Silencing FUNDC1 alleviates chronic obstructive pulmonary disease by inhibiting mitochondrial autophagy and bronchial epithelium cell apoptosis under hypoxic environment

Chronic obstructive pulmonary disease (COPD) is a major global epidemic with increasing incidence worldwide. The pathogenesis of COPD is involved with mitochondrial autophagy. Recently, it has been reported that FUN14 domain containing 1 (FUNDC1) is a mediator of mitochondrial autophagy. Therefore, we hypothesized that FUNDC1 was involved in cigarette smoke (CS)-induced COPD progression by regulating mitochondrial autophagy. In vitro cigarette smoke extract (CSE)-treated human bronchial epithelial cell (hBEC) Beas-2B cell line and in vivo CS-induced COPD mouse models were developed, in which FUNDC1 expression was measured. Next, whether FUNDC1 interacted with dynamin-related protein 1 (DRP1) in COPD was investigated. The functional mechanism of FUNDC1 in COPD was evaluated through gain- or loss-of-function studies. Then, pulmonary function, mitochondrial transmembrane potential (MTP) and mucociliary clearance (MCC) were examined. Levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) and expression of autophagy-specific markers (light chain 3 [LC3] II, LC3 I, and Tom20) were measured. Finally, apoptosis and mitochondrial autophagy were assessed. FUNDC1 was highly expressed in CSE-treated hBECs and COPD mice. Meanwhile, FUNDC1 was proved to interact with DRP1 in CSE-treated cells. Moreover, in CSE-treated hBECs, silencing FUNDC1 was observed to reduce levels of IL-6 and TNF-alpha, and MTP but increase MCC, and inhibit CSE-induced mitochondrial autophagy and Beas-2B cell apoptosis, which was consistent with the trend in COPD mouse models. In addition, pulmonary function of COPD mouse models was increased in response to FUNDC1 silencing. Finally, silencing of DRP1 also inhibited mitochondrial autophagy and Beas-2B cell apoptosis. Collectively, FUNDC1 silencing could suppress the progression of COPD by inhibiting mitochondrial autophagy and hBEC apoptosis through interaction with DRP1, highlighting a potential therapeutic target for COPD treatment.