Effects of Gabexate,a Protease Inhibitor,on Smooth Muscle of Guinea-Pig Stomach Fundus

Abstract: A protease inhibitor, gabexate (ethyl-p-6-guanidinohexanoyloxy benzoate), was found to have an antimuscarinic action in muscle strips of the guinea-pig gastric fundus. Gabexate reversibly inhibited carbachol-induced contractions in the presence of prostaglandin synthesis inhibitors (indomethacin or meclofenamate) with a pA₂ of 5.66 for the circular and 5.25 for the longitudinal muscle. The effect was not affected by tetrodotoxin. Gabexate also inhibited contractions produced by prostaglandin E₂ (PGE₂) (21.7 ± 7.3% with 30 μM, n = 12). The inhibition was markedly potentiated by anticholinesterase, diisopropyl fluorophosphate, but converted to contraction by atropine. In the absence of PGE₂, gabexate produced no mechanical response on its own even after atropine application. Treatment with hemicholinium, an acetylcholine synthesis inhibitor, also converted the relaxant effect of gabexate, applied during PGE₂-induced contraction, to contraction. Gabexate also inhibited contracture induced by 30 mM K⁺ weakly (13 ± 2% with 30 μM, n=5). This relaxation was abolished by atropine, without converting to contraction. PGE₂ and excess K⁺ are likely to release acetylcholine from nerve fibres. These results suggest that the inhibitory effect of gabexate is mainly due to the muscarinic receptor blocking action. In addition, gabexate has a potentiating action on the prostaglandin-induced contraction.     

THROMBOXANE B2 INHIBITS PROSTAGLANDIN E2 INACTIVATION BY THE RAT ISOLATED PERFUSED LUNG

1. The effect of thromboxane B₂ (T×B₂) on inactivation of prostaglandin E₂ (PGE₂) by the rat isolated perfused lung has been studied. 2. TxB₂ when infused in low concentrations (100 ng/ml) into the pulmonary artery reduced PGE₂ inactivation approximately two-fold. 3. The rat isolated fundus strip was contracted by higher concentrations of TxB₂ (1.0 Mg/ml) in the presence of hyoscine, mepyramine, methysergide, phenoxy-benzamine and propranolol. The size of contraction was reduced by indomethacin in concentrations known to inhibit prostaglandin synthetase. 4. Thus, in circumstances in which T×B₂ and PGE₂ are released concomitantly by the lung, low concentrations of TxB₂ may augment PGE₂ release by reducing its inactivation.     

857-860Anti-inflammatory Effect of Magnolol,Isolated from Magnolia officinalis,on A23187-induced Pleurisy in Mice

In the present study, A23187-induced pleurisy in mice was used to investigate the anti-inflammatory effect of magnolol, a phenolic compound isolated from Chinese medicine Hou p'u (cortex of Magnolia officinalis). A23187-induced protein leakage was reduced by magnolol (10mgkg^?1, i.p.), indomethacin (10mgkg^?1, i.p.) and BW755C (30mgkg^?1, i.p.). A23187-induced polymorphonuclear (PMN) leucocyte infiltration in the pleural cavity was suppressed by magnolol and BW755C, while enhanced by indomethacin. Like BW755C, magnolol reduced both prostaglandin E₂ (PGE₂) and leukotriene B₄ (LTB₄) levels in the pleural fluid of A23187-induced pleurisy, while indomethacin reduced PGE₂ but increased LTB₄ formation. In the rat isolated peripheral neutrophil suspension, magnolol (3.7 μM) and BW755C (10 μM) also suppressed the A23187-induced thromboxane B₂ (TXB₂) and LTB₄ formation. These results suggest that magnolol, like BW755C, might be a dual cyclo-oxygenase and lipoxygenase inhibitor. The inhibitory effect of magnolol on the A23187-induced pleurisy is proposed to be, at least partly, dependent on the reduction of the formation of eicosanoids mediators in the inflammatory site.     

Prostanoid receptors of the EP3 subtype mediate the inhibitory effect of prostaglandin E2 on noradrenaline release in the mouse brain cortex

Mouse or rat brain cortex slices were preincubated with ³H-noradrenaline and superfused with physiological salt solution containing desipramine. We studied the effects of prostaglandin E₂ (PGE₂), prostaglandin D₂ (PGD₂) and related drugs on the electrically evoked (50 mA, 2 ms, 0.3 Hz) tritium overflow.PGE₂ inhibited the electrically evoked tritium overflow from mouse brain cortex slices; the maximum effect of PGE₂ (79010) was attenuated by the ₂-adrenoceptor agonist talipexole (to 52010) and enhanced by the ₂-adrenoceptor antagonist rauwolscine (to 92%). Rauwolscine was added to the superfusion medium in all subsequent experiments. The effect of PGE₂ was readily reversible upon withdrawal from the medium and remained constant upon prolonged exposure of the tissue to the prostanoid. Studies with EP receptor agonists, mimicking the inhibitory effect of PGE₂, showed the following potencies (pIC₅₀): sulprostone (8.22); misoprostol (8.00); PGE₂ (7.74); PGEZ (7.61); iloprost (5.86). The concentration-response curve of PGE₂ was marginally shifted to the right by the EP₁ receptor antagonist AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid; apparent pA₂ 3.97) and by the TP receptor antagonist vapiprost (4.50). AH 6809, by itself, did not affect the evoked overflow whereas vapiprost increased it. PGD2 inhibited the evoked overflow at high concentrations (pIC₅₀ 4.90); this effect was not altered by the DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexyl-2hydroxyethylamino)hydantoin), which, by itself, did not affect the evoked overflow. Indometacin slightly increased the evoked overflow and tended to increase the inhibitory effect of PGE₂. PGE₂ inhibited the electrically evoked tritium overflow also in rat brain cortex slices. The maximum effect (obtained in the presence of rauwolscine) was 61%; the pIC₃₀ value was 7.67.The present study suggests that PGE₂ inhibits noradrenaline release from mouse brain cortex via EP₃ receptors and that its maximum effect is more marked in the mouse than in the rat. The inhibitory effect of PGD₂ (in the mouse brain) does not involve DP receptors and may also be related to EP₃ receptors. The EP₃ receptors interact with a2-adrenoceptors and may be activated by endogenous prostanoids.     

PROSTAGLANDINS: ANTINOCICEPTIVE EFFECT OF PROSTAGLANDIN E1 IN THE RAT

1. The antinociceptive effect of prostaglandins E₁, E₂ and F_2α was studied in albino rats. Though all three prostaglandins produced similar degrees of sedation, only prostaglandin E₁ (PGE₁) produced a dose-related antinociceptive activity. 2. The antinociceptive activities of equi-analgesic doses of morphine (7.5 mg/kg, i.p.) and PGE₁ (2.0 mg/kg, i.p.) were inhibited to almost similar extents after pretreatment with drugs known to reduce central turnover of serotonin receptors, namely reserpine, fenclonine (p-chlorophenylalanine), methysergide and 5,6-dihydroxytryptamine. 3. Prostaglandin F_2α (2.0 mg/kg, i.p.) significantly inhibited the antinociceptive effects of both morphine and PGE₁. 4. The prostaglandin synthesis inhibitors, indomethacin and diclofenac, significantly inhibited morphine analgesia. 5. Probenecid markedly prolonged the duration of antinociceptive effect of morphine and the duration of PGE₁-induced potentiation of subanalgesic dose of morphine. 6. The results suggest that, in albino rats, PGE₁-induced antinociceptive activity is serotonin mediated and that morphine analgesia is not only mediated through serotonin but also through prostaglandins (PGE₁?) and 5-hydroxyindole acetic acid, the serotonin metabolite.     

Prostaglandin E1 increases binding of 123I-low-density lipoprotein to the human liver in vivo

Previous in vitro radioligand binding data have shown that prostaglandin E₁ (PGE₁) increases the number and the binding affinity of low-density lipoprotein (LDL) receptors of the human liver. Experimental data in normo- and hypercholesterolaemic rabbits have confirmed these findings, showing a significant increase in LDL-binding to the liver in vivo after prolonged PGE₁ therapy. Methods: This study aimed to confirm the experimental and animal data in human in vivo. ¹²³I-LDL binding to the liver was quantified in vivo in patients suffering from peripheral vascular disease, seven of them with heterozygous familial hypercholesterolaemia (HC) and five with normal total plasma cholesterol, after PGE₁ administration (5 ng·kg^–1·min^–1; 6 h daily for 5 days/week for 5 weeks). LDL uptake by the liver was quantified by single photon emission computer tomography (SPECT). Results: The amount of LDL trapped by the liver in normocholesterolaemics (45.6%) was significantly higher than in hypercholesterolaemics (22.0%). PGE₁ induced an increase in liver LDL binding, which was more pronounced in HC (+38.2%) than in normocholesterolaemic patients (+8.11%).     

Effects of prostaglandin E2 and indomethacin on the rebound of the guinea-pig taenia coli.

The effects of prostaglandin E₂ (0.2 μM) and indomethacin (50 μM) on the rebound of smooth muscle cells of the guinea-pig taenia coli were studied. Stimulation of the non-cholinergic, non-adrenergic, intramural nerves caused membrane hyperpolarizaiton, known as the inhibitory junction potential (I.J.P.). This hyperpolarization was followed by a rebound depolarization and a rather small rebound contraction in quiescent preparations; the rebound depolarization was often accompanied by action potentials, resulting in a pronounced rebound contration. The effects of prostaglandin E₂ (PGE₂) on the membrane were comparable with the phenomena observed during the rebound, i.e. membrane depolarization, development of action potentials and contraction of the smooth muscle cells. Furthermore, an increase in amplitude of the I.J.P., enhancement of the spike discharge and a concomitant increase in rebound contraction were observed in the presence of PGE₂. Indomethacin did not modify the membrane potential or the amplitude of the I.J.P., but inhibited the rebound contraction and suppressed the development of action potentials during the rebound. The action of PGE₂ on the smooth muscle cell membrane was not modified by indomethacin, but the rebound contraction in the presence of both compounds was decreased. These experimental results indicate: that the rebound contraction is accompanied by depolarization of the membrane following the hyperpolarization caused by stimulation of the non-cholinergic non-adrenergic nerves; that the rebound activity can be mimicked by PGE₂; that indomethacin does not interfere with the action of PGE₂ applied exogenously and that the observations are consistent with the assumption that prostaglandins might be involved in the rebound.     

The action of prostaglandin E2 on the smooth muscle cell of the guinea-pig taenia coli

The effect of prostaglandin E₂ (PGE₂) on the smooth muscle cell of guinea pig taenia coli was investigated by measuring changes in membrane potential, membrane resistance, muscle contraction and ion fluxes. The action of PGE₂ caused depolarization of the cell membrane, and increased spike activity and muscle contraction. The amplitude of the PGE₂ depolarization was concentration-dependent. The action of PGE₂ could be mimicked by depolarizing the muscle membrane with an external current with as result a decrease in membrane resistance similar to that observed in the presence of PGE₂. The PGE₂ depolarization was not abolished when the sodium pump was inhibited by omitting external potassium or in the presence of K-strophantin, persisted in low chloride Krebs and in low sodium solution, but was reduced in calcium-free solution and in the presence of D600. ⁴⁵Ca influx was enhanced by PGE₂, but ⁴⁵Ca efflux was not affected. The ⁴²K efflux was increased in the presence of PGE₂, but this response was blocked by Ca-free solution. These results indicate that calcium permeability is enhanced by PGE₂, and that this enhancement is associated with a depolarization of the muscle cell membrane of the guinea-pig taenia coli.     

Activation of arachidonoyl phospholipase A2 in prostaglandin-mediated action of sucralfate

1. The mechanism of sucralfate-induced gastric mucosal prostaglandin generation was investigated using mucosal cells labeled with [¹⁴C]choline and [³H]arachidonic acid.2. In comparison to the controls, the cells maintained in the presence of sucralfate showed a concentration dependent increase in lysophosphatidylcholine (LPC) synthesis and PGE₂ generation. The maximal effect was attained at 25 μM sucralfate giving a 45.7% increase in LPC and 70% increase in PGE₂.3. Pretreatment with indomethacin prior to sucralfate, while causing inhibition in PGE₂ generation, had no effect on LPC production and led to accumulation of free arachidonic acid. In the case of pretreatment with NDGA, the sucralfate caused increased LPC synthesis accompanied by enhanced PGE₂ generation without free arachidonic acid accumulation.4. The stimulatory effect of sucralfate on LPC synthesis and PGE₂ generation was inhibited by phospholipase A₂ inhibitors, mepacrine and BPB. The inhibitory effect was concentration dependent and attained maximum at 40 μM for BPB and 80 μM for mepacrine.5. The results for the first time demonstrate that the enhancement in gastric mucosal prostaglandin generation by sucralfate results from the stimulation of mucosal phospholipase A₂ for arachidonic acid release.     

Platelet activating factor and the responses of rat isolated stomach strip to prostaglandin E2

Abstract— The effect of platelet activating factor (PAF) on contractions evoked by acetylcholine, 5-hydroxytryptamine (5-HT) and prostaglandin E₂ (PGE₂) was studied in-vitro on rat stomach strip. Addition of PAF to the organ bath increased PGE- but not 5-HT- or acetylcholine-evoked responses. The effect of PAF was unaffected by atropine, methysergide or indomethacin, but prevented by a specific PAF receptor antagonist BN 52021. The data support a specific interaction between PAF and PGE₂ on rat stomach strip.     

Acetylcholine release from the myenteric plexus of guinea-pig ileum by prostaglandin E1

Release of acetylcholine (ACh) by prostaglandin E₁ from the nerve terminals of the guinea-pig longitudinal muscle strip was studied in order to reveal the effect of PGE₁ on myenteric plexus activity. The ACh released was collected in the presence of physostigmine (2·1 μg ml^?1) and choline (0·1 μg ml^?1) at 38° C. Five to 100 ng ml^?1 PGE₁ enhanced the release dose-dependently. The effect was maintained during the presence of PGE₁ in the organ bath, while rapid tachyphylaxis was observed with the ACh-releasing action of nicotine. Tetrodotoxin or morphine almost completely inhibited the effect of PGE₁ on ACh release. Hexamethonium, in a concentration which completely blocked the effect of nicotine, partially inhibited the effect of PGE₁. In the late phase of nicotine action, the tissue was still sensitive to PGE₁ despite the continued exposure to nicotine. These data suggest the presence in the myenteric plexus of PG receptors which can increase ACh release.     

Effect of prostaglandin E2 on acetylcholine release from some peripheral cholinergic nerve terminals

The effect of prostaglandin E₂ (PGE₂) on the acetylcholine (ACh) release evoked from rat phrenic nerve terminals and from Auerbach's plexus of the guinea-pig ileum was investigated. PGE₂ enhanced the evoked release of ACh from phrenic nerve terminals and from Aurbach's plexus in a concentration-dependent manner. Preincubation with 7-oxa-13-prostynoic acid, the PGE receptor blocker, and indomethacin inhibited the PGE₂-induced increase of evoked release of ACh while atropine failed to do so. Whereas a single administration of either 7-oxa-13-prostynoic acid or indomethacin significantly inhibited the control evoked release of ACh from the Auerbach's plexus, they failed to alter the control evoked release of ACh from the phrenic nerve terminals. The study indicates that the PGE₂-induced increase in release of ACh from cholinergic nerve terminals is accomplished through activation of prostaglandin receptors and that PGE₂ may play a physiological role in ACh liberation from the cholinergic autonomic nerve terminals but not from motor nerve terminals.     

Gastric acid is the key modulator in the pathogenesis of non‐steroidal anti‐inflammatory drug‐induced ulceration in rats

1. In the present study, we investigated the role of gastric acid (GA) secretion on non‐steroidal anti‐inflammatory drug (NSAID)‐induced ulcerogenesis in vivo. Rats were administered single oral doses of selective cyclo‐oxygenase (COX)‐1 (SC‐560; 2.5 mg/kg), COX‐2 (DFU; 25 mg/kg) or non‐selective COX (indomethacin; 25 mg/kg) inhibitors. Three groups (basal, histamine‐stimulated and histamine with lansoprazole) were pylorus ligated 2 h after inhibitor administration and killed 2 h later. Another group without pylorus ligation received only inhibitors and was killed after 18 h. 2. At 4 h, indomethacin increased the ulcer index (UI) and myeloperoxidase (MPO) activity in basal and histamine‐stimulated states, whereas SC‐560 only increased MPO activity. Histamine‐stimulated, but not basal, GA was further enhanced by indomethacin and SC‐560 via increased proton pump expression. Lansoprazole (10 mg/kg) reduced the UI, MPO activity and GA to basal levels with SC‐560 and DFU and to near basal with indomethacin. Indomethacin and SC‐560 significantly inhibited prostaglandin (PG) E₂, without significantly affecting COX‐1 and COX‐2 expression. Although DFU inhibited PGE₂ by one‐third, it did not affect COX expression. 3. At 18 h, indomethacin significantly increased the UI and MPO activity, whereas PGE₂ synthesis was less inhibited, indicating a return to control levels. In contrast, PGE₂ synthesis was higher than control with SC‐560. Furthermore, COX‐2 expression was significantly elevated with indomethacin and SC‐560, explaining the source of augmented PGE₂ synthesis. Proton pump expression remained elevated, comparable with 4 h levels, with indomethacin and SC‐560. However, DFU had no significant effect on the aforementioned parameters. 4. The data suggest that NSAID‐induced ulcerogenesis is dependent on the amount of GA secretion derived from increased proton pump expression and requires inhibition of both COX‐1 and COX‐2.     

Air Pollution Particulate SRM 1648 Causes Oxidative Stress in RAW 264.7 Macrophages Leading to Production of Prostaglandin E2, a Potential Th2 Mediator

Particulates in air pollution have been strongly associated with asthma symptoms. These particulates are a conglomeration of many components, including metals, polyaromatic hydrocarbons, and lipopolysaccharide, that may cause oxidative stress upon uptake by alveolar macrophages. The objective of this study was to assess whether uptake of a model air particulate (SRM 1648) causes oxidative stress in macrophages resulting in the production of the eicosanoid mediator prostaglandin E₂ (PGE₂) that might exacerbate asthma. SRM 1648 suspended in phosphate-buffered saline (PBS) was introduced into wells with plated RAW 264.7 monocyte/macrophages. Following incubation of SRM 1648 with RAW 264.7 macrophages, prostaglandin E₂ was measured by enzyme immunosorbent assay (EIA), and oxidative stress was assessed by the levels of intracellular reduced glutathione (GSH) as well as by the oxidation of dihydrodichlorofluorescein (H₂DCFDA) to the fluorescent dichlorofluoresecein (DCF). The results indicated that SRM 1648 caused oxidative stress in RAW 264.7 macrophages, as shown by a compensatory increase in GSH levels in comparison to the controls of titanium dioxide and media alone. Prostaglandin E₂ levels significantly increased at the 3-, 6-, and 12-h time points. Introduction of GSH ester to buffer against oxidative stress was able to block the elevation of PGE₂. The data show that SRM 1648 causes oxidative stress in RAW 264.7 macrophages resulting in formation of the potential Th2 mediator prostaglandin E₂.     

Modulation by prostaglandins of the release of [3H]noradrenaline evoked by potassium and nerve stimulation in the isolated rat heart

In the isolated rat heart perfused with Krebs solution and prelabeled with [³H]noradrenaline, we examined the effect of prostaglandins (PG) I₂, E₂, 6-keto-PGF_1α and their precursor, arachidonic acid, on the overflow of tritium elicited by potassium (K⁺) and by stimulation of cardiac sympathetic nerve plexus. Prostaglandins E₂, I₂ and arachidonic acid but not 6-keto-PGF_1α reduced K⁺ and nerve stimulation-induced overflow of tritium. Administration of indomethacin, an inhibitor of cyclooxygenase, increased tritium overflow elicited by either K⁺ or by nerve stimulation. During infusion of indomethacin, the inhibitory effect of both PGE₂ and PGI₂ on the K⁺ or nerve stimulation-induced overflow of tritium remained unaltered. In contrast, the effect of arachidonic acid to reduce K⁺ or nerve stimulation-induced overflow of tritium was abolished by indomethacin, indicating that the fatty acid inhibits release of tritium by its conversion to a product(s) of cyclooxygenase, presumably PGI₂ and PGE₂. These data suggest that prostaglandins, particularly PGI₂ and PGE₂ sythesized in the isolated rat heart act on prejunctional sites to modulate release of the adrenergic transmitter.     

PLGA Microparticles Encapsulating Prostaglandin E1-Hydroxypropyl-β-cyclodextrin (PGE1-HPβCD) Complex for the Treatment of Pulmonary Arterial Hypertension (PAH)

Purpose  

To test the efficacy and viability of poly (lactic-co-glycolic acid) (PLGA) microspheres encapsulating an inclusion complex of prostaglandin E₁ (PGE₁) and 2-hydroxypropyl-β-cyclodextrin (HPβCD) for pulmonary delivery of PGE₁ for treatment of pulmonary arterial hypertension (PAH), a disease of pulmonary circulation.     

On the effect of prostaglandins E2 and F2alpha on bronchial tonus in cats

The effects of the prostaglandins E₂ and F_2α on bronchotonus were studied in cats anesthetized with chloralose, vagotomized, relaxed by suxamethonium, and ventilated at a constant tidal volume.Under conditions of normal bronchotonus, PGE₂ (0.5–10 μg/kg) had a weak and PGF_2α (0.1–50 μg/kg) a moderate bronchoconstrictor effect; in the case of PGE₂ only, there was a clear correlation to the concomitant rises in pulmonary arterial pressure. During bronchoconstriction induced by infusion of 5-HT, carbachol or paraoxon, PGE₂ had a dose dependent bronchodilator effect in the majority of the experiments. Some cats, however, reacted with a further increase in airway pressure to this prostaglandin. PGE₂ had no dilator effect when bronchoconstriction had been induced by histamine.Experiments in which the cats were treated with α-methyltyrosine, guanethidine, cocaine, reserpine, phentolamine, propranolol, chlorisondamine or atropine did not reveal a dependence of the bronchial actions of the prostaglandins on the autonomic nervous system or its transmitters.Inhibition of prostaglandin synthetase by indomethacin increased sensitivity to both the constrictor and dilator effects of both prostaglandins.     

EFFECT OF INDOMETHACIN ON RESPONSES OF SHEEP ISOLATED CORONARY ARTERY TO ARACHIDONIC ACID

Indomethacin (2.8 μmol/1) did not consistently affect basal tone of sheep coronary artery strips, while a ten-fold higher concentration increased tension in 50% of the preparations tested. When acetylcholine was used as a spasmogen, oscillations in induced tone and relaxations produced by arachidonic acid (6.6 μmol/1) were abolished by indomethacin, 2.8 μmol/1 and 7 μmol/1, respectively. Prostacyclin (PGI₂) and prostaglandin E₁ decreased and PGE₂ increased arterial tension while PGF_2α was inactive. Responses to PGI₂ were reduced by indomethacin (28 μmol/1) but not by indomethacin (2.8 μmol/1). It is suggested that sheep isolated coronary arteries synthesize and release prostacyclin in the presence of acetylcholine and arachidonic acid and that such synthesis can be inhibited by indomethacin.     

Prostaglandin production by intact isolated gastric parietal cells

An enriched population of isolated gastric parietal cells was obtained from canine gastric mucosa. Parietal cells incubated with [¹⁴C]arachidonic acid produced radiolabelled PGF_2α. PGE₂, PGD₂ and 6-keto PGF_1α (acid hydrolysis product of PGI₂). The prostaglandin synthesis was inhibited by indomethacin. Prostaglandin production, as measure by gas chromatography-mass spectrometry demonstrated that PGF_2α was produced in the highest quantity followed by PGE₂ and 6-keto PGAF_1α. This demonstrates that isolated parietal cells are capable of producing prostaglandins. Since prostaglandins have a potent effect on gastric acid secretion, local prostaglandin synthesis could modulate parietal cell function.     

Diphlorethohydroxycarmalol,Isolated from Ishige okamurae,Increases Prostaglandin E2 through the Expression of Cyclooxygenase-1 and -2 in HaCaT Human Keratinocytes

Prostaglandin (PG) E₂, the most abundant prostaglandin in the human body, is synthesized from arachidonic acid via the actions of cyclooxygenase (COX) enzymes. PGE₂ exerts homeostatic, cytoprotective, inflammatory, and in some cases anti-inflammatory effects. Also, it has been reported that PGE₂ is involved in hair growth. Diphlorethohydroxycarmalol (DPHC) is a phlorotannin compound isolated from the brown algae Ishige okamurae, with various biological activities in vitro and in vivo. In this study, the biological effect and mechanism of action of DPHC on prostaglandin synthesis in HaCaT human keratinocytes was examined. The results showed that, in these cells, DPHC significantly and dose-dependently induced PGE₂ synthesis by increasing the protein and mRNA levels of COX-1 and COX-2. Interestingly, DPHC-induced COX-1 expression preceded that of COX-2. Also, while both rofecoxib and indomethacin inhibited PGE₂ production, the latter was seems to be the more potent. From above results, we can expect that DPHC has some beneficial effects via increasing of PGE₂ production.