Effects of nicotine on pulmonary surfactant proteins A and D in ovine lung epithelia

Abstract

Maternal smoking during pregnancy increases the incidence and severity of respiratory infections in neonates. Surfactant proteins A and D (SP-A and SP-D, respectively) are components of pulmonary innate immunity and have an important role in defense against inhaled pathogens. The purpose of this study was to determine if nicotine exposure during the third trimester of pregnancy alters the expression of SP-A and SP-D of fetal lung epithelia. Pregnant ewes were assigned to four groups; a nicotine-exposed full-term and pre-term group, and control full-term and pre-term group. Lung tissue was collected for Western blot and IHC analysis of SP-A level, Western blot analysis of SP-D level and qPCR analysis of SP-A and SP-D mRNA expression. Exposure to nicotine significantly decreased SP-A gene expression (P = 0.01) and SP-A protein level in pre-term lambs. This finding suggests that maternal nicotine exposure during the last trimester of pregnancy alters a key component of lung innate immunity in offspring.

Fig. 1

The relative SP-A mRNA and SP-D mRNA expression in PTC and FTC lambs as well as PTN and FTN lambs. The FTC and PTC values are equal to one. The PTN and FTN values are presented relative to the corresponding controls. The SP-A mRNA expression is significantly reduced (P = 0.01) in PTN lambs (n = 7 lambs) when compared to PTC lambs (n = 6 lambs). There is no significant change in SP-A mRNA expression between FTN and FTC lambs. Although maternal nicotine administration had a tendency to decrease the SP-D mRNA expression in the PTN lambs (n = 7 lambs) when compared to the PTC (n = 6 lambs), this difference was not statistically significant (P = 0.09). There is no significant change in SP-D mRNA expression between FTN and FTC lambs.

Fig. 2

Representative immunohistochemical detection of SP-A protein in bronchial/bronchiolar epithelium of FTC-(A), FTN-(B), PTC-(C), and PTN-(D) lambs. Arrows depict epithelial cells with SP-A protein expression. There was no statistically significant difference in SP-A level between PTN and PTC group. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Fig. 3

Representative Western blot detection of the SP-A and SP-D proteins in the lung tissue of the PTC and PTN lambs. The SP-A protein bands in PTN group are less detectable when compared to PTC group. There is no difference in SP-D protein bands between PTN and PTC group.

Fig. 4

Representative Western blot detection of the SP-A and SP-D proteins in the lung tissue of the FTC and FTN lambs. There are no differences in SP-A and SP-D protein bands between FTN and FTC groups.