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Effects of angiotensin Ⅱ on extracellular signal--regulated protein kinases signaling pathway in cultured vascular smooth muscle cells from Wistar--Kyoto rats and spontaneously hypertensive rats

Zhu Jianhua, Liu Zhong, Huang Zhaoyang, Li Shan

Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University.Hangzhou 310003,Zhejiang

Abstract

The aim of this study was to investigate the effects of angiotensinⅡ (Ang Ⅱ) on extracellular signal-regulated protein kinase (ERK) signaling pathway in cultured vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. VSMCs from SHR and WKY rats were treated with 1×10~(-7) mmol/L AngⅡfor 24h in the absence or presence of 30 min of pre-treatment of valsartan (1×10~(-5) mmol/L) or PD98059 (1×10~(-5) mmol/L), selective inhibitor of ERKs- dependent pathways, when they were cultured in 20% calf serum medium. VSMCs of SHR and WKY cultured in serum-free medium were used as control groups. Among the different treatments, VSMCs from the SHR and WKY were devided into four groups: (1) control, (2) AngⅡ, (3) AngⅡ+valsartan, (4) Ang Ⅱ+PD98059. ERK activity in VSMCs was measured by immuno-precipitation. Proteins of total ERK (t-ERK), phosphorylated-ERK (p-ERK) and mitogen-activated protein kinases phosphatase-1 (MKP-1) in VSMCs were detected by Western blot. MKP-1 mRNA in VSMCs was measured by RT-PCR. In VSMCs from WKY or SHR rats, ERK activity, p-ERK, MKP-1 and MKP-1 mRNA in AngⅡgroup were higher than those in control group (P<0.05). In both SHRs and WKYs, there were no significant differences in ERK activity, p-ERK, MKP-1 and MKP-1 mRNA among the control group, AngⅡ+valsartan group and AngⅡ+PD98059 group. ERK activity, p-ERK, MKP-1 and MKP-1 mRNA in SHRs were significantly higher than those in WKYs with same treatments (P<0.01). There was no significant difference in t-ERK among different groups and no difference in t-ERK between SHRs and WKYs (P>0.05). Our results show that AngⅡactivates VSMCs ERK signaling pathways via AngⅡtype 1 (AT_(1)) receptors. Ang Ⅱincreased ERK activity and p-ERK, but not t-ERK, accompanied by an increase in MKP-1 mRNA expression and protein. Among the different treatments, ERK activity and p-ERK were higher in SHR than in WKY. Valsartan and PD98059 blocked AngⅡ-stimulated ERK activation. These results suggest that ERK signaling pathway plays an important role in the pathogenesis of hypertension. The effect of AngⅡon SHR and WKY VSMCs’ERK signaling pathway may be mediated by AT_(1) receptors, enhancing ERK activity and the amount of p-ERK, and then increasing MKP-1 mRNA and its expression.

Key words: angiotensinⅡ;mitogen-activated protein kinases;extracellular signal-regulated protein kinase;Vascular smooth muscle cells;Rats;spontaneously hypertensive

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Citing This Article：

Zhu Jianhua, Liu Zhong, Huang Zhaoyang, Li Shan. Effects of angiotensin Ⅱ on extracellular signal--regulated protein kinases signaling pathway in cultured vascular smooth muscle cells from Wistar--Kyoto rats and spontaneously hypertensive rats . Acta Physiol Sin 2005; 57 (5): (in Chinese with English abstract).