The Effect Of Heparin And Low-molecular Weight Heparin On Expression Of Advanced Glycation End Products(AGE)Receptors On Human Monocytes

Background: In Maillard reaction, sugar aldehyde groups reaction with protein amino groups undergoes nonenzymatic glycation to further convert into advanced glycation end products (AGE). The interaction between AGE- modified protein and their receptors on monocytes result in corresponding effects. In normal condition, the receptors of AGE (RAGE) on monocytes selectively recognize, endocyte and degrade AGE modified proteins. However, in the pathophysiologic condition such as diabetes and Alzheimer disesase, the accumulation of AGE would stimulate production of proinflammaory cytokines form human monocytes. The polyanionic compound such as heparin, to be the most usually using anti-coagulants in hemodialysis patients, has been reported to inhibit scavenger receptor and RAGE has been showed to be a member of scavenger receptor family. Our study was conducted to elucidate the effect of heparin on binding of AGE-protein with human monocytes and on the secretion of tumor necrosis factor a (TNF a) and interleukin-l P (IL-i fl) by monocytes stimulated by AGE. Methods: Human peripheral blood monocytes from hemodialysis (H])) patients and from normal volunteers were isolated by Ficoll-hypaque centrifugation technique. Human serum albumn (HSA) modified with AGE (AGE-HSA) was prepared in vitro by incubation of USA with glocose. AGE was radioiodinated with carried free [125 I]. Specific binding ?51-AGE-HSA to RAGE on monocytes was measured by radioactive ligand-receptor binding assay. Human peripheral blood monocytes were cultured in vitro with or without 3 AGE-HSA. The level of TNF a and IL-i P in the suj,ematants were detected by sandwich enzyme immunoassay (ELISA). Results: The binding of ?51-AGE-HSA to its receptors in HD patients was inhibited by 27% 15 minutes after starting of hemodialysis using heparin as anti- coagulant. These effects continued 6 hours and resume to the level of prehemodialysis after 24 hours. There was no difference in binding of 1251-AGE- HSA to monocytes between pre-and post-hemodialysis session when used low- molecular weight heparin (LMWH) as the anti-coagulant. In vitro study demonstrated that exposure of human monocytes to heparin-containing media inhibited the binding of ?51-AGE-HSA to its receptor with a dose-dependent manner. LMWH did not inhibit such binding. AGE-LISA induced secretion of TNF a and IL-i P by cultured human monocytes. The level of TNF a and IL-i P were significantly higher in the supernatants of monocytes from LID patients compared with those from normal control. Proinflammatory cytokines secretion was significantly inhibited in monocytes from both ED patients and normal subjects when heparin was included into the culture. Conclusion: Heparin blocks the binding of AGE to its receptors on monocytes and therefore might interrupt the clearance and degradation of AGE. This may be one of the mechanisms by which AGE accumulation occurs on patients with hemodialysis. AGE-LISA induced proinflammatory cytokines production was increased in monocytes from LID patients compared with those from normal subjects. This may contribute to the enhanced plasma level of proinflammatory cytokines seen in ED patients. Heparin inhibited AGE-LISA- induced proinflammatory cytokines secretion by monocytes form LID patients.