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 3

BRAF-V600E mutation is associated with increased cell viability and expression of the antiapoptotic protein B cell lymphoma leukemia-x molecule.

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BRAF-V600E mutation is associated with increased cell viability and expr...
(A) Phospho-ERK (p-ERK) expression in BMDCs from WT and BRAFV-600E mice following the administration of Cre Recombinase Adenovirus mCherry (Ad-Cre) to induce BRAFV-600E expression was determined by flow cytometry. In indicated groups, 1 μM PLX4720 (BRAF inhibitor) was added to the BMDC culture at day 6. Data shown are representative of 4 independent experiments. (B) Absolute number of BMDCs (n = 4 WT/day; n = 4 BRAFVE/day) determined by flow cytometry at the indicated times. (C) BRAFV-600E expression increases BMDC viability in vitro. GM-CSF was removed from the culture medium at day 7, and apoptosis was quantified by annexin V and PI staining after 16 hours using flow cytometry. Live cells are annexin V– and PI–. Data shown are representative of 4 independent experiments. (D) BRAFV-600E expression increases antiapoptotic protein Bcl-xL expression in vitro. The expression of the antiapoptotic marker Bcl-xL in BMDCs was measured by flow cytometry. Data shown are representative of 4 independent experiments. (E) BRAFV-600E expression increases CD11c+ cell viability in vivo. CD11c cells were isolated from WT and BRAFVE mice, and the viability was assessed by flow cytometry as described above. Data are shown as the mean ± SEM; n = 4 per each group. For the experiments shown, B and E used 1-way ANOVA with Tukey’s multiple-comparisons test. Data shown are mean ± SEM. *P < 0.05.