Relationship of IgG and IgM autoantibodies and immune complexes to oxidized LDL with markers of oxidation and inflammation and cardiovascular events: results from the EPIC-Norfolk Study

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Abstract

Levels of IgG and IgM autoantibodies (AA) to malondialdehyde (MDA)-LDL and apoB-immune complexes (ICs) were measured in 748 cases and 1,723 controls in the EPIC-Norfolk cohort and their association to coronary artery disease (CAD) events determined. We evaluated whether AA and IC modify CAD risk associated with secretory phospholipase A(2) (sPLA(2)) type IIA mass and activity, lipoprotein-associated PLA(2) activity, lipoprotein (a) [Lp(a)], oxidized phospholipids on apoB-100 (OxPL/apoB), myeloperoxidase, and high sensitivity C-reactive protein. IgG ICs were higher in cases versus controls (P = 0.02). Elevated levels of IgM AA and IC were inversely associated with Framingham Risk Score and number of metabolic syndrome criteria (p range 0.02-0.001). In regression analyses adjusted for age, smoking, diabetes, LDL-cholesterol, HDL-cholesterol, and systolic blood pressure, the highest tertiles of IgG and IgM AA and IC were not associated with higher risk of CAD events compared with the lowest tertiles. However, elevated levels of IgM IC reduced the risk of Lp(a) (P = 0.006) and elevated IgG MDA-LDL potentiated the risk of sPLA(2) mass (P = 0.018). This epidemiological cohort of initially healthy subjects shows that IgG and IgM AA and IC are not independent predictors of CAD events but may modify CAD risk associated with elevated levels of oxidative biomarkers.

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Most cited references 41

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Oxidized low-density lipoprotein and atherosclerosis.

Joseph Witztum, Daniel Steinberg (2010)

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Monoclonal autoantibodies specific for oxidized phospholipids or oxidized phospholipid-protein adducts inhibit macrophage uptake of oxidized low-density lipoproteins.

Sohvi Hörkkö, Michael R. Miller, H Itabe … (1998)

We recently cloned monoclonal IgM autoantibodies which bind to epitopes of oxidized low-density lipoprotein (OxLDL) from apoE-deficient mice (EO- autoantibodies). We now demonstrate that those EO- autoantibodies that were originally selected for binding to copper-oxidized low-density lipoproteins (CuOx-LDL), also bound both to the oxidized protein and to the oxidized lipid moieties of CuOx-LDL. The same EO- autoantibodies showed specific binding to products of oxidized 1-palmitoyl-2-arachidonoyl-phosphatidylcholine (OxPAPC) and to the specific oxidized phospholipid, 1-palmitoyl-2-(5-oxovaleroyl)-phosphatidyl-choline (POVPC), whereas oxidation of fatty acids (linoleic or arachidonic acid) or cholesteryl esters (cholesteryl-oleate or cholesteryl-linoleate) did not yield any binding activity. Those EO- autoantibodies that bound to oxidized phospholipids (e.g., EO6) inhibited the binding and degradation of CuOx-LDL by mouse peritoneal macrophages up to 91%, whereas other IgM EO- autoantibodies, selected for binding to malondialdehyde (MDA)-LDL, had no influence on binding of either CuOx-LDL or MDA-LDL by macrophages. F(ab')2 fragments of EO6 were equally effective as the intact EO6 in preventing the binding of CuOx-LDL by macrophages. The molar ratios of IgM to LDL needed to maximally inhibit the binding varied from approximately 8 to 25 with different CuOx-LDL preparations. Finally, a POVPC-bovine serum albumin (BSA) adduct also inhibited CuOx-LDL uptake by macrophages. These data suggest that oxidized phospholipid epitopes, present either as lipids or as lipid-protein adducts, represent one class of ligands involved in the recognition of OxLDL by macrophages, and that apoE-deficient mice have IgM autoantibodies that can bind to these neoepitopes and inhibit OxLDL uptake.

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Serum myeloperoxidase levels are associated with the future risk of coronary artery disease in apparently healthy individuals: the EPIC-Norfolk Prospective Population Study.

A. Miert, Johanna R. Schaub, Jan A. Kuivenhoven … (2007)

We evaluated whether serum myeloperoxidase (MPO) levels are associated with the risk of future development of coronary artery disease (CAD) in apparently healthy individuals. An enzyme of the innate immune system, MPO exhibits a wide array of proatherogenic effects. These include induction of oxidative damage to low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol and promotion of plaque vulnerability. Recent studies revealed that MPO independently predicts adverse outcomes in patients with chest pain or suspected acute coronary syndrome. Myeloperoxidase was measured in baseline samples of a case-control study nested in the prospective EPIC (European Prospective Investigation into Cancer and Nutrition)-Norfolk population study. Case subjects (n = 1,138) were apparently healthy men and women who developed CAD during 8-year follow-up. Control subjects (n = 2,237), matched for age, gender, and enrollment time, remained free of CAD. The MPO levels were significantly higher in case subjects than in control subjects and correlated with C-reactive protein (CRP) (rho = 0.25; p 728 pmol/l) similarly predicted increased risk of future CAD among participants with either LDL-cholesterol 50 mg/dl, or CRP <2.0 mg/l (OR 1.52 [95% CI 1.21 to 1.91], 1.59 [95% CI 1.24 to 2.05], and 1.42 [95% CI 1.14 to 1.77)], respectively). Elevated MPO levels predict future risk of CAD in apparently healthy individuals. This study suggests that inflammatory activation precedes the onset of overt CAD by many years.