Acrolein (CH 2 ACHOCHO) is known as a ubiquitous pollutant in the environment. Here we show that this notorious aldehyde is not just a pollutant, but also a lipid peroxidation product that could be ubiquitously generated in biological systems. Upon incubation with BSA, acrolein was rapidly incorporated into the protein and generated the protein-linked carbonyl derivative, a putative marker of oxidatively modified proteins under oxidative stress. To verify the presence of protein-bound acrolein in vivo, the mAb (mAb5F6) against the acrolein-modified keyhole limpet hemocyanin was raised. It was found that the acrolein-lysine adduct, N -(3-formyl-3,4-dehydropiperidino)lysine, constitutes an epitope of the antibody. Immunohistochemical analysis of atherosclerotic lesions from a human aorta demonstrated that antigenic materials recognized by mAb5F6 indeed constituted the lesions, in which intense positivity was associated primarily with macrophage-derived foam cells and the thickening neointima of arterial walls. The observations that (i) oxidative modification of low-density lipoprotein with Cu 2؉ generated the acrolein-low-density lipoprotein adducts and (ii) the ironcatalyzed oxidation of arachidonate in the presence of protein resulted in the formation of antigenic materials suggested that polyunsaturated fatty acids are sources of acrolein that cause the production of protein-bound acrolein. These data suggest that the protein-bound acrolein represents potential markers of oxidative stress and long-term damage to protein in aging, atherosclerosis, and diabetes.

Lipoprotein peroxidation, especially the modification of apolipoprotein B-100, has been implicated to play an important role in the pathogenesis of atherosclerosis. However, there have been few detailed insights into the chemical mechanism of derivatization of apolipoproteins during oxidation. In the present study, we provide evidence that the formation of the toxic pollutant acrolein (CH2‫؍‬CH-CHO) and its conjugate with lysine residues is involved in the oxidative modification of human low density lipoprotein (LDL). Upon incubation with LDL, acrolein preferentially reacted with lysine residues. To determine the structure of acrolein-lysine adduct in protein, the reaction of acrolein with a lysine derivative was carried out. Employing N ␣ -acetyllysine, we detected a single product, which was identified to be a novel acrolein-lysine adduct, N ␣ -acetyl-N ⑀ -(3-formyl-3,4-dehydropiperidino)lysine. The acid hydrolysis of the adduct led to the derivative that was detectable with amino acid analysis. It was revealed that, upon in vitro incubation of LDL with acrolein, the lysine residues that had disappeared were partially recovered by N ⑀ -(3-formyl-3,4-dehydropiperidino)lysine. In addition, we found that the same derivative was detected in the oxidatively modified LDL with Cu 2؉ and that the adduct formation was correlated with LDL peroxidation assessed by the consumption of ␣-tocopherol and cholesteryl ester and the concomitant formation of cholesteryl ester hydroperoxide. Enzyme-linked immunosorbent assay that measures free acrolein revealed that a considerable amount of acrolein was released from the Cu 2؉ -oxidized LDL. Furthermore, metal-catalyzed oxidation of arachidonate was associated with the formation of acrolein, indicating that polyunsaturated fatty acids including arachidonate represent potential sources of acrolein generated during the peroxidation of LDL. These results indicate that acrolein is not just a pollutant but also a lipid peroxidation product that could be ubiquitously generated in biological systems.Atherosclerosis is a complex vascular disorder that can lead to more serious conditions such as myocardial infarction. The events in atherosclerosis are monocyte migration from the blood stream, its differentiation into macrophage in situ, uptake of LDL by macrophage-scavenger receptor, transformation of lipid-laden macrophage into foam cells, smooth muscle cell proliferation and transformation into foam cells, and thus the accumulation of foam cells leading to fatty streaks and subsequent plaque formation. Various lines of evidence indicate that an important part of the pathogenesis of atherosclerosis is the oxidative modification of plasma low density lipoprotein (LDL) 1 (1-5). It has been proposed that LDL undergoes oxidative modification before it can give rise to foam cells, the key component of the progression of atherosclerosis. It has been believed that the oxidation of LDL in vivo can be reproduced by in vitro incubation of LDL with cultured cells such as endothelial cells (6 -9), sm...