The Mechanism Of BDNF-TrkB/proBDNF-p75^NTR Pathway In Lipid Emulsion Rescues Bupivacaine-induced Central Neurotoxicity In Rats

Objective To investigate the mechanism of BDNF-TrkB/proBDNF-p75^NTR pathway in lipid emulsion rescue bupivacaine-induced neurotoxicity in hippocampal neurons in rat.Methods The 7-9 days primary cultured hippocampal neurons randomly divided into 6groups（n=3）:the blank control group（Ctrl）,Bupivacaine group（BPV）,The lipid emulsion group（LE）,Bupivacaine+lipid emulsion group（BPV+LE）,Bupivacaine+lipid emulsion+tyrosine kinase receptor B（TrkB）inhibitor group（BPV+LE+K252a）,Bupivacaine+lipid emulsion+p75 neurotrophic factor receptor(p75^NTR)inhibitor group（BPV+LE+TAT-Pep5）.All hippocampal neurons incubated 24 hours,the growth state of hippocampal neurons was observed by light microscope.The relative TrkB and p75^NTR mRNA levels were detected by Realtime-PCR.The expressions of protein BDNF,proBDNF,TrkB,p75^NTR and Cleaved caspase-3 were detected by western blot.ResultsCompared with group Ctrl,the expression of protein BDNF was increased in BPV group,LE group and BPV+LE group,the expression of protein TrkB was decreased in group BPV,BPV+LE+K252a group and BPV+LE+TAT-Pep5 group,the expression of protein TrkB was increased in group LE,the expression of protein p75^NTR was decreased in BPV group,BPV+LE group and BPV+LE+TAT-Pep5 group,the expression of protein Cleaved caspase-3 was increased in group BPV,BPV+LE group and BPV+LE+K252a group,the expression of TrkB mRNA was decreased in BPV group,the expressionof p75^NTR mRNA was decreased in BPV group,LE group,BPV+LE group,BPV+LE+K252a group and BPV+LE+TAT-Pep5 group,these differences were all significant（P<0.05）.Compared with group BPV,the expression of protein BDNF and protein Cleaved caspase-3 were decreased in LE group,BPV+LE group,BPV+LE+K252a group and BPV+LE+TAT-Pep5 group and the expression of TrkB mRNA were increased in these groups,the expression of protein TrkB was increased in group LE and group BPV+LE group and which was decreased in BPV+LE+TAT-Pep5 group,the expression of protein p75^NTR and p75^NTR mRNA were increased in LE group and BPV+LE+K252a group,these differences were all significant（P<0.05）.Compared with group LE,the expression of protein TrkB,protein p75^NTR and p75^NTR mRNA were decreased in BPV+LE group,BPV+LE+K252a and BPV+LE+TAT-Pep5 group,the expression of protein Cleaved caspase-3 was increased in BPV+LE group and BPV+LE+K252a group,these differences were all significant（P<0.05）.Compared with BPV+LE group,the expression of protein BDNF and protein TrkB were decreased in BPV+LE+K252a group and BPV+LE+TAT-Pep5 group,the expression of protein Cleaved caspase-3 was decreased in BPV+LE+TAT-Pep5 group,these differences were all significant（P<0.05）.Compared with the BPV+LE+K252a group,the expression of protein TrkB,protein Cleaved caspase-3 and p75^NTR mRNA were decreased in BPV+LE+TAT-Pep5 group was decreased,these differences were all significant（P<0.05）.ConclusionLipid emulsion may reduce apoptosis and promote survival of hippocampal neurons by upregulates BDNF-TrkB and downregulates proBDNF-p75^NTR pathway to rescues bupivacaine-induced central neurotoxicity in rats.