Our long range objective is to understand molecular mechanisms involved in the pathophysiology of hypertension and hypertrophy. The Renin- angiotensin system plays an important role in the development of these diseases through the action of angiotensin-II, which is one of the most potent vasoactive substance known. Angiotensin-II is synthesized from its precursor molecule, angiotensinogen, by the combined action of renin and angiotensin converting enzyme. Recent studies have shown the presence of an independent renin-angiotensin system in vascular walls. Since angiotensin-II increases the growth of vascular smooth muscle cells (VSMC) and aberrant growth of VSMC is a fundamental pathogenetic feature of hypertension and atherosclerosis, an increased synthesis of angiotensinogen and its conversion into angiotensin_II in vascular walls may have an important role in the development of hypertension and hypertrophy. Since angiotensinogen is the only precursor of angiotensin- II, it is crucial to understand various factors involved in the regulation of angiotensinogen gene expression in VSMC. In order to understand these regulatory factors, we have synthesized an expression plasmid pRA688CAT by attaching 688 bp. 5-flanking region of the rat angiotensinogen gene pRA688CAT has shown that it expresses the CAT gene in primary cultures of VSMC isolated from rat thoracic aorta. Our DNase-I footprint analysis and gel mobility shift assay have also shown that VSMC nuclear extract binds to specific nucleotide sequences present in the promoter of rat angiotensinogen gene. We have also shown that serum, insulin, angiotensin-II transforming growth factor-beta, and dexamethasone modulate the CAT gene expression on transient transfection of pRA688CAT in Hep G2 cells. We now propose to: (a) identify cis-acting DNA elements and transcription factors that are involved in the regulation of tissue specific expression of this gene in VSMC and (b) to compare the expression of angiotensinogen gene in VSMC of normotensive WKY and Spontaneously hypertensive rat, SHR. Theses studies will help us understand the molecular mechanisms involved in hypertension and hypertrophy in other experimental animal models and in humans.
Showing the most recent 10 out of 14 publications
