Signaling Mechanisms in Cardiovascular Disease

Our research effort focuses on the intracellular signaling pathways that control cell survival and inflammation, and how these contribute to cardiovascular disease. To address these issues, we have used a combination of germline and somatic genetic manipulations in the context of pathophysiologically relevant in vitro and in vivo models of diseases including vascular inflammation/atherosclerosis, ischemic heart disease, and heart failure. Highlights of ongoing projects in each of the two major areas of investigation are discussed below.

1. Vascular diseases and inflammation: In many vascular conditions including atherosclerosis, transplant arteriosclerosis, and reperfusion injury, leukocytes play a pivotal role in disease progression. For this reason, we are interested in understanding the molecular basis of leukocyte-endothelial cell interactions. Our focus is on the role of specific intercellular signals (such as chemokines) and the intracellular cascades they initiate. Through somatic gene transfer, we have established realistic models both in vitro and in vivo to dissect the key pathways modulating the recruitment of specific leukocyte subsets and to elucidate the roles of these subsets in disease pathogenesis. For example, we have identified a novel mechanism by which chemokines induce monocyte recruitment: conversion of monocyte rolling to firm adhesion. This ability to convert leukocyte rolling to arrest appears to be an important, general mechanism of chemokine action with relevance to a wide variety of inflammatory disorders. Studies on the intracellular mechanisms involved in endothelial activation have recently focused on modulation of NF-kB activation. Using somatic gene transfer, we have identified novel inhibitors of NF-kB signaling in both cardiomyocytes and endothelial cells that may prove useful as therapeutic targets. In addition to somatic gene transfer studies, we are currently pursuing a Cre-lox strategy that enables tissue-specific and temporally controlled deletion of key components of NF-kB signaling. Ongoing breeding of recently established mouse lines should allow us to determine the effects of both endothelial- and cardiomyocyte-specific deletion of these molecules, at baseline and in models of cardiovascular disease. Finally, a series of clinical studies utilizing microarray analyses in patients with unstable angina and, more recently, transplant rejection, are aimed at identifying both transcriptional patterns providing useful diagnostic or prognostic information, as well as novel effectors that contribute to disease pathogenesis.

2. Congestive heart failure: We have also used somatic gene transfer and germline manipulations to directly test the contribution of specific intracellular pathways to cardiac dysfunction both in isolated cardiomyocytes and whole hearts in vivo. Recent work has characterized intracellular signaling pathways that modulate cardiomyocyte apoptosis. Interestingly, in the context of BADERC, many of these pathways are key signaling components downstream of the insulin receptor. Specfically, we have been able to demonstrate critical roles for kinases such as Akt (Prgtein Kinase B) in preserving survival and function of cardiomyocytes both in vitro and in vivo. This pathway was also demonstrated to be a dominant determinant of cardiomyocyte size in vivo. Additional studies have identified novel downstream effectors that appear to contribute to the observed phenotypes by modulating cardiomyocyte growth, metabolism, and survival. Translational implications of these findings are also being explored in efforts to optimize cardioprotection through expression of secreted ligands that activate Akt in both an autocrine and paracrine manner.

References:

1.       Gerszten RE, Garcia-Zepeda E, Lim Y-C, Yoshida M, Ding H, Gimbrone MA, Luster A, Luscinskas FW, Rosenzweig A. The chemokines MCP-1 and IL-8 trigger firm adhesion of monocytes to vascular endothelium under flow conditions. Nature 1999;398:718-23.

2.       Matsui T, Tao J, del Monte F, Lee KH, Li L, Picard M, Force TL, FrankeT, Hajjar RJ, Rosenzweig A. Akt activation preserves cardiac function and prevents injury after transient cardiac ischemia in vivo. Circulation 2001;104:330-335.

3.       Gerszten RE, Friedrich EB, Matsui T, Hung RR, Li L, Force TL, Rosenzweig A. Role of phosphoinositide 3-kinase in monocyte recruitment under flow conditions. Journal of Biological Chemistry 2001;276:26846-51.

4.       Matsui T, Li L, Wu JC, Cook SA, Nagoshi T, Picard M, Liao R, Rosenzweig A. Phenotypic spectrum caused by transgenic overexpression of activated Akt in the heart. Journal of Biological Chemistry. 2002;277:22896-22901.

5.       Cook SA, Matsui T, Li L, Rosenzweig A. Transcriptional effects of chronic Akt activation in the heart. Journal of Biological Chemistry. 2002;277:22528-22533.

6.       Chao W, Shen Y, Li L, Rosenzweig A. Importance of FADD signaling in serum-deprivation- and hypoxia-induced cardiomyocyte apoptosis. Journal of Biological Chemistry, 2002;277:31639-45.

7.       Chao W, Matsui T, Novikov M, Tao J, Li L, Liu H, Ahn Y, Rosenzweig A. Strategic advantages of Insulin-like Growth Factor-I expression for cardioprotection. J Gene Medicine, 2003; 5: 277-286.

8.       Cook SA, Novikov M, Ahn Y, Matsui T, Rosenzweig A. A20 is dynamically regulated in the heart and inhibits the hypertrophic response. Circulation, 2003; 108:664-7.

9.    Kuhlencordt PJ, Rosel E, Gerszten RE, Morales-Ruiz M, Dombkowski D, Atkinson WJ, Han F, Preffer F, Rosenzweig A, Sessa WC, Gimbrone MA Jr, Ertl G, Huang PL. Role of endothelial nitric oxide synthase in endothelial activation: insights from eNOS knockout endothelial cells. Am J Physiol Cell Physiol. 2004;286:C1195-202.