Glucose-modified proteins modulate essential functions and apoptosis of polymorphonuclear leukocytes

Any modulation of the activity of polymorphonuclear leukocytes (PMNL) is a potential cause of the altered immune response in uremia, Because the level of glycation products is elevated in uremic sera and peritoneal effluents, the effect of glycated proteins on essential functions and on apoptosis of PMNL was investigated. Proteins from sera of healthy donors were incubated with and without glucose. The extent of early glycation was monitored by b oronate chromatography and the fructosamine assay. The formation of late gl ycation products was assessed by fluorescence spectroscopy and Western blot ting that used a specific antibody for imidazolone, a late glycation produc t. With the addition of aminoguanidine, a compound that inhibits the format ion of late but not of early glycation products, protein samples with early glycation only were obtained. Glucose-modified proteins increased chemotax is and activation of the 2-deoxy-D-glucose uptake of PMNL obtained from hea lthy donors, compared with those of unmodified proteins. PMNL apoptosis, as sessed by morphologic changes, by detecting DNA strand breaks, and by measu rement of the caspase 3 activity, was increased in the presence of glucose- modified serum proteins. It was found that the formation of late glycation products is necessary for the effect on PMNL chemotaxis. In contrast, early glycation of proteins is responsible for the increase of glucose uptake an d apoptosis. It was concluded that the accumulation of glycated proteins in uremic sera and peritoneal fluid may contribute to the diminished immune f unction observed in uremia, by modulation of essential PMNL functions and a cceleration of PMNL apoptosis.