Effects Of Multiple Propofol Anesthesia On Cognitive Function In Aged Rats And Its Related Mechanisms

Background Postoperative cognitive dysfunction(POCD)is a common perioperative brain-related complication in elderly patients.Except that age is an independent risk factor,anesthetics are also important factors affecting cognitive function.At present,propofol is the most common intravenous anesthetic,which is widely used in various clinical examinations,as well as interventional or endoscopic operations.According to the elderly patients,multiple examinations and treatments are required due to the diseases.Thus,elderly patients will undergo multiple intravenous anesthesia.Previous studies have reported the protective effect of propofol on cognition,but it is not clear whether there is a cumulative effect on the cognitive function because of multiple intravenous injections.Therefore,it is of important to explore the effects of propofol administration with different periods and doses on the cognitive function of the elderly.At present,neuroinflammation is an important molecular mechanism of POCD.Besides,autophagy is involved in the survival of nerve cells and inflammation.However,the interaction of inflammation and autophagy in the propofol induced cognitive dysfunction remains unclear,which needs to be further explored.Objective1.To explore the effects of propofol with different doses on the cognition of aged rats and discuss related molecular mechanisms;2.To explore the effects of propofol with different periods on the cognition of aged rats and discuss related molecular mechanisms;3.To reveal the regulatory mechanism of NF-κB-mediated neuroinflammation in the propofol-induced cognitive dysfunction;4.To reveal the mechanism of m TOR-mediated autophagy in the cognitive impairment and neuroinflammation induced by propofol.Methods1.To explore the effect of propofol anesthesia with different doses on cognition,the aged rats were divided into 4 groups: intralipid group,50mg/kg propofol group,100mg/kg propofol group and 200mg/kg propofol group.The injection was performed once a day,for 6 times.Morris water maze and fear condition test were performed before administration,and then the propofol were injected for 6 times.Twenty-four hours after the last injection,the cognitive function was evaluated by MWM and FCT.After the behavioral tests,the rats were sacrificed,and the samples were collected.TUNEL staining was used to detect the apoptosis of hippocampal CA1 region.Western Blot was used to determine the expression of NF-κB/NLRP3 pathway and m TOR-mediated autophagy related proteins(LC3I/II,p62)in the hippocampus.ELISA was used to detect the levels of interleukin-6(IL-6),IL-1β,and tumor necrosis factor α(TNF-α)in the peripheral blood and hippocampus.2.Based on the examination period of gastroenteroscopy,the aged rats were randomly divided into 4 groups: intralipid 6×9 group(1 time every 9 days,6 consecutive times),propofol 6×9 group,intralipid 6 ×1 group(1 time a day,6 consecutive times),propofol 6×1group.Intralipid was the control group.Training of morris water maze(MWM)and fear condition tests(FCT)were initially performed,after that,propofol(200mg/kg)was intraperitoneally injected for 6 times.Twenty-four hours after the last administration of propofol,the cognitive function was evaluated by MWM and FCT.After the behavioral tests,the rats were sacrificed,and the samples were collected.TUNEL staining was used to detect the apoptosis of hippocampal CA1 region.Western Blot was used to determine the expression of NF-κB/NLRP3 pathway and m TOR-mediated autophagy related proteins(LC3I/II,p62)in the hippocampus.ELISA was used to detect the levels of interleukin-6(IL-6),IL-1β,and tumor necrosis factor α(TNF-α)in the peripheral blood and hippocampus.3.To explore the role of NF-κB/NLRP3-mediated inflammation in propofol-induced cognitive impairment.The rats were divided into 4 groups,the control group,the Bay11-7082 group(NF-κB inhibitor,1 mg/kg),the propofol group(200 mg/kg)and the propofol+Bay 11-7082 group.Propofol and Bay 11-7082 were injected intraperitoneally once a day for 6 consecutive times.Twenty-four hours after the last injection,the cognitive function was evaluated by MWM and FCT.After the behavioral tests,the rats were sacrificed,and the samples were collected.TUNEL staining was used to detect the apoptosis of hippocampal CA1 region.Western Blot was used to determine the expression of NF-κB/NLRP3 pathway and m TOR-mediated autophagy related proteins(LC3I/II,p62)in the hippocampus.ELISA was used to detect the levels of interleukin-6(IL-6),IL-1β,and tumor necrosis factor α(TNF-α)in the peripheral blood and hippocampus.4.To explore the role of m TOR-mediated autophagy in the propofol-induced cognitive impairment,the rats were divided into 4 groups: control group,Rapamycin group(m TOR inhibitor,10mg/kg),propofol group(200mg/kg)and propofol+Rapamycin group.Propofol and Rapamycin were injected intraperitoneally once a day for 6 consecutive times.Twenty-four hours after the last administration,the cognitive function were evaluated by MWM and FCT.After the behavioral tests,the rats were sacrificed,and the samples were collected.TUNEL staining was used to detect the apoptosis of hippocampal CA1 region.Western Blot was used to determine the expression of NF-κB/NLRP3 pathway and m TOR-mediated autophagy related proteins(LC3I/II,p62)in the hippocampus.ELISA was used to detect the levels of interleukin-6(IL-6),IL-1β,and tumor necrosis factor α(TNF-α)in the peripheral blood and hippocampus.Results1.After 200mg/kg propofol(once a day,for 6 times)intervention,the freezing time in the FCT,the time stayed in the targeted quadrant with original platform,and the crossings of the platform in the MWM were all significantly reduced.Besides,apoptotic cells in the hippocampal CA1 area were significantly upregulated,followed with a significant increase of the expression of activated caspase-3,and the activation of NF-κB/NLRP3 pathway.The autophagy related protein LC3II/I also decreased significantly.The levels of IL-1β,IL-6 and TNF-α in peripheral blood and hippocampus increased significantly.However,in the50mg/kg propofol group,the autophagy related protein LC3II/I increased significantly.There was no difference in other indicators among the 50mg/kg,100mg/kg propofol groups and the control group.2.Propofol treatment every 9 days for 6 consecutive times,failed to induce hippocampal apoptosis and cognitive dysfunction in the aged rats.However,propofol treatent once a day for 6 consecutive times significantly reduced the freezing time in the FCT,the time stayed in the targeted quadrant with original platform,and the crossings of the platform in the MWM.Besides,apoptotic cells in the hippocampal CA1 area increased significantly,followed with a significant over-expression of activated caspase-3,and the activation of NF-κB/NLRP3 pathway.The levels of IL-1β,IL-6 and TNF-α in peripheral blood and hippocampus were also significantly upregulated.The autophagy related protein LC3II/I decreased significantly.3.Bay 11-7082 had no effect on the inflammation,apoptosis,autophagy and cognitive function of rats in the normal group.However,in the group treated with propofol,Bay11-7082 could significantly prolong the freezing time in the FCT and the time staying in the targeted quadrant with the original platform in the MWM.The crossings of the platform increased significantly,while the apoptotic cells in the hippocampal CA1 area decreased.Besides,Bay 11-7082 treatment significantly decreased the expression of activated caspase-3and inhibited the NF-κB /NLRP3 pathway.The levels of IL-1β,IL-6 and TNF-α in the peripheral blood and hippocampus decreased,the autophagy protein LC3II/I was significantly upregulated.4.Rapamycin had no effect on the inflammation,apoptosis,autophagy and cognitive function of rats in the normal group.However,in the group treated with propofol,Rapamycin could significantly prolong the freezing time in the FCT and the time staying in the targeted quadrant with the original platform in the MWM.The crossings of the platform also increased significantly,while the apoptotic cells in the hippocampal CA1 region decreased.Besides,after Rapamycin treatment,the expression of activated caspase-3 and the NF-κB/NLRP3 pathway was inhibited.The levels of IL-1β,IL-6 and TNF-α in the peripheral blood and hippocampus decreased,the autophagy protein LC3II/I significantly increased.ConclusionsIn vivo experiments,we found that propofol had a cumulative effect on the cognitive function in the aged brain.200mg/kg propofol treatment once a day for 6 consecutive days could induce neuronal apoptosis in the hippocampus and cognitive dysfunction of the aged rats,which might be related with the activation of NF-κB/NLRP3 pathway,peripheral and central inflammation,as well as inhibition of autophagy.Bay 11-7082(a NF-κB inhibitor)could effectively inhibit inflammation,promote autophagy,and improve cognitive impairment;Similarly,Rapamycin(an autophagy activator)also inhibited inflammation,promote autophagy,and cell apoptosis,as well as played a cognitive protective role.