COMPARATIVE INTERACTION OF GLYCATED AND OXIDIZED LOW-DENSITY LIPOPROTEINS WITH HUMAN MONOCYTE-DERIVED MACROPHAGES

We explored the interaction of human in vitro glycated and oxidized lo w density lipoproteins (LDL) with human macrophages and compared their stimulation of protease secretion by these cells. Uptake of labelled glycated LDL (glc-LDL) and labelled oxidized LDL (oxi-LDL) was studied in cell culture experiments using macrophages obtained by countercurr ent centrifugal elutriation and used after 8 days of primary culture. In competition experiments glc-LDL was able to displace up to 35% of I -125-oxi-LDL at a ten-fold concentration. Conversely, oxi-1,DL displac ed 45% of I-125-glc-LDL, in the same conditions. Glc-LDL was not signi ficantly oxidized before cell culture experiments. Proteinase secretio n by macrophages was explored; c-LDL showed a 27% stimulation over bas al protease secretion, increment was 80% for glc-LDL and 137% for oxi- LDL. Our data show that a fraction or subpopulation of glycated and ox idized LDL are able to compete with each other for their uptake by mac rophages. This uptake of glycated LDL through poorly-regulated pathway s may contribute to foam cell generation in diabetic patients.