PINK1 deficiency alleviates bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disorder marked by deteriorating dyspnea and declining pulmonary function. Despite its rising prevalence and incidence, therapeutic options remain limited. PTEN-induced kinase 1 (PINK1), known for its role in PINK1/Parkin-dependent mitophagy, contributes to the pathogenesis of various lung diseases. In this study, we elucidate a previously unrecognized mechanism of PINK1, beyond its canonical mitophagy function, during pulmonary fibrosis. We established a bleomycin (BLM)-induced pulmonary fibrosis model in Pink1 knockout (Pink1^-/-) mice and treated BEAS-2B cells with transforming growth factor-beta 1 (TGF-β1) to simulate the microenvironment of pulmonary fibrosis. A significant elevation in PINK1 expression was observed in vivo and in vitro systems. While PINK1/Parkin-dependent mitophagy was activated, mitophagy mediated by BCL2-interacting protein 3 (BNIP3) and FUN14 domain-containing 1 (FUNDC1) was suppressed. Further experiments in carbonyl cyanide m-chlorophenyl hydrazone (CCCP)-treated PINK1 knockout (KO) HEK293 cells and YFP-Parkin-expressing HeLa cells demonstrated that PINK1 deficiency enhanced BNIP3- and FUNDC1-mediated mitophagy, whereas PINK1 overexpression inhibited it. Moreover, dual BNIP3/FUNDC1 knockdown significantly reversed the anti-apoptotic effect of PINK1 KO. We conclude that PINK1 deficiency promotes the clearance of damaged mitochondria via BNIP3/FUNDC1 upregulation, preserving mitochondrial homeostasis, mitigating alveolar epithelial injury, and attenuating fibrosis. Thus, PINK1 may inhibit BNIP3- and FUNDC1-mediated mitophagy besides driving PINK1-dependent mitophagy during pulmonary fibrosis.