The Study On The Relation Between Toll-like Receptor 4 And The Inflammation In Diabetic Nephropathy

Background: Among the 10 human TLRs, TLR4 is the most thoroughly studied. It recognizes LPS as well as other pathogen associated molecular pattern (PAMP). TLR4 has both a MyD88-dependent and–independent pathway. Endogenous ligands, such as HSP, heparan sulfate are found to activate TLR4 and cause the production of inflammatory factors.A lot of studies have shown that the expression of TLR4 is correlated with the production of inflammatory factors. Many factors affect the expression of TLR4.Evidences from patients and the laboratories have shown that inflammation might play a critical role in the pathogenesis of diabetic nephropathy. High glucose is involved in the inflammatory mechanism of diabetic nephropathy by promoting renal innate cells to secret inflammatory factors through PKC, p38MAPK and oxidative stress. However, it is not known if TLR4 and the signal pathway are related with high glucose induced inflammation. Object: (1)to explore the effect of high glucose on the expression of TLR4 and its'pathway in MCT cells; (2)to explore the effect of high glucose on the expression of TLR4, the co-effect of high glucose and LPS on the expression of TLR4 and the production of MCP-1; (3)to explore the relation between the expression of TLR4 on the peripheral blood monocytes from patients with diabetic nephropathy and the concentration of plasma MCP-1.Methods: (1)the expression of TLR4mRNA is analyzed with RT-PCR; (2)the expression of TRL4 protein is analyzed with flow cytomety and western blot; (3) the correlation of TLR4 with MyD88 is analyzed with Western Blot and immunoprecipitation; (4) ELISA is undertaken to measure the excretion of MCP-1 and the concentration of plasma MCP-1.Results: (1) high glucose upregulated the expression of TLR4 protein and activated MyD88-dependent pathyway in MCT cells; (2) high glucose upregulated the expression of TLR4 in HUVEC cells and induced the production of MCP-1. The expression of TLR4 and the production of MCP-1 were further increased when co-stimulated with LPS; (3) the expression level of TLR4 was significantly increased on the peripheral blood monocytes from patients with diabetic nephropathy compared with the healthy people; the expression of TLR4 was positively correlated with the concentration of plasma MCP-1.Conclusion: (1) high glucose upregulated the expression of TLR4 and activated MyD88-dependent pathyway in proximal tubular eplithelial cells;(2) high glucose upregulated the expression of TLR4 in human umbilical venous endothelial cells, further increasing the expression of TLR4 and the production of MCP-1 when co-stimulated with LPS. The enhanced expression of TLR4 is related with the production of MCP-1;(3) the expression of TLR4 on the peripheral blood monocytes from the patients with diabetic nephropathy is increased compared with those from the health control, the expression of TLR4 on the peripheral blood monocytes is positively related with the concentration of plasma MCP-1.High glucose upregulated the expression of TLR4 in renal innate cells. TLR4 is involved in the inflammation in diabetic nephropathy.