The Role Of Hippocampal Autophagy In Cognitive Dysfunction Induced By Sevoflurane In Aged Rats

BackgroundAlthough Sevoflurane is the most widely used halogenated inhaled anesthetics in clinical practice, characterized by low pungency, non-irritating odor and low blood/gas partition coefficient, increasing evidence has suggested that sevoflurane may induce cognitive impairment in both animals and humans with the exact mechanism unkown. Autophagy, an evolutionarily conserved process of self-digestion, has been reported to play an important role in many neurodegenerative diseases. However, it is still unkown that whether and how autophagy may participate the progress of seovlfurane induced cognitive dysfunction.ObjectiveThis study aims to investigate the role of hippocampal autophagy in cognitive dysfunction induced by sevoflurane in aged ratsMethodsNinety rats were randomly divided into 6 groups (n=15):control group (CON), rapamycin group (RAP), chloroquine group (CQ), sevoflurane group (SEV), sevoflurane plus rapamycin group (SEV+RAP), sevoflurane plus choroquine group (SEV+CQ). Rats in the RAP group and SEV+RAP group were intraperitoneally injected with rapamycin (20 mg/kg/d), rats in the CQ group and SEV+CQ group were intraperitoneally injected with choroquine (20mg/kg/d) and the other two groups received same dose vesicle solution from two days before sevoflurane exposure and lasted for a week.24 h after the sevoflurane exposure, rats were subjected to Morris Water Maze Test (MWM) to evaluate the spatial memory abilities. After the Morris water maze test,6 rats from each group were perfused transcardially with 200 ml normal saline followed by 300 ml 4% paraformaldehyde. Half of them were used for TEM observation and the other half were used for TUNEL assay The hippocampus of the other rats were quickly dissected and frozen immediately in dry ice then stored at-80℃ for protein analysis.Results1. Sevoflurane induced cognitive dysfunction in aged rats, increased the number of autophagical vacuoles in the hippocampus and upregulated the expression of LC3-Ⅱ/Ⅰ and p62. The expression of Bax, cleaved caspase3 and number of TUNEL positive cells were also increased by sevoflurane.2. Rapamycin ameliorated the cognitive dysfunction induced by sevoflurane, further increased the number of autophagical vacuoles, upregulated the ratio of LC3-Ⅱ/Ⅰ and reduced the expression of p62. The increased expression of Bax, cleaved caspase3 and TUNEL positive cells were also inhibited by rapamycin.3. CQ aggravated the cognitive dysfunction induced by sevoflurane, further increased the number of autophagical vacuoles, upregulated the ratio of LC3-Ⅱ/Ⅰ and p62. The increased expression of Bax, cleaved caspase3 and TUNEL positive cells were also further increased by CQ. ConclusionThe impairment of autophagy may be responsible for the sevoflurane-induced neuron apoptosis and cognitive dysfunction in aged rats. Activation of autophagy by rapamycin ameliorated the neuron apoptosis and cognitive dysfunction induced by sevoflurane, while CQ effected on the opposite way, suggesting that...