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Jo Anne S. Richards - One of the best experts on this subject based on the ideXlab platform.
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the selective prostaglandin endoperoxide Synthase 2 inhibitor ns 398 reduces prostaglandin production and ovulation in vivo and in vitro in the rat
Biology of Reproduction, 1998Co-Authors: Masato Mikuni, Jo Anne S. Richards, Mats Brannstrom, Marita Pall, C M Peterson, C A Peterson, Par Hellberg, L HedinAbstract:Two isoforms of prostaglandin G/H Synthase, PGS-1 and PGS-2, catalyze the formation of prostaglandins (PG). Nonselective PGS inhibitors, e.g., indomethacin, reduce the number of ovulations and PG levels in many animal models. This study evaluated the effects of the selective PGS-2 inhibitor NS-398, compared to indomethacin, on ovulation number and on PG and steroid production both in vivo and in vitro in the rat. NS-398 reduced the synthesis of PGE2 in isolated, LH-stimulated preovulatory follicles incubated in vitro. The inhibition by NS-398 was similar to that of indomethacin. Maximal inhibition was noted from 0.1 microM. Neither progesterone nor cAMP production was affected by NS-398 or indomethacin. The effect of in vivo administration of NS-398 (1, 3, or 10 mg/kg BW, s. c.) to proestrous rats 1 h after the injection of an ovulatory dose of hCG was monitored in follicles extirpated 10 h after hCG. These follicles were incubated in vitro, and NS-398 dose-dependently reduced PGE2 production. The synthesis of cAMP and progesterone was not altered. In separate experiments, the same doses of NS-398 were injected to determine their effect on ovulation in vivo. The number of ovulations was decreased by the highest dose of NS-398. In the in vitro ovarian perfusion model, NS-398 (10 microM) reduced the number of ovulations initiated by LH and isobutylmethylxanthine. Lower doses of NS-398 (0.1 and 1 microM) were less effective. The production of prostanoids (PGE2, PGF2alpha, and 6-keto-PGF1alpha) was reduced in a dose-dependent manner by NS-398. The secretion of steroids was not affected. This study demonstrates that selective inhibition of PGS-2 by NS-398 reduces LH/hCG-stimulated production of prostanoids and the number of ovulations both in vivo and in vitro. These results provide direct evidence to strengthen the role of the inducible, granulosa cell-expressed PGS-2 as one of the key regulators in the ovulatory process and also document that the elevated and perhaps sustained levels of PG are obligatory for ovulation.
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An E-box Region within the Prostaglandin Endoperoxide Synthase-2 (PGS-2) Promoter Is Required for Transcription in Rat Ovarian Granulosa Cells
The Journal of biological chemistry, 1996Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:Abstract The prostaglandin endoperoxide Synthase-2 (PGS-2) gene encodes an isoform of prostaglandin Synthase that is transiently induced by protein kinase A (luteinizing hormone/cAMP) and protein kinase C (gonadotropin-releasing hormone) agonists in granulosa cells of ovulating follicles. The promoter of the rat PGS-2 gene contains a CAAT enhancer-binding protein consensus site (CAAT box) which can confer hormone inducibility to a PGS-2·CAT reporter gene, as well as a putative E-box region. To determine if the E-box region was involved in hormone induced trans-activation of the rat PGS-2 gene, constructs with the CAAT box and E-box regions (−192 PGS-2·CAT), only the putative E-box (−110 PGS-2·CAT), or neither region (−52 PGS-2·CAT) were transiently transfected into rat granulosa cell cultures. CAT activity was induced in both the −192 and −110 PGS-2·CAT vectors by luteinizing hormone (10-fold) and gonadotropin-releasing hormone (6-fold), whereas CAT activity of the −52 PGS-2·CAT construct did not differ from the promoterless vector (pCAT-Basic). Deletion of 1 base pair from the E-box within the −110 PGS-2·CAT construct, as well as point mutations within the CAAT box, E-box, or both regions of the −192 PGS-2·CAT construct, demonstrated that the E-box is critical for basal transcription, and that regions, in addition to the CAAT box, are involved in hormone induction of the PGS-2 gene. An oligonucleotide spanning the rat PGS-2 E-box bound two specific protein complexes which were supershifted in the presence of antibody specific for the upstream stimulatory factor. Thus, in rat granulosa cells, the PGS-2 E-box region appears to interact with upstream cis-acting elements other than the CAAT box to confer hormonal regulation of the gene. The E-box region of the rat PGS-2 promoter does not contain ATF/CRE activity found in the human and mouse PGS-2 promoters, but is critical for basal transcription of the PGS-2 gene in rat granulosa cells and binds the upstream stimulatory factor (as do E-box regions of other genes regulated in the ovary).
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luteinizing hormone induces prostaglandin endoperoxide Synthase 2 and luteinization in vitro by a kinase and c kinase pathways
Endocrinology, 1995Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:The LH surge induces ovulation [prostaglandin Synthase-2 (PGS-2)] and luteinization (progesterone synthesis) of preovulatory follicles by cAMP-dependent mechanisms. Peptides, such as GnRH and angiotensin-II, that activate other cellular signaling pathways have been shown to mimic some of the effects of LH. Therefore, the relative functional importance of different cellular signaling pathways in mediating the induction of PGS-2 and luteinization was analyzed using the agonists (LH, GnRH, and angiotensin-II) and selective inhibitors of A-kinase (H-89), C-kinase (calphostin-C), and calmodulin kinase-II (KN93). LH or GnRH, but not angiotensin-II, markedly induced PGS-2 protein in preovulatory follicles. H-89 and calphostin-C, but not KN93 inhibited LH induction of PGS-2, whereas calphostin-C selectively blocked induction by GnRH. In contrast, the A- and C-kinase inhibitors prevented both LH and GnRH induction of granulosa cell luteinization. Taken together, these results provide biological evidence that the r...
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luteinizing hormone induces prostaglandin endoperoxide Synthase 2 and luteinization in vitro by a kinase and c kinase pathways
Endocrinology, 1995Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:The LH surge induces ovulation [prostaglandin Synthase-2 (PGS-2)] and luteinization (progesterone synthesis) of preovulatory follicles by cAMP-dependent mechanisms. Peptides, such as GnRH and angiotensin-II, that activate other cellular signaling pathways have been shown to mimic some of the effects of LH. Therefore, the relative functional importance of different cellular signaling pathways in mediating the induction of PGS-2 and luteinization was analyzed using the agonists (LH, GnRH, and angiotensin-II) and selective inhibitors of A-kinase (H-89), C-kinase (calphostin-C), and calmodulin kinase-II (KN93). LH or GnRH, but not angiotensin-II, markedly induced PGS-2 protein in preovulatory follicles. H-89 and calphostin-C, but not KN93 inhibited LH induction of PGS-2, whereas calphostin-C selectively blocked induction by GnRH. In contrast, the A- and C-kinase inhibitors prevented both LH and GnRH induction of granulosa cell luteinization. Taken together, these results provide biological evidence that the response of granulosa cells to the LH surge appears to involve the activation of A- and C-kinase pathways.
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transcriptional regulation of the rat prostaglandin endoperoxide Synthase 2 gene in granulosa cells evidence for the role of a cis acting c ebp beta promoter element
Journal of Biological Chemistry, 1993Co-Authors: J Sirois, Jo Anne S. RichardsAbstract:Abstract The promoter of the rat prostaglandin endoperoxide Synthase 2 (PGS-2) gene has recently been shown to confer gonadotropic hormone (follicle-stimulating hormone (FSH), luteinizing hormone (LH), cAMP) inducibility when ligated to a CAT (chloramphenicol acetyltransferase) reporter gene and transfected into primary cultures of differentiated granulosa cells. To delineate cis-acting elements and trans-activating factors mediating this response, deletions of the active promoter region (-192/-53 base pairs upstream of the transcriptional start site) were tested for their ability to bind protein of granulosa cell nuclear extracts and activate reporter gene activity. Electrophoretic mobility shift assays revealed that the DNA subregion -142/-120 inhibited protein/DNA binding observed between granulosa cell nuclear extracts and the labeled PGS-2 fragment -192/-53. The subregion -142/-120 acting element C/EBP beta, 5'-TTATGCAAT-3'. Point mutations within the C/EBP beta element abolished protein/DNA binding and resulted in a 50% loss of forskolin/LH/FSH inducibility of reporter gene activity. C/EBP beta mRNA and protein were induced rapidly in granulosa cells in vivo by an ovulatory dose of human chorionic gonadotropin (hCG). Collectively, these results indicate that C/EPB beta appears to play a key role in regulating induction of the PGS-2 gene in granulosa cells prior to ovulation.
Jonathan P Arm - One of the best experts on this subject based on the ideXlab platform.
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regulation of prostaglandin endoperoxide Synthase 2 and il 6 expression in mouse bone marrow derived mast cells by exogenous but not endogenous prostanoids
Journal of Immunology, 2002Co-Authors: Bruno L Diaz, Yoshihide Kanaoka, Yoshihiro Urade, Hiroshi Fujishima, Jonathan P ArmAbstract:Mouse bone marrow-derived mast cells (BMMC), stimulated with stem cell factor, IL-1β, and IL-10, secrete IL-6 and demonstrate a delayed phase of PGD2 generation that is dependent upon the induced expression of PG endoperoxide Synthase (PGHS)-2. We have examined the potential for exogenous prostanoids, acting in a paracrine fashion, and endogenous prostanoids, acting in an autocrine fashion, to regulate PGHS-2 induction and IL-6 secretion in mouse BMMC. Exogenous PGE2, which acts through G protein-coupled receptors, and 15-deoxy-Δ12,14-PGJ2, which is a ligand for peroxisome proliferator-activated receptor (PPAR)γ, elicited a 2- to 3-fold amplification of PGHS-2 induction, delayed-phase PGD2 generation, and IL-6 secretion in response to stem cell factor, IL-1β, and IL-10. The effect of PGE2 was reproduced by the E prostanoid (EP)1 receptor agonist 17-trinor-PGE2, and the EP1/EP3 agonist, sulprostone, but not the EP2 receptor agonist, butaprost. Although BMMC express PPARγ, the effects of 15-deoxy-Δ12,14-PGJ2 were not reproduced by the PPARγ agonists, troglitazone and ciglitazone. PGHS-2 induction, but not IL-6 secretion, was impaired in cPLA2-deficient BMMC. However, there was no impairment of PGHS-2 induction in BMMC deficient in hematopoietic PGD Synthase or PGHS-1 in the presence or absence of the PGHS-2 inhibitor, NS-398. Thus, although exogenous prostanoids may contribute to amplification of the inflammatory response by augmenting PGD2 generation and IL-6 secretion from mast cells, endogenous prostanoids do not play a role.
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ige dependent activation of cytokine primed mouse cultured mast cells induces a delayed phase of prostaglandin d2 generation via prostaglandin endoperoxide Synthase 2
Journal of Immunology, 1995Co-Authors: M Murakami, Clifton O Bingham, R Matsumoto, K F Austen, Jonathan P ArmAbstract:Mouse bone marrow-derived mast cells (BMMC) developed with IL-3 generate prostaglandin D2 (PGD2) through the utilization of prostaglandin endoperoxide Synthase (PGHS)-1 within several minutes of cross-linking the high affinity Fc receptor for IgE (Fc epsilon RI) by hapten-specific IgE and Ag. We now report that this immediate generation of PGD2 is followed by a 15-fold induction of steady-state transcripts for PGHS-2, with a maximum at 30 min, accompanied by transient expression of PGHS-2 protein. When BMMC were pretreated with c-kit ligand (KL) in combination with IL-10 for 2 h, sensitized with IgE, and activated with Ag, their expression of steady-state transcripts for PGHS-2 increased 111-fold and their expression of PGHS-2 protein was markedly enhanced, with maximal expression at 1 h and 5 h, respectively, after activation. These events were accompanied by PGD2 generation from 1 to 10 h after activation that accounted for approximately 50% of total PGD2 generation. The expression of PGHS-1 protein did not change during this period. The optimal priming interval for the effect of KL plus IL-10 on the IgE-dependent induction of PGHS-2 was 2 h, at which time only this particular cytokine combination acted synergistically with activation by IgE and Ag. In contrast, at 2 days the accessory cytokines that could provide priming with KL included IL-3 and IL-9 in addition to IL-10. Dexamethasone, which inhibited the expression of PGHS-2 but not PGHS-1, and NS-398, a selective inhibitor of PGHS-2, each suppressed the delayed phase but not the immediate phase of PGD2 generation. Conversely, valeryl salicylate, a selective inhibitor of PGHS-1, suppressed the immediate but not the delayed phase of PGD2 generation after cell priming and IgE-dependent activation.
Jacqueline K Morris - One of the best experts on this subject based on the ideXlab platform.
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An E-box Region within the Prostaglandin Endoperoxide Synthase-2 (PGS-2) Promoter Is Required for Transcription in Rat Ovarian Granulosa Cells
The Journal of biological chemistry, 1996Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:Abstract The prostaglandin endoperoxide Synthase-2 (PGS-2) gene encodes an isoform of prostaglandin Synthase that is transiently induced by protein kinase A (luteinizing hormone/cAMP) and protein kinase C (gonadotropin-releasing hormone) agonists in granulosa cells of ovulating follicles. The promoter of the rat PGS-2 gene contains a CAAT enhancer-binding protein consensus site (CAAT box) which can confer hormone inducibility to a PGS-2·CAT reporter gene, as well as a putative E-box region. To determine if the E-box region was involved in hormone induced trans-activation of the rat PGS-2 gene, constructs with the CAAT box and E-box regions (−192 PGS-2·CAT), only the putative E-box (−110 PGS-2·CAT), or neither region (−52 PGS-2·CAT) were transiently transfected into rat granulosa cell cultures. CAT activity was induced in both the −192 and −110 PGS-2·CAT vectors by luteinizing hormone (10-fold) and gonadotropin-releasing hormone (6-fold), whereas CAT activity of the −52 PGS-2·CAT construct did not differ from the promoterless vector (pCAT-Basic). Deletion of 1 base pair from the E-box within the −110 PGS-2·CAT construct, as well as point mutations within the CAAT box, E-box, or both regions of the −192 PGS-2·CAT construct, demonstrated that the E-box is critical for basal transcription, and that regions, in addition to the CAAT box, are involved in hormone induction of the PGS-2 gene. An oligonucleotide spanning the rat PGS-2 E-box bound two specific protein complexes which were supershifted in the presence of antibody specific for the upstream stimulatory factor. Thus, in rat granulosa cells, the PGS-2 E-box region appears to interact with upstream cis-acting elements other than the CAAT box to confer hormonal regulation of the gene. The E-box region of the rat PGS-2 promoter does not contain ATF/CRE activity found in the human and mouse PGS-2 promoters, but is critical for basal transcription of the PGS-2 gene in rat granulosa cells and binds the upstream stimulatory factor (as do E-box regions of other genes regulated in the ovary).
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luteinizing hormone induces prostaglandin endoperoxide Synthase 2 and luteinization in vitro by a kinase and c kinase pathways
Endocrinology, 1995Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:The LH surge induces ovulation [prostaglandin Synthase-2 (PGS-2)] and luteinization (progesterone synthesis) of preovulatory follicles by cAMP-dependent mechanisms. Peptides, such as GnRH and angiotensin-II, that activate other cellular signaling pathways have been shown to mimic some of the effects of LH. Therefore, the relative functional importance of different cellular signaling pathways in mediating the induction of PGS-2 and luteinization was analyzed using the agonists (LH, GnRH, and angiotensin-II) and selective inhibitors of A-kinase (H-89), C-kinase (calphostin-C), and calmodulin kinase-II (KN93). LH or GnRH, but not angiotensin-II, markedly induced PGS-2 protein in preovulatory follicles. H-89 and calphostin-C, but not KN93 inhibited LH induction of PGS-2, whereas calphostin-C selectively blocked induction by GnRH. In contrast, the A- and C-kinase inhibitors prevented both LH and GnRH induction of granulosa cell luteinization. Taken together, these results provide biological evidence that the r...
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luteinizing hormone induces prostaglandin endoperoxide Synthase 2 and luteinization in vitro by a kinase and c kinase pathways
Endocrinology, 1995Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:The LH surge induces ovulation [prostaglandin Synthase-2 (PGS-2)] and luteinization (progesterone synthesis) of preovulatory follicles by cAMP-dependent mechanisms. Peptides, such as GnRH and angiotensin-II, that activate other cellular signaling pathways have been shown to mimic some of the effects of LH. Therefore, the relative functional importance of different cellular signaling pathways in mediating the induction of PGS-2 and luteinization was analyzed using the agonists (LH, GnRH, and angiotensin-II) and selective inhibitors of A-kinase (H-89), C-kinase (calphostin-C), and calmodulin kinase-II (KN93). LH or GnRH, but not angiotensin-II, markedly induced PGS-2 protein in preovulatory follicles. H-89 and calphostin-C, but not KN93 inhibited LH induction of PGS-2, whereas calphostin-C selectively blocked induction by GnRH. In contrast, the A- and C-kinase inhibitors prevented both LH and GnRH induction of granulosa cell luteinization. Taken together, these results provide biological evidence that the response of granulosa cells to the LH surge appears to involve the activation of A- and C-kinase pathways.
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hormone induction of luteinization and prostaglandin endoperoxide Synthase 2 involves multiple cellular signaling pathways
Endocrinology, 1993Co-Authors: Jacqueline K Morris, Jo Anne S. RichardsAbstract:To determine the cellular signaling pathways involved in granulosa cell luteinization, known activators of protein kinase-A (LH and FSH) and protein kinase-C [GnRH and phorbol 12-myristate 13-acetate (PMA)] as well as inhibitors of tyrosine kinases (AG18 and genistein) were tested in an in vitro system using specific markers of luteinization (cell hypertrophy, side-chain cleavage cytochrome P450, and progesterone) and ovulation [prostaglandin endoperoxide Synthase-2 (PGS-2)]. When preovulatory follicles were incubated in the presence of an ovulatory (500 ng/ml) dose of LH or high GnRH (1 microM), the granulosa cells harvested from these follicles assumed and maintained a stable luteal cell phenotype in vitro. Granulosa cells harvested from follicles incubated in subovulatory doses of LH (5 and 50 ng/ml), lower doses of GnRH (5, 50, and 500 nM), or PMA alone were unable to form a stable luteal cell phenotype. When PMA was combined with subovulatory doses of LH, granulosa cells luteinized, and PGS-2 protein...
Joseph V Bonventre - One of the best experts on this subject based on the ideXlab platform.
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group iva phospholipase a2 optimizes ovulation and fertilization in rodents through induction of and metabolic coupling with prostaglandin endoperoxide Synthase 2
The FASEB Journal, 2012Co-Authors: Shiro Kurusu, Adam Sapirstein, Joseph V BonventreAbstract:Female mice lacking group IVA phospholipase A2 (Pla2g4a−/−) have a smaller litter size, which is due, in part, to defective implantation. We examined PLA2G4A dependence of the processes of ovulation and fertilization. Following induction of ovulation by equine chorionic gonadotropin (eCG)/human CG (hCG) treatment and mating, ovulation and fertilization rates were reduced significantly in Pla2g4a−/− mice as compared to wild-type littermates. Human CG triggered robust ovarian prostaglandin (PG) E2 production in the preovulatory period that was significantly attenuated in Pla2g4a−/− mice. Human CG transiently enhanced ovarian expression of PLA2G4A and prostaglandin endoperoxide Synthase 2 (PTGS2) in wild-type mice. This PTGS2 induction was decreased in Pla2g4a−/− mice and also in immature rats treated with the PLA2G4A inhibitor, archidonyl trifluoromethyl ketone. A close spatiotemporal association of PLA2G4A with PTGS2 was found in mouse and rat preovulatory follicles examined by immunohistochemistry. Less association was observed with 4 other forms of PLA2. Our data strongly suggest that PLA2G4A amplifies hCG induction of PTGS2 and colocalizes with the induced PTGS2, thus contributing to robust PG production required for optimal ovulation and fertilization in rodents.—Kurusu, S., Sapirstein, A., Bonventre, J. V. Group IVA phospholipase A2 optimizes ovulation and fertilization in rodents through induction of and metabolic coupling with prostaglandin endoperoxide Synthase 2.
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cytosolic phospholipase a2 is essential for both the immediate and the delayed phases of eicosanoid generation in mouse bone marrow derived mast cells
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Hiroshi Fujishima, Adam Sapirstein, Joseph V Bonventre, Rene Sanchez O Mejia, Clifton O Bingham, Frank K AustenAbstract:We have used mice in which the gene for cytosolic phospholipase A2 (cPLA2) has been disrupted to demonstrate the absolute requirement for cPLA2 in both the immediate and the delayed phases of eicosanoid generation by bone marrow-derived mast cells. For the immediate phase, quantitative analysis of the products of the 5-lipoxygenase pathway showed that gene disruption of cPLA2 prevented the provision of arachidonic acid substrate for biosynthesis of proximal intermediates. By analogy, we conclude that arachidonic acid substrate was also not available to prostaglandin endoperoxide Synthase 1 in the immediate phase of prostaglandin (PG) D2 generation. These defects occurred with two distinct stimuli, stem cell factor and IgE/antigen, which were, however, sufficient for signal transduction defined by exocytosis of β-hexosaminidase. Whereas cPLA2 is essential for immediate eicosanoid generation by providing arachidonic acid, its role in delayed-phase PGD2 generation is more complex and involves the activation-dependent induction of prostaglandin endoperoxide Synthase 2 and the supply of arachidonic acid for metabolism to PGD2.
Hiroshi Fujishima - One of the best experts on this subject based on the ideXlab platform.
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regulation of prostaglandin endoperoxide Synthase 2 and il 6 expression in mouse bone marrow derived mast cells by exogenous but not endogenous prostanoids
Journal of Immunology, 2002Co-Authors: Bruno L Diaz, Yoshihide Kanaoka, Yoshihiro Urade, Hiroshi Fujishima, Jonathan P ArmAbstract:Mouse bone marrow-derived mast cells (BMMC), stimulated with stem cell factor, IL-1β, and IL-10, secrete IL-6 and demonstrate a delayed phase of PGD2 generation that is dependent upon the induced expression of PG endoperoxide Synthase (PGHS)-2. We have examined the potential for exogenous prostanoids, acting in a paracrine fashion, and endogenous prostanoids, acting in an autocrine fashion, to regulate PGHS-2 induction and IL-6 secretion in mouse BMMC. Exogenous PGE2, which acts through G protein-coupled receptors, and 15-deoxy-Δ12,14-PGJ2, which is a ligand for peroxisome proliferator-activated receptor (PPAR)γ, elicited a 2- to 3-fold amplification of PGHS-2 induction, delayed-phase PGD2 generation, and IL-6 secretion in response to stem cell factor, IL-1β, and IL-10. The effect of PGE2 was reproduced by the E prostanoid (EP)1 receptor agonist 17-trinor-PGE2, and the EP1/EP3 agonist, sulprostone, but not the EP2 receptor agonist, butaprost. Although BMMC express PPARγ, the effects of 15-deoxy-Δ12,14-PGJ2 were not reproduced by the PPARγ agonists, troglitazone and ciglitazone. PGHS-2 induction, but not IL-6 secretion, was impaired in cPLA2-deficient BMMC. However, there was no impairment of PGHS-2 induction in BMMC deficient in hematopoietic PGD Synthase or PGHS-1 in the presence or absence of the PGHS-2 inhibitor, NS-398. Thus, although exogenous prostanoids may contribute to amplification of the inflammatory response by augmenting PGD2 generation and IL-6 secretion from mast cells, endogenous prostanoids do not play a role.
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cytosolic phospholipase a2 is essential for both the immediate and the delayed phases of eicosanoid generation in mouse bone marrow derived mast cells
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Hiroshi Fujishima, Adam Sapirstein, Joseph V Bonventre, Rene Sanchez O Mejia, Clifton O Bingham, Frank K AustenAbstract:We have used mice in which the gene for cytosolic phospholipase A2 (cPLA2) has been disrupted to demonstrate the absolute requirement for cPLA2 in both the immediate and the delayed phases of eicosanoid generation by bone marrow-derived mast cells. For the immediate phase, quantitative analysis of the products of the 5-lipoxygenase pathway showed that gene disruption of cPLA2 prevented the provision of arachidonic acid substrate for biosynthesis of proximal intermediates. By analogy, we conclude that arachidonic acid substrate was also not available to prostaglandin endoperoxide Synthase 1 in the immediate phase of prostaglandin (PG) D2 generation. These defects occurred with two distinct stimuli, stem cell factor and IgE/antigen, which were, however, sufficient for signal transduction defined by exocytosis of β-hexosaminidase. Whereas cPLA2 is essential for immediate eicosanoid generation by providing arachidonic acid, its role in delayed-phase PGD2 generation is more complex and involves the activation-dependent induction of prostaglandin endoperoxide Synthase 2 and the supply of arachidonic acid for metabolism to PGD2.
