Maternal exposure to fine particulate air pollution induces epithelial-to-mesenchymal transition resulting in postnatal pulmonary dysfunction mediated by transforming growth factor-β/Smad3 signaling

Abstract

Fine particles from air pollution, also called particulate matter, less than 2.5 micrometers in diameter (PM2.5), are a threat to child health. Epidemiological investigations have related maternal exposure to PM2.5 to postnatal respiratory symptoms, such as frequent wheezing, chronic cough, and lung function decrements. However, only few experimental animal studies have been performed to study the effects of PM2.5.The aim of this study was to investigate the effects of maternal exposure to PM2.5 on postnatal pulmonary dysfunction in a rat model and to examine the mechanism of PM2.5-induced morphological pulmonary changes.Timed pregnant Sprague-Dawley rats were treated with PM2.5 (0.1, 0.5, 2.5, or 7.5mg/kg) once every three days from day 0 to 18 of pregnancy. After delivery, pups were sacrificed on postnatal day (PND)1 and 28. The effects of transforming growth factor-beta (TGF-β) on epithelial-mesenchymal transition (EMT) were determined by immunohistochemistry, Western blotting, and quantitative RT-PCR. The offspring underwent pulmonary function measurements on PND28, lung tissues were histopathologically examined, and markers of oxidative stress were measured. Maternally PM2.5-exposed offspring pups displayed significant decreases in lung volume parameters, compliance, and airflow during expiration on PND28. The PM2.5-exposed group showed interstitial proliferation in lung histology, significant oxidative stress in lungs, and up-regulation of TGF-β-induced EMT via increased vimentin and α-smooth muscle actin and decreased E-cadherin levels on PND1 and PND28.These results suggest that EMT up-regulation mediated by the TGF-β/Smad3 pathway plays a role in postnatal pulmonary dysfunction associated with maternal exposure to PM2.5.