Effect Of Ischemic Preconditioning On TLR4 And Related Proinflammatory Cytokines In Myocardial Ischemic Reperfusion Injury Rat Model

Objective:To investigate the Effect of ischemic preconditioning on TLR4 and related proinflammatory cytokines in myocardial ischemic reperfusion injury rat modelMethods:18 male Sprague–Dawley rats were randomly separated into Sham, IR (Ischemic Reperfusion) and IPC (Ischemic Preconditioning) groups (n=6 ). Sham group: exposing heart directly. IR group: disconnecting anterior descending artery for 30 minutes, then reconnecting to reperfusion for 120 minutes. IPC group: disconnecting anterior descending artery for 5 minutes, then reconnecting to reperfusion for 5minutes, then disconnecting again; repeating the processes for 4 times; then disconnecting for 30 minutes, finally reconnecting to reperfusion for 120 minutes. Blood and myocardial samples were collected after the establishment of the above three animal models. Proinflammatory cytokines TNF-αand IL-1βin serum of these animals were detected by ELISA. TLR4 mRNA expressions were detected by RT-PCR. And TLR4 protein expressions were studied by Western Blot.Results:Detected by RT-PCR, the expressions of TLR4 Mrna in myocardium were 0.43±0.08 in IPC,0.72±0.10 in IR and 0.25±0.03in Sham respectively. The TLR4 in the IPC was significantly lower than that in the IR group ( p<0.01). Detected by Western blot, the protein expressions of TLR4 were 0.41±0.02 in IPC, 0.54±0.04 in IR and 0.21±0.03 in Sham respectively;The TLR4 in the IPC group was significantly lower than that in the IR(p<0.05).Detected by ELISA, the serum expressions of TNF-αwere 25.57±4.89 in IPC, 33.60±6.14 in IR, 18.85±3.23 in Sham;the serum expressions of IL-1βwere 36.73±5.64 in IPC, 48.22±6.73 in IR, 23.38±5.46 in Sham. Both TNF-αand IL-1βin serum were significantly lower in the IPC group than those in the IR ( p<0.01 ).Conclusion:The expressions of TLR4 and proinflammatory cytokines were increased in MIRI. The result indicated that inflammatory reaction did happen in both the IPC group and the IR group, but was significantly inhibited by IPC. The mechanism might be closely related to that the lower expression level of TLR-4 in myocardium after IPC would further decrease the level of proinflammatory cytokines in serum.Therefore, the extent of damage in myocardium due to inflammatory reaction could be reduced by ischemic preconditioning.