This project aims to determine the effects of chronic ethanol ingestion by dams on the concentration and function of atRA (all-trans-retinoic acid) in the embryo hippocampus during normal vitamin A nutriture, using new techniques for quantifying atRA and new insights into retinoid function in the hippocampus. The effects of ethanol on retinoid metabolism and function are poorly understood. The notion persists that ethanol inhibits bioactivation of retinol into atRA, but has not been tested directly in vivo during normal vitamin A nutriture. To test this premise, we developed an LC/MS/MS assay capable of quantifying atRA in specific brain areas. We determined during normal vitamin A nutriture that chronic ethanol exposure (36% of calories for 1 month) increases atRA in the adult mouse cortex (2-fold) and hippocampus (20-fold), without affecting other brain areas. Chronic ethanol exposure also increases atRA in the testis, but does not change atRA in several other mouse retinoid-target tissues. Chronic ethanol fed to dams starting e13 increases embryo atRA in the cortex (up to 50-fold) and the hippocampus (up to 20-fold), depending on blood alcohol content, quantified on e19. Emerging insight indicates that atRA affects learning and cognitive ability, besides nervous system development and neuron specification. Because excessive atRA produces teratogenic CNS effects, and the hippocampus relies on retinoid signaling to establish short-term memory, super physiological concentrations of atRA could contribute to ethanol toxicity, including fetal alcohol syndrome. We will test the hypothesis that ethanol-induced increases in embryo hippocampus atRA contributes to ethanol toxicity.
Each aim will determine the effects of dam ethanol ingestion on embryo hippocampus retinoid concentrations and/or function. Wild type and CrbpI-null mice will be evaluated, because ethanol does not increase atRA in hippocampus of CrbpI-null mice.
Aim 1 will determine retinoid concentrations in the embryo hippocampus during development. We will focus on e13 to e18 because hippocampus begins developing between e13-e15 and concludes in the CA1 region by e18.
Aim 2 will test whether dam ethanol ingestion alters embryo atRA-regulated gene expression (transcription and translation).
Aim 3 will test whether ethanol and/or increased atRA affect neurogenesis in the developing hippocampus.
Aim 4 will test chronic ethanol effects on atRA-induced dendritic growth. We propose to answer: 1) what are the effects of chronic ethanol ingestion by dams on concentrations of atRA in the embryo hippocampus during normal vitamin A nutriture;2) do ethanol- induced changes in atRA affect atRA-regulated transcription and translation, atRA processes as a whole (pathway and principle component analysis), or atRA-stimulated dendritic growth or neurogenesis? Even if the outcome reveals the impact of ethanol on atRA is not a major mechanism of its pathology, these studies will provide new insight into mechanisms of ethanol toxicity and retinoid function, and should influence approaches to treating alcoholics.
Vitamin A is essential for vertebrate life, because it is necessary for embryonic development, regulation of metabolism and function of the central nervous system, among many other functions. Alcohol (ethanol) ingestion causes severe depletion of vitamin A storage in the liver, and has been postulated to inhibit activation of vitamin A into its hormonal form, all-trans-retinoic acid (atRA). This project seeks to understand how chronic ethanol ingestion affects the concentrations of atRA in tissues during normal dietary vitamin A intake in the hippocampus area of the brain (the area needed to develop short-term memory), and to determine the effects of ethanol on atRA function in the hippocapus.
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