Effects Of Zinc Oxide Nanoparticles On Intracellular Calcium Homeostasis And Cytotoxicity

Nanomaterials have been widely used in various aspects of the social life,at the same time,they may cause adverse effects on the environment and human health through various channels.In recent years,there are quite a lot of achievements about the toxicity of Zn O NPs.However,the researches on the toxicological effects and the safety evaluation are not enough.Therefore,this thesis studied the interruption of calcium homeostasis and related toxicological effects after exposure to Zn O NPs in Human Umbilical Vein Endothelial Cells.Zn O NPs was supplied from Institute for Health and Consumer Protection for the project of European Commission seventh framework program.Its mean size,zeta potentials and code is 150 nm,-6.14 m V and NM110,respectively,and its uncoated.It will provide the theoretical foundation for the safety evaluation of nanomaterials.The specific results are as follows.In the first part,this thesis studied the effects of Zn O NPs on calcium homeostasis.The assays with two different methods demonstrated that the [Ca2+]i increased to more than 2 fold,compared with control group,and remained at the high levels for a long time when Zn O NPs were diluted in free-calcium/magnesium culture and added into cells.In endocytosis inhibitors and TG tests Zn O NPs directly inhibited the release of calcium from ER and stimulated slowly ER calcium release,respectively.All these results indicated that Zn O NPs can induce ER release calcium and interrupt calcium homeostasis,which would affect many intracellular physiological processes.In the second part,the toxicology mechanism relevant to the unbalanced calcium homeostasis were researched.After adding Zn O NPs into culture medium of cells,the cell viability,damage of cell membrane,mitochondrial dysfunction(transformation of mitochondrial membrane potential,release of cytochrome C and mitochondrial autophagy),inflammatory factors,apoptosis,expression of DNA methylation related protein and mitochondria fusion protein were detected.The studies indicated that Zn O NPs inhibited the cell viability and destroied the integrity of the cell membrane in a dose-and time-dependent manner.Zn O NPs led to mitochondrial dysfunction,such as reducing the mitochondrial membrane potential,releasing cytochrome C to cytoplasm and inducing mitochondrial autophagy.Besides resulted in release of inflammatory factors,apoptosis and reduced the ratio of Bcl-2/Bax.However,Zn O NPs had no obvious impacts on expression of DNA methylation related proteins and mitochondria fusion proteins.The above experimental results indicated that Zn O NPs induced a series of toxicological effects related to the high [Ca2+]i and finally caused apoptosis.In conclusion,Zn O NPs induced the endoplasmic reticulum to release calcium ions and the [Ca2+]i increased.The increased [Ca2+]i may trigger apoptosis by multiple pathways.The above researches brought a further understanding about the mechanisms of cytotoxic effects caused by Zn O NPs,which has guiding significance to the safety evaluation of nanomaterials.