Bilirubin encephalopathy: A study of neuronal subpopulations and neurodegenerative mechanisms in 12 autopsy cases

Bilirubin encephalopathy (BE), which includes acute (kernicterus) and chronic (postkernicteric) forms, results from severe neonatal jaundice. In order to investigate neurodegenerative mechanisms in autopsy cases of BE, we immunohistochemically examined expressions of neurotransmitters, neuropeptides, and calcium-binding proteins in the basal ganglia; and deposition of oxidative products. Expression of tyrosine hydroxylase was reduced in the putamen in cases of acute BE, and in the globus pallidus in cases of acute and chronic postkernicteric BE. Methionine–enkephalin expression was reduced in the external segment of the globus pallidus in cases of acute and chronic postkernicteric BE, and immunoreactivity for substance P was severely altered in both internal and external segments in cases of chronic postkernicteric BE. A decrease in the number of parvalbumin-immunoreactive interneurons in the external segment of the globus pallidus was observed predominantly in cases of acute BE, whereas the number of interneurons immunoreactive for calbindin-D28K was reduced in the putamen in cases of chronic postkernicteric BE. Nuclear immunoreactivity for 8-hydroxy-2′-deoxyguanosine was seen in the putamen in half of the BE cases. These findings indicated that the putamen was impaired in BE and the pallidal external segment was also damaged in the acute form of BE, suggesting that oxidative damage to DNA is implicated in lesions of the basal ganglia.