Regulation of endothelial cell nitric oxide synthase mRNA expression by shear stress

Abstract

Shear stress enhances expression of Ca(2+)-calmodulin-sensitive endothelial cell nitric oxide synthase (ecNOS) mRNA and protein in bovine aortic endothelial cells (BAEC). The present studies were performed to investigate mechanisms responsible for regulation of ecNOS mRNA expression by shear stress and to determine if this induction of ecNOS mRNA is accompanied by an enhanced nitric oxide (NO) production. Shear stresses of 15 dyn/cm2 for 3-24 h resulted in a two- to threefold increase of ecNOS mRNA content quantified by Northern analysis in BAEC. Shear stresses (1.2-15 dyn/cm2) for 3 h resulted in an induction of ecNOS mRNA in a dose-dependent manner. In human aortic endothelial cells, shear stresses of 15 dyn/cm2 for 3 h also resulted in ecNOS mRNA induction. In BAEC, this induction in ecNOS mRNA was prevented by coincubation with actinomycin D (10 micrograms/ml). The K+ channel antagonist tetraethylammonium chloride (3 mM) prevented increase in ecNOS mRNA in response to shear stress. The ecNOS promotor contains putative binding domains for AP-1 complexes, potentially responsive to activation of protein kinase C (PKC). However, selective PKC inhibitor calphostin C (100 nM) did not inhibit ecNOS induction by shear stress. Finally, production of nitrogen oxides under both basal conditions and in response to the calcium ionophore A-23187 (1 microM) by BAEC exposed to shear stress was increased approximately twofold compared with cells not exposed to shear stress. These data suggest that ecNOS mRNA expression is regulated by K+ channel opening, but not by activation of PKC, and that shear not only enhances ecNOS mRNA expression but increases capacity of endothelial cells to release NO.

Mechanisms of H2O2-induced oxidative stress in endothelial cells

“…Shear stress has also been shown to increase pro-oxidants, including NOS formation of NO and SOD (Malek et al 1995;Uematsu et al 1995;Corson et al 1996;Dimmeler et al 1999;Woodman et al 1999 under H 2 O 2 -induced oxidative stress under both shear and static conditions. The overall goal of these studies is to provide a possible model for disease development within the vasculature.…”

Ventilation and oxygenation induce endothelial nitric oxide synthase gene expression in the lungs of fetal lambs.

“…In vivo, endothelial cells are exposed to fluid mechanical forces, including hydrostatic pressure, strain, and shear stress (25,26,38,39). Shear stress is proportional to the velocity of blood and its viscosity and inversely proportional to the internal radius of the blood vessel to the third power (38,39).…”

“…Initially, NOS activity and NO production are increased when endothelial cells are exposed to increased shear stress (12,14,15,(20)(21)(22)(23). If the shear is maintained there are then subsequent increases in eNOS mRNA and protein expression (24)(25)(26). The immediate increase in pulmonary blood flow at birth may increase shear forces on the pulmonary vascular endothelium inducing eNOS mRNA and protein expression.…”

Vascular Responses to Shear Stress: The Involvement of Mechanosensors in Endothelial Cells

“…Whole-cell patch-clamp recordings of single arterial endothelial cells exposed to controlled levels of laminar shear stress in capillary flow tubes demonstrated the evidence for a K + selective, shear stress-activated ionic current [41]. Treatment of endothelial cells with blocking agents to K + channel such as barium chloride or tetraethylammonium inhibited the induction of NO by shear stress and the induced expression of endothelial cell NO synthase (eNOS) and transforming growth factor beta-1 [43,44]. The findings support that K + channel is important in mediating shear stress responsiveness.…”