Silver nanoparticles stimulate neutrophils oxidative burst through the activation of protein kinase C

Silver nanoparticles (AgNPs) have a wide range of applications. Despite the widespread use of AgNPs in several products, such as cosmetics, textiles, certain types of packaging, etc., its safety is still elusive, namely in what concerns the putative effects in the immune system. Neutrophils are believed to be among the first and primary cell types that process systemic nanoparticles, mediating host inflammatory and immunological response, involving the production of reactive prooxidant species. The main objective of this study was to evaluate the effect of different sized polyvinylpyrrolidone (PVP)-coated AgNPs (5, 10 and 50 nm) on human neutrophils oxidative burst in vitro. It was observed that AgNPs stimulated the production of neutrophils oxidative burst, reaching a maximum value 2 hours after the start of exposure. The smaller AgNPs were more active than the other tested sizes, this effect being abolished with the use of diphenyleneiodonium (DPI), a NADPH oxidase inhibitor and Go6983, a protein kinace C (PKC) inhibitor. These results suggest that neutrophils oxidative burst stimulated by AgNPs occurs via NADPH oxidase, through the activation of PKC. These data contribute for a better understand of the pro-inflammatory mechanisms associated to the use of AgNPs.