[Dynamic expression of toll like receptor 2 and 4 in a rat model of myocardial ischemia/reperfusion injury]

Abstract

Objective: To explore the role of toll-like receptor 2 (TLR2) and toll-like receptor 4 (TLR4) in myocardial ischemia/reperfusion injury (MI/RI) by observing the dynamic expression changes at mRNA and protein levels early after myocardial ischemia/reperfusion (I/ R).

Methods: The Wistar rats were randomly divided into Sham and I/R group (n = 42), and killed according to different reperfusion time (1, 2, 4, 6, 12, 24 h and 7 d). Structural and morphous changes of myocytes were observed under optical microscope. The mRNA and protein levels of TLR2 and TLR4 were detected using real-time PCR (RT-PCR). Monocyte chemokine protein-1 (MCP-1) and interleukine-6 (IL-6) mRNA levels were measured by reverse transcriptase-polymerase chain reaction (rt-PCR).

Results: (1) With the extension of reperfusion time, the myocardial infarct size increased smoothly, and reached the plateau at 4 h, then stayed in the platform. After reperfusion for 7 d, the ventricular had been remodeled. (2) At the beginning of reperfusion, myocardial structure showed no significant change in Sham group, but had different degrees of injury in I/R group. In rats of the group reperfused for 7 d the left ventricular remodeling could be visible. (3) Compared to sham group,TIR2, TLR4, MCP-1, IL-6 mRNA level were increased in myocardium in I/R group. TLR2 and TLR4 both peaked at 4 h of reperfusion, IL6 peaked at 6 h, followed by a gradually decrease. TLR4 and IL-6 mRNA levels rose again at 7 d. MCP-1 level in I/R group remained fairly with sham group at the beginning of reperfusion, and markedly elevated at 7 d.

Conclusion: Expression of TLRs mRNA in myocardium during early after myocardial ischemia/reperfusion increased rapidly and activated TLRs might play an important role in MI/RI through promoting the generation of inflammatory factors. At the late reperfusion, TLRs levels raise again and the expression of inflammatory factors increase once again, Those may probably affect the remodeling of ventricular, and injure myocardial structure and function.