Role of inducible nitric oxide synthase in the vascular smooth muscle cells cycle arrest induced by 17 beta-estradiol / 生理学报

ABSTRACT

Clinical epidemiologic data and animal experimental studies regard estrogen as being protective against the development of cardiovascular diseases. The mechanisms by which estrogen affects the development of vascular diseases are not clear. Recent studies demonstrated that the cardiovascular protective effects of estrogen are closely related to nitric oxide (NO) pathway. Our previous study proved that estrogen inhibited the proliferation and oncogene expression of vascular smooth muscle cells (VSMCs) induced by endothlin 1 (ET-1) and serum,this effect was mediated by NO release. In the present study, we investigated the role of inducible nitric oxide synthase (iNOS) in the VSMCs cycle arrest induced by 17 beta-estradiol (E(2)). The effects of E(2) on iNOS activity and protein expression in cultured rat VSMCs and the influence of NOS inhibitor N(G)-nitro-L-arginine methylester (L-NAME) on the inhibitory effect of E(2) on cell cycle were investigated. NOS assay kit was used to measure the activity of iNOS and protein expression of iNOS was determined by Western-blot. Cell cycle analysis was accessed by flow cytometry. The results obtained showed that E(2) increased iNOS activity of VSMCs but not in a dose-dependent manner. E(2) 10 nmol/L increased the iNOS activity of VSMCs distinctly at two time points 30 min and 12 h. These effects were significantly inhibited by estrogen receptor (ER) antagonist Tamoxifen (0.1 micromol/L) and NOS inhibitor L-NAME (1 micromol/L). E(2) increased iNOS protein expression of VSMCs in a dose-dependent manner. The effect of E(2) on iNOS protein expression of VSMCs started at 3 h, distinctly increased at 12 h and then decreased. Tamoxifen significantly inhibited the E(2)-induced iNOS protein expression of VSMCs. ET-1 increased cell percentage of S phase and G(2)+S/G(1). This effect was inhibited by E(2). L-NAME significantly attenuated the inhibitory effect of E(2) on cell cycle of VSMCs. The results suggest that E(2) induced G(1) arrest of VSMCs, which was associated with an increase in iNOS activity and protein expression of VSMCs. These effects were at least mediated by estrogen receptor partly.