Long-term effect of full-mouth tooth extraction on the responsiveness of peripheral blood monocytes

Association between periodontitis and inflammatory comorbidities: The common role of innate immune cells, underlying mechanisms and therapeutic targets

Periodontitis, which is related to various systemic diseases, is a chronic inflammatory disease caused by periodontal dysbiosis of the microbiota. Multiple factors can influence the interaction of periodontitis and associated inflammatory disorders, among which host immunity is an important contributor to this interaction. Innate immunity can be activated aberrantly because of the systemic inflammation induced by periodontitis. This aberrant activation not only exacerbates periodontal tissue damage but also impairs systemic health, triggering or aggravating inflammatory comorbidities. Therefore, innate immunity is a potential therapeutic target for periodontitis and associated inflammatory comorbidities. This review delineates analogous aberrations of innate immune cells in periodontitis and comorbid conditions such as atherosclerosis, diabetes, obesity, and rheumatoid arthritis. The mechanisms behind these changes in innate immune cells are discussed, including trained immunity and clonal hematopoiesis of indeterminate potential (CHIP), which can mediate the abnormal activation and myeloid-biased differentiation of hematopoietic stem and progenitor cells. Besides, the expansion of myeloid-derived suppressor cells (MDSCs), which have immunosuppressive and osteolytic effects on peripheral tissues, also contributes to the interaction between periodontitis and its inflammatory comorbidities. The potential treatment targets for relieving the risk of both periodontitis and systemic conditions are also elucidated, such as the modulation of innate immunity cells and mediators, the regulation of trained immunity and CHIP, as well as the inhibition of MDSCs' expansion.

Illuminating the oral microbiome and its host interactions: animal models of disease

Periodontitis and caries are driven by complex interactions between the oral microbiome and host factors, i.e. inflammation and dietary sugars, respectively. Animal models have been instrumental in our mechanistic understanding of these oral diseases, although no single model can faithfully reproduce all aspects of a given human disease. This review discusses evidence that the utility of an animal model lies in its capacity to address a specific hypothesis and, therefore, different aspects of a disease can be investigated using distinct and complementary models. As in vitro systems cannot replicate the complexity of in vivo host-microbe interactions and human research is typically correlative, model organisms-their limitations notwithstanding-remain essential in proving causality, identifying therapeutic targets, and evaluating the safety and efficacy of novel treatments. To achieve broader and deeper insights into oral disease pathogenesis, animal model-derived findings can be synthesized with data from in vitro and clinical research. In the absence of better mechanistic alternatives, dismissal of animal models on fidelity issues would impede further progress to understand and treat oral disease.

Neutrophils in the periodontium: Interactions with pathogens and roles in tissue homeostasis and inflammation

Neutrophils are of key importance in periodontal health and disease. In their absence or when they are functionally defective, as occurs in certain congenital disorders, affected individuals develop severe forms of periodontitis in early age. These observations imply that the presence of immune-competent neutrophils is essential to homeostasis. However, the presence of supernumerary or hyper-responsive neutrophils, either because of systemic priming or innate immune training, leads to imbalanced host-microbe interactions in the periodontium that culminate in dysbiosis and inflammatory tissue breakdown. These disease-provoking imbalanced interactions are further exacerbated by periodontal pathogens capable of subverting neutrophil responses to their microbial community's benefit and the host's detriment. This review attempts a synthesis of these findings for an integrated view of the neutrophils' ambivalent role in periodontal disease and, moreover, discusses how some of these concepts underpin the development of novel therapeutic approaches to treat periodontal disease.

Periodontitis, edentulism and glycemic control in patients with type 2 diabetes: a cross-sectional study

OBJECTIVES

To compare the glycemic control in non-smoking patients with type 2 diabetes according to their periodontal and dental status.

RESEARCH DESIGN AND METHODS

This cross-sectional study investigated patients previously diagnosed with type 2 diabetes and under antidiabetic medication. Clinical data and fasting blood glucose (FBG) levels were collected from medical and dental records. Patients were divided into three groups according to dental and periodontal diagnosis: no or mild periodontitis (NO/MILD, n=96), moderate or severe periodontitis (MOD/SEV, n=74) and edentulous (n=141). FBG levels were compared between groups. Logistic regression was also applied to estimate the OR of presenting hyperglycemia.

RESULTS

Edentulous patients had significantly higher FBG levels of 155.7±70.9 (mean±SD mg/dL) than those in the MOD/SEV (136.6±33.8) and the NO/MILD (123.1±36.7) groups. Differences between the latter two groups were also significant. Edentulous patients had adjusted ORs of 4.53, 4.27 and 3.95 of having FBG≥126, ≥150 and ≥180 mg/dL, respectively, in comparison with NO/MILD group. The MOD/SEV group also presented significant odds of having FBG≥126 mg/dL (OR=2.66) and ≥150 mg/dL (OR=2.45) than the NO/MILD group.

CONCLUSIONS

Patients in the MOD/SEV group had worse glycemic control than the ones in the NO/MILD group. However, edentulous patients presented higher glycemic levels than both dentate groups, and also presented with higher odds of having hyperglycemia.

Evidence that periodontal treatment improves biomarkers and CVD outcomes

AIM

The aim of this review was to critically appraise the evidence on the impact of periodontal treatment of cardiovascular diseases (CVDs) biomarkers and outcomes.

METHODS

A systematic search was performed in Cinhal, Cochrane, Embase and Medline for relevant articles up to July 2012. Duplicate screening and reference hand searching were performed. Data were then summarized and evidence graded in tables.

RESULTS

The search resulted in: (a) no evidence on the effects of periodontal therapy on subclinical atherosclerosis, serum levels of CD40 ligand, serum amyloid A and monocyte chemoattractant protein-1, (b) limited evidence on the effects of periodontal therapy on arterial blood pressure, leucocyte counts, fibrinogen, tissue necrosis factor-α, sE-selectin, von Willebrand factors, d-dimers, matrix metalloproteinases, oxidative stress and CVD events, and (c) moderate evidence suggesting a negligible effect of periodontal therapy in reducing interleukin-6 and lipids levels, whilst a positive effect in reducing serum C-reactive protein levels and improving endothelial function.

CONCLUSIONS

Periodontal therapy triggers a short-term inflammatory response followed by (a) a progressive and consistent reduction of systemic inflammation and (b) an improvement in endothelial function. There is however limited evidence that these acute and chronic changes will either increase or reduce CVD burden of individuals suffering from periodontitis in the long term.

Evidence that periodontal treatment improves biomarkers and CVD outcomes

AIM

The aim of this review was to critically appraise the evidence on the impact of periodontal treatment of cardiovascular diseases (CVDs) biomarkers and outcomes.

METHODS

A systematic search was performed in Cinhal, Cochrane, Embase and Medline for relevant articles up to July 2012. Duplicate screening and reference hand searching were performed. Data were then summarized and evidence graded in tables.

RESULTS

The search resulted in: (a) no evidence on the effects of periodontal therapy on subclinical atherosclerosis, serum levels of CD40 ligand, serum amyloid A and monocyte chemoattractant protein-1, (b) limited evidence on the effects of periodontal therapy on arterial blood pressure, leucocyte counts, fibrinogen, tissue necrosis factor-a, sE-selectin, von Willebrand factors, d-dimers, matrix metalloproteinases, oxidative stress and CVD events, and (c) moderate evidence suggesting a negligible effect of periodontal therapy in reducing interleukin-6 and lipids levels, whilst a positive effect in reducing serum C-reactive protein levels and improving endothelial function.

CONCLUSIONS

Periodontal therapy triggers a short-term inflammatory response followed by (a) a progressive and consistent reduction of systemic inflammation and (b) an improvement in endothelial function. There is however limited evidence that these acute and chronic changes will either increase or reduce CVD burden of individuals suffering from periodontitis in the long term.

Novel Endothelial Biomarkers: Implications for Periodontal Disease and CVD

Endothelial cells are actively involved in various aspects of vascular biology and different stages of atherosclerosis. Endothelial function is increasingly used as an important outcome measure in cardiovascular research. Endothelial progenitor cells (EPCs) are closely linked to endothelial function, and their biomarkers have received much attention. EPCs may not only serve as a pool of progenitor cells and possess the capacity to repair the damaged vasculature, but also act as potent effectors in systemic inflammation, suggesting that EPCs may play a critical role in maintaining endothelial function and the progression of cardiovascular disease (CVD). Emerging evidence shows an association of periodontal infections (gingivitis and periodontitis) with endothelial dysfunction, while the relevant mechanisms remain unknown. Our recent finding of the association of periodontitis with EPCs warrants their utilization as additional biomarkers in future studies on periodontal medicine. This review starts with a brief account on the current understanding of the nature of periodontal infections and their link with systemic inflammation and endothelial dysfunction. The paper also provides an update on endothelial biology and function as well as the novel biomarkers of EPCs and concludes with clinical studies on periodontal diseases and CVD.

Increased levels of circulating endothelial progenitor cells in subjects with moderate to severe chronic periodontitis

AIM

Emerging evidence shows that periodontal disease is associated with endothelial dysfunction. The purpose of this study was to determine the association between chronic periodontitis (CP) and circulating endothelial progenitor cells (EPC).

MATERIALS AND METHODS

Eighty-six non-smoking subjects (36 males and 50 females, aged 35-80 years) were recruited, including 23 subjects with no or mild CP and 63 subjects with moderate to severe CP. The levels of circulating EPC were quantitatively determined by fluorescence-activated cell analysis, including CD34+/kinase insert domain-containing receptor (KDR)+ (more mature EPC) and CD133+/KDR+ (less mature EPC). Periodontal conditions, the intima-media thickness of carotid arteries and circulating biomarkers were examined.

RESULTS

Subjects with moderate to severe CP exhibited an increased risk of high EPC count, compared with those with no or mild CP: CD34+/KDR+ EPC [odds ratio (OR)=9.5, 95% confidence interval (95% CI) 1.5-61.0, p=0.018; CD133+/KDR+ EPC, OR=4.6, 95% CI 1.1-19.5, p=0.039]. C-reactive protein was significantly associated with high CD34+/KDR+ EPC count and age was inversely related with high EPC count. Age, gender and CD34+/KDR+ EPC were independent variables of increased carotid intima-media thickness (p<0.05).

CONCLUSION

This study shows for the first time that moderate to severe CP is associated with an increased level of circulating EPC.

Automatic mining of the literature to generate new hypotheses for the possible link between periodontitis and atherosclerosis: lipopolysaccharide as a case study

AIM

The aim of the current report was to generate and explore new hypotheses into how, in a pathophysiological sense, atherosclerosis and periodontitis could be linked.

MATERIAL AND METHODS

Two different biomedical informatics techniques were used: an association-based technique that generated a ranked list of genes associated with the diseases, and a natural language processing tool that extracted the relationships between the retrieved genes and lipopolysaccharide (LPS).

RESULTS

This combined approach of association-based and natural language processing-based literature mining identified a hit list of 16 candidate genes, with PON1 as the primary candidate.

CONCLUSIONS

Further study of the literature prompted the hypothesis that PON1 might connect periodontitis with atherosclerosis in both an LPS-dependent and a non-LPS-dependent manner. Furthermore, the resulting genes not only confirmed already known associations between the two diseases, but also provided genes or gene products that have only been investigated separately in the two disease states, and genes or gene products previously reported to be involved in atherosclerosis. These findings remain to be investigated through clinical studies. This example of multidisciplinary research illustrates how collaborative efforts of investigators from different fields of expertise can result in the discovery of new hypotheses.

Neutrophil hyper-responsiveness in periodontitis

Peripheral neutrophil hyper-responsiveness in chronic periodontitis leads to excessive reactive oxygen species (ROS) production. We aimed to determine whether neutrophil hyper-responsiveness was constitutive or reactive, and to discover the effect of non-surgical therapy. Peripheral blood neutrophils from patients (n = 19), before and 3 months after therapy, and matched control individuals were Fc gamma-receptor-stimulated with/without priming with P. gingivalis and F. nucleatum. Total and extracellular ROS were determined by luminol/isoluminol chemiluminescence. The high total ROS generation of patients' neutrophils compared with that of control individuals (P = 0.016) continued at a reduced level post-therapy (P = 0.059). Reduced activity post-therapy was also seen with priming. Unstimulated total ROS levels did not differ between patients and control individuals before or after therapy. However, the high unstimulated, extracellular ROS production by patients' neutrophils compared with control individuals (P < 0.05) continued post-therapy and was unaffected by priming. Therapy reduced Fc gamma-receptor-stimulated total ROS production, but not unstimulated extracellular radical release, suggesting that constitutive and reactive mechanisms underlie neutrophil hyper-responsiveness.

Low-grade inflammation in chronic infectious diseases: paradigm of periodontal infections

Increasing evidence implicates periodontitis, a chronic inflammatory disease of the tooth-supporting structures, as a potential risk factor for increased morbidity or mortality for several systemic conditions including cardiovascular disease (atherosclerosis, heart attack, and stroke), pregnancy complications (spontaneous preterm birth [SPB]), and diabetes mellitus. Cross-sectional, case-control, and cohort studies indicate that periodontitis may confer two- and up to sevenfold increase in the risk for cardiovascular disease and premature birth, respectively. Given the recently acquired knowledge that systemic inflammation may contribute in the pathogenesis of atherosclerosis and may predispose to premature birth, research in the field of periodontics has focused on the potential of this chronic low-grade inflammatory condition to contribute to the generation of a systemic inflammatory phenotype. Consistent with this hypothesis clinical studies demonstrate that periodontitis patients have elevated markers of systemic inflammation, such as C-reactive protein (CRP), interleukin 6 (IL-6), haptoglobin, and fibrinogen. These are higher in periodontal patients with acute myocardial infarction (AMI) than in patients with AMI alone, supporting the notion that periodontal disease is an independent contributor to systemic inflammation. In the case of adverse pregnancy outcomes, studies on fetal cord blood from SBP babies indicate a strong in utero IgM antibody response specific to several oral periodontal pathogens, which induces an inflammatory response at the fetal-placental unit, leading to prematurity. The importance of periodontal infections to systemic health is further strengthened by pilot intervention trials indicating that periodontal therapy may improve surrogate cardiovascular outcomes, such as endothelial function, and may reduce four- to fivefold the incidence of premature birth. Nevertheless, further research is needed to fully discern the underlying mechanisms by which local chronic infections can have an impact on systemic health, and in this endeavor periodontal disease may serve as an ideal disease model.

Interleukin-1 beta, interleukin-12 and interleukin-18 levels in gingival fluid and serum of patients with gingivitis and periodontitis

INTRODUCTION

Cytokines are of major importance in periodontal disease progression. Interleukin-12 (IL-12) stimulates interferon-gamma production by T helper type 1 (Th1) cells while IL-18 induces Th1 responses when present with IL-12 but Th2 responses in the absence of IL-12. IL-1beta has been correlated with periodontal disease destruction. This study determined the local concentrations of these cytokines in sites of gingivitis and periodontitis.

METHODS

Gingival crevicular fluid was collected from two sites in each of 10 gingivitis patients and from two gingivitis sites and two periodontitis sites from each of 10 periodontitis patients. Serum samples were also collected. IL-1beta, biologically active IL-12 p70, the IL-12 p40 subunit and IL-18 concentrations were determined by enzyme-linked immunoabsorbent assay.

RESULTS

IL-1beta and IL-18 concentrations were higher in the gingival crevicular fluid from periodontitis patients than in that from gingivitis patients; IL-18 concentrations were higher than those of IL-1beta. Very little IL-12, either p40 or p70, was detected in the gingival crevicular fluid samples. In the serum, very low levels of cytokines were found. The level of serum IL-12 p40, however, was higher than in the fluid from periodontitis sites of periodontitis patients.

CONCLUSION

The local production of IL-1beta and IL-18 in the gingival crevicular fluid increased with increasing inflammation and IL-18 was the predominant cytokine at both gingivitis and periodontitis sites. Very little IL-12 was detected with levels decreasing with increasing inflammation. These results suggest that there is an association between severity of periodontal disease and levels of IL-1, IL-12 and IL-18.

Hyper-reactive mononuclear cells and neutrophils in chronic periodontitis

OBJECTIVES

Stimulated mono- and polymorphonuclear cells from patients with periodontitis have shown increased release of interleukin-1beta (IL-1beta) and oxygen radicals, respectively. The aim was to study whether this hyper-reactivity could be found both in mono- and polymorphonuclear cells from the same patient, and whether there was a relation to the gene coding for IL-1beta (IL-1beta(+3953)).

MATERIAL AND METHODS

Peripheral mononuclear cells from 14 non-smoking and well-treated patients and pair-matched controls were incubated with opsonized Staphylococcus aureus and lipopolysaccharide (LPS). Released IL-1beta and tumour necrosis factor (TNF)-alpha were determined with ELISA. Generation of oxygen radicals from the Fcgamma-receptor-stimulated neutrophils was measured with chemiluminescence and the polymorphism at IL-1beta(+3953) was measured with polymerase chainreaction.

RESULTS

The mononuclear cells from the patients released more IL-1beta after incubation with LPS (p<0.001) and with bacteria (p<0.05). The release of TNF-alpha tended to be higher in the patient group. The peripheral neutrophils from the patients generated more oxygen radicals (p<0.06). We found no differences between the study groups regarding the IL-1beta(+3953) polymorphism.

CONCLUSION

The similarity in systemic inflammation between patients and controls suggests that the increased release/generation of IL-1beta and oxygen radicals from peripheral leukocytes in periodontitis patients is of a constitutional nature and of pathogenic relevance.