Robert Danziger - US grants

DESCRIPTION (provided by applicant): Dietary salt has a major impact on blood pressure in many patients and is considered to be an important environmental risk factor for hypertension. Understanding the genetic underpinnings causing hypertensin is a necessary step for developing novel and customized therapeutic strategies for hypertension. We hypothesized that genes important in salt-sensitivity and hypertension might be discovered by identifying genes that undergo changes in abundance in normotensive rats when subjected to a high salt diet-- but do not undergo the same change abundance in rats that become hypertensive on a high salt diet. To distinguish such genes, we applied transcriptional profiling, a powerful new technology in which the abundance of thousands of genes is simultaneously measured, to Sprague Dawley and Dahl salt-sensitive (Dahl SS/Jr) rat strains on 0.4% and 8% NaCI diets. We identified 26 genes that meet this criteria from over 5,000 genes profiled. 2 of these 26 genes, i.e., aminopeptidase N, serum and glucocorticoid inducible kinase-1 (SGK), directly impact on the renin-angiotensin-aldosterone signaling pathway (RAS). The purpose of this proposal is to test the hypothesis that genes for aminopeptidase N and SGK contribute salt-sensitive hypertension in the Dahl rat. Supportive preliminary data shows corresponding changes in abundance of proteins coded for by these genes in the kidneys and that the genes map to known quantitative trait loci (QTLs) for blood pressure. Aim 1 is to determine whether there is preferential association of specific aminopeptidase N and SGK gene polymorphism(s) in Dahl SS/Jr compared to Dahl salt-resistant (SR/Jr) rat strains. Specific Aim 2 is to determine whether candidate genes cosegregate with salt-sensitive hypertension. Specific Aim 3 is to determine salt-sensitivity in congenic Dahl SS/Jr with chromosomal segments from Dahl SR/Jr rats containing SGK and aminopeptidase N genes introgressed. In this Aim, we will develop congenic lines of Dahl SS/Jr introgressed with SR/Jr regions containing aminopeptidase N and SGK genes. This is a first step in the goal of developing novel and customized therapeutic approaches to hypertension based on genetics.

DESCRIPTION (provided by applicant): Heart failure affects 2-4 million individuals in America and over 15 million people worldwide. Hypertension is the greatest risk factor with over two-thirds of heart failure patients having a history of high blood pressure. Cardiac remodeling in hypertension or pressure overload is defined by concentric cardiac hypertrophy followed by dilatation with systolic failure. Many individual signaling elements and pathways that can regulate cardiovascular remodeling have been identified, however there is a great need to integrate this data and to discover novel mechanisms which will lead to the development of new therapeutic targets and approaches to heart failure. A commonality of the findings to date is the importance of kinases and regulation of proteins by phosphorylations in cardiac hypertrophy and function. The development of proteomics technology has made it possible to simultaneously analyze the abundance of several hundred phosphoproteins in a tissue or cell without apriori knowledge of function or distribution. Advances in analytic approaches use changes in phosphoprotein expression patterns to discover new phosphorylation signaling pathways and networks. This proposal focuses solely on serine and threonine phosphorylations in hypertensive heart failure since several serine-threonine kinases, including MAPKs, are implicated in myocyte hypertrophy, fibrosis, and apoptosis. We will apply phosphoprotein profiling to three defined cardiac phenotypes;1) normal;2) compensated hypertrophic;and 3) dilated/failing from three different rodent models of hypertensive and pressure-overload, i.e., Dahl salt-sensitive (S), spontaneously hypertensive - heart failure prone (SHHF), and aortic banded Wistar rats. Aim 1 is to identify novel patterns of serine-threonine phosphorylated proteins that cluster with cardiac hypertrophy. After measuring cardiac size/function, we will identify phosphoprotein expression patterns that are uniquely common to hypertrophic hearts from Dahl S, SHHF rats, and aortic banded Wistar rats, and specifically not observed in normal hearts from their control counterparts: Dahl R and Wistar rats. These are candidate phosphoproteins for cardiac hypertrophy. Aim 2 is to identify novel patterns of serine-threonine phosphorylated proteins that cluster with cardiac dilatation/failure. We will identify phosphoprotein expression patterns that are uniquely common to dilated hearts from Dahl S. SHHF, and aortic-banded Wistar rats and specifically not in both normal and hypertrophic hearts from their counterparts. These will be the best candidate phosphoproteins for cardiac dilation/failure. The identification of major patterns of phosphoproteins in the heart associated with hypertrophy and dilatation/failure will provide critical and new signaling insights into pathogenesis and function in hypertensive cardiac remodeling. The results will lead to testable hypotheses for specific signaling pathways in heart failure and the development of phosphorylation signaling pathways or networks. This will move us toward our overall goal of determining new therapeutic approaches and novel targets for heart failure. PUBLIC HEALTH RELEVANCE: Heart failure affects 2-4 million individuals in America and over 15 million people world- wide. The overall goal of this project is to discover underlying signaling pathways and molecular mechanisms important in its pathogenesis and cardiac remodeling with the overall goal of developing new therapeutic strategies and targets.