Cytotoxic Effects of Periodontopathic Bacteria on Human Gingival Epithelial Cell Cultured in Serum-Free Medium.

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The purpose of this investigation was to study the effects of selected periodontal pathogens on cell proliferation, protein synthesis and cell injury in vitro.The ultrasonic extracts from microorganisms included A. actinomycetemcomitans, P. gingivalis, P. intermedia, C. sputigena, E. corrodens, F. nucleatum, A. viscosus and St. mutans. Target cells were keratinocytes SCC9 and gingival keratinocytes cultured in serum-free medium. The results showed that cell proliferation and rate of protein synthesis by SCC9 were strongly inhibited by E. corrodens ; at similar concentrations A. actinomycetemcomitans, P. gingivalis and C. sputigena also significantly reduced the proliferation and synthesis whereas P. intez-media, F. nucleatum, A. viscosus and St. mutans had only minor ef f ects. These results indicate that keratinocyte function may be modulated by periodontopathic bacteria.The cell detachment assay was subjected by polymorphonuclear leukocytes and/or bacterial ultrasonic extracts from A … More . actinomycetemcomitans, B. forsythus, F. nucleatum, C. sputigena and E. corrodens. The bacterial extracts alone caused no cell disruption of the keratinocyte monolayers. Polymorphonuclear leukocyte alone caused only a minimal cell detachment. On the contrary, when the bacterial extracts were added to the co-culture of keratinocytes and polymorphonuclear leukocytes, cell detachment of keratinocytes was observed except for the bacterial extract f rom E. corrodens. The effect of A. actinomycetemcomitans was strongest. This effect was heat labile and not inhibited by polymyxin B. Cell detachment was inhibited by alpha 1-antitrypsin but not by catalase and superoxide dismutase. Hydrogen peroxide and leukocyte elastase also caused keratinocyte detachment, and keratinocyte lysis was not observed. These results indicate that polymorphonuclear leukocyte can cause non-lytic cell detachment of the gingival keratinocytes when encountering some bacteria, which may lead to the increase of the permeability of the keratinocyte layers. Less