Early Postnatal Secondhand Smoke Exposure Disrupts Bacterial Clearance and Abolishes Immune Responses in Muco-Obstructive Lung Disease

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Secondhand smoke (SHS) exposure has been linked to the worsening of ongoing lung diseases. However, whether SHS exposure affects the manifestation and natural history of imminent pediatric muco-obstructive airway diseases such as cystic fibrosis remains unclear. To address these questions, we exposed transgenic (-Tg) mice to SHS from postnatal day (PND) 3-21 and lung phenotypes were examined at PND22. Although a majority of filtered air (FA)-exposed -Tg (FA-Tg) mice successfully cleared spontaneous bacterial infections by PND22, the SHS-exposed -Tg (SHS-Tg) mice failed to resolve these infections. This defect was associated with suppressed antibacterial defenses, i.e., phagocyte recruitment, IgA secretion, and Muc5b expression. Whereas the FA-Tg mice exhibited marked mucus obstruction and responses, SHS-Tg mice displayed a dramatic suppression of these responses. Mechanistically, downregulated expression of IL-33, a stimulator of type II innate lymphoid cells, in lung epithelial cells was associated with suppression of neutrophil recruitment, IgA secretions, responses, and delayed bacterial clearance in SHS-Tg mice. Cessation of SHS exposure for 21 d restored previously suppressed responses, including phagocyte recruitment, IgA secretion, and mucous cell metaplasia. However, in contrast with FA-Tg mice, the SHS-Tg mice had pronounced epithelial necrosis, alveolar space consolidation, and lymphoid hyperplasia; indicating lagged unfavorable effects of early postnatal SHS exposure in later life. Collectively, our data show that early postnatal SHS exposure reversibly suppresses IL-33 levels in airspaces which, in turn, results in reduced neutrophil recruitment and diminished response. Our data indicate that household smoking may predispose neonates with muco-obstructive lung disease to bacterial exacerbations.

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Journal of immunology (Baltimore, Md. : 1950)

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