title: Induction of apoptotic cell death in peripheral blood mononuclear and polymorphonuclear cells by an oral bacterium, Fusobacterium nucleatum.
abstract: It is largely unknown why a variety of bacteria present in the oral cavity are capable of establishing themselves in the periodontal pockets of nonimmunocompromised individuals in the presence of competent immune effector cells. In this paper we present evidence for the immunosuppressive role of Fusobacterium nucleatum, a gram-negative oral bacterium which plays an important role in the generation of periodontal disease. Our studies indicate that the immunosuppressive role of F. nucleatum is largely due to the ability of this organism to induce apoptotic cell death in peripheral blood mononuclear cells (PBMCs) and in polymorphonuclear cells (PMNs). F. nucleatum treatment induced apoptosis of PBMCs and PMNs as assessed by an increase in subdiploid DNA content determined by DNA fragmentation and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling assays. The ability of F. nucleatum to induce apoptosis was abolished by either heat treatment or proteinase digestion but was retained after formaldehyde treatment, suggesting that a heat-labile surface protein component is responsible for bacterium-mediated cell apoptosis. The data also indicated that F. nucleatum-induced cell apoptosis requires activation of caspases and is protected by NF-kappaB. Possible mechanisms of F. nucleatum's role in the pathogenesis of periodontal disease are discussed.
authors.affiliation: Department of Oral Biology and Oral Medicine, Dental Research Institute, University of California, Los Angeles, California 90095, USA. ajewett@ucla.edu
authors.forename: A
authors.initials: A
authors.lastname: Jewett
authors.forename: W R
authors.initials: WR
authors.lastname: Hume
authors.forename: H
authors.initials: H
authors.lastname: Le
authors.forename: T N
authors.initials: TN
authors.lastname: Huynh
authors.forename: Y W
authors.initials: YW
authors.lastname: Han
authors.forename: G
authors.initials: G
authors.lastname: Cheng
authors.forename: W
authors.initials: W
authors.lastname: Shi
mesh_terms: D017209:Apoptosis; D020170:Caspase 1 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D016967:Fusobacterium nucleatum / Q000502:physiology*; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology; D007165:Immunosuppression Therapy; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear / Q000473:pathology*; D009055:Mouth / Q000382:microbiology*; D016328:NF-kappa B / Q000378:metabolism; D009504:Neutrophils / Q000473:pathology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D016328:NF-kappa B; D011994:Recombinant Proteins; D020170:Caspase 1