BILIRUBIN ENCEPHALOPATHY--MODELS AND METABOLIC STUDIES

这项建议的主要目的是发展候选人的能力

The prime objective of this proposal is to development of the candidate's skills in basic research while gaining insight into the pathophysiology and mechanisms of kernicterus and bilirubin toxicity. By coursework, discussions and supervised investigation, understanding will be gained in cellular metabolism and physiology at a level particularly appropriate for a clinical investigator in neonatology and developmental biology. The scientific objective of this proposal is aimed at understanding the still obscure underlying cellular injuries fundamental kernicterus. Kernicterus, although primarily associated with erythroblastosis fetalis previously, has been found in 15-25% of autopsied newborns. The development of kernicterus depends on not only on serum level of unconjugated bilirubin; apparently binding to albumin and integrity of the blood-brain barrier are at least two mitigating factors affecting bilirubin injury. Prior models have been developed to determine what are the characteristic histopathologic and behavioral changes of kernicterus. However, previous studies including our own have shown that some of these models produce only a transient bilirubin encephalopathy (TBE) in these animals. In vitro, bilirubin has been shown to be toxic to many cellular functions of many different types of cells. Which of these toxicities predominates in kernicterus is known; determining this depends upon demonstration of comparable physiologic dysfunction in both in vivo and in vitro models. This proposed research plan initially develops and characterizes different animal models of kernicterus, including a hemolysis-induced model simulating hemolytic conditions associated with kernicterus. Histopathology and behavioral observations will define kernicterus injury. Kernicterus injury will then be characterized by neurophysiology, magnetic resonance imaging and spectroscopy studies, including evaluation of energy metabolism changes. Using these physiologic and metabolic markers, similarities and distinction between kernicterus and TBE will be studied. In vivo studies will also examine therapies to decrease bilirubin production and their ability to prevent kernicterus. In vitro studies will further evaluate bilirubin toxicity on neural-derived cells. Magnetic resonance spectroscopy studies of energy metabolism will allow direct comparison to in vivo animal models of kernicterus and the brain energy metabolism changes seen by our planned studies. This will help validate the use of this model for further studies of bilirubin toxicity. Subsequent studies will evaluate cellular environment including pH and albumin concentration, as it affects bilirubin toxicity in these cells. Finally, investigation of bilirubin toxicity will include assaying effects on membrane physiology of ion channels. These channels are well- characterize in neuroblastoma cells but not as affected by bilirubin. If necessary, contingencies are planned to develop alternate cell lines for in vitro studies of bilirubin toxicity.