The role of the tumor suppressor p53 pathway in the cellular DNA damage response to zinc oxide nanoparticles.

In this paper, we explored how ZnO nanoparticles cross-interact with a critical tumor suppressive pathway centered around p53, which is one of the most important known tumor suppressors that protects cells from developing cancer phenotypes through its control over major pathways like apoptosis, senescence and cell cycle progression. We showed that the p53 pathway was activated in BJ cells (skin fibroblasts) upon ZnO nanoparticles treatment with a concomitant decrease in cell numbers. This suggests that cellular responses like apoptosis in the presence of ZnO nanoparticles require p53 as the molecular master switch towards programmed cell death. This also suggests that in cells without robust p53, protective response can be tipped towards carcinogenesis when stimulated by DNA damage inducing agents like ZnO nanoparticles. We observed this precarious tendency in the same BJ cells with p53 knocked down using endogeneous expressing shRNA. These p53 knocked down BJ cells became more resistant to ZnO nanoparticles induced cell death and increased cell progression. Collectively, our results suggest that cellular response towards specific nanoparticle induced cell toxicity and carcinogenesis is not only dependent on specific nanoparticle properties but also (perhaps more importantly) the endogenous genetic, transcriptomic and proteomic landscape of the target cells.

Ng KW ，Khoo SP ，Heng BC ，Setyawati MI ，Tan EC ，Zhao X ，Xiong S ，Fang W ，Leong DT ，Loo JS ... -  《-》

Zinc oxide nanoparticles induce oxidative DNA damage and ROS-triggered mitochondria mediated apoptosis in human liver cells (HepG2).

Sharma V ，Anderson D ，Dhawan A 《-》

ZnO nanoparticles induce apoptosis in human dermal fibroblasts via p53 and p38 pathways.

The production of engineered nanoparticles is growing rapidly as the field of nanotechnology continues to expand. Zinc oxide nanoparticles (ZnO NPs) are used in various applications, including catalysis, electronics, biosensors, medicine, paints, sunscreens and cosmetics, thus it is important to understand the biological effects and risks of ZnO NPs. This study was designed to investigate the apoptosis induction by ZnO NPs via mitogen-activated protein kinase p38 and cell cycle checkpoint protein p53 pathways in human dermal fibroblasts. MTT-based cell viability assay showed a significant decrease in cell survivorship after ZnO NP exposure, and phase contrast images revealed that ZnO NP treated cells had lower density and a rounded morphology. Apoptosis induction was confirmed by the annexin V assay and Western blot analysis showed the up-regulation of p53 and phospho-p38 proteins. Furthermore, in ZnO NP exposed cells, p53 protein was phosphorylated at Ser33 and Ser46 sites known to be phosphorylated by p38. Our results suggest that ZnO NPs have the potential to induce apoptosis in human dermal fibroblasts via p53-p38 pathways.

Meyer K ，Rajanahalli P ，Ahamed M ，Rowe JJ ，Hong Y ... -  《-》

Induction of oxidative stress, DNA damage and apoptosis in mouse liver after sub-acute oral exposure to zinc oxide nanoparticles.

Zinc oxide (ZnO) nanoparticles are finding applications in a wide range of products including cosmetics, food packaging, imaging, etc. This increases the likelihood of human exposure to these nanoparticles through dermal, inhalation and oral routes. Presently, the majority of the studies concerning ZnO nanoparticle toxicity have been conducted using in vitro systems which lack the complex cell-cell, cell-matrix interactions and hormonal effects found in the in vivo scenario. The present in vivo study in mice was aimed at investigating the oral toxicity of ZnO nanoparticles. Our results showed a significant accumulation of nanoparticles in the liver leading to cellular injury after sub-acute oral exposure of ZnO nanoparticles (300 mg/kg) for 14 consecutive days. This was evident by the elevated alanine aminotransferase (ALT) and alkaline phosphatase (ALP) serum levels and pathological lesions in the liver. ZnO nanoparticles were also found to induce oxidative stress indicated by an increase in lipid peroxidation. The DNA damage in the liver and kidney cells of mice was evaluated by the Fpg-modified Comet assay which revealed a significant (p<0.05) increase in the Fpg-specific DNA lesions in liver indicating oxidative stress as the cause of DNA damage. The TUNEL assay revealed an induction of apoptosis in the liver of mice exposed to ZnO nanoparticles compared to the control. Our results conclusively demonstrate that sub-acute oral exposure to ZnO nanoparticles in mice leads to an accumulation of nanoparticles in the liver causing oxidative stress mediated DNA damage and apoptosis. These results also suggest the need for a complete risk assessment of any new engineered nanoparticle before its arrival into the consumer market.

Sharma V ，Singh P ，Pandey AK ，Dhawan A ... -  《-》

Effect of zinc oxide nanomaterials-induced oxidative stress on the p53 pathway.

Excessive production of reactive oxygen species (ROS) is a hallmark feature in nanomaterials (NMs) induced cellular toxicity. However, the inter-relationship between NMs induced ROS generation and the cells innate ability to regulate intracellular ROS level in effecting a particular cellular outcome is currently underexplored. Here, using a BJ fibroblast p53 knockdown system, we showed that p53 may be implicated in playing a dual regulatory role to determine cell survivability in response to oxidative stress induced by ZnO NMs. At low level of ZnO NMs induced ROS, p53 triggers expression of antioxidant genes such as SOD2, GPX1, SESN1, SESN2 and ALDH4A1 to restore oxidative homeostasis while at high concentration of ZnO NMs, the elevated level of intracellular ROS activated the apoptotic pathway through p53. The implication of our finding that p53 can function as an important regulator in determining ZnO induced cytotoxicity is highlighted by the differential action of ZnO on p53 deficient and proficient colorectal cell lines. p53 deficient cells cancer cells such as DLD-1 and SW480 are more susceptible to ZnO induced cell death compared to p53 proficient cells such as colon epithelial cells NCM460 and HCT116 cells in a ROS dependent manner. Collectively, our findings showcased a role p53 plays in the context of nanotoxicity and highlights the need to consider the interplay of physicochemical properties of NMs and cell biology.

Setyawati MI ，Tay CY ，Leong DT 《-》