| Objective: With the development of medical technology,the indications for pediatric and even neonatal surgery are increased rapidly.Many difficult operations are gradually performed,and anesthesia time is getting longer and longer.Sevoflurane is widely used in pediatric anesthesia because of its unique anesthetic merits,such as a sweet smell,analgesia,sedation and muscle relaxation,little disturbance to cardiovascular system,strong controllability and less metabolism in human body.Despite these benefits,sevoflurane has been reported to exert potentially neurotoxic effects on the developing brain and to induce neuronal apoptosis and learning deficits in adolescence.Cx43 is the most abundant protein expressed in astrocytes.Cx43 can form hemichannels or gap junction(GJ)channels on cellular plasma membranes.Many studies had demonstrated that Cx43 was associated with neuroinflammation,synaptic plasticity,learning,memory and other functions.The purpose of this study is to investigate whether inhaled sevoflurane affects the expression of Cx43 protein in7-day-old SD rats and whether Cx43 protein expression is related to sevoflurane-induced cognitive impairment in developing brain.We also explore the possible mechanism.Method: Seven-day-old SD rats(P7)were exposed to 3% sevoflurane for 4 hours to establish a hippocampal injury model.Western Blot was used to examine Cx43 protein,phosphorylation,total MAPKs protein,phosphorylation and total c-Jun and c-Fos protein expression in the hippocampus of SD rats at 6h,1d,3d and 7d after anesthesia.The expression of Cx43 protein,Bax protein and Bcl-2 protein was observed by intracerebroventricular injection of Cx43 channel inhibitor carbenoxolone(Cbx)50mg/Kg 2 hours before anesthesia.According to the activated MAPKs signaling pathway,one or several inhibitors of MAPKs were injected 2 hours before anesthesia and the expression of Cx43 protein,phosphorylation and total MAPKs protein,phosphorylation and total c-Jun and c-Fos protein in hippocampus of SD rats were examined again.Neuronal apoptosis was detected usingImmunohistochemistry(IHC).The Morris water maze(MWM)was performed to evaluate cognitive function from P28 to P33.Results: The results showed that anesthesia with 3% sevoflurane for 4h increased Cx43 levels in the rat hippocampus from 6h to 1d,and compared with sevoflurane exposure in the control group rats,exposure in P7 SD rats also increased the ratios of phosphorylated JNK to JNK and,phosphorylated c-Jun to c-Jun in the hippocampus from 6 h to 3 d.All these effects could be alleviated by pretreatment with the JNK inhibitor SP600125(10mg/kg).Neuroapoptosis was similarly increased from 6h to 1d after inhaled sevoflurane exposure.Compared with sevoflurane group,the expression of Bax protein and Bcl-2 protein in hippocampus of SD rats could not be changed by intracerebroventricular injection of Cbx 50mg/Kg before anesthesia exposure.At the same time,Cbx could not reduce cumulative optical density of positive Caspase-3cells in hippocampal neurons.Finally,the MWM indicated that sevoflurane could increase the escape latency and,decrease the number of platform crossings from P28 to P33,and SP600125 but not Cbx could improve the learning and memory ability of long-term rats after exposure to sevoflurane.Conclusions: Overall,for the first time,we demonstrated that sevoflurane exposure in P7 SD rats could induce Cx43 upregulation and lead to apoptosis by activating the JNK/c-Jun/AP-1 signaling pathway in the hippocampus of developing rats,and could cause cognitive decline in adolescence.The JNK inhibitor SP600125 but not Cbx could inhibit the JNK/c-Jun/AP-1 signaling pathway and alleviate sevofluraneinduced Cx43 expression and apoptosis,improving learning and memory functions after sevoflurane exposure in the brains of developing rats. |
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