Hydrogen sulfide induces apoptosis in human periodontium cells

Background and Objective: The existence of hydrogen sulfide (H ₂S) at high concentrations in periodontal pockets is a characteristic feature of periodontitis. Periodontal pathogens play a key role in the production of H₂S under these etiology conditions. This study was designed to examine the cytotoxicity of H₂S in periodontium cells, including human periodontal ligament (PDL) cells and human gingival fibroblasts (HGFs), as well as the role of H₂S in apoptosis induction. Material and Methods: Human PDL cells and HGFs were cultured in the presence of Na ₂S/HCl or in the presence of H₂S 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. Results: Among the three products obtained following degradation of l-cysteine by T. denticola cystalysin, only H₂S induced significant apoptosis in HGF cells. Hydrogen sulfide also induced typical apoptotic morphology in cultured PDL cells. The changes were dependent on the H₂S dose and on the treatment time with H₂S. Hydrogen sulfide-induced apoptosis was also confirmed by staining with annexin V and propidium iodide. In addition, treatment with H₂S led to caspase activation in these cells. Conclusion: These results showed that physiological concentrations of H₂S can induce apoptosis of PDL cells and HGFs in periodontitis, suggesting that H₂S may play an important role in periodontal tissue damage in periodontal diseases.