Charged molecular silica trigger in vitro NETosis in human granulocytes via both oxidative and autophagic pathways

OBJECTIVE: Neutrophils play a key role in immunity and are known to respond to exogenous threats by releasing neutrophil extracellular traps (NETs) through NETosis, a process involving the release of neutrophils nuclear DNA decorated with proteins into the extracellular space. In this study, attention has been focused on the ability of differently charged molecular systems polyhedral oligomeric silsesquioxanes (POSS) to induce NETosis. MATERIALS AND METHODS: NETs formation was induced by phorbol myristate acetate (PMA) (positive control) and POSS treatment and visualized by confocal microscopy. Moreover, NETs production was quantified by Sytox green staining. Oxidative stress, autophagy as well as endocytosis involvement in the observed phenomena was evaluated by a specific inhibitory approach. RESULTS: Results obtained in this study demonstrate a POSS time and dose-dependent ability in inducing NETs release irrespectively to their charge. POSS induced NETosis is a consequence of their internalization, as demonstrated by the strong reduction in NETs formation after endocytosis inhibition. Moreover, POSS induced NETosis involves both an increase in superoxide anion generation and autophagy pathway activation as demonstrated by the protective effect displayed by sodium azide and wortmannin. CONCLUSIONS: Data presented in this study indicate that nanomaterials and molecular systems could have a role in the onset of inflammatory phenomena.