Alterations of Prostanoid Expression and Intestinal Epithelial Barrier Functions in Ileus

INTRODUCTION

Intestinal manipulation (IM)-induced inflammation could contribute to postoperative ileus (POI) pathophysiology via the modulation of prostanoid pathways. To identify the prostanoids involved, we aimed to characterize the profile of prostanoids and their synthesis enzyme expression in a murine model of POI and to determine whether the altered prostanoids could contribute to POI.

METHODS

Four or 14 h after IM in mice, gastrointestinal (GI) motility and intestinal epithelial barrier (IEB) permeability were assessed in vivo and ex vivo in Ussing chambers. Using high sensitivity liquid chromatography-tandem mass spectrometry, we characterized the tissue profile of polyunsaturated fatty acid metabolites in our experimental model. Finally, we evaluated in vivo the effects of the prostanoids studied upon IM-induced gut dysfunctions.

RESULTS

We first showed that 14 h after IM was significantly faster than jejunal transit at 4 h post-IM, although it remained significantly increased compared to the control. In contrast, we showed that IM-induced inflammation increase in jejunum permeability was similar after four and 14 h. We next showed that expression of prostacyclin synthase and hemopoietic prostaglandin-D synthase mRNA and their products were significantly reduced 14 h after IM as compared to controls. Furthermore, 15-deoxy-delta 12,14-Prostaglandin J2 reduced the IM-induced inflammation increase in IEB permeability but had no effect on GI motility. In contrast, PGI2 increased IM-induced IEB permeability and motility dysfunctions.

CONCLUSIONS

Arachidonic acid derivative contributes differentially to GI dysfunction in POI. The decrease of 15-deoxy-delta 12,14-Prostaglandin J2 levels induced by IM could contribute to impaired GI dysfunctions in POI and could be considered as putative therapeutic targets to restore barrier dysfunctions associated with POI.

The vasoconstrictor activities of prostaglandin D2 via the thromboxane prostanoid receptor and E prostanoid receptor-3 outweigh its concurrent vasodepressor effect mainly through D prostanoid receptor-1 ex vivo and in vivo

Prostaglandin (PG) D2, a commonly considered vasodilator through D prostanoid receptor-1 (DP1), might also evoke vasoconstriction via acting on the thromboxane (Tx)-prostanoid receptor (the original receptor of TxA2; TP) and/or E prostanoid receptor-3 (one of the vasoconstrictor receptors of PGE2; EP3). This study aimed to test the above hypothesis in the mouse renal vascular bed (main renal arteries and perfused kidneys) and/or mesenteric resistance arteries and determine how the vasoconstrictor mechanism influences the overall PGD2 effect on systemic blood pressure under in vivo conditions. Experiments were performed on control wild-type (WT) mice and mice with deficiencies in TP (TP-/-) and/or EP3 (EP3-/-). Here we show that PGD2 indeed evoked vasoconstrictor responses in the above-mentioned tissues of WT mice, which were however not only reduced by TP-/- or EP3-/-, but also reversed by TP-/-/EP3-/- in some of the above tissues (mesenteric resistance arteries or perfused kidneys) to dilator reactions that were reduced by non-selective DP antagonism. A slight or mild pressor response was also observed with PGD2 under in vivo conditions, and this was again reversed to a depressor response in TP-/- or TP-/-/EP3-/- mice. Non-selective DP antagonism reduced the PGD2-evoked depressor response in TP-/-/EP3-/- mice as well. These results thus demonstrate that like other PGs, PGD2 activates TP and/or EP3 to evoke vasoconstrictor activities, which can outweigh its concurrent vasodepressor activity mediated mainly through DP1, and hence result in a pressor response, although the response might only be of a slight or mild extent.

Continuous Prostanoid Initiation in Severe Pulmonary Hypertension in the Pediatric Cardiac Intensive Care Unit

OBJECTIVE

Limited data exists regarding prostanoid (PGI2) use in critically ill patients with pulmonary hypertension. (PH) in the pediatric cardiac intensive care unit (CICU) setting.

MATERIALS AND METHODS

Single center, retrospective study of patients with diagnosis of PH who received continuous PGI2 and were admitted to CICU from January/2015 to April/2022. Data collected included patient demographics and clinical characteristics including diagnosis, etiology of PH, vasoactive and ventilatory support, length of stay, and survival. Type, initial, maximum, and final dose of PGI2 as well as hemodynamic data was obtained. Data reported as mean ± standard deviation. Significance taken p value < 0.05.

RESULTS

24 patients received PGI2 therapy at a mean age of 3.1 years, range (0-16.6 years). PGI2 was in the form of IV epoprostenol in 12 patients, IV treprostinil in 6, and SQ treprostinil in 6 patients. Mean initial dose was 2.79 ng/kg/min, max dose 18.75 ng/kg/min, and mean duration of therapy was 38.5 days. At PGI2 initiation, 21 (87.5%) were on vasoactive infusions, 19 (79.2%) mechanically ventilated (MV), and 6 (25%) were on extracorporeal membrane oxygenation (ECMO). The in-hospital mortality rate was 37.5% (n = 9). Patients MV and on ECMO support had higher risk of death (p = 0.04, and < 0.01, respectively).

CONCLUSION

PGI2 therapy was tolerated in approximately 50% of patients with the most common side effect being hypotension leading to discontinuation in 1/3rd of patients. Ongoing evaluation of the benefits of PGI2 for patients in the CICU setting will help better identify patient selection, type, and dosing of PGI2.

Pulmonary artery pressure-directed therapies in pulmonary arterial hypertension?

Pulmonary arterial hypertension is a rare dyspnea-fatigue syndrome defined by an increase in mean pulmonary artery pressure above 20 mmHg combined with an increase in pulmonary vascular resistance higher than 2 Wood units. The condition is of poor prognosis and still incurable in spite of progress achieved in recent decades. The approach is currently optimized by multi-drug combinations titrated on serial risk assessments using recently validated scores. In this issue of Vascular Pharmacology argument is made based on retrospective registry data from three reference centers in favor of initial multi-drug therapies including a parenteral prostanoid dosed to decrease mPAP to normal. This objective was achieved in only a minority of patients, but improved outcome was demonstrated when mPAP can be brought to below 35 mmHg. This data suggest that pulmonary artery pressure-directed multi-drug therapies in PAH may reverse right heart remodeling and limit progression, or even reverse pulmonary vascular disease. However, further studies are needed to validate mPAP as a primary endpoint in PAH drug trials. In the meantime, aggressive initial prescription of parenteral prostanoids combined with one or two oral drugs targeting the pulmonary circulation under careful clinical, imaging and hemodynamic follow-up may be the best therapeutic strategy.

The biological actions of prostanoids in adipose tissue in physiological and pathophysiological conditions

Adipose tissue has been established as an endocrine organ that plays an important role in maintaining metabolic homeostasis. Adipose tissue releases several bioactive molecules called adipokines. Inflammation, dysregulation of adipokine synthesis, and secretion are observed in obesity and related diseases and cause adipose tissue dysfunction. Prostanoids, belonging to the eicosanoid family of lipid mediators, can be synthesized in adipose tissue and play a critical role in adipose tissue biology. In this review, we summarized the current knowledge regarding the interaction of prostanoids with adipokines, the expression of prostanoid receptors, and prostanoid synthase enzymes in adipose tissues in health and disease. Furthermore, the involvement of prostanoids in the physiological function or dysfunction of adipose tissue including inflammation, lipolysis, adipogenesis, thermogenesis, browning of adipocytes, and vascular tone regulation was also discussed by examining studies using pharmacological approaches or genetically modified animals for prostanoid receptors/synthase enzymes. Overall, the present review provides a perspective on the evidence from literature regarding the biological effects of prostanoids in adipose tissue. Among prostanoids, prostaglandin E2 (PGE₂) is prominent in regards to its substantial role in both adipose tissue physiology and pathophysiology. Targeting prostanoids may serve as a potential therapeutic strategy for preventing or treating obesity and related diseases.

Characterization of prostanoids response to Bordetella pertussis antigen BscF and Tdap in LPS-challenged monocytes

Prostanoids are potent inflammatory mediators that play a regulatory role in the innate immune activation of the adaptive immune response to determine the duration of protection against infection. We aim to quantify the modulation of prostanoids profiles in lipopolysaccharide (LPS)-stimulated THP-1 cells treated with the novel pertussis antigen BscF. We compared the effect with pertussis antigens present in the current Tdap vaccine to understand the immunomodulatory effect that might contribute to the diminished Tdap vaccine effectiveness. The inflammatory challenge with LPS induced a robust elevation of most prostanoid family members compared to the control treatment. Treatment with BscF and Tdap significantly reduced the LPS-stimulated elevation of prostaglandins (PGs) D2, E2, and F2α, as well as thromboxane (TX) A2 levels. An opposite trend was observed for PGI2, as both antigens accelerated the LPS-stimulated upregulation. Further, we quantified cyclooxygenases (COXs) that catalyze the biosynthesis of prostanoids and found that both antigens significantly reduced LPS-stimulated COX-1 and COX-2, demonstrating that the waning of acellular pertussis vaccines' protective immunity may be due to other downstream enzymes not related to COXs. Our present study validates the potential role of BscF as an adjuvant, resulting in the next-generation pertussis vaccine discovery.

[Characteristics of patients with connective tissue disease-associated pulmonary arterial hypertension treated with prostanoids: A multicenter retrospective study]

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a severe complication of connective tissue disease (CTD). Data on use of prostanoids in this particular subset of patients are lacking. We aimed to describe the characteristics of patients with PAH-CTD treated with prostanoids and the outcomes under treatment.

METHODS

In this multicenter retrospective study, all patients treated with prostanoids since 2006 were included. Data on PAH and CTD were collected at the time of prostanoid introduction and under treatment.

RESULTS

Twenty-one patients were included, of whom 20 (95%) had limited cutaneous systemic sclerosis. Nineteen patients were treated with oral monotherapy or combination before addition of prostanoid. Treprostinil was the most used molecule (57% of patients). At the time of prostanoid introduction, 90% of patients were considered at high risk for death. Among patients who had right heart catheterization during follow-up, there was no significant difference in haemodynamics. No extrarespiratory worsening of the CTD was reported. The 1-year survival under prostanoid was 62%. In univariate analysis, NYHA functional class was associated with survival under treatment.

CONCLUSION

This study provides original data on use of prostanoids in a cohort consisting mainly of systemic sclerosis. It underlines the difficulty to achieve a standardized assessment in this subset of patients. Safety profile was comparable with data reported in idiopathic PAH.

Prostanoid receptor agonists for glaucoma treatment

Intraocular pressure reduction is the only available and evidence-based medical therapy for glaucoma. Currently, the first-line eye drops are prostaglandin analogues including latanoprost, travoprost, bimatoprost, and tafluprost. These drugs stimulate intraocular prostanoid false positive (FP) receptors and reduce intraocular pressure by increasing mainly uveoscleral aqueous outflow. For 2 decades since latanoprost was launched, no drug has been comparable in its efficacy. In 2018, a prostanoid EP2 agonist, omidenepag, was launched in Japan. Current FP agonists and EP2 agonists indicate comparable intraocular pressure reduction by stimulating prostanoid FP or EP2 receptors. However, their safety profiles are quite different because of the differences between the intracellular signaling pathways through their own receptors. Including these commercially available FP and EP2 receptor agonists, prostanoid receptors have a large potential to control intraocular pressure. In this review I will trace the history and development of FP and EP2 receptor agonists from their original function, and explain their potential as first-line drugs including elucidation of their efficacy and safety.

Larger endothelium-dependent contractions in iliac arteries of adult SHRs are attributed to differential downregulation of TP and EP3 receptors in the vessels of WKYs and SHRs during the transition from adolescence to adulthood

This study was to determine how endothelium-dependent contractions (EDCs) change in iliac arteries of Wistar-Kyoto (WKYs) and spontaneously hypertensive rats (SHRs) during the transition from adolescence to adulthood and the underlying mechanism(s). We also aimed to elucidate effects of L-798106, an EP3 receptor antagonist, on EDCs and the blood pressure increase in adolescent SHRs. Blood vessels were isolated for functional and biochemical analyses. EDCs were comparable in adolescent iliac arteries of both strains, and contractions to ACh, prostacyclin (PGI2), the EP3 receptor agonist sulprostone and the TP receptor agonist U46619 in adult vessels were less prominent compared with those in the adolescents, while the attenuation of vasoconstrictions to ACh, PGI2 or U46619 with age was to a lesser extent in SHRs. PGI2 production was decreased to a similar level in adult arteries. TP and EP3 expressions were downregulated in adult vessels, whereas the extent of TP downregulation was less in SHRs. L-798106 partially suppressed the vasoconstrictions to U46619 and attenuated EDCs to a greater extent than SQ29548, and administration of L-798106 blunted the blood pressure increase with age in prehypertensive SHRs. These results demonstrate the comparable EDCs in iliac arteries of the adolescents are decreased in the adults, but relatively larger EDCs in adult SHRs can be a reflection of differential downregulation of TP and EP3 receptors during the transition from adolescence to adulthood. Also, our data suggest that blockade of both TP and EP3 receptors starting from the prehypertensive stage suppresses EDCs and the development of hypertension in SHRs.

Contemporary Pharmacotherapeutic Approach in Pulmonary Arterial Hypertension

Since the 1973 World Symposium on Pulmonary Hypertension, advancements in the understanding of pathophysiology and pathobiology have led to a myriad of pharmacotherapies for the disease. This article journeys through the development of therapeutic approaches for pulmonary arterial hypertension.

Development and evaluation of a simultaneous and efficient quantification strategy for final prostanoid metabolites in urine

Prostanoids (PNs) play critical roles in various physiological and pathological processes. Therefore, it is important to understand the alternation of PN expression profiles. However, a simultaneous and efficient quantification system for final PN metabolites in urine has not yet been established. Here, we developed and evaluated a novel method to quantify all final PN metabolites. By purification using a reverse phase solid phase extraction (SPE) column, the matrix effects against the final PGD₂, PGE₂, and PGF_2α metabolites were low, and their accuracies were nearly 100%. The matrix effects against the final PGI₂ and TXA₂ metabolites were high using reverse phase SPE column purification alone. By applying a tandem SPE method that combined reverse phase and ion exchange SPE columns, the matrix effects decreased so that the accuracy was nearly 100%. To validate the reliability of the method, each final metabolite was quantified from mouse urine to which the PNs (PGD₂, PGE₂, and PGI₂) were intravenously administered. As a result, the amounts of PN metabolites were correlated with those of the PNs administered to the blood in a dose-dependent manner. To validate the method using human samples, the urinary metabolites of Crohn's disease (CD, a PN-related disease) patients and healthy individuals were quantified. All five metabolites were successfully quantified. Only final PGE₂ metabolite levels were significantly higher in CD patients than those in healthy individuals, so that the urinary metabolite profiles of CD patients is determined. In conclusion, we developed a novel method to quantify all final PN metabolites simultaneously and efficiently and demonstrated the practicality of the method using human CD patient samples.

The enzymology of the human prostanoid pathway

Prostanoids are short-lived autocrine and paracrine signaling molecules involved in a wide range of biological functions. They have been shown to be intimately involved in many different disease states when their regulation becomes dysfunctional. In order to fully understand the progression of any disease state or the biological functions of the well state, a complete evaluation of the genomics, proteomics, and metabolomics of the system is necessary. This review is focused on the enzymology for the enzymes involved in the synthesis of the prostanoids (prostaglandins, prostacyclins and thromboxanes). In particular, the isolation and purification of the enzymes, their enzymatic parameters and catalytic mechanisms are presented.

NTP42, a novel antagonist of the thromboxane receptor, attenuates experimentally induced pulmonary arterial hypertension

BACKGROUND

NTP42 is a novel antagonist of the thromboxane prostanoid receptor (TP), currently in development for the treatment of pulmonary arterial hypertension (PAH). PAH is a devastating disease with multiple pathophysiological hallmarks including excessive pulmonary vasoconstriction, vascular remodelling, inflammation, fibrosis, in situ thrombosis and right ventricular hypertrophy. Signalling through the TP, thromboxane (TX) A₂ is a potent vasoconstrictor and mediator of platelet aggregation. It is also a pro-mitogenic, pro-inflammatory and pro-fibrotic agent. Moreover, the TP also mediates the adverse actions of the isoprostane 8-iso-prostaglandin F_2α, a free-radical-derived product of arachidonic acid produced in abundance during oxidative injury. Mechanistically, TP antagonists should treat most of the hallmarks of PAH, including inhibiting the excessive vasoconstriction and pulmonary artery remodelling, in situ thrombosis, inflammation and fibrosis. This study aimed to investigate the efficacy of NTP42 in the monocrotaline (MCT)-induced PAH rat model, alongside current standard-of-care drugs.

METHODS

PAH was induced by subcutaneous injection of 60 mg/kg MCT in male Wistar-Kyoto rats. Animals were assigned into groups: 1. 'No MCT'; 2. 'MCT Only'; 3. MCT + NTP42 (0.25 mg/kg BID); 4. MCT + Sildenafil (50 mg/kg BID), and 5. MCT + Selexipag (1 mg/kg BID), where 28-day drug treatment was initiated within 24 h post-MCT.

RESULTS

From haemodynamic assessments, NTP42 reduced the MCT-induced PAH, including mean pulmonary arterial pressure (mPAP) and right systolic ventricular pressure (RSVP), being at least comparable to the standard-of-care drugs Sildenafil or Selexipag in bringing about these effects. Moreover, NTP42 was superior to Sildenafil and Selexipag in significantly reducing pulmonary vascular remodelling, inflammatory mast cell infiltration and fibrosis in MCT-treated animals.

CONCLUSIONS

These findings suggest that NTP42 and antagonism of the TP signalling pathway have a relevant role in alleviating the pathophysiology of PAH, representing a novel therapeutic target with marked benefits over existing standard-of-care therapies.

Hypoactivity of rat detrusor muscle in a model of cystitis: exacerbation by non-selective COX inhibitors and amelioration by a selective DP1 receptor antagonist

Various studies have confirmed that prostaglandins (PG) alter the bladder motor activity and micturition reflex in both human and animals. However, no sufficient data is reported about the effect of cyclooxygenase (COX) inhibitors neither in normal bladder physiology nor in pathological conditions. This study aims to compare the potential effects of some COX inhibitors with varying COX-1/COX-2 selectivities (indomethacin, ketoprofen, and diclofenac) with that of the selective COX-2 inhibitor (DFU) on bladder function. The role played by some PGs and their receptors in controlling detrusor muscle function in normal condition and in cystitis is also studied. Organ bath experiments were performed using isolated rat detrusor muscle. Direct and neurogenic contractions were induced using ACh and electric stimulation (EFS), respectively. A model of hemorrhagic cystitis was induced by single injection of cyclophosphamide (300 mg/kg) in rats, and confirmed by histophathological examination. Results are expressed as mean ± SEM of 5-9 rats. Alprostadil and iloprost (1 nM- 10 µM) concentration-dependently potentiated ACh (100 μM)- and EFS (4 Hz)-induced contraction, with maximum potentiation of 40.01 ± 5.29 and 27.59 ± 6.64%, respectively, in case of ACh contractions. In contrast, ONO-AE1-259 (selective EP₂ agonist, 1 nM-10 μM) inhibited muscle contraction. SC51322 (EP₁-antagonist, 10 μM) and RO1138452 (IP antagonist, 10 μM) inhibited both direct and neurogenic responses. Hemorrhagic cystitis reduced both ACh and EFS responses as well as the potentiatory effect of iloprost and the inhibitory effect of RO1138452 on ACh contractions. ONO-AE3-237 (DP₁ antagonist, 1 μM) significantly potentiated contractions in cystitis but showed no effect in normal bladder. A significant inhibition of contractile response was observed in presence of indomethacin, ketoprofen, and diclofenac at all tested concentrations (20, 50, and 100 μM). Highest effect was induced by diclofenac. The effect of these COX inhibitors on EFS contractions was intensified in case of cystitis, indomethacin being the most potent. Atropine (1 nM) significantly reduced indomethacin effect on ACh contraction only in normal rats. On the other hand, DFU (10^-6 M) significantly potentiated the contractile effect of ACh in case of cystitis although it showed no effect in normal rats. EP₁ receptors seem to play an important role in rat bladder contractility. DP₁ receptors as COX-2, on the other hand, gain an important role only in case of cystitis. The use of non-selective COX inhibitors in cystitis may be associated with bladder hypoactivity; selective COX-2 inhibitors may be a safer option.

Endothelial cell transient receptor potential channel C5 (TRPC5) is essential for endothelium-dependent contraction in mouse carotid arteries

Augmented endothelium-dependent contractions (EDC) contributes to endothelial dysfunction and vascular disease progression. An early signal in EDC is cytosolic [Ca²⁺]_i rise in endothelial cells, which stimulates the production of contractile prostanoids, leading to vascular contraction. In this study, the molecular identity of Ca²⁺-permeable channels in endothelial cells and its function were investigated. Vascular tension was measured by wire myograph. EDCs were elicited by acetylcholine (ACH) in the presence of N^G-nitro-l-arginine methyl ester (L-NAME). [Ca²⁺]_i was measured using a Ca²⁺-sensitive fluorescence dye. Enzyme Immunoassay (EIA) was used for prostaglandin measurement. Immunohistochemical staining found the expression of transient receptor potential channel C5 (TRPC5) in endothelial and smooth muscle cells of mouse carotid arteries. ACH-induced EDC in male mouse carotid arteries was found to be substantially reduced in TRPC5 knockout (KO) mice than in wild-type (WT) mice. TRPC5 inhibitors clemizole and ML204 also reduced the EDC. Furthermore, ACH-induced Ca²⁺ entry in endothelial cells was lower in TRPC5 KO mice than in WT mice. Moreover, the EDC was abolished by a cyclooxygenase-2 (COX-2) inhibitor NS-398, but not affected by a COX-1 inhibitor valeryl salicylate (VAS). Enzyme immunoassay results showed that TRPC5 stimulated the COX-2-linked production of prostaglandin F_2α (PGF_2α), prostaglandin E₂ (PGE₂), and prostaglandin D₂ (PGD₂). Exogeneous PGF_2α, PGE₂, and PGD₂ could induce contractions in carotid arteries. Our present study demonstrated that TRPC5 in endothelial cells contributes to EDC by stimulating the production of COX-2-linked prostanoids. The finding extends our knowledge about EDC.

Identification and expression of prostaglandin E synthase (PGES) gene in the central nervous system and ovary during ovarian maturation of the female mud crab, Scylla olivacea

Prostaglandins have important physiological roles in marine invertebrates, including larval development and reproduction. The prostaglandin E concentration fluctuates during the ovarian development of crustaceans. The biosynthetic pathway of prostaglandin, however, has not been well studied in portunid crabs, including in the mud crab, Scylla olivacea. In this study, the aim was to investigate the presence of prostaglandin E synthase (PGES), enzyme that catalyzes the terminal conversion in the prostaglandin E2 (PGE₂) biosynthesis, and its gene expression in the central nervous system (CNS) and ovary during ovarian maturation of S. olivacea. cDNA sequence encoding PGES was cloned from the S. olivacea ovary. The PGES transcript of S. olivacea (Scyol-PGES) consists of 1258 nucleotides, which encodes for 420 amino acid PGES protein precursor. Investigation of gene expression by RT-PCR indicated that Scyol-PGES was detected in all organs studied. Based on in situ hybridization, Scyol-PGES was detected in the I to III stages for oocyte development of Stage 3 of ovarian development, and in the CNS, including the various neuronal clusters of the brain. In the ventral nerve cord, the Scyol-PGES gene was expressed in the neurons within the subesophageal, thoracic and abdominal ganglia. The Scyol-PGES gene expression as indicated by relative abundance of mRNA in the Stage 4 of ovarian development was greater than that at Stages 1 to 3 of ovarian development. This is the first report on PGES in the mud crab, S. olivacea, and its gene expression suggested the involvement of PGES in the ovarian development of this species.

Decreased contraction induced by endothelium-derived contracting factor in prolonged treatment of rat renal artery with endoplasmic reticulum stress inducer

Recent evidence suggests that endoplasmic reticulum (ER) stress is involved in the regulation of various physiological functions, including those of the vascular system. However, the relationship between ER stress and vascular function is poorly understood. The endothelial cells control the vascular tone by releasing endothelium-derived relaxing factors and contracting factors (EDCFs). We hypothesized that tunicamycin, an inducer of ER stress, modifies endothelium-dependent contraction and prostaglandins (PGs), a major class of EDCFs, induced contractions in the rat renal artery in rats. An organ-culture technique was used to purely investigate the effects of ER stress on the vascular tissue. We observed that tunicamycin treatment (20 μg/mL for 23 ± 1 h) did not affect acetylcholine (ACh)-induced relaxation and decreased EDCF-mediated contractions under nitric oxide synthase (NOS) inhibition induced by ACh, ATP, or A23187 (a calcium ionophore) in the renal arteries. Under NOS inhibition, U46619 (a thromboxane A₂ mimetic)- and beraprost (a prostacyclin analog)-induced contractions were also decreased in the renal arteries of the tunicamycin-treated group (vs. vehicle), while PGE₂- and PGF_2α-induced contractions were similar between the groups. Tunicamycin treatment slightly enhanced the contractions induced by phenylephrine, an α₁ adrenoceptor ligand. Isotonic high-K⁺-induced contractions were similar between the vehicle- and tunicamycin-treated groups. Another ER stress inducer, thapsigargin (4 μmol/L for 23 ± 1 h), also caused substantial reduction of ACh-induced EDCF-mediated contraction (vs. vehicle-treated group). In the cultured renal arteries, tunicamycin and thapsigargin increased the expression of binding immunoglobulin protein (BiP), an ER stress marker. In conclusion, ER stress induction directly affects renal arterial function, especially in reducing EDCF-mediated contractions.

Celecoxib-mediated reduction of prostanoid release in Hoffa's fat pad from donors with cartilage pathology results in an attenuated inflammatory phenotype

OBJECTIVE

The Hoffa's fat pad (HFP) is an intra-articular adipose tissue which is situated under and behind the patella. It contains immune cells next to adipocytes and secretes inflammatory factors during osteoarthritis (OA). In this study, we compared the release profile of prostanoids, which are involved in inflammation, of HFP from OA patients vs patients with a focal cartilage defect (CD) without evidence for OA on MRI and investigated the prostanoid modulatory anti-inflammatory action of celecoxib on HFP.

DESIGN

Prostanoid release was analyzed in conditioned medium of HFP explant cultures from 17 osteoarthritic patients and 12 CD patients, in the presence or absence of celecoxib. Furthermore, gene expression of COX enzymes and expression of genes indicative of a pro-inflammatory or anti-inflammatory phenotype of HFP was analyzed.

RESULTS

Prostanoid release by HFP from knee OA patients clustered in two subgroups with high and low prostanoid producers. HFP from high prostanoid producers released higher amounts of PGE₂, PGF_2α and PGD₂ compared to HFP from CD patients. PGE₂ release by OA HFP was positively associated with expression of genes known to be expressed by M1 macrophages, indicating a role for macrophages. Celecoxib modulated prostanoid release by HFP, and also modulated the inflammation ratio towards a more favorable anti-inflammatory M2 phenotype, most effectively in patients with higher prostanoid release profiles.

CONCLUSION

In knee OA patients with inflamed HFP's, celecoxib may exert positive effects in the knee joint via decreasing the release of prostanoids produced by the HFP and by favorably modulating the anti-inflammatory marker expression in HFP.

Discovery of furan and dihydrofuran-fused tricyclic benzo[d]imidazole derivatives as potent and orally efficacious microsomal prostaglandin E synthase-1 (mPGES-1) inhibitors: Part-1

This letter describes the synthesis and biological evaluation of furan and dihydrofuran-fused tricyclic benzo[d]imidazole derivatives as novel mPGES-1 inhibitors, capable of inhibiting an increased PGE₂ production in the disease state. Structure-activity optimization afforded many potent mPGES-1 inhibitors having <50 nM potencies in the A549 cellular assay and adequate metabolic stability in liver microsomes. Lead compounds 8l and 8m demonstrated reasonable in vitro pharmacology and pharmacokinetic properties over other compounds. In particular, 8m revealed satisfactory oral pharmacokinetics and bioavailability in multiple species like rat, guinea pig, dog and cynomolgus monkey. In addition, the representative compound 8m showed in vivo efficacy by inhibiting LPS-induced thermal hyperalgesia with an ED₅₀ of 14.3 mg/kg in guinea pig.

Successful transition from Treprostinil to Selexipag in patient with severe pulmonary arterial hypertension

Background

In this report, we describe the first successful case of transition from subcutaneous administration of treprostinil to selexipag in a patient with severe pulmonary arterial hypertension (PAH), by evaluating hemodynamic changes and exercise tolerance.

Case presentation

A 38-year-old female with idiopathic PAH (IPAH) had received initial triple combination therapy (macitentan PO, tadalafil PO, and treprostinil SC) and achieved excellent improvement in hemodynamics. Afterwards, due to the development of side effects from subcutaneous administration, we replaced treprostinil therapy with oral selexipag, resulting in stable hemodynamic parameters and exercise capacities.

Conclusions

We report the first case of successful replacement of treprostinil (20.1 ng/kg/min) with selexipag (1600 μg BID) as a component of triple combination therapy, which provides incentive to perform a larger, prospective exchange study.

Prostanoids in the pathophysiology of human coronary artery

Coronary artery disease is one of the leading causes of death in wordwide. There is growing evidence that prostanoids are involved in the physiology and pathophysiology of the human coronary artery by controlling vascular tone, remodelling of the vascular wall or angiogenesis. In this review, the production of prostanoids and the expression of prostanoid receptors in human coronary artery in health or disease are described. In addition, the interactions between sex hormones and prostanoids, their participations in the development of coronary artery diseases have been addressed. Globally, most of the studies performed in human coronary artery preparations have shown that prostacyclin (PGI₂) has beneficial effects by inducing vasodilatation and promoting angiogenesis while reverse effects are confirmed by thromboxane A₂ (TxA₂). More studies are needed to determine the roles of the other prostanoids (PGE₂, PGD₂ and PGF_2α) in vascular functions of the human coronary artery. Finally, in addition to the in vitro data about the human coronary artery, myocardial infarction induced by cyclooxygenase-2 (COX-2) inhibitor and the protective effects of aspirin after coronary artery bypass surgery suggest that prostanoids are key mediators in coronary homeostasis.

Control of adipogenesis by oxylipins, GPCRs and PPARs

Oxylipins are bioactive metabolites derived from the oxygenation of ω3 and ω6 polyunsaturated fatty acids, triggered essentially by cyclooxygenase and lipoxygenase activities. Oxylipins are involved in the development and function of adipose tissue and their productions are strictly related to diet quality and quantity. Oxylipins signal via cell surface membrane (G Protein-coupled receptors) and nuclear receptors (peroxisome proliferator-activated receptors), two pathways playing a pivotal role in adipocyte biology. In this review, we made an attempt to cover the available knowledge about synthesis and molecular function of oxylipins known to modulate adipogenesis, adipocyte function and phenotype conversion, with a focus on their interaction with peroxisome proliferator-activated nuclear receptor family.

Norepinephrine responses in rat renal and femoral veins are reinforced by vasoconstrictor prostanoids

Norepinephrine (NE) responses are larger in renal and femoral veins compared to phenylephrine (PE). These differences may be due to the subtypes of adrenoceptor involved in these responses or to the involvement of local modulatory mechanisms. Therefore, the present study investigated in organ bath the adrenoceptor subtypes involved in the NE and PE responses in both renal and femoral veins as well as the influence of local mechanisms related to NO and to prostanoids upon these responses. The obtained data showed that the NE responses in these veins were not significantly modified by the selective inhibition of β1 or β2-adrenoceptors as well as AT1 or AT2 receptors. However, yohimbine reduced the NE Rmax in renal veins and, in parallel, right shifted the NE concentration-response curves in femoral veins. In both veins, prazosin reduced the NE Rmax and the clonidine induced a measurable contraction. The endothelium removal attenuated the NE responses in femoral veins, thereby abolishing the differences of NE and PE responses. Furthermore, the NE responses in renal and femoral veins were attenuated by indomethacin, which suppressed the statistical difference in relation to the PE response. In conclusion, a synergism between α1- and α2-adrenoceptors is essential to assure full NE contractile responses in both renal and femoral veins. Thus, by acting simultaneously in these adrenoceptors, NE induces more pronounced contractile responses, in comparison to PE, not only in renal but also in femoral veins. Moreover, this pronounced NE response in both renal and femoral veins appears to involve endothelium-derived vasoconstrictor prostanoids.

Prostanoids in allergy

Prostanoids, which include prostaglandin and thromboxane, are metabolites of arachidonic acid released in various pathophysiological conditions. They induce a range of actions mediated through their respective receptors expressed on target cells. It has been demonstrated that each prostanoid receptor has multiple functions and that the effect of receptor stimulation can vary depending on context; this sometimes results in opposing effects, such as simultaneous excitatory and inhibitory outcomes. The balance between the production of each prostanoid and the expression of its receptors has been shown to be important for maintaining homeostasis but also involved in the development of various pathological conditions such as allergy. Here, we review the recent findings on the roles of prostanoids in allergy, especially focusing on atopic dermatitis and asthma.

Prostaglandin E2-induced inflammation: Relevance of prostaglandin E receptors

Prostaglandin E2 (PGE2) is one of the most typical lipid mediators produced from arachidonic acid (AA) by cyclooxygenase (COX) as the rate-limiting enzyme, and acts on four kinds of receptor subtypes (EP1-EP4) to elicit its diverse actions including pyrexia, pain sensation, and inflammation. Recently, the molecular mechanisms underlying the PGE2 actions mediated by each EP subtype have been elucidated by studies using mice deficient in each EP subtype as well as several compounds highly selective to each EP subtype, and their findings now enable us to discuss how PGE2 initiates and exacerbates inflammation at the molecular level. Here, we review the recent advances in PGE2 receptor research by focusing on the activation of mast cells via the EP3 receptor and the control of helper T cells via the EP2/4 receptor, which are the molecular mechanisms involved in PGE2-induced inflammation that had been unknown for many years. We also discuss the roles of PGE2 in acute inflammation and inflammatory disorders, and the usefulness of anti-inflammatory therapies that target EP receptors. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Identification of novel IP receptor agonists using historical ligand biased chemical arrays

By considering published structural information we have designed high throughput biaryl lipophilic acid arrays leveraging facile chemistry to expedite their synthesis. We rapidly identified multiple hits which were of suitable IP agonist potency. These relatively simple and strategically undecorated molecules present an ideal opportunity for optimization towards our target candidate profile.

Endothelin-1 but not angiotensin II contributes to functional aging in murine carotid arteries

AIMS

Aging is a major risk factor for carotid artery disease and stroke. Endothelin-1 (ET-1) and angiotensin II (Ang II) are important modifiers of vascular disease, partly through increased activity of NADPH oxidase and vasoconstrictor prostanoids. Since the renin-angiotensin and endothelin systems become activated with age, we hypothesized that aging affects NADPH oxidase- and prostanoid-dependent contractions to ET-1 and Ang II.

MAIN METHODS

Carotid artery rings of young (4 month-old) and old (24 month-old) C57BL6 mice were pretreated with the NO synthase inhibitor L-NAME to exclude differential effects of NO. Contractions to ET-1 and Ang II were determined in the presence and absence of the NADPH oxidase-selective inhibitor gp91ds-tat or the thromboxane-prostanoid receptor antagonist SQ 29,548. Gene expression of endothelin and angiotensin receptors was measured by qPCR.

KEY FINDINGS

Aging reduced ET-1-induced contractions and diminished ETA but increased ETB receptor gene expression levels. Gp91ds-tat inhibited contractions to ET-1 in young and to a greater extent in old animals, whereas SQ 29,548 had no effect. Ang II-induced contractions were weak compared to ET-1 and unaffected by aging, gp91ds-tat, and SQ 29,548. Aging had also no effect on AT1A and AT1B receptor gene expression levels.

SIGNIFICANCE

Aging in carotid arteries decreases ETA receptor gene expression and responsiveness to ET-1, which nevertheless becomes increasingly dependent upon NAPDH oxidase activity with age; responses to Ang II and gene expression of its receptors are however unaffected. These findings suggest that physiological aging differentially regulates functional responses to G protein-coupled receptor agonists and the signaling pathways associated with their activation.

Cyclooxygenase metabolism mediates vasorelaxation to 2-arachidonoylglycerol (2-AG) in human mesenteric arteries

Objective

The vasorelaxant effect of 2-arachidonoylglycerol (2-AG) has been well characterised in animals. 2-AG is present in human vascular cells and is up-regulated in cardiovascular pathophysiology. However, the acute vascular actions of 2-AG have not been explored in humans.

Approach

Mesenteric arteries were obtained from patients receiving colorectal surgery and mounted on a myograph. Arteries were contracted and 2-AG concentration–response curves were carried out. Mechanisms of action were characterised pharmacologically. Post hoc analysis was carried out to assess the effects of cardiovascular disease/risk factors on 2-AG responses.

Results

2-AG caused vasorelaxation of human mesenteric arteries, independent of cannabinoid receptor or transient receptor potential vanilloid-1 activation, the endothelium, nitric oxide or metabolism via monoacyglycerol lipase or fatty acid amide hydrolase. 2-AG-induced vasorelaxation was reduced in the presence of indomethacin and flurbiprofen, suggesting a role for cyclooxygenase metabolism 2-AG. Responses to 2-AG were also reduced in the presence of Cay10441, L-161982 and potentiated in the presence of AH6809, suggesting that metabolism of 2-AG produces both vasorelaxant and vasoconstrictor prostanoids. Finally, 2-AG-induced vasorelaxation was dependent on potassium efflux and the presence of extracellular calcium.

Conclusions

We have shown for the first time that 2-AG causes vasorelaxation of human mesenteric arteries. Vasorelaxation is dependent on COX metabolism, activation of prostanoid receptors (EP₄ & IP) and ion channel modulation. 2-AG responses are blunted in patients with cardiovascular risk factors.

Prostaglandin D(2) is crucial for seizure suppression and postictal sleep

Epilepsy is a neurological disorder with the occurrence of seizures, which are often accompanied by sleep. Prostaglandin (PG) D2 is produced by hematopoietic or lipocalin-type PGD synthase (H- or L-PGDS) and involved in the regulation of physiological sleep. Here, we show that H-PGDS, L/H-PGDS or DP1 receptor (DP1R) KO mice exhibited more intense pentylenetetrazole (PTZ)-induced seizures in terms of latency of seizure onset, duration of generalized tonic-clonic seizures, and number of seizure spikes. Seizures significantly increased the PGD2 content of the brain in wild-type mice. This PTZ-induced increase in PGD2 was attenuated in the brains of L- or H-PGDS KO and abolished in L/H-PGDS KO mice. Postictal non-rapid eye movement sleep was observed in the wild-type and H-PGDS or DP2R KO, but not in the L-, L/H-PGDS or DP1R KO, mice. These findings demonstrate that PGD2 produced by H-PGDS and acting on DP1R is essential for seizure suppression and that the L-PGDS/PGD2/DP1R system regulates sleep that follows seizures.