Could Lipoxins Represent a New Standard in Ischemic Stroke Treatment?

INTRODUCTION: Cardiovascular diseases including stroke are one of the most common causes of death. Their main cause is atherosclerosis and chronic inflammation in the body. An ischemic stroke may occur as a result of the rupture of unstable atherosclerotic plaque. Cardiovascular diseases are associated with uncontrolled inflammation. The inflammatory reaction produces chemical mediators that stimulate the resolution of inflammation. One of these mediators is lipoxins-pro-resolving mediators that are derived from the omega-6 fatty acid family, promoting inflammation relief and supporting tissue regeneration. AIM: The aim of the study was to review the available literature on the therapeutic potential of lipoxins in the context of ischemic stroke. MATERIAL AND METHODS: Articles published up to 31 January 2021 were included in the review. The literature was searched on the basis of PubMed and Embase in terms of the entries: 'stroke and lipoxin' and 'stroke and atherosclerosis', resulting in over 110 articles in total. Studies that were not in full-text English, letters to the editor, and conference abstracts were excluded. RESULTS: In animal studies, the injection/administration of lipoxin A4 improved the integrity of the blood-brain barrier (BBB), decreased the volume of damage caused by ischemic stroke, and decreased brain edema. In addition, lipoxin A4 inhibited the infiltration of neutrophils and the production of cytokines and pro-inflammatory chemokines, such as interleukin (Il-1ß, Il-6, Il-8) and tumor necrosis factor-α (TNF-α). The beneficial effects were also observed after introducing the administration of lipoxin A4 analog-BML-111. BML-111 significantly reduces the size of a stroke and protects the cerebral cortex, possibly by reducing the permeability of the blood-brain barrier. Moreover, more potent than lipoxin A4, it has an anti-inflammatory effect by inhibiting the production of pro-inflammatory cytokines and increasing the amount of anti-inflammatory cytokines. CONCLUSIONS: Lipoxins and their analogues may find application in reducing damage caused by stroke and improving the prognosis of patients after ischemic stroke.

Metabolism pathways of arachidonic acids: mechanisms and potential therapeutic targets.

The arachidonic acid (AA) pathway plays a key role in cardiovascular biology, carcinogenesis, and many inflammatory diseases, such as asthma, arthritis, etc. Esterified AA on the inner surface of the cell membrane is hydrolyzed to its free form by phospholipase A2 (PLA2), which is in turn further metabolized by cyclooxygenases (COXs) and lipoxygenases (LOXs) and cytochrome P450 (CYP) enzymes to a spectrum of bioactive mediators that includes prostanoids, leukotrienes (LTs), epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid (diHETEs), eicosatetraenoic acids (ETEs), and lipoxins (LXs). Many of the latter mediators are considered to be novel preventive and therapeutic targets for cardiovascular diseases (CVD), cancers, and inflammatory diseases. This review sets out to summarize the physiological and pathophysiological importance of the AA metabolizing pathways and outline the molecular mechanisms underlying the actions of AA related to its three main metabolic pathways in CVD and cancer progression will provide valuable insight for developing new therapeutic drugs for CVD and anti-cancer agents such as inhibitors of EETs or 2J2. Thus, we herein present a synopsis of AA metabolism in human health, cardiovascular and cancer biology, and the signaling pathways involved in these processes. To explore the role of the AA metabolism and potential therapies, we also introduce the current newly clinical studies targeting AA metabolisms in the different disease conditions.

A novel role for lipoxin A4 in driving a lymph node-eye axis that controls autoimmunity to the neuroretina.

The eicosanoid lipoxin A4 (LXA4) has emerging roles in lymphocyte-driven diseases. We identified reduced LXA4 levels in posterior segment uveitis patients and investigated the role of LXA4 in the pathogenesis of experimental autoimmune uveitis (EAU). Immunization for EAU with a retinal self-antigen caused selective downregulation of LXA4 in lymph nodes draining the site of immunization, while at the same time amplifying LXA4 in the inflamed target tissue. T cell effector function, migration and glycolytic responses were amplified in LXA4-deficient mice, which correlated with more severe pathology, whereas LXA4 treatment attenuated disease. In vivo deletion or supplementation of LXA4 identified modulation of CC-chemokine receptor 7 (CCR7) and sphingosine 1- phosphate receptor-1 (S1PR1) expression and glucose metabolism in CD4+ T cells as potential mechanisms for LXA4 regulation of T cell effector function and trafficking. Our results demonstrate the intrinsic lymph node LXA4 pathway as a significant checkpoint in the development and severity of adaptive immunity.

Lipoxin A4 attenuates hyperoxia­induced lung epithelial cell injury via the upregulation of heme oxygenase­1 and inhibition of proinflammatory cytokines.

The present study examined whether lipoxin A4 (LXA4) increases the expression of HO­1, and inhibits the production of interleukin 6 (IL­6) and monocyte chemotactic protein 1 (MCP­1) in LXA4­induced protection during hyperoxia­induced injury in murine lung epithelial cells (MLE­12) and what signal pathway may participate in the actions of LXA4 inhibiting IL­6 and MCP­1. MLE­12 cells were exposed to air or hyperoxia with or without pretreatment with LXA4, Zinc protoporphyrin IX (ZnPP­IX), IL­6, anti­IL­6, MCP­1, anti­MCP­1, inhibitors of p38 mitogen­activated protein kinase (p38 MAPK), protein kinase B (Akt) and extracellular signal­regulated kinase 1/2 (ERK1/2) signaling pathways. The cell survival rates, cell viability, apoptosis rates, expression of superoxide dismutase (SOD), heme oxygenase­1 (HO­1), IL­6 and MCP­1, and the activations of p38 MAPK, ERK1/2 and Akt were measured. LXA4 significantly increased the cell survival rates, cell viability, SOD levels and HO­1 expression, reduced the apoptosis rates, and inhibited the MCP­1 and IL­6 levels induced by hyperoxia in cells. ZnPP­IX, an inhibitor of HO­1, blocked LXA4­induced protection on cell viability in cells exposed to hyperoxia. Anti­IL­6 and anti­MCP­1 improved the cell viability of cells exposed to hyperoxia. Inhibition of p38 MAPK and ERK1/2 blocked the expression of MCP­1 and IL­6 induced by hyperoxia. LXA4 inhibited the activation of p38 MAPK and ERK1/2 induced by hyperoxia, and increased the activation of the Akt signaling pathway, which was inhibited by hyperoxia. Therefore, LXA4 attenuated hyperoxia­induced injury in MLE­12 cells via the upregulation of HO­1 expression. The protection of LXA4 in hyperoxia­induced cell injury may be associated with the downregulation IL­6 and MCP­1 levels via the inhibition of the p38 MAPK and ERK1/2 signaling pathways.

Downregulation of TNF-α/TNF-R1 Signals by AT-Lipoxin A4 May Be a Significant Mechanism of Attenuation in SAP-Associated Lung Injury.

Our previous studies verified the potent anti-inflammatory effects against severe acute pancreatitis (SAP) of AT-Lipoxin A4 and their analogues. However, the anti-inflammatory effects of AT-Lipoxin A4 on SAP-associated lung injury are not thoroughly known. We used western blot, polymerase chain reaction (PCR), and immunofluorescence to investigate the downregulation of TNF-α signals in cellular and animal models of SAP-associated lung injury following AT-Lipoxin A4 intervention. In vitro, we found that AT-Lipoxin A4 markedly suppressed protein expression in TNF-α signals in human pulmonary microvascular endothelial cell, such as tumor necrosis factor receptor-associated factor 2 (TRAF2), TNF-R1-associated death domain (TRADD), receptor-interacting protein (RIP), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Moreover, AT-Lipoxin A4 inhibited downstream signals activated by TNF-α, including NF-κB/p65, JNK/MAPK, and ERK/MAPK. In vivo, AT-Lipoxin A4 significantly decreased pathological scores of the pancreas and lungs and the serum levels of IL-6 and TNF-α. Immunofluorescence, western blotting, and real-time PCR assay showed that AT-Lipoxin A4 significantly attenuated the expression of TNF-R1, TRADD, TRAF2, and RIP in the lungs of SAP rats. In addition, the activation of NF-κB was also downregulated by AT-Lipoxin A4 administration as compared with SAP rats. AT-Lipoxin A4 could inhibit the production of proinflammatory mediators and activation of TNF-α downstream signals such as NF-κB and MAPK. Downregulation of TNF-α signals by AT-Lipoxin A4 may be a significant mechanism in the attenuation of SAP-associated lung injury.

New pro-resolving n-3 mediators bridge resolution of infectious inflammation to tissue regeneration.

While protective, the acute inflammatory response when uncontrolled can lead to further tissue damage and chronic inflammation that is now widely recognized to play important roles in many commonly occurring diseases, such as cardiovascular disease, neurodegenerative diseases, metabolic syndrome, and many other diseases of significant public health concern. The ideal response to initial challenges of the host is complete resolution of the acute inflammatory response, which is now recognized to be a biosynthetically active process governed by specialized pro-resolving mediators (SPM). These chemically distinct families include lipoxins, resolvins, protectins and maresins that are biosynthesized from essential fatty acids. The biosynthesis and complete stereochemical assignments of the major SPM are established, and new profiling procedures have recently been introduced to document the activation of these pathways in vivo with isolated cells and in human tissues. The active resolution phase leads to tissue regeneration, where we've recently identified new molecules that communicate during resolution of inflammation to activate tissue regeneration in model organisms. This review presents an update on the documentation of the roles of SPMs and the biosynthesis and structural elucidation of novel mediators that stimulate tissue regeneration, coined conjugates in tissue regeneration. The identification and actions of the three families, maresin conjugates in tissue regeneration (MCTR), protectin conjugates in tissue regeneration (PCTR), and resolvin conjugates in tissue regeneration (RCTR), are reviewed here. The identification, structural elucidation and the pathways and biosynthesis of these new mediators in tissue regeneration demonstrate the host capacity to protect from collateral tissue damage, stimulate clearance of bacteria and debris, and promote tissue regeneration via endogenous pathways and molecules in the resolution metabolome.

Specialized proresolving lipid mediators in patients with coronary artery disease and their potential for clot remodeling.

Inflammation in arterial walls leads to coronary artery disease (CAD). Because specialized proresolving lipid mediators (SPMs; lipoxins, resolvins, and protectins) stimulate resolution of inflammation in animal models, we tested whether n-3 fatty acids impact SPM profiles in patients with CAD and promote clot remodeling. Six patients with stable CAD were randomly assigned to either treatment with daily 3.36 g Lovaza for 1 yr or without. Targeted lipid mediator-metabololipidomics showed that both groups had absence of resolvin D1 (RvD1), RvD2, RvD3, RvD5 and resolvin E1-all of which are present in healthy patients. Those not taking Lovaza had an absence of aspirin-triggered resolvin D3 (AT-RvD3) and aspirin-triggered lipoxin B4 (AT-LXB4). Lovaza treatment restored AT-RvD3 and AT-LXB4 and gave levels of RvD6 and aspirin-triggered protectin D1 (AT-PD1) twice as high (resolvin E2 ∼5 fold) as well as lower prostaglandins. Principal component analysis indicated positive relationships for patients with CAD who were receiving Lovaza with increased AT-RvD3, RvD6, AT-PD1, and AT-LXB4 SPMs identified in Lovaza-treated patients with CAD enhanced ∼50% at 1 nM macrophage uptake of blood clots. These results indicate that patients with CAD have lower levels and/or absence of specific SPMs that were restored with Lovaza; these SPMs promote macrophage phagocytosis of blood clots. Together, they suggest that low vascular SPMs may enable progression of chronic vascular inflammation predisposing to coronary atherosclerosis and to thrombosis.-Elajami, T. K., Colas, R. A., Dalli, J., Chiang, N., Serhan, C. N., Welty, F. K. Specialized proresolving lipid mediators in patients with coronary artery disease and their potential for clot remodeling.

Lipoxin A4 augments host defense in sepsis and reduces Pseudomonas aeruginosa virulence through quorum sensing inhibition.

Bacterial infections can quickly turn into sepsis, with its attendant clinical sequelae of inflammation, tissue injury, and organ failure. Paradoxically, sustained inflammation in sepsis may lead to immune suppression, because of which the host is unable to clear the existing infection. Use of agents that suppress the inflammatory response may accelerate host immune suppression, whereas use of traditional antibiotics does not significantly affect inflammation. In this study, we investigated whether lipoxin A4 (LXA4), a specialized, proresolution lipid mediator, could increase neutrophil phagocytic activity as well as reduce bacterial virulence. Using the mouse cecal ligation and puncture (CLP) model of sepsis, the administration of LXA4 (7 µg/kg i.v.) 1 h after surgery increased neutrophil phagocytic ability and Fcγ receptor I (CD64) expression. Ex vivo studies have confirmed that the direct addition of LXA4 to CLP neutrophils increased phagocytic ability but not CD64 expression. LXA4 did not affect neutrophils taken from control mice in which CD64 expression was minimal. Taken together with in vivo data, these results suggest that LXA4 directly augments CD64-mediated neutrophil phagocytic ability but does not directly increase neutrophil CD64 expression. Bacterial communication and virulence is regulated by quorum sensing inducers. In Pseudomonas aeruginosa, virulence is induced with release of various virulence factors, by N-3-oxododecanolyl homoserine lactone binding to the quorum sensing receptor, LasR. We show that LXA4 is an inhibitor of LasR in P. aeruginosa and that it decreases the release of pyocyanin exotoxin. These results suggest that LXA4 has the novel dual properties of increasing host defense and decreasing pathogen virulence by inhibiting quorum sensing.-Wu, B., Capilato, J., Pham, M. P., Walker, J., Spur, B., Rodriguez, A., Perez, L. J., Yin, K. Lipoxin A4 augments host defense in sepsis and reduces Pseudomonas aeruginosa virulence through quorum sensing inhibition.

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

OBJECTIVES: Specialized proresolving lipid mediators have emerged as powerful modulators of inflammation and activators of resolution. Animal models show significant benefits of specialized proresolving lipid mediators on survival and wound healing after major burn trauma. To date, no studies have investigated specialized proresolving lipid mediators and their relation to other lipid mediator pathways in humans after trauma. Here we determine if patients with poor outcomes after trauma have dysregulated lipid mediator pathways. DESIGN: We studied blood leukocyte expression of 18 genes critical to the synthesis, signaling, and metabolism of specialized proresolving lipid mediators and proinflammatory lipid mediators, and we correlated these expression patterns with clinical outcomes in trauma patients from the Inflammation and the Host Response to Injury study. SETTING: Seven U.S. medical trauma centers. SUBJECTS: Ninety-six patients enrolled in the Inflammation and Host Response to Injury study, after blunt trauma and unambiguously classified as having uncomplicated or complicated recoveries. Twenty-eight healthy volunteers were enrolled as controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Within each patient, the 18 genes of interest were used to calculate scores for distinct families of lipid mediators, including resolvins, lipoxins, prostaglandins, and leukotrienes, as well as leukotriene to resolvin score ratios. Scores were built using a simple weighting scheme, taking into consideration both dependent and independent activities of enzymes and receptors responsible for lipid mediator biosynthesis and function. Individually, ALOX12, PTGS2, PTGES, PTGDS, ALOX5AP, LTA4H, FPR2, PTGER2, LTB4R, HPGD, PTGR1, and CYP4F3 were expressed differentially over 28 days posttrauma between patients with uncomplicated and complicated recoveries (p < 0.05). When all genes were combined into scores, patients with uncomplicated recoveries had differential and higher resolvin scores (p < 0.001) and lower leukotriene scores (p < 0.001). A final combined ratio was calculated for each patient, and posttrauma leukotriene score to resolvin score ratios were significantly lower in patients with uncomplicated clinical courses (p < 0.001). CONCLUSIONS: proresolving lipid mediator lipidomics and/or protein expression, and identifying associated therapeutic targets, may influence the clinical management of trauma patients.

Neutrophils rapidly transit inflamed lymphatic vessel endothelium via integrin-dependent proteolysis and lipoxin-induced junctional retraction.

Neutrophils are the first leukocyte population to be recruited from the circulation following tissue injury or infection, where they play key roles in host defense. However, recent evidence indicates recruited neutrophils can also enter lymph and shape adaptive immune responses downstream in draining lymph nodes. At present, the cellular mechanisms regulating neutrophil entry to lymphatic vessels and migration to lymph nodes are largely unknown. Here, we have investigated these events in an in vivo mouse Mycobacterium bovis bacillus Calmette-Guérin vaccination model, ex vivo mouse dermal explants, and in vitro Transwell system comprising monolayers of primary human dermal lymphatic endothelial cells. We demonstrate that neutrophils are reliant on endothelial activation for adhesion, initially via E-selectin and subsequently, by integrin-mediated binding to ICAM-1 and VCAM-1, combined with CXCL8-dependent chemotaxis. Moreover, we reveal that integrin-mediated neutrophil adhesion plays a pivotal role in subsequent transmigration by focusing the action of matrix metalloproteinases and the 15-lipoxygenase-1-derived chemorepellent 12(S)-hydroxyeicosatetraenoic acid at neutrophil:endothelial contact sites to induce transient endothelial junctional retraction and rapid, selective neutrophil trafficking. These findings reveal an unexpectedly intimate collaboration between neutrophils and the lymphatic vessel endothelium, in which these phagocytic leukocytes act as pathfinders for their own transit during inflammation.

Roles of lipoxin A4 receptor activation and anti-interleukin-1ß antibody on the toll-like receptor 2/mycloid differentiation factor 88/nuclear factor-κB pathway in airway inflammation induced by ovalbumin.

Previous studies investigating the role of toll-like receptors (TLRs) in asthma have been inconclusive. It has remained elusive whether the toll-like receptors (TLR2)/mycloid differentiation factor 88 (MyD88)/nuclear factor (NF)-κB signaling pathway is involved in lipoxin A4 (LXA4)-induced protection against asthma. Therefore, the present study investigated whether ovalbumin (OVA)-induced airway inflammation is mediated by upregulation of the TLR2/MyD88/NF-κB signaling pathway, and whether it proceeds via the inhibition of the activation of the LXA4 receptor and anti-interleukin (IL)-1ß antibodies. Mice with airway inflammation induced by OVA administration were treated with or without a LXA4 receptor agonist, BML-111 and anti-IL-1ß antibody. Serum levels of IL-1ß, IL-4, IL-8 and interferon-γ (IFN-γ) were assessed, and levels of IL-1ß, IL-4, IL-8 and OVA-immunoglobulin (Ig)E, as well as leukocyte counts in the bronchoalveolar lavage fluid (BALF) were measured. Pathological features and expression of TLR2, MyD88 and NF-κB in the lungs were analyzed. Expression of TLR2 and MyD88, and activation of NF-κB in leukocytes as well as levels of IL-4, IL-6 and IL-8 released from leukocytes exposed to IL-1ß were assessed. OVA treatment increased the levels of IL-1ß, IL-4 and IL-8 in the serum and BLAF, the number of leukocytes and the levels of OVA-IgE in the BALF, the expression of TLR2 and MyD88, and the activation of NF-κB in the lung. These increments induced by OVA were inhibited by treatment with BML-111 and anti-IL-1ß antibodies. Treatment of the leukocytes with BML-111 or TLR2 antibody, or MyD88 or NF-κB inhibitor, all blocked the IL-1ß-triggered production of IL-4, IL-6 and IL-8 and activation of NF-κB. Treatment of the leukocytes with BML-111 or TLR2 antibody suppressed IL-1ß-induced TLR2 and MyD88 expression. The present study therefore suggested that OVA-induced airway inflammation is mediated by the TLR2/MyD88/NF-κB pathway. IL-1ß has a pivotal role in the airway inflammation and upregulation of the TLR2/MyD88/NF-κB pathway induced by OVA. BML-111 and anti-IL-1ß antibody restrains the OVA-induced airway inflammation via downregulation of the TLR2/MyD88/NF-κB pathway.

Effect of diclofenac on the levels of lipoxin A4 and Resolvin D1 and E1 in the post-ERCP pancreatitis.

OBJECTIVES: Acute pancreatitis is one of the most common complications of endoscopic retrograde cholangiopancreatography (ERCP). Numerous studies have shown that administered nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the incidence of acute pancreatitis after ERCP. Little is known, however, about the mechanism of NSAIDs in preventing pancreatitis (PEP). METHODS: In this study, we assigned patients to receive a single dose of intramuscular diclofenac 75 mg immediately after ERCP (diclofenac group) or without (control group). The primary outcome measure was the occurrence of PEP. The serum amylase levels were measured before ERCP and at 3 and 24 h post-procedure in all patients. The Lipoxin A4 (LXA4), Resolvin D1 (Rvd1), and Resolvin E1 (RvE1) levels were measured before ERCP, and 3 and 24 h after the procedure in 30 patients from the diclofenac group and 30 patients from the control group. RESULTS: A total of 120 patients were enrolled and completed the follow-up. The overall incidence of PEP was 13.3% (16/120). It occurred in four of 60 patients (6.67%) in the diclofenac group and in 12 of 60 patients (20.00%) in the control group (p = 0.032). The LxA4, RvD1, and RvE1 levels in the diclofenac group at 3 h after ERCP were significantly increased compared with before ERCP (p < 0.05). Compared with the control group, the LxA4, RvD1, and RvE1 levels in the diclofenac group at 3 and 24 h after ERCP were significantly increased (p < 0.05). CONCLUSIONS: Intramuscular diclofenac after ERCP can reduce the incidence of PEP. This may be related to the fact that diclofenac can increase the levels of LxA4, RvD1, and RvE1.

Expression of anti-inflammatory mediator lipoxin A4 and inflammation responsive transcriptive factors NF-kappa B in patients with preeclampsia.

OBJECTIVE: To evaluate the role of lipoxin A4 (LXA4), NF-kappaB p65 in preeclampsia. MATERIALS AND METHODS: LXA4 in blood serum and the lipoxin A4 receptor (ALX-R), NF-kappaB p65 mRNA, protein expressions in placenta-specific tissues were obtained from patients with preeclampsia and normal pregnancy. RESULTS: Levels of lipoxin A4 in women with mild preeclampsia was significantly high (p < 0.05). There was no significant statistical difference between normal pregnancy and severe preeclampsia (p > 0.05). The mRNA expression of ALX-R was significantly low in women with preeclampsia than in control group (p < 0.01) and mRNA expression of NF- kappaB p65 was significantly high in preeclampsia (p < 0.01). The immunohistochemical staining of NF-kappaB p65 protein was stronger in severe preeclampsia group whereas staining of ALX-R in placental tissue was weaker than in control group (p < 0.01). ALX-R mRNA was negatively correlated with NF-kappaB (p < 0.0001), but there was no correlation between LXA4 and ALX-R mRNA. CONCLUSION: There was an excessive maternal inflammatory response in preeclampsia. LXA4, ALX-R, and NF-kappaB p65 may be involved in the disease process ofpreeclampsia.

Pro-resolution mediator lipoxin A4 and its receptor in upper airway inflammation.

OBJECTIVES: The resolution of inflammation is an active process controlled by several anti-inflammatory and pro-resolution mediators. Lipoxin A4, an endogenous lipid mediator, is a potential pro-resolution mediator that could attenuate inflammation. This study was conducted to elucidate the role of lipoxin A4 in upper airway inflammation. METHODS: Nasal secretions were collected from patients with chronic rhinosinusitis with nasal polyposis, patients with allergic rhinitis, and control subjects. The concentration of lipoxin A4 was measured by enzyme-linked immunosorbent assay. Nasal tissues were obtained from nasal polyps and inferior turbinates during endonasal surgery. The mRNA expressions of lipoxygenases (LOXs), lipoxin receptor (formyl peptide receptor-like 1; FPRL-1), and cysteinyl leukotriene type 1 receptor (CysLT1R) in nasal tissues were examined by reverse-transcription polymerase chain reaction. Tissue localization of FPRL-1 was determined by immunohistochemical staining. The in vitro effect of lipoxin A4 on airway epithelial cells was also examined. RESULTS: A significant concentration of lipoxin A4 was found in nasal secretions, and the concentration was increased in patients with allergic rhinitis. The mRNA expressions of 5-LOX, 15-LOX-1, FPRL-1, and CysLT1R were significantly greater in nasal polyps than in inferior turbinates. FPRL-1 was localized in nasal epithelial cells. Lipoxin A4 inhibited tumor necrosis factor alpha-induced interleukin 8 release from airway epithelial cells via its receptor FPRL-1. CONCLUSIONS: These results indicate that lipoxin A4 may play a role in the resolution of upper airway inflammation. A low concentration of lipoxin A4 may be involved in chronic inflammation of the upper airways.

Resolvin D1 inhibits TGF-ß1-induced epithelial mesenchymal transition of A549 lung cancer cells via lipoxin A4 receptor/formyl peptide receptor 2 and GPR32.

Epithelial-mesenchymal-transition (EMT) is a key event for tumor cells to initiate metastasis which lead to switching of E-cadherin to N-cadherin. Resolvins are known to promote the resolution of inflammation and phagocytosis of macrophages. However, the role of resolvins in EMT of cancer is not known. Therefore, we examined the effects of resolvins on transforming growth factor, beta 1 (TGF-ß1)-induced EMT. Expression of E-cadherin and N-cadherin in A549 lung cancer cells was evaluated by Western blot and confocal microscopy. Involvement of lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2) was examined by gene silencing. TGF-ß1 induced expression of N-cadherin in A549 lung cancer cells, and resolvin D1 and D2 inhibited the expression of N-cadherin at low concentrations (1-100 nM). Resolvin D1 and D2 also suppressed the expression of zinc finger E-box binding homeobox 1 (ZEB1). The effects of resolvin D1 and D2 were confirmed in other lung cancer cell lines such as H838, H1299, and H1703. Resolvin D1 and D2 did not affect the proliferation of A549 lung cancer cells. Resolvin D1 and D2 also suppressed the TGF-ß1-induced morphological change. Resolvin D1 and D2 also inhibited the TGF-ß1-induced migration and invasion of A549 cells. Resolvin D1 is known to act via ALX/FPR2 and GPR32. Thus, we examined the involvement of ALX/FPR2 and GPR32 in the suppressive effects of resolvin D1 on TGF-ß1-induced EMT of A549 cells. Gene silencing of ALX/FPR2 and GPR32 blocked the action of resolvin D1. Overexpression of ALX/FPR2 or GPR32 increased the effects of resolvin D1. These results suggest that resolvin D1 inhibited TGF-ß1-induced EMT via ALX/FPR2 and GPR32 by reducing the expression of ZEB1.

Resolvin D1 protects periodontal ligament.

Resolution agonists are endogenous mediators that drive inflammation to homeostasis. We earlier demonstrated in vivo activity of resolvins and lipoxins on regenerative periodontal wound healing. The goal of this study was to determine the impact of resolvin D1 (RvD1) on the function of human periodontal ligament (PDL) fibroblasts, which are critical for wound healing during regeneration of the soft and hard tissues around teeth. Primary cells were cultured from biopsies obtained from three individuals free of periodontal diseases. Peripheral blood mononuclear cells were isolated by density gradient centrifugation from whole blood of healthy volunteers. PGE2, leukotriene B4 (LTB4), and lipoxin A4 (LXA4) in culture supernatants were measured by ELISA. The direct impact of RvD1 on PDL fibroblast proliferation was measured and wound closure was analyzed in vitro using a fibroblast culture "scratch assay." PDL fibroblast function in response to RvD1 was further characterized by basic FGF production by ELISA. IL-1ß and TNF-α enhanced the production of PGE2. Treatment of PDL cells and monocytes with 0.1-10 ng/ml RvD1 (0.27-27 M) reduced cytokine induced production of PGE2 and upregulated LXA4 production by both PDL cells and monocytes. RvD1 significantly enhanced PDL fibroblast proliferation and wound closure as well as basic FGF release. The results demonstrate that anti-inflammatory and proresolution actions of RvD1 with upregulation of arachidonic acid-derived endogenous resolution pathways (LXA4) and suggest resolution pathway synergy establishing a novel mechanism for the proresolution activity of the ω-3 docosahexaenoic acid-derived resolution agonist RvD1.

Aspirin-triggered 15-epi-lipoxin A4 predicts cyclooxygenase-2 in the lungs of LPS-treated mice but not in the circulation: implications for a clinical test.

Inhibition of cyclooxygenase (COX)-2 increases cardiovascular deaths. Identifying a biomarker of COX-2 is desirable but difficult, since COX-1 and COX-2 ordinarily catalyze formation of an identical product, prostaglandin H2. When acetylated by aspirin, however, COX-2 (but not COX-1) can form 15(R)-HETE, which is metabolized to aspirin-triggered lipoxin (ATL), 15-epi-lipoxin A4. Here we have used COX-1- and COX-2-knockout mice to establish whether plasma ATL could be used as a biomarker of vascular COX-2 in vivo. Vascular COX-2 was low but increased by LPS (10 mg/kg; i.p). Aspirin (10 mg/kg; i.v.) inhibited COX-1, measured as blood thromboxane and COX-2, measured as lung PGE2. Aspirin also increased the levels of ATL in the lungs of LPS-treated wild-type C57Bl6 mice (vehicle: 25.5±9.3 ng/ml; 100 mg/kg: 112.0±7.4 ng/ml; P<0.05). Despite this, ATL was unchanged in plasma after LPS and aspirin. This was true in wild-type as well as COX-1(-/-) and COX-2(-/-) mice. Thus, in mice in which COX-2 has been induced by LPS treatment, aspirin triggers detectable 15-epi-lipoxin A4 in lung tissue, but not in plasma. This important study is the first to demonstrate that while ATL can be measured in tissue, plasma ATL is not a biomarker of vascular COX-2 expression.

Molecular mechanisms elucidating why old stomach is more vulnerable to indomethacin-induced damage than young stomach.

BACKGROUND/AIMS: Detailed underlying changes have never been explored to explain how old stomach is more susceptible to non-steroidal anti-inflammatory drugs (NSAIDs)-induced gastric damage than young stomach, although presumptively speculated as weakened mucosal defense system as well as attenuated regenerating capacity in old stomach. METHODS: In order to investigate molecular mechanisms relevant to NSAID-induced gastric damage, we administered indomethacin to 6-week-old and 60-week-old rats. RESULTS: In spite of the same oral administration of indomethacin (0.1 mg indomethacin dissolved in 1 ml carboxyl methylcellulose) irrespective of body weights of rat, gastric mucosal damages were significantly increased in the older rats compared to the younger rats (p < 0.05). Before indomethacin administration, inflammatory mediators including cytokines, chemokines, proteases, and adhesion molecules were significantly increased in old stomach and these differences were further increased after indomethacin administration (p < 0.05). Furthermore, the levels of total oxidants and apoptotic executors were significantly increased in old stomach, whereas lipoxin A4 and anti-apoptotic proteins such as survivin and Bcl-2 were significantly decreased. Increased NF-κB-DNA binding activity as well as the activation of JNK and p38 was responsible for the increased expressions of inflammatory mediators as well as oxidants. CONCLUSIONS: A preventive strategy to reduce either redox activation or pro-inflammatory mediators should be considered in older patients taking long-standing NSAID administration.

Up-regulation of Annexin-A1 and lipoxin A(4) in individuals with ulcerative colitis may promote mucosal homeostasis.

BACKGROUND: One of the characteristics of an active episode of ulcerative colitis (UC) is the intense mucosal infiltration of leukocytes. The pro-resolution mediators Annexin-A1 (AnxA1) and lipoxin A(4) (LXA(4)) exert counter-regulatory effects on leukocyte recruitment, however to date, the dual/cumulative effects of these formyl peptide receptor-2 (FPR2/ALX) agonists in the context of human intestinal diseases are unclear. To define the contribution of these mediators, we measured their expression in biopsies from individuals with UC. METHODS: Colonic mucosal biopsies were collected from two broad patient groups: healthy volunteers without ('Ctrl' n  = 20) or with a prior history of UC ('hx of UC' n = 5); individuals with UC experiencing active disease ('active' n = 8), or in medically-induced remission ('remission' n = 16). We assessed the mucosal expression of LXA(4), AnxA1, and the FPR2/ALX receptor in each patient group using a combination of fluorescence microscopy, biochemical and molecular analyses. RESULTS: Mucosal expression of LXA(4) was elevated exclusively in biopsies from individuals in remission (3-fold, P<0.05 vs. Ctrl). Moreover, in this same group we observed an upregulation of AnxA1 protein expression (2.5-fold increase vs. Ctrl, P<.01), concurrent with an increased level of macrophage infiltration, and an elevation in FPR2/ALX mRNA (7-fold increase vs. Ctrl, P<.05). Importantly, AnxA1 expression was not limited to cells infiltrating the lamina propria but was also detected in epithelial cells lining the intestinal crypts. CONCLUSIONS: Our results demonstrate a specific up-regulation of this pro-resolution circuit in individuals in remission from UC, and suggest a significant role for LXA(4) and AnxA1 in promoting mucosal homeostasis.

An ex vivo model of severe asthma using reconstituted human bronchial epithelium.

BACKGROUND: Structural changes to the airways are features of severe asthma. The bronchial epithelium facilitates this remodeling process. Learning about the changes that develop in the airway epithelium could improve our understanding of asthma pathogenesis and lead to new therapeutic approaches. OBJECTIVE: We sought to determine the feasibility and relevance of air-liquid interface cultures of bronchial epithelium derived from endobronchial biopsy specimens of patients with different severities of asthma for studying the airway epithelium. METHODS: Human bronchial epithelial cells derived from endobronchial biopsy specimens of patients with mild and severe asthma were maintained in culture for 21 days in an air-liquid interface to reproduce a fully differentiated airway epithelium. Initially, features of remodeling that included epithelial and subepithelial layers, as well as mucus production, were assessed in paraffin-embedded endobronchial biopsy specimens to evaluate morphologic characteristics of asthmatic patients' epithelia. Ex vivo differentiated epithelia were then analyzed for morphology and function based on ultrastructural analysis, IL-8 release, lipoxin A(4) generation, mucin production, and lipoxygenase gene expression. RESULTS: Morphologic and inflammatory imbalances initially observed in endobronchial biopsy specimens obtained from patients with severe or mild asthma persisted in the air-liquid interface reconstituted epithelium throughout the differentiation process to 21 days. Epithelium from patients with severe asthma produced greater levels of mucin, released more IL-8, and produced lower levels of lipoxin A(4) than that from patients with mild asthma. Expression of 15-lipoxygenase 2 was increased in epithelium from patients with severe asthma, whereas expression levels of MUC5AC, MUC5B, 5-lipoxygenase, and 15-lipoxygeanse 1 were similar to those of patients with mild asthma. CONCLUSION: Ex vivo cultures of fully differentiated bronchial epithelium from endobronchial biopsy specimens maintain inherent phenotypic differences specifically related to the severity of asthma.