The Effects Of Sleep Deprivation On Microglia-mediated Synaptic Pruning

Sleep maintains the homeostasis of central nervous system(CNS),and it is critical to performing memory function.However,with the advancement of science,and the augument of life and mental pressure,which has caused that sleep deprivation becoming a common social phenomenon.As we all know,Sleep deprivation leads to impaired memory function.But the internal mechanism is not clear and needs to be further explored.The formation and consolidation of memory require the formation of new synapses or the elimination of weak synapses in order to enhance the activity of specific functional synapses.In the CNS,microglia are important immune cells,which regulate the development and homeostasis of the brain.During sleep,microglia act as primary "maintainer" of synaptic circuits,selectively pruning synapses to strengthen specific neuronal circuits.The refinement of synaptic circuits facilitates memory formation.Therefore,we hypothesized that sleep deprivation caused memory impairments,which was associated with impaired microglia-mediated synaptic pruning.First,in order to examine the effect of sleep deprivation on synaptic plasticity in the CNS.Glogi-Cox staining was used to detect changes in dendritic spines,which can represent the number of synapses.Besides,for detecting the plasticity,Western-blot and RT-q PCR were used to detect the changes of presynapsin and postsynaptic protein(PSD95).These results indicates that sleep deprivation leads to abnormal increase of spines and synaptic number.To investigate the role of microglia in the mechanism by which sleep deprivation increases the number of synapses,immunofluorescence methods was used to examine the morphological and functional changes of microglia.The results showed that sleep deprivation led to over activation of microglia in the hippocampus.The expression of lysosome in microglia was significantly decreased.The results of microglia and PSD95co-staining showed that the synaptic pruning of microglia was impaired.Then,the molecular mechanisms involved in synaptic pruning abnormalities were further investigated.Since CX3CR1 plays an important role in microglial migration and phagocytosis process,we hypothesized that CX3CR1 is responsible for the abnormal synaptic pruning of microglia caused by sleep deprivation.In vitro experiments,BV2 microglia were cultured and stimulated by CX3CL1 to detect the regulation of CX3CR1 on synaptic pruning function of microglia.Results confirmed that CX3CR1 expression can enhance the phagocytosis ability of microglia.Therefore,we further tested the effect of sleep deprivation on the expression of CX3CR1 in vivo,and found that sleep deprivation significantly reduced the m RNA and protein expression levels of CX3CR1 in the hippocampus of mice.These results provided evidence for the mechanism that CX3CR1 is involved in impaired microglia-mediated synaptic pruning caused by sleep deprivation.In conclusion,based on the synaptic thinning theory during sleep,this study examined the changes in microglia morphology,expression factors and synaptic phagocytosis ability,and concluded that sleep deprivation leads to impaired synaptic pruning function of microglia,leading to decreased memory ability,and this mechanism is related to CX3CR1.The elucidations of this mechanism provide an important theoretical basis for the subsequent treatment of cognitive impairment caused by passive sleep deprivation.