| NAD(P)H oxidase is upregulated in aortic smooth muscle cells (VSMCs) in response to growth factor stimulation, concomitant with increased reactive oxygen species (ROS) production in these cells. We investigated the role of ROS production by the NAD(P)H oxidase in SMC responses to growth factors and in atherosclerotic lesion formation in ApoE(-/-) mice. VSMCs, from wild type, p47phox(-/-) and gp91 phox(-/-) mice treated with serum or thrombin differed markedly with respect to growth factor responsiveness and ROS generation. p47phox(-/-) VSMCs had a decreased proliferative response to growth factors when compared to wild type cells, whereas the response of gp91phox(-/-) VSMCs were indistinguishable from wild type VSMCs. Consistent with these observations, p47phox (-/-) VSMCs had increased aconitase activity compared with wild type and gp91phox(-/-) cells, indicating diminished superoxide production by p47phox(-/-) VSMCs.;The relevance of these in vitro observations was tested by measuring atherosclerotic lesion formation in genetically modified (wild type, p47phox(-/-), ApoE(-/-) and ApoE(-/-)/p47phox(-/-)) mice by oil red O staining of aortas. ApoE(-/-)/p47phox(-/-) mice had less total lesion area than ApoE(-/-) mice, as determined by quantitative lesion measurements, regardless of whether mice were fed chow or high fat "Western" diet. Together, these data indicate that p47phox is an essential component of the NAD(P)H oxidase in VSMCs and that generation of superoxide by NAD(P)H oxidase has a requisite role in atherosclerotic lesion formation in ApoE(-/-) mice. |
