The Neuroprotective Role Of NF-κB Inhibition By TAT-NBD In SD Rat Kernicterus Modle

Objective: To investigate the activity of nuclear factor kappa B(NF-κB) and to identify the effect of TAT-NBD(NF-κB specific inhibitor)on a newborn rat kernicterus model.Methods: Kernicterus model was established in 5-day-old Sprague-Dawley(SD) rats by injecting unconjugated bilirubin solution into the cisterna magna(CM). The activity of NF-κB and the peak time of which were assessed by EMSA at various time points after bilirubin injection. TAT-NBD was administered intraperitoneally at 0h and 2h after model established based on the peak time of NF-κB activity. Meanwhile, to identify if the NBD sequence is specific to inhibit NF-κB activity, a group of model established SD rats were treated with mutant TAT-NBD. Typical neurological manifestations and bodyweight were dynamically recorded、mortality was calculated. Apoptosis was detected by H & E staining 、TUNEL and Western blotting. The expression of IL-1 β and TNF- α inhomogenate of rats brain tissue were tested by ELISA. At the age of 28 days, the extent of the neurological deficit was measured by the neurological evaluation, the balance and motor coordination was assessed by the rotarod test, the learning and memory ability were performed by the Morris water maze test.Results: NF-κB activity was significantly higher at 1h to 3h(P < 0.05)and returned to background level at 6h after bilirubin injection compared with the control group. Treatment with TAT-NBD at 0h and 2h after model established showed apparently neuroprotective effects, NF-κB activity was prevented as determined at 3h after modeling, clinical manifestation scores and mortality were significantly lower compared with the vehicle group(P< 0.01), and bodyweight gain was markedly increased(P < 0.01). The TAT-NBD treatment group showed dramatically decreased pro-apoptotic protein Bax expression and mitochondrial cytochrome-c releasing than that of the vehicle group(P < 0.05), meanwhile, the level of anti-apoptotic factor Bcl-2 was significantly increased(P < 0.01). Treated with TAT-NBD also showed remarkably reduced apoptosis rate(P < 0.01) and lower level of IL-1β and TNF-α(P < 0.01). After weaning, the TAT-NBD treatment rats performed better than the vehicles on the neurological evaluation, rotarod test and Morris water maze test(P < 0.05). The mutant peptide had no any significant effect.Conclusion: These results suggested that NF-κB was activated, andinhibition of NF-κB activation by TAT-NBD not only attenuated the acute neurotoxicity, apoptosis, and inflammation, but also improved the long term neurobehavioral impairments in the kernicterus model rats in vivo.Thus, inhibiting NF-κB activation might be a potential therapeutic approach for kernicterus.