Treponema denticola may stimulate both epithelial proliferation and apoptosis through MAP kinase signal pathways.
Mitogen-activated protein kinases (MAP kinases) play a key role in the regulation of cell survival and death. Effects of Treponema denticola ATCC 35405 on ERK, p38 and JNK MAP kinases, and cell behavior was studied using non-keratinizing periodontal ligament epithelial cells (PLE) in vitro. Compared to Chinese hamster ovary cells, human cervix adenocarcinoma cells, human osteosacroma cells and human gingival fibroblasts, PLE cells were much more resistant to T. denticola-induced reduction in cell viability, assayed by tetrazolium and crystal violet assays. A low dose of 5 x 10(7) T. denticola cells/ml increased DNA synthesis ([3H]thymidine uptake) in PLE cells but at higher concentrations DNA synthesis was decreased. TUNEL staining analysis showed that about 50% of epithelial cells in onolayers died through apoptosis when exposed to a high dose of 10(11) T. denticola/ml for 24 h. Morphological light and electron microscopic analysis supported the idea that both apoptotic and necrotic cell death took place. Rounding, membrane damage, fragmentation and detachment were observed in selective cells of both mono- and multilayered PLE cultures challenged with T. denticola. Western blot analysis using MAP kinase phosphospecific antibodies showed that T. denticola strongly but transiently activated ERK1 and ERK2, signals mediating cell proliferation, and JNK and p38, kinases mediating apoptosis. While a specific inhibitor of the ERK MAP kinase pathway prevented the T. denticola stimulation of cell proliferation, inhibitor of p38 increased the cell numbers in T. denticola-treated cultures. The results suggest that T. denticola activates epithelial cell MAP kinase signal pathways controlling cell proliferation and cell survival. In addition, T. denticola exerts cytotoxic effects that appear to predominate at higher bacterial concentrations.
Leung
W Keung
WK
Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, Canada.
Wu
Qiang
Q
Hannam
Pauline M
PM
McBride
Barry C
BC
Uitto
Veli-Jukka
VJ
D000230:Adenocarcinoma / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000648:ultrastructure; D048429:Cell Size / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis; D004847:Epithelial Cells / Q000473:pathology / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology; D005881:Gingiva / Q000166:cytology; D006801:Humans; D020287:In Situ Nick-End Labeling; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008854:Microscopy, Electron; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D012516:Osteosarcoma / Q000473:pathology; D010513:Periodontal Ligament / Q000166:cytology / Q000502:physiology*; D014208:Treponema / Q000502:physiology*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases