Refractory periodontitis population characterized by a hyperactive oral neutrophil phenotype

Sinensetin protects against periodontitis through binding to Bach1 enhancing its ubiquitination degradation and improving oxidative stress

Periodontitis is a chronic inflammatory and immune reactive disease induced by the subgingival biofilm. The therapeutic effect for susceptible patients is often unsatisfactory due to excessive inflammatory response and oxidative stress. Sinensetin (Sin) is a nature polymethoxylated flavonoid with anti-inflammatory and antioxidant activities. Our study aimed to explore the beneficial effect of Sin on periodontitis and the specific molecular mechanisms. We found that Sin attenuated oxidative stress and inflammatory levels of periodontal ligament cells (PDLCs) under inflammatory conditions. Administered Sin to rats with ligation-induced periodontitis models exhibited a protective effect against periodontitis in vivo. By molecular docking, we identified Bach1 as a strong binding target of Sin, and this binding was further verified by cellular thermal displacement assay and immunofluorescence assays. Chromatin immunoprecipitation-quantitative polymerase chain reaction results also revealed that Sin obstructed the binding of Bach1 to the HMOX1 promoter, subsequently upregulating the expression of the key antioxidant factor HO-1. Further functional experiments with Bach1 knocked down and overexpressed verified Bach1 as a key target for Sin to exert its antioxidant effects. Additionally, we demonstrated that Sin prompted the reduction of Bach1 by potentiating the ubiquitination degradation of Bach1, thereby inducing HO-1 expression and inhibiting oxidative stress. Overall, Sin could be a promising drug candidate for the treatment of periodontitis by targeting binding to Bach1.

Sports Diet and Oral Health in Athletes: A Comprehensive Review

Food and fluid supply is fundamental for optimal athletic performance but can also be a risk factor for caries, dental erosion, and periodontal diseases, which in turn can impair athletic performance. Many studies have reported a high prevalence of oral diseases in elite athletes, notably dental caries 20-84%, dental erosion 42-59%, gingivitis 58-77%, and periodontal disease 15-41%, caused by frequent consumption of sugars/carbohydrates, polyunsaturated fats, or deficient protein intake. There are three possible major reasons for poor oral health in athletes which are addressed in this review: oxidative stress, sports diet, and oral hygiene. This update particularly summarizes potential sports nutritional effects on athletes' dental health. Overall, sports diet appropriately applied to deliver benefits for performance associated with oral hygiene requirements is necessary to ensure athletes' health. The overall aim is to help athletes, dentists, and nutritionists understand the tangled connections between sports diet, oral health, and oral healthcare to develop mitigation strategies to reduce the risk of dental diseases due to nutrition.

TNF-α promotes expression of inflammatory factors by upregulating nicotinamide adenine dinucleotide phosphate oxidase-2 expression in human gingival fibroblasts

Background/purpose

Periodontitis is a chronic infectious disease. The oxidative stress environment can cause or exacerbate the inflammation in periodontitis. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) may be the most important source of reactive oxygen species (ROS) in periodontal tissues. The pathological mechanism of periodontitis may be related to the increased ROS caused by enhanced NOX activity. The purpose was to investigate the effect of tumor necrosis factor (TNF-α) on inflammatory cytokines and ROS, and the role of NOX-2 in human gingival fibroblasts (HGFs).

Materials and methods

HGFs were cultured and divided into the normal control group (NC group) and the inflammatory model group (TNF-α group) induced by 10 ng/ml TNF-α. Thereafter, NOX-2 siRNA was used to knock down NOX-2 gene expression. Quantitative real-time PCR was applied to detect IL-6, MCP-1, and NOX-2 mRNA levels. The levels of IL-6 and MCP-1 protein were examined by ELISA. The level of NOX-2 was evaluated by Western blot. ROS expression was measured by the fluorescence microplate.

Results

The mRNA and protein expression levels of IL-6, MCP-1, and NOX-2 were significantly increased, and the expression of ROS was significantly elevated in response to 10 ng/ml TNF-α. Compared with the si-NC group, the mRNA and protein expression levels of IL-6 and MCP-1 were significantly down-regulated and ROS expression was significantly decreased in the si-NOX2 group stimulated by 10 ng/ml TNF-α.

Conclusion

TNF-α promotes the expression of NOX-2 in human gingival fibroblasts and enhances the expression of inflammatory factors and ROS in human gingival fibroblasts through the upregulation of NOX-2 partly.

Knockdown of Bach1 protects periodontal bone regeneration from inflammatory damage

Periodontal bone regeneration is a major challenge in the treatment of periodontitis. However, the regenerative vitality of periodontal ligament cells (PDLCs) declines in the environment of periodontitis and accompanying oxidative stress. This study aimed to investigate the functional mechanisms of Bach1, a transcriptional suppressor involved in oxidative stress response, and its regulation of PDLC osteogenesis under inflammatory conditions. We observed a significant elevation in Bach1 expression in periodontal tissues with periodontitis and PDLCs under inflammatory conditions. Knockdown of Bach1 alleviated the inflammation-induced oxidative stress level and partly offset the inhibitory effect of inflammatory conditions on osteogenesis, as well as the expression of osteogenic genes BMP6, OPG and RUNX2. Similarly, knockdown of Bach1 protects PDLCs from inflammatory damage to periodontal bone regeneration in vivo. Furthermore, we found that Bach1 could bind to the histone methyltransferase EZH2, and the binding increased under inflammatory conditions. Bach1 enhanced the ability of EZH2 to catalyse H3K27me3 on the promoter region of RUNX2 and BMP6, thus repressing the expression of osteoblastic genes. In conclusion, our study revealed that knockdown of Bach1 effectively rescued the osteogenesis and oxidative stress of PDLCs with inflammation. Bach1 could be a promising target for enhancing periodontal tissue regeneration under periodontitis conditions.

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.

Neutrophil N1 and N2 Subsets and Their Possible Association with Periodontitis: A Scoping Review

Periodontitis is a chronic non-communicable disease caused by dysbiotic changes that affect the subgingival microbiota. During periodontitis, neutrophils play a central role in the initial recognition of bacteria, and their number increases with the appearance of the first signs of periodontal inflammation. Recent evidence has led to the proposition that neutrophils can also functionally polarize, determining selective activity patterns related to different diseases. Two well-defined neutrophil phenotypes have been described, the pro-inflammatory N1 subset and the suppressor N2 subset. To date, it has not been established whether these different neutrophil subtypes play a role in the pathogenesis of periodontitis. Thus, this scoping review aimed to determine whether there was evidence to suggest that the neutrophils present in periodontal tissues can be associated with certain phenotypes. The research question, population, concept, and context sought to identify original articles, in humans, that detected the presence of neutrophils in the periodontal tissues of people affected by periodontitis. Based on the search strategy, we found 3658 studies. After removing the papers with abstracts not related to the outcome measures and eligibility criteria, 16 articles were included for qualitative analysis. Several studies identified the presence of different neutrophil subsets, specifically, the naive, pro- and para-inflammatory, hyper-reactive and hyper-active, and high- and low-responder phenotypes. The existing evidence demonstrates the presence of pro-inflammatory, hyper-reactive and high-responder neutrophils in periodontal tissues affected with periodontitis. There is no evidence demonstrating the presence of the N1 or N2 phenotypes in periodontal tissues during periodontitis. However, the existence of pro-inflammatory phenotypes, which increase NETosis and degranulation, and increase the production of pro-inflammatory cytokines, could be suggestive of the N1 phenotypes.

NLRP3 Is Involved in Neutrophil Mobilization in Experimental Periodontitis

The NLRP3 inflammasome is overexpressed in gingiva of periodontitis patients but its role remains unclear. In our study, we use a periodontitis mouse model of ligature, impregnated or not with Porphyromonas gingivalis, in WT or NLRP3 KO mice. After 28 days of induction, ligature alone provoked exacerbated periodontal destruction in KO mice, compared to WT mice, with an increase in activated osteoclasts. No difference was observed at 14 days, suggesting that NLRP3 is involved in regulatory pathways that limit periodontitis. In contrast, in the presence of P. gingivalis, this protective effect of NLRP3 was not observed. Overexpression of NLRP3 in connective tissue of WT mice increased the local production of mature IL-1β, together with a dramatic mobilization of neutrophils, bipartitely distributed between the site of periodontitis induction and the alveolar bone crest. P. gingivalis enhanced the targeting of NLRP3-positive neutrophils to the alveolar bone crest, suggesting a role for this subpopulation in bone loss. Conversely, in NLRP3 KO mice, mature IL-1β expression was lower and almost no neutrophils were mobilized. Our study sheds new light on the role of NLRP3 in periodontitis by highlighting the ambiguous role of neutrophils, and P. gingivalis which affects NLRP3 functions.

Innate Phagocyte Polarization in the Oral Cavity

The oral cavity is a complex environment constantly exposed to antigens from food and the oral microbiota. Innate immune cells play an essential role in maintaining health and homeostasis in the oral environment. However, these cells also play a significant role in disease progression. This review will focus on two innate phagocytes in the oral cavity: macrophages and neutrophils, and examine their roles during homeostasis and disease development, with a focus on periodontal disease and cancer. Macrophages have a well-known ability to polarize and be activated towards a variety of phenotypes. Several studies have found that macrophages’ polarization changes can play an essential role in maintaining health in the oral cavity and contribute to disease. Recent data also finds that neutrophils display phenotypic heterogeneity in the oral cavity. In both cases, we focus on what is known about how these cellular changes alter these immune cells’ interactions with the oral microbiota, including how such changes can lead to worsening, rather than improving, disease states.

Inhibiting PHD2 in human periodontal ligament cells via lentiviral vector-mediated RNA interference facilitates cell osteogenic differentiation and periodontal repair

Periodontal defect regeneration in severe periodontitis remains a challenging task in clinic owing to poor survival of seed cells caused by the remaining oxidative stress microenvironment. Recently, the reduction of prolyl hydroxylase domain-containing protein 2 (PHD2), a primary cellular oxygen sensor, has shown an incredible extensive effect on skeletal muscle tissue regeneration by improving cell resistance to reactive oxygen species, whereas its role in periodontal defect repair is unclear. Here, through lentivirus vector-mediated RNA interference, the PHD2 gene in human periodontal ligament cells (hPDLCs) is silenced, leading to hypoxia-inducible factor-1α stabilization in normoxia. In vitro, PHD2 silencing not only exhibited a satisfactory effect on cell proliferation, but also induced distinguished osteogenic differentiation of hPDLCs. Real-time polymerase chain reaction and Western blotting revealed significant up-regulation of osteocalcin, alkaline phosphatase (ALP), runt-related transcription factor 2, and collagen type I (COL I). Under oxidative stress conditions, COL I and ALP expression levels, suppressed by 100 μM H₂ O₂ , were elevated by PHD2-gene-silencing in hPDLCs. In vivo, periodontal fenestration defects were established in 18 female Sprague-Dawley rats aged 6 wk old, followed by implantation of PHD2 silencing hPDLCs in situ for 21 d. Persistent and stable silencing of PHD2 in hPDLCs promoted better new bone formation according to microcomputed tomography 3D reconstruction and related bone parameter analysis. This work demonstrates the therapeutic efficiency of PHD2 gene interference in osteogenic differentiation and periodontal defect repair for highly efficient periodontal regeneration.

Maintaining homeostatic control of periodontal epithelial tissue

Years of coevolution with resident microbes has made them an essential component of health. Yet, little is known about oral commensal bacteria's contribution to and role in the maintenance of oral health and homeostasis. Commensal bacteria are speculated to play a host protective role in the maintenance of health. In this review, we describe and provide examples of the coordinate regulation that occurs between oral commensal bacteria and the host innate immune response to modulate and maintain oral homeostasis.

Stressed-Out Oral Immunity: A Gateway From Socioeconomic Adversity to Periodontal Disease

OBJECTIVE

It has been suggested that adverse socioeconomic conditions "get under the skin" by eliciting a stress response that can trigger periodontal inflammation. We aimed to a) estimate the extent to which socioeconomic position (SEP) is associated with periodontal disease (PD) and proinflammatory oral immunity, and b) determine the contribution of psychosocial stress and stress hormones to these relationships.

METHODS

In this cross-sectional study (n = 102), participants (20-59 years old) completed financial and perceived stress questionnaires and underwent full-mouth periodontal examinations. SEP was characterized by annual household income and educational attainment. Cortisol, a biological correlate of chronic stress, was assessed in hair samples. Oral immunity was characterized by assessing oral inflammatory load and proinflammatory oral neutrophil function. Blockwise Poisson and logistic regression models were applied.

RESULTS

Compared with lower SEP, individuals in the middle- and higher-income categories had a significantly lower probability of PD (incidence rate ratio [IRR] = 0.5 [confidence interval {CI} = 0.3-0.7] and IRR = 0.4 [95% CI = 0.2-0.7]) and oral inflammatory load (IRR = 0.6 [95% CI = 0.3-0.8] and IRR = 0.5 [95% CI = 0.3-0.7]) and were less likely to have a proinflammatory oral immune function (odds ratio [OR] = 0.1 [95% CI = 0.0-0.7] and OR = 0.1 [95% CI = 0.0-0.9]). PD and oral immune parameters were significantly associated with financial stress and cortisol. Adjusting for financial stress and cortisol partially attenuated the socioeconomic differences in PD to IRR = 0.7 (95% CI = 0.5-0.8) and IRR = 0.6 (95% CI = 0.5-0.7) for the middle- and higher-income categories, respectively. Similar results were observed for proinflammatory immunity (OR = 0.2 [95% CI = 0.0-1.8] and OR = 0.3 [95% CI = 0.0-2.3]).

CONCLUSION

These findings suggest that psychosocial stress may contribute to a proinflammatory immunity that is implicated in PD pathobiology and provide insight into social-to-biological processes in oral health.

Inflammation in Periodontal Disease: Possible Link to Vascular Disease

Inflammation is a well-organized protective response to pathogens and consists of immune cell recruitment into areas of infection. Inflammation either clears pathogens and gets resolved leading to tissue healing or remains predominantly unresolved triggering pathological processes in organs. Periodontal disease (PD) that is initiated by specific bacteria also triggers production of inflammatory mediators. These processes lead to loss of tissue structure and function. Reactive oxygen species and oxidative stress play a role in susceptibility to periodontal pathogenic bacterial infections. Periodontal inflammation is a risk factor for systemic inflammation and eventually cardiovascular disease (CVD). This review discusses the role of inflammation in PD and its two way association with other health conditions such as diabetes and CVD. Some of the mechanisms underpinning the links between inflammation, diabetes, CVD and PD are also discussed. Finally, we review available epidemiological data and other reports to assess possible links between oral health and CVD.

Association of bacterial vaginosis with periodontitis in a cross-sectional American nationwide survey

To explore the association between bacterial vaginosis (BV) and periodontitis (PD) and to determine whether PD and BV might be linked with systemic serum alterations. We used the National Health and Nutrition Examination Survey 2001-2004, with women aged 18-49 years old and diagnosed with or without BV according to Nugent's method. PD was defined according to the 2012 case definition. We compared serum counts according to the presence of PD and the presence of BV. Multivariable regression was used to explore and identify relevant variables towards the presence of BV. 961 women fulfilled the inclusion criteria. In women with BV, PD was associated with higher inflammation, characterized by increased white blood cells (p = 0.006) and lymphocyte (p = 0.009) counts. Predictive models presented a statistically significant association between PD and BV [Odds Ratio (OD) = 1.69, 95% Confidence Interval (CI): 1.09-2.61 for periodontitis; OD = 2.37, 95% CI: 1.30-4.29 for severe PD]. Fully adjusted models for age, smoking, body mass index, diabetes mellitus and number of systemic conditions reinforced this association [OD = 1.71, 95% CI: 1.06-2.76 for PD; OD = 2.21, 95% CI: 1.15-4.25 for severe PD]. An association between BV and PD is conceivable. PD was associated with higher systemic markers of inflammation in women with BV. Our data is novel and could serve as a foundation to guide future studies in the confirmation of this association and the underlying mechanisms.

Periodontal Pathogens' strategies disarm neutrophils to promote dysregulated inflammation

Periodontitis is an irreversible, chronic inflammatory disease where inflammophilic pathogenic microbial communities accumulate in the gingival crevice. Neutrophils are a major component of the innate host response against bacterial challenge, and under homeostatic conditions, their microbicidal functions typically protect the host against periodontitis. However, a number of periodontal pathogens developed survival strategies to evade neutrophil microbicidal functions while promoting inflammation, which provides a source of nutrients for bacterial growth. Research on periodontal pathogens has largely focused on a few established species: Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis. However, advances in culture-independent techniques have facilitated the identification of new bacterial species in periodontal lesions, such as the two Gram-positive anaerobes, Filifactor alocis and Peptoanaerobacter stomatis, whose characterization of pathogenic potential has not been fully described. Additionally, there is not a full understanding of the pathogenic mechanisms used against neutrophils by organisms that are abundant in periodontal lesions. This presents a substantial barrier to the development of new approaches to prevent or ameliorate the disease. In this review, we first summarize the neutrophil functions affected by the established periodontal pathogens listed above, denoting unknown areas that still merit a closer look. Then, we review the literature on neutrophil functions and the emerging periodontal pathogens, F. alocis and P. stomatis, comparing the effects of the emerging microbes to that of established pathogens, and speculate on the contribution of these putative pathogens to the progression of periodontal disease.

Periodontal Inflammation Primes the Systemic Innate Immune Response

The presence of periodontal diseases (PDs) often strongly correlates with other severe chronic inflammatory conditions, including cardiovascular disease, diabetes, and arthritis. However, the mechanisms through which these diseases interact are unclear. In PD, tissue and bone destruction in the mouth is driven by elevated recruitment of polymorphonuclear neutrophils (PMNs), which are primed and recruited from the circulation to sites of inflammation. We predicted that systemic effects on PMN mobilization or priming could account for the interaction between PD and other inflammatory conditions. We tested this using a mouse model of ligature-induced PD and found elevated PMN counts specifically in bone marrow, supporting a systemic effect of periodontal tissue inflammation on PMN production. In contrast, mice with induced peritonitis had elevated PMN counts in the blood, peritoneum, and colon. These elevated counts were further significantly increased when acute peritonitis was induced after ligature-induced PD in mice, revealing a synergistic effect of multiple inflammatory events on PMN levels. Flow cytometric analysis of CD marker expression revealed enhanced priming of PMNs from mice with both PD and peritonitis compared to mice with peritonitis alone. Thus, systemic factors associated with PD produce hyperinflammatory PMN responses during a secondary infection. To analyze this systemic effect in humans, we induced gingival inflammation in volunteers and also found significantly increased activation of blood PMNs in response to ex vivo stimulation, which reverted to normal following resolution of gingivitis. Together, these results demonstrate that periodontal tissue inflammation has systemic effects that predispose toward an exacerbated innate immune response. This indicates that peripheral PMNs can respond synergistically to simultaneous and remote inflammatory triggers and therefore contribute to the interaction between PD and other inflammatory conditions. This suggests larger implications of PD beyond oral health and reveals potential new approaches for treating systemic inflammatory diseases that interact with PD.

Periodontitis and circulating blood cell profiles: a systematic review and meta-analysis

Periodontitis is a chronic inflammatory disease with local and systemic implications. Evidence suggests consistent hematologic changes associated with periodontitis. Our aim was to critically appraise the available evidence on hemogram, leukogram, and thrombogram alterations in otherwise healthy patients suffering from periodontitis when compared with controls. For this systematic review (SR), we searched MEDLINE, Web of Science, EMBASE, and the Cochrane Library (CENTRAL) for studies published up to June 2020. Both observational and interventional studies with baseline standard hematologic levels were included. Outcomes of interest were baseline hemogram, leukogram, and thrombogram values and the impact of periodontitis treatment on these outcomes. Upon risk of bias assessment, data extraction and both qualitative and quantitative (standardized mean differences) analyses were performed. Random-effects meta-analyses were performed to provide pooled estimates. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed (PROSPERO Reg. No. CRD42020164531). A total of 45 studies, eight intervention and 37 case-control studies, were identified after the final search of 3,012 titles. Following quality assessment, 43 articles were deemed to have low risk of bias, and two articles moderate risk. Meta-analyses confirmed that periodontitis was associated with both white and red cell lineages. Severe chronic periodontitis was associated with greater white blood cell counts (mean difference [MD] = 0.53, 95% confidence interval [CI]: 0.26-0.79) when compared with controls. Periodontitis was associated with a larger number of neutrophils (MD = 7.16%, 95% CI: 5.96-8.37) and lower mean platelet volume (MD = 0.30 fL, 95% CI: 0.49 to -0.10) compared with healthy participants. Nonsurgical periodontal treatment was associated with a decrease in white blood cell (WBC) levels (MD = 0.28 10⁹/L, 95% CI: -0.47 to -0.08) in patients with chronic periodontitis. Periodontitis is associated with hematologic changes (Strength of Recommendation Taxonomy [SORT] A recommendation). Higher WBC levels, higher neutrophil levels, higher erythrocyte sedimentation rate, and lower mean platelet volumes are the most common blood count findings. The association between periodontitis and WBC could be causal in nature. Further assessment to determine whether periodontitis causes changes in circulating blood cells and to identify the molecular mechanisms underlying these associations is warranted.

Periodontitis is an inflammatory disease of oxidative stress: We should treat it that way

Periodontitis is a highly prevalent disease. As it progresses, it causes serious morbidity in the form of periodontal abscesses and tooth loss and, in the latter stages, pain. It is also now known that periodontitis is strongly associated with several nonoral diseases. Thus, patients with periodontitis are at greater risk for the development and/or exacerbation of diabetes, chronic obstructive pulmonary disease, and cardiovascular diseases, among other conditions. Although it is without question that specific groups of oral bacteria which populate dental plaque play a causative role in the development of periodontitis, it is now thought that once this disease has been triggered, other factors play an equal, and possibly more important, role in its progression, particularly in severe cases or in cases that prove difficult to treat. In this regard, we allude to the host response, specifically the notion that the host, once infected with oral periodontal pathogenic bacteria, will mount a defense response mediated largely through the innate immune system. The most abundant cell type of the innate immune system - polymorphonuclear neutrophils - can, when protecting the host from microbial invasion, mount a response that includes upregulation of proinflammatory cytokines, matrix metalloproteinases, and reactive oxygen species, all of which then contribute to the tissue damage and loss of teeth commonly associated with periodontitis. Of the mechanisms referred to here, we suggest that upregulation of reactive oxygen species might play one of the most important roles in the establishment and progression of periodontitis (as well as in other diseases of inflammation) through the development of oxidative stress. In this overview, we discuss both innate and epigenetic factors (eg, diabetes, smoking) that lead to the development of oxidative stress. This oxidative stress then provides an environment conducive to the destructive processes observed in periodontitis. Therefore, we shall describe some of the fundamental characteristics of oxidative stress and its effects on the periodontium, discuss the diseases and other factors that cause oxidative stress, and, finally, review potentially novel therapeutic approaches for the management (and possibly even the reversal) of periodontitis, which rely on the use of therapies, such as resveratrol and other antioxidants, that provide increased antioxidant activity in the host.

Resveratrol and insulin association reduced alveolar bone loss and produced an antioxidant effect in diabetic rats

BACKGROUND

The present investigation studied the effects of systemic administration of resveratrol (RSV) on the development of experimental periodontitis (EP) and on the release of markers of inflammation, bone metabolism, and oxidative stress in diabetic rats.

METHODS

Seventy-five male rats were divided into five groups: DM+PLAC: Diabetes Mellitus + placebo solution; DM+INS: DM + insulin therapy; DM+RSV: DM + RSV; DM+RSV+INS: DM + RSV and insulin; NDM: non-diabetic. Streptozotocin was used to induce DM and EP was induced by the placement of a ligature at the fist mandibular and the second maxillary molars. Euthanasia occurred 30 days after the initiation of the study and mandible specimens were subjected for morphometric analysis of bone level. Gingival tissues from mandibular molars were collected for quantification of inflammatory and oxidative stress markers by multiplex assay system and ELISA assay, respectively. Maxillary gingival tissues were processed for real-time polymerase chain reaction (real-time PCR) assessment of markers of bone metabolism and oxidative stress.

RESULTS

Morphometric analysis revealed greater bone loss in DM+PLAC and DM+INS in comparison to the other treatments (P < 0.05). RSV used in conjunction with INS reduced the levels of interleukin (IL)-1β, IL-6, IL-17, interferon-gamma (IFN-γ) and superoxide dismutase 1 (SOD) (P < 0.05). RSV alone reduced nicotinamide adenine dinucleotide phosphatase oxidase (NADPH oxidase) levels, in comparison to DM+INS and DM+RSV+INS (P < 0.05). All treatments upregulated mRNA levels for osteoprotegerin (OPG) in comparison to PLAC (P < 0.05). Sirtuin 1 (SIRT) mRNA levels were lower in PLAC when compared to DM+RSV, DM+RSV+INS and NDM (P < 0.05).

CONCLUSION

RSV reduced the progression of EP and the levels of NADPH oxidase. Co-treatment with RSV and insulin reduced the levels of pro-inflammatory factors (either proteins or mRNA) and increased the levels of SOD. The data also demonstrated that treatment with RSV and INS alone or in combination had beneficial effects on bone loss.

Relationship between Blood and Standard Biochemistry Levels with Periodontitis in Parkinson's Disease Patients: Data from the NHANES 2011-2012

People with Parkinson's Disease (PD) are associated with the presence of periodontitis. We aimed to compare blood and standard biochemical surrogates of PD patients diagnosed with periodontitis with PD individuals without periodontitis. This retrospective cohort study used a sample from the National Health and Nutrition Examination Survey (NHANES) 2011-2012 that underwent periodontal diagnosis (n = 3669). PD participants were identified through specific PD reported medications. Periodontitis was defined according to the 2012 case definition, using periodontal examination data provided. Then, we compared blood levels and standard chemical laboratory profiles of PD patients according to the presence of periodontitis. Multivariable regression was used to explore this dataset and identify relevant variables towards the presence of periodontitis. According to the medication report, 37 participants were eligible, 29 were secure and 8 were unsecure PD medications regimens. Overall, PD cases with periodontitis presented increased levels of White Blood Cells (WBC) (p = 0.002), Basophils (p = 0.045) and Segmented neutrophils (p = 0.009), and also, lower levels of Total Bilirubin (p = 0.018). In the PD secure medication group, a significant difference was found for WBC (p = 0.002) and Segmented neutrophils (p = 0.002) for the periodontitis group. Further, WBC might be a discriminating factor towards periodontitis in the global sample. In the secure PD medication, we found gender, segmented neutrophils and Vitamin D2 to be potential discriminative variables towards periodontitis. Thus, periodontitis showed association with leukocyte levels alterations in PD patients, and therefore with potential systemic changes and predictive value. Furthermore, Vitamin D2 and gender showed to be associated with periodontitis in with secure medication for PD. Future studies should assess in more detail the potential systemic repercussion of the presence of periodontitis in PD patients.

Dentistry and OMICS: Transcriptome Dynamics of an Oral Ecosystem as Measured by Changes in Oral Polymorphonuclear Neutrophils in Experimental Gingivitis

Oral health and dentistry are essential components of systems medicine, which has received lesser attention in comparison to other medical fields, such as cancer biology. In this context, oral polymorphonuclear neutrophils (oPMNs) play an important role in the maintenance of oral health. To the best of our knowledge, this is the first study to report original observations on the transcriptional responses of oPMNs during experimentally induced gingivitis, by temporarily refraining from regular oral care. Oral rinses were prospectively collected at four different time points for oPMNs isolation from healthy volunteers: day 1 (start of the experimental gingivitis challenge), day 9 (during challenge), day 14 (end of the challenge), and day 21 (postchallenge). Transcriptome of oPMNs was determined by RNA sequencing. Differentially expressed genes (DEGs) were selected at p < 0.01 level, and evaluated for pathway regulation using Ingenuity Pathway Analysis suite. We found four major clusters of DEGs, consisting of 256 initial response DEGs (day 9 only), 221 late response DEGs (day 14 only), 53 persistent responsive DEGs (consistent at day 9 and 14), and 524 DEGs showing responses only in the postchallenge phase (day 21 only). Pathway analysis of the initial and late response DEGs showed involvement in many immune regulatory pathways and PMN function, whereas DEGs at day 21 were associated with epithelial adherence signaling and other miscellaneous related signaling pathways. The results from this pilot study showed that oPMNs mediate oral inflammatory processes, suggesting their immunomodulatory role in oral equilibrium.

The Possible Role of Neutrophils in the Induction of Osteoclastogenesis

The ligand of the receptor activator of NF-κB (RANKL) is a key molecule in the formation of osteoclasts, the key cells that cause the disease-associated alveolar bone resorption in periodontitis. We hypothesized that polymorphonuclear leukocytes (PMNs), found as the most prominent cells of inflamed periodontal tissues, could play an important role in providing signals to trigger osteoclastogenesis and thus activating pathological bone resorption in periodontitis. RANKL expression was investigated on circulatory PMNs (cPMNs) and oral PMNs (oPMNs) taken from both controls and periodontitis patients. On average, 2.3% and 2.4% RANKL expression was detected on the cPMNs and oPMNs from periodontitis patients, which did not differ significantly from healthy controls. Since cPMNs may acquire a more osteoclastogenesis-facilitating phenotype while migrating into the inflamed periodontium, we next investigated whether stimulated (with LPS, TNF-α, or IL-6) cPMNs have the capacity to contribute to osteoclastogenesis. Enduring surface expression of RANKL for short-lived cells as cPMNs was achieved by fixating stimulated cPMNs. RANKL expression on stimulated cPMNs, as assessed by flow cytometry and immunohistochemistry, was limited (6.48 ± 0.72%, mean expression ± SEM) after 24 and 48 hours of stimulation with LPS. Likewise, stimulation with TNF-α and IL-6 resulted in limited RANKL expression levels. These limited levels of expression did not induce osteoclastogenesis when cocultured with preosteoclasts for 10 days. We report that, under the aforementioned experimental conditions, neither cPMNs nor oPMNs directly induced osteoclastogenesis. Further elucidation of the key cellular players and immune mediators that stimulate alveolar bone resorption in periodontitis will help to unravel its pathogenesis.

Host modulation therapy using anti-inflammatory and antioxidant agents in periodontitis: A review to a clinical translation

OBJECTIVE

To highlight the shifting paradigm of periodontitis, describe mechanism of periodontal bone destruction, and propose an updated host modulation therapy (HMT) strategy. To add further clinical relevance, related studies investigating the efficacy of several HMT agents in periodontitis will be discussed.

DESIGN

Literature searches were conducted from articles published in PubMed using keywords "periodontal disease AND periodontitis AND host modulation therapy AND anti-inflammatory AND antioxidant", and then the findings were comprehensively summarized and elaborated.

RESULT

Accumulating evidence indicates that periodontitis is no longer defined solely as a pathogen-induced disease; rather, it is now recognized as a consequence of uncontrolled immune response and oxidative stress leading to periodontal tissue damage. Although periodontopathic bacteria initiate the disease, inflammation and oxidative stress were reported to be the main causes for the severity of tissue destruction. Thus, since the concept of periodontitis has shifted, our approach to its management needs to be adjusted to accommodate the latest paradigm. Nowadays, the modulation of inflammation and oxidative stress is considered a target of HMT. HMT agents, such as probiotics, anti-inflammatory drugs, anti-chemokines, lipid mediators, and bio-active fatty acids, have been extensively investigated for their remarkable functions in modulating the immune response and providing antioxidant effects.

CONCLUSION

Findings from in vitro, in vivo, and human studies frequently demonstrate positive association by the administration of HMT in periodontitis. HMT strategy targeted on anti-inflammatory and antioxidant in periodontitis might serve as an excellent therapeutic approach to reach the level of clinical benefit.

Oral Neutrophils Characterized: Chemotactic, Phagocytic, and Neutrophil Extracellular Trap (NET) Formation Properties

Maintenance of oral health is in part managed by the immune-surveillance and antimicrobial functions of polymorphonuclear leukocytes (PMNs), which migrate from the circulatory system through the oral mucosal tissues as oral PMNs (oPMNs). In any microorganism-rich ecosystem, such as the oral cavity, PMNs migrate toward various exogenous chemoattractants, phagocytose bacteria, and produce neutrophil extracellular traps (NETs) to immobilize and eliminate pathogens. PMNs obtained from the circulation through venipuncture (hereafter called cPMNs) have been widely studied using various functional assays. We aimed to study the potential of oPMNs in maintaining oral health and therefore compared their chemotactic and antimicrobial functions with cPMNs. To establish chemotactic, phagocytic, and NET forming capacities, oPMNs and cPMNs were isolated from healthy subjects without obvious oral inflammation. Directional chemotaxis toward the chemoattractant fMLP was analyzed using an Insall chamber and video microscopy. fMLP expression was assessed by flow cytometry. Phagocytosis was analyzed by flow cytometry, following PMN incubation with heat-inactivated FITC-labeled micro-organisms. Furthermore, agar plate-based killing assays were performed with Escherichia coli (Ec). NET formation by oPMNs and cPMNs was quantified fluorimetrically using SYTOX™ Green, following stimulation with either PMA or RPMI medium (unstimulated control). In contrast to cPMNs, the chemotactic responses of oPMNs to fMLP did not differ from controls (mean velocity ± SEM of cPMNs: 0.79 ± 0.24; of oPMNs; 0.10 ± 0.07 micrometer/min). The impaired directional movement toward fMLP by oPMNs was explained by significantly lower fMLP receptor expression. Increased adhesion and internalization of various micro-organisms by oPMNs was observed. oPMNs formed 13 times more NETs than stimulated cPMNs, in both unstimulated and stimulated conditions. Compared to cPMNs, oPMNs showed a limited ability for intracellular killing of Ec. In conclusion, oPMNs showed exhausted capacity for efficient chemotaxis toward fMLP which may be the result of migration through the oral tissues into the oral cavity, being a highly “hostile” ecosystem. Overall, oPMNs' behavior is consistent with hyperactivity and frustrated killing. Nevertheless, oPMNs most likely contribute to maintaining a balanced oral ecosystem, as their ability to internalize microbes in conjunction with their abundant NET production remains after entering the oral cavity.

Resveratrol attenuates oxidative stress during experimental periodontitis in rats exposed to cigarette smoke inhalation

OBJECTIVES

This study aimed at investigating the effect of the systemic administration of resveratrol (RESV) on oxidative stress during experimental periodontitis in rats subjected to cigarette smoke inhalation.

MATERIAL AND METHODS

Experimental periodontitis (EP) was induced in 26 male Wistar rats by the insertion of a ligature around one of the first mandibular and maxillary molars. The animals were assigned randomly to the following groups: cigarette smoke inhalation (CSI; 3 times/d, 8 minutes/d) + resveratrol (10 mg/Kg), that is, SMK + RESV (n = 13) and cigarette smoke inhalation + placebo, that is, SMK + PLAC (n = 13). The substances were administered daily for 30 days (19 days prior and 11 days following EP induction), and then, the animals were euthanized. The maxillary specimens were processed for morphometric analysis of bone loss, and the tissue surrounding the first maxillary molars was collected for mRNA quantification of Sirtuin 1 (SIRT1) by real-time PCR. The gingival tissues surrounding the mandibular first molars were collected for quantification of superoxide dismutase 1 (SOD1) and nicotinamide adenine dinucleotide phosphatase oxidase (NADPH) using an ELISA assay.

RESULTS

Reduced bone loss was demonstrated in animals in the SMK + RESV group as compared to those in the SMK + PLAC (P < 0.05) group on the basis of morphometric analysis. Resveratrol promoted higher levels of SIRT and SOD (P < 0.05) as well as reduced levels of NADPH oxidase (P < 0.05) were found in tissues derived from animals in the SMK + RESV group when compared to those in the SMK + PLAC group.

CONCLUSION

Resveratrol is an efficient therapeutic agent that reduces exacerbation of bone loss found in animals with EP that were also exposed to smoke. The results suggest that its effects could be mediated, at least in part, by its antioxidant and anti-inflammatory properties which attenuate the effects of oxidative stress on EP in the presence of cigarette smoke.

Characterization of oral polymorphonuclear neutrophils in periodontitis patients: a case-control study

Background

Maintaining oral health is a continuous and dynamic process that also involves the immune system. Polymorphonuclear neutrophils (PMNs) migrate from blood circulation and become apparent in the oral fluid. Controversies exist regarding the specific role of the oral PMNs (oPMNs) in the presence of chronic oral inflammation, such as periodontitis. In this study we characterized cell counts, activation status, apoptosis, and reactive oxygen species (ROS) generation by oPMNs and circulatory (cPMNs), and the salivary protease activity, in subjects with and without periodontitis.

Methods

Venous blood and oral rinse samples were obtained from 19 patients with untreated periodontitis and 16 control subjects for PMN isolation. Apoptosis and expression of cell activation markers CD11b, CD63, and CD66b were analyzed using flow cytometry. Constitutive ROS generation was detected using dihydrorhodamine123. Additionally, ROS production in response to stimulation was evaluated in samples incubated with 10 μM phorbol myristate acetate (PMA) or Fusobacterium nucleatum. Total protease activity was measured using substrate PEK-054.

Results

Periodontitis patients presented with over 4 times higher oPMN counts compared to controls (p = 0.007), which was a predictor for the total protease activity (r² = 0.399, P = 0.007). More oPMNs were apoptotic in periodontitis patients compared to the controls (P = 0.004). All three activation markers were more expressed on the oPMNs compared to the cPMNs (p < 0.05), and a higher expression of CD11b on the oPMNs from periodontitis patients was observed compared to the control subjects (P = 0.024). Constitutive ROS production per oPMN was higher compared to the cPMN (P < 0.001). Additional analysis showed that the oPMNs retained their ability to respond to stimulation, with no apparent differences between the periodontitis and control subjects.

Conclusions

Higher numbers of oral PMNs, being more apoptotic and having increased levels of degranulation markers were found in periodontitis compared to periodontal health. However, since the oPMNs in periodontitis were responsive to ex vivo stimulation, we conclude that the oPMNs are active in the oral ecosystem. It is currently unknown whether the oPMN counts, which correlated with the detected protease levels, are detrimental in the long term for the oral mucosa integrity.

Trial registration

This study was retrospectively registered at the ISRCTN registry (trial ID ISRCTN15252886). Registration date August 11, 2017.

Oral and Blood Neutrophil Activation States during Experimental Gingivitis

Polymorphonuclear neutrophils (PMNs) are the primary leukocytes present in the healthy and inflamed oral cavity. While unique PMN activation states have been shown to differentiate health and periodontitis, little is known about the changes in PMN activation states that occur during the transition from periodontal health to gingivitis. The objective of this study was to characterize oral and circulatory PMNs during induction and resolution of experimental gingivitis. Healthy volunteers were recruited to undergo experimental gingivitis. Clinical assessment of pocket depths, bleeding on probing, gingival index, and plaque index, as well as flow cytometric analysis of CD (cluster of differentiation) activation markers on blood and oral PMNs, was performed weekly. All clinical parameters increased significantly during the induction period and returned to baseline levels during the resolution phase. During the induction phase, while oral PMN counts increased, oral PMN activation state based on surface expression of CD63, CD11b, CD16, and CD14 was diminished compared to those seen in health and during the resolution phase. PMNs in circulation during onset showed increased activation based on CD55, CD63, CD11b, and CD66a. Using clinical parameters and oral PMN counts assessed at day 21, we noted 2 unique disease patterns where one-third of subjects displayed an exaggerated influx of oral PMNs with severe inflammation compared to the majority of the population who experienced a moderate level of inflammation and PMN influx. This supports the notion that PMN influx and severe inflammatory changes during gingivitis could identify subjects at risk for the development of severe gingival inflammation and progression toward destructive periodontitis. This study demonstrates that oral PMN activation states are reduced in gingivitis and suggest that only in periodontitis do PMNs become hyperactivated and tissue damaging.

Knowledge Transfer Statement: Our article creates a paradigm for future studies of the evolution of essential oral and circulatory biomarkers to identify individuals at risk to develop periodontitis at an early stage of periodontal disease, which is reversible upon proper oral hygiene practices and dental treatments.

Oxidative Stress and Antioxidant System in Periodontitis

Periodontitis is a common inflammatory disease, which is initiated by bacterial infection and subsequently progressed by aberrant host response. It can result in the destruction of teeth supporting tissues and have an influence on systemic health. When periodontitis occurs, reactive oxygen species, which are overproduced mostly by hyperactive neutrophils, could not be balanced by antioxidant defense system and cause tissues damage. This is characterized by increased metabolites of lipid peroxidation, DNA damage and protein damage. Local and systemic activities of antioxidants can also be influenced by periodontitis. Total antioxidant capacity, total oxidant status and oxidative stress index have been used to evaluate the oxidative stress associated with periodontitis. Studies have confirmed that inflammatory response in periodontitis is associated with an increased local and systemic oxidative stress and compromised antioxidant capacity. Our review focuses on increased oxidative stress in periodontal disease, specifically, on the relationship between the local and systemic biomarkers of oxidative stress and periodontitis and their association with the pathogenesis of periodontitis. Also, the relationship between periodontitis and systemic inflammation, and the effects of periodontal therapy on oxidative stress parameters will be discussed.

The Role of NrF2 in the Regulation of Periodontal Health and Disease

Immune-related disease tolerance is an important defense strategy that facilitates the maintenance of health in organs and tissues that are commonly colonized by bacteria. Immune tolerance to dysbiotic, tooth-borne biofilms is a poorly understood yet clinically relevant concept in the immunopathological mechanisms that are involved in the pathogenesis of periodontitis, particularly those related to neutrophil and macrophage responses. In periodontal health, neutrophils and macrophages respond to the formation of pathogenic bacterial biofilms by the production of bactericidal reactive oxygen species (ROS). However, when released in excess, ROS cause tissue damage and exacerbate inflammation. To counter these destructive responses, many cell types, including neutrophils and macrophages, launch a dedicated antioxidant system that limits the cell and tissue-damaging effects of ROS. The expression of antioxidants is primarily regulated by genetic response elements in their promoters. Here we consider the roles of nuclear factor erythroid 2-related factor (NrF2), a transcription factor, and other key regulators of antioxidants. The concept of disease tolerance, neutrophil and macrophage-generated oxidative stress, and their relationship to the pathogenesis of periodontitis is reviewed. We focus on the regulation of NrF2 and recent evidence suggesting that NrF2 plays a central role in host protection against tissue destruction in periodontitis.

Manipulation of Neutrophils by Porphyromonas gingivalis in the Development of Periodontitis

The pathogenesis of the chronic periodontal disease is associated with a skewed host inflammatory response to periodontal pathogens, such as Porphyromonas gingivalis, that accounts for the majority of periodontal tissue damage. Neutrophils are the most abundant leukocytes in periodontal pockets and depending on the stage of the disease, also plentiful PMNs are present in the inflamed gingival tissue and the gingival crevice. They are the most efficient phagocytes and eliminate pathogens by a variety of means, which are either oxygen-dependent or -independent. However, these secretory lethal weapons do not strictly discriminate between pathogens and host tissue. Current studies describe conflicting findings about neutrophil involvement in periodontal disease. On one hand literature indicate that hyper-reactive neutrophils are the main immune cell type responsible for this observed tissue damage and disease progression. Deregulation of neutrophil survival and functions, such as chemotaxis, migration, secretion of antimicrobial peptides or enzymes, and production of reactive oxygen species, contribute to observed tissue injury and the clinical signs of periodontal disease. On the other hand neutrophils deficiencies in patients and mice also result in periodontal phenotype. Therefore, P. gingivalis represents a periodontal pathogen that manipulates the immune responses of PMNs, employing several virulence factors, such as gingipains, serine proteases, lipid phosphatases, or fimbriae. This review will sum up studies devoted to understanding different strategies utilized by P. gingivalis to manipulate PMNs survival and functions in order to inhibit killing by a granular content, prolong inflammation, and gain access to nutrient resources.

The Effect of Closed-Eye Tear Film Conditions on Blood-Isolated Neutrophils, In Vitro

PURPOSE

Eyelid closure results in influx of neutrophils onto the ocular surface, which are non-responsive to inflammatory stimuli. This investigation examined whether incubation of blood-isolated neutrophils in closed-eye conditions induce a tear-film neutrophil phenotype.

METHODS

Blood-isolated neutrophils were incubated combining various conditions: hypoxia, corneal epithelial cells (HCEC), artificial tear solution (ATS).

RESULTS

A hypoxic environment induced no differential effect on membrane receptor expression. Incubation in the presence of HCEC resulted in membrane receptor upregulation and increase in caspase activation.

CONCLUSIONS

Hypoxia, corneal epithelial cell exposure, or artificial tear fluid are insufficient to replicate a tear-film neutrophil phenotype using blood-isolated neutrophils.

Oral polymorphonuclear neutrophil characteristics in relation to oral health: a cross-sectional, observational clinical study

Polymorphonuclear neutrophils (PMNs) have a major role in the innate immune system. However, little is known about PMN contribution in relation to oral health. The objective of this study was to investigate the numbers and functional characteristics of oral PMNs (oPMNs) compared with circulatory PMNs (cPMNs). Oral rinse and venous blood samples were obtained from 268 systemically and orally healthy volunteers in a cross-sectional observational study. PMN counts, cell cycle analysis and cellular activation state were investigated. Also, reactive oxygen species (ROS) production was analyzed, with and without bacterial stimulation (Fusobacterium nucleatum). In males, 1.2 × 10⁶±1.0 × 10⁶ oPMNs were collected, and showed a tendency to correlate with the levels of gingival bleeding (r=0.215, P=0.008). Comparable oPMNs counts were found among females (1.0 × 10⁶±0.7 × 10⁶). More late-stage apoptotic/necrotic cells were found among the oPMNs (53.1%) compared with the cPMNs (8.5% P<0.001). Without additional stimulation, oPMNs were more activated than cPMNs, as indicated by higher expression of CD11b, CD63 and CD66b, and higher constitutive ROS levels (P<0.001). Notably, in response to bacterial stimulation, oPMNs released comparable ROS levels as cPMNs (P=0.042). In conclusion, this study provides data on viable oPMNs showing high levels of activation in orally and systemically healthy individuals, free of apparent caries lesions and periodontal disease. These data suggests that although the oPMNs are in a more mature stage of their life cycle compared with the cPMNs, oPMNs are still responsive to stimulation, which indicates their functional potential and possible contribution to a healthy oral ecosystem.

Human neutrophils and oral microbiota: a constant tug-of-war between a harmonious and a discordant coexistence

Neutrophils are a major component of the innate host response, and the outcome of the interaction between the oral microbiota and neutrophils is a key determinant of oral health status. The composition of the oral microbiome is very complex and different in health and disease. Neutrophils are constantly recruited to the oral cavity, and their protective role is highlighted in cases where their number or functional responses are impeded, resulting in different forms of periodontal disease. Periodontitis, one of the more severe and irreversible forms of periodontal disease, is a microbial-induced chronic inflammatory disease that affects the gingival tissues supporting the tooth. This chronic inflammatory disease is the result of a shift of the oral bacterial symbiotic community to a dysbiotic more complex community. Chronic inflammatory infectious diseases such as periodontitis can occur because the pathogens are able to evade or disable the innate immune system. In this review, we discuss how human neutrophils interact with both the symbiotic and the dysbiotic oral community; an understanding of which is essential to increase our knowledge of the periodontal disease process.

Distinct Oral Neutrophil Subsets Define Health and Periodontal Disease States

Neutrophils exit the vasculature and swarm to sites of inflammation and infection. However, these cells are abundant in the healthy, inflammation-free human oral environment, suggesting a unique immune surveillance role within the periodontium. We hypothesize that neutrophils in the healthy oral cavity occur in an intermediary parainflammatory state that allows them to interact with and contain the oral microflora without eliciting a marked inflammatory response. Based on a high-throughput screen of neutrophil CD (cluster of differentiation) marker expression and a thorough literature review, we developed multicolor flow cytometry panels to determine the surface marker signatures of oral neutrophil subsets in periodontal health and disease. We define here 3 distinct neutrophil subsets: resting/naive circulatory neutrophils, parainflammatory neutrophils found in the healthy oral cavity, and proinflammatory neutrophils found in the oral cavity during chronic periodontal disease. Furthermore, parainflammatory neutrophils manifest as 2 distinct subpopulations-based on size, granularity, and expression of specific CD markers-and exhibit intermediate levels of activation as compared with the proinflammatory oral neutrophils. These intermediately activated parainflammatory populations occur in equal proportions in the healthy oral cavity, with a shift to one highly activated proinflammatory neutrophil population in chronic periodontal disease. This work is the first to identify and characterize oral parainflammatory neutrophils that interact with commensal biofilms without inducing an inflammatory response, thereby demonstrating that not all neutrophils trafficking through periodontal tissues are fully activated. In addition to establishing possible diagnostic and treatment monitoring biomarkers, this oral neutrophil phenotype model builds on existing literature suggesting that the healthy periodontium may be in a parainflammatory state.

Nuclear Factor Erythroid 2-Related Factor 2 Down-Regulation in Oral Neutrophils Is Associated with Periodontal Oxidative Damage and Severe Chronic Periodontitis

The balance between reactive oxygen species and antioxidants plays an important role in periodontal health. We previously demonstrated that high reactive oxygen species production by oral polymorphonuclear neutrophils (oPMNs) in chronic periodontitis (CP) refractory to conventional therapy is associated with severe destruction of periodontium. Herein, we show that inhibition of antioxidant production through down-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in oPMN, despite enhanced recruitment in the oral cavity, is associated with severe CP. Twenty-four genes in the Nrf2-mediated oxidative stress response pathway were down-regulated in PMNs of diseased patients. Downstream of Nrf2, levels of oPMN superoxide dismutase 1 and catalase were decreased in severe CP, despite increased recruitment. Nrf2(-/-) mice had more severe loss of periodontium in response to periodontitis-inducing subgingival ligatures compared with wild-types. Levels of 8-hydroxy-deoxyguanosine were increased in periodontal lesions of Nrf2(-/-) mice, indicating high oxidative damage. We report, for the first time, Nrf2 pathway down-regulation in oPMNs of patients with severe CP. PMNs of CP patients may be primed for low antioxidant response in the context of high recruitment in the oral cavity, resulting in increased oxidative tissue damage.

The use of systemic antibiotics in the treatment of refractory periodontitis: A systematic review

BACKGROUND

The goal in treating refractory periodontitis (RP) is to arrest or slow disease progression, which usually has included the use of systemic antibiotics adjunct to conventional mechanical debridement. The aim of this systematic review was to evaluate the evidence that the association of systemic antibiotics with conventional mechanical debridement increases the efficacy of periodontal therapy in the treatment of RP.

TYPES OF STUDIES REVIEWED

The authors searched for studies in PubMed MEDLINE, Cochrane Central Register of Controlled Trials, Thomson Reuters Web of Science, Scopus, Latin American and Caribbean Center on Health Sciences Information, and Scientific Electronic Library Online electronic databases by using selected key words from the earliest records up through October 31, 2014. Only clinical intervention studies in which investigators compared the treatment of participants with RP with either mechanical debridement alone or associated with systemic antibiotics were eligible for selection. Two authors independently assessed the risk of bias of each selected study.

RESULTS

The authors identified 13 articles and included 6 of them. Investigators in all studies reported greater reductions in probing depth or in loss of clinical attachment level after adjunct systemic antibiotic therapy when compared with mechanical debridement alone. Antibiotics tested included metronidazole, clindamycin, tetracycline hydrochloride, amoxicillin, and amoxicillin and potassium clavulanate. Five studies presented a high risk of bias, and 1 study presented an unclear risk.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The overall quality of the evidence does not allow the conclusion that adjunct systemic antibiotics are of additional benefit to conventional mechanical debridement alone.

Identification of neutrophil surface marker changes in health and inflammation using high-throughput screening flow cytometry

Neutrophils are the most abundant white blood cell and are an essential component of the innate immune system. A complete cataloguing of cell surface markers has not been undertaken for neutrophils isolated from circulation as well as healthy and inflamed tissues. To identify cell-surface markers specific to human neutrophils, we used high-throughput flow cytometry to screen neutrophil populations isolated from blood and oral rinses from healthy and chronic periodontitis patients against a panel of 374 known cluster of differentiation (CD) antibodies. This screen identified CD11b, CD16, and CD66b as markers that are consistently expressed on neutrophils independent of the cell location, level of activation and disease state. Cell sorting against CD11b, CD16 and CD66b allowed for the enrichment of mature neutrophils, yielding neutrophil populations with up to 99% purity. These findings suggest an ideal surface marker set for isolating mature neutrophils from humans. The screen also demonstrated that tissue neutrophils from chronically inflamed tissue display a unique surface marker set compared to tissue neutrophils present in healthy, non-inflamed tissues.

Neutrophil Functions in Periodontal Homeostasis

Oral tissues are constantly exposed to damage from the mechanical effort of eating and to microorganisms, mostly bacteria. In healthy gingiva tissue remodeling and a balance between bacteria and innate immune cells are maintained. However, excess of bacteria biofilm (plaque) creates an inflammation state that recruits more immune cells, mainly neutrophils to the gingiva. Neutrophils create a barrier for bacteria to reach inside tissues. When neutrophils are insufficient, bacteria thrive causing more inflammation that has been associated with systemic effects on other conditions such as atherosclerosis, diabetes, and cancer. But paradoxically when neutrophils persist, they can also promote a chronic inflammatory state that leads to periodontitis, a condition that leads to damage of the bone-supporting tissues. In periodontitis, bone loss is a serious complication. How a neutrophil balance is needed for maintaining healthy oral tissues is the focus of this review. We present recent evidence on how alterations in neutrophil number and function can lead to inflammatory bone loss, and how some oral bacteria signal neutrophils to block their antimicrobial functions and promote an inflammatory state. Also, based on this new information, novel therapeutic approaches are discussed.

Social-Biological Interactions in Oral Disease: A 'Cells to Society' View

Oral diseases constitute a major worldwide public health problem, with their burden concentrating in socially disadvantaged and less affluent groups of the population, resulting in significant oral health inequalities. Biomedical and behavioural approaches have proven relatively ineffective in reducing these inequalities, and have potentially increased the health gap between social groups. Some suggest this stems from a lack of understanding of how the social and psychosocial contexts in which behavioural and biological changes occur influence oral disease. To unravel the pathways through which social factors affect oral health outcomes, a better understanding is thus needed of how the social 'gets under the skin,' or becomes embodied, to alter the biological. In this paper, we present the current knowledge on the interplay between social and biological factors in oral disease. We first provide an overview of the process of embodiment in chronic disease and then evaluate the evidence on embodiment in oral disease by reviewing published studies in this area. Results show that, in periodontal disease, income, education and perceived stress are correlated with elevated levels of stress hormones, disrupted immune biomarkers and increased allostatic load. Similarly, socioeconomic position and increased financial stress are related to increased stress hormones and cariogenic bacterial counts in dental caries. Based on these results, we propose a dynamic model depicting social-biological interactions that illustrates potential interdependencies between social and biological factors that lead to poor oral health. This work and the proposed model may aid in developing a better understanding of the causes of oral health inequalities and implicate the importance of addressing the social determinants of oral health in innovating public health interventions.

Neutrophil homeostasis and inflammation: novel paradigms from studying periodontitis

Once viewed as simply antibacterial effector cells packed with antimicrobials, neutrophils are now increasingly appreciated for their regulatory roles in immunity and inflammation. The homeostatic regulation of neutrophils is thus crucial for optimal operation of the immune system. An attractive model to understand mechanistically the role of neutrophils is periodontitis, an oral inflammatory disease that is particularly sensitive to neutrophil alterations in numbers or function. The recruitment and proper activation of neutrophils are largely dependent on leukocyte integrins and complement. This review discusses how these processes are affected by host genetic or microbial factors leading to the development of periodontitis. For instance, both hypo- and hyper-recruitment of neutrophils as a result of deficiencies in the expression of β2 integrins or their negative regulators, respectively, causes unwarranted IL-17-dependent inflammatory bone loss. Moreover, microbial hijacking of C5aR (CD88) signaling in neutrophils impairs their antimicrobial function while promoting destructive inflammatory responses. These studies not only support the concept that neutrophil homeostasis is key to periodontal health but also reveal promising, new therapeutic targets as discussed in the review.

Oral neutrophil transcriptome changes result in a pro-survival phenotype in periodontal diseases

Background

Periodontal diseases are inflammatory processes that occur following the influx of neutrophils into the periodontal tissues in response to the subgingival bacterial biofilm. Current literature suggests that while neutrophils are protective and prevent bacterial infections, they also appear to contribute to damage of the periodontal tissues. In the present study we compare the gene expression profile changes in neutrophils as they migrate from the circulation into the oral tissues in patients with chronic periodontits and matched healthy subjects. We hypothesized that oral neutrophils in periodontal disease patients will display a disease specific transcriptome that differs from the oral neutrophil of healthy subjects.

Methods

Venous blood and oral rinse samples were obtained from healthy subjects and chronic periodontitis patients for neutrophil isolation. mRNA was isolated from the neutrophils, and gene expression microarray analysis was completed. Results were confirmed for specific genes of interest by qRT-PCR and Western Blot analysis.

Results and Discussion

Chronic periodontitis patients presented with increased recruitment of neutrophils to the oral cavity. Gene expression analysis revealed differences in the expression levels of genes from several biological pathways. Using hierarchical clustering analysis, we found that the apoptosis network was significantly altered in patients with chronic inflammation in the oral cavity, with up-regulation of pro-survival members of the Bcl-2 family and down-regulation of pro-apoptosis members in the same compartment. Additional functional analysis confirmed that the percentages of viable neutrophils are significantly increased in the oral cavity of chronic periodontitis patients.

Conclusions

Oral neutrophils from patients with periodontal disease displayed an altered transcriptome following migration into the oral tissues. This resulted in a pro-survival neutrophil phenotype in chronic periodontitis patients when compared with healthy subjects, resulting in a longer-lived neutrophil. This is likely to impact the severity and length of the inflammatory response in this oral disease.

Oral neutrophils display a site-specific phenotype characterized by expression of T-cell receptors

BACKGROUND

Neutrophils, key cells of the innate immune system, were previously thought to be terminally differentiated cells, incapable of altering their gene expression after differentiation and maturation in the bone marrow. Only recently has it been shown that neutrophils perform rapid and complex changes in gene expression during inflammatory responses. Previous work by the authors has demonstrated differences in reactive oxygen species production between oral and peripheral blood neutrophils isolated from patients with chronic periodontitis, suggesting that oral neutrophils present with a unique oral phenotype. Understanding differences in the neutrophil transcriptome after transit from circulation into the site of inflammation will give new insights into how these innate immune cells function during inflammation.

METHODS

Venous blood and oral rinse samples were obtained from five healthy participants. Blood neutrophils were isolated using a standard gradient method. Oral neutrophils were isolated through nylon mesh filters of different pore sizes (40 to 10 μm). RNA was purified from isolated neutrophils, and gene expression microarray analysis was completed. Results were confirmed by quantitative reverse transcription-polymerase chain reaction and immunofluorescence microscopy.

RESULTS

Oral neutrophil isolation, which is critical when analyzing gene expression with samples clear of epithelial cell contamination, was optimized. It was also demonstrated that oral neutrophils present with a significant increase in T-cell receptor expression compared with circulating neutrophils, suggesting a role for oral neutrophils in crosstalk between the innate and adaptive immune system in the mouth.

CONCLUSION

To the best of the authors' knowledge, it is demonstrated for the first time that, compared with circulating neutrophils, oral neutrophils present a site-specific gene expression profile in healthy individuals.