Association of increased phagocytic NADPH oxidase-dependant superoxide production with diminished nitric oxide generation in essential hypertension

Objective Oxidative stress has been implicated in the pathogenesis of hypertension and its complications through alterations in nitric oxide (NO) metabolism. This study was designed to investigate whether a relationship exists between phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide anion (.O-2(-)) production and NO generation in patients with essential hypertension. Methods Superoxide production was assayed by chemiluminescence under baseline and stimulated conditions on mononuclear cells obtained from hypertensives (n = 51) and normotensives (n = 43). NO production was evaluated by determining serum NO metabolites, nitrate plus nitrite (Nix). Results Although there were no differences in baseline .O-2(-) production between normotensives and hypertensives, the .O-2(-) production in phorbol myristate acetate (PMA)-stimulated mononuclear cells was increased (P < 0.05) in hypertensives compared with normotensives. The PMA-induced .O-2(-) production was completely abolished by apocynin, a specific inhibitor of NADPH oxidase. Moreover, stimulation of .O-2(-) production by angiotensin II and endothelin-1 was higher (P< 0.05) in cells from hypertensives than in cells from normotensives. In addition, diminished (P < 0.001) serum NOx wasdetected in hypertensives compared with normotensives. Interestingly, an inverse correlation (r= 0.493, P < 0.01) was found between .O-2(-) production and NOx in hypertensives. Conclusions Generation of .O-2(-) mainly dependent on NADPH oxidase is abnormally enhanced in stimulated mononuclear cells from hypertensives. It is suggested that this alteration could be involved in the diminished NO production observed in these patients. (C) 2004 Lippincott Williams Wilkins.