Abstract
Advanced glycation endβproducts (AGE) play a role in the pathogenesis of several diseases, including diabetic complications and atherosclerosis. In atherosclerotic lesions of human aortas, AGE are localized in the extracellular matrix and intracellularly in foam cells. Two interpretations are possible for AGE accumulation inside macrophages, one is endocytic uptake of extracellular AGEβproteins by scavenger receptors; the other is intracellular AGE formation inside the macrophages. In the present study, we determined the pathways involved in AGE accumulation inside macrophages. RAW 264.7 cells, a murine macrophage cell line, incubated with BSA and 1600 mM glucose for 40 weeks, recognized heavily modified AGEβ BSA. In contrast, the cells showed no ligand activity for mildly modified AGEβBSA, prepared by incubating BSA with 50 mM glucose for 24 weeks. NΞ΅β(carboxymethyl)lysine (CML)βmodified proteins of about 65 kDa were detected in human monocyteβderived macrophages incubated for 7 days with 30 mM glucose and phorbol myristate acetate. Furthermore, CML was generated when glycated protein was incubated with hypochloric acid. Taken together, our results indicate that AGE detected inside foam cells in atherosclerotic lesions are generated intracellularly rather than representing endocytic uptake of extracellular AGEβproteins by scavenger receptors.