Low rates of Angiotensin II (Ang II) infusion increase reactive oxygen species (ROS), upregulate key renalcomponents of NADPH oxidase (p22phox, NOX-1) and downregulate EC-SOD. Antioxidant drugs implicateROS in the development of hypertension, yet the specific roles of renal and systemic ROS invasoconstriction, salt retention and the mediation by NADPH oxidase, or by reduced SOD-dependentdefense in the kidney, are largely undefined. We will study BP homeostasis (telemetric BP), salt handlingand sensitivity and microvascular mechanisms in mice (isolated, perfused renal afferent and mesentericresistance vessels and in vivo intravital microscopy) to explore the roles of an endothelium-derivedcontracting factor (EDCF) and enhanced VSMC contractility in the microvessels. We will relate thesefunctional studies to ROS, NO, and calcium activity in individual microdissected vessels and pre-glomerularvascular smooth muscle cells. Our primary strategy is the use of knockout models and small interferenceRNAs (siRNAs) directed at target genes delivered intrarenally to assess specifically renal mechanisms ofhypertension. This will be extended with kidney cross-transplantation combined with a cre-lox strategy toknockout genes specifically in VSMC to establish, for the first time, the roles of the kidney and its afferentarterioles in mediating hypertension with ROS.
Aim 1 will use the EC-SOD -/- mouse model of stable, sustained microvascular oxidative stress to test the hypothesis that oxidativestress releases endothelin, which acts on type A or B receptors to engage a cyclooxygenase-derived EDCFthat activates adjacent VSMCs where contractility is enhanced by a Ca++ sensitizing pathway mediated byrho/rho kinase.
Aim 2 will use EC-SOD -/- mice administered siRNA to IC-SOD delivered selectively to thekidney to test the hypothesis that IC-SOD is the major antioxidant defense in the kidney and that its renaldeficiency promotes renal vasoconstriction, salt retention, and hypertension.
Aim 3 will use normal micewith siRNA to p22phox delivered to the kidney or systemically to test the hypothesis that renal NADPHoxidase mediates increased afferent arteriolar contractility, RVR, salt retention and hypertension with Ang II.These projects are an integrated approach to dissect the roles of ROS in renal microvascular reactivity andsalt handling that constitute renal mechanisms of hypertension.
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