Fra-2–expressing macrophages promote lung fibrosis
Alvaro C. Ucero, Latifa Bakiri, Ben Roediger, Masakatsu Suzuki, Maria Jimenez, Pratyusha Mandal, Paola Braghetta, Paolo Bonaldo, Luis Paz-Ares, Coral Fustero-Torre, Pilar Ximenez-Embun, Ana Isabel Hernandez, Diego Megias, Erwin F. Wagner
Alvaro C. Ucero, Latifa Bakiri, Ben Roediger, Masakatsu Suzuki, Maria Jimenez, Pratyusha Mandal, Paola Braghetta, Paolo Bonaldo, Luis Paz-Ares, Coral Fustero-Torre, Pilar Ximenez-Embun, Ana Isabel Hernandez, Diego Megias, Erwin F. Wagner
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Research Article Inflammation Pulmonology

Fra-2–expressing macrophages promote lung fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a deadly disease with limited therapies. Tissue fibrosis is associated with type 2 immune response, although the causal contribution of immune cells is not defined. The AP-1 transcription factor Fra-2 is upregulated in IPF lung sections, and Fra-2 transgenic mice (Fra-2Tg) exhibit spontaneous lung fibrosis. Here, we show that bleomycin-induced lung fibrosis is attenuated upon myeloid inactivation of Fra-2 and aggravated in Fra-2Tg bone marrow chimeras. Type VI collagen (ColVI), a Fra-2 transcriptional target, is upregulated in 3 lung fibrosis models, and macrophages promote myofibroblast activation in vitro in a ColVI- and Fra-2–dependent manner. Fra-2 or ColVI inactivation does not affect macrophage recruitment and alternative activation, suggesting that Fra-2/ColVI specifically controls the paracrine profibrotic activity of macrophages. Importantly, ColVI-KO mice and ColVI-KO bone marrow chimeras are protected from bleomycin-induced lung fibrosis. Therapeutic administration of a Fra-2/AP-1 inhibitor reduces ColVI expression and ameliorates fibrosis in Fra-2Tg mice and in the bleomycin model. Finally, Fra-2 and ColVI positively correlate in IPF patient samples and colocalize in lung macrophages. Therefore, the Fra-2/ColVI profibrotic axis is a promising biomarker and therapeutic target for lung fibrosis and possibly other fibrotic diseases.

Authors

Alvaro C. Ucero, Latifa Bakiri, Ben Roediger, Masakatsu Suzuki, Maria Jimenez, Pratyusha Mandal, Paola Braghetta, Paolo Bonaldo, Luis Paz-Ares, Coral Fustero-Torre, Pilar Ximenez-Embun, Ana Isabel Hernandez, Diego Megias, Erwin F. Wagner

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Figure 7

AP-1 inhibition reverts lung fibrosis in Fra-2Tg mice.

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AP-1 inhibition reverts lung fibrosis in Fra-2Tg mice. (A) Schematic for...
(A) Schematic for AP-1 inhibitor T-5224 therapeutic protocol in Fra-2Tg mice. All data originate from 3 independent experiments designed as randomized blocks. Asterisks indicate when the plethysmography was performed within the experiment timeline. (B) Quantification of sirius red–positive areas in lungs at the end of the experiment. **P < 0.01, 1-way ANOVA; Bonferroni’s post test. (C) Hydroxyproline content in lungs (left lobe). **P < 0.01; ***P < 0.001, 1-way ANOVA; Bonferroni’s post test. (D) Immunoblot analysis of Fra-2, procollagen I, type I collagen, and fibronectin in lung lysates at the end of the experiment. Band density quantification is shown in the graph, with individual values relative to vinculin (loading control). **P < 0.01, unpaired 2-tailed t test. (E) Quantification of Fra-2–positive nuclei in lung IF relative to total cells. *P < 0.05, unpaired 2-tailed t test. (F) qRT-PCR analysis of ColVI genes in the lungs of Fra-2Tg and WT controls treated with T-5224 or PVP at the end of the experiment. Relative expression in WT+PVP is set to 1. *P < 0.05; **P < 0.01, 1-way ANOVA; Bonferroni’s post test. (G) Quantification of lung ColVI-positive area in IHC staining. *P < 0.05, 1-way ANOVA; Bonferroni’s post test. (H) Longitudinal analyses of respiratory function of Fra-2Tg and WT controls with T-5224 or PVP. Note that the T-5224 or vehicle treatment started around 12 weeks of age, when animal respiratory function was already compromised (arrow). *P < 0.05; **P < 0.01; ***P < 0.001, 2-way ANOVA; Bonferroni’s post test.