Oxidative stress and renal dysfunction cause cardiovascular and renal disease and hypertension (HTN), but our understanding of pathophysiological mechanisms is incomplete. We find that male WT mice develop Ang II- induced HTN (AIH), with a smaller blood pressure (BP) increase in females. Importantly, global genetic deletion of NoxA1 prevents AIH in males. We shall elucidate the renal phenotype by testing the hypotheses that excess superoxide anion generated by NoxA1-dependent Nox1 NADPH oxidase distorts renal function, magnifies vasoconstriction and promotes Na+ retention to produce AIH. We postulate that Ang II/AT1R activate these renal mechanisms to produce AIH in males and are reversed by knockdown of Nox1/NoxA1 signaling. We predict weaker HTN actions of Ang II in intact females by greater offsetting actions mediated by estrogen, AT2R and antioxidant systems, with diminished anti-HTN effects during ovariectomy. The role of Nox1/NoxA1 signaling in controlling vascular and renal tubular function is to be tested in health and AIH. AIH is likely attenuated in VSMC- &/or collecting duct (CD)-specific NoxA1 deletion with reduced peripheral vasoconstriction and/or Na+ excretion. Our comprehensive studies combine genetic, functional, and biochemical approaches to analyze Nox1/NoxA1 signaling in vascular reactivity and Na+ excretion. Pharmacological Nox1 inhibition by a novel inhibitor (INH-25) plus GKT136901 and ML171 compliments gene targeting.
AIM 1. Determine the BP effect of genetic NoxA1 deletion (global, VSMC- & CD-specific) early in AIH, with more severe HTN in WT males than females, and less in ovariectomized vs. intact females. Does the Nox1 inhibitor GKT136901 attenuate AIH? Are renal ROS production and urinary excretion greater and NO metabolite excretion reduced in severe HTN? Are renal vascular and tubular Nox isoforms/subunits upregulated and SOD and NOS isoforms reduced in AIH? Radioligand binding will assess AT1, AT2, V1 and TxA2 receptor affinity/density in the vasculature and distal nephron. Are major distal nephron Na+ transporter protein levels and activity upregulated? Does diuretic inhibition of ENaC and other specific Na+ transporters prevent AIH development.
AIM 2. Assess the participation of Nox1/NoxA1 signaling in regulation of renal Na+ excretion and tubular Na+ transport in global and VSMC- and CD-specific NoxA1-KO mice. Animal studies will determine the kidney's ability to excrete an acute salt load before and early in AIH. Electrophysiological patch-clamp studies of isolated CD will identify changes in ENaC activity and dependency on AT1R and Nox1 activity.
AIM 3. Identify whether Nox1/NoxA1 modulate vascular reactivity in vitro and in vivo in health and HTN, evaluating vasoactive pathways in global and VSMC-NoxA1-null mice in combination with Nox1 pharmacological inhibition. Fura-2 fluorescence will assess Ang II/AT1R stimulation on Nox1 signaling effects on Ca2+ entry and mobilization in afferent arterioles of WT and global- and VSMC- NoxA1-/-mice. Collectively, our studies will establish a role of NoxA1-dependent Nox1 activity in Na+ balance and BP control, providing new insights for therapeutic targeting of cardio-renal disease and AIH.
We study mechanisms that alter blood vessel and kidney function to cause hypertension (high blood pressure). This condition is relatively painless and is termed the ?silent killer?, whereas is it a major risk factor for cardiovascular and kidney disease. We investigate the consequences of oxidative stress on blood vessels and tubules in the kidney that promote an imbalance in sodium excretion to cause exaggerated sodium retention, an increase in extracellular fluid volume and blood pressure.
