Abstract 303: Differentiating Normal Coronary Arteries, Stable Atheromatous Lesions and Unstable Atheromatous Lesions: MAA-Protein Adducts and Anti-MAA Antibodies Isotypes in Patients with Atherosclerotic Disease and Acute Myocardial Infarction

Abstract

Introduction: Oxidized proteins have been implicated in the development and progression of atherosclerosis. Malondialdehyde (MDA)-acetaldehyde (AA) adduct (MAA), is produced and is the dominant epitope formed following incubation of proteins with the oxidative product MDA. Additionally, these MAA-modified proteins have been detected in JCR atherosclerotic rat aortic tissue and the human model of atherosclerosis. MAA-modified proteins have been implicated in the progression of atherosclerotic disease. Objective: The purpose of this study was to evaluate the association of MAA-adducted proteins and circulating IgM, IgG and IgA anti-MAA antibody isotypes to patients with normal coronary arteries and patients with stable and unstable atherosclerotic lesions. Methods: Over a six-month period, serum samples from normal controls (n=82), stable angina (n=42), acute myocardial infarction (AMI) (n=41), and coronary artery bypass graph surgery (CABG) (n=72) patients were collected and tested for the presence of anti-MAA antibody isotypes. All samples were collected prior to heparinization, intervention and/or bypass pump initiation. Aortic punch biopsies from CABG patients were subjected to immunohistochemical (IHC) staining using a monoclonal mouse anti-MAA antibody and detection by confocal microscopy. Results: Normal control patients had a significantly lower circulating anti-MAA IgG (97 ng/ml, SE=6.9) and IgA (82 ng/ml) as compared to patients with coronary artery disease (p<0.001). AMI patients had a significantly increased level of circulating anti-MAA IgG antibodies (242 ng/ml, SE=30.5) compared to stable angina (186 ng/ml, SE= 20.7) (p<0.04) or CABG patients (163 ng/ml, SE=14.6) (p<0.004). Serum samples from patients with CABG had significantly increased levels of circulating anti-MAA IgA antibodies (2495 ng/ml, SE=334) compared to stable angina (367 ng/ml, SE=64.4) (p<0.001) or AMI patients (361 ng/ml, SE=65.0) (p<0.001). Anti-MAA IgM antibodies were significantly different across the groups in similar fashion to IgG results. Confocal microscopy of aortic punch biopsies confirms an increased level of the MAA-adducts within the interstitial spaces of the aorta media. Conclusions: These data show that MAA-modified proteins are present in atherosclerotic tissues and there is a significant increase in the levels of circulating anti-MAA antibodies (IgM, IgG and IgA) in patients with coronary artery disease. Anti-MAA IgM and IgG phenotypes are significantly increased in patients who present with an AMI compared to normal coronary artery and stable CAD patients, whereas, the anti-MAA IgA phenotype is significantly increased in patients who present for CABG compared to all other groups. The immunoglobulin phenotype (IgM, IgG and/or IgA) is hypothesized secondary to differences in antigenic sensitization (Th1 vs. Th2) of MAA-modified proteins in diseased tissue. Implications: Anti-MAA IgM, IgG and IgA antibody isotypes and MAA-modified proteins may serve as biomarkers for subclinical atherosclerotic disease (IgM, IgG and IgA) as well as differentiate CAD patients who have stable (IgA) and unstable (IgG) atherosclerotic plaques.