Porphyromonas gingivalis may play an important role in the pathogenesis of periodontitis-associated rheumatoid arthritis
ABSTRACT Rheumatoid arthritis (RA) is a common, systemic autoimmune disease which leads to destruction of the joint architecture and consequent disability. Although the aetiology of RA remains unknown, accumulating studies have established a strong association between RA and periodontitis (PD). Recently, anti-cyclic citrullinated peptide (anti-CCP) autoantibody and citrullinated peptide have been realized to be involved in the breaking of self-tolerance and development of autoimmune in RA. The citrullinated peptide is generated by post-translational modification (citrullination) of protein-bound arginine by peptidylarginine deiminase (PAD). Porphyromonas gingivalis(P. gingivalis), the major aetiological agent of PD and the only bacterium known to express a PAD enzyme, has been reported to be significantly associated with RA. The antibody titers to P. gingivalis are significantly increased in patients with RA and P. gingivalis antibody titers are significantly correlated with anti-CCP antibody isotypes that are specific to RA. Recent study indicates that the major synovial targets of the RA-specific anti-CCP autoantibodies are deiminated forms of the alpha- and beta- chains of fibrin. Meanwhile, it is also confirmed that bacterial PAD produced by P. gingivalis has the capacity of deiminating arginine in fibrin found in the periodontal lesion. What's more, it has been demonstrated that citrullination of HLA binding peptide causes a 100-fold increase in peptide-MHC affinity and leads to the activation CD4(+)T cells in HLA DRB1 0401 transgenic mice. Therefore, we postulate that P. gingivalis may play a crucial role in the pathogenesis of periodontitis-associated RA. P. gingivalis, which colonizes in the oral cavity, produces PAD enzyme continuously that leads to the citrullination of RA autoantigen such as fibrin in synovium joint. These PAD engendered antigens, presented in association with major histocompatibility complex (MHC) molecules by antigen-presenting cells (APC), ultimately lead to production of the anti-CCP antibody. The anti-CCP antibodies form immune complexes with citrullinated proteins, which can be bound by inflammatory cells via their Fc receptors. The roles of these immune complexes and inflammatory cells are mediated by a complex cascade involving complement activation. These mechanisms result in a release of mediators of inflammation and joint destruction ultimately leading to the onset of RA. This hypothesis reveals that oral bacterial infection may play a role in peptide citrullination which might be involved in loss of self-tolerance and development of autoimmune in RA.
SourceAvailable from: Koji Nakayama[Show abstract] [Hide abstract]
ABSTRACT: Porphyromonas gingivalis is a gram-negative, non-motile, anaerobic bacterium implicated as a major pathogen in periodontal disease. P. gingivalis grows as black-pigmented colonies on blood agar, and many bacteriologists have shown interest in this property. Studies of colonial pigmentation have revealed a number of important findings, including an association with the highly active extracellular and surface proteinases called gingipains that are found in P. gingivalis. The Por secretion system, a novel type IX secretion system (T9SS), has been implicated in gingipain secretion in studies using non-pigmented mutants. In addition, many potent virulence proteins, including the metallocarboxypeptidase CPG70, 35 kDa hemin-binding protein HBP35, peptidylarginine deiminase PAD and Lys-specific serine endopeptidase PepK, are secreted through the T9SS. These findings have not been limited to P. gingivalis but have been extended to other bacteria belonging to the phylum Bacteroidetes. Many Bacteroidetes species possess the T9SS, which is associated with gliding motility for some of these bacteria.Journal of Periodontal Research 12/2014; 50(1). DOI:10.1111/jre.12255 · 2.22 Impact Factor
Reumatología Clínica 12/2014; 11(2). DOI:10.1016/j.reuma.2014.11.001
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ABSTRACT: Periodontal diseases are characterized by localized infections and inflammatory conditions that directly affect teeth supporting structures which are the major cause of tooth loss. Several studies have demonstrated the involvement of autoimmune responses in periodontal disease. Evidences of involvement of immunopathology have been reported in periodontal disease. Bacteria in the dental plaque induce antibody formation. Autoreactive T cells, natural killer cells, ANCA, heat shock proteins, autoantibodies, and genetic factors are reported to have an important role in the autoimmune component of periodontal disease. The present review describes the involvement of autoimmune responses in periodontal diseases and also the mechanisms underlying these responses. This review is an attempt to throw light on the etiopathogenesis of periodontal disease highlighting the autoimmunity aspect of the etiopathogenesis involved in the initiation and progression of the disease. However, further clinical trials are required to strengthen the role of autoimmunity as a cause of periodontal disease.05/2014; 2014:596824. DOI:10.1155/2014/596824