Aim
The objective is to identify the molecular mechanisms underlying the proapoptotic effects of ZnO and SiO2 NPs in differentiated hepatoblastoma cells (HepG2) and mesenchymal liver cancer cells (SNU449).
Conclusion
SiO2 demonstrated no cytotoxic profile against liver cancer cells. ZnO NPs demonstrated to accumulate in mitochondria impacting cell respiration and cell death in liver cancer cells. ZnO induced apoptosis and necroptosis in HepG2 and SNU449, respectively.
Methods
Dose-dependent induction of cell cytotoxicity by ZnO and SiO2 NPs (5 to 50 µg/mL) was determined in HepG2 and SNU449 cells. NPs intracellular localization was assessed using transmission electron microscopy (TEM). Cell death was determined by trypan blue staining and caspase-3 and -8 activities. Cell respiration was determined using MitroStress assay (Seahorse, Agilent).
Results
ZnO NPs, but not SiO2 NPs, reduced cell viability in HepG2 and SNU449. Interestingly, SNU449 appeared to be more susceptible than HepG2 to ZnO NPs (IC50 of 27.4 ± 1.4 µg/mL and 41.8 ± 0.4 µg/mL, respectively). SiO2 NPs tended to be localized in lysosomes in both cell lines, while ZnO NPs demonstrated a random distribution with a high presence in mitochondria and related structures. As expected, SiO2 NPs did not reduce cell survival and cell respiration, while ZnO NPs promoted cell death and decreased oxygen consumption rate. ZnO NPs mitochondrial accumulation was associated with increased apoptosis in HepG2, while necroapoptosis was mainly involved in ZnO-induced cell death in SNU449.