The role of inflammation and genetics in periodontal disease

Periodontitis is a complex disease: (a) various causative factors play a role simultaneously and interact with each other; and (b) the disease is episodic in nature, and bursts of disease activity can be recognized, ie, the disease develops and cycles in a nonlinear fashion. We recognize that various causative factors determine the immune blueprint and, consequently, the immune fitness of a subject. Normally, the host lives in a state of homeostasis or symbiosis with the oral microbiome; however, disturbances in homeostatic balance can occur, because of an aberrant host response (inherited and/or acquired during life). This imbalance results from hyper- or hyporesponsiveness and/or lack of sufficient resolution of inflammation, which in turn is responsible for much of the disease destruction seen in periodontitis. The control of this destruction by anti-inflammatory processes and proresolution processes limits the destruction to the tissues surrounding the teeth. The local inflammatory processes can also become systemic, which in turn affect organs such as the heart. Gingival inflammation also elicits changes in the ecology of the subgingival environment providing optimal conditions for the outgrowth of gram-negative, anaerobic species, which become pathobionts and can propagate periodontal inflammation and can further negatively impact immune fitness. The factors that determine immune fitness are often the same factors that determine the response to the resident biofilm, and are clustered as follows: (a) genetic and epigenetic factors; (b) lifestyle factors, such as smoking, diet, and psychosocial conditions; (c) comorbidities, such as diabetes; and (d) local and dental factors, as well as randomly determined factors (stochasticity). Of critical importance are the pathobionts in a dysbiotic biofilm that drive the viscious cycle. Focusing on genetic factors, currently variants in at least 65 genes have been suggested as being associated with periodontitis based on genome-wide association studies and candidate gene case control studies. These studies have found pleiotropy between periodontitis and cardiovascular diseases. Most of these studies point to potential pathways in the pathogenesis of periodontal disease. Also, most contribute to a small portion of the total risk profile of periodontitis, often limited to specific racial and ethnic groups. To date, 4 genetic loci are shared between atherosclerotic cardiovascular diseases and periodontitis, ie, CDKN2B-AS1(ANRIL), a conserved noncoding element within CAMTA1 upstream of VAMP3, PLG, and a haplotype block at the VAMP8 locus. The shared genes suggest that periodontitis is not causally related to atherosclerotic diseases, but rather both conditions are sequelae of similar (the same?) aberrant inflammatory pathways. In addition to variations in genomic sequences, epigenetic modifications of DNA can affect the genetic blueprint of the host responses. This emerging field will yield new valuable information about susceptibility to periodontitis and subsequent persisting inflammatory reactions in periodontitis. Further studies are required to verify and expand our knowledge base before final cause and effect conclusions about the role of inflammation and genetic factors in periodontitis can be made

Periodontitis: a host-mediated disruption of microbial homeostasis. Unlearning learned concepts

Article first published online: 11 APR 2013New concepts evolve when existing ones fail to address known factors adequately or are invalidated by new evidence. For decades periodontitis has been considered to be caused by specific bacteria or groups of bacteria and, accordingly, treatment protocols have largely been based on anti-infective therapies. However, close inspection of current data leads one to question whether these bacteria are the cause or the result of periodontitis. Good evidence is emerging to suggest that it is indeed the host response to oral bacteria that leads to the tissue changes noted in gingivitis. These changes lead to an altered subgingival environment that favors the emergence of 'periodontal pathogens' and the subsequent development of periodontitis if the genetic and external environmental conditions are favorable for disease development. Thus, it seems that it is indeed the initial early host-inflammatory and immune responses occurring during the development of gingivitis, and not specific bacteria or their so-called virulence factors, which determine whether periodontitis develops and progresses. In this review we consider these concepts and their potential to change the way in which we view and manage the inflammatory periodontal diseases.P. Mark Bartold and Thomas E. Van Dyk

An appraisal of the role of specific bacteria in the initial pathogenesis of periodontitis

BACKGROUND:Historically, inflammatory periodontal diseases (gingivitis and periodontitis) have been recognized as being primarily of bacterial origin. Bacteria are necessary for disease development, but the presence of specific bacteria does not guarantee progression to periodontitis. Periodontitis is a multifactorial disease; specific bacteria are associated with disease, but may not be the target of treatment. Gingivitis and periodontitis are inflammatory conditions associated with bacterial overgrowth. AIM:To analyse evidence for established thought that specific bacteria directly participate in the pathogenesis of periodontitis and question the long-held tenet that penetration of the periodontal connective tissues by bacteria and their products is a significant phase in the initial development of periodontitis. METHODS:The literature was searched for studies on initiation of gingivitis and periodontitis by specific pathogens. The search results were insufficient for a systematic review and have been summarized in a commentary instead. RESULTS:There is very little evidence in the literature to support the commonly held concept that specific bacteria initiate periodontitis. CONCLUSION:We present evidence for a paradigm supporting the central role of inflammation, rather than specific microbiota, in the early pathogenesis of periodontitis, and discuss whether controlling the inflammation can influence the character and composition of the periodontal infection.Peter Mark Bartold, Thomas E. Van Dyk

PDK1 Regulates Chemotaxis in Human Neutrophils

Phosphoinositide-dependent kinase (PDK1) plays a central role in signal transduction mediated by phosphatidylinositol 3-kinases (PI3K) and regulates cellular functions in neutrophils. Neutrophils from individuals diagnosed with localized aggressive periodontitis (LAP) present an in vivo phenotype with depressed chemotaxis. The aim of this study was to test the hypothesis that PDK1 regulates chemotaxis in neutrophils and is responsible for the abnormal neutrophil chemotaxis LAP. Neutrophil chemotaxis was significantly suppressed by the PDK1 inhibitor staurosporine. When cells were transfected with PDK1 siRNA, there was a significant reduction in chemotaxis, while superoxide generation was not significantly affected. In primary neutrophils from persons with LAP, PDK1 expression and activation levels were significantly reduced, and this reduction was associated with the reduced phosphorylation of Akt (Thr308) and chemotaxis. Analysis of these data demonstrates that PDK1 is essential for the chemotactic migration of neutrophils, and in the absence of PDK1, neutrophil chemotaxis is impaired

sj-docx-1-jdr-10.1177_00220345231197156 – Supplemental material for RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion

Supplemental material, sj-docx-1-jdr-10.1177_00220345231197156 for RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion by Y-C. Wu, N. Yu, C.A. Rivas, N. Mehrnia, A. Kantarci and T.E. Van Dyke in Journal of Dental Research</p

sj-pdf-1-jdr-10.1177_00220345231197156 – Supplemental material for RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion

Supplemental material, sj-pdf-1-jdr-10.1177_00220345231197156 for RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion by Y-C. Wu, N. Yu, C.A. Rivas, N. Mehrnia, A. Kantarci and T.E. Van Dyke in Journal of Dental Research</p

Salivary Immunoglobulins and Prevalent Coronary Artery Disease

Previous studies examined the serum immunoglobulin levels in relation to coronary artery disease (CAD). We hypothesized that the salivary immunoglobulins might better estimate oral infections in this relationship. Multivariate logistic regression analyses utilizing the data from 256 angiographically confirmed CAD patients and 250 non-CAD individuals that controlled for age, sex, smoking, diabetes, total/HDL cholesterol ratio, hypertension, and education revealed the trends that salivary IgA was positively and salivary IgG was inversely associated with CAD. The odds ratios (OR) of each increasing quartile of salivary IgA were 1.00 (first and second quartiles combined), 1.97, and 1.37 (p-value for trend = 0.06), while those for salivary IgG were 1.00, 0.77, 0.60, and 0.51 (p-value for trend = 0.02). Additionally, salivary IgA correlated positively with C-reactive protein and Asymptotic Dental Score (dental infection score), while IgG was inversely associated with these inflammation markers. Salivary IgA warrants further studies to confirm its role in the risk assessment of CAD