Maternal Nicotine Exposure Exacerbates Neonatal Hyperoxia-Induced Lung Fibrosis in Rats

Abstract

Background: Maternal nicotine exposure increases lung collagen in fetal and newborn animals. Connective tissue growth factor (CTGF) plays a role in hyperoxia-induced pulmonary fibrosis. Objective: To determine whether pre- and postnatal nicotine exposure can augment CTGF expression and postnatal hyperoxia-induced lung fibrosis. Methods: Nicotine was administered to pregnant Sprague-Dawley rats at a dose of 6 mg/kg/day from gestational days 7-21 (prenatal nicotine-treated group) and gestational day 7 to postnatal day 14 (pre- and postnatal nicotine-treated group). A control group of pregnant dams was injected with an equal volume of saline. Within 12 h of birth, rats were exposed to room air or 1 week of >95% O₂ and an additional 2 weeks of 60% O₂ (3 weeks of hyperoxia). Lungs were taken for total collagen, CTGF expression and histological analyses. Results: In each maternal treatment group, the rats reared in hyperoxia had a higher total collagen compared with rats reared in room air on postnatal days 7 and 21. Collagen content was significantly higher in rats born to pre- and postnatal nicotine-treated dams than rats born to saline-treated and prenatal nicotine-treated dams on postnatal days 7 and 21. Pre- and postnatal nicotine exposure and neonatal hyperoxia exposure increased CTGF expression on postnatal days 7 and 21. Conclusions: CTGF may be involved in the pathogenesis of lung fibrosis induced by maternal nicotine and neonatal hyperoxia, and maternal nicotine exposure exacerbates neonatal hyperoxia-induced lung fibrosis. These results are relevant to neonates who require supplemental oxygen and are exposed to the breast milk of smoking mothers during infancy.