Role of iron in the interaction of red blood cells with methylglyoxal. Modification of L-arginine by methylglyoxal is catalyzed by iron redox cycling

Diabetes mellitus. is characterized by increased methylglyoxal (MG) product ion. The aim of the present study was to investigate the role of iron in th e cellular and molecular effects of MG. A red blood cell (RBC) model and L- arginine were used to study the effects of MG in the absence and presence o f iron. Intracellular free radical formation and calcium concentration were measured using dichlorofluorescein and Fura-2-AM, respectively. Effects of MG were compared to the effect of ferrous iron. Reaction Of L-arginine wit h MG was investigated by electron spin resonance (ESR) spectroscopy and by a spectro photometric method. MG caused an iron dependent oxidative stress in RBCs and an elevation of the intracellular calcium concentration due to formation of reactive oxygen species. Results of co-incubation of MG with f errous iron in the RBC model suggested an interaction of MG and iron; one i nteraction was a reduction of ferric iron by MG. A role of iron in the MG-L -arginine reaction was also verified by ESR spectroscopy and by spectrophot ometry. Ferric iron increased free radical formation as detected by ESR in the MG-L-arginine reaction; however, ferrous iron decreased it. The reactio n of MG with L-arginine yielded a brown product as detected spectrophotomet rically and this reaction was catalyzed at a lower rate with ferric iron bu t at a higher rate with ferrous iron. These data suggest that MG causes oxi dative stress in cells. which is due at least in part to ferric iron reduct ion by MG and to the modification of amino acids e.g. L-arginine by MG, whi ch is catalyzed by iron redox cycling. (C) 2001 Elsevier Science Ireland Lt d. All rights reserved.