Irisin Protects Brain against Ischemia/Reperfusion Injury through Suppressing TLR4/MyD88 Pathway

Abstract

Background: Inflammatory response exerts an important role in ischemia/reperfusion (I/R) injury. TLR4 and myeloid differentiation factor 88 (MyD88) are key components in inflammation and are involved in the cerebral I/R injury. Irisin is a skeletal muscle-derived myokine produced after exercise, which was found to suppress inflammation. In this study, we investigated whether irisin could protect the brain from I/R injury through the TLR4/MyD88 pathway. Methods: Male Sprague Dawley rats (20 months, 190 ∼ 240 g) were pretreated with irisin at 10, 50, or 100 mg/kg for consecutive 3 days and then subjected to surgery of middle cerebral artery occlusion or sham operation. Infarct size and neuron loss were measured to evaluate brain damage. The mRNA and protein levels of TLR4 and MyD88 were measured by in situ hybridization and immunohistochemistry, respectively. NF-κB activation was assessed by electrophoretic mobility shift assay. Neurological function was evaluated by neurobehavior score test and passive avoidance test. Results: Irisin could reduce neuronal damage and neurofunctional impairment after I/R injury. This effect was mediated by downregulating the TLR4/MyD88 and inhibiting NF-κB activation. Conclusion: Irisin plays a beneficial effect in I/R injury through regulating the TLR4/MyD88 pathway.