The Biphasic Activation Of Nuclear Factor-kappaB In Brain And Its Role After Subarachnoid Hemorrhage

part? IntroductionIn this part,the background of this study is introduced,including reviews of the mechanism of brain injury after subarachnoid hemorrhage(SAH),the nuclear factor-kappa B(NF-?B)signaling pathway,the relationship between NF-?B and other transcriptional factors,the role of NF-?B in nervous system,and the role of NF-?B inhibitor pyrrolidine dithiocarbamate(PDTC)in clinical therapy.Part? Biphasic activation of nuclear factor-kappa B in experimental models of subarachnoid hemorrhage in vivo and in vitroIt has been proven that nuclear factor-kappa B(NF-?B)is activated as a well-known transcription factor after subarachnoid hemorrhage(SAH).However,the panoramic view of NF-?activity after SAH remained obscure.In this study,cultured neurons were signed into control group and six hemoglobin(Hb)incubated groups.One-hemorrhage rabbit SAH model was produced and the rabbits were divided randomly into one control group and five SAH groups.NF-?B activity was detected by electrophoretic mobility shift assay(EMSA)and immunohistochemistry.Real time polymerase chain reaction(PCR)was performed to assess the downstream genes of NF-?B,such as TNF-?,IL-1?,Bcl-2 and caspase-3.NeuN immunofluorescence and lactate dehydrogenase(LDH)quantification were used to estimate the neuron injury.Double drastically elevated NF-?B activity peaks were detected in rabbit brains and cultured neurons.The downstream gene expressions showed an accordant phase peaks.NeuN positive cells decreased significantly in day 3 and day 10 groups.LDH leakage exhibited significantly increasing in Hb incubated groups,but no significant difference was found between the Hb incubated groups.These results suggest that biphasic increasing of NF-?B activity were induced after SAH,and the early NF-?B activity peak indicated the injury role on neurons;however,the late peak may not involve in the deteriorated effects on neurons.Part ? Potential dual role of nuclear factor-kappa B in brain injury after experimental subarachnoid hemorrhage in rabbitsNuclear factor-kappa B(NF-?B)is an important transcription factor with multiple physiological and pathological functions.The role of NF-?B can be protective or destructive.We aim to discover that NF-?B showing biphasic activity peaks may play decisive roles on neuronal fate after subarachnoid hemorrhage(SAH).Eighty male New Zealand rabbits are assigned to control,SAH,vehicle and pyrrolidine dithiocarbamate(PDTC)groups.Immunofluorescence and electrophoretic mobility shift assay(EMSA)were performed to assess the activation of NF-?B.The levels of inflammatory and apoptosis mediators,such as TNF-?,IL-1?,Bcl-2,caspase-3 were detected by enzyme-linked immunosorbent assay(ELISA)and real-time polymerase chain reaction(PCR).Nissl and immunofluorescent stain was performed to evaluate the neuron injury.NF-?B activity in the brain cortex showed 2 peaks after SAH.Inflammatory mediators also exhibited similar dual phases.PDTC could significantly inhibit the NF-?B activity and inflammatory mediators on two peaks.The suppression of early NF-?B activity significantly decreased neuron injury,while inhibiting the late one could statistically increase neuron injury.The biphasic NF-?B activation in the brain cortex after SAH played a decisive role on neuronal fate.The early NF-?B activity contributed to the brain injury after SAH.Nevertheless,the late NF-?B activity may serve as a protector.