Repeated bronchoconstriction attenuates the cough response to bronchoconstriction in naïve guinea pigs

BackgroundCough variant asthma (CVA) is recognized as a precursor of bronchial asthma (BA). However, the cough response to bronchoconstriction differs between these similar diseases. Repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators may impact the cough response.MethodsWe investigated the influence of repeated bronchoconstriction on the cough response to bronchoconstriction using naïve guinea pigs. Bronchoconstriction was induced for 3 consecutive days and changes in the cough response and lipid mediators, such as PGE₂, PGI₂, and cysteinyl-LTs (Cys-LTs), in BAL fluid (BALF) were assessed. We investigated the effect of endogenous PGI₂ on the cough response by employing a PGI₂ receptor antagonist. In order to investigate the cough response over a longer period, we re-evaluated the cough response 2 weeks after repeated bronchoconstriction.ResultsThe number of coughs induced by bronchoconstriction were significantly decreased by repeated bronchoconstriction. The levels of PGE₂, PGI₂, and Cys-LTs, and the ratio of PGI₂/PGE₂ were significantly increased, following repeated bronchoconstriction. This decrease in the cough response was suppressed by pretreatment with a PGI₂ receptor antagonist. Two weeks after repeated bronchoconstriction, the cough response returned to the same level as before repeated bronchoconstriction along with a concomitant return of lipid mediators, such as PGE₂, PGI₂, and Cys-LTs and the ratio of PGI₂/PGE₂.ConclusionsOur results suggest that repeated bronchoconstriction and the resulting imbalance of endogenous lipid mediators contribute to the difference in cough responses to bronchoconstriction in CVA and BA.     

Gastrointestinal Protection by Low-Dose Oral Prostaglandin E2 in Rheumatic Diseases

In a previous study oral prostaglandin E₂ (PGE₂) was shown to protect against indomethacin-induced gastrointestinal bleeding in patients with rheumatic diseases. This study examined whether a lower oral dose of PGE₂, without acid antisecretory effect, is protective. Its methylated analogue 15(R)15 Me PGE₂, which has effect on the acid secretion given orally, was also tested. Indomethacin, 50 mg three times daily, induced an increase in gastrointestinal bleeding measured by the ⁵¹Cr technique. PGE₂, 0.33 mg three times daily, taken concomitantly significantly reduced fecal blood loss. 15(R)15 Me PGE₂, 40 μg three times daily, was also effective. The prostaglandins did not increase joint symptoms and had no significant side effects. It is suggested that the combination of nonsteroidal anti-inflammatory drugs with a low oral dose of E₂ prostaglandins could be used clinically, especially in patients with rheumatic diseases.     

Interaction between inducible nitric oxide synthase and cyclooxygenase-2 after cerebral ischemia

Focal cerebral ischemia is associated with expression of both inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), enzymes whose reaction products contribute to the evolution of ischemic brain injury. We tested the hypothesis that, after cerebral ischemia, nitric oxide (NO) produced by iNOS enhances COX-2 activity, thereby increasing the toxic potential of this enzyme. Cerebral ischemia was produced by middle cerebral artery occlusion in rats or mice. Twenty-four hours after ischemia in rats, iNOS-immunoreactive neutrophils were observed in close proximity (<20 μm) to COX-2-positive cells at the periphery of the infarct. In the olfactory bulb, only COX-2 positive cells were observed. Cerebral ischemia increased the concentration of the COX-2 reaction product prostaglandin E₂ (PGE₂) in the ischemic area and in the ipsilateral olfactory bulb. The iNOS inhibitor aminoguanidine reduced PGE₂ concentration in the infarct, where both iNOS and COX-2 were expressed, but not in the olfactory bulb, where only COX-2 was expressed. Postischemic PGE₂ accumulation was reduced significantly in iNOS null mice compared with wild-type controls (C57BL/6 or SV129). The data provide evidence that NO produced by iNOS influences COX-2 activity after focal cerebral ischemia. Pro-inflammatory prostanoids and reactive oxygen species produced by COX-2 may be a previously unrecognized factor by which NO contributes to ischemic brain injury. The pathogenic effect of the interaction between NO, or a derived specie, and COX-2 is likely to play a role also in other brain diseases associated with inflammation.     

Prostaglandin E1 in critical limb ischemia transcutaneous PO2: A predictor of efficacy?

Prostaglandin E₁ (PGE₁) has found a widespread use in treating patients with critical limb ischemia. Because therapy with PGE₁ is time and cost intensive, a parameter for identifying nonresponders and consecutive therapy failures would be helpful. Therefore, the aim of this study was to evaluate the role of transcutaneous PO₂ (tcPO₂), before and after IV application of PGE₁, in patients with critical limb ischemia as a predictor of efficacy.Twenty patients with arterial occlusive disease stage IV according to Fontaine and a tcPO₂ of less than 30 mmHg (dorsum of the foot) received one IV infusion of 40 µg PGE₁ in 125 mL saline over thirty minutes. In 11 patients tcPO₂ increased by more than 5 mmHg. These patients were classified as responders. Two patients revealing only a small increase in tcPO₂, 5 patients with unchanged tcPO₂, and 2 patients who showed a decrease in tcPO₂ were considered as nonresponders. Only 2 patients among the responders had baseline tcPO₂ values below 5 mmHg, whereas 6 of the nonresponders showed such low values. Three of the responder group had to undergo an operation in comparison to 6 of the nonresponders.The increase in tcPO₂ induced by IV infusion of PGE₁ may have predictive value for the effectiveness of conservative treatment. Further validation is necessary.Presented at the 35th World Congress, International College of Angiology, Copenhagen, Denmark, July 1993     

Effects of indomethacin on prostanoid synthesis and vasomotor responsiveness in endothelium-denuded abdominal and thoracic aortas of Wistar rats

In endothelium-denuded abdominal (but not thoracic) aortas of rats, the nonselective cyclooxygenase (COX) inhibitor, indomethacin, suppressed contractions evoked by α-adrenergic agonists hypothetically mediated by prostanoids. We aimed to identify these non-endothelial-derived contractile prostanoids released by α-adrenergic receptors activation. Endothelium-denuded abdominal and thoracic aortas of Wistar rats were used for biochemical and functional analyses. Western blot analysis showed that COX-1 and COX-2 protein levels were respectively equivalent in endothelium-denuded abdominal and thoracic aortas. Enzyme immunoassay data supported direct evidence of phenylephrine-stimulated release of prostanoids (PGI₂, PGE₂, and PGF_2α) by thoracic and abdominal aortas without endothelium, and their almost complete inhibition by 1 μM indomethacin. Isometric force measurements established that 10 μM indomethacin—but no lower concentrations—inhibited the contractions evoked by phenylephrine in endothelium-denuded abdominal aorta. In this preparation, 10 μM indomethacin also depressed the contractions provoked by angiotensin II and high K⁺ (80 mM). In fact, indomethacin (up to 1 mM) caused concentration-dependent reductions in all abovementioned contractile responses. In endothelium-denuded thoracic aortas, however, only 1 mM indomethacin significantly depressed the contractile activity stimulated by either phenylephrine, angiotensin II, or high K⁺. Hence, there was a clear quantitative difference in response to indomethacin between abdominal and thoracic aortas without endothelium. Altogether, the results indicate that prostanoids induced by phenylephrine in abdominal and thoracic aortas were derived from non-endothelial COX-mediated metabolism; notably, the decrease in prostanoid synthesis could not account for the inhibition of vasoconstrictor responses by indomethacin: Through COX-independent actions, indomethacin inhibited aortic smooth muscle contractility.     

Production of prostanoids by rheumatic synovial cells in vitro: effects of anti-inflammatory drugs on arachidonic acid metabolism

Summary To evaluate the role of prostanoids in rheumatoid arthritis the effects of anti-inflammatory drugs on prostanoid concentrations and their ratios were studied in a primary culture of adherent synovial cells from patients with rheumatoid arthritis. Cells from rheumatoid synovium have a great capacity for prostanoid production. PGE₂ is the main prostanoid but synovial cells are also capable of producing 6-keto-PGF₁ and PGF₂. There were also very low TxB₂ concentrations in the culture medium after incubation. All nonsteroidal anti-inflammatory drugs used (diclofenac, indomethacin and tolfenamic acid) reduced markedly in concentrations achieved therapeutically (0.13 mol/l) the production of all the prostanoids from endogenous substrate. There were no differences in the efficacity of the drugs. Hydrocortisone was needed for higher concentrations to inhibit PGE₂, 6-keto-PGF₁ and PGF₂ production. TxB₂ formation remained almost unaltered. After the drug incubation there were also clear alterations in the ratios between these prostanoids, which may have therapeutic importance. It is suggested that this kind of synovial cell culture can be used for testing the effects and mechanisms of different anti-inflammatory drygs in standardized cell culture conditions.     

The role of PGE<Subscript>2</Subscript> in human atherosclerotic plaque on platelet EP<Subscript>3</Subscript> and EP<Subscript>4</Subscript> receptor activation and platelet function in whole blood

Atherosclerosis has an important inflammatory component. Macrophages accumulating in atherosclerotic arteries produce prostaglandin E₂ (PGE₂), a main inflammatory mediator. Platelets express inhibitory receptors (EP₂, EP₄) and a stimulatory receptor (EP₃) for this prostanoid. Recently, it has been reported in ApoE^−/− mice that PGE₂ accumulating in inflammatory atherosclerotic lesions might contribute to atherothrombosis after plaque rupture by activating platelet EP₃, and EP₃ blockade has been proposed to be a promising new approach in anti-thrombotic therapy. The aim of our investigation was to study the role of PGE₂ in human atherosclerotic plaques on human platelet function and thrombus formation. Plaque PGE₂ might either activate or inhibit platelets depending on stimulation of either EP₃ or EP₄, respectively. We found that the two EP₃-antagonists AE5-599 (300 nM) and AE3-240 (300 nM) specifically and completely inhibited the synergistic effect of the EP₃-agonist sulprostone on U46619-induced platelet aggregation in blood. However, these two EP₃-antagonists neither inhibited atherosclerotic plaque-induced platelet aggregation, GPIIb/IIIa exposure, dense and alpha granule secretion in blood nor reduced plaque-induced platelet thrombus formation under arterial flow. The EP₄-antagonist AE3-208 (1–3 μM) potentiated in combination with PGE₂ (1 μM) ADP-induced aggregation, demonstrating that PGE₂ enhances platelet aggregation when the inhibitory EP₄-receptor is inactivated. However, plaque-induced platelet aggregation was not augmented after platelet pre-treatment with AE3-208, indicating that plaque PGE₂ does not stimulate the EP₄-receptor. We found that PGE₂ was present in plaques only at very low levels (15 pg PGE₂/mg plaque). We conclude that PGE₂ in human atherosclerotic lesions does not modulate (i.e. stimulate or inhibit) atherothrombosis in blood after plaque rupture.     

Traditional Oriental Herbal Medicine,Bakumondo-to,Suppresses Vagal Neuro-effector Transmission in Guinea Pig Trachea

Objective.?Bakumondo-to (Maimendong tang) is a traditional oriental herbal medicine that has been used as an antitussive agent. We previously demonstrated that Bakumondo-to attenuates airway hyperresponsiveness induced by ozone. However, the mechanism(s) responsible for this effect remains unclear. In the present study, we examined the mechanism whereby Bakumondo-to inhibits ozone-induced airway hyperresponsiveness. First, we examined the effect of Bakumondo-to on prostanoids production, which are key mediators to airway hyperresponsiveness after ozone exposure. Second, we studied its effects on the vagal neuroeffector transmission, because vagal nerve is likely to play an important role in airway hyperresponsiveness after ozone. Methods.?We measured the effects of Bakumondo-to on the concentrations of prostanoids in bronchoalveolar lavage fluid before and after ozone. We evaluated the effects of Bakumondo-to on the contraction of guinea pig tracheal smooth muscle evoked by electrical field stimulation (EFS) or the exogenous application of acetylcholine (ACh). Isometric tension of tracheal strips was measured in the presence of indomethacin (10^?6 M) and of guanethidine (10^?6 M). Results.?Ozone caused significant increase in prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂); however, Bakumondo-to did not affect the increase in these prostanoids. Bakumondo-to (0.01 mg/mL–1 mg/mL) significantly suppressed the contraction evoked by EFS, but did not affect the ACh-evoked contraction, indicating that Bakumondo-to suppressed tracheal smooth muscle contraction pre-junctionally. Conclusion.?These results suggest that the mechanism by which Bakumondo-to inhibits airway hyperresponsiveness depends on inhibiting the release of acetylcholine from vagal nerve terminals.     

Comparisons of prostaglandin vasoactive effects and interactions in the in vivo microcirculation of the rat urinary bladder

A combination of techniques for in vivo transillumination, topical application of vasoactive agents, and direct microscopic observation of microcirculatory responses was utilized to evaluate the vasomotor actions of prostaglandins (PGs) E₁, E₂, F_1α, F_2α, A₁, and A₂ on rat urinary bladder arterioles and venules. The effects of PGE₁ and histamine (HIS) on arteriolar responsiveness to norepinephrine (NE), serotonin (5-HT), and PGF_2α were measured. Histochemical studies were completed to determine the primary site of prostaglandin (PG) metabolic deactivation in the urinary bladder. Arteriolar dilatation occurred with HIS, PGE₁, PGE₂, PGA₁, PGA₂, and PGF_1α, all of which (with the exception of HIS) demonstrated significant dose-related responses. Overall, PGE₁ and PGE₂ were of greatest potency. Significant dose-related arteriolar constriction occurred with NE > PGF_2α > 5-HT (in order of decreasing potency). HIS, PGE₁, PGE₂, and PGA₁ produced significant venular dilatation; PGE₁ and HIS were dose related. Only NE resulted in significant venoconstriction. Arteriolar responsiveness to NE and PGF_2α decreased after pretreatment with PGE₁ but was unchanged by HIS pretreatment, whereas application of 5-HT following pretreatment with PGE₁ or HIS produced equivalent levels of arteriolar constriction. The primary site of deactivation of PGE₁ was histochemically localized to bundles of smooth muscle fibers in the muscular coat of the rat urinary bladder wall.     

Cough,asthma, and cysteinyl-leukotrienes

Asthma is a chronic inflammatory disease of the lower airways, involving various cells such as eosinophils, and cytokines and mediators. Cyteinyl-leukotrienes (cys-LTs) are one of the chemical mediators that play major pathophysiological roles in asthma. They are produced by eosinophils and mast cells, and induce bronchoconstriction, mucous hypersecretion, microvascular leakage, eosinophil chemotaxis and airway remodeling. Anti-leukotrienes, including leukotriene receptor antagonists (LTRAs) which block cysLT1 receptors, exert both bronchodilatory and anti-inflammatory effects and are utilized as second- to third-line controller medication of persistent asthma.Cough is a major symptom of asthma, and cough variant asthma (CVA) is an asthma phenotype that solely presents with coughing. Sputum levels of cys-LTs are increased in patients with CVA. Antitussive effects of monotherapy with LTRAs in patients with CVA have been reported. We have recently demonstrated that 4 weeks' treatment with an LTRA montelukast exerted anti-inflammatory effect as proved by a decrease of sputum eosinophils, in addition to attenuation of cough VAS and capsaicin cough sensitivity, as reported previously. Spirometry, airway responsiveness, and impulse oscillation indices (respiratory resistance and reactance) were unchanged. These results suggested that the antitussive effect of montelukast in CVA might be attributable to its anti-inflammatory ability rather than bronchodilation. The treatment did not affect sputum levels of mediators (cys-LTs, LTB₄, PGD₂, PGE₂, PGF_2α, and TXB₂). Since inhaled corticosteroid does not seem to affect cough sensitivity while attenuating cough in patients with CVA, LTRAs may involve different mechanism(s) from that of corticosteroid.LTRAs must theoretically be effective against cough of asthmatic subjects through its “anti-asthma” effects, while evidence supporting direct antitussive effects of cys-LTs on “cough receptors” is scarce. An important clinical question is that whether LTRAs involve non-specific antitussive effects. While a definite answer is not available yet, this possibility seems unlikely at the moment, although some secondary anti-inflammatory properties have been reported for montelukast. This issue needs to be clarified by future research to avoid overuse of this expensive class of medication.     

Effects of third ventricle injection of prostaglandins on gonadotropin secretion in goldfish,Carassius auratus

The effects of injection of prostaglandin (PG) E₁, PGE₂, and PGF_2α into the third ventricle on serum gonadotropin (GTH) concentrations in the goldfish were tested. Blood samples were taken at 30 min postinjection for radioimmunoassay of serum GTH. PG dosages of 0.5 and 1.0 μg were ineffective. However, PGE₂ and PGF_2α at the 2.0-μg dosage significantly suppressed serum GTH. PGE₁ at a 2.0-μg dosage had no effect. There were no effects on serum GTH when 2.0 μg of PGE₁, PGE₂, or PGF_2α were injected intraperitoneally. The results indicate that PGE₂ and PGF_2α suppress gonadotropin secretion by some action, presumably on the hypothalamus. However, action of PGE₂ and PGF_2α by diffusion from the site of injection to some other brain site or the pituitary cannot be eliminated in the present study.     

Effect of methotrexate on the release of prostaglandins E2, D2, and I2 from small intestine in the rat in vivo

Summary Intraperitoneal administration of methotrexate in a single dose of 40 mg/kg induces fluid accumulation in the small intestine of rats, significantly increasing jejunal PGE₂ formation and simultaneously the amounts of PGE₂ in the intestinal contents in vivo. Concomitantly, jejunal PGD₂ and 6-keto-PGF₁ generation and the amounts of these prostaglandins in the intestinal contents were significantly lowered. However, PGD₂ and 6-keto-PGF jejunal release, and the amounts of these prostaglandins found in the intestinal contents, were already low after a subletal dose (4 mg/kg) of methotrexate, whereas the jejunal release as well as the amounts in the intestinal contents of PGE₂ were not altered. Fluid accumulation, the amounts of prostaglandins in the intestinal contents and jejunal release of prostaglandins are siginificantly inhibited by indomethacin. The increased jejunal synthesis of PGE₂, with its enteropooling effect, may play a significant role in methotrexate-induced diarrhea in rats.Abbreviation PGE₂, PGD₂, PGI₂ prostaglandins E₂, D₂, I₂     

Microcirculatory effects of prostacyclin (PGI2) in the hamster cheek pouch.

The effects of prostacyclin (PGI₂) on small blood vessels in the hamster cheek pouch microcirculation were studied microscopically. Prostacyclin applied systemically or locally caused an increase in the diameter of precapillary arterioles (10–50 μm diameter) with inherent or induced tone. It was more potent prostaglandin PGE₁, PGE₂, or bradykinin. In animals treated with indomethacin (4 mg/kg po), the relative vasodilator potency of prostacyclin to PGE₁ and PGE₂ was increased. The cyclic endoperoxide precursor of prostaglandins, PGH₂, and the stable chemical breakdown product of prostacyclin, 6-oxo-PGF_1α, were also dilators but were less potent than prostacyclin itself. In some experiments, responses of arterioles to PGH₂ were biphasic, a long-lasting dilatation being preceded by a short-lasting vasoconstriction. The postcapillary venules (20–50 μm diameter) in this preparation were inactive and did not respond by dilatation or constriction to PGI₂, PGE₁, PGE₂, PGH₂, 6-oxo-PGF_1α, bradykinin, or noradrenaline.     

Effect of acute and chronic alcohol feeding on prostaglandin E2 biosynthesis in rat stomach

The effect of acute and chronic alcohol ingestion on gastric prostaglandin E₂ synthesis and the PGE₂ content in the stomach was studied in rats. Up to 8 hr following a single oral load of 20% alcohol (v/v; 4 g/kg body weight), the PGE₂ synthesis in isolated microsomes from rat stomach remained unchanged as compared with control values. Feeding a liquid alcohol-containing diet (37% of total Joules) for 1,6, or 12 weeks significantly decreased the rate of PGE₂ synthesis (percentage inhibition as compared with control values 39, 27, and 57, respectively). In addition, chronic alcohol feeding led to a drop in the tissue content of PGE₂, the decrease being more pronounced after 6 (–49%) and 12 (–58%) weeks than after 1 week (–24%). The results suggest that the inhibition of endogenous PGE₂ synthesis in the stomach following ingestion of appreciable quantities of alcohol might play a role in the pathogenesis of alcohol-induced injury of the gastric mucosa.     

Comparison of the effects of different anti-inflammatory drugs on synovial fluid prostanoid concentrations in patients with rheumatoid arthritis

Summary The effects of one-day treatment with nine nonsteroidal anti-inflammatory drugs and prednisolone on human synovial fluid concentrations of prostanoids were studied. The doses were calculated so as to be approximately equipotent according to clinical experience and the recommendations of the manufacturs. Most of the drugs used reduced clearly PGE₂ and TxB₂ levels in synovial fluid, but only a slight diminution in 6-keto-PGF₁ values was found. Carprofen, diclofenac, indomethacin, naproxen and tolfenamic acid reduced significantly the synovial fluid PGE₂ concentrations. Diclofenac and indomethacin also reduced significantly the synovial TxB₂ concentrations.     

Role of hepatocyte growth factor in endothelial regulation: prevention of high D-glucose-induced endothelial cell death by prostaglandins and phosphodiesterase type 3 inhibitor

Summary Injury of endothelial cells (EC) has been postulated as the initial trigger of the progression of atherosclerosis in patients with diabetes mellitus. We previously reported that decrease in a novel endothelium-specific growth factor, hepatocyte growth factor (HGF), by high d-glucose might be a trigger of endothelial injury. However, the physiological role of the local vascular HGF system has not yet been clarified. To investigate the role of HGF in endothelial injury, we initially examined the effects of HGF on endothelial injury induced by serum deprivation. Decrease in EC number by serum deprivation was significantly attenuated by addition of HGF as well as recombinant basic fibroblast growth factor, whereas vascular endothelial growth factor showed no effect. Apoptotic changes in EC induced by serum deprivation were also significantly attenuated by addition of HGF (p < 0.01). Given the protective action of HGF, we next studied the physiological role of local HGF production in endothelial regulation. We focused on the protective actions of prostaglandin (PG) I₂, PGE and a phosphodiesterase type 3 inhibitor (cilostazol) on endothelial injury by high glucose, since these agents are widely used in the treatment of peripheral arterial disease which is frequently observed in diabetic patients. Treatment of human aortic EC with PGE₁, PGE₂, and a PGI₂ analogue (beraprost sodium) as well as cilostazol stimulated EC growth. HGF concentration in conditioned medium from EC treated with PGE₁, PGE₂ or PGI₂ analogue as well as cilostazol was significantly higher than that with vehicle (p < 0.01). Interestingly, treatment with PGI₂ analogue or cilostazol attenuated high d-glucose-induced EC death, which was abolished by neutralizing anti-HGF antibody. Moreover, decreased local HGF production by high d-glucose was also significantly attenuated by PGI₂ analogue or cilostazol. Finally, we tested the effects of PGE, PGI₂ analogue and cilostazol on local HGF production in human aortic vascular smooth muscle cells (VSMC). Although high d-glucose treatment resulted in a significant increase in VSMC number, PGI₂ analogue and/or cilostazol treatment had no effects on VSMC growth. However, the decrease in local HGF production by high d-glucose was significantly attenuated by addition of PGI₂ analogue or cilostazol. Overall, this study demonstrated that treatment with PGE, PGI₂ analogue or cilostazol prevented aortic EC death induced by high d-glucose, probably through the activation of local HGF production. Increased local vascular HGF production by prostaglandins and cilostazol may prevent endothelial injury, potentially resulting in the improvement of peripheral arterial disease. [Diabetologia (1997) 40: 1053–1061] Received: 17 February 1997 and in revised form: 7 May 1997     

Enhanced levels of prostaglandin E2 and matrix metalloproteinase-2 correlate with the severity of airflow limitation in stable COPD

Background and objective: Cyclooxygenase-2 (COX-2) and its product prostaglandin E₂ (PGE₂) have been demonstrated to play critical roles in inflammation in respiratory diseases. However, the role of COX-2 in airway remodelling in COPD remains to be elucidated. Matrix metalloproteinase-2 (MMP-2) is associated with both inflammation and airway remodelling in COPD. The objective of this study was to measure the expression of COX-2 and the concentrations of PGE₂ and MMP-2, and to investigate the role of COX-2 and PGE₂ in airflow limitation mediated by MMP-2, in the pathogenesis of COPD. Methods: Forty-three patients with stable COPD, twelve smoking control subjects and ten non-smoking control subjects were enrolled. Induced sputum was obtained for measurement of the concentrations of PGE₂ and MMP-2 by ELISA. COX-2 protein expression was assessed by western blotting. Results: PGE₂ and MMP-2 concentrations were significantly higher in both smoking control subjects and patients with COPD than in non-smoking control subjects (P < 0.01). Moreover, the levels of PGE₂ and MMP-2 were inversely correlated with FEV₁% predicted in COPD patients (PGE₂: r = −0.748, P < 0.01; MMP-2: r = −0.801, P < 0.01). Levels of PGE₂ were also positively correlated with those of MMP-2 in patients with COPD (r = 0.775, P < 0.01). Expression of COX-2 protein was significantly higher in COPD patients than in non-smoking control subjects. Conclusions: COX-2 and its product PGE₂ are not only involved in airway inflammation, but may also contribute to the severity of airflow limitation mediated by MMP-2 during progression of COPD.     

Induction of oviposition in the domestic hen by prostaglandins

Single intrauterine injection of prostaglandins E₁, E₂, and F₂α in this order of potency induce premature oviposition in the hen within a few minutes. Similarly, arachidonic acid, a prostaglandin precursor, was also effective in initiating egglaying. PGE₁ and PGE₂ are about 10–20 times more potent than oxytocin, suggesting a possible physiological role in the regulation of oviposition.     

Regulatory effect of PGE2 on microbicidal activity and inflammatory cytokines in canine leishmaniasis

Canine leishmaniasis (CanL) is caused by the intracellular parasite Leishmania infantum. Prostaglandin E2 (PGE₂) exerts potent regulatory effects on the immune system in experimental model Leishmania infection, but this influence has not yet been studied in CanL. In this study, PGE₂ and PGE₂ receptor levels and the regulatory effect of PGE₂ on arginase activity, NO₂, IL-10, IL-17, IFN-γ, TNF-α and parasite load were evaluated in cultures of splenic leucocytes obtained from dogs with CanL in the presence of agonists and inhibitors. Our results showed that splenic leucocytes from dogs with CanL had lower EP2 receptor levels than those of splenic leucocytes from healthy animals. We observed that NO₂ levels decreased when the cells were treated with a PGE₂ receptor agonist (EP1/EP2/EP3) or COX-2 inhibitor (NS-398) and that TNF-α, IL-17 and IFN-γ cytokine levels decreased when the cells were treated with a PGE₂ receptor agonist (EP2) or PGE₂ itself. The parasite load in splenic leucocyte cell cultures from dogs with CanL decreased after stimulation of the cells with PGE₂. We conclude that Leishmania infection of dogs modulates PGE₂ receptors and speculate that the binding of PGE₂ to its receptors may activate the microbicidal capacity of cells.     

Roles of Ca2+ and protein kinase C in regulation of prostaglandin E2 release by cultured rabbit gastric epithelial cells

Prostaglandin (PG) has been reported to be one of the important protective factors in the gastric mucosa. However the mechanism of the regulation of endogenous PG production has not been well studied. We investigated the possible roles of Ca²⁺, cAMP, and protein kinase C (PKC) in the regulation of PGE₂ release from cultured rabbit gastric mucosal cells. PGE₂ was measured by radioimmunoassay. A23187 (Ca²⁺ ionophore) at 2×10^?6 M significantly increased PGE₂ release. Deprivation of Ca²⁺ from the medium blocked the A23187-induced increase of PGE₂. TMB-8 (a putative inhibitor of Ca²⁺ release from intracellular stores) did not have any significant effects on the increase of PGE₂-induced by A23187. Thus, A23187 increased PGE₂ through the influx of extracellular Ca²⁺. W7 or compound 48/80 (calmodulin inhibitors) did not alter the response of PGE₂ caused by A23187. Exogenous administration of cAMP, forskolin (an activator of adenylate cyclase), or 2-chloroadenosine (a possible activator of adenylate cyclase through adenosine A₂ receptor) had neither significant effects on PGE₂ release nor an effect on A23187-induced increase of PGE₂ release. 12-O-tetradecanoylphorbol 13-acetate (TPA, an activator of PKC) significantly stimulated PGE₂ release in a dose-dependent fashion, whereas another phorbol ester with no biological activity did not. A23187 at 0.8×10^?6 M, but not cAMP, potentiated the TPA-induced increase of PGE₂. Mepacrine (a phospholipase A₂ inhibitor) reduced the A23187-and TPA-induced increase of PGE₂. These results suggest that Ca²⁺ and protein kinase C may play important roles in the regulation of PGE₂ release by cultured rabbit gastric cells.