Angiotensin II-induced over-activation of p47phox in fibroblasts friorn hypertensives: which role in the enhanced ERK1/2 responsiveness to angiotensin II?

Background Fibroblasts Eire involved in the remodeling of the heart and of the vasculature associated to arterial hypertension, and an abnormal extracellular signal-regulated kinase 1/2 (ERK1/2) activation by angiotensin II (Ang II) plays a pivotal role in this process. However, the intracellular pathways leading to cell hypertrophy and hyperplasia, as well as to collagen production, are still incompletely known. Objective To investigate the role of superoxide anion (O-2(-)) and of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase in Ang II-stimulated ERK1/2 over-activation in fibroblasts from hypertensive patients. Methods O-2(-) production was measured in skin fibroblasts from hypertensives (HT, n = 11) and from normotensive controls (NT, n = 10) by electron spin resonance technique. ERK1/2 phosphorylation and p47phox NAD(P)H oxidase subunit translocation were measured by western blot. Results Ang II (1 mu mol/l) induced a larger p47phox subunit translocation and increased intracellular O-2(-) production to a larger extent in HT in comparison to NT and this effect was blocked by apocynin, an inhibitor of the NAD(P)H oxidase. Ang II increased ERK1/2 phosphorylation more in HT than in NT. The Ang III-induced ERK1/2 phosphorylation was inhibited by apocynin in a dose-dependent manner in NT, but not in HT. Conclusions The chain of cellular events leading to increased ERK1/2 responsiveness to Ang II in hypertension include an exaggerated response of p47phox, NAD(P)H oxidase and O-2(-), but it is partially resistant to apocynin. Therefore, NAD(P)H-dependent reactive oxygen species (ROS) production is not the only determinant of the exaggerated ERK1/2 responsiveness in fibroblasts of hypertensives (HT).