OBJECTIVETo investigate the role of nuclear factor-κB (NF-κB) activation in bilirubin-induced apoptosis of rat hippocampal neurons and the effect of TAT-NBD intervention on bilirubin neurotoxicity.

METHODSPrimary-cultured rat hippocampal neurons were treated with TAT-NBD in the initial 6 or 24 h or in the latter 6 h during a 24-h bilirubin exposure of the cells (early, continuous and late intervention groups, respectively). Immunocytochemistry was performed to detect NF-κB p65 protein expression, and the cell survival and apoptosis were assessed with a modified MTT assay, Annexin V-FITC/PI and TUNEL assay. IL-1β concentration in the supernatant was determined with ELISA.

RESULTSCompared with the control cells, bilirubin-treated cells showed a significantly increased NF-κB p65 protein expression (P<0.01), which reached the peak level at 6 and 24 h (P<0.01). The cell survival rate in early TAT-NBD intervention group was (80.784∓9.767)%, significantly lower than that of the control group (P<0.01) but higher than that of bilirubin group (P<0.01); the apoptotic rate in early TAT-NBD intervention group was significantly higher than that of control group (P<0.01) but lower than that of bilirubin group (P<0.01). IL-1β concentration was significantly lower in early TAT-NBD intervention group (15.348∓0.812 pg/ml) than in bilirubin group (P<0.05). The continuous and late TAT-NBD intervention groups showed comparable cell survival rate, apoptotic rate and IL-1β concentration with bilirubin group (P>0.05).

CONCLUSIONNF-κB bidirectionally regulates bilirubin-induced apoptosis of rat hippocampal neurons. Selective inhibition of the early peak of NF-κB by TAT-NBD offers neuroprotective effect. TAT-NBD can be potentially used for prophylaxis of bilirubin-induced brain injury.