It is well known that inappropriate angiotensin II (ANGII) activation plays a primary pathogenic role in the progression of chronic kidney disease (CKD), irrespective of the initiating cause. The source of the ANGII (vascular, renal epithelial, etc) and the signaling pathways that are involved in this process are poorly understood. The goal of this application is to establish the importance of the coupling between angiotensin II (ANGII) signaling and Janus kinase 2 (Jak2) in vascular smooth muscle cells (VSMC) in the progression of CKD. This pilot project involves the phenotyping of a novel conditional knockout mouse that lacks Jak2 expression within VSMC and is resistant to the development of chronic ANGII-induced hypertension, implicating a primary role of the vascular smooth muscle Jak2 signaling pathway. Our preliminary studies have demonstrated that the VSMC Jak2 null mouse is also highly resistant to chronic ANGII-induced CKD and this beneficial effect is pressure independent. Thus, we hypothesize that it is the renal actions of ANGII, mediated by Jak2, that are largely responsible for the hypertension and CKD associated with high dose chronic ANGII infusion. The first specific aim extends our observations on the chronic ANGII-infusion model of CKD and specifically investigates the role of VSMC-derived Jak2 on renal function and dysfunction during ANGII- induced CKD. The second specific aim uses a kidney cross transplant model and an intrarenal infusion of a selective Jak2 inhibitor to determine whether VSMC-derived Jak2 in the kidney is responsible for ANGII- mediated hypertension and CKD. In the third specific aim, we will determine if the deleterious actions of VSMC-derived Jak2, in response to chronic ANGII infusion, involve inhibition of nitric oxide (NO) and increases in reactive oxygen species (ROS). All experiments will be done on an FVB background. These mice are susceptible to ANGII-induced hypertension and CKD. The VSMC Jak2 null genotype is SM22?Cre(+);Jak2fl/fl while the control genotype is SM22?Cre(-);Jak2fl/fl. All animals studied will be chronically instrumented for blood pressure measurement by telemetry, will have metabolic cage studies to follow the development of proteinuria and total NO production and tissues/blood will be harvested for assessment of renal pathology, 24 hour creatinine clearance (Ccr), determinants of NO and ROS production, plasma and renal tissue ANGII and levels of components of the intrarenal renin angiotensin system at the transcript, protein and activity level. Collectively, our proposed studies will (i) provide evidence for our hypothesis (ii) provid a better mechanistic understanding for how VSMC-derived Jak2 mediates CKD in response to chronic ANGII and (iii) position us to translate our investigation into a clinical study for the us of Jak2 inhibitors for the treatment of hypertension and CKD.
Angiotensin II plays a key role in the progression of many forms of kidney disease and this application uses a unique transgenic mouse and novel drug to investigate how angiotensin II signaling in the blood vessel (vascular smooth muscle) contributes to this injury process.
