Specialized pro‐resolving lipid mediators in experimental periodontitis: A systematic review

Periodontitis is associated with decreased experimental pressure pain tolerance: The Tromsø Study 2015-2016

AIM

To assess the relationship between periodontitis and experimental pain tolerance.

MATERIALS AND METHODS

Participants from the population-based seventh survey of the Tromsø Study with data on periodontitis were included (n = 3666, 40-84 years old, 51.6% women). Pain tolerance was assessed through (i) pressure pain tolerance (PPT) test with a computerized cuff pressure algometry on the leg, and (ii) cold-pressor tolerance (CPT) test where one hand was placed in circulating 3°C water. Cox proportional hazard regression was used to assess the association between periodontitis and pain tolerance adjusted for age, sex, education, smoking and obesity.

RESULTS

In the fully adjusted model using the 2012 Centers for Disease Control/American Academy of Periodntology case definitions for surveillance of periodontitis, moderate (hazard ratio [HR] = 1.09; 95% confidence interval [CI]: 1.01, 1.18) and severe (HR = 1.25, 95% CI: 1.11, 1.42) periodontitis were associated with decreased PPT. Using the 2018 classification of periodontitis, having Stage II/III/IV periodontitis was significantly associated with decreased PPT (HR = 1.09; 95% CI: 1.01, 1.18) compared with having no or stage I periodontitis. There were no significant associations between periodontitis and CPT in fully adjusted models.

CONCLUSIONS

Moderate and severe periodontitis was associated with experimental PPT.

Diabetes mellitus promotes susceptibility to periodontitis-novel insight into the molecular mechanisms

Diabetes mellitus is a main risk factor for periodontitis, but until now, the underlying molecular mechanisms remain unclear. Diabetes can increase the pathogenicity of the periodontal microbiota and the inflammatory/host immune response of the periodontium. Hyperglycemia induces reactive oxygen species (ROS) production and enhances oxidative stress (OS), exacerbating periodontal tissue destruction. Furthermore, the alveolar bone resorption damage and the epigenetic changes in periodontal tissue induced by diabetes may also contribute to periodontitis. We will review the latest clinical data on the evidence of diabetes promoting the susceptibility of periodontitis from epidemiological, molecular mechanistic, and potential therapeutic targets and discuss the possible molecular mechanistic targets, focusing in particular on novel data on inflammatory/host immune response and OS. Understanding the intertwined pathogenesis of diabetes mellitus and periodontitis can explain the cross-interference between endocrine metabolic and inflammatory diseases better, provide a theoretical basis for new systemic holistic treatment, and promote interprofessional collaboration between endocrine physicians and dentists.

Roles of specialized pro-resolving mediators and omega-3 polyunsaturated fatty acids in periodontal inflammation and impact on oral microbiota

Periodontitis is a chronic inflammatory disease induced by dysbiotic dental biofilms. Management of periodontitis is primarily anti-bacterial via mechanical removal of bacterial biofilm. The successful resolution requires wound healing and tissue regeneration, which are not always achieved with these traditional methods. The discovery of specialized pro-resolving mediators (SPMs), a class of lipid mediators that induce the resolution of inflammation and promote local tissue homeostasis, creates another option for the treatment of periodontitis and other diseases of chronic inflammation. In this mini-review, we discuss the host-modulatory effects of SPMs on periodontal tissues and changes in the taxonomic composition of the gut and oral microbiome in the presence of SPMs and SPM precursor lipids. Further research into the relationship between host SPM production and microbiome-SPM modification has the potential to unveil new diagnostic markers of inflammation and wound healing. Expanding this field may drive the discovery of microbial-derived bioactive therapeutics to modulate immune responses.

Resolution of inflammation in oral diseases

The resolution of inflammation is an essential endogenous process that protects host tissues from an exaggerated chronic inflammatory response. Multiple interactions between host cells and resident oral microbiome regulate the protective functions that lead to inflammation in the oral cavity. Failure of appropriate regulation of inflammation can lead to chronic inflammatory diseases that result from an imbalance between pro-inflammatory and pro-resolution mediators. Thus, failure of the host to resolve inflammation can be considered an essential pathological mechanism for progression from the late stages of acute inflammation to a chronic inflammatory response. Specialized pro-resolving mediators (SPMs), which are essential polyunsaturated fatty acid (PUFA)-derived autacoid mediators, aid in regulating the endogenous inflammation resolving process by stimulating immune cell-mediated clearance of apoptotic polymorphonuclear neutrophils, cellular debris, and microbes, restricting further neutrophil tissue infiltration, and counter-regulating pro-inflammatory cytokine production. The SPM superfamily contains four specialized lipid mediator families: lipoxins, resolvins, protectins, and maresins that can activate resolution pathways. Understanding the crosstalk between resolution signals in the tissue response to injury has therapeutic application potential for preventing, maintaining, and regenerating chronically damaged tissues. Here, we discuss the fundamental concepts of resolution as an active biochemical process, novel concepts demonstrating the role of resolution mediators in tissue regeneration in periodontal and pulpal diseases, and future directions for therapeutic applications with particular emphasis on periodontal therapy.

Current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome

Sjögren's syndrome is a chronic inflammatory autoimmune disease characterized by diminished secretory function of the exocrine glands. Although extensive investigation has been done to understand Sjögren's syndrome, the causes of the disease are as yet unknown and treatments remain largely ineffective, with established therapeutic interventions being limited to use of saliva substitutes with modest effectiveness. A primary feature of Sjögren's syndrome is uncontrolled inflammation of exocrine tissues and previous studies have demonstrated that lipid-based specialized pro-resolving mediators reduce inflammation and restores tissue integrity in salivary glands. However, these studies are limited to a single specialized pro-resolving lipid mediator's family member resolvin D1 or RvD1 and its aspirin-triggered epimer, AT-RvD1. Consequently, additional studies are needed to explore the potential benefits of other members of the specialized pro-resolving lipid mediator's family and related molecules (e.g., additional resolvin subtypes as well as lipoxins, maresins and protectins). In support of this goal, the current review aims to briefly describe the range of current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome, including both strengths and weaknesses of each approach where this information is known. With this article, the possibilities presented by specialized pro-resolving lipid mediators will be introduced to a wider audience in immunology and practical advice is given to researchers who may wish to take up this work.

Host Response Modulation Therapy in the Diabetes Mellitus—Periodontitis Conjuncture: A Narrative Review

The inflammatory response of the host in periodontitis is the phenomenon that underlies the onset and evolution of periodontal destructive phenomena. A number of systemic factors, such as diabetes mellitus (DM), can negatively affect the patient with periodontitis, just as the periodontal disease can aggravate the status of the DM patient. Host response modulation therapy involves the use of anti-inflammatory and anti-oxidant products aimed at resolving inflammation, stopping destructive processes, and promoting periodontal healing, all important aspects in patients with high tissue loss rates, such as diabetic patients. This paper reviews the data available in the literature on the relationship between DM and periodontitis, the main substances modulating the inflammatory response (nonsteroidal anti-inflammatory drugs, sub-antimicrobial doses of doxycycline, or omega-3 fatty acids and their products, specialized pro-resolving mediators), as well as their application in diabetic patients.

Resolvins as a Treatment Modality in Experimental Periodontitis: A Systematic Review of Preclinical Studies

This systematic review aimed to assess scientific data of existing literature to identify the efficacy of resolvins (Rv) in the treatment of periodontitis. The electronic databases, Web of Science (WOS), Medline/PubMed, The Cochrane Library, Scopus, and Saudi digital library (SDL), were searched for eligible studies in the field of periodontics. A thorough analysis of the retrieved literature provided five articles that were assessed and included in this systematic review. The quality of these studies was assessed by updated Essential Animal Research: Reporting of In-Vivo Experiments (ARRIVE) guidelines. The five included studies were published between 2005 and 2018 and investigated resolvins as a treatment approach in experimental periodontitis of animals. Among the study animals employed, New Zealand white rabbits were used in three studies, Wistar rats and Albino mice in two studies, respectively. Four studies have evaluated eicosapentaenoic acid-derived RvE1, and one study evaluated docosahexaenoic acid-derived RvD2. Oral-topical application of Rv was followed in four studies, and intra-peritoneal Rv injection was administered in one study. The study duration in these studies have ranged between 4-12 weeks, and the Rv dose was between 0.1 μg to 0.5 μg. One study evaluated the influence of RvE1 topical application on both the prevention and treatment of experimental periodontitis. Resolvins (RvE1 and RvD2) have been studied in periodontitis-induced animal models to assess their potential role in periodontal inflammation resolution. There are promising preclinical data of using resolvins as a treatment modality in experimental periodontitis. Resolvins have been demonstrated to inhibit the destructive inflammatory process and alveolar bone loss in laboratory-induced periodontitis under controlled experimental conditions.

Nature of the Interplay Between Periodontal Diseases and COVID-19

The coronavirus disease 2019 (COVID-19) is mostly a mild condition, however, in some patients, it could progress into a severe and even fatal disease. Recent studies have shown that COVID-19 infection and severity could be associated with the presence of periodontitis, one of the most prevalent chronic diseases. This association could be explained by the fact that periodontitis and COVID-19 share some common risk factors that included chronic diseases, such as diabetes and hypertension as well as conditions such as age, sex, and genetic variants. Another possible explanation could be the systemic inflammation and the aspiration of periodontopathogens seen in patients with periodontitis, which could have a synergism with the virus or compromise the reaction of the body against COVID-19. This narrative review explores the nature of these associations, the evidence behind them, and their implications.

Yeast Beta-Glucans Ingestion Does Not Influence Body Weight: A Systematic Review and Meta-Analysis of Pre-Clinical Studies

Dietary fiber supplementation has been studied as a promising strategy in the treatment of obesity and its comorbidities. A systematic review and meta-analysis were performed to verify whether the consumption of yeast beta-glucan (BG) favors weight loss in obese and non-obese rodents. The PICO strategy was employed, investigating rodents (Population), subjected to the oral administration of yeast BG (Intervention) compared to animals receiving placebo (Comparison), evaluating body weight changes (Outcome), and based on preclinical studies (Study design). Two reviewers searched six databases and the grey literature. We followed the PRISMA 2020 guidelines, and the protocol was registered on PROSPERO (CRD42021267788). The search returned 2467 articles. Thirty articles were selected for full-text evaluation, and seven studies remained based on the eligibility criteria. The effects of BG intake on body weight were analyzed based on obese (n = 4 studies) and non-obese animals (n = 4 studies). Even though most studies on obese rodents (75%) indicated a reduction in body weight (qualitative analysis), the meta-analysis showed this was not significant (mean difference −1.35 g—95% CI −5.14:2.45). No effects were also observed for non-obese animals. We concluded that the ingestion of yeast BG barely affects the body weight of obese and non-obese animals.

Specialized pro-resolving receptors are expressed in salivary glands with Sjögren's syndrome

Our previous studies demonstrated that resolvin D1 (RvD1) and its aspirin-trigged (AT) form AT-RvD1, are effective in decreasing inflammation while restoring saliva flow rates in a Sjögren's syndrome (SS)-like mouse model before and after disease onset. Resolvins are specialized pro-resolving mediators (SPM) that actively regulate inflammation. However, we only have extensive data within the salivary glands for RvD1 and AT-RvD1, both of which bind to the receptor ALX/FPR2. As such, the presence of other SPM receptors is unknown within salivary glands. Therefore, the goal of this study was to determine the expression of SPM receptors in non-SS and SS patients. For this purpose, six human minor salivary glands from female subjects were analyzed by H&E using the Chisholm and Mason classification to determine the degree of lymphocytic infiltration. Next, confocal immunofluorescence analysis was performed to determine the presence and distribution of different SPM receptors in mucous acini and striated ducts. We observed diffuse presence of lymphocytic infiltration and clinical data were consistent with SS diagnosis in three patients. Moreover, confocal immunofluorescence analysis indicated the presence of the receptors ALX/FPR2, BLT1 and CMKLR1 in the mucous acini and striated ducts of both non-SS and SS patients. GPR32 was absent in SS and non-SS minor salivary glands. In summary, our results showed that various SPM receptors are expressed in non-SS and SS minor salivary glands, all of which may pose as potential targets for promoting pro-epithelial and anti-inflammatory/pro-resolution signaling on SS patients.

The pathogenic mechanism of oral bacteria and treatment with inhibitors

OBJECTIVES

The objective of this study was to introduce the evidence obtained through extensive research that periodontitis increases risk of many systemic diseases.

METHOD

Analysis of some oral bacteria (P. gingivalis, T. denticola, T. forsythia, A. actinomycetemcomitans, and F. nucleatum) and its related treatments and mediators by the specific methods (western blot, ELISA, etc).

RESULTS

This article reviews in detail the evidence obtained through extensive research that periodontitis increases risk of many systemic diseases, including cardiovascular disease, rheumatoid arthritis, and Alzheimer's disease. These diseases are known to be associated with some certain specific gram-negative bacteria as periodontal pathogens, which induce inflammation and related diseases through TLR receptors, kinases, transcriptional factors and other cytokines. We also reviewed the latest research for inhibitors against inflammation and related diseases that have potential to be further applied clinically. In addition, based on a large amount of research evidence, we draw two tables about the mechanism of disease caused by periodontal bacteria, so that readers can easily search and analyze these research results.

DISCUSSION

This review details how the periodontal bacteria and their virulence factors can trigger host immune defense and induce many systemic diseases via inflammation and invasion. This Review also addressed the latest research around inhibitors against inflammation.

New tendencies in non-surgical periodontal therapy

The aim of this review was to update the evidence of new approaches to non-surgical therapy (NSPT) in the treatment of periodontitis. Preclinical and clinical studies addressing the benefits of adjunctive antimicrobial photodynamic therapy, probiotics, prebiotics/synbiotics, statins, pro-resolving mediators, omega-6 and -3, ozone, and epigenetic therapy were scrutinized and discussed. Currently, the outcomes of these nine new approaches, when compared with subgingival debridement alone, did not demonstrate a significant added clinical benefit. However, some of these new alternative interventions may have the potential to improve the outcomes of NSPT alone. Future evidence based on randomized controlled clinical trials would help clinicians and patients in the selection of different adjunctive therapies.

Subgingival Microbiome and Specialized Pro-Resolving Lipid Mediator Pathway Profiles Are Correlated in Periodontal Inflammation

Failure of resolution pathways in periodontitis is reflected in levels of specialized pro-resolving lipid mediators (SPMs) and SPM pathway markers but their relationship with the subgingival microbiome is unclear. This study aimed to analyze and integrate lipid mediator level, SPM receptor gene expression and subgingival microbiome data in subjects with periodontitis vs. healthy controls. The study included 13 periodontally healthy and 15 periodontitis subjects that were evaluated prior to or after non-surgical periodontal therapy. Samples of gingival tissue and subgingival plaque were collected prior to and 8 weeks after non-surgical treatment; only once in the healthy group. Metabololipidomic analysis was performed to measure levels of SPMs and other relevant lipid mediators in gingiva. qRT-PCR assessed relative gene expression (2-ΔΔCT) of known SPM receptors. 16S rRNA sequencing evaluated the relative abundance of bacterial species in subgingival plaque. Correlations between lipid mediator levels, receptor gene expression and bacterial abundance were analyzed using the Data Integration Analysis for Biomarker discovery using Latent cOmponents (DIABLO) and Sparse Partial Least Squares (SPLS) methods. Profiles of lipid mediators, receptor genes and the subgingival microbiome were distinct in the three groups. The strongest correlation existed between lipid mediator profile and subgingival microbiome profile. Multiple lipid mediators and bacterial species were highly correlated (correlation coefficient ≥0.6) in different periodontal conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to healthy controls revealed that one bacterial species, Corynebacterium durum, and five lipid mediators, 5(S)6(R)-DiHETE, 15(S)-HEPE, 7-HDHA, 13-HDHA and 14-HDHA, were identified in both conditions. Comparing individual correlated lipid mediators and bacterial species in periodontitis before treatment to after treatment revealed that one bacterial species, Anaeroglobus geminatus, and four lipid mediators, 5(S)12(S)-DiHETE, RvD1, Maresin 1 and LTB4, were identified in both conditions. Four Selenomonas species were highly correlated with RvD1, RvE3, 5(S)12(S)-DiHETE and proinflammatory mediators in the periodontitis after treatment group. Profiles of lipid mediators, receptor gene and subgingival microbiome are associated with periodontal inflammation and correlated with each other, suggesting inflammation mediated by lipid mediators influences microbial composition in periodontitis. The role of correlated individual lipid mediators and bacterial species in periodontal inflammation have to be further studied.

Specialized pro-resolving lipid mediators in endodontics: a narrative review

Endodontics is the branch of dentistry concerned with the morphology, physiology, and pathology of the human dental pulp and periradicular tissues. Human dental pulp is a highly dynamic tissue equipped with a network of resident immunocompetent cells that play major roles in the defense against pathogens and during tissue injury. However, the efficiency of these mechanisms during dental pulp inflammation (pulpitis) varies due to anatomical and physiological restrictions. Uncontrolled, excessive, or unresolved inflammation can lead to pulp tissue necrosis and subsequent bone infections called apical periodontitis. In most cases, pulpitis treatment consists of total pulp removal. Although this strategy has a good success rate, this treatment has some drawbacks (lack of defense mechanisms, loss of healing capacities, incomplete formation of the root in young patients). In a sizeable number of clinical situations, the decision to perform pulp extirpation and endodontic treatment is justifiable by the lack of therapeutic tools that could otherwise limit the immune/inflammatory process. In the past few decades, many studies have demonstrated that the resolution of acute inflammation is necessary to avoid the development of chronic inflammation and to promote repair or regeneration. This active process is orchestrated by Specialized Pro-resolving lipid Mediators (SPMs), including lipoxins, resolvins, protectins and maresins. Interestingly, SPMs do not have direct anti-inflammatory effects by inhibiting or directly blocking this process but can actively reduce neutrophil infiltration into inflamed tissues, enhance efferocytosis and bacterial phagocytosis by monocytes and macrophages and simultaneously inhibit inflammatory cytokine production. Experimental clinical application of SPMs has shown promising result in a wide range of inflammatory diseases, such as renal fibrosis, cerebral ischemia, marginal periodontitis, and cancer; the potential of SPMs in endodontic therapy has recently been explored. In this review, our objective was to analyze the involvement and potential use of SPMs in endodontic therapies with an emphasis on SPM delivery systems to effectively administer SPMs into the dental pulp space.

Intersection between macrophages and periodontal pathogens in periodontitis

Periodontitis is a chronic infectious disease characterized by loss of periodontal attachment and resorption of alveolar bone. Dysregulated oral microbial community is the initial factor of periodontitis and causes excessive infiltration of immune cells in periodontal tissues. Macrophage, as an important part of the innate immune system, interacts continually with oral pathogens. Macrophages can recognize and phagocytize pathogens and apoptotic neutrophils and produce the specialized pro-resolving mediators (SPMs) playing an important role in maintaining the homeostasis of tissue microenvironment. However, macrophages may also induce abnormal immune responses with the overstimulation from pathogens, leading to the destruction of periodontal tissues and alveolar bone. Looking for targeted drugs that can regulate the activities of oral pathogens and the functions of macrophages provides a new idea for periodontitis treatment. This review summarizes the interaction between macrophages and periodontal pathogens in periodontitis, focusing on the pro-inflammation and anti-inflammation phenotypes of macrophages, and briefly concludes potential new methods of periodontitis therapy targeted at oral pathogens and macrophages.

Developments of specialized pro-resolving mediators in periodontitis

Resolution of inflammation plays an important part in maintaining homeostasis. It is an actively programmed progress involving multiple immune cells and mediators. Specialized pro-resolving mediators (SPMs) derived from Ω-3 polyunsaturated fatty acids include resolvins, protectins and maresins, and they exert abilities in the resolution of inflammation, host defense, organ protection, and tissue generation. Periodontitis is an inflammatory and destructive disease in the periodontal tissue initiated by dental plaque. Inadequate proinflammatory or proresolving responses, or the imbalance between the two, may contribute to the pathogenesis of the disease. Studies have shown that activating specialized receptors SPMs displayed multiple biological effects towards periodontitis, including resolution of inflammation, alveolar bone protection, periodontal tissue regeneration, and pathogen resistance. Thus, the relationship between SPM and periodontitis and the potentials and challenges in SPM application were reviewed.

Specialized proresolving mediators in infection and lung injury

Specialized proresolving mediators (SPMs) are endogenous lipid metabolites of long-chain polyunsaturated fatty acids that are involved in promoting the resolution of inflammation. Many disease conditions characterized by excessive inflammation have impaired or altered SPM biosynthesis, which may lead to chronic, unresolved inflammation. Exogenous administration of SPMs in infectious conditions has been shown to be effective at improving infection clearance and survival in preclinical models. SPMs have also shown tremendous promise in the context of inflammatory lung conditions, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease, mostly in preclinical settings. To date, SPMs have not been studied in the context of the novel Coronavirus, severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), however their preclinical efficacy in combatting infections and improving acute respiratory distress suggest they may be a valuable resource in the fight against Coronavirus disease-19 (COVID-19). Overall, while the research on SPMs is still evolving, they may offer a novel therapeutic option for inflammatory conditions.

Distinct Profiles of Specialized Pro-resolving Lipid Mediators and Corresponding Receptor Gene Expression in Periodontal Inflammation

Polyunsaturated fatty acid-derived specialized pro-resolving lipid mediators (SPMs) play an important role in modulating inflammation. The aim of the study was to compare profiles of SPMs, SPM related lipid mediators and SPM receptor gene expression in gingiva of subjects with periodontitis to healthy controls. A total of 28 subjects were included; 13 periodontally healthy and 15 periodontitis before or after non-surgical periodontal therapy. Gingival tissues were collected from two representative posterior teeth prior to and 8 weeks after scaling and root planning; only once in the healthy group. Lipid mediator-SPM metabololipidomics was performed to identify metabolites in gingiva. qRT-PCR was performed to assess relative gene expression (2^−ΔΔCT) of known SPM receptors. Intergroup comparisons were made using Wilcoxon tests. Thirty-six omega-6 or omega-3 fatty acid-derived lipid mediators and seven receptor genes were identified in gingiva. Profiles of lipid mediators and receptor gene expression were significantly different between the three groups. Levels of six lipid mediators, 5-HETE, 15-HETE, 15(S)-HEPE, 4-HDHA, 7-HDHA, and 17-HDHA in periodontitis before treatment were significantly higher than in periodontitis after treatment. The expression of BLT1 in the healthy group was significantly higher than periodontitis subjects before and after treatment. The expression of GPR18 in periodontitis before treatment was significantly higher than in periodontitis after treatment while the expression of GPR32 in periodontitis before treatment was significantly lower than in periodontitis after treatment. Elevated levels of SPM biosynthetic pathway markers in periodontitis subjects before treatment indicated inflammation induced pro-resolution activity in gingiva, but receptors for these molecules were deficient in periodontitis pre-treatment suggesting that failure of resolution of inflammation contributes to excess, chronic inflammation in periodontitis.

Can Resveratrol Treatment Control the Progression of Induced Periodontal Disease? A Systematic Review and Meta-Analysis of Preclinical Studies

Resveratrol is an anti-inflammatory compound found in several foods. Periodontal disease (PD) is associated to other systemic diseases, and inflammation may be responsible for the association. Consequently, controlling inflammation not only may benefit oral health but also may assist with the management of other chronic inflammatory conditions. We aimed to investigate the effects of resveratrol administration on PD control in preclinical studies. A systematic search was performed for scientific articles using both electronic databases and a manual search using combinations of the following keywords: "resveratrol" OR "3,5,4'-trihydroxystilbene" AND "periodontal disease" OR "periodontitis" OR "gingivitis". Only in vivo original studies investigating resveratrol treatment on experimental animal models of PD were selected. A quality assessment of the studies was performed using the Animal Research Reporting In Vivo Experiment (ARRIVE) guidelines, and the risk of bias was assessed using the Syrcle tool. The search returned 570 articles, and 11 matched the inclusion criteria. A meta-analysis showed that resveratrol treatment attenuated alveolar bone loss (τ2 = 0.0041; 95% CI: -0.14; -0.04). The ARRIVE criteria reported a good quality of studies in general (mean score 28.5 ± 2.5). However, five Syrcle domains indicated a high risk of bias or did not present information clearly. We concluded that, in preclinical studies, resveratrol treatment prevented PD progression.