Oscillatory and Steady Laminar Shear Stress Differentially Affect Human Endothelial Redox State: Role of a Superoxide-Producing NADH Oxidase

• Published in: Circulation research Vol. 82; no. 10; pp. 1094 - 1101
• Main Authors: De Keulenaer, Gilles W, Chappell, David C, Ishizaka, Nobukazu, Nerem, Robert M, Alexander, R. Wayne, Griendling, Kathy K
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01.06.1998; Lippincott; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Arteriosclerosis - metabolism; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cells, Cultured; Endothelium, Vascular - metabolism; Free Radicals; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing) - genetics; Heme Oxygenase (Decyclizing) - metabolism; Heme Oxygenase-1; Hemorheology; Humans; Medical sciences; Membrane Proteins; Multienzyme Complexes - metabolism; NADH, NADPH Oxidoreductases - metabolism; Oxidation-Reduction; Space life sciences; Stress, Mechanical; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; Superoxides - metabolism; NADPH; Human; Redox state; Oxidative stress; Endothelial cell; Enzyme; Heme oxygenase (decyclizing); Cardiovascular disease; Superoxide dismutase; Gene expression; Free radical; Endothelium; Northern blotting; Vascular disease; NADH; Blood vessel; Atherosclerosis; Immunoblotting assay; Hyperoxides Anions; Circulatory system; Oxidoreductases; Umbilical vein
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.82.10.1094

Atherosclerotic lesions are found opposite vascular flow dividers at sites of low shear stress and oscillatory flow. Since endothelial proinflammatory genes prominent in lesions are regulated by oxidation-sensitive transcriptional control mechanisms, we examined the redox state of cultured human umbilical vein endothelial cells after either oscillatory or steady laminar fluid shear stress. Endothelial oxidative stress was assessed by measuring activity of the superoxide (O2 [center dot])-producing NADH oxidase (a major source of reactive oxygen species in vascular cells), intracellular O2 [center dot] levels, induction of the redox-sensitive gene heme oxygenase-1 (HO-1), and abundance of Cu/Zn superoxide dismutase (Cu/Zn SOD), an antioxidant defense enzyme whose level of expression adapts to changes in oxidative stress. When cells were exposed to oscillatory shear (+/- 5 dyne/cm (), 1 Hz) for 1, 5, and 24 hours, NADH oxidase activity and the amount of HO-1 progressively increased up to 174 +/- 16% (P<0.05) and 505 +/- 111% (P<0.05) versus static conditions, respectively, whereas levels of Cu/Zn SOD remained unchanged. This upregulation of HO-1 was completely blocked by the antioxidant N-acetylcysteine (NAC, 20 mmol/L). In contrast, steady laminar shear (5 dyne/cm) induced NADH oxidase activity and NAC-sensitive HO-1 mRNA expression only at 1 and 5 hours, a transient response that returned toward baseline at 24 hours. Levels of Cu/Zn SOD mRNA and protein were increased after 24 hours of steady laminar shear. Furthermore, intracellular O2 [center dot], as measured by dihydroethidium fluorescence, was higher in cells exposed to oscillatory than to laminar shear. These data are consistent with the hypothesis that continuous oscillatory shear causes a sustained activation of pro-oxidant processes resulting in redox-sensitive gene expression in human endothelial cells. Steady laminar shear stress initially activates these processes but appears to induce compensatory antioxidant defenses. We speculate that differences in endothelial redox state, orchestrated by different regimens of shear stress, may contribute to the focal nature of atherosclerosis. (Circ Res. 1998;82:1094-1101.)