Kaur H, Chien A, Jialal I
Diabetes is a proinflammatory state. The pattern recognition receptors, Toll like receptors (TLRs) are increased in diabetic patients and have been suggested to play a role in Diabetic Nephropathy (DN). Progression of DN involves altered mesangial cell (MC) function with an expansion of mesangial matrix. There is a paucity of data examining the role of TLR and its expression in MC. We hypothesize the expression of TLRs in mesangium might be important factor contributing towards mesangium expansion and nephropathy. Thus we evaluated the effect of high glucose on TLR2 & TLR4 expression in mouse mesangial cells (MMC) in-vitro. Exposure of MMC to 25mM glucose for 24h resulted in increased TLR4 mRNA and cell surface receptor expression compared to 5.5mM glucose (P<0.05). Interestingly we were not able to detect expression of TLR2 in MMC. Furthermore expression of TLR4 downstream signaling cascade including Myeloid differentiation factor 88 (MyD88), Interferon regulatory factor 3 (IRF3), TRIF-related adaptor molecule (TRAM) were significantly increased in cells exposed to 25mM glucose (P<0.05). There was also significant increase in nuclear factor κB (NF-κB) activation along with increased secretion of inflammatory cytokines interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1). Levels of TGF-β were also significantly increased in presence of 25mM glucose (P<0.05). Collectively this data suggests that hyperglycemia activate TLR4 expression and activity in MC and could contribute to DN.