A combined microRNA and proteome profiling to investigate the effect of ZnO nanoparticles on neuronal cells

Zinc oxide nanoparticles (ZnO NPs) are one of the most broadly used engineered nanomaterials. The toxicity potential of ZnO NPs has been explored in several studies; however, its neurotoxicity, especially its molecular mechanism, has not been studied in depth. In this study, we have used a cellular model of neuronal differentiation (nerve growth factor differentiated PC12 cells) to compare the effect of ZnO NPs exposure on neuronal (differentiated or mature neurons) and non-neuronal (undifferentiated) cells. Our studies have shown that the noncytotoxic concentration of ZnO NPs causes neurite shortening and degeneration in differentiated PC12 cells. Brain-specific microRNA (miRNA) array and liquid chromatography with tandem mass spectrometry (LC-MS/MS) are used to carry out profiling of miRNAs and proteins in PC12 cells exposed with ZnO NPs. Exposure of ZnO NPs produced significant deregulation of a higher number of miRNAs (15) and proteins (267) in neuronal cells in comparison to miRNAs (8) and proteins (207) of non-neuronal cells (8). In silico pathway analysis of miRNAs and proteins deregulated in ZnO NPs exposed differentiated PC12 cells have shown pathways leading to neurodegenerative diseases and mitochondrial dysfunctions are primarily targeted pathways. Further, a bioenergetics study carried out using Seahorse XFp metabolic flux analyzer has confirmed the involvement of mitochondrial dysfunctions in ZnO NPs exposed differentiated PC12 cells. In conclusion, differentiated PC12 cells (neuronal) were found more vulnerable than undifferentiated (non-neuronal PC12 cells) toward the exposure of ZnO NPs and deregulation of miRNAs and mitochondrial dysfunctions play a significant role in its toxicity.