Leukotriene B4: Metabolism and Signal Transduction

Yokomizo, Takehiko; Izumi, Tohru; Shimizu, Takao

doi:10.1006/abbi.2000.2168

Cited by 207 publications

(186 citation statements)

References 104 publications

Supporting

Mentioning

178

Contrasting

Unclassified

Order By: Relevance

“…In granulocytes and some cell lines, BLT1 was shown to transduce intracellular signals through the Gi-and G16-classes of G proteins, which inhibit cAMP production and raise the intracellular calcium concentration (5). However, the BLT1-dependent signaling pathways in osteoclasts were largely unknown.…”

Section: Discussionmentioning

confidence: 99%

“…We previously cloned two distinct BLTs, BLT1 and BLT2 (3,4). BLT1 is a high-affinity receptor that mediates the inhibition of adenylate cyclase and calcium entry by coupling with the Gi-and Gq-classes of G proteins (5). BLT2 transduces comparable intracellular signals but has a lower affinity to LTB 4 (5).…”

mentioning

confidence: 99%

“…BLT1 is a high-affinity receptor that mediates the inhibition of adenylate cyclase and calcium entry by coupling with the Gi-and Gq-classes of G proteins (5). BLT2 transduces comparable intracellular signals but has a lower affinity to LTB 4 (5). Although several hydroxyeicosatetraenoic acids were found to activate BLT2 (6), we recently identified 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid (12-HHT) as a very potent endogenous ligand for BLT2 (7).…”

mentioning

confidence: 99%

See 2 more Smart Citations

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss

Hikiji

Ishii

Yokomizo

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

Although leukotriene B4 (LTB4) is produced in various inflammatory diseases, its functions in bone metabolism remain unknown. Using mice deficient in the high-affinity LTB4 receptor BLT1, we evaluated the roles of BLT1 in the development of two bone resorption models, namely bone loss induced by ovariectomy and lipopolysaccharide. Through observations of bone mineral contents and bone morphometric parameters, we found that bone resorption in both models was significantly attenuated in BLT1-deficient mice. Furthermore, osteoclasts from BLT1-deficient mice showed reduced calcium resorption activities compared with wild-type osteoclasts. Osteoclasts expressed BLT1, but not the low-affinity LTB4 receptor BLT2, and produced LTB4. LTB4 changed the cell morphology of osteoclasts through the BLT1-Gi protein-Rac1 signaling pathway. Given the causal relationship between osteoclast morphology and osteoclastic activity, these findings suggest that autocrine/paracrine LTB4 increases the osteoclastic activity through the BLT1-Gi protein-Rac1 signaling pathway. Inhibition of BLT1 functions may represent a strategy for preventing bone resorption diseases.bone remodeling ͉ G protein-coupled receptor ͉ knockout mice ͉ lipid mediator ͉ osteoporosis ͉ L eukotriene B 4 (LTB 4 ), a metabolite of arachidonic acid, is a potent lipid mediator with various biological activities toward neutrophils and differentiated T cells, including chemotaxis, degranulation, and production of superoxide anions (1, 2). These actions of LTB 4 are mediated by specific cell surface receptors (BLTs). We previously cloned two distinct BLTs, BLT1 and BLT2 (3,4). BLT1 is a high-affinity receptor that mediates the inhibition of adenylate cyclase and calcium entry by coupling with the Gi-and Gq-classes of G proteins (5). BLT2 transduces comparable intracellular signals but has a lower affinity to LTB 4 (5). Although several hydroxyeicosatetraenoic acids were found to activate BLT2 (6), we recently identified 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid (12-HHT) as a very potent endogenous ligand for BLT2 (7). LTB 4 is produced in inf lammatory diseases such as psoriasis (8), bronchial asthma (9), ulcerative colitis (10), postischemic tissue injuries (11), and rheumatoid arthritis (12-15).Bone remodeling consists of old bone resorption by osteoclasts and new bone deposition by osteoblasts. Osteoclasts and osteoblasts participate in bone remodeling under the control of many hormones, cytokines (16,17), and autacoids, including lipid mediators (18). The effects of LTB 4 on bone resorption were investigated using organ cultures of mouse calvariae (19,20). LTB 4 enhanced calcium efflux from the mouse calvariae, suggesting that LTB 4 stimulates bone resorption (19). LTB 4 increased the formation of resorption pits by osteoclasts in rat bone tissues (20), suggesting that LTB 4 modulates bone resorption by increasing the number and/or activity of osteoclasts. However, few reports have provided definitive biochemical information about the mRNA/protein expression and ...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss

Hikiji

Ishii

Yokomizo

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…LTB4R2 is closely related to its mouse homolog with 93% identity. The close location of these genes indicates that they are likely to be the result of gene duplication (87). LTB 4 R1 and LTB 4 R2 show high homology in transmembrane domains 3 and 7 suggesting that this is the site for LTB 4 binding (85).…”

Section: Ltb 4 Receptorsmentioning

confidence: 99%

Leukotriene pathway genetics and pharmacogenetics in allergy

Duroudier

Tulah

Sayers

2009

Allergy

100

View full text Add to dashboard Cite

Leukotrienes (LT) are a family of potent eicosanoid lipid mediators with central importance in disease processes such as inflammation and proliferation most notably observed in allergic conditions like asthma (1). There are two general classes of LT according to the presence of a cysteine residue in their amino acid chain: the cysteinyl leukotrienes (CysLTs) including LTC 4 , LTD 4 and LTE 4 and the dihydroxyleukotriene LTB 4 (2). The 5-lipoxygenase pathwayLeukotrienes are produced in a multi-step enzyme pathway called the 5-lipoxygenase (5-LO) pathway, which is active in leucocytes such as neutrophils, eosinophils, mast cells and monocytes (Fig. 1). Arachidonic acid is the precursor for LT synthesis and is hydrolysed from the plasma membrane by cytosolic phospholipase A 2 (and other isoforms) (3, 4) in a calcium-dependent process (5). Upon activation, the rate-limiting enzyme 5-LO oxygenates first free arachidonic acid into the unstable intermediate 5-hydroperoxyeicosatetraenoic acid (5-HPETE) which is then either hydrolysed to 5-hydroxyeicosatetraenoic acid (5-HETE) or transformed into the unstable epoxide leukotriene A 4 (LTA 4 ) by forming a conjugated triene system through dehydration (6). 5-LO translocates from either the nucleus (in macrophages) or cyotosol (in neutrophils) to the nuclear envelope in response to cell activation (7,8). This movement occurs as 5-LO is dependent on a 5-LO activating protein (FLAP) for its function. FLAP remains associated with the nuclear membrane (9) and acts as a Ôtransfer proteinÕ presenting arachidonic acid to 5-LO, a system which allows the favourable conversion of 5-HPETE to LTA 4 compared to 5-HETE (10). Both 5-LO and FLAP are expressed in cells of myeloid lineage (11) restricting the pathway to these cell types. LTA 4 can be further metabolised to the cysteinyl leukotrienes (CysLTs) or LTB 4 . The specific glutathione S-transferase leukotriene C 4 synthase (LTC 4 S) conjugates LTA 4 to form LTC 4 which can then be rapidly converted to LTD 4 by a gammaglutamyl transpeptidase and to LTE 4 by a dipeptidase once exported out the cell by membrane transport proteins such as multi-drug related protein 1 (MRP1) (12-15). A specific zinc metallohydrolase, LTA 4 hydrolase (LTA 4 H) is responsible for the conversion of LTA 4 to LTB 4 (16). CysLTs and LTB 4 act on different G-protein coupled receptors (GPCRs). Each bind to at least two different receptors: CysLTs to CYSLTR1 and CYSLTR2 and LTB 4 to LTB 4 R1 and LTB 4 R2 (or BLT1 and BLT2) (17).Leukotrienes (LT) are biologically active lipid mediators known to be involved in allergic inflammation. Leukotrienes have been shown to mediate diverse features of allergic conditions including inflammatory cell chemotaxis/activation and smooth muscle contraction. Cysteinyl leukotrienes (LTC 4 , LTD 4 and, LTE 4 ) and the dihydroxy leukotriene LTB 4 are generated by a series of enzymes/ proteins constituting the LT synthetic pathway or 5-lipoxygenase (5-LO) pathway. Their function is mediated by interacting with multiple receptors. Leukotr...

show abstract

“…Recently, we have reported that the LTB 4 receptor 1 (BLT1) is overexpressed in pancreatic cancer cells and tissues as well as islets adjacent to the tumour . LTB 4 receptors are G-proteincoupled receptors which belong to the chemoattractant receptor group (Yokomizo et al, 2001). BLT1 was isolated and cloned by Yokomizo's group in 1997 (Yokomizo et al, 1997).…”

mentioning

confidence: 99%

BLT2 is expressed in PanINs, IPMNs, pancreatic cancer and stimulates tumour cell proliferation

et al. 2008

View full text Add to dashboard Cite

Pancreatic cancer has an abysmal prognosis. Targets for early detection, prevention and therapy are desperately needed. Inflammatory pathways have an important impact on tumour growth and progression. Expression of BLT2 (the second leukotriene B 4 receptor) was investigated by real-time RT -PCR and immunohistochemistry. Cell proliferation was studied after stable transfection with BLT2, after treatment with siRNA and Compound A as an agonist. BLT2 is expressed in all pancreatic cancer cell lines. Results from real-time RT -PCR revealed significant overexpression of BLT2 in malignant intraductal papillary mucinous neoplasias (IPMNs) and pancreatic adenocarcinoma. Intense staining was evident in IPMNs, infiltrating tumour cells and advanced pancreatic intraepithelial neoplasias (PanINs) but not in normal ductal cells. Overexpression of BLT2 as well as stimulation of Colo357, Panc-1 and AsPC1 cells with Compound A caused a significant increase in tumour cell proliferation, an effect reversed after siRNA treatment. This study demonstrates for the first time the expression of BLT2 in the pancreas and overexpression in pancreatic cancers and malignant IPMNs in particular. Upregulation of BLT2 is already evident in precursor lesions (PanINs, IPMNs). Overexpression of this receptor leads to significant growth stimulation. Therefore, we suggest BLT2 as a new target for chemoprevention and therapy for pancreatic cancer.

show abstract

Leukotriene B4: Metabolism and Signal Transduction

Cited by 207 publications

References 104 publications

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss

Leukotriene pathway genetics and pharmacogenetics in allergy

BLT2 is expressed in PanINs, IPMNs, pancreatic cancer and stimulates tumour cell proliferation

Contact Info

Product

Resources

About

Leukotriene B4: Metabolism and Signal Transduction

Cited by 207 publications

References 104 publications

A distinctive role of the leukotriene B 4 receptor BLT1 in osteoclastic activity during bone loss

A distinctive role of the leukotriene B 4 receptor BLT1 in osteoclastic activity during bone loss

Leukotriene pathway genetics and pharmacogenetics in allergy

BLT2 is expressed in PanINs, IPMNs, pancreatic cancer and stimulates tumour cell proliferation

Contact Info

Product

Resources

About

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss

A distinctive role of the leukotriene B ₄ receptor BLT1 in osteoclastic activity during bone loss