The Role Of Adrenomedullin-2 In Vascular Smooth Muscle Cell Proliferation Induced By Angiotensin Ⅱ

Aims:Intermedin/adrenomedullin-2(IMD/ADM2)is a novel member of the calcitonin gene-related peptide(CGRP).Angiotensinâ…¡(Angâ…¡)-induced vascular smooth muscle cells(VSMCs)proliferation is a complicated cellular signal transduction process and is considered to contribute to the development of various cardiovascular diseases such as hypertension,atherosclerosis,restenosin and so on. Angâ…¡activates multiple celluar signal transduction pathways through the action of the G protein-coupled AT1 receptor.Extracellular regulated kinase(ERK) cascade is one of the important signal transduction pathway of VSMC proliferation mediated by Angâ…¡.The present study aimed to evaluate the role of IMD/ADM2 in vascular smooth muscle cell proliferation induced by angiotensinâ…¡and investigate the possible mechanism.Methods:Aortic VSMCs(vascular smooth muscle cells)from 5-week-old male Wistar-Kyoto(WKY)rats were used for the present studies.VSMCs proliferation were determined by measuring ³H-Thymidine incorporation,cell number,and uptake of 3-(4,5-dimethylthiazol-2-yl)-diphenyl-tetrazolium bromide(MTT). Expression of p-ERK1/2,p-Akt,total-ERK,total-Akt were determined by Western blot.Results:Under ischemic conditions,cell number was significantly increased by 21%,24%and 30%(P＜0.01).After the cells were stimulated by angiotensinâ…¡(1×10^-7mol/L),the cell number was significantly increased by 78%compared with control.VSMCs were pretreated with different concentration of IMD/ADM2 (1nM,10nM,100nM)for 48h,Angâ…¡induced VSMCs proliferation were inhibited by IMD/ADM2.The inbibitive rate was 28%,32%and 44%, respectively(P＜0.01).Infusion of CGRP8-37 and ADM22-52 could significantly inhibit the cell proliferation.Densitometric analysis of the Western blots was performed,and abundance of phosphorylation of ERK protein decreased by 18%at 1nM IMD/ADM2,38%at 10nM IMD/ADM2,and 62%at 100nM IMD/ADM2, respectively(P＜0.01),but had no effect on P-Akt signaling in cells tested.Conclusion:Our present study showed that IMD/ADM2 significantly inhibited Angâ…¡induced VSMCs proliferation.One possible molecular mechanism mediating the anti-proliferative effect of IMD/ADM2 is the inhibition of P-ERK1/2 activation. These findings may offer a new insight into the anti-hypertension mechanisms of IMD/ADM2 and provide the pharmacological basis for the clinical application of IMD/ADM2 in essential hypertension.