Study for periodontal pathogenesis and apoptosis in periodontal tissues induced by volatile sulfur compounds

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Hydrogen sulfide (H_2S) is one of the main reasons of halitosis and periodontally pathogenic. H_2S causes apoptotic cell death in aorta smooth muscle cells and other tissues, and apoptosis plays an important role in the onset and progress of periodontitis. Therefore, we investigated if H_2S causes apoptosis in human gingival fibroblasts (HGF). Materials and Methods : Necrotic cell were determined using lactate dehydrogenase assay. Apoptosis was ascertained with detecting histone-complexed DNA fragments and a flow cytometry. Caspase 3, a key enzyme in apoptotic signaling, was assessed. Reactive oxygen species (ROS) were also detected and inhibition of superoxide dismutase (SOD) by H_2S was verified. DNA damage was examined with single-cell gel electrophoresis (SCGE). Results : Necrosis was found less than 10% of HGF during 72 hours incubation with 100 ng/ml H_2S, whereas significant increment of DNA fragmentation in cytoplasm was found (p < 0.05). Apoptotic HGF cells were also increased in a flow cytometry. Caspase 3 activity was significantly increased at 72 hours incubation (p < 0.01). Tail length, %DNA in tail and Tail moment obtained by SCGE increased in HGF exposed to H_2S for 48 and 72 hours. Moreover, ROS was significantly increased at 48 and 72 hour incubation with H_2S (p < 0.005 and p < 0.001, respectively), and SOD of HGF was strongly inhibited. Conclusion : H_2S caused apoptosis in HGF, and an inhibition of SOD by H_2S increased ROS, then induced apoptosis and DNA strand breaks.