Neuroglobin expression and function in the temporal cortex of bilirubin encephalopathy rats

Bilirubin encephalopathy (BE) is a neurological syndrome in newborns, mainly caused by neuronal injury due to excessive oxidative stress produced by unconjugated bilirubin (UCB). Neuroglobin (NGB) can protect the brain by removing oxidative stress species, but its expression and significance in BE are not clear. To address this question, the neonatal BE model was established by injecting UCB into the cerebellomedullary cistern of 7-day-old SD rats. Rats were divided into a sham and BE 6 hr group, BE 12 hr group, BE 24 hr group, and BE 7 d group according to UCB action times. Hematoxylin/eosin and Nissl staining, and electron microscopy were employed to observe the pathological and ultrastructural changes of nerve cells in each group. Immunofluorescence staining was used to detect NGB expression sites and cell types. Western blotting and quantitative PCR served to detect NGB expression and test the mitochondrial apoptosis signal pathway. The results confirm that UCB can lead to pathological damage and ultrastructural changes in rats' temporal cortex, increasing the expression of apoptosis-related proteins Bax, Bcl-2, Cyt c, Caspase-3, and neuronal NGB. UCB promotes NGB expression with an increase in action time and reach a peak at 12 hr. In summary, brain damage induced by UCB will cause an increase in NGB expression, the increasing NGB can inhibit neuron apoptosis in early BE phases. Therefore, promoting the expression of endogenous NGB, to act as a neuroprotective agent may be a potential treatment strategy for BE.