Impaired Synaptic Development And Eph-ephrin Signaling Following Maternal Immune Activation In Rats

BackgroundMaternal immune activation during pregnancy is an important environmental risk factor of(SZ),which has a lasting and harmful effect on the neurodevelopment of offspring.More and more evidences suggest that impaired synaptic plasticity may be one important pathology of SZ,but its potential molecule mechanism is unclear.Eph-Ephrin pathway regulates the formation and maturation of dendritic spines.The disruption of Eph-Ephrin signaling pathway may be an important molecular mechanism of neuron development deficiency in offspring of maternal immune activation.ObjectiveThe animal model of schizophrenia induced by maternal immune activation treatment with polyinsinic acid-polycytidylic acid(Poly I:C)in early pregnancy was used to observe the synaptic injury,the expression change of Eph-Ephrin pathway genes and downstream targeting molecules in different developmental stages of MIA animal modal.Methods1.Pregnant female Sprague-Dawley(SD)rats were randomly injected into tail vein with 10mg/kg poly I:C(n=10)and 0.9% sterile saline of equal volume(n=10)on the 9th day(G9).The offspring of the Poly I:C group and the NaCl control group were separated from the lactation cage at the age of 21 days,and only male rats were selected as the subjects.The prefrontal cortex were selected for transcriptome sequencing and biological analysis in adolescence(PND40).2.Two developmental stages of adolescence and adult(PND60)were used for behavioral test,such as open field,elevated maze,Y maze,passive avoidance and prepulse inhibition behavior of the two groups of rats.3.The development of dendritic spines of cortical neurons were observed by Golgi staining in adolescence and adult.4.Immunoblotting(Western Blot,WB)and real-time fluorescence quantitative PCR(qPCR)were used to test the expression of Eph signaling and its downstream target molecules(p-LIMK1/LIMK1,p-Cofilin/Cofilin,GluR1)in prefrontal cortex and hippocampus.5.All of the data was presented with means ± standard deviations.The independent sample t test was used to compare the unrelated two groups of samples,the two independent sample tests in the nonparametric test were used to analyze the sample data of the two groups of non-normal distribution,and the SPSS20.0 software was used to analyze the experimental results of each group.The test results P< 0.05 can be considered to be statistically different,and GraphPad Prime6 is used to draw.Results1.The results of behavior test suggest that the offspring of model group display lower innate anxiety and increased locomotor activity in adolescence.In adult the offspring of model group showed moderate increase of anxiety-related behavior,decreased locomotor activity,cognitive impairment and pre-pulse inhibition deficit behavioral phenotype(P< 0 05).2.Golgi staining showed that decreased density of dendritic spines of cortical neuron of model group(P< 0 05).3.The results of KEGG pathway analysis showed that 104 pathways changed in adolescent model group,and Eph-Ephrin pathway were in the forefront.The mRNA levels of six receptors in Eph-Ephrin family were significantly elevated in the prefrontal cortex which confirmed the results of transcriptome sequencing(P< 0 05).4.The expression of EphB1-3 and EphB2 proteins in prefrontal cortex were significantly increased in the model group since puberty,but in the hippocampus they only significantly increased in adulthood(P< 0 05).5.The downstream molecules of the EphB signaling pathway decreased significantly in prefrontal cortex and hippocampus,such as phosphorylation-LIMK1(p-LIMK1),p-Cofilin in puberty and adulthood(P< 0 05).6.The glutamate receptor GluR1 markedly decreased in prefrontal cortex and hippocampus in adulthood and prefrontal cortex in adolescence(P< 0 05).Conclusions1.The offspring infected with poly I:C in the early trimester showed synaptic structure damage and abnormal expression of Eph pathway related genes at different developmental stages.Synaptic dysfunction mediated by Eph pathway may be the pathological basis of schizophrenia-like behavior in offspring infected with poly I during pregnancy.2.The changes of EphB2 receptors and its downstream molecules,especially increased Cofilin activity,may be an important molecular mechanism of the impairment of synaptic plasticity,dysfunction of prefrontal cortex and hippocampus due to immune activation during pregnancy,which ultimately cause the behavioral and cognitive dysfunction.