Role of reactive oxygen species-mediated mitochondrial pathway of apoptosis in long-term cognitive impairment induced by multiple exposures to sevoflurane in neonatal rats / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of reactive oxygen species (ROS)-mediated mitochondrial pathway of apoptosis in long-term cognitive impairment induced by multiple exposures to sevoflurane in the neonatal rats.Methods:Sixty SPF healthy neonatal Sprague-Dawley rats, weighing 12-20 g, were divided into 3 groups ( n=20 each) using a random number table method: control group (group C), multiple exposures to sevoflurane for anesthesia group (group S) and ROS inhibitor group (group A). Group S and group A inhaled 3% sevoflurane for 2 h starting from 6, 7 and 8 days after birth, while group C inhaled air.In group A, ROS inhibitor N-acetylcysteine (NAC) 150 mg/kg was intraperitoneally injected before each anesthesia with sevoflurane.The spontaneous activity was evaluated by open field test on day 35 after birth.The cognitive function was determined by Morris water maze test on day 36 after birth.The rats were sacrificed after the end of Morris water maze test, and the hippocampal tissues were obtained for determination of the apoptosis rate of hippocampal neurons, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) (by flow cytometry) and levels of Cyt c and cleaved caspase-9 and caspase-3 (by Western blot). The expression of Bcl-2 and Bax mRNA was detected by real-time polymerase chain reaction.The ultrastructure of mitochondria in hippocampal neurons was observed with a transmission electron microscope. Results:Compared with group C, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, the apoptosis rate of hippocampal neurons and levels of ROS and MMP were increased, the expression of Cyt c, cleaved caspase-9, cleaved caspase-3 and Bax mRNA was up-regulated, the expression of Bcl-2 mRNA was down-regulated, the ratio of Bax/Bcl-2 was increased ( P<0.05), mitochondria were swollen, and mitochondrial cristae structure was broken in group S. Compared with group S, the escape latency was significantly shortened, the number of crossing the original platform was increased, the apoptosis rate of hippocampal neurons and levels of ROS and MMP were decreased, the expression of Cyt c, cleaved caspase-9, cleaved caspase-3 and Bax mRNA was down-regulated, the expression of Bcl-2 mRNA was up-regulated, the ratio of Bax/Bcl-2 was decreased ( P<0.05), and the mitochondrial swelling and rupture of cristae structure were improved in group A. Conclusion:The mechanism by which multiple exposures to sevoflurane induce long-term cognitive impairment may be related to activating the ROS-mediated mitochondrial pathway of apoptosis in neonatal rats.