Effects of Zinc Oxide Nanoparticles in HUVEC: Cyto- and Genotoxicity and Functional Impairment After Long-Term and Repetitive Exposure in vitro.
Purpose
The present study focuses on threshold levels for cytotoxicity after long-term and repetitive exposure for HUVEC as a model for the specific microvascular endothelial system. Furthermore, possible genotoxic effects and functional impairment caused by ZnO NPs in HUVEC are elucidated.


Methods
Thresholds for cytotoxic effects are determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Annexin V assay. To demonstrate DNA damage, single-cell microgel electrophoresis (comet) assay is performed after exposure to sub-cytotoxic concentrations of ZnO NPs. The proliferation assay, dot blot assay and capillary tube formation assay are also carried out to analyze functional impairment.


Results
NPs showed to be spherical in shape with an average size of 45-55 nm. Long-term exposure as well as repetitive exposure with ZnO NPs exceeding 25 µg/mL lead to decreased viability in HUVEC. In addition, DNA damage was indicated by the comet assay after long-term and repetitive exposure. Twenty-four hours after long-term exposure, the proliferation assay does not show any difference between negative control and exposed cells. Forty-eight hours after exposure, HUVEC show an inverse concentration-related ability to proliferate. The dot blot assay provides evidence that ZnO NPs lead to a decreased release of VEGF, while capillary tube formation assay shows restriction in the ability of HUVEC to build tubes and meshes as a first step in angiogenesis.


Conclusion
Sub-cytotoxic concentrations of ZnO NPs lead to DNA damage and functional impairment in HUVEC. Based on these data, ZnO NPs may affect neo-angiogenesis. Further investigation based on tissue cultures is required to elucidate the impact of ZnO NPs on human cell systems.
['Poier|Nikolaus|N|', 'Hochstöger|Johannes|J|', 'Hackenberg|Stephan|S|', 'Scherzad|Agmal|A|', 'Bregenzer|Maximilian|M|', 'Schopper|Dominik|D|', 'Kleinsasser|Norbert|N|']
D017304:Annexin A5 D017209:Apoptosis D002452:Cell Count D002470:Cell Survival D004249:DNA Damage D061307:Human Umbilical Vein Endothelial Cells D006801:Humans D053768:Metal Nanoparticles D018919:Neovascularization, Physiologic D015034:Zinc Oxide
zinc oxide nanoparticles genotoxicity cytotoxicity toxicity