Study On The Role And Mechanism Of Akt1 Mediated Lipopolysaccharide-induced Changes In Sleep And Wakefulness Behavior

Sleep disorders are a chronic disease with high prevalence and great damages to public safety and health,which are a major public health problem with rising prevalence rate.Sleep and inflammation are bidirectionally linked.Inflammatory infection induces sleep disorders such as lethargy,and sleep disorders affect the occurrence and progress of inflammatory infectious diseases.Studies have reported that intraperitoneal injection of lipopolysaccharide（LPS）,a cell wall component of Gram-negative bacteria,induces systemic inflammatory infections,leading to increased slow-wave sleep and inhibiting paradoxical sleep.Although there are many studies on the relationship between sleep and inflammation,the specific molecular mechanism of inflammatory infection induced the change of sleep wake behavior is still unclear.Based on previous studies that inflammatory signals regulate sleep,at first,this study detected the effect of LPS on the sleep-wake cycle of wild type mice and the changes in the activity of LPS-induced inflammation-related signaling pathways,aiming to explore the specific mechanism of LPS-induced changes in sleep-wake behavior.In this study,the sleep-wake recording system was used to record the electroencephalogram/electromyography（EEG/EMG）and analyze the sleep-wake cycle of wild type mice after normal saline or LPS administration,in order to confirm that the existence of sleep disorders in the systemic inflammatory infection model induced by LPS.The results showed that intraperitoneal injection of LPS induced the changes in sleep wake behavior,which showed an increase in slow-wave sleep and a decrease in wakefulness and paradoxical sleep.In order to explore the inflammation signal molecules that may be involved in the changes of LPS-induced sleep-wake behavior,the activation of LPS-induced inflammation-related signal pathways in cortex and hypothalamus was detected by western blot,including Akt and its subtypes Akt1,Akt2,p38 MAPK and its downstream signal molecule MK2,as well as the transcription factor NF-κB.The experimental data indicated that LPS induced the activation of Akt and its subtypes Akt1,Akt2,and transcription factor NF-κB in the cortex.In addition to Akt,Akt1,and Akt2,the phosphorylation of p38 MAPK in the hypothalamus was also significantly increased,suggesting that Akt1 and Akt2 might be involved in LPS-induced the changes of sleep and wake.Based on this,we analyzed the sleep-wake cycle of Akt1^-/-and Akt2^-/-mice treated with saline and LPS.The results showed that in the normal saline group,Akt1^-/-and Akt2^-/-mice exhibited a decrease in slow-wave sleep and an increase in wakefulness compared with WT mice;LPS induced an increase in slow-wave sleep and a decrease in wakefulness in WT mice,and the deletion of Akt1 gene reversed LPS-induced changes in sleep-wake behavior.However,the absence of Akt2 gene had no significant effect on LPS-induced changes in sleep-wake behavior.The above results indicated that both Akt1 and Akt2 played a role in the regulation of sleep wakefulness after administration of normal saline.Akt1 was involved in improving sleep-wake disorders induced by LPS infection,but Akt2 did not.To further explore the mechanism of Akt1 and Akt2 involved in the regulation of sleep and wake,it was found that the deletion of Akt1 and Akt2 genes both resulted in significant activation of orexin neurons in the lateral hypothalamus of mice;the activity of orexin neurons was significantly inhibited in LPS-stimulated mice;after Akt1 gene knockout,the activity of orexin neurons induced by LPS recovered and exceeded the normal saline control of wild mice,while Akt2 gene knockout had no significant effect on LPS-induced changes in orexin neuron activity.In summary,after administration of normal saline,both Akt1 and Akt2 participated in the regulation of sleep-wake behavior by activating orexin neurons.In LPS-induced sleep-wake disorders,Akt1 reversed the changes in sleep-wake behavior by increasing the activity of orexin neurons inhibited by LPS,while Akt2 was not involved in the regulation of LPS-induced changes of sleep-wake behavior.This study has provided a new idea for the regulatory mechanism and prevention and treatment of sleep disorders related to inflammatory infectious diseases.