The primary goal of this research project is to delineate the mechanisms of cellular injury underlying the genesis of malformations that result from maternal alcohol abuse. We have previously identified specific cell populations in early mouse embryos that are selectively vulnerable to the cytotoxic effects of ethanol. Lethal injury to these cell populations, including cranial neural crest cells (NCCs), appear to be a major factor in subsequent malformations that typify Fetal Alcohol Syndrome. We have shown that ethanol-induced death of cultured mouse NCCs is diminished by GMl ganglioside, as well as by the free radical scavengers superoxide dismutase (SOD), alpha tocopherol, and catalase. SOD also protects cultured whole embryos against ethanol-induced malformations. For the current proposal, the primary hypothesis that we will test is that ethanol-induced injury to NCCs is mediated by free radical generation, culminating in apoptotic cell death. Primarily utilizing laser scanning confocal microscopy (LSCM) and parameter-specific fluorophores to examine living cultured NCCs, we will analyze sequential cellular changes that follow ethanol exposure. Specifically, we will monitor free radical generation, alterations in cytoplasmic and mitochondrial Ca2+ concentrations and mitochondrial membrane potential, onset of the mitochondrial permeability transition, and loss of viability. Cell death will be characterized as apoptosis versus necrosis using vital staining, morphological criteria, and in situ labeling. The ability of selected agents to either exacerbate or ameliorate the observed specific cellular changes will be examined to provide information regarding the role of these various parameters in ethanol-induced cellular injury. These studies will be extended to analyses of the mechanisms of ethanol's cytotoxicity and teratogenicity in whole embryos. Additionally, the potential for early embryos and NCCs to generate free radicals via ethanol metabolism catalyzed by the cytochrome P450 enzyme, CYP2El, and the significance of this route of metabolism relative to ethanol-induced free radical generation, cytotoxicity and teratogenesis will be examined using cyp2el knockout mice and immunocytochemical analyses. We will also test the hypothesis that lethal cellular injury or malformation may occur at relatively low ethanol concentration as a result of concurrent free radical-based reperfusion injury (as is expected in vivo to follow ethanol-induced vasoconstriction and subsequent clearance). For this, both cultured NCCs and mouse embryos will be exposed concurrently to ethanol and stimulated reperfusion and monitored primarily using LSCM for analyses of cellular changes, and using morphological parameters and vital staining for end point determinations in whole organisms.
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