Angiotensin II Induces p67 phox mRNA Expression and NADPH Oxidase Superoxide Generation in Rabbit Aortic Adventitial Fibroblasts

Abstract

Abstract —Superoxide radical (O 2 − ) is ubiquitously critical to the bioactivity of endothelial nitric oxide. In angiotensin-dependent hypertension, vascular O 2 − levels rise and impede endothelium/nitric oxide–dependent vascular relaxation. We have reported that the major O 2 − source in the rabbit aorta is adventitial fibroblast phagocyte-like NADPH oxidase and shown that angiotensin (Ang) II treatment of adventitial fibroblasts causes a concentration-dependent increase in particulate NADPH-dependent O 2 − . From cultured rabbit aortic adventitial fibroblasts treated or not treated with Ang II, we prepared particulate fractions and measured lucigenin-enhanced chemiluminescence. Because [Sar 1 ,Thr 8 ]-Ang II, a generalized antagonist of Ang II and plausible inhibitor of the conversion of Ang II, reversed Ang II (10 nmol/L)–induced NADH- and NADPH-dependent O 2 − to basal levels, we tested the effect of the inhibitor of aminopeptidase N, amastatin (10 μmol/L), and found no effect on Ang II–stimulated O 2 − . Ang(1-7), Ang III, and Ang IV also were not effective in stimulating O 2 − levels at concentrations similar to those of Ang II. Kinetic analysis showed a rise in NADPH oxidase O 2 − production in response to Ang II, which peaks at 3 hours and returns to basal levels by 16 hours. p67 phox , a cytosolic factor, appears to be affected at both the level of transcription and protein synthesis because actinomycin and cycloheximide individually inhibited the observed effect. A partial sequence of p67 phox was recovered by reverse transcriptase from mRNA harvested from cultured rabbit aortic adventitial fibroblasts. Furthermore, the p67 phox mRNA transcript in aortic fibroblasts is induced by Ang II before the peak of NADPH oxidase by Northern analysis and ribonuclease protection assays. These data suggest that Ang II stimulates NAD(P)H oxidase O 2 − generation in fibroblasts of aortic adventitia via transcriptional activation of p67 phox . These data also provide preliminary evidence for the regulation of factors of the NADPH oxidase and potentially provide a novel means by which to abrogate the development of O 2 − -dependent hypertension.