Title: Epithelial Expression of an Interstitial Lung Disease-Associated Mutation in Surfactant Protein-C Modulates Recruitment and Activation of Key Myeloid Cell Populations in Mice.
Authors: Venosa, Alessandro; Katzen, Jeremy; Tomer, Yaniv; Kopp, Meghan; Jamil, Sarita; Russo, Scott J; Mulugeta, Surafel; Beers, Michael F
Published In J Immunol, (2019 05 01)
Abstract: Patients with idiopathic pulmonary fibrosis (IPF) often experience precipitous deteriorations, termed "acute exacerbations" (AE), marked by diffuse alveolitis and altered gas exchange, resulting in a significant loss of lung function or mortality. The missense isoleucine to threonine substitution at position 73 (I73T) in the alveolar type 2 cell-restricted surfactant protein-C (SP-C) gene (SFTPC) has been linked to clinical IPF. To better understand the sequence of events that impact AE-IPF, we leveraged a murine model of inducible SP-CI73T (SP-CI73T/I73TFlp+/- ) expression. Following administration of tamoxifen to 8-12-wk-old mice, an upregulation of SftpcI73T initiated a diffuse lung injury marked by increases in bronchoalveolar lavage fluid (BALF) protein and histochemical evidence of CD45+ and CD11b+ cell infiltrates. Flow cytometry of collagenase-digested lung cells revealed a transient, early reduction in SiglecFhiCD11blowCD64hiCD11chi macrophages, countered by the sequential accumulation of SiglecFloCD11b+CD64-CD11c-CCR2+Ly6C+ immature macrophages (3 d), Ly6G+ neutrophils (7 d), and SiglecFhiCD11bhiCD11clo eosinophils (2 wk). By mRNA analysis, BALF cells demonstrated a time-dependent phenotypic shift from a proinflammatory (3 d) to an anti-inflammatory/profibrotic activation state, along with serial elaboration of monocyte and eosinophil recruitment factors. The i.v. administration of clodronate effectively reduced total BALF cell numbers, CCR2+ immature macrophages, and eosinophil influx while improving survival. In contrast, resident macrophage depletion from the intratracheal delivery of clodronate liposomes enhanced SftpcI73T -induced mortality. These results using SftpcI73T mice provide a detailed ontogeny for AE-IPF driven by alveolar epithelial dysfunction that induces a polycellular inflammation initiated by the early influx of proinflammatory CCR2+Ly6Chi immature macrophages.
PubMed ID: 30910861
MeSH Terms: Animals; Antigens, CD/genetics; Antigens, CD/immunology; Eosinophils/immunology; Eosinophils/pathology; Intercellular Signaling Peptides and Proteins/genetics; Intercellular Signaling Peptides and Proteins/immunology*; Lung Diseases, Interstitial/drug therapy; Lung Diseases, Interstitial/genetics; Lung Diseases, Interstitial/immunology*; Lung Diseases, Interstitial/pathology; Macrophages/immunology*; Macrophages/pathology; Mice; Mice, Transgenic; Mutation*; Neutrophils/immunology; Neutrophils/pathology; Respiratory Mucosa/immunology*; Respiratory Mucosa/pathology; Tamoxifen/pharmacology; Up-Regulation/drug effects; Up-Regulation/immunology*