Hydrogen sulfide inhibits cell proliferation and induces cell cycle arrest via an elevated p21Cip1 level in Ca9-22 cells

Background and Objective: Volatile sulfur compounds such as hydrogen sulfide (H 2 S) and methyl mercaptan (CH 3 SH) are the main causes of oral malodor. However, the physiological functions of H 2 S have not been investigated in oral tissues. The aim of this study was to evaluate the effect of H 2 S on cell proliferation and the cell cycle in oral epithelial-like cells. Material and Methods: Ca9-22 cells were used in this study. Cells were cultured in 5% CO 2 /95% air with (5 or 10 ng/mL) or without H 2 S. DNA synthesis was measured using a 5-bromo-2-deoxyuridine enzyme-linked immunosorbent assay. The cell cycle was analyzed using a flow cytometer. The expressions of phosphorylated retinoblastoma protein (Rb), p21 Cipl and p27 Kip1 were evaluated by western blotting. Results: Exposure to 5 and 10 ng/mL of H 2 S significantly decreased DNA synthesis (p < 0.05). Cell cycle analysis also showed that exposure to both concentrations of H 2 S significantly increased the proportion of cells in G 1 phase (p < 0.001) and significantly decreased the proportion of cells in S phase (p < 0.01). Western blotting showed that Rb phosphorylation was reduced and p21 Cipl was enhanced by exposure to H 2 S. Conclusion: The results indicated that H 2 S inhibits cell proliferation and induces cell cycle arrest via the expression of p21 Cipl in Ca9-22 cells.