Flow regulation of ecNOS and Cu/Zn SOD mRNA expression in porcine coronary arterioles

Abstract

The purpose of this study was to test the hypothesis that increased flow through coronary arterioles increases endothelial cell nitric oxide synthase (ecNOS) and Cu/Zn superoxide dismutase (SOD) mRNA expression. Single porcine coronary arterioles (ID 100–160 μm; pressurized) were cannulated, perfused, and exposed to intraluminal flow sufficient to produce maximal flow-induced dilation of coronary arterioles (high flow; 7.52 ± 0.22 μl/min), low flow (0.84 ± 0.05 μl/min), or no flow for 2 or 4 h. Mean shear stress was calculated to be 5.7 ± 1.0 dyn/cm2 for high-flow arterioles and 1.6 ± 1.0 dyn/cm2 for low-flow arterioles. At the end of the treatment period, mRNA was isolated from each vessel, and ecNOS and SOD mRNA expression was assessed using a semiquantitative RT-PCR. All data were standardized by coamplifying ecNOS or SOD with glyceraldehyde-3-phosphate dehydrogenase. The results indicate that ecNOS mRNA expression is increased in arterioles exposed to 2 or 4 h of high flow. In contrast, SOD mRNA expression was increased only after 4 h of high flow. Neither gene is induced by exposure to low flow. On the basis of these data, we concluded that ecNOS and SOD mRNA expression is regulated by flow in porcine coronary arterioles. In addition, we concluded that a threshold level of flow and shear stress must be sustained to elicit the upregulation of ecNOS and SOD mRNA expression.

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.…”

“…In addition, endothelial nitric oxide synthase (NOS) can produce large amounts of O 2 .-when the enzyme becomes uncoupled from its normal substrates (Milstien et al 1999;Witteveen et al 1999;Vasquez-Vivar et al 2002;Zou et al 2002;Landmesser et al 2003 (Beckman et al 1990;Pryor et al 1995), although this has not been demonstrated experimentally. Finally, endothelial cells in vivo are exposed to shear stress, which modulates many key aspects of endothelial metabolism and function, including NO release (Griffith 2002), NOS expression (Dimmeler et al 1999;Davis et al 2004), copper/zinc superoxide dismutase expression (Dimmeler et al 1999;Woodman et al 1999), and the expression of other endothelial cell genes (Malek et al 1995 …”

“…As multiple endothelial cell mechanisms including nitric oxide release (Griffith 2002), nitric oxide synthase expression (Dimmeler et al 1999;Davis et al 2004), copper/zinc superoxide dismutase expression (Dimmeler et al 1999;Woodman et al 1999), and endothelial cell gene expression (Malek et al 1995) are shear dependant.…”

Aging induces muscle-specific impairment of endothelium-dependent dilation in skeletal muscle feed arteries

“…During exercise, blood flow increases to provide muscle with an adequate supply of oxygen and nutrients. It is well documented that flow/shear stress is an important signal regulating eNOS expression in blood vessels (19,27). Consequently, age-associated reductions in physical activity and associated increases in blood flow may remove an important signal for the maintenance of eNOS expression.…”

“…The mechanism for decreased SOD-1 protein expression may involve age-associated reductions in resting blood flow and associated shear stress. Similar to eNOS, shear stress is a primary signal regulating SOD-1 expression in cultured endothelial cells (12) and in intact arteries (27). In addition, decreased soleus muscle blood flow, induced by hindlimb unweighting, is associated with reductions in SOD-1 expression and ACh-induced dilation in SFA (28).…”