Background-Patients with an activated renin-angiotensin system (RAS) or genetic alterations of the RAS are at increased risk of myocardial infarction (MI). Administration of ACE inhibitors reduces the risk of MI, and acute coronary syndromes are associated with increased interleukin 6 (IL-6) serum levels. Accordingly, the present study evaluated the expression of angiotensin II (Ang II) in human coronary atherosclerotic plaques and its influence on IL-6 expression in patients with coronary artery disease. Methods and Results-Immunohistochemical colocalization of Ang II, ACE, Ang II type 1 (AT 1 ) receptor, and IL-6 was examined in coronary arteries from patients with ischemic or dilated cardiomyopathy undergoing heart transplantation (nϭ12), in atherectomy samples from patients with unstable angina (culprit lesion; nϭ8), and in ruptured coronary arteries from patients who died of MI (nϭ13). Synthesis and release of IL-6 was investigated in smooth muscle cells and macrophages after Ang II stimulation. Colocalization of ACE, Ang II, AT 1 receptor, and IL-6 with CD68-positive macrophages was observed at the shoulder region of coronary atherosclerotic plaques and in atherectomy tissue of patients with unstable angina. Ang II was identified in close proximity to the presumed rupture site of human coronary arteries in acute MI. Ang II induced synthesis and release of IL-6 shortly after stimulation in vitro in macrophages and rat smooth muscle cells. Conclusions-Ang II, AT 1 receptor, and ACE are expressed at strategic sites of human atherosclerotic coronary arteries, suggesting that Ang II is produced primarily by ACE within coronary plaques. The observation that Ang II induces IL-6 and their colocalization with the AT 1 receptor and ACE is consistent with the notion that the RAS may contribute to inflammatory processes within the vascular wall and to the development of acute coronary syndromes. (Circulation. 2000;101:1372-1378.)Key Words: interleukins Ⅲ angiotensin Ⅲ angina Ⅲ myocardial infarction Ⅲ arteries Ⅲ receptors R upture of atherosclerotic plaques occurs predominantly at the edges of the plaque's fibrous cap, the shoulder region, that is, areas of accumulated inflammatory cells, for example, macrophages, T-lymphocytes, and mast cells in close proximity to vascular smooth muscle cells (SMC). [1][2][3][4][5][6] The activated inflammatory cells stimulate their neighboring cells to erode the extracellular matrix through the release of inflammatory cytokines. The decay of the framework that forms the plaque cap leads to plaque rupture 1,7,8 and resembles the morphological correlate of an acute coronary syndrome. Serum levels of interleukin 6 (IL-6) are increased in patients with unstable angina 9 and may trigger the onset of an acute coronary syndrome. 10 IL-6 is known to be involved in the stimulation of matrix-degrading enzymes, for example, metalloproteinases. 11In parallel, the renin-angiotensin system (RAS) has been suggested to be involved in the development of acute coronary syndromes, based on the observat...

Our previous study has shown that angiotensin II induces the rapid tyrosine phosphorylation and activation of phospholipase C-gamma 1 in cultured rat aortic smooth muscle (RASM) cells (Marrero, M.B., Paxton, W.G., Duff, J. L., Berk, B. C., and Bernstein, K. E. (1994) J. Biol. Chem, 269, 10935-10939). This signaling pathway is initiated by ligand binding to the AT1 receptor, a cell surface G protein-coupled receptor. Antibodies to pp60c-src were introduced into RASM cells by electroporation. Angiotensin II-stimulated tyrosine phosphorylation of phospholipase C-gamma 1 was eliminated by the anti-pp60c-src antibodies but not by anti-mouse IgG or bovine serum albumin. Angiotensin II also induced the rapid tyrosine phosphorylation of pp120, a known pp60c-src kinase substrate, and this phosphorylation was also specifically inhibited by anti-pp60c-src antibodies. Electroporation of RASM cells with anti-pp60c-src antibodies had no effect on platelet-derived growth factor-stimulated tyrosine phosphorylation of PLC-gamma 1. Anti-pp60c-src also reduced the angiotensin II-stimulated inositol 1,4,5-trisphosphate production by 78%, while it had no effect on the platelet-derived growth factor-stimulated inositol 1,4,5-trisphosphate production. These data provide the first evidence for a direct involvement of pp60c-src kinase in angiotensin II-mediated PLC-gamma 1 phosphorylation and activation. Furthermore, it also describes a pathway in which a seven-transmembrane receptor can stimulate an intracellular tyrosine kinase.

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(1) Kinins inhibit the interstitial accumulation of collagen but do not modulate cardiomyocyte hypertrophy after MI. (2) Kinins contribute to the reduction of myocardial collagen accumulation by ACE inhibition and AT1 receptor blockade. (3) The effects of ACE inhibition and AT1 receptor blockade on cardiomyocyte hypertrophy are related to a reduced generation/receptor blockade of angiotensin II.