Hyperbilirubinemic Serum Is Cytotoxic and Induces Apoptosis in Murine Astrocytes

Background: High levels of unconjugated bilirubin can be neurotoxic and gliotoxic. However, the effect of serum from patients with neonatal indirect hyperbilirubinemia on astrocyte viability has never been investigated. Objectives: In the present study, we searched for the possible toxic effect of hyperbilirubinemic serum on murine astrocytes. Methods: Heat-inactivated patient serum was added to astrocyte cultures at different concentrations varying from 1 to 20%, and cultures were incubated for 24, 48, and 72 h. Sera from healthy infants without hyperbilirubinemia were used as controls. Cytotoxicity was evaluated according to the release of lactate dehydrogenase in the culture medium. Apoptotic cell death was determined by anti-single-strand DNA immunostaining. Results: The results of the present study show that hyperbilirubinemic serum induces cytotoxicity and apoptotic astrocyte death in a concentration- and time-dependent manner. Conclusions: We conclude that serum from patients with neonatal indirect hyperbilirubinemia is cytotoxic to murine astrocytes.