PurposeTransforming growth factor (TGF)-β1 triggers epithelial–mesenchymal transition (EMT) through autophagy, which is partly driven by reactive oxygen species (ROS). The aim of this study was to determine whether leaking lysosomes and enhanced degradation of H-ferritin could be involved in EMT and whether it could be possible to prevent EMT by iron chelation targeting of the lysosome.Materials and methodsEMT, H-ferritin, and autophagy were evaluated in TGF-β1-stimulated A549 human lung epithelial cells cultured in vitro using Western blotting, with the additional morphological assessment of EMT. By using immunofluorescence and flow cytometry, lysosomes and ROS were assessed by acridine orange and 6-carboxy-2′,7′-dichlorodihydrofluorescein acetate assays, respectively.ResultsTGF-β1-stimulated cells demonstrated a loss of H-ferritin, which was prevented by the antioxidant N-acetyl-L-cysteine (NAC) and inhibitors of lysosomal degradation. TGF-β1 stimulation generated ROS and autophagosome formation and led to EMT, which was further promoted by the additional ROS-generating cytokine, tumor necrosis factor-α. Lysosomes of TGF-β1-stimulated cells were sensitized to oxidants but also completely protected by lysosomal loading with dextran-bound deferoxamine (DFO). Autophagy and EMT were prevented by NAC, DFO, and inhibitors of autophagy and lysosomal degradation.ConclusionThe findings of this study support the role of enhanced autophagic degradation of H-ferritin as a mechanism for increasing the vulnerability of lysosomes to iron-driven oxidant injury that triggers further autophagy during EMT. This study proposes that lysosomal leakage is a novel pathway of TGF-β1-induced EMT that may be prevented by iron-chelating drugs that target the lysosome.

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Background: Common features among patients with more advanced chronic obstructive pulmonary disease (COPD) are systemic inflammation and a loss of both muscle mass and normal muscle composition. In the present study, we investigated COPD subjects to better understand how thigh muscle fat infiltration (MFI) and energy metabolism relate to each other and to clinical features of COPD with emphasis on systemic inflammation. Methods: Thirty-two Caucasians with stable COPD were investigated using questionnaires, lung function tests, blood analysis and magnetic resonance imaging (MRI) for analysis of body-and thigh muscle composition. Bioenergetics in the resting thigh muscle, expressed as the PCr/Pi ratio, were analysed using 31 phosphorus magnetic resonance spectroscopy ( 31 P-MRS). Results: Based on the combination of the MFI adjusted for sex (MFI a ) and the thigh fat-tissue free muscle volume, expressed as the deviation from the expected muscle volume of a matched virtual control group (FFMV vcg ), all COPD subjects displayed abnormally composed thigh muscles. Clinical features of increased COPD severity, including a decrease of blood oxygenation (r = −0.44, p < 0.05) and FEV 1 /FVC ratio, reflecting airway obstruction (r = −0.53, p < 0.01) and an increase of COPD symptoms (r = 0.37, p < 0.05) and breathing frequency at rest (r = 0.41, p < 0.05), were all associated with a raise of the PCr/Pi ratio in the thigh muscle. Increased MFI a of the thigh muscle correlated positively with markers of systemic inflammation (white blood cell count, r = 0.41, p < 0.05; fibrinogen, r = 0.44, p < 0.05), and negatively with weekly physical activity (r = −0.40, p < 0.05) and the PCr/Pi ratio in the resting thigh muscle (r = −0.41, p < 0.05). Conclusion:The present study implies a link between systemic inflammation, excessive MFI and a loss of bioenergetics in subjects with stable COPD.

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