Resolvin E1 regulates inflammation at the cellular and tissue level and restores tissue homeostasis in vivo

Animal models for periodontal regeneration and peri-implant responses

Translation of experimental data to the clinical setting requires the safety and efficacy of such data to be confirmed in animal systems before application in humans. In dental research, the animal species used is dependent largely on the research question or on the disease model. Periodontal disease and, by analogy, peri-implant disease, are complex infections that result in a tissue-degrading inflammatory response. It is impossible to explore the complex pathogenesis of periodontitis or peri-implantitis using only reductionist in-vitro methods. Both the disease process and healing of the periodontal and peri-implant tissues can be studied in animals. Regeneration (after periodontal surgery), in response to various biologic materials with potential for tissue engineering, is a continuous process involving various types of tissue, including epithelia, connective tissues and alveolar bone. The same principles apply to peri-implant healing. Given the complexity of the biology, animal models are necessary and serve as the standard for successful translation of regenerative materials and dental implants to the clinical setting. Smaller species of animal are more convenient for disease-associated research, whereas larger animals are more appropriate for studies that target tissue healing as the anatomy of larger animals more closely resembles human dento-alveolar architecture. This review focuses on the animal models available for the study of regeneration in periodontal research and implantology; the advantages and disadvantages of each animal model; the interpretation of data acquired; and future perspectives of animal research, with a discussion of possible nonanimal alternatives. Power calculations in such studies are crucial in order to use a sample size that is large enough to generate statistically useful data, whilst, at the same time, small enough to prevent the unnecessary use of animals.

Neutrophil Resolvin E1 Receptor Expression and Function in Type 2 Diabetes

Unresolved inflammation is key in linking metabolic dysregulation and the immune system in type 2 diabetes. Successful regulation of acute inflammation requires biosynthesis of specialized proresolving lipid mediators, such as E-series resolvin (RvE) 1, and activation of cognate G protein-coupled receptors. RvE1 binds to leukotriene B4 (BLT-1) on neutrophils and to ERV-1/ChemR23 on monocyte/macrophages. We show novel actions of RvE1 and expression patterns of neutrophil receptors in type 2 diabetes. Neutrophils from healthy subjects express functional BLT-1, low levels of minimally functional ERV-1, and inversed coexpression when compared to neutrophils from type 2 diabetes subjects. Stimulation with TNF-α or LPS increased the expression of ERV-1 by healthy and diabetic neutrophils. RvE1 counteracted LPS and TNF-α induction of ERV-1 overexpression and endogenous diabetic overexpression, activating phagocytosis and resolution signals. Functional ERV-1 was determined by phosphorylation of the signaling protein ribosomal S6. Receptor-antagonism experiments revealed that the increase in phosphorylation of ribosomal S6 was mediated by BLT-1 in healthy subject neutrophils and by ERV-1 in diabetes. Metabololipidomics reveal a proinflammatory profile in diabetic serum. Cell phagocytosis is impaired in type 2 diabetes and requires RvE1 for activation. The dose of RvE1 required to activate resolution signals in type 2 diabetic neutrophils was significantly higher than in healthy controls. RvE1 rescues the dysregulation seen on neutrophil receptor profile and, following a therapeutic dosage, activates phagocytosis and resolution signals in type 2 diabetes. These findings reveal the importance of resolution receptors in health, disease, and dysregulation of inflammation in type 2 diabetes.

An imbalance between specialized pro-resolving lipid mediators and pro-inflammatory leukotrienes promotes instability of atherosclerotic plaques

Chronic unresolved inflammation plays a causal role in the development of advanced atherosclerosis, but the mechanisms that prevent resolution in atherosclerosis remain unclear. Here, we use targeted mass spectrometry to identify specialized pro-resolving lipid mediators (SPM) in histologically-defined stable and vulnerable regions of human carotid atherosclerotic plaques. The levels of SPMs, particularly resolvin D1 (RvD1), and the ratio of SPMs to pro-inflammatory leukotriene B₄ (LTB₄), are significantly decreased in the vulnerable regions. SPMs are also decreased in advanced plaques of fat-fed Ldlr^−/− mice. Administration of RvD1 to these mice during plaque progression restores the RvD1:LTB₄ ratio to that of less advanced lesions and promotes plaque stability, including decreased lesional oxidative stress and necrosis, improved lesional efferocytosis, and thicker fibrous caps. These findings provide molecular support for the concept that defective inflammation resolution contributes to the formation of clinically dangerous plaques and offer a mechanistic rationale for SPM therapy to promote plaque stability.

Atherosclerosis progression is linked to inflammatory processes in the blood vessel wall. Here, the authors show that, with the progression of atherosclerosis, the resolution of inflammation is impaired as the result of an imbalance between specialized pro-resolving lipid mediators and leukotrienes.

Resolvin E1 Reverses Experimental Periodontitis and Dysbiosis

Periodontitis is a biofilm-induced inflammatory disease characterized by dysbiosis of the commensal periodontal microbiota. It is unclear how natural regulation of inflammation affects the periodontal biofilm. Promoters of active resolution of inflammation, including resolvin E1 (RvE1), effectively treat inflammatory periodontitis in animal models. The goals of this study were 1) to compare periodontal tissue gene expression in different clinical conditions, 2) to determine the impact of local inflammation on the composition of subgingival bacteria, and 3) to understand how inflammation impacts these changes. Two clinically relevant experiments were performed in rats: prevention and treatment of ligature-induced periodontitis with RvE1 topical treatment. The gingival transcriptome was evaluated by RNA sequencing of mRNA. The composition of the subgingival microbiota was characterized by 16S rDNA sequencing. Periodontitis was assessed by bone morphometric measurements and histomorphometry of block sections. H&E and tartrate-resistant acid phosphatase staining were used to characterize and quantify inflammatory changes. RvE1 treatment prevented bone loss in ligature-induced periodontitis. Osteoclast density and inflammatory cell infiltration in the RvE1 groups were lower than those in the placebo group. RvE1 treatment reduced expression of inflammation-related genes, returning the expression profile to one more similar to health. Treatment of established periodontitis with RvE1 reversed bone loss, reversed inflammatory gene expression, and reduced osteoclast density. Assessment of the rat subgingival microbiota after RvE1 treatment revealed marked changes in both prevention and treatment experiments. The data suggest that modulation of local inflammation has a major role in shaping the composition of the subgingival microbiota.

Scaffolds to control inflammation and facilitate dental pulp regeneration

In dentistry, the maintenance of a vital dental pulp is of paramount importance because teeth devitalized by root canal treatment may become more brittle and prone to structural failure over time. Advanced carious lesions can irreversibly damage the dental pulp by propagating a sustained inflammatory response throughout the tissue. Although the inflammatory response initially drives tissue repair, sustained inflammation has an enormously destructive effect on the vital pulp, eventually leading to total necrosis of the tissue and necessitating its removal. The implications of tooth devitalization have driven significant interest in the development of bioactive materials that facilitate the regeneration of damaged pulp tissues by harnessing the capacity of the dental pulp for self-repair. In considering the process by which pulpitis drives tissue destruction, it is clear that an important step in supporting the regeneration of pulpal tissues is the attenuation of inflammation. Macrophages, key mediators of the immune response, may play a critical role in the resolution of pulpitis because of their ability to switch to a proresolution phenotype. This process can be driven by the resolvins, a family of molecules derived from fatty acids that show great promise as therapeutic agents. In this review, we outline the importance of preserving the capacity of the dental pulp to self-repair through the rapid attenuation of inflammation. Potential treatment modalities, such as shifting macrophages to a proresolving phenotype with resolvins are described, and a range of materials known to support the regeneration of dental pulp are presented.

Seminal Fluid-Mediated Inflammation in Physiology and Pathology of the Female Reproductive Tract

Inflammation is a multifaceted process involving a host of resident and recruited immune cells that eliminate the insult or injury and initiate tissue repair. In the female reproductive tract (FMRT), inflammation-mediated alterations in epithelial, vascular, and immune functions are important components of complex physiological processes and many local and systemic pathologies. It is well established that intracoital and postcoital function of seminal fluid (SF) goes beyond nutritive support for the spermatozoa cells. SF, in particular, the inflammatory bioactive lipids, and prostaglandins present in vast quantities in SF, have a role in localized immune modulation and regulation of pathways that can exacerbate inflammation in the FMRT. In sexually active women SF-mediated inflammation has been implicated in physiologic processes such as ovulation, implantation, and parturition while also enhancing tumorigenesis and susceptibility to infection. This review highlights the molecular mechanism by which SF regulates inflammatory pathways in the FMRT and how alterations in these pathways contribute to physiology and pathology of the female reproductive function. In addition, based on findings from TaqMan® 96-Well Plate Arrays, on neoplastic cervical cells treated with SF, we discuss new findings on the role of SF as a potent driver of inflammatory and tumorigenic pathways in the cervix.

Infection and inflammatory mechanisms

This introductory article examines the potential mechanisms that may play a role in the associations between periodontitis and the systemic conditions being considered in the EFP/AAP Workshop in Segovia, Spain. Three basic mechanisms have been postulated to play a role in these interactions; metastatic infections,inflammation and inflammatory injury, and adaptive immunity. The potential role of each alone and together is considered in in vitro and animal studies and in human studies when available. This is not a systematic or critical review, but rather an overview of the field to set the stage for the critical reviews in each of the working groups.

Proresolving and cartilage-protective actions of resolvin D1 in inflammatory arthritis

Rheumatoid arthritis (RA) is a debilitating disease characterized by persistent accumulation of leukocytes within the articular cavity and synovial tissue. Metabololipidomic profiling of arthritic joints from omega-3 supplemented mice identified elevated levels of specialized proresolving lipid mediators (SPM) including resolvin D1 (RvD1). Profiling of human RA synovial fluid revealed physiological levels of RvD1, which - once applied to human neutrophils - attenuated chemotaxis. These results prompted analyses of the antiarthritic properties of RvD1 in a model of murine inflammatory arthritis. The stable epimer 17R-RvD1 (100 ng/day) significantly attenuated arthritis severity, cachexia, hind-paw edema, and paw leukocyte infiltration and shortened the remission interval. Metabololipidomic profiling in arthritic joints revealed 17R-RvD1 significantly reduced PGE2 biosynthesis, while increasing levels of protective SPM. Molecular analyses indicated that 17R-RvD1 enhanced expression of genes associated with cartilage matrix synthesis, and direct intraarticular treatment induced chondroprotection. Joint protective actions of 17R-RvD1 were abolished in RvD1 receptor-deficient mice termed ALX/fpr2/3-/- . These investigations open new therapeutic avenues for inflammatory joint diseases, providing mechanistic substance for the benefits of omega-3 supplementation in RA.

A bacterial-biofilm-induced oral osteolytic infection can be successfully treated by immuno-targeting an extracellular nucleoid-associated protein

Periodontal disease exemplifies a chronic and recurrent infection with a necessary biofilm component. Mucosal inflammation is a hallmark response of the host seen in chronic diseases, such as colitis, gingivitis, and periodontitis (and the related disorder peri-implantitis). We have taken advantage of our recently developed rat model of human peri-implantitis that recapitulates osteolysis, the requirement of biofilm formation, and the perpetuation of the bona fide disease state, to test a new therapeutic modality with two novel components. First we used hyperimmune antiserum directed against the DNABII family of proteins, now known to be a critical component of the extracellular matrix of bacterial biofilms. Second we delivered the antiserum as cargo in biodegradable microspheres to the site of the biofilm infection. We demonstrated that delivery of a single dose of anti-DNABII in poly(lactic-co-glycolic acid) (PLGA) microspheres induced significant resolution of experimental peri-implantitis, including marked reduction of inflammation. These data support the continued development of a DNABII protein-targeted therapeutic for peri-implantitis and other chronic inflammatory pathologies of the oral cavity in animals and humans.

Cytokines during periodontal wound healing: potential application for new therapeutic approach

Regeneration of periodontal tissues is one of the main goals of periodontal therapy. However, current treatment, including surgical approach, use of membrane to allow maturation of all periodontal tissues, or use of enamel matrix derivatives, presents limitations in their indications and outcomes leading to the development of new tissue engineering strategies. Several cytokines are considered as key molecules during periodontal destruction process. However, their role during each phase of periodontal wound healing remains unclear. Control and modulation of the inflammatory response and especially, release of cytokines or activation/inhibition in a time- and spatial-controlled manner may be a potential perspective for periodontal tissue engineering. The aim of this review was to summarize the specific role of several cytokines during periodontal wound healing and the potential therapeutic interest of inflammatory modulation for periodontal regeneration especially related to the expression sequence of cytokines.

Complement inhibition in pre-clinical models of periodontitis and prospects for clinical application

Periodontitis is a dysbiotic inflammatory disease leading to the destruction of the tooth-supporting tissues. Current therapies are not always effective and this prevalent oral disease continues to be a significant health and economic burden. Early clinical studies have associated periodontitis with elevated complement activity. Consistently, subsequent genetic and pharmacological studies in rodents have implicated the central complement component C3 and downstream signaling pathways in periodontal host-microbe interactions that promote dysbiosis and inflammatory bone loss. This review discusses these mechanistic advances and moreover focuses on the compstatin family of C3 inhibitors as a novel approach to treat periodontitis. In this regard, local application of the current lead analog Cp40 was recently shown to block both inducible and naturally occurring periodontitis in non-human primates. These promising results from non-human primate studies and the parallel development of Cp40 for clinical use highlight the feasibility for developing an adjunctive, C3-targeted therapy for human periodontitis.

Inhibition of pre-existing natural periodontitis in non-human primates by a locally administered peptide inhibitor of complement C3

AIM

Human periodontitis is associated with overactivation of complement, which is triggered by different mechanisms converging on C3, the central hub of the system. We assessed whether the C3 inhibitor Cp40 inhibits naturally occurring periodontitis in non-human primates (NHPs).

MATERIALS AND METHODS

Non-human primates with chronic periodontitis were intra-gingivally injected with Cp40 either once (5 animals) or three times (10 animals) weekly for 6 weeks followed by a 6-week follow-up period. Clinical periodontal examinations and collection of gingival crevicular fluid and biopsies of gingiva and bone were performed at baseline and during the study. A one-way repeated-measures anova was used for data analysis.

RESULTS

Whether administered once or three times weekly, Cp40 caused a significant reduction in clinical indices that measure periodontal inflammation (gingival index and bleeding on probing), tissue destruction (probing pocket depth and clinical attachment level) or tooth mobility. These clinical changes were associated with significantly reduced levels of pro-inflammatory mediators and decreased numbers of osteoclasts in bone biopsies. The protective effects of Cp40 persisted, albeit at reduced efficacy, for at least 6 weeks following drug discontinuation.

CONCLUSION

Cp40 inhibits pre-existing chronic periodontal inflammation and osteoclastogenesis in NHPs, suggesting a novel adjunctive anti-inflammatory therapy for treating human periodontitis.

Gene Expression of Proresolving Lipid Mediator Pathways Is Associated With Clinical Outcomes in Trauma Patients

OBJECTIVES

Specialized proresolving lipid mediators have emerged as powerful modulators of inflammation and activators of resolution. Animal models show significant benefits of specialized proresolving lipid mediators on survival and wound healing after major burn trauma. To date, no studies have investigated specialized proresolving lipid mediators and their relation to other lipid mediator pathways in humans after trauma. Here we determine if patients with poor outcomes after trauma have dysregulated lipid mediator pathways.

DESIGN

We studied blood leukocyte expression of 18 genes critical to the synthesis, signaling, and metabolism of specialized proresolving lipid mediators and proinflammatory lipid mediators, and we correlated these expression patterns with clinical outcomes in trauma patients from the Inflammation and the Host Response to Injury study.

SETTING

Seven U.S. medical trauma centers.

SUBJECTS

Ninety-six patients enrolled in the Inflammation and Host Response to Injury study, after blunt trauma and unambiguously classified as having uncomplicated or complicated recoveries. Twenty-eight healthy volunteers were enrolled as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Within each patient, the 18 genes of interest were used to calculate scores for distinct families of lipid mediators, including resolvins, lipoxins, prostaglandins, and leukotrienes, as well as leukotriene to resolvin score ratios. Scores were built using a simple weighting scheme, taking into consideration both dependent and independent activities of enzymes and receptors responsible for lipid mediator biosynthesis and function. Individually, ALOX12, PTGS2, PTGES, PTGDS, ALOX5AP, LTA4H, FPR2, PTGER2, LTB4R, HPGD, PTGR1, and CYP4F3 were expressed differentially over 28 days posttrauma between patients with uncomplicated and complicated recoveries (p < 0.05). When all genes were combined into scores, patients with uncomplicated recoveries had differential and higher resolvin scores (p < 0.001) and lower leukotriene scores (p < 0.001). A final combined ratio was calculated for each patient, and posttrauma leukotriene score to resolvin score ratios were significantly lower in patients with uncomplicated clinical courses (p < 0.001).

CONCLUSIONS

proresolving lipid mediator lipidomics and/or protein expression, and identifying associated therapeutic targets, may influence the clinical management of trauma patients.

Omega-3 fatty acids as an adjunct for periodontal therapy-a review

OBJECTIVES

The aim of this article is to present an overview of omega-3 fatty acids, their anti-inflammatory properties and potential use as an adjunct for periodontal therapy.

MATERIALS AND METHODS

A general literature search was conducted to provide an overview of omega-3 fatty acids, their metabolism and anti-inflammatory properties. A more specific literature search of PubMed and EMBASE was conducted to identify articles dealing studies investigating the effects of omega-3 fatty acids in the treatment of periodontitis in animals and humans and included cross-sectional, longitudinal and intervention designs.

RESULTS

To date, there is good emerging evidence that dietary supplementation with fish oil may be of some benefit and this is enhanced if combined with aspirin. All clinical intervention studies to date have been on small sample sizes, and this indicates there is need for larger and more robust clinical trials to verify these initial findings.

CONCLUSIONS

Dietary supplementation with fish oil could be a cost-effective adjunctive therapy to the management of periodontal disease.

CLINICAL RELEVANCE

The host modulatory properties of omega-3 fatty acids warrant further assessment of their use as an adjunct in the management of periodontitis.

Recent advances in host defense mechanisms/therapies against oral infectious diseases and consequences for systemic disease

The innate and adaptive immune systems are both crucial to oral disease mechanisms and their impact on systemic health status. Greater understanding of these interrelationships will yield opportunities to identify new therapeutic targets to modulate disease processes and/or increase host resistance to infectious or inflammatory insult. The topics addressed reflect the latest advances in our knowledge of the role of innate and adaptive immune systems and inflammatory mechanisms in infectious diseases affecting the oral cavity, including periodontitis and candidiasis. In addition, several potential links with systemic inflammatory conditions, such as cardiovascular disease, are explored. The findings elucidate some of the defense mechanisms utilized by host tissues, including the role of IL-17 in providing immunity to oral candidiasis, the antimicrobial defense of mucosal epithelial cells, and the pro-resolution effects of the natural inflammatory regulators, proresolvins and lipoxins. They also describe the role of immune cells in mediating pathologic bone resorption in periodontal disease. These insights highlight the potential for therapeutic benefit of immunomodulatory interventions that bolster or modulate host defense mechanisms in both oral and systemic disease. Among the promising new therapeutic approaches discussed here are epithelial cell gene therapy, passive immunization against immune cell targets, and the use of proresolvin agents.

Specialized pro-resolving mediators: endogenous regulators of infection and inflammation

The immune response comprises not only pro-inflammatory and anti-inflammatory pathways but also pro-resolution mechanisms that serve to balance the need of the host to target microbial pathogens while preventing excess inflammation and bystander tissue damage.

Specialized pro-resolving mediators (SPMs) are enzymatically derived from essential fatty acids to serve as a novel class of immunoresolvents that limit acute responses and orchestrate the clearance of tissue pathogens, dying cells and debris from the battlefield of infectious inflammation.

SPMs are composed of lipoxins, E-series and D-series resolvins, protectins and maresins. Individual members of the SPM family serve as agonists at cognate receptors to induce cell-type specific responses.

Important regulatory roles for SPMs have been uncovered in host responses to several microorganisms, including bacterial, viral, fungal and parasitic pathogens.

SPMs also promote the resolution of non-infectious inflammation and tissue injury. Defects in host SPM pathways contribute to the development of chronic inflammatory diseases.

With the capacity to enhance host defence and modulate inflammation, SPMs represent a promising translational approach to enlist host resolution programmes for the treatment of infection and excess inflammation.

Here, the authors detail our current understanding of specialized pro-resolving mediators (SPMs), a family of endogenous mediators that have important roles in promoting the resolution of inflammation. With a focus on the lungs, they discuss the contribution of SPMs to infectious and chronic inflammatory diseases and their emerging therapeutic potential.

Specialized pro-resolving mediators (SPMs) are enzymatically derived from essential fatty acids and have important roles in orchestrating the resolution of tissue inflammation — that is, catabasis. Host responses to tissue infection elicit acute inflammation in an attempt to control invading pathogens. SPMs are lipid mediators that are part of a larger family of pro-resolving molecules, which includes proteins and gases, that together restrain inflammation and resolve the infection. These immunoresolvents are distinct from immunosuppressive molecules as they not only dampen inflammation but also promote host defence. Here, we focus primarily on SPMs and their roles in lung infection and inflammation to illustrate the potent actions these mediators play in restoring tissue homeostasis after an infection.

Maresin 1 Biosynthesis and Proresolving Anti-infective Functions with Human-Localized Aggressive Periodontitis Leukocytes

Localized aggressive periodontitis (LAP) is a distinct form of early-onset periodontitis linked to periodontal infection with uncontrolled inflammation and leukocyte-mediated tissue destruction. The resolution of inflammation is an active process orchestrated by specialized proresolving lipid mediators (SPMs). Since the level of the Maresin pathway marker 14-hydroxy-docosahexaenoic acid (14-HDHA) was lower in activated peripheral blood from LAP patients, we investigated the Maresin 1 (MaR1) biosynthetic pathway in these subjects and its role in regulating phagocyte functions. Macrophages from LAP patients had a lower level of expression of 12-lipoxygenase (∼30%) and reduced MaR1 (LAP versus healthy controls [HC], 87.8 ± 50 pg/10(6) cells versus 239.1 ± 32 pg/10(6) cells). Phagocytosis by LAP macrophages was reduced ∼40% compared to that of HC, and killing of periodontal pathogens, including Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, were similarly reduced. LAP neutrophils also displayed slower kinetics (∼30%) and decreased maximal phagocytosis (∼20% lower) with these pathogens than those of HC. The administration of MaR1 at 1 nM enhanced phagocytosis (31 to 65% increase), intracellular antimicrobial reactive oxygen species production (26 to 71% increase), bacterial killing of these periodontal pathogens (22 to 38% reduction of bacterial titers), and restored impairment of LAP phagocytes. Together, these results suggest that therapeutics targeting the Maresin pathway have clinical utility in treating LAP and other oral diseases associated with infection, inflammation, and altered phagocyte functions.

Inflammatory and immune pathways in the pathogenesis of periodontal disease

The pathogenesis of periodontitis involves a complex immune/inflammatory cascade that is initiated by the bacteria of the oral biofilm that forms naturally on the teeth. The susceptibility to periodontitis appears to be determined by the host response; specifically, the magnitude of the inflammatory response and the differential activation of immune pathways. The purpose of this review was to delineate our current knowledge of the host response in periodontitis. The role of innate immunity, the failure of acute inflammation to resolve (thus becoming chronic), the cytokine pathways that regulate the activation of acquired immunity and the cells and products of the immune system are considered. New information relating to regulation of both inflammation and the immune response will be reviewed in the context of susceptibility to, and perhaps control of, periodontitis.

Diet-Induced Obesity and Its Differential Impact on Periodontal Bone Loss

Obesity is associated with abnormal lipid metabolism and impaired bone homeostasis. The aim of our study was to investigate the impact of specific elevated fatty acid (FA) levels on alveolar bone loss in a Porphyromonas gingivalis-induced model of periodontal disease and to analyze underlying cellular mechanisms in bone-resorbing osteoclasts and bone-forming osteoblasts in mice. Four-week-old male C57BL/6 mice were randomly divided in groups and subjected to a palmitic acid (PA)- or oleic acid (OA)-enriched high-fat diet (HFD) (20% of calories from FA) or a normal caloric diet (C group) (10% of calories from FA) for 16 wk. Starting at week 10, mice were infected orally with P. gingivalis (W50) or placebo to induce alveolar bone loss. Animals were sacrificed, and percentage fat, serum inflammation (tumor necrosis factor [TNF]-α), and bone metabolism (osteocalcin [OC], carboxy-terminal collagen crosslinks [CTX], and N-terminal propeptides of type I procollagen [P1NP]) markers were measured. Osteoblasts and osteoclasts were cultured in the presence of elevated PA or OA levels and exposed to P. gingivalis. Animals on FA-enriched diets weighed significantly more compared with animals on a normal caloric diet (P < 0.05). Both obese groups had similar percentages of fat (P = nonsignificant); however, alveolar bone loss was significantly greater in animals that were on the PA-enriched HFD (P < 0.05). TNF-α levels were highest in the PA group (P < 0.001) and increased in all groups in response to P. gingivalis inoculation (P < 0.01), whereas bone remodeling markers OC, CTX, and P1NP were lowest in the PA group (P < 0.001) and highest in the C group. Bacterial challenge decreased bone metabolism markers in all groups (P < 0.01). Further, osteoclasts showed an augmented inflammatory response to P. gingivalis in the presence of hyperlipidemic PA levels as opposed to OA cultures, which responded similarly to controls. These findings indicate that the specific FA profile of diet rather than weight gain and obesity alone modulates bone metabolism and can therefore influence alveolar bone loss.

Complement therapeutics in inflammatory diseases: promising drug candidates for C3-targeted intervention

There is increasing appreciation that complement dysregulation lies at the heart of numerous immune-mediated and inflammatory disorders. Complement inhibitors are therefore being evaluated as new therapeutic options in various clinical translation programs and the first clinically approved complement-targeted drugs have profoundly impacted the management of certain complement-mediated diseases. Among the many members of the intricate protein network of complement, the central component C3 represents a 'hot-spot' for complement-targeted therapeutic intervention. C3 modulates both innate and adaptive immune responses and is linked to diverse immunomodulatory systems and biological processes that affect human pathophysiology. Compelling evidence from preclinical disease models has shown that C3 interception may offer multiple benefits over existing therapies or even reveal novel therapeutic avenues in disorders that are not commonly regarded as complement-driven, such as periodontal disease. Using the clinically developed compstatin family of C3 inhibitors and periodontitis as illustrative examples, this review highlights emerging therapeutic concepts and developments in the design of C3-targeted drug candidates as novel immunotherapeutics for oral and systemic inflammatory diseases.

The association between subgingival periodontal pathogens and systemic inflammation

AIM

To investigate associations between periodontal disease pathogens and levels of systemic inflammation measured by C-reactive protein (CRP).

METHODS

A representative sample of dentate 60-70-year-old men in Northern Ireland had a comprehensive periodontal examination. Men taking statins were excluded. Subgingival plaque samples were analysed by quantitative real time PCR to identify the presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia. High-sensitivity CRP (mg/l) was measured from fasting blood samples. Multiple linear regression analysis was performed using log-transformed CRP concentration as the dependent variable, with the presence of each periodontal pathogen as predictor variables, with adjustment for various potential confounders.

RESULTS

A total of 518 men (mean age 63.6 SD 3.0 years) were included in the analysis. Multiple regression analysis showed that body mass index (p < 0.001), current smoking (p < 0.01), the detectable presence of P. gingivalis (p < 0.01) and hypertension (p = 0.01), were independently associated with an increased CRP. The detectable presence of P. gingivalis was associated with a 20% (95% confidence interval 4-35%) increase in CRP (mg/l) after adjustment for all other predictor variables.

CONCLUSION

In these 60-70-year-old dentate men, the presence of P. gingivalis in subgingival plaque was significantly associated with a raised level of C-reactive protein.

Activation and resolution of periodontal inflammation and its systemic impact

Inflammation is a highly organized event impacting upon organs, tissues and biological systems. Periodontal diseases are characterized by dysregulation or dysfunction of resolution pathways of inflammation that results in failure to heal and in a dominant chronic, progressive, destructive and predominantly unresolved inflammation. The biological consequences of inflammatory processes may be independent of the etiological agents, such as trauma, microbial organisms and stress. The impact of the inflammatory pathological process depends upon the tissues or organ system affected. Whilst mediators are similar, there is tissue specificity for the inflammatory events. It is plausible that inflammatory processes in one organ could directly lead to pathologies in another organ or tissue. Communication between distant parts of the body and their inflammatory status is also mediated by common signaling mechanisms mediated via cells and soluble mediators. This review focuses on periodontal inflammation, its systemic associations and advances in therapeutic approaches based on mediators acting through orchestration of natural pathways to resolution of inflammation. We also discuss a new treatment concept in which natural pathways of resolution of periodontal inflammation can be used to limit systemic inflammation and promote healing and regeneration.

Microbial protection and virulence in periodontal tissue as a function of polymicrobial communities: symbiosis and dysbiosis

This review discusses polymicrobial interactions with the host in both health and disease. As our ability to identify specific bacterial clonal types, with respect to their abundance and location in the oral biofilm, improves, we will learn more concerning their contribution to both oral health and disease. Recent studies examining host- bacteria interactions have revealed that commensal bacteria not only protect the host simply by niche occupation, but that bacterial interactions with host tissue can promote the development of proper tissue structure and function. These data indicate that our host-associated polymicrobial communities, such as those found in the oral cavity, co-evolved with us and have become an integral part of who we are. Understanding the microbial community factors that underpin the associations with host tissue that contribute to periodontal health may also reveal how dysbiotic periodontopathic oral communities disrupt normal periodontal tissue functions in disease. A disruption of the oral microbial community creates dysbiosis, either by overgrowth of specific or nonspecific microorganisms or by changes in the local host response where the community can now support a disease state. Dysbiosis provides the link between systemic changes (e.g. diabetes) and exogenous risk factors (e.g. smoking), and the dysbiotic community, and can drive the destruction of periodontal tissue. Many other risk factors associated with periodontal disease, such as stress, aging and genetics, are also likely to affect the microbial community, and more research is needed, utilizing sophisticated bacterial taxonomic techniques, to elucidate these effects on the microbiome and to develop strategies to target the dysbiotic mechanisms and improve periodontal health.

Diabetes and Its Effect on Bone and Fracture Healing

Diabetes mellitus is a metabolic disorder that increases fracture risk, interferes with bone formation, and impairs fracture healing. Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) both increase fracture risk and have several common features that affect the bone including hyperglycemia and increased advanced glycation end product (AGE) formation, reactive oxygen species (ROS) generation, and inflammation. These factors affect both osteoblasts and osteoclasts leading to increased osteoclasts and reduced numbers of osteoblasts and bone formation. In addition to fracture healing, T1DM and T2DM impair bone formation under conditions of perturbation such as bacteria-induced periodontal bone loss by increasing osteoblast apoptosis and reducing expression of factors that stimulate osteoblasts such as BMPs and growth factors.

Role of bacteria in leukocyte adhesion deficiency-associated periodontitis

Leukocyte adhesion deficiency Type I (LAD-I)-associated periodontitis is an aggressive form of inflammatory bone loss that has been historically attributed to lack of neutrophil surveillance of the periodontal infection. However, this form of periodontitis has proven unresponsive to antibiotics and/or mechanical removal of the tooth-associated biofilm. Recent studies in LAD-I patients and relevant animal models have shown that the fundamental cause of LAD-I periodontitis involves dysregulation of a granulopoietic cytokine cascade. This cascade includes interleukin IL-23 (IL-23) and IL-17 that drive inflammatory bone loss in LAD-I patients and animal models and, moreover, foster a nutritionally favorable environment for bacterial growth and development of a compositionally unique microbiome. Although the lack of neutrophil surveillance in the periodontal pockets might be expected to lead to uncontrolled bacterial invasion of the underlying connective tissue, microbiological analyses of gingival biopsies from LAD-I patients did not reveal tissue-invasive infection. However, bacterial lipopolysaccharide was shown to translocate into the lesions of LAD-I periodontitis. It is concluded that the bacteria serve as initial triggers for local immunopathology through translocation of bacterial products into the underlying tissues where they unleash the dysregulated IL-23-IL-17 axis. Subsequently, the IL-23/IL-17 inflammatory response sustains and shapes a unique local microbiome which, in turn, can further exacerbate inflammation and bone loss in the susceptible host.

Clopidogrel Enhances Mesenchymal Stem Cell Proliferation Following Periodontitis

Bone formation is dependent on the differentiation of osteoblasts from mesenchymal stem cells (MSCs). In addition to serving as progenitors, MSCs reduce inflammation and produce factors that stimulate tissue formation. Upon injury, MSCs migrate to the periodontium, where they contribute to regeneration. We examined the effect of clopidogrel and aspirin on MSCs following induction of periodontitis in rats by placement of ligatures. We showed that after the removal of ligatures, which induces resolution of periodontal inflammation, clopidogrel had a significant effect on reducing the inflammatory infiltrate. It also increased the number of osteoblasts and MSCs. Mechanistically, the latter was linked to increased proliferation of MSCs in vivo and in vitro. When given prior to inducing periodontitis, clopidogrel had little effect on MSC or osteoblasts numbers. Applying aspirin before or after induction of periodontitis did not have a significant effect on the parameters measured. These results suggest that clopidogrel may have a positive effect on MSCs in conditions where a reparative process has been initiated.

LXA4 actions direct fibroblast function and wound closure

Timely resolution of inflammation is crucial for normal wound healing. Resolution of inflammation is an active biological process regulated by specialized lipid mediators including the lipoxins and resolvins. Failure of resolution activity has a major negative impact on wound healing in chronic inflammatory diseases that is manifest as excess fibrosis and scarring. Lipoxins, including Lipoxin A4 (LXA4), have known anti-fibrotic and anti-scarring properties. The goal of this study was to elucidate the impact of LXA4 on fibroblast function. Mouse fibroblasts (3T3 Mus musculus Swiss) were cultured for 72 h in the presence of TGF-β1, to induce fibroblast activation. The impact of exogenous TGF-β1 (1 ng/mL) on LXA4 receptor expression (ALX/FPR2) was determined by flow cytometry. Fibroblast proliferation was measured by bromodeoxyuridine (BrdU) labeling and migration in a "scratch" assay wound model. Expression of α-smooth muscle actin (α-SMA), and collagen types I and III were measured by Western blot. We observed that TGF-β1 up-regulates LXA4 receptor expression, enhances fibroblast proliferation, migration and scratch wound closure. α-SMA levels and Collagen type I and III deposition were also enhanced. LXA4 slowed fibroblast migration and scratch wound closure at early time points (24 h), but wound closure was equal to TGF-β1 alone at 48 and 72 h. LXA4 tended to slow fibroblast proliferation at both concentrations, but had no impact on α-SMA or collagen production by TGF-β1 stimulated fibroblasts. The generalizability of the actions of resolution molecules was examined in experiments repeated with resolvin D2 (RvD2) as the agonist. The activity of RvD2 mimicked the actions of LXA4 in all assays, through an as yet unidentified receptor. The results suggest that mediators of resolution of inflammation enhance wound healing and limit fibrosis in part by modulating fibroblast function.

Implications for eicosapentaenoic acid- and docosahexaenoic acid-derived resolvins as therapeutics for arthritis

Omega-3 polyunsaturated fatty acids are essential for health and are known to possess anti-inflammatory properties, improving cardiovascular health as well as benefiting inflammatory diseases. Indeed, dietary supplementation with omega-3 polyunsaturated fatty acids has proved efficacious in reducing joint pain, morning stiffness and nonsteroidal anti-inflammatory drugs usage in rheumatoid arthritis patients. However, the mechanisms by which omega-3 polyunsaturated fatty acids exert their beneficial effects have not been fully explored. Seminal discoveries by Serhan and colleagues have unveiled a novel class of bioactive lipid mediators that are enzymatically biosynthesized in vivo from omega-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), termed resolvins, protectins and maresins. These bioactive pro-resolving lipid mediators provide further rationale for the beneficial effects of fish-oil enriched diets. These endogenous lipid mediators are spatiotemporally biosynthesized to actively regulate resolution by acting on specific G protein-coupled receptors (GPCRs) to initiate anti-inflammatory and pro-resolving signals that terminate inflammation. In this review, we will discuss the mechanism of actions of these molecules, including their analgesic and bone-sparing properties making them ideal therapeutic agonists for the treatment of inflammatory diseases such as rheumatoid arthritis.

Diabetes mellitus related bone metabolism and periodontal disease

Diabetes mellitus and periodontal disease are chronic diseases affecting a large number of populations worldwide. Changed bone metabolism is one of the important long-term complications associated with diabetes mellitus. Alveolar bone loss is one of the main outcomes of periodontitis, and diabetes is among the primary risk factors for periodontal disease. In this review, we summarise the adverse effects of diabetes on the periodontium in periodontitis subjects, focusing on alveolar bone loss. Bone remodelling begins with osteoclasts resorbing bone, followed by new bone formation by osteoblasts in the resorption lacunae. Therefore, we discuss the potential mechanism of diabetes-enhanced bone loss in relation to osteoblasts and osteoclasts.

Oral infections and cardiovascular disease

Oral infections are the most common diseases of mankind. Numerous reports have implicated oral infections, particularly periodontitis, as a risk factor for atherosclerotic cardiovascular disease (CVD). In this review we examine the epidemiology and biologic plausibility of this association with an emphasis on oral bacteria and inflammation. Longitudinal studies of incident cardiovascular events clearly show excess risk for CVD in individuals with periodontitis. It is likely that systemic exposure to oral bacteria impacts upon the initiation and progression of CVD through triggering of inflammatory processes. Given the high prevalence of periodontitis, any risk attributable to future CVD is important to public health. Unraveling the role of the oral microbiome in CVD will lead to new preventive and treatment approaches.

Resolvin E1 (RvE1) Attenuates Atherosclerotic Plaque Formation in Diet and Inflammation-Induced Atherogenesis

OBJECTIVE

Epidemiological and recent clinical studies implicate periodontitis as an independent risk factor for cardiovascular disease. Previously, we demonstrated that rabbits with experimental periodontitis and cholesterol diet exhibit more aortic plaque compared with diet alone. We also showed that a proresolution mediator, Resolvin E1 (RvE1), reverses the experimental periodontitis. Here, we determined whether oral/topical application of RvE1 attenuates aortic atherosclerosis induced by both diet and periodontal inflammation.

APPROACH AND RESULTS

Thirty-nine rabbits on a 13-week regimen of 0.5% cholesterol diet were included. Periodontitis was induced by Porphyromonas gingivalis in 24 rabbits and 15 rabbits were placed in no-periodontitis groups. Interventions were no-treatment, vehicle, and RvE1 treatment (4 μg/site or 0.4 μg/site) topically applied 3× per week. At 13 weeks, both periodontitis and atherosclerosis were quantified. Atherosclerotic plaques were assessed by Sudan IV staining, histology, and ex vivo MRI. Serum levels of C-reactive protein were evaluated as a measure of systemic inflammation. RvE1, used as an oral/topical agent, significantly diminished atherogenesis and prevented periodontitis (P<0.05). In the absence of periodontal inflammation, oral/topical application of RvE1 resulted in significantly less arterial plaque, a lower intima/media ratio, and decreased inflammatory cell infiltration compared with no-treatment (P<0.001). Local oral RvE1 application significantly reduced systemic levels of C-reactive protein (P<0.05).

CONCLUSIONS

The results suggest that oral/topical RvE1 attenuates enhanced atherogenesis induced by periodontitis and prevents vascular inflammation and atherogenesis in the absence of periodontitis. The inhibition of vascular inflammation with endogenous mediators of resolution of inflammation provides a novel approach in the prevention of atherogenic events.

The resolution of inflammation: Principles and challenges

The concept that chemokines, cytokines and pro-inflammatory mediators act in a co-ordinated fashion to drive the initiation of the inflammatory reaction is well understood. The significance of such networks acting during the resolution of inflammation however is poorly appreciated. In recent years, specific pro-resolving mediators were discovered which activate resolution pathways to return tissues to homeostasis. These mediators are diverse in nature, and include specialized lipid mediators (lipoxins, resolvins, protectins and maresins) proteins (annexin A1, galectins) and peptides, gaseous mediators including hydrogen sulphide, a purine (adenosine), as well as neuromodulator release under the control of the vagus nerve. Functionally, they can act to limit further leukocyte recruitment, induce neutrophil apoptosis and enhance efferocytosis by macrophages. They can also switch macrophages from classical to alternatively activated cells, promote the return of non-apoptotic cells to the lymphatics and help initiate tissue repair mechanisms and healing. Within this review we highlight the essential cellular aspects required for successful tissue resolution, briefly discuss the pro-resolution mediators that drive these processes and consider potential challenges faced by researchers in the quest to discover how inflammation resolves and why chronic inflammation persists.

Natural resolution of inflammation

Inflammation is a protective response essential for maintaining human health and for fighting disease. As an active innate immune reaction to challenge, inflammation gives rise to clinical cardinal signs: rubor, calor, dolor, tumor and functio laesa. Termination of acute inflammation was previously recognized as a passive process; a natural decay of pro-inflammatory signals. We now understand that the natural resolution of inflammation involves well-integrated, active, biochemical programs that return tissues to homeostasis. This review focuses on recent advances in the understanding of the role of endogenous lipid mediators that modulate cellular fate and inflammation. Biosynthesis of eicosanoids and other lipids in exudates coincides with changes in the types of inflammatory cells. Resolution of inflammation is initiated by an active class switch in lipid mediators, such as classic prostaglandins and leukotrienes, to the production of proresolution mediators. Endogenous pro-resolving lipid mediators, including arachidonic acid-derived lipoxins, aspirin-triggered lipoxins, ω3-eicosapentaenoic acid-derived resolvins of the E-series, docosahexaenoic acid-derived resolvins of the D-series, protectins and maresins, are biosynthesized during the resolution phase of acute inflammation. Depending on the type of injury and the type of tissue, the initial cells that respond are polymorphonuclear leukocytes, monocytes/macrophages, epithelial cells or endothelial cells. The selective interaction of specific lipid mediators with G protein-coupled receptors expressed on innate immune cells (e.g. G protein-coupled receptor 32, lipoxin A4 receptor/formyl peptide receptor2, chemokine-like receptor 1, leukotriene B4 receptor type 1 and cabannoid receptor 2) induces cessation of leukocyte infiltration; vascular permeability/edema returns to normal with polymorphonuclear neutrophil death (mostly via apoptosis), the nonphlogistic infiltration of monocyte/macrophages and the removal (by macrophages) of apoptotic polymorphonuclear neutrophils, foreign agents (bacteria) and necrotic debris from the site. While an acute inflammatory response that is resolved in a timely manner prevents tissue injury, inadequate resolution and failure to return tissue to homeostasis results in neutrophil-mediated destruction and chronic inflammation. A better understanding of the complex mechanisms of lipid agonist mediators, cell targets and actions allows us to exploit and develop novel therapeutic strategies to treat human inflammatory diseases, including periodontal diseases.

The resolution code of acute inflammation: Novel pro-resolving lipid mediators in resolution

Studies into the mechanisms in resolution of self-limited inflammation and acute reperfusion injury have uncovered a new genus of pro-resolving lipid mediators coined specialized pro-resolving mediators (SPM) including lipoxins, resolvins, protectins and maresins that are each temporally produced by resolving-exudates with distinct actions for return to homeostasis. SPM evoke potent anti-inflammatory and novel pro-resolving mechanisms as well as enhance microbial clearance. While born in inflammation-resolution, SPM are conserved structures with functions discovered in microbial defense, pain, organ protection and tissue regeneration, wound healing, cancer, reproduction, and neurobiology-cognition. This review covers these SPM mechanisms and other new omega-3 PUFA pathways that open their path for functions in resolution physiology.

Pros and cons of fatty acids in bone biology

Despite the growing interest in deciphering the causes and consequences of obesity-related disorders, the mechanisms linking fat intake to bone behaviour remain unclear. Since bone fractures are widely associated with increased morbidity and mortality, most notably in elderly and obese people, bone health has become a major social and economic issue. Consistently, public health system guidelines have encouraged low-fat diets in order to reduce associated complications. However, from a bone point of view, mechanisms linking fat intake to bone alteration remain quite controversial. Thus, after more than a decade of dedicated studies, this timely review offers a comprehensive overview of the relationships between bone and fatty acids. Using clinical evidences as a starting-point to more complex molecular elucidation, this work highlights the complexity of the system and reveals that bone alteration that cannot be solved simply by taking ω-3 pills. Fatty acid effects on bone metabolism can be both direct and indirect and require integrated investigations. Furthermore, even at the level of a single cell, one fatty acid is able to trigger several different independent pathways (receptors, metabolites…) which may all have a say in the final cellular metabolic response.

P. gingivalis in Periodontal Disease and Atherosclerosis - Scenes of Action for Antimicrobial Peptides and Complement

According to the NHS, it is estimated that over 50% of the adult population are, to some extent, affected by gum disease and approximately 15% of UK population have been diagnosed with severe periodontitis. Periodontitis, a chronic polymicrobial disease of the gums, causes inflammation in its milder form, whereas in its severe form affects the surrounding tissues and can result in tooth loss. During periodontitis, plaque accumulates and sits between the junctional epithelium and the tooth itself, resulting in inflammation and the formation of a periodontal pocket. An interface is formed directly between the subgingival bacteria and the junctional epithelial cells. Bacterial pathogens commonly associated with periodontal disease are, among others, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, together known as the "red complex." This review will mostly concentrate on the role of P. gingivalis, a Gram-negative anaerobic bacterium and one of the major and most studied contributors of this disease. Because periodontal disease is associated with the development of atherosclerosis, it is important to understand the local immune response to P. gingivalis. Innate immune players, in particular, complement and antimicrobial peptides and their effects with regard to P. gingivalis during periodontitis and in the development of atherosclerosis will be presented.

Complement Involvement in Periodontitis: Molecular Mechanisms and Rational Therapeutic Approaches

The complement system is a network of interacting fluid-phase and cell surface-associated molecules that trigger, amplify, and regulate immune and inflammatory signaling pathways. Dysregulation of this finely balanced network can destabilize host-microbe homeostasis and cause inflammatory tissue damage. Evidence from clinical and animal model-based studies suggests that complement is implicated in the pathogenesis of periodontitis, a polymicrobial community-induced chronic inflammatory disease that destroys the tooth-supporting tissues. This review discusses molecular mechanisms of complement involvement in the dysbiotic transformation of the periodontal microbiome and the resulting destructive inflammation, culminating in loss of periodontal bone support. These mechanistic studies have additionally identified potential therapeutic targets. In this regard, interventional studies in preclinical models have provided proof-of-concept for using complement inhibitors for the treatment of human periodontitis.

Impact of resolvin E1 on murine neutrophil phagocytosis in type 2 diabetes

Diabetic complications involve inflammation-mediated microvascular and macrovascular damage, disruption of lipid metabolism, glycosylation of proteins, and abnormalities of neutrophil-mediated events. Resolution of inflamed tissues to health and homeostasis is an active process mediated by endogenous lipid agonists, including lipoxins and resolvins. This proresolution system appears to be compromised in type 2 diabetes (T2D). The goal of this study was to investigate unresolved inflammation in T2D. Wild-type (WT) and genetically engineered mice, including T2D mice (db/db), transgenic mice overexpressing the human resolvin E1 (RvE1) receptor (ERV1), and a newly bred strain of db/ERV1 mice, were used to determine the impact of RvE1 on the phagocytosis of Porphyromonas gingivalis in T2D. Neutrophils were isolated and incubated with fluorescein isothiocyanate-labeled P. gingivalis, and phagocytosis was measured in a fluorochrome-based assay by flow cytometry. Mitogen-activated protein kinase (MAPK) (p42 and p44) and Akt (Thr308 and Ser473) phosphorylation was analyzed by Western blotting. The mouse dorsal air pouch model was used to evaluate the in vivo impact of RvE1. Results revealed that RvE1 increased the neutrophil phagocytosis of P. gingivalis in WT animals but had no impact in db/db animals. In ERV1-transgenic and ERV1-transgenic diabetic mice, phagocytosis was significantly increased. RvE1 decreased Akt and MAPK phosphorylation in the transgenic animals. In vivo dorsal air pouch studies revealed that RvE1 decreases neutrophil influx into the pouch and increases neutrophil phagocytosis of P. gingivalis in the transgenic animals; cutaneous fat deposition was reduced, as was macrophage infiltration. The results suggest that RvE1 rescues impaired neutrophil phagocytosis in obese T2D mice overexpressing ERV1.

The omega-3 fatty acid docosahexaenoic acid attenuates organic dust-induced airway inflammation

Workers exposed to organic dusts from concentrated animal feeding operations (CAFOs) are at risk for developing airway inflammatory diseases. Available preventative and therapeutic measures for alleviating dust-induced lung disease are inadequate. Because omega-3 fatty acids can mitigate inflammatory processes, we aimed to determine whether nutritional supplementation with the omega-3 fatty acid docosahexaenoic acid (DHA) could reduce the airway inflammatory consequences of exposures to organic dust. Aqueous extracts of organic dusts from swine CAFOs (ODE) were utilized. In DHA-pretreated human bronchial epithelial cells, lung fibroblasts, monocyte cell cultures, and precision-cut murine lung slices, we found that DHA pretreatment dose-dependently decreased ODE-induced inflammatory cytokine production. To determine the in vivo significance of DHA, C57BL/6 mice were orally administered DHA for seven days prior to treatment with intranasal ODE or saline inhalations. Animals treated with 2 mg DHA demonstrated significant reductions in ODE-induced bronchial alveolar lavage neutrophil influx and pro-inflammatory cytokine/chemokine production compared to mice exposed to ODE alone. Collectively, these data demonstrate that DHA affects several lung cells to reduce the airway inflammatory response to organic dust exposures. Dietary supplementation with DHA may be an effective therapeutic strategy to reduce the airway inflammatory consequences in individuals exposed to agriculture dust environments.

Non-surgical periodontal therapy: An update on current evidence

Periodontal disease is an inflammatory condition that involves a complex interaction between pathogenic bacteria, environmental and acquired factors and host related factors. Till recently periodontal treatment was directed primarily towards reduction of bacterial load by subgingival debridement of root surfaces and modification of environmental risk factors. The current paradigm of periodontal disease stresses greater role of host-mediated inflammatory response in tissue destruction characteristic of periodontal disease. Various therapeutic modalities have been developed adjuvant to mechanical periodontal therapy. The use of laser and photodynamic therapy show great promise but their effectiveness has still not been conclusively proven. Chemotherapeutic agents, either systemic and local antimicrobials or host modulating drugs, played pivotal role in better and more predictable management of periodontal disease. The present review focuses on the best available evidence, for the current management of the chronic periodontal patients, gathered from systematic reviews and meta-analysis of mechanical non surgical periodontal therapy (NSPT) (subgingival debridement, laser therapy and photodynamic therapy) and the adjunctive chemotherapeutic approaches such as systematic and local antibiotics and antiseptics, subgingival pocket irrigation and host modulation therapies. The review also attempts to briefly introduce future developments in some of these modalities. At the end, the review summarizes the analysis of the current evidence that suggests that thorough subgingival debridement remains the mainstay of NSPT and that adjunct use of chemotherapeutic agents may offer better management of clinical parameters in periodontitis patients.

Defective neutrophil recruitment in leukocyte adhesion deficiency type I disease causes local IL-17-driven inflammatory bone loss

Leukocyte adhesion deficiency type I (LAD-I), a disease syndrome associated with frequent microbial infections, is caused by mutations on the CD18 subunit of β₂ integrins. LAD-I is invariably associated with severe periodontal bone loss, which historically has been attributed to the lack of neutrophil surveillance of the periodontal infection. We provide an alternative mechanism by showing that the cytokine interleukin-17 (IL-17) plays a major role in the oral pathology of LAD-I. Defective neutrophil recruitment in LAD-I patients or in LFA-1 (CD11a/CD18)-deficient mice--which exhibit the LAD-I periodontal phenotype--was associated with excessive production of predominantly T cell-derived IL-17 in the periodontal tissue, although innate lymphoid cells also contributed to pathological IL-17 elevation in the LFA-1-deficient mice. Local treatment with antibodies to IL-17 or IL-23 in LFA-1-deficient mice not only blocked inflammatory periodontal bone loss but also caused a reduction in the total bacterial burden, suggesting that the IL-17-driven pathogenesis of LAD-I periodontitis leads to dysbiosis. Therefore, our findings support an IL-17-targeted therapy for periodontitis in LAD-I patients.

Proresolving nanomedicines activate bone regeneration in periodontitis

Therapies to reverse tissue damage from osteolytic inflammatory diseases are limited by the inability of current tissue-engineering procedures to restore lost hard and soft tissues. There is a critical need for new therapeutics in regeneration. In addition to scaffolds, cells, and soluble mediators necessary for tissue engineering, control of endogenous inflammation is an absolute requirement for success. Although significant progress has been made in understanding natural resolution of inflammation pathways to limit uncontrolled inflammation in disease, harnessing the biomimetic properties of proresolving lipid mediators has not been demonstrated. Here, we report the use of nano-proresolving medicines (NPRM) containing a novel lipoxin analog (benzo-lipoxin A4, bLXA4) to promote regeneration of hard and soft tissues irreversibly lost to periodontitis in the Hanford miniature pig. In this proof-of-principle experiment, NPRM-bLXA4 dramatically reduced inflammatory cell infiltrate into chronic periodontal disease sites treated surgically and dramatically increased new bone formation and regeneration of the periodontal organ. These findings indicate that NPRM-bLXA4 is a mimetic of endogenous resolving mechanisms with potent bioactions that offers a new therapeutic tissue-engineering approach for the treatment of chronic osteolytic inflammatory diseases.

MFG-E8, a novel homeostatic regulator of osteoclastogenesis

Although the glycoprotein MFG-E8 (milk fat globule-epidermal growth factor-factor 8) has been investigated extensively as an anti-inflammatory and homeostatic molecule, a possible role in bone homeostasis and disease was not addressed until recently. Our group has now shown that MFG-E8 is expressed by human and mouse osteoclasts and regulates their differentiation and function (Abe et al., J Immunol 2014;193:1383-1391). Whereas genetic deficiency or antibody-mediated neutralization of MFG-E8 enhances osteoclastogenesis and promotes inflammation-induced bone loss in mice, local administration of recombinant MFG-E8 blocks bone loss. These findings establish MFG-E8 as a novel homeostatic regulator of osteoclastogenesis and suggest that MFG-E8 could be exploited therapeutically to treat disorders associated with inflammatory bone loss, such as periodontitis and rheumatoid arthritis.

Roles of resolvins in the resolution of acute inflammation

Resolution is an active process that terminates inflammatory response to maintain health. Acute inflammation and its timely resolution are important in host response to danger signals. Unresolved inflammation is associated with widely recurrent diseases. Resolvins, including the D and E series, are endogenous lipid mediators generated during the resolution phase of acute of inflammation from the ω-3 PUFAs, DHA, and EPA. They have anti-inflammatory and pro-resolving properties that have been determined in many inflammation studies in animal models. In this review, we provide an updated overview of biosynthesis, actions, and signaling pathways of resolvins, thereby underscoring their diverse protective roles and introducing novel therapeutic strategies for inflammation-associated diseases.

The inflammophilic character of the periodontitis-associated microbiota

In periodontitis, dysbiotic microbial communities exhibit synergistic interactions for enhanced protection from host defenses, nutrient acquisition, and persistence in an inflammatory environment. This review discusses evidence that periodontitis-associated communities are 'inflammo-philic' (=loving or attracted to inflammation) in that they have evolved to not only endure inflammation but also to take advantage of it. In this regard, inflammation can drive the selection and enrichment of these pathogenic communities by providing a source of nutrients in the form of tissue breakdown products (e.g. degraded collagen peptides and heme-containing compounds). In contrast, those species that cannot benefit from the altered ecological conditions of the inflammatory environment, or for which host inflammation is detrimental, are likely to be outcompeted. Consistent with the concept that inflammation fosters the growth of dysbiotic microbial communities, the bacterial biomass of human periodontitis-associated biofilms was shown to increase with increasing periodontal inflammation. Conversely, anti-inflammatory treatments in animal models of periodontitis were shown to diminish the periodontal bacterial load, in addition to protecting from bone loss. The selective flourishing of inflammophilic bacteria can perpetuate inflammatory tissue destruction by setting off a 'vicious cycle' for disease progression, in which dysbiosis and inflammation reinforce each other. Therefore, the control of inflammation appears to be central to the treatment of periodontitis, as it is likely to control both dysbiosis and disease progression.

Risks for infection in patients with asthma (or other atopic conditions): is asthma more than a chronic airway disease?

Most of the research effort regarding asthma has been devoted to its causes, therapy, and prognosis. There is also evidence that the presence of asthma can influence patients' susceptibility to infections, yet research in this aspect of asthma has been limited. There is additional debate in this field, with current literature tending to view the increased risk of infection among atopic patients as caused by opportunistic infections secondary to airway inflammation, especially in patients with severe atopic diseases. However, other evidence suggests that such risk and its underlying immune dysfunction might be a phenotypic or clinical feature of atopic conditions. This review argues (1) that improved understanding of the effects of asthma or other atopic conditions on the risk of microbial infections will bring important and new perspectives to clinical practice, research, and public health concerning atopic conditions and (2) that research efforts into the causes and effects of asthma must be juxtaposed because they are likely to guide each other.

Historical and contemporary hypotheses on the development of oral diseases: are we there yet?

Dental plaque is an oral biofilm that much like the rest of our microbiome has a role in health and disease. Specifically, it is the cause of very common oral diseases such as caries, gingivitis, and periodontitis. The ideas about oral disease development have evolved over time. In the nineteenth century, scientists could not identify bacteria related to disease due to the lack of technology. This led to the "Non-Specific Plaque Hypothesis" or the idea that the accumulation of dental plaque was responsible for oral disease without discriminating between the levels of virulence of bacteria. In the twentieth century this idea evolved with the techniques to analyze the changes from health to disease. The first common hypothesis was the "Specific Plaque Hypothesis" (1976) proposing that only a few species of the total microflora are actively involved in disease. Secondly, the "Non-Specific Plaque Hypothesis" was updated (1986) and the idea that the overall activity of the total microflora could lead to disease, was enriched by taking into account difference in virulence among bacteria. Then, a hypothesis was considered that combines key concepts of the earlier two hypotheses: the "Ecological Plaque Hypothesis" (1994), which proposes that disease is the result of an imbalance in the microflora by ecological stress resulting in an enrichment of certain disease-related micro-organisms. Finally, the recent "Keystone-Pathogen Hypothesis" (2012) proposes that certain low-abundance microbial pathogens can cause inflammatory disease by interfering with the host immune system and remodeling the microbiota. In this comprehensive review, we describe how these different hypotheses, and the ideas around them, arose and test their current applicability to the understanding of the development of oral disease. Finally, we conclude that an all-encompassing ecological hypothesis explaining the shifts from health to disease is still lacking.