Effect of repeated ischaemic preconditioning on TLR4 and proinflammatory cytokines TNF-α and IL-1β in myocardial ischaemia-reperfusion injury in a rat model

Introduction: The role of TLR4 in ischaemic preconditioning is still unclear; we do not know the change of the expression of TLR4 in the process. In this study, we used ischaemic preconditioning models to observe the change of TLR4 expression and the level of proinflammatory cytokines INF-alpha and IL-1 beta to investigate the protective mechanism of TLR4 in ischaemic preconditioning for myocardial ischaemia-reperfusion injury (MI/RI) in rats. Material and methods: Eighteen male Sprague-Dawley (SD) rats were randomly separated into sham, ischaemic reperfusion (IR) and ischaemic preconditioning (IP) groups (6/group). Peripheral blood and cardiac muscle with pathological changes were collected after the establishment of the above three animal models. We used ELISA to determine proinflammatory cytokines INF-a and IL-1 beta production in serum of these animals. RT-PCR and Western blot were used to assay the transcriptional level and protein level of TLR4 in cardiac muscle tissue with pathological changes, respectively. Results: We found that compared with the IR group, ischaemic preconditioning could effectively reduce the expression levels of INF-a and IL-1 beta in sera of rats in the IP group (p < 0.01). Meanwhile, TLR4 mRNA and protein levels were down-regulated (p < 0.01 and p < 0.05, respectively). We also found that infarct size decreased in the IP group compared with the IR group (p < 0.05). Conclusions: Based on the results, we can conclude that the specific mechanism of ischaemic preconditioning for RI might be closely associated with decreasing expression levels of TLR4 and proinflammatory cytokines such as TNF-alpha and IL-1 beta.