Stable Prostacyclin Analogue Research Articles

Restoration of normal vascular relaxation mechanisms in cerebral arteries by chromosomal substitution in consomic SS.13BNrats

This study sought to identify the mechanisms of vascular relaxation that are rescued in middle cerebral arteries (MCA) of SS.13BN consomic rats by substituting chromosome 13 containing the renin gene from Brown Norway (BN) rats into the Dahl salt-sensitive (SS) genetic background. Isolated MCA from SS rats exhibited an indomethacin-sensitive constriction in response to acetylcholine (ACh) and hypoxia. ACh-induced dilation was NO dependent and hypoxic dilations were cyclooxygenase (COX) dependent in BN and SS.13BN rats. In SS rats, hypoxic dilation was restored by indomethacin and abolished by inhibiting cytochrome P-450 epoxygenases, suggesting a role for epoxyeicosatrienoic acids. MCA from SS and SS.13BN rats constricted and MCA from BN rats dilated in response to the stable prostacyclin analog iloprost. MCA from SS.13BN and BN rats (but not SS rats) dilated in response to the prostaglandin E2 receptor agonist butaprost. Hypoxia increased prostacyclin release in cerebral arteries from all the strains, whereas thromboxane A2 production was reduced in BN rat vessels only. These data suggest that SS rats may be less sensitive to vasodilator prostaglandins and that normalization of renin-angiotensin system regulation causes a switch from production of COX-derived vasoconstrictor metabolites (in SS rats) toward NO-dependent relaxation in response to ACh- and prostaglandin-dependent dilation in response to hypoxia in SS.13(BN) rats.

Early protective effects of iloprost, a stable prostacyclin analog, during spinal cord ischemia in a rabbit model

Spinal cord ischemia may develop into paraplegia in some cases during operation of the thoracoabdominal aorta. This is attributable to the vulnerability of spinal motor neurons to ischemia. In this study, iloprost was used as an agent to decrease the severity of ischemia and reperfusion injury to the spinal cord motor neurons. Twenty-one rabbits were randomized into three groups of seven animals each: group A (iloprost not administered), group B (25 ng/kg per minute iloprost), and group S (sham-operated). The spinal cord ischemia model was created by a 15-min occlusion of the aorta just caudal to the renal artery with a balloon catheter. Administration of iloprost began 10 min before occlusion of the aorta, and continued thereafter for 60 min. The pre- and postocclusion arterial pressure and heart rate recordings, results of blood gas analyses, and hematocrit and glucose levels were recorded. The spinal cords were removed after 8-h monitoring of neurologic function. Viable and nonviable motor neurons in the anterior horn of the spinal cord were counted under light microscopy. Any significant alteration in hemodynamics, blood gases, and other physiologic parameters could not be detected within the groups. Iloprost had a moderately hypotensive effect. Neurologic function in terms of Johnson scoring was significantly better in the iloprost group (P<0.05). The number of viable cells was higher, whereas the number of nonviable cells was lower in iloprost group, when compared with the control group (P<0.05). Higher numbers of viable motor neurons were consistent with the neurological findings. As a result of this study we concluded that iloprost infused during clamping of the aorta mitigates the spinal cord injury due to ischemia and reperfusion, and has a significant protective effect.

Iloprost for idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension is a rare but serious and life-threatening disease that leads to right heart failure and death within 2.8 years without specific treatment. This review focuses on the stable prostacyclin analog iloprost, its biologic action and pharmacology and, finally, on its clinical development, efficacy and safety in patients with idiopathic pulmonary arterial hypertension, which led to its approval for this indication. Furthermore, this review assesses the role of iloprost compared with other newly developed drugs, such as the endothelin receptor antagonist bosentan and the phosphodiesterase-5 inhibitor sildenafil, as well as other modes of application of prostacyclin and its analogs for the treatment of idiopathic pulmonary arterial hypertension. Based on the different modes of action of these substances, a combination of these treatments could be most promising for the future.

Permissive contributions of NO and prostacyclin in CO-induced cerebrovascular dilation in piglets

Endogenously produced CO is an important dilator in newborn cerebrovascular circulation. CO dilates cerebral arterioles by activating Ca2+-activated K+ channels, but modulatory actions of other effectors and second messenger inputs are unclear. Specifically, the mechanisms behind the obligatory permissive roles of prostacyclin and NO are uncertain. Therefore, the present study was performed using acutely implanted, closed cranial windows in newborn pigs to address the hypothesis that the permissive roles of NO and prostacyclin in cerebrovascular dilation in response to CO involve a common mechanism. The NO donor sodium nitroprusside restored dilation in response to CO after inhibition of that dilation with the prostaglandin cyclooxygenase inhibitor indomethacin. The stable prostacyclin analog iloprost restored CO-induced dilation blocked by the NO synthase inhibitor Nomega-nitro-L-arginine. Restoration of dilation in response to CO by the cGMP-dependent phosphodiesterase inhibitor zaprinast and blockade of CO dilation by the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazole-[4,3-a]quinoxalin-1-one (ODQ) suggests involvement of the cGMP/PKG pathway. Iloprost or the cAMP-dependent dilator isoproterenol restored dilation in response to CO after ODQ administration. However, CO-induced dilation blocked by the cGMP-dependent PKG inhibitor Rp-8-[(4-chlorophenyl)thio]-cGMPS triethylamine could not be reversed by administration of sodium nitroprusside, iloprost, or isoproterenol. Conversely, PKA inhibition did not block dilation in response to CO. Overall, data indicate that activation of PKG is the predominant mechanism of the permissive actions of NO and prostacyclin for CO-induced pial arteriolar dilation.

Decrease in circulating endothelial cell adhesion molecule and thrombomodulin levels during oral iloprost treatment in rheumatoid arthritis patients: preliminary results

Rheumatoid arthritis is a chronic inflammatory autoimmune disease with proinflammatory cytokines involved in its pathogenesis. Recently in vitro as well as in vivo studies have shown that iloprost, a stable prostacyclin analogue, can reduce the release of these cytokines. This study was performed to further investigate the anti-inflammatory effects of iloprost by determining plasma adhesion molecules as markers of endothelial cell activation, and plasma thrombomodulin as a parameter of endothelial cell injury in patients with rheumatoid arthritis receiving oral iloprost therapy. Plasma thrombomodulin levels and the values of the plasma adhesion molecules VCAM-1 (vascular cell adhesion molecule 1), E-selectin (CD62E), and ICAM-1 (intercellular adhesion molecule 1, CD 54) were measured by ELISA during a 7-day period of treatment with orally-administered iloprost in 14 patients with active rheumatoid arthritis. Finally, the same parameters were determined at the end of the observation period (1 week after the end of therapy). In addition, the disease activity was measured using the DAS (disease activity score) as well as the patients' self-assessed pain severity, and correlated with the changes of plasma adhesion molecule and thrombomodulin levels. The plasma levels of all three adhesion molecules as well as of thrombomodulin significantly decreased under therapy with oral iloprost. After 1 week (day 7 of therapy), the mean percent changes from day 0 were -20.1% for VCAM-1 (p = 0.008), -21.2 for ICAM-1 (p = 0.003), -24.6% for E-selectin (p = 0.001), and -21.7% for thrombomodulin (p = 0.003). This decrease lasted up to 1 week after the end of therapy in the case of VCAM-1 (p = 0.023) and ICAM-1 (p = 0.001). Further analysis of the results revealed additional significant correlations between different parameters of clinical disease activity, thrombomodulin and adhesion molecules. This study showed hints towards clinical effects in patients with rheumatoid arthritis receiving oral iloprost therapy. Pathophysiologically, the decrease of adhesion molecules points at an immunomodulating effect of iloprost. The observed thrombomodulin-lowering effect of iloprost may indicate stabilisation of endothelial cell function by diminishing endothelial cell injury.

Up-regulation of the enzymes involved in prostacyclin synthesis via Ras induces vascular endothelial growth factor

The constitutive activation of Ras is an important step in the development and progression of several different cancers and is known to increase the level of cyclooxygenase 2 (COX-2). Prostaglandins are the downstream bioactive lipid mediators produced by the COX-2 enzyme. We sought to determine the role of Ras-induced up-regulation of the enzymes involved in prostacyclin biosynthesis in nontransformed rat intestinal epithelial cells (IECs). Messenger RNA (mRNA) and protein expression were analyzed by Northern and Western analysis, respectively, to determine the level of enzymes induced by Ras. In vitro assays were used to determine the production of vascular endothelial growth factor (VEGF) and prostaglandins as well as the promoter and enzymatic activation of the rate-limiting enzyme in prostaglandin production (phospholipase A(2) [cPLA(2)]). The inducible expression of Ha-Ras(V12) increased the production of prostaglandin (PG)F(2alpha) and prostacyclin by 2- and 13-fold, respectively. The induction of Ha-Ras(V12) also up-regulated the mRNA and protein levels of cPLA(2), COX-2, and prostacyclin synthase, as well as the promoter and enzyme activity of cPLA(2). Furthermore, oncogenic Ras increased the production of the pro-angiogenic factor VEGF. The increase of VEGF was abolished after treatment with celecoxib, a selective COX-2 inhibitor. The addition of PGI 2 alone also induced the expression of VEGF. Inducible Ha-Ras(V12) increases the production of PGI(2) through the coordinate up-regulation of cPLA(2), COX-2, and prostacyclin synthase (PGIS). The production of PGI(2) leads to an increase in the level of the pro-angiogenic factor VEGF, which is known to play a crucial role in the regulation of tumor-associated angiogenesis.

Salt-induced ANG II suppression impairs the response of cerebral artery smooth muscle cells to prostacyclin

Recent studies have demonstrated that cerebral arteries from rats fed a high-salt (HS) diet exhibit impaired vasodilation and altered electrophysiological response to reduction in PO2. The present study examined whether an increase in salt intake alters the response of vascular smooth muscle cells (VSMC) to prostacyclin, a crucial mediator of hypoxic dilation in cerebral arteries. VSMC were isolated from cerebral arteries of male Sprague-Dawley rats maintained on an HS (4% NaCl) or a low-salt diet (0.4% NaCl) for 3 days. The stable prostacyclin analog iloprost (10 ng/ml) inhibited serotonin (0.1-10 microM)-induced contractions and the increase in intracellular Ca2+ concentration ([Ca2+]i) in VSMC isolated from arteries of animals fed the low-salt diet. In contrast, iloprost had no effect on serotonin-induced contractions and increases in [Ca2+]i in VSMC isolated from arteries of rats fed the HS diet. Preventing the fall in ANG in rats fed the HS diet by infusion of a low dose of ANG II (5 ng.kg(-1).min(-1) i.v.) restored the inhibitory effect of iloprost on serotonin-induced contractions and increases in [Ca2+]i in VSMC from animals fed the HS diet. These effects were reversed by AT1 receptor blockade with losartan. These results indicate that ANG II suppression secondary to elevated dietary salt intake impairs vascular relaxation and Ca2+ regulation by prostacyclin.

Differential effects of vasodilatory prostaglandins on focal adhesions, cytoskeletal architecture, and migration in human aortic smooth muscle cells.

Cyclooxygenases 1 and 2 are expressed in atherosclerotic arteries, and local generation of prostacyclin and prostaglandin E2 (PGE2) occurs. However, the role of cyclooxygenases and individual prostaglandins during plaque progression is currently uncertain. The present study characterizes the effect of vasodilatory prostaglandins on morphology, focal adhesion (FA) function, and migration in human aortic smooth muscle cells (SMCs). The stable prostacyclin analog iloprost transiently induced: (1) disassembly of FA and stress fibers, (2) partial retraction and rounding of SMCs, (3) hypophosphorylation of FA kinase (FAK) and paxillin, and (4) inhibition of platelet-derived growth factor-BB-induced migration. Inhibition of FAK phosphorylation and morphological changes were mimicked by forskolin, inhibited by H89, and prevented by the protein tyrosine phosphatase inhibitor vanadate and by calpeptin. PGE2 was by far less efficient with respect to all parameters investigated. This difference correlated with the respective cAMP induction in response to iloprost and PGE2. Inhibition of FAK phosphorylation and FA function is a new target of vasodilatory prostaglandins, which might be causally involved in the antimigratory effects of prostaglandins. Importantly, prostacyclin analogs and PGE2 differ dramatically with respect to dephosphorylation of FAK and inhibition of migration, which might be of relevance for their respective functions in atherosclerosis.

Treprostinil, a Prostacyclin Analogue, in Pulmonary Arterial Hypertension Associated With Connective Tissue Disease

To assess the efficacy and safety of continuous subcutaneous infusion of treprostinil, a stable prostacyclin analogue, for treating pulmonary arterial hypertension (PAH) in patients with connective tissue disease (CTD). Two multicenter, randomized, double-blind, placebo-controlled, prospective trials of treprostinil vs placebo in 470 patients with PAH. A subset of 90 patients with PAH and CTD, including systemic lupus erythematosus, diffuse scleroderma, limited scleroderma, and mixed CTD/overlap syndrome. Patients received either treprostinil (initiated at 1.25 ng/kg/min, and titrated upward) or placebo via continuous subcutaneous infusion. The maximum dose of treprostinil allowed was 22.5 ng/kg/min. Six-minute walk (6MW) distance and dyspnea-fatigue scores were determined at baseline, and at 6 weeks and 12 weeks. Hemodynamic measures were obtained at baseline and at 12 weeks. At baseline, most patients had New York Heart Association class III symptoms. The mean baseline 6MW distance was 289 m (range, 60 to 448 m). The mean dose of treprostinil at week 12 was 8.4 ng/kg/min (range, 1.25 to 17.5 ng/kg/min). After 12 weeks, the change in cardiac index from baseline was + 0.2 +/- 0.08 L/min/m(2) in the treprostinil group and - 0.07 +/- 0.07 L/min/m(2) in the placebo group (p = 0.007). The pulmonary vascular resistance index decreased by 4 +/- 2 U x m(2) in the treprostinil group and increased by 1 +/- 1 U x m(2) in the placebo group (p = 0.006). The placebo-corrected median improvement from baseline in 6MW distance was 25 m in treprostinil-treated patients (p = 0.055); this improvement appeared to be dose related. Dyspnea fatigue scores also improved in the treprostinil group compared with the placebo group (p = 0.014). Adverse events included infusion site pain and typical side effects related to prostaglandins, and were tolerated by most patients. Continuous subcutaneous infusion of treprostinil in patients with PAH associated with CTD improved exercise capacity, symptoms of PAH, and hemodynamics.

A stable prostacyclin analogue reduces high serum TNF-alpha levels in diabetic patients.

To confirm whether a prostacyclin (prostaglandin I (2)) affects the increased TNF-alpha concentration in sera of diabetic patients, we measured serum TNF-alpha concentration and treated these patients with oral administration of the stable prostacyclin analogue (Beraprost). Twelve of 20 type II diabetic patients were investigated for follow up-study and 6 of those patients were for therapy with Beraprost for diabetic neuropathy. Serum TNF-alpha concentration was quantified by EASIA using monoclonal antibodies directed against distinct epitopes of TNF-alpha. In diabetic patients, serum TNF-alpha concentration was significantly increased compared with that of healthy subjects. The augmented TNF-alpha concentration in these patients was not decreased by diabetic control using antihyperglycemic agents for 8 weeks but was reduced with oral administration of a stable prostacyclin (prostaglandin I (2)) analogue for 5 weeks without any changes of blood glucose levels. Stable prostacyclin analogue administration for a short term period reduced increased TNF-alpha levels in diabetic patients, not through the improved hyperglycemic condition but another pathway, probably a cAMP system. These results imply that treatment with the prostacyclin analogue may contribute to the prevention of progression in diabetic complications.

Prostacyclin enhances the implantation and live birth potentials of mouse embryos.

Recently we reported that iloprost, a stable analogue of prostacyclin, enhanced mouse embryo hatching. Here we present a follow-up study to determine whether exposure to iloprost augments the implantation and live birth potentials of mouse embryos. Two-cell embryos (C3B6F1) were harvested 42 h after HCG injection and cultured in medium supplemented with iloprost. After 48 h, the embryos were transferred to 2.5 day pseudopregnant gestational carriers. The number of gestation sacs was counted 72 h later; the number of live pups and the weight of pups and placentae were determined 14 days later. The implantation rate was defined as gestation sac per embryo transferred; the live birth rate was defined as live pup per embryo transferred. The prostacyclin analogue enhanced the implantation rate from 42 to 76% [relative risk 1.84, 95% confidence interval (CI) 1.38-2.43]. The rate of live pups also increased from 28 to 36% (relative risk 1.28, 95% CI 1.04-1.56). The weights of the pups and of the placentae of the two groups were comparable. Prostacyclin enhances the potentials of implantation and live birth of mouse embryos.

Effect of Iloprost ® on endothelin-1-induced free radical activation in rabbit brain stem

Iloprost, a stable analogue of prostacyclin, was used to reverse the early period of vasoconstriction provoked by Endothelin-1 by administering into the rabbit basilar artery. We observed if this produced an effect on the central nervous system parenchyma mediated by free radical system. The red neurons were counted in brain stem sections stained with haematoxylin and eosin, while superoxide dismutase and malondialdehyde levels were measured in brain stem tissue samples as a marker of reactive oxygen metabolites; both 30 and 90 min after administration of either Endothelin-1 (0.25 ng) alone or Endothelin-1 followed by Iloprost (0.5 μg/kg) into the basilar artery. Endothelin-1 significantly increased the number of red neurons, while Iloprost significantly reduced them after 30 and 90 min. However, regarding the reactive oxygen metabolites; a similar reversing effect of Iloprost was not observed although superoxide dismutase levels were significantly decreased after Endothelin-1 infusion.

Prostacyclin analogue (beraprost) relief of cold intolerance after digital replantation and revascularization

Cold intolerance frequently occurs after successful digital revascularization and replantation. A series of 11 patients with cold intolerance 6 to 24 months after digital revascularization/replantation were treated daily for 2 weeks with beraprost, a stable prostacyclin analogue. That pain was reduced in 9 of 11 cases after treatment and digital thermography showed significantly increased surface temperature after the 2-week course of beraprost. These findings support the use of beraprost to relieve symptoms of cold intolerance under these clinical conditions. Journal of Hand Surgery (British and European Volume, 2004).

The regulation of interleukin-6 secretion by prostanoids and members of the tumor necrosis factor superfamily in fresh villous fragments of term human placenta.

To determine whether prostanoids, nonsteroidal anti-inflammatory drugs (NSAIDs), and members of the tumor necrosis factor superfamily can regulate placental secretion of interleukin-6 (IL-6) and whether labor influences any such effects. Villous fragments of term, human placenta were kept in culture for up to 4 hours, and IL-6 concentrations were measured in the supernatant. We assessed the effects of the following prostanoids: PGE(2), PGF(2alpha), thromboxane A(2) mimetic (U-46619), and carbacyclin, a stable prostacyclin analogue (all at 1 microM); NSAIDs: indomethacin (150 microM) or nimesulide (100 microM); and Fas ligand (5 ng/mL). Secretion (mean +/- standard error) of IL-6 was, for control conditions, 1.92 +/- 0.28 fmol/mg wet weight per 3 hours; for PGE(2), 3.57 +/- 0.29 fmol/mg wet weight per 3 hours, P <.01; and for carbacyclin, 3.11 +/- 0.44 fmol/mg wet weight per 3 hours, P <.01. Incubation with PGF(2alpha) or the thromboxane A(2) analogue, U46619, had no effect on IL-6 secretion under these conditions. Fas ligand stimulated IL-6 secretion (3.06 +/- 0.38 fmol/mg wet weight per 3 hours, P <.05). Labor did not alter the effects of prostanoids or FasL. The effects of NSAIDs were assessed over 4 hours. Secretion (median, interquartile range) was, under control conditions 3.26, 2.83-6.23 fmol/mg wet weight per 4 hours, with indomethacin 1.4, 1.28-3.21 (P <.05), and with nimesulide 0.75, 0.50-1.56 fmol/mg wet weight per 4 hours. The magnitude of the effect of Fas ligand in the presence of NSAIDs depended on whether the placentas were delivered before or after labor. Prostanoids, NSAIDs, and the Fas ligand regulate placental IL-6 secretion. Although the effects of individual agents did not vary with the presence or absence of labor, modulation of IL-6 secretion by labor became apparent when agents were combined.

Overview of treprostinil sodium for the treatment of pulmonary arterial hypertension.

Pulmonary arterial hypertension is a life-threatening disorder that refers to a group of diseases characterized by an abnormal elevation of the blood pressure within the pulmonary circulation due to a vasculopathy of the pulmonary microcirculation (1). If left untreated, the overall prognosis of pulmonary arterial hypertension is poor, with a 5-year survival rate of 34%. The most common cause of death is progressive right-sided heart failure (2). There is no pharmacologic cure for pulmonary arterial hypertension, and a team approach is required for the proper care of these patients (3). Treatment is directed at improving clinical symptoms, increasing exercise tolerance and extending survival. Until just a few years ago, standard treatment options for the treatment of pulmonary arterial hypertension were limited and included coumarin derivatives, calcium channel blockers, diuretics, digoxin and oxygen supplementation (4). In the last decade, the therapeutic options for pulmonary arterial hypertension have made considerable advances. In at least three major randomized controlled trials, the continuous intravenous infusion of epoprostenol, a synthetic salt of prostacyclin with potent vasodilatory ability, has been shown to improve exercise tolerance, hemodynamics, survival and quality of life in patients with New York Heart Association (NYHA) functional classes III and IV with either primary pulmonary hypertension or pulmonary arterial hypertension associated with scleroderma (5-9). Epoprostenol has now become a mainstay therapy in the long-term treatment of primary pulmonary hypertension or pulmonary arterial hypertension associated with scleroderma. Nevertheless, epoprostenol is far from an ideal form of therapy. Issues such as the short half-life of the drug, need for continuous central intravenous access and significant side effects have led to the development of more stable prostacyclin analogues as alternative therapies for primary pulmonary hypertension. These alternative therapies include iloprost (inhaled delivery) and treprostinil (subcutaneous delivery). As a result, the Food and Drug Administration (FDA) recently approved treprostinil for the treatment of pulmonary arterial hypertension in patients with NYHA classes II-IV. This review will offer a discussion of the basic pharmacology of treprostinil, its similarities to and differences from epoprostenol, the animal studies as well as the initial investigational studies leading to its FDA approval, and clinical uses of the drug alone or in combination with newer therapies directed at pulmonary arterial hypertension developed over the last decade.

Beneficial effect of iloprost on the course of acute taurocholate pancreatitis in rats and its limitation by antecedent acute ethanol intake

The effects of stable prostacyclin analogue iloprost on the trypsinogen activation, labilization of lysosomal membranes, lipolytic enzymes activities, histopathological and ultrastructural changes in the pancreas of rats with severe, taurocholate acute pancreatitis (AP), preceded for 6 h by acute ethanol intake have been investigated. Iloprost (1 microg/kg b.w., i.p.) was applied every 6 hours after inducing of taurocholate AP. The antecedent intragastric 40% ethanol intake (5 g/kg b.w.) increased an index of trypsinogen activation in AP lasting 18 h. Treatment with iloprost prevented this increase in the rats with AP given earlier alcohol, and limited the labilization of lysosomal membranes in nonalcoholized rats with AP. Phospholipase A2 and lipase activities were reduced by iloprost only in the rats not given ethanol. The additional damaging effect of acute ethanol abuse prior to AP could be dependent on augmented activation of trypsinogen. The protective effect of iloprost in AP seems to be dependent on the attenuation of trypsinogen activation, decrease of total potential trypsin and the decrease of lysosomal membranes labilization. Its protective effect could be limited in taurocholate acute pancreatitis preceded by acute ethanol intake as evidenced by the differences in the cathepsin B, phospholipase A2 and lipase activities and by histopathological and ultrastructural examination.

Comparative analysis of the in vivo angiogenic properties of stable prostacyclin analogs: a possible role for peroxisome proliferator-activated receptors

Objective. – Until recently, prostacyclin (PGI 2) biological activities were thought to be exclusively mediated by cell surface receptors named IP. Recent studies have instead identified a novel pathway of PGI 2 signaling, occurring through activation of peroxisome proliferator-activated receptors (PPARs) located in the nucleus. The availability of stable PGI 2 analogs with different affinity for IP receptors and PPARs provides the possibility to test the importance and function of this dual pathway in vitro and in vivo. In this study, the in vivo angiogenic properties of different PGI 2 analogs and the potential relationship between PPAR-mediated pathways, vascular endothelial growth factor (VEGF), and angiogenesis were investigated. Methods and results. – By using the murine corneal model of angiogenesis, we found that PGI 2 analogs able to act on nuclear PPARs, such as iloprost and carbaprostacyclin (cPGI), induce angiogenesis in vivo. In contrast, cicaprost, a PGI 2 analog that only acts on IP receptors, has no in vivo angiogenic activity. Interestingly, angiogenesis induced by iloprost and cPGI does not differ in extent and morphology from that induced by VEGF and is associated with local increment of VEGF mRNA expression and protein levels. Finally, iloprost-induced angiogenesis is significantly decreased by systemic inhibition of VEGF activity, obtained by gene transfer of a soluble form of the VEGF receptor Flt-1. Conclusions. – These data demonstrate that stable PGI 2 analogs may have angiogenic properties in vivo, depending on their ability to act on PPARs. The resulting angiogenic process appears to be mediated by VEGF. These findings indicate that important physiological activities in the cardiovascular system, such as angiogenesis and VEGF induction, may be modulated by PGI 2 through specific activation of the PPAR signaling pathway in vivo, with potentially important fundamental and clinical implications.

Inhibition of intracellular tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 production in human monocytes by iloprost.

To investigate the effects of iloprost as a stable prostacyclin analogue on intracellular expression of IL-6 and TNF-alpha of lipopolysaccharide (LPS)-stimulated human monocytes in a whole blood system assessed by flow cytometry. Whole blood of six healthy volunteers processed immediately after withdrawal and twice on different days (six measurements per experiment) was stimulated in two different settings with LPS (final concentrations 0.2 ng mL(-1) and 10 ng mL(-1)) and incubated with iloprost (final concentrations in each experiment were 0.01 nm, 0.1 nm, 0.3 nm, 1 nm, 3 nm, 10 nm, 30 nm and 100 nm) for 3 h at 37 degrees C and 5% CO2. Intracellular expression of IL-6 and TNF-alpha was assessed by flow cytometry. Our investigations showed, for the first time, that iloprost (0.1 nm up to 100 nm) caused a dose-dependent inhibitory effect of IL-6 production in human monocytes stimulated with LPS (10 ng mL(-1)), which was even more obvious in monocytes stimulated with lower concentrated LPS (0.2 ng mL(-1)). Iloprost (0.1 nm up to 100 nm) was found to inhibit TNF-alpha production of LPS-stimulated monocytes in a dose-dependent fashion not influenced by LPS concentration. Apart from the vasodilatory and antithrombotic effects, iloprost may also down-regulate the intracellular expression of IL-6 and TNF-alpha in human monocytes.

Pharmacodynamics and Pharmacokinetics of Inhaled Iloprost, Aerosolized by Three Different Devices, in Severe Pulmonary Hypertension

Inhalation of iloprost, a stable prostacyclin analog, is an effective therapy for pulmonary hypertension with few side effects. This approach may, however, be handicapped by limitations of currently available nebulization devices. We assessed whether the physical characterization of a device is sufficient to predict drug deposition and pharmacologic effects. We investigated the effects of a standardized iloprost aerosol dose (5 micro g; inhaled within approximately 10 min) in 12 patients with severe pulmonary hypertension in a crossover design employing three well-characterized nebulizers. The nebulizers use different techniques to increase efficiency and alveolar targeting (Ilo-Neb/Aerotrap [Nebu-Tec; Elsenfeld, Germany], Ventstream [MedicAid; Bognor Regis, UK], and HaloLite [Profile Therapeutics; Bognor Regis, UK]). Measurements were performed using a Swan-Ganz catheter and determination of arterial iloprost plasma levels. During inhalation of iloprost, the pulmonary vascular resistance decreased substantially (baseline, approximately 1,250 dyne.s.cm(-5); decrease, - 35.5 to - 38.0%) and pulmonary artery pressure decreased substantially (baseline, approximately 58 mm Hg; decline, - 18.4 to -21.8%), whereas the systemic arterial pressure was largely unaffected. Cardiac output and mixed venous and arterial oxygen saturation displayed a marked increase. The pharmacodynamic profiles with the three devices were superimposable. Moreover, rapid entry of iloprost into the systemic circulation was noted, peaking immediately after termination of the inhalation maneuver, with very similar maximum serum concentrations (158 pg/mL, 155 pg/mL, and 157 pg/mL), and half-lives of serum levels (6.5 min, 9.4 min, and 7.7 min) for the three nebulizers, respectively. Interestingly, the "half-life" of the pharmacodynamic effects in the pulmonary vasculature (eg, decrease in pulmonary vascular resistance, ranging between 21 and 25 min) clearly outlasted this serum level-based pharmacokinetic half-life. A standardized dose of aerosolized iloprost delivered by different nebulizer types induces comparable pharmacodynamic and pharmacokinetic responses. Pulmonary vasodilation, persisting after disappearance of the drug from the systemic circulation, supports the hypothesis that local drug deposition largely contributes to the preferential pulmonary vasodilation in response to inhaled iloprost.

Inhaled iloprost in patients with chronic thromboembolic pulmonary hypertension: effects before and after pulmonary thromboendarterectomy

Background In primary pulmonary hypertension, aerosolized prostanoids selectively reduce pulmonary vascular resistance and improve right ventricular function. In this study, hemodynamic effects of inhaled iloprost, a stable prostacyclin analogue, were evaluated in patients with chronic thromboembolic pulmonary hypertension (CTEPH) before and early after pulmonary thromboendarterctomy (PTE). Methods Ten patients (mean age 49 years old [32 to 70 years old], New York Heart Association functional class III and IV) received a dose of 33 μg aerosolized iloprost immediately before surgery (T1), after intensive care unit admission (T2), and 12-hours postoperatively (T3). Effects on pulmonary and systemic hemodynamics and gas exchange were recorded and compared with preinhalation baseline values. Results Preoperatively, inhaled iloprost did not significantly change mean pulmonary artery pressure (mPAP), cardiac index (CI), or pulmonary vascular resistance (PVR). Postoperatively, inhaled iloprost induced a significant reduction of mPAP and PVR and a significant increase of CI at T2 and T3. Preinhalation versus postinhalation PVR was as follows: at T1, 847 versus 729 dynes · s · cm −5, p = 0.45; at T2, 502 versus 316 dynes · s · cm −5, p = 0.008; and at T3, 299 versus 227 dynes · s · cm −5, p = 0.004. Conclusions In patients with CTEPH, inhalation of iloprost elicits no significant pulmonary vasodilation before surgery, and may have detrimental effects on systemic hemodynamics. Postoperatively, it significantly reduces mPAP and PVR, and enhances CI. Following PTE, inhalation of iloprost is useful to improve early postoperative hemodynamics.