The Effect Of TRPC6on Left Ventricular Hypertrophy In SHR

Cardiac fibroblasts (CFs) constituting90%of total cardiac nonmyocytes, which areessential for the maintenance of myocardial structure and function. It is well known thatpathological cardiac hypertrophy is associated with abnormal growth of CFs and collagensynthesis. It has been reported that the changes of proliferative characteristics of CFsaccelerate cardiac hypertrophy in hypertension. Research on the mechanisms of changes inproliferation of hypertensive CFs will help to find new targets for prevention andtreatment of hypertensive cardiac hypertrophy. Transient Receptor Potential Canonical6(TRPC6), a new identified ion channel, is found to be closely related to cardiachypertrophy and cell proliferation. This study aims to explore the mechanism ofdevelopment in hypertensive cardiac hypertrophy by investigating the effect of TRPC6onleft ventricular hypertrophy in SHR and the relationship between TRPC6and BNP.Part1The study of the expression of TRPC6on left ventricular hypertrophy in SHRand its relationship to BNP systemObjective: To investigate the correlation of the expression of TRPC6and BNP as well asthe receptor of BNP (natriuretic peptide receptor, NPR-A) in left ventricular hypertrophyof SHR. To explore the possible mechanisms of hypertensive left ventricle hypertrophy.Methods: Eighteen-week-old male SHR were used as the experimental group (n=10), andage-matched male Wistar-Kyoto rats (WKY) as the control group (n=10). Systolic bloodpressure (SBP) and left ventricular mass (LVM) and left ventricular mass index (LVMI) ofrats was measured and calculated respectively. Sirius red staining was employed to assessthe myocardial collagen volume fraction (CVF) and perivascular collagen volume area(PVCA). The expression of TRPC6, BNP and NPR-A on left ventricule (LV) of rats weredetermined with Western blot and immunohistochemistry.Results: SBP, LVM, LVMI, PVCA and CVF were markedly increased in SHR group compared to WKY group (P<0.05). The expression of TRPC6and BNP on LV weresignificantly higher, while NPR-A was significantly lower in SHR group than those inWKY group (P <0.05)Conclusion: Left ventricle hypertrophy of SHR may be related to upregulation of TRPC6and BNP and downregulation of NPR-A in the left ventricle..Part2: The effect of TRPC6on the proliferation of cardiac fibroblasts(CFs)----The intervention experiment of brain natriuretic peptide (BNP)Objective: To investigate the role of TRPC6on the proliferation of cultured CFs derivedfrom SHR and the effects of BNP on the expression of TRPC6and the proliferation of CFsderived from both SHR and WKY rats. To explore the molecular mechanism of abnormalproliferation of CFs in hypertension.Methods: CFs were cultured derived from18-week-old male SHR and WKY respectively,and the third passage of cells was used in all experiments. Cell proliferation was assessedwith both WST-1and Brd-U ELISA. The expressions of TRPC6, BNP and NPR-A weredetected by Western blot. Different concentrations of AngII (0,10-8,10-7, and10-6mol/L)were used to induce the proliferation and the expression of TRPC6on CFs. The mosteffective concentration (10-6mol/L) of AngII was used in the following experiments. CFsderived from SHR were divided into the following groups:(1) control group,(2) AngIIgroup,(3) AngII+SKF96365Group,(4) AngII+BTP2Group,(5) AngII+BNP Group.CFs derived from WKY were classified as three groups:(1) control group,(2) AngIIGroup,(3) AngII+BNP group.Results:(1) AngII induced the proliferation and upregulated the expression of TRPC6inCFs derived from SHR with a pattern of dose-dependent. Both SKF96365and BTP2(TRPC Inhibitors) significantly inhibited the proliferation and downregulated theexpression of TRPC6on CFs derived from SHR induced with AngII (P <0.05).(2) Theproliferation and expression of TRPC6on CFs in the SHR group induced by AngII(10-6mol/L) were significantly higher than those in the WKY group (P <0.05).(3) BNPinhibited the proliferation of and the upregulation TRPC6on CFs derived from WKY induced by AngII (P <0.05). However, the proliferation of and the expression of TRPC6on CFs derived from SHR were not significantly changed with or without the present ofBNP.(4) The expression of NPR-A on CFs was significantly lower in the SHR groupwhen compared to the WKY group (P <0.05). There was no significant differences in theexpression of BNP on CFs between the two groups (P>0.05).Conclusions:(1) TPRC6plays an important role in the proliferation of CFs derived fromSHR;(2) BNP can downregulate the expression of TRPC6and inhibit the proliferation ofCFs derived from WKY, but it does not have the same effects on CFs derived from SHR.The downregulation of NPR-A on CFs derived from SHR may be responsible for themechanism that BNP has no effects on proliferation of CFs from SHR.