ABSTRACT
Several types of cytotoxic insults disrupt endoplasmic reticulum (ER) homeostasis, cause ER stress, and activate the unfolded protein response (UPR). The role of ER stress and UPR activation in hypersensitivity pneumonitis (HP) has not been described. HP is an immune-mediated interstitial lung disease that develops following repeated inhalation of various antigens in susceptible and sensitized individuals. The aim of this study was to investigate the lung expression and localization of the key effectors of the UPR, BiP/GRP78, CHOP, and sXBP1 in HP patients compared with control subjects. Furthermore, we developed a mouse model of HP to determine whether ER stress and UPR pathway are induced during this pathogenesis. In human control lungs, we observed weak positive staining for BiP in some epithelial cells and macrophages, while sXBP1 and CHOP were negative. Conversely, strong BiP, sXBP1- and CHOP-positive alveolar and bronchial epithelial, and inflammatory cells were identified in HP lungs. We also found apoptosis and autophagy markers colocalization with UPR proteins in HP lungs. Similar results were obtained in lungs from an HP mouse model. Our findings suggest that the UPR pathway is associated with the pathogenesis of HP.
Subject(s)
Alveolitis, Extrinsic Allergic , Endoplasmic Reticulum Chaperone BiP , Endoplasmic Reticulum Stress , Epithelial Cells , Heat-Shock Proteins , Transcription Factor CHOP , Unfolded Protein Response , X-Box Binding Protein 1 , Animals , Alveolitis, Extrinsic Allergic/pathology , Alveolitis, Extrinsic Allergic/immunology , Alveolitis, Extrinsic Allergic/metabolism , Humans , Mice , X-Box Binding Protein 1/metabolism , X-Box Binding Protein 1/genetics , Heat-Shock Proteins/metabolism , Transcription Factor CHOP/metabolism , Epithelial Cells/metabolism , Epithelial Cells/pathology , Female , Male , Lung/pathology , Lung/immunology , Lung/metabolism , DNA-Binding Proteins/metabolism , Regulatory Factor X Transcription Factors/metabolism , Transcription Factors/metabolism , Disease Models, Animal , Middle Aged , Mice, Inbred C57BL , Adult , Inflammation/pathology , Inflammation/metabolism , Inflammation/immunologyABSTRACT
Autophagy has been involved in the pathogenesis of various lung diseases. However, it is not yet known whether autophagy plays a role in hypersensitivity pneumonitis (HP). HP is an interstitial lung disease resulting from exposure to a wide variety of antigens that provoke an exaggerated immune response in susceptible individuals. The aim of this study was to explore the localization of autophagy key proteins in lungs from HP patients and controls by immunohistochemistry and analyze their expression levels by immunoblot. Macrophages and epithelial cells were strongly positive for the autophagosome biomarker LC3B (microtubule-associated protein light chain 3 beta) in HP lungs compared with controls. A similar pattern was found for the autophagy receptor p62 and the enzyme ATG4B. Unexpectedly, nuclear p62 signal was also noticed in macrophages from HP lungs. Regarding ATG5 and ATG7 localization, we observed positive staining in neutrophils, vascular smooth muscle cells, and endothelial cells. Our findings provide for the first time evidence that proteins from the autophagy machinery are highly expressed in the lungs of HP patients and describe the specific cellular and subcellular localization of LC3B, p62, ATG4B, ATG5, and ATG7 in HP lungs.
