title: Uncoupling between inflammatory and fibrotic responses to silica: evidence from MyD88 knockout mice.
abstract: The exact implication of innate immunity in granuloma formation and irreversible lung fibrosis remains to be determined. In this study, we examined the lung inflammatory and fibrotic responses to silica in MyD88-knockout (KO) mice. In comparison to wild-type (WT) mice, we found that MyD88-KO animals developed attenuated lung inflammation, neutrophil accumulation and IL-1β release in response to silica. Granuloma formation was also less pronounced in MyD88-KO mice after silica. This limited inflammatory response was not accompanied by a concomitant attenuation of lung collagen accumulation after silica. Histological analyses revealed that while pulmonary fibrosis was localized in granulomas in WT animals, it was diffusely distributed throughout the parenchyma in MyD88-KO mice. Robust collagen accumulation was also observed in mice KO for several other components of innate immunity (IL-1R, IL-1, ASC, NALP3, IL-18R, IL-33R, TRIF, and TLR2-3-4,). We additionally show that pulmonary fibrosis in MyD88-KO mice was associated with the accumulation of pro-fibrotic regulatory T lymphocytes (T regs) and pro-fibrotic cytokine expression (TGF-β, IL-10 and PDGF-B), not with T helper (Th) 17 cell influx. Our findings indicate that the activation of MyD88-related innate immunity is central in the establishment of particle-induced lung inflammatory and granuloma responses. The development of lung fibrosis appears uncoupled from inflammation and may be orchestrated by a T reg-associated pathway.
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: Sandra Lo
authors: SL
authors: Re
authors: Giulia
authors: G
authors: Giordano
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: Yousof
authors: Y
authors: Yakoub
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: Raynal
authors: R
authors: Devosse
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: Francine
authors: F
authors: Uwambayinema
authors: University of Orleans, CNRS, UMR7355, INEM, Transgenose Institute, Orleans, France.
authors: Isabelle
authors: I
authors: Couillin
authors: University of Orleans, CNRS, UMR7355, INEM, Transgenose Institute, Orleans, France.
authors: Bernard
authors: B
authors: Ryffel
authors: de Duve Institute, Université catholique de Louvain, Brussels, Belgium.
authors: Etienne
authors: E
authors: Marbaix
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: Dominique
authors: D
authors: Lison
authors: Louvain centre for Toxicology and Applied Pharmacology (LTAP), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium.
authors: François
authors: F
authors: Huaux
mesh_terms: D000818:Animals; D016207:Cytokines / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D006099:Granuloma / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics / Q000276:immunology; D007150:Immunohistochemistry; D007249:Inflammation / Q000139:chemically induced / Q000235:genetics / Q000276:immunology*; D053582:Interleukin-1alpha / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000235:genetics / Q000276:immunology*; D017472:Receptors, Interleukin-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D012822:Silicon Dioxide / Q000276:immunology* / Q000633:toxicity; D012829:Silicosis / Q000209:etiology / Q000235:genetics / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism; D058504:Th17 Cells / Q000276:immunology / Q000378:metabolism
chemical_list: D016207:Cytokines; D053582:Interleukin-1alpha; D053583:Interleukin-1beta; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D017472:Receptors, Interleukin-1; D012822:Silicon Dioxide