Parasitic infections: A new frontier for PGD2 functions

A Prostaglandin D2 system in the human testis

In isolated rat liver perfused at constant pressure perivascular nerve stimulation caused an increase of glucose and lactate output and a reduction of perfusion flow. The metabolic and hemodynamic nerve effects could be inhibited by inhibitors of prostanoid synthesis, which led to the suggestion that the effects of nerve stimulation were, at least partially, mediated by prostanoids [Iwai, M. & Jungermann, K. (1987) FEBS Lett. 221, 155-160]. This suggestion is corroborated by the present study. 1. Prostaglandin D2, E2 and F2 alpha as well as the thromboxane A2 analogue U46619 enhanced glucose and lactate release and lowered perfusion flow similar to nerve stimulation. 2. The extents, the kinetics and the concentration dependencies of the metabolic and hemodynamic actions of the various prostanoids were different. Prostaglandin F2 alpha and D2 caused relatively stronger changes of metabolism, while prostaglandin E2 and U46619 had stronger effects on hemodynamics. Prostaglandin F2 alpha elicited greater maximal alterations than D2 with similar half-maximally effective concentrations. Prostaglandin F2 alpha mimicked the nerve actions on both metabolism and hemodynamics best with respect to the relative extents and the kinetics of the alterations. 3. The hemodynamic effects of prostaglandin F2 alpha could be prevented completely by the calcium antagonist nifedipine without impairing the metabolic actions of the prostanoid. Apparently, prostaglandin F2 alpha influenced metabolism directly rather than indirectly via hemodynamic changes. The present results, together with the previously described effects of prostanoid synthesis inhibitors, suggest that prostanoids, probably prostaglandin F2 alpha and/or D2, could be involved in the actions of sympathetic hepatic nerves on liver carbohydrate metabolism. Since prostanoids are synthesized only in non-parenchymal cells, nervous control of metabolism appears to depend on complex intra-organ cell-cell interactions between the nerve, non-parenchymal and parenchymal cells.

1 Intradermal injection of prostaglandin (PG) D1 and D2 in the human forearm produced a long-lasting dose-related erythema. When compared with prostaglandin E1 or E2 the order of potency for erythema production was PGE1 greater than PGE2 greater than PGD2 greater than PGD1. 2 In rat skin, prostaglandin D2 but not D1 caused an increase in vascular permeability as quantitated by the Evans blue method and the 125I-albumin extravasation technique. Prostaglandin E2 was 3-5 times more potent than prostaglandin D2. 3 Prostaglandin D2 (10 ng) potentiated the increase in vascular permeability in rat skin produced by histamine, but not that produced by bradykinin. 4 Prostaglandin D2 (10, 20 and 50 ng) did not elicit oedema or hyperalgesia in the rat paw oedema test, but potentiated carrageenan-induced oedema; hyperalgesia was potentiated by doses of 100 ng and above.

Vascular smooth muscle cells (VSMCs) as well as macrophages have been shown to generate a substantial amount of NO in inflammatory vascular lesions. Prostaglandin (PG) D2 (PGD2) is produced by inflammatory cells, including mast cells and macrophages. We investigated whether PGD2 modulates NO metabolism in rat VSMCs. PGD2 at a concentration of 10(-7) mol/L or greater dose-dependently inhibited nitrite accumulation in the medium of cultured VSMCs stimulated with interleukin 1beta (IL-1beta). In a dose-response analysis of IL-1beta and nitrite accumulation, PGD2 was seen to decrease the maximal ability of VSMCs to generate NO, arguing against competition by PGD2 at cytokine receptors. Northern analysis showed that PGD2 suppresses induction of inducible NO synthase (iNOS) mRNA in IL-1beta-stimulated VSMCs, with consequent inhibition of iNOS protein expression in Western analysis. A thromboxane A2 (TXA2) analogue, U46619 (10(-5) mol/L), produced less inhibition of NO generation than did PGD2. Neither the PGI2 analog carbaprostacyclin nor PGE1 showed any inhibition. PGD2 dose-dependently inhibited NO generation despite the addition of the TXA2 antagonist SQ29548. PGJ2, delta12-PGJ2, and 15-deoxy-delta12,14-PGJ2, all metabolites of PGD2, were as potent as or slightly stronger than PGD2 in the inhibition of NO generation. These data suggest that PGD2 suppresses NO generation in VSMCs by inhibiting iNOS mRNA expression, most likely through the cascade of the PGJ2 series rather than through the TX receptor or cAMP upregulation. Such action makes it likely that PGD2 regulates NO metabolism in vascular lesions.

Dietary Lutein/Zeaxanthin Decreases Ultraviolet B-Induced Epidermal Hyperproliferation and Acute Inflammation in Hairless Mice

This study explores the computational isolation of prostaglandin (PG) isomers, specifically PG E2 (PGE2) and D2 (PGD2), to enhance method development efficiency and provide insights into their retention behavior during supercritical fluid extraction (SFE) combined with supercritical fluid chromatography (SFC)-tandem mass spectrometry (MS/MS). Although PGE2 and PGD2 are positional isomers that yield identical product ions in MS/MS, they serve distinct biological roles. This research illustrates the efficacy of selected reaction monitoring (SRM)-based techniques for differentiating coeluting isomers. Despite the challenges posed by baseline resolution, simplified computational methods successfully distinguished between PGE2 and PGD2, demonstrating the potential for high-throughput PG analysis without the necessity for complete chromatographic peak resolution. By employing least-squares estimation to solve a linear system, the abundance ratio of PGE2 to PGD2 was derived from intensity ratios across four SRM transitions, achieving precise quantification even with poorly resolved SFC peaks. The study highlights critical factors affecting PG retention, such as the choice of the stationary phase, temperature regulation, and reduction of stainless steel interactions, which can diminish signal intensity. A significant observation is the concentration-dependent suppression effect of the entrainer when interacting with the hepatocyte matrix, underscoring the importance of effective matrix management in SFE/SFC-MS/MS. These findings advance the development of a robust, high-throughput analytical platform for PG quantification and lipidomics research applications.

LC–MS/MS-analysis of prostaglandin E2 and D2 in microdialysis samples of rats

Superfused rat brain cortex slices, hypothalamic slices and cortex synaptosomes preincubated with 3H-serotonin or 3H-noradrenaline were used to study the effects of eicosanoids on tritium overflow evoked either electrically (3 Hz; slices) or by potassium 12 mmol/l (synaptosomes). 1. The electrically evoked 3H overflow from cortex slices preincubated with 3H-serotonin was inhibited by prostaglandins E1 and E2 and by the prostacyclin analogue iloprost. No effect was seen with prostaglandin F2 alpha, prostaglandin D2, CG 4203 (another prostacyclin analogue), U 46619 (a thromboxane A2 analogue) and leukotriene C4. The same held true for indomethacin and the prostaglandin receptor antagonists SC 19220 and N-0164. The inhibitory effect of prostaglandin E2 was slightly more pronounced in the presence of indomethacin than in its absence, but was not affected by SC 19220, N-0164 or forskolin plus AH 21-132 (an inhibitor of cAMP phosphodiesterase). Yohimbine and the serotonin receptor antagonist metitepin failed to influence the inhibitory effect of prostaglandin E1. 2. The potassium-evoked 3H overflow from cortex synaptosomes preincubated with 3H-serotonin was inhibited by prostaglandin E2. 3. Prostaglandin E2 also inhibited the electrically evoked 3H overflow from hypothalamic slices preincubated with 3H-serotonin. 4. The electrically evoked 3H overflow from cortex slices preincubated with 3H-noradrenaline was inhibited by prostaglandin E2, but was not affected by SC 19220, which, in turn, did also not alter the effect of prostaglandin E2. The present results are compatible with the view that presynaptic SC 19220-insensitive prostaglandin E receptors may be involved in the inhibitory effect of prostaglandins E1 and E2 on serotonin (and noradrenaline) release.

Hyperalgesic actions in mice of intracerebroventricularly (i.c.v.) administered arachidonic acid, prostaglandin (PG) E2, PG F2 alpha and PG D2 were studied. For the analgesic assay, the mouse tail pressure method was employed. The i.c.v. administration of arachidonic acid (0.01-100 micrograms/mouse), PG E2 (0.01-100 ng/mouse), PG F2 alpha (0.1-1000 ng/mouse) and PG D2 (0.1-1000 ng/mouse) decreased the pain threshold in a dose dependent manner. The doses that produced the maximal decrease in pain threshold for arachidonic acid, PG E2, PG F2 alpha and PG D2 were 10 micrograms/mouse, 10 ng/mouse, 100 ng/mouse and 100 ng/mouse, respectively. Acidic nonsteroidal antiinflammatory drugs (NSAIDs) produced much more potent analgesic effects in arachidonic acid-induced hyperalgesic mice than in normal mice and in PG E2-, PG F2 alpha- and PG D2-induced hyperalgesic mice, but nonacidic NSAIDs and morphine produced the same analgesic effect in both hyperalgesic and normal mice. Linoleic acid, linolenic acid and gamma-linolenic acid induced weak hyperalgesia, but this unsaturated fatty acids-induced hyperalgesia was not affected by indomethacin (2 mg/kg, p.o.). These findings indicate that the arachidonic acid and its metabolites were related to mediation or modulation of central pain pathways and that the central nervous system may be partially involved in the action of acidic NSAIDs.

We studied the effect of prostaglandins on presynaptic NMDA receptors. Prostaglandin E2 inhibited NMDA-induced (45)Ca2+ uptake by synaptosomes in low concentrations (IC50 approximately 10 microM), but potentiated it in higher concentrations. Prostaglandin D2 increased (45)Ca2+ uptake by synaptosomes during stimulation of NMDA receptors. Our results indicate that prostaglandins D2 and E2 modulate function of presynaptic NMDA receptors.

BackgroundProstanoids are important regulators of platelet aggregation and thrombotic arterial diseases. Their involvement in the development of portal vein thrombosis, frequent in decompensated liver cirrhosis, is still not investigated.MethodsTherefore, we used pro-thrombotic venous milieu generation by bare metal stent transjugular intrahepatic portosystemic shunt insertion, to study the role of prostanoids in decompensated liver cirrhosis. Here, 89 patients receiving transjugular intrahepatic portosystemic shunt insertion were included in the study, and baseline levels of thromboxane B2, prostaglandin D2 and prostaglandin E2 were measured in the portal and the hepatic vein.ResultsWhile the hepatic vein contained higher levels of thromboxane B2 than the portal vein, levels of prostaglandin E2 and D2 were higher in the portal vein (all P<0.0001). Baseline concentrations of thromboxane B2 in the portal vein were independently associated with an increase of portal hepatic venous pressure gradient during short term follow-up, as an indirect sign of thrombogenic potential (multivariable P = 0.004). Moreover, severity of liver disease was inversely correlated with portal as well as hepatic vein levels of prostaglandin D2 and E2 (all P<0.0001).ConclusionsElevated portal venous thromboxane B2 concentrations are possibly associated with the extent of thrombogenic potential in patients with decompensated liver cirrhosis.Trial registrationClinicalTrials.gov identifier: NCT03584204.

Using the stop-flow peritubular capillary microperfusion method the inhibitory potency (apparent Ki values) of cyclic nucleotides and prostanoids against contraluminal p-aminohippurate (PAH), dicarboxylate and sulphate transport was evaluated. Conversely the contraluminal transport rate of labelled cAMP, cGMP, prostaglandin E2, and prostaglandin D2 was measured and the inhibition by different substrates was tested. Cyclic AMP and its 8-bromo and dibutyryl analogues inhibited contraluminal PAH transport with an app. Ki,PAH of 3.4, 0.63 and 0.52 mmol/l. The respective app. Ki,PAH values of cGMP and its analogues are with 0.27, 0.04 and 0.05 mmol/l, considerably lower. None of the cyclic nucleotides tested interacted with contraluminal dicarboxylate, sulphate and N1-methylnicotinamide transport. ATP, ADP, AMP, adenosine and adenine as well as GTP, GDP, GMP, guanosine and guanine did not inhibit PAH transport while most of the phosphodiesterase inhibitors tested did. Time-dependent contraluminal uptake of [3H]cAMP and [3H]cGMP was measured at different starting concentrations and showed facilitated diffusion kinetics with the following parameters for cAMP: Km = 1.5 mmol/l, Jmax = 0.34 pmol S-1 cm-1, r (extracellular/intracellular amount at steady state) = 0.91; for cGMP: Km = 0.29 mmol/l, Jmax = 0.31 pmol S-1 cm-1, r = 0.55. Comparison of app. Ki,cGMP with app. Ki,PAH of ten substrates gave a linear relation with a ratio of 1.83 +/- 0.5. All prostanoids applied inhibited the contraluminal PAH transport; the prostaglandins E1, F1 alpha, A1, B1, E2, F2 alpha, D2, A2 and B2 with an app. Ki,PAH between 0.08 and 0.18 mmol/l. The app. Ki of the prostacyclins 6,15-diketo-13,14-dihydroxy-F1 alpha (0.22 mmol/l) and Iloprost (0.17 mmol/l) as well as that of leukotrienes B4 (0.2 mmol/l) was in the same range, while the app. Ki,PAH of the prostacyclins PGI2 (0.55 mmol/l), 6-keto-PGF1 alpha (0.77 mmol/l) and 2,3-dinor-6-keto-PGF1 alpha (0.57 mmol/l) as well as that of thromboxane B2 (0.36 mmol/l) was somewhat higher. None of these prostanoids inhibited contraluminal dicarboxylate transport and only PGB1, E2 and D2 inhibited contraluminal sulphate transport (app. Ki,SO4(2-) 5.4, 11.0, 17.9 mmol/l respectively). Contraluminal influx of labelled PGE2 showed complex transport kinetics with a mixed Km = 0.61 mmol/l and Jmax of 4.26 pmol S-1 cm-1. It was inhibited by probenecid, sulphate and indomethacin. Contraluminal influx of PGD2, however, was only inhibited by probenecid. The data indicate that cyclic nucleotides as well as prostanoids are transported by the contraluminal PAH transporter. For prostaglandin E2 a significant uptake through the sulphate transporter occurs in addition.(ABSTRACT TRUNCATED AT 400 WORDS)

Beyond cyclooxygenase

Objective Prostaglandin D2 (PGD2) has been shown to have regulating functions of the differentiation, maturation, migration and recruitment on eosinophils(EOS). This occurs through the interaction of PGD2 with the receptor expressed on EOS. This study attempts to understand the levels of prostaglandins and the change of DP1/CRTH2 receptors on EOS in asthma,to explore the mechanism of the infiltration of EOS in airway. Methods Twenty male SD rats were randomly divided into normal control group( n = 10), asthma group( n = 10). Asthma was induced by ovalbumin challenge. PGD2 receptor on EOS were measured by radiological binding assay. PGD2 levels in peripheral blood was measured by ELISA. The left lung was used for histological examinations and bronchalveolar lavage fluid (BALF) was collected from the right lung. Results Compared with the normal control group, asthma group had significant infiltration of EOS and lymphocytes in bronchial wall,there was the typical changes of asthma. PGD2 in peripheral blood in asthma group was significantly higher than the normal control group ( P ＜ 0.01 ＝, EOS count in peripheral blood and BALF in normal control group increased significantly ( P ＜0.01 ＝. DP total binding capacity and CRTH2 binding capacity on EOS in asthma group were significantly higher than the control group ( P ＜0.01 ＝. DP1 was no significant differences ( P ＞0. 05). Conclusions PGD2 was significantly increased in asthma, and the CRTH2 receptor on EOS increased expression. The increased production of PGD2 EOS will strengthen the role of chemotaxis,infiltration to the airway,leading to arguments on EOS infiltration characteristics in asthma. Key words: Asthma ; Prostaglandin D2 receptor ; Eosinophil

This study determines the inotropic effects of prostaglandin D2 (PGD2) and prostaglandin E1 (PGE1) in the isolated, arterial perfused newborn (NB) and adult (A) rabbit heart. Significant positive inotropism of PGD2 was observed at all concentrations studied (1 X 10(-17) to 1 X 10(-7) M) in the two age groups; the effect in the NB was significantly greater (p less than 0.05) than that in the A at PGD2 concentrations higher than 1 X 10(-17) M. Significant positive inotropism of PGE1 was observed at PGE1 concentrations higher than 1 X 10(-8) M in the NB, and only at 1 X 10(-6) M in the A. In the NB, the relaxation parameters [1/2 RT and the ratio of +dT/dt (max) to -dT/dt (max)] decreased to 80% of control after PGE1 infusion, but not after PGD2 infusion. In contrast, relaxation parameters in the A were not different from control. Propranolol (1 X 10(-6) M) did not alter the positive inotropic action of PGD2 and PGE1 in the NB. These data indicate that: 1) the positive inotropic effects of PGD2 and PGE1 in NB are greater than that in the A, 2) PGE1 and not PGD2, enhances myocardial relaxation only in the NB, 3) the contractile effects of PGD2 and PGE1 are not mediated by beta-receptors.