Effect of acupuncture plus mild hypothermia on MAPK/ERK pathway of brain tissues in rats with cerebral ischemia-reperfusion injury

Objective： To observe the protective effect of acupuncture plus mild hypothermia on brain tissues in rats with cerebral ischemia-reperfusion injury （CIRI）, and the influence on protein expression levels of phosphorylated Raf-1, MEK-2 and ERK3/2 in the mitogen-activated protein kinase （MAPK）/extracellular regulated protein kinases （ERK） pathway, and to explore the mechanism of acupuncture plus mild hypothermia therapy for the ischemic stroke. Methods： Ninety Sprague-Dawley （SD） rats were randomly divided into a blank control group, a sham operation group, a model group, an acupuncture group, a mild hypothermia group and an acupuncture plus mild hypothermia group, 15 rats in each group. Except the rats in the blank control group, the remaining rats were used to prepare the middle cerebral artery occlusion （MCAO） models according to the modified occlusion method using lines, while only the occlusion lines were inserted without blocking the brain arteries of rats in the sham operation group. When the vital signs of rats were stable, rats in the blank control group did not receive any intervention; rats in the sham operation group and the model group received fastening without treatment; rats in the acupuncture group, the mild hypothermia group, and the acupuncture plus mild hypothermia group were treated with the corresponding therapeutic methods. 72 h later, observed neurologic injury score, evaluated infarction area ratio by 2,3,5-tripheyl tetrazolium chloride （TTC） staining, determined apoptosis by TUNEL assay, and measured the phosphorylated Raf-1, MEK-2 and ERK3/2 protein expression levels in rat ischemic hippocampal tissues by Western blot assay. Results： Compared with the blank control group and the sham operation group, after modeling, the neurologic injury score, infarction area ratio and apoptotic cells were increased, and phosphorylated Raf-1, MEK-2 and ERK：1/2 protein expression levels were significantly increased in the model group; the differences were statistically significant （P〈0.05 or P〈0.01）. Compared with the model group, after acupuncture or mild hypothermia therapy, neurologic injury score and infarction area ratio were decreased; apoptotic cells and phosphowlated Raf-1, MEK-2 and ERK1/2 protein expression levels were significantly decreased; the differences were statistically significant （P〈0.05 or P〈0.01）. Compared with the acupuncture group, neurologic injury score and phosphorylated Raf-1, MEK-2 and ERK3/2 protein expression levels were decreased in the acupuncture plus mild hypothermia group; differences between the groups were statistically significant （P〈0.05 or P〈0.01）. Compared with the mild hypothermia group, phosphorylated Raf-1, MEK-2 and ERK1/2 protein expression levels decreased in the acupuncture plus mild hypothermia group, and differences were statistically significant （P〈0.01）. Conclusion： Acupuncture or mild hypothermia therapy can improve neurologic injury, reduce infarction area and apoptosis, which brought about protective effect on the brain tissues, in the MCAO model. The protective effect of acupuncture plus mild hypothermia group is the strongest. The mechanism may involve the MAPK/ERK pathway, by reducing the phosphorylated Raf-l, MEK-2 and ERK：1/2 protein expression levels.