Title: Peroxisome Proliferator-activated Receptor-γ Deficiency Exacerbates Fibrotic Response to Mycobacteria Peptide in Murine Sarcoidosis Model.

Authors: Malur, Anagha; Mohan, Arjun; Barrington, Robert A; Leffler, Nancy; Malur, Amrita; Muller-Borer, Barbara; Murray, Gina; Kew, Kim; Zhou, Chuanzhen; Russell, Josh; Jones, Jacob L; Wingard, Christopher J; Barna, Barbara P; Thomassen, Mary Jane

Published In Am J Respir Cell Mol Biol, (2019 08)

Abstract: We established a murine model of multiwall carbon nanotube (MWCNT)-elicited chronic granulomatous disease that bears similarities to human sarcoidosis pathology, including alveolar macrophage deficiency of peroxisome proliferator-activated receptor γ (PPARγ). Because lymphocyte reactivity to mycobacterial antigens has been reported in sarcoidosis, we hypothesized that addition of mycobacterial ESAT-6 (early secreted antigenic target protein 6) to MWCNT might exacerbate pulmonary granulomatous pathology. MWCNTs with or without ESAT-6 peptide 14 were instilled by the oropharyngeal route into macrophage-specific PPARγ-knockout (KO) or wild-type mice. Control animals received PBS or ESAT-6. Lung tissues, BAL cells, and BAL fluid were evaluated 60 days after instillation. PPARγ-KO mice receiving MWCNT + ESAT-6 had increased granulomas and significantly elevated fibrosis (trichrome staining) compared with wild-type mice or PPARγ-KO mice that received only MWCNT. Immunostaining of lung tissues revealed elevated fibronectin and Siglec F expression on CD11c+ infiltrating alveolar macrophages in the presence of MWCNT + ESAT-6 compared with MWCNT alone. Analyses of BAL fluid proteins indicated increased levels of transforming growth factor (TGF)-β and the TGF-β pathway mediator IL-13 in PPARγ-KO mice that received MWCNT + ESAT-6 compared with wild-type or PPARγ-KO mice that received MWCNT. Similarly, mRNA levels of matrix metalloproteinase 9, another requisite factor for TGF-β production, was elevated in PPARγ-KO mice by MWCNT + ESAT-6. Analysis of ESAT-6 in lung tissues by mass spectrometry revealed ESAT-6 retention in lung tissues of PPARγ-KO but not wild-type mice. These data indicate that PPARγ deficiency promotes pulmonary ESAT-6 retention, exacerbates macrophage responses to MWCNT + ESAT-6, and intensifies pulmonary fibrosis. The present findings suggest that the model may facilitate understanding of the effects of environmental factors on sarcoidosis-associated pulmonary fibrosis.

PubMed ID: 30741559

MeSH Terms: Animals; Antigens, Bacterial/pharmacology*; Bacterial Proteins/pharmacology*; Bronchoalveolar Lavage; Bronchoalveolar Lavage Fluid; CD11 Antigens/metabolism; Disease Models, Animal; Fibronectins/metabolism; Fibrosis/metabolism; Inflammation; Lung/pathology; Macrophages, Alveolar/metabolism*; Macrophages/metabolism; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Knockout; Nanotubes, Carbon/chemistry; PPAR gamma/deficiency*; PPAR gamma/genetics; Pulmonary Fibrosis/genetics; Pulmonary Fibrosis/microbiology*; Sarcoidosis, Pulmonary/microbiology*; Sarcoidosis, Pulmonary/pathology