Early Life Exposure To Antibiotic Induces Abnormal Behavior In Offspring Mice:The Regulatory Mechanism Of MTOR Signaling Pathway In The Gut-brain Axis

Objective: The aim of this study was to explore the effects of exposure to Sulfamonomethoxine(SMM)in the early life(pregnancy or lactation)on the behavior of exploring,anxiety and cognition in the offspring.Based on gut-brain axis,it is to be investigated that the molecular mechanism of behavior changes by the mTOR signaling pathway mediated by fecal short-chain fatty acids.Methods: ICR mice were randomly assigned to the SMM-treated groups and orally administered with SMM(0,10,50,200 mg/kg)during gestation or lactation.The exposure time was 18 days during gestation and 21 days during lactation respectively,then their offspring were separated with gender,raised normally until postnatal 56 days.Some of the offspring were sacrificed when they weaned,collected feces,serum and hippocampus.The behavioral tests involved in open-field test,elevated plus maze and Morris water maze,began at PND 48.At the end of the experiment,the mice were killed and their feces and hippocampus were collected.The T3,T4 concentration in serum were detected by radioimmunoassay.The BH4,5-HT,BDNF levels were detected via enzyme-linked immunoassay.The content of feces SCFAs were determined by gas chromatography.The expression of mTOR signal pathway in hippocampus was detected by Western blotting(WB)and real-time PCR.Results:1.(1)The content of total SCFAs was significantly lower in maternal feces during lactation exposure(P<0.05).There was no significant difference in total SCFAs in maternal feces during pregnant exposure.(2)In the lactation exposure groups,on PND 22 and PND 56,the content of total SCFAs in middle or high dose groups of male offspring mice were significant increased,including acetate and propionate(P<0.05).The content of total SCFAs in female mice were also increased(P<0.05).(3)In the gestation exposure groups,on PND 22 and PND 56,the content of total SCFAs were significant increased in male offspring,including acetate and propionate(P<0.05).However,there were no significant differences in total SCFAs in female feces.2.(1)The results of serum components and behavioral tests in offspring mice were changed by maternal exposure to SMM during lactation.(2)In gestation groups,in open field test,the total distance and the numbers of squares crossed were significantly reduced in middle-dose groups both in male and female mice(P<0.05).The entries of central area were obviously decreased in male middle-dose group and female low or high dose groups(P<0.05).The time in central area was also reduced in female low-dose group.In elevated plus maze,the number and time of entries into closed arms were increased in male mice compared with controls(P<0.05).In the meantime,the time spend in closed arms was increased in female high-dose group,too(P<0.05).In Morris water maze,the escape latency of male mice was significantly delayed in the second and third day in high-dose group,and the middle-dose group was obviously delayed on the second day(P<0.05).The time of spend in target area was reduced in male low or middle dose group compared with controls(P<0.05).The concentrations of BH4 and BDNF were significantly decreased in male high-dose group compared with controls(P<0.05),but no significantly difference in female mice.3.(1)During lactation exposure,there were no statistical difference of SPR expression in the hippocampus between SMM treatment groups and controls on PND 22.The expression of SPR in female middle and high dose groups were obviously reduced compared with controls(P<0.05)on PND 56.(2)During gestation exposure,on PND22,the expression of SPR were significantly reduced in male middle or high groups(P<0.01)and female offspring mice(P<0.05).On PND 56,the expression of SPR were obviously decreased in male offspring(P<0.01)and female middle or high dose groups(P<0.001).4.(1)During lactation exposure,compared with controls,on PND 22,the expression of Rheb,mTOR in low or high dose groups and S6K1 in middle-dose group were highly increased(P<0.05)in male offspring.In female,the expression of PI3 K,S6K1 in SMM groups,Akt and Eif4EBP1 in high dose and Rheb,mTOR in low or high dose were significantly increased(P<0.05).On PND 56,the proteins expression of Akt in high dose,Rheb and Eif4EBP1 in middle dose,mTOR and S6K1 in middle or high dose were significantly increased in male offspring(P<0.05).The expression of Akt,PI3 K,Rheb and S6K1 in high dose group and mTOR were obviously increased in female mice(P<0.05).The expression of P-mTOR(Ser2448)were significantly increased during lactation SMM exposure both in male and female mice on PND 22 and PND 56(P<0.01).(2)During gestation SMM exposure,compared with controls,the expression of m RNA in Pi3k3 ca,Akt1 and the protein of Akt,S6K1 and mTOR were significantly increased in male offspring on PND 22(P<0.05).At the same time,the expression of m RNA in Pi3k3 ca,Akt1,mTOR and Eif4ebp1 were significantly up-regulated(P<0.05),and the expression of PI3 K,S6K1,Eif4EBP1 protein in each group and mTOR protein in middle and high dose groups were obviously increased in male mice on PND 56.Conclusion: 1.The content of total SCFAs were significant increased in offspring mice,including acetate and propionate when maternal exposure to SMM during pregnancy or lactation.2.The mTOR signaling pathway in hippocampus of offspring mice will sustained activated followed exposure to SMM in early life,This may be lead to depression,anxiety and cognitive impairment in offspring mice.