The Effect of Propofol on Hypoxia- and TNF-α-Mediated Brain-Derived Neurotrophic Factor/Tyrosine Kinase Receptor B Pathway Dysregulation in Primary Rat Hippocampal Neurons

Background: Brain-derived neurotrophic factor/tyrosine kinase receptor B (BDNF/TrkB) pathway dysregulation may be induced by hypoxia and inflammation, and play pivotal roles during the development of neurological disorders. Propofol is an anesthetic agent with neuro-protective properties. We aimed to verify whether propofol affected BDNF/TrkB pathway in neurons and astrocytes exposed to hypoxia and inflammation.Methods: Primary rat hippocampal neurons and astrocytes were cultured and exposed to propofol followed by hypoxia or TNF-α treatment. The production of BDNF and the expression/truncation/phosphorylation of TrkB were measured. The underlying mechanisms such as ERK, CREB, p35 and Cdk5 were investigated.Results: In hippocampal neurons and astrocytes, hypoxia and TNF-α reduced the production of BDNF. Pretreatment of hippocampal neurons with 25μM propofol reversed the inhibitory effect of hypoxia or TNF-α on BDNF production. However, even 100μM propofol had no such effect in astrocytes. Further, we found that in hippocampal neurons hypoxia and TNF-α increased the phosphorylation of ERK (p-ERK) and CREB at Ser142 (p-CREB Ser142), while reduced the phosphorylation of CREB at Ser133 (p-CREB Ser133), which were all reversed by 25μM propofol and 10μM ERK inhibitor. In addition, we reported that hypoxia- and TNF-α-mediated reduction of BDNF was mitigated by 10μM ERK inhibitor, and the beneficial effect of propofol was abolished by 10μM ERK activator. We also found neither hypoxia nor TNF-α affected TrkB expression, truncation or phosphorylation in hippocampal neurons and astrocytes. However 50μM propofol induced TrkB phosphorylation without affecting its expression and truncation only in hippocampal neurons. Furthermore, we detected that in hippocampal neurons, 50μM propofol induced p35 expression and Cdk5 activation, and blockade of p35 or Cdk5 mitigated propofol-induced TrkB phosphorylation.Conclusions: Propofol, via ERK/CREB and p35/Cdk5, may modulate BDNF/TrkB pathway in hippocampal neurons that were exposed to hypoxia or TNF-α.