Mitochondria-Dependent Oxidative Stress Mediates ZnO Nanoparticle (ZnO NP)-Induced Mitophagy and Lipotoxicity in Freshwater Teleost Fish

Due to many special characteristics, zinc oxide nanoparticles (ZnO NPs) are widely used all over the world, leading to their wide distribution in the environment. However, the toxicities and mechanisms of environmental ZnO NP-induced changes of physiological processes and metabolism remain largely unknown. Here, we found that addition of dietary ZnO NPs disturbed hepatic Zn metabolism, increased hepatic Zn and lipid accumulation, downregulated lipolysis, induced oxidative stress, and activated mitophagy; N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN, Zn2+ ions chelator) alleviated high ZnO NP-induced Zn and lipid accumulation, oxidative stress, and mitophagy. Mechanistically, the suppression of mitochondrial oxidative stress attenuated ZnO NP-activated mitophagy and ZnO NP-induced lipotoxicity. Taken together, our study elucidated that mitochondrial oxidative stress mediated ZnO NP-induced mitophagy and lipotoxicity; ZnO NPs could be dissociated to free Zn2+ ions, which partially contributed to ZnO NP-induced changes in oxidative stress, mitophagy, and lipid metabolism. Our study provides novel insights into the impacts and mechanism of ZnO NPs as harmful substances inducing lipotoxicity of aquatic organisms, and accordingly, metabolism-relevant parameters will be useful for the risk assessment of nanoparticle materials in the environment.