Anti-proliferative capsular-like polysaccharide antigen from Actinobacillus actinomycetemcomitans induces apoptotic cell death in mouse osteoblastic MC3T3-E1 cells.
Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) has been implicated in the etiology of localized juvenile periodontitis (LJP), and produces a multiplicity of tissue-damaging products. Among those products, the capsular-like polysaccharide antigen (CPA) from A. actinomycetemcomitans is a potent mediator of bone resorption. In fact, this CPA (serotype b) is known to promote osteoclast-like cell formation via interleukin (IL)-1alpha production in mouse marrow cultures. Although osteoblasts complete bone formation, there are few reports focusing on the effect of CPA in bone-forming activity of osteoblasts in inflammatory disease sites. We hypothesized that CPA plays a mediating role in osteoblastic cells. Therefore, the purpose of this study was to examine the effect of CPA from A. actinomycetemcomitans on the mouse osteoblastic cell line MC3T3-E1 and human osteosarcoma SaOS-2 cells. A. actinomycetemcomitans serotype c resulted in a potent dose-dependent inhibition of cell proliferation of both cell lines. Characterization of the antiproliferative activity in the CPA demonstrated that it was not cytotoxic for MC3T3-E1. A 20-hour incubation with CPA-c resulted in a significant increase in apoptotic cell death in the cells, as evaluated by both cellular DNA fragmentation ELISA and FACS analysis. In contrast to the results obtained with a cytokine mixture (tumor necrosis factor-alpha, IL-1beta, and interferon-gamma), no inducible nitric oxide (NO) synthase gene expression or NO release could be detected in MC3T3-E1 after incubation with CPA-c. Further, both CPA-b and -c caused potent induction of apoptosis-related modifiers, e.g., Fas mRNA, whereas bcl-2 mRNA levels were unchanged. Therefore, this study has shown that CPA from A. actinomycetemcomitans contains a potent antiproliferative polysaccharide whose activity is associated with apoptotic cell death in MC3T3-E1, and that CPA per se is an inducer of apoptosis mediated by the Fas system but not by NO.
Yamamoto
S
S
Department of Periodontology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan.
Mogi
M
M
Kinpara
K
K
Ishihara
Y
Y
Ueda
N
N
Amano
K
K
Nishihara
T
T
Noguchi
T
T
Togari
A
A
D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology*; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D017209:Apoptosis; D016667:Bacterial Capsules / Q000276:immunology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D053938:DNA Fragmentation; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D018836:Inflammation Mediators / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology; D007375:Interleukin-1 / Q000276:immunology; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics; D010006:Osteoblasts / Q000276:immunology / Q000473:pathology*; D012516:Osteosarcoma / Q000276:immunology / Q000473:pathology; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology; D015854:Up-Regulation; D019014:fas Receptor / Q000235:genetics
D000942:Antigens, Bacterial; D018836:Inflammation Mediators; D007375:Interleukin-1; D011135:Polysaccharides, Bacterial; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase