PGE2-like Activity Research Articles

Release and inhibitory effects of prostaglandin D2 in guinea pig urinary bladder and the role of urothelium

BackgroundWhile studying a urothelium-derived inhibitory factor in guinea pig urinary bladders we observed considerable release of prostanoids, including PGD2-like activity. The present study was carried out to identify the prostanoids and to study their roles in modulating guinea pig urinary bladder motility. MethodsRelease of PGE2 and PGD2 in isolated guinea pig urinary bladder preparations was analyzed by high performance liquid chromatography (HPLC) combined with bioassay on bladder strips. Isolated urothelium-intact (UI) or -denuded (UD) bladder strips were subjected to electrical field stimulation (EFS) and applications of PGE2 and PGD2. ResultsA resting release of 95±9 (n=5) nggtissue−1h−1 PGE2-like activity and 210±34 (n=4) nggtissue−1h−1 PGD2-like activity was found, where PGD2-like was subject to marked spontaneous inactivation during isolation. Prostanoids release was decreased by 70–90% by the cyclo-oxygenase inhibitor diclofenac in UI preparations. Urothelium removal decreased prostanoids release by more than 90%.PGE2 increased basal tone and spontaneous contractions, whereas PGD2 had little or no effect on these. Exogenous PGE2 enhanced and PGD2 inhibited contractile responses to EFS, exogenous acetylcholine- and ATP, whereas PGD2 caused marked dose-dependent inhibition. PGE2 and PGD2 effects were more pronounced in diclofenac-treated UD tissues. ConclusionsPGD2 and PGE2 are released from guinea pig bladder urothelium and PGD2 has inhibitory effects on bladder motility, mainly through a postjunctional action on smooth muscle responsiveness. General significanceThe release and inhibitory effects merit further studies in relation to normal biological function as well as overactive bladder syndrome.

BOSENTAN, A NON-SPECIFIC ENDOTHELIN ANTAGONIST, STIMULATES FRACTURE HEALING

It is assumed that bosentan, a non-selective ET-1 receptor antagonist, will enhance fracture healing. The aim of this prospective randomized controlled study was to investigate the effects of transcutaneous bosentan administration into diaphyseal bone fractures using radiology, histology, prostaglandin E2 (PGE2) and leukotrien C 4 (LTC4) activity measurements. A closed diaphyseal fracture was created in the hind limbs following intramedullary rod fixation of Guinea pigs. Bosentan was administred by repetitive weekly 0.1 μg transcutaneous injections into the fracture site. The effects of bosentan were evaluated by radiology and histology on weeks 1, 2 and 4, whereas prostaglandin E2 (PGE2)-like and leukotrien C 4 (LTC4)-like activity was assessed on weeks 1 and 2. The radiological degree of union (p = 0.001) at the fracture site and cortex-callus ratio (p = 0.02) was significantly better in the bosentan administered site at week 1 when compared to the control. Histology presented an initial stimulation of bone formation on weeks 1 and 2 in the experimental group. PGE2-like activity was significantly higher (p = 0.002) on week 1 and 2 in the bosentan-administered side. LTC4-like activity remained constant on week one and decreased on week two. Transcutaneous repetitive bosentan administration into the fracture site initially stimulated periosteal bone healing that resulted with extracellular matrix mineralization. The inflammatory mediators PGE2/LTC4 played a significant role in this process.

Effects of nitric oxide donor and inhibitor on prostaglandin E2-like activity, malondialdehyde and reduced glutathione levels after skeletal muscle ischemia-reperfusion

Oxygen free radicals are implicated in the pathophysiology of ischemia-reperfusion (I/R) injury in skeletal muscle. Nitric oxide (NO) and prostaglandin E2 (PGE2) are important regulators of the microcirculation in skeletal muscle. The effects of L-arginine, substrate for NO, and NG-nitro L-arginine methyl ester (L-NAME) on PGE2 synthesis, lipid peroxidation and reduced glutathione (GSH) levels was investigated in the rat gastrocnemius muscle after 3 h of reperfusion following 2 h of ischemia.Lipid peroxidation and GSH levels showed a non-significant changes in the I/R groups compared to the control group. According to these results, it can be assumed that skeletal muscle can resist 2 h of ischemia followed by 3 h of reperfusion-induced oxidative stress.PGE2-like activity in the gastrocnemius muscle increased in the L-NAME treated and I/R groups. L-arginine administration reversed the increase in PGE2-like activity of reperfused skeletal muscle. These findings support the conclusion that endothelium-derived PGE2 synthesis increases during reperfusion and suggest that PGE2 may have a protective role in the maintenance of endothelial function.

The effect of granulocyte macrophage-colony stimulating factor on the prostaglandin E2-like activity of the small intestine of rat during total body irradiation

Radiation-induced gastrointestinal toxicity is important for subjects receiving radiation to the pelvis. Eicosanoids and free radicals may be involved in the mechanism. rHuGM-CSF is a subcutaneously administered drug which may reduce some side effects of radiation. This experimental study was undertaken to determine the effectiveness of rHuGM-CSF on PGE2-like activity of the small intestine in rats. Thirty-two adult male Wistar-Albino rats entered the study to be randomized to one of the four groups: Group I. Control; II. Drug administered; III. Irradiated; IV. Irradiated and drug administered. Radiation was by total body irradiation, 800 rads with Cobalt 60. On the 9th day the animals were killed and biopsies were taken from the terminal ileum. PGE2-like activity was evaluated. Animals were weighed on the day of irradiation and end of the experiment. A statistically significant difference was found according to pre- and post-treatment weights in the irradiated and nonirradiated drug administered groups (Groups II and IV) (P=0.035 and 0.018, respectively). PGE2-like activity in the intestinal tissue was statistically significant higher in the drug-treated animals, both in non-irradiated and irradiated groups. Surprisingly, irradiation was found to decrease the PGE2-like activity in the intestinal tissue (P=0.008). rHuGM-CSF was found to increase PGE2-like activity in the intestinal tissue. The cellular mechanisms underlying this must be clearly determined and weighed carefully in considering the drug for clinical usage.

Leukotriene B 4 and prostaglandin E 2-like activity in synovial fluid in osteoarthritis

LTB 4 and PGE 2-like activity in synovial fluid samples from patients with osteoarthritis of the knee joint were determined and found to be significantly higher than in samples obtained from normal patients. The results suggest that leukotrienes and prostaglandins may have a role in the pathogenesis of osteoarthritis.

Tissue-cage model for the collection of inflammatory exudate in ponies

In a series of experiments to examine equine inflammatory exudates for the presence of metabolites of arachidonic acid, including prostaglandin E2 (PGE2), a model for the induction and collection of exudates in ponies has been developed. Multiperforated polypropylene practice golf balls implanted subcutaneously in the mid-neck region were well tolerated and proved to be the most successful model. One such cage was implanted in the neck of each of seven ponies. Inflammatory exudates were induced by injecting 3.0 or 0.5 ml carrageenin into the cages and aspirates collected between three and 48 hours later. These were examined for PGE2-like activity, total protein concentration and leucocytes. All three variables increased following the injection of both dose levels of carrageenin.

Extremely decreased release of prostaglandin E2-like activity from chopped lung of ethyl linolenate-supplemented rats.

Three groups of weanling male rats were reared on a fat-free diet for 13 weeks. One group received only the fat-free diet (FF rats), the other 2 groups received the fat-free diet and a daily supplement of 2 energy% ethyl linoleate ([n-6] rats), or 2 energy% ethyl linolenate ([n-3] rats). The chopped lung preparation was used to illustrate an in vitro prostaglandin formation. PGE2-like activity was quantified on rat stomach strip. The release of PGE2-like activity expressed as ng PGE2-equivalent per g lung tissue (mean +/- SD) was 23 +/- 7, less than 6, and 65 +/- 20 for the FF rats, the (n-3) rats, and the (n-6) rats, respectively. PGE2 quantification by radioimmunoassay of the chopped lung effluent collected after passing over the rat stomach strip revealed the same release pattern as the bioassay. Fractionation of chopped lung effluent on HPLC with radioimmunoassay detection indicated that the lung tissue from (n-3) rats released very little PGE3, if any, in spite of a 20:5(n-3)/20:4(n-6) ratio of 5.2 in the lipids of the lung. It is suggested that the pool of arachidonic acid for prostaglandin production in vitro is different from the one which functions in vivo, and the these pools are differently affected by dietary EFA.

Effect of topical and intraperitoneal indomethacin on the generation of PGE 2-like activity in rabbit conjunctiva and iris-ciliary body

A significant difference was observed in the generation of prostaglandin (PG)E2-like activity between rabbit iris-ciliary body and conjunctiva. The amount of PGE2-like activity produced at any given concentration of arachidonic acid (AA) by the iris-ciliary body was 2–3 times greater than the amount synthesized by the conjunctiva under identical experimental conditions. Also, synthesis of PGE2-like activity was dose-dependent in the iris-ciliary body in the concentration range of 1, 5 and 10 μg AA while in the conjunctiva it was dose-dependent in the concentration range of 10, 50 and 100 μg AA. The effect of indomethacin (INDO) in vivo on the generation of PGE2-like activity in the rabbit conjuctiva and iris-ciliary body was also assessed. Topical INDO (50μl), in concentrations of 0·1%, 0·25% and 0·5%, inhibited the generation of PGE2-like activity from AA in iris-ciliary body and conjunctiva at 2 hr after instillation, respectively. Similarly, intraperitoneal (i.p.) INDO treatment (5 mg/kg, 50mg/kg and 100 mg/kg) inhibited the generation of PGE2-like activity produced from various concentrations of AA in the iris-ciliary body and conjunctiva. However, again a significant difference was observed in the susceptibility of the production of PGE2-like activity to inhibition by INDO between the iris-ciliary body and conjunctiva especially when these tissues were incubated with higher concentrations (>10 μg) of AA. Under these conditions, INDO was less effective in inhibiting PGE2-like activity production in the iris-ciliary body than in the conjunctiva. These results indicate that the substrate concentration is a limiting factor in assessing the inhibitory effects of INDO. However, differences between the distribution of INDO into the anterior uvea and conjunctiva following i.p. or topical pretreatment cannot be excluded. The significance of these findings is discussed.

Distribution of prostaglandins in gastric and duodenal mucosa of healthy subjects and duodenal ulcer patients: effects of aspirin and paracetamol.

The distribution of mucosal PGE2-like activity was determined by bioassay technique in the body and antrum of the stomach and in the duodenum of healthy subjects and duodenal ulcer patients before and after administration of aspirin, paracetamol, or histamine. In healthy subjects, the oxyntic, antral and duodenal mucosa was found to be capable of generating large amounts of PGE2, which were not significantly different from those found in duodenal ulcer patients. No correlation was found between the generation of PGE2 and gastric acid secretory status or serum gastrin level. Aspirin-and to a much lesser extent, paracetamol-caused a dramatic reduction in the ability of the gastric mucosa to biosynthesis PGE2 and this was accompanied by marked side-effects and injury to the gastric mucosa. Administration of histamine caused small but significant reduction in the biosynthesis of PGE2 but it was accompanied by marked mucosal damage. This study indicates that the gastric and duodenal mucosa is capable of generating PGE2-like activity which may be involved in the mechanism that protects the mucosa against the damage caused by aspirin.

Prostaglandin action, release and inactivation by rat isolated perfused mesenteric blood vessels.

1 The following experiments were undertaken to confirm that prostaglandin is necessary for noradrenaline to exert its full vasoconstrictor effect in rat mesenteric blood vessels. Prostaglandin release and inactivation were also studied. 2 The cyclo-oxygenase inhibitor, 5, 8, 11, 14-eicosatetraynoic acid caused a significant depression of the concentration-effect curve to noradrenaline. As with indomethacin, responses were restored to control levels by prostaglandin E2 (PGE2) but PGE2 did not restore responses to noradrenaline depressed by papaverine. 3 PGE2-like activity was released from tissues at rest, equivalent to 50 +/- 20 pg PGE2/min. The substance was probably a stable prostaglandin since activity remained on acidifying and extracting into chloroform. The increase in release stimulated by noradrenaline was reduced below resting values by indomethacin. 4 There was a net loss of 7 +/- 1 and 1 +/- 0.2 ng PGE2/min from tissues perfused with 40 and 4 ng/min PGE2 respectively. No uptake occurred at lower PGE2 perfusion rates. 5 When indomethacin was used to depress responses to noradrenaline 15(S)-15-methyl PGE2 methyl ester was 12 times more potent than PGE2 in restoring responses to control values. The cyclic endoperoxide analogue U-46619 caused only partial restoration of indomethacin-depressed responses to noradrenaline but increased perfusion pressure at 2 ng/ml and above. 6 The results confirm that endogenous prostaglandin release, possible of PGE2, is obligatory to the full vasoconstrictor effect of noradrenaline. Noradrenaline increases the amount of prostaglandin released which may be taken up and inactivated by 15-hydroxy prostaglandin dehydrogenase or beta-oxidase. U-46619 may mimic both PGE2 and thromboxane A2.

Selective inhibition of prostaglandin production in inflammatory exudates and gastric mucosa.

A major clinical problem encountered in the use of non-steroid anti-inflammatory drugs has been the high incidence of gastrointestinal irritation. The mechanisms underlying damage to the gastric mucosa evoked by these drugs are complex. The normal resistance of the gastric mucosa to the back-diffusion of gastric acid from the lumen into the mucosal tissue can be disrupted by topical administration of aspirin as well as several irritants such as ethanol, bile salts and detergents; this results in gastric mucosal damage1. Such an action, however, cannot be the sole mechanism because many non-steroid anti-inflammatory drugs cause gastrointestinal damage when administered parenterally2,3. It has been proposed that a reduction in prostaglandin biosynthesis by aspirin-like drugs4 in the gastric mucosa leads to a fall in local blood flow which, in turn, gives rise to areas of focal ischaemia ultimately developing into erosions5. However, a combination of the direct topical irritant actions and inhibition of prostaglandin formation can lead to a marked potentiation of gastric damage3. Such a situation is likely to be encountered in the clinical use of these compounds following oral administration. We have investigated the relationship between gastric damage and inhibition of cyclooxygenase in the gastric mucosa following oral administration of anti-inflammatory compounds. For these studies, we have measured the ex vivo formation of prostacyclin (PGI2), the major cyclooxygenase product in the rat gastric mucosa which, like other prostaglandins such as PGE2, has gastro-protective actions6. In the inflammatory exudate induced by carrageenin, PGE2 predominates and has pro-inflammatory actions7. We have, therefore, investigated whether selective inhibition of prostaglandin production, assayed as PGE2-like activity, in the inflammatory exudate can be achieved in vivo. We report here that it can.

Prostaglandins E 2, F 2α, 6-keto-F 1α and thromboxane B 2 levels in carrageenin-induced inflammatory exudates in the rat air-pouch granuloma

Levels of PGE 2, PGF 2α, PGI 2 (measured as 6-keto-PGF 1α), and thromboxane B 2 were determined in rat inflammatory exudates induced 1, 3, and 7 days after carrageenin injection into air-pouch granuloma. The PGE 2 and 6-keto-PGF 1α levels found in the exudate could not account for the differences in PGE 2-like activity as measured by biologic and serologic methods.