Hydrogen sulfide increases glutathione production and suppresses oxidative stress in mitochondria

Hydrogen sulfide: Therapeutic or injurious in ischemic stroke?

Hydrogen sulfide (H2S) has been identified as a vasodilatory, neuromodulatory, and anti-inflammatory gasotransmitter with antioxidant properties. Studies focused in cardiac tissue suggest H2S functions as a protective agent; however in the central nervous system (CNS) the effects of H2S during states of stress or injury, such as stroke, remain controversial. Currently, the application of H2S donors and modulators in stroke depends on the type of H2S donor and the timing of the therapy.

Molecular Adaptations of Bacterial Mercuric Reductase to the Hypersaline Kebrit Deep in the Red Sea

The hypersaline Kebrit Deep brine pool in the Red Sea is characterized by high levels of toxic heavy metals. Here, we describe two structurally related mercuric reductases (MerAs) from this site which were expressed in Escherichia coli Sequence similarities suggest that both genes are derived from proteobacteria, most likely the Betaproteobacteria or Gammaproteobacteria We show that one of the enzymes (K35NH) is strongly inhibited by NaCl, while the other (K09H) is activated in a NaCl-dependent manner. We infer from this difference that the two forms might support the detoxification of mercury in bacterial microorganisms that employ the compatible solutes and salt-in strategies, respectively. Three-dimensional structure modeling shows that all amino acid substitutions unique to each type are located outside the domain responsible for formation of the active MerA homodimer, and the vast majority of these are found on the surface of the molecule. Moreover, K09H exhibits the predominance of acidic over hydrophobic side chains that is typical of halophilic salt-dependent proteins. These findings enhance our understanding of how selection pressures imposed by two environmental stressors have endowed MerA enzymes with catalytic properties that can potentially function in microorganisms that utilize distinct mechanisms for osmotic balance in hypersaline environments.IMPORTANCE Analysis of two structurally homologous but catalytically distinct mercuric reductases from the Kebrit Deep brine in the Red Sea sheds light on the adaptations that enable microorganisms to cope simultaneously with extreme salinity and toxic mercury compounds. One is strongly inhibited by high NaCl concentrations, while the other exhibits NaCl-dependent activation. Their different activity profiles imply that they may derive from bacterial microorganisms that utilize compatible solutes and salt-in strategies, respectively, to maintain osmotic balance. Three-dimensional modeling reveals that regions not involved in formation of the active homodimer are conserved between the two. However, in the NaCl-dependent form, distinct amino acid substitutions are found in areas that are critical for stability in high salt. The work provides insights into how two environmental stressors have shaped the structure of orthologous enzymes through selection and adaptation, enabling them to retain their catalytic function in what may be very different cellular contexts.

Nitric Oxide: Its Generation and Interactions with Other Reactive Signaling Compounds

Nitric oxide (NO) is an immensely important signaling molecule in animals and plants. It is involved in plant reproduction, development, key physiological responses such as stomatal closure, and cell death. One of the controversies of NO metabolism in plants is the identification of enzymatic sources. Although there is little doubt that nitrate reductase (NR) is involved, the identification of a nitric oxide synthase (NOS)-like enzyme remains elusive, and it is becoming increasingly clear that such a protein does not exist in higher plants, even though homologues have been found in algae. Downstream from its production, NO can have several potential actions, but none of these will be in isolation from other reactive signaling molecules which have similar chemistry to NO. Therefore, NO metabolism will take place in an environment containing reactive oxygen species (ROS), hydrogen sulfide (H₂S), glutathione, other antioxidants and within a reducing redox state. Direct reactions with NO are likely to produce new signaling molecules such as peroxynitrite and nitrosothiols, and it is probable that chemical competitions will exist which will determine the ultimate end result of signaling responses. How NO is generated in plants cells and how NO fits into this complex cellular environment needs to be understood.

Hepatoprotection of Herpetospermum caudigerum Wall. against CCl4-induced liver fibrosis on rats

ETHNOPHARMACOLOGICAL RELEVANCE

Herpetospermum caudigerum Wall. (HCW) is a traditional Tibetan medicine, which has been used to ameliorate liver injuries in the folk.

AIM OF THE STUDY

Liver fibrosis has been recognized as a major lesion of the liver that leads to liver cirrhosis/hepatocarcinoma and even to death in the end. This study aims to demonstrate the protective effect of HCW against CCl₄-induced liver injury in rats and to explore the underlying mechanisms.

MATERIALS AND METHODS

Hepatic fibrosis was induced by intraperitoneal injection of CCl₄. Liver function markers, fibrosis markers, serum anti-oxidation enzymes as well as elements levels were determined. Serum and liver tissues were subjected to NMR-based metabolomics and multivariate statistical analysis.

RESULTS

HCW could significantly reduce the elevated levels of fibrosis markers such as hyaluronidase, laminin, Type III procollagen and Type IV collagen in the serum, improve the activities of the antioxidant enzymes, and effectively reverse the abnormal levels of elements in liver fibrosis rats. Correlation network analysis revealed that HCW could treat liver fibrosis by ameliorating oxidative stress, repairing the impaired energy metabolisms and reversing the disturbed amino acids and nucleic acids metabolisms.

CONCLUSION

This integrated metabolomics approach confirmed the validity of the traditional use of HCW in the treatment of liber fibrosis, providing new insights into the underlying mechanisms.

Immunomodulatory Effects of Glutathione, Garlic Derivatives, and Hydrogen Sulfide

Glutathione and aged garlic extract are sulfur-containing products that play important protective and regulatory roles within the immune system and in oxidative processes. Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has also been shown to be involved in the regulation of inflammation. Recent studies have shown that sulfur-containing compounds from garlic have beneficial effects in attenuating outcomes associated with cardiovascular disease and inflammation by a mechanism that may be related to the H₂S signaling pathway. In this review, we summarize the main functions of glutathione (GSH), garlic derivatives and H₂S and their role in the immune response and impact on health and disease.

Impaired Vascular Redox Signaling in the Vascular Complications of Obesity and Diabetes Mellitus

Significance: Oxidative stress, a crucial regulator of vascular disease pathogenesis, may be involved in the vascular complications of obesity, systemic insulin resistance (IR), and diabetes mellitus (DM). Recent Advances: Excessive production of reactive oxygen species in the vascular wall has been linked with vascular disease pathogenesis. Recent evidence has revealed that vascular redox state is dysregulated in cases of obesity, systemic IR, and DM, potentially participating in the well-known vascular complications of these disease entities. Critical Issues: The detrimental effects of obesity and the metabolic syndrome on vascular biology have been extensively described at a clinical level. Further, vascular oxidative stress has often been associated with the presence of obesity and IR as well as with a variety of detrimental vascular phenotypes. However, the mechanisms of vascular redox state regulation under conditions of obesity and systemic IR, as well as their clinical relevance, are not adequately explored. In addition, the notion of vascular IR, and its relationship with systemic parameters of obesity and systemic IR, is not fully understood. In this review, we present all the important components of vascular redox state and the evidence linking oxidative stress with obesity and IR. Future Directions: Future studies are required to describe the cellular effects and the translational potential of vascular redox state in the context of vascular disease. In addition, further elucidation of the direct vascular effects of obesity and IR is required for better management of the vascular complications of DM.

Comparative localization of cystathionine beta synthases and cystathionine gamma lyase in canine, non-human primate and human retina

Chronic exposure of the retina to light and high concentrations of polyunsaturated fatty acid in photoreceptor cells make this tissue susceptible to oxidative damage. As retinal degenerative diseases are associated with photoreceptor degeneration, the antioxidant activity of both hydrogen sulfide (H₂S) and glutathione (GSH) may play an important role in ameliorating disease progression. H₂S production is driven by cystathionine-γ-lyase (CSE) and cystathionine-β-synthase (CBS), the key enzymes that also drive transsulfuration pathway (TSP) necessary for GSH production. As it is currently unclear whether localized production of either H₂S or GSH contributes to retinal homeostasis, we undertook a comparative analysis of CBS and CSE expression in canine, non-human primate (NHP) and human retinas to determine if these antioxidants could play a regulatory role in age-related or disease-associated retinal degeneration. Retinas from normal dogs, NHPs and humans were used for the study. Laser capture microdissection (LCM) was performed to isolate individual layers of the canine retina and analyze CBS and CSE gene expression by qRT-PCR. Immunohistochemistry and western blotting were performed for CBS and CSE labeling and protein expression in dog, NHP, and human retina, respectively. Using qRT-PCR, western blot, and immunohistochemistry (IHC), we showed that CBS and CSE are expressed in the canine, NHP, and human retina. IHC results from canine retina demonstrated increased expression levels of CBS but not CSE with post-developmental aging. IHC results also showed non-overlapping localization of both proteins with CBS presenting in rods, amacrine, horizontal, and nerve fiber cell layers while CSE was expressed by RPE, cones and Mϋller cells. Finally, we demonstrated that these enzymes localized to all three layers of canine, NHP and human retina: photoreceptors, outer plexiform layer (OPL) and notably in the ganglion cells layer/nerve fiber layer (GCL/NFL). QRT-PCR performed using RNA extracted from tissues isolated from these cell layers using laser capture microdissection (LCM) confirmed that each of CBS and CSE are expressed equally in these three layers. Together, these findings reveal that CSE and CBS are expressed in the retina, thereby supporting further studies to determine the role of H₂S and these proteins in oxidative stress and apoptosis in retinal degenerative diseases.

Measurements for Sulfide-Mediated Inhibition of Myeloperoxidase Activity

Oxidative stress-alleviating and inflammation-mediatory functions of hydrogen sulfide were reported to be key features of its biological actions. However, the underlying molecular mechanisms of these biological observations are not fully understood. In conditions where sulfide was proposed to be protective against oxidative stress- or inflammation-induced tissue damage (e.g., reperfusion injury, atherosclerosis, vascular inflammation), the reactive oxidant-producing function of a key neutrophil enzyme, myeloperoxidase, was reported to be a protagonist on the detrimental side. We recently described favorable interactions between sulfide and myeloperoxidase and proposed that the potent inhibition of myeloperoxidase activities could contribute to sulfide's beneficial functions in a number of cardiovascular pathologies. Our chapter is dedicated to aid future studies and drug development endeavors in this area by providing methodological guidance on how to assess the inhibitory potential of sulfide on myeloperoxidase enzymatic activities in isolated protein systems, in neutrophil homogenates, and in live neutrophil preparations.

Hydrogen sulfide donor, NaHS, stimulates ANP secretion via the KATP channel and the NOS/sGC pathway in rat atria

Hydrogen sulfide (H₂S) is normally produced from l-cysteine in mammalian tissues and related to the pathogenesis of cardiovascular diseases. The aim of this study is to investigate the effects of H₂S donor on atrial natriuretic peptide (ANP) secretion and define its mechanism using normal and isoproterenol (ISP)-treated rats. Several H₂S donors were perfused into isolated beating rat atria, and atrial pressure (AP) and ANP secretion were measured. NaHS augmented high stretch-induced ANP secretion and decreased AP in a dose-dependent manner. The high stretch-induced ANP secretion was stimulated by Na₂S but was not changed by GYY4137 and sodium thiosulfate. NaHS and Na₂S produced very high amount of H₂S rapidly whereas GYY4137 produced very low amount of H₂S slowly. NaHS-stimulated ANP secretion was blocked by the pretreatment with inhibitor for K_ATP channel, nitric oxide synthase (NOS), soluble guanylyl cyclase (sGC), phosphoinositol 3 kinase (PI3K) or protein kinase B. H₂S synthesis enzyme inhibitor (DL-propargylglycine) did not show any significant changes in atrial parameters. However, the response of ANP secretion to NaHS markedly attenuated and DL-propargylglycine suppressed ANP secretion in ISP-treated rat atria. The expression of eNOS protein was decreased but the expression of cardiomyocyte-specific H₂S producing enzyme, cystathione γ-lyase, was not changed in ISP-treated rat atria. The attenuation of NaHS-induced ANP secretion in ISP-treated rat atria may be due to the low expression of eNOS protein. These findings clarify that NaHS stimulates ANP secretion via the K_ATP channel and the PI3K/Akt/NOS/sGC pathway in rat atria.

Hydrogen Sulfide: A Therapeutic Option in Systemic Sclerosis

Systemic sclerosis (SSc) is a lethal disease that is characterized by auto-immunity, vascular injury, and progressive fibrosis of multiple organ systems. Despite the fact that the exact etiology of SSc remains unknown, oxidative stress has been associated with a large range of SSc-related complications. In addition to the well-known detrimental properties of reactive oxygen species (ROS), gasotransmitters (e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S)) are also thought to play an important role in SSc. Accordingly, the diverse physiologic actions of NO and CO and their role in SSc have been previously studied. Recently, multiple studies have also shown the importance of the third gasotransmitter H₂S in both vascular physiology and pathophysiology. Interestingly, homocysteine (which is converted into H₂S through the transsulfuration pathway) is often found to be elevated in SSc patients; suggesting defects in the transsulfuration pathway. Hydrogen sulfide, which is known to have several effects, including a strong antioxidant and vasodilator effect, could potentially play a prominent role in the initiation and progression of vasculopathy. A better understanding of the actions of gasotransmitters, like H₂S, in the development of SSc-related vasculopathy, could help to create early interventions to attenuate the disease course. This paper will review the role of H₂S in vascular (patho-)physiology and potential disturbances in SSc. Moreover, current data from experimental animal studies will be reviewed. Lastly, we will evaluate potential interventional strategies.

Ameliorative effects of hydrogen sulfide (NaHS) on chronic kidney disease-induced brain dysfunction in rats: implication on role of nitric oxide (NO) signaling

Chronic kidney disease (CKD) is a major public health problem worldwide and is associated with spatial learning deficits. The aim of the present study was to evaluate the protective effects of hydrogen sulfide (H2S) on CKD-mediated behavioral deficits with emphasis to the role of nitric oxide (NO) in these effects. Fifty rats were randomly allocated to five experimental groups including: sham, Five-sixth (5/6) nephrectomy (Nx), 5/6Nx + NaHS, 5/6Nx + NaHS+L-nitroarginine methyl ester (L-NAME), and 5/6Nx + NaHS+aminoguanidine (AMG). Twelve weeks after 5/6Nx, we evaluated proteinuria, creatinine clearance (CrCl), oxidative/antioxidant status, and hippocampus neuro-inflammation and NO synthase genes in all groups. Furthermore, training trials of all animals were conducted in the Morris water maze (MWM) task one day before animal euthanizing. As predicted, 5/6Nx induced several injuries, including enhancement of proteinuria and reduction of CCr, oxidant/antioxidant imbalance and up-regulation of TNF-α and IL-1β gene expressions in the hippocampus tissues. As predicted, 5/6Nx resulted in learning and memory impairments, and increased escape latency during acquisition trials in the MWM task. Interestingly, NaHS (H2S donor) improved behavioral deficits, renal dysfunction, accelerated anti-oxidant/anti-inflammatory responses and increased eNOS and decreased iNOS. Moreover, these effects of NaHS were prevented by L-NAME but not AMG co-administration. In conclusion, H2S ameliorates CKD-mediated brain dysfunctions, through interaction with NO signaling in the hippocampus.

Effect of Hydrogen Sulfide on Kidney Injury in Rat Model of Crush Syndrome

BACKGROUND

Acute kidney injury is the most serious complication of crush syndrome. Hydrogen sulfide (H₂S) is an endogenously produced gaseous signaling molecule. It is involved in homeostatic functions, such as blood pressure control, apoptosis, oxidative stress, and inflammation. In this study, effects of H₂S on kidney injury were investigated in a rat model of crush syndrome.

METHODS

Rats were divided into six groups (n = 8): Sham (steril saline ip), crush (sterile saline ip), crush + NaHS (sodium hydrosulfide, an H₂S donor) (100 μmol/kg ip). All these groups were also separated as 3 and 24 h after decompression. Crush injury was induced by 6 h of direct compression to both hindlimbs of anesthetized rats with blocks weighing 3.6 kg each sides, followed by 3 or 24 h of decompression. Kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, tumor-necrotizing factor-α, transforming growth factor-β, tissue total oxidant status, and total antioxidant status levels were measured in kidney homogenates 3 and 24 h after decompression. Serum creatine kinase, blood urea nitrogen, and creatinine levels were also measured. Apoptosis was assessed by TUNEL method. Bcl-2 was assessed by immunohistochemistry. Glomerular and tubular structures were also examined histopathologically.

RESULTS

NaHS reduced kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, tumor-necrotizing factor-α, transforming growth factor-β, total oxidant status levels, and increased total antioxidant status levels in kidney 3 and 24 h after decompression. Serum urea, creatinine, and creatine kinase levels also reduced with NaHS. NaHS decreased renal damage and apoptosis in crush-related acute kidney injury.

CONCLUSIONS

These results suggest that H₂S could reduce crush-related acute kidney injury via anti-inflammatory, antioxidant, and antiapoptotic effects.

Lysosome-Assisted Mitochondrial Targeting Nanoprobe Based on Dye-Modified Upconversion Nanophosphors for Ratiometric Imaging of Mitochondrial Hydrogen Sulfide

Hydrogen sulfide (H₂S) is a versatile modulator in mitochondria and involved in numerous diseases caused by mitochondrial dysfunction. Therefore, many efforts have been made to develop fluorescent probes for mitochondrial H₂S detection. However, these cationic small molecule probes are inapplicable for in vivo imaging because of the shallow tissue penetration and poor biostability. Herein, a ratiometric upconversion luminescence nanoprobe with an acid-activated targeting strategy is developed for detecting and bioimaging of mitochondrial H₂S. The merocyanine triphenylamine-merocyanine (TPAMC)-modified upconversion nanophosphors, acting as the targeting and response component, are encapsulated into a pH-sensitive husk, composed of 1,2-distearoyl- sn-glycero-3-phosphoethanolamine- N-[methoxy-(poly(ethylene glycol))-2000] (DSPE-PEG) and poly(l-histidine)- b-PEG, which improved the nanoprobe's stability during transport in vivo. Under lysosomal pH, the PEG shell is interrupted and the targeting sites are exposed to further attach to mitochondria. Taking advantage of the luminescence resonance energy transfer process between TPAMC and upconversion nanophosphors, the ratiometric detection of mitochondrial H₂S can be achieved with high selectivity and sensitivity. Cellular testing reveals the precise targeting to mitochondria via a lysosome delivery process. Importantly, the nanoprobe can be used for monitoring mitochondrial H₂S levels in living cells and colon cancer mouse models.

Restoration of skeletal muscle homeostasis by hydrogen sulfide during hyperhomocysteinemia-mediated oxidative/ER stress condition 1

Elevated homocysteine (Hcy), i.e., hyperhomocysteinemia (HHcy), causes skeletal muscle myopathy. Among many cellular and metabolic alterations caused by HHcy, oxidative and endoplasmic reticulum (ER) stress are considered the major ones; however, the precise molecular mechanism(s) in this process is unclear. Nevertheless, there is no treatment option available to treat HHcy-mediated muscle injury. Hydrogen sulfide (H₂S) is increasingly recognized as a potent anti-oxidant, anti-apoptotic/necrotic/pyroptotic, and anti-inflammatory compound and also has been shown to improve angiogenesis during ischemic injury. Patients with CBS mutation produce less H₂S, making them vulnerable to Hcy-mediated cellular damage. Many studies have reported bidirectional regulation of ER stress in apoptosis through JNK activation and concomitant attenuation of cell proliferation and protein synthesis via PI3K/AKT axis. Whether H₂S mitigates these detrimental effects of HHcy on muscle remains unexplored. In this review, we discuss molecular mechanisms of HHcy-mediated oxidative/ER stress responses, apoptosis, angiogenesis, and atrophic changes in skeletal muscle and how H₂S can restore skeletal muscle homeostasis during HHcy condition. This review also highlights the molecular mechanisms on how H₂S could be developed as a clinically relevant therapeutic option for chronic conditions that are aggravated by HHcy.

Hydrogen Sulfide Ameliorates Developmental Impairments of Rat Offspring with Prenatal Hyperhomocysteinemia

Maternal high levels of the redox active amino acid homocysteine—called hyperhomocysteinemia (hHCY)—can affect the health state of the progeny. The effects of hydrogen sulfide (H₂S) treatment on rats with maternal hHCY remain unknown. In the present study, we characterized the physical development, reflex ontogeny, locomotion and exploratory activity, muscle strength, motor coordination, and brain redox state of pups with maternal hHCY and tested potential beneficial action of the H₂S donor—sodium hydrosulfide (NaHS)—on these parameters. Our results indicate a significant decrease in litter size and body weight of pups from dams fed with methionine-rich diet. In hHCY pups, a delay in the formation of sensory-motor reflexes was observed. Locomotor activity tested in the open field by head rearings, crossed squares, and rearings of hHCY pups at all studied ages (P8, P16, and P26) was diminished. Exploratory activity was decreased, and emotionality was higher in rats with hHCY. Prenatal hHCY resulted in reduced muscle strength and motor coordination assessed by the paw grip endurance test and rotarod test. Remarkably, administration of NaHS to pregnant rats with hHCY prevented the observed deleterious effects of high homocysteine on fetus development. In rats with prenatal hHCY, the endogenous generation of H₂S brain tissues was lower compared to control and NaHS administration restored the H₂S level to control values. Moreover, using redox signaling assays, we found an increased level of malondialdehyde (MDA), the end product of lipid peroxidation, and decreased activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the brain tissues of rats of the hHCY group. Notably, NaHS treatment restored the level of MDA and the activity of SOD and GPx. Our data suggest that H₂S has neuroprotective/antioxidant effects against homocysteine-induced neurotoxicity providing a potential strategy for the prevention of developmental impairments in newborns.

[Pathophysiological functions of gas mediators in neurodegeneration]

Since the discovery of nitric oxide (NO) as gaseous signaling molecule, two other gaseous mediators, carbon monoxide (CO) and hydrogen sulfide (H₂S) have been found to be also involved in many physiological and pathophysiological functions. This review will briefly summarize our recent progress in the pathophysiology of NO and H₂S. In the photoreceptor cells, the level of intracellular Ca²⁺ is kept relatively low by H₂S. Intraperitoneal injection of H₂S donor to mice protected photoreceptor cells from light-induced retinal degeneration caused by oxidative stress and elevation of intracellular Ca²⁺. Another gaseous mediator NO induces Ca²⁺ release from the endoplasmic reticulum via S-nitrosylated type 1 ryanodine receptor (RyR1) Ca²⁺ release channel. NO-induced Ca²⁺ release (NICR) was abolished in primary cultured neurons from the knock-in mice, in which the S-nitrosylation site Cys-3636 of RyR1 was replaced by Ala (Ryr1^C3636A). The neurons in hippocampal CA3 region of Ryr1^C3636A mice were protected against seizure-induced neuronal cell death. The result indicates that NICR is critical for status epilepticus-induced neurodegeneration. The developments in the pathophysiology of gaseous mediators in the central nervous system will provide a better pharmacological advances for the treatment of neurodegenerative diseases.

The biologic effect of hydrogen sulfide and its function in various diseases

INTRODUCTION

Hydrogen sulfide (H2S), a colorless, water soluble, flammable gas with a characteristic smell of rotten eggs, has been known as a highly toxic gas for several years. However, much like carbon monoxide (CO) and nitric oxide (NO), the initial negative perception of H2S has developed with the discovery that H2S is generated enzymatically in animals under normal conditions. With the result of this discovery, much more work is needed to elucidate the biologic effects of H2S. In recent years, its cytoprotective properties have been recognized in multiple organs and tissues. In particular, H2S plays important roles in combating oxidative species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) and protect the body from oxidative stress. Therefore, this review discusses the biologic effect of H2S and how it protects cells in various diseases by acting as an antioxidant that reduces excessive amounts of ROS and RNS.

ETHICS AND DISSEMINATION

Ethical approval and informed consent are not required, as the study will be a literature review and will not involve direct contact with patients or alterations to patient care.

CONCLUSION

H2S has been found to be cytoprotective in oxidative stress in a wide range of physiologic and pathologic conditions, an increasing number of therapeutic potentials of H2S also have been revealed. However, there is still much debate on the clear mechanism of action of H2S, so that the mechanisms of cell signaling that promote cellular survival and organ protection need to be further investigated to provide better H2S-based therapeutics.

Hydrogen Sulfide (H₂S) Releasing Capacity of Isothiocyanates from Moringa oleifera Lam

Moringa oleifera Lam. is rich in phytochemical compounds especially glucosinolates (GSs) and isothiocyanates (ITCs), which are active compounds for cancer chemoprevention benefits of Brassicaceae vegetables. In this study, we determined the total contents of GSs and ITCs and their specific profiles in different Moringa tissues including seeds, stems, leaves and roots. Seeds (seeds with shell and seed kernel) showed significantly higher levels of total GSs and ITCs than that of other Moringa tissues. The hydrogen sulfide (H₂S) releasing capacity of total ITCs extracted from different Moringa tissues was determined by lead (II) acetate assay in 24-well plates. The H₂S releasing capacity of different Moringa tissues were evaluated and compared. Moringa seeds showed the highest H₂S releasing capacity, followed by roots, leaves and stems. Our results suggest that Moringa based foods may exhibit health benefits due to its GSs and ITCs contents that are the precursors for H₂S, in addition to the recognized action mechanisms of ITCs.

Cystathionine-γ-lyase expression is associated with mitochondrial respiration during sepsis-induced acute kidney injury in swine with atherosclerosis

Background

Sepsis is associated with disturbed glucose metabolism and reduced mitochondrial activity and biogenesis, ultimately leading to multiple organ dysfunction, e.g., acute kidney injury (AKI). Cystathionine-γ-lyase (CSE), the major cardiovascular source of endogenous H₂S release, is implicated in the regulation of glucose metabolism and mitochondrial activity through a PGC1α-dependent mechanism, and critical for kidney function. Atherosclerosis is associated with mitochondrial dysfunction and reduced CSE expression. Thus, the aim of this post hoc study was to test the hypothesis whether there is an interplay between CSE expression and kidney dysfunction, mitochondrial activity, and oxidative/nitrosative stress in porcine septic AKI with underlying coronary artery disease.

Methods

This study is a post hoc analysis of material from anesthetized and instrumented swine with a high fat diet-induced hypercholesterolemia and atherosclerosis undergoing faecal peritonitis-induced septic shock or sham procedure and intensive care (comprising fluid resuscitation and continuous i.v. noradrenaline (NoA) infusion) for 24 h. Glucose metabolism was quantified from blood ¹³C₆-glucose and expiratory ¹³CO₂/¹²CO₂ isotope enrichment during ¹³C₆-glucose infusion. Mitochondrial activity was determined by high-resolution respirometry. CSE and PGC1α expression, as well as nitrotyrosine formation and albumin extravasation, were quantified by immunohistochemistry of formalin-fixed kidney paraffin sections.

Results

Sepsis was associated with lactic acidosis (p = 0.004) and AKI (50% fall of creatinine clearance (CrCl), p = 0.019). While both whole-body glucose production (p = 0.004) and oxidation (p = 0.006) were increased, kidney tissue mitochondrial respiration was reduced (p = 0.028), coinciding with decreased CSE (p = 0.003) and PGC1α (p = 0.003) expression. Albumin extravasation (p = 0.011) and nitrotyrosine formation (p = 0.008) were increased in septic kidneys.

Conclusions

Sepsis-induced AKI is associated with disturbed mitochondrial respiration and biogenesis, which may be aggravated by oxidative and nitrosative stress. Our results confirm previous data in murine septic shock and porcine hemorrhage and resuscitation on the crucial role of CSE for barrier integrity and kidney function.

Electronic supplementary material

The online version of this article (10.1186/s40635-018-0208-z) contains supplementary material, which is available to authorized users.

Hydrogen Sulfide Affects Radical Formation in the Hippocampus of LPS Treated Rats and the Effect of Antipsychotics on Hydrogen Sulfide Forming Enzymes in Human Cell Lines

Objectives: Psychiatric disorders, such as schizophrenia and other neuroinflammatory diseases are accompanied by an increase in the oxidative stress and changes in the immune system and in the metabolic, hormonal and neurological components of the central nervous system (CNS). Hydrogen sulfide (H2S) is a gaseous molecule that is endogenously produced in the peripheral and central nervous system through cysteine by the following major H2S producing enzymes in the brain: cystathionine-γlyase (CSE), cystathionine ß-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST). The physiological effects of H2S are broad, with antioxidative properties being a major role in the body. The aims of our investigation were to analyze the central nervous antioxidant, metabolic and neuronal effects in the hippocampus of the rat after inflammatory peripheral lipopolysaccharide (LPS) treatment; and to examine the effects of antipsychotics on the expression of these enzymes in human cell lines. Material and Methods: Male Lewis rats (250 g) received an i.p. LPS injection (1 mg/kg) 24 h before microdialysis experiments. Conscious rats were infused via these probes (1.5 μl/min) with a radical scavenger 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) in Krebs-Ringer solution. Sodiumhydrogensulfide (NaHS, 10 μg/min) was infused after a 2- h baseline for 1 h. Corticosterone, glutamate, glucose and lactate were measured by Elisa. Reactive oxygen species (ROS) were detected by electron spin resonance spectroscopy (ESR). The impact of the antipsychotics haloperidol, clozapine, olanzapine and risperidone on the expression of genes encoding the key enzymes of H2S synthesis was studied at the human neuroblastoma SH-SY5Y and monocytic U-937 cell lines. The cells were incubated for 24 h with 30 μM antipsychotic following which mRNA levels were measured by polymerase chain reaction. Results: Microdialysate glucose and lactate levels dramatically increased in the hippocampus of LPS untreated rats by local application of NaHS. By contrast, in the LPS pretreated rats, there was no effect of NaHS infusion on glucose but a further significant increase in microdialysate lactate was found. It was LPS pretreatment alone that particularly enhanced lactate levels. There was a marked increase in hippocampal microdialysate glutamate levels after local NaHS infusion in LPS untreated animals. In LPS treated rats, no change was observed by NaHS, but LPS itself had the strongest effect on microdialysate glutamate levels. Microdialysate corticosterone levels were reduced by NaHS in both LPS pretreated and untreated rats. The formation of free radicals in the hippocampus significantly reduced in LPS pretreated rats, while in LPS untreated rats a significant increase was observed after NaHS infusion. In human SH-SY5Y and U-937 cells, all three major enzymes of H2S-Synthesis, namely cystathionine-γ-lyase, cystathione ß-synthase and 3-mercaptopyruvate sulfurtransferase, could be detected by PCR. The antipsychotics haloperidol, clozapine, olanzapine and risperidone affected all three enzymes in different ways; with haloperidol and risperidone showing major effects that led to reductions in CBS or CSE expression. Discussion: The local application of NaHS in the hippocampus of the rat strongly affected glucose, lactate and glutamate release. Contrastingly, in LPS pretreated rats, a decreased radical formation was the only effect found. H2S synthetizing enzymes may be involved in antipsychotic mechanisms, although no clear common mechanism could be found.

Experimental research into the potential therapeutic effect of GYY4137 on Ovariectomy-induced osteoporosis

BACKGROUND

Evidence has shown that endogenous H2S plays an important role in the physiological and pathophysiological processes of many organs. The study aimed to explore whether exogenous H2S has a potential therapeutic effect on a rat ovariectomy-induced model of osteoporosis.

METHODS

The OVX osteoporosis model was established in female Sprague-Dawley rats by full bilateral ovariectomy. The rats were randomly divided into four groups, with the two experimental groups receiving an intraperitoneal injection of GYY4137 or sodium alendronate. The level of H2S in the plasma was determined and common laboratory indicators to diagnose osteoporosis, such as alkaline phosphatase (ALP) activity and the levels of osteocalcin (OCN), calcitonin, parathyroid hormone and leptin were measured. The bone mineral density (BMD) of the 4th and 5th lumbar vertebrae was measured using dual-energy X-ray absorptiometry. The maximum stress of femoral fracture was obtained through a three-point bending test of the femur.

RESULTS

The OVX osteoporosis model was successfully established. GYY4137 was injected to increase the level of H2S in the plasma in one group, designated OVX-GYY during the observation period (p < 0.05). At 12 weeks, the BMD value of the fourth lumbar vertebra in the OVX-GYY group had increased (p < 0.05). The BMD femur value in the OVX-vehicle group had decreased (p < 0.05). Bilateral ovariectomy leads to biochemical disorders related to bone metabolism and hormone levels in rat plasma (all p < 0.05). Ovariectomy also reduced blood calcium, blood phosphate and calcitonin, and increased parathyroid hormone and leptin. The opposite results were obtained for the groups with alendronate sodium or GYY4137 treatment (all p < 0.05).

CONCLUSIONS

Through the slow release of H2S, GYY4137 did an excellent job of simulating endogenous neuroendocrine gaseous signaling molecules. Exogenous H2S had a regulatory effect on osteoporosis in ovariectomized rats, showing potential value for the treatment of human postmenopausal osteoporosis.

Role of Hydrogen Sulfide in NRF2- and Sirtuin-Dependent Maintenance of Cellular Redox Balance

Hydrogen sulfide (H₂S) has arisen as a critical gasotransmitter signaling molecule modulating cellular biological events related to health and diseases in heart, brain, liver, vascular systems and immune response. Three enzymes mediate the endogenous production of H₂S: cystathione β-synthase (CBS), cystathione γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). CBS and CSE localizations are organ-specific. 3-MST is a mitochondrial and cytosolic enzyme. The generation of H₂S is firmly regulated by these enzymes under normal physiological conditions. Recent studies have highlighted the role of H₂S in cellular redox homeostasis, as it displays significant antioxidant properties. H₂S exerts antioxidant effects through several mechanisms, such as quenching reactive oxygen species (ROS) and reactive nitrogen species (RNS), by modulating cellular levels of glutathione (GSH) and thioredoxin (Trx-1) or increasing expression of antioxidant enzymes (AOE), by activating the transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2). H₂S also influences the activity of the histone deacetylase protein family of sirtuins, which plays an important role in inhibiting oxidative stress in cardiomyocytes and during the aging process by modulating AOE gene expression. This review focuses on the role of H₂S in NRF2 and sirtuin signaling pathways as they are related to cellular redox homeostasis.

Eugenol Confers Cadmium Tolerance via Intensifying Endogenous Hydrogen Sulfide Signaling in Brassica rapa

Eugenol, a plant-derived small compound, shows great medicinal potential. However, whether and how eugenol regulates crop physiology remains elusive. Here we reported that eugenol induced Cd (cadmium) tolerance in the root of Brassica rapa. Roots were treated with eugenol and CdCl₂ simultaneously (eugenol + Cd) or pretreated with eugenol followed by CdCl₂ treatment (eugenol → Cd). Eugenol significantly attenuated Cd-induced growth inhibition, ROS accumulation, oxidative injury, and cell death, which were confirmed by in vivo histochemical analysis. Eugenol remarkably decreased free Cd²⁺ accumulation in root. Eugenol intensified GSH (glutathione) accumulation in roots upon CdCl₂ exposure, which explained the decrease in free Cd²⁺ and attenuation of oxidative injury. Eugenol stimulated endogenous H₂S (hydrogen sulfide) generation by upregulating the expression of BrLCD ( l-cysteine desulfhydrase) and BrDCD ( d-cysteine desulfhydrase) as well as their enzymatic activities in CdCl₂-treated root. Application of H₂S biosynthesis inhibitor or H₂S scavenger led to the decrease in endogenous H₂S level in Cd-treated root, which further compromised all the above effects of eugenol. These findings suggested that eugenol triggered H₂S → GSH signaling cassette in plants to combat Cd stress, which shed new light on eugenol-modulated plant physiology and the interaction between eugenol and H₂S.

Remote ischemic conditioning as a cytoprotective strategy in vasculopathies during hyperhomocysteinemia: An emerging research perspective

Higher levels of nonprotein amino acid homocysteine (Hcy), that is, hyperhomocysteinemia (HHcy) (~5% of general population) has been associated with severe vasculopathies in different organs; however, precise molecular mechanism(s) as to how HHcy plays havoc with body's vascular networks are largely unknown. Interventional modalities have not proven beneficial to counter multifactorial HHcy's effects on the vascular system. An ancient Indian form of exercise called 'yoga' causes transient ischemia as a result of various body postures however the cellular mechanisms are not clear. We discuss a novel perspective wherein we argue that application of remote ischemic conditioning (RIC) could, in fact, deliver anticipated results to patients who are suffering from chronic vascular dysfunction due to HHcy. RIC is the mechanistic phenomenon whereby brief episodes of ischemia-reperfusion events are applied to distant tissues/organs; that could potentially offer a powerful tool in mitigating chronic lethal ischemia in target organs during HHcy condition via simultaneous reduction of inflammation, oxidative and endoplasmic reticulum stress, extracellular matrix remodeling, fibrosis, and angiogenesis. We opine that during ischemic conditioning our organs cross talk by releasing cellular messengers in the form of exosomes containing messenger RNAs, circular RNAs, anti-pyroptotic factors, protective cytokines like musclin, transcription factors, small molecules, anti-inflammatory, antiapoptotic factors, antioxidants, and vasoactive gases. All these could help mobilize the bone marrow-derived stem cells (having tissue healing properties) to target organs. In that context, we argue that RIC could certainly play a savior's role in an unfortunate ischemic or adverse event in people who have higher levels of the circulating Hcy in their systems.

An Update on Hydrogen Sulfide and Nitric Oxide Interactions in the Cardiovascular System

Hydrogen sulfide (H₂S) and nitric oxide (NO) are now recognized as important regulators in the cardiovascular system, although they were historically considered as toxic gases. As gaseous transmitters, H₂S and NO share a wide range of physical properties and physiological functions: they penetrate into the membrane freely; they are endogenously produced by special enzymes, they stimulate endothelial cell angiogenesis, they regulate vascular tone, they protect against heart injury, and they regulate target protein activity via posttranslational modification. Growing evidence has determined that these two gases are not independent regulators but have substantial overlapping pathophysiological functions and signaling transduction pathways. H₂S and NO not only affect each other's biosynthesis but also produce novel species through chemical interaction. They play a regulatory role in the cardiovascular system involving similar signaling mechanisms or molecular targets. However, the natural precise mechanism of the interactions between H₂S and NO remains unclear. In this review, we discuss the current understanding of individual and interactive regulatory functions of H₂S and NO in biosynthesis, angiogenesis, vascular one, cardioprotection, and posttranslational modification, indicating the importance of their cross-talk in the cardiovascular system.

Hydrogen sulfide improves postischemic neoangiogenesis in the hind limb of cystathionine-β-synthase mutant mice via PPAR-γ/VEGF axis

Neoangiogenesis is a fundamental process which helps to meet energy requirements, tissue growth, and wound healing. Although previous studies showed that Peroxisome proliferator-activated receptor (PPAR-γ) regulates neoangiogenesis via upregulation of vascular endothelial growth factor (VEGF), and both VEGF and PPAR-γ expressions were inhibited during hyperhomocysteinemic (HHcy), whether these two processes could trigger pathological effects in skeletal muscle via compromising neoangiogenesis has not been studied yet. Unfortunately, there are no treatment options available to date for ameliorating HHcy-mediated neoangiogenic defects. Hydrogen sulfide (H2 S) is a novel gasotransmitter that can induce PPAR-γ levels. However, patients with cystathionine-β-synthase (CBS) mutation(s) cannot produce a sufficient amount of H2 S. We hypothesized that exogenous supplementation of H2 S might improve HHcy-mediated poor neoangiogenesis via the PPAR-γ/VEGF axis. To examine this, we created a hind limb femoral artery ligation (FAL) in CBS+/- mouse model and treated them with GYY4137 (a long-acting H2 S donor compound) for 21 days. To evaluate neoangiogenesis, we used barium sulfate angiography and laser Doppler blood flow measurements in the ischemic hind limbs of experimental mice post-FAL to assess blood flow. Proteins and mRNAs levels were studied by Western blots and qPCR analyses. HIF1-α, VEGF, PPAR-γ and p-eNOS expressions were attenuated in skeletal muscle of CBS+/- mice after 21 days of FAL in comparison to wild-type (WT) mice, that were improved via GYY4137 treatment. We also found that the collateral vessel density and blood flow were significantly reduced in post-FAL CBS+/- mice compared to WT mice and these effects were ameliorated by GYY4137. Moreover, we found that plasma nitrite levels were decreased in post-FAL CBS+/- mice compared to WT mice, which were mitigated by GYY4137 supplementation. These results suggest that HHcy can inhibit neoangiogenesis via antagonizing the angiogenic signal pathways encompassing PPAR-γ/VEGF axis and that GYY4137 could serve as a potential therapeutic to alleviate the harmful metabolic effects of HHcy conditions.

Effect of H2S on gastric ischemia-reperfusion injury in rats

AIM

To assess the effect of H₂S on oxidative stress in gastric mucosal injury induced by gastric ischemia-reperfusion (GI-R) in rats.

METHODS

GI-R was induced in rats by clamping the celiac artery for 30 min followed by 1 h reperfusion. Based on this, the rats were intraperitoneally pre-injected with different concentrations of NaHS for 14 d. Image J software and HE staining were employed to analyze the gastric mucosal damage area and deep damage, respectively. Oxidative stress indexes of the gastric mucosa were detected using commercial kits and Western blot.

RESULTS

The effects of different concentrations of NaHS on gastric mucosal injury induced by GI-R were different. Pretreatment with 10 μmol/L NaHS significantly reduced the area and depth of gastric mucosal injury induced by GI-R, with no effect on plasma H₂S. Compared with the GI-R group, pretreatment with NaHS significantly decreased the levels of malondialdehyde and H₂O₂ as well as the expression of XOD, gp91phox, and p67phox, but increased the level of reduced glutathione and the activity of SOD.

CONCLUSION

Exogenous H₂S can protect the gastric mucosa by reducing oxidative stress induced by GI-R.

Hydrogen Sulfide Ameliorates Blood-Spinal Cord Barrier Disruption and Improves Functional Recovery by Inhibiting Endoplasmic Reticulum Stress-Dependent Autophagy

Spinal cord injury (SCI) induces the disruption of blood-spinal cord barrier (BSCB), which elicits neurological deficits by triggering secondary injuries. Hydrogen sulfide (H₂S) is a gaseous mediator that has been reported to have neuroprotective effect in the central nervous system. However, the relationship between H₂S and BSCB disruption during SCI remains unknown. Therefore, it is interesting to evaluate whether the administration of NaHS, a H₂S donor, can protect BSCB integrity against SCI and investigate the potential mechanisms underlying it. In present study, we found that SCI markedly activated endoplasmic reticulum (ER) stress and autophagy in a rat model of complete crushing injury to the spinal cord at T9 level. NaHS treatment prevented the loss of tight junction (TJ) and adherens junction (AJ) proteins both in vivo and in vitro. However, the protective effect of NaHS on BSCB restoration was significantly reduced by an ER stress activator (tunicamycin, TM) and an autophagy activator (rapamycin, Rapa). Moreover, SCI-induced autophagy was remarkably blocked by the ER stress inhibitor (4-phenylbutyric acid, 4-PBA). But the autophagy inhibitor (3-Methyladenine, 3-MA) only inhibited autophagy without obvious effects on ER stress. Finally, we had revealed that NaHS significantly alleviated BSCB permeability and improved functional recovery after SCI, and these effects were markedly reversed by TM and Rapa. In conclusion, our present study has demonstrated that NaHS treatment is beneficial for SCI recovery, indicating that H₂S treatment is a potential therapeutic strategy for promoting SCI recovery.

Neuroprotective Effect of Hydrogen Sulfide in Hyperhomocysteinemia Is Mediated Through Antioxidant Action Involving Nrf2

Homocysteine (Hcy) is a sulfur-containing amino acid derived from methionine metabolism. Elevated plasma Hcy levels (> 15 µM) result in a condition called hyperhomocysteinemia (HHcy), which is an independent risk factor in the development of various neurodegenerative disorders. Reactive oxygen species (ROS) produced by auto-oxidation of Hcy have been implicated in HHcy-associated neurological conditions. Hydrogen sulfide (H₂S) is emerging as a potent neuroprotective and neuromodulator molecule. The present study was aimed to evaluate the ability of NaHS (a source of H₂S) to attenuate Hcy-induced oxidative stress and altered antioxidant status in animals subjected to HHcy. Impaired cognitive functions assessed by Y-maze and elevated plus maze in Hcy-treated animals were reversed on NaHS administration. Increased levels of ROS, lipid peroxidation, protein carbonyls, and 4-hydroxynonenal (4-HNE)-modified proteins were observed in the cortex and hippocampus of Hcy-treated animals suggesting accentuated oxidative stress. This increase in Hcy-induced oxidative stress was reversed following NaHS supplementation. GSH/GSSG ratio, activity of antioxidant enzymes viz; superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were decreased in Hcy-treated animals. NaHS supplementation, on the otherhand, restored redox ratio and activity of antioxidant enzymes in the brains of animals with HHcy. Further, NaHS administration normalized nuclear factor erythroid 2-related factor 2 expression and acetylcholinesterase (AChE) activity in the brain of Hcy-treated animals. Histopathological studies using cresyl violet indicated higher number of pyknotic neurons in the cortex and hippocampus of HHcy animals, which were reversed by NaHS administration. The results clearly demonstrate that NaHS treatment significantly ameliorates Hcy-induced cognitive impairment by attenuating oxidative stress, improving antioxidant status, and modulating AChE activity thereby suggesting potential of H₂S as a therapeutic molecule.

The Drug Developments of Hydrogen Sulfide on Cardiovascular Disease

The recognition of hydrogen sulfide (H₂S) has been evolved from a toxic gas to a physiological mediator, exhibiting properties similar to NO and CO. On the one hand, H₂S is produced from L-cysteine by enzymes of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3MST) in combination with aspartate aminotransferase (AAT) (also called as cysteine aminotransferase, CAT); on the other hand, H₂S is produced from D-cysteine by enzymes of D-amino acid oxidase (DAO). Besides sulfide salt, several sulfide-releasing compounds have been synthesized, including organosulfur compounds, Lawesson's reagent and analogs, and plant-derived natural products. Based on garlic extractions, we synthesized S-propargyl-L-cysteine (SPRC) and its analogs to contribute our endeavors on drug development of sulfide-containing compounds. A multitude of evidences has presented H₂S is widely involved in the roles of physiological and pathological process, including hypertension, atherosclerosis, angiogenesis, and myocardial infarcts. This review summarizes current sulfide compounds, available H₂S measurements, and potential molecular mechanisms involved in cardioprotections to help researchers develop further applications and therapeutically drugs.

Thymoquinone increases the expression of neuroprotective proteins while decreasing the expression of pro-inflammatory cytokines and the gene expression NFκB pathway signaling targets in LPS/IFNγ -activated BV-2 microglia cells

Neuroinflammation and microglial activation are pathological markers of a number of central nervous system (CNS) diseases. Chronic activation of microglia induces the release of excessive amounts of reactive oxygen species (ROS) and pro-inflammatory cytokines. Additionally, chronic microglial activation has been implicated in several neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Thymoquinone (TQ) has been identified as one of the major active components of the natural product Nigella sativa seed oil. TQ has been shown to exhibit anti-inflammatory, anti-oxidative, and neuroprotective effects. In this study, lipopolysaccharide (LPS) and interferon gamma (IFNγ) activated BV-2 microglial cells were treated with TQ (12.5 μM for 24 h). We performed quantitative proteomic analysis using Orbitrap/Q-Exactive Proteomic LC-MS/MS (Liquid chromatography-mass spectrometry) to globally assess changes in protein expression between the treatment groups. Furthermore, we evaluated the ability of TQ to suppress the inflammatory response using ELISArray™ for Inflammatory Cytokines. We also assessed TQ's effect on the gene expression of NFκB signaling targets by profiling 84 key genes via real-time reverse transcription (RT2) PCR array. Our results indicated that TQ treatment of LPS/IFNγ-activated microglial cells significantly increased the expression of 4 antioxidant, neuroprotective proteins: glutaredoxin-3 (21 fold; p < 0.001), biliverdin reductase A (15 fold; p < 0.0001), 3-mercaptopyruvate sulfurtransferase (11 fold; p < 0.01), and mitochondrial lon protease (>8 fold; p < 0.001) compared to the untreated, activated cells. Furthermore, TQ treatment significantly (P < 0.0001) reduced the expression of inflammatory cytokines, IL-2 = 38%, IL-4 = 19%, IL-6 = 83%, IL-10 = 237%, and IL-17a = 29%, in the activated microglia compared to the untreated, activated which expression levels were significantly elevated compared to the control microglia: IL-2 = 127%, IL-4 = 151%, IL-6 = 670%, IL-10 = 133%, IL-17a = 127%. Upon assessing the gene expression of NFκB signaling targets, this study also demonstrated that TQ treatment of activated microglia resulted in >7 fold down-regulation of several NFκB signaling targets genes, including interleukin 6 (IL6), complement factor B (CFB), chemokine (CC motif) ligand 3 (CXCL3), chemokine (CC) motif ligand 5 (CCL5) compared to the untreated, activated microglia. This modulation in gene expression counteracts the >10-fold upregulation of these same genes observed in the activated microglia compared to the controls. Our results show that TQ treatment of LPS/IFNγ-activated BV-2 microglial cells induce a significant increase in expression of neuroprotective proteins, a significant decrease in expression inflammatory cytokines, and a decrease in the expression of signaling target genes of the NFκB pathway. Our findings are the first to show that TQ treatment increased the expression of these neuroprotective proteins (biliverdin reductase-A, 3-mercaptopyruvate sulfurtransferase, glutaredoxin-3, and mitochondrial lon protease) in the activated BV-2 microglial cells. Additionally, our results indicate that TQ treatment decreased the activation of the NFκB signaling pathway, which plays a key role in neuroinflammation. In conclusion, our results demonstrate that TQ treatment reduces the inflammatory response and modulates the expression of specific proteins and genes and hence potentially reduce neuroinflammation and neurodegeneration driven by microglial activation.

Sulfite protects neurons from oxidative stress

BACKGROUND AND PURPOSE

Hydrogen sulfide (H₂ S) and polysulfides (H₂ S_n ) are signalling molecules that mediate various physiological responses including cytoprotection. Their oxidized metabolite sulfite (SO₃ ^2- ) is found in blood and tissues. However, its physiological role remains unclear. In this study, we investigated the cytoprotective effect of sulfite on neurons exposed to oxidative stress caused by high concentrations of the neurotransmitter glutamate, known as oxytosis.

EXPERIMENTAL APPROACH

Concentrations of sulfite as well as those of cysteine and GSH in rats were measured by HPLC. Cytoprotective effects of sulfite on primary cultures of rat neurons against oxytosis was examined by WST-8 cytoprotective and LDH cytotoxicity assays and compared with that of H₂ S, H₂ S_n and thiosulfate.

KEY RESULTS

Free sulfite, present at approximately 2 μM in the rat brain, converts cystine to cysteine more efficiently than H₂ S and H₂ S_n and facilitates transport of cysteine into cells. Physiological concentrations of sulfite protected neurons from oxytosis and were accompanied by increased intracellular concentrations of cysteine and GSH probably due to converting extracellular cystine to cysteine, more efficiently than H₂ S and H₂ S_n . In contrast, thiosulfate only slightly protected neurons from oxytosis.

CONCLUSIONS AND IMPLICATIONS

Our present data have shown sulfite to be a novel cytoprotective molecule against oxytosis, through maintaining cysteine levels in the extracellular milieu, leading to increased intracellular cysteine and GSH. Although there may be adverse clinical effects in sensitive individuals, our results provide a new insight into the therapeutic application of sulfite to neuronal diseases caused by oxidative stress.

LINKED ARTICLES

This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.

Hydrogen Sulfide As a Potential Target in Preventing Spermatogenic Failure and Testicular Dysfunction

AIMS

Testis and sperm are particularly susceptible to inflammation and oxidative stress. Although hydrogen sulfide (H₂S) has been considered an important biological signaling molecule in inflammatory and oxidative stress processes, its role in the male reproductive system was poorly understood. The aim of this study was to investigate the role of H₂S in the regulation of male reproductive system.

RESULTS

We found that both subfertile and infertile patients, especially asthenospermic patients, exhibited decreased concentration of H₂S in their seminal plasma and diminished expression of H₂S-generating enzyme (cystathionine β-synthase [CBS]) in sperm. Supplying exogenous H₂S to semen improved sperm motility of these asthenospermic patients. Furthermore, decreased sperm motility was observed in animal models with a defective in H₂S generation such as lipopolysaccharide-treated mice, diabetic mice, and CBS-deficient mice. Our research showed that stress-induced reductions of endogenous H₂S production and CBS expression are correlated with impaired spermatogenesis and a defective blood-testis barrier. Supplying exogenous H₂S or overexpressing CBS could relieve the spermatogenic failure. This occurred primarily through the combination of anti-inflammatory and antioxidative effects.

INNOVATION

These results provide the first indication that H₂S is important for maintaining male fertility and protecting testicular function.

CONCLUSION

H₂S plays an important role in spermatogenic failure and testicular dysfunction mainly by its anti-inflammatory and antioxidative effects. Antioxid. Redox Signal. 28, 1447-1462.

A Hibernation-Like State for Transplantable Organs: Is Hydrogen Sulfide Therapy the Future of Organ Preservation?

SIGNIFICANCE

Renal transplantation is the treatment of choice for end-stage renal disease, during which renal grafts from deceased donors are routinely cold stored to suppress metabolic demand and thereby limit ischemic injury. However, prolonged cold storage, followed by reperfusion, induces extensive tissue damage termed cold ischemia/reperfusion injury (IRI) and puts the graft at risk of both early and late rejection. Recent Advances: Deep hibernators constitute a natural model of coping with cold IRI as they regularly alternate between 4°C and 37°C. Recently, endogenous hydrogen sulfide (H₂S), a gas with a characteristic rotten egg smell, has been implicated in organ protection in hibernation.

CRITICAL ISSUES

In renal transplantation, H₂S also seems to confer cytoprotection by lowering metabolism, thereby creating a hibernation-like environment, and increasing preservation time while allowing cellular processes of preservation of homeostasis and tissue remodeling to take place, thus increasing renal graft survival.

FUTURE DIRECTIONS

Although the underlying cellular and molecular mechanisms of organ protection during hibernation have not been fully explored, mammalian hibernation may offer a great clinical promise to safely cold store and reperfuse donor organs. In this review, we first discuss mammalian hibernation as a natural model of cold organ preservation with reference to the kidney and highlight the involvement of H₂S during hibernation. Next, we present recent developments on the protective effects and mechanisms of exogenous and endogenous H₂S in preclinical models of transplant IRI and evaluate the potential of H₂S therapy in organ preservation as great promise for renal transplant recipients in the future. Antioxid. Redox Signal. 28, 1503-1515.

A hypothesis for treating inflammation and oxidative stress with hydrogen sulfide during age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness and is becoming a global crisis since affected people will increase to 288 million by 2040. Genetics, age, diabetes, gender, obesity, hypertension, race, hyperopia, iris-color, smoking, sun-light and pyroptosis have varying roles in AMD, but oxidative stress-induced inflammation remains a significant driver of pathobiology. Eye is a unique organ as it contains a remarkable oxygen-gradient that generates reactive oxygen species (ROS) which upregulates inflammatory pathways. ROS becomes a source of functional and morphological impairments in retinal pigment epithelium (RPE), endothelial cells and retinal ganglion cells. Reports demonstrated that hydrogen sulfide (H₂S) acts as a signaling molecule and that it may treat ailments. Therefore, we propose a novel hypothesis that H₂S may restore homeostasis in the eyes thereby reducing damage caused by oxidative injury and inflammation. Since H₂S has been shown to be a powerful antioxidant because of its free-radicals' inhibition properties in addition to its beneficial effects in age-related conditions, therefore, patients may benefit from H₂S salubrious effects not only by minimizing their oxidant and inflammatory injuries to retina but also by lowering retinal glutamate excitotoxicity.

Activation of autophagic flux and the Nrf2/ARE signaling pathway by hydrogen sulfide protects against acrylonitrile-induced neurotoxicity in primary rat astrocytes

Hydrogen sulfide (H₂S), the third gasotransmitter, has been shown to act as a neuroprotective factor in numerous pathological processes; however, its underlying mechanism(s) of action remain unclear. It is widely accepted that activation of moderate autophagy and the Nrf2/ARE signaling pathway play important roles in the biological self-defense systems. In the present study, we investigated whether exogenous H₂S protects against the cytotoxicity of acrylonitrile (AN), a neurotoxin, in primary rat astrocytes. We found that pretreatment for 1 h with sodium hydrosulfide (NaHS), a donor of H₂S (200-800 µM), significantly attenuated the AN-induced decrease in cell viability, increase in lactate dehydrogenase release and morphological changes. Furthermore, NaHS significantly attenuated AN-induced oxidative stress by reducing reactive oxygen species (ROS) levels and increasing glutathione (GSH) concentration. Moreover, NaHS activated the autophagic flux, detectable as a change in autophagy-related proteins (Beclin-1, Atg5 and p62), the formation of acidic vesicular organelles and LC3B aggregation, confirmed by adenoviral expression of mRFP-GFP-LC3. Additionally, NaHS stimulated translocation of Nrf2 into the nucleus and increased expression of heme oxygenase-1 and γ-glutamylcysteine synthetase, downstream targets of Nrf2. Notably, the autophagy inhibitor 3-methyladenine and Beclin-1, or Nrf2-targeted siRNA, significantly attenuated the neuroprotective effects of NaHS against AN-induced neurotoxicity. In conclusion, we identified a crucial role of  autophagy and the Nrf2/ARE signaling pathway in H₂S-mediated neuroprotection against AN-induced toxicity in primary rat astrocytes. Our findings provide novel insights into the mechanisms of H₂S-mediated neuroprotection, and suggest that H₂S-based donors may serve as potential new candidate drugs to treat AN-induced neurotoxicity.

The effects of graded levels of calorie restriction: XI. Evaluation of the main hypotheses underpinning the life extension effects of CR using the hepatic transcriptome

Calorie restriction (CR) may extend longevity by modulating the mechanisms involved in aging. Different hypotheses have been proposed for its main mode of action. We quantified hepatic transcripts of male C57BL/6 mice exposed to graded levels of CR (0% to 40% CR) for three months, and evaluated the responses relative to these various hypotheses. Of the four main signaling pathways implied to be linked to the impact of CR on lifespan (insulin/insulin like growth factor 1 (IGF-1), nuclear factor-kappa beta (NF-ĸB), mechanistic target of rapamycin (mTOR) and sirtuins (SIRTs)), all the pathways except SIRT were altered in a manner consistent with increased lifespan. However, the expression levels of SIRT4 and SIRT7 were decreased with increasing levels of CR. Changes consistent with altered fuel utilization under CR may reduce reactive oxygen species production, which was paralleled by reduced protection. Downregulated major urinary protein (MUP) transcription suggested reduced reproductive investment. Graded CR had a positive effect on autophagy and xenobiotic metabolism, and was protective with respect to cancer signaling. CR had no significant effect on fibroblast growth factor-21 (FGF21) transcription but affected transcription in the hydrogen sulfide production pathway. Responses to CR were consistent with several different hypotheses, and the benefits of CR on lifespan likely reflect the combined impact on multiple aging related processes.

Use of gasotransmitters for the controlled release of polymer-based nitric oxide carriers in medical applications

Nitric Oxide (NO) is a small molecule gasotransmitter synthesized by nitric oxide synthase in almost all types of mammalian cells. NO is synthesized by NO synthase by conversion of l-arginine to l-citrulline in the human body. NO then stimulates soluble guanylate cyclase, from which various physiological functions are mediated in a concentration-dependent manner. High concentrations of NO induce apoptosis or antibacterial responses whereas low NO circulation leads to angiogenesis. The bidirectional effect of NO has attracted considerable attention, and efforts to deliver NO in a controlled manner, especially through polymeric carriers, has been the topic of much research. This naturally produced signaling molecule has stood out as a potentially more potent therapeutic agent compared to exogenously synthesized drugs. In this review, we will focus on past efforts of using the controlled release of NO via polymer-based materials to derive specific therapeutic results. We have also added studies and our future suggestions on co-delivery methods with other gasotransmitters as a step towards developing multifunctional carriers.

Hydrogen sulfide in physiology and pathogenesis of bacteria and viruses

An increasing number of studies have established hydrogen sulfide (H₂S) gas as a major cytoprotectant and redox modulator. Following its discovery, H₂S has been found to have pleiotropic effects on physiology and human health. H₂S acts as a gasotransmitter and exerts its influence on gastrointestinal, neuronal, cardiovascular, respiratory, renal, and hepatic systems. Recent discoveries have clearly indicated the importance of H₂S in regulating vasorelaxation, angiogenesis, apoptosis, ageing, and metabolism. Contrary to studies in higher organisms, the role of H₂S in the pathophysiology of infectious agents such as bacteria and viruses has been less studied. Bacterial and viral infections are often accompanied by changes in the redox physiology of both the host and the pathogen. Emerging studies indicate that bacterial-derived H₂S constitutes a defense system against antibiotics and oxidative stress. The H₂S signaling pathway also seems to interfere with redox-based events affected on infection with viruses. This review aims to summarize recent advances on the emerging role of H₂S gas in the bacterial physiology and viral infections. Such studies have opened up new research avenues exploiting H₂S as a potential therapeutic intervention.

Increased H2S and its synthases in urothelial cell carcinoma of the bladder, and enhanced cisplatin-induced apoptosis following H2S inhibition in EJ cells

H²S, synthesized by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (MPST), functions as a signalling molecule in mammalian cells. H²S serves complex functions in physiological and pathological processes, including in bladder cancer. In the present study, H²S production, the expression of the associated enzymes and the effect of H²S on human urothelial cell carcinoma of the bladder (UCB) tissue and cell lines were evaluated, and whether decreasing H²S levels influenced cell viability and tumour growth following treatment with cisplatin (CDDP) was assessed in UCB cells in vitro and in vivo. H²S production and the expression of CBS, CSE and MPST in bladder tissue specimens and the UCB cell lines 5637, EJ and UM-UC-3 were analysed using a sulfur-sensitive electrode and western blotting. UCB cells were subjected to different treatments, and viability and protein expression were determined. H²S production was inhibited to examine its influence on EJ cell tumour growth following CDDP treatment in vivo. It was identified that CBS, CSE and MPST protein were up-regulated in UCB tissues and cells. The H²S production and enzyme expression levels were the highest in UCB tissue and EJ cells. The inhibition of endogenous H²S biosynthesis decreased EJ cell viability and tumour growth in response to CDDP treatment. H²S levels and the associated biosynthetic enzymes were increased in human UCB tissue and cells compared with adjacent tissue and normal cells, which may have increased the resistance to CDDP-induced apoptosis in UCB. Therefore, H²S and its production may be an alternative therapeutic target for UCB.

Cystathionine γ-Lyase Is Involved in the Renoprotective Effect of Brief and Repeated Ischemic Postconditioning After Renal Ischemia/Reperfusion Injury in Diabetes Mellitus

BACKGROUND

The aim of this study was to determine whether the protective effects of brief and repeated ischemic postconditioning (IPoC) are associated with the modulation of cystathionine γ-lyase (CSE) expression after renal ischemia/reperfusion (I/R) injury in diabetes mellitus (DM).

METHODS

We subjected diabetic rats to 45 minutes of ischemia followed by reperfusion at 24 hours. Before reperfusion, diabetic rats were treated with 3 cycles of 6 seconds of reperfusion, followed by 6 seconds of ischemia. DL-Propargylglycine (PAG, a CSE inhibitor) was administered to the diabetic rats to investigate its effects on the severity of renal I/R injury in diabetes mellitus (DM). Blood samples and left kidneys were collected for the measurement of blood urea nitrogen (BUN) and serum creatinine (SCr) levels and renal pathologic changes. Western blot and immunochemistry techniques were also performed for the localization of CSE. Levels of superoxidase dismutase (SOD), malonyldialdehyde (MDA), tumor necrosis-alpha (TNF-α), and hydrogen sulfide (H₂S) were quantified using commercially available kits.

RESULTS

The results showed that BUN and SCr levels increased on renal ischemia/reperfusion injury (RI/RI) in the DM group. Diabetic rats treated with IPoC exhibited significantly less renal damage on I/R. Kit measurements showed that IPoC could markedly inhibit the levels of MDA and TNF-α and also improve SOD and H₂S levels. Western blot and immunochemistry showed that expression of CSE was downregulated on I/R in the DM group and IPoC upregulated CSE expression, whereas PAG treatment resulted in opposite effects.

CONCLUSION

Our findings show that brief and repeated IPoC increased the expression of CSE after I/R in DM, and the modulation of CSE may underlie the renoprotective effect of IPoC.

A timeline of hydrogen sulfide (H2S) research: From environmental toxin to biological mediator

The history of H2S - as an environmental toxin - dates back to 1700, to the observations of the Italian physician Bernardino Ramazzini, whose book "De Morbis Artificum Diatriba" described the painful eye irritation and inflammation of "sewer gas" in sewer workers. The gas has subsequently been identified as hydrogen sulfide (H2S), and opened three centuries of research into the biological roles of H2S. The current article highlights the key discoveries in the field of H2S research, including (a) the toxicological studies, which characterized H2S as an environmental toxin, and identified some of its modes of action, including the inhibition of mitochondrial respiration; (b) work in the field of bacteriology, which, starting in the early 1900s, identified H2S as a bacterial product - with subsequently defined roles in the regulation of periodontal disease (oral bacterial flora), intestinal epithelial cell function (enteral bacterial flora) as well as in the regulation of bacterial resistance to antibiotics; and (c), work in diverse fields of mammalian biology, which, starting in the 1940s, identified H2S as an endogenous mammalian enzymatic product, the functions of which - among others, in the cardiovascular and nervous system - have become subjects of intensive investigation for the last decade. The current review not only enumerates the key discoveries related to H2S made over the last three centuries, but also compiles the most frequently cited papers in the field which have been published over the last decade and highlights some of the current 'hot topics' in the field of H2S biology.

Gasotransmitter hydrogen sulfide signaling in neuronal health and disease

Hydrogen sulfide is a gaseous signaling molecule or gasotransmitter which plays important roles in a wide spectrum of physiologic processes in the brain and peripheral tissues. Unlike nitric oxide and carbon monoxide, the other major gasotransmitters, research on hydrogen sulfide is still in its infancy. One of the modes by which hydrogen sulfide signals is via a posttranslational modification termed sulfhydration/persulfidation, which occurs on reactive cysteine residues on target proteins, where the reactive SH group is converted to an SSH group. Sulfhydration is a substantially prevalent modification, which modulates the structure or function of proteins being modified. Thus, precise control of endogenous hydrogen sulfide production and metabolism is critical for maintenance of optimal cellular function, with excess generation and paucity, both contributing to pathology. Dysregulation of the reverse transsulfuration pathway which generates hydrogen sulfide occurs in several neurodegenerative diseases such as Parkinson's disease, Huntington's disease and Alzheimer's disease. Accordingly, treatment with donors of hydrogen sulfide or stimulation of the reverse transsulfuration have proved beneficial in several neurodegenerative states. In this review we focus on hydrogen sulfide mediated neuronal signaling processes that contribute to neuroprotection.