Mechanism of Xiangsha Liujunzi Tang in Regulation of RhoA/ROCK2/MYPT1 Pathway to Improve Gastric Motility in Rats with Functional Dyspepsia / 中国实验方剂学杂志

ObjectiveTo explore the intervention mechanism of Xiangsha Liujunzi Tang in rats with functional dyspepsia （FD） based on the Ras homolog gene family member A （RhoA）/Rho-associated coiled-coil containing protein kinase 2 （ROCK2）/Myosin phosphatase target Subunit 1 （MYPT1） pathway. MethodSixty male SD suckling rats in SPF grades were randomly divided into blank group （n=10） and model group （n=50）. The comprehensive modeling method （gavage administration of iodoacetamide+exhaustion of swimming+disturbance of hunger and satiety） was used to replicate the rat model of FD. After successful replication of the model， the rats in the model group were randomly divided into model group， mosapride group， and high， middle， and low-dose Xiangsha Liujunzi Tang groups， with 10 rats in each group. Rats in the blank group and model group were given 10 mL kg-1·d-1 normal saline， those in the mosapride group were given 1.35 mg·kg-1·d-1 mosapride， and those in the high， middle， and low-dose Xiangsha Liujunzi Tang groups were given 12， 6， and 3 g·kg-1·d-1 Xiangsha Liujunzi Tang， respectively. The intervention lasted 14 days. The general living conditions of rats were observed before and after modeling and administration， and the 3-hour food intake and body mass of rats were measured. After intervention， the intestinal propulsion rate of rats was measured， and the pathological changes in the gastric tissue were observed by hematoxylin-eosin （HE） staining. The content of choline acetyl transferase （ChAT） and vasoactive intestinal peptide （VIP） in the medulla oblongata and gastric tissue homogenate was determined by enzyme-linked immunosorbent assay （ELISA）， the distribution of adenosine triphosphate （ATP） enzyme in gastric antrum smooth muscle was observed by frozen section staining， and the protein expression levels of RhoA， ROCK2， and phosphorylated-myosin phosphatase target subunit 1 （p-MYPT1） in the gastric tissue were detected by Western blot. ResultCompared with the blank group， the model group had withered hair， lazy movement， slow action， poor general living condition， lower 3-hour food intake， body mass， and lower intestinal propulsion rate （P<0.05）， whereas no obvious abnormality in gastric histopathology. In the model group， the content of ChAT in the medulla oblongata and gastric tissue decreased， the content of VIP in gastric tissue increased， the distribution of ATP enzyme in gastric antrum smooth muscle decreased significantly， and the protein expression levels of RhoA， ROCK2， and p-MYPT1 in the gastric tissue decreased significantly （P<0.05）. As compared with the model group， the general living condition of rats in each intervention group was significantly improved， and the 3-hour food intake， body mass， and intestinal propulsion rate were significantly increased （P<0.05）. There was no significant difference in gastric pathology in the intervention groups. The content of ChAT in the medulla oblongata and gastric tissue increased significantly， the content of VIP in the gastric tissue decreased， the distribution of ATP enzyme in gastric antrum smooth muscle increased significantly， and the protein expression levels of RhoA， ROCK2， and p-MYPT1 in the gastric tissue increased significantly （P<0.05）. The intervention effect of Xiangsha Liujunzi Tang group on the above indexes was dose-dependent. ConclusionXiangsha Liujunzi Tang can effectively improve the general living condition and gastric motility of rats with FD， and its specific mechanism may be related to the activation of the RhoA/ROCK2/MYPT1 pathway in the gastric tissue to regulate smooth muscle relaxation and contraction and promote gastric motility.

Hypothermia Inhibits Endothelium-Independent Vascular Contractility via Rho-kinase Inhibition

The present study was undertaken to investigate the influence of hypothermia on endothelium-independent vascular smooth muscle contractility and to determine the mechanism underlying the relaxation. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Hypothermia significantly inhibited fluoride-, thromboxane A2-, phenylephrine-, and phorbol ester-induced vascular contractions regardless of endothelial nitric oxide synthesis, suggesting that another pathway had a direct effect on vascular smooth muscle. Hypothermia significantly inhibited the fluoride-induced increase in pMYPT1 level and phorbol ester-induced increase in pERK1/2 level, suggesting inhibition of Rho-kinase and MEK activity and subsequent phosphorylation of MYPT1 and ERK1/2. These results suggest that the relaxing effect of moderate hypothermia on agonist-induced vascular contraction regardless of endothelial function involves inhibition of Rho-kinase and MEK activities.

Endothelium Independent Effect of Pelargonidin on Vasoconstriction in Rat Aorta

In this study, we investigated the effects of pelargonidin, an anthocyanidin found in many fruits and vegetables, on endothelium-independent vascular contractility to determine the underlying mechanism of relaxation. Isometric contractions of denuded aortic muscles from male rats were recorded, and the data were combined with those obtained in western blot analysis. Pelargonidin significantly inhibited fluoride-, thromboxane A2-, and phorbol ester-induced vascular contractions, regardless of the presence or absence of endothelium, suggesting a direct effect of the compound on vascular smooth muscles via a different pathway. Pelargonidin significantly inhibited the fluoride-dependent increase in the level of myosin phosphatase target subunit 1 (MYPT1) phosphorylation at Thr-855 and the phorbol 12,13-dibutyrate-dependent increase in the level of extracellular signal-regulated kinase (ERK) 1/2 phosphorylation at Thr202/Tyr204, suggesting the inhibition of Rho-kinase and mitogen-activated protein kinase kinase (MEK) activities and subsequent phosphorylation of MYPT1 and ERK1/2. These results suggest that the relaxation effect of pelargonidin on agonist-dependent vascular contractions includes inhibition of Rho-kinase and MEK activities, independent of the endothelial function.

Cardamonin inhibits agonist-induced vascular contractility via Rho-kinase and MEK inhibition

The present study was undertaken to investigate the influence of cardamonin on vascular smooth muscle contractility and to determine the mechanism(s) involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Cardamonin significantly relaxed fluoride-, phenylephrine-, and phorbol ester-induced vascular contractions, suggesting that it has an anti-hypertensive effect on agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, cardamonin significantly inhibited the fluoride-induced increase in pMYPT1 level and phenylephrine-induced increase in pERK1/2 level, suggesting inhibition of Rho-kinase and MEK activity and subsequent phosphorylation of MYPT1 and ERK1/2. This study provides evidence that the relaxing effect of cardamonin on agonist-induced vascular contraction regardless of endothelial function involves inhibition of Rho-kinase and MEK activity.

Endothelium-Independent Effect of Fisetin on the Agonist-Induced Regulation of Vascular Contractility

Fisetin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of fisetin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Fisetin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, fisetin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of fisetin on agonist-induced vascular contraction regardless of endothelial function.

The Inhibitory Effect of Shikonin on the Agonist-Induced Regulation of Vascular Contractility

Shikonin, a natural flavonoid found in the roots of Lithospermum erythrorhizon, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of shikonin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Shikonin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, shikonin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and the inhibition of MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of shikonin on agonist-induced vascular contraction regardless of endothelial function.

The Inhibitory Effect of Apigenin on the Agonist-Induced Regulation of Vascular Contractility via Calcium Desensitization-Related Pathways

Apigenin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of apigenin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Apigenin significantly relaxed fluoride-, thromboxane A2 mimetic- or phorbol ester-induced vascular contraction, which suggests that apigenin could be an anti-hypertensive that reduces agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, apigenin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels, which suggests the mechanism involving the inhibition of Rho-kinase and MEK activity and the subsequent phosphorylation of MYPT1 and ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of apigenin on agonist-induced vascular contraction regardless of endothelial function.

The Inhibitory Effect of Eupatilin on the Agonist-Induced Regulation of Vascular Contractility

The present study was undertaken to investigate the influence of eupatilin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Eupatilin more significantly relaxed fluoride-induced vascular contraction than thromboxane A2 or phorbol ester-induced contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, eupatilin significantly inhibited fluoride-induced increases in pMYPT1 levels. On the other hand, it didn't significantly inhibit phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the primarily inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1. This study provides evidence regarding the mechanism underlying the relaxation effect of eupatilin on agonist-induced vascular contraction regardless of endothelial function.

Flavone Attenuates Vascular Contractions by Inhibiting RhoA/Rho Kinase Pathway

Our previous study demonstrated that flavone inhibits vascular contractions by decreasing the phosphorylation levelof the myosin phosphatase target subunit (MYPT1). In the present study, we hypothesized that flavone attenuates vascular contractions through the inhibition of the RhoA/Rho kinase pathway. Rat aortic rings were denuded of endothelium, mounted in organ baths, and contracted with either 30 nM U46619 (a thromboxane A2 analogue) or 8.0 mM NaF 30 min after pretreatment with either flavone (100 or 300 micrometer) or vehicle. We determined the phosphorylation level of the myosin light chain (MLC20), the myosin phophatase targeting subunit 1 (MYPT1) and the protein kinase C-potentiated inhibitory protein for heterotrimeric myosin light chain phophatase of 17-kDa (CPI17) by means of Western blot analysis. Flavone inhibited, not only vascular contractions induced by these contractors, but also the levels of MLC20 phosphorylation. Furthermore, flavone inhibited the activation of RhoA which had been induced by either U46619 or NaF. Incubation with flavone attenuated U46619-or NaF-induced phosphorylation of MYPT1(Thr855) and CPI17(Thr38), the downstream effectors of Rho-kinase. In regards to the Ca2+-free solution, flavone inhibited the phosphorylation of MYPT1(Thr855) and CPI17(Thr38), as well as vascular contractions induced by U46619. These results indicate that flavone attenuates vascular contractions, at least in part, through the inhibition of the RhoA/Rho-kinase pathway.