Lipoxin A4 analogue, BML-111, reduces platelet activation and protects from thrombosis

Formyl peptide receptors (FPRs) are members of seven transmembrane G protein-coupled receptors superfamily that exhibit different responses based on the nature of stimulating ligand type. FPRs have been shown to be present in platelets and regulate their function. However, the effect of formyl peptide receptor 2 (FPR2/ALX) lipid ligands on platelets has not yet been addressed. Hence, we sought to study the role of FPR2/ALX ligand and lipoxin A4 lipid analogue, BML-111, in the modulation of platelet function and thrombus formation. Immunofluorescence microscopy showed subcellular distribution and peripheral mobilisation of FPR2/ALX in stimulated platelets. This variation in distribution was further confirmed using flow cytometry. BML-111 inhibited a range of platelet activities in a dose-dependent manner in response to several platelet agonists. This included aggregation, fibrinogen binding to integrin αIIbβ3, α-granule secretion, dense granule secretion, Ca2 + mobilisation and integrin αIIbβ3-mediated outside-in signaling. The selectivity of BML-111 for FPR2/ALX was confirmed using FPR2/ALX deficient mice in flow cytometry assays. In vitro thrombus formation was also inhibited by various concentrations of BML-111. Moreover, the levels of vasodilator stimulated phosphorylation (VASP-S157) increased significantly after BML-111 treatment in resting and stimulated platelets via protein kinase A (PKA) independently of cyclic adenosine monophosphate (cAMP) signaling. Together, our findings demonstrate the significance of BML-111 as a modulator of platelet function via FPR2/ALX and unravel the thrombo-protective potentials of BML-111 induced signaling against thrombo-inflammatory diseases.

Pro- and anti-inflammatory bioactive lipids imbalance contributes to the pathobiology of autoimmune diseases

Autoimmune diseases are driven by T_H17 cells that secrete pro-inflammatory cytokines, especially IL-17. Under normal physiological conditions, autoreactive T cells are suppressed by TGF-β and IL-10 secreted by microglia and dendritic cells. When this balance is upset due to injury, infection and other causes, leukocyte recruitment and macrophage activation occurs resulting in secretion of pro-inflammatory IL-6, TNF-α, IL-17 and PGE2, LTs (leukotrienes) accompanied by a deficiency of anti-inflammatory LXA4, resolvins, protecting, and maresins. PGE2 facilitates T_H1 cell differentiation and promotes immune-mediated inflammation through T_H17 expansion. There is evidence to suggest that autoimmune diseases can be suppressed by anti-inflammatory bioactive lipids LXA4, resolvins, protecting, and maresins. These results imply that systemic and/or local application of LXA4, resolvins, protecting, and maresins and administration of their precursors AA/EPA/DHA could form a potential therapeutic approach in the prevention and treatment of autoimmune diseases.

Resolution of Inflammation in Retinal Disorders: Briefly the State

The most frequent retinal diseases, such as diabetic retinopathy, age-related macular degeneration and posterior uveitis, are underlined by oxidative stress or aging-induced retinal inflammation, which contributes to vision impairing or loss. Resolution of inflammation is emerging as a critical phase able to counteract the inflammatory process leading to the progression of retinal damage. Particularly, pro-resolving mediators (PMs) play a key role in the modulation of inflammatory exudates and could be considered a new target to be investigated in different inflammatory-autoimmune pathologies. Here, we highlight the most recent studies concerning the role of the main PMs (lipoxins, resolvins, prtectins, maresins and annexins) in retinal inflammation, in order to collect the best evidence in the field of inflammatory retinal damage resolution and to propose novel pharmacological approaches in the management of the most common retinal diseases.

Leukotriene B4 receptors as therapeutic targets for ophthalmic diseases

Leukotriene B₄ (LTB₄) is an inflammatory lipid mediator produced from arachidonic acid by multiple reactions catalyzed by two enzymes 5-lipoxygenase (5-LOX) and LTA₄ hydrolase (LTA₄H). The two receptors for LTB₄ have been identified: a high-affinity receptor, BLT1, and a low-affinity receptor, BLT2. Our group identified 12(S)-hydroxy-5Z,8E,10E-heptadecatrienoic acid (12-HHT) as a high-affinity BLT2 ligand. Numerous studies have revealed critical roles for LTB₄ and its receptors in various systemic diseases. Recently, we also reported the roles of LTB₄, BLT1 and BLT2 in the murine ophthalmic disease models of mice including cornea wound, allergic conjunctivitis, and age-related macular degeneration. Moreover, other groups revealed the evidence of the ocular function of LTB₄. In the present review, we introduce the roles of LTB₄ and its receptors both in ophthalmic diseases and systemic inflammatory diseases. LTB₄ and its receptors are putative novel therapeutic targets for systemic and ophthalmic diseases.

Colony-stimulating factor 1 receptor inhibition prevents disruption of the blood-retina barrier during chronic inflammation

BACKGROUND

Microglia-associated inflammation is closely related to the pathogenesis of various retinal diseases such as uveitis and diabetic retinopathy, which are associated with increased vascular permeability. In this study, we investigated the effect of systemic lipopolysaccharide (LPS) exposure to activation and proliferation of retinal microglia /macrophages.

METHODS

Balb/c and Cx3cr1^gfp/+ mice were challenged with LPS (1 mg/kg) daily for four consecutive days. For microglia depletion, mice were treated with colony-stimulating factor 1 receptor (CSF-1R) inhibitor PLX5622 1 week before the first LPS challenge and until the end of the experiment. In vivo imaging of the retina was performed on days 4 and 7 after the first LPS challenge, using optical coherence tomography and fluorescein angiography. Flow cytometry analysis, retinal whole mount, and retinal sections were used to investigate microglia and macrophage infiltration and proliferation after LPS challenge. Cytokines were analyzed in the blood as well as in the retina. Data analysis was performed using unpaired t tests, repeated measures one-way ANOVA, or ordinary one-way ANOVA followed by Tukey's post hoc analysis. Kruskal-Wallis test followed by Dunn's multiple comparison tests was used for the analysis of non-normally distributed data.

RESULTS

Repeated LPS challenge led to activation and proliferation of retinal microglia, infiltration of monocyte-derived macrophages into the retina, and breakdown of the blood-retina barrier (BRB) accompanied by accumulation of sub-retinal fluid. Using in vivo imaging, we show that the breakdown of the BRB is highly reproducible but transitory. Acute but not chronic systemic exposure to LPS triggered a robust release of inflammatory mediators in the retina with minimal effects in the blood plasma. Inhibition of the CSF-1R by PLX5622 resulted in depletion of retinal microglia, suppression of cytokine production in the retina, and prevention of BRB breakdown.

CONCLUSIONS

These findings suggest that microglia/macrophages play an important role in the pathology of retinal disorders characterized by breakdown of the BRB, and suppression of their activation may be a potential therapeutic target for such retinopathies.

BML-111, a lipoxin receptor agonist, protects against acute injury via regulating the renin angiotensin-aldosterone system

BACKGROUND

The renin angiotensin-aldosterone system (RAAS) and lipoxins (LXs) have similar roles in many processes. We previously reported that BML-111, a Lipoxin receptor agonist, inhibited chronic injury hepatic fibrosis by regulating RAAS, but whether LXs are involved in BML-111-mediated protection from acute injury is unclear still.

METHODS

We established models of acute liver/lung injury and confirmed them with histopathology and myeloperoxidase (MPO) measurements. BML-111, a lipoxin receptor agonist, was applied to mimic the effects of LXs. The contents and activities of angiotensin converting enzyme(ACE) and angiotensinconverting enzyme 2 (ACE2) were measured through ELISA and activity assay kits respectively. Angiotensin II (AngII), angiotensin-(1-7) (Ang-1-7), AngII type 1 receptor (AT1R), and Mas receptor were quantified with ELISA and Western blot.

RESULTS

Models of acute injury were established successfully and BML-111 protected LPS-induced acute lung injury and LPS/D-GalN-induced acute liver injury. BML-111 repressed the activity of ACE, but increased the activity of ACE2. BML-111 decreased the expression levels of ACE, AngII, and AT1R, meanwhile increased the levels of ACE2, Ang-(1-7), and Mas. Furthermore, BOC-2, an inhibitor of lipoxin receptor, reversed all the effects.

CONCLUSION

BML-111 could protect against acute injury via regulation RAAS.

Resveratrol Modulates SIRT1 and DNMT Functions and Restores LINE-1 Methylation Levels in ARPE-19 Cells under Oxidative Stress and Inflammation

The role of epigenetic alterations in the pathogenesis of retinal degenerative diseases, including age-related macular degeneration (AMD), has been pending so far. Our study investigated the effect of oxidative stress and inflammation on DNA methyltransferases (DNMTs) and Sirtuin 1 (SIRT1) functions, as well as on long interspersed nuclear element-1 (LINE-1) methylation, in human retinal pigment epithelial (ARPE-19) cells. Therefore, we evaluated whether treatment with resveratrol may modulate DNMT and SIRT1 functions and restore changes in LINE-1 methylation. Cells were treated with 25 mU/mL glucose oxidase (GOx) or 10 µg/mL lipopolysaccharide (LPS) to mimic oxidative or inflammatory conditions, respectively. Oxidative stress decreased DNMT1, DNMT3a, DNMT3b, and SIRT1 expression (p-values < 0.05), as well as total DNMTs (-28.5%; p < 0.0001) and SIRT1 (-29.0%; p < 0.0001) activities. Similarly, inflammatory condition decreased DNMT1 and SIRT1 expression (p-values < 0.05), as well as total DNMTs (-14.9%; p = 0.007) and SIRT1 (-20.1%; p < 0.002) activities. Interestingly, GOx- and LPS-treated cells exhibited lower LINE-1 methylation compared to controls (p-values < 0.001). We also demonstrated that treatment with 10 μM resveratrol for 24 h counteracted the detrimental effect on DNMT and SIRT1 functions, and LINE-1 methylation, in cells under oxidative and inflammatory conditions. However, further studies should explore the perspectives of resveratrol as a suitable strategy for the prevention and/or treatment of retinal degenerative diseases.

Lipoxin A4 attenuates LPS-induced acute lung injury via activation of the ACE2-Ang-(1-7)-Mas axis

Previous studies have reported that lipoxin A4 (LXA4) and the angiotensin I-converting enzyme 2 (ACE2), angiotensin-(1-7) [Ang-(1-7)], and its receptor Mas [ACE2-Ang-(1-7)-Mas] axis play important protective roles in acute lung injury (ALI). However, there is still no direct evidence of LXA4-mediated protection via the ACE2-Ang-(1-7)-Mas axis during ALI. This work was performed using an LPS-induced ALI mouse model and the data indicated the following. First, the animal model was established successfully and LXA4 ameliorated LPS-induced ALI. Second, LXA4 could increase the concentration and activity of ACE2 and the levels of Ang-(1-7) and Mas markedly. Third, LXA4 decreased the levels of TNF-α, IL-1β, and reactive oxygen species while increasing IL-10 levels. Fourth, LXA4 inhibited the activation of the NF-κB signal pathway and repressed the degradation of inhibitor of NF-κB, the phosphorylation of NF-κB, and the translocation of NF-κB. Finally, and more importantly, BOC-2 (LXA4 receptor inhibitor), MLN-4760 (ACE2 inhibitor), and A779 (Mas receptor antagonist) were found to reverse all of the effects of LXA4. Our data provide evidence that LXA4 protects the lung from ALI through regulation of the ACE2-Ang-(1-7)-Mas axis.

Lipoxin A4 attenuates LPS-induced mouse acute lung injury via Nrf2-mediated E-cadherin expression in airway epithelial cells

A fundamental element of acute lung injury (ALI) is the inflammation that is part of the body's immune response to a variety of local or systemic stimuli. Lipoxins (LXs) are important endogenous lipids that mediate resolution of inflammation. Previously, we demonstrated that LXA4 reduced the LPS inhalation-induced pulmonary edema, neutrophil infiltration and TNF-α production in mice. With the same model, the current investigation focused on the role of the airway epithelium, a first-line barrier and a prime target of inhaled toxicants. We report that LXA4 strongly inhibited LPS-induced ALI in mice, in part by protecting the airway epithelium and preserving the E-cadherin expression and airway permeability. Using a cryo-imaging assay and fluorescence detection, LXA4 was shown to block LPS-induced ROS generation and preserve mitochondrial redox status both in vivo and in vitro. To further assess whether and how NF-E2-related factor 2 (Nrf2) was involved in the protective effect of LXA4, fluorescence resonance energy transfer (FRET) analysis was employed in human epithelial cell line (16HBE), to determine the relative distance between Nrf2 and its negative regulator or cytosolic inhibitor, Kelch-like ECH-associated protein 1 (Keap1). It provided us the evidence that LXA4 further promoted the dissociation of Nrf2 and Keap1 in LPS-treated 16HBE cells. The results also showed that LXA4 activates Nrf2 by phosphorylating it on Ser40 and triggering its nuclear translocation. Moreover, when the plasmid expression dominant negative mutation of Nrf2 was transfected as an inhibitor of wild-type Nrf2, the protective effect of LXA4 on E-cadherin expression was almost completely blocked. These results provide a new mechanism by which LXA4 inhibits LPS-induced ALI through Nrf2-mediated E-cadherin expression.

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.

Inhibition of Corneal Inflammation by the Resolvin E1

PURPOSE

To investigate the role of the lipid mediator, resolvin E1 (RvE1), in corneal inflammation.

METHODS

The effect of RvE1 on stimulated human corneal epithelial cells (HCECs) and neutrophils, and mouse macrophage was assessed. C57BL/6 mouse corneas were abraded and treated with RvE1 either before or after stimulation with lipopolysaccharide (LPS) and antibiotic-killed Pseudomonas aeruginosa and Staphylococcus aureus. The levels of CXC chemokines in the cornea were quantified, and the presence of neutrophils in corneal infiltrates was detected by immunohistochemistry and by in vivo confocal microscopy. The effect of RvE1 on apoptosis in the corneal epithelium was assessed using the TUNEL assay.

RESULTS

RvE1 significantly inhibited cytokine production in HCECs and neutrophils, and mouse macrophages and cornea. The development of corneal infiltrates, specifically neutrophils, in response to stimulation with LPS, P. aeruginosa, and S. aureus was also significantly reduced. There was no apoptotic effect of RvE1 on mouse corneal epithelial cells.

CONCLUSIONS

RvE1 inhibits corneal inflammation induced by LPS, Gram negative (P. aeruginosa) and Gram positive (S. aureus) bacteria. These findings indicate that RvE1 as a potential anti-inflammatory therapy for patients with corneal inflammation and also, when given together with antibiotics, for bacterial keratitis.

Lipoxin A4 attenuates radicular pain possibly by inhibiting spinal ERK, JNK and NF-κB/p65 and cytokine signals, but not p38, in a rat model of non-compressive lumbar disc herniation

Inflammatory response induced by protrused nucleus pulposus (NP) has been shown to play a crucial role in the process of radicular pain. Lipoxins represent a unique class of lipid mediators that have anti-inflammatory and pro-resolving action. The present study was undertaken to investigate if intrathecal lipoxin A4 (LXA4) could alleviate mechanical allodynia in the rat models of application of NP to the L5 dorsal root ganglion (DRG). Non-compressive models of application of NP to L5 DRG were established and intrathecal catheterization for drug administration was performed in rats. Daily intrathecal injection of vehicle or LXA4 (10ng or 100ng) was performed for three successive days post-operation. Mechanical thresholds were tested and the ipsilateral lumbar (L4-L6) segment of spinal dorsal horns were removed for the determination of tumor necrosis factor-α (TNF-α), IL-1β, transforming growth factor-β1 (TGF-β1) and IL-10 expression and NF-κB/p65, extracellular signal-regulated kinase (ERK), C-Jun N-terminal kinase (JNK) and P38 expression. Application of NP to DRG in rats induced mechanical allodynia, increased the expression of pro-inflammatory factors (TNF-α and IL-1β), NF-κB/p65, the phosphorylated-ERK (p-ERK), -JNK (p-JNK) and -P38 (p-p38) and decreased the expression of anti-inflammatory cytokines (TGF-β1 and IL-10) in the ipsilateral lumbar (L4-L6) segment of spinal dorsal horns. Intrathecal injection of LXA4 alleviated the development of neuropathic pain, inhibited the upregulation of pro-inflammatory cytokines (TNF-α and IL-1β), upregulated the expression of anti-inflammatory cytokines (TGF-β1 and IL-10) and attenuated the activation of NF-κB/p65, p-ERK, p-JNK, but not p-p38, in a dose-dependent manner. In this study, we have demonstrated that LXA4 potently alleviate radicular pain in a rat model of non-compressive lumbar disc herniation. The anti-inflammatory and pro-resolution properties of LXA4 have shown a great promise for the management of radicular pain caused by intervertebral disc herniation.

The anti-inflammatory effects of palmitoylethanolamide (PEA) on endotoxin-induced uveitis in rats

The aim of this study was to investigate the effects of palmitoylethanolamide (PEA), an endogenous fatty acid amide belonging to the family of the N-acylethanolamines (NAEs), in rats subjected to endotoxin-induced uveitis (EIU). EIU was induced in male rats by a single footpad injection of 200μg lipopolysaccharide (LPS). PEA was administered intraperitoneally at 1h before and 7h after injection of LPS. Another group of animals was treated with vehicle. Dexamethasone (DEX) was administered as a positive control. Rats were sacrificed 16h after injection and the eyes tissues were collected for histology, immunohistochemical and western blot analyses. The histological evaluation of the iris-ciliary body showed an increase of neutrophilic infiltration and nuclear modification of vessel of endothelial cells. PEA treatment decreased the inflammatory cell infiltration and improved histological damage of eye tissues. In addition, PEA treatment reduced pro-inflammatory tumor necrosis factor (TNF-α) levels, protein extravasion and lipid peroxidation. Immunohistochemical analysis for intracellular adhesion molecule (ICAM)-1 and nitrotyrosine showed a positive staining from LPS-injected rats. The degree of staining for ICAM-1 and nitrotyrosine was significantly reduced in eye sections from LPS-injected rats treated with PEA. In addition, an increase of inducible nitric oxide synthase (iNOS) and nuclear factor (NF-κB) was also evaluated in inflammed ocular tissues by western blot. PEA strongly inhibited iNOS expression and nuclear NF-κB translocation. Thus, in this study we demonstrated that PEA reduces the degree of ocular inflammation in a rat model of EIU.

Anti-inflammatory effects of cannabinoid CB(2) receptor activation in endotoxin-induced uveitis

BACKGROUND AND PURPOSE

Cannabinoid CB2 receptors mediate immunomodulation. Here, we investigated the effects of CB2 receptor ligands on leukocyte-endothelial adhesion and inflammatory mediator release in experimental endotoxin-induced uveitis (EIU).

EXPERIMENTAL APPROACH

EIU was induced by intraocular injection of lipopolysaccharide (LPS, 20 ng·μL(-1) ). Effects of the CB2 receptor agonist, HU308 (1.5% topical), the CB2 receptor antagonist, AM630 (2.5 mg·kg(-1) i.v.), or a combination of both compounds on leukocyte-endothelial interactions were measured hourly for 6 h in rat iridial vasculature using intravital microscopy. Anti-inflammatory actions of HU308 were compared with those of clinical treatments for uveitis - dexamethasone, prednisolone and nepafenac. Transcription factors (NF-κB, AP-1) and inflammatory mediators (cytokines, chemokines and adhesion molecules) were measured in iris and ciliary body tissue.

KEY RESULTS

Leukocyte-endothelium adherence was increased in iridial microvasculature between 4-6 h after LPS. HU308 reduced this effect after LPS injection and decreased pro-inflammatory mediators: TNF-α, IL-1β, IL-6, CCL5 and CXCL2. AM630 blocked the actions of HU-308, and increased leukocyte-endothelium adhesion. HU-308 decreased levels of the transcription factors NF-κB and AP-1, while AM630 increased levels of NF-κB. Topical treatments with dexamethasone, prednisolone or nepafenac, failed to alter leukocyte adhesion or mitigate LPS-induced increases in inflammatory mediators during the 6 h of EIU.

CONCLUSION AND IMPLICATIONS

Activation of CB2 receptors was anti-inflammatory in a model of acute EIU and involved a reduction in NF-κB, AP-1 and inflammatory mediators. CB2 receptors may be promising drug targets for the development of novel ocular anti-inflammatory agents.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

FPR2/ALXR agonists and the resolution of inflammation

The resolution of inflammation (RoI), once believed to be a passive process, has lately been shown to be an active and delicately orchestrated process. During the resolution phase of acute inflammation, novel mediators, including lipoxins and resolvins, which are members of the specialized pro-resolving mediators of inflammation, are produced. FPR2/ALXR, a receptor modulated by some of these lipids as well as by peptides (e.g., annexin A1), has been shown to be one of the receptors involved in the RoI. The aim of this perspective is to present the concept of the RoI from a medicinal chemistry point of view and to highlight the effort of the research community to discover and develop anti-inflammatory/pro-resolution small molecules to orchestrate inflammation by activation of FPR2/ALXR.

Neuroprotective effects of lipoxin A4 in central nervous system pathologies

Many diseases of the central nervous system are characterized and sometimes worsened by an intense inflammatory response in the affected tissue. It is now accepted that resolution of inflammation is an active process mediated by a group of mediators that can act in synchrony to switch the phenotype of cells, from a proinflammatory one to another that favors the return to homeostasis. This new genus of proresolving mediators includes resolvins, protectins, maresins, and lipoxins, the first to be discovered. In this short review we provide an overview of current knowledge into the cellular and molecular interactions of lipoxins in diseases of the central nervous system in which they appear to facilitate the resolution of inflammation, thus exerting a neuroprotective action.

Dual role of lipoxin A4 in pneumosepsis pathogenesis

Lipoxin A4 (LXA4) is an endogenous lipid mediator with potent anti-inflammatory actions but its role in infectious processes is not well understood. We investigated the involvement of LXA4 and its receptor FPR2/ALX in the septic inflammatory dysregulation. Pneumosepsis was induced in mice by inoculation of Klebsiella pneumoniae. LXA4 levels and FPR2/ALX expression in the infectious focus as well as the effects of treatment with receptor agonists (LXA4 and BML-111) and antagonists (BOC-2 and WRW(4)) in early (1h) and late (24h) sepsis were studied. Sepsis induced an early increase in LXA4, FPR2/ALX lung expression, local and systemic infection and inflammation, and mortality. Treatment with BOC-2 in early sepsis increased leukocyte migration to the focus, and reduced bacterial load and dissemination. Inhibition of 5- and 15-lipoxygenase in early sepsis also increased leukocyte migration. Early treatment with WRW(4) and BOC-2 improved survival. Treatment with authentic LXA4 or BML-111 in early sepsis decreased cell migration and worsened the infection. In late sepsis, treatment with BOC-2 had no effect, but LXA4 improved the survival rate by reducing the excessive inflammatory response, this effect being abolished by pretreatment with BOC-2. Thus, the anti-inflammatory and pro-resolution mediator LXA4 and its receptor FPR2/ALX levels were increased in the early phase of sepsis, contributing to the septic inflammatory dysregulation. In addition, LXA4 has a dual role in sepsis and that its beneficial or harmful effects are critically dependent on the time. Therefore, a proper interference with LXA4 system may be a new therapeutic avenue to treat sepsis.

Efficacy and safety of 15(R/S)-methyl-lipoxin A(4) in topical treatment of infantile eczema

BACKGROUND

 Lipoxins are potential anti-inflammatory mediators and serve as an endogenous 'braking signal' in the inflammatory process. Accumulating evidence has indicated the efficacy of lipoxin A(4) (LXA(4) ) and its analogs in the treatment of many animal models of inflammatory diseases.

OBJECTIVES

 This study investigates the efficacy and safety of 15(R/S)-methyl-lipoxin A(4) in the topical treatment of infantile eczema.

PATIENTS AND METHODS

In this two-centre, double-blind, placebo-controlled, randomized, parallel-groups comparative study, 60 patients were randomly assigned to receive either the 15(R/S)-methyl-lipoxin A(4) cream, mometasone furoate (Eloson, Schering-Plough, Shanghai, China) or placebo for 10days. The efficacy was determined using the Severity Scale Score (SSS), Eczema Area and Severity Index (EASI) and the Infants' Dermatitis Quality of Life Index (IDQOL). Safety was monitored by physical examination, laboratory investigation and documentation of clinical adverse events.

RESULTS

 The treatment of eczema with 15(R/S)-methyl-LXA(4) cream significantly relieved the severity, induced a recovery, and improved the quality of life of the patients, as demonstrated by significantly reduced SSS, EASI and IDQOL, respectively, in a way similar to the efficacy of Eloson. All safety parameters remained within normal limits. No clinical adverse event was found in the three patient groups.

CONCLUSIONS

 15(R/S)-methyl-LXA(4) was well tolerated, and significantly reduced the severity of eczema. The results of this small exploratory study suggest that 15(R/S)-methyl-LXA(4) warrants further investigation in the treatment of eczema.

Anti-inflammatory mechanisms of the annexin A1 protein and its mimetic peptide Ac2-26 in models of ocular inflammation in vivo and in vitro

Annexin A1 (AnxA1) is a protein that displays potent anti-inflammatory properties, but its expression in eye tissue and its role in ocular inflammatory diseases have not been well studied. We investigated the mechanism of action and potential uses of AnxA1 and its mimetic peptide (Ac2-26) in the endotoxin-induced uveitis (EIU) rodent model and in human ARPE-19 cells activated by LPS. In rats, analysis of untreated EIU after 24 and 48 h or EIU treated with topical applications or with a single s.c. injection of Ac2-26 revealed the anti-inflammatory actions of Ac2-26 on leukocyte infiltration and on the release of inflammatory mediators; the systemic administration of Boc2, a formylated peptide receptor (fpr) antagonist, abrogated the peptide's protective effects. Moreover, AnxA1(-/-) mice exhibited exacerbated EIU compared with wild-type animals. Immunohistochemical studies of ocular tissue showed a specific AnxA1 posttranslational modification in EIU and indicated that the fpr2 receptor mediated the anti-inflammatory actions of AnxA1. In vitro studies confirmed the roles of AnxA1 and fpr2 and the protective effects of Ac2-26 on the release of chemical mediators in ARPE-19 cells. Molecular analysis of NF-κB translocation and IL-6, IL-8, and cyclooxygenase-2 gene expression indicated that the protective effects of AnxA1 occur independently of the NF-κB signaling pathway and possibly in a posttranscriptional manner. Together, our data highlight the role of AnxA1 in ocular inflammation, especially uveitis, and suggest the use of AnxA1 or its mimetic peptide Ac2-26 as a therapeutic approach.

Aspirin-triggered lipoxin A4 stimulates alternative activation of microglia and reduces Alzheimer disease-like pathology in mice

Microglia play an essential role in innate immunity, homeostasis, and neurotropic support in the central nervous system. In Alzheimer disease (AD), these cells may affect disease progression by modulating the buildup of β-amyloid (Aβ) or releasing proinflammatory cytokines and neurotoxic substances. Discovering agents capable of increasing Aβ uptake by phagocytic cells is of potential therapeutic interest for AD. Lipoxin A4 (LXA4) is an endogenous lipid mediator with potent anti-inflammatory properties directly involved in inflammatory resolution, an active process essential for appropriate host responses, tissue protection, and the return to homeostasis. Herein, we demonstrate that aspirin-triggered LXA4 (15 μg/kg) s.c., twice a day, reduced NF-κB activation and levels of proinflammatory cytokines and chemokines, as well as increased levels of anti-inflammatory IL-10 and transforming growth factor-β. Such changes in the cerebral milieu resulted in recruitment of microglia in an alternative phenotype, as characterized by the up-regulation of YM1 and arginase-1 and the down-regulation of inducible nitric oxide synthase expression. Microglia in an alternative phenotype-positive cells demonstrated improved phagocytic function, promoting clearance of Aβ deposits and ultimately leading to reduction in synaptotoxicity and improvement in cognition. Our data indicate that activating LXA4 signaling may represent a novel therapeutic approach for AD.

LipoxinA(4) induced antinociception and decreased expression of NF-κB and pro-inflammatory cytokines after chronic dorsal root ganglia compression in rats

Inflammatory and immune responses following nerve injury have been shown to play an important role in neuropathic pain. Lipoxins are endogenous lipoxygenase-derived eicosanoids performing protective roles in a range of pathophysiologic processes. Here, we examined the effects of intrathecal lipoxinA4 (LXA4) on NF-κB activation and pro-inflammatory cytokine (TNF-α, IL-1β and IL-6) expression in dorsal root ganglia (DRG) following chronic compression of DRG (CCD), a model of neuropathic pain. Daily intrathecal injection of vehicle or LXA4 (10 ng or 100 ng) was performed for three successive days post-CCD. CCD induced both mechanical allodynia and thermal hyperalgesia, and increased the expression of TNF-α, IL-1β, IL-6 and NF-κB. Intrathecal injection of LXA4 prevented the development of neuropathic pain and inhibited NF-κB activation and pro-inflammatory cytokine upregulation in a dose-dependent manner. In this study, we have shown the strong protective effect of intrathecal LXA4 on the development of nociceptive behaviors induced by CCD and that these effects might be associated with its anti-inflammatory and pro-resolution properties.

Lipoxin A4 inhibits 5-lipoxygenase translocation and leukotrienes biosynthesis to exert a neuroprotective effect in cerebral ischemia/reperfusion injury

Lipoxin A(4) (LXA(4)), a biologically active eicosanoid with anti-inflammatory and pro-resolution properties, was recently found to have neuroprotective effects in brain ischemia. As 5-lipoxygenase (5-LOX) and leukotrienes are generally considered to aggravate cerebral ischemia/reperfusion (I/R) injury, we investigated their effects on LXA(4)-mediated neuroprotection by studying middle cerebral artery occlusion (MCAO)/reperfusion in rats and oxygen-glucose deprivation (OGD)/recovery in neonatal rat astrocyte primary cultures. LXA(4) effectively reduced infarct volumes and brain edema, and improved neurological scores in the MCAO/reperfusion experiments; this effect was partially blocked by butoxycarbonyl-Phe-Leu-Phe-Leu-Phe (Boc2), a specific antagonist of the LXA(4) receptor (ALXR). Total 5-LOX expression did not change, regardless of treatment, but LXA(4) could inhibit nuclear translocation induced by MCAO or OGD. We also found that LXA(4) inhibits the upregulation of both leukotriene B(4) (LTB(4)) and leukotriene C(4) (LTC(4)) and the phosphorylation of extracellular signal-regulated kinase (ERK) induced by MCAO or OGD. The phosphorylation of the 38-kDa protein kinase (p38) and c-Jun N-terminal kinase (JNK) was not altered throughout the experiment. These results suggest that the neuroprotective effects of LXA(4) are probably achieved by anti-inflammatory mechanisms that are partly mediated by ALXR and through an ERK signal transduction pathway.

Aspirin-triggered lipoxin A4 attenuates LPS-induced pro-inflammatory responses by inhibiting activation of NF-κB and MAPKs in BV-2 microglial cells

Background

Microglial activation plays an important role in neurodegenerative diseases through production of nitric oxide (NO) and several pro-inflammatory cytokines. Lipoxins (LXs) and aspirin-triggered LXs (ATLs) are considered to act as 'braking signals' in inflammation. In the present study, we investigated the effect of aspirin-triggered LXA₄ (ATL) on infiammatory responses induced by lipopolysaccharide (LPS) in murine microglial BV-2 cells.

Methods

BV-2 cells were treated with ATL prior to LPS exposure, and the effects of such treatment production of nitric oxide (NO), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) were analysed by Griess reaction, ELISA, western blotting and quantitative RT-PCR. Moreover, we investigated the effects of ATL on LPS-induced nuclear factor-κB (NF-κB) activation, phosphorylation of mitogen-activated protein kinases (MAPKs) and activator protein-1 (AP-1) activation.

Results

ATL inhibited LPS-induced production of NO, IL-1β and TNF-α in a concentration-dependent manner. mRNA expressions for iNOS, IL-1β and TNF-α in response to LPS were also decreased by ATL. These effects were inhibited by Boc-2 (a LXA₄ receptor antagonist). ATL significantly reduced nuclear translocation of NF-κB p65, degradation of the inhibitor IκB-α, and phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK in BV-2 cells activated with LPS. Furthermore, the DNA binding activity of NF-κB and AP-1 was blocked by ATL.

Conclusions

This study indicates that ATL inhibits NO and pro-inflammatory cytokine production at least in part via NF-κB, ERK, p38 MAPK and AP-1 signaling pathways in LPS-activated microglia. Therefore, ATL may have therapeutic potential for various neurodegenerative diseases.

Novel biphasic role of LipoxinA(4) on expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts

Fibroblasts are important to host defence and immunity, can also as initiators of inflammation as well. As the endogenous “braking signal”, Lipoxins can regulate anti-inflammation and the resolution of inflammation. We investigated the effect of lipoxinA₄ on the expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts. We demonstrated that the expression of cyclooxygenase-2 protein was significantly increased and peaked initially at 6 hours, with a second increase, with maximal levels occurring 24 hours after lipopolysaccharide challenge. ProstaglandinE₂ levels also peaked at 6 hours, and prostaglandinD₂ levels were increased at both 6 and 24 hours. Exogenous lipoxinA₄ inhibited the first peak of cyclooxygenase-2 expression as well as the production of prostaglandinE₂ induced by lipopolysaccharide in a dose-dependent manner. In contrast, exogenous lipoxinA₄ increased the second peak of cyclooxygenase-2 expression as well as the production of prostaglandinD₂ induced by lipopolysaccharide in a dose-dependent manner. LipoxinA₄ receptor mRNA expression was markedly stimulated by lipopolysaccharide but inhibited by lipoxinA₄. We present evidence for a novel biphasic role of lipoxinA₄ on the expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts, whereby LXA₄ has an anti-inflammatory and proresolving activity in lung fibroblasts following LPS stimulation.

Aspirin-triggered lipoxin A4 (15-epi-LXA4) increases the endothelial viability of human corneas storage in Optisol-GS

PURPOSE

The human corneal endothelium has a very low mitotic rate, and with aging there is a decrease in the number of cells. 15-epi-LXA4 is an anti-inflammatory, bioactive lipid formed when aspirin acetylates cyclooxygenease-2 and redirects cyclooxygenease-2 catalytic activity away from prostaglandins. The purpose of the current study was to evaluate the action of 15-epi-LXA4 in the endothelium viability of human corneas stored in Optisol-GS.

METHODS

Human corneal endothelial (HCE) cells along with the Descemet's membrane were isolated from fresh human eyes obtained from National Disease Research Interchange. Cell phenotype was identified by using the tight junctions cell marker ZO-1. LXA4 receptor (FPR2/ALX) was detected by immunostaining of HCE cells and human corneal tissue using a polyclonal antibody. Cell proliferation was evaluated with Ki-67 antibody. To measure cell migration, confluent HCE cells were wounded by a linear scraping with a sterile pipette tip in the center of the well and incubated for 24 h with or without 15-epi-LXA4. To evaluate the reparative capacity of 15-epi-LXA4, 7 pairs of human corneas were incubated in Dulbecco's modified Eagle's medium/F12 media at 37°C with or without 100 nM 15-epi-LXA4 for 24 h and then stored at 4°C in Optisol-GS for 12 days. Endothelial viability was assessed by 2 staining techniques: a viability/cytotoxicity kit and trypan blue combined with alizarin red S.

RESULTS

HCE cells and the endothelium of human corneal sections strongly expressed the LXA4 receptor. There was a 3-fold increase in cell proliferation when HCE cells were incubated with 100 nM 15-epi-LXA4 for 24 h. No significant migration was observed after 24 h incubation with 15-epi-LXA4. Corneas incubated for 24 h in Dulbecco's modified Eagle's medium/F12 media in the presence of 15-epi-LXA4 and then stored for 12 days in Optisol-GS had a 36% to 56% increase in viability compared with controls without 15-epi-LXA4.

CONCLUSIONS

15-epi-LXA4 is an important mediator that protects the integrity of the human endothelium during corneal preservation in Optisol-GS.

Emerging role of antioxidants in the protection of uveitis complications

Current understanding of the role of oxidative stress in ocular inflammatory diseases indicates that antioxidant therapy may be important to optimize the treatment. Recently investigated antioxidant therapies for ocular inflammatory diseases include various vitamins, plant products and reactive oxygen species scavengers. Oxidative stress plays a causative role in both non-infectious and infectious uveitis complications, and novel strategies to diminish tissue damage and dysfunction with antioxidant therapy may ameliorate visual complications. Preclinical studies with experimental animals and cultured cells demonstrate significant anti-inflammatory effects of a number of promising antioxidant agents. Many of these antioxidants are under clinical trial for various inflammatory diseases other than uveitis such as cardiovascular, rheumatoid arthritis and cancer. Well planned interventional clinical studies in the field of ocular inflammation will be necessary to sufficiently investigate the potential medical benefits of antioxidant therapies for uveitis. This review summarizes the recent investigations of novel antioxidant agents for ocular inflammation, with selected studies focused on uveitis.

Lipoxin A4 and its analogue suppress the tumor growth of transplanted H22 in mice: the role of antiangiogenesis

Tumor angiogenesis plays an essential role in carcinogenesis, cancer progression, and metastasis. Some studies indicate that lipoxins, endogenous anti-inflammatory lipid mediators, might be involved in tumor angiogenesis; however, the governing mechanisms are still unknown. In the present study, we examined the effects of exogenous lipoxin A(4) (LXA(4)) in mouse hepatocarcinoma cell line (H22) and H22-bearing mice model. It was found that in H22 cells, LXA(4) inhibited the production of vascular endothelial growth factor and reduced hypoxia-inducible factor-1 alpha level. In addition, its analogue, BML-111, blocked the expression of vascular endothelial growth factor in serum and tumor sections from H22-bearing mice. H&E staining and immunostaining with antibodies against CD34 revealed that BML-111 suppressed tumor-related angiogenesis in vivo, but LXA(4) could not influence the proliferation of primary cultured human umbilical vein endothelial cells. The tumor growth was also inhibited by BML-111. We also found that BML-111 enhanced the in situ apoptosis while inhibiting macrophage infiltration in tumor tissue. The results provide new evidence that LXA(4) suppresses the growth of transplanted H22 tumor in mice through inhibiting tumor-related angiogenesis.

Resolution, the grail for healthy ocular inflammation

Acute inflammation is a frequent, essential and beneficial response to maintain normal tissue function. PMN are the primary effector cells of acute inflammatory responses and their timely resolution by macrophages from an injured, stressed or infected tissues are required for the successful execution of this routine tissue response. Dysregulation of this fundamental program is a major factor in the global disease burden and contributes to many ocular diseases. Counter-regulatory signals are critical to the controlled activation of innate and adaptive immune responses in the eye and recent studies have identified two circuits in the cornea, uvea and/or retina, namely 15-lipoxygenase and heme-oxygenase, which control inflammation, promote resolution of PMN and afford neuroprotection. The role of these counter-regulator and pro-resolution circuits may provide insight into ocular inflammatory diseases and opportunities to restore stressed ocular tissue to a pre-inflammatory state, namely homeostasis, rather than limiting therapeutic options to palliative inhibition of pro-inflammatory circuits.

Neuroprotective effect of lipoxin A4 methyl ester in a rat model of permanent focal cerebral ischemia

Neuroprotective effect of lipoxin A(4) methyl ester (LXA(4) ME) was tested in a rat model of permanent middle cerebral artery occlusion. LXA(4) ME was administrated through intracerebroventricular injection immediately after middle cerebral artery was occluded. Administration of LXA(4) ME ameliorated neurological deficit, reduced infarct volume, attenuated histological damage, and decreased number of apoptotic neuron induced by ischemic insult. These neuroprotective effects of LXA(4) ME were associated with inhibition of neutrophil infiltration, lipid peroxidation, and astrocyte activation. In addition, LXA(4) ME also attenuated proinflammatory cytokines (TNF-alpha and IL-1beta) production. These data suggest that LXA(4) ME protects neuron against permanent cerebral ischemia by inhibiting inflammatory responses.

Lipoxin A(4) inhibited hepatocyte growth factor-induced invasion of human hepatoma cells

AIM

Inflammation is a critical component of tumor progression. Lipoxin A(4) (LXA(4)) has been approved for potent anti-inflammatory properties. Recently, it was reported that LXA(4) repressed the expression and activity of cyclooxygenase-2 (COX-2), which is essential for invasion. However, there are few reports dealing with its effects on cancer. To explore whether LXA(4) regulate invasion, the effects of LXA(4) and its receptor agonist BML-111 on hepatocyte growth factor (HGF)-induced invasion of hepatoma cells and the possible mechanisms were researched.

METHODS

Lipoxin A(4) receptor (ALX) expression in HepG2 cells were measured through reverse transcription polymerase chain reaction and western blot. Cytotoxicity of LXA(4) and BML-111 to HepG2 cells was detected by MTT and ((3)H)-TdR incorporation assay. Cell migration and invasion assays were performed using a Boyden chemotaxis chamber. COX-2 expression was detected by real-time polymerase chain reaction and western blot, respectively. Moreover, the expressions of matrix metalloproteinases (MMP)-2, MMP-9, IkappaBalpha and nuclear factor-kappaB (NF-kappaB) p65 were observed via western blot, and NF-kappaB transcriptional activity was tested by transfections and luciferase activities assay.

RESULTS

ALX expression was detected in HepG2 cells, and suitable concentrations of LXA(4) and BML-111 had no cytotoxicity to cells. LXA(4) and BML-111 inhibited HGF-induced migration and invasion; downregulated COX-2, MMP-2 and -9; restrained HGF-induced IkappaBalpha degradation, NF-kappaB translocation and the transcriptional activity of NF-kappaB in HepG2 cells. Furthermore, exogenous PGE2 could reverse the inhibitory effects of LXA(4) also BML-111 on HGF-induced invasion and migration partially.

CONCLUSION

LXA(4) inhibited HGF-induced invasion of HepG2 cells through NF-kappaB/COX-2 signaling pathway partially.

Effects of the immunomodulator, VGX-1027, in endotoxin-induced uveitis in Lewis rats

BACKGROUND AND PURPOSE

VGX-1027 is a novel, low molecular weight, immunomodulatory compound that has shown efficacy against a variety of immuno-inflammatory disease models in animals including autoimmune diabetes in NOD mice, collagen-induced arthritis and chemically induced inflammatory colitis. Here, we have studied the effects of VGX-1027 on the development of endotoxin-induced uveitis (EIU) in male Lewis rats, as a model of inflammatory ocular diseases in humans.

EXPERIMENTAL APPROACH

EIU was induced by a single footpad injection of 200 microg lipopolysaccharide (LPS). Groups of rats were treated with either VGX-1027 (25 mg kg(-1)) or its vehicle at different time points (30 min, 6 h or 12 h) after the challenge with LPS or, as positive control, with dexamethasone. The rats were killed within 16 h after LPS challenge, and the eyes and aqueous humor were collected to study serological, immunological and histological signs of EIU.

KEY RESULTS

The rats treated with VGX-1027 within 6 h after LPS challenge exhibited milder clinical, histological and laboratory signs of EIU than those treated with vehicle.

CONCLUSION AND IMPLICATIONS

This study provides the first evidence that systemic treatment with VGX-1027 counteracts the uveitis-inducing effect of LPS in rats and suggests that this drug may have potential in the treatment of immuno-inflammatory conditions of the eye in humans.