Peroxynitrite induces formation of Nε-(carboxymethyl)lysine by the cleavage of Amadori product and generation of glucosone and glyoxal from glucose: Novel pathways for protein modification by peroxynitrite

Accumulation of advanced glycation end products (AGEs) on tissue proteins increases with pathogenesis of diabetic complications and atherosclerosis. Here we examined the effect of peroxynitrite (ONOO^-) on the formation of Nε(carboxymethyl)lysine (CML), a major AGE-structure. When glycated human serum albumin (HSA; Amadori-modified protein) was incubated with ONOO^-, CML formation was detected by both enzyme-linked immunosorbent assay and high-performance liquid chromatography (HPLC) and increased with increasing ONOO^- concentrations. CML was also formed when glucose, preincubated with ONOO^-, was incubated with HSA but was completely inhibited by aminoguanidine, a trapping reagent for α-oxoaldehydes. For identifying the aldehydes that contributed to ONOO^--induced CML formation, glucose was incubated with ONOO^- in the presence of 2,3-diaminonaphthalene. This experiment led to identification of glucosone and glyoxal by HPLC. Our results provide the first evidence that ONOO^- can induce protein modification by oxidative cleavage of the Amadori product and also by generation of reactive α-oxoaldehydes from glucose.