Endogenous Prostaglandin Synthesis Research Articles

Role of intraluteal and intrauterine prostaglandin signaling in LH-induced luteolysis in pregnant rats.

Luteal dysfunctions lead to fertility disorders and pregnancy complications. Normal luteal function is regulated by many factors, including luteinizing hormone (LH).The luteotropic roles of LH have been widely investigated but its role in the process of luteolysis has received little attention. LH has been shown to have luteolytic effects during pregnancy in rats and the role of intraluteal prostaglandins (PGs)in LH-mediated luteolysis has been demonstrated by others. However, the status of PG signaling in the uterus during LH-mediated luteolysis remains unexplored. In this study, we utilized the repeated LH administration (4×LH)model for luteolysis induction. We have examined the effect of LH-mediated luteolysis on the expression of genes involved in luteal/uterine PG synthesis, luteal PGF2α signaling, and uterine activation during different stages (mid and late) of pregnancy. Further, we analyzed the effect of overall PG synthesis machinery blockage on LH-mediated luteolysis during late pregnancy. Unlike the midstage of pregnancy, the expression of genes involved in PG synthesis, PGF2α signaling, and uterine activation in late-stage pregnant rats' luteal and uterine tissue increase 4×LH. Since the cAMP/PKApathway mediates LH-mediated luteolysis, we analyzed the effect of inhibition of endogenous PG synthesis on the cAMP/PKA/CREBpathway, followed by the analysis of the expression of markers of luteolysis. Inhibition of endogenous PG synthesis did not affect the cAMP/PKA/CREBpathway. However, in the absence of endogenous PGs, luteolysis could not be activated to the full extent. Our results suggest that endogenous PGs may contribute to LH-mediated luteolysis, but this dependency on endogenous PGs is pregnancy-stage dependent. These findings advance our understanding of the molecular pathways that regulate luteolysis.

Prostaglandin F2α regulation and function during ovulation and luteinization in cows

Although prostaglandins are important in the ovulation process, a precise role for prostaglandin F2α (PGF) has not been elucidated. This study aimed to evaluate the regulation of PGF receptor mRNA (PTGFR) in granulosa cells and the local effect of PGF on ovulation and luteinization. In Experiment 1, using samples collected in vivo before (Day 2), during (Day 3) and after (Day 4) follicular deviation, expression of PTGFR in bovine granulosa cells was more abundant in the dominant follicle after deviation than in subordinates (P < 0.05). However, the expression of PTGFR was not regulated (P = 0.1) in preovulatory follicles at different time-points (0, 3, 6, 12 and 24 h) after ovulation induction with GnRH. In Experiment 2, to assess the role of systemic PGF treatment on luteinization and vascularization of preovulatory follicles, flunixin meglumine (FM), a nonsteroidal anti-inflammatory drug, was used to inhibit endogenous prostaglandin synthesis. Cows with preovulatory follicles were induced to ovulate with GnRH (0 h) and allocated to three groups: Control, with no further treatment; FM, treated with 2.2 mg/kg FM im 17 h after GnRH treatment; and FM + PGF, treated with FM 17 h after GnRH, followed by 25 mg dinoprost tromethamine (PGF) 23 h after GnRH treatment. FM injection was able to reduce the concentration of PGF in the follicular fluid (FF) (P < 0.001). However, contrary to our hypothesis, color Doppler ultrasound evaluations revealed decreased vascular flow in FM + PGF group (P < 0.05), and no effect of the treatments on intrafollicular P4 and E2 concentrations 24 h after GnRH. The prostaglandin metabolite (PGFM) concentrations in the FF were greater in cows receiving systemic PGF (P < 0.001), which prompted us to further check its role on ovulation. Therefore, in Experiment 3, in a final attempt to demonstrate the local effect of PGF on ovulation, cows with preovulatory follicles received an intrafollicular injection (IFI) of PBS (Control) or 100 ng/mL purified PGF (PGF group). PGF treatment did not affect the time of ovulation after IFI (66 ± 6.4 and 63 ± 8.5 h for control and PGF, respectively; P > 0.05), further suggesting that it has no direct effect in the ovulatory process. Based on our findings, we concluded that FM decreased PGF synthesis within the follicle, whereas PGF treatment decreased follicular vascularization. In addition, the in vivo model of intrafollicular injection evidenced that PGF alone is not able to locally induce ovulation.

REBAMIPIDE: EFFECTIVE DRUG PREVENTION OF NSAID ENTEROPATHY IS POSSIBLE

Prevention of gastrointestinal tract (GIT) complications is the most important element for the rational use of nonsteroidal anti-inflammatory drugs (NSAIDs) and low-dose aspirin (LDA). Proton pump inhibitors (PPIs) have long been the only medication to prevent these complications. However, PPIs are only effective in preventing and treating upper GIT diseases (NSAID gastropathy) rather than small intestinal injury (NSAID enteropathy). Rebamipide has emerged as a novel agent to protect the gastrointestinal mucosa today. The effect of the drug differs from that of PPIs: it is a typical gastroand enteroprotector that enhances the synthesis of endogenous prostaglandins and possesses a significant anti-inflammatory potential. Rebamipide has long been widely used by doctors inJapan,South Korea, andChinaas an effective and safe agent for the treatment of many diseases of the digestive system. There is a strong evidence base for the efficacy of rebamipide in preventing and treating NSAID gastropathy and NSAID enteropathy (including LDA-induced injuries). Controlled studies have found that the drug is not inferior to the classic gastroprotective agent misoprostol, significantly outperforming the latter in its tolerability. This review describes the mechanism of action of rebamipide and main clinical trials of its therapeutic effect in NSAID gastropathy and NSAID enteropathy.

Basic Studies on the Stability of Flavored Oral Solutions of Rebamipide

Stomatitis frequently occurs during chemotherapy and radiotherapy for cancer. Because of its pharmacological properties including anti-inflammatory activity and stimulatory effects on endogenous prostaglandin synthesis, rebamipide has been suggested as a potentially effective treatment against stomatitis. In the present study we tested the stability of oral rebamipide solutions prepared in our hospital pharmacy using sodium alginate as a thickener to increase retention of this agent in the oral cavity, and the addition of different flavoring mixtures intended for use in enteral diets to reduce the bitterness of rebamipide and sodium alginate. Samples of oral rebamipide solution prepared with 13 kinds of flavoring and sodium alginate were evaluated in terms of their appearance, redispersibility, pH, viscosity, and rebamipide content immediately after preparation and 1, 3, 7, and 10 days after storage at room temperature under ambient light or in a cool, dark place. After 10 days of storage, favorable stability was observed in four sample solutions supplemented with green apple, pineapple, yogurt, and tomato flavoring mixtures intended for use in Elental(®) diets. These oral solutions may have potential clinical application.

The effects of 1% prednisolone acetate on pupil diameter and intraocular pressure in healthy dogs treated with 0.005% latanoprost.

Prostaglandin analogs contribute to blood-aqueous barrier breakdown and may exacerbate uveitis. As these analogs induce de novo synthesis of endogenous prostaglandins, their therapeutic, hypotensive effect could potentially be inhibited by anti-inflammatory treatment. We therefore evaluated whether topical 1% prednisolone acetate alters the effects of 0.005% latanoprost on pupil diameter (PD) and intraocular pressure (IOP). Ten healthy Labrador retriever dogs from the Israel Guide Dog Center for the Blind. Pupil diameter and IOP were measured hourly, 8 AM-4 PM, with the right and left eyes serving as control (CE) and treated (TE) eyes, respectively. Measurements were conducted during four sessions: (1) without treatment (n = 10), (2) following latanoprost treatment (n = 10) at 8 AM, (3) following prednisolone treatment (n = 7) at 8 AM, and (4) bilateral latanoprost treatment at 8 AM, prednisolone treatment in TE at 11 AM (n = 8). The different number of dogs in sessions 3 and 4 is because some dogs were matched with their new owners earlier than expected. Pupil diameters were not affected by the addition of prednisolone and, at 4 PM, were 3.82 ± 0.47 and 3.97 ± 0.36 mm in TE and CE, respectively (P = 0.175, Wilcoxon). IOPs were not affected by the addition of prednisolone and, at 4 PM, were 9.0 ± 0.8 and 9.3 ± 0.8 mm Hg in TE and CE, respectively (P = 0.339, Wilcoxon). Prednisolone did not alter latanoprost's miotic and hypotensive effects in normal dogs during this study period.

Inhibition of the Prostaglandin Transporter PGT Lowers Blood Pressure in Hypertensive Rats and Mice.

Inhibiting the synthesis of endogenous prostaglandins with nonsteroidal anti-inflammatory drugs exacerbates arterial hypertension. We hypothesized that the converse, i.e., raising the level of endogenous prostaglandins, might have anti-hypertensive effects. To accomplish this, we focused on inhibiting the prostaglandin transporter PGT (SLCO2A1), which is the obligatory first step in the inactivation of several common PGs. We first examined the role of PGT in controlling arterial blood pressure blood pressure using anesthetized rats. The high-affinity PGT inhibitor T26A sensitized the ability of exogenous PGE2 to lower blood pressure, confirming both inhibition of PGT by T26A and the vasodepressor action of PGE2 T26A administered alone to anesthetized rats dose-dependently lowered blood pressure, and did so to a greater degree in spontaneously hypertensive rats than in Wistar-Kyoto control rats. In mice, T26A added chronically to the drinking water increased the urinary excretion and plasma concentration of PGE2 over several days, confirming that T26A is orally active in antagonizing PGT. T26A given orally to hypertensive mice normalized blood pressure. T26A increased urinary sodium excretion in mice and, when added to the medium bathing isolated mouse aortas, T26A increased the net release of PGE2 induced by arachidonic acid, inhibited serotonin-induced vasoconstriction, and potentiated vasodilation induced by exogenous PGE2. We conclude that pharmacologically inhibiting PGT-mediated prostaglandin metabolism lowers blood pressure, probably by prostaglandin-induced natriuresis and vasodilation. PGT is a novel therapeutic target for treating hypertension.

Mucosal healing in inflammatory bowel diseases: is there a place for nutritional supplementation?

Advanced mucosal healing (MH) after intestinal mucosal inflammation coincides with sustained clinical remission and reduced rates of hospitalization and surgical resection, explaining why MH is increasingly considered as a full therapeutic goal and as an endpoint for clinical trials. Intestinal MH is a complex phenomenon viewed as a succession of steps necessary to restore tissue structure and function. These steps include epithelial cell migration and proliferation, cell differentiation, restoration of epithelial barrier functions, and modulation of cell apoptosis. Few clinical studies have evaluated the needs for specific macronutrients and micronutrients and their effects on intestinal MH, most data having been obtained from animal and cell studies. These data suggest that supplementation with specific amino acids including arginine, glutamine, glutamate, threonine, methionine, serine, proline, and the amino acid-derived compounds, polyamines can favorably influence MH. Short-chain fatty acids, which are produced by the microbiota from undigested polysaccharides and protein-derived amino acids, also exert beneficial effects on the process of intestinal MH in experimental models. Regarding supplementation with lipids, although the effects of ω-3 and ω-6 fatty acids remain controversial, endogenous prostaglandin synthesis seems to be necessary for MH. Finally, among micronutrients, several vitamin and mineral deficiencies with different frequencies have been observed in patients with inflammatory bowel diseases and supplementation with some of them (vitamin A, vitamin D3, vitamin C, and zinc) are presumed to favor MH. Future work, including clinical studies, should evaluate the efficiency of supplementation with combination of dietary compounds as adjuvant nutritional intervention for MH of the inflamed intestinal mucosa.

Effects of non-selective (piroxicam) and selective (meloxicam) cyclo-oxygenase inhibitors on the intestinal contractility of rabbits

Background: To shed some light on full characterization and utilization of non-steroidal anti-inflammatory drugs (NSAIDs) in veterinary medicine, this study, therefore, was designed to clarify the pharmacological effects of two NSAIDs (one selective, that is meloxicam, and the other is non-selective, that is piroxicam) on intestinal contractility of rabbit as a farm animal species. Methods: Rabbits were humanely slaughtered, and segments from different parts of intestinal tracts were dissected out and an intestinal segment of about 2 cm long was fixed in an organ bath containing warm oxygenated Tyrode’s solution at 37°C. The tissue was subjected to a resting tension of 2 g and allowed to equilibrate for 30 min and then the effects of graded increased concentrations of piroxicam and meloxicam were demonstrated on the normal rhythmic motility of the isolated intestinal segments. The sites of action of piroxicam and meloxicam were tried. Results: Piroxicam and meloxicam exhibited concentration-dependent relaxations of intestinal smooth muscle segments with minimal and maximal effects of more potency by prioxicam than meloxicam. Calculated inhibitory concentration 50% were 15.45 and 23.10 μg/ml bath for piroxicam and meloxicam, respectively. Effects of either piroxicam or meloxicam did not involve cholinergic, adrenergic, histaminergic, nitrergic, or purinergic pathways as the application of the corresponding agonists/antagonists did not affect the inhibitory response of piroxicam and meloxicam. It was assumed that the effects of the drugs were attributed to the direct effects of the drugs on the intestines in addition to inhibiting endogenous prostaglandin synthesis activity via their cyclo-oxygenase inhibiting properties. Conclusions: Data of the present study may indicate that piroxicam and meloxicam could be used effectively and safely in rabbits for their anti-inflammatory actions in small therapeutic doses. However, in large doses, they (particularly, piroxicam) may produce depressant effects on gastrointestinal tract motility that should be taken in consideration in the case of introducing these drugs in therapy with larger doses.

Cultured Preadipocytes Undergoing Stable Transfection with Cyclooxygenase-1 in the Antisense Direction Accelerate Adipogenesis During the Maturation Phase of Adipocytes

The arachidonate cyclooxygenase (COX) pathway is involved in the generation of several types of endogenous prostaglandins (PGs) with opposite effects on adipogenesis at different life stages of adipocytes. However, the specific role of COX isoforms, the rate-limiting enzymes for the pathway, remains elusive in the regulation of the endogenous synthesis of PGs. This study was aimed at the selective suppression of the constitutive COX-1 in cultured preadipocytes by the isolation of cloned preadipocytes transfected stably with a mammalian expression vector harboring cDNA encoding mouse COX-1 in the antisense direction. The gene expression analysis revealed that the transcript and protein levels of the constitutive COX-1 were substantially suppressed in the isolated cloned transfectants with antisense COX-1. By contrast, the expression of the inducible COX-2 was not affected in the stable transfectants with antisense COX-1. All of the cloned stable transfectants with antisense COX-1 exhibited a significant reduction in the immediate synthesis of PGE2 serving as an anti-adipogenic factor. The sustained expression of COX-1 in the antisense direction induced the appreciable stimulation of fat storage in adipocytes during the maturation phase, which was associated with the higher expression levels of adipocyte-specific genes, indicating the positive regulation of adipogenesis program. Moreover, the up-regulation of adipogenesis is accompanied by a higher production of J2 series PGs including 15-deoxy-Δ(12,14)-PGJ2 and Δ(12)-PGJ2, known as pro-adipogenic factors by the transfectants with antisense COX-1. The results suggest that the inducible COX-2 can contribute to the endogenous synthesis of PGJ2 derivatives acting as autocrine mediators to simulate adipogenesis during the maturation phase by way of compensation for the suppressed expression of the constitutive COX-1.

Platelet lysate suppresses the expression of lipocalin-type prostaglandin D2 synthase that positively controls adipogenic differentiation of human mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have been shown to display a considerable therapeutic potential in cellular therapies. However, harmful adipogenic maldifferentiation of transplanted MSCs may seriously threaten the success of this therapeutic approach. We have previously demonstrated that using platelet lysate (PL) instead of widely used fetal calf serum (FCS) diminished lipid accumulation in adipogenically stimulated human MSCs and identified, among others, lipocalin-type prostaglandin D2 synthase (L-PGDS) as a gene suppressed in PL-supplemented MSCs. Here, we investigated the role of PL and putatively pro-adipogenic L-PGDS in human MSC adipogenesis.Next to strongly reduced levels of L-PGDS we show that PL-supplemented MSCs display markedly decreased expression of adipogenic master regulators and differentiation markers, both before and after induction of adipocyte differentiation. The low adipogenic differentiation capability of PL-supplemented MSCs could be partially restored by exogenous addition of L-PGDS protein. Conversely, siRNA-mediated downregulation of L-PGDS in FCS-supplemented MSCs profoundly reduced adipocyte differentiation. In contrast, inhibiting endogenous prostaglandin synthesis by aspirin did not reduce differentiation, suggesting that a mechanism such as lipid shuttling but not the prostaglandin D2 synthase activity of L-PGDS is critical for adipogenesis.Our data demonstrate that L-PGDS is a novel pro-adipogenic factor in human MSCs which might be of relevance in adipocyte metabolism and disease. L-PGDS gene expression is a potential quality marker for human MSCs, as it might predict unwanted adipogenic differentiation after MSC transplantation.

Prostaglandin E2-EP4 signaling suppresses adipocyte differentiation in mouse embryonic fibroblasts via an autocrine mechanism

The prostaglandin (PG) receptors EP4 and FP have the potential to exert negative effects on adipogenesis, but the exact contribution of endogenous PG-driven receptor signaling to this process is not fully understood. In this study, we employed an adipocyte differentiation system from mouse embryonic fibroblasts (MEF) and compared the effects of each PG receptor-deficiency on adipocyte differentiation. In wild-type (WT) MEF cells, inhibition of endogenous PG synthesis by indomethacin augmented the differentiation, whereas exogenous PGE₂, as well as an FP agonist, reversed the effect of indomethacin. In EP4-deficient cells, basal differentiation was upregulated to the levels in indomethacin-treated WT cells, and indomethacin did not further enhance differentiation. Differentiation in FP-deficient cells was equivalent to WT and was still sensitive to indomethacin. PGE₂ or indomethacin treatment of WT MEF cells for the first two days was enough to suppress or enhance transcription of the Pparg2 gene as well as the subsequent differentiation, respectively. Differentiation stimuli induced COX-2 gene and protein expression, as well as PGE₂ production, in WT MEF cells. These results suggest that PGE₂-EP4 signaling suppresses adipocyte differentiation by affecting Pparg2 expression in an autocrine manner and that FP-mediated inhibition is not directly involved in adipocyte differentiation in the MEF system.

Entacapone promotes cAMP-dependent colonic Cl− secretion in rats

Entacapone is a promising drug used widely for the treatment of Parkinson's disease (PD) as a catechol-O-methyl transferase (COMT) inhibitor. However, entacapone has gastrointestinal side effects. The aim of this study was to investigate the effects of entacapone on the epithelial ion transport in rat distal colon, and explore the underlying mechanism. The study was performed on freshly isolated colonic mucosa-only, submucosa-only and mucosa-submucosa preparations in rat. The short circuit current (I(SC) ) was measured to determine electrogenic ion transport, and a scanning ion-selective electrode technique (SIET) was used to directly measure Cl(-) flux across the epithelium. The content of intracellular cAMP was measured with radioimmunoassay (RIA). Entacapone increased mucosal I(SC) in the rat distal colon. I(SC) was inhibited significantly by apical addition of diphenylamine-2,2'-dicarboxylic acid (DPC), a blocker of the Cl(-) channel, basolateral application of bumetanide, an inhibitor of Na(+) -K(+) -2Cl(-) co-transporter (NKCC), removal of Cl(-) from the bathing solution, and pretreatment with MDL 12330A, an inhibitor of adenylate cyclase. Inhibiting endogenous prostaglandin (PG) synthesis with indomethacin, and eliminating submucosal enteric neural activity with tetrodotoxin (TTX)-inhibited entacapone-evoked I(SC) increases. Similar results were also obtained when Cl(-) flux was measured with SIET. Entacapone significantly increased intracellular cAMP content, which was greatly inhibited by either indomethacin or TTX in the tissues containing submucosal plexus, and by only indomethacin in the mucosa-only preparations. Entacapone stimulates cAMP-dependent Cl(-) secretion in the rat colon, and this process is regulated by endogenous PG and the submucosal enteric nervous system.

Stimulant action of pethidine on the pregnant rat uterus in-vitro.

Pethidine's stimulant action on the 22-day pregnant rat isolated uterus does not involve receptors sensitive to methysergide and is unlikely to involve the synthesis and release of endogenous prostaglandins. The sensitivity of pethidine-induced contractions to verapamil suggests that mobilization of extracellular calcium is necessary for pethidine's action.

The Effect of Lysine Acetylsalicylate on Somatostatin Inhibition of Insulin Secretion Induced by Arginine

The inhibitory effect of somatostatin (SRIF) on immunoreactive insulin release and on many other hormonal secretions has been widely studied in both animal and man. However, the mechanism by which SRIF acts on these functions remains poorly defined. Aim of this study is to determine the inhibitory effect of SRIF on insulin secretion induced by arginine after the administration of lysine acetylsalicylate (LAS) in a dose which inhibits the endogenous synthesis of prostaglandins. Ten healthy informed volunteer subjects were studied. Four studies were carried out in randomized order, each one separated by a three day interval. The first study was a test of arginine (25 g i.v. in 30 min). The second study was a test of arginine with SRIF infusion (150 micrograms bolus followed by 100 micrograms/h for 120 min). The third study was a test of arginine with an infusion of SRIF and LAS (66 mg/min for 120 min). The fourth study was a test of arginine with LAS infusion. Plasma insulin levels were determined by radioimmunoassay. After arginine administration the typical biphasic insulin response was observed with a precocious peak at 3 min and a late peak at 30 min. This response is not significantly modified under LAS infusion. With the infusion of SRIF at a dose of 100 micrograms/hr after arginine administration only a very modest insulin response was observed. The addition of LAS does not modify the inhibitory effect of SRIF on insulin secretion induced by arginine. This result demonstrates that the inhibitory action of SRIF on the secretion of insulin is not dependent upon the activation of the endocellular prostaglandin system.

Effect of prostaglandin E2 and of indomethacin upon cerebral and pulmonary consequences of exposure to hyperbaric oxygen in rats

There are few data in the literature suggesting that endogenous prostaglandins (PGs) might be involved in the pathomechanism of seizures. Since the mechanism of seizures inducted by exposure to oxygen high pressure (OHP) is not fully elucidated, this study was designed to investigate the effect of exogenous PG s and of indomethacin (a Pg synthesis inhibitor) upon the development and consequences of seizures in rats exposed to OHP (5 ata). In the animals pretreated with PGE2 (1 ng/kg s.c.) pre-seizure time was shortened, lung weight : body weight index increased and symptoms of respiratory failure potentiated, as compared with the control group. Indomethacin (5 mg/kg i.p) prevented the development of seizures and of pulmonary consequences of OHP exposure. Biochemical examination of brains has shown that velocity of free radical oxidation of lipids (reactions manifested by the breakdown of phospholipid fatty acids, mainly unsaturated ones) enhanced by OHP exposure, is further potentiated in rats pretreated with PGE2. Electron microscopic study has shown the alterations similar to those seen in brain ischemia and/or hypoxia, and the magnitude of changes was related to the intensity of symptoms evoked by OHP. The results show that cerebral and pulmonary consequences of OHP exposure are potentiated by exogenous PGE2 and prevented by inhibition of endogenous PG synthesis. This suggests that PGs and/or their active metabolites might be involved in the mechanism of oxygen toxicity during exposure to hyperbaric oxygen.

Hypertonic induction of COX2 expression requires TonEBP/NFAT5 in renal epithelial cells

TonEBP/NFAT5 transcription factor is a master regulator of genes involved in osmoprotection. Cyclooxygenase 2 (COX2) has been reported to be a cytoprotective molecule in the inner renal medulla, where cells are physiologically exposed to the highest osmolality of the body. Our aim was to study whether COX2 expression requires TonEBP/NFAT5. Incubation of MDCK cells in hypertonic NaCl medium (500 mOsm/kg H 2O) caused fully translocation of TonEBP/NFAT5 from cytoplasm to nucleoplasm and significantly increased COX2 mRNA, protein and activity levels. TonEBP/NFAT5- siRNA prevented hypertonic induction of COX2 mRNA and protein, leading to a depressed-prostaglandin synthesis and to a decreased cell survival. By using COX2- siRNA and COX2 specific inhibitor NS398, we found that cell survival does not depend on endogenous COX2-induced prostaglandin synthesis, but that cytoprotection strongly correlates with COX2 protein levels. These results demonstrate a new function for TonEBP/NFAT5, i.e., to mediate hypertonic-induced COX2 expression, and suggest that osmoprotection strongly depends on COX2 protein levels.

Tumor Necrosis Factor-α Suppresses Sustained Potassium Currents in Rat Small Diameter Sensory Neurons

Tumor necrosis factor- (TNF- ), a pro-inflammatory cytokine, produces pain and hyperalgesia by activating and/or sensitizing nociceptive sensory neurons. In the present study, using whole-cell patch clamp techniques, the regulation of potassium currents by TNF- was examined in acutely dissociated small dorsal root ganglion neurons. We found that acute application of TNF- inhibited, in a dose-dependent manner, the non-inactivating sustained potassium current without changing the rapidly inactivating transient current or the voltage-dependence of steady-state inactivation. The effects of TNF- on potassium currents were similar to that of prostaglandin E2 as reported previously and also demonstrated in the current study. Furthermore, indomethacin, a potent inhibitor for both cyclo-oxygenase (COX)-1 and COX-2, completely blocked the effect of TNF- on potassium currents. These results suggest that TNF- may sensitize or activate sensory neurons by suppressing the sustained potassium current in nociceptive DRG neurons, possibly via stimulating the intracellular production i.e. the synthesis and/or release of endogenous prostaglandins.

Effects of prostaglandin E 2 and lipopolysaccharide on osteoclastogenesis in RAW 264.7 cells

Introduction Prostaglandins (PGs) can act on both hematopoietic and osteoblastic lineages to enhance osteoclast formation. Methods We examined PGE 2 stimulated osteoclastogenesis in RAW 264.7 cells and the role of endogenous PGE 2 in lipopolysaccharide (LPS) stimulated osteoclastogenesis. Results RANKL (1–100 ng/ml) increased formation of osteoclasts, defined as tartrate resistant acid phosphatase multinucleated cells, with peak effects at 30 ng/ml. Addition of PGE 2 (0.01–1.0 μM) to RANKL (30 ng/ml) dose dependently increased osteoclast number 30–150%. Use of NS-398 (0.1 μM) or indomethacin (Indo, 1.0 μM) to block endogenous PG synthesis had little effect on the response to RANKL alone but significantly decreased the response to PGE 2. Addition of LPS (100 ng/ml) to RANKL increased osteoclast number 50%, and this response was significantly decreased by NS-398 and Indo. RANKL and PGE 2 produced small, additive increases in COX-2 mRNA levels, while LPS produced a larger increase. PG release into the medium was not increased by RANKL and PGE 2 but markedly increased by LPS. Conclusion We conclude that RANKL stimulated osteoclastogenesis can be enhanced by PGE 2 and LPS though direct effects on the hematopoietic cell lineage and that these effects may be mediated in part by induction of COX-2 and enhanced intracellular PG production.

Efficacy of misoprostol and ranitidine in the prevention of duodenal ulcer relapse and its correlation with endogenous gastric prostanoid synthesis

We determined endogenous gastric prostaglandin synthesis and its correlation with the prevention of duodenal ulcer relapse by misoprostol and ranitidine. Sixty-one patients with recent endoscopically healed duodenal ulcer were randomly allocated in a double-blind fashion for one year of treatment with misoprostol 400 micrograms nocte, ranitidine 150 mg nocte or placebo. Patients were followed every two months. Endoscopy was repeated at six and 12 months or beforehand, if relapse was suspected. Antral and fundic biopsies, 3-4 from each region, were obtained at each endoscopy for determination of prostaglandin synthesis. During the one year of treatment, 11 out of the 12 placebo treated patients flared up, as opposed to 10 out of 25 and four out of 24 misoprostol and ranitidine treated patients, respectively. The difference between all treatment groups was significant (P less than 0.0001). In all subjects who flared up, pretrial endogenous antral and fundic prostaglandin E2 synthesis were not different from their respective synthesis in those who did not relapse.

Cholecystokinin (CCK) down regulates PGE 2 and PGI 2 release in inflamed Guinea pig gallbladder smooth muscle cell cultures

This study examines the hypothesis that cholecystitis down-regulates Guinea pig gallbladder (GPGB) smooth muscle cholecystokinin (CCK)-stimulated prostaglandin (PG) release. Guinea pig gallbladder from Control and 48 h bile duct ligated (BDL) animals were placed in cell culture and grown to confluence. The cultures underwent Western Blot analysis for smooth muscle cell content of COX-1, COX-2, Prostacyclin Synthase (PS), or were incubated with CCK at 10 −8 M or 10 −6 M with and without indomethacin for 1 h and analyzed for release of 6-keto-PGF 1 α , PGE 2 and TxB 2 by EIA. BDL increased Guinea pig gallbladder cell culture basal PGE 2 and PGI 2 release which was in part due to increased COX-2 content. CCK incubation down-regulated BDL Guinea pig gallbladder cell culture release of 6-keto-PGF 1 α and PGE 2 and down-regulated COX-2 content but did not alter the Control group. The decrease in CCK-mediated BDL cell Guinea pig gallbladder release may be an endogenous mechanism to limit physiologic derangements induced by increased endogenous gallbladder PG synthesis during early acute cholecystitis.