Research On The Role Of Toll-like Receptor4in Pancreatic Injury Of ICR Mice By Coxsackievirus B4Infection

Background and Objective: Coxsackievirus B4(CVB4)， a member ofEnterovirus, have been demonstrated to contribute to Type1diabetes（T1D）orinsulin-dependent diabetes mellitus (IDDM) pathogenesis, but the mechanism wasunclear up to now. Toll-like receptors (TLRs), a kind of pattern recognition receptorsfor pathogen, play a key role in activation of innate immunity. TLR4which is animportant member of TLRs, generally exists on pancreatic duct epithelial cells andvascular endothelial cells of pancreas of both human and rat. It has reported thatTLR4would be responsible for the inflammatory injury of the pancreatic tissues insome diseases, such as chronic or acute pancreatitis. Therefore, it may be related tothe development of T1D that CVB4infection can trigger the production ofproinflammatory cytokine by TLR4-dependent pathway, and these cytokines seem tobe involved in the damage to the insulin-producing cells. To study the action ofTLR4in CVB4infection of pancreas of ICR mice, we detected the expression levelsof TLR4mRNA and protein, and the production of related proinflammatorycytokines.Materials and Methods: In this study, we established infected ICR mice modelwith intraperitoneal injection of CVB4jlu06strain which is a laboratory strain thatstored in Department of Pathogeny Biology of Jilin University in China, while thecontrol mice were dealed with phosphate Buffered Saline(PBS) in the same way.They are grouped in experimental groups and control groups of19、35and50daysrespectively（10mice per group）. The ICR mice serum glucose concentration andCVB4presence in pancreas were detected by special test kits. Real-Time PCR andflow cytometry methods were used to measure the TLR4expression in pancreatictissues at the mRNA and protein levels at the designated time points(19days、35daysand50days). Meanwhile, the production of proinflammatory cytokines IL-6、IL-10、 TNF-α、MCP-1were also measured by ELISA method.Results and Conclusions: The CVB4infection can cause mice increasedglucose concentration，and the body weight of infected mice were increased moreslowly than the normal mice, especially after19days. At19days post infection，thereare significant presence of CVB4in pancreas, and it can detect less virus existence at35days. It was shown that CVB4jlu06infection, especially after35days, can inducehigh level expression of TLR4at mRNA and protein level compared with the controlgroups（p<0.05）, and led to an increased expression of proinflammatory cytokinesIL-6、TNF-α、MCP-1in pancreatic cells. We concluded that CVB4jlu06inducesproinflammatory cytokine production through a TLR4-dependent pathway in micepancreatic cells, and the damage of pancreatic cells by the inflammatory response isresponsible for the T1D.