ROS/mtROS promotes TNTs formation via PI3K/AKT/mTOR pathway to protect against mitochondrial damages induced by engineering nanomaterialsin human glial cells

Abstract

Abstract Background As the demand and application of engineering nanomaterials rise, their potential toxicity in the central nervous system has drawn increasing concerns. As a novel cell-cell communication, tunneling nanotubes (TNTs) plays a crucial role in pathology and physiology. Unfortunately, the relationship between TNTs and nanomaterials neurotoxicity remains scarce. Here, three types of commonly used engineering nanomaterials, Cobalt nanoparticles (CoNPs), titanium dioxide nanoparticles (TiO2NPs), and multi-walled carbon nanotubes (MWCNTs) were selected to address this limitation. Results After complete characterization of the nanomaterials, the induction of TNTs formation by all of the nanomaterials was observed by high-content screening system and confocal microscopy in both primary astrocyte and U251 cells. The positive role of TNTs formation was further unveiled, which protected against the nanomaterials-induced neurotoxicity from cell apoptosis to ATP production dysfunction. We then ought to determine the underline mechanism of TNTs positive role. Since the generation of oxidative stress is a common mechanism in nanotoxicity, we first observed a significant increase in total and mitochondrial reactive oxygen species (namely ROS, mtROS), causing mitochondrial damage. Moreover, the pretreatment of U251 cells with either a ROS scavenger N-acetylcysteine or a mtROS scavenger mitoquinone attenuated the nanomaterial-induced neurotoxicity and TNTs generation, suggesting the central role of ROS in nanomaterials-induced TNTs formation. Furthermore, a vigorous downstream pathway of ROS, i.e., PI3K/AKT/mTOR pathway was found to be actively involved in the nanomaterials-promoted TNTs development, which was abolished by LY294002, Perifosine and Rapamycin, the inhibitors of PI3K, AKT, and mTOR, respectively. Finally, Western blot analysis demonstrated that ROS and mtROS scavenger suppressed PI3K/AKT/mTOR pathway, which then abrogated TNTs formation. Conclusion Our findings indicate that various types of nanomaterials promote TNTs formation through the generation of ROS/mtROS and the activation of downstream PI3K/AKT/mTOR pathway, which could fight against cell apoptosis and ATP production dysfunction induced by nanomaterials. Our study contributes to a better understanding of the intercellular protection mechanism against neurotoxicity induced by various kinds of nanomaterials, and sheds light on potential treatments to activate the cell-cell defense system against environmental toxicants.