Protein kinase D is increased and activated in lung epithelial cells and macrophages in idiopathic pulmonary fibrosis.

Huachen Gan,Steven Idell,Raymond Mckenzie,Hua Tang,Qin Hao,Vladimir V Kalinichenko

doi:10.1371/journal.pone.0101983

Huachen Gan, Steven Idell + Show 4 more

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https://doi.org/10.1371/journal.pone.0101983

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Abstract

Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive and usually fatal lung disease of unknown etiology for which no effective treatments currently exist. Hence, there is a profound need for the identification of novel drugable targets to develop more specific and efficacious therapeutic intervention in IPF. In this study, we performed immunohistochemical analyses to assess the cell type-specific expression and activation of protein kinase D (PKD) family kinases in normal and IPF lung tissue sections. We also analyzed PKD activation and function in human lung epithelial cells. We found that PKD family kinases (PKD1, PKD2 and PKD3) were increased and activated in the hyperplastic and regenerative alveolar epithelial cells lining remodeled fibrotic alveolar septa and/or fibroblast foci in IPF lungs compared with normal controls. We also found that PKD family kinases were increased and activated in alveolar macrophages, bronchiolar epithelium, and honeycomb cysts in IPF lungs. Interestingly, PKD1 was highly expressed and activated in the cilia of IPF bronchiolar epithelial cells, while PKD2 and PKD3 were expressed in the cell cytoplasm and nuclei. In contrast, PKD family kinases were not apparently increased and activated in IPF fibroblasts or myofibroblasts. We lastly found that PKD was predominantly activated by poly-L-arginine, lysophosphatidic acid and thrombin in human lung epithelial cells and that PKD promoted epithelial barrier dysfunction. These findings suggest that PKD may participate in the pathogenesis of IPF and may be a novel target for therapeutic intervention in this disease.

Highlights

Idiopathic pulmonary fibrosis (IPF), the most common form of the idiopathic interstitial pneumonias, is a chronic, relentlessly progressive and usually fatal lung disease of unknown etiology for which no effective pharmacologic treatments currently exist [1,2,3,4]
In non-fibrotic areas of IPF lung alveoli, we found that PKD1 was expressed in the cytoplasm and nuclei of macrophages and alveolar epithelial cells (AECs), including type II pneumocytes (Fig. 2B)
We found that TEER of control 16HBE14o- cell monolayers on the Transwell inserts was significantly increased by co-culturing with primary lung fibroblasts derived from IPF lungs (99A and 110A) and normal subjects (131N and 13N) (Fig. 7A) or with human pulmonary artery endothelial cells (HPAECs) (Fig. 7B) in the bottom chamber

Summary

Introduction

Idiopathic pulmonary fibrosis (IPF), the most common form of the idiopathic interstitial pneumonias, is a chronic, relentlessly progressive and usually fatal lung disease of unknown etiology for which no effective pharmacologic treatments currently exist [1,2,3,4]. A number of recent clinical trials of novel drugs, including interferon-c, endothelin antagonists, the platelet-derived growth factor receptor inhibitor imatinib, tumor necrosis factor-a antibody etanercept, and anticoagulants (warfarin and heparin), have all failed to show significant benefit for IPF patients who have mild to moderate lung functional impairment. Most of these drugs showed early promise in the bleomycin-induced murine lung fibrosis model [1,2,3,4], in which pulmonary fibrosis is spontaneously reversible [5].

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