Lipoxin A₄ inhibits porphyromonas gingivalis-induced aggregation and reactive oxygen species production by modulating neutrophil-platelet interaction and CD11b expression

Resolution pharmacology and the treatment of infectious diseases

Inflammation is elicited by the host in response to microbes, and is believed to be essential for protection against infection. However, we have previously hypothesized that excessive or misplaced inflammation may be a major contributor to tissue dysfunction and death associated with viral and bacterial infections. The resolutive phase of inflammation is a necessary condition to achieve homeostasis after acute inflammation. It is possible that targeting inflammation resolution may be beneficial for the host during infection. In this review, we summarize the evidence demonstrating the expression, roles and effects of the best described pro-resolving molecules in the context of bacterial and viral infections. Pro-resolving molecules play a pivotal role in modulating a spectrum of pathways associated with tissue inflammation and damage during both viral and bacterial infections. These molecules offer a blend of anti-inflammatory, pro-resolving and sometimes anti-infective benefits, all the while circumventing the undesired and immune-suppressive unwanted effects associated with glucocorticoids. Whether these beneficial effects will translate into benefits to patients clearly deserve further investigation.

Immunomodulation of periodontitis with SPMs

Inflammation is a critical component in the pathophysiology of numerous disease processes, with most therapeutic modalities focusing on its inhibition in order to achieve treatment outcomes. The resolution of inflammation is a separate, distinct pathway that entails the reversal of the inflammatory process to a state of homoeostasis rather than selective inhibition of specific components of the inflammatory cascade. The discovery of specialized pro-resolving mediators (SPMs) resulted in a paradigm shift in our understanding of disease etiopathology. Periodontal disease, traditionally considered as one of microbial etiology, is now understood to be an inflammation-driven process associated with dysbiosis of the oral microbiome that may be modulated with SPMs to achieve therapeutic benefit.

Lipoxin alleviates oxidative stress: a state-of-the-art review

OBJECTIVE

This review aims to summarize the capability of lipoxin in regulating oxidative stress.

BACKGROUND

Oxidative stress is defined as an imbalance between the production of free radicals and the antioxidant system, and it is associated with the existence of a large number of oxidation products, such as reactive oxygen species (ROS) and reaction nitrogen species (RNS), causing damage to human tissues through immunoinflammatory responses. Therefore, reducing oxidative stress is vital to alleviate pathological damage. Lipoxin, an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. Previous studies have shown that lipoxin is associated with a variety of biological functions, including anti-inflammatory, regulating immune responses, promoting the repair of damaged cells, etc. The deficiency of lipoxin is a critical pathological mechanism in different diseases. Moreover, the ability of lipoxin to attenuate oxidative stress is noteworthy, thereby protecting the human body from diverse diseases.

METHODS

We searched papers from PubMed database using search terms, such as lipoxin, lipoxin A4, oxidative stress, and other relevant terms.

RESULTS

A total of 103 articles published over the past 20 years were identified for inclusion. We summarized the capability of lipoxin in regulating oxidative stress and mechanism.

CONCLUSION

Lipoxin is provided with a protective role in attenuating oxidative stress.

Resolution of Inflammation after Skeletal Muscle Ischemia-Reperfusion Injury: A Focus on the Lipid Mediators Lipoxins, Resolvins, Protectins and Maresins

Skeletal muscle ischemia reperfusion is very frequent in humans and results not only in muscle destruction but also in multi-organ failure and death via systemic effects related to inflammation and oxidative stress. In addition to overabundance of pro-inflammatory stimuli, excessive and uncontrolled inflammation can also result from defects in resolution signaling. Importantly, the resolution of inflammation is an active process also based on specific lipid mediators including lipoxins, resolvins and maresins that orchestrate the potential return to tissue homeostasis. Thus, lipid mediators have received growing attention since they dampen deleterious effects related to ischemia–reperfusion. For instance, the treatment of skeletal muscles with resolvins prior to ischemia decreases polymorphonuclear leukocyte (PMN) infiltration. Additionally, remote alterations in lungs or kidneys are reduced when enhancing lipid mediators’ functions. Accordingly, lipoxins prevented oxidative-stress-mediated tissue injuries, macrophage polarization was modified and in mice lacking DRV2 receptors, ischemia/reperfusion resulted in excessive leukocyte accumulation. In this review, we first aimed to describe the inflammatory response during ischemia and reperfusion in skeletal muscle and then discuss recent discoveries in resolution pathways. We focused on the role of specialized pro-resolving mediators (SPMs) derived from polyunsaturated fatty acids (PUFAs) and their potential therapeutic applications.

Oral Microbiota-Driven Cell Migration in Carcinogenesis and Metastasis

The oral cavity harbors approximately 1,000 microbial species, and both pathogenic and commensal strains are involved in the development of carcinogenesis by stimulating chronic inflammation, affecting cell proliferation, and inhibiting cell apoptosis. Moreover, some substances produced by oral bacteria can also act in a carcinogenic manner. The link between oral microbiota and chronic inflammation as well as cell proliferation has been well established. Recently, increasing evidence has indicated the association of the oral microbiota with cell migration, which is crucial in regulating devastating diseases such as cancer. For instance, increased cell migration induced the spread of highly malignant cancer cells. Due to advanced technologies, the mechanistic understanding of cell migration in carcinogenesis and cancer metastasis is undergoing rapid progress. Thus, this review addressed the complexities of cell migration in carcinogenesis and cancer metastasis. We also integrate recent findings on the molecular mechanisms by which the oral microbiota regulates cell migration, with emphasis on the effect of the oral microbiota on adhesion, polarization, and guidance. Finally, we also highlight critical techniques, such as intravital microscopy and superresolution microscopy, for studies in this field.

Specialized Pro-Resolving Lipid Mediators: New Therapeutic Approaches for Vascular Remodeling

Vascular remodeling is a typical feature of vascular diseases, such as atherosclerosis, aneurysms or restenosis. Excessive inflammation is a key mechanism underlying vascular remodeling via the modulation of vascular fibrosis, phenotype and function. Recent evidence suggests that not only augmented inflammation but unresolved inflammation might also contribute to different aspects of vascular diseases. Resolution of inflammation is mediated by a family of specialized pro-resolving mediators (SPMs) that limit immune cell infiltration and initiate tissue repair mechanisms. SPMs (lipoxins, resolvins, protectins, maresins) are generated from essential polyunsaturated fatty acids. Synthases and receptors for SPMs were initially described in immune cells, but they are also present in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), where they regulate processes important for vascular physiology, such as EC activation and VSMC phenotype. Evidence from genetic models targeting SPM pathways and pharmacological supplementation with SPMs have demonstrated that these mediators may play a protective role against the development of vascular remodeling in atherosclerosis, aneurysms and restenosis. This review focuses on the latest advances in understanding the role of SPMs in vascular cells and their therapeutic effects in the vascular remodeling associated with different cardiovascular diseases.

PAMPs and DAMPs as the Bridge Between Periodontitis and Atherosclerosis: The Potential Therapeutic Targets

Atherosclerosis is a chronic artery disease characterized by plaque formation and vascular inflammation, eventually leading to myocardial infarction and stroke. Innate immunity plays an irreplaceable role in the vascular inflammatory response triggered by chronic infection. Periodontitis is a common chronic disorder that involves oral microbe-related inflammatory bone loss and local destruction of the periodontal ligament and is a risk factor for atherosclerosis. Periodontal pathogens contain numerous pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide, CpG DNA, and Peptidoglycan, that initiate the inflammatory response of the innate immunity depending on the recognition of pattern-recognition receptors (PRRs) of host cells. The immune-inflammatory response and destruction of the periodontal tissue will produce a large number of damage-associated molecular patterns (DAMPs) such as neutrophil extracellular traps (NETs), high mobility group box 1 (HMGB1), alarmins (S100 protein), and which can further affect the progression of atherosclerosis. Molecular patterns have recently become the therapeutic targets for inflammatory disease, including blocking the interaction between molecular patterns and PRRs and controlling the related signal transduction pathway. This review summarized the research progress of some representative PAMPs and DAMPs as the molecular pathological mechanism bridging periodontitis and atherosclerosis. We also discussed possible ways to prevent serious cardiovascular events in patients with periodontitis and atherosclerosis by targeting molecular patterns.

Lipoxins modulate neutrophil oxidative burst, integrin expression and lymphatic transmigration differentially in human health and atherosclerosis

Dysregulated chronic inflammation plays a crucial role in the pathophysiology of atherosclerosis and may be a result of impaired resolution. Thus, restoring levels of specialized pro‐resolving mediators (SPMs) to promote the resolution of inflammation has been proposed as a therapeutic strategy for patients with atherosclerosis, in addition to standard clinical care. Herein, we evaluated the effects of the SPM lipids, lipoxin A₄ (LXA₄) and lipoxin B₄ (LXB₄), on neutrophils isolated from patients with atherosclerosis compared with healthy controls. Patients displayed altered endogenous SPM production, and we demonstrated that lipoxin treatment in whole blood from atherosclerosis patients attenuates neutrophil oxidative burst, a key contributor to atherosclerotic development. We found the opposite effect in neutrophils from healthy controls, indicating a potential mechanism whereby lipoxins aid the endogenous neutrophil function in health but reduce its excessive activation in disease. We also demonstrated that lipoxins attenuated upregulation of the high‐affinity conformation of the CD11b/CD18 integrin, which plays a central role in clot activation and atherosclerosis. Finally, LXB₄ enhanced lymphatic transmigration of human neutrophils isolated from patients with atherosclerosis. This finding is noteworthy, as impaired lymphatic function is now recognized as an important contributor to atherosclerosis. Although both lipoxins modulated neutrophil function, LXB₄ displayed more potent effects than LXA₄ in humans. This study highlights the therapeutic potential of lipoxins in atherosclerotic disease and demonstrates that the effect of these SPMs may be specifically tailored to the need of the individual.

Safety and Preliminary Efficacy of a Novel Host-Modulatory Therapy for Reducing Gingival Inflammation

Background

Periodontal disease is among the sixth most common inflammatory diseases worldwide with high risk to promote complications from other inflammatory diseases including diabetes, cardiovascular disease and Alzheimer’s Disease. Failure of active resolution of inflammation pathways is implicated in pathogenesis of periodontal diseases, including gingivitis. Lipoxin A4 (LXA4), a member of the specialized pro-resolving lipid mediators (SPMs) that drive resolution of inflammation via GPC-receptor mediated pathways, offered therapeutic advantages in preclinical models of periodontitis.

Methods

We conducted a randomized, placebo-controlled, parallel-group Phase 1 clinical trial to determine the safety and preliminary efficacy of an LXA4 analog in patients with gingival inflammation. One hundred twenty-seven (127) individuals were randomized to daily use of an oral rinse containing a LXA4 mimetic, methyl ester-benzo-lipoxin A4 (BLXA4), placebo rinse or a no-rinse control group for 28 days. Treatment emergent adverse events (TEAEs) were assessed for safety, the primary outcome. Secondary outcomes included the change in the level of gingival inflammation and periodontal pocket depth (PD). Serum SPMs were monitored using targeted lipid mediator lipidomics to assess potential systemic impact of BLXA4.

Results

The frequency of TEAEs was similar in BLXA4 and placebo-treated groups with no study-related SAEs. Once-daily rinsing with BLXA4 for 28-days resulted in a greater decrease in gingival inflammation compared to placebo rinse and no-rinse control groups (mean change: 0.26 GI unit vs 0.21 and 0.17, respectively). PD reduction was also greater with BLXA4 oral rinse compared to placebo and no-rinse groups (mean reduction: 1.23 mm vs. 0.71 mm and 0.46 mm, respectively). Topical application of BLXA4 increased serum levels of SPMs.

Conclusion

Treatment with BLXA4 reduces local inflammation, and increases abundance of pro-resolution molecules systemically, which may dampen inflammation that can mediate progression and course of inflammatory diseases beyond periodontitis.

Clinical Trial Registration

ClinicalTrials.gov, identifier (NCT02342691).

Lipid mediator lipoxin A4 and its analog BML-111 exert antitumor effects in melanoma

Background

LipoxinA4 (LXA4) is an anti-inflammatory lipid mediator which was recently proposed to have antitumor potential. However, the therapeutic effect of LXA4 in melanoma is still unclear. This work aimed to investigate the function of LXA4 and its analog in melanoma invasion through in vivo and in vitro experiments.

Methods

The expression of the LXA4 receptor (ALXR) was detected in melanoma tissues and A375 human melanoma cells, using benign melanocytic nevi tissues and human melanocytes as negative controls, respectively. The invasive and apoptotic abilities of A375 cells in the presence or absence of LXA4 were examined by cell invasion assay and flow cytometric analysis. Finally, mice melanoma models were established, and the antitumor effects of BML-111 [5(S), 6(R)-7-trihydroxymethyl heptanoate], an agonist of ALXR, were examined in vivo.

Results

ALXR was abundantly expressed in human melanoma tissues. The ALXR messenger RNA (mRNA) and protein expression levels were higher in A375 melanoma cells than in the controls (P<0.05). LXA4 could significantly attenuate the invasion ability of A375 cells (P<0.05). This trend was further enhanced by BML-111, which tended to control the tumor development in A375 melanoma models.

Conclusions

LXA4 and its analog BML-111 exert antitumor effects in vivo and in vitro, and may be potential therapeutic options for patients with invasive melanoma.

Porphyromonas gingivalis Promotes Colorectal Carcinoma by Activating the Hematopoietic NLRP3 Inflammasome

Porphyromonas gingivalis (P. gingivalis) is a keystone periodontal pathogen associated with various digestive cancers. However, whether P. gingivalis can promote colorectal cancer and the underlying mechanism associated with such promotion remains unclear. In this study, we found that P. gingivalis was enriched in human feces and tissue samples from patients with colorectal cancer compared with those from patients with colorectal adenoma or healthy subjects. Cohort studies demonstrated that P. gingivalis infection was associated with poor prognosis in colorectal cancer. P. gingivalis increased tumor counts and tumor volume in the Apc^Min/+ mouse model and increased tumor growth in orthotopic rectal and subcutaneous carcinoma models. Furthermore, orthotopic tumors from mice exposed to P. gingivalis exhibited tumor-infiltrating myeloid cell recruitment and a proinflammatory signature. P. gingivalis promoted colorectal cancer via NLRP3 inflammasome activation in vitro and in vivo. NLRP3 chimeric mice harboring orthotopic tumors showed that the effect of NLRP3 on P. gingivalis pathogenesis was mediated by hematopoietic sources. Collectively, these data suggest that P. gingivalis contributes to colorectal cancer neoplasia progression by activating the hematopoietic NLRP3 inflammasome. SIGNIFICANCE: This study demonstrates that the periodontal pathogen P. gingivalis can promote colorectal tumorigenesis by recruiting myeloid cells and creating a proinflammatory tumor microenvironment. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/10/2745/F1.large.jpg.

Resolution-Based Therapies: The Potential of Lipoxins to Treat Human Diseases

Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response.

Platelet plug formation in whole blood is enhanced in the presence of Porphyromonas gingivalis

Porphyromonas gingivalis is a gram-negative anaerobic bacterium and an etiologic agent of adult periodontitis. By inducing a dysbiotic state within the host microbiota it contributes to a chronic inflammatory environment in the oral cavity. Under some circumstances, the oral bacteria may gain access to systemic circulation. While the most widely recognized function of platelets is to reduce hemorrhage in case of vascular damage, it is known that platelets are also involved in the hematologic responses to bacterial infections. Some pathogenic bacteria can interact with platelets, triggering their activation and aggregation. The aim of this study was to assess platelet responses to the presence of P. gingivalis in whole blood. Human whole blood was pretreated with P. gingivalis and then platelet plug formation was measured under high shear conditions using the PFA-100. In the presence of P. gingivalis, time for a platelet plug to occlude the aperture in the collagen/ADP cartridge was shortened in a manner dependent on bacterial concentration and the duration of bacterial preincubation of blood. P. gingivalis enhances thrombus forming potential of platelets in whole blood.

The role of serum lipoxin A4 levels in the association between periodontal disease and metabolic syndrome

Purpose

An unresolved inflammatory state contributes to the pathogenesis of periodontal disease and metabolic syndrome (MetS). Therefore, the purpose of this study was to evaluate the role of lipoxin A4 (LXA4), a proresolving lipid mediator, in the association between periodontal disease and MetS.

Methods

Sixty-seven patients with MetS and 65 patients without MetS were included in the study. Sociodemographic information was obtained via a questionnaire, and detailed medical diagnoses were made. Periodontal parameters (plaque index [PI], gingival index [GI], probing pocket depth [PD], and clinical attachment level [CAL]) and metabolic parameters were measured, and serum LXA4 levels were determined. The associations among MetS, periodontal parameters, and serum LX levels were evaluated by adjusted multivariate linear regression analyses.

Results

Patients with MetS were older and had a higher body mass index than patients without MetS. Periodontal parameters (PI, GI, PD, and CAL) were higher in patients with MetS than in those without MetS. Serum LXA4 levels were higher in patients without MetS. Multivariate linear regression analysis indicated a positive association between MetS and periodontal parameters (PD and CAL). Negative associations were established between MetS and LXA4 levels, and between LXA4 and periodontal parameters (PI, PD, and CAL).

Conclusions

The presence of higher values of periodontal parameters in patients with MetS and the negative relationship of LXA4 with MetS and periodontal disease may support the protective role of proresolving lipid mediators in the association between periodontal disease and MetS.

Modified lipoproteins in periodontitis: a link to cardiovascular disease?

There is a strong association between periodontal disease and atherosclerotic cardiovascular disorders. A key event in the development of atherosclerosis is accumulation of modified lipoproteins within the arterial wall. We hypothesise that patients with periodontitis have an altered lipoprotein profile towards an atherogenic form. Therefore, the present study aims at identifying modifications of plasma lipoproteins in periodontitis. Lipoproteins from ten female patients with periodontitis and gender- and age-matched healthy controls were isolated by density-gradient ultracentrifugation. Proteins were separated by 2D gel-electrophoresis and identified by map-matching or by nano-LC followed by MS. Apolipoprotein (Apo) A-I (ApoA-I) methionine oxidation, Oxyblot, total antioxidant capacity and a multiplex of 71 inflammation-related plasma proteins were assessed. Reduced levels of apoJ, phospholipid transfer protein, apoF, complement C3, paraoxonase 3 and increased levels of α-1-antichymotrypsin, apoA-II, apoC-III were found in high-density lipoprotein (HDL) from the patients. In low-density lipoprotein (LDL)/very LDL (VLDL), the levels of apoL-1 and platelet-activating factor acetylhydrolase (PAF-AH) as well as apo-B fragments were increased. Methionine oxidation of apoA-I was increased in HDL and showed a relationship with periodontal parameters. α-1 antitrypsin and α-2-HS glycoprotein were oxidised in LDL/VLDL and antioxidant capacity was increased in the patient group. A total of 17 inflammation-related proteins were important for group separation with the highest discriminating proteins identified as IL-21, Fractalkine, IL-17F, IL-7, IL-1RA and IL-2. Patients with periodontitis have an altered plasma lipoprotein profile, defined by altered protein levels as well as post-translational and other structural modifications towards an atherogenic form, which supports a role of modified plasma lipoproteins as central in the link between periodontal and cardiovascular disease (CVD).

Resolution of inflammation in periodontitis: a review

Inflammation is a physiological response to an injury or infection. It is supposed to be self-limiting, stopping when the situation recovers to normal to protect the tissue. This self-limiting action is called "resolution of inflammation". Currently, periodontitis is thought to be the result of failed resolution of inflammation; specifically, it is the result of excessive inflammation that leads to gingival recession and alveolar bone loss. In this review, we will focus on the processes of resolution of inflammation in periodontitis, which may be a therapeutic target of periodontitis.

Lipoprotein modifications by gingipains of Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Several studies have shown an association between periodontitis and cardiovascular disease (CVD). Atherosclerosis is the major cause of CVD, and a key event in the development of atherosclerosis is accumulation of lipoproteins within the arterial wall. Bacteria are the primary etiologic agents in periodontitis and Porphyromonas gingivalis is the major pathogen in the disease. Several studies support a role of modified low-density lipoprotein (LDL) in atherogenesis; however, the pathogenic stimuli that induce the changes and the mechanisms by which this occur are unknown. This study aims to identify alterations in plasma lipoproteins induced by the periodontopathic species of bacterium, P. gingivalis, in vitro.

MATERIAL AND METHODS

Plasma lipoproteins were isolated from whole blood treated with wild-type and gingipain-mutant (lacking either the Rgp- or Kgp gingipains) P. gingivalis by density/gradient-ultracentrifugation and were studied using 2-dimensional gel electrophoresis followed by matrix-assisted laser desorption/ionization mass spectrometry. Porphyromonas gingivalis-induced lipid peroxidation and antioxidant levels were measured by thiobarbituric acid-reactive substances and antioxidant assay kits, respectively, and lumiaggregometry was used for measurement of reactive oxygen species (ROS) and aggregation.

RESULTS

Porphyromonas gingivalis exerted substantial proteolytic effects on the lipoproteins. The Rgp gingipains were responsible for producing 2 apoE fragments, as well as 2 apoB-100 fragments, in LDL, and the Kgp gingipain produced an unidentified fragment in high-density lipoproteins. Porphyromonas gingivalis and its different gingipain variants induced ROS and consumed antioxidants. Both the Rgp and Kgp gingipains were involved in inducing lipid peroxidation.

CONCLUSION

Porphyromonas gingivalis has the potential to change the expression of lipoproteins in blood, which may represent a crucial link between periodontitis and CVD.

Infectious Agents in Atherosclerotic Cardiovascular Diseases through Oxidative Stress

Accumulating evidence demonstrates that vascular oxidative stress is a critical feature of atherosclerotic process, potentially triggered by several infectious agents that are considered as risk co-factors for the atherosclerotic cardiovascular diseases (CVDs). C. pneumoniae has been shown to upregulate multiple enzymatic systems capable of producing reactive oxygen species (ROS) such as NADPH oxidase (NOX) and cyclooxygenase in vascular endothelial cells, NOX and cytochrome c oxidase in macrophages as well as nitric oxide synthase and lipoxygenase in platelets contributing to both early and late stages of atherosclerosis. P. gingivalis seems to be markedly involved in the atherosclerotic process as compared to A. actinomycetemcomitans contributing to LDL oxidation and foam cell formation. Particularly interesting is the evidence describing the NLRP3 inflammasome activation as a new molecular mechanism underlying P. gingivalis-induced oxidative stress and inflammation. Amongst viral agents, immunodeficiency virus-1 and hepatitis C virus seem to have a major role in promoting ROS production, contributing, hence, to the early stages of atherosclerosis including endothelial dysfunction and LDL oxidation. In conclusion, oxidative mechanisms activated by several infectious agents during the atherosclerotic process underlying CVDs are very complex and not well-known, remaining, thus, an attractive target for future research.

Effect of Alox-15 Polymorphism on GCF Levels of Lipoxin-A4 in Chronic Periodontitis: A Preliminary Study

Lipoxins play an important role in periodontal resolution, hence, investigation of genetic polymorphism of lipoxin gene may provide important information on the role of lipoxins in periodontal disease pathogenesis. The aim of this study was to investigate a polymorphism of C-to-T substitution at position c.-292 in ALOX15 (reticulocyte-type 15 lipoxygenase 1) gene in patients with chronic periodontitis and to associate the polymorphism with gingival crevicular fluid (GCF) lipoxin A4 (LXA4) levels. Forty-five chronic periodontitis and 45 periodontally healthy patients were included in this case-control study. Plaque index, calculus index, sulcus bleeding index, full mouth probing depth (PD) and clinical attachment loss (CAL) were recorded. GCF and blood samples were collected. GCF was analyzed for LXA4 levels by enzyme linked immunosorbant assay. Genotyping of ALOX15 polymorphism was studied using PCR. Mean LXA4 was lower in periodontitis group compared to the periodontally healthy group. There was a negative correlation between CAL and LXA4. The CC genotype was higher in the study group than in the control group. In the study group, mean CAL was significantly lower among individuals with the CT genotype. Mean LXA4 was significantly lower in CC genotype (45.0±7.11 ng/mL) compared to CT genotype (50.81±5.81 ng/mL) among the patients with periodontitis. The results suggest that LXA4 and c.-292T allele are associated with periodontal health. Polymorphisms in the ALOX15 gene may influence periodontal disease pathogenesis. Hence, investigation of such polymorphisms could benefit the evaluation of lipoxins role in periodontal disease.

Reduced platelet hyper-reactivity and platelet-leukocyte aggregation after periodontal therapy

Background

Platelets from untreated periodontitis patients are hyper-reactive and form more platelet-leukocyte complexes compared to cells from individuals without periodontitis. It is not known whether the improvement of the periodontal condition achievable by therapy has beneficial effects on the platelet function. We aimed to assess the effects of periodontal therapy on platelet reactivity.

Methods

Patients with periodontitis (n = 25) but unaffected by any other medical condition or medication were included and donated blood before and after periodontal therapy. Reactivity to ADP or oral bacteria was assessed by flow cytometric analysis of membrane markers (binding of PAC-1, P-selectin, CD63) and platelet-leukocyte complex formation. Reactivity values were expressed as ratio between the stimulated and unstimulated sample. Plasma levels of soluble (s) P-selectin were determined by enzyme-linked immunosorbent assay (ELISA).

Results

Binding of PAC-1, the expression of P-selectin and CD63 in response to the oral bacterium P. gingivalis were lower at recall (1.4 ± 1.1, 1.5 ± 1.2, and 1.0 ± 0.1) than at baseline (2.7 ± 4.1, P = 0.026, 6.0 ± 12.5, P = 0.045, and 2.7 ± 6.7, P = 0.042, respectively). Formation of platelet-leukocyte complexes in response to P. gingivalis was also reduced at recall compared to baseline (1.2 ± 0.7 vs. 11.4 ± 50.5, P = 0.045). sP-selectin levels were significantly increased post-therapy.

Conclusions

In periodontitis patients, the improvement of the periodontal condition is paralleled by a reduction in platelet hyper-reactivity. We suggest that periodontal therapy, as an intervention for improved oral health, can facilitate the management of thrombotic risk, and on the long term can contribute to the prevention of cardiovascular events in patients at risk.

Trial registration

Current Controlled Trials identifier ISRCTN36043780. Retrospectively registered 25 September 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s12959-016-0125-x) contains supplementary material, which is available to authorized users.

Diabetic macular edema, retinopathy and age-related macular degeneration as inflammatory conditions

Diabetic macular edema (DME) and diabetic retinopathy (DR) are complications affecting about 25% of all patients with long-standing type 1 and type 2 diabetes mellitus and are a major cause of significant decrease in vision and quality of life. Age-related macular degeneration (AMD) is not uncommon, and diabetes mellitus affects the incidence and progression of AMD through altering hemodynamics, increasing oxidative stress, accumulating advanced glycation end products, etc. Recent studies suggest that DME, DR and AMD are inflammatory conditions characterized by a breakdown of the blood-retinal barrier, inflammatory processes and an increase in vascular permeability. Key factors that seem to have a dominant role in DME, DR and AMD are angiotensin II, prostaglandins and the vascular endothelial growth factor and a deficiency of anti-inflammatory bioactive lipids. The imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DME, DR and AMD. This implies that bioactive lipids that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DME, DR and AMD.

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

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

Lipoxin A4 Preconditioning Attenuates Intestinal Ischemia Reperfusion Injury through Keap1/Nrf2 Pathway in a Lipoxin A4 Receptor Independent Manner

Oxidative stress plays a critical role in the pathogenesis of intestinal ischemia reperfusion (IIR) injury. Enhancement in endogenous Lipoxin A4 (LXA4), a potent antioxidant and mediator, is associated with attenuation of IIR. However, the effects of LXA4 on IIR injury and the potential mechanisms are unknown. In a rat IIR (ischemia 45 minutes and subsequent reperfusion 6 hours) model, IIR caused intestinal injury, evidenced by increased serum diamine oxidase, D-lactic acid, intestinal-type fatty acid-binding protein, and the oxidative stress marker 15-F2t-Isoprostane. LXA4 treatment significantly attenuated IIR injury by reducing mucosal 15-F2t-Isoprostane and elevating endogenous antioxidant superoxide dismutase activity, accompanied with Keap1/Nrf2 pathway activation. Meanwhile, LXA4 receptor antagonist Boc-2 reversed the protective effects of LXA4 on intestinal injury but failed to affect the oxidative stress and the related Nrf2 pathway. Furthermore, Nrf2 antagonist brusatol reversed the antioxidant effects conferred by LXA4 and led to exacerbation of intestinal epithelium cells oxidative stress and apoptosis, finally resulting in a decrease of survival rate of rat. Meanwhile, LXA4 pretreatment upregulated nuclear Nrf2 level and reduced hypoxia/reoxygenation-induced IEC-6 cell damage and Nrf2 siRNA reversed this protective effect of LXA4 in vitro. In conclusion, these findings suggest that LXA4 ameliorates IIR injury by activating Keap1/Nrf2 pathway in a LXA4 receptor independent manner.

Intracellular periodontal pathogen exploits recycling pathway to exit from infected cells

Although human gingival epithelium prevents intrusions by periodontal bacteria, Porphyromonas gingivalis, the most well-known periodontal pathogen, is able to invade gingival epithelial cells and pass through the epithelial barrier into deeper tissues. We previously reported that intracellular P. gingivalis exits from gingival epithelial cells via a recycling pathway. However, the underlying molecular process remains unknown. In the present study, we found that the pathogen localized in early endosomes recruits VAMP2 and Rab4A. VAMP2 was found to be specifically localized in early endosomes, although its localization remained unclear in mammalian cells. A single transmembrane domain of VAMP2 was found to be necessary and sufficient for localizing in early endosomes containing P. gingivalis in gingival epithelial cells. VAMP2 forms a complex with EXOC2/Sec5 and EXOC3/Sec6, whereas Rab4A mediates dissociation of the EXOC complex followed by recruitment of RUFY1/Rabip4, Rab4A effector, and Rab14. Depletion of VAMP2 or Rab4A resulted in accumulation of bacteria in early endosomes and disturbed bacterial exit from infected cells. It is suggested that these novel dynamics allow P. gingivalis to exploit fast recycling pathways promoting further bacterial penetration of gingival tissues.

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.

Human Periodontal Stem Cells Release Specialized Proresolving Mediators and Carry Immunomodulatory and Prohealing Properties Regulated by Lipoxins

The actions of human periodontal ligament stem cells (hPDLSCs) on polymorphonuclear neutrophil (PMN) apoptosis and antimicrobial functions, and the impact of lipoxin A₄ (LXA₄) on hPDLSCs were investigated. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. hPDLSCs also were found to biosynthesize proresolving lipid mediators and prostaglandins. This study also demonstrated that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Unresolved inflammation and tissue destruction are underlying mechanisms of periodontitis, which is linked to dysregulated polymorphonuclear neutrophil (PMN) functions. Lipoxin A₄ (LXA₄) is a specialized proresolving lipid mediator (SPM) that dampens excessive inflammation, promotes resolution, and protects from leukocyte-mediated tissue damage. Human periodontal ligament stem cells (hPDLSCs) represent key players during tissue regeneration and may contribute to resolution of inflammation; thus, they may represent a promising tool in regenerative dentistry. In the present study, we investigated the actions of hPDLSCs on PMN apoptosis and antimicrobial functions, and determined the impact of LXA₄ on hPDLSCs. hPDLSCs significantly reduced apoptosis and stimulated microbicidal activity of human PMNs, via both cell-cell interactions and paracrine mechanisms. Lipid mediator metabololipidomics analysis demonstrated that hPDLSCs biosynthesize SPMs, including resolvin D1, D2, D5, and D6; protectin D1; maresins; and LXB₄; as well as prostaglandins D₂, E₂, and F_2α. LXA₄ significantly enhanced proliferation, migration, and wound healing capacity of hPDLSCs through the activation of its cognate receptor ALX/FPR2, expressed on hPDLSCs. Together, these results demonstrate that hPDLSCs modulate PMN functions, and provide the first evidence that stem cells generate SPM and that the LXA₄-ALX/FPR2 axis regulates regenerative functions of hPDLSCs by a novel receptor-mediated mechanism.

Significance

These findings uncovered unappreciated features of stem cells from the periodontal ligament, supporting the notion that these cells may act as master regulators of pathophysiological events through the release of mediators that promote the resolution of inflammation and bacterial killing. The study also demonstrated that it is possible to modulate important functions of periodontal stem cells using lipoxin A₄, a potent endogenous stop signal of inflammation. Thus, this study revealed an unappreciated anti-inflammatory proregenerative circuit that may be exploited to combat periodontal pathologies using resident stem cells. Moreover, the data may represent a more general template to explain the immunomodulatory functions of stem cells.

Lipoxin A4 Attenuates Cell Invasion by Inhibiting ROS/ERK/MMP Pathway in Pancreatic Cancer

Lipoxin A₄ (LXA₄), an endogenous arachidonic acid metabolite, was previously considered an anti-inflammatory lipid mediator. But it also has the potential to inhibit cancer progression. To explore the therapeutic effect of LXA₄ in pancreatic cancer, we used Panc-1 cells to investigate the mechanism by which LXA₄ can attenuate pancreatic cancer cell invasion. Our data showed that LXA₄ significantly inhibited both cell invasion and the expression of matrix metalloproteinase- (MMP-) 9 and MMP-2. Further experiments implied that LXA₄ decreased the levels of intracellular reactive oxygen species (ROS) and the activity of the extracellular signal regulated kinases (ERK) pathway to achieve similar outcome to ROS scavenger N-acetyl-l-cysteine (NAC). However, a decreased level of intracellular ROS was not observed in cells treated with the specific ERK pathway inhibitor FR180204. The blocking of either intracellular ROS or ERK pathway caused the downregulation of MMP-9 and MMP-2 expression. Furthermore, tests revealed that LXA₄ inhibited MMP-9 and MMP-2 at the mRNA, protein, and functional levels. Finally, LXA₄ dramatically limited the invasion of CoCl₂-mimic hypoxic cells and abrogated intracellular ROS levels, ERK activity, and MMPs expression. These results suggest that LXA₄ attenuates cell invasion in pancreatic cancer by suppressing the ROS/ERK/MMPs pathway, which may be beneficial for preventing the invasion of pancreatic cancer.

Lipoxin Inhibits Fungal Uptake by Macrophages and Reduces the Severity of Acute Pulmonary Infection Caused by Paracoccidioides brasiliensis

Cysteinyl leukotrienes (CysLTs) and lipoxins (LXs) are lipid mediators that control inflammation, with the former inducing and the latter inhibiting this process. Because the role played by these mediators in paracoccidioidomycosis was not investigated, we aimed to characterize the role of CysLT in the pulmonary infection developed by resistant (A/J) and susceptible (B10.A) mice. 48 h after infection, elevated levels of pulmonary LTC₄ and LXA₄ were produced by both mouse strains, but higher levels were found in the lungs of susceptible mice. Blocking the CysLTs receptor by MTL reduced fungal loads in B10.A, but not in A/J mice. In susceptible mice, MLT treatment led to reduced influx of PMN leukocytes, increased recruitment of monocytes, predominant synthesis of anti-inflammatory cytokines, and augmented expression of 5- and 15-lipoxygenase mRNA, suggesting a prevalent LXA₄ activity. In agreement, MTL-treated macrophages showed reduced fungal burdens associated with decreased ingestion of fungal cells. Furthermore, the addition of exogenous LX reduced, and the specific blockade of the LX receptor increased the fungal loads of B10.A macrophages. This study showed for the first time that inhibition of CysLTs signaling results in less severe pulmonary paracoccidioidomycosis that occurs in parallel with elevated LX activity and reduced infection of macrophages.

Gingival crevicular fluid interleukin-8 and lipoxin A4 levels of smokers and nonsmokers with different periodontal status: a cross-sectional study

BACKGROUND AND OBJECTIVE

Smoking is an important risk factor for periodontal disease and effects the pathogenesis of the disease. This study evaluated the impact of smoking on gingival crevicular fluid interleukin-8 (IL-8) and lipoxin A4 (LxA4 ) levels in patients with and without periodontal disease.

MATERIAL AND METHODS

A total of 122 participants were grouped as follows: smokers with generalized aggressive periodontitis (S-GAgP, n = 15); smokers with chronic periodontitis (S-CP, n = 17); smokers with gingivitis (SG, n = 15); smokers classified as periodontally healthy (SH, n = 15); nonsmokers with generalized aggressive periodontitis (N-GAgP, n = 15); nonsmokers with chronic periodontitis (N-CP, n = 15); nonsmokers with gingivitis (NG, n = 15); and nonsmokers classified as periodontally healthy (NH, n = 15). Gingival index, plaque index, probing pocket depth and clinical attachment level were recorded. Gingival crevicular fluid IL-8 and LxA4 levels were analyzed by ELISA.

RESULTS

Gingival crevicular fluid IL-8 levels varied among groups, as follows: S-GAgP>S-CP>SG>SH and N-GAgP>N-CP>NG>NH. The gingival crevicular fluid IL-8 levels were significantly higher in the S-GAgP group compared with the N-GAgP group and in the S-CP group compared with the N-CP group (p < 0.05); differences between the SG and NG and the SH and NH groups were not statistically significant (p > 0.05). Gingival crevicular fluid LxA4 levels also varied among groups, but in an inverse direction when compared with the IL-8 levels, as follows: S-GAgP<S-CP<SG and N-GAgP<N-CP<NG. (The gingival crevicular fluid LxA4 levels in SH and NH groups were below the limits of detection.) The gingival crevicular fluid LxA4 levels were significantly lower in the S-GAgP group than in the N-GAgP group and in the S-CP group than in the N-CP group (p < 0.05); differences between the SG and NG groups were not statistically significant (p > 0.05).

CONCLUSION

The study findings suggest that the observed increases in gingival crevicular fluid IL-8 levels and decreases in gingival crevicular fluid LxA4 levels reflect changes in immune and inflammatory responses that occur as a result of smoking.

Lipoxin A4 and Neutrophil/Lymphocyte Ratio: A Possible Indicator in Achieved Systemic Risk Factors for Periodontitis

Background

The aim of this study was to evaluate the serum lipoxin A₄ (LXA₄) and neutrophil/lymphocyte (Ne/Ly) ratio in individuals with achieved systemic risk factors for periodontitis.

Material/Methods

One hundred and eighty volunteers (69 male, 111 female) who were categorized as systemically healthy control, diabetes, hyperlipidemia, obese and menopause were recruited for this cross-sectional study. Sociodemographic characteristics and oral health behaviors were recorded via questionnaire. Clinical periodontal parameters, including plaque index (PI), gingival index (GI), probing pocket depth (PD), clinical attachment level (CAL), sulcus bleeding index (SBI) and decayed, missing, and filled teeth index (DMFT), were assessed. Systemic parameters and LXA₄ levels were evaluated in serum samples.

Results

Clinical periodontal parameters and DMFT were higher in subjects with achieved systemic risk factors than in healthy subjects. The systemically healthy with periodontitis group had higher serum LXA₄ levels than the systemically healthy with non-periodontitis group (P<0.05). The Ne/Ly ratio was higher in the hyperlipidemic group with periodontitis than in the hyperlipidemic group with non-periodontitis (P<0.05). In the control group, serum LXA₄ levels were positively correlated with the PD, CAL and SBI.

Conclusions

In the presence of periodontitis, an increase in LXA₄ levels and the Ne/Ly ratio in hyperlipidemic patients could contribute to the hypothesis that these parameters could be an indicator in periodontitis and its systemic risk factors.

Maresin 1 mitigates LPS-induced acute lung injury in mice

BACKGROUND AND PURPOSE

Acute lung injury (ALI) is a severe illness with a high rate of mortality. Maresin 1 (MaR1) was recently reported to regulate inflammatory responses. We used a LPS-induced ALI model to determine whether MaR1 can mitigate lung injury.

EXPERIMENTAL APPROACH

Male BALB/c mice were injected, intratracheally, with either LPS (3 mg·kg(-1) ) or normal saline (1.5 mL·kg(-1) ). After this, normal saline, a low dose of MaR1 (0.1 ng per mouse) or a high dose of MaR1 (1 ng per mouse) was given i.v. Lung injury was evaluated by detecting arterial blood gas, pathohistological examination, pulmonary oedema, inflammatory cell infiltration, inflammatory cytokines in the bronchoalveolar lavage fluid and neutrophil-platelet interactions.

KEY RESULTS

The high dose of MaR1 significantly inhibited LPS-induced ALI by restoring oxygenation, attenuating pulmonary oedema and mitigating pathohistological changes. A combination of elisa and immunohistochemistry showed that high-dose MaR1 attenuated LPS-induced increases in pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), chemokines [keratinocyte chemokine, monocyte chemoattractant protein-5, macrophage inflammatory protein (MIP)-1α and MIP-1γ], pulmonary myeloperoxidase activity and neutrophil infiltration in the lung tissues. Consistent with these observations, flow cytometry and Western blotting indicated that MaR1 down-regulated LPS-induced neutrophil adhesions and suppressed the expression of intercellular adhesion molecule (ICAM)-1, P-selection and CD24.

CONCLUSIONS AND IMPLICATIONS

High-dose MaR1 mitigated LPS-induced lung injury in mice by inhibiting neutrophil adhesions and decreasing the levels of pro-inflammatory cytokines.

Effects of Lipoxin A4 on antimicrobial actions of neutrophils in sepsis

In sepsis, hyperactivation of neutrophils can lead to tissue injury. Later, neutrophil dysregulation with reduced levels of migration, decreased apoptosis and inadequate phagocytosis may impair the host׳s ability to clear infection. Lipoxin A4 (LXA4) is a pro-resolution lipid mediator which reduces neutrophil migration and inflammatory mediator expression. As neutrophil migration and activation are important in bacterial clearance, the role of LXA4 in regulating neutrophil function for bacterial clearance is unclear. Using the cecal ligation and puncture (CLP) rat model of sepsis, LXA4 given after 1h reduced blood bacterial load at 24h. LXA4 treatment decreased neutrophil migration to the peritoneum but augmented blood neutrophil phagocytic ability and promoted apoptosis without affecting free radical production. In contrast, LXA4 increased peritoneal neutrophil phagocytic ability without affecting apoptosis or free radical production suggesting that in vivo effects of LXA4 were compartment specific. To investigate if LXA4 acted directly on neutrophils, blood and peritoneal leukocytes were taken from CLP rats 1h after surgery and incubated ex vivo with and without LXA4. LXA4 (1nM) increased phagocytosis in blood neutrophils without affecting apoptosis or free radical production. Ex vivo LXA4 had no effect on peritoneal neutrophils which suggests that LXA4 enhanced peritoneal neutrophil phagocytic ability in vivo by an indirect mechanism. The results suggest that LXA4 reduced neutrophil migration, but increased neutrophil bacteria clearing function without excessive free radical production. This phenotype was associated with reduced blood bacteria load.

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.

The role of Porphyromonas gingivalis gingipains in platelet activation and innate immune modulation

Platelets are considered to have important functions in inflammatory processes and as actors in the innate immunity. Several studies have shown associations between cardiovascular disease and periodontitis, where the oral anaerobic pathogen Porphyromonas gingivalis has a prominent role in modulating the immune response. Porphyromonas gingivalis has been found in atherosclerotic plaques, indicating spreading of the pathogen via the circulation, with an ability to interact with and activate platelets via e.g. Toll-like receptors (TLR) and protease-activated receptors. We aimed to evaluate how the cysteine proteases, gingipains, of P. gingivalis affect platelets in terms of activation and chemokine secretion, and to further investigate the mechanisms of platelet-bacteria interaction. This study shows that primary features of platelet activation, i.e. changes in intracellular free calcium and aggregation, are affected by P. gingivalis and that arg-gingipains are of great importance for the ability of the bacterium to activate platelets. The P. gingivalis induced a release of the chemokine RANTES, however, to a much lower extent compared with the TLR2/1-agonist Pam3 CSK4 , which evoked a time-dependent release of the chemokine. Interestingly, the TLR2/1-evoked response was abolished by a following addition of viable P. gingivalis wild-types and gingipain mutants, showing that both Rgp and Kgp cleave the secreted chemokine. We also demonstrate that Pam3 CSK4 -stimulated platelets release migration inhibitory factor and plasminogen activator inhibitor-1, and that also these responses were antagonized by P. gingivalis. These results supports immune-modulatory activities of P. gingivalis and further clarify platelets as active players in innate immunity and in sensing bacterial infections, and as target cells in inflammatory reactions induced by P. gingivalis infection.

The periodontal pathogen Porphyromonas gingivalis changes the gene expression in vascular smooth muscle cells involving the TGFbeta/Notch signalling pathway and increased cell proliferation

BACKGROUND

Porphyromonas gingivalis is a gram-negative bacterium that causes destructive chronic periodontitis. In addition, this bacterium is also involved in the development of cardiovascular disease. The aim of this study was to investigate the effects of P. gingivalis infection on gene and protein expression in human aortic smooth muscle cells (AoSMCs) and its relation to cellular function.

RESULTS

AoSMCs were exposed to viable P. gingivalis for 24 h, whereafter confocal fluorescence microscopy was used to study P. gingivalis invasion of AoSMCs. AoSMCs proliferation was evaluated by neutral red assay. Human genome microarray, western blot and ELISA were used to investigate how P. gingivalis changes the gene and protein expression of AoSMCs. We found that viable P. gingivalis invades AoSMCs, disrupts stress fiber structures and significantly increases cell proliferation. Microarray results showed that, a total of 982 genes were identified as differentially expressed with the threshold log2 fold change > |1| (adjust p-value <0.05). Using bioinformatic data mining, we demonstrated that up-regulated genes are enriched in gene ontology function of positive control of cell proliferation and down-regulated genes are enriched in the function of negative control of cell proliferation. The results from pathway analysis revealed that all the genes belonging to these two categories induced by P. gingivalis were enriched in 25 pathways, including genes of Notch and TGF-beta pathways.

CONCLUSIONS

This study demonstrates that P. gingivalis is able to invade AoSMCs and stimulate their proliferation. The activation of TGF-beta and Notch signaling pathways may be involved in the bacteria-mediated proliferation of AoSMCs. These findings further support the association between periodontitis and cardiovascular diseases.

Resolution of PMA-induced skin inflammation involves interaction of IFN-γ and ALOX15

BACKGROUND

Acute inflammation and its timely resolution play important roles in the body's responses to the environmental stimulation. Although IFN-γ is well known for the induction of inflammation, its role in the inflammation resolution is still poorly understood.

METHODOLOGY AND PRINCIPAL FINDINGS

In this study, we investigated the function of interferon gamma (IFN-γ) during the resolution of PMA-induced skin inflammation in vivo. The results revealed that the expression levels of IL-6, TNF-α, and monocyte chemoattractant protein 1 (MCP-1) in skin decreased during the resolution stage of PMA-induced inflammation, while IFN-γ is still maintained at a relatively high level. Neutralization of endogenous IFN-γ led to accelerated reduction of epidermal thickness and decreased epithelial cell proliferation. Similarly, decreased infiltration of inflammatory cells (Gr1(+) or CD11b(+) cells) and a significant reduction of proinflammatory cytokines were also observed upon the blockade of IFN-γ. Furthermore, neutralization of IFN-γ boosted ALOX15 expression of the skin during inflammation resolution. In accordance, application of lipoxin A4 (LXA4, a product of ALOX15) obtained a proresolution effect similar to neutralization of IFN-γ. These results demonstrated that through upregulating ALOX15-LXA4 pathway, blockage of IFN-γ can promote the resolution of PMA-induced skin inflammation.

Amniotic fluid induces platelet-neutrophil aggregation and neutrophil activation

OBJECTIVE

Amniotic fluid embolism syndrome is a fatal disease in pregnant women. The exact role of platelets and neutrophils in amniotic fluid embolism syndrome is not clear. We examined whether amniotic fluid could affect platelet-neutrophil aggregation and activation and the possible mechanisms.

STUDY DESIGN

Blood samples from the pregnant women were pretreated ex vivo with their own amniotic fluid. Flow cytometry was used to measure platelet-neutrophil aggregation and activation. Neutrophil-mediated activity of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinases 1 and 2 was analyzed by Western blotting.

RESULTS

Amniotic fluid significantly induced platelet-neutrophil aggregation, neutrophil CD11b expression, and reactive oxygen species production. Amniotic fluid induced minimal platelet P-selectin expression. The increase of intracellular calcium level of neutrophils and the activity of p38 mitogen-activated protein kinase were enhanced by amniotic fluid stimulation.

CONCLUSION

Amniotic fluid was able to induce neutrophil activation and platelet-neutrophil aggregation with minimal effect on platelet activation. These findings may provide a new insight in the understanding of the pathophysiologic condition of amniotic fluid embolism syndrome.

Arachidonic acid and lipoxin A4 as possible endogenous anti-diabetic molecules

In both type 1 and type 2 diabetes mellitus, increased production of pro-inflammatory cytokines and reactive oxygen species (ROS) occurs that induce apoptosis of β cells and cause peripheral insulin resistance respectively though the degree of their increased production is higher in type 1 and less in type 2 diabetes mellitus. Despite this, the exact mechanism(s) that lead to increased production of pro-inflammatory cytokines: interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) and ROS is not known. Studies showed that plasma concentrations of arachidonic acid (AA) and lipoxin A4 (LXA4) are low in alloxan-induced type 1 diabetes mellitus in experimental animals and patients with type 2 diabetes mellitus. Prior administration of AA, eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively) and transgenic animals that produce increased amounts of EPA and DHA acids were protected from chemical-induced diabetes mellitus that was associated with enhanced formation of LXA4 and resolvins, while protectin D1 ameliorated peripheral insulin resistance. AA, LXA4, resolvins and protectins inhibit IL-6 and TNF-α production and suppress ROS generation. Thus, AA and lipoxins, resolvins and protectins may function as endogenous anti-diabetic molecules implying that their administration could be useful in the prevention and management of both types of diabetes mellitus.

Fish and mammalian phagocytes differentially regulate pro-inflammatory and homeostatic responses in vivo

Phagocytosis is a cellular mechanism that is important to the early induction of antimicrobial responses and the regulation of adaptive immunity. At an inflammatory site, phagocytes serve as central regulators for both pro-inflammatory and homeostatic anti-inflammatory processes. However, it remains unclear if this is a recent evolutionary development or whether the capacity to balance between these two seemingly contradictory processes is a feature already displayed in lower vertebrates. In this study, we used murine (C57BL/6) and teleost fish (C. auratus) in vitro and in vivo models to assess the evolutionary conservation of this dichotomy at a site of inflammation. At the level of the macrophage, we found that teleost fish already displayed divergent pro-inflammatory and homeostatic responses following internalization of zymosan or apoptotic bodies, respectively, and that these were consistent with those of mice. However, fish and mice displayed significant differences in vivo with regards to the level of responsiveness to zymosan and apoptotic bodies, the identity of infiltrating leukocytes, their rate of infiltration, and the kinetics and strength of resulting antimicrobial responses. Unlike macrophages, significant differences were identified between teleost and murine neutrophilic responses. We report for the first time that activated murine, but not teleost neutrophils, possess the capacity to internalize apoptotic bodies. This internalization translates into reduction of neutrophil ROS production. This may play an important part in the recently identified anti-inflammatory activity that mammalian neutrophils display during the resolution phase of inflammation. Our observations are consistent with continued honing of inflammatory control mechanisms from fish to mammals, and provide added insights into the evolutionary path that has resulted in the integrated, multilayered responses that are characteristic of higher vertebrates.