The cytotoxicity of zinc oxide nanoparticles to 3D brain organoids results from excessive intracellular zinc ions and defective autophagy

Abstract

Cytotoxicity caused by high levels of ZnO NPs (64 μg/mL) correlated with high intracellular Zn ion levels but not superoxide levels. Exposure to a noncytotoxic concentration of ZnO NPs (16 μg/mL) increased the autophagy-marker proteins LC3B-II/I but decreased p62 accumulation, whereas a cytotoxic concentration of ZnO NPs (64 μg/mL) decreased LC3B-II/I proteins but did not affect p62 accumulation. Fluorescence micro-optical sectioning tomography revealed that 64 μg/mL ZnO NPs led to decreases in LC3B proteins that were more obvious at the outer layers of the organoids, which were directly exposed Abstract Although the neurotoxicity of ZnO nanoparticles (NPs) has been evaluated in animal and nerve cell culture models, these models cannot accurately mimic human brains. Three-dimensional (3D) brain organoids based on human-induced pluripotent stem cells have been developed to study the human brains, but this model has rarely been used to evaluate NP neurotoxicity. We used 3D brain organoids that express cortical layer proteins to investigate the mechanisms of ZnO NP-induced neurotoxicity.Liangliang Liu and Junkang Wang contributed equally to this work. Highlights 3D human brain organoids were used to evaluate neurotoxicity of ZnO NPs. ZnO NPs induced cytotoxicity by inducing intracellular Zn ions and defective autophagy. ZnO NPs decreased LC3B proteins and increased the appearance of micronuclei more obviously in the outlayers of organoids. Chemical inhibition of autophagy increased ZnO NPinduced cytotoxicity and intracellular Zn ions.

The cytological and electrophysiological effects of silver nanoparticles on neuron-like PC12 cells

“…Human iPSC-derived neurons-based 3D brain organoids containing a variety of neurons and glial cells possess a more complete organization and are more similar to the human central nervous system [ 57 ]. The toxic effects of silver nanoparticles [ 58 ] and zinc oxide nanoparticles [ 59 ] have been investigated using brain organoids. Researchers also use MEA [ 60 ] and whole-cell patch-clamp [ 61 ] to record brain organoids’ electrophysiological response to external stimulation.…”

Autophagy regulation by inorganic, organic, and organic/inorganic hybrid nanoparticles: Organelle damage, regulation factors, and potential pathways

“…Mitochondrial injury and oxidative stress caused by impaired autophagy flux ultimately result in cell death. [ 83 ] Liu et al [ 35 ] found that low doses of ZnONPs (16 μg/mL) induced autophagy and reduced p62 accumulation. In contrast, high doses of ZnONPs (64 μg/mL) caused defective autophagy and elevate intracellular levels of Zn 2+ , resulting in cytotoxicity.…”

Piezoelectric biomaterials for neural tissue engineering

“…30 Different from several inorganic piezoelectric nanomaterials mentioned above, ZnO nanomaterials exhibited inhibitory effects on nerve cells at subtoxic concentrations (10 −4 -10 −1 μg/ mL). 31,32 Therefore, the integration with polymer materials and the surface modification of nanoparticles are often used to reduce the biological toxicity of inorganic ZnO nanoparticles, and the ZnO-based biomaterials have been used in the repair of PNI, drug delivery, and bioimaging. [33][34][35] It's worth mentioning that ZnO-based wound dressings can accelerate the healing process of chronic wounds due to the antibacterial properties and piezoelectric properties of ZnO nanomaterials.…”

“…With the US‐driven piezoelectric effect, pheochromocytoma cells (PC12 cells) treated with BN nanotubes showed increased neurites, indicating the application prospect in ES of nerve tissue engineering 30 . Different from several inorganic piezoelectric nanomaterials mentioned above, ZnO nanomaterials exhibited inhibitory effects on nerve cells at subtoxic concentrations (10 −4 –10 −1 μg/mL) 31,32 . Therefore, the integration with polymer materials and the surface modification of nanoparticles are often used to reduce the biological toxicity of inorganic ZnO nanoparticles, and the ZnO‐based biomaterials have been used in the repair of PNI, drug delivery, and bioimaging 33–35 .…”