Impaired defenses of neonatal mouse alveolar macrophage with cftr deletion are modulated by glutathione and TGFβ1

Abstract

Our understanding of the intrinsic effects of cystic fibrosis (CF) transmembrane conductance regulator (cftr) deletion on resident neonatal alveolar macrophage (AM) remains limited. We previously demonstrated that diminished glutathione (GSH) or excessive AM transforming growth factor beta one (TGFβ1) contributes to AM dysfunction in a variety of disease states. In this study, using a gut-corrected cftr neonatal knockout (KO) mouse model and a siRNA-manipulated macrophage-like cell line (THP-1 cell), we hypothesized (1) that cftr mutation alone increases neonatal AM oxidant stress and cellular TGFβ1 signaling via altered GSH, thereby impairing cellular function, and (2) that exogenous GSH attenuates AM alterations and dysfunction in the KO AM. In neonatal KO mice, the baseline bronchoalveolar lavage fluid demonstrated a near doubling in mixed disulfides (P ≤ 0.05) and oxidized GSSG (P ≤ 0.05) without concurrent inflammation compared to WT littermates. KO AM demonstrated diminished AM thiols (P ≤ 0.05), increased AM mitochondrial ROS (P ≤ 0.05), increased AM TGFβ1 (P ≤ 0.05) with increased TGFβ1 signaling (P ≤ 0.05), and impaired phagocytosis (P ≤ 0.05). KO AM mitochondrial ROS was modulated by exogenous GSH (P ≤ 0.05). Conversely, TGFβ1 was reduced (P ≤ 0.05) and impaired phagocytosis was rescued (P ≤ 0.05) by exogenous GSH in the KO AM. These results suggest that an altered neonatal AM phenotype may contribute to the initiation of lung inflammation/infection in the CF lung. Modulation of the AM in the neonatal CF lung may potentially alter progression of disease.