Silver nanoparticles induce apoptosis through the Toll-like receptor 2 pathway

Objective. The objective of this study was to evaluate the effects of silver nanoparticles (AgNPs) on the Toll-like receptor 2 (TLR-2) pathway in cultured cells. Study Design. Human chondrocytes, periodontal ligament (PDL) cells, and SCC-9 cells (squamous cell carcinoma from the tongue) were cultured and subjected to cytotoxicity assays. To evaluate the effects of AgNPs on the TLR-2 pathway, TLR-2 small interfering (si) RNA or TLR-2 antibodies were applied to the chondrocytes, followed by the application of AgNPs. Results. AgNPs induced dose-dependent effects on the examined cell types in terms of both cytotoxicity and TLR-2 expression levels. AgNP-mediated apoptosis was reduced after treatment with TLR-2 siRNA in both PDL cells and chondrocytes. Furthermore, functional blocking of TLR-2 with anti-TLR2 antibodies inhibited AgNP-mediated cytotoxicity. AgNPs increased c-Jun phosphorylation, an effect that was reversed after treatment with TLR-2 siRNA. Conclusions. The results indicate that AgNP-mediated apoptosis most likely occurs via the TLR-2 pathway.