Angiotensin II (AII) has several important actions in the cardiovascular system which include regulation of aldosterone biosynthesis and potent vasoconstrictive and growth promoting effects. This proposal examines whether lipoxygenase (LO) products of arachidonic and linoleic acid metabolism can mediate the growth promoting effects of AII. This hypothesis is based on observations that LO products are key mediators of AII-induced aldosterone synthesis and pressor effects and that several LO products have been linked to changes in cellular proliferation. Specifically, the role of 12- and 15-LO products such as 12- and 15- hydroxyeicosatetraenoic acids (HETEs) and 9- and 13- hydroxyoctadecadienoic acids (HODEs) in the hypertrophic and hyperplastic effects of AII will be evaluated. Studies will be performed in two cell models 1) porcine aortic smooth muscle cells (PVSMC) since AII predominantly has hypertrophic effects in SMC, and 2) a bovine adrenocortical cell line termed AC1 cells - in which AII has hyperplastic effects. Another key aim of this proposal is to examine effects of AII and LO activation under normoglycemic as well as hyperglycemic conditions. This is based on the observation that AII vasopressor action is enhanced in the diabetic state and that AII as well as elevated glucose and insulin can alter LO product formation. Initial studies will be devoted to evaluation of LO product formation with AII under increasing glucose and insulin concentrations. to establish whether increased LO product formation by these agents is at the transcriptional or translational level, the regulation of 12- and 15-LO protein and mRNA expression by AII will be examined in normal and elevated glucose using Western immunoblotting and Northern/PCR analysis, respectively. Studies will then examine the role of LO activation in AII-induced growth and proliferative effects. Here, the effects of AII on protein as well as DNA synthesis and also the expression of the oncogenes c-fos and c-myc and also IGF-I and PDGF A-chain genes in normal and high glucose will be examined. The effect of LO inhibition and direct addition of LO products on growth effects will be studied. Since AII action is mediated by the diacylglycerol/protein kinase C (PKC) messenger system, this grant will also examine whether LO products mediate their effects by altering these key second messengers. The preliminary results are exciting and suggest that LO products can mediate proliferative effects of AII and glucose via activation of PKC. These completed studies should provide key mechanisms of AII- and glucose-induced growth promoting actions and can therefore provide the rationale for new therapeutic modalities to reduce morbidity and mortality of hypertensive and diabetic vascular disease associated with enhanced AII action.
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