EVIDENCE OF HIGH-LEVELS OF METHYLGLYOXAL IN CULTURED CHINESE-HAMSTER OVARY CELLS

Methylglyoxal is an cu-ketoaldehyde and dicarbonyl formed in cells as a side product of normal metabolism, Endogenously produced dicarbonyls , such as methylglyoxal, are involved in numerous pathogenic processes in vivo, including carcinogenesis and advanced glycation end-product formation; advanced glycation end-products are contributors to the pat hophysiology of aging and chronic diabetes. Despite recent advances in understanding of the systemic effects of methylglyoxal, the full sign ificance of this compound remains unknown, Herein we provide evidence that the majority of the methylglgoxal present in vivo is bound to bio logical ligands, The basis for our finding is an experimental approach that provides a measure of the bound methylglyoxal present in living systems, in this instance Chinese hamster ovary cells; with our approa ch, as much as 310 mu M methylglyoxal was detected, 100- to 1,000-fold more than observed previously in biological systems. Several artifact s were considered before concluding that the methylglyoxal was associa ted with cellular structures, including phosphate elimination from tri ose phosphates, carbohydrate degradation under the assay conditions, a nd interference from the derivatizing agent used as part of the assay procedure. A major source of the recovered methylglyoxal is most proba bly modified cellular proteins, With methylglyoxal at about 300 mu M, 0.02% of cellular amino acid residues could be modified. As few as one or two ''hits'' with methylglyoxal per protein molecule have previous ly been reported to be sufficient to cause protein endocytosis and sub sequent degradation. Thus, 5-10% of cellular proteins may be modified to physiologically significant levels.