Comparing the toxicity of nanomaterials between the HL-60 neutrophil-like cell line & primary human neutrophils in vitro

Owing to their extremely small size (1 – 100 nm), nanomaterials (NMs) can exhibit a variety of novel, functional characteristics in contrast with their macroscopic counterparts. Many areas of society have exploited and since benefited from these properties, including agriculture, industry and medicine. However, the same unique properties of NMs also raise concerns about their potential risks to human health and the environment; as a result, nanotoxicology research is becoming increasingly relevant. Assessment of NM-safety has relied on rodent testing via the evaluation of inflammatory responses. However, due to ethical, financial and legislative reasons, there is a drive to seek out alternative and relevant testing models.

Here, we investigate in vitro (non-rodent) models for assessing the stimulation and resolution of NM-mediated inflammation, with a focus on the neutrophil; the most abundant type of white blood cell and one of the earliest responders to sites of inflammation.

We compare the inflammatory responses of the human HL-60 neutrophil-like cell line, with that of primary neutrophils isolated from human blood. A panel of nanoparticles with well-documented in vivo rodent data has been tested, and inflammatory responses assessed using a variety of endpoints including cytotoxicity, cytokine production and activation of a respiratory burst.

Our results suggest that in vitro cell models exhibit a similar pattern of NM toxicity as seen in rodent in vivo models. Their use should be encouraged to better align nanotoxicity testing with the principles of the 3Rs; to Reduce, Refine and Replace animal testing in research.