Cardioprotective effects and pharmacokinetic properties of a controlled release formulation of a novel hydrogen sulfide donor in rats with acute myocardial infarction

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.

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 4 mg/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.

Cardioprotective properties of Artemisia herba alba nanoparticles against heart attack in rats: A study of the antioxidant and hypolipidemic activities

Recently, pharmaceutical scientists' interest has increased to find novel pharmaceutical natural substances with potent antioxidant capacity and very low side effects to be used safely in preventive medicine. One of the most common types of diseases with a large spread globally is cardiovascular diseases, which cause a high rate of deaths annually. The present study evaluated the use of Artemisia herba alba leaves' extract (AHALE) and AHALE zinc oxide nanoparticles (AHALE-ZnONPs) against isoproterenol (ISO) inducing myocardial infarction (MI) in male rats. Several groups of Wistar male rats fed a high-fat diet (HFD) were pretreated with several doses of AHALE or AHALE-ZnONPs for one month followed by exposure to ISO for two days. After treatment, samples of the rats' heart tissues and blood were collected for several molecular biological and biochemical analyses. Heart enzymes, antioxidant enzymes, lipid peroxidation compounds, lipid markers, activities, ROS generation, apoptosis, DNA damage and expression of lipid metabolism genes were analyzed in rats pretreated with AHALE or AHALE-ZnONPs followed by exposure to ISO. The results showed an increase in the levels of AST, ALT, LDH, CK, CK-MB, and cTnT (heart markers), elevation in TG, TC, and LDL levels (lipid profile markers), levels of TBARS and LOOH (lipid peroxidation products), ROS generation, DNA damage, apoptosis, and upregulation of PPAR-α, ADD1, FASN, and ACC genes in animals exposed to ISO in comparison with the control animals. Moreover, a decrease in antioxidant enzyme activities, including GPx, GRx, and GST, was observed in animals exposed to ISO in comparison with control rats. In male rats pretreated with AHALE or AHALE-ZnONPs followed by exposure to ISO, the oxidative stress induced by ISO was prevented. The results suggest that Artemisia extract could be considered for use as one of the natural compounds for prevention of atherosclerosis and heart diseases due to its high antioxidant and hypolipidemic activities. The reduced oxidative stress of Artemisia extract may be a result of the existence of flavonoids and phenolic substances.

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.

A novel dendritic mesoporous silica based sustained hydrogen sulfide donor for the alleviation of adjuvant-induced inflammation in rats

Purpose

S-propargyl-cysteine (SPRC), an excellent endogenous hydrogen sulfide (H₂S) donor, could elevate H₂S levels via the cystathionine γ-lyase (CSE)/H₂S pathway both in vitro and in vivo. However, the immediate release of H₂S in vivo and daily administration of SPRC potentially limited its clinical use.

Methods

To solve the fore-mentioned problem, in this study, the dendritic mesoporous silica nanoparticles (DMSN) was firstly prepared, and a sustained H₂S delivery system consisted of SPRC and DMSN (SPRC@DMSN) was then constructed. Their release profiles, both in vitro and in vivo, were investigated, and their therapeutical effect toward adjuvant-induced arthritis (AIA) rats was also studied.

Results

The spherical morphology of DMSN could be observed under scanning Electron Microscope (SEM), and the transmission electron microscope (TEM) images showed a central-radiational pore channel structure of DMSN. DMSN showed excellent SPRC loading capacity and attaining a sustained releasing ability than SPRC both in vitro and in vivo, and the prolonged SPRC releasing could further promote the release of H₂S in a sustained manner through CSE/H₂S pathway both in vitro and in vivo. Importantly, the SPRC@DMSN showed promising anti-inflammation effect against AIA in rats was also observed.

Conclusions

A sustained H₂S releasing donor consisting of SPRC and DMSN was constructed in this study, and this sustained H₂S releasing donor might be of good use for the treatment of AIA.

The Preparation of a Novel Poly(Lactic Acid)-Based Sustained H2S Releasing Microsphere for Rheumatoid Arthritis Alleviation

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease that mainly erodes joints and surrounding tissues, and if it is not treated in time, it can cause joint deformities and loss of function. S-propargyl-cysteine (SPRC) is an excellent endogenous hydrogen sulfide donor which can relieve the symptoms of RA through the promotion of H₂S release via the CSE/H₂S pathway in vivo. However, the instant release of H₂S in vivo could potentially limit its further clinical use. To solve this problem, in this study, a SPRC-loaded poly(lactic acid) (PLA) microsphere (SPRC@PLA) was prepared, which could release SPRC in vitro in a sustained manner, and further promote sustained in vivo H₂S release. Furthermore, its therapeutical effect on RA in rats was also studied. A spherical-like SPRC@PLA was successfully prepared with a diameter of approximately 31.61 μm, yielding rate of 50.66%, loading efficiency of 6.10% and encapsulation efficiency of 52.71%. The SPRC@PLA showed significant prolonged in vitro SPRC release, to 4 days, and additionally, an in vivo H₂S release around 3 days could also be observed. In addition, a better therapeutical effect and prolonged administration interval toward RA rats was also observed in the SPRC@PLA group.

Astaxanthin promotes M2 macrophages and attenuates cardiac remodeling after myocardial infarction by suppression inflammation in rats

Background

Cardiac remodeling after acute myocardial infarction (AMI) is an important process. The present study aimed to assess the protective effects of astaxanthin (ASX) on cardiac remodeling after AMI.

Methods

The study was conducted between April and September 2018. To create a rat AMI model, rats were anesthetized, and the left anterior descending coronary artery was ligated. The rats in the ASX group received 10 mg·kg⁻¹·day⁻¹ ASX by gavage for 28 days. On the 1st day after AMI, but before ASX administration, six rats from each group were sacrificed to evaluate changes in the heart function and peripheral blood (PB) levels of inflammatory factors. On the 7th day after AMI, eight rats from each group were sacrificed to evaluate the PB levels of inflammatory factors and the M2 macrophage count using both immunofluorescence (IF) and flow cytometry (FC). The remaining rats were observed for 28 days. Cardiac function was examined using echocardiography. The inflammatory factors, namely, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-10, were assessed using enzyme-linked immunosorbent assay. The heart weight/body weight (BW), and lung weight (LW)/BW ratios were calculated, and myocardial fibrosis in the form of collagen volume fraction was measured using Masson trichrome staining. Hematoxylin and eosin (H&E) staining was used to determine the myocardial infarct size (MIS), and TdT-mediated dUTP nick-end labeling staining was used to analyze the myocardial apoptosis index. The levels of apoptosis-related protein, type I/III collagen, transforming growth factor β1 (TGF-β1), metalloproteinase 9 (MMP9), and caspase 3 were assessed by Western blotting. Unpaired t-test, one-way analysis of variance, and non-parametric Mann-Whitney test were used to analyze the data.

Results

On day 1, cardiac function was worse in the ASX group than in the sham group (left ventricular end-systolic diameter [LVID_s]: 0.72 ± 0.08 vs. 0.22 ± 0.06 cm, t = −11.38; left ventricular end-diastolic diameter [LVID_d]: 0.89 ± 0.09 vs. 0.48 ± 0.05 cm, t = −9.42; end-systolic volume [ESV]: 0.80 [0.62, 0.94] vs. 0.04 [0.03, 0.05] mL, Z = −2.89; end-diastolic volume [EDV]: 1.39 [1.03, 1.49] vs. 0.28 [0.22, 0.32] mL, Z = −2.88; ejection fraction [EF]: 0.40 ± 0.04 vs. 0.86 ± 0.05, t = 10.00; left ventricular fractional shortening [FS] rate: 0.19 [0.18, 0.20] %FS vs. 0.51 [0.44, 0.58] %FS, Z = −2.88, all P < 0.01; n = 6). The levels of inflammatory factors significantly increased (TNF-α: 197.60 [133.89, 237.94] vs. 50.48 [47.21 57.10] pg/mL, Z = −2.88; IL-1β: 175.23 [160.74, 215.09] vs. 17.78 [16.83, 19.56] pg/mL, Z = −2.88; IL-10: 67.64 [58.90, 71.46] vs. 12.33 [11.64, 13.98] pg/mL, Z = −2.88, all P < 0.01; n = 6). On day 7, the levels of TNF-α and IL-1β were markedly lower in the ASX group than in the AMI group (TNF-α: 71.70 [68.60, 76.00] vs. 118.07 [106.92, 169.08] pg/mL, F = 42.64; IL-1β: 59.90 [50.83, 73.78] vs. 151.60 [108.4, 198.36] pg/mL, F = 44.35, all P < 0.01, n = 8). Conversely, IL-10 levels significantly increased (141.84 [118.98, 158.36] vs. 52.96 [42.68, 74.52] pg/mL, F = 126.67, P < 0.01, n = 8). The M2 macrophage count significantly increased (2891.42 ± 211.29 vs. 1583.38 ± 162.22, F = 274.35, P < 0.01 by immunofluorescence test; 0.96 ± 0.18 vs. 0.36 ± 0.05, F = 46.24, P < 0.05 by flowcytometry test). On day 28, cardiac function was better in the ASX group than in the AMI group (LVID_s: 0.50 [0.41, 0.56] vs. 0.64 [0.56, 0.74] cm, Z = −3.60; LVID_d: 0.70 [0.60, 0.76] vs. 0.80 [0.74 0.88] cm, Z = −2.96; ESV: 0.24 [0.18, 0.45] vs. 0.58 [0.44, 0.89] mL, Z = −3.62; EDV: 0.76 [0.44, 1.04] vs. 1.25 [0.82, 1.46] mL, Z = −2.54; EF: 0.60 ± 0.08 vs. 0.50 ± 0.12, F = 160.48; %FS: 0.29 [0.24, 0.31] vs. 0.20 [0.17, 0.21], Z = −4.43, all P < 0.01; n = 16). The MIS and LW/BW ratio were markedly lower in the ASX group than in the AMI group (myocardial infarct size: 32.50 ± 1.37 vs. 50.90 ± 1.73, t = 23.63, P < 0.01, n = 8; LW/BW: 1.81 ± 0.15 vs. 2.17 ± 0.37, t = 3.66, P = 0.01, n = 16). The CVF was significantly lower in the ASX group than in the AMI group: 12.88 ± 2.53 vs. 28.92 ± 3.31, t = 10.89, P < 0.01, n = 8. The expression of caspase 3, TGF-β1, MMP9, and type I/III collagen was lower in the ASX group than in the AMI group (caspase 3: 0.38 ± 0.06 vs. 0.66 ± 0.04, t = 8.28; TGF-β1: 0.37 ± 0.04 vs. 0.62 ± 0.07, t = 6.39; MMP9: 0.20 ± 0.06 vs. 0.40 ± 0.06, t = 4.62; type I collagen: 0.42 ± 0.09 vs. 0.74 ± 0.07, t = 5.73; type III collagen: 0.13 ± 0.02 vs. 0.74 ± 0.07, t = 4.32, all P < 0.01; n = 4).

Conclusions

ASX treatment after AMI may promote M2 macrophages and effectively attenuate cardiac remodeling by inhibiting inflammation and reducing myocardial fibrosis.

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.

Protective mechanisms of hydrogen sulfide in myocardial ischemia

Hydrogen sulfide (H₂ S), which has been identified as the third gaseous signaling molecule after nitric oxide (NO) and carbon monoxide (CO), plays an important role in maintaining homeostasis in the cardiovascular system. Endogenous H₂ S is produced mainly by three endogenous enzymes: cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfur transferase. Numerous studies have shown that H₂ S has a significant protective role in myocardial ischemia. The mechanisms by which H₂ S affords cardioprotection include the antifibrotic and antiapoptotic effects, regulation of ion channels, protection of mitochondria, reduction of oxidative stress and inflammatory response, regulation of microRNA expression, and promotion of angiogenesis. Amplification of NO- and CO-mediated signaling through crosstalk between H₂ S, NO, and CO may also contribute to the cardioprotective effect. Exogenous H₂ S donors are expected to become effective drugs for the treatment of cardiovascular diseases. This review article focuses on the protective mechanisms and potential therapeutic applications of H₂ S in myocardial ischemia.

Protective role of poly(lactic-co-glycolic) acid nanoparticle loaded with resveratrol against isoproterenol-induced myocardial infarction

Our study is aimed at evaluating the effects of pretreatment with Poly(lactic-co-glycolic) acid nanoparticle loaded with resveratrol (RSV PLGA NPs) compared to conventional resveratrol (RSV) on isoproterenol (ISO) induced myocardial infarction (MI) in rats. Sixty rats were randomly divided into six groups of 10 rats each. RSV and RSV PLGA NPs were given by gavage in two different doses (50 mg/kg body weight [BW] and 100 mg/kg BW) for 3 weeks. RSV and RSV PLGA NPs were given for 2 weeks starting 1 week before ISO administration. The blood samples were taken 24 hr after the last dose of ISO. The antioxidant, anti-inflammatory, and cardioprotective effects were evaluated in all groups. Only 100 mg/kg dose of RSV and both doses of RSV PLGA NPs offered a cardioprotective effect by preventing cardiac troponin T (cTnT) levels, lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) activities leakage from cardiomyocytes, with the best result for RSV PLGA NPs. All the oxidative stress parameters were significantly improved after RSV PLGA NPs compared to RSV pretreatment. RSV PLGA NPs were more efficient than RSV in limiting the increase in inflammatory cytokine expressions such as tumor necrosis factor-alpha (TNF-α), interleukin 1 beta (IL-1β), and NF-kappaB (NF-kB) expression. In addition, RSV PLGA NPs significantly upregulated eNOS expression and downregulated iNOS expression. RSV PLGA NPs better prevented myocardial necrosis and reduced interstitial edema and neutrophil infiltration than RSV, on histopathological examination. Therefore, improving the bioactivity of RSV by nanotechnology may help limit cardiac injury after myocardial infarction.

A Novel Liposomal S-Propargyl-Cysteine: A Sustained Release of Hydrogen Sulfide Reducing Myocardial Fibrosis via TGF-β1/Smad Pathway

Purpose

S-propargyl-cysteine (SPRC; alternatively known as ZYZ-802) is a novel modulator of endogenous tissue H₂S concentrations with known cardioprotective and anti-inflammatory effects. However, its rapid metabolism and excretion have limited its clinical application. To overcome these issues, we have developed some novel liposomal carriers to deliver ZYZ-802 to cells and tissues and have characterized their physicochemical, morphological and pharmacological properties.

Methods

Two liposomal formulations of ZYZ-802 were prepared by thin-layer hydration and the morphological characteristics of each liposome system were assessed using a laser particle size analyzer and transmission electron microscopy. The entrapment efficiency and ZYZ-802 release profiles were determined following ultrafiltration centrifugation, dialysis tube and HPLC measurements. LC-MS/MS was used to evaluate the pharmacokinetic parameters and tissue distribution profiles of each formulation via the measurements of plasma and tissues ZYZ-802 and H₂S concentrations. Using an in vivo model of heart failure (HF), the cardio-protective effects of liposomal carrier were determined by echocardiography, histopathology, Western blot and the assessment of antioxidant and myocardial fibrosis markers.

Results

Both liposomal formulations improved ZYZ-802 pharmacokinetics and optimized H₂S concentrations in plasma and tissues. Liposomal ZYZ-802 showed enhanced cardioprotective effects in vivo. Importantly, liposomal ZYZ-802 could inhibit myocardial fibrosis via the inhibition of the TGF-β1/Smad signaling pathway.

Conclusion

The liposomal formulations of ZYZ-802 have enhanced pharmacokinetic and pharmacological properties in vivo. This work is the first report to describe the development of liposomal formulations to improve the sustained release of H₂S within tissues.

An Appraisal of Developments in Allium Sulfur Chemistry: Expanding the Pharmacopeia of Garlic

Alliums and allied plant species are rich sources of sulfur compounds that have effects on vascular homeostasis and the control of metabolic systems linked to nutrient metabolism in mammals. In view of the multiple biological effects ascribed to these sulfur molecules, researchers are now using these compounds as inspiration for the synthesis and development of novel sulfur-based therapeutics. This research has led to the chemical synthesis and biological assessment of a diverse array of sulfur compounds representative of derivatives of S-alkenyl-l-cysteine sulfoxides, thiosulfinates, ajoene molecules, sulfides, and S-allylcysteine. Many of these synthetic derivatives have potent antimicrobial and anticancer properties when tested in preclinical models of disease. Therefore, the current review provides an overview of advances in the development and biological assessment of synthetic analogs of allium-derived sulfur compounds.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H2S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.

S-propargyl-cysteine attenuates inflammatory response in rheumatoid arthritis by modulating the Nrf2-ARE signaling pathway

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder. Hydrogen sulfide (H₂S), the third physiological gasotransmitter, is well recognized as an anti-inflammatory mediator in various inflammatory conditions. Herein, we explored the protective effects of S-propargyl-cysteine (SPRC, also known as ZYZ-802), an endogenous H₂S modulator, on RA and determined the underlying mechanisms. In the present study, SPRC concentration-dependently attenuated inflammatory mediator expression, reactive oxidase species generation, and the expression and activity of matrix metalloproteinases (MMP)-9 in interleukin (IL)-1β-induced human rheumatoid fibroblast-like synoviocytes MH7A. In addition, SPRC blocked IL-1β-mediated migration and invasion of MH7A cells. As expected, the protective effects of SPRC were partially abrogated by DL-propargylglycine (PAG, a H₂S biosynthesis inhibitor). In vivo study also demonstrated that SPRC treatment markedly ameliorated the severity of RA in adjuvant-induced arthritis rats, and this effect was associated with the inhibition of inflammatory response. We further identified that SPRC remarkably induced heme oxygenase-1 expression associated with the degradation of Kelch-like ECH-associated protein 1 (Keap1) and nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2); this effect was attributed to the sulfhydrylation of the cysteine residue of Keap1. Our data demonstrated for the first time that SPRC, an endogenous H₂S modulator, exerted anti-inflammatory properties in RA by upregulating the Nrf2-antioxidant response element (ARE) signaling pathway.