Role Of Nuclear Factor-ΚB Activation In Bilirubin-induced Rat Hippocampal Neuronal Apoptosis And The Effect Of TAT-NBD Intervention

ObjectiveTo investigate the role of nuclear factor-κB (NF-κB) activation inbilirubin-induced apoptosis of rathippocampal neurons and the effect ofTAT-NBD intervention on bilirubin neurotoxicity.To study the effect of intraperitoneal administration of TAT-NBD onbilirubin encephalopathy and on improving learning and memory ability.MethodsPrimary-cultured rat hippocampal neurons were treated with TAT-NBDin the initial6or24h or in the latter6h during a24-h bilirubin exposure of thecells (early, continuous and late intervention groups, respectively).Immunocytochemistry was performed to detect NF-κB p65proteinexpression, and the cell survival and apoptosis were assessed with amodified MTT assay, Annexin V-FITC/PI and TUNEL assay. IL-1βconcentration in the supernatant was determined with ELISA.We randomly divided5-day Sprague-Dawley rat pups(10-15g) into three groups: control group, bilirubin encephalopathy group and TAT-NBDintervention group. Weight was daily recorded within3days after modelingand acute and chronic mortality rate was also calculated. Morris watermaze was performed at the age of28days.ResultsCompared with the control cells, bilirurin-treated cells showed asignificantly increased NF-κB p65protein expression (P<0.01), whichreached the peak level at6and24h (P <0.01). The cell survival rate in earlyTAT-NBD intervention group was (80.784±9.767)%, significantly lowerthan that of the control group (P <0.01) but higher than that of bilirubingroup (P <0.01); the apoptotic rate in early TAT-NBD intervention groupwas significantly higher than that of control group (P <0.01) but lower thanthat of bilirubin group (P <0.01). IL-1β concentration was significantlylower in early TAT-NBD intervention group (15.348±0.812pg/ml) than inbilirubin group (P <0.05). The continuous and late TAT-NBD interventiongroups showed comparable cell survival rate, apoptotic rate and IL-1βconcentration with bilirubin group (P>0.05).Bodyweight gain in TAT-NBD intervetion group was higher thanbilirubin encephalopathy group but no significant differences（P>0.05）,lower than control group(P＜0.01). The acute mortality rate of TAT-NBDintervention group was dramatically lower than bilirubin encephalopathygroup（P<0.01）. In morris water maze, the excape latency of TAT-NBD intervention group rats was dramatically shorter than that of bilirubinencephalopathy rat（sP <0.05）,higher than that of control group（P <0.05）;the times acrossing the platform and time percentage searching platform insafety quadrant of TAT-NBD intervention group rats were apparentlylonger than these of bilirubin encephalopathy rats（P<0.05）ConclusionNF-κB bidirectionally regulates bilirubin-induced apoptosis of rathippocampal neurons. Selective inhibition of the early peak of NF-κB byTAT-NBD offers neuroprotective effect. TAT-NBD can be potentially usedfor prophylaxis of bilirubin-induced brain injury.Early intraperitoneal administration of TAT-NBD could markedlyimprove learning and memory ability of bilirubin encephalopathy rats,meanwhile reducing the acute mortality rate apparently, and improvingforaging ability.