MAPK mutations and cigarette smoke promote the pathogenesis of pulmonary Langerhans cell histiocytosis
Huan Liu, Andrew R. Osterburg, Jennifer Flury, Zulma Swank, Dennis W. McGraw, Nishant Gupta, Kathryn A. Wikenheiser-Brokamp, Ashish Kumar, Abdellatif Tazi, Yoshikazu Inoue, Masaki Hirose, Francis X. McCormack, Michael T. Borchers
Huan Liu, Andrew R. Osterburg, Jennifer Flury, Zulma Swank, Dennis W. McGraw, Nishant Gupta, Kathryn A. Wikenheiser-Brokamp, Ashish Kumar, Abdellatif Tazi, Yoshikazu Inoue, Masaki Hirose, Francis X. McCormack, Michael T. Borchers
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Research Article Immunology Pulmonology

MAPK mutations and cigarette smoke promote the pathogenesis of pulmonary Langerhans cell histiocytosis

Abstract

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare smoking-related lung disease characterized by dendritic cell (DC) accumulation, bronchiolocentric nodule formation, and cystic lung remodeling. Approximately 50% of patients with PLCH harbor somatic BRAF-V600E mutations in cells of the myeloid/monocyte lineage. However, the rarity of the disease and lack of animal models have impeded the study of PLCH pathogenesis. Here, we establish a cigarette smoke–exposed (CS-exposed) BRAF-V600E–mutant mouse model that recapitulates many hallmark characteristics of PLCH. We show that CD11c-targeted expression of BRAF-V600E increases DC responsiveness to stimuli, including the chemokine CCL20, and that mutant cell accumulation in the lungs of CS-exposed mice is due to both increased cellular viability and enhanced recruitment. Moreover, we report that the chemokine CCL7 is secreted from DCs and human peripheral blood monocytes in a BRAF-V600E–dependent manner, suggesting a possible mechanism for recruitment of cells known to dominate PLCH lesions. Inflammatory lesions and airspace dilation in BRAF-V600E mice in response to CS are attenuated by transitioning animals to filtered air and treatment with a BRAF-V600E inhibitor, PLX4720. Collectively, this model provides mechanistic insights into the role of myelomonocytic cells and the BRAF-V600E mutation and CS exposure in PLCH pathogenesis and provides a platform to develop biomarkers and therapeutic targets.

Authors

Huan Liu, Andrew R. Osterburg, Jennifer Flury, Zulma Swank, Dennis W. McGraw, Nishant Gupta, Kathryn A. Wikenheiser-Brokamp, Ashish Kumar, Abdellatif Tazi, Yoshikazu Inoue, Masaki Hirose, Francis X. McCormack, Michael T. Borchers

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Figure 4

BRAF-V600E mutation increases the recruitment of DCs to the lung in a CCL20-dependent manner.

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BRAF-V600E mutation increases the recruitment of DCs to the lung in a CC...
(A) Representative IHC staining for CCL20 in lung sections from healthy controls (HC) and patients with PLCH (n = 3/group). Scale bar: 100 μm. (B) CCL20 concentration in the BAL of mice (n = 5/group) exposed to FA or CS for 4 months was measured by ELISA. Data shown are mean ± SEM of 5 independent experiments. (C) CCL20 secretion by WT or BRAFVE donor BMDCs (n = 6/group) treated with/without LPS plus IFN-γ was measured by ELISA. Data are representative of 5 independent experiments. (D) Intracellular cAMP levels in WT or BRAFVE BMDCs (n = 5/group) were measured after treatment with forskolin followed by CCL20 stimulation (300 ng/mL). Data are representative of 3 independent experiments. (E) The number of WT or BRAFVE BMDCs that migrated from the upper to lower chamber of a Transwell plate toward CCL20 (300 ng/mL) was determined by flow cytometry after 3 hours (n = 6/group). Data are representative of 3 independent experiments. (F) Two million WT or BRAFVE CD45.2 donor BMDCs were intravenously injected into recipient CD45.1 mice that had been previously exposed to FA/CS for 6 months. The lungs were harvested 2 days later, and the numbers of donor cells in the lung and mLNs of the recipient mice were determined by gating on CD45.2 expression. Data shown are mean ± SEM of 3 independent experiments. (B–F) *P < 0.05, ANOVA (1 way in B and C, 2 way in D–F) with Tukey’s multiple-comparisons test. Data shown are mean ± SEM.