Influence of hydrogen-occluding-silica on migration and apoptosis in human esophageal cells in vitro

In the last decade, many studies have shown that hydrogen gas or hydrogen water can reduce the levels of reactive oxygen species in the living body. Molecular hydrogen has antioxidant and antiapoptotic effects and a preventive effect on oxidative stress-induced cell death. In the present study, we investigated solidified hydrogen-occluding-silica (H2-silica) that can release molecular hydrogen into cell culture medium because the use of hydrogen gas has strict handling limitations in hospital and medical facilities and laboratories, owing to its physicochemical characteristics. Human esophageal squamous cell carcinoma (KYSE-70) cells and normal human esophageal epithelial cells (HEEpiCs) were used to investigate the effects of H2-silica on cell viability and proliferation. Cell migration was examined with wound healing and culture-insert migration assays. The intracellular levels of reactive oxygen species were evaluated with a nitroblue tetrazolium assay. To assess the apoptotic status of the cells, the Bax/Bcl-2 ratio and cleaved caspase-3 were analyzed by western blot. The results showed that KYSE-70 cells and HEEpiCs were generally inhibited by H2-silica administration, and there was a significant proliferation-inhibitory effect in an H2-silica concentration-dependent manner compared with the control group (P < 0.05) in KYSE-70. Apoptosis-inducing effect on KYSE-70 cells was observed in 10, 300, 600, and 1,200 ppm H2-silica, and only 1,200 ppm H2-silica caused a 2.4-fold increase in apoptosis in HEEpiCs compared with the control group as the index of Bax/Bcl-2. H2 silica inhibited cell migration in KYSE-70 cells, and high concentrations had a cytotoxic effect on normal cells. These findings should provide insights into the mechanism of inhibition of H2-silica on human cancer cells in vitro.