Angiotensin ll-infused rats exhibit increases in renal angiotensinogen (AGT) mRNA and protein, and this may be one mechanism by which low levels of circulating angiotensin II induce progressive hypertension. Using an interesting transgenic mouse model in which human AGT is expressed only in the kidney, it is possible to enhance angiotensin II content only in the kidney without altering circulating levels of angiotensin II. The goal of this research project is to define and characterize the mechanisms responsible for the intrarenal enhancement of AGT expression by angiotensin II. My hypothesis is that the augmented intrarenal AGT expression by angiotensin II involves angiotensin II type 1 (AT1) receptor-dependent and c-Src/MAPK-, ROS-, or Rho-kinase/NFkB-dependent pathways. In accord with this hypothesis, the following specific aims are targeted for the proposed period of support: 1) To demonstrate that chronic overproduction of angiotensin II only in the kidney elicited by stimulating human AGT expression in the presence of human renin will cause increases in endogenous mouse AGT mRNA expression as well as endogenous mouse AGT protein levels in proximal tubular cells leading to slowly progressive hypertension in gene-targeted male mice. 2) To demonstrate that subacute overproduction of angiotensin II only in the kidney elicited by stimulating human AGT expression in the presence of human renin will cause increases in endogenous mouse AGT mRNA expression as well as endogenous mouse AGT protein levels in proximal tubular cells leading to progressive hypertension in gene-targeted female mice. 3) To demonstrate that the enhancement of the endogenous mouse AGT production in proximal tubular cells involves AT1 receptor-mediated mechanisms in gene- targeted female mice. 4) To determine if AT1 receptor-dependent AGT enhancement by angiotensin II involves c-Src/MAPK-, ROS-, or Rho-kinase/NFkB-dependent mechanisms in primary-cultured mouse proximal tubular cells. 5) To examine whether the 5'-upstream promoter region of mouse AGT gene has positive responsive element(s) by angiotensin II. The results obtained from the proposed studies will provide important information regarding the intrarenal augmentation of AGT expression by angiotensin II, which may help to develop a novel concept to treat angiotensin ll-dependent hypertensive subjects and to establish the importance of the tubular renin-angiotensin system in the genesis of angiotensin ll-dependent hypertension.
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