n-3 Polyunsaturated Fatty Acids Modulate LPS-Induced ARDS and the Lung-Brain Axis of Communication in Wild-Type versus Fat-1 Mice Genetically Modified for Leukotriene B4 Receptor 1 or Chemerin Receptor 23 Knockout.

Specialized pro-resolving mediators (SPMs) and especially Resolvin E1 (RvE1) can actively terminate inflammation and promote healing during lung diseases such as acute respiratory distress syndrome (ARDS). Although ARDS primarily affects the lung, many ARDS patients also develop neurocognitive impairments. To investigate the connection between the lung and brain during ARDS and the therapeutic potential of SPMs and its derivatives, fat-1 mice were crossbred with RvE1 receptor knockout mice. ARDS was induced in these mice by intratracheal application of lipopolysaccharide (LPS, 10 µg). Mice were sacrificed at 0 h, 4 h, 24 h, 72 h, and 120 h post inflammation, and effects on the lung, liver, and brain were assessed by RT-PCR, multiplex, immunohistochemistry, Western blot, and LC-MS/MS. Protein and mRNA analyses of the lung, liver, and hypothalamus revealed LPS-induced lung inflammation increased inflammatory signaling in the hypothalamus despite low signaling in the periphery. Neutrophil recruitment in different brain structures was determined by immunohistochemical staining. Overall, we showed that immune cell trafficking to the brain contributed to immune-to-brain communication during ARDS rather than cytokines. Deficiency in RvE1 receptors and enhanced omega-3 polyunsaturated fatty acid levels (fat-1 mice) affect lung-brain interaction during ARDS by altering profiles of several inflammatory and lipid mediators and glial activity markers.

Leukotriene receptors as potential therapeutic targets.

Leukotrienes, a class of arachidonic acid-derived bioactive molecules, are known as mediators of allergic and inflammatory reactions and considered to be important drug targets. Although an inhibitor of leukotriene biosynthesis and antagonists of the cysteinyl leukotriene receptor are clinically used for bronchial asthma and allergic rhinitis, these medications were developed before the molecular identification of leukotriene receptors. Numerous studies using cloned leukotriene receptors and genetically engineered mice have unveiled new pathophysiological roles for leukotrienes. This Review covers the recent findings on leukotriene receptors to revisit them as new drug targets.

The yin and yang of leukotriene B4 mediated inflammation in cancer.

The high affinity leukotriene B4 receptor, BLT1 mediates chemotaxis of diverse leukocyte subsets to the sites of infection or inflammation. Whereas the pathological functions of LTB4/BLT1 axis in allergy, autoimmunity and cardiovascular disorders are well established; its role in cancer is only beginning to emerge. In this review, we summarize recent findings on LTB4/BLT1 axis enabling distinct outcomes toward tumor progression. In a mouse lung tumor model promoted by silicosis-induced inflammation, genetic deletion of BLT1 attenuated neutrophilic inflammation and tumor promotion. In contrast, in a spontaneous model of intestinal tumorigenesis, absence of BLT1 led to defective mucosal host response, altered microbiota and bacteria dependent colon tumor progression. Furthermore, BLT1 mediated CD8+ T cell recruitment was shown to be essential for initiating anti-tumor immunity in number of xenograft models and is critical for effective PD1 based immunotherapy. BLT2 mediated chemotherapy resistance, tumor promotion and metastasis are also discussed. This new information points to a paradigm shift in our understanding of the LTB4 pathways in cancer.

In vivo modulation of LPS induced leukotrienes generation and oxidative stress by sesame lignans.

The role of inflammation and oxidative stress is critical during onset of metabolic disorders and this has been sufficiently established in literature. In the present study, we evaluated the effects of sesamol and sesamin, two important bioactive molecules present in sesame oil, on the generation of inflammatory and oxidative stress factors in LPS injected rats. Sesamol and sesamin lowered LPS induced expression of cPLA2 (61 and 56%), 5-LOX (44 and 51%), BLT-1(32 and 35%) and LTC4 synthase (49 and 50%), respectively, in liver homogenate. The diminished serum LTB4 (53 and 64%) and LTC4 (67 and 44%) levels in sesamol and sesamin administered groups, respectively, were found to be concurrent with the observed decrease in the expression of cPLA2 and 5-LOX. The serum levels of TNF-α (29 and 19%), MCP-1 (44 and 57%) and IL-1ß (43 and 42%) were found to be reduced in sesamol and sesamin group, respectively, as given in parentheses, compared to LPS group. Sesamol and sesamin offered protection against LPS induced lipid peroxidation in both serum and liver. Sesamol, but not sesamin, significantly restored the loss of catalase and glutathione reductase activity due to LPS (P<.05). However, both sesamol and sesamin reverted SOD activities by 92 and 98%, respectively. Thus, oral supplementation of sesamol and sesamin beneficially modulated the inflammatory and oxidative stress markers, as observed in the present study, in LPS injected rats. Our report further advocates the potential use of sesamol and sesamin as an adjunct therapy wherein, inflammatory and oxidative stress is of major concern.

Critical Role of LTB4/BLT1 in IL-23-Induced Synovial Inflammation and Osteoclastogenesis via NF-κB.

IL-23 activates the synthesis and production of leukotriene B4 (LTB4) in myeloid cells, which modulate inflammatory arthritis. In this study we investigated the role of LTB4 and its receptor LTB4R1 (BLT1) in synovial inflammation and osteoclast differentiation. Specifically, we used IL-23 in vivo gene transfer to induce arthritis in mice and showed that elevated serum LTB4 and synovial expression of 5-lipoxygenase correlated with increased disease severity by histological evaluation and paw swelling compared with GFP gene transfer controls. To further investigate the effect of the LTB4 pathway in bone loss, we performed osteoclast differentiation assays by stimulating with M-CSF and receptor activator of NF-κB ligand bone marrow cells derived from BLT1+/+ and/or BLT1-/- mice and used quantitative PCR for gene expression analysis in terminally differentiated osteoclasts. Deficiency in BLT1 resulted in the upregulation of osteoclast-related genes and an increase in the formation of giant, multinucleated TRAP+ cells capable of F-actin ring formation. Additionally, BLT1 deficiency showed an increase of phosphorylated NF-κB and phosphorylated IκB levels in osteoclasts. We also performed real-time calcium imaging to study the effect of BLT1 deficiency in receptor activator of NF-κ-B ligand-induced activation of intracellular calcium flux in vitro. Our data show that LTB4 and its receptor BLT1 exacerbate synovial inflammation in vivo and bone resorption in vitro, suggesting that LTB4 and BLT1 could be effectively targeted for the treatment of musculoskeletal diseases.

Anti-inflammatory action of ethanolic extract of Ramulus mori on the BLT2-linked cascade.

Mulberry tree twigs (Ramulus mori) contain large amounts of oxyresveratrols and have traditionally been used as herbal medicines because of their anti-inflammatory properties. However, the signaling mechanism by which R. mori exerts its anti-inflammatory action remains to be elucidated. In this study, we observed that R. mori ethanol extracts (RME) exerted an inhibitory effect on the lipopolysaccharide (LPS)-induced production of the pro-inflammatory cytokine interleukin-6 (IL-6) in Raw264.7 macrophage cells. Additionally, RME inhibited IL-6 production by blocking the leukotriene B4 receptor- 2 (BLT2)-dependent-NADPH oxidase 1 (NOX1)-reactive oxygen species (ROS) cascade, leading to anti-inflammatory activity. Finally, RME suppressed the production of the BLT2 ligands LTB4 and 12(S)-HETE by inhibiting the p38 kinase- cytosolic phospholipase A2-5-/12-lipoxygenase cascade in LPS-stimulated Raw264.7 cells. Overall, our results suggest that RME inhibits the 'BLT2 ligand-BLT2'-linked autocrine inflammatory axis, and that this BLT2-linked cascade is one of the targets of the anti-inflammatory action of R. mori. [BMB Reports 2016; 49(4): 232-237].

Leukotriene production profiles and actions in the bovine endometrium during the oestrous cycle.

We have previously shown the influence of leukotrienes (LTs) on reproductive functions in vivo: LTB4 is luteotrophic and supports corpus luteum function inducing PGE2 and progesterone (P4) secretion, whereas LTC4 is luteolytic and stimulates PGF2α secretion in cattle. The aim of this study was to examine expression and production profiles of LTs and their actions in the endometrium. LT receptors (LTB4R for LTB4 and CysLTR2 for LTC4), 5-lipoxygenase (LO), 12-LO synthase (LTCS) and LTA4 hydrolase (LTAH) mRNA and protein expression, as well as LT production were measured in bovine endometrial tissue during the luteal phases of the oestrous cycle. The action of LTs on uterine function was studied by measuring the level of PGs after stimulating uterine slices with LTs on Days 8-10 of the cycle. Expression of 5-LO and LTB4R mRNA and protein were highest on Days 2-4 of the cycle, while CysLTR2 and LTCS were highest on Days 16-18 (P<0.05). LTB4 concentration was highest on Days 2-4 of the cycle, whereas the greatest LTC4 level was on Days 16-18 (P<0.05). Both LTB4 and C4 increased the content of PGE2 and F2α in endometrial slices at a dose of 10(-7)M (P<0.05). In summary, mRNA expression and activation of receptors for LTB4 and production occur in the first part of the cycle, whereas LTC4 and its receptors predominate at the end of the cycle. The 12-LO and 5-LO pathways are complementary routes of LT production in the bovine uterus.

DanQi Pill protects against heart failure through the arachidonic acid metabolism pathway by attenuating different cyclooxygenases and leukotrienes B4.

BACKGROUND: Chinese herbal formulae are composed of complex components and produce comprehensive pharmacological effects. Unlike chemical drugs that have only one clear single target, the components of Chinese herbal formulae have multiple channels and targets. How to discover the pharmacological targets of Chinese herbal formulae and their underlying molecular mechanism are still under investigation. METHODS: DanQi pill (DQP), which is one of the widely prescribed traditional Chinese medicines, is applied as an example drug. In this study, we used the drug target prediction model (DrugCIPHER-CS) to examine the underlying molecular mechanism of DQP, followed by experimental validation. RESULTS: A novel therapeutic effect pattern of DQP was identified. After determining the compounds in DQP, we used DrugCIPHER-CS to predict their potential targets. These potential targets were significantly enriched in well-known cardiovascular disease-related pathways. For example, the biological processes of neuroactive ligand-receptor interaction, calcium-signaling pathway, and aminoacyl-tRNA biosynthesis were involved. A new and significant pathway, arachidonic acid (AA) metabolism, was also identified in this study. This predicted pathway alteration was validated with an animal model of heart failure (HF). Results show that DQP had effect both on thromboxane B2 (TXB2) and Prostaglandin I2 (PGI2) in different patterns. It can down-regulate the TXB2 and up-regulate the PGI2 in diverse way. Remarkably, it also had effect on cyclooxygenase (COX)-1 and COX2 by suppressing their levels, which may be the critical and novel mechanism of cardiacprotective efficacy for DQP. Furthermore, leukotrienes B4 (LTB4) receptor, another key molecule of AA metabolism which finally mediated gastrotoxic leukotrienes, was also reduced by DQP. CONCLUSIONS: The combination of drug target prediction and experimental validation provides new insights into the complicated mechanism of DQP.

Effect of a low-fat fish oil diet on proinflammatory eicosanoids and cell-cycle progression score in men undergoing radical prostatectomy.

We previously reported that a 4- to 6-week low-fat fish oil (LFFO) diet did not affect serum insulin-like growth factor (IGF)-1 levels (primary outcome) but resulted in lower omega-6 to omega-3 fatty acid ratios in prostate tissue and lower prostate cancer proliferation (Ki67) as compared with a Western diet. In this post hoc analysis, the effect of the LFFO intervention on serum pro-inflammatory eicosanoids, leukotriene B4 (LTB4) and 15-S-hydroxyeicosatetraenoic acid [15(S)-HETE], and the cell-cycle progression (CCP) score were investigated. Serum fatty acids and eicosanoids were measured by gas chromatography and ELISA. CCP score was determined by quantitative real-time reverse transcriptase PCR (RT-PCR). Associations between serum eicosanoids, Ki67, and CCP score were evaluated using partial correlation analyses. BLT1 (LTB4 receptor) expression was determined in prostate cancer cell lines and prostatectomy specimens. Serum omega-6 fatty acids and 15(S)-HETE levels were significantly reduced, and serum omega-3 levels were increased in the LFFO group relative to the Western diet group, whereas there was no change in LTB4 levels. The CCP score was significantly lower in the LFFO compared with the Western diet group. The 15(S)-HETE change correlated with tissue Ki67 (R = 0.48; P < 0.01) but not with CCP score. The LTB4 change correlated with the CCP score (r = 0.4; P = 0.02) but not with Ki67. The LTB4 receptor BLT1 was detected in prostate cancer cell lines and human prostate cancer specimens. In conclusion, an LFFO diet resulted in decreased 15(S)-HETE levels and lower CCP score relative to a Western diet. Further studies are warranted to determine whether the LFFO diet antiproliferative effects are mediated through the LTB4/BLT1 and 15(S)-HETE pathways.

Cigarette smoke increases BLT2 receptor functions in bronchial epithelial cells: in vitro and ex vivo evidence.

Leukotriene B(4) (LTB(4)) is a neutrophil chemotactic molecule with important involvement in the inflammatory responses of chronic obstructive pulmonary disease (COPD). Airway epithelium is emerging as a regulator of innate immune responses to a variety of insults including cigarette smoke, the major risk factor for COPD. In this study we have explored whether cigarette smoke extracts (CSE) or soluble mediators present in distal lung fluid samples (mini-bronchoalveolar lavages) from smokers alter the expression of the LTB(4) receptor 2 (BLT2) and peroxisome proliferator-activated receptor-α (PPAR-α) in bronchial epithelial cells. We also evaluated the effects of CSE on the expression of intercellular adhesion molecule 1 (ICAM-1) and on the binding of signal transducer and activator of transcription 1 (STAT-1) to ICAM-1 promoter as well as the adhesiveness of neutrophils to bronchial epithelial cells. CSE and mini-bronchoalveolar lavages from smokers increased BLT2 and ICAM-1 expression as well as the adhesiveness of neutrophils to bronchial epithelial cells and decreased PPAR-α expression. CSE induced the activation of STAT-1 and its binding to ICAM-1 promoter. These findings suggest that, in bronchial epithelial cells, CSE promote a prevalent induction of pro-inflammatory BLT2 receptors and activate mechanisms leading to increased neutrophil adhesion, a mechanism that contributes to airway neutrophilia and to tissue damage.

Nonredundant roles for leukotriene B4 receptors BLT1 and BLT2 in inflammatory arthritis.

Lipid mediators derived from arachidonic acid through the cyclooxygenase and lipoxygenase pathways are known to be important mediators of inflammation. Studies in mouse models demonstrated an important role for the high-affinity leukotriene B(4) receptor BLT1 in arthritis, atherosclerosis, and asthma. BLT2, a low-affinity leukotriene B(4) receptor, was also shown to be a high-affinity receptor for cyclooxygenase-1 derived 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid. However, its biochemical activities and physiological roles remain unknown. In this study, we developed mice deficient in BLT2 by targeted disruption. The BLT2(-/-) mice developed normally, and analysis of immune cells showed that disruption of BLT2 did not alter BLT1 expression or function. Mast cells from the C57BL/6 mice but not from the BLT2(-/-) mice showed intracellular calcium mobilization in response to 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid. In an autoantibody-induced inflammatory arthritis model, the BLT2(-/-) mice showed reduced incidence and severity of disease, including protection from bone and cartilage loss. Reciprocal bone marrow transplant experiments identified that loss of BLT2 expression on a bone marrow-derived cell lineage offers protection against severe disease. Thus, BLT2, a unique receptor for 5-lipoxygenase- and cyclooxygenase-1-derived lipid mediators, represents a novel target for therapies directed at treating inflammation associated with arthritis.

Intracerebroventricular injection of leukotriene B4 attenuates antigen-induced asthmatic response via BLT1 receptor stimulating HPA-axis in sensitized rats.

BACKGROUND: Basic and clinical studies suggest that hypothalamic-pituitary-adrenal (HPA) axis is the neuroendocrine-immune pathway that functionally regulates the chronic inflammatory disease including asthma. Our previous studies showed corresponding changes of cytokines and leukotriene B4 (LTB4) between brain and lung tissues in antigen-challenged asthmatic rats. Here, we investigated how the increased LTB4 level in brain interacts with HPA axis in regulating antigen-induced asthmatic response in sensitized rats. METHODS: Ovalbumin-sensitized rats were challenged by inhalation of antigen. Rats received vehicle, LTB4 or U75302 (a selective LTB4 BLT1 receptor inhibitor) was given via intracerebroventricular injection (i.c.v) 30 min before challenge. Lung resistance (RL) and dynamic lung compliance (Cdyn) were measured before and after antigen challenge. Inflammatory response in lung tissue was assessed 24 h after challenge. Expression of CRH mRNA and protein in hypothalamus were evaluated by RT-PCR and Western Blot, and plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were measured using the ELISA kits. RESULTS: Antigen challenge decreased pulmonary function and induced airway inflammation, evoked HPA axis response in sensitized rats. Administration of LTB4 via i.c.v markedly attenuated airway contraction and inflammation. Meanwhile, LTB4 via i.c.v markedly increased CORT and ACTH level in plasma before antigen challenge, and followed by further increases in CORT and ACTH levels in plasma after antigen challenge in sensitized rats. Expression of CRH mRNA and protein in hypothalamus were also significantly increased by LTB4 via i.c.v in sensitized rats after antigen challenge. These effect were completely blocked by pre-treatment with BLT1 receptor antagonist U75302 (10 ng), but not by BLT2 antagonist LY255283. CONCLUSIONS: LTB4 administered via i.c.v down-regulates the airway contraction response and inflammation through activation of the HPA axis via its BLT1 receptor. This study expands our concept of the regulatory role of intracranial inflammatory mediators in inflammatory diseases including asthma. The favourable effects of LTB4 on the HPA axis may help to explain the phenomenon of self-relief after an asthmatic attack.

Discovery of novel and potent leukotriene B4 receptor antagonists. Part 1.

The inhibition of LTB(4) binding to and activation of G-protein-coupled receptors BLT1 and BLT2 is the premise of a treatment for several inflammatory diseases. In a lead optimization effort starting with the leukotriene B(4) (LTB(4)) receptor antagonist (2), members of a series of 3,5-diarylphenyl ethers were found to be highly potent inhibitors of LTB(4) binding to BLT1 and BLT2 receptors, with varying levels of selectivity depending on the substitution. In addition, compounds 33 and 38 from this series have good in vitro ADME properties, good oral bioavailability, and efficacy after oral delivery in guinea pig LTB(4) and nonhuman primate allergen challenge models. Further profiling in a rat non-GLP toxicity experiment provided the rationale for differentiation and selection of one compound (33) for clinical development.

Resolvin E1 as a novel agent for the treatment of asthma.

BACKGROUND: Asthma is characterized by airway hyperresponsiveness and chronic airway inflammation. Inflammatory cells, including eosinophils and lymphocytes, infiltrate peribronchial tissue in patients with asthma. Resolvin E1 (RvE1) is an anti-inflammatory lipid mediator derived from the omega-3 fatty acid, eicosapentaenoic acid, and has been shown to be involved in resolving inflammation. Although little is known about the actions of RvE1 in the resolution of inflammation due to asthma, recent studies in a mouse model have shown the possibilities of RvE1 in asthma. OBJECTIVE/METHODS: We review the current understanding of the mechanism of RvE1 action in connection with asthma pathogenesis and treatment. RESULTS/CONCLUSION: Findings provide evidence for the use of RvE1 as a pivotal counter-regulatory signal in allergic inflammation and offer the possibility of novel multi-pronged therapeutic approaches for human asthma.

The role of leukotriene B(4) in allergic diseases.

Leukotriene B(4) (LTB(4)) is a lipid mediator with potent chemoattractant properties and that is rapidly generated from activated innate immune cells such as neutrophils, macrophages, and mast cells. Elevated levels of LTB(4) have been reported in various allergic diseases and these levels have been related to disease activity and response to treatment. Recent studies using LTB(4) receptor-1 (BLT1) antagonists or BLT1-deficient mice have revealed that ligation of BLT1 by LTB(4) is important for the activation and recruitment of inflammatory cells including neutrophils, eosinophils, monocytes/macrophages, mast cells, dendritic cells, and more recently, effector T cells to inflamed tissues in various inflammatory diseases. The LTB(4)/BLT1 pathway appears to play an important role in the pathogenesis of severe persistent asthma, aspirin- and exercise-induced asthma, allergic rhinitis, and atopic dermatitis together with other mediators including cysteinyl leukotrienes, cytokines, and chemokines. LTB(4) production is in general resistant to corticosteroid treatment. In fact, corticosteroids can upregulate BLT1 expression on corticosteroid-resistant inflammatory cells such as neutrophils, monocytes, and effector memory CD8+ T cells. As a result, this corticosteroid-resistant LTB(4)/BLT1 pathway may contribute to the development of inflammation in allergic diseases that do not respond to the introduction of corticosteroids. Inhibition of this pathway has potential therapeutic benefit in various allergic diseases that have involvement of corticosteroid-insensitivity.

Involvement of the BLT2 receptor in the itch-associated scratching induced by 12-(S)-lipoxygenase products in ICR mice.

BACKGROUND AND PURPOSE: Recently, we reported that 12(S)-HPETE (12(S)-hydroperoxyeicosa-5Z,8Z,10E,14Z-tetraenoic acid) induces scratching in ICR mice. We hypothesized that 12(S)-HPETE might act as an agonist of the low-affinity leukotriene B4 receptor BLT2. To confirm the involvement of the BLT2 receptor in 12(S)-HPETE-induced scratching, we studied the scratch response using the BLT2 receptor agonists compound A (4'-[[pentanoyl (phenyl) amino]methyl]-1,1'-biphenyl-2-carboxylic acid) and 12(S)-HETE (12(S)-hydroxyeicosa-5Z,8Z,10E,14Z-tetraenoic acid). EXPERIMENTAL APPROACH: A video recording was used to determine whether the BLT2 receptor agonists caused itch-associated scratching in ICR mice. Selective antagonists and several chemicals were used. KEY RESULTS: Both 12(S)-HETE and compound A dose dependently induced scratching in the ICR mice. The dose-response curve for compound A showed peaks at around 0.005-0.015 nmol per site. Compound A- and 12(S)-HETE-induced scratching was suppressed by capsaicin and naltrexon. We examined the suppressive effects of U75302 (6-[6-(3-hydroxy-1E,5Z-undecadienyl)-2-pyridinyl]-1,5-hexanediol, the BLT1 receptor antagonist) and LY255283 (1-[5-ethyl-2-hydroxy-4-[[6-methyl-6-(1H-tetrazol-5-yl)heptyl]oxy]phenyl]-ethanone, the BLT2 receptor antagonist) on the BLT2 agonist-induced scratching. LY255283 suppressed compound A- and 12(S)-HETE-induced scratching, but U75302 did not. LY255283 required a higher dose to suppress the compound A-induced scratching than it did to suppress the 12(S)-HETE-induced scratching. One of the BLT(2) receptor agonists, 12(R)-HETE (12(R)-hydroxyeicosa-5Z,8Z,10E,14Z-tetraenoic acid), also induced scratching in the ICR mice. CONCLUSIONS AND IMPLICATIONS: Our present results corroborate the hypothesis that the BLT2 receptor is involved in 12(S)-lipoxygenase-product-induced scratching in ICR mice. We also confirmed that this animal model could be a valuable means of evaluating the effects of BLT2 receptor antagonists.

Corticosteroids enhance CD8+ T cell-mediated airway hyperresponsiveness and allergic inflammation by upregulating leukotriene B4 receptor 1.

BACKGROUND: Leukotriene B4 (LTB4) is a potent inflammatory lipid mediator that binds to LTB4 receptor 1 (BLT1). Ligation of BLT1 by LTB4 plays an important role in the recruitment of effector memory CD8+ T cells into the airways of sensitized and challenged mice. OBJECTIVES: The effects of the corticosteroid dexamethasone (DEX) on BLT1-expressing effector memory CD8+ T cells and effector memory CD8+ T cell-mediated airway hyperresponsiveness (AHR) and allergic inflammation were determined. METHODS: Effector memory CD8+ T cells were generated from ovalbumin(257-264)-primed mononuclear cells from OT-1 mice in the presence of IL-2. In some cultures DEX was added. The effects of DEX on BLT1 expression, LTB4-induced Ca2+ influx, phosphorylation of extracellular signal-regulated kinase 1/2, chemotaxis, and effector memory CD8+ T cell-mediated AHR were examined. RESULTS: DEX-treated effector memory CD8+ T cells showed significant increases in surface expression of BLT1, LTB4-induced intracellular Ca2+ influx, phosphorylation of extracellular signal-regulated kinase 1/2, and chemotaxis. Upregulation of BLT1 by DEX was accompanied by increased IL-2 receptor expression. Adoptive transfer of DEX-treated effector memory CD8+ T cells into ovalbumin-sensitized and ovalbumin-challenged CD8-/- mice resulted in significant increases in AHR, allergic inflammation, goblet cell metaplasia, and numbers of both CD8+ and CD4+ T cells in the bronchoalveolar lavage fluid and lungs. CONCLUSIONS: Corticosteroids upregulate BLT1 on effector memory CD8+ T cells and related signaling pathways and potentiate allergic airway inflammation and AHR induced by these cells.

Preparation of 2-, 3-, 4- and 7-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans and their BLT1 and/or BLT2 inhibitory activities.

Several 2-alkylcarbamoyl-1-alkylvinylbenzo[b]furans were designed to find a selective leukotriene B4 (LTB4) receptor antagonist. 2-(2-Alkylcarbamoyl-1-alkylvinyl)benzo[b]furans having a substituent group at the 3-position, 4-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans having a substituent group at the 3-position, and 7-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans and 3-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans were prepared and evaluated for LTB4 receptor (BLT1 and BLT2) inhibitory activities. (E)-3-Amino-4-[2-[2-(3,4-dimethoxyphenyl)ethylcarbamoyl]-1-methylvinyl]benzo[b]furan ((E)-17c) showed potent and selective inhibitory activity for BLT2. On the other hand, (E)-7-(2-diethylcarbamoyl-1-methylvinyl)benzo[b]furan ((E)-27a) showed potent inhibitory activity for both BLT1 and BLT2.

Leukotriene B4 receptor antagonists as therapeutics for inflammatory disease: preclinical and clinical developments.

Leukotriene B(4) (LTB(4)) is a lipid inflammatory mediator derived from membrane phospholipids by the sequential actions of cytosolic phospholipase A2 (PLA2), 5-lipoxygenase (5-LO) and leukotriene A(4) (LTA(4)) hydrolase. Several inflammatory diseases, including asthma, chronic obstructive pulmonary disease, arthritis and inflammatory bowel disease, have been associated with elevated levels of LTB(4). As a result, pharmacological strategies to modulate the synthesis of LTB(4) (inhibition of PLA2, 5-LO or LTA(4) hydrolase) or the effects of LTB(4) itself (antagonism of LTB(4) receptors) are being developed by several companies. Two G-protein-coupled receptors mediate the effects of LTB(4), namely BLT1 and BLT2. The pharmacology, expression and function of these two receptors were last reviewed by Tager and Luster in 2004. Since then, there has been an increased understanding of the function of these receptors, in particular for the lesser understood of the two receptors, BLT2. Furthermore, since last reviewed in 1996, there have been several clinical developments in the use of BLT receptor antagonists for inflammatory diseases. This review summarizes the latest preclinical and clinical developments in BLT antagonism for inflammatory diseases and discusses potential future developments.

House dust mite allergen activates human eosinophils via formyl peptide receptor and formyl peptide receptor-like 1.

The objective was to evaluate which receptors house dust mite (HDM) and birch pollen extracts engage to activate human eosinophils. Chemotaxis and degranulation were studied in eosinophils pretreated with pertussis toxin and other antagonists of G protein-coupled receptors, e.g. the formyl peptide receptor (FPR), CC chemokine receptor 3 (CCR3) and leukotriene receptor B4 (LTB(4)R). Inhibition of the FPR as well as desensitization of the receptor rendered eosinophils anergic to activation by the allergens. Blockade of CCR3 or LTB(4)R did not affect eosinophilic reactivity. It was determined by PCR that human eosinophils express the FPR family members FPR and FPR-like 1 (FPRL1). HDM, unlike birch pollen, evoked calcium fluxes in HL-60 cells transfected with FPR or FPRL1. Although both allergens gave rise to calcium transients in neutrophils, which also express FPR and FPRL1, only the HDM response was decreased by the FPR antagonist. Moreover, neutrophils migrated toward HDM but not to birch pollen. Eosinophils pretreated with inhibitors of MAPK p38, ERK1/2 or protein kinase C exhibited diminished responsiveness to the aeroallergens. This study indicates that FPR and FPRL1 mediate the activation of eosinophils by HDM, whereas birch pollen employs other pathways shared with FPR to activate human eosinophils.