Prenatal nicotine and lung development: role of CHRNA5, addiction and epigenetics

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DESCRIPTION (provided by applicant): Maternal smoking during pregnancy remains a major cause of perinatal morbidity and causes lifelong decreases in pulmonary function and increased risk of asthma in offspring. Despite significant efforts to reduce maternal smoking through public health campaigns and smoking cessation interventions, approximately 13% of all women self-report smoking during pregnancy and this effects the lifelong respiratory health of over 400,000 infants each year. Nicotine addiction is clearly a driving force in the inability of some women to quit smoking during pregnancy and both GWAS and genotyping studies have identified a common polymorphism (rs16969968) in the ¿5 nicotinic acetylcholine receptor (nAChR) that is associated with heavier cigarette use and reduced smoking cessation. Remarkably, our preliminary data suggests that this same polymorphism that increases the likelihood of maternal smoking during pregnancy also increases the degree to which maternal smoking during pregnancy adversely affects offspring pulmonary function. Thus, the primary objective of this proposal is to determine the mechanism by which alterations in the ¿5 nAChR subunit mediate the effects of maternal smoking during pregnancy on lung development and to assess the relative contribution of nicotine addiction versus the direct effects of nicotine on lung. This fundamental question of the role of nicotine addiction versus direct consequences of nicotine on cellular processes is applicable to all smoking related diseases and ultimately must be addressed to prevent and treat smoking related diseases. To decipher between addiction mediated effects and direct end organ mediated effects of perinatal nicotine, we will employ transgenic mouse models combined with both addiction and lung development paradigms. Specifically, we will first use ¿5 knockout mice to delineate the role of ¿5 in lung development. Next we will use mice expressing the wild-type ¿5 subunit and mice with a knockin for the polymorphic ¿5 subunit to compare the effects of a set dose of nicotine to that of the higher doses of nicotine that are self-administered by mice with the polymorphic ¿5 subunit. Lastly, we will examine the role of DNA methylation in the regulation of target genes so as to understand the mechanisms by which in utero nicotine induces persistent changes in lung. This goal will be met by performing quantitative CpG methylation analysis by pyrosequencing within the promoter regions of select genes involved in pulmonary structure and function and in nAChR genes in both mouse and human tissues. The objectives and training components of this proposal will be met by learning basic approaches to studying lung development and function in mice and basics of clinical research. The proposed research project will additionally introduce concepts and models of addiction to successfully unravel the mechanism by which nAChR polymorphisms influences lung development within the setting of heightened addiction. This research has great public health significance to potentially identify the molecular mechanisms by which specific genotypes increase the consequences and likelihood of maternal smoking during pregnancy.