TUMOR-NECROSIS-FACTOR-ALPHA ACTIVATES A P22(PHOX)-BASED NADH OXIDASE IN VASCULAR SMOOTH-MUSCLE

Increasing experimental evidence suggests that non-phagocytic cells ex press a potent superoxide (O-2(-.))-producing NADH oxidase that might be related to the phagocytic NADPH oxidase. Here we show that the cyto kine tumour necrosis factor alpha (TNF-alpha) activates, in a time-and dose-dependent manner, a O-2(-.)- producing NADH oxidase in cultured rat aortic smooth-muscle cells. Dose-response experiments for NADH sho wed an upward shift of the curve for TNF-alpha-treated cells, suggesti ng that TNF-alpha increased the amount of available enzyme. Using the anti-sense transfection technique, we further demonstrate that the mol ecular identity of this oxidase includes p22(phox) (the alpha subunit of cytochrome b(558) and part of the electron transfer component of th e phagocytic NADPH oxidase), which we recently cloned from a rat vascu lar smooth-muscle cell cDNA library. In addition, prolonged treatment with TNF-alpha increased p22(phox) mRNA expression without affecting p 22(phox) mRNA stability, and only when transcriptional activity was in tact. These findings identify a p22(phox)-containing NADH oxidase as a source for cytokine-induced free radical production in vascular smoot h-muscle cells and clarify some of the mechanisms involved in the regu lation of vascular oxidase activity.