Hydrogen sulfide induces apoptosis in human periodontium cells

Abstract

The existence of hydrogen sulfide (H(2)S) at high concentrations in periodontal pockets is a characteristic feature of periodontitis. Periodontal pathogens play a key role in the production of H(2)S under these etiology conditions. This study was designed to examine the cytotoxicity of H(2)S in periodontium cells, including human periodontal ligament (PDL) cells and human gingival fibroblasts (HGFs), as well as the role of H(2)S in apoptosis induction. Human PDL cells and HGFs were cultured in the presence of Na(2)S/HCl or in the presence of H(2)S produced enzymatically by the action of Treponema denticola cystalysin (l-cysteine desulfhydrase) on l-cysteine. Apoptosis was assessed morphologically after nuclear staining with DAPI or was quantified by flow cytometry after staining with annexin V. Caspase activation was measured by an enzymatic assay using DEVD-AMC, a synthetic caspase substrate. Among the three products obtained following degradation of l-cysteine by T. denticola cystalysin, only H(2)S induced significant apoptosis in HGF cells. Hydrogen sulfide also induced typical apoptotic morphology in cultured PDL cells. The changes were dependent on the H(2)S dose and on the treatment time with H(2)S. Hydrogen sulfide-induced apoptosis was also confirmed by staining with annexin V and propidium iodide. In addition, treatment with H(2)S led to caspase activation in these cells. These results showed that physiological concentrations of H(2)S can induce apoptosis of PDL cells and HGFs in periodontitis, suggesting that H(2)S may play an important role in periodontal tissue damage in periodontal diseases.