Effects of Zinc Oxide Nanoparticles in HUVEC: Cyto- and Genotoxicity and Functional Impairment after Long-Term and Repetitive Exposure in vitro

Background Zinc oxide nanoparticles (ZnO NPs) come into contact with human cells in various ways. NPs target the vascular system via inhalation and ingestion. Defective skin as well as children’s skin may allow ZnO NPs to reach deeper skin layers and blood vessels. The present study focuses threshold levels for cytotoxicity after long-term and repetitive exposure for human umbilical vein endothelial cells (HUVEC). Furthermore, possible genotoxic effects and functional impairment are elucidated.

Methods Thresholds for cytotoxic effects are determined by 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 carried out to analyze functional impairment.

Results Long-term exposure as well as repetitive exposure with ZnO NPs exceeding 25 µg/ml lead to decreased viability in HUVEC. DNA damage was indicated by the comet assay after long-term and repetitive exposure. 24 hours after long-term exposure, the proliferation assay does not show any difference between negative control and exposed cells. 48 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 HUVEC´s ability to build tubes and meshes as a first step in angiogenesis.

Discussion Sub-cytotoxic concentrations of ZnO NPs lead to DNA damage and functional impairment in HUVEC. Based on this 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.

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Artikel online veröffentlicht:
10. Juni 2020