According to the latest statistics from the CDC in 1999, 12.3% of American women smoked during pregnancy, translating to over 400,000 smoke-exposed infants. Smoking during pregnancy is the largest preventable cause of low birth weight, premature delivery, neonatal morbidity, and mortality. Indeed it has been estimated that 10% of all fetal and neonatal deaths are due to smoking during pregnancy. Perhaps less well appreciated is the recent, evidence that smoking during pregnancy directly and adversely affects lung development as manifested by altered pulmonary function and increased respiratory illness in children born of smoking mothers. Remarkably, how smoking produces these effects is unknown. While the cause of pulmonary damage caused by maternal smoking is likely to be multifactorial, it is the basic hypothesis of this application that part of the effect of maternal smoking on lung is mediated by nicotine transported across the placenta to interact with alpha7 nicotinic receptors in developing lung. Our preliminary evidence indicates 1) that alpha7 nicotinic receptors are highly expressed in developing lung; 2) that prenatal nicotine exposure alters alpha7 nicotinic receptor expression in lung; and 3) that collagen gene expression is markedly up-regulated in areas of altered alpha7. Suggesting that nicotine's effect on collagen is mediated by alpha7 receptors, prenatal nicotine exposure has no effect on collagen gene expression in the lungs of cx7 knockout mice. In exciting preliminary data, nicotine inhibits fibroblast proliferation from cells isolated from wildtype neonatal mouse lung, but has no effect on proliferation of fibroblasts from alpha7 knockout mice. This suggests that some of the growth retardation caused by smoking during pregnancy may be mediated by the interaction of nicotine with alpha7 receptors. In this application, using alpha7 knockout and alpha7 gain of function mice, we propose to first demonstrate a link between the effects of prenatal nicotine exposure and alpha7 nAChR, then using cultured pulmonary fibroblasts and epithelial cells begin to determine the mechanism by which nicotine produces these effects. Based on our preliminary data and epidemiologic data on human infants, we will focus on 3 aspects of smoking's effects on lung development: pulmonary function as measured by active and passive tests, cell growth, and collagen expression. From these studies will come some of the first explanations of the molecular mechanisms that underlie the effects of smoking during pregnancy on lung development. These findings will also potentially point to ways to block some of those effects of smoking during pregnancy as well as assist in fighting smoking during pregnancy.
| Wongtrakool, Cherry; Wang, Ningshan; Hyde, Dallas M et al. (2012) Prenatal nicotine exposure alters lung function and airway geometry through ?7 nicotinic receptors. Am J Respir Cell Mol Biol 46:695-702 |
