Project III- Impact of Hypoxia-Ischemia and/or Inflammation on Lipid Rafts in Cerebellum

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In the term newborn (equivalent to the postnatal day (PN) 10 rat), the cerebellum is vulnerable to the effects of hypoxia-ischemia. During this period of time, rapid change in the cerebellum is taking place: the cerebellar Purkinje neurons, the deep cerebellar nuclear neurons and the cerebellar granule cells are rapidly proliferating, and extending their axons and the numbers of cerebellar microglia are increasing. Our lab is focused on lipid raft function and dysfunction in the cerebellum and in other neurodevelopmental disorders with a primary focus on ethanol, the causative agent of fetal alcohol spectrum disorder. Lipid rafts are dynamic microdomains of the plasma membrane which regulate signal transduction and protein trafficking. Hypoxia/ischemia (H/I) may cause alterations in signaling or generate reactive oxygen species (ROS). ROS may cause oxidation of lipids and therefore lipid raft dysfunction. These changes can lead to altered cerebellar development with long term consequences for cerebellar function. L1 cell adhesion molecule (L1), a molecule critical for brain development, and the toll like receptor, TLR4, can be used as reporters for lipid raft function in cerebellar granule neurons (CGN), Purkinje neurons (PN), deep cerebellar nuclear neurons (DCN) and cerebellar microglia. Choline, an essential nutrient and precursor to phosphatidylcholine (PtdCho) and sphingomyelin (SM), both important in lipid raft regulation, improves lipid raft function and behavior following alcohol exposure. Our preliminary data using PN7 rats shows that lipid rafts are dysfunctional in the cortex following H/I and that choline/GM1 ganglioside partially prevents this effect. In addition, choline supplementation protects L1 signaling, lipid raft distribution and cerebellar mediated behavior from the effects of other neurotoxicants. Our hypothesis is that H/I at PN10 causes lipid raft dysfunction in CGN, PN, DCN and microglia leading to poor cerebellar function. Inflammation caused by LPS synergistically increases this dysfunction, and hypothermia, choline, and/or ceftriaxone will partially ameliorate these effects. We will use PN10 rat pups (term equivalent) and the modified Rice-Vanucci model of H/I. Our three specific aims are: 1) Determine lipid raft function and composition in whole cerebellum and CGN, PN and DCN following H/I with or without prior LPS induced inflammation; 2) Determine lipid raft function and composition in cerebellar microglia following H/I with or without prior LPS induced inflammation; 3) Determine if hypothermia, choline, and/or ceftriaxone ameliorates 1) the acute alterations in function and composition of lipid rafts after H/I and H/I with prior inflammation in cerebellum, CGN, PN, DCN and microglia; 2) effects of H/I with or without inflammation on cerebellar related behaviors. Our overarching goal is to reduce the morbidity associated with H/I in neonates.