Evaluating the Toxicity of Silver Nanoparticles by Detecting Phosphorylation of Histone H3 in Combination with Flow Cytometry Side-Scattered Light

Post-translational modification of histones is linked to a variety of biological processes and disease states. This paper focuses on phosphorylation of histone H3 at serine 10 (p-H3S10), induced by silver nanoparticles (AgNPs) and discusses the usefulness of p-H3S10 as a marker to evaluate the toxicity of AgNPs. Cultured human cells showed remarkable p-H3S10 immediately after treatment with AgNPs but not with Ag microparticles. p-H3S10 lasts up to 24 h and strongly depends upon the cellular uptake of AgNPs. Removal of Ag ions suppressed p-H3S10, while adding an excess of Ag ions augmented p-H3S10. We expected that p-H3S10 requires two events: cellular uptake of AgNPs and continuous release of Ag ions from intracellular AgNPs. AgNPs enhanced the expression of the proto-oncogene <i>c-jun</i>, and p-H3S10 increased in the promoter sites of the gene, indicating that p-H3S10 might indicate a biological reaction related to carcinogenesis. We previously showed that side-scattered light from flow cytometry could be used to measure the uptake potential of nanoparticles [Suzuki, H.; Toyooka, T.; Ibuki, Y. Simple and easy method to evaluate uptake potential of nanoparticles in mammalian cells using a flow cytometric light scatter analysis. Environ. Sci. Technol. 2007, 41 (8), 3018−3024]. Our current findings suggest that p-H3S10 can be used to evaluate the toxicity of AgNPs and Ag ion release in combination with detection of side-scattered light from flow cytometry