Zinc Oxide Nanoparticles: Mechanism(s) of Cell Death Induced in Human Epidermoid Larynx Cell Line (HEp-2)

Zinc oxide nanoparticles (ZnO-NPs, 12 +/- 3 nm) have attracted due to their unique properties and immense potential application. Over various physicochemical applications, the cytotoxic profile of ZnO-NPs in human epidermoid larynx cell line (HEp-2) has not been completely determined till date. Since, human exposure to ZnO-NPs may occur through the exposure routes of inhalation and ingestion at occupational level. The HEp-2 cells were exposed to ZnO-NPs at 2-20 mu g/mL concentrations for 24 h. ZnO-NPs depicted a concentration dependent cytotoxic, ROS and mitochondrial membrane potential (MMP) response observed in HEp-2 cells. The events of cytotoxicity and ROS were found to be associated with up-regulation in mRNA expressions of pro-apoptotic marker genes viz., p53, Bax, caspase-3, and caspase-9 and down-regulation of anti-apoptoticmarker gene, Bcl-2. The findings of this study indicates that ZnO-NPs induced cytotoxicity in HEp-2 cells is likely through ROS generation and mitochondria mediated apoptosis involving p53, Bax/Bcl-2 and caspase-3/9 genes.