Enhanced Prostaglandin E2 Release Research Articles

Involvement of H+-gradient dependent transporter in PGE2 release from A549 cells

The purpose of this study was to identify the transporter involved in the release of prostaglandin E2 (PGE2). In the present study, transport assays were conducted using membrane vesicles prepared from human lung adenocarcinoma A549 cells, thus enabling identification of the novel exporter present in A549 cells. PGE2 transport into A549 vesicles was higher in the presence of a proton (H+)-gradient, thus suggesting the involvement of PGE2H+ symporter in PGE2 transport. Results from our experiments showed enhanced PGE2 release in A549 cells in the presence of H+-gradient ([H+]extracellular < [H+]intracellular). Moreover, in vesicular transport assays, H+-gradient-dependent transport of PGE2 did not show saturation up to 500 μM PGE2, and 10 mM aromatic monocarboxylic acids (acetylsalicylic acid, salicylic acid, and p-nitrobenzoic acid) significantly inhibited PGE2 transport by 62–70%. These results suggest, the involvement of monocarboxylate transporters in the H+-gradient-dependent PGE2 export.

Gastroprotective effect of crocin in ethanol-induced gastric injury in rats

The present study investigated the gastroprotective effect of crocin in ethanol-induced gastric injury in rats. Rats were allocated into a normal group, an ulcer group, a crocin-treated group, an ulcer group pretreated with crocin, and an ulcer group pretreated with omeprazole as a reference anti-ulcer drug. Rats were sacrificed 3h after ethanol administration. Prophylactic administration of crocin (50mg/kg/day, i.p.) for 3 consecutive days before the administration of 70% ethanol (10ml/kg, orally) resulted in significant gastroprotection compared to ethanol-ulcerated rats as manifested by significant reduction in the gastric ulcer index. Crocin pretreatment increased ethanol-lowered levels of gastric juice mucin and mucosal prostaglandin E2 (PGE2) and interleukin-6 (IL-6). Moreover, crocin significantly decreased ethanol-elevated tumor necrosis factor-alpha (TNF-α) level, myeloperoxidase activity and heat shock protein 70 mRNA and protein levels. It also restored ethanol-altered mucosal levels of glutathione, malondialdehyde and superoxide dismutase activity. Furthermore, crocin-pretreatment alleviated ethanol-induced mucosal apoptosis as revealed by significant down-regulation of cytochrome c and caspase-3 mRNA expression, significant decrease in caspase-3 activity and mitigated DNA fragmentation as indicated by significant decrements in comet parameters. The protective efficacy of crocin was further supported by histological assessment. No significant difference was observed between crocin and omeprazole (20mg/kg orally 1h before ethanol administration) regarding their mucin-secretagogue and antioxidant effects, as well as their effects on TNF-α, IL-6 and cytochrome c. On the other hand, omeprazole was superior in enhancing PGE2 level and in alleviating neutrophil infiltration, caspase-3 activation and DNA fragmentation. Conclusively, crocin protects rat gastric mucosa against ethanol-induced injury via anti-inflammatory, anti-oxidative, anti-apoptotic and mucin-secretagogue mechanisms that are probably mediated by enhanced PGE2 release.

Resistance of cyclooxygenase-2 expressing pancreatic ductal adenocarcinoma cells against γδ T cell cytotoxicity

The prostaglandin (PG) synthetase cyclooxygenase 2 (Cox-2) promotes tumorigenesis, tumor progression, and metastasis in a variety of human cancer entities including pancreatic ductal adenocarcinoma (PDAC). In this study, we demonstrate that in PDAC cells such as Colo357 cells, enhanced Cox-2 expression and increased release of the Cox-2 metabolite prostaglandin E2 (PGE2) promotes resistance against γδ T cell-mediated lysis. Co-culture with activated γδ T cells induced an upregulation of Cox-2 expression in Colo357 cells, and thereby an enhanced PGE2 release, in response to tumor necrosis factor α (TNFα) secretion from γδ T cells. The PGE2-mediated inhibition of γδ T cell cytotoxicity against Cox-2-expressing PDAC cells can be partially overcome by Cox-2 inhibitors. Our results show that differences between PDAC cells in regards to sensitivity to γδ T-cell cytotoxicity can be due to distinct levels of Cox-2 expression associated with varying amounts of PGE2 release. While γδ T cell cytotoxicity against PDAC cells expressing low levels of Cox-2 can be effectively enhanced by tribody [(Her2)2×Vγ9] with specificity for Vγ9 T cell receptor and HER-2/neu on PDAC cells, a combination of tribody [(Her2)2×Vγ9] and Cox-2 inhibitor is necessary to induce complete lysis of Cox-2 high expressing Colo357. In conclusion, our results suggest that the application of tribody [(Her2)2×Vγ9] that enhances γδ T-cell cytotoxicity and Cox-2 inhibitors that overcome PGE2-mediated resistance of PDAC cells to the cytotoxic activity of γδ T cells might offer a promising combined immunotherapy for pancreatic cancer.

Connexin43 hemichannels mediate small molecule exchange between chondrocytes and matrix in biomechanically-stimulated temporomandibular joint cartilage

Connexin (Cx) 43 hemichannels play a role in mechanotransduction. This study was undertaken in order to determine if Cx43 hemichannels were activated in rat temporomandibular joint (TMJ) chondrocytes under mechanical stimulation. Sprague-Dawley rats were stimulated dental-mechanically. Cx43 expression in rat TMJ cartilage was determined with immunohistochemistry and real-time PCR, and Cx43 hemichannel opening was evaluated by the extra- and intracellular levels of prostaglandin E2 (PGE2). Both primary rat chondrocytes and ATDC5 cells were treated with fluid flow shear stress (FFSS) to induce hemichannel opening. The Cx43 expression level was then determined by real-time PCR or Western blotting, and the extent of Cx43 hemichannel opening was evaluated by measuring both PGE2 release and cellular dye uptake. Cx43 expression and intra- and extracellular PGE2 levels were increased in mechanically-stimulated rat TMJ cartilage compared to the unstimulated control. The FFSS treatment increased Cx43 expression and induced Cx43 hemichannel opening in primary rat chondrocytes and ATDC5 cells indicated by enhanced PGE2 release and dye uptake. Furthermore, the Cx43 hemichannel opening could be blocked by the addition of 18β-glycyrrhetinic acid, a Cx channel inhibitor, Cx43-targeting siRNA, or by withdrawal of FFSS stimulation. The migration of cytosolic Cx43 protein to the plasma membrane in ATDC5 cells was still significant after 8h post 2-h FFSS treatment, and the Cx43 protein level was still high at 48h, which returned to control levels at 72h after treatment. Cx43 hemichannels are activated and mediate small molecule exchange between TMJ chondrocytes and matrix under mechanical stimulation.

791 CHRONIC HYPERLIPIDEMIA CAUSES DETRUSOR OVERACTIVITY AND INCREASE IN URINARY PROSTAGLANDIN E2 RELEASE IN RABBITS

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Basic Research1 Apr 2011791 CHRONIC HYPERLIPIDEMIA CAUSES DETRUSOR OVERACTIVITY AND INCREASE IN URINARY PROSTAGLANDIN E2 RELEASE IN RABBITS Masaki Yoshida, Koichi Masunaga, Takashi Nagata, Akito Inadome, Yutaka Miyamoto, Tomomi Haba, and Junzo Kudoh Masaki YoshidaMasaki Yoshida Kumamoto, Japan More articles by this author , Koichi MasunagaKoichi Masunaga Tokyo, Japan More articles by this author , Takashi NagataTakashi Nagata Saitama, Japan More articles by this author , Akito InadomeAkito Inadome Kumamoto, Japan More articles by this author , Yutaka MiyamotoYutaka Miyamoto Kumamoto, Japan More articles by this author , Tomomi HabaTomomi Haba Kumamoto, Japan More articles by this author , and Junzo KudohJunzo Kudoh Kumamoto, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.609AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Recently, we demonstrated that chronic hyperlipidemia caused bladder dysfunction including detrusor overactivity in heritable hyperlipidemic rabbits (WHHLMI rabbits). Various pathologic conditions cause prostaglandins synthesis in both bladder smooth muscle and mucosa, resulting in bladder dysfunction. To evaluate the effects of hyperlipidemia on lower urinary tract function, we examined the relationship between hyperlipidemia-induced bladder dysfunction and urinary prostaglandin E2 (PGE2) level in WHHLMI rabbits. METHODS WHHLMI rabbits and the age and sex-matched Japanese white rabbits (control group) were prepared. In all rabbits, the urinary volume and frequency were recorded for three days, and 24-h urine samples of all rabbits were collected. Cystometrograms were performed under anesthesia using constant infusion of saline into the bladder to elicit voiding, and voided volume, residual urine, micturition pressure, and micturition interval were evaluated. 24-h urinary PGE2 levels were assayed by enzyme immunoassay (EIA) by using PGE2 EIA kit-Monoclonal. In addition, immunohistochemical staining of COX-2 of bladder tissue of WHHLMI and control rabbits was performed, using mouse monoclonal anti-COX-2 antibody. RESULTS The number of micturition per day was higher in WHHLMI rabbits (4.24±1.07 times/day) than in control rabbits (1.8±0.3 times/day), and the voided volume was lower in WHHLMI rabbits (14.81±4.60 ml) than in control rabbits (43.8±5.1 ml). In cystometrograms, WHHLMI rabbits showed detrusor overactivity, higher frequency of micturition (7.55±1.25 times/20 min) and lower voided volume (6.92±1.5 ml) than in control rabbits (1.44 ± 2.51 times/20 min and 20.8±3.2 ml, respectively). The urinary excretion of PGE2 was significantly higher in WHHLMI rabbits (6.44±1.87 ng/ml) than in control rabbits (0.91±0.14 ng/ml). Analysis of relationship between parameters of bladder function and urinary PGE2 level in WHHLMI rabbits indicated a significantly negative correlation (r=0.81) between urinary PGE2 level and voided volume, and a significant positive correlation between urinary PGE2 level and the number of micturition (r=0.86). Immunohistochemical staining of COX-2 showed a significant higher immunoreactivity in bladder mucosa of WHHLMI rabbits, as compared to control. CONCLUSIONS The present study suggested that chronic hyperlipidemia caused increase of COX-2 activity in bladder mucosa, which might cause the enhanced PGE2 release, resulting in activation of sensory input and detrusor overactivity. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e318 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Masaki Yoshida Kumamoto, Japan More articles by this author Koichi Masunaga Tokyo, Japan More articles by this author Takashi Nagata Saitama, Japan More articles by this author Akito Inadome Kumamoto, Japan More articles by this author Yutaka Miyamoto Kumamoto, Japan More articles by this author Tomomi Haba Kumamoto, Japan More articles by this author Junzo Kudoh Kumamoto, Japan More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Envelope glycoprotein (gp120) from HIV-1 enhances Mycobacterium avium growth in human bronchoalveolar macrophages; an effect mediated by enhanced prostaglandin synthesis.

Human bronchoalveolar lavage (BAL) macrophages were obtained from normal human volunteers and infected with an AIDS-associated strain of Mycobacterium avium. Infected cells were exposed to purified envelope glycoprotein (gp120) from HIV-1 or to the recombinant non-glycosylated gp120 fragments PBI-RF and PBI-IIIB. Native gp120 increased Myco. avium growth in human cells from six separate donors, whereas the non-glycosylated fragments of gp120 had no such effect. Moreover, gp120 induced a substantial secretion of prostaglandin E2 (PGE2) from macrophages; inclusion of indomethacin blocked the enhanced permissiveness of infected cells treated with gp120. Soluble CD4 also neutralized the effect of gp120. Overall, these results indicate a role for gp120 in the susceptibility of AIDS patients to Myco. avium infections, mediated by an enhanced PGE2 release.

Platelet‐derived growth factor‐induced arachidonic acid release for enhancement of prostaglandin E2 synthesis in human gingival fibroblasts pretreated with interleukin‐1β

Platelet-derived growth factor (PDGF) is a biological mediator for connective tissue cells and plays a critical role in a wide variety of physiological and pathological processes. We here investigated the effect of PDGF on arachidonic acid release and prostaglandin E(2) (PGE(2)) synthesis in human gingival fibroblasts (HGF). PDGF induced arachidonic acid release in a time- and dose-dependent manner, and simultaneously induced a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), but less provoked PGE(2) release and cyclooxygenase-2 (COX-2) mRNA expression. When [Ca(2+)](i) was increased by Ca(2+)-mobilizing reagents, arachidonic acid release was increased. The PDGF-induced arachidonic acid release and increase in [Ca(2+)](i) were prevented by a tyrosine kinase inhibitor. On the other hand, in the HGF pre-stimulated with interleukin-1beta (IL-1beta), PDGF clearly increased PGE(2) release. The PDGF-induced PGE(2) release was inhibited by a tyrosine kinase inhibitor. In the HGF pretreated with IL-1beta, arachidonic acid strongly enhanced PGE(2) release and COX-2 mRNA expression. These results suggest that PDGF stimulates arachidonic acid release by the increase in [Ca(2+)](i) via tyrosine kinase activation, and which contributes to PGE(2) production via COX-2 expression in HGF primed with IL-1beta.

Pretreatment with mild irritant enhances prostaglandin E2 release from isolated canine gastric mucosal mast cells.

Endogenous prostaglandin E2 has been indicated to have an important role in preventing gastric mucosal damage from noxious agents (i.e., in adaptive cytoprotection). However, the response of endogenous prostaglandin E2 to a mild irritant is controversial. In this study, we attempted to determine whether pretreatment with a low concentration of ethanol could induce endogenous prostaglandin E2 production by isolated canine fundic mucosal cells and to identify cells that are responsible for an increase of prostaglandin E2 production. Canine fundic mucosa was digested by collagenase, dispase, and EDTA. The cells were separated into five fractions with an elutriator rotor. Pretreatment with 5% ethanol induced a significant increase of prostagladin E2 release only from the secondary small-sized cell fraction, which was rich in mast cells and endocrine cells, and not from the other four fractions. Further cell separation by density gradient centrifugation revealed that the mast cell-enriched fraction (54%) was responsible for the increase of prostaglandin E2 release induced by the pretreatment with 5% ethanol. The results suggest that mast cells of the gastric mucosa play an important role in the production of endogenous prostaglandin E2 in adaptive cytoprotection.

Pulsating Fluid Flow Increases Nitric Oxide (NO) Synthesis by Osteocytes but Not Periosteal Fibroblasts - Correlation with Prostaglandin Upregulation

Osteocytes are extremely sensitive to fluid shear stress, a phenomenon that may be related to mechanical adaptation of bone (FASEB J 9:441,1995). Here we examined the effect of pulsating fluid flow (PFF, 0.5±0.02 Pa, 5 Hz, 0.4 Pa/sec) on the release of NO, in relation with upregulation of prostaglandin E2 (PGE2). Chicken calvarial osteocytes, but not periosteal fibroblasts, as well as mouse calvarial cells responded to PFF with a rapid and transient 2 to 3-fold stimulation of NO release. The effect was maximal after 5 min and leveled off thereafter. PFF also stimulated PGE2 release. This effect was significant after 10 min and continued throughout 60 min PFF treatment. Inhibition of NO release bq NG-monomcthyl-L-arginine prevented the effect of PFF on NO as well as PGE2 release. These results suggest that NO is a mediator of mechanical effects in bone, leading to enhanced PGE2 release. They further strengthen the hypothesis that fluid flow through the osteocyte canalicular network provides the physical stimulus for mechanosensation in bone.

Autoregulation by eicosanoids of human Kupffer cell secretory products. A study of interleukin-1, interleukin-6, tumor necrosis factor-alpha, transforming growth factor-beta, and nitric oxide.

Methods employed previously to analyze the secretory behavior of rodent Kupffer cells (KC) were used to examine the human KC's secretory response to lipopolysaccharide (LPS). As the resident hepatic macrophage, the KC resides at the interface between the portal and systemic circulations. Consequently, this cell may play an integral role in the immune response to antigens and bacteria in the sinusoid. Study of cytokine production by the KC has relied predominantly on the rat as the source of these cells. Whether human KCs respond similarly to rat KCs after LPS stimulation has been a matter of speculation. Kupffer cells obtained from seven human livers were tested under conditions identical to those used to study rat KCs. Kupffer cells rested for 12 hours after isolation were stimulated with LPS (2.5 micrograms/mL). Arginine concentration in the culture medium varied from 0.01 to 1.2 mM. To examine the role of eicosanoids, parallel culture wells received indomethacin (10 microM). Culture supernatants were assayed for interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), prostaglandin E2 (PGE2), and nitric oxide. Similar to the rat KC, LPS-stimulated human KCs released IL-1, IL-6, TNF-alpha, TGF-beta, and PGE2. However, unlike rat KCs, nitric oxide could not be detected, regardless of whether the human KCs were exposed to LPS, interferon-gamma (INF-gamma), or LPS + IFN-gamma. Similar to rat KCs, indomethacin prevented PGE2 release while significantly upregulating TNF-alpha, IL-1, and IL-6, but not TGF-beta, consistent with an autoregulatory control of eicosanoids over proinflammatory cytokines. As has been shown in the rat, physiologic levels of L-arginine (0.01 mM) significantly enhanced LPS-induced PGE2 secretion relative to the response in medium containing standard L-arginine concentration (1.2 mM); however, unlike the rat KC, the human's cytokine response to LPS was not downregulated by this enhanced PGE2 release. Although many functional features are shared by rat and human KCs, significant differences do exist. Such discrepancies reinforce the need to proceed with caution when generalizing from the results obtained in other species to human physiology.

Transmembrane signals mediating neural peptide secretion: role of protein kinase C activators and arachidonic acid metabolites in luteinizing hormone-releasing hormone secretion.

The present experiments were designed to determine the effects of different activators of protein kinase C on the secretion of LHRH from median eminence nerve terminals incubated in vitro. The release of prostaglandin E2 (PGE2), a metabolite of arachidonic acid intimately involved in the secretion of LHRH, was also evaluated. Synthetic diacylglycerol [1,2-didecanoylglycerol (DiC10)] significantly enhanced PGE2 release in a concentration-dependent manner. Blockade of phospholipase A2 (PLA2) activity nullified this effect. LHRH release, on the other hand, was not increased by DiC10. However, in the presence of a lipoxygenase inhibitor, DiC10 produced a concentration-related increase in LHRH release, which paralleled that in PGE2. Phospholipase C (PLC) increased both PGE2 and LHRH secretion. Again, blockade of the lipoxygenase pathway enhanced the release of LHRH by PLC without affecting the stimulated secretion of PGE2. A phorbol ester, phorbol 12,13-dibutyrate (PDBu), markedly increased LHRH secretion while inducing a modest increase in PGE2 release. Both effects of PDBu were unaffected by lipoxygenase inhibition. DiC10, PDBu, and PLC significantly augmented LHRH secretion from tissues in which metabolism of arachidonic acid had been prevented by inhibition of both cyclooxygenase and lipoxygenase pathways, suggesting that activation of protein kinase C, independent of PLA2 activation, can lead to the secretion of this neural peptide. Some lipoxygenase metabolites had either no effect on [5- and 15-hydroxyeicosatetraenoic (5- and 15-HETE)] or induced a marginal stimulation of (12-HETE) LHRH release. At certain concentrations, 12-HETE enhanced the stimulatory effect of the phorbol ester on LHRH release. Our results suggest that activation of protein kinase C can stimulate LHRH secretion from nerve terminals in vitro and, further, that diacylglycerol may represent an important intracellular messenger participating in the events leading to LHRH secretion. In addition, stimulation with DiC10 and PLC uncovered inhibitory [unknown arachidonic acid metabolite(s) via lipoxygenase] and stimulatory (PGE2 via cyclooxygenase) pathways through with arachidonic acid metabolites may participate in the intracellular transduction of signals modulating neural peptide secretion.

Calcium, calmodulin, and cyclic adenosine monophosphate modulate prostaglandin E2 release from isolated human gastric mucosal cells.

We studied prostaglandin E2 (PGE2) release from isolated cells of the human gastric mucosa. Mucosal cells were enzymatically isolated from biopsy specimens of human fundic mucosa. The results from these crude cell preparations were compared to those obtained in fractions with enriched (65-80%) or depleted parietal cell content (3-7%) which were prepared from gastric mucosa obtained at surgery. PGE2 release in the enriched parietal cell fractions exceeded that from crude or parietal cell depleted preparations 3- and 13-fold, respectively. However, despite this quantitative difference, all preparations responded similarly to the test agents. Newly synthesized PGE2 was not stored intracellularly but was released into the incubation medium. Release increased linearly for 30 min. Addition of the calcium ionophore A23187 enhanced PGE2 release 4- to 5-fold. The effect of A23187 required the presence of extracellular Ca2+ (10(-3) mol/liter). Assuming that A23187 alters Ca2+ flux in gastric cells as it does in other cell systems our data indicate that increased Ca2+ influx enhances PGE2 release. Since calmodulin is of importance for intracellular Ca2+ action, the calmodulin antagonists trifluoperazine and W7 were tested. Both antagonists inhibited PGE2 release by 65-85%, trifluoperazine being slightly more effective. Activation of the adenylate cyclase system by forskolin or direct addition of (Bu)2cAMP, a stable cAMP-analog, also inhibited PGE2 release. We conclude that PGE2 is released from parietal and from nonparietal cells of the human gastric mucosa, although the major quantity is released from the light density fraction that is enriched in parietal cells. In parietal and nonparietal cells Ca2+ is of importance in the regulation of gastric mucosal PGE2 release and calmodulin seems to mediate this intracellular action of Ca2+. cAMP inhibits PGE2-release from gastric cells.

Stimulation of renal prostaglandin synthesis by the pressor activity of vasopressin.

Renal prostaglandin E2 (PGE2) synthesis is enhanced by exogenous vasopressin (AVP). To determine whether the pressor or the antidiuretic activities of AVP are related to its effect on PGE2 synthesis, AVP and the nonpressor analog, 1-deamino-8-D-arginine vasopressin (dD'AVP), were administered to the isolated perfused rabbit kidney, PGE2 was measured in the renal venous effluent by RIA and validated by bioassay. AVP in doses of 20, 200, and 2,000 ng progressively increased perfusion pressore by 12.1 +/- 2.4, 62.0 +/- 7.9, and 74.3 +/- 13.5 mm Hg, respectively, and increased PGE2 by 28 +/- 7, 80 +/- 3, and 129 +/- 57 ng/50 ml effluent, respectively. Bradykinin and angiotensin II induced a similar dose response on PGE2 release. However, dD'AVP in doses up to 20,000 ng minimally enhanced PGE2 release (20 +/- 16 ng/50 ml) and did not alter perfusion pressure. Simultaneous administration of AVP (200 ng) with the specific AVP pressor antagonist, d-cyclo-O-methyl-tyrosine-AVP, in a 1:10 (agonist to antagonist) weight ratio blunted the increase in perfusion pressure by 59 +/- 9% and blunted the increase in PGE2 release by 59 +/- 10% (P < 0.05). In a 1:100 weight ratio, the pressure antagonist reduced the AVP pressure response by 86 +/- 6% and reduced PGE2 by 84 +/- 7% (P < 0.01). These data suggest that the AVP stimulation of renal PGE2 synthesis is related primarily to its pressor and not to its antidiuretic activity in this in vitro kidney model. (Endocrinology 108: 495, 1981)