Modification by Acrolein, a Component of Tobacco Smoke and Age-Related Oxidative Stress, Mediates Functional Impairment of Human Apolipoprotein E

Abstract

Oxidative damage to proteins such as apolipoprotein B100 increases the atherogenicity of low density lipoproteins (LDL). However, little is known about the potential oxidative damage to apolipoprotein E (apoE), an exchangeable anti-atherogenic apolipoprotein. ApoE plays an integral role in lipoprotein metabolism by regulating the plasma cholesterol and triglyceride levels. Hepatic uptake of lipoproteins is facilitated by apoE's ability to bind with cell surface heparan sulfate proteoglycans and to lipoprotein receptors via basic residues in its 22 kDa N-terminal domain (NT). We investigated the effect of acrolein, an aldehydic product of endogenous lipid peroxidation and a tobacco smoke component, on the conformation and function of recombinant human apoE3-NT. Acrolein caused oxidative modification of apoE3-NT as detected by Western blot with acrolein-lysine-specific antibodies, and tertiary conformational alterations. Acrolein-modification impairs the ability of apoE3-NT to interact with heparin and the LDL receptor. Furthermore, acrolein-modified apoE3-NT displayed a 5-fold decrease in its ability to interact with lipid surfaces. Our data indicate that acrolein disrupts the functional integrity of apoE3, which likely interferes with its role in regulating plasma cholesterol homeostasis. These observations have implications regarding the role of apoE in the pathogenesis of smoking-and oxidative stress-mediated cardiovascular and cerebrovascular diseases. KeywordsCardiovascular disease; apolipoprotein E; acrolein; tobacco smoke; oxidative stress; aging; LDL receptor; heparan sulfate proteoglycan; lysine modification Oxidative stress is recognized as a major factor in the onset of atherosclerosis, cardiovascular disease and stroke in humans; of several factors that lead to increased oxidative stress, aging and life style (diet, smoking) play crucial roles. Atherosclerosis is characterized by the intracellular and extra cellular deposition of low density lipoproteins (LDL) in macrophages (1). Oxidative modification of plasma LDL leads to their uptake by scavenger receptors located The role of apoE in cholesterol metabolism emerged from studies with transgenic mice over expressing apoE, which manifested decreased plasma cholesterol levels on a chow diet and a marked resistance to hypercholesterolemia when fed a cholesterol rich diet (4). On the other hand, apoE-deficient subjects develop symptoms of type III hyperlipoproteinemia (5), with elevated plasma cholesterol levels and accumulation of particles bearing size in the very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL) range (6,7). Further, inactivation of apoE by gene targeting leads to accumulation of cholesterol-rich remnant lipoproteins and spontaneous atherosclerotic lesions in mice (8,9). Taken together, these early studies have established the key role of apoE in regulating plasma cholesterol and triglyceride levels, which are recognized as indicators of heart disease. The focus of this study is to investigate the role ...

Protein modification by acrolein: Relevance to pathological conditions and inhibition by aldehyde sequestering agents

“…Employing recombinant human protein and Western blot with ACR-Lys-specific antibodies, other authors [45] demonstrated that ACR severely compromises the functional integrity of apolipoprotein E (apoE, an exchangeable antiatherogenic apolipoprotein), in terms of heparin binding, lipid binding, and the LDLr-binding interaction. A combined analytical approach based on circular dichroism, infrared spectroscopy, and fluorescence indicated significant tertiary structural changes in ACR-modified apoE3-NT, although the chemical nature of ACR crosslinking or adduct formation with apoE3 is not known at present.…”

Antithrombin activity is inhibited by acrolein and homocysteine thiolactone: Protection by cysteine

“…Acrolein is an environmental pollutant that is formed during combustion of organic substances (such as super heated cooking oil) and is one of the major components in the gaseous phase of tobacco smoke: up to 400 μg/cigarette (Kehrer and Biswal, 2000;Mercado and Jaimes, 2007;Fujioka and Shibamoto, 2006;Tamamizu-Kato et al, 2007). Lipid peroxidation and threonine oxidation by myeloperoxidase are potential sources of endogenous acrolein in inflammatory processes such as atherosclerosis (Uchida et al, 1998;Tamamizu-Kato et al, 2007).…”

“…Lipid peroxidation and threonine oxidation by myeloperoxidase are potential sources of endogenous acrolein in inflammatory processes such as atherosclerosis (Uchida et al, 1998;Tamamizu-Kato et al, 2007). Acrolein is the most reactive of all the alpha-beta unsaturated aldehydes and causes oxidative modification of proteins by reacting with the sulfhydryl side chain of cysteines, ε-amino groups of lysines, and the imidazole group of histidines (Kehrer and Biswal, 2000).…”

Mechanisms Underlying Acrolein-Mediated Inhibition of Chromatin Assembly

“…Acr has been implicated in the development of multiple human diseases, such as bladder cancer (4), lung cancer (5-7), Alzheimer's disease (8)(9)(10), and cardiovascular diseases (11,12). Acr contains a carbonyl group and an olefinic double bond, which makes it highly reactive to many cellular molecules, including proteins and DNA (13)(14)(15)(16).…”

“…Recent studies show that Acr could be a potential major carcinogen of smoking-related lung cancer via induction of DNA damage and inhibition of DNA repair (14,15,17,18). In addition to its role in inducing DNA damage and mutagenicity, the other biological effects of Acr are most likely through its direct interaction with nucleophilic amino acids, primarily cysteine, lysine, and histidine, in critical protein targets (11,12,19). These proteins include transcription activation factor NF-B (20,21), caspases that regulate cell apoptosis (7,22), and proteins involved in redox signaling regulation (16,19).…”