Unique antibody responses to malondialdehyde-acetaldehyde (MAA)-protein adducts predict coronary artery disease

Abstract

Malondialdehyde-acetaldehyde adducts (MAA) have been implicated in atherosclerosis. The purpose of this study was to investigate the role of MAA in atherosclerotic disease. Serum samples from controls (n = 82) and patients with; non-obstructive coronary artery disease (CAD), (n = 40), acute myocardial infarction (AMI) (n = 42), or coronary artery bypass graft (CABG) surgery due to obstructive multi-vessel CAD (n = 72), were collected and tested for antibody isotypes to MAA-modifed human serum albumin (MAA-HSA). CAD patients had elevated relative levels of IgG and IgA anti-MAA, compared to control patients (p<0.001). AMI patients had a significantly increased relative levels of circulating IgG anti-MAA-HSA antibodies as compared to stable angina (p<0.03) or CABG patients (p<0.003). CABG patients had significantly increased relative levels of circulating IgA anti-MAA-HSA antibodies as compared to non-obstructive CAD (p<0.001) and AMI patients (p<0.001). Additionally, MAA-modified proteins were detected in the tissue of human AMI lesions. In conclusion, the IgM, IgG and IgA anti-MAA-HSA antibody isotypes are differentially and significantly associated with non-obstructive CAD, AMI, or obstructive multi-vessel CAD and may serve as biomarkers of atherosclerotic disease.

Figure 1. Relative Serum Concentrations of anti-MAA IgM, IgG and IgA Antibodies are Increased in Individuals with Coronary Artery Disease (CAD) and in Individuals who Present with an Acute Myocardial Infarction (AMI).

CAD patients were grouped in the following categories; control patients (n = 82), patients with chest pain and CAD (Non-Obstructive CAD, n = 40), patients presenting with AMI (n = 42), and patients with significant Multi-Vessel Obstructive CAD requiring coronary bypass grafting (n = 72). Serum anti-MAA antibodies were evaluated for the isotypes IgM (Figure 1A), IgG (Figure 1B), and IgA (Figure 1C). *P<0.001 significantly increased compared to controls. #P<0.03 significantly increased compared to Non-Obstructive CAD. $P<0.003 significantly increased compared to Multi-Vessel Obstructive CAD.

Figure 2. Relative Serum Concentrations of anti-MDA LDL and anti-MAA LDL IgG Antibody are not Different in Individuals with Coronary Artery Disease (CAD) and in Individuals who Present with an Acute Myocardial Infarction (AMI).

CAD patients were grouped in the following categories; control patients (n = 82), patients with chest pain and CAD (Non-Obstructive CAD, n = 40), patients presenting with AMI (n = 42), and patients with significant Multi-Vessel Obstructive CAD requiring coronary bypass grafting (n = 72). Serum anti-MDA LDL (Figure 2A) and anti-MAA LDL (Figure 2B). There is no significant difference in serum antibody levels when comparing all study groups (p>0.5).

Figure 3. Serum Concentrations of IgM, IgG and IgA Antibodies 24 Hours post-AMI.

A subgroup of patients (n = 10) were evaluated 24 hours post-AMI for the presence of circulating IgM, IgG and IgA anti-MAA antibody levels (Figure 3A) and the total serum IgM, IgG, and IgA concentrations (Figure 3B). Results are expressed as relative mg/L or g/L of Human IgM, IgG, and IgA using a standard curve. *P<0.01 significantly different comparing AMI and 24 hours post-AMI.

Figure 4. Light and Confocal Microscopy of MAA in the Culprit AMI Aspirated Tissue.

Panel A and B illustrates a Masson’s Trichrome staining at low (20X) and high magnification (80X) with panel B as the inset box of panel A. Panel C is the rabbit IgG isotype control stain. Panel D illustrates the rabbit anti-MAA staining with Cy3 reporter (80X). Note the absence of collagen or fibrosis and the presence of cholesterol clefts in Panel A which are typical of an atheroma. Also note the localization of MAA in Panel D (white arrows) to cellular vacuolization and necrosis as noted by the arrows on the Masson’s Trichrome in Panel B (black arrows).