Hydrogen Sulfide Mitigates Myocardial Infarction via Promotion of Mitochondrial Biogenesis-Dependent M2 Polarization of Macrophages

An injectable hydrogel dressing for controlled release of hydrogen sulfide pleiotropically mediates the wound microenvironment

The healing of scalded wounds faces many challenges such as chronic inflammation, oxidative stress, wound infection, and difficulties in vascular and nerve regeneration. Treating a single problem cannot effectively coordinate the complex regenerative microenvironment of scalded wounds, limiting the healing and functional recovery of the skin. Therefore, there is a need to develop a multi-effect treatment plan that can adaptively address the issues at each stage of wound healing. In this study, we propose a scheme for on-demand release of hydrogen sulfide (H2S) based on the concentration of reactive oxygen species (ROS) in the wound microenvironment. This is achieved by encapsulating peroxythiocarbamate (PTCM) in the ROS-responsive polymer poly(ethylene glycol)-poly(L-methionine) (PMet) to form nanoparticles, which are loaded into a thermosensitive injectable hydrogel, F127-poly(L-aspartic acid-N-hydroxysuccinimide) (F127-P(Asp-NHS)), to create a scald dressing. The H2S released by the hydrogel dressing on demand regulates the wound microenvironment by alleviating infection, reducing oxidative stress, and remodeling inflammation, thereby accelerating the healing of full-thickness scalded wounds. This hydrogel dressing for the adaptive release of H2S has great potential in addressing complex scalded wounds associated with infection and chronic inflammation.

Recent advances in potential targets for myocardial ischemia reperfusion injury: Role of macrophages

Myocardial ischemia-reperfusion injury (MIRI) is a complex process that occurs when blood flow is restored after myocardium infarction (MI) with exacerbated tissue damage. Macrophages, essential cell type of the immune response, play an important role in MIRI. Macrophage subpopulations, namely M1 and M2, are distinguished by distinct phenotypes and functions. In MIRI, macrophages infiltrate in infarcted area, shaping the inflammatory response and influencing tissue healing. Resident cardiac macrophages interact with monocyte-derived macrophages in MIRI, and influence injury progression. Key factors including chemokines, cytokines, and toll-like receptors modulate macrophage behavior in MIRI. This review aims to address recent findings on the classification and the roles of macrophages in the myocardium, spanning from MI to subsequent MIRI, and highlights various signaling pathways implicated in macrophage polarization underlining the complexity of MIRI. This article will shed light on developing advanced therapeutic strategies for MIRI management.

Role of the 3-mercaptopyruvate sulfurtransferase in colon/colorectal cancers

The 3-mercaptopyruvate sulfurtransferase (MPST) is a protein persulfidase, occurring mainly in mitochondria. Although function of this protein in cancer cells has been already studied, no clear outcome can be postulated up to now. Therefore, we focused on the determination of function of MPST in colon (HCT116 cells)/colorectal (DLD1 cells) cancers. In silico analysis revealed that in gastrointestinal cancers, MPST together with its binding partners can be either of a high risk or might have a protective effect. Silencing of MPST gene resulted in decreased ATP, while acetyl-CoA levels were elevated. Increased apoptosis was detected in cells with silenced MPST gene, which was accompanied by decrease in mitochondrial membrane potential, but no changes in IP3 receptor's protein. Mitochondria underwent activation of fission and elevated DRP1 expression after MPST silencing. Proliferation and migration of DLD1 and HCT116 cells were markedly affected, showing the importance of MPST protein in colon/colorectal cancer development.

Endothelium-Mimicking Bilayer Vascular Grafts with Dual-Releasing of NO/H2S for Anti-Inflammation and Anticalcification

Vascular complications caused by diabetes impair the activities of endothelial nitric oxide synthase (eNOS) and cystathionine γ-lyase (CSE), resulting in decreased physiological levels of nitric oxide (NO) and hydrogen sulfide (H2S). The low bioavailability of NO and H2S hinders the endothelialization of vascular grafts. In this study, endothelium-mimicking bilayer vascular grafts were designed with spatiotemporally controlled dual releases of NO and H2S for in situ endothelialization and angiogenesis. Keratin-based H2S donor was synthesized and electrospun with poly(l-lactide-co-ε-caprolactone) (PLCL) as the outer layer of the graft to release H2S. Hyaluronic acid, one of the major glycosaminoglycans in endothelial glycocalyx, was complexed with Cu ions as the inner layer to mimic glutathione peroxidase (GPx) and maintain long-term physiological NO flux. The synergistic effects of NO and H2S of bilayer grafts selectively promoted the regeneration and migration of human umbilical vascular endothelial cells (HUVECs), while inhibiting the overproliferation of human umbilical artery smooth muscle cells (HUASMCs). Bilayer grafts could effectively prevent vascular calcification, reduce inflammation, and alleviate endothelial dysfunction. The in vivo study in a rat abdominal aorta replacement model for 1 month showed that the graft had a good patency rate and had potential for vascular remodeling in situ.

M2 exosomes modified by hydrogen sulfide promoted bone regeneration by moesin mediated endocytosis

Bone defects caused by trauma or tumor led to high medical costs and poor life quality for patients. The exosomes, micro vesicles of 30-150 nm in diameter, derived from macrophages manipulated bone regeneration. However, the role of hydrogen sulfide (H2S) in the biogenesis and function of exosomes and its effects on bone regeneration remains elusive. In this study, we used H2S slow releasing donor GYY4137 to stimulate macrophages and found that H2S promoted the polarization of M2 macrophages to increase bone regeneration of MSCs in vitro and in vivo. Moreover, we developed the H2S pre-treated M2 macrophage exosomes and found these exosomes displayed significantly higher capacity to promote bone regeneration in calvarial bone defects by re-establishing the local immune microenvironment. Mechanically, H2S treatment altered the protein profile of exosomes derived from M2 macrophages. One of the significantly enriched exosomal proteins stimulated by H2S, moesin protein, facilitated the exosomes endocytosis into MSCs, leading to activated the β-catenin signaling pathway to promote osteogenic differentiation of MSCs. In summary, H2S pretreated M2 exosomes promoted the bone regeneration of MSCs via facilitating exosomes uptake by MSCs and activate β-catenin signaling pathway. This study not only provides new strategies for promoting bone regeneration, but also provides new insights for the effect and mechanism of exosomes internalization.

Cystathionine γ-lyase S-sulfhydrates SIRT1 to attenuate myocardial death in isoprenaline-induced heart failure

OBJECTIVE

Hydrogen sulfide (H₂S), the third gasotransmitter, plays a critical role in protecting against heart failure. Sirtuin-1 (SIRT1) is a highly conserved histone deacetylase that has a protective role in the treatment of heart failure by regulating the deacetylation of some functional proteins. This study investigates the interaction between SIRT1 and H₂S in heart failure and the underlying mechanisms.

METHODS AND RESULTS

Using endogenous H₂S-generating enzyme cystathionine γ-lyase (CSE) knockout mice, we found that CSE deficiency aggravated isoprenaline-induced cardiac injury. Treatment with H₂S attenuated atrial natriuretic peptide level, brain natriuretic peptide level, improved cardiac function. Moreover, H₂S treatment potentiated myocardial SIRT1 expression. Silencing CSE abolished intracellular SIRT1 expression. Furthermore, CSE/ H₂S S-sulfhydrated SIRT1 at its zinc finger domains and augmented its zinc ion binding activity to stabilize the alpha-helix structure.

DISCUSSION

In conclusion, these results uncover that a novel mechanism that CSE/H₂S S-sulfhydrated SIRT1 to prevent heart dysfunction through modulating its activity.

Macrophage Activity under Hyperglycemia: A Study of the Effect of Resveratrol and 3H-1,2-Dithiole-3-thione on Potential Polarization

Currently, research is focused on bioactive compounds with the potential to promote macrophage polarization with the aim of reducing the development of inflammatory-related diseases. However, the effect of bioactive compounds under oxidative-stress-induced hyperglycemia on macrophage polarization has been scarcely investigated. RAW 264.7 macrophages were incubated under standard (SG) or high glucose (HG) conditions and stimulated with lipopolysaccharide (LPS) (10, 60 and 100 ng/mL) to monitor macrophage polarization after resveratrol (RSV) or 3H-1,2-dithiole-3-thione (D3T) supplementation (2.5, 5, 10 and 20 µM). Under SG and HG conditions without LPS stimulation, RSV significantly decreased macrophage viability at the highest concentration (20 µM), whereas D3T had no or low effect. LPS stimulation at 60 and 100 ng/mL, under SG and HG conditions, increased significantly macrophage viability. Both RSV and D3T significantly decreased NO production in LPS-stimulated macrophages under HG condition, whereas only D3T increased GSH levels at 100 ng/mL and normalized MDA values at 60 ng/mL of LPS under HG condition. Under 60 ng/mL LPS stimulation and HG, mRNA IL-1 and IL-6 were higher. Interestingly, RSV decreased pro-inflammatory interleukins; meanwhile, D3T increased Arg1 and IL-10 relative expression. Overall, our results indicate that hyperglycemia plays a fundamental role in the modulation of macrophage-induced inflammation in response to bioactive compounds.

Microbial metabolites in the pathogenesis of periodontal diseases: a narrative review

The purpose of this narrative review is to highlight the importance of microbial metabolites in the pathogenesis of periodontal diseases. These diseases, involving gingivitis and periodontitis are inflammatory conditions initiated and maintained by the polymicrobial dental plaque/biofilm. Gingivitis is a reversible inflammatory condition while periodontitis involves also irreversible destruction of the periodontal tissues including the alveolar bone. The inflammatory response of the host is a natural reaction to the formation of plaque and the continuous release of metabolic waste products. The microorganisms grow in a nutritious and shielded niche in the periodontal pocket, protected from natural cleaning forces such as saliva. It is a paradox that the consequences of the enhanced inflammatory reaction also enable more slow-growing, fastidious, anaerobic bacteria, with often complex metabolic pathways, to colonize and thrive. Based on complex food chains, nutrient networks and bacterial interactions, a diverse microbial community is formed and established in the gingival pocket. This microbiota is dominated by anaerobic, often motile, Gram-negatives with proteolytic metabolism. Although this alternation in bacterial composition often is considered pathologic, it is a natural development that is promoted by ecological factors and not necessarily a true "dysbiosis". Normal commensals are adapting to the gingival crevice when tooth cleaning procedures are absent. The proteolytic metabolism is highly complex and involves a number of metabolic pathways with production of a cascade of metabolites in an unspecific manner. The metabolites involve short chain fatty acids (SCFAs; formic, acetic, propionic, butyric, and valeric acid), amines (indole, scatole, cadaverine, putrescine, spermine, spermidine) and gases (NH₃, CO, NO, H₂S, H₂). A homeostatic condition is often present between the colonizers and the host response, where continuous metabolic fluctuations are balanced by the inflammatory response. While it is well established that the effect of the dental biofilm on the host response and tissue repair is mediated by microbial metabolites, the mechanisms behind the tissue destruction (loss of clinical attachment and bone) are still poorly understood. Studies addressing the functions of the microbiota, the metabolites, and how they interplay with host tissues and cells, are therefore warranted.

Development of Spleen Targeting H2S Donor Loaded Liposome for the Effective Systemic Immunomodulation and Treatment of Inflammatory Bowel Disease

Nanoparticles are primarily taken up by immune cells after systemic administration. Thus, they are considered an ideal drug delivery vehicle for immunomodulation. Because the spleen is the largest lymphatic organ and regulates the systemic immune system, there have been studies to develop spleen targeting nanoparticles for immunomodulation of cancer and immunological disorders. Inflammatory bowel disease (IBD) includes disorders involving chronic inflammation in the gastrointestinal tract and is considered incurable despite a variety of treatment options. Hydrogen sulfide (H₂S) is one of the gasotransmitters that carries out anti-inflammatory functions and has shown promising immunomodulatory effects in various inflammatory diseases including IBD. Herein, we developed a delicately tuned H₂S donor delivering liposome for spleen targeting (ST-H₂S lipo) and studied its therapeutic effects in a dextran sulfate sodium (DSS) induced colitis model. We identified the ideal PEG type and ratio of liposome for a high stability, loading efficiency, and spleen targeting effect. In the treatment of the DSS-induced colitis model, we found that ST-H₂S lipo and conventional long-circulating liposomes loaded with H₂S donors (LC-H₂S lipo) reduced the severity of colitis, whereas unloaded H₂S donors did not. Furthermore, the therapeutic effect of ST-H₂S lipo was superior to that of LC-H₂S lipo due to its better systemic immunomodulatory effect than that of LC-H₂S lipo. Our findings demonstrate that spleen targeting H₂S lipo may have therapeutic potential for IBD.

Hydrogen Sulfide Regulates Macrophage Function in Cardiovascular Diseases

Significance: Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that plays a vital role in immune system regulation. Recently, the regulation of macrophage function by H₂S has been extensively and actively recognized. Recent Advances: The mechanisms by which endogenous H₂S controls macrophage function have attracted increasing attention. The generation of endogenous H₂S from macrophages is mainly catalyzed by cystathionine-γ-lyase. H₂S is involved in the macrophage activation and inflammasome formation, which contributes to macrophage apoptosis, adhesion, chemotaxis, and polarization. In addition, H₂S has redox ability and interacts with reactive oxygen species to prevent oxidative stress. Moreover, H₂S epigenetically regulates gene expression. Critical Issues: In this article, the generation of endogenous H₂S in macrophages and its regulatory effect on macrophage function are reviewed. In addition, the signal transduction targeting macrophages by H₂S is also addressed. Finally, the potential therapeutic effect of H₂S on macrophages is discussed. Future Directions: Further experiments are required to explore the involvement of endogenous H₂S in the regulation of macrophage function in various physiological and pathophysiological processes and elucidate the mechanisms involved. Regarding the clinical translation of H₂S, further exploration of the application of H₂S in inflammation-related diseases is needed. Antioxid. Redox Signal. 38, 45-56.

Hydrogen sulfide protects against ischemic heart failure by inhibiting RIP1/RIP3/MLKL-mediated necroptosis

The aim of the present study was to explore whether hydrogen sulfide (H2S) protects against ischemic heart failure (HF) by inhibiting the necroptosis pathway. Mice were randomized into Sham, myocardial infarction (MI), MI + propargylglycine (PAG) and MI + sodium hydrosulfide (NaHS) group, respectively. The MI model was induced by ligating the left anterior descending coronary artery. PAG was intraperitoneally administered at a dose of 50 mg/kg/day for 4 weeks, and NaHS at a dose of 4mg/kg/day for the same period. At 4 weeks after MI, the following were observed: A significant decrease in the cardiac function, as evidenced by a decline in ejection fraction (EF) and fractional shortening (FS); an increase in plasma myocardial injury markers, such as creatine kinase-MB (CK-MB) and cardiac troponin I (cTNI); an increase in myocardial collagen content in the heart tissues; and a decrease of H2S level in plasma and heart tissues. Furthermore, the expression levels of necroptosis-related markers such as receptor interacting protein kinase 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) were upregulated after MI. NaHS treatment increased H2S levels in plasma and heart tissues, preserving the cardiac function by increasing EF and FS, decreasing plasma CK-MB and cTNI and reducing collagen content. Additionally, NaHS treatment significantly downregulated the RIP1/RIP3/MLKL pathway. While, PAG treatment aggravated cardiac function by activated the RIP1/RIP3/MLKL pathway. Overall, the present study concluded that H2S protected against ischemic HF by inhibiting RIP1/RIP3/MLKL-mediated necroptosis which could be a potential target treatment for ischemic HF.

Construction of a Band-Aid Like Cardiac Patch for Myocardial Infarction with Controllable H2 S Release

Excessive or persistent inflammation incites cardiomyocytes necrosis by generating reactive oxygen species in myocardial infarction (MI). Hydrogen sulfide (H₂ S), a gaseous signal molecule, can quickly permeate cells and tissues, growing concerned for its cardioprotective effects. However, short resident time and strong side effects greatly restrict its application. Herein, a complex scaffold (AAB) is first developed to slowly release H₂ S for myocardial protection by integrating alginate modified with 2-aminopyridine-5-thiocarboxamide (H₂ S donor) into albumin electrospun fibers. Next, a band-aid like patch is constructed based on AAB (center) and nanocomposite scaffold which comprises albumin scaffold and black phosphorus nanosheets (BPNSs). With near-infrared laser (808 nm), thermal energy generated by BPNSs can locally change the molecular structure of fibrous scaffold, thereby attaching patch to the myocardium. In this study, it is also demonstrated that AAB can enhance regenerative M2 macrophage and attenuate inflammatory polarization of macrophages via reduction in intracellular ROS. Eventually, this engineered cardiac patch can relieve inflammation and promote angiogenesis after MI, and thereby recover heart function, providing a promising therapeutic strategy for MI treatment.

S-Propargyl-cysteine prevents concanavalin A-induced immunological liver injury in mice

CONTEXT

S-Propargyl-cysteine (SPRC), an endogenous H₂S modulator, exerts anti-inflammatory effects on cardiovascular and neurodegenerative disease, but it remains unknown whether SPRC can prevent autoimmune hepatitis.

OBJECTIVE

To evaluate the preventive effect of SPRC on concanavalin A (Con A)-induced liver injury and uncover the underlying mechanisms.

MATERIALS AND METHODS

Mice were randomly divided into five groups: control, Con A, SPRC (5 and 10 mg/kg injected intravenously once a day for 7 days), and propargylglycine (PAG; 50 mg/kg injected intraperitoneally 0.5 h before SPRC for 7 days). All mice except the controls were intravenously injected with Con A (20 mg/kg) on day 7. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were evaluated using kits. Inflammatory cytokines (TNF-α and IFN-γ) in the blood and in the liver were detected by ELISA Kit and real-time PCR, respectively. The expression of mitogen-activated protein kinase (MAPK) pathway proteins (p-JNK and p-Akt) and apoptosis proteins (Bax and Bcl-2) was detected using western blotting.

RESULTS

SPRC reduced the levels of AST (p < 0.05) and ALT (p < 0.01) and decreased the release of the inflammatory cytokines. Mechanistically, SPRC increased H₂S level (p < 0.05) and promoted cystathionine γ-lyase (CSE) expression (p < 0.05). SPRC inhibited the MAPK pathway activation and the apoptosis pathway. All the effects of SPRC were blocked by the CSE inhibitor PAG.

CONCLUSIONS

SPRC prevents Con A-induced liver injury in mice by promoting CSE expression and producing endogenous H₂S. The mechanisms include reducing the release of inflammatory cytokines, attenuating MAPK pathway activation, and alleviating apoptosis.

On-demand therapeutic delivery of hydrogen sulfide aided by biomolecules

Hydrogen sulfide (H₂S), known as the third gasotransmitter, exerts various physiological functions including cardiac protection, angiogenesis, anti-inflammatory, and anti-cancer capability. Given its promising therapeutic potential as well as severe perniciousness if improper use, the sustained and tunable H₂S delivery systems are highly required for H₂S-based gas therapy with enhanced bioactivity and reduced side effects. To this end, a series of stimuli-responsive compounds capable of releasing H₂S (termed H₂S donors) have been designed over the past two decades to mimic the endogenous generation of H₂S and elucidate the biological functions. Further to improve the stability of H₂S donors and achieve the targeted delivery, various delivery systems have been constructed. In this review, we focus on the recent advances of an emerging subset, biomolecular-based H₂S delivery systems, which combine H₂S donors with biomolecular vectors including polysaccharide, peptide, and protein. We demonstrated their basic structures, building strategies, and therapeutic applications respectively to unfold their inherent merits endued by biomolecules including biocompatibility, biodegradability as well as expansibility. The varied development potentials of biomolecular-based H₂S delivery systems based on their specific properties are also discussed. At the end, brief future outlooks and upcoming challenges are presented as well.

The Role of Hydrogen Sulfide in Plaque Stability

Atherosclerosis is the greatest contributor to cardiovascular events and is involved in the majority of deaths worldwide. Plaque rapture or erosion precipitates life-threatening thrombi, resulting in the obstruction blood flow to the heart (acute coronary syndrome), brain (ischemic stroke) or low extremities (peripheral vascular diseases). Among these events, major causation dues to the plaque rupture. Although the initiation, procession, and precise time of controlling plaque rupture are unclear, foam cell formation and apoptosis, cell death, extracellular matrix components, protease expression and activity, local inflammation, intraplaque hemorrhage, and calcification contribute to the plaque instability. These alterations tightly associate with the function regulation of intraplaque various cell populations. Hydrogen sulfide (H₂S) is gasotransmitter derived from methionine metabolism and exerts a protective role in the genesis of atherosclerosis. Recent progress also showed H₂S mediated the plaque stability. In this review, we discuss the progress of endogenous H₂S modulation on functions of vascular smooth muscle cells, monocytes/macrophages, and T cells, and the molecular mechanism in plaque stability.

Anti-inflammatory hydrogel dressings and skin wound healing

Hydrogels are promising and widely utilized in the biomedical field. In recent years, the anti-inflammatory function of hydrogel dressings has been significantly improved, addressing many clinical challenges presented in ongoing endeavours to promote wound healing. Wound healing is a cascaded and highly complex process, especially in chronic wounds, such as diabetic and severe burn wounds, in which adverse endogenous or exogenous factors can interfere with inflammatory regulation, leading to the disruption of the healing process. Although insufficient wound inflammation is uncommon, excessive inflammatory infiltration is an almost universal feature of chronic wounds, which impedes a histological repair of the wound in a predictable biological step and chronological order. Therefore, resolving excessive inflammation in wound healing is essential. In the past 5 years, extensive research has been conducted on hydrogel dressings to address excessive inflammation in wound healing, specifically by efficiently scavenging excessive free radicals, sequestering chemokines and promoting M₁ -to-M₂ polarization of macrophages, thereby regulating inflammation and promoting wound healing. In this study, we introduced novel anti-inflammatory hydrogel dressings and demonstrated innovative methods for their preparation and application to achieve enhanced healing. In addition, we summarize the most important properties required for wound healing and discuss our analysis of potential challenges yet to be addressed.

Dual-Action Icariin-Containing Thermosensitive Hydrogel for Wound Macrophage Polarization and Hair-Follicle Neogenesis

Bone morphogenetic protein (BMP) pathway is essential for M2 macrophage polarization and hair-follicle neogenesis. Icariin, a flavonoid derived from Epimedium, is a mediator of the BMP pathway. Here, we develop a hydrogel formulation functionalized with icariin for regulation of macrophage polarization to accelerate wound healing and hair-follicle neogenesis. Compared to skin defects without icariin treatment, those treated with icariin+PEG hydrogel healed faster and had new hair follicles. Results in vivo showed that icariin+PEG hydrogel induced a higher level of M2 phenotypic transformation of macrophages. Moreover, icariin+PEG hydrogel significantly accelerated wound-repair process by reducing the invasion of inflammation, excessive deposition of collagen, immoderate activation of myofibroblasts, and increasing the regeneration of hair follicles. Furthermore, studies in vitro demonstrated that the icariin+PEG hydrogel induced macrophages to polarize to the M2 phenotype and dermal papilla cell to hair follicles. Finally, molecular analysis demonstrated that the icariin+PEG hydrogel increased the expression of BMP4 and Smad1/5 phosphorylation in skin wounds. These results demonstrate the therapeutic potential of icariin-containing thermosensitive hydrogels for inducing M2 macrophage polarization to accelerate wound healing and promote hair-follicle neogenesis by regulating the BMP pathway.

L-Cysteine Alleviates Myenteric Neuron Injury Induced by Intestinal Ischemia/Reperfusion via Inhibitin the Macrophage NLRP3-IL-1β Pathway

Ischemia/reperfusion injury is a common pathophysiological process in the clinic. It causes various injuries, multiple organ dysfunction, and even death. There are several possible mechanisms about ischemia/reperfusion injury, but the influence on intestinal myenteric neurons and the underlying mechanism are still unclear. C57BL6/J mice were used to establish the ischemia/reperfusion model in vivo. Peritoneal macrophages were used for ATP depletion and hypoxia/reoxygenation experiment in vitro. L-cysteine, as the substrate of hydrogen sulfide, is involved in many physiological and pathological processes, including inflammation, metabolism, neuroprotection, and vasodilation. In the current study, we confirmed that intestinal ischemia/reperfusion led to the injury of myenteric neurons. From experiments in vitro and in vivo, we demonstrated that L-cysteine protected myenteric neurons from the injury. AOAA reversed the protective effect of L-cysteine. Also, L-cysteine played a protective role mainly by acting on intestinal macrophages via decreasing the expression of NLRP3, cleaved caspase-1, and mature IL-1β. L-cysteine increased cystathionine beta synthase and H₂S produced by intestinal macrophages to protect myenteric mature neurons and enteric neural precursor cells from apoptosis. Moreover, the addition of IL-1β-neutralizing antibody alleviated the injury of myenteric neurons and enteric neural precursor cells caused by intestinal ischemia/reperfusion. Our study provided a new target for the protection of myenteric neurons in clinical intestinal ischemia/reperfusion injury.

A two photon fluorescent probe for highly selective detection and endogenous imaging of hydrogen sulfide

Hydrogen sulfide (H₂S), one of redox-active sulfur species, is known as a signaling molecule and an antioxidant in biological tissues to maintain cellular functions. The development of selective and sensitive H₂S detection is important to understand the role of H₂S in vivo. Herein, a new two-photon probe NNE was developed to detect hydrogen sulfide using 6-acetyl-N-methyl-2-naphthylamine with an attachment of 7-nitrobenzo-oxadiazole. The probe NNE exhibits high selectivity towards hydrogen sulfide over other anions. Nucleophilic substitution of H₂S leads to a turn-on response with 28-fold enhancement in quantum yield (from 0.004 to 0.117). NNE shows a high sensitivity towards hydrogen sulfide with an extremely low detection limit at 6.8 nM. Furthermore, the probe NNE exhibits two-photon excited fluorescence, making it a suitable probe for monitoring H₂S distribution in live cells and tissues without background fluorescence interference.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Bioresponsive nano-antibacterials for H2S-sensitized hyperthermia and immunomodulation against refractory implant-related infections

There is an increasingly growing demand for nonantibiotic strategies to overcome drug resistance in bacterial biofilm infections. Here, a novel "gas-sensitized hyperthermia" strategy is proposed for appreciable bacteria killing by the smart design of a metal-organic framework (MOF)-sealed Prussian blue-based nanocarrier (MSDG). Once the biofilm microenvironment (BME) is reached, the acidity-activated MOF degradation allows the release of diallyl trisulfide and subsequent glutathione-responsive generation of hydrogen sulfide (H₂S) gas. Upon near-infrared irradiation, H₂S-sensitized hyperthermia arising from MSDG can efficiently eliminate biofilms through H₂S-induced extracellular DNA damage and heat-induced bacterial death. The generated H₂S in the biofilm can stimulate the polarization of macrophages toward M2 phenotype for reshaping immune microenvironment. Subsequently, the secretion of abundant regeneration-related cytokines from M2 macrophages accelerates tissue regeneration by reversing the infection-induced pro-inflammatory environment in an implant-related infection model. Collectively, such BME-responsive nano-antibacterials can achieve biofilm-specific H₂S-sensitized thermal eradiation and immunomodulatory tissue remodeling, thus realizing the renaissance of precision treatment of refractory implant-related infections.

Nanoparticles to Target and Treat Macrophages: The Ockham's Concept?

Nanoparticles are nanomaterials with three external nanoscale dimensions and an average size ranging from 1 to 1000 nm. Nanoparticles have gained notoriety in technological advances due to their tunable physical, chemical, and biological characteristics. However, the administration of functionalized nanoparticles to living beings is still challenging due to the rapid detection and blood and tissue clearance by the mononuclear phagocytic system. The major exponent of this system is the macrophage. Regardless the nanomaterial composition, macrophages can detect and incorporate foreign bodies by phagocytosis. Therefore, the simplest explanation is that any injected nanoparticle will be probably taken up by macrophages. This explains, in part, the natural accumulation of most nanoparticles in the spleen, lymph nodes, and liver (the main organs of the mononuclear phagocytic system). For this reason, recent investigations are devoted to design nanoparticles for specific macrophage targeting in diseased tissues. The aim of this review is to describe current strategies for the design of nanoparticles to target macrophages and to modulate their immunological function involved in different diseases with special emphasis on chronic inflammation, tissue regeneration, and cancer.

New Therapeutic Approaches Using Hydrogen Sulfide Donors in Inflammation and Immune Response

Significance: Inflammation and immune response are associated with many pathological disorders, including rheumatoid arthritis, lupus, heart failure, and cancer(s). In recent times, important roles of hydrogen sulfide (H₂S) have been evidenced by researchers in inflammatory responses, as well as immunomodulatory effects in several disease models. Recent Advances: Numerous biological targets, including cytochrome c oxidase, various kinases, enzymes involved in epigenetic changes, transcription factors, namely nuclear factor kappa B and nuclear factor erythroid 2-related factor 2, and several membrane ion channels, are shown to be sensitive to H₂S and have been widely investigated in various preclinical models. Critical Issues: A complete understanding of the effects of H₂S in inflammatory and immune response is vital in the development of novel H₂S generating therapeutics. In this review, the biological effects and pharmacological properties of H₂S in inflammation and immune response are addressed. The review also covers some of the novel H₂S releasing prodrugs developed in recent years as tools to study this fascinating molecule. Future Directions: H₂S plays important roles in inflammation and immunity-related processes. Future researches are needed to further assess the immunomodulatory effects of H₂S and to assist in the design of more efficient H₂S carrier systems, or drug formulations, for the management of immune-related conditions in humans. Antioxid. Redox Signal. 35, 341-356.

Hydrogen Sulfide Attenuated Sepsis-Induced Myocardial Dysfunction Through TLR4 Pathway and Endoplasmic Reticulum Stress

Aims: We examined the change in endogenous hydrogen sulfide (H₂S) production and its role in sepsis-induced myocardial dysfunction (SIMD). Results: Significant elevations in plasma cardiac troponin I (cTnI), creatine kinase (CK), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were noted in SIMD patients, whereas left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), and plasma H₂S were significantly decreased relative to those in the controls. Plasma H₂S was linearly related to LVEF and LVFS. Subsequently, an SIMD model was developed in mice by injecting lipopolysaccharide (LPS), and NaHS, an H₂S donor, was used to elucidate the pathophysiological role of H₂S. The mice showed decreased ventricular function and increased levels of TNF-α, IL-1β, cTnI, and CK after LPS injections. Toll-like receptor (TLR) 4 protein and endoplasmic reticulum stress (ERS) proteins were over expressed in the SIMD mice. All of the parameters above showed more noticeable variations in cystathionine γ-lyase knockout mice relative to those in wild type mice. The administration of NaHS could improve ventricular function and attenuate inflammation and ERS in the heart. Conclusion: Overall, these findings indicated that endogenous H₂S deficiency contributed to SIMD and exogenous H₂S ameliorated sepsis-induced myocardial dysfunction by suppressing inflammation and ERS via inhibition of the TLR4 pathway.

Spaceflight and simulated microgravity suppresses macrophage development via altered RAS/ERK/NFκB and metabolic pathways

Spaceflight-associated immune system weakening ultimately limits the ability of humans to expand their presence beyond the earth's orbit. A mechanistic study of microgravity-regulated immune cell function is necessary to overcome this challenge. Here, we demonstrate that both spaceflight (real) and simulated microgravity significantly reduce macrophage differentiation, decrease macrophage quantity and functional polarization, and lead to metabolic reprogramming, as demonstrated by changes in gene expression profiles. Moreover, we identified RAS/ERK/NFκB as a major microgravity-regulated pathway. Exogenous ERK and NFκB activators significantly counteracted the effect of microgravity on macrophage differentiation. In addition, microgravity also affects the p53 pathway, which we verified by RT-qPCR and Western blot. Collectively, our data reveal a new mechanism for the effects of microgravity on macrophage development and provide potential molecular targets for the prevention or treatment of macrophage differentiation deficiency in spaceflight.

Macrophage p47phox regulates pressure overload-induced left ventricular remodeling by modulating IL-4/STAT6/PPARγ signaling

NADPH oxidase (Nox) mediates ROS production and contributes to cardiac remodeling. However, macrophage p47^phox, a Nox subunit regulating cardiac remodeling, is unclear. We aimed to investigate the role of macrophage p47^phox in hypertensive cardiac remodeling. Pressure-overload induced by Angiotensin II (AngII) for two weeks in young adult male p47^phox deficient (KO) mice showed aggravated cardiac dysfunction and hypertrophy as indicated from echocardiographic and histological studies in comparison with wild-type littermates (WT). Additionally, LV of AngII-infused KO mice showed augmented interstitial fibrosis, collagen deposition and, myofibroblasts compared to AngII-infused WT mice. Moreover, these changes in AngII-infused KO mice correlated well with the gene analysis of hypertrophic and fibrotic markers. Similar results were also found in the transverse aortic constriction model. Further, AngII-infused KO mice showed elevated circulating immunokines and increased LV leukocytes infiltration and CD206⁺ macrophages compared to AngII-infused WT mice. Likewise, LV of AngII-infused KO mice showed upregulated mRNA expression of anti-inflammatory/pro-fibrotic M2 macrophage markers (Ym1, Arg-1) compared to AngII-infused WT mice. AngII and IL-4 treated bone marrow-derived macrophages (BMDMs) from KO mice showed upregulated M2 macrophage markers and STAT6 phosphorylation (Y641) compared to AngII and IL-4 treated WT BMDMs. These alterations were at least partly mediated by macrophage as bone marrow transplantation from KO mice into WT mice aggravated cardiac remodeling. Mechanistically, AngII-infused KO mice showed hyperactivated IL-4/STAT6/PPARγ signaling and downregulated SOCS3 expression compared to AngII-infused WT mice. Our studies show that macrophage p47^phox limits anti-inflammatory signaling and extracellular matrix remodeling in response to pressure-overload.

Macrophage Polarization in Cardiac Tissue Repair Following Myocardial Infarction

Cardiovascular disease is the leading cause of mortality and morbidity around the globe, creating a substantial socio-economic burden as a result. Myocardial infarction is a significant contributor to the detrimental impact of cardiovascular disease. The death of cardiomyocytes following myocardial infarction causes an immune response which leads to further destruction of tissue, and subsequently, results in the formation of non-contractile scar tissue. Macrophages have been recognized as important regulators and participants of inflammation and fibrosis following myocardial infarction. Macrophages are generally classified into two distinct groups, namely, classically activated, or M1 macrophages, and alternatively activated, or M2 macrophages. The phenotypic profile of cardiac macrophages, however, is much more diverse and should not be reduced to these two subsets. In this review, we describe the phenotypes and functions of macrophages which are present in the healthy, as well as the infarcted heart, and analyze them with respect to M1 and M2 polarization states. Furthermore, we discuss therapeutic strategies which utilize macrophage polarization towards an anti-inflammatory or reparative phenotype for the treatment of myocardial infarction.

Energy, Entropy and Quantum Tunneling of Protons and Electrons in Brain Mitochondria: Relation to Mitochondrial Impairment in Aging-Related Human Brain Diseases and Therapeutic Measures

Adult human brains consume a disproportionate amount of energy substrates (2-3% of body weight; 20-25% of total glucose and oxygen). Adenosine triphosphate (ATP) is a universal energy currency in brains and is produced by oxidative phosphorylation (OXPHOS) using ATP synthase, a nano-rotor powered by the proton gradient generated from proton-coupled electron transfer (PCET) in the multi-complex electron transport chain (ETC). ETC catalysis rates are reduced in brains from humans with neurodegenerative diseases (NDDs). Declines of ETC function in NDDs may result from combinations of nitrative stress (NS)-oxidative stress (OS) damage; mitochondrial and/or nuclear genomic mutations of ETC/OXPHOS genes; epigenetic modifications of ETC/OXPHOS genes; or defects in importation or assembly of ETC/OXPHOS proteins or complexes, respectively; or alterations in mitochondrial dynamics (fusion, fission, mitophagy). Substantial free energy is gained by direct O2-mediated oxidation of NADH. Traditional ETC mechanisms require separation between O2 and electrons flowing from NADH/FADH2 through the ETC. Quantum tunneling of electrons and much larger protons may facilitate this separation. Neuronal death may be viewed as a local increase in entropy requiring constant energy input to avoid. The ATP requirement of the brain may partially be used for avoidance of local entropy increase. Mitochondrial therapeutics seeks to correct deficiencies in ETC and OXPHOS.

Hydrogen Sulfide, an Endogenous Stimulator of Mitochondrial Function in Cancer Cells

Hydrogen sulfide (H₂S) has a long history as toxic gas and environmental hazard; inhibition of cytochrome c oxidase (mitochondrial Complex IV) is viewed as a primary mode of its cytotoxic action. However, studies conducted over the last two decades unveiled multiple biological regulatory roles of H₂S as an endogenously produced mammalian gaseous transmitter. Cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST) are currently viewed as the principal mammalian H₂S-generating enzymes. In contrast to its inhibitory (toxicological) mitochondrial effects, at lower (physiological) concentrations, H₂S serves as a stimulator of electron transport in mammalian mitochondria, by acting as an electron donor—with sulfide:quinone oxidoreductase (SQR) being the immediate electron acceptor. The mitochondrial roles of H₂S are significant in various cancer cells, many of which exhibit high expression and partial mitochondrial localization of various H₂S producing enzymes. In addition to the stimulation of mitochondrial ATP production, the roles of endogenous H₂S in cancer cells include the maintenance of mitochondrial organization (protection against mitochondrial fission) and the maintenance of mitochondrial DNA repair (via the stimulation of the assembly of mitochondrial DNA repair complexes). The current article overviews the state-of-the-art knowledge regarding the mitochondrial functions of endogenously produced H₂S in cancer cells.

Hydrogen sulfide and vascular regulation - An update

BACKGROUND

Hydrogen sulfide (H₂S) is considered to be the third gasotransmitter after carbon monoxide (CO) and nitric oxide (NO). It plays an important role in the regulation of vascular homeostasis. Vascular remodeling have has proved to be related to the impaired H₂S generation.

AIM OF REVIEW

This study aimed to summarize and discuss current data about the function of H₂S in vascular physiology and pathophysiology as well as the underlying mechanisms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Endogenous hydrogen sulfide (H₂S) as a third gasotransmitter is primarily generated by the enzymatic pathways and regulated by several metabolic pathways. H₂S as a physiologic vascular regulator, inhibits proliferation, regulates its apoptosis and autophagy of vascular cells and controls the vascular tone. Accumulating evidence shows that the downregulation of H₂S pathway is involved in the pathogenesis of a variety of vascular diseases, such as hypertension, atherosclerosis and pulmonary hypertension. Alternatively, H₂S supplementation may greatly help to prevent the progression of the vascular diseases by regulating vascular tone, inhibiting vascular inflammation, protecting against oxidative stress and proliferation, and modulating vascular cell apoptosis, which has been verified in animal and cell experiments and even in the clinical investigation. Besides, H₂S system and angiotensin-converting enzyme (ACE) inhibitors play a vital role in alleviating ischemic heart disease and left ventricular dysfunction. Notably, sulfhydryl-containing ACEI inhibitor zofenopril is superior to other ACE inhibitors due to its capability of H₂S releasing, in addition to ACE inhibition. The design and application of novel H₂S donors have significant clinical implications in the treatment of vascular-related diseases. However, further research regarding the role of H₂S in vascular physiology and pathophysiology is required.

Hydrogen Sulfide: a Novel Immunoinflammatory Regulator in Rheumatoid Arthritis

Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has been shown to have vasodilative, anti-oxidative, anti-inflammatory, and cytoprotective activities. Increasing evidence also indicates that H₂S can suppress the production of inflammatory mediators by immune cells, for example, T cells and macrophages. Inflammation is closely related to an immune response in several diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE), and cancer. Considering these biological effects of H₂S, a potential role in the treatment of immune-related RA is being exploited. In the present review, we will provide an overview of the therapeutic potential of H₂S in RA treatment.

The Role of Host-Generated H2S in Microbial Pathogenesis: New Perspectives on Tuberculosis

For centuries, hydrogen sulfide (H₂S) was considered primarily as a poisonous gas and environmental hazard. However, with the discovery of prokaryotic and eukaryotic enzymes for H₂S production, breakdown, and utilization, H₂S has emerged as an important signaling molecule in a wide range of physiological and pathological processes. Hence, H₂S is considered a gasotransmitter along with nitric oxide (•NO) and carbon monoxide (CO). Surprisingly, despite having overlapping functions with •NO and CO, the role of host H₂S in microbial pathogenesis is understudied and represents a gap in our knowledge. Given the numerous reports that followed the discovery of •NO and CO and their respective roles in microbial pathogenesis, we anticipate a rapid increase in studies that further define the importance of H₂S in microbial pathogenesis, which may lead to new virulence paradigms. Therefore, this review provides an overview of sulfide chemistry, enzymatic production of H₂S, and the importance of H₂S in metabolism and immunity in response to microbial pathogens. We then describe our current understanding of the role of host-derived H₂S in tuberculosis (TB) disease, including its influences on host immunity and bioenergetics, and on Mycobacterium tuberculosis (Mtb) growth and survival. Finally, this review discusses the utility of H₂S-donor compounds, inhibitors of H₂S-producing enzymes, and their potential clinical significance.

The role of hydrogen sulphide signalling in macrophage activation

Hydrogen sulphide (H₂S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H₂S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H₂S in particular, is increasingly being appreciated. Endogenous H₂S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H₂S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H₂S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H₂S studies in macrophages, and to discuss with focus on the therapeutic potential of H₂S donors by targeting macrophages. The feasibility of H₂S signalling component as a macrophage biomarker under disease conditions would be also discussed.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

Hydrogen Sulfide Treatment Improves Post-Infarct Remodeling and Long-Term Cardiac Function in CSE Knockout and Wild-Type Mice

Hydrogen sulfide (H₂S) is recognized as an endogenous gaseous signaling molecule generated by cystathionine γ-lyase (CSE) in cardiovascular tissues. H₂S up-regulation has been shown to reduce ischemic injury, and H₂S donors are cardioprotective in rodent models when administered concurrent with myocardial ischemia. We evaluated the potential utility of H₂S therapy in ameliorating cardiac remodeling with administration delayed until 2 h post-infarction in mice with or without cystathionine γ-lyase gene deletion (CSE^−/−). The slow-release H₂S donor, GYY4137, was administered from 2 h after surgery and daily for 28 days following myocardial infarction (MI) induced by coronary artery ligation, comparing responses in CSE^−/− with wild-type (WT) mice (n = 5–10/group/genotype). Measures of cardiac function and expression of key genes associated with cardiac hypertrophy, fibrosis, and apoptosis were documented in atria, ventricle, and kidney tissues. Post-MI GYY4137 administration reduced infarct area and restored cardiac function, accompanied by reduction of the elevated ventricular expression of genes mediating cardiac remodeling to near-normal levels. Few differences between WT and CSE^−/− mice were observed, except CSE^−/− mice had higher blood pressures, and higher atrial Mir21a expression across all treatment groups. These findings suggest endogenous CSE gene deletion does not substantially exacerbate the long-term response to MI. Moreover, the H₂S donor GYY4137 administered after onset of MI preserves cardiac function and protects against adverse cardiac remodeling in both WT and CSE-deficient mice.

Endogenous hydrogen sulfide sulfhydrates IKKβ at cysteine 179 to control pulmonary artery endothelial cell inflammation

BACKGROUND

Pulmonary artery endothelial cell (PAEC) inflammation is a critical event in the development of pulmonary arterial hypertension (PAH). However, the pathogenesis of PAEC inflammation remains unclear.

METHODS

Purified recombinant human inhibitor of κB kinase subunit β (IKKβ) protein, human PAECs and monocrotaline-induced pulmonary hypertensive rats were employed in the study. Site-directed mutagenesis, gene knockdown or overexpression were conducted to manipulate the expression or activity of a target protein.

RESULTS

We showed that hydrogen sulfide (H2S) inhibited IKKβ activation in the cell model of human PAEC inflammation induced by monocrotaline pyrrole-stimulation or knockdown of cystathionine γ-lyase (CSE), an H2S generating enzyme. Mechanistically, H2S was proved to inhibit IKKβ activity directly via sulfhydrating IKKβ at cysteinyl residue 179 (C179) in purified recombinant IKKβ protein in vitro, whereas thiol reductant dithiothreitol (DTT) reversed H2S-induced IKKβ inactivation. Furthermore, to demonstrate the significance of IKKβ sulfhydration by H2S in the development of PAEC inflammation, we mutated C179 to serine (C179S) in IKKβ. In purified IKKβ protein, C179S mutation of IKKβ abolished H2S-induced IKKβ sulfhydration and the subsequent IKKβ inactivation. In human PAECs, C179S mutation of IKKβ blocked H2S-inhibited IKKβ activation and PAEC inflammatory response. In pulmonary hypertensive rats, C179S mutation of IKKβ abolished the inhibitory effect of H2S on IKKβ activation and pulmonary vascular inflammation and remodeling.

CONCLUSION

Collectively, our in vivo and in vitro findings demonstrated, for the first time, that endogenous H2S directly inactivated IKKβ via sulfhydrating IKKβ at Cys179 to inhibit nuclear factor-κB (NF-κB) pathway activation and thereby control PAEC inflammation in PAH.

Hydrogen sulfide inhibits cigarette smoke-induced inflammation and injury in alveolar epithelial cells by suppressing PHD2/HIF-1α/MAPK signaling pathway

Chronic obstructive pulmonary fibrosis (COPD) is a chronic and fatal lung disease with few treatment options. Sodium hydrosulfide (NaHS), a donor of hydrogen sulfide (H2S), was found to alleviate cigarette smoke (CS)-induced emphysema in mice, however, the underlying mechanisms have not yet been clarified. In this study, we investigated its effects on COPD in a CS-induced mouse model in vivo and in cigarette smoke extract (CSE)-stimulated alveolar epithelial A549 cells in vitro. The results showed that NaHS not only relieved emphysema, but also improved pulmonary function in CS-exposed mice. NaHS significantly increased the expressions of tight junction proteins (i.e., ZO-1, Occludin and claudin-1), and reduced apoptosis and secretion of pro-inflammatory cytokines (i.e., TNF-α, IL-6 and IL-1β) in CS-exposed mouse lungs and CSE-incubated A549 cells, indicating H2S inhibits CS-induced inflammation, injury and apoptosis in alveolar epithelial cells. NaHS also upregulated prolyl hydroxylase (PHD)2, and suppressed hypoxia-inducible factor (HIF)-1α expression in vivo and in vitro, suggesting H2S inhibits CS-induced activation of PHD2/HIF-1α axis. Moreover, NaHS inhibited CS-induced phosphorylation of ERK, JNK and p38 MAPK in vivo and in vitro, and treatment with their inhibitors reversed CSE-induced ZO-1 expression and inflammation in A549 cells. These results suggest that NaHS may prevent emphysema via the suppression of PHD2/HIF-1α/MAPK signaling pathway, and subsequently inhibition of inflammation, epithelial cell injury and apoptosis, and may be a novel strategy for the treatment of COPD.

Mechanical load-induced H2S production by periodontal ligament stem cells activates M1 macrophages to promote bone remodeling and tooth movement via STAT1

Background

Tooth movement is a unique bone remodeling process induced by mechanical stimulation. Macrophages are important in mediating inflammatory processes during mechanical load-induced tooth movement. However, how macrophages are regulated under mechanical stimulation remains unclear. Mesenchymal stem cells (MSCs) can modulate macrophage polarization during bone remodeling. Hydrogen sulfide (H₂S) can be produced by MSCs and have been linked to bone homeostasis. Therefore, this study aimed to investigate whether H₂S contributed to periodontal ligament stem cell (PDLSC)-regulated macrophage polarization and bone remodeling under mechanical stimulation.

Methods

An experimental mechanical load-induced tooth movement animal model was established. Changes in cystathionine-β-synthase (CBS), markers of M1/M2 macrophages, tooth movement distance, and the number of osteoclasts were examined. The conditioned medium of PDLSCs with or without mechanical loading was utilized to treat THP-1 derived macrophages for 24 h to further investigate the effect of PDLSCs on macrophage polarization. Different treatments with H₂S donor, CBS inhibitor, or the inhibitor of STAT1 were used to investigate the related mechanism. Markers of M1/M2 polarization and STAT1 pathway expression were evaluated in macrophages.

Results

Mechanical load promoted tooth movement and increased the number of M1-like macrophages, M1-associated pro-inflammatory cytokines, and the expression of CBS on the compression side of the periodontal ligament. The injection of CBS inhibitor or H₂S donor could further repress or increase the number of M1-like macrophages, tartrate-resistant acid phosphatase-positive osteoclasts and the distance of tooth movement. Mechanistically, load-induced PDLSCs enhanced H₂S production, which increased the expression of M1-associated cytokines in macrophages. These effects could be blocked by the administration of CBS inhibitor. Moreover, load-induced H₂S steered M1 macrophage polarization via the STAT1 signaling pathway.

Conclusions

These data suggest a novel mechanism indicating that mechanical load-stimulated PDLSCs produce H₂S to polarize macrophages toward the M1 phenotype via the STAT1 signaling pathway, which contributes to bone remodeling and tooth movement process. These results provide new insights into the role of PDLSCs in regulating macrophage polarization and mediating bone remodeling under mechanical stimulation, and indicate that appropriate H₂S supplementation may accelerate tooth movement.

Electronic supplementary material

Supplementary information accompanies this paper at 10.1186/s13287-020-01607-9.

Salvianolic acid B regulates macrophage polarization in ischemic/reperfused hearts by inhibiting mTORC1-induced glycolysis

Macrophages play important roles in the healing and remodeling of cardiac tissues after myocardial ischemia/reperfusion (MI/R) injury. Here we investigated the potential effects of salvianolic acid B (SalB), one of the abundant and bioactive compounds extracted from Chinese herb Salvia Miltiorrhiza (Danshen), on macrophage-mediated inflammation after MI/R and the underlying mechanisms. In primary cultured bone marrow-derived macrophages (BMDMs), SalB attenuated lipopolysaccharide (LPS)-induced M1 biomarkers (IL-6, iNOS, CCL2 and TNF-α) mRNA expression in a concentration-dependent manner. In contrast, M2 biomarkers (Arg1, Clec10a and Mrc) mRNA levels following interleukinin-4 (IL-4) stimulation were significantly upregulated by SalB. In addition, LPS stimulation potently induced transcriptional upregulation of RagD, an important activation factor of mammalian target of rapamycin complex 1 (mTORC1). Interestingly, SalB inhibited RagD upregulation and mTORC1 activation, decreased glycolysis, and reduced inflammatory cytokine production in LPS-stimulated macrophages, all of which were blunted in RagD knockdown macrophages. In mice subjected to MI/R, SalB treatment decreased cardiac M1-macrophages and increased M2-macrophages at 3 days post-MI/R, followed by decreased collagen deposition and ameliorated cardiac dysfunction at 7 days post-MI/R. Collectively, our data have shown that SalB decreases M1-polarized macrophages in MI/R hearts via inhibiting mTORC1-dependent glycolysis, which might contribute to alleviated inflammation and improved cardiac dysfunction afforded by SalB after MI/R.

H2S alleviates renal injury and fibrosis in response to unilateral ureteral obstruction by regulating macrophage infiltration via inhibition of NLRP3 signaling

Renal fibrosis is a key pathological feature in chronic kidney diseases (CKDs). Dysregulation of hydrogen sulfide (H₂S) homeostasis is implicated in the pathogenesis of CKDs. Here, C57/BL6 mice were allocated to Sham and unilateral ureteral obstruction (UUO) groups, which were treated with NaHS or NLRP3 inflammasome inhibitor 16673-34-0 for 3-14 days. UUO mice displayed downregulation of H₂S production and increased macrophage infiltration in obstructed kidneys. H₂S donor NaHS treatment attenuated renal damage and fibrosis and inhibited M1 and M2 macrophage infiltration. NLPR3 inflammasome was activated and levels of phosphorylated nuclear factor κB (NF-κB) p65 subunit, phosphorylated signal transducer and activator of transcription 6 (STAT6) and interleukin (IL)-4 protein were increased in the kidneys after UUO. NLRP3 inhibitor inactivated NF-κB and IL-4/STAT6 signaling, suppressed M1 and M2 macrophage infiltration and attenuated renal damage and fibrosis in UUO mice. NaHS treatment also suppressed NLRP3, NF-κB and IL-4/STAT6 activation in the obstructed kidneys. In conclusion, the therapeutic effects of H₂S on UUO-induced renal injury and fibrosis are at least in part by inhibition of M1 and M2 macrophage infiltration. H₂S suppresses NLRP3 activation and subsequently inactivates NF-κB and IL-4/STAT6 signaling, which may contribute to the anti-inflammatory and anti-fibrotic effects of H₂S.

Hydrogen sulfide signaling in mitochondria and disease

Hydrogen sulfide can signal through 3 distinct mechanisms: 1) reduction and/or direct binding of metalloprotein heme centers, 2) serving as a potent antioxidant through reactive oxygen species/reactive nitrogen species scavenging, or 3) post-translational modification of proteins by addition of a thiol (-SH) group onto reactive cysteine residues: a process known as persulfidation. Below toxic levels, hydrogen sulfide promotes mitochondrial biogenesis and function, thereby conferring protection against cellular stress. For these reasons, increases in hydrogen sulfide and hydrogen sulfide-producing enzymes have been implicated in several human disease states. This review will first summarize our current understanding of hydrogen sulfide production and metabolism, as well as its signaling mechanisms; second, this work will detail the known mechanisms of hydrogen sulfide in the mitochondria and the implications of its mitochondrial-specific impacts in several pathologic conditions.-Murphy, B., Bhattacharya, R., Mukherjee, P. Hydrogen sulfide signaling in mitochondria and disease.

Macrophage polarization in atherosclerosis

Atherosclerosis is a chronic inflammatory response that increases the risk of cardiovascular diseases. An in-depth study of the pathogenesis of atherosclerosis is critical for the treatment of atherosclerotic cardiovascular disease. The development of atherosclerosis involves many cells, such as endothelial cells, vascular smooth muscle cells, macrophages, and others. The considerable effects of macrophages in atherosclerosis are inextricably linked to macrophage polarization and the resulting phenotype. Moreover, the significant impact of macrophages on atherosclerosis depend not only on the function of the different macrophage phenotypes but also on the relative ratio of different phenotypes in the plaque. Research on atherosclerosis therapy indicates that the reduced plaque size and enhanced stability are partly due to modulating macrophage polarization. Therefore, regulating macrophage polarization and changing the proportion of macrophage phenotypes in plaques is a new therapeutic approach for atherosclerosis. This review provides a new perspective for atherosclerosis therapy by summarizing the relationship between macrophage polarization and atherosclerosis, as well as treatment targeting macrophage polarization.

Hydrogen Sulfide in Bone Tissue Regeneration and Repair: State of the Art and New Perspectives

The importance of hydrogen sulfide (H₂S) in the regulation of multiple physiological functions has been clearly recognized in the over 20 years since it was first identified as a novel gasotransmitter. In bone tissue H₂S exerts a cytoprotective effect and promotes bone formation. Just recently, the scientific community has begun to appreciate its role as a therapeutic agent in bone pathologies. Pharmacological administration of H₂S achieved encouraging results in preclinical studies in the treatment of systemic bone diseases, such as osteoporosis; however, a local delivery of H₂S at sites of bone damage may provide additional opportunities of treatment. Here, we highlight how H₂S stimulates multiple signaling pathways involved in various stages of the processes of bone repair. Moreover, we discuss how material science and chemistry have recently developed biomaterials and H₂S-donors with improved features, laying the ground for the development of H₂S-releasing devices for bone regenerative medicine. This review is intended to give a state-of-the-art description of the pro-regenerative properties of H₂S, with a focus on bone tissue, and to discuss the potential of H₂S-releasing scaffolds as a support for bone repair.

ZYZ-803 Mitigates Endoplasmic Reticulum Stress-Related Necroptosis after Acute Myocardial Infarction through Downregulating the RIP3-CaMKII Signaling Pathway

Acute myocardial infarction (AMI) is a leading cause of morbidity and mortality worldwide, and both cardiac necroptosis and endoplasmic reticulum stress (ERS) have been involved in the pathophysiology of AMI. ZYZ-803 is a hybrid molecule of a dual donor for gasotransmitters H₂S and NO. The aim of the present study is to investigate the antinecroptosis role and potential mechanisms of ZYZ-803 in the setting of ERS during AMI injury. In vivo, ZYZ-803 preserves cardiac function and reduces infarct size significantly after 24-hour left coronary artery ligation through revising H₂S and NO imbalance. In addition, ZYZ-803 relieves ERS and necroptosis in an AMI heart. In vitro, ZYZ-803 ameliorates ERS-related necroptosis induced by tunicamycin, and such effect has been depending on the receptor-interacting protein 3- (RIP3-) Ca²⁺-calmodulin-dependent protein kinase (CaMKII) signaling pathway. These findings have identified a novel antinecroptosis potential of ZYZ-803, providing a valuable candidate for cardioprotection in acute myocardial ischemia.

Conductive Hydrogen Sulfide-Releasing Hydrogel Encapsulating ADSCs for Myocardial Infarction Treatment

Hydrogen sulfide (H₂S) exhibits extensive protective actions in cardiovascular systems, such as anti-inflammatory and stimulating angiogenesis, but its therapeutic potential is severely discounted by the short half-life and the poorly controlled releasing behavior. Herein, we developed a macromolecular H₂S prodrug by grafting 2-aminopyridine-5-thiocarboxamide (a small-molecule H₂S donor) on partially oxidized alginate (ALG-CHO) to mimic the slow and continuous release of endogenous H₂S. In addition, tetraaniline (a conductive oligomer) and adipose-derived stem cells (ADSCs) were introduced to form a stem cell-loaded conductive H₂S-releasing hydrogel through the Schiff base reaction between ALG-CHO and gelatin. The hydrogel exhibited adhesive property to ensure a stable anchoring to the wet and beating hearts. After myocardial injection, longer ADSCs retention period and elevated sulfide concentration in rat myocardium were demonstrated, accompanied by upregulation of cardiac-related mRNA (Cx43, α-SMA, and cTnT) and angiogenic factors (VEGFA and Ang-1) and downregulation of inflammatory factors (tumor necrosis factor-α). Echocardiography and histological analysis strongly demonstrated an increase in the ejection fraction value and smaller infarction size, suggesting a remarkable improvement of the cardiac functions of Sprague-Dawley rats. The ADSC-loaded conductive hydrogen sulfide-releasing hydrogel dramatically promoted the therapeutic effects, offering a promising therapeutic strategy for treating myocardial infarction.

Regulation of Type 2 Immunity in Myocardial Infarction

Type 2 immunity participates in the pathogeneses of helminth infection and allergic diseases. Emerging evidence indicates that the components of type 2 immunity are also involved in maintaining metabolic hemostasis and facilitating the healing process after tissue injury. Numerous preclinical studies have suggested regulation of type 2 immunity-related cytokines, such as interleukin-4, -13, and -33, and cell types, such as M2 macrophages, mast cells, and eosinophils, affects cardiac functions after myocardial infarction (MI), providing new insights into the importance of immune modulation in the infarcted heart. This review provides an overview of the functions of these cytokines and cells in the setting of MI as well as their potential to predict the severity and prognosis of MI.

Cystathionine γ-lyase deficiency aggravates obesity-related insulin resistance via FoxO1-dependent hepatic gluconeogenesis

Hepatic gluconeogenesis makes a significant contribution to the pathogenesis of obesity and its related insulin resistance. Cystathionine γ-lyase (CSE; also cystathionase), a principal hydrogen sulfide (H₂S)-synthesizing enzyme in the liver, is involved in glucose and lipid metabolism disorders. However, the roles and precise mechanisms of CSE/H₂S in obesity and its related insulin resistance remain obscure. Here we show that CSE knockout exacerbated high-fat diet-induced mouse obesity as well as its related insulin resistance. Further study elucidated that the inhibition of insulin and AMPK signaling pathways by CSE deficiency resulted in nuclear accumulation of Forkhead box protein O1 and subsequently promoted hepatic gluconeogenesis. These phenomena can be reversed by NaHS supplementation. However, in wild-type mice, NaHS treatment ameliorates high fat diet-induced obesity and metabolism disorders, indicating that maintaining an appropriate level of H₂S is critical for its mutual change of positive and negative effects of obesity-associated insulin resistance. Our study reveals a double-edged sword effect and a novel mechanism for CSE/H₂S in obesity associated with insulin resistance and provides evidence for CSE/H₂S as a promising therapeutic potential target for obesity-related insulin resistance.-Guo, W., Li, D., You, Y., Li, W., Hu, B., Zhang, S., Miao, L., Xian, M., Zhu, Y., Shen, X. Cystathionine γ-lyase deficiency aggravates obesity-related insulin resistance via FoxO1-dependent hepatic gluconeogenesis.

Resolution of inflammation pathways in preeclampsia-a narrative review

Preeclampsia (PE) is one of the leading causes of maternal morbidity and mortality worldwide. This disease is believed to occur in two stages with placental dysfunction in early pregnancy leading to maternal clinical findings after 20 weeks of gestation, as consequence of systemic inflammation, oxidative stress, and endothelial dysfunction. Much evidence suggests that PE women display an overshooting inflammatory response throughout pregnancy due to an unbalanced regulation of innate and adaptive immune responses. Recently, it has been suggested that dysregulation of endogenous protective pathways might be associated with PE etiopathogenesis. Resolution of inflammation is an active process coordinated by mediators from diverse nature that regulate key cellular events to restore tissue homeostasis. Inadequate or insufficient resolution of inflammation is believed to play an important role in the development of chronic inflammatory diseases, like PE. In this narrative review, we discuss possible pro-resolution pathways that might be compromised in PE women, which could be targets to novel therapeutic strategies in this disease.