Differential Effects of Vasodilatory Prostaglandins on Focal Adhesions, Cytoskeletal Architecture, and Migration in Human Aortic Smooth Muscle Cells

OBJECTIVE

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).

METHODS AND RESULTS

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.

CONCLUSIONS

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.

Cardiopulmonary effects of iloprost in experimental acute lung injury

Iloprost, a prostacyclin analogue with a prolonged plasma half-life has beneficial effects in chronic pulmonary hypertension, whereas the effects in acute lung injury (ALI) are unknown. The present study was performed to evaluate the cardiopulmonary effects of iloprost in experimental ALI. ALI was induced in 18 pigs by repeated lung lavage. Animals were randomised to controls, i.v. or inhaled iloprost for 15 min. Haemodynamics, gas exchange and ventilation-perfusion distribution were measured at the end of iloprost application and after 1 and 2 h. As a short-term effect, both i.v. and inhaled iloprost significantly decreased pulmonary artery pressure without major effects on gas exchange or systemic haemodynamics. After 1 and 2 h, a reduction of pulmonary hypertension was no longer present. As a long-term effect, inhaled, but not i.v., iloprost decreased pulmonary shunt and significantly improved gas exchange after 1 and 2 h. In conclusion, the single application of iloprost revealed short-term pulmonary vasodilation without other major cardiopulmonary effects. However, inhaled iloprost improved gas exchange due to a decrease of pulmonary shunt as a long-term effect, possibly as a result of a reduction of lung oedema formation.

Collagen-induced platelet shape change is not affected by positive feedback pathway inhibitors and cAMP-elevating agents

Shape change is the earliest response of platelets to stimuli; it is mainly dependent upon Ca(2+)/calmodulin interaction subsequent to Ca(2+) mobilization and is mediated by myosin light chain kinase (MLCK) activation. It has been recently suggested that collagen itself is not able to elicit platelet shape change in the absence of ADP and thromboxane A(2) costimulation but is capable of inducing MLCK activation. Since we hypothesize that the morphological changes of the few platelets that adhere to collagen might not be revealed by turbidimetry, the aim of this study was to assess platelet shape change using transmission electron microscopy, in the absence of the amplificatory feedback pathways of ADP and thromboxane A(2). Our results demonstrated that only the platelets in contact with insoluble collagen fibers underwent a typical shape change, whereas those further away remained quiescent. Moreover, since cAMP enhances Ca(2+) mobilization in response to collagen, in the present study, we also investigated whether cAMP is involved in the inhibition of collagen-induced platelet shape change and MLC phosphorylation. Platelets were thus treated with iloprost (28 nm) prior to stimulation. Electron microscopy studies demonstrated that iloprost did not modify collagen-induced shape change, whereas immunoblotting studies showed a slight inhibition of MLC phosphorylation in the presence of enhanced cAMP levels. We can thus conclude that collagen is able to cause platelet shape change through activation of Ca(2+)/calmodulin-dependent MLCK, without the involvement of amplificatory pathways. Enhanced cytosolic cAMP levels do not inhibit collagen-induced platelet shape change but exert a weak inhibitory action on MLCK.

Regulation of thrombomodulin expression in human vascular smooth muscle cells by COX-2-derived prostaglandins

There is concern that cyclooxygenase (COX)-2 inhibitors may promote atherothrombosis by inhibiting vascular formation of prostacyclin (PGI2) and an increased thrombotic risk of COX-2 inhibitors has been reported. It is widely accepted that the prothrombotic effects of COX-2 inhibitors can be explained by the removal of platelet-inhibitory PGI2. Using microarray chip technology, we have previously demonstrated that thrombomodulin (TM) mRNA is upregulated in cultured human coronary artery smooth muscle cells by the stable prostacyclin mimetic iloprost. This study is the first to demonstrate a stimulation of the expression of functionally active thrombomodulin in human smooth muscle cells by prostaglandins, endogenously formed via the COX-2 pathway. Because TM is an important inhibitor of blood coagulation, these findings provide a novel platelet-independent mechanism to explain the prothrombotic effects of COX-2 inhibitors. The full text of this article is available online at http://circres.ahajournals.org.

Neutrophil elastase contributes to the development of ischemia-reperfusion-induced liver injury by decreasing endothelial production of prostacyclin in rats

We previously reported that nitric oxide (NO) derived from endothelial NO synthase (NOS) increased endothelial prostacyclin (PGI(2)) production in rats subjected to hepatic ischemia-reperfusion (I/R). The present study was undertaken to determine whether neutrophil elastase (NE) decreases endothelial production of PGI(2), thereby contributing to the development of I/R-induced liver injury by decreasing hepatic tissue blood flow in rats. Hepatic tissue levels of 6-keto-PGF(1alpha), a stable metabolite of PGI(2), were transiently increased and peaked at 1 h after reperfusion, followed by a gradual decrease until 3 h after reperfusion. Sivelestat sodium hydrochloride and L-658,758, two NE inhibitors, reduced I/R-induced liver injury. These substances inhibited the decreases in hepatic tissue levels of 6-keto-PGF(1alpha) at 2 and 3 h after reperfusion but did not affect the levels at 1 h after reperfusion. These NE inhibitors significantly increased hepatic tissue blood flow from 1 to 3 h after reperfusion. Both hepatic I/R-induced increases in the accumulation of neutrophils and the microvascular permeability were inhibited by these two NE inhibitors. Protective effects induced by the two NE inhibitors were completely reversed by pretreatment with nitro-l-arginine methyl ester, an inhibitor of NOS, or indomethacin. Administration of iloprost, a stable derivative of PGI(2), produced effects similar to those induced by NE inhibitors. These observations strongly suggest that NE might play a critical role in the development of I/R-induced liver injury by decreasing endothelial production of NO and PGI(2), leading to a decrease in hepatic tissue blood flow resulting from inhibition of vasodilation and induction of activated neutrophil-induced microvascular injury.

Excitatory action of prostanoids on the ferret isolated vagus nerve preparation

We have investigated the actions of various prostanoid receptor agonists on an isolated preparation of the ferret cervical vagus using a grease-gap extracellular recording technique. The potency ranking for depolarization was BW245C (5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl) hydantoin; DP-selective, EC50=0.14 microM)>prostaglandin E2 (nonselective EP agonist)>U-46619 (11alpha, 9alpha-epoxymethano-15S-hydroxyprosta-5Z,13E-dienoic acid; TP agonist)>prostaglandin F2alpha (FP receptor agonist). Sulprostone (EP1/EP3-selective), fluprostenol (FP-selective) and cicaprost and iloprost (both IP-selective) had minimal effects. It is likely that DP, EP2/EP4 and TP receptors are present on the vagal fibres of the ferret.

Pharmacological management of aseptic osteonecrosis in children

Aseptic osteonecrosis (AON) in children can progress during ossification of cartilage in periods of increased growth or excessive physical stain and may occur in various locations in the skeleton. Disturbance of blood supply to the bone has been suggested as the main pathological mechanism involved in AON, which is characterised by the death of bone marrow and trabecular bone. The extent and development of osteonecrosis and the duration of disease until restorative healing, depend on the formation of new blood vessels, the spreading of vessels in the affected bony areas, the absorption of osteonecrotic tissue and the structure of new bone. Conservative and operative treatment options for AON vary according to the location and development of the disease and the age of the patient. The goal of all treatment options currently used today is to achieve relief of physical load in the affected bone and to promote and regulate blood supply. Treatment should be started early in order to minimise the extent of osteonecrosis and allow restorative healing. As the processes of myelopoiesis, myelophthisis and fracture healing become more clear, interest has focused on advances in the utilisation of bioactive factors to salvage bone in children affected by AON. Such methods include the use of osteoinductive agents, such as cytokines and bone morphogenetic proteins, as well as factors that stimulate angiogenesis and regulate blood supply. Currently, the prostacyclin analogue, iloprost (Ilomedin, Schering AG), has been successfully used in a pilot study in children suffering from early stages of AON.

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

OBJECTIVE

Until recently, prostacyclin (PGI2) biological activities were thought to be exclusively mediated by cell surface receptors named IP. Recent studies have instead identified a novel pathway of PGI2 signaling, occurring through activation of peroxisome proliferator-activated receptors (PPARs) located in the nucleus. The availability of stable PGI2 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 PGI2 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 PGI2 analogs able to act on nuclear PPARs, such as iloprost and carbaprostacyclin (cPGI), induce angiogenesis in vivo. In contrast, cicaprost, a PGI2 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 PGI2 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 PGI2 through specific activation of the PPAR signaling pathway in vivo, with potentially important fundamental and clinical implications.

Cyclooxygenase-2-derived endogenous prostacyclin enhances mouse embryo hatching

INTRODUCTION

The role of prostaglandins (PGs) in embryo hatching remains controversial. In addition, there is no direct evidence that mouse embryos synthesize PGs.

METHODS

The effects of endogenous PG on mouse embryo hatching were evaluated by blocking endogenous PG synthesis with indomethacin. Specific cyclooxygenase (COX) inhibitors were used to identify the role of COX-1- and COX-2-derived PGs. An eicosanoid profile was generated by incubating blastocysts with [3H]arachidonic acid and analysing the metabolites by high performance liquid chromatography. The expression and the localization of COX-1, COX-2 and prostacyclin synthase (PGIS) were examined by western blot analysis and immunohistochemistry.

RESULTS

The hatching of embryos cultured in 30 microl of protein-free medium was blocked by indomethacin (P = 0.007) or a selective COX-2 inhibitor (P = 0.004). Adding back iloprost, a prostacyclin analogue, abolished the effects of the COX-2 inhibitor. Prostacyclin was the most abundant PG produced by mouse blastocysts, which expressed COX-1, COX-2 and PGIS. COX-1, COX-2 and PGIS were expressed in 4-cell stage embryos and beyond; they were present in the inner cell mass and the trophectoderm of the blastocysts.

CONCLUSION

Mouse embryos express COX-1, COX-2 and PGIS which catalyse the formation of PGI2; COX-2-derived PGI2 plays a critical role in embryo hatching.

Selective inhibition of cyclooxygenase-2 enhances platelet adhesion in hamster arterioles in vivo

BACKGROUND

Selective inhibitors of cyclooxygenase-2 (Cox-2) are reported to cause cardiovascular side effects in patients at risk. However, direct proof of prothrombotic effects of these drugs is lacking. We investigated in the microcirculation in vivo whether selective inhibition of Cox-2 induces platelet activation.

METHODS AND RESULTS

The behavior of fluorescence-labeled human platelets was studied in hamster arterioles (dorsal skinfold chamber) by intravital microscopy. Transient platelet-vessel wall interactions (PVWIs), firm platelet adhesion to the vessel wall, and vessel occlusion after FeCl3-induced wall injury were analyzed as platelet activation parameters. In vitro experiments in human umbilical vein endothelial cells (HUVECs) were performed to assess specific effects of Cox-2 inhibition on platelet adhesion under shear stress (16 dyn/cm2) and on endothelial release of 6-ketoprostaglandin (PG) F(1alpha). Selective inhibition of Cox-2 (NS-398, 0.5 mg/kg) increased platelet adhesion to the vessel wall in vivo (11.9+/-3.9 platelets/mm2; controls, 1.4+/-1.4 platelets/mm2, P<0.05) and platelet adhesion after ADP stimulation in vitro. PVWIs were significantly enhanced in NS-398-treated animals, which were reduced by platelet pretreatment with aspirin (5 mg/kg) or iloprost (1 nmol/L). Inhibition of Cox-2 reduced levels of 6-keto-PGF1alpha in vivo and in HUVEC supernatants. Time to occlusion after vessel wall injury was significantly shortened by NS-398 (125.4+/-13.6 seconds in NS-398-treated animals versus 270.8+/-46 seconds in controls; P<0.01).

CONCLUSIONS

Selective inhibition of Cox-2 reduces 6-keto-PGF(1alpha) endothelial release, increases PVWIs, and increases firm platelet adhesion in hamster arterioles. Moreover, it leads to faster occlusion of damaged microvessels. Thus, selective inhibition of Cox-2 may trigger thrombotic events by diminishing the antiplatelet properties of the endothelium.

Effects of PGI2 and TxA2 analogs and inhibitors in orthodontic tooth movement

This study evaluates the effects of prostacyclin (PGI2) and thromboxane A2 (TxA2) in orthodontic tooth movement and osteoclastic activity in rats. The study sample consisted of 150 male Sprague-Dawley rats. The rats were randomly divided into five equal groups, and each group was again equally divided into three subgroups (SGs). Twenty grams of reciprocal force was applied to maxillary incisors of the rats with a spring bent from 0.35 mm stainless steel wire, except for the rats in the last SG. Iloprost (PGI2 analog), indomethacin (PGI2 inhibitor), U 46619 (TxA2 analog), and imidazole (TxA2 inhibitor) were dissolved in 0.9% NaCl (saline solution), and each material was prepared in three different concentrations (10(-4), 10(-5), and 10(-6) M/L). Iloprost was administered (20 microL/12 hours) in the first three SGs with the sequence of 10(-4), 10(-5), and 10(-6) M/L. Indomethacin, U 46619, and imidazole were administered in the next nine SGs with the same sequence and dose. In SG 13, 0.9% NaCl solution was administered (20 microL/ 12 hours) to the rats together with orthodontic force. Only orthodontic force was not used in SG 14, and neither any solution nor orthodontic force was used in the last SG. The rats were sacrificed on the fifth day of the experiment, premaxillae were dissected, and cross samples were taken. The results showed that PGI2 and TxA2 analogs increased the number of multinuclear osteoclasts, osteoclastic bone resorption, and rate of orthodontic tooth movement.

Investigation of the effect of the farnesyl protein transferase inhibitor R115777 on isoprenylation and intracellular signalling by the prostacyclin receptor

The human (h) and mouse (m) prostacyclin receptors (IPs) undergo isoprenylation through attachment of a C-15 farnesyl moiety within their conserved carboxyl terminal -CSLC sequences. Herein, the effects of a novel farnesyl transferase inhibitor R115777 on signalling by the hIP and mIP, overexpressed in human embryonic kidney 293 cells, and by the hIP endogenously expressed in human erythroleukaemia cells were investigated. R115777 significantly impaired IP-mediated cyclic AMP generation (IC(50) 0.37-0.60 nm) and intracellular calcium ([Ca(2+)](i)) mobilization (IC(50) 37-65 nm), but had no effect on signalling by the control nonisoprenylated beta(2) adrenergic receptor or the alpha or beta isoforms of the human thromboxane A(2) receptor (TP). Additionally, R115777 significantly reduced IP-mediated cross-desensitization of signalling by the TP alpha, but not by the TP beta, isoform of the human TP and impaired the farnesylation-dependent processing of the chaperone HDJ-2 protein (IC(50) 4.5 nm). Furthermore, R115777 fully impaired isoprenylation of both the Ha-Ras(WT) and Ha-Ras(CSLC) in vitro and in whole cells confirming that, unlike N-Ras and Ki-Ras, the -CSLC motif associated with the IP cannot support alternative geranylgeranylation in the presence of R115777 and does not act as a substrate for geranylgeranyl transferase 1 in vitro or in whole cells. In conclusion, these data confirm that R115777 potently impairs IP isoprenylation and signalling, and suggest that clinically it may not only target Ras proteins but may also disrupt IP isoprenylation, events which could impact on physiologic processes in which prostacyclin and its receptor are implicated.

Effect of the statin atorvastatin on intracellular signalling by the prostacyclin receptor in vitro and in vivo

Prostacyclin plays a central role within the vasculature. We have previously established that the prostacyclin receptor (IP) undergoes isoprenylation, a lipid modification obligate for its function. The aim of the current study was to investigate the effect of the hydroxy methyl glutaryl co-enzyme A reductase inhibitor atorvastatin on signalling and function of the IP expressed in mammalian whole cells and in platelets isolated from patients undergoing therapeutic intervention with atorvastatin. Initially, the effect of atorvastatin on signalling by the human (h) and mouse (m) IP overexpressed in human embryonic kidney 293 cells and the hIP endogenously expressed in human erythroleukaemic 92.1.7 cells was investigated. Atorvastatin significantly reduced IP-mediated cAMP generation (IC(50) 6.6-11.1 microm) and [Ca(2+)](i) mobilization (IC(50) 7.2-16.4 microm) in a concentration-dependent manner, but had no effect on signalling by the nonisoprenylated beta(2) adrenergic receptor or the alpha or beta isoforms of the human thromboxane A(2) receptor (TP). Moreover, atorvastatin significantly reduced IP-mediated crossdesensitization of signalling by TP alpha (IC(50) 10.4 microm), but not by TP beta. In contrast to the whole-cell data, atorvastatin therapy did not interfere with IP-mediated cAMP generation or IP-induced inhibition of TP-mediated aggregation of platelets isolated from human volunteers undergoing therapeutic intervention with atorvastatin (10-80 mg per daily dose). In conclusion, while data generated in whole cells indicated that atorvastatin significantly impairs signalling by both the hIP and mP, the in vivo clinical data indicated that, at the administered therapeutic dose, atorvastatin does not significantly compromise IP signalling and function in humans.

Inhaled iloprost: in primary pulmonary hypertension

Iloprost is a stable prostacyclin analogue with a pharmacokinetic profile allowing nebulised administration in patients with primary pulmonary hypertension (PPH). Inhaled iloprost is a potent acute pulmonary vasodilator with a duration of action of about 60 minutes. It may exert additional long-term benefit through antiproliferative and antithrombotic effects. Inhaled iloprost 2.5 or 5 microg six or nine times daily for 12 weeks (n = 101) significantly (p < 0.01) improved a combined clinical endpoint of a > or =10% increase in distance walked in 6 minutes and an improvement of > or =1 class in New York Heart Association functional class without clinical deterioration or death (16.8 versus 4.9% of placebo recipients, n = 102) in patients with severe PPH or selected forms of nonprimary pulmonary hypertension. Statistical analysis of the response for the PPH subgroup (20.8 versus 5.5% with placebo; n = 51 and 51) was not reported. Improvements from baseline in exercise capacity and haemodynamic/gas exchange variables have been reported in patients with PPH with continued use of inhaled iloprost. In addition, improvement in preinhalation vascular resistance occurred after 12 weeks of inhaled iloprost (p < 0.01 versus placebo) in a large randomised trial. Increased cough, headache, flushing and an influenza-like syndrome were the most common adverse events in the largest trial of patients receiving inhaled iloprost. Headache, flushing and jaw pain occurred significantly more frequently with inhaled iloprost than with placebo.

Prostacyclin enhances embryo hatching but not sperm motility

BACKGROUND

Recently we discovered that the human oviduct synthesizes abundant prostacyclin (PGI(2)). Gene knock-out studies suggest that PGI(2) is essential to endometrial decidualization, but the effects of PGI(2) on sperm and embryos have not been reported.

METHODS

The effects of PGI(2) on human sperm were analysed by a computer-assisted semen analysis system. The effects of PGI(2) on mouse embryos were examined based on the rates of complete hatching. The expression of PGI(2) receptor (IP) was evaluated by Western blot analysis and immunohistochemistry. The binding of PGI(2) to embryos was confirmed by radioligand binding assay. Finally, cAMP levels were assessed in PGI(2)-challenged embryos.

RESULTS

Iloprost (a stable PGI(2) analogue) did not affect the motility or the overnight survivability of human sperm. Western blot analysis did not detect IP in the sperm plasma membrane. In contrast, the hatching of mouse embryos was enhanced by iloprost (ED(50) 6.7 nmol/l). Exposure to iloprost during 8-cell to morulae or morulae to early blastocyst stages was critical to enhanced hatching. This coincided with the developmental stage-specific expression of IP. Although iloprost bound to blastocysts, it did not significantly increase cAMP.

CONCLUSION

PGI(2) enhanced the hatching of mouse embryos but not the motility of human sperm.

Impaired synthesis and action of antiaggregating cyclic nucleotides in platelets from obese subjects: possible role in platelet hyperactivation in obesity

BACKGROUND

Subjects with central obesity exhibit platelet hyperactivity, which is involved in the atherosclerotic process and therefore can account for the increased risk of cardiovascular morbidity and mortality. The aim of the study was to evaluate whether alterations of platelet function in obesity involve synthesis and/or action of the two antiaggregating cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP).

MATERIALS AND METHODS

In platelets from 16 obese and 15 control subjects we investigated the influence on platelet responses to the Adenosine-5-diphosphate sodium salt (ADP) exerted by (i) prostacyclin analogue Iloprost (0.31-5 nmol L(-1)) and the cAMP analogue 8-bromo-cAMP (10-500 micro mol L(-1)); and by (ii) nitric oxide (NO) donor sodium nitroprusside (SNP) (5-100 micro mol L(-1)) and the cGMP analogue 8-bromo-cGMP (10-500 micro mol L(-1)). IC(50) (minimal concentration of each inhibitor necessary to reduce platelet response to ADP by half) was determined. Iloprost and SNP ability to increase cyclic nucleotides was also measured.

RESULTS

Significantly greater IC(50) were observed in obese subjects than in healthy controls (1.59 +/- 0.16 vs. 0.80 +/- 0.08 nmol L(-1), P = 0.0001 for Iloprost, and 27.6 +/- 6.5 vs. 7.0 +/- 1.7 micro mol L(-1), P = 0.006, for SNP); when data from control and obese subjects were pooled together, IC(50) of Iloprost and SNP correlated with the homeostasis model assessment (HOMA IR), which is a parameter used to measure the insulin resistance (r = 0.588, P = 0.029 and r = 0.640, P = 0.006, respectively). Also the antiaggregating effect of 8-Br-cAMP and 8-Br-cGMP was smaller in the obese subjects. Finally, the ability of Iloprost to increase platelet cAMP and the ability of SNP to increase both cGMP and cAMP were reduced in obese subjects.

CONCLUSIONS

Platelet resistance to the antiaggregating effects of prostacyclin and NO in obesity is attributable to impairment of cyclic nucleotide synthesis and action. As cyclic nucleotides are the main effectors of platelet antiaggregation, the resistance to them can account for platelet hyperactivity in obesity.

Temporal expression and signalling of prostacyclin receptor in the human endometrium across the menstrual cycle

Prostacyclin (PGI(2)) synthesis and function in the human uterus has been implicated in the regulation of the process of normal and dysfunctional menstruation. PGI(2) synthesis is elevated during normal menstruation and is also associated with blood loss in women who suffer from heavy menses. This study was designed to outline further the role of PGI(2) in menstruation by investigating the temporal pattern and site of expression of prostaglandin I synthase (PGIS) and the prostacyclin receptor (IP receptor) in the non-pregnant human endometrium across the menstrual cycle. Quantitative RT-PCR demonstrated increased expression of PGIS and IP receptor during the menstrual phase of the cycle compared with all other phases (P < 0.05). Furthermore, PGIS and IP receptor were localised to the glandular epithelium, stromal and endothelial cells in the basal and functional layers of the endometrium. Functionality of the IP receptor in the human endometrium was assessed by measuring cAMP generation following treatment with 100 nmol l(-1) of the PGI(2) analogue, iloprost. cAMP generation was significantly higher in endometrial tissue collected during the proliferative compared with the secretory phase of the menstrual cycle (P < 0.05). In conclusion, this study has confirmed increased expression and signalling of PGIS and IP receptor during the menstrual phase and outlines a potential autocrine/paracrine role for PGI(2) on several cellular compartments in the endometrium including the endothelium. This may underscore a pivotal role for PGI(2) receptor signalling in normal and dysfunctional menstruation.

Prostanoid-induced modulation of neuropeptide Y and noradrenaline release from the rat mesenteric bed

1. A variety of prostanoids were examined for their ability to alter the periarterial nerve stimulation-induced release of noradrenaline (NA) and neuropeptide Y immunoreactive compounds (NPY-ir) from the perfused mesenteric arterial bed of the rat. 2. Periarterial nerve stimulation (16 Hz) increased the overflow of NA, NPY-ir and perfusion pressure. 3. The prostacyclin (PGI2) analogues, carbaPGI2 and cicaprost both produced a concentration-dependent attenuation of the nerve stimulation-induced increase in NA, NPY-ir overflow and perfusion pressure. 4. The prostaglandin (PG) analogue PGE2 attenuated the evoked increase in NPY-ir overflow as well as a modest decrease in NA. 5. PGE1, sulprostone and iloprost attenuated the nerve stimulation-induced increase in NA overflow but not NPY-ir. 6. Neither PGF2alpha nor the thromboxane A2 analogue U46619 altered the evoked increase in NA or NPY-ir overflow. 7. The results support the view that sympathetic co-transmitter release can be differentially modulated by paracrine/autocrine mediators at sympathetic neuroeffector junctions.

Pharmacological characterization and identification of EP3 prostanoid receptor binding sites in hamster uterus homogenates

The pharmacological properties of [(3)H]-prostaglandin E(2) ([(3)H]-PGE(2)) binding to washed homogenates of hamster uterus were determined. Scatchard analysis of competition data yielded dissociation constants (K(d)s) of 30.9 +/- 5.6 nM (n = 3) and apparent receptor density (B(max)) of 25.25 +/- 1.89 pmol g(-1) wet weight tissue (74 +/- 8% specific binding). Competition studies yielded the following affinity parameters (K(i)) for various prostanoids: GR63799X = 13 4 nM; PGE(2) = 17 +/- 3 nM; sulprostone = 64 +/- 5 nM; enprostil = 67 +/- 3 nM; misoprostol = 124 +/- 15 nM; cloprostenol = 187 +/- 33 nM; carba-prostacyclin = 260 +/- 167 nM; iloprost = 555 +/- 162 nM; PGF(2 alpha) = 767 +/- 73 nM; PGD(2) > 3560 nM; fluprostenol = 11 790 +/- 2776 nM; RS93520 = 21 558 +/- 14 228 nM. These data closely matched the pharmacological profile of previously described EP(3) receptors such as in bovine corpus luteum (BCLM) and the cloned mammalian EP(3) receptors. The high correlation between the current hamster uterus pharmacology data vs the EP(3) receptor binding in BCLM (r = 0.94; P < 0.0001), vs cloned human EP(3) receptor (r = 0.94, P < 0.0001), vs the cloned mouse EP(3) receptor binding (r = 0.78; P < 0.002), vs cloned rat EP(3) receptor (r = 0.9, P < 0.0004), and vs EP(3) receptor-mediated functional responses (r = 0.72, P < 0.02) substantiated the conclusion that the hamster uterus contains EP(3) receptor binding sites.

Prostacyclin enhances the implantation and live birth potentials of mouse embryos

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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

Histopathological and immunohistochemical detection of protective effects of University of Wisconsin solution supplemented with iloprost on donor lung damage

OBJECTIVE

Histopathological evaluation and immunohistochemical markers of surfactant B and CD34 were used to detect alveolar type II cell and pulmonary endothelial cell damage in order to assess the efficacy on donor lung protection of University of Wisconsin (UW) solution supplementation with iloprost.

METHODS

Twelve rats were divided into two groups: UW solution was used alone in group I, and UW iloprost solution in group II. Lung samples were taken at regular intervals for pathological examination to evaluate alveolar cell integrity with hematoxylin and eosin staining. Preservation, of alveolar type II cell and pulmonary endothelial cells was assessed using surfactant B and CD34 immunomarkers, respectively.

RESULTS

In both groups, alveolar integrity, surfactant, and CD34 revealed time-dependent, progressive damage, although this deterioration was less apparent among the iloprost-supplemented group. Alveolar integrity was better preserved at 4, 6, 8, 12, and 48 hours among group II rate. Surfactant staining showed significantly more deterioration at 12 and 24 hours in group I. Similarly, CD34 demonstrated significantly more injury at 6, 12, 24, and 48 hours in group I.

CONCLUSION

Although progressive lung tissue damage assessed by histopathological and immunohistochemical methods was observed in both groups, our findings suggest less deterioration in the iloprost-supplemented group.

Microcirculation and tolerability following i.v. infusion of PGE1 and iloprost: a randomized cross-over study in patients with critical limb ischemia

In a randomized cross-over study, the effect of PGE(1) and iloprost on microcirculation as well as the tolerability was investigated in 36 patients with peripheral arterial occlusive disease stage III and IV according to Fontaine. Patients received PGE(1) and iloprost by single 3-h i.v. infusions on two different days at doses recommended by the manufacturers or in previous studies (PGE(1): first hour 20 microg, next 2h 30 microg each. Iloprost: first hour 0.5 ng/kg/min, next 2h 1.0 ng/kg/min). Transcutaneous oxygen pressure (tcPO(2)) values increased much more with PGE(1). Median tcPO(2) increase over baseline 30 min after the end of infusion was 9 and 2 mmHg for PGE(1) and iloprost, respectively, corresponding to median AUC differences from baseline of 1050 and 210 min mmHg. Because of its exploratory character, the study was not powered to test for significance. Adverse effects occurred in 19.4% (PGE(1)) and 30.6% (iloprost) of patients. Dose reduction was required in 3 patients receiving iloprost (hypotension, nausea, irritation of the infused vein), and in none receiving PGE(1).

Long-term agonist stimulation of IP prostanoid receptor depletes the cognate G(s)alpha protein in membrane domains but does not change the receptor level

Iloprost (IP) stimulation (1 microM, 2 h) of Flag-epitope-tagged human IP prostanoid receptor (FhIPR) expressed in HEK293 cells resulted in specific decrease of endogenous G(s)alpha protein in detergent-insensitive, caveolin-enriched, membrane domains (DIMs). Receptor protein FhIPR, caveolin, G(i)alpha and GPI-linked, domain markers CD55 and CD59 were unchanged. The same result was obtained in HEK293 cells expressing FhIPR-G(s)alpha fusion protein. The endogenous G(s)alpha decreased, but the level of Flag-hIPR-G(s)alpha protein did not change. The specific depletion of domain-bound pool of G(s)alpha as consequence of iloprost stimulation was also demonstrated in membrane domains prepared according to alkaline treatment plus sonication protocol (detergent-free procedure of Song et al.). Our data further indicated that in control, quiescent cells only a very small amount of IP prostanoid receptor was present in DIMs together with large amount of its cognate G(s)alpha protein. Expressed in quantitative terms, DIMs contained 30-40% of the total cellular amount of G proteins whereas the content of IP prostanoid receptors was 1-3%. The dominant portion (>95%) of FhIPR as well as FhIPR-G(s)alpha was localised in high-density area of the gradient containing detergent-solubilised proteins. FhIPR and FhIPR-G(s)alpha distribution was similar to that of transmembrane plasma membrane (PM) markers (CD147, MHCI, CD29, Tapa1, the alpha subunit of Na,K-ATPase, transmembrane form of CD58 and CD44). All these proteins are known to be fully solubilised by detergent and thus unable to float in density gradient. Our data indicate that (i) long-term agonist stimulation of IP prostanoid receptor is associated with preferential decrease of its cognate G protein G(s)alpha from membrane domains; receptor level is unchanged. (ii) Very small fraction (1-3%) of total cellular amount of receptors is recovered in DIMs together with roughly 40% of G proteins. These data suggest a "supra-stoichiometric" arrangement of G proteins and corresponding receptors in DIMs.

Agonists can discriminate between cloned human and mouse prostacyclin receptors

The ability of prostacyclin analogues to stimulate adenylyl cyclase (AC) and phospholipase C (PLC) in Chinese hamster ovary (CHO) cells expressing cloned human (hIP) or cloned mouse (mIP) prostacyclin receptors has been compared. For hIP, the order of potency (pEC(50)) for stimulating AC and PLC pathways was similar: AFP-07 (9.3, 8.4)>cicaprost (8.3, 6.9), iloprost (7.9, 6.8)>taprostene (7.4, 6.8)>carbacyclin (6.9, 6.6), PGE(1) (6.6, 5.1). Although the standard IP agonists cicaprost and iloprost behaved similarly in both hIP and mIP receptor-expressing cells, carbacyclin and PGE(1) showed significantly higher potency at the mIP receptor, suggesting that the agonist recognition sites on hIP and mIP receptors are not identical. A further distinction between hIP and mIP receptors was found with taprostene, which had greater efficacy at hIP receptors (AC 94%, PLC 14%) than at mIP receptors (AC 77%, PLC 0%) (cicaprost=100% in each assay).

Activation of IP prostanoid receptors prevents cardiomyocyte hypertrophy via cAMP-dependent signaling

The antihypertrophic action of angiotensin-converting enzyme inhibitors in the heart results partly from local potentiation of bradykinin. We have demonstrated that the antihypertrophic action of bradykinin is mediated by the release of nitric oxide from endothelium and elevation of cardiomyocyte cGMP. Whether other paracrine factors derived from the coronary endothelium, such as prostacyclin (PGI2), may act to prevent hypertrophy has not been explored. In the vasculature, activation by PGI2 of IP and EP1 prostanoid receptors elicits vasodilatation (via cAMP-dependent signaling) and vasoconstriction, respectively. The present objective was to determine whether IP prostanoid receptor activation has antihypertrophic actions in adult rat cardiomyocytes (ARCM). The selective IP agonist cicaprost (1 microM) virtually abolished the increase in [3H]phenylalanine incorporation (a marker of hypertrophy) induced either by endothelin-1 (ET-1; 60 nM, n = 10, P < 0.005) or by angiotensin II (1 microM, n = 6, P < 0.005). Cicaprost also inhibited ET-1 induction of c-fos mRNA expression, an additional marker of hypertrophy in ARCM (n = 5, P < 0.005). In the absence of hypertrophic stimuli, cicaprost alone did not significantly influence either marker. The antihypertrophic actions of cicaprost were mimicked by the dual IP/EP1 agonist iloprost (1 microM) in the presence of the EP1 antagonist AH-6809 (3 microM). Furthermore, cicaprost modestly but significantly increased cardiomyocyte cAMP content by 13 +/- 6% (P < 0.05, n = 4), and the antihypertrophic effect of cicaprost was lost in the presence of the cAMP-dependent protein kinase inhibitor H-89 (1 microM, n = 5, P < 0.05). However, ET-1 also induced increases in the activity of the intracellular growth signals ERK1 (by 3-fold) and ERK2 (by 5-fold) in ARCM, and these were not inhibited by cicaprost (P < 0.01, n = 5). Activation of IP receptors thus represents a novel approach to prevention of hypertrophy, and this effect is linked to cAMP-dependent signaling.