Effects of isoflurane preconditioning on expression of TLR4 and MyD88 during focal cerebral ischemiareperfusion in rats

Objectiye To investgate the effects of isoflurane preconditioning on expression of Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) during focal cerebral ischemia-reperfusion (IR) in rats. Methods Thirty male SD rats weighing 250-300 g were randomly divided into 3 groups ( n = 10 each):sham operation group (group S);focal cerebral IR group and isoflurane preconditioning group (group IP). The animals were anesthetized with intraperitoneal pentobarbital 40 mg/kg. In group IR and IP a nylon thread with rounded tip was inserted into right internal jugular vein and threaded cranially until resistance was met. Mid-cerebral artery was occluded (MCAO) for 2 h followed by 24 h reperfusion. In group IP the animals inhaled 2% isoflurane98 % O2 for 1 h once a day for 5 consecutive days at 24 h before MCAO. Neurologic function was assessed and scored and cerebral infarct volume was measured at 24 h of reperfusion. The animals were sacrificed at 24, 48 and 72 h of reperfusion respectively. The right ischemic frontal lobes were removed for determination of TLR4, MyD88and NF-κB expression by Western blot analysis. Results MCAO significantly worsened neurologic function. The neurologic function deficit scores were significantly increased and the TLR4, MyD88 and NF-κB expression were significantly up-regulated in group IR as compared with group S (P ＜ 0.05). Isoflurane preconditioning significantly decreased cerebral infarct volumes and neurologic function deficit scores and down-regulated the expression of TLR4, MyD88 and NF-κB in group IP as compared with group IR ( P ＜ 0.05). Conclusion Isoflurane preconditioning can reduce inflammatory response and focal cerebral IR injury by down-regulating the expression of TLR4and Myd88. Key words: Isoflurane; Ischemic preconditioning; Toll-like receptor 4; Myeloid differentiation factor 88; Reperfusion injury; Brain