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

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

Hydrogen sulfide and its donors for the treatment of cerebral ischaemia-reperfusion injury: A comprehensive review

As an endogenous gas signalling molecule, hydrogen sulfide (H₂S) is frequently present in a variety of mammals and plays a significant role in the cardiovascular and nervous systems. Reactive oxygen species (ROS) are produced in large quantities as a result of cerebral ischaemia-reperfusion, which is a very serious class of cerebrovascular diseases. ROS cause oxidative stress and induce specific gene expression that results in apoptosis. H₂S reduces cerebral ischaemia-reperfusion-induced secondary injury via anti-oxidative stress injury, suppression of the inflammatory response, inhibition of apoptosis, attenuation of cerebrovascular endothelial cell injury, modulation of autophagy, and antagonism of P2X7 receptors, and it plays an important biological role in other cerebral ischaemic injury events. Despite the many limitations of the hydrogen sulfide therapy delivery strategy and the difficulty in controlling the ideal concentration, relevant experimental evidence demonstrating that H₂S plays an excellent neuroprotective role in cerebral ischaemia-reperfusion injury (CIRI). This paper examines the synthesis and metabolism of the gas molecule H₂S in the brain as well as the molecular mechanisms of H₂S donors in cerebral ischaemia-reperfusion injury and possibly other unknown biological functions. With the active development in this field, it is expected that this review will assist researchers in their search for the potential value of hydrogen sulfide and provide new ideas for preclinical trials of exogenous H₂S.

Protection against Hypoxia-Reoxygenation Injury of Hippocampal Neurons by H2S via Promoting Phosphorylation of ROCK2 at Tyr722 in Rat Model

The RhoA-ROCK signaling pathway is associated with the protective effects of hydrogen sulfide (H₂S) against cerebral ischemia. H₂S protects rat hippocampal neurons (RHNs) against hypoxia-reoxygenation (H/R) injury by promoting phosphorylation of RhoA at Ser188. However, effect of H₂S on the phosphorylation of ROCK₂-related sites is unclear. The present study was designed to investigate whether H₂S can play a role in the phosphorylation of ROCK₂ at Tyr722, and explore whether this role mediates the protective effect of H/R injury in RHNs. Prokaryotic recombinant plasmids ROCK₂^wild-pGEX-6P-1 and ROCK₂^Y722F-pGEX-6P-1 were constructed and transfected into E. coli in vitro, and the expressed protein, GST-ROCK₂^wild and GST-ROCK₂^Y722F were used for phosphorylation assay in vitro. Eukaryotic recombinant plasmids ROCK₂^Y722-pEGFP-N1 and ROCK₂^Y722F-pEGFP-N1 as well as empty plasmid were transfected into the RHNs. Western blot assay and whole-cell patch-clamp technique were used to detect phosphorylation of ROCK₂ at Tyr722 and BK_Ca channel current in the RHNs, respectively. Cell viability, leakages of intracellular enzymes lactate dehydrogenase (LDH), and nerve-specific enolase (NSE) were measured. The H/R injury was indicated by decrease of cell viability and leakages of intracellular LDH and NSE. The results of Western blot have shown that NaHS, a H₂S donor, significantly promoted phosphorylation of GST-ROCK₂^wild at Tyr722, while no phosphorylation of GST-ROCK₂^Y722F was detected. The phosphorylation of ROCK₂^wild promoted by NaHS was also observed in RHNs. NaHS induced more potent effects on protection against H/R injury, phosphorylation of ROCK₂ at Tyr722, inhibition of ROCK₂ activity, as well as increase of the BK_Ca current in the ROCK₂^Y722-pEGFP-N1-transfected RHNs. Our results revealed that H₂S protects the RHNs from H/R injury through promoting phosphorylation of ROCK₂ at Tyr722 to inhibit ROCK₂ activity and potentially by opening channel currents.

Roles of the RhoA-ROCK Signaling Pathway in the Endothelial H2S Production and Vasodilation in Rat Cerebral Arteries

Cerebral endothelial H₂S protects against cerebral ischemia-reperfusion injury through vasodilation, but its cerebral vasodilation mechanism and regulation of production are poorly understood. The RhoA-ROCK pathway plays important roles in vascular function. In this study, the roles of this pathway in the endothelial H₂S production and vasodilation in rat cerebral arteries were investigated. Acetylcholine significantly increased H₂S-generating enzyme cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) protein expressions and H₂S production in rat cerebrovascular endothelial cells (ECs), but the increases were markedly decreased by the M receptor blocker atropine or the CSE inhibitor dl-propargylglycine. Pretreatment with dl-propargylglycine or the 3-MST inhibitor l-aspartic acid markedly reduced the acetylcholine-increased H₂S; CSE protein expression and H₂S levels in the ECs were obviously attenuated by the RhoA agonist U₄₆₆₁₉ but increased by the RhoA inhibitor C3 transferase. U₄₆₆₁₉ also reduced 3-MST protein expression; Acetylcholine markedly inhibited RhoA protein expression and activity, but the inhibition was obviously reversed by atropine, dl-propargylglycine, and l-aspartic acid, respectively; Acetylcholine-induced endothelium-dependent vasodilation in rat cerebral basilar artery was significantly attenuated by pretreatment with dl-propargylglycine or l-aspartic acid or RhoA inhibitor CCG-1423 or ROCK inhibitor KD025, and was further decreased by co-pretreatment with dl-propargylglycine (or l-aspartic acid) and CCG-1423 (or KD025); NaHS significantly relaxed rat cerebral basilar artery vascular smooth muscle cells and inhibited ROCK_1/2 activities, phosphorylated myosin light chain (MLC) protein expression, and KCl-increased [Ca²⁺]_i, but these relaxation and inhibitions were markedly attenuated by pretreatment with C3 transferase or ROCK inhibitor Y27632. Our results demonstrated that endothelial H₂S production is promoted by activation of the M receptor but inhibited by the RhoA-ROCK pathway in rat cerebral arteries; the endothelial H₂S induces cerebral vasodilation by inhibiting this pathway to reduce phosphorylation of MLC and [Ca²⁺]_i in vascular smooth muscle cells.

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

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

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

Hydrogen sulfide (H₂S) and hydrogen polysulfides (H₂S_n) are essential regulatory signaling molecules generated by the entire body, including the central nervous system. Researchers have focused on the classical H₂S signaling from the past several decades, whereas the last decade has shown the emergence of H₂S-induced protein S-sulfhydration signaling as a potential therapeutic approach. Cysteine S-persulfidation is a critical paradigm of post-translational modification in the process of H₂S signaling. Additionally, studies have shown the cross-relationship between S-sulfhydration and other cysteine-induced post-translational modifications, namely nitrosylation and carbonylation. In the central nervous system, S-sulfhydration is involved in the cytoprotection through various signaling pathways, viz. inflammatory response, oxidative stress, endoplasmic reticulum stress, atherosclerosis, thrombosis, and angiogenesis. Further, studies have demonstrated H₂S-induced S-sulfhydration in regulating different biological processes, such as mitochondrial integrity, calcium homeostasis, blood-brain permeability, cerebral blood flow, and long-term potentiation. Thus, protein S-sulfhydration becomes a crucial regulatory molecule in cerebrovascular and neurodegenerative diseases. Herein, we first described the generation of intracellular H₂S followed by the application of H₂S in the regulation of cerebral blood flow and blood-brain permeability. Further, we described the involvement of S-sulfhydration in different biological and cellular functions, such as inflammatory response, mitochondrial integrity, calcium imbalance, and oxidative stress. Moreover, we highlighted the importance of S-sulfhydration in cerebrovascular and neurodegenerative diseases.

VEGFR2 in vascular smooth muscle cells mediates H2S-induced dilation of the rat cerebral basilar artery

INTRODUCTION

The aim of present study was to study whether the vascular endothelial growth factor receptor 2 (VEGFR₂) mediates hydrogen sulfide (H₂S)-induced relaxation of the rat cerebral vasculature.

METHODS

Relaxation of cerebral basilar artery (CBA) and vascular smooth muscle cells (VSMCs) was measured by using a pressure myograph system and image analysis system, respectively. The intracellular calcium concentration ([Ca²⁺]_i) in VSMCs was detected using fluorescence imaging analysis.

RESULTS

We found that H₂S donor NaHS induced significant relaxation of VSMCs from the CBA of wild type rat, but in VEGFR₂ knockdown VSMCs, NaHS-induced relaxation reduced markedly. In addition, NaHS-induced vasodilation of rat CBA also attenuated obviously when the expression of VEGFR₂ was knocked down in vivo. In addition, pretreatment with the VEGFR₂ blocker SU5416 likewise lowered the NaHS-induced relaxation of rat CBA. Nevertheless, the VEGFR₂ agonist, vascular endothelial growth factor 164 (VEGF164), induced a concentration-dependent relaxation of CBA, which is similar to the effect of NaHS. Furthermore, we found that both NaHS and VEGF164 significantly inhibited the U₄₆₆₁₉-induced increase of [Ca²⁺]_i fluorescence intensity in the VSMCs. However, the inhibitory effect of NaHS on the [Ca²⁺]_i fluorescence intensity in VSMCs was markedly inhibited by pretreatment with SU5416 or VEGFR₂ knockdown.

CONCLUSION

These findings indicated that H₂S-induced CBA dilation and reduction of [Ca²⁺]_i in VSMCs occur by acting on VEGFR₂.

Endothelium-derived hydrogen sulfide acts as a hyperpolarizing factor and exerts neuroprotective effects via activation of large-conductance Ca2+ -activated K+ channels

BACKGROUND AND PURPOSE

Endothelium-derived hyperpolarizing factor (EDHF) has been suggested as a therapeutic target for vascular protection against ischaemic brain injury. However, the molecular entity of EDHF and its action on neurons remains unclear. This study was undertaken to demonstrate whether the hydrogen sulfide (H₂ S) acts as EDHF and exerts neuroprotective effect via large-conductance Ca²⁺ -activated K⁺ (BK_Ca /K_Ca 1.1) channels.

EXPERIMENTAL APPROACH

The whole-cell patch-clamp technology was used to record the changes of BK_Ca currents in rat neurons induced by EDHF. The cerebral ischaemia/reperfusion model of mice and oxygen-glucose deprivation/reoxygenation (OGD/R) model of neurons were used to explore the neuroprotection of EDHF by activating BK_Ca channels in these neurons.

KEY RESULTS

Increases of BK_Ca currents and membrane hyperpolarization in hippocampal neurons induced by EDHF could be markedly inhibited by BK_Ca channel inhibitor iberiotoxin or endothelial H₂ S synthase inhibitor propargylglycine. The H₂ S donor, NaHS-induced BK_Ca current and membrane hyperpolarization in neurons were also inhibited by iberiotoxin, suggesting that H₂ S acts as EDHF and activates the neuronal BK_Ca channels. Besides, we found that the protective effect of endothelium-derived H₂ S against mice cerebral ischaemia/reperfusion injury was disrupted by iberiotoxin. Importantly, the inhibitory effect of NaHS or BK_Ca channel opener on OGD/R-induced neuron injury and the increment of intracellular Ca²⁺ level could be inhibited by iberiotoxin but enhanced by co-application with L-type but not T-type calcium channel inhibitor.

CONCLUSION AND IMPLICATIONS

Endothelium-derived H₂ S acts as EDHF and exerts neuroprotective effects via activating the BK_Ca channels and then inhibiting the T-type calcium channels in hippocampal neurons.

Hydrogen sulfide and vascular regulation - An update

BACKGROUND

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

AIM OF REVIEW

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

KEY SCIENTIFIC CONCEPTS OF REVIEW

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

Connexins: Key Players in the Control of Vascular Plasticity and Function

Of the 21 members of the connexin family, 4 (Cx37, Cx40, Cx43, and Cx45) are expressed in the endothelium and/or smooth muscle of intact blood vessels to a variable and dynamically regulated degree. Full-length connexins oligomerize and form channel structures connecting the cytosol of adjacent cells (gap junctions) or the cytosol with the extracellular space (hemichannels). The different connexins vary mainly with regard to length and sequence of their cytosolic COOH-terminal tails. These COOH-terminal parts, which in the case of Cx43 are also translated as independent short isoforms, are involved in various cellular signaling cascades and regulate cell functions. This review focuses on channel-dependent and -independent effects of connexins in vascular cells. Channels play an essential role in coordinating and synchronizing endothelial and smooth muscle activity and in their interplay, in the control of vasomotor actions of blood vessels including endothelial cell reactivity to agonist stimulation, nitric oxide-dependent dilation, and endothelial-derived hyperpolarizing factor-type responses. Further channel-dependent and -independent roles of connexins in blood vessel function range from basic processes of vascular remodeling and angiogenesis to vascular permeability and interactions with leukocytes with the vessel wall. Together, these connexin functions constitute an often underestimated basis for the enormous plasticity of vascular morphology and function enabling the required dynamic adaptation of the vascular system to varying tissue demands.

Imbalance of Homocysteine and H2S: Significance, Mechanisms, and Therapeutic Promise in Vascular Injury

While the role of hyperhomocysteinemia in cardiovascular pathogenesis continuously draws attention, deficiency of hydrogen sulfide (H₂S) has been growingly implicated in cardiovascular diseases. Generation of H₂S is closely associated with the metabolism of homocysteine via key enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The level of homocysteine and H₂S is regulated by each other. Metabolic switch in the activity of CBS and CSE may occur with a resultant operating preference change of these enzymes in homocysteine and H₂S metabolism. This paper presented an overview regarding (1) linkage between the metabolism of homocysteine and H₂S, (2) mutual regulation of homocysteine and H₂S, (3) imbalance of homocysteine and H₂S in cardiovascular disorders, (4) mechanisms underlying the protective effect of H₂S against homocysteine-induced vascular injury, and (5) the current status of homocysteine-lowering and H₂S-based therapies for cardiovascular disease. The metabolic imbalance of homocysteine and H₂S renders H₂S/homocysteine ratio a potentially reliable biomarker for cardiovascular disease and development of drugs or interventions targeting the interplay between homocysteine and H₂S to maintain the endogenous balance of these two molecules may hold an even bigger promise for management of vascular disorders than targeting homocysteine or H₂S alone.

Total flavones of Rhododendron simsii Planch flower protect rat hippocampal neuron from hypoxia-reoxygenation injury via activation of BKCa channel

OBJECTIVES

To study the effects of total flavones of Rhododendra simsii Planch flower (TFR) on hypoxia/reoxygenation (H/R) injury in rat hippocampal neurons and its underlying mechanism.

METHOD

Model of H/R was established in newborn rat primary cultured hippocampal neuron. Lactate dehydrogenase (LDH) and neuron-specific enolase (NSE) activity as well as malondialdehyde (MDA) content in cultured supernatants of the neurons were examined. Methyl thiazolyl tetrazolium assay and Hoechst33258 staining were, respectively, used to detect cell viability and apoptosis of neurons. Protein expression and current of BK_Ca channel were assessed by using Western blotting and whole-cell patch-clamp methods, respectively.

KEY FINDINGS

In the ranges of 3.7-300 mg/l, TFR significantly inhibited H/R-induced decrease of neuronal viability and increases of LDH, NSE and MDA in the supernatants as well as apoptosis; TFR 33.3, 100 and 300 mg/l markedly increased current of BK_Ca channel rather than the BK_Ca channel protein expression in the neurons.

CONCLUSIONS

Total flavones of R. simsii Planch flower had a protective effect against H/R injury in rat hippocampal neuron, and activation of BK_Ca channel may contribute to the neuroprotection.

Role of CSE-Produced H2S on Cerebrovascular Relaxation via RhoA-ROCK Inhibition and Cerebral Ischemia-Reperfusion Injury in Mice

The role of CSE-produced H₂S on cerebrovascular relaxation and cerebral ischemia-reperfusion (I/R) injury was investigated using CSE knockout (CSE^-/-) and wild-type (CSE^+/+) mice. The relaxation of the cerebral basilar artery (BA) to CSE-produced H₂S and its mechanism were detected. The results revealed that both NaHS, a donor of exogenous H₂S, and ROCK inhibitor Y27632 could induce significant relaxation of the BA, but the relaxation of the BA to NaHS was significantly attenuated by Y27632. In addition, removal of endothelium could reduce the relaxation of the BA to Y27632; CSE knockout also significantly attenuated Y27632-induced BA relaxation with endothelium rather than without endothelium. By contrast, the contraction of the BA from CSE^-/- mice to RhoA agonist LPA or U₄₆₆₁₉ was stronger than that from CSE^+/+ mice. Furthermore, RhoA activity and ROCK protein expression remarkably increased in the BA vascular smooth muscle cells (VSMCs) from CSE^-/- mouse, which were inhibited by NaHS pretreatment. These findings revealed that the CSE-produced H₂S induced cerebrovascular relaxation is generated from endothelial cells and the mechanism of vascular relaxation may relate to inhibition of RhoA-ROCK pathway. We next sought to confirm the protective effect of CSE-produced H₂S on cerebral I/R injury produced by middle cerebral artery occlusion and bilateral common carotid artery occlusion in mice. We investigated the changes of neurological deficit, cerebral infarct, brain water content, LDH decrease, MDA increase as well as impairment of learning and memory function. The results showed that the cerebral injury became more grievous in CSE^-/-mice than that in CSE^+/+mice, which could be remarkably alleviated by NaHS pretreatment.

Connexins in the control of vasomotor function

Vascular endothelial cells, as well as smooth muscle cells, show heterogeneity with regard to their receptor expression and reactivity. For the vascular wall to act as a functional unit, the various cells' responses require integration. Such an integration is not only required for a homogeneous response of the vascular wall, but also for the vasomotor behaviour of consecutive segments of the microvascular arteriolar tree. As flow resistances of individual sections are connected in series, sections require synchronization and coordination to allow effective changes of conductivity and blood flow. A prerequisite for the local coordination of individual vascular cells and different sections of an arteriolar tree is intercellular communication. Connexins are involved in a dual manner in this coordination. (i) By forming gap junctions between cells, they allow an intercellular exchange of signalling molecules and electrical currents. In particular, the spread of electrical currents allows for coordination of cell responses over longer distances. (ii) Connexins are able to interact with other proteins to form signalling complexes. In this way, they can modulate and integrate individual cells' responses also in a channel-independent manner. This review outlines mechanisms allowing the vascular connexins to exert their coordinating function and to regulate the vasomotor reactions of blood vessels both locally, and in vascular networks. Wherever possible, we focus on the vasomotor behaviour of small vessels and arterioles which are the main vessels determining vascular resistance, blood pressure and local blood flow.

Vascular Protection of Hydrogen Sulfide on Cerebral Ischemia/Reperfusion Injury in Rats

This study was undertaken to demonstrate the vascular protection of exogenous and endogenous hydrogen sulfide (H₂S) on cerebral ischemia/reperfusion (I/R) injury. The effect of H₂S on cerebrovascular dysfunction in middle cerebral artery (MCA) and neuronal damage were measured after cerebral I/R induced by transient middle cerebral artery occlusion (MCAO) in cystathionine c-lyase (CSE) knockdown and wild-type rats. The effect of sodium hydrosulfide (NaHS, donor of exogenous H₂S), L-cysteine (L-Cys, substrate of endogenous H₂S), and endothelium cells on the responses of isolated MCA derived from non-ischemic rats was also evaluated to assess the underlying mechanism of H₂S-mediate cerebral vasodilation. The results revealed that the contraction and dilation of MCA profoundly decreased after cerebral I/R. The vascular dysfunction became more grievous in CSE knockdown rats than in wild-type rats. Interestingly, this vascular dysfunction was significantly alleviated by NaHS supplementation. Moreover, both NaHS and L-cysteine could induce remarkable relaxation in the isolated MCA, which was eliminated by co-application of potassium channel blockers ChTx and Apamin, or endothelial removal. By contrast, adding endothelium cells cultured in vitro together with ACh into the luminal perfusate could mimic non-NO and non-PGI₂ relaxation in endothelium-denuded MCA, once CSE was knocked down from endothelium cells, and its effect on vasorelaxation was abolished. Furthermore, the indexes of neuronal injury were measured after cerebral I/R to confirm the neuroprotection of H₂S, and we found that the neurological scores, cerebral infarction volume, brain water content, malondialdehyde content, and serum lactate dehydrogenase activity (a marker of cellular membrane integrity) were significantly higher in CSE knockdown rats than in normal control rats. It is not surprising that NaHS could alleviate the cerebral injury. These findings revealed that H₂S has a protective effect on cerebral I/R injury via its upregulation of the endothelium-dependent contraction and dilation function of cerebral vessels, which may be related to activating potassium channel.

Total Flavones of Rhododendron simsii Planch Flower Protect against Cerebral Ischemia-Reperfusion Injury via the Mechanism of Cystathionine-γ-Lyase-Produced H2S

Total flavones of Rhododendron simsii Planch flower (TFR) have a significant protective effect against cerebral ischemia-reperfusion injury. However, its mechanism is unclear. This study investigated the protection of TFR against cerebral ischemia-reperfusion injury via cystathionine-γ-lyase- (CSE-) produced H2S mechanism. CSE-/- mice and CSE-siRNA-transfected rat were used. Relaxation of cerebral basilar artery (CBA), H2S, and CSE mRNA were measured. TFR significantly inhibited cerebral ischemia-reperfusion-induced abnormal neurological symptom and cerebral infarct in the normal rats and the CSE+/+ mice, but not in the CSE-/- mice, and the inhibition was markedly attenuated in CSE-siRNA-transfected rat; TFR elicited a significant vasorelaxation in rat CBA, and the relaxation was markedly attenuated by removal of endothelium or CSE-siRNA transfection or coapplication of NO synthase inhibitor L-NAME and PGI2 synthase inhibitor Indo. CSE inhibitor PPG drastically inhibited TFR-evoked vasodilatation resistant to L-NAME and Indo in endothelium-intact rat CBA. TFR significantly increased CSE mRNA expression in rat CBA endothelial cells and H2S production in rat endothelium-intact CBA. The increase of H2S production resistant to L-NAME and Indo was abolished by PPG. Our data indicate that TFR has a protective effect against the cerebral ischemia-reperfusion injury via CSE-produced H2S and endothelial NO and/or PGI2 to relax the cerebral artery.