Objective: To explore the role of TLR4 in myocardial ischemia reperfusion injury (MI/RI) by observing the dynamic TLR4 expression changes at mRNA and protein levels early after myocardial ischemia reperfusion.
Methods: Male SD rats were randomly divided into Sham and IR group and the rats were killed according to different reperfusion time (0, 0.5, 1, 2, 4 and 8 hours). Myocardial changes under light microscope and transmission electronic microscope were observed. TLR4 expressions at protein and mRNA levels were detected by immunohistochemistry and realtime RT-PCR respectively. Myocardial TNF-alpha was determined by ELISA.
Results: (1) Myocardial injury was observed in IR but not in Sham group and histopathological and ultrastructural changes in IR group remained unchanged up to 8 hours after reperfusion. (2) Positive TLR4 protein staining was visualized in both Sham and IR groups and significantly increased and peaked at 1 hour of reperfusion in IR group. (3) Compared to Sham group, TLR4 mRNA level was upregulated in myocardium in IR group and peaked at 1 hour of reperfusion. (4) Concentration of TNF-alpha in IR group was significantly higher than that of Sham group at corresponding time points (all P < 0.05), and myocardial TLR4 mRNA level correlated positively with myocardial TNF-alpha (r = 0.728, P < 0.01).
Conclusion: Expression of TLR4 in myocardium during early after myocardial ischemia reperfusion was upregulated and actived TLR4 might play an important role in MI/RI through promoting myocardial TNF-alpha excretion.