Insufficient autophagy in idiopathic pulmonary fibrosis

Abstract

Autophagy, a process that helps maintain homeostatic balance between the synthesis, degradation, and recycling of organelles and proteins to meet metabolic demands, plays an important regulatory role in cellular senescence and differentiation. Here we examine the regulatory role of autophagy in idiopathic pulmonary fibrosis (IPF) pathogenesis. We test the hypothesis that epithelial cell senescence and myofibroblast differentiation are consequences of insufficient autophagy. Using biochemical evaluation of in vitro models, we find that autophagy inhibition is sufficient to induce acceleration of epithelial cell senescence and myofibroblast differentiation in lung fibroblasts. Immunohistochemical evaluation of human IPF biospecimens reveals that epithelial cells show increased cellular senescence, and both overlaying epithelial cells and fibroblasts in fibroblastic foci (FF) express both ubiquitinated proteins and p62. These findings suggest that insufficient autophagy is an underlying mechanism of both accelerated cellular senescence and myofibroblast differentiation in a celltype-specific manner and is a promising clue for understanding the pathogenesis of IPF. myofibroblast; p62; senescence

Autophagy Induction by SIRT6 through Attenuation of Insulin-like Growth Factor Signaling Is Involved in the Regulation of Human Bronchial Epithelial Cell Senescence

“…Knockdown of ATG5 and LC3B were assessed by WB (Fig. 6A), and autophagy inhibition was confirmed as previously described (data not shown) (5,20). ATG5 and LC3B knockdown significantly diminished the antisenescence property of SIRT6 in HBECs, especially in the presence of CSE (1.0%; Fig.…”

“…HBECs were isolated with protease treatment, and freshly isolated HBECs were plated onto rattail collagen type I-coated (10 mg/ml) dishes, incubated overnight, and then the medium was changed to bronchial epithelial growth medium (BEGM; Clonetics, San Diego, CA). Cultures were characterized immunohistochemically using anti-cytokeratin Abs (Lu-5; BioCare Medical, Concord, CA) and anti-vimentin (Sigma-Aldrich, Tokyo, Japan), as previously described (20). HBECs showed .95% positive staining with anticytokeratin and ,5% positive staining with the anti-vimentin Ab (data not shown).…”

PARK2-mediated mitophagy is involved in regulation of HBEC senescence in COPD pathogenesis

“…7,45 PARK2 immunostaining were assessed by counting total and positively staining cells in small airways at a magnification of £400 and percentage of positive staining was scored in a semi-quantitative fashion; 0 (less than 10%), 1 (11 to 49%), and 2 (more than 50%). Immunofluorescence staining was also performed as previously described.…”

“…Immunofluorescence staining was also performed as previously described. 7,45 BEAS-2B cells expressing EGFP-LC3B grown on 8-well culture slides were fixed with 4% paraformaldehyde for 15 min followed by permeabilization with 0.03% Triton X-100 (Wako, 160-24751) for 60 min. After blocking with 0.1% BSA (SigmaAldrich, A2153) for 60 min, the primary and secondary antibodies were applied according to the manufacturer's instructions.…”

Persistent activation of autophagy in kidney tubular cells promotes renal interstitial fibrosis during unilateral ureteral obstruction

“…Intriguingly, depending on the cell or tissue type and pathological settings, autophagy can be profibrotic or antifibrotic in these organs. [22][23][24][25] For example, autophagy induced in hepatic stellate cells can break down lipids to fuel the activation of these cells to promote liver fibrosis. 26,27 In contrast, autophagy in hepatic macrophages and hepatocytes inhibits inflammation and apoptosis, resulting in the prevention of liver fibrosis.…”