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

Abstract

(2015) PARK2-mediated mitophagy is involved in regulation of HBEC senescence in COPD pathogenesis , Autophagy, 11:3, 547-559, DOI: 10.1080/15548627.2015 Abbreviations: Baf A1, bafilomycin A 1 ; COPD, chronic obstructive pulmonary disease; CS, cigarette smoke; CSE, cigarette smoke extract; EM, electron microscopy; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; HBEC, human bronchial epithelial cell; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; NAC, N-acetylcysteine; PCD, programmed cell death; PINK1, PTEN-induced putative kinase 1; ROS, reactive oxygen species; SA-b-Gal, senescence-associated b-galactosidase;TLR, toll-like receptor; WB, western blotting.Cigarette smoke (CS)-induced mitochondrial damage with increased reactive oxygen species (ROS) production has been implicated in COPD pathogenesis by accelerating senescence. Mitophagy may play a pivotal role for removal of CS-induced damaged mitochondria, and the PINK1 (PTEN-induced putative kinase 1)-PARK2 pathway has been proposed as a crucial mechanism for mitophagic degradation. Therefore, we sought to investigate to determine if PINK1-PARK2-mediated mitophagy is involved in the regulation of CS extract (CSE)-induced cell senescence and in COPD pathogenesis. Mitochondrial damage, ROS production, and cell senescence were evaluated in primary human bronchial epithelial cells (HBEC). Mitophagy was assessed in BEAS-2B cells stably expressing EGFP-LC3B, using confocal microscopy to measure colocalization between TOMM20-stained mitochondria and EGFP-LC3B dots as a representation of autophagosome formation. To elucidate the involvement of PINK1 and PARK2 in mitophagy, knockdown and overexpression experiments were performed. PINK1 and PARK2 protein levels in lungs from patients were evaluated by means of lung homogenate and immunohistochemistry. We demonstrated that CSE-induced mitochondrial damage was accompanied by increased ROS production and HBEC senescence. CSE-induced mitophagy was inhibited by PINK1 and PARK2 knockdown, resulting in enhanced mitochondrial ROS production and cellular senescence in HBEC. Evaluation of protein levels demonstrated decreased PARK2 in COPD lungs compared with non-COPD lungs. These results suggest that PINK1-PARK2 pathway-mediated mitophagy plays a key regulatory role in CSE-induced mitochondrial ROS production and cellular senescence in HBEC. Reduced PARK2 expression levels in COPD lung suggest that insufficient mitophagy is a part of the pathogenic sequence of COPD.

Heme oxygenase‐1 induction attenuates senescence in chronic obstructive pulmonary disease lung fibroblasts by protecting against mitochondria dysfunction

“…A COPD specific impaired mitophagy could be one of these mechanisms. Indeed, a decreased Parkin expression was reported in lung tissues of COPD patients (Ahmad et al, 2015; Ito et al, 2015). Interestingly, this reduction was correlated with a decrease in lung function in COPD patients (Ito et al, 2015).…”

“…Indeed, a decreased Parkin expression was reported in lung tissues of COPD patients (Ahmad et al, 2015; Ito et al, 2015). Interestingly, this reduction was correlated with a decrease in lung function in COPD patients (Ito et al, 2015). In our study, we noted the same correlation between protein expression of Parkin and FEV1 in fibroblasts from COPD patient (data not shown).…”

“…In fact, Ahmad and coworkers (Ahmad et al, 2015) showed that overexpression of Parkin reduces cigarette smoke‐induced DNA damage and cellular senescence when used in combination with a scavenger of mitochondria ROS. In addition, Ito and coworkers demonstrated that the knockdown of Pink1 or Parkin in human bronchial epithelial cells (HBECs) enhanced cellular senescence induced by cigarette smoke exposure (Ito et al, 2015). Our findings showing a protective effect of hemin against both impaired mitophagy and mitochondrial dysfunction and consecutive prevention of replicative senescence further support a cause–effect relationship between the two phenomena in COPD.…”

“…This event facilitates the targeting of mitochondria to form autophagosomes (Hattori, Saiki, & Imai, 2014). PINK1 and Parkin knockout mice exhibit increased ROS levels and dysfunctional mitochondria (Gispert et al, 2009; Palacino et al, 2004) and bronchial epithelial deleted from Parkin or PINK1 exposed to CS display an enhanced mtROS production and cellular senescence (Ito et al, 2015). These results reinforce the role of oxidative stress as an inducer of cell senescence upon CS exposure and suggest that an impaired mitophagy could be a mechanism inducing ROS‐mediated cell senescence in COPD.…”

Mitochondrial-Related Gene Expression and Macrophage Signatures in Non-Small Cell Lung Cancer, Including Patients with Emphysema as Co-Morbidity

“…We therefore focused on factors involved in mitophagy as there is a paucity of data regarding its role in non-small lung cancer pathogenesis despite dysregulation of mitophagy being implicated in the pathogenesis of other cancers [27,28]. Furthermore, changes in the Pink1-parkin mitophagy pathway are known to be involved in the pathogenesis of COPD [30,31].…”