Identification in human atherosclerotic lesions of GA-pyridine, a novel structure derived from glycolaldehyde-modified proteins

Glycolaldehyde (GA) is formed from serine by action of myeloperoxidase and reacts with proteins to form several products. Prominent among them is N-epsilon-(carboxymethyl)lysine (CML), which is also known as one of the advanced glycation end products. Because CML is formed from a wide range of precursors, we have attempted to identify unique structures characteristic of the reaction of GA with protein. To this end, monoclonal (GA5 and 1A12) and polyclonal (non-CML-GA) antibodies specific for GA-modified proteins were prepared. These antibodies specifically reacted with GA-modified and with hypochlorous acid-modified BSA, but not with BSA modified by other aldehydes, indicating that the epitope of these antibodies could be a specific marker for myeloperoxidase-induced protein modification. By HPLC purification from GA-modified N-alpha-(carbobenzyloxy)-L-lysine, GA5-reactive compound was isolated, and its chemical structure was characterized as 3-hydroxy-4-hydroxymethyl-l-(5-amino-5-carboxypentyl) pyridinium cation. This compound named as GA-pyridine was recognized both by 1A12 and non-CML-GA, indicating that GA-pyridine is an important antigenic structure in GA-modified proteins. Immunohistochemical studies with GA5 demonstrated the accumulation of GA-pyridine in the cytoplasm of foam cells and extracellularly in the central region of atheroma in human atherosclerotic lesions. These results suggest that myeloperoxidase-mediated protein modification via GA may contribute to atherogenesis.