Alcoholism is a common condition found in veterans and alcohol abuse is a complicating factor in most chronic medical and psychiatric illnesses. Physical dependence and associated withdrawal constitute a powerful motivational force that perpetuates continued alcohol use/abuse and contributes to relapse. In humans, the identification of genes that influence physical dependence and withdrawal has been limited. Thus, the use of preclinical (animal) models of that closely approximate the clinical situation is essential for finding the gene networks involved. In previous work, we identified a gene for alcohol withdrawal in mice that is now being studied in populations of human alcoholics by NIH-NIAAA intramural scientists. Quantitative trait loci (QTL) are chromosome sites containing alleles (genes) that affect complex traits. We have confirmed QTL on chromosomes (Chr) 1, 4, 11 and 19 that have a major influence on alcohol withdrawal in mice. This proposal is focused Chr 1 QTL (Alcdp1/Alcw1) of large effect on withdrawal after chronic and acute alcohol exposure, which we fine-mapped to a 1.1 Mb interval syntenic with human 1q23.2-23.3. Although there is considerable evidence that vulnerability to withdrawal from a variety of sedative-hypnotics have genetic factors in common, Alcdp1/Alcw1 does not influence pentobarbital (PB) withdrawal. This is a crucial clue in identifying the genes(s) QTG) and mechanism by which Alcdp/Alcw1 affects alcohol withdrawal. Candidate QTG prioritization and testing has and will continue to be informed by probing for effects specific to alcohol and not barbiturates. Alcohol exposure induces oxidative stress, and contrasts with a neutral/antioxidative effect of barbiturate exposure in brain. A major strength of this proposal is that we have identified three Alcdp1/Alcw1 candidates that encode mitochondrial proteins with primary effects on oxidative stress. Additionally, a gene network more broadly involved in oxidative stress is trans-regulated by the QTG or a linked gene and may also contribute to the phenotype. An innovative feature of this proposal is to combine robust behavioral models of alcohol withdrawal with state-of-the-art methods to test the role of oxidative stress in response to alcohol. Using a congenic strain that isolates the 1.1 Mb QTL interval on a uniform background, we propose: (1) Test genetically correlated responses to ethanol and other sedative-hypnotics. (2) Test the hypothesis that genotype- dependent differences in chronic ethanol withdrawal are related to oxidative stress and mitochondrial function. (3) Test that genetic vulnerability to acute ethanol (but not PB) withdrawal is related to oxidative stress and mitochondrial function. (4) Compare gene expression profiles to detect QTL associated gene networks and identify key drivers of gene networks or 'hub' genes. (5) To modify oxidative stress and the expression/function of 'hub' genes to test their role in ethanol withdrawal in vivo. We expect that our results will facilitate progress in human genetics by setting the stage for translational/mechanistic studies.
NARRATIVE Abuse and dependence on alcohol and other sedative-hypnotic drugs continue to be substantial mental health problems that face United States veterans. There are a host of biological (genetic) and environmental factors interacting in a complex manner throughout the addictive process to influence alcohol and drug use/abuse and relapse. We recently identified a chromosomal region with a large effect on alcohol physical dependence and associated withdrawal in a preclinical model, and identified a network of genes involved in oxidative stress that plausibly underlies its mechanism of action on withdrawal behaviors. The focus and overall objective of this renewal application is to utilize robust mouse models of alcohol withdrawal to rigorously test the hypothesis that genotype-dependent differences in oxidative stress and mitochondrial respiratory function contribute to genetic susceptibility for severe alcohol physical dependence and associated withdrawal, as well as genetically correlated behaviors (i.e., ethanol preference drinking, and withdrawal from other abused sedative-hypnotic drugs). The animal models developed for the proposed work will provide a powerful foundation for translational research in which gene networks important in determining liability for development of physical dependence and withdrawal in humans are studied, and for developing gene and drug therapies to enhance treatment and prevention.
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