Figure 3. Endothelial cells are heavily exposed to oxidative stress.

All components of the vascular wall including endothelial cells produce ROS from endogenous sources. Enzymatic sources include the NADPH oxydase complexes, lipoxygenases, xanthine oxidase, uncoupled eNOS, uncoupled mitochondrial electron transport. They are also exposed to exogenous sources of ROS generated by drugs, ionizing radiation, ischemia/reoxygenation, shear stress and circulating cells including neutrophils and cancer cells.