiple Sclerosis

Multiple sclerosis (MS) is a progressive neuro-inflammatory and neuro-autoimmune disease. Although hydrogen sulfide has recently shown potential therapeutic impacts in different neurological diseases, its effects on MS are still obscure. MiR-146a is considered a vital target for different therapeutic approaches in treating MS. The present study is directed to explore the therapeutic effects of NaHS (hydrogen sulfide donor) on cuprizone-induced MS and to explore whether NaHS can mediate its effects via regulating miR-146a expression. A total of 28 male C57Bl/6 mice were divided into 4 groups; control, cuprizone-intoxicated, NaHS control (100 μmol/kg/day, i.p), and NaHS-treated groups. Intriguingly, NaHS treatment managed to improve locomotor coordination and curb neuronal inflammation and demyelination as evidenced by hematoxylin & eosin, and Luxol fast blue staining and the increased myelin basic protein (MBP) content. Additionally, NaHS reduced interleukin-1 receptor-associated kinase-1 (IRAK-1), nuclear transcription factor kappa B (NF-κB), interleukin (IL)-17, and IL-1β brain levels along with downregulation of miR-146a expression compared with the untreated cuprizone-intoxicated group. Furthermore, NaHS-treated animals revealed much less oxidative stress compared to the untreated animals as evidenced by elevated glutathione and reduced malondialdehyde contents. Altogether, the current work reported that NaHS could improve motor dysfunction and reduce axonal demyelination, oxidative stress, as well as neuro-inflammation in mice with MS. Thus, using H2S-releasing compounds could be a promising approach in MS treatment strategies. The mechanism of these beneficial effects may involve the regulation of miR-146a/NF-κB/IL-1β axis.

The Role of Hydrogen Sulfide (H2S) in Epigenetic Regulation of Neurodegenerative Diseases: A Systematic Review

This review explores the emerging role of hydrogen sulfide (H2S) in modulating epigenetic mechanisms involved in neurodegenerative diseases. Accumulating evidence has begun to elucidate the multifaceted ways in which H2S influences the epigenetic landscape and, subsequently, the progression of various neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease. H2S can modulate key components of the epigenetic machinery, such as DNA methylation, histone modifications, and non-coding RNAs, impacting gene expression and cellular functions relevant to neuronal survival, inflammation, and synaptic plasticity. We synthesize recent research that positions H2S as an essential player within this intricate network, with the potential to open new therapeutic avenues for these currently incurable conditions. Despite significant progress, there remains a considerable gap in our understanding of the precise molecular mechanisms and the potential therapeutic implications of modulating H2S levels or its downstream targets. We conclude by identifying future directions for research aimed at exploiting the therapeutic potential of H2S in neurodegenerative diseases.

The biological functions of protein S-sulfhydration in eukaryotes and the ever-increasing understanding of its effects on bacteria

As a critical endogenous signaling molecule, hydrogen sulfide may induce reversible post-translational modifications on cysteine residues of proteins, generating a persulfide bond known as S-sulfhydration. A systemic overview of the biofunctions of S-sulfhydration will equip us better to characterize its regulatory roles in antioxidant defense, inflammatory response, and cell fate, as well as its pathological mechanisms related to cardiovascular, neurological, and multiple organ diseases, etc. Nevertheless, the understanding of S-sulfhydration is mostly built on mammalian cells and animal models. We subsequently summarized the mediation effects of this specific post-transcriptional modification on physiological processes and virulence in bacteria. The high-sensitivity and high-throughput detection technologies are required for studying the signal transduction mechanism of H₂S and protein S-sulfhydration modification. Herein, we reviewed the establishment and development of different approaches to assess S-sulfhydration, including the biotin-switch method, modified biotin-switch method, alkylation-based cysteine-labelled assay, and Tag-switch method. Finally, we discussed the limitations of the impacts of S-sulfhydration in pathogens-host interactions and envisaged the challenges to design drugs and antibiotics targeting the S-sulfhydrated proteins in the host or pathogens.

S-sulfhydration of SIRT3 combats BMSC senescence and ameliorates osteoporosis via stabilizing heterochromatic and mitochondrial homeostasis

Senescence of bone marrow mesenchymal stem cells (BMSCs) is one of the leading causes of osteoporosis. SIRT3, an essential NAD-dependent histone deacetylase, is highly correlated with BMSC senescence-mediated bone degradation and mitochondrial/heterochromatic disturbance. S-sulfhydration of cysteine residues favorably enhances SIRT3 activity by forming persulfides. Nevertheless, the underlying molecular mechanism of SIRT3 S-sulfhydration on mitochondrial/heterochromatic homeostasis involved in BMSC senescence remains unknown. Here, we demonstrated that CBS and CSE, endogenous hydrogen sulfide synthases, are downregulated with BMSC senescence. Exogenous H₂S donor NaHS-mediated SIRT3 augmentation rescued the senescent phenotypes of BMSCs. Conversely, SIRT3 deletion accelerated oxidative stress-induced BMSC senescence through mitochondrial dysfunction and the detachment of the heterochromatic protein H3K9me3 from the nuclear envelope protein Lamin B1. H₂S-mediated SIRT3 S-sulfhydration modification rescued the disorganized heterochromatin and fragmented mitochondria induced by the S-sulfhydration inhibitor dithiothreitol, thus leading to elevated osteogenic capacity and preventing BMSC senescence. The antisenescence effect of S-sulfhydration modification on BMSCs was abolished when the CXXC sites of the SIRT3 zinc finger motif were mutated. In vivo, aged mice-derived BMSCs pretreated with NaHS were orthotopically transplanted to the ovariectomy-induced osteoporotic mice, and we proved that SIRT3 ameliorates bone loss by inhibiting BMSC senescence. Overall, our study for the first time indicates a novel role of SIRT3 S-sulfhydration in stabilizing heterochromatin and mitochondrial homeostasis in counteracting BMSC senescence, providing a potential target for the treatment of degenerative bone diseases.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Protein persulfidation: Rewiring the hydrogen sulfide signaling in cell stress response

The past few decades have witnessed significant progress in the discovery of hydrogen sulfide (H₂S) as a ubiquitous gaseous signaling molecule in mammalian physiology, akin to nitric oxide and carbon monoxide. As the third gasotransmitter, H₂S is now known to exert a wide range of physiological and cytoprotective functions in the biological systems. However, endogenous H₂S concentrations are usually low, and its potential biologic mechanisms responsible have not yet been fully clarified. Recently, a growing body of evidence has demonstrated that protein persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH) elicited by H₂S, is a fundamental mechanism of H₂S-mediated signaling pathways. Persulfidation, as a biological switch for protein function, plays an important role in the maintenance of cell homeostasis in response to various internal and external stress stimuli and is also implicated in numerous diseases, such as cardiovascular and neurodegenerative diseases and cancer. In this review, the biological significance of protein persulfidation by H₂S in cell stress response is reviewed providing a framework for understanding the multifaceted roles of H₂S. A mechanism-guided perspective can help open novel avenues for the exploitation of therapeutics based on H₂S-induced persulfidation in the context of diseases.

Implications of hydrogen sulfide in colorectal cancer: Mechanistic insights and diagnostic and therapeutic strategies

Hydrogen sulfide (H₂S) is an important signaling molecule in colorectal cancer (CRC). It is produced in the colon by the catalytic synthesis of the colonocytes' enzymatic systems and the release of intestinal microbes, and is oxidatively metabolized in the colonocytes' mitochondria. Both endogenous H₂S in colonic epithelial cells and exogenous H₂S in intestinal lumen contribute to the onset and progression of CRC. The up-regulation of endogenous synthetases is thought to be the cause of the elevated H₂S levels in CRC cells. Different diagnostic probes and combination therapies, as well as tumor treatment approaches through H₂S modulation, have been developed in recent years and have become active area of investigation for the diagnosis and treatment of CRC. In this review, we focus on the specific mechanisms of H₂S production and oxidative metabolism as well as the function of H₂S in the occurrence, progression, diagnosis, and treatment of CRC. We also discuss the present challenges and provide insights into the future research of this burgeoning field.

Hydrogen Sulfide Attenuates Lipopolysaccharide-Induced Inflammation via the P-glycoprotein and NF-κB Pathway in Astrocytes

Astrocyte activation is key in neurodegenerative diseases. Hydrogen sulfide (H2S) exhibits neuroprotective effects on astrocytes, although the underlying molecular mechanism remains unclear. Here, we explored the effects of H2S on lipopolysaccharide (LPS)-induced astrocyte activation and astrocyte-mediated neuroinflammation. After inducing primary astrocytes via LPS exposure, H2S levels were altered. The generation and secretion of inflammatory mediators by astrocytes and their interrelation with P-glycoprotein (P-gp), an important transporter belonging to the ABC transporter family, were assessed. Activated astrocytes showed upregulated glial fibrillary acidic protein (GFAP) mRNA expression, and significantly increased proinflammatory factor mRNA/protein expression and release. The secretory capacity of astrocytes was reduced, with significantly decreased proinflammatory factor levels in culture supernatant after P-gp inhibitor verapamil pretreatment. The increase in the intracellular H2S level inhibited LPS-induced GFAP expression and P65 nuclear entry in astrocytes. mRNA expression and release of proinflammatory factors were reduced significantly, with no significant changes in cytoplasmic protein expression. S-sulfhydration levels increased significantly with the increased concentration of sodium hydrosulfide or S-adenosyl-l-methionine addition, with only moderate changes in astrocyte P-gp expression. H2S regulates NF-κB activation, leads to S-sulfhydration of P-gp, and inhibits the biosynthesis and secretion of proinflammatory factors by astrocytes. The regulatory effects of H2S on astrocytes may have clinical value for exploring new therapeutic strategies against neurodegenerative diseases.

Surface-fill H2S-releasing silk fibroin hydrogel for brain repair through the repression of neuronal pyroptosis

Traumatic brain injury (TBI) remains the major cause of disability and mortality worldwide due to the persistent neuroinflammation and neuronal death induced by TBI. Among them, pyroptosis, a specific type of programmed cell death (PCD) triggered by inflammatory signals, plays a significant part in the pathological process after TBI. Inhibition of neuroinflammation and pyroptosis is considered a possible strategy for the treatment of TBI. In our previous study, exogenous hydrogen sulfide(H₂S) exerted a neuroprotective effect after TBI. Here, we developed a surface-fill H₂S-releasing silk fibroin (SF) hydrogel (H₂S@SF hydrogel) to achieve small-dose local administration and avoid volatile and toxic side effects. We used a controlled cortical impact (CCI) to establish a mild TBI model in mice to examine the effect of H₂S@SF hydrogel on TBI-induced pyroptosis. We found that H₂S@SF hydrogel inhibited the expression of H₂S synthase in neurons after TBI and significantly inhibited TBI-induced neuronal pyroptosis. In addition, immunofluorescence staining results showed that the necroptosis protein receptor-interacting serine/threonine-protein kinase 1 (RIPK1) partially colocalized with the pyroptosis protein Gasdermin D (GSDMD) in the same cells. H₂S@SF hydrogel can also inhibit the expression of the necroptosis protein. Moreover, H₂S@SF hydrogel also alleviates brain edema and the degree of neurodegeneration in the acute phase of TBI. The neuroprotective effect of H₂S@SF hydrogel was further confirmed by wire-grip test, open field test, Morris water maze, beam balance test, radial arm maze, tail suspension, and forced swimming test. Lastly, we also measured spared tissue volume, reactive astrocytes and activated microglia to demonstrate H₂S@SF hydrogel impacts on long-term prognosis in TBI. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel. STATEMENT OF SIGNIFICANCE: Silk fibroin (SF) hydrogel controls the release of hydrogen sulfide (H₂S) to inhibit neuronal pyroptosis and neuroinflammation in injured brain tissue. In this study, we synthesized a surface-fill H₂S-releasing silk fibroin hydrogel, which could slowly release H₂S to reshape the homeostasis of endogenous H₂S in injured neurons and inhibit neuronal pyroptosis in a mouse model of traumatic brain injury. Meanwhile, H₂S@SF hydrogel could alleviate brain edema and the degree of neurodegeneration, improve motor dysfunction, anxious behavior and memory impairment caused by TBI, reduce tissue loss and ameliorate neuroinflammation. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel.

The role of adipose tissue-derived hydrogen sulfide in inhibiting atherosclerosis

Hydrogen sulfide (H₂S) is the third gaseous signaling molecule discovered in the body after NO and CO and plays an important organismal protective role in various diseases. Within adipose tissue, related catalytic enzymes (cystathionine-β-synthetase, cystathionine-γ-lyase, and 3-mercaptopyruvate transsulfuration enzyme) can produce and release endogenous H₂S. Atherosclerosis (As) is a pathological change in arterial vessels that is closely related to abnormal glucose and lipid metabolism and a chronic inflammatory response. Previous studies have shown that H₂S can act on the cardiovascular system, exerting effects such as improving disorders of glycolipid metabolism, alleviating insulin resistance, protecting the function of vascular endothelial cells, inhibiting vascular smooth muscle cell proliferation and migration, regulating vascular tone, inhibiting the inflammatory response, and antagonizing the occurrence and development of As.