The Effects And Mechanisms Of TRPV1 On Regulating Vascular Smooth Muscle Cells Proliferation

Background and Objectives:Hypertension is a common disease worldwide. C hronic hypertension could thicken artery intima- media thickness, increase the ratio of wall to lumen(RWL) and ultimately lead to vascular remodeling. Abnormal proliferation of vascular smooth muscle cells(VSMCs) is the main pathological mechanism for vascular remodeling. Under normal condition,VSMC s are located in artery media and express a series of contractile proteins which implement systolic function, but they do not have the proliferative and migratory capacities. Under pathological condition such as persistent hypertension, VSMC s can be activated and then gain the ability to proliferate and migrate aberrantly thus cause vascular remodeling. Vascular remodeling can promote the development of hypertension in turn, and then damage function of the important target organs such as heart, brain and kidney. Above all it is important to inhibit the abnormal proliferat ion of VSMCs for preventing the progress of vascular remodeling and damage of target organs.In recent years,the research on transient receptor potential vanilloid 1(TRPV1) attracted more and more attention gradually regarding hypertension. TRPV1 is member of V subfamily of the transient receptor potential(TRP) family. TRPV1 could be activated by capsaicin and positive immunoreactivity in the fat cells, vessel endothelial cells, VSMCs and cardiac fibroblasts. Activation of TRPV1 by capsaicin could improve endothelium- dependent vasodilation and reduce blood pressure of spontaneously hypertensive rats(SHR). Studies have suggested that activation of TRPV1 by capsaicin could inhibit the proliferation of cardiac fibroblasts stimulated by angiotensin II. Whether TRPV1 excerts proliferation inhibitory effect on VSMCs, especially under hypertension, is unknown. Accordingly we postulate that TRPV1 may inhibit the proliferation of SHR-VSMCs and thus ameliorate vascular remodeling during hypertension.Phosphatidylinositol 3-kinase/serine/threonine kinase(PI3K /Akt) signal pathway participated in cell proliferation and gro wth. It was reported that activating TRPV1 by cannabidiol in colon cancer can inhibit the Akt phosphorylation process induced by azoxymethane. Therefore, we further speculate that activation of TRPV1 might improve vascular remodeling via affecting Akt phosphorylation.In an attempt to confirm this hypothesis, our experiments include three parts: 1. Primary culture and identification of VSMCs from WK Y and SHR. 2. Investigation of the activation of TRPV1 by capsaicin on proliferation of VSMCs. 3. Explore of the possible mechanism of TRPV1 on VSMCs proliferation.Methods:1. Primary vascular smooth muscle cells from SHR and WK Y were cultured by explant method.2. Cell proliferation ability was examined by CCK-8 test.3. The protein changes were detected using western blot.Results:1. We cultured and identified the primary VSMCs from WKY and SHR.2. The TRPV1 protein was expressed in VSMCs from both WK Y and SHR. Expression of TRPV1 protein was lower in VSMC from SHR than from WKY. TRPV1 activator, capsaicin, upregulated the expression of TRPV1 protein.3. VSMCs from SHR have a higher proliferation ability than VSMCs from WKY. Capsaicin could inhibit the proliferation capability of SHR from VSMC s in a dose-dependent manner. However, this effect could be resisted by TRPV1 antagonist iRTX. TRPV1 did not have significant effect on the proliferation of VSMCs from WKY.4. Higher expression of p-Akt was found in VSMC s from SHR than VSMC s from WKY. Capsaicin could induce the expression of p-Akt in VSMCs and TRPV1 antagonist iRTX could resist this manner.5. LY294002(PI3K inhibitor) group and LY294002+capsaicin group, obviously suppressed the proliferation of VSMCs from SHR, but not significant effect on VSMCs from WKY. Compared with capsaicin group, the proliferation inhibitory rate in LY294002+capsaicin group showed no significant change.6. LY294002 +capsaicin group could down- regulate p-Akt more effectively compared with LY294002 group.Conclusions: The activation of TRPV1 receptor could down-regulate p- Akt and thereby inhibit the proliferation of VSMCs from SHR.