Green tea polyphenol EGCg induces cell fusion via reactive oxygen species

Osteoclasts are multinucleated cells formed by macrophage cell fusion that are responsible for bone resorption. Previously, we found that treating osteoclastic progenitor cells with (−)-epigallocatechin gallate (EGCg) increased cell fusion. In this study, we aimed to identify factors involved in the cell fusion induced by EGCg. We hypothesized that EGCg-induced oxidative stress might be involved in cell fusion, and used macrophage cell line RAW264.7 cells. We evaluated cell fusion activity after adding the antioxidants N-acetyl-l-cysteine (NAC) or catalase in addition to EGCg. The mRNA expressions of genes related to cell fusion and bone resorption were quantified by real-time PCR. Finally, we added hydrogen peroxide and examined its effects on cell fusion and TRAP activity. EGCg-induced cell fusion was strongly inhibited by the addition of NAC in a dose-dependent manner (EGCg with 5 mM NAC; decreased to 1.5%; p