Endothelin B receptor deficiency is associated with an increased rate of neuronal apoptosis in the dentate gyrus

Abstract

The dentate gyrus retains neuronal proliferative potential throughout life. Using immature endothelin B receptor-deficient (sl/sl) rats, a rabbit model of pneumococcal meningitis and autopsy brains from humans who died from pneumococcal meningitis, we explored the role of endothelin B receptors in physiological and pathological neuronal apoptosis in the dentate gyrus. At postnatal days 3–4, the rate of apoptosis in the dentate gyrus was high in all rats, declining to low levels in wild-type rats (+/+) on days 14 and 22, but remaining high in both homozygous (sl/sl) and heterozygous (sl/+) endothelin B receptor-deficient rats. Increased apoptosis was not significantly compensated for by neuronal proliferation. Hippocampal neuronal cultures also exhibited genotype-dependent apoptosis with the highest rate in neurons from homozygous endothelin B receptor-deficient (sl/sl) rats. In rabbit and human pneumococcal meningitis, increased apoptosis in the dentate gyrus was associated with loss of neuronal endothelin B receptor immunoreactivity. In conclusion, endothelin B receptors appear to act as neuronal survival factors in the dentate gyrus in rodents and man, both during postnatal development and under pathological conditions.