USP13 Suppresses Cellular Senescence Via Promoting Beclin-1 Dependent Autophagy In Pulmonary Fibrosis

BackgroundIdiopathic pulmonary fibrosis(IPF)is a severe chronic and lethal disease with an unknown etiology and unclear pathogenesis.It is usually associated with worsening respiratory symptoms,lung function decline,and limited responses to therapies.The median survival time of IPF patients is 3-4 years from diagnosis and the prognosis is poor.The incidence and prevalence of IPF rises with age cellular senescence is a common molecular and cellular mechanism of ageing and ageing-associated diseases and has been found to drive progressive pulmonary fibrosis.Moreover,depletion of senescent cells by senolytic drugs presents a potential therapeutic option for the treatment of pulmonary fibrosis.However,the pathogenesis of cellular senescence involved in IPF is largely unknown.Autophagy is a predominantly cytoprotective process that has a prominent role in determine the life span of many model organisms.Reduced autophagy has been associated with ageing,whereas stimulation of autophagy might have potent anti-ageing effects.ubiquitin-specific protease 13(USP13)is a member of deubiquitinating enzymes(DUBs)superfamily,which functions by cleaving the polyubiquitin chain off protein substrate to reverse ubiquitin-mediated protein degradation.USP 13 has been implicated in neurodegenerative disease and was involved in cell apoptosis via inducing autophagy.We have found that USP 13 may be involved in the activation of IPF lung fibroblasts in previous studies,but the role of USP13 in IPF lung epithelial cells and its relationship with cellular senescence and autophagy are still unclear.ObjectiveWe are aim to explore the mechanism of USP 13 involved in IPF alveolar epithelial cells and its relationship with cellular senescence and autophagy.Materials and MethodsFirstly,we used lung tissue specimens from IPF patients and age-matched normal control lung tissue specimens to explore the different expression of USP 13 and its expression in lung alveolar epithelial cells.The phenotype of cellular senescence and autophagy was verified in IPF lung alveolar epithelial cells.Then the lung epithelial cell line MLE12 was used to construct a cell senescence model in vitro,and the cells were transfected with overexpressing USP13 lentivirus and cellular senescence markers and autophagy-related proteins and autophagic flux were detected to investigated the relationship among USP13 and cellular senescence and autophagy.We also found the protein substrate of USP13 in MLE12 cells by immunoprecipitation.Finally,we used USP13 deficiency mice to construct an experimental pulmonary fibrosis mouse model to explore whether USP13 has a protective effect and its relationship with cell senescence and autophagy in pulmonary fibrosis models.Results1.USP13 was do wnregulated both in IPF lung tissues and in ? types of alveolar epithelial cells.2.Cellular senescence was accumulated in IPF lung tissues and in ? types of alveolar epithelial cells.3.Autophagy was reduced in IPF lung tissues and in ? types of alveolar epithelial cells.4.Bleomycin(BLM)induced MLE12 cellular senescence,and the expression of USP13 was decreased in senescent cells.5.USP 13 suppressed cellular senescence.6.USP 13 promoted autophagy in senescent cells.7.USP 13 suppressed cellular senescence is dependent on autophagy process.8.USP13 deubiquitinates Beclin-1 in MLE12 cells.9.USP13 promoting autophagy is dependent on Beclin-1.10.USP 13 was decline with age in BLM-induced lung fibrosis.11.USP 13 deficiency exacerbated BLM-induced lung fibrosis in 12-month old mice.12.USP 13 deficiency exacerbated cellular senescence in vivo.13.USP 13 deficiency inhibited autophagy in vivo.ConclusionsIPF is an age-related disease.USP 13 was do wnregulated in IPF lung tissues and in II type alveolar epithelial cells.USP 13 has a protective effect on BLM-induced age-related lung fibrosis.USP 13 involved in pulmonary fibrosis possibly by suppressing alveolar epithelial cellular senescence via inducing Beclin-1 dependent autophagy.