Expressional changes of the vascular antioxidant system in atherosclerotic coronary arteries.

Oxidative stress induced by reactive oxygen species (ROS) plays an important role in atherogenesis, and the redox state is determined by the balance between antioxidants and the ROS generating system. To defend against enhanced ROS, mammalian cells have a complex network of antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase. To clarify the role of the vascular antioxidant system, we investigated by immunohistochemistry the expressional changes of antioxidative enzymes in coronary arteries obtained from autopsied cases. In nonatherosclerotic coronary arteries, Cu/Zn SOD and Mn SOD were expressed in medial smooth muscle cells (SMC), whereas cytosolic GPx (GPx-1) was expressed mainly in endothelium and weakly in medial SMC. Catalase was expressed in medial SMC and endothelium. Progression of atherosclerosis did not result in an additional increase in the expression of antioxidative enzymes in SMC in the media or endothelium. However, migrating SMC and macrophages in atheromatous plaques expressed these four antioxidative enzymes intensively. Double staining with cell markers confirmed the cell-specific expression of the antioxidative enzymes. Thus, the expressional pattern showed regional heterogeneity. In response to oxidative stress, the vascular antioxidant system was upregulated in atherosclerotic lesions. The imbalance between vascular antioxidant and oxidant systems might play an important role in coronary atherogenesis.