How cadmium (Cd) induces mitochondrial loss in the context of its hepatotoxic effects remains enigmatic. The purpose of the study was to investigate whether mitophagy contributes to mitochondrial loss in cadmium-induced hepatotoxicity and to determine the potential mechanism. In normal human liver L02 cells, we observed that Cd treatment led to a significant increase in LC3-II formation, the number of GFP-LC3 puncta and lysosomal colocalization with mitochondria. These results were associated with mitochondrial loss and bioenergetic deficit. Additionally, the abrogation of excessive mitophagy by ATG5 siRNA treatment efficiently suppressed the mitochondrial loss and cytotoxicity of Cd. Before overactivating mitophagy, Cd induced excessive mitochondrial fragmentation as a result of increasing dynamin 1-like (DNM1L) expression and enhancing the DNM1L mitochondrial translocation. Moreover, reversing the excessive mitochondrial fragmentation via the administration of DNM1L siRNA significantly inhibited the observed overactivation of mitophagy in Cd-induced hepatotoxicity. Notably, the selective DNM1L inhibitor Mdivi-1 blocked abnormal mitophagy and subsequently ameliorated Cd-induced hepatotoxicity in vivo. Together, our data indicated that Cd induces mitochondrial loss via the overactivation of mitophagy following DNM1L-dependent mitochondrial fragmentation. The balanced activity of DNM1L and mitophagy signaling may be a potential therapeutic approach to treat Cd-induced hepatotoxicity.

Oral squamous cell carcinoma (OSCC) is the most common type of oral malignancy, and metastasis accounts for the poor prognosis of OSCC. Autophagy is considered to facilitate OSCC development by mitigating various cellular stresses; nevertheless, the mechanisms of autophagy in OSCC cell proliferation and metastasis remain unknown. In our study, high-sensitivity label-free quantitative proteomics analysis revealed nuclear protein 1 (NUPR1) as the most significantly upregulated protein in formalin-fixed paraffin-embedded tumour samples derived from OSCC patients with or without lymphatic metastasis. Moreover, NUPR1 is aberrantly expressed in the OSCC tissues and predicts low overall survival rates for OSCC patients. Notably, based on tandem mass tag-based quantitative proteomic analysis between stable NUPR1 knockdown OSCC cells and scrambled control OSCC cells, we confirmed that NUPR1 maintained autophagic flux and lysosomal functions by directly increasing transcription factor E3 (TFE3) activity, which promoted OSCC cell proliferation and metastasis in vitro and in vivo. Collectively, our data revealed that the NUPR1–TFE3 axis is a critical regulator of the autophagic machinery in OSCC progression, and this study may provide a potential therapeutic target for the treatment of OSCC.