BDNF-TrkB-CREB Signaling Pathway And Methylation Regulation Involve In The Neurotoxicity Of Male Mice Induced By Bisphenol S

Objective: To study the effect of Bisphenol S(BPS)on the nervous system of C57BL/6 adult male mice,and to explore the role of BDNF-TrkB-CREB signaling pathway and methylation regulation in BPS induced neurotoxicity,so as to provide new theoretical and experimental basis for further toxicological research and health standard formulation of BPS.Methods:1.C57BL/6 adult male mice was gavaged by different concentrations of BPS(0,2,20 and 200 mg/kg BW/d)for 28 days,during which the weight changes of mice were recorded.After sacrifice,the brain was weighed to calculate the organ index,hematoxylin eosin(H&E)staining was used to observe the pathological changes of brain,transmission electron microscope(TEM)was used to observe the ultrastructural changes of hippocampus,,qRT-PCR was used to analyse the mRNA levels of postsynaptic density protein-95(PSD-95)、 Growth associated protein-43(GAP-43)and Western blot was used to analyse the changes protein levels of synaptophysin(SYP),PSD-95 and α-amino-3-hydroxy-5-methyl-4-isozolyl propionic acid receptor subunit Glu A1 were detected by Western blot.2.The mRNA and protein levels of BDNF,TrkB and CREB were detected by qRT-PCR and Western blot.3.Bisulfite sequencing PCR(BSP)was used to detect the methylation rate of BDNF gene promoter ⅣB the mRNA and protein levels of DNMT 1,DNMT 3a and DNMT 3b were respectively detected by qRT-PCR and Western blot.Results:1.H&E staining showed that the hippocampus of the control group and BPS mice showed normal morphological structure,and no obvious pathological changes were found in the hippocampus.At the doses of 20 and 200 mg/kg,the nuclear membrane was irregular.In BPS group,myelin sheath around many axons was incomplete compared with control group.Each dose of BPS reduced the number of synapses.Compared with the control group,BPS groups decreased the mRNA levels of PSD-95 and GAP-43.2 mg/kg,20 mg/kg and 200 mg/ kg BPS decreased the protein levels of SYP,PSD-95 and Glu A1.2.Compared with the control group,the BDNF mRNA levels in 2,20 and 200mg/kg BPS groups were significantly decreased.There was no significant difference in TrkB mRNA expression between BPS group and control group.20 mg/kg BPS could reduce CREB mRNA expression.With the increase of BPS concentration,the protein expression of BDNF and TrkB decreased gradually.The expression of pCREB/CREB in hippocampus of BPS treated mice decreased.3.The total methylation rates of BDNF gene promoter Ⅳ in control group and2 mg/kg,20 mg/kg and 200 mg/kg BPS groups were 0%,9.5%,5.8% and 6.8%.After BPS treatment,the expression of DNMT1 mRNA and protein levels in 2 mg/kg and 200 mg/ kg BPS groups decreased compared with the control group.2 mg/kg and 200 mg/kg BPS could increase the mRNA level of DNMT3 a,but only 200mg/kg BPS could increase the protein expression of DNMT 3a.Compared with the control group,the mRNA level of DNMT 3b in 200 mg/kg BPS treatment group was increased,and the protein level of DNMT 3b in BPS treatment group was increased.Conclusion:1.BPS exposure can cause changes in the myelin structure,decrease in the number of synapses,the level of synapse related mRNA and proteins in the hippocampus of mice,leading to neurotoxicity.2.BDNF-TrkB-CREB signaling pathway participates in the neurotoxic effect of BPS.3.BPS exposure regulates the levels of DNMTs,increases the methylation level of BDNF promoter Ⅳ to change the expression of BDNF.