Stable Prostacyclin Analogue Research Articles

Designer high-density lipoprotein particles enhance endothelial barrier function and suppress inflammation.

High-density lipoprotein (HDL) nanoparticles promote endothelial cell (EC) function and suppress inflammation, but their utility in treating EC dysfunction has not been fully explored. Here, we describe a fusion protein named ApoA1-ApoM (A1M) consisting of apolipoprotein A1 (ApoA1), the principal structural protein of HDL that forms lipid nanoparticles, and ApoM, a chaperone for the bioactive lipid sphingosine 1-phosphate (S1P). A1M forms HDL-like particles, binds to S1P, and is signaling competent. Molecular dynamics simulations showed that the S1P-bound ApoM moiety in A1M efficiently activated EC surface receptors. Treatment of human umbilical vein ECs with A1M-S1P stimulated barrier function either alone or cooperatively with other barrier-enhancing molecules, including the stable prostacyclin analog iloprost, and suppressed cytokine-induced inflammation. A1M-S1P injection into mice during sterile inflammation suppressed neutrophil influx and inflammatory mediator secretion. Moreover, systemic A1M administration led to a sustained increase in circulating HDL-bound S1P and suppressed inflammation in a murine model of LPS-induced endotoxemia. We propose that A1M administration may enhance vascular endothelial barrier function, suppress cytokine storm, and promote resilience of the vascular endothelium.

Inhaled iloprost is an effective alternative therapy for persistent pulmonary hypertension in newborns.

Persistent pulmonary hypertension of the newborn(PPHN) is one of the diseases of the neonate with severe potential morbidity and mortality. Inhaled iloprost, a stable prostacyclin analog, has been suggested as an alternative treatment for inhaled nitric oxide (iNO). However, more data on neonates' dosing, setting, and effectiveness still needs to be solved. This study suggests using inhaled iloprost as rescue therapy for PPHN based on our experience. This was a retrospective study. The data from medical records of six newborns diagnosed with PPHN and had received inhaled iloprost from December 2019 to April 2022 were collected. Demographic and clinical features, dosing regimen, changes in oxygenation index, echocardiographic findings, and mortality were evaluated. The inhalation dose was 2-4 mcg/dose, and 3-48 inhalations per day were applied over 2-7 days. Inhaled iloprost was effective in all patients. No side effects were attributable to inhaled iloprost, and no mortality was recorded. Our experience suggests that inhaled iloprost can be used as a first-line therapy in newborn infants with PPHN when iNO is unavailable. However, there are large fluctuations in the oxygenation index due to the setting.

Efficacy, safety, and pharmacokinetics of inhaled treprostinil in Japanese patients with pulmonary arterial hypertension.

Treprostinil is a chemically stable analog of prostacyclin, and inhaled treprostinil was developed to deliver the effects directly to the pulmonary vasculature while minimizing systemic side effects. The objective of the study was to evaluate the efficacy on hemodynamics and exercise capacity, safety, and pharmacokinetics (PK) of inhaled treprostinil in Japanese patients with pulmonary arterial hypertension (PAH). Inhaled treprostinil was administered at three breaths (18 μg)/session four times daily, and the dose was gradually increased to a maximum of nine breaths (54 μg)/session. Endpoints included change in pulmonary vascular resistance index (PVRI) as primary, other efficacy parameters, safety, and PK. SeventeenPAH patients, the majority of whom (76.5%) had been receiving both an endothelin receptor antagonist (ERA) and a phosphodiesterase type-5 (PDE5) inhibitor/soluble guanylate cyclase (sGC) stimulator, received inhaled treprostinil. At Week 12, PVRI statistically decreased by -39.4 ± 25.5% (95% confidence interval: -52.6 to -26.3). The most frequently reported adverse events related to treprostinil were headache, cough, throat irritation, and hot flush. Regarding PK, there were no notable differences in the geometric mean C max and AUClast between Japanese and non-Japanese patients. Treatment with inhaled treprostinil using the dosing regimen approved in the United States resulted in significant improvement in hemodynamics, exercise capacity, and symptoms with a favorable tolerability and safety profile in Japanese patients. Inhaled treprostinil could be a valuable therapeutic option for Japanese patients with PAH, including those receiving a combination therapy with an ERA and a PDE5 inhibitor/sGC stimulator. Trial registration: JAPIC Clinical Trials Information [JapicCTI-194651].

Progress in the development of treprostinil for the treatment of pulmonary hypertension

Pulmonary arterial hypertension is a progressive pulmonary vascular disease, which can cause right heart failure and even death in severe cases. Treprostinil is a stable prostacyclin analogue and a powerful drug for dilating pulmonary vessels. It can be administered in different ways, with a long half-life, good stability and is suited for diverse types of PAH. It is approved for the treatment of Group 1 PAH, but some studies show that treprostinil is effective in patients with Group 3 or Group 4 PAH. Therefore, this article will review the progress of evidence-based medicine evidence of traprostanil in the treatment of type 1, 3 and 4 pulmonary hypertension.

Riociguat in children with pulmonary arterial hypertension: The PATENT-CHILD study.

Riociguat, a soluble guanylate cyclase stimulator, is approved for treatment of adults with pulmonary arterial hypertension (PAH). The safety, tolerability, and pharmacokinetics (PK) of oral riociguat in a pediatric population with PAH was assessed in PATENT–CHILD (NCT02562235), a multicenter, single‐arm, 24‐week, open‐label, Phase 3 study. Patients aged 6–17 years in World Health Organization functional class (WHO‐FC) I–III treated with stable endothelin receptor antagonists and/or prostacyclin analogs received riociguat equivalent to 0.5–2.5 mg three times daily in adults, as either oral pediatric suspension or tablets, based on bodyweight. Primary outcomes were safety, tolerability, and PK of riociguat. Twenty‐four patients (mean age 12.8 years), 18 of whom were in WHO‐FC II, were enrolled. Adverse events (AEs), mostly mild or moderate, were reported in 20 patients (83%). Four patients (17%) experienced a serious AE; all resolved by study end and two (8%) were considered study‐drug related. Hypotension was reported in three patients and hemoptysis in one (all mild/moderate intensity). Riociguat plasma concentrations in pediatric patients were consistent with those published in adult patients. From baseline to Week 24, mean ± standard deviation increase in 6‐minute walking distance was 23 ± 69 m (n = 19), and mean decrease in NT‐proBNP was –66 ± 585 pg/ml (n = 14). There was no change in WHO‐FC. Two patients experienced clinical worsening events of hospitalization for right heart failure. PK results confirmed a suitable riociguat dosing strategy for pediatric patients with PAH. The data suggest an acceptable safety profile with potential efficacy signals.

USP10 exacerbates neointima formation by stabilizing Skp2 protein in vascular smooth muscle cells

The underlying mechanism of neointima formation remains unclear. Ubiquitin-specific peptidase 10 (USP10) is a deubiquitinase that plays a major role in cancer development and progression. However, the function of USP10 in arterial restenosis is unknown. Herein, USP10 expression was detected in mouse arteries and increased after carotid ligation. The inhibition of USP10 exhibited thinner neointima in the model of mouse carotid ligation. In vitro data showed that USP10 deficiency reduced proliferation and migration of rat thoracic aorta smooth muscle cells (A7r5) and human aortic smooth muscle cells (HASMCs). Mechanically, USP10 can bind to Skp2 and stabilize its protein level by removing polyubiquitin on Skp2 in the cytoplasm. The overexpression of Skp2 abrogated cell cycle arrest induced by USP10 inhibition. Overall, the current study demonstrated that USP10 is involved in vascular remodeling by directly promoting VSMC proliferation and migration via stabilization of Skp2 protein expression.

The Prostacyclin Analogue, Treprostinil, Used in the Treatment of Pulmonary Arterial Hypertension, is a Potent Antagonist of TREK-1 and TREK-2 Potassium Channels.

Pulmonary arterial hypertension (PAH) is an aggressive vascular remodeling disease that carries a high morbidity and mortality rate. Treprostinil (Remodulin) is a stable prostacyclin analogue with potent vasodilatory and anti-proliferative activity, approved by the FDA and WHO as a treatment for PAH. A limitation of this therapy is the severe subcutaneous site pain and other forms of pain experienced by some patients, which can lead to significant non-compliance. TWIK-related potassium channels (TREK-1 and TREK-2) are highly expressed in sensory neurons, where they play a role in regulating sensory neuron excitability. Downregulation, inhibition or mutation of these channels leads to enhanced pain sensitivity. Using whole-cell patch-clamp electrophysiological recordings, we show, for the first time, that treprostinil is a potent antagonist of human TREK-1 and TREK-2 channels but not of TASK-1 channels. An increase in TASK-1 channel current was observed with prolonged incubation, consistent with its therapeutic role in PAH. To investigate treprostinil-induced inhibition of TREK, site-directed mutagenesis of a number of amino acids, identified as important for the action of other regulatory compounds, was carried out. We found that a gain of function mutation of TREK-1 (Y284A) attenuated treprostinil inhibition, while a selective activator of TREK channels, BL-1249, overcame the inhibitory effect of treprostinil. Our data suggests that subcutaneous site pain experienced during treprostinil therapy may result from inhibition of TREK channels near the injection site and that pre-activation of these channels prior to treatment has the potential to alleviate this nociceptive activity.

Airway Progenitor Dysfunction Predicts Persistence of Bronchial Dysplasia Setting the Stage for Squamous Cell Lung Cancer

Squamous cell lung cancer arises from premalignant dysplasias characterized by squamous replacement of the normal mucociliary airway epithelium. Individuals with persistent, compared to regressive, dysplasias are at increased risk for lung cancer. Most studies have focused on genomic changes accrued in dysplasia, but the failure of normal epithelial repair has not been addressed. We hypothesized that basal progenitor cells, responsible for normal repair, are impaired in dysplasia. Functional analysis of basal progenitors from dysplastic bronchial biopsies showed decreased self-renewal and multipotentiality compared to non-dysplastic biopsies. The stable prostacyclin analog iloprost, the only drug to have improved dysplasia in a clinical trial, also rescued progenitor function and reversed dysplasia in a subset of lesions. In a series of 32 dysplastic lesions followed in 19 subjects who underwent serial bronchoscopic biopsies, baseline progenitor function predicted dysplasia persistence or regression. Epithelial repair dysfunction is an early and potentially manipulable event in bronchial premalignancy.

Treatment With Treprostinil and Metformin Normalizes Hyperglycemia and Improves Cardiac Function in Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction.

Pulmonary hypertension (PH) due to left heart disease (group 2), especially in the setting of heart failure with preserved ejection fraction (HFpEF), is the most common cause of PH worldwide; however, at present, there is no proven effective therapy available for its treatment. PH-HFpEF is associated with insulin resistance and features of metabolic syndrome. The stable prostacyclin analog, treprostinil, is an effective and widely used Food and Drug Administration-approved drug for the treatment of pulmonary arterial hypertension. While the effect of treprostinil on metabolic syndrome is unknown, a recent study suggests that the prostacyclin analog beraprost can improve glucose intolerance and insulin sensitivity. We sought to evaluate the effectiveness of treprostinil in the treatment of metabolic syndrome-associated PH-HFpEF. Approach and Results: Treprostinil treatment was given to mice with mild metabolic syndrome-associated PH-HFpEF induced by high-fat diet and to SU5416/obese ZSF1 rats, a model created by the treatment of rats with a more profound metabolic syndrome due to double leptin receptor defect (obese ZSF1) with a vascular endothelial growth factor receptor blocker SU5416. In high-fat diet-exposed mice, chronic treatment with treprostinil reduced hyperglycemia and pulmonary hypertension. In SU5416/Obese ZSF1 rats, treprostinil improved hyperglycemia with similar efficacy to that of metformin (a first-line drug for type 2 diabetes mellitus); the glucose-lowering effect of treprostinil was further potentiated by the combined treatment with metformin. Early treatment with treprostinil in SU5416/Obese ZSF1 rats lowered pulmonary pressures, and a late treatment with treprostinil together with metformin improved pulmonary artery acceleration time to ejection time ratio and tricuspid annular plane systolic excursion with AMPK (AMP-activated protein kinase) activation in skeletal muscle and the right ventricle. Our data suggest a potential use of treprostinil as an early treatment for mild metabolic syndrome-associated PH-HFpEF and that combined treatment with treprostinil and metformin may improve hyperglycemia and cardiac function in a more severe disease.

Orotracheal treprostinil administration attenuates bleomycin-induced lung injury, vascular remodeling, and fibrosis in mice.

Pulmonary fibrosis is a progressive disease characterized by disruption of lung architecture and deregulation of the pulmonary function. Prostacyclin, a metabolite of arachidonic acid, is a potential disease mediator since it exerts anti-inflammatory and anti-fibrotic actions. We investigated the effect of treprostinil, a prostacyclin analogue, in bleomycin-induced experimental pulmonary fibrosis. Bleomycin sulfate or saline was administrated intratracheally to mice (n = 9–10/group) at day 0. Orotracheal aspiration of treprostinil or vehicle was administered daily and started 24 h prior to bleomycin challenge. Evaluation of lung pathology was performed in tissue samples and bronchoalveolar lavage fluid collected 7, 14 and 21 days after bleomycin exposure. Lung injury was achieved due to bleomycin exposure at all time points as indicated by impaired lung mechanics, pathologic lung architecture (from day 14), and cellular and protein accumulation in the alveolar space accompanied by a minor decrease in lung tissue VE-cadherin at day 14. Treprostinil preserved lung mechanics, and reduced lung inflammation, fibrosis, and vascular remodeling (day 21); reduced cellularity and protein content of bronchoalveolar lavage fluid were additionally observed with no significant effect on VE-cadherin expression. Bleomycin-induced collagen deposition was attenuated by treprostinil from day 14, while treprostinil involvement in regulating inflammatory processes appears mediated by NF-κB signaling. Overall, prophylactic administration of treprostinil, a stable prostacyclin analogue, maintained lung function, and prevented bleomycin-induced lung injury, and fibrosis, as well as vascular remodeling, a hallmark of pulmonary hypertension. This suggests potential therapeutic efficacy of treprostinil in pulmonary fibrosis and possibly in pulmonary hypertension related to chronic lung diseases.

The prostacyclin analogue treprostinil in the treatment of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a rare but life-threatening disease that progresses rapidly and is currently without a cure. Pharmacological treatments aim to slow down disease progression and to reduce symptoms by targeting the prostacyclin, the endothelin or the nitric oxide pathway. Drugs targeting the prostacyclin pathway have been shown to be favourable for PAH patients by causing vasodilatative, anti-proliferative as well as anti-inflammatory effects, but tend to be underused, partially due to adverse effects and difficulties associated with their intravenous administration. Treprostinil, a stable prostacyclin analogue, was FDA-approved in 2002 to improve exercise capacity in PAH patients and is available in intravenous, subcutaneous, inhaled and oral form. The four different possible ways of administration, a long half-life and its stability at room temperature give treprostinil an advantage over epoprostenol, iloprost and selexipag, the three other FDA-approved drugs targeting the prostacyclin pathway. In clinical trials, treprostinil improved exercise capacity, quality of life (QOL), functional class and clinical status. While the different forms of treprostinil lead to specific complications, its general adverse effects are dizziness, nausea, pain in the jaw and extremities, diarrhoea, flushing and headache. This MiniReview will assess the benefits and drawbacks of treprostinil in the treatment of PAH by examining its specific mechanism of action and pharmacological properties, such as pharmacokinetics, pharmacodynamics, adverse effects and interactions. In addition, we will analyse and discuss results from different clinical trials, comparing treprostinil's four different forms to each other as well as to other drugs targeting the prostacyclin pathway.

Organozinc-aided, HMPA-free, stoichiometric three-component coupling for the general synthesis of prostaglandins and stable prostacyclin analogs with biological significance

A three-component coupling procedure was developed to construct the entire prostaglandin (PG) skeleton under HMPA-free and stoichiometric conditions via a combination of dimethylzinc-aided conjugate addition of an ω-side-chain vinyllithium with (R)-4-hydroxy-2-cyclopentenone and the direct trapping of the resulting enolate with an α-side-chain propargyl triflate. Dimethylzinc effectively regulated both the conjugate addition and alkynylation reactions. Thus, the method afforded protected 5,6-didehydro-PGE2, a common intermediate for the general synthesis of natural PGs and the stable artificial prostacyclin (PGI2) analog isocarbacyclin in 88% yield. The utility of the method was further applied to the syntheses of novel intermediates, which are useful for the straightforward synthesis of 15R-TIC and 15-deoxy-TIC in 79% and 86% yield, respectively.

Iloprost infusion prevents the insulin-induced reduction in skeletal muscle microvascular blood volume but does not enhance peripheral glucose uptake in type 2 diabetic patients.

In type 2 diabetes impaired insulin-induced muscle perfusion is thought to contribute to reduced whole-body glucose uptake. In this study, we examined the effects of iloprost, a stable prostacyclin analogue, on insulin-induced muscle capillary recruitment and whole-body glucose uptake. In a randomized cross-over design, 12 type 2 diabetes patients (age, 55 [46-69] years; BMI, 33.1 [31.0-39] kg/m2 ) underwent two hyperinsulinaemic-euglycaemic clamps, one with and one without simultaneous low-dose iloprost infusion. Contrast-enhanced ultrasonography of the vastus lateralis muscle was performed before and during the clamp. Muscle capillary recruitment was calculated as percentage change in microvascular blood volume (MBV) before and during the clamp. Insulin infusion reduced skeletal muscle MBV by ~50% compared to the fasting state (fasting, 1.77·10-4 [1.54·10-5 -2.44·10-3 ] arbitrary units (AU); hyperinsulinaemia, 6.69·10-5 [2.68·10-6 -5.72·10-4 ] AU; P = 0.050). Infusion of iloprost prevented this insulin-induced skeletal muscle capillary derecruitment, from (-49.5 [-89.5 to 55.3] %) to (8.0 [-68.8 to 306.6] %), for conditions without and with iloprost, respectively. The rate of glucose disappearance (Rd ) did not change significantly during iloprost infusion (17.3 [10.0-40.8] μmol/kg/min) compared with insulin infusion alone (17.6 [9.9-68.7] μmol/kg/min). Our data suggest that acute improvement in insulin-stimulated muscle perfusion is not an attractive therapeutic approach to bypass cellular resistance to glucose uptake in type 2 diabetes. Whether long-term improvements in insulin-induced muscle perfusion may prove beneficial for glucose disposal remains to be determined.

Prevention of lung injury by iloprost following hind limb ischemia and reperfuison model in rats

Aim: The major part of tissue damage occurs upon reperfusion and is mediated by activated neutrophils that release oxygen free radicals. Following hind-limb ischemia/reperfusion, lung injury due to neutrophil infiltration and oxygen free radicals has been demonstrated. Previous studies have shown that this injury can be prevented pharmacologically. Iloprost is a long acting stable analog of prostacyclin. The aim of this study is to test the effect of iloprost in prevention of lung injury due to lower limb ischemia/reperfusion. Material and Methods: Through a midline laparotomy infrarenal abdominal aorta was approached and cross-clamped in 20 male Spraque-Dawley rats for 2 hours. At the time of declamping Group I animals (n=8) received iloprost (0,1µg/kg/min) and Group II animals (n=8) received normal saline (0,1ml/kg/min) continously for 4 hours. Third group was the sham group (n=4). The lung tissue assays were performed for measurement of lipid peroxidation end product malondealdehyde and also total glutathione. Lung tissues were also examined histopathologically under light microscopy. Results: The malondealdehyde levels in the iloprost group were significantly lower than the control group (p<0,05). The glutathione levels did not show any difference between the iloprost and the control groups (p>0,05). Histopathological examination revealed that the structure of the lung tissue was preserved in the iloprost group whereas lung tissue of the control group had evidence of injury. Conclusion: Our results suggest that iloprost reduces the production of oxygen free radicals and prevents lung injury due to lower limb ischemia reperfusion.

Inhalation of repurposed drugs to treat pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a rare, but severe and life-threatening disease characterized by vasoconstriction and remodeling of the pulmonary arterioles, leading to progressive increase in pulmonary vascular resistance and ultimately to right-heart failure. In the last two decades, significant progress in treatment of PAH has been made, with currently 12 drugs approved for targeted therapy. Among these, the stable prostacyclin analogues iloprost and treprostinil have been repurposed for inhalation. The paper highlights the development of the two drugs emphasizing the rationale and advantages of the inhalative approach. Despite substantial advances in the specific, mainly vasodilatory PAH therapy, disease progression is mostly inevitable and mortality remains unacceptably high. Thus, introduction of new drugs targeting the cancer-like remodeling of the diseased pulmonary arteries is urgently needed. Inhalation offers pulmonary selectivity and will hopefully pioneer the repurposing of novel highly potent drugs for effective aerosol therapy of PAH.

The Role of the K2P Channels TASK‐1, TREK‐1 and TREK‐2 in the Use of Treprostinil Therapy in Pulmonary Arterial Hypertension

IntroductionPulmonary arterial hypertension (PAH) is a progressive and ultimately fatal disease affecting ~6 people per million, per year (1). Recent studies have reported mutations in the two‐pore domain potassium (K2P) channel TASK‐1 (KCNK3) giving rise to PAH (2). Treprostinil is a stable prostacyclin analogue often administered as a therapy in PAH, to keep blood vessels open. Its mode of action is thought to occur through an interaction with prostanoid receptors, DP2, EP2 and IP (3). Patients undergoing continuous subcutaneous treprostinil infusion can often exhibit severe pain at the site of delivery (4). In this study we investigate the action of treprostinil on TASK‐1 and on two other K2P channels, TREK‐1 (KCNK2) and TREK‐2 (KCNK10), which regulate the excitability of sensory neurons and are implicated in pain (5).MethodUsing the whole‐cell patch‐clamp technique, currents were measured through human TASK‐1, TREK‐1 and TREK‐2 channels transiently expressed in tsA‐201 cells. TASK‐1 was also co‐expressed with prostanoid receptors (IP, DP2 and EP2). Data are expressed as mean ± SEM (n = cells) of current measured at −40 mV and mean % change ± SEM (n = cells), with statistical analysis performed using a paired t‐test.ResultsAcute application of treprostinil (1 μM) on cells expressing TASK‐1 channels had no effect on current (control: 234 ± 80 pA; treprostinil: 240 ± 53 pA, n = 5, p > 0.05). Co‐expression of TASK‐1 with various prostanoid receptors, followed by acute application of treprostinil (1 μM) resulted in varying effects on TASK‐1 current. In cells expressing WT TASK‐1 and IP receptors, the average TASK‐1 current significantly decreased by 50% in the presence of treprostinil (control: 333 ± 82 pA; treprostinil (1 μM): 173 ± 46 pA, n = 6, p < 0.05). Whilst co‐expression of TASK‐1 with EP2 receptors saw a 30% increase in TASK‐1 current (control: 294 ± 65 pA; treprostinil (1 μM): 368 ± 78 pA, n = 8, p < 0.05). Co‐expression of TASK‐1 with DP2 receptors saw no significant change (3%) in TASK‐1 current (control: 387 ± 45 pA; treprostinil (1 μM): 398 ± 54 pA, n = 5, p > 0.05). Interestingly, treprostinil had a potent inhibitory effect on TREK‐1 (80 ± 8%, n = 5, p < 0.05) and TREK‐2 channels (59 ± 9%, n = 5, p < 0.05) in the absence of prostanoid receptors.ConclusionIn this study, acutely applied treprostinil did not appear to have a direct action on the TASK‐1 channels, themselves, instead its effects appeared to occur through the activation of prostanoid receptors and their associated signalling pathways. Conversely, treprostinil demonstrated a direct inhibitory effect on TREK‐1 and TREK‐2 channels. This effect of treprostinil may explain infusion site pain, a common side‐effect of patients on subcutaneous treatment (4). Acute enhancement of TREK channel activity at the infusion site could therefore help to reduce discomfort in PAH patients.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Long-term exposure to PGE2 causes homologous desensitization of receptor-mediated activation of protein kinase A.

BackgroundAcute exposure to prostaglandin E2 (PGE2) activates EP receptors in sensory neurons which triggers the cAMP-dependent protein kinase A (PKA) signaling cascade resulting in enhanced excitability of the neurons. With long-term exposure to PGE2, however, the activation of PKA does not appear to mediate persistent PGE2-induced sensitization. Consequently, we examined whether homologous desensitization of PGE2-mediated PKA activation occurs after long-term exposure of isolated sensory neurons to the eicosanoid.MethodsSensory neuronal cultures were harvested from the dorsal root ganglia of adult male Sprague-Dawley rats. The cultures were pretreated with vehicle or PGE2 and used to examine signaling mechanisms mediating acute versus persistent sensitization by exposure to the eicosanoid using enhanced capsaicin-evoked release of immunoreactive calcitonin gene-related peptide (iCGRP) as an endpoint. Neuronal cultures chronically exposed to vehicle or PGE2 also were used to study the ability of the eicosanoid and other agonists to activate PKA and whether long-term exposure to the prostanoid alters expression of EP receptor subtypes.ResultsAcute exposure to 1 μM PGE2 augments the capsaicin-evoked release of iCGRP, and this effect is blocked by the PKA inhibitor H-89. After 5 days of exposure to 1 μM PGE2, administration of the eicosanoid still augments evoked release of iCGRP, but the effect is not attenuated by inhibition of PKA or by inhibition of PI3 kinases. The sensitizing actions of PGE2 after acute and long-term exposure were attenuated by EP2, EP3, and EP4 receptor antagonists, but not by an EP1 antagonist. Exposing neuronal cultures to 1 μM PGE2 for 12 h to 5 days blocks the ability of PGE2 to activate PKA. The offset of the desensitization occurs within 24 h of removal of PGE2 from the cultures. Long-term exposure to PGE2 also results in desensitization of the ability of a selective EP4 receptor agonist, L902688 to activate PKA, but does not alter the ability of cholera toxin, forskolin, or a stable analog of prostacyclin to activate PKA.ConclusionsLong-term exposure to PGE2 results in homologous desensitization of EP4 receptor activation of PKA, but not to neuronal sensitization suggesting that activation of PKA does not mediate PGE2-induced sensitization after chronic exposure to the eicosanoid.

Iloprost as an acute kidney injury-triggering agent in severely atherosclerotic patients.

SummaryBackgroundIloprost, a stable prostacyclin analog, is used as a rescue therapy for severe peripheral arterial disease (PAD). It has systemic vasodilatory and anti-aggregant effects, with severe vasodilatation potentially causing organ ischaemia when severe atherosclerosis is the underlying cause. In this study, we retrospectively analysed renal outcomes after iloprost infusion therapy in 86 patients.MethodsEighty-six patients with PAD who received iloprost infusion therapy were retrospectively analysed. Clinical and biochemical parameters were recorded before (initial, Cr1), during (third day, Cr2), and after (14th day following the termination of infusion therapy, Cr3) treatment. Acute kidney injury (AKI) was defined according to KDIGO guidelines as a ≥ 0.3 mg/dl (26.52 μmol/l) increase in creatinine levels from baseline within 48 hours.Results:Cr2 (1.46 ± 0.1 mg/dl) (129.06 ± 8.84 μmol/l) and Cr3 (1.53 ± 0.12 mg/dl) (135.25 ± 10.61 μmol/l) creatinine levels were significantly higher compared to the initial value (1.15 ± 0.6 mg/dl) (101.66 ± 53.04 μmol/l). AKI was observed in 36 patients (41.86%) on the third day of iloprost infusion. Logistic regression analysis revealed smoking and not using acetylsalicylic acid as primary predictors (p = 0.02 and p = 0.008, respectively) of AKI during iloprost treatment. On the third infusion day, patients’ urinary output significantly increased (1813.30 ± 1123.46 vs 1545.17 ± 873.00 cm3) and diastolic blood pressure significantly decreased (70.07 ± 15.50 vs 74.14 ± 9.42 mmHg) from their initial values.ConclusionWhile iloprost treatment is effective in patients with PAD who are not suitable for surgery, severe systemic vasodilatation can cause renal ischaemia, resulting in nonoliguric AKI. Smoking, no acetylsalicylic acid use, and lower diastolic blood pressure are the clinical risk factors for AKI during iloprost treatment.

IP-receptor and PPARs trigger the conversion of human white to brite adipocyte induced by carbaprostacyclin

Brite adipocytes recently discovered in humans are of considerable importance in energy expenditure by converting energy excess into heat. This property could be useful in the treatment of obesity, and nutritional aspects are relevant to this important issue. Using hMADS cells as a human cell model which undergoes a white to a brite adipocyte conversion, we had shown previously that arachidonic acid, the major metabolite of the essential nutrient Ω6-linoleic acid, plays a major role in this process. Its metabolites PGE2 and PGF2 alpha inhibit this process via a calcium-dependent pathway, whereas in contrast carbaprostacyclin (cPGI2), a stable analog of prostacyclin, activates white to brite adipocyte conversion. Herein, we show that cPGI2 generates via its cognate cell-surface receptor IP-R, a cyclic AMP-signaling pathway involving PKA activity which in turn induces the expression of UCP1. In addition, cPGI2 activates the pathway of nuclear receptors of the PPAR family, i.e. PPARα and PPARγ, which act separately from IP-R to up-regulate the expression of key genes involved in the function of brite adipocytes. Thus dual pathways are playing in concert for the occurrence of a browning process of human white adipocytes. These results make prostacyclin analogs as a new class of interesting molecules to treat obesity and associated diseases.

1-Methylnicotinamide protects against liver injury induced by concanavalin A via a prostacyclin-dependent mechanism: A possible involvement of IL-4 and TNF-α

We have recently demonstrated that concanavalin A (Con A)-induced hepatitis is associated with the release of endogenous 1-methylnicotinamide (MNA). Here we study the mechanism by which exogenous MNA alleviates Con A-induced liver inflammation and injury in vivo.The involvement of prostacyclin (PGI2) in hepatoprotective action of MNA (30–100mgkg−1; i.v.) was studied by the use of IP receptor antagonist RO3244794 (10mgkg−1; p.o.) given prior to Con A (5–20mgkg−1; i.v.). Liver damage was assessed by measurements of: liver specific transaminases in plasma (alanine aminotransferase; aspartate aminotransferase); cytokines release (IL-4, IFN-γ and TNF-α); liver histopathology; and 24h survival rates. Additionally, the effect of a stable analog of prostacyclin (carbaprostacyclin) on IL-4, IFN-γ and TNF-α production by isolated spleen lymphocytes in response to Con A was analyzed.MNA diminished Con A-induced rise in liver specific transaminases, alleviated histopathological injury and improved 24h survival rates, the latter effect in a degree comparable with the pretreatment of animals with dexamethasone (0.5mgkg−1; i.p.). MNA inhibited also a rise in IL-4 and TNF-α concentration in plasma measured 2h after Con A administration, while IFN-γ was less affected. The effects of MNA were reversed by pretreatment with IP antagonist RO3244794. In isolated spleen lymphocytes, carbaprostacyclin profoundly decreased production of IL-4, the effect on TNF-α was modest with no effect on IFN-γ production.In conclusion, MNA attenuated Con A-induced hepatitis by a prostacyclin-dependent mechanism involving the inhibition of lymphocytes-derived IL-4 and the inhibition of Kuppfer-cells derived TNF-α.