Role of matrix proteins and protein kinase C in endothelial oxidative response to cyclic strain

Atherosclerotic lesions in diseased arteries exhibit nonuniform distribution. Local alterations in flow-generated mechanical forces impinging on the arterial endothelium may play an important role in the localization of atherosclerotic lesions. It is hypothesized that cyclic wall strain, a circumferential stretching force, promotes atherogenesis by inducing oxidative stress in endothelial cells, resulting in increased endothelial adhesiveness to monocytes. In this study, the signaling mechanisms involved were investigated. Transformed human umbilical vein endothelial cells (ECV304) were plated on flexible silicone strips which were uncoated or coated with either vitronectin, fibronectin, or collagen I. Cells were then subjected to uniform sinusoidal stretch (10%; 60 cycles/min) for 6 hours by horizontal stretching of the silicone strips. Endothelial superoxide production, as measured by lucigenin chemiluminescence, was enhanced in cells exposed to cyclic strain as compared to static conditions. Furthermore, endothelial oxidative response to strain was matrix dependent. Cells plated on silicone alone, vitronectin, fibronectin, or collagen I exhibited increased endothelial superoxide production of 1.3, 1.8, 3.6, and 4.5 fold, respectively. The oxidative response to strain of cells plated on collagen I was reduced significantly by application of α₂ (to 1.3 fold) and β₁ (to 1.5 fold) integrin antibodies and the protein kinase C (PKC) inhibitors, staurosporin and calphostin C. To investigate the source of superoxide anions, cells were incubated with allopurinol or diphenyliodonium (DPI) during exposure to cyclic strain. Whereas allopurinol had very little effect, cyclic strain-induced superoxide anion production was significantly reduced by DPI, suggesting an important role of NAD(P)H oxidase. Thus, interaction between specific matrix proteins and endothelial cells, possibly via surface integrins such as α₂ and β₁, modulates endothelial oxidative response to cyclic strain. The source of cyclic strain-induced superoxide production involves a PKC-sensitive NAD(P)H oxidase.