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...

The accumulation of activated mast cells (200-fold more than in the unaffected coronary intima) at the site of atheromatous erosion or rupture suggests that in thrombotic coronary occlusion the role played by mast cells is significant.

Studies on the development of the immune response suggest that the repertoire of expressed antibody specificities is strongly influenced by antigen (reviewed in ref. 1). One way in which this influence is manifested is by a progressive increase in the affinity of antibody for antigen with time after immunization. This phenomenon, termed the 'maturation' of the immune response, must be due to a change in the structure of the antibody being synthesized. However, the precise nature of the changes involved and the genetic mechanisms used to produce them have not been clearly defined. We have now investigated the maturation of the immune response to the hapten 2-phenyloxazolone by mRNA sequencing of specific hybridomas. We conclude that somatic mutation of germ-line encoded genes plays a major role in the generation of antibodies with increased affinity for oxazolone with time after immunization.