The Role of Nrf2 Pathway Activation in Hippocampal Neuron Injury of Neonatal Rats with Bilirubin Encephalopathy

  Objective   To explore the effect of nuclear factor-erythroid 2-related factor (Nrf2) pathway activation on hippocampal neuron damage in neonatal rats with bilirubin encephalopathy.

  Methods   Neonatal rats were randomly assigned to a control group (Control), a model group (Model) and an Nrf2 activator TBHQ (tert-Butylhydroquinone) group (TBHQ), with 20 rats in each group. Bilirubin solution was injected through the cerebellomedullary cistern to establish the neonatal rat model of bilirubin encephalopathy. Neurobehavioral changes were observed in rats and the water content of the brain tissue was measured. Nissl staining was done to observe the damage of hippocampal neurons. TUNEL staining was used to observe the apoptosis of hippocampal neurons. Colorimetric analysis was done to determine the Caspase-3 activity in the hippocampus. The content of malondialdehyde (MDA) and reduced glutathione (GSH) and the activity of superoxide dismutase (SOD) in the hippocampus were examined by chemical analysis. qRT-PCR and Western blot were done to measure the expression of Nrf2 and heme oxygenase-l (HO-1) mRNA and proteins in the hippocampus.

  Results   After injection of bilirubin into the cerebellomedullary cistern, the young rats in the Model group and the TBHQ group showed different degrees of neurological abnormalities, while those in the control group showed no significant neurobehavioral abnormalities. Compared with the Control group, the Model group had severe neuronal damage, and the water content of brain tissue, the apoptosis of hippocampal neurons, the activity of Caspase-3 and the content of MDA content significantly increased (P<0.01), while the SOD activity, GSH content, the expression of Nrf2 and HO-1 mRNA and proteins significantly decreased (P<0.05). Compared with the Model group, neuronal damage was improved in the TBHQ group, and the water content of brain tissue, apoptosis of hippocampal neurons, activity of Caspase-3 and MDA content were all significantly reduced (P<0.01), while SOD activity, GSH content and the expression of Nrf2 and HO-1 mRNA and proteins were significantly increased (P<0.05).

  Conclusion   Activation of the Nrf2 pathway can improve hippocampal neuronal damage in neonatal rats with bilirubin encephalopathy and inhibit neuronal apoptosis and the oxidation reaction.