The role of the RhoA/ROCK pathway in gender-dependent differences in gastric smooth muscle contraction

A human stomach cell type transcriptome atlas

BACKGROUND

The identification of cell type-specific genes and their modification under different conditions is central to our understanding of human health and disease. The stomach, a hollow organ in the upper gastrointestinal tract, provides an acidic environment that contributes to microbial defence and facilitates the activity of secreted digestive enzymes to process food and nutrients into chyme. In contrast to other sections of the gastrointestinal tract, detailed descriptions of cell type gene enrichment profiles in the stomach are absent from the major single-cell sequencing-based atlases.

RESULTS

Here, we use an integrative correlation analysis method to predict human stomach cell type transcriptome signatures using unfractionated stomach RNAseq data from 359 individuals. We profile parietal, chief, gastric mucous, gastric enteroendocrine, mitotic, endothelial, fibroblast, macrophage, neutrophil, T-cell, and plasma cells, identifying over 1600 cell type-enriched genes.

CONCLUSIONS

We uncover the cell type expression profile of several non-coding genes strongly associated with the progression of gastric cancer and, using a sex-based subset analysis, uncover a panel of male-only chief cell-enriched genes. This study provides a roadmap to further understand human stomach biology.

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.

Research on the Mechanism and Prevention of Hypertension Caused by Apatinib Through the RhoA/ROCK Signaling Pathway in a Mouse Model of Gastric Cancer

Hypertension is one of the main adverse effects of antiangiogenic tumor drugs and thus limits their application. The mechanism of hypertension caused by tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factors is mainly related to inhibition of the nitric oxide (NO) pathway and activation of the endothelin pathway, as well as vascular rarefaction and increased salt sensitivity; consequently, prevention and treatment differ for this type of hypertension compared with primary hypertension. Apatinib is a highly selective TKI approved in China for the treatment of advanced or metastatic gastric cancer. The RhoA/ROCK pathway is involved in the pathogenesis of hypertension and mediates smooth muscle contraction, eNOS inhibition, endothelial dysfunction and vascular remodeling. In this study, in vivo experiments were performed to explore whether the RhoA/ROCK signaling pathway is part of a possible mechanism of apatinib in the treatment of gastric cancer-induced hypertension and the impairment of vascular remodeling and left ventricular function. Y27632, a selective small inhibitor of both ROCK1 and ROCK2, was combined with apatinib, and its efficacy was evaluated, wherein it can reduce hypertension induced by apatinib treatment in gastric cancer mice and weaken the activation of the RhoA/ROCK pathway by apatinib and a high-salt diet (HSD). Furthermore, Y-27632 improved aortic remodeling, fibrosis, endothelial dysfunction, superior mesenteric artery endothelial injury, left ventricular dysfunction and cardiac fibrosis in mice by weakening the activation of the RhoA/ROCK pathway. The expression of RhoA/ROCK pathway-related proteins and relative mRNA levels in mice after apatinib intervention were analyzed by various methods, and blood pressure and cardiac function indexes were compared. Endothelial and cardiac function and collagen levels in the aorta were also measured to assess vascular and cardiac fibrosis and to provide a basis for the prevention and treatment of this type of hypertension.

Valsartan inhibits RhoA-ROCK2-MYL pathway in rat model of alcoholic cardiomyopathy

The present study aimed to investigate variations in the Ras homolog gene family, member A (RhoA)-Rho-associated protein kinase 2 (ROCK2)-myosin light chain (MYL) pathway in a rat model of alcoholic cardiomyopathy (ACM) and the role of angiotensin-converting enzyme inhibitor drugs. Rat models of ACM were established via alcoholic gavage + free access to alcohol. The structural and functional changes of the heart were analyzed by hematoxylin-eosin staining, Masson's trichrome staining, immunohistochemistry staining, western blotting and fluorescence quantitative polymerase chain reaction. A total of 16 weeks later, a decreased ejection fraction and left ventricular fractional shortening in the alcohol group compared with the control group were demonstrated resulting in an increased left ventricular end diastolic diameter. These adverse effects were ameliorated following treatment with valsartan. In addition, the alcohol group revealed a disorganized arrangement of myocardial filaments, which was improved upon treatment with valsartan. RhoA and ROCK2 protein expression significantly increased in myocardial cells in the alcohol compared with the control group. Following drug intervention with valsartan, expression of RhoA and ROCK2 proteins were inhibited in the alcohol group. Furthermore, significantly elevated RhoA and ROCK2 and decreased MYL protein and mRNA expression in the alcohol group was demonstrated compared with the control group. Administration of valsartan reversed the expression profile of RhoA, ROCK and MYL in ACM. Expression of RhoA and ROCK were elevated with downregulation of MYL resulting in heart failure. However, the angiotensin receptor antagonist diminished the expression of RhoA and ROCK and enhanced the expression of MYL. The results of the present study suggest a curative effect of valsartan in ACM.

Protective effects of oxymatrine against DSS-induced acute intestinal inflammation in mice via blocking the RhoA/ROCK signaling pathway

Oxymatrine (OMT) is an important quinoxaline alkaloid that has a wide range of pharmacological effects and has been shown to alleviate ulcerative colitis due to its profound anti-inflammatory effects. The RhoA/ROCK (Rho kinase) signaling pathway has been shown to be related to the pathogenesis of several autoimmune diseases; however, the specific mechanisms of RhoA/ROCK signaling in inflammatory bowel disease (IBD) remain elusive. Therefore, we sought to determine whether OMT could ameliorate acute intestinal inflammation by targeting the RhoA/ROCK signaling pathway. The potential therapeutic effect of OMT on acute intestinal inflammation and its impact on the RhoA/ROCK signaling pathway were assessed in six groups of mice treated with low, medium and high doses of OMT (25, 50 and 100 mg/kg, respectively), and an inhibitor of ROCK, Y-27632, as a positive control, after initiating dextran sodium sulfate (DSS)-induced acute intestinal inflammation. The model group and normal group were injected intraperitoneally with equal doses of PBS. Our results showed that OMT treatment could protect the integrity of the epithelial barrier, relieve oxidative stress, inhibit the expression of inflammatory mediators and pro-inflammatory cytokines, restrain the differentiation of Th17 cells and promote the differentiation of Treg cells via inhibition of the RhoA/ROCK pathway, thus providing therapeutic benefits for ulcerative colitis (UC). Therefore, inhibiting the RhoA/ROCK pathway might be a new approach that can be used in UC therapy, which deserves to be investigated further.

Changes in Gastric Smooth Muscle Cell Contraction during Pregnancy: Effect of Estrogen

It is well known that pregnancy is associated with frequent gastrointestinal (GI) disorders and symptoms. Moreover, previous reports have shown that estrogen, which changes in levels during pregnancy, participates in the regulation of GI motility and is involved in the pathogenesis of various functional disorders in the stomach. The aim of the current study was to explore the changes in the expression of estrogen receptors (ERs) and examine the effect of estrogen on nitric oxide- (NO-) cyclic guanosine monophosphate (cGMP) pathway and thus relaxation in gastric smooth muscle cells (GSMC) during pregnancy. Single GSMC from early-pregnant and late-pregnant Sprague-Dawley rats were used. Protein and mRNA expression levels of ERs were measured via specifically designed enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), respectively. NO and cGMP levels were measured via specifically designed ELISA kits. Effect of estrogen on acetylcholine- (ACh-) induced contraction of single GSMC was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor, N-nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Estrogen increased both NO and cGMP levels and their levels were greater in early compared to late pregnancy. Expression of ERs was greater in early compared to late pregnancy. ACh induced greater contraction of GSMC in late pregnancy compared to early pregnancy. Estrogen inhibited ACh-induced contraction in both periods of pregnancy. Importantly, pretreatment of GSMC with either L-NNA or ODQ abolished estrogen inhibitory action on muscle contraction. In conclusion, GSMC contractile behavior undergoes drastic changes in response to estrogen during pregnancy and this might explain some of the pregnancy-associated gastric disorders.

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.

Tyrosine Kinase Pyk2 is Involved in Colonic Smooth Muscle Contraction via the RhoA/ROCK Pathway

The contraction of gastrointestinal (GI) smooth muscles is regulated by both Ca(2+)-dependent and Ca(2+) sensitization mechanisms. Proline-rich tyrosine kinase 2 (Pyk2) is involved in the depolarization-induced contraction of vascular smooth muscle via a Ca(2+) sensitization pathway. However, the role of Pyk2 in GI smooth muscle contraction is unclear. The spontaneous contraction of colonic smooth muscle was measured by using isometric force transducers. Protein and phosphorylation levels were determined by using western blotting. Pyk2 protein was expressed in colonic tissue, and spontaneous colonic contractions were inhibited by PF-431396, a Pyk2 inhibitor, in the presence of tetrodotoxin (TTX). In cultured colonic smooth muscle cells (CSMCs), PF-431396 decreased the levels of myosin light chain (MLC20) phosphorylated at Ser19 and ROCK2 protein expression, but myosin light chain kinase (MLCK) expression was not altered. However, Y-27632, a Rho kinase inhibitor, increased phosphorylation of Pyk2 at Tyr402 and concomitantly decreased ROCK2 levels; the expression of MLCK in CSMCs did not change. The expression of P(Tyr402)-Pyk2 and ROCK2 was increased when CSMCs were treated with Ach. Pyk2 is involved in the process of colonic smooth muscle contraction through the RhoA/ROCK pathway. These pathways may provide very important targets for investigating GI motility disorders.

Effect of progesterone on nitric oxide/cyclic guanosine monophosphate signaling and contraction in gastric smooth muscle cells

Previous studies have shown that progesterone could inhibit muscle contraction in various sites of the gastrointestinal tract. The underlying mechanisms responsible for these inhibitory effects of progesterone are not fully known. The aim of the current study was to investigate the effect of progesterone on the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway and muscle contraction in the stomach. Single gastric smooth muscle cells from female Sprague-Dawley rats were used. The expression of progesterone receptor (PR) mRNA was analyzed by reverse transcription polymerase chain reaction. NO and cGMP levels were measured via specific ELISAs. Acetylcholine (ACh)-induced contraction of single gastric muscle cells preincubated with progesterone was measured via scanning micrometry in the presence or absence of the NO synthase inhibitor, Nω-Nitro-L-arginine (L-NNA), or guanylyl cyclase inhibitor, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and expressed as percent shortening from resting cell length. PR expression was detected in the stomach muscle cells. Progesterone inhibited ACh-induced gastric muscle cell contraction. Furthermore, progesterone increased NO and cGMP levels in single gastric muscle cells. Most notably, pre-incubation of muscle cells with either L-NNA or ODQ abolished the inhibitory action of progesterone on muscle contraction. These present observations suggest that progesterone promotes muscle cell relaxation in the stomach potentially via the NO/cGMP pathway.

Estrogen relaxes gastric muscle cells via a nitric oxide- and cyclic guanosine monophosphate-dependent mechanism: A sex-associated differential effect

Various gastrointestinal (GI) disorders have a higher prevalence in women than in men. In addition, estrogen has been demonstrated to have an inhibitory effect on the contractility of GI smooth muscle. Although increased plasma estrogen levels have been implicated in GI disorders, the role of gastric estrogen receptor (ER) in these sex-specific differences remains to be fully elucidated. The present study was designed to investigate the sex-associated differences in the expression of the two ER isoforms, ERα and ERβ, and the effect of estrogen on gastric muscle contraction via the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway. Experiments were performed on single gastric smooth muscle cells (GSMCs) isolated from male and female Sprague Dawley rats. The effect of acetylcholine (ACh), a muscarinic agonist, on the contraction of GSMCs was measured via scanning micrometry in the presence or absence of 1 µM 17β-estradiol (E2), an agonist to the majority of ERs, 1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT), an ERα agonist, or diarylpropionitrile (DPN), an ERβ agonist. The protein expression levels of ER subtypes in GSMCs were measured using a specifically designed ELISA. GSMCs from female rats had a higher expression of ERα and ERβ protein compared with GSMCs from males. ACh induced less contraction in female that in male GSMCs. Pre-treatment of GSMCs with E2 reduced the contraction of GSMCs from both sexes, but to a greater extent in those from females. PPT and DPN inhibited ACh-induced contraction in GSMCs from females. Furthermore, E2 increased NO and cGMP levels in GSMCs from males and females; however, higher levels were measured in females. Of note, pre-incubation of female GSMCs with Nω-nitro-L-arginine, a NO synthase inhibitor, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a guanylyl cyclase inhibitor, reduced the inhibitory effect of estrogen on GSMC contraction. In conclusion, estrogen relaxes GSMCs via an NO/cGMP-dependent mechanism, and the reduced contraction in GSMCs from females by estrogen may be associated with the sex-associated increased expression of ERα and ERβ, and greater production of NO and cGMP, compared with that in GSMCs from males.

Gender differences in the regulation of MLC20 phosphorylation and smooth muscle contraction in rat stomach

Evidence of sex-related differences in gastrointestinal (GI) functions has been reported in the literature. In addition, various GI disorders have disproportionate prevalence between the sexes. An essential step in the initiation of smooth muscle contraction is the phosphorylation of the 20-kDa regulatory myosin light chain (MLC₂₀) by the Ca²⁺/calmodulin-dependent myosin light chain kinase (MLCK). However, whether male stomach smooth muscle inherits different contractile signaling mechanisms for the regulation of MLC₂₀ phosphorylation from that in females has not been established. The present study was designed to investigate sex-associated differences in the regulation of MLC₂₀ phosphorylation and thus muscle contraction in gastric smooth muscle cells (GSMCs). Experiments were performed on GSMCs freshly isolated from male and female rats. Contraction of the GSMCs in response to acetylcholine (ACh), a muscarinic agonist, was measured via scanning micrometry in the presence or absence of the MLCK inhibitor, ML-7. Additionally, the protein levels of MLC₂₀, MLCK and phosphorylated MLC₂₀ were measured by ELISA. The protein levels of MLC₂₀ and MLCK were indifferent between the sexes. ACh induced greater contraction (P<0.05) as well as greater MLC₂₀ phosphorylation (P<0.05) in male GSMCs compared with female. Pretreatment of GSMCs with ML-7 significantly reduced the ACh-induced contraction (P<0.05) and MLC₂₀ phosphorylation (P<0.05) in the male and female cells, and notably, abolished the contractile differences between the sexes. In conclusion, MLC₂₀ phosphorylation and thus muscle contraction may be activated to a greater extent in male rat stomach compared with that in females.