The Role Of RhoA/Rho Kinase Signaling Pathway In Visfatin-Induced Cardiac Myocyte Hypertrophy In Rats

Objective: It is well known that adipose tissue is not only a body'senergy storage organ, but also an endocrine organ, which is able to secretesoluble factors. The soluble factors is also called adipocytokines, includingleptin, adiponectin, resistin, tumor necrosis factor-βand so on. Visfatin hasbeen discovered as a adipocytokine in recent years. They can partly explainthe relationship of obesity, insulin resistance, beta-cell dysfunction,endothelial dysfunction, and atherosclerosis[1].Visfatin is mainly produced and secreted by visceral adipose tissue,which is a polypeptide of molecular weight of52KDa and its amino acidsequence is highly conserved in biological evolution. Visfatin not only has theinsulin-like action to reduce blood glucose, but also can promote adipocytedifferentiation and lipid storage. In addition, visfatin also has diversebiological functions, which is closely related to obesity, inflammation, insulinresistance and atherosclerosis. Visfatin has a protective effect oncardiovascular disease in recent studies[2].Rho protein as a small guanylate binding protein is thought to be themolecular switch of cellular signaling pathways. Rho kinase (ROCK)discovered firstly as a Rho downstream effector is a serine/threonine proteinkinase. RhoA/Rock signaling pathway plays an important role in thedevelopment of a variety of diseases, such as hypertension, atherosclerosis,heart failure, myocardial hypertrophy and diabetes-related diseases.Myocardial hypertrophy is a compensatory response to cardiac overloadcaused by a variety of reasons, including hypertension, myocardial infarction,valvular heart disease, dilated cardiomyopathy and so on. It is mainlymanifested that protein synthesis increases in myocardial cells, which resultsthe increase of heart weight including the increase of cell volume and stromal hyperplasia. However, the compensatory is not unlimited, if its causescan not be eliminated, which will eventually lead to heart failure and evensudden death.Therefore, the study of cardiac hypertrophy signaling pathwaycan help to prevent or even reverse the cardiac hypertrophy, and also toprovide new ideas for drug intervention. Although there has been some reportsabout the relationship between RhoA/ROCK signaling pathway andmyocardial hypertrophy caused by angiotensin II, spontaneously hypertensive,isoproterenol, pressure overload in recent years, so far no research clarify theinfluence of inhibiting Rho kinase on visfatin-induced myocardial hypertrophy.In this study, we used Rho kinase inhibitor Y27632to study the role of RhoA/ROCK signaling pathways in visfatin-induced cardiac myocyte hypertrophy inrats.Methods: we extract cardiomyocytes of neonatal SD rats in sterileconditions and culture them in vitro. Cells in good conditions are selected andput into4groups randomly.①normal control group,②recombinant ratvisfatin intervention group(we use100ng/ml recombinant rat visfatin tointervene cardiomyocytes for48hours),③Y-27632group(we use10umol/lY-27632to intervene cardiomyocytes for48hours),④Y-27632+recombinantrat visfatin intervention group (we use10umol/l Y-27632to intervenecardiomyocytes for2hours before48hours intervention of100ng/mlrecombinant rat visfatin). We apply the American Image-Proplus professionalimage analysis software to determine the surface area of myocardial cells.Moreover, Real time-PCR and ELISA method are used to detect theBNP-mRNA expression of myocardial cells and BNP level in culture mediumrespectively.Results:1Recombinant rat visfatin can increase the surface area of myocardialcells in rats and Rho kinase inhibitor Y-27632can inhibit the effect.2Recombinant rat visfatin can increase the expression of BNP-mRNAof myocardial cells in rats and BNP level in culture medium, Rho kinaseinhibitor Y-27632can inhibit the effect. Conclusion: RhoA/ROCK signaling pathway mediates visfatin-inducedcardiac myocyte hypertrophy in rats.