Hydrogen sulphide protects mice against the mutual aggravation of cerebral ischaemia/reperfusion injury and colitis

Protective effects and mechanism of quercetin from Rhododendron dauricum against cerebral ischemia-reperfusion injury

METHODS

This study seeks to identify the bioactive compounds within Rhododendron dauricum and explore potential mechanisms for treating cerebral I/R injury through a comprehensive analysis employing network pharmacology, complemented by experimental validation.

RESULTS

The core targets associated with quercetin in the treatment of cerebral I/R injury are TNF-α, IL-6, IL-1β, and AKT1. Notably, we propose for the first time that its mode of action primarily involves the inhibition of the TNF-α/RhoA/ROCK2 pathway.

CONCLUSION

Our findings reveal that quercetin emerges as a pivotal bioactive component of Rhododendron dauricum in the context of cerebral I/R injury treatment.

H2S Regulates the Phenotypic Transformation of Astrocytes Following Cerebral Ischemia/Reperfusion via Inhibiting the RhoA/ROCK Pathway

The role of hydrogen sulfide (H2S) on the phenotypic change of astrocytes following cerebral ischemia/reperfusion (I/R) in mice was investigated in present study. We tested the expression of glial fibrillary acidic protein (GFAP), A2 phenotype marker S100a10, and A1 phenotype marker C3 protein and assessed the change of BrdU/GFAP-positive cells, GFAP/C3-positive cells, and GFAP/S100a10-positive cells in mice hippocampal tissues to evaluate the change of astrocyte phenotypes following cerebral I/R. The role of H2S on the phenotypic change of astrocytes following cerebral I/R in mice was investigated by using H2S synthase cystathionine-γ-lyase (CSE) knockout mice (KO). The results revealed that cerebral I/R injury promoted the astrocytes proliferation of both A1 and A2 phenotypes, which were more significant in mice of H2S synthase CSE KO than in mice of wild type (WT). Interestingly, supplement with H2S could inhibit the A1 phenotype proliferation but promote the proliferation of A2 phenotype, suggesting that H2S could regulate the transformation of astrocytes to A2 phenotype following cerebral I/R, which is beneficial for neuronal recovery. Besides, we found that H2S-mediated change of astrocyte phenotype is related to inhibiting the RhoA/ROCK pathway. Furthermore, both H2S and ROCK inhibitor could ameliorate the brain injury of mice at 9 days after cerebral I/R. In conclusion, H2S regulates the phenotypic transformation of astrocytes to A2 phenotype following the cerebral I/R via inhibiting RhoA/ROCK pathway and then exerts the neuroprotective effect against the subacute brain injury.

H2S-RhoA/ROCK Pathway and Glial Cells in Axonal Remyelination After Ischemic Stroke

Ischemic stroke is one of the main reasons of disability and death. Stroke-induced functional deficits are mainly due to the secondary degeneration of the white matter characterized by axonal demyelination and injury of axon-glial integrity. Enhancement of the axonal regeneration and remyelination could promote the neural functional recovery. However, cerebral ischemia-induced activation of RhoA/Rho kinase (ROCK) pathway plays a crucial and harmful role in the process of axonal recovery and regeneration. Inhibition of this pathway could promote the axonal regeneration and remyelination. In addition, hydrogen sulfide (H2S) has the significant neuroprotective role during the recovery of ischemic stroke via inhibiting the inflammatory response and oxidative stress, regulating astrocyte function, promoting the differentiation of endogenous oligodendrocyte precursor cells (OPCs) to mature oligodendrocyte. Among all of these effects, promoting the formation of mature oligodendrocyte is a crucial part of axonal regeneration and remyelination. Furthermore, numerous studies have uncovered the crosstalk between astrocytes and oligodendrocyte, microglial cells and oligodendrocyte in the axonal remyelination following ischemic stroke. The purpose of this review was to discuss the relationship among H2S, RhoA/ROCK pathway, astrocytes, and microglial cells in the axonal remyelination following ischemic stroke to reveal new strategies for preventing and treating this devastating disease.

The role of RhoA/ROCK pathway in the ischemic stroke-induced neuroinflammation

It is widely known that ischemic stroke is the prominent cause of death and disability. To date, neuroinflammation following ischemic stroke represents a complex event, which is an essential process and affects the prognosis of both experimental stroke animals and stroke patients. Intense neuroinflammation occurring during the acute phase of stroke contributes to neuronal injury, BBB breakdown, and worse neurological outcomes. Inhibition of neuroinflammation may be a promising target in the development of new therapeutic strategies. RhoA is a small GTPase protein that activates a downstream effector, ROCK. The up-regulation of RhoA/ROCK pathway possesses important roles in promoting the neuroinflammation and mediating brain injury. In addition, nuclear factor-kappa B (NF-κB) is another vital regulator of ischemic stroke-induced neuroinflammation through regulating the functions of microglial cells and astrocytes. After stroke onset, the microglial cells and astrocytes are activated and undergo the morphological and functional changes, thereby deeply participate in a complicated neuroinflammation cascade. In this review, we focused on the relationship among RhoA/ROCK pathway, NF-κB and glial cells in the neuroinflammation following ischemic stroke to reveal new strategies for preventing the intense neuroinflammation.

Hydrogen sulfide inhibits lipopolysaccharide-based neuroinflammation-induced astrocyte polarization after cerebral ischemia/reperfusion injury

The effect of lipopolysaccharide (LPS)-based neuroinflammation following cerebral ischemia/reperfusion (I/R) on the genotypic transformation of reactive astrocytes and its relationship with endogenous hydrogen sulfide (H₂S) were investigated in present study. We found that LPS promoted the cerebral I/R-induced A1 astrocytes proliferation in mouse hippocampal tissues and deteriorated the reduction of hydrogen sulfide (H₂S) content in mouse sera, H₂S donor NaHS could inhibitA1 astrocytes proliferation. Similarly, knockout of cystathionine γ-lyase (CSE), one of endogenous H₂S synthases, likewise up-regulated the cerebral I/R-induced A1 astrocytes proliferation, which could also be blocked by NaHS. Besides, supplement with H₂S promoted the A2 astrocytes proliferation in hippocampal tissues of CSE knockout (CSE KO) mice or LPS-treated mice following cerebral I/R. In the oxygen glucose deprivation/reoxygenation (OGD/R) model of astrocytes, H₂S also promoted the transformation of astrocytes into A2 subtype. Moreover, we found that H₂S could up-regulate the expression of α-subunit of large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels in astrocytes, and the channel opener BMS-191011 likewise promoted the transformation of astrocyte into A2 subtype. In conclusion, H₂S inhibits the proliferation of A1 astrocytes induced by LPS-based neuroinflammation following cerebral I/R and promotes the transformation of astrocytes into A2 subtype, which may be related to up-regulation of BK_Ca channels.

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.

Total flavones of Rhododendron induce the transformation of A1/A2 astrocytes via promoting the release of CBS-produced H2S

BACKGROUND

We previously found that total flavones of Rhododendron (TFR) protected against the cerebral ischemia/reperfusion (I/R) injury. But the detailed mechanism is not clear. Recent research revealed that reactive astrocytes were divided into A1 and A2 phenotypes for their morphological and functional remodeling and neurotoxic- vs-neuroprotective effect on the injury of the central nervous system (CNS).

PURPOSE

The present study was undertaken to explore the role and mechanism of TFR on the phenotypic change of astrocytes following cerebral I/R in vivo and oxygen glucose deprivation/re-oxygenation (OGD/R) in vitro.

STUDY DESIGN AND METHODS

We tested the expression of astrocytes marker glial fibrillary acidic protein (GFAP), A1 astrocytes marker C3 protein and A2 astrocytes marker S100a10, as well as the BrdU/GFAP-positive cells, GFAP/S100a10-positive cells and GFAP/C3-positive cells in mice hippocampal tissues to evaluate the phenotypic change of astrocytes. Besides, we assessed the change of astrocyte phenotypes following OGD/R in vitro.

RESULTS

We found that mice cerebral I/R promoted the astrocytes proliferation of both A1 and A2 phenotypes in hippocampal tissues. While treatment with TFR could promote the proliferation of A2 astrocytes but inhibit the A1 astrocytes proliferation in mice hippocampal tissues, suggesting that TFR could accelerate the astrocytes transformation into A2 subtype following cerebral I/R. Whereas, in OGD/R model of astrocytes, we found that TFR inhibited the proliferation of both A1 and A2 astrocytes. Besides, we found that TFR could up-regulate the release of cystathionine β-synthase (CBS)-produced hydrogen sulfide (H₂S) and inhibit RhoA/Rho kinase pathway, and revealed that the inhibitory effect of TFR on astrocytes proliferation could be blocked by aminooxyacetic acid (AOAA), an CBS inhibitor. Furthermore, TFR could ameliorate the mice cerebral I/R injury and the OGD/R-induced astrocytic damage.

CONCLUSION

These findings suggested that TFR could affect the transformation of astrocytes subtypes following cerebral I/R, which may be related to up-regulation of CBS-produced H₂S and subsequent inhibition of RhoA/ROCK pathway.

Inhibition of A1 Astrocytes and Activation of A2 Astrocytes for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) is a serious injury to the central nervous system that causes significant physical and psychological trauma to the patient. SCI includes primary spinal cord injuries and secondary spinal cord injuries. The secondary injury refers to the pathological process or reaction after the primary injury. Although SCI has always been thought to be an incurable injury, the human nerve has the ability to repair itself after an injury. However, the reparability is limited because glial scar formation impedes functional recovery. There is a type of astrocyte that can differentiate into two forms of reactive astrocytes known as 'A1' and 'A2' astrocytes. A1 astrocytes release cytotoxic chemicals that cause neurons and oligodendrocytes to die and perform a harmful role. A2 astrocytes can produce neurotrophic factors and act as neuroprotectors. This article discusses ways to block A1 astrocytes while stimulating A2 astrocytes to formulate a new treatment for spinal cord injury.

Protection of H2S against Hypoxia/Reoxygenation Injury in Rat Hippocampal Neurons through Inhibiting Phosphorylation of ROCK2 at Thr436 and Ser575

BACKGROUND

H2S (hydrogen sulfide) protects cerebral vasodilatation and endothelial cells against oxygen-glucose deprivation/reoxygenation injury via the inhibition of the RhoA-ROCK pathway and ROCK2 expression. However, the inhibitory mechanism of H2S on ROCK2 expression is still unclear. The study aimed to investigate the target and mechanism of H2S in inhibition of ROCK2.

METHODS

His-ROCK2wild protein was constructed, expressed, and was used for phosphorylation assay in vitro. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the potential phosphorylation sites of ROCK2. Recombinant ROCK2wild-pEGFP-N1, ROCK2T436A-pEGFP-N1, and ROCK2S575F-pEGFP-N1 plasmids were constructed and transfected into rat hippocampal neurons (RHNs). ROCK2 expression, cell viability, the release of lactate dehydrogenase (LDH), nerve-specific enolase (NSE), and Ca2+ were detected to evaluate the neuroprotective mechanism of H2S.

RESULTS

Phosphorylation at Thr436 and Ser575 of ROCK2 was observed by mass spectrometry when Polo-like kinase 1 (PLK1) and protein kinase A (PKA) were added in vitro, and NaHS significantly inhibited phosphorylation at Thr436 and Ser575. Additionally, NaHS significantly inhibited the expression of ROCK2 and recombinant proteins GFP-ROCK2, GFP-ROCK2T436A, and GFP-ROCK2S575F in transfected RHNs. Compared with empty plasmid, GFP-ROCK2T436A, and GFP-ROCK2S575F groups, NaHS significantly inhibited the release of LDH, NSE, and Ca2+ and promoted ROCK2 activity in the GFP-ROCK2wild group. Thr436 and Ser575 may be dominant sites that mediate NaHS inhibition of ROCK2 protein activity in RHNs. Compared with the empty plasmid, GFP-ROCK2T436A, and the GFP-ROCK2S575F group, NaHS had more significant inhibitory effects on hypoxia/reoxygenation (H/R) injury-induced cell viability reduction and increased LDH and NSE release in the GFP-ROCK2wild group.

CONCLUSION

Exogenous H2S protected the RHNs against H/R injury via Thr436 and Ser575 of ROCK2. These findings suggested that Thr436 and Ser575 may be the dominant sites that mediated the effect of NaHS on protecting RHNs against H/R injury.

H2S-mediated inhibition of RhoA/ROCK pathway and noncoding RNAs in ischemic stroke

Ischemic stroke is one of major causes of disability. In the pathological process of ischemic stroke, the up-regulation of Ras homolog gene family, member A (RhoA) and its downstream effector, Ras homolog gene family (Rho)-associated coiled coil-containing kinase (ROCK), contribute to the neuroinflammation, blood-brain barrier (BBB) dysfunction, neuronal apoptosis, axon growth inhibition and astrogliosis. Accumulating evidences have revealed that hydrogen sulphide (H₂S) could reduce brain injury in animal model of ischemic stroke via inhibiting the RhoA/ROCK pathway. Recently, noncoding RNAs (ncRNAs) such as circular RNAs (circRNAs), long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) have attracted much attention because of their essential role in adjusting gene expression both in physiological and pathological conditions. Numerous studies have uncovered the role of RhoA/ROCK pathway and ncRNAs in ischemic stroke. In this review, we focused on the role of H₂S, RhoA/ROCK pathway and ncRNAs in ischemic stroke and aimed to reveal new strategies for preventing and treating this devastating disease.

CSE/H2S ameliorates colitis in mice via protection of enteric glial cells and inhibition of the RhoA/ROCK pathway

The enteric glial cells (EGCs) participate in the homeostasis of the gastrointestinal tract, and RhoA/ROCK signaling pathway plays a vital role in colonic tight junctions. Hydrogen sulfide (H₂S) has been reported to alleviate colitis. However, the effect and mechanism of endogenous H₂S on colitis remain unclear. This study established a Cystathionine-γ-lyase (CSE) knockout mouse model, a significant source of H₂S production in the gut. The role of CSE-produced H₂S on EGCs and the RhoA/ROCK signaling pathway was investigated in experimental colitis using CSE knockout (KO) and wild-type (WT) mice. CSE gene knockout animals presented with disease progression, more deteriorated clinical scores, colon shortening, and histological damage. EGCs dysfunction, characterized by decreased expression of the glial fibrillary acidic protein (GFAP), C3, and S100A10, was observed in the colon of WT and KO mice, especially in KO mice. RhoA/ROCK pathway was significantly upregulated in colon of colitis mice, which was more evident in KO mice. Pretreatment with NaHS, an exogenous H₂S donor, significantly ameliorated mucosal injury and inhibited the expression of proinflammatory factors. Furthermore, we found that NaHS promoted the transformation of EGCs from “A1” to “A2” type, with decreased expression of C3 and increased expression of S100A10. These findings suggest that CSE/H₂S protects mice from colon inflammation, which may be associated with preserving EGCs function by promoting EGCs transformation and inhibiting the RhoA/ROCK pathway.

Hypothermia-Triggered Mesoporous Silica Particles for Controlled Release of Hydrogen Sulfide to Reduce the I/R Injury of the Myocardium

Despite the fact that heart transplantation (HTx) is a relatively mature procedure, heart ischemic and reperfusion (I/R) injury during HTx remains a challenge. Even after a successful operation, the heart will be at risk of primary graft failure and mortality during the first year. In this study, temperature-sensitive polymer poly(N-n-propylacrylamide-co-N-tert-butyl acrylamide) (PNNTBA) was coated on diallyl trisulfide (DATS)-loaded mesoporous silica nanoparticles (DATS-MSN) to synthesize hypothermia-triggered hydrogen sulfide (H₂S) releasing particles (HT-MSN). Because the PNNTBA shell dissolves in phosphate-buffered saline at 4 °C, the loaded DATS could continuously release H₂S within 6 h when activated by glutathione (GSH). Furthermore, after co-culturing biocompatible HT-MSN with cardiomyocytes, H₂S released from HT-MSN at 4 °C was found to protect cardiomyocytes from ischemic and reperfusion (I/R) injury. In detail, the rate of cell apoptosis and lactate dehydrogenase activity was decreased, as manifested by increased BCL-2 expression and decreased BAX expression. More importantly, in an isolated heart preservation experiment, HT-MSN demonstrated potent protection against cardiac I/R injury and reduced expression of inflammatory factors TNF-α and IL-1β. This study provided a new method for the controlled release of H₂S by the donor and myocardial protection from I/R injury.

Recruitment of α4β7 monocytes and neutrophils to the brain in experimental colitis is associated with elevated cytokines and anxiety-like behavior

Background

Behavioral comorbidities, such as anxiety and depression, are a prominent feature of IBD. The signals from the inflamed gut that cause changes in the brain leading to these behavioral comorbidities remain to be fully elucidated. We tested the hypothesis that enhanced leukocyte–cerebral endothelial cell interactions occur in the brain in experimental colitis, mediated by α4β7 integrin, to initiate neuroimmune activation and anxiety-like behavior.

Methods

Female mice treated with dextran sodium sulfate were studied at the peak of acute colitis. Circulating leukocyte populations were determined using flow cytometry. Leukocyte–cerebral endothelial cell interactions were examined using intravital microscopy in mice treated with anti-integrin antibodies. Brain cytokine and chemokines were assessed using a multiplex assay in animals treated with anti-α4β7 integrin. Anxiety-like behavior was assessed using an elevated plus maze in animals after treatment with an intracerebroventricular injection of interleukin 1 receptor antagonist.

Results

The proportion of classical monocytes expressing α4β7 integrin was increased in peripheral blood of mice with colitis. An increase in the number of rolling and adherent leukocytes on cerebral endothelial cells was observed, the majority of which were neutrophils. Treatment with anti-α4β7 integrin significantly reduced the number of rolling leukocytes. After anti-Ly6C treatment to deplete monocytes, the number of rolling and adhering neutrophils was significantly reduced in mice with colitis. Interleukin-1β and CCL2 levels were elevated in the brain and treatment with anti-α4β7 significantly reduced them. Enhanced anxiety-like behavior in mice with colitis was reversed by treatment with interleukin 1 receptor antagonist.

Conclusions

In experimental colitis, α4β7 integrin-expressing monocytes direct the recruitment of neutrophils to the cerebral vasculature, leading to elevated cytokine levels. Increased interleukin-1β mediates anxiety-like behavior.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02431-z.