Hydrogen sulfide induces apoptosis in epithelial cells derived from human gingiva

Hydrogen sulfide (H(2)S) is not only one of the main causes of halitosis but is also an agent of toxicity against periodontal cells and tissues in biofilm-related periodontal diseases. Also, apoptosis of gingival epithelial cells may play an important role in the onset and progress of periodontitis. We examined the effect of H(2)S on the induction of apoptosis, using human gingival fibroblasts (HGF) and keratinocyte-like Ca9-22 cells derived from human gingiva. The cells were incubated with H(2)S (100 ng ml(-1)) for 24, 48 or 72 h by adding H(2)S to air containing 5% CO(2), supplied constantly to the culture environment during incubation. The incidence of apoptosis caused by H(2)S was determined with Annexin V staining by flow cytometry. The proportion of apoptotic cells was significantly increased by exposure to H2S for 48 h in comparison with the control in both Ca9-22 cells and HGF. A concentration of 100 ng ml(-1) H(2)S in air is possible in the gingival sulcus. This study indicates that apoptosis in gingival epithelial cells and HGF by H(2)S may occur in the oral cavity, which may cause a periodontal condition.