Research progress on toxicity, function, and mechanism of metal oxide nanoparticles on vascular endothelial cells

Metal oxide nanoparticles present stable and unique performance that makes them suitable for various biomedical applications. There are four common exposure ways that nanoparticles enter our body: injection, inhalation, skin penetration, and ingestion. Among them, injection, ingestion, and skin routes may become significant ways for nano-scale treatment and cosmetics, and inhalation is the essential way for occupational exposure. All those nanoparticles could pass through the exposure routes and enter the circulation, which could cause damage on the cardiovascular system. So it is necessary to evaluate the toxicity of metal oxide nanoparticles and to explore the mechanism. This review chose four commonly used nanometal oxides to discuss about the toxicity they produced, the function they affected, and the mechanisms on cardiovascular endothelial cells. First, we discussed the toxicity they caused. These nanoparticles are less toxic when applied in low doses, but owing to the small particle size and large specific surface area, acute exposure or the metal ions released by nanoparticles will lead to phenotypic changes of endothelial cells, oxidative stress, and apoptosis. An endothelial cell is an essential part of blood vessels and could act as a barrier, maintain vascular tension, and keep the balance between coagulation and anticoagulation. Once vascular endothelium is injured or exposed to vascular risk factors, it would cause endothelial activation, endothelial dysfunction, and nitric oxide (NO) synthase (NOS) dysfunction, which are closely related to the cardiovascular disease. Finally, we talked about the mechanisms by four levels, and we especially mentioned inflammation, the production of reactive oxygen species, and NO.