Role of NOX2 in the regulation of afferent arteriole responsiveness.

NADPH oxidases (NOX) are the major source of reactive oxygen species (ROS) in the vasculature and contribute to the control of renal perfusion. The role of NOX2 in the regulation of blood pressure and afferent arteriole responsiveness was investigated in NOX2(-/-) and wild-type mice. Arteriole constrictions to ANG II (10(-14)-10(-6) mol/l) were weaker in NOX2(-/-) compared with wild types. N(omega)-nitro-l-arginine methyl ester (l-NAME; 10(-4) mol/l) treatment reduced basal diameters significantly more in NOX2(-/-) (-18%) than in wild types (-6%) and augmented ANG II responses. Adenosine (10(-11)-10(-4) mol/l) constricted arterioles of wild types but not of NOX2(-/-). However, simultaneous inhibition of adenosine type-2 receptors induced vasoconstriction, which was stronger in NOX2(-/-). Adenosine (10(-8) mol/l) enhanced the ANG II response in wild type, but not in NOX2(-/-). This sensitizing effect by adenosine was abolished by apocynin. Chronic ANG II pretreatment (14 days) did not change the ANG II responses in NOX2(-/-), but strengthened the response in wild types. ANG II pretreatment augmented the l-NAME response in NOX2(-/-) (-33%), but not in wild types. Simultaneous application of l-NAME and ANG II caused a stronger constriction in the NOX2(-/-) (-64%) than in wild types (-46%). Basal blood pressures were similar in both genotypes, however, chronic ANG II infusion elevated blood pressure to a greater extent in wild-type (15 +/- 1%) than in NOX2(-/-) (8 +/- 1%) mice. In conclusion, NOX2 plays an important role in the control of afferent arteriole tone and is involved in the contractile responses to ANG II and/or adenosine. NOX2 can be activated by elevated ANG II and may play an important role in ANG II-induced hypertension. NOX2-derived ROS scavenges nitric oxide, causing subsequent nitric oxide-deficiency.