BDNF-TrkB/proBDNF-p75NTR pathway regulation by lipid emulsion rescues bupivacaine-induced central neurotoxicity in rats

Bupivacaine (BPV) can cause severe central nervous system toxicity when absorbed into the blood circulation system. Rapid intravenous administration of lipid emulsion (LE) could be used to treat local anaesthetic toxicity. This study aimed to investigate the mechanism by which the BDNF-TrkB/proBDNF-p75(NTR) pathway regulation by LE rescues BPV induced neurotoxicity in hippocampal neurons in rats. Seven- to nine-day-old primary cultured hippocampal neurons were randomly divided into 6 groups: the blank control group (Ctrl), the bupivacaine group (BPV), the lipid emulsion group (LE), the bupivacaine+lipid emulsion group (BPV+LE), the bupivacaine+lipid emulsion+tyrosine kinase receptor B (TrkB) inhibitor group (BPV+LE+K252a), the bupivacaine+lipid emulsion+p75 neurotrophic factor receptor (p75(NTR)) inhibitor group (BPV+LE+TAT-Pep5). All hippocampal neurons were incubated for 24 h, and their growth state was observed by light microscopy. The relative TrkB and p75(NTR) mRNA levels were detected by real-time PCR. The protein expression levels of brain-derived neurotrophic factor (BDNF), proBDNF, TrkB, p75(NTR) and cleaved caspase-3 were detected by western blotting. The results showed that primary hippocampal neuron activity was reduced by BPV. As administration of LE elevated hippocampal neuronal activity, morphology was also somewhat improved. The protein expression and mRNA levels of TrkB and p75(NTR) were decreased when BPV induced hippocampal neuronal toxicity, while the expression of BDNF was increased. At the same time, BPV increased the original generation of cleaved caspase-3 protein content by hippocampal neurons, while the content of cleaved caspase-3 protein in hippocampal neurons cotreated with LE and BPV was decreased. Thus, this study has revealed LE may reduce apoptosis and promote survival of hippocampal neurons by regulating the BDNF-TrkB pathway and the proBDNF-p75(NTR) pathway to rescue BPV induced central neurotoxicity in rats.