Lipoxin A4 Counteracts Synergistic Activation of Human Fibroblast-like Synoviocytes

Arachidonic acid metabolism as a therapeutic target in AKI-to-CKD transition

Arachidonic acid (AA) is a main component of cell membrane lipids. AA is mainly metabolized by three enzymes: cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (CYP450). Esterified AA is hydrolysed by phospholipase A2 into a free form that is further metabolized by COX, LOX and CYP450 to a wide range of bioactive mediators, including prostaglandins, lipoxins, thromboxanes, leukotrienes, hydroxyeicosatetraenoic acids and epoxyeicosatrienoic acids. Increased mitochondrial oxidative stress is considered to be a central mechanism in the pathophysiology of the kidney. Along with increased oxidative stress, apoptosis, inflammation and tissue fibrosis drive the progressive loss of kidney function, affecting the glomerular filtration barrier and the tubulointerstitium. Recent studies have shown that AA and its active derivative eicosanoids play important roles in the regulation of physiological kidney function and the pathogenesis of kidney disease. These factors are potentially novel biomarkers, especially in the context of their involvement in inflammatory processes and oxidative stress. In this review, we introduce the three main metabolic pathways of AA and discuss the molecular mechanisms by which these pathways affect the progression of acute kidney injury (AKI), diabetic nephropathy (DN) and renal cell carcinoma (RCC). This review may provide new therapeutic targets for the identification of AKI to CKD continuum.

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.

Lipoxin A4-Mediated p38 MAPK Signaling Pathway Protects Mice Against Collagen-Induced Arthritis

The aim of the article was to study the mechanism of Lipoxin A4 (LXA4)-mediated p38 MAPK pathway protecting mice against collagen-induced arthritis (CIA). The impact of LXA4 (0, 5, 10, 15 nM) on synoviocytes proliferation of CIA mice was detected using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. CIA mice were treated with LXA4, SB203580 (a p38 inhibitor), and/or anisomycin (a p38 agonist), and the arthritis severity score in each mouse was determined. The gene or protein expressions were detected with Western Blotting, ELISA, or qRT-PCR. LXA4 inhibited the synoviocytes proliferation of CIA mice with decreased levels of TNF-α, IL-6, IL-1β, and IFN-γ and reduced p-p38/total p38 expression in synoviocytes in a dose-dependent manner. LXA4 levels were decreased in synovial tissues and plasma of CIA mice, but p-p38/total p38 expression was increased in synovial tissues. LXA4 could downregulate p-p38/total p38 expression in synovial tissues of CIA mice. Both LXA4 and SB203580 reduced arthritis severity score of CIA mice with the reduction of synovial tissue hyperplasia and inflammatory cell infiltration. CIA mice treated with LXA4 and SB203580 had lower levels of TNF-α, IL-6, IL-1β, and IFN-γ, accompanying decreased MDA as well as increased SOD, CAT,and GPx. However, anisomycin could reverse the protect effects of LXA4 on CIA mice regarding the abovementioned inflammatory factors and oxidative stress indexes. LXA4 protected mice against collagen-induced arthritis via inhibiting p38 MAPK signaling pathway, which may be a potential new therapeutic target for rheumatoid arthritis.

Simvastatin Improves Cardiac Function through Notch 1 Activation in BALB/c Mice with Chronic Chagas Cardiomyopathy

Chagas disease, caused by the protozoan Trypanosoma cruzi, endemic in Latin America but distributed worldwide because of migration. Without appropriate treatment, the disease progresses from an acute asymptomatic phase to a chronic, progressive inflammatory cardiomyopathy causing heart failure and death. Despite specific trypanocidal therapy, heart damage progression cannot be stopped or reversed. Statins, as part of their pleiotropic actions, can modulate chagasic myocarditis by inducing the production of 15-epi-lipoxin A4 (15-epi-LXA4), a proresolution lipid mediator in inflammation. Furthermore, several reports suggest that simvastatin activates the Notch pathway after stroke in cerebral endothelial cells, enhancing blood flow by promoting angiogenesis. Thus, statins are an attractive therapeutic strategy for modulating the Notch pathway to reverse the chronic heart damage induced by T. cruzi BALB/c mice chronically infected with T. cruzi were treated with 1 mg/kg/day simvastatin or 25 μg/kg/day 15-epi-LXA4 for 20 days. During the treatment period, cardiac function was evaluated by echocardiography. At 80 days postinfection, the heart tissues were assessed for Notch 1 activity. T. cruzi infection activated the Notch 1 pathway, and simvastatin (but not 15-epi-lipoxin A4) produced a further increase in that activity, correlating with improvement in the ejection fraction and histopathologic findings typical of T. cruzi infection, including improvements in inflammation and fibrosis. Moreover, simvastatin increased the number of isolectin B4-positive cells, suggesting active angiogenesis in the chronically infected hearts without alteration of the parasitic load. Simvastatin, probably acting through the Notch 1 pathway, decreases inflammation, improving cardiac function in mice chronically infected with T. cruzi.

Analysis of Drug Effects on Primary Human Coronary Artery Endothelial Cells Activated by Serum Amyloid A

Background

RA patients have a higher incidence of cardiovascular diseases compared to the general population. Serum amyloid A (SAA) is an acute-phase protein, upregulated in sera of RA patients.

Aim

To determine the effects of medications on SAA-stimulated human coronary artery endothelial cells (HCAEC).

Methods

HCAEC were preincubated for 2 h with medications from sterile ampules (dexamethasone, methotrexate, certolizumab pegol, and etanercept), dissolved in medium (captopril) or DMSO (etoricoxib, rosiglitazone, meloxicam, fluvastatin, and diclofenac). Human recombinant apo-SAA was used to stimulate HCAEC at a final 1000 nM concentration for 24 hours. IL-6, IL-8, sVCAM-1, and PAI-1 were measured by ELISA. The number of viable cells was determined colorimetrically.

Results

SAA-stimulated levels of released IL-6, IL-8, and sVCAM-1 from HCAEC were significantly attenuated by methotrexate, fluvastatin, and etoricoxib. Both certolizumab pegol and etanercept significantly decreased PAI-1 by an average of 43%. Rosiglitazone significantly inhibited sVCAM-1 by 58%.

Conclusion

We observed marked influence of fluvastatin on lowering cytokine production in SAA-activated HCAEC. Methotrexate showed strong beneficial effects for lowering released Il-6, IL-8, and sVCAM-1. Interesting duality was observed for NSAIDs, with meloxicam exhibiting opposite-trend effects from diclofenac and etoricoxib. This represents unique insight into specific responsiveness of inflammatory-driven HCAEC relevant to atherosclerosis.

Rat Basophilic Leukemia Cells (RBL-2H3) Generate Prostaglandin D2 (PGD2) after Regulated upon Activation, Normal T-cell Expressed and Secreted (RANTES) activation

Increasing evidence indicates that local neurogenic inflammation, possibly in response to different stimuli, may be involved in sensory nerve sensitization, migraine generation and some other precipitating events leading to neuronal dysfunction in the brain. In addition, mast cells generate eicosanoids that are linked to asthma and other inflammatory diseases. Regulated upon activation, normal T-cell expressed and secreted (RANTES) is a small protein and a prototype member of the CC chemokine-beta subfamily with chemoattractant and inflammatory properties. In this study we used the RBL-2H3 cell line to determine whether or not these cells generate prostaglandin D2 (PGD2) after treatment with RANTES. After 4 hours of incubation, RBL-2H3 cells cultured with RANTES at 20 ng/mL released large amounts of PGD2 in a dose-response manner compared to control. Moreover, RBL-treated RANTES generated a large quantity of histamine. Our study confirms once again the proinflammatory action of RANTES, in this case acting on the stimulation of the arachidonic acid cascade product PGD2.

Lipoxin A4 and Serum Amyloid a Differentially Modulate Phospholipase D in Human Fibroblast-Like Synoviocytes

Lipoxin A4 (LXA4) and scrum amyloid A (SAA) are endogenous negative and positive modulators of inflammation, respectively. Both molecules bind the shared lipoxin A4 receptor (ALX) and elicit opposing effects on the production of inflammatory cytokines and matrix metalloproteinases. The aim of these studies is to examine the divergence of the intracellular signaling pathways triggered by lipid LXA4 (1 nM) and protein SAA (200 nM) ligands of ALX. Phospholipase D (PLD) is a phosphohydrolase enzyme that catalyzes the generation of phosphatidic acid (PA) from membrane phospholipids. Our results showed that in fibroblast-like synoviocytes, activation of PLD occurred only in response to LXA4, and not SAA. PA (30 μM) mimicked LXA4 and demonstrated inhibition of IL-8 production induced by SAA or interleukin-1β. In sharp contrast to LXA4, SAA confirmed the stimulation of IL-8 release as determined previously. Taken together, these findings suggest that two physiologic ligands sharing the common ALX receptor, LXA4 and SAA, differentially regulate the level of PLD activation and differentially modulate IL-8. These results may have important implications for understanding the regulation of inflammatory responses under physiologic and pathological conditions.

Targeting resolution of neuroinflammation after ischemic stroke with a lipoxin A4 analog: Protective mechanisms and long-term effects on neurological recovery

BACKGROUND

Resolution of inflammation is an emerging new strategy to reduce damage following ischemic stroke. Lipoxin A₄ (LXA ₄) is an anti-inflammatory, pro-resolution lipid mediator that reduces neuroinflammation in stroke. Since LXA ₄ is rapidly inactivated, potent analogs have been synthesized, including BML-111. We hypothesized that post-ischemic, intravenous treatment with BML-111 for 1 week would provide neuroprotection and reduce neurobehavioral deficits at 4 weeks after ischemic stroke in rats. Additionally, we investigated the potential protective mechanisms of BML-111 on the post-stroke molecular and cellular profile.

METHODS

A total of 133 male Sprague-Dawley rats were subjected to 90 min of transient middle cerebral artery occlusion (MCAO) and BML-111 administration was started at the time of reperfusion. Two methods of week-long BML-111 intravenous administration were tested: continuous infusion via ALZET ^® osmotic pumps (1.25 and 3.75 μg μl^-1 hr^-1), or freshly prepared daily single injections (0.3, 1, and 3 mg/kg). We report for the first time on the stability of BML-111 and characterized an optimal dose and a dosing schedule for the administration of BML-111.

RESULTS

One week of BML-111 intravenous injections did not reduce infarct size or improve behavioral deficits 4 weeks after ischemic stroke. However, post-ischemic treatment with BML-111 did elicit early protective effects as demonstrated by a significant reduction in infarct volume and improved sensorimotor function at 1 week after stroke. This protection was associated with reduced pro-inflammatory cytokine and chemokine levels, decreased M1 CD40+ macrophages, and increased alternatively activated, anti-inflammatory M2 microglia/macrophage cell populations in the post-ischemic brain.

CONCLUSION

These data suggest that targeting the endogenous LXA ₄ pathway could be a promising therapeutic strategy for the treatment of ischemic stroke. More work is necessary to determine whether a different dosing regimen or more stable LXA ₄ analogs could confer long-term protection.

Constitutive and Stimulated Production of Vegf by Human Megakaryoblastic Cell Lines: Effect on Proliferation and Signaling Pathway

Release of vascular endothelial growth factor (VEGF) and other candidate angiogenic factors such as basic fibroblast growth factor and transforming growth factor β, may play a role in sustaining neoplastic cell proliferation and tumor growth. We evaluated VEGF expression and synthesis in the two erythro-megakaryocytic cell lines B1647, HEL and one megakaryocyte cell line MO7 expressing erythroid markers. In this study RT-PCR was performed to evaluate VEGF expression and that of its receptor KDR; VEGF production was assayed by Elisa test and western blot analysis; sensitivity to VEGF was tested by thymidine incorporation. VEGF and its receptor KDR were expressed in B1647 and HEL, both as mRNAs and as proteins, while only KDR transcript was found in MO7 cells. Only B1647 and HEL cells showed a strong spontaneous proliferating activity. In fact, measurable amounts of VEGF were present in the unstimulated cell medium, thus suggesting an autocrine production of VEGF by B1647 and HEL cells, but not by MO7, which was inhibited in mRNA-silencing conditions. This production could not be further boosted by other growth factors, whereas it was inhibited by TGF-β1. Finally, analysis of She signal transduction proteins following stimulation with VEGF indicated that only p46 was tyrosine phosphorylated. These data indicate that leukemic cells may be capable of autocrine production of VEGF which, in turn, maintains cell proliferation, possibly mediated by She p46 phosphorylation.

Effect of Mirtazapine on Thyroid Hormones in Adult Patients with Major Depression

Hypothalamic pituitary thyroid (HPT) axis abnormalities and alterations in major depression are reported in literature. The aim of our study was to evaluate the effect of mirtazapine on thyroid hormones after 6 months of therapy in a sample of adult outpatients with Major Depression (MD). 17 adult outpatients (7 men, 10 women) with MD according to DSM-IV criteria, were included in the study. All participants had to have met criteria for a major depressive episode with a score of at least 15 on the Hamilton Depression Rating Scale (HAM-D). Fasting venous blood samples were obtained for determination of serum Thyroid Stimulating Hrmone (TSH), Free T3 (FT3) and Free T4 (FT4) concentrations both at baseline and after 6 months of therapy. HAM-D scores decreased significantly from the first day of treatment to the end of the treatment period (p<0.001) and twelve patients (70.6%) were classified as responders. A significant increase in FT3 concentrations was found between baseline and the end of treatment period (P=0.015) whereas FT4 concentrations decreased (P=0.046). No significant changes were found in TSH levels. Higher FT4 concentrations at baseline predicted higher HAM-D scorers both at baseline and at the end of the treatment period. Furthermore, higher FT3 concentrations at endpoint were found to be predictors of lower HAM-D scores. Long-term treatment with mirtazapine increases FT3 levels and decreases FT4 maybe involving the deiodination process of T4 into T3.

Novel Evidence of PLC δ2 Involvement in the Regulation of the Differential Evolution of Aneurysms

The biological and molecular mechanisms which are responsible for the formation and possible evolution of human aneurysms are unknown. Previous investigations have pointed to the possible involvement of inositol specific-phospholipase C (PLC) in the mechanisms related to the formation or evolution of intracranial aneurysms, but, thus far, a relationship of one or more PLC isoforms with the biological signals influencing the fate of this lesion has not been demonstrated. The aim of this study was to investigate the expression, activity and possible modification of PLC isoforms in intracranial aneurysms in patients undergoing elective surgical repair after casual identification of unruptured aneurysms, or during emergency surgical repair of ruptured aneurysms. PLC and proliferating cell nuclear antigen (PCNA) expressions were detected by immunoistochemical analysis; PLC activity was obtained by measuring its hydrolytic activity on labelled PIP2; PKC activity was measured by total kinase activity assay. Results indicated no substantial differences between controls and aneurysms, with the only exception being PLC 52 which was nearly absent in controls and ruptured aneurysms, while strongly expressed and functionally active in almost all unruptured aneurysms. In addition, its expression always correlated with the proliferation cell marker PCNA, while its specific activity always correlated to PKC activity. PLC δ2 distribution, regulation and role in human tissues are still unknown Therefore, although preliminary, these data provide a novel insight into the signalling machinery influencing the aneurismal progression.

Serum Evaluation of Angiogenic Cytokines Basic Fibroblast Growth Factor, Hepatocyte Growth Factor and TNF-ALPHA in Patients with Myelodysplastic Syndromes: Correlation with Bone Marrow Microvascular Density

Recent studies have documented that angiogenesis plays a significant role in haematological malignancies, including mylodysplastic syndromes (MDS). Basic fibroblast growth factor (b-FGF), Hepatocyte growth factor (HGF) and Tumor necrosis factor-α (TNF-α) are multifunctional cytokines that potently stimulate angiogenesis. The aim of the present study was to evaluate the microvascular density (MVD) and the serum levels of these angiogenic factors in patients with myelodysplastic syndromes (MDS). In 61 patients with MDS, MVD was measured in bone marrow biopsies and b-FGF, HGF and TNF-α were determined in the serum of the same patients by enzyme-linked immunosorbent assay (ELISA). Serum levels of b-FGF, HGF and TNF-α as well as MVD in the bone marrow were increased in MDS patients compared to healthy controls (p<0.0001). Levels of b-FGF, HGF and TNF-α were also significantly higher in high-risk for leukemic transformation MDS than in low-risk (p<0.0001). Significant differences were also found regarding MVD in high and low risk patients (p<0.001). Both b-FGF and HGF levels were significant predictors of survival (p<0.0005, log-rank test). The present study showed that serum levels of b-FGF, HGF and TNF-α are significantly increased and dependent on the severity of MDS suggesting that the determination of these parameters may offer considerable information regarding disease progression and prognosis.

A Scavenger Role for Nitric Oxide in the Aged Rat Kidney

Progressive ageing is associated with an increment of biomolecules modified through oxidation as a result of the action of free radicals deriving from reactive oxygen species that attack biomolecules. During ageing many alterations of renal functions have been reported. Renal ageing is associated with a progressive decline of glomerular filtration, renal blood flow and augmented vascular resistance. The kidney is a very important source of inducible nitric oxide synthase (iNOS) in both epithelial and vascular structures. In this study we have investigated mRNA and protein iNOS expression and localization and nitric oxide (NO) production in young and aged rats. An increased expression of iNOS occurs in rat kidney during ageing. In the aged rat, an increase in the values of both iNOS-RNA and iNOS protein was observed through rtPCR and Western blot analysis. The activities of three isoforms of NOS were also seen. In the aged rat kidney the production of NO decreased, due to the reduction of the activities of the three NOS. This suggests that in the aged rat a progressive increase of superoxide anion does not imply an increase in the production of NO which functions as a scavenger molecule, causing oxidative stress with accumulation of reactive oxygen species (ROS).

Infliximab Monotherapy for Refractory Psoriasis: Preliminary Results

Tumour necrosis factor (TNF)-alpha plays an important role in the pathogenesis of psoriasis. Infliximab is an anti-TNF-alpha chimeric monoclonal antibody, which is licensed for the treatment of rheumatoid arthritis and Crohn's disease. Some reports have shown the efficacy of infliximab, either in monotherapy or in combination with methotrexate, for the treatment of psoriatic arthropathy and psoriasis.

The efficacy and tolerability of infliximab monotherapy was evaluated in 29 patients with moderate to severe psoriasis, unresponsive to conventional treatments. Fourteen patients suffered from concomitant arthropathy. Patients received intravenous infliximab, 5mg/kg, at weeks 0, 2, and 6. After this 3-dose-induction regimen, patients were followed-up at monthly intervals and retreated with a single-dose infusion in case of relapse of signs and symptoms. Clinical assessment was performed using the psoriasis area and severity index (PASI) to monitor psoriasis activity; pruritus and joint pain were assessed on a scale of 0 to 3. A marked improvement of skin lesions and subjective symptoms was noted in the majority of patients; an excellent reduction of PASI score (⩾75%) was observed in 13.8% of cases at week 2, 71.4% at week 6 and 78.6% at week 10. During the follow-up period, some patients maintained satisfactory clinical results without requiring any additional infusions. In general, skin lesions showed a trend towards a more prolonged and sustained improvement as compared with subjective symptoms. Treatment was well tolerated and no serious adverse events occurred.

Expression of the High-Affinity Laminin Receptor (67 kDa) in Normal Human Skin and Appendages

The interaction of cells with extracellular matrix components plays a significant role in the regulation of cell biology. Laminin is a large glycoprotein involved in fundamental interactions between cells and the basement membrane. Several cell surface receptors are responsible for cell-matrix interactions. The 67 kDa high affinity laminin receptor, 67LR, is involved in the adhesion of normal cells to the laminin network and is also associated with the metastatic phenotype of some tumoral cells. We have investigated the expression of laminin and of the 67LR in normal human skin using immunoperoxidase staining. Twenty samples of skin were analyzed. Antibody against laminin reacted in a continuous linear band at the dermal-epidermal junction, as well as basement membranes of hair follicles, sebaceous and eccrine sweat glands, and dermal blood vessels. The epidermis and the follicular epithelium were negative for laminin. The 67LR seemed not to be expressed on the basal surface of basal keratinocytes. The major expression of this receptor may be detected in the upper half of the spinous layer and in the granular layer. The cells of the outer root sheath in hair follicle showed the same immunohistochemical pattern described for epidermis. In sebaceous glands and in eccrine sweat glands the secreting epithelium was positive. Endothelial cells of dermal blood vessels were routinely positive for 67LR. We observed that the expression of the 67LR in normal human skin is mostly located in epidermal areas in which the keratinizing process was particularly advanced.

Modulation of voltage-dependent and inward rectifier potassium channels by 15-epi-lipoxin-A4 in activated murine macrophages: implications in innate immunity

Potassium channels modulate macrophage physiology. Blockade of voltage-dependent potassium channels (Kv) by specific antagonists decreases macrophage cytokine production and inhibits proliferation. In the presence of aspirin, acetylated cyclooxygenase-2 loses the activity required to synthesize PGs but maintains the oxygenase activity to produce 15R-HETE from arachidonate. This intermediate product is transformed via 5-LOX into epimeric lipoxins, termed 15-epi-lipoxins (15-epi-lipoxin A4 [e-LXA4]). Kv have been proposed as anti-inflammatory targets. Therefore, we studied the effects of e-LXA4 on signaling and on Kv and inward rectifier potassium channels (Kir) in mice bone marrow-derived macrophages (BMDM). Electrophysiological recordings were performed in these cells by the whole-cell patch-clamp technique. Treatment of BMDM with e-LXA4 inhibited LPS-dependent activation of NF-κB and IκB kinase β activity, protected against LPS activation-dependent apoptosis, and enhanced the accumulation of the Nrf-2 transcription factor. Moreover, treatment of LPS-stimulated BMDM with e-LXA4 resulted in a rapid decrease of Kv currents, compatible with attenuation of the inflammatory response. Long-term treatment of LPS-stimulated BMDM with e-LXA4 significantly reverted LPS effects on Kv and Kir currents. Under these conditions, e-LXA4 decreased the calcium influx versus that observed in LPS-stimulated BMDM. These effects were partially mediated via the lipoxin receptor (ALX), because they were significantly reverted by a selective ALX receptor antagonist. We provide evidence for a new mechanism by which e-LXA4 contributes to inflammation resolution, consisting of the reversion of LPS effects on Kv and Kir currents in macrophages.

Molecular mechanism of the inhibition effect of Lipoxin A4 on corneal dissolving pathology process

AIM

Excessive dissolve of corneal tissue induced by MMPs which were activated by cytokins and chemokines will lead to corneal ulcer. The molecular mechanism of Lipoxin A4 (LXA4) on corneal collagen degradation in three dimensions was investigated.

METHODS

Rabbit corneal fibroblasts were harvested and suspended in serum-free MEM. Type I collagen, DMEM, collagen reconstitution buffer and corneal fibroblast suspension were mixed on ice. The resultant mixture solidified in an incubator, after which test reagents and plasminogen was overlaid and the cultures were returned to the incubator. The supernatants from collagen gel incubations were collected and the amount of hydroxyproline in the hydrolysate was measured. Immunoblot analysis of MMP-1, -3 and TMMP-1,-2 was performed. MMP-2,-9 was detected by the method of Gelatin zymography. Cytotoxicity assay was measured.

RESULTS

LXA4 inhibited corneal collagen degradation in a dose and time manner. LXA4 inhibited the IL-1β induced increases in the pro-MMP-1, -2, -3, -9 and active MMP-1, -2, -3, -9 in a concentration dependent manner. LXA4 could also inhibit the IL-1β induced increases in TIMP-1, -2.

CONCLUSION

As a potent anti-inflammation reagent, LXA4 can inhibit corneal collagen degradation induced by IL-1β in corneal fibroblasts thus inhibiting corneal dissolving pathology process.

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.

Old and new generation lipid mediators in acute inflammation and resolution

Originally regarded as just membrane constituents and energy storing molecules, lipids are now recognised as potent signalling molecules that regulate a multitude of cellular responses via receptor-mediated pathways, including cell growth and death, and inflammation/infection. Derived from polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), each lipid displays unique properties, thus making their role in inflammation distinct from that of other lipids derived from the same PUFA. The diversity of their actions arises because such metabolites are synthesised via discrete enzymatic pathways and because they elicit their response via different receptors. This review will collate the bioactive lipid research to date and summarise the findings in terms of the major pathways involved in their biosynthesis and their role in inflammation and its resolution. It will include lipids derived from AA (prostanoids, leukotrienes, 5-oxo-6,8,11,14-eicosatetraenoic acid, lipoxins and epoxyeicosatrienoic acids), EPA (E-series resolvins), and DHA (D-series resolvins, protectins and maresins).

Lipoxins: update and impact of endogenous pro-resolution lipid mediators

Lipoxins (LXs) are endogenously produced eicosanoids that are typically generated by transcellular biosynthesis. These trihydroxytetraene-containing lipid mediators and their stable synthetic analogues possess a wide spectrum of anti-inflammatory and pro-resolution bioactions both in vitro and in vivo. More recently, LXs have emerged as potential anti-fibrotic mediators that may influence pro-fibrotic cytokines and matrix-associated gene expression in response to platelet-derived growth factor (PDGF). Here we review the biosynthesis, metabolism and bioactions of LXs and LX analogues and their therapeutic potential.

New endogenous anti-inflammatory and proresolving lipid mediators: implications for rheumatic diseases

Prostaglandins and leukotrienes are lipid mediators that carry out pivotal roles in host defense and acute inflammation. Failure to completely resolve an acute inflammatory response can lead to chronic inflammation, scarring, and eventual loss of tissue function. Until recently, it was thought that tissue resolution of acute inflammation was a passive event. However, it is now known than lipoxins, which--like prostaglandins and leukotrienes--are also derived from arachidonic acid, are active anti-inflammatory and proresolution mediators, acting in part by reducing neutrophil entry to the inflammation site and stimulating the uptake of apoptotic polymorphonuclear leukocytes by macrophages. Novel families of locally acting and locally generated mediators derived from omega-3 polyunsaturated fatty acids have also been identified as biosynthetically active components in the resolution phase of inflammation. The new families of chemical mediators are termed 'resolvins' and 'protectins' because individual members of each family are stereospecific in controlling the duration and magnitude of inflammation in animal models. Possible deficiencies in the biosynthesis of lipoxins, resolvins, and protectins, and/or their signal transduction, might underlie some aspects of pathogenesis in chronic inflammatory diseases.

Resolution phase of inflammation: novel endogenous anti-inflammatory and proresolving lipid mediators and pathways

Resolution of inflammation and the return of tissues to homeostasis are essential. Efforts to identify molecular events governing termination of self-limited inflammation uncovered pathways in resolving exudates that actively generate, from essential omega fatty acids, new families of local-acting mediators. These chemical mediator families, termed resolvins and protectins, are potent stereoselective agonists that control the duration and magnitude of inflammation, joining the lipoxins as signals in resolution. This review examines the mapping of these circuits and recent advances in our understanding of the biosynthesis and actions of these novel proresolving lipid mediators. Aspirin jump-starts resolution by triggering biosynthesis of specific epimers of these mediators. In addition to their origins in inflammation resolution, these compounds also display potent protective roles in neural systems, liver, lung, and eye. Given the potent actions of lipoxins, resolvins, and protectins in models of human disease, deficiencies in resolution pathways may contribute to many diseases and offer exciting new potential for therapeutic control via resolution.

The lipoxin receptor ALX: potent ligand-specific and stereoselective actions in vivo

Lipoxins (LXs) and aspirin-triggered LX (ATL) are trihydroxytetraene-containing eicosanoids generated from arachidonic acid that are distinct in structure, formation, and function from the many other proinflammatory lipid-derived mediators. These endogenous eicosanoids have now emerged as founding members of the first class of lipid/chemical mediators involved in the resolution of the inflammatory response. Lipoxin A(4) (LXA(4)), ATL, and their metabolic stable analogs elicit cellular responses and regulate leukocyte trafficking in vivo by activating the specific receptor, ALX. ALX was the first receptor cloned and identified as a G protein-coupled receptor (GPCR) for lipoxygenase-derived eicosanoids with demonstrated cell type-specific signaling pathways. ALX at the level of DNA has sequence homology to the N-formylpeptide receptor and as an orphan GPCR was initially referred to as the N-formylpeptide receptor-like 1. Although LXA(4) is the endogenous potent ligand for ALX activation, a number of peptides can also activate this receptor to stimulate calcium mobilization and chemotaxis in vitro. In contrast with LXA(4), the counterparts of many of these peptides in vivo remain to be established. The purpose of this review is to highlight the molecular characterization of the ALX receptor and provide an overview of the ALX-LXA(4) axis responsible for anti-inflammatory and proresolving signals in vivo. The information in this review provides further support for the initial nomenclature proposition for this GPCR as ALX.

Lipoxin A4 modifies platelet-derived growth factor-induced pro-fibrotic gene expression in human renal mesangial cells

Lipoxins (LXs), endogenously produced eicosanoids, possess potent anti-inflammatory, pro-resolution bioactivities. We investigated the potential of LXA(4) (1 to 10 nmol/L) to modify the effects of platelet-derived growth factor (PDGF)-induced gene expression in human renal mesangial cells (hMCs). Using oligonucleotide microarray analysis we profiled pro-fibrotic cytokines and matrix-associated genes induced in response to PDGF. LXA(4) modulated the expression of many PDGF-induced genes, including transforming growth factor-beta1, fibronectin, thrombospondin, matrix metalloproteinase 1, and several collagens. Analysis of both transcript and protein levels confirmed these findings. Because the activated glomerulus is frequently a source of injurious mediators that contribute to tubulointerstitial damage, we investigated the effect of hMC-secreted products on the integrity of renal proximal tubular epithelial cells using an in vitro model of progressive renal disease. Cell supernatant from PDGF-stimulated hMCs caused morphological and genetic changes in proximal tubular epithelial cells, consistent with a pro-fibrotic phenotype. Interestingly, supernatant from cells pre-exposed to LXA(4) and PDGF did not induce these effects. These results suggest a novel role for LXA(4) as a potent modulator of matrix accumulation and pro-fibrotic change and suggest a potential protective role in progressive renal disease.