P22(PHOX) IS A CRITICAL COMPONENT OF THE SUPEROXIDE-GENERATING NADH NADPH OXIDASE SYSTEM AND REGULATES ANGIOTENSIN-II-INDUCED HYPERTROPHY IN VASCULAR SMOOTH-MUSCLE CELLS/

Superoxide anion formation is vital to the microbicidal activity of ph agocytes. Recently, however, there is accumulating evidence that it is also involved in cell growth in vascular smooth muscle cells (VSMCs). We have shown that the hypertrophic agent angiotensin II stimulates s uperoxide production by activating the membrane-bound NADH/NADPH oxida se and that inhibition of this oxidase attenuates vascular hypertrophy . However, the molecular identity of this oxidase in VSMCs is unknown, We have recently cloned the cytochrome b(558) alpha-subunit, p22(phox ) (one of the key electron transfer elements of the NADPH oxidase in p hagocytes), from a rat VSMC cDNA library, but its role in VSMC oxidase activity remains unclarified. Here we report that the complete inhibi tion of p22(phox) mRNA expression by stable transfection of antisense p22(phox) cDNA into VSMCs results in a decrease in cytochrome b conten t, which is accompanied by a significant inhibition of angiotensin II- stimulated NADH/NADPH-dependent superoxide production, subsequent hydr ogen peroxide production, and [H-3]leucine incorporation. We provide t he first evidence that p22(phox) is a critical component of superoxide -generating vascular NADH/NADPH oxidase and suggest a central role for this oxidase system in vascular hypertrophy.