u-75302 and Inflammation

Resolvin E1 (RvE1) is a potent anti-inflammatory and proresolving mediator derived from omega-3 eicosapentaenoic acid generated during the resolution phase of inflammation. RvE1 possesses a unique structure and counterregulatory actions that stop human polymorphonuclear leukocyte (PMN) transendothelial migration and PMN infiltration in several murine inflammatory models. To examine the mechanism(s) underlying anti-inflammatory actions on PMNs, we prepared [(3)H]RvE1 and characterized its interactions with human PMN. Results with membrane fractions of human PMN demonstrated specific binding with a K(d) of 48.3 nM. [(3)H]RvE1 specific binding to human PMN was displaced by leukotriene B(4) (LTB(4)) and LTB(4) receptor 1 (BLT1) antagonist U-75302, but not by chemerin peptide, a ligand specific for another RvE1 receptor ChemR23. Recombinant human BLT1 gave specific binding with [(3)H]RvE1 with a K(d) of 45 nM. RvE1 selectively inhibited adenylate cyclase with BLT1, but not with BLT2. In human PBMC, RvE1 partially induced calcium mobilization, and blocked subsequent stimulation by LTB(4). RvE1 also attenuated LTB(4)-induced NF-kappaB activation in BLT1-transfected cells. In vivo anti-inflammatory actions of RvE1 were sharply reduced in BLT1 knockout mice when given at low doses (100 ng i.v.) in peritonitis. In contrast, RvE1 at higher doses (1.0 mug i.v.) significantly reduced PMN infiltration in a BLT1-independent manner. These results indicate that RvE1 binds to BLT1 as a partial agonist, potentially serving as a local damper of BLT1 signals on leukocytes along with other receptors (e.g., ChemR23-mediated counterregulatory actions) to mediate the resolution of inflammation.

Topics: Animals; Calcium Signaling; Cell Movement; Chemokines; Dose-Response Relationship, Drug; Eicosapentaenoic Acid; Fatty Alcohols; Glycols; Humans; Inflammation; Intercellular Signaling Peptides and Proteins; Ligands; Mice; Mice, Knockout; Neutrophils; Peptides; Receptors, Chemokine; Receptors, Leukotriene B4

Leukotriene B4 (LTB4)-mediated leukocyte recruitment and inflammatory cytokine production make crucial contributions to chronic inflammation and sepsis; however, the role of LTB4 in lipopolysaccharide (LPS)-induced cardiac dysfunction remains unclear. Therefore, the present study addressed this issue using an LTB4 receptor 1 (BLT1) inhibitor. Administration of LPS to mice resulted in decreased cardiovascular function. Inhibition of LTB4/BLT1 with the BLT1 inhibitor U75302 significantly improved survival and attenuated the LPS-induced acute cardiac dysfunction. During LPS challenge, the phosphorylated AMPK/ACC signaling pathway was slightly activated, and this effect was enhanced by U75302. Additionally, pNF-κB, Bax and cleaved caspase-3 were upregulated by LPS, and Bcl-2, IκB-α, mitochondrial complex I, complex II, and OPA1 were downregulated; however, these effects were reversed by U75302. The results indicated that the BLT1 antagonist suppressed cardiac apoptosis, inflammation, and mitochondrial impairment. Furthermore, the protection provided by the BLT1 inhibitor against LPS-induced cardiac dysfunction was significantly reversed by the AMPK inhibitor Compound C. In conclusion, inhibiting the LTB4/BLT1 signaling pathway via AMPK activation is a potential treatment strategy for septic cardiac dysfunction because it efficiently attenuates cardiac apoptosis, which may occur via the inhibition of inflammation and mitochondrial dysfunction.

Topics: Acetyl-CoA Carboxylase; AMP-Activated Protein Kinases; Animals; Anti-Inflammatory Agents; bcl-2-Associated X Protein; Cardiomyopathies; Cardiotonic Agents; Caspase 3; Fatty Alcohols; Gene Expression Regulation; Glycols; I-kappa B Proteins; Inflammation; Leukotriene B4; Lipopolysaccharides; Male; Mice; Mice, Inbred C57BL; Mitochondria; NF-kappa B; Oxazines; Proto-Oncogene Proteins c-bcl-2; Receptors, Leukotriene B4; Signal Transduction; Survival Analysis

Leukotriene B4 (LTB4 ) is a lipid mediator that is rapidly generated in inflammatory sites, and its functional receptor, BLT1, is mostly expressed on immune cells. Contact dermatitis is a common inflammatory skin disease characterized by skin oedema and abundant inflammatory infiltrates, primarily including neutrophils and CD8(+) T cells. The role of the LTB4 -BLT1 axis in contact dermatitis remains largely unknown. In this study, we found up-regulated gene expression of 5-lipoxygenase and leukotriene A4 hydrolase, two critical enzymes for LTB4 synthesis, BLT1 and elevated LTB4 levels in skin lesions of oxazolone (OXA)-induced contact dermatitis. BLT1 deficiency or blockade of LTB4 and BLT1 by the antagonists, bestatin and U-75302, respectively, in the elicitation phase caused significant decreases in ear swelling and skin-infiltrating neutrophils and CD8(+) T cells, which was accompanied by significantly reduced skin expression of CXCL1, CXCL2, interferon-γ and interleukin-1β. Furthermore, neutrophil depletion during the elicitation phase of OXA-induced contact dermatitis also caused significant decreases in ear swelling and CD8(+) T-cell infiltration accompanied by significantly decreased LTB4 synthesis and gene expression of CXCL2, interferon-γ and interleukin-1β. Importantly, subcutaneous injection of exogenous LTB4 restored the skin infiltration of CD8(+) T cells in neutrophil-depleted mice following OXA challenge. Collectively, our results demonstrate that the LTB4 -BLT1 axis contributes to OXA-induced contact dermatitis by mediating skin recruitment of neutrophils, which are a major source of LTB4 that sequentially direct CD8(+) T-cell homing to OXA-challenged skin. Hence, LTB4 and BLT1 could be potential therapeutic targets for the treatment of contact dermatitis.

Topics: Animals; Arachidonate 5-Lipoxygenase; CD8-Positive T-Lymphocytes; Chemokine CXCL1; Chemokine CXCL2; Dermatitis, Contact; Epoxide Hydrolases; Fatty Alcohols; Female; Glycols; Inflammation; Interferon-gamma; Interleukin-1beta; Leucine; Leukotriene B4; Mice; Mice, Inbred C57BL; Mice, Knockout; Neutrophils; Oxazolone; Receptors, Leukotriene B4; Skin

We recently demonstrated that the T-helper type 1 (Th1) immune response plays an important role in the development of non-eosinophilic inflammation induced by airway exposure of an allergen plus double-stranded RNA (dsRNA). However, the role of lipoxygenase (LO) metabolites in the development of Th1 inflammation is poorly understood.. To evaluate the role of LO metabolites in the development of Th1 inflammation induced by sensitization with an allergen plus dsRNA.. A Th2-allergic inflammation mouse model was created by an intraperitoneal injection of lipopolysaccharide-depleted ovalbumin (OVA, 75 microg) and alum (2 mg) twice, and the Th1 model was created by intranasal application of OVA (75 microg) and synthetic dsRNA [10 microg of poly(I : C)] four times, followed by an intranasal challenge with 50 microg of OVA four times. The role of LO metabolites was evaluated using two approaches: a transgenic approach using 5-LO(-/-) and 15-LO(-/-) mice, and a pharmacological approach using inhibitors of cysteinyl leucotriene receptor-1 (cysLTR1), LTB4 receptor (BLT1), and 15-LO.. We found that the Th1-allergic inflammation induced by OVA+dsRNA sensitization was similar between 5-LO(-/-) and wild-type (WT) control mice, although Th2 inflammation induced by sensitization with OVA+alum was reduced in the former group. In addition, dsRNA-induced Th1 allergic inflammation, which is associated with down-regulation of 15-hydroxyeicosateraenoic acids production, was not affected by treatment with cysLTR1 or BLT1 inhibitors, whereas it was significantly lower in 12/15-LO(-/-) mice compared with WT control mice. Moreover, dsRNA-induced allergic inflammation and the recruitment of T cells following an allergen challenge were significantly inhibited by treatment with a specific 15-LO inhibitor (PD146176).. 15-LO metabolites appear to be important mediators in the development of Th1-allergic inflammation induced by sensitization with an allergen plus dsRNA. Our findings suggest that the 15-LO pathway is a novel therapeutic target for the treatment of virus-associated asthma characterized by Th1 inflammation.

Topics: Acetates; Allergens; Alum Compounds; Animals; Arachidonate 15-Lipoxygenase; Arachidonate 5-Lipoxygenase; Cyclopropanes; Disease Models, Animal; Fatty Alcohols; Fluorenes; Glycols; Hypersensitivity; Inflammation; Leukotriene Antagonists; Lipoxygenase Inhibitors; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Ovalbumin; Poly I-C; Quinolines; Receptors, Leukotriene; Receptors, Leukotriene B4; RNA, Double-Stranded; Sulfides; Th1 Cells; Th2 Cells

BLT1 and BLT2 were both recently cloned and identified as two subtypes of leukotrine B4 (LTB4) receptors. With the usage of U-75302 and LY255283, the specific antagonists of BLT1 and BLT2 respectively, the involvement of BLT1 and BLT2 in the inflammatory and immunological responses was in vitro explored.. (1) To investigate inhibition of U-75302 and LY255283 on the proliferation of rat synovial cells, 3H-TdR incorporation into the cells was quantified. (2) Flow cytometric assay for interferon-gamma (IFN-gamma) and interleukine 4 (IL-4) profiles in CD4+ T lymphocytes from rat spleen was carried out to determine the ratio of Th1/Th2.. (1) For inhibition on rat synovial cells proliferation, U-75302 exerted its effect only at a high concentration of 10 micromol/L and LY255283 at the concentrations of 10 micromol/L-10 micromol/L. (2) Both U-75302 and LY255283 could elevate the percentage of Th2, but could not influence that of Th1.. BLT1 and BLT2 were involved in the synovial cells proliferation change the ratio of Th1/Th2. Their meaning served as targets for prevention and treatment of infectious diseases should be emphasized.

Topics: Animals; Cell Line; Cell Proliferation; Fatty Alcohols; Glycols; Inflammation; Male; Rats; Rats, Wistar; Receptors, Leukotriene B4; Synovial Membrane; Tetrazoles; Th1-Th2 Balance