iloprost and cicaprost

Prostaglandin (PG)I(2) has important regulatory functions on the innate and adaptive immune systems. Recent experimental evidence reveals that PGI(2) modulates the development and function of CD4+ T cells subsets, including Th1, Th2, and Th17 cell responses. In vitro and in vivo studies support that PGI(2) generally has an inhibitory effect on Th1 and Th2 activation, differentiation, and cytokine production. In contrast, PGI(2) seems to enhance Th17-favoring polarization conditions, resulting in Th17 cytokine production. Therefore, PGI(2) may either promote or inhibit individual CD4+ cell subsets and impact adaptive immune responses.

Topics: Adaptive Immunity; Animals; Cell Differentiation; Cells, Cultured; Cytokines; Epoprostenol; Humans; Iloprost; Immunity, Innate; Lymphocyte Activation; Mice; Mice, Knockout; Prostaglandins, Synthetic; Signal Transduction; Th1 Cells; Th17 Cells; Th2 Cells; Vasodilator Agents

Much attention has recently focused on the role of tumor cell-platelet interaction in the metastatic cascade. Prostacyclin and stable prostacyclin analogues have been shown to inhibit specifically the formation of metastases in experimental tumor models. This action is based on their ability to reduce the attachment of tumor cells to platelets and to inhibit adhesion of tumor cells-platelet aggregates to the endothelial lining. To investigate the antimetastatic potential of two prostacyclin analogues (Iloprost and Eptaloprost, Schering AG), we have tested these compounds in the spontaneously metastasizing R 3327 MAT Lu prostate carcinoma of the Cop rat in two types of experiments. Treatment was performed for 33 days, starting one day before s.c. implantation of the tumor. The primary s.c.-implanted tumor remained in situ throughout the experiment. In the first test, Iloprost (0.3 micrograms/kg/min) and Eptaloprost (0.1 micrograms/kg/min) were administered via Alzet mini pumps s.c.. There was a considerable reduction of the number of visible lung metastases by Eptaloprost. In the second test, Eptaloprost was administered p.o. in doses of 0.1 and 0.5 mg/kg daily. The number of lung metastases was significantly reduced. Both compounds had no effect on the growth of the primary tumor in the first as well as in the second test. These data show that the prostacyclin analogue Eptaloprost has a significant antimetastatic activity in a spontaneously metastasizing tumor model and thus merits further investigation.

Topics: Animals; Antineoplastic Agents; Epoprostenol; Iloprost; Molecular Structure; Neoplasms, Experimental; Platelet Aggregation Inhibitors; Prodrugs

Topics: Animals; Antineoplastic Agents; Epoprostenol; Iloprost; Immunocompetence; Melanoma, Experimental; Neoplasm Metastasis

Prostaglandin I(2) (PGI(2)), a lipid mediator currently used in treatment of human disease, is a critical regulator of adaptive immune responses. Although PGI(2) signaling suppressed Th1 and Th2 immune responses, the role of PGI(2) in Th17 differentiation is not known.. In mouse CD4(+)CD62L(+) naïve T cell culture, the PGI(2) analogs iloprost and cicaprost increased IL-17A and IL-22 protein production and Th17 differentiation in vitro. This effect was augmented by IL-23 and was dependent on PGI(2) receptor IP signaling. In mouse bone marrow-derived CD11c(+) dendritic cells (BMDCs), PGI(2) analogs increased the ratio of IL-23/IL-12, which is correlated with increased ability of BMDCs to stimulate naïve T cells for IL-17A production. Moreover, IP knockout mice had delayed onset of a Th17-associated neurological disease, experimental autoimmune encephalomyelitis (EAE), and reduced infiltration of IL-17A-expressing mononuclear cells in the spinal cords compared to wild type mice. These results suggest that PGI(2) promotes in vivo Th17 responses.. The preferential stimulation of Th17 differentiation by IP signaling may have important clinical implications as PGI(2) and its analogs are commonly used to treat human pulmonary hypertension.

Topics: Animals; Antineoplastic Agents; Cell Differentiation; Cells, Cultured; Encephalomyelitis, Autoimmune, Experimental; Epoprostenol; Female; Humans; Iloprost; Interleukin-12; Interleukin-17; Interleukin-23; Mice; Mice, Inbred BALB C; Mice, Knockout; Platelet Aggregation Inhibitors; Receptors, Epoprostenol; Spinal Cord; Th17 Cells

Prostacyclin analogs, used to treat idiopathic pulmonary arterial hypertension (IPAH), are assumed to work through prostacyclin (IP) receptors linked to cyclic AMP (cAMP) generation, although the potential to signal through peroxisome proliferator-activated receptor-γ (PPARγ) exists.. IP receptor and PPARγ expression may be depressed in IPAH. We wished to determine if pathways remain functional and if analogs continue to inhibit smooth muscle proliferation.. We used Western blotting to determine IP receptor expression in peripheral pulmonary arterial smooth muscle cells (PASMCs) from normal and IPAH lungs and immunohistochemistry to evaluate IP receptor and PPARγ expression in distal arteries.. Cell proliferation and cAMP assays assessed analog responses in human and mouse PASMCs and HEK-293 cells. Proliferative rates of IPAH cells were greater than normal human PASMCs. IP receptor protein levels were lower in PASMCs from patients with IPAH, but treprostinil reduced replication and treprostinil-induced cAMP elevation appeared normal. Responses to prostacyclin analogs were largely dependent on the IP receptor and cAMP in normal PASMCs, although in IP(-/-) receptor cells analogs inhibited growth in a cAMP-independent, PPARγ-dependent manner. In IPAH cells, antiproliferative responses to analogs were insensitive to IP receptor or adenylyl cyclase antagonists but were potentiated by a PPARγ agonist and inhibited (∼ 60%) by the PPARγ antagonist GW9662. This coincided with increased PPARγ expression in the medial layer of acinar arteries.. The antiproliferative effects of prostacyclin analogs are preserved in IPAH despite IP receptor down-regulation and abnormal coupling. PPARγ may represent a previously unrecognized pathway by which these agents inhibit smooth muscle proliferation.

Topics: Animals; Antihypertensive Agents; Blotting, Western; Cell Proliferation; Down-Regulation; Epoprostenol; HEK293 Cells; Humans; Hypertension, Pulmonary; Iloprost; Immunohistochemistry; Mice; Muscle, Smooth, Vascular; PPAR gamma; Prostaglandins, Synthetic; Receptors, Epoprostenol; Rosiglitazone; Thiazolidinediones; Vasodilator Agents

An anti-inflammatory effect of PGI(2) has been suggested by increased inflammation in mice that are deficient in the PGI(2) receptor (IP) or in respiratory syncytial viral- or OVA-induced CD4 T cell-associated responses. To determine the mechanism of the anti-inflammatory effect, we hypothesized that PGI(2) analogs inhibit CD4 T cell effector cytokine production. To test this hypothesis, we activated purified CD4 T cells with anti-CD3 and anti-CD28 antibodies under Th1 and Th2 polarizing conditions for 4 days and restimulated the T cells with anti-CD3 in the presence of PGI(2) analogs for 2 days. We found that PGI(2) analogs (cicaprost and iloprost) inhibited the production of Th1 cytokines (IFN-gamma) and Th2 cytokines (IL-4, IL-10, and IL-13) in a dose-dependent pattern. The inhibitory effect was partially dependent on the IP receptor signaling and was correlated with elevated intracellular cAMP and down-regulated NF-kappaB activity. Pretreatment of the CD4 T cells with 8-bromoadenosine-3',5'-cyclic monophosphorothioate, Rp-isomer, to inhibit a key signaling molecule in the cAMP pathway, protein kinase A (PKA), attenuated the suppressive effect of PGI(2) analogs significantly, suggesting that PKA, in part, mediates the inhibition of the cytokine production. These data indicate that PGI(2) analogs have an immune-suppressive effect on previously activated and differentiated CD4 T cells in vitro and suggest that PGI(2) may have a similar function in vivo.

Topics: Animals; CD4-Positive T-Lymphocytes; Cells, Cultured; Cyclic AMP; Cytokines; Dose-Response Relationship, Drug; Down-Regulation; Epoprostenol; Iloprost; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Knockout; NF-kappa B; Receptors, Prostaglandin; Signal Transduction; Structure-Activity Relationship; Th1 Cells; Th2 Cells

We describe new fully stereocontrolled syntheses of the prostacyclin analogues iloprost (2), the most active component of the drugs Ilomedin and Ventavis, and 3-oxa-iloprost (3), a derivative that is expected to have a significantly higher metabolic stability than 2 perhaps allowing an oral application. The syntheses are based on the same strategy and chiral bicyclic building block as used in the synthesis of cicaprost (4), the third most potent analogue that exhibits, besides prostacyclin-like activities, antimetastatic activities. Reaction of the enantiopure C6-C13 bicyclic aldehyde 17 with Cl(3)CCOOH/Cl(3)CCOONa afforded trichlorocarbinol 24 which was converted via mesylate 25 to the C6-C14 bicyclic alkyne 9. The palladium-catalysed hydrostannylation of alkyne 9 gave with high regio- and stereoselectivity the alkenylstannane 26, Sn/Li exchange of which afforded the E-configured alkenyllithium derivative 8. Coupling of the C6-C14 building block 8 with the enantiopure C15-C20 building block, the N-methoxyamide 7, gave the C6-C20 bicyclic ketone 6 in high yield without epimerisation at C16. The configuration at C15 of iloprost (2) and 3-oxa-iloprost (3) was established through a highly diastereoselective reduction of ketone 6 with catecholborane and the chiral oxazaborolidine 28 which furnished alcohol (15S)-29. The highly stereoselective conversions of alcohol (15S)-29 to iloprost (2) and 3-oxa-iloprost (3), which include as key stereoselective steps an olefination with a chiral phosphonoacetate and a copper-mediated allylic alkylation, have already been described.

Topics: Epoprostenol; Iloprost; Prostaglandins, Synthetic; Stereoisomerism; Vasodilator Agents

Like Ras, farnesylation of the IP (prostacyclin receptor) is required for its efficient intracellular signalling, and hence the IP represents a potential target for inhibition by FTIs [FTase (farnesyl protein transferase) inhibitors]. Herein, the effect of SCH66336 on the isoprenylation and function of the human and mouse IPs overexpressed in human embryonic kidney 293 cells, and by the IP endogenously expressed in human erythroleukaemia cells, was investigated. SCH66336 yielded concentration-dependent decreases in IP-mediated cAMP generation (IC50 0.27-0.62 nM), [Ca2+]i mobilization (IC50 26.6-48.3 nM) and IP internalization, but had no effect on signalling by the non-isoprenylated beta2 adrenergic receptor or b isoform of the TP (prostanoid thromboxane A2 receptor). Additionally, SCH66336 impaired IP-mediated crossdesensitization of TPa signalling (IC50 56.1 nM) and reduced farnesylation of the molecular chaperone protein HDJ-2 (IC50 3.1 nM). To establish whether farnesylation of the IP is inhibited and/or whether its 'CaaX motif' might undergo alternative geranylgeranylation in the presence of SCH66336, a series of chimaeric Ha (Harvey)-Ras fusions were generated by replacing its CaaX motif (-CVLS) with that of the IP (-CSLC) or, as controls, of Ki (Kirsten)-Ras 4B (-CVIM) or Rac 1 (-CVLL). Whereas SCH66336 had no effect on Ha-RasCVLL isoprenylation in vitro or in whole cells, it supported alternative geranylgeranylation of Ha-RasCVIM, but completely impaired isoprenylation of both Ha-RasCVLS and Ha-RasCSLC. These data confirm that the -CSLC motif of the IP is a direct target for inhibition by the FTI SCH66336, and in the presence of strong FTase inhibition, the IP does not undergo compensatory geranylgeranylation

Topics: Adrenergic beta-Agonists; Alkyl and Aryl Transferases; Amino Acid Motifs; Animals; Calcium Signaling; Carrier Proteins; Cell Line; Cell Line, Tumor; Cyclic AMP; Dose-Response Relationship, Drug; Endocytosis; Epoprostenol; Farnesyltranstransferase; Heat-Shock Proteins; HSP40 Heat-Shock Proteins; Humans; Iloprost; Isoproterenol; Kidney; Leukemia, Erythroblastic, Acute; Mice; Mutagenesis, Site-Directed; Organophosphorus Compounds; Piperidines; Proline; Propanolamines; Protein Prenylation; Protein Processing, Post-Translational; Proto-Oncogene Proteins p21(ras); Pyridines; Receptors, Adrenergic, beta-2; Receptors, Epoprostenol; Receptors, Thromboxane A2, Prostaglandin H2; Recombinant Fusion Proteins; Signal Transduction; Transfection

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.

Topics: Alprostadil; Blood Coagulation; Bucladesine; Carotid Artery Diseases; Carotid Artery, Internal; Cells, Cultured; Colforsin; Coronary Vessels; Culture Media, Serum-Free; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Diclofenac; Dinoprostone; Epoprostenol; Etoricoxib; Gene Expression Profiling; Gene Expression Regulation; Humans; Iloprost; Isoquinolines; Mammary Arteries; Membrane Proteins; Models, Biological; Myocytes, Smooth Muscle; Oligonucleotide Array Sequence Analysis; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Pyridines; Receptors, Prostaglandin; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP3 Subtype; RNA, Messenger; Saphenous Vein; Second Messenger Systems; Sulfonamides; Sulfones; Tetradecanoylphorbol Acetate; Thrombomodulin; Thrombophilia; Vasodilator Agents

Hyaluronic acid (HA) is a prominent constituent of the extracellular matrix of atherosclerotic vascular lesions in humans known to modulate vascular smooth muscle phenotype. The regulation of HA synthesis by vasodilatory prostaglandins was analyzed in human arterial smooth muscle cells (SMCs). The prostacyclin analogue, iloprost (100 nmol/L), markedly increased pericellular formation of HA coats and HA secretion into the cell culture medium in human arterial SMCs (8.7+/-1.6-fold). Expression of HA synthase 2 (HAS2) was determined by semiquantitative RT-PCR and found to be strongly upregulated at concentrations of iloprost between 1 and 100 nmol/L after 3 hours. Furthermore, endogenous cyclooxygenase-2 (COX2) activity was required for basal expression of HAS2 mRNA in SMCs in vitro. Total HA secretion in response to iloprost was markedly decreased by RNA interference (RNAi), specific for HAS2. In addition, siRNA targeting HAS2 strongly increased the spreading of human SMCs compared with mock-transfected cells. HAS2 mRNA levels were also stimulated by a selective prostacyclin receptor (IP) agonist, cicaprost (10 nmol/L), prostaglandin E(2) (10 nmol/L), and the EP(2) receptor agonist, butaprost (1 micromol/L). Induction of HAS2 mRNA and HA synthesis by prostaglandins was mimicked by stable cAMP analogues and forskolin. In human atherectomy specimens from the internal carotid artery, HA deposits and COX2 expression colocalized frequently. In addition, strong EP(2) receptor expression was detected in SMCs in HA-rich areas. Therefore, upregulation of HAS2 expression via EP(2) and IP receptors might contribute to the accumulation of HA during human atherosclerosis, thereby mediating proatherosclerotic functions of COX2.

Topics: 6-Ketoprostaglandin F1 alpha; Acetophenones; Alprostadil; Arteriosclerosis; Becaplermin; Benzopyrans; Bucladesine; Carotid Artery Diseases; Carotid Artery, Internal; Cells, Cultured; Colforsin; Cyclic AMP; Cyclooxygenase 2; Enzyme Induction; Epoprostenol; Extracellular Matrix; Glucuronosyltransferase; Humans; Hyaluronan Synthases; Hyaluronic Acid; Iloprost; Indoles; Isoenzymes; Isoquinolines; Macrophages; Maleimides; Membrane Proteins; Muscle Cells; Muscle, Smooth, Vascular; Pertussis Toxin; Platelet-Derived Growth Factor; Prostaglandin-Endoperoxide Synthases; Proto-Oncogene Proteins c-sis; Receptors, Prostaglandin E; Receptors, Prostaglandin E, EP2 Subtype; RNA, Messenger; RNA, Small Interfering; Sulfonamides; Vasodilator Agents

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.. 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.. 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.

Topics: Animals; Antineoplastic Agents; Corneal Neovascularization; Epoprostenol; Extracellular Matrix Proteins; Iloprost; Mice; Myosin Heavy Chains; Nonmuscle Myosin Type IIB; Platelet Aggregation Inhibitors; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Transcription Factors; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-1

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).

Topics: Adenylyl Cyclases; Animals; Cloning, Molecular; COS Cells; Cricetinae; Enzyme Activation; Epoprostenol; Gene Expression; Humans; Iloprost; Mice; Prostaglandins, Synthetic; Rats; Receptors, Epoprostenol; Receptors, Prostaglandin; Recombinant Proteins; Signal Transduction; Species Specificity; Type C Phospholipases

Mesangial cells play an important role in glomerular function. They are an important source of cyclooxygenase (COX)-derived arachidonic acid metabolites, including prostaglandin E(2) and prostacyclin. Prostacyclin receptor (IP) mRNA was amplified from cultured mesangial cell total RNA by RT-PCR. While the prostaglandin E(2) receptor subtype EP(2) was not detected, EP(1,3,4) mRNA was amplified. Also, IP protein was noted in mesangial cells, proximal tubules, inner medullary collecting ducts, and the inner and outer medulla. But no protein was detected in whole cortex preparations. Prostacyclin analogues: cicaprost and iloprost, increased cAMP levels in mesangial cells. On the other hand, arginine-vasopressin and angiotensin II increased intracellular calcium in mesangial cells, but cicaprost, iloprost and prostaglandin E(2) had no effect. Moreover, a 50% inhibition of cicaprost- and iloprost-cAMP stimulation was observed upon mesangial cell exposure to 25 and 35 mM glucose for 5 days. But no change in IP mRNA was observed at any glucose concentration or time exposure. Although 25 mM glucose had no effect on COX-1 protein levels, COX-2 was increased up to 50%. In contrast, PGIS levels were reduced by 50%. Thus, we conclude that the prostacyclin/IP system is present in cultured rat mesangial cells, coupling to a cAMP stimulatory pathway. High glucose altered both enzymes in the PGI(2) synthesis pathway, increasing COX-2 but reducing PGIS. In addition, glucose diminished the cAMP response to prostacyclin analogues. Therefore, glucose attenuates the PGI(2)/IP system in cultured rat mesangial cells.

Topics: Angiotensin II; Animals; Arachidonic Acid; Calcium; Calcium Signaling; Cells, Cultured; Cyclic AMP; Cyclooxygenase 1; Cyclooxygenase 2; Dinoprostone; Epoprostenol; Glomerular Mesangium; Glucose; Iloprost; Isoenzymes; Membrane Proteins; Oxytocics; Prostaglandin-Endoperoxide Synthases; Rats; Receptors, Prostaglandin; RNA, Messenger; Vasoconstrictor Agents; Vasopressins

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.

Topics: Angiotensin II; Animals; Biomarkers; Cardiomegaly; Cyclic AMP; Endothelin-1; Epoprostenol; Iloprost; Male; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Myocytes, Cardiac; Rats; Rats, Sprague-Dawley; Receptors, Epoprostenol; Receptors, Prostaglandin; Signal Transduction

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.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Biguanides; Dinoprost; Dinoprostone; Dose-Response Relationship, Drug; Electrophysiology; Epoprostenol; Ferrets; Hydantoins; Iloprost; In Vitro Techniques; Male; Prostaglandins; Prostaglandins F, Synthetic; Serotonin; Vagus Nerve

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.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Alprostadil; Animals; Dinoprost; Dinoprostone; Electric Stimulation; Epoprostenol; Iloprost; Male; Mesenteric Arteries; Neuropeptide Y; Norepinephrine; Perfusion; Prostaglandins; Radioimmunoassay; Rats; Rats, Sprague-Dawley

Primary pulmonary hypertension is characterized by increased pulmonary vascular resistance and smooth muscle proliferation. Stable analogs are increasingly being used to treat this disease, although no data exists comparing their effects on proliferation. We therefore investigated the antiproliferative activity of several prostacyclin (PGI(2)) analogs on human pulmonary arterial smooth muscle cells, including UT-15 and iloprost, analogs that have recently completed successful clinical trials. Serum-induced proliferation, as assessed by [(3)H]thymidine incorporation (30 h) or cell number (48 h), was significantly inhibited with a 10-fold difference in potency, ranking in effectiveness UT-15 > iloprost > cicaprost > beraprost. Effects were reversed by the adenylyl cyclase inhibitor, 2,5'dideoxyadenosine (DDA) but not SQ22536. Intracellular cyclic AMP (cAMP) was elevated by all analogs and inhibited by DDA, although SQ22536 was a highly variable inhibitor, suggesting that different pathways might mediate cAMP generation. UT-15 produced a significantly larger and more sustained increase in cAMP compared with other analogs, with iloprost being the weakest elevator. Thus, PGI(2) analogs potently inhibit proliferation of human pulmonary artery, probably via a cAMP-dependent pathway, although cAMP elevation in itself is not a good predictor of antiproliferative potency.

Topics: Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Cell Division; Cells, Cultured; Cyclic AMP; Enzyme Inhibitors; Epoprostenol; Humans; Iloprost; Molecular Structure; Muscle, Smooth, Vascular; Platelet-Derived Growth Factor; Pulmonary Artery

In order to characterize prostanoid receptors present in the non-pregnant porcine uterus, the effects of naturally occurring prostaglandins (D2, E2, F2alpha, I2) and synthetic prostanoid receptor agonists on contractility of the longitudinal and circular muscles were examined in vitro. The potent contractile actions of prostaglandin F2alpha and cloprostenol indicate the presence of excitatory FP receptors in the porcine uterus. The longitudinal muscle was more sensitive to FP receptor agonists than was the circular muscle. Prostaglandin D2 produced an excitatory response in the longitudinal muscle but completely inhibited the spontaneous contraction of the circular muscle. BW-245C (5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin, 1 nM-10 microM, a DP receptor agonist) inhibited the spontaneous contractions of both muscles, but the inhibition was conspicuously stronger in the circular muscle. Prostaglandin I2 caused excitatory and inhibitory responses in the longitudinal and circular muscles, respectively, at relatively high concentrations (10-100 microM). Cicaprost, an IP receptor agonist caused inhibition of the contraction in the circular muscle but contracted the longitudinal muscle. Iloprost, an EP(1)/IP receptor agonist, caused excitatory responses in both muscles at relative high concentrations. Prostaglandin E2 caused excitatory responses at 1-100 nM and inhibitory responses at 100 nM-10 microM in both muscle layers. ONO-DI-004 ((17S)-2,5-ethano-6-oxo-17,20-dimethyl prostaglandin E1, an EP1 receptor agonist) and ONO-AE-248 ((16S)-9-deoxy-9beta-chloro-15-deoxy-16-hyfroxy-17,17-trimethylene-19,20-didehydro prostaglandin F2, an EP3 receptor agonist) contracted the longitudinal muscle but had little effect on the circular muscle. ONO-AE1-259 (11,15-O-dimethyl prostaglandin E2, an EP2 receptor agonist) inhibited the spontaneous contractions of both muscle layers to almost the same degree, but ONO-AE1-329 (16-(3-methoxymethyl)phenyl-omega-tetranor-3,7-dithia prostaglandin E1, an EP4 receptor agonist) did not inhibit the myometrial contraction. The present results indicate that contractile (FP, EP1, EP3) and relaxatory (DP, IP, EP2) prostanoid receptors are present in the non-pregnant porcine uterus. There are marked muscle layer-related differences in the degree of responsiveness of prostanoid receptor agonists, and these differences suggest that there is a heterogeneous distribution of prostanoid receptors in the longitudinal and circular m

Topics: Animals; Cloprostenol; Dinoprost; Dinoprostone; Dose-Response Relationship, Drug; Epoprostenol; Female; Hydantoins; Iloprost; In Vitro Techniques; Muscle Contraction; Myometrium; Prostaglandin D2; Receptors, Prostaglandin; Swine

1. Primary cultures of adult rat dorsal root ganglia (DRG) were prepared to examine the properties of prostacyclin (IP) receptors and prostaglandin E(2) (EP) receptors in sensory neurones. 2. IP receptor agonists, cicaprost and iloprost, stimulated adenylyl cyclase activity with EC(50) values of 22 and 28 nM, respectively. Prostaglandin E(1) (PGE(1)) and prostaglandin E(2) (PGE(2)) were 7 fold less potent than cicaprost and iloprost, with PGE(2) displaying a lower maximal response. 3. Adenylyl cyclase activation by iloprost, PGE(1) and PGE(2), but not by forskolin, was highly dependent on DRG cell density. Although the potency of iloprost and PGE(2) for stimulating adenylyl cyclase was unchanged, their maximal responses were significantly increased at low cell density. 4. Both IP and EP(2/4) receptors could be down-regulated by agonist pretreatment, however the presence of cyclo-oxygenase (COX) inhibitors did not prevent this apparent down-regulation of IP and EP(2/4) receptors at high DRG cell densities. 5. Stimulation of adenylyl cyclase by the neuropeptide calcitonin gene-related peptide was also decreased at high DRG cell density, whereas the responses to beta-adrenoceptor agonists were increased at high DRG cell density. 6. Addition of nerve growth factor (NGF), or the addition of anti-neurotrophin antibodies during the 5-day culture of DRG cells, had no effect on IP receptor-mediated responses. 7. These results indicate that G(s)-coupled receptors involved in nociception are regulated in a variable manner in adult rat sensory neurones, and that this cell density-dependent regulation may be agonist-independent for IP and EP(2/4) receptors.

Topics: Adenylyl Cyclases; Aging; Alprostadil; Animals; Antineoplastic Agents; Cell Count; Cells, Cultured; Colforsin; Cyclic AMP; Cyclooxygenase Inhibitors; Dinoprostone; Down-Regulation; Enzyme Activation; Epoprostenol; Ganglia, Spinal; Iloprost; Male; Neurons, Afferent; Rats; Rats, Sprague-Dawley; Receptors, Epoprostenol; Receptors, Prostaglandin

1. Chinese hamster ovary (CHO) cells were transiently transfected with the mouse prostacyclin (mIP) receptor to examine IP agonist-mediated stimulation of [(3)H]-cyclic AMP and [(3)H]-inositol phosphate production. 2. The prostacyclin analogues, cicaprost, iloprost, carbacyclin and prostaglandin E(1), stimulated adenylyl cyclase activity with EC(50) values of 5, 6, 25 and 95 nM, respectively. These IP agonists also stimulated the phospholipase C pathway with 10 - 40 fold lower potency than stimulation of adenylyl cyclase. 3. The non-prostanoid prostacyclin mimetics, octimibate, BMY 42393 and BMY 45778, also stimulated adenylyl cyclase activity, with EC(50) values of 219, 166 and 398 nM, respectively, but failed to stimulate [(3)H]-inositol phosphate production. 4. Octimibate, BMY 42393 and BMY 45778 inhibited iloprost-stimulated [(3)H]-inositol phosphate production in a non-competitive manner. 5. Activation of the endogenously-expressed P(2) purinergic receptor by ATP led to an increase in [(3)H]-inositol phosphate production which was inhibited by the non-prostanoid prostacyclin mimetics in non-transfected CHO cells. Prostacyclin analogues and other prostanoid receptor ligands failed to inhibit ATP-stimulated [(3)H]-inositol phosphate production. 6. A comparison between the IP receptor-specific non-prostanoid ONO-1310 and the structurally-related EP(3) receptor-specific agonist ONO-AP-324, indicated that the inhibitory effect of non-prostanoids was specific for those compounds known to activate IP receptors. 7. The non-prostanoid prostacyclin mimetics also inhibited phospholipase C activity when stimulated by constitutively-active mutant Galpha(q)RC, Galpha(14)RC and Galpha(16)QL transiently expressed in CHO cells. These drugs did not inhibit adenylyl cyclase activity when stimulated by the constitutively-active mutant Galpha(s)QL. 8. These results suggest that non-prostanoid prostacyclin mimetics can specifically inhibit [(3)H]-inositol phosphate production by targeting G(q/11) and/or phospholipase C in CHO cells, and that this effect is independent of IP receptors.

Topics: Acetates; Adenylyl Cyclases; Alprostadil; Animals; Cell Survival; CHO Cells; Cricetinae; Cyclic AMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Epoprostenol; Iloprost; Imidazoles; Inositol Phosphates; Oxazoles; Phenoxyacetates; Pyridines; Receptors, Epoprostenol; Receptors, Prostaglandin; Transfection; Tritium; Type C Phospholipases

Prostacyclin has proved to be a beneficial treatment for patients with severe pulmonary hypertension. We postulated that the response may reflect, at least in part, inhibition of pulmonary artery smooth muscle cell (PASMC) growth.. Human PASMCs were derived from distal (<1-mm external diameter, n=8) and proximal (>8-mm external diameter, n=12) pulmonary arteries obtained at transplant surgery and pneumonectomy. The effects of the stable prostacyclin analogues on [methyl-(3)H]thymidine incorporation and cell proliferation were investigated by using immunohistochemically characterized cells. Distal cells proliferated faster than did proximal PASMCs and displayed a distinct sensitivity to cicaprost and iloprost. Both analogues inhibited thymidine uptake over 24 hours (20% to 60%, P<0.001; n=8) and abolished stimulation of DNA synthesis by platelet-derived growth factor-BB (10 ng/mL) in distal but not proximal cells. The inhibitory effect of cicaprost was mimicked by isoproterenol (10(-5) mol/L), forskolin (10(-5) mol/L), and dibutyryl cAMP (5x10(-4) mol/L) and was potentiated by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (5x10(-5) mol/L). Cicaprost (10(-10) to 10(-6) mol/L) inhibited the proliferation of PASMCs, which had been stimulated with either platelet-derived growth factor-BB or serum, and increased cAMP production. These effects were potentiated by 3-isobutyl-1-methylxanthine and attenuated by the adenylyl cyclase inhibitor 2',5'-dideoxyadenosine (10(-5) to 10(-4) mol/L).. ++Cicaprost and iloprost inhibit DNA synthesis and proliferation to a greater extent in distal compared with proximal human PASMCs, acting at least in part via a cAMP-dependent mechanism. The results are consistent with the hypothesis that prostacyclin analogues inhibit vascular remodeling in pulmonary hypertension and demonstrate heterogeneity among human PASMCs.

Topics: Adult; Aged; Cell Division; Cells, Cultured; Cyclic AMP; Depression, Chemical; DNA; Epoprostenol; Female; Fluorescent Antibody Technique; Humans; Iloprost; Male; Middle Aged; Muscle, Smooth, Vascular; Phenotype; Pulmonary Artery; Vasodilator Agents

PGs of the E series are involved in the control of LHRH secretion. The present experiments were conducted to clarify whether PGI2 (prostacyclin) might be also involved in such a control, using multiple methodological approaches on immortalized LHRH-secreting neurons. A RT-PCR procedure to detect mouse PGI2 receptor (IP) messenger RNA was first applied, and the results obtained showed the presence of a specific transcript in two cell lines of immortalized LHRH neurons (GT1-1 and GN11 cell lines). Receptor binding assays on membrane preparations from GT1-1 cells showed the presence of a single specific and saturable class of binding sites (Kd = 4.6 nM; 10,000 sites/cell) for [3H]iloprost, a stable analog of PGI2. Competition experiments showed that the binding sites labeled by [3H]iloprost possess the pharmacological characteristics of IP receptors. In functional studies, PGI2 and its analogs, iloprost and cicaprost, were able to stimulate LHRH release from the GT1-1 cells with elevated potencies (EC50 = 0.6-4.3 nM); PGE1 was only slightly less active (EC50 = 28.5 nM), whereas PGE2, considered the major PG involved in LHRH secretion, was poorly effective (EC50 = 921 nM). The relative potencies (EC50) of these compounds in stimulating the intracellular accumulation of cAMP were in line with their LHRH-releasing activities. In conclusion, these results indicate that immortalized LHRH-secreting neurons express IP receptors through which PGI2 may exert relevant effects on LHRH release.

Topics: Animals; Cell Line, Transformed; Cell Membrane; Cyclic AMP; Dinoprostone; Dose-Response Relationship, Drug; Epoprostenol; Gonadotropin-Releasing Hormone; Humans; Iloprost; Mice; Neurons; Polymerase Chain Reaction; Receptors, Epoprostenol; Receptors, Prostaglandin

This study was designed to determine the effects of cyclooxygenase inhibition and prostacyclin agonists on the hypertension induced by nitric oxide synthase blockade in a previously characterized rat model of preeclampsia.. A condition similar to preeclampsia was induced by infusing pregnant rats with the nitric oxide synthase inhibitor N G -nitro- L -arginine methyl ester through subcutaneously implanted osmotic minipumps. Blood pressure was measured with the tail cuff method. In the first experiment the rats received either vehicle alone (control group), N G -nitro- L -arginine methyl ester (50 mg/d), indomethacin (0.1 mg/d), or N G -nitro- L -arginine methyl ester plus indomethacin beginning on day 17 of pregnancy. In the second experiment the rats received vehicle alone (control group), N G -nitro- L -arginine methyl ester (50 mg/d), or N G -nitro- L -arginine methyl ester plus iloprost (31 microgram/d). In a third experiment cicaprost (15 microgram/d) was substituted for iloprost.. Except for an increase on the day after insertion of the pump indomethacin had no significant effect on the hypertension induced by N G -nitro- L -arginine methyl ester. Both prostacyclin agonists (iloprost and cicaprost), however, attenuated the rise in blood pressure usually seen after N G -nitro- L -arginine methyl ester administration.. Nonselective inhibition of the cyclooxygenase enzymatic system does not influence the hypertension seen in the rat preeclampsia model induced by chronic nitric oxide deficiency. The hypertension in this model can be partially reversed with prostacyclin analogs.

Topics: Animals; Blood Pressure; Cyclooxygenase Inhibitors; Disease Models, Animal; Enzyme Inhibitors; Epoprostenol; Female; Gestational Age; Iloprost; Indomethacin; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Pre-Eclampsia; Pregnancy; Prostaglandins, Synthetic; Rats

Secondary postoperative ischaemia due to venous occlusion is the most detrimental insult to free microvascular flaps. In an experimental rat free flap model the efficacy of long acting prostacyclin analogues iloprost (Ilomedin) and cicaprost in venous occlusion induced postoperative ischaemia was studied. Free, microvascular groin flaps were transplanted to the neck and the draining veins were temporarily occluded on the first postoperative day for a total of 20 min. In the untreated control group, haemorrhagic flap necrosis occurred. Intravital microscopy after secondary ischaemia revealed flap areas without reperfusion. The functional vessel density was significantly reduced. Reperfused capillaries were tortuous and significantly dilated. After reperfusion the interstitial leakage of macromolecular dextran increased, indicating loss of microvascular endothelial integrity. Intraarterial and intravenous applications of iloprost were able to diminish the ischaemic effects, giving a flap survival rate of 83%. Similar results were obtained by intravenous and enteral administration of cicaprost. Transcutaneous oxygen partial pressure measurements confirmed the viability of the surviving flaps. We conclude that both iloprost and cicaprost are effective in preventing venous occlusion induced failure of free microvascular groin flaps.

Topics: Animals; Epoprostenol; Graft Rejection; Iloprost; Ischemia; Male; Oxygen; Partial Pressure; Postoperative Complications; Prostaglandins, Synthetic; Rats; Rats, Sprague-Dawley; Surgical Flaps; Vasodilator Agents

The role of K+ channels in mediating vasorelaxation induced by two prostacyclin analogues was investigated in guinea-pig aorta. Iloprost caused substantial relaxation of tissues contracted with phenylephrine or 25 mM K+ but not 60 mM K+. In endothelial-denuded tissues, maximal relaxations to iloprost, cicaprost or isoprenaline were inhibited by approximately 40-50% with tetraethylammonium or iberiotoxin, both blockers of large conductance Ca2+-activated K+ (BKCa) channels. In contrast, the response to forskolin, an activator of adenylate cyclase was marginally inhibited by tetraethylammonium. The K(ATP) channel blocker, glibenclamide significantly augmented the response to iloprost but not cicaprost. These effects were largely inhibited by the EP1 receptor antagonist, 8-chlorodibenz[b,f][1,4]oxazepine-10(11H)-carboxylic acid 2-[1-oxo-3(4-pyridinyl)propyl]hydrazide, monohydrochloride (SC-51089) and partially by indomethacin, suggesting that iloprost relaxation is counterbalanced by activation of EP1 receptors, in part through a constrictor prostaglandin. We conclude that BKCa channels play an important role in mediating the effects of iloprost and cicaprost and raises the possibility that cyclic AMP-independent pathways might be involved.

Topics: Animals; Antineoplastic Agents; Calcium; Dose-Response Relationship, Drug; Endothelium, Vascular; Epoprostenol; Guinea Pigs; Hydrazines; Iloprost; Isoproterenol; Male; Muscle, Smooth, Vascular; Oxazepines; Phenylephrine; Potassium Channel Blockers; Potassium Channels; Prostaglandin Antagonists; Tetraethylammonium; Vasodilation; Vasodilator Agents

The specific prostacyclin (IP) receptor agonist cicaprost relaxed human pulmonary artery preparations precontracted with phenylephrine [50% inhibitory concentration (IC50) approximately 0.6 nM], U-46619 (IC50 approximately 0.9 nM), and K+ (approximately 40% maximal relaxation); endothelium removal had little effect on relaxant activity. Ranking of relaxant potencies for prostacyclin and five of its analogs was 17 alpha, 20-dimethyl-delta 6,6a-6a-carba PGI1 (TEI-9063) > or = cicaprost > iloprost > prostacyclin > taprostene > benzodioxane prostacyclin > 15-deoxy-16 alpha-hydroxy-16 beta,20-dimethyl-delta 6,6a-6a-carba PGI1 (TEI-3356). The potency of the isocarbacyclin TEI-3356 may have been under-estimated because of its contractile (EP3 receptor agonist) activity. The potency ranking of four nonprostanoid prostacyclin mimetics was 3-[4-(4,5-diphenyl-2-oxazolyl)-5-oxazolyl]phenoxy] acetic acid (BMY 45778; IC50 approximately 2.5 nM) > > 2-[3-[2-(4, 5-diphenyl-2-oxazolyl)ethyl]phenoxy]acetic acid (BMY 42393) > octimibate > CU 23 (a novel diphenylindole). From IP receptor binding affinities obtained on human platelet membranes, it is suggested that the slightly shallower log concentration-response curves for BMY 45778, BMY 42393, and CU 23 may reflect the near-maximal receptor occupancy required for complete relaxation. A fifth nonprostanoid, CU 602, had much shallower log concentration-response curves than cicaprost against phenylephrine tone but not against U-46619 tone; this may indicate IP receptor partial agonism coupled with TP receptor antagonism. The relaxant actions of the nonprostanoid mimetics were more persistent than those of the prostacyclin analogs on washout of the organ bath; by the inhalation route, this type of compound may be retained within pulmonary tissue and thus afford greater pulmonary/systemic selectivity than currently used pulmonary vasodilators.

Topics: Acetates; Aged; Cardiovascular Agents; Child; Child, Preschool; Dose-Response Relationship, Drug; Enzyme Inhibitors; Epoprostenol; Fatty Acids; Humans; Iloprost; Imidazoles; Indoles; Middle Aged; Muscle, Smooth, Vascular; Oxazoles; Phenoxyacetates; Platelet Aggregation Inhibitors; Prostaglandins, Synthetic; Pulmonary Artery; Receptors, Epoprostenol; Receptors, Prostaglandin; Structure-Activity Relationship; Vasoconstrictor Agents; Vasodilator Agents

Topics: Acetates; Animals; Cell Aggregation; Cyclic AMP; Epoprostenol; Iloprost; Imidazoles; Isoquinolines; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Oxazoles; Peritoneal Cavity; Phenoxyacetates; Pyrrolidinones; Rats; Rolipram; Second Messenger Systems; Sulfonamides

Topics: Acetates; Cell Line; Cyclic AMP; Epoprostenol; Humans; Iloprost; Imidazoles; Kinetics; Neuroblastoma; Neurons; Oxazoles; Phenoxyacetates

The effects of three non-prostanoid prostacyclin mimetics on rat peritoneal neutrophil activity have been investigated and compared with the effects of the prostacyclin analogues cicaprost and iloprost. Cicaprost, iloprost, BMY 22389 (octimibate), BMY 42393 and BMY 45778 inhibited N-formyl-methionyl-leucyl-phenylalanine (FMLP)-stimulated neutrophil aggregation with IC50 values of 2.1, 4.5, 286, 462 and 20 nM, respectively. Cicaprost and iloprost produced clear concentration-related increases in [3H]cyclic AMP accumulation; EC50 values were 20 and 44 nM, respectively. In contrast, the three BMY compounds showed low efficacy as activators of adenylyl cyclase. The inhibitory effect of prostacyclin mimetics does not appear to depend on effects on intracellular calcium concentration, or on KATP channels. Extensive studies using cyclic AMP mimetics and antagonists suggest that the anti-aggregatory activity of the non-prostanoid prostacyclin mimetics on rat neutrophils may involve highly localized increases in cyclic AMP.

Topics: Acetates; Animals; Calcium; Cell Aggregation; Cyclic AMP; Drug Design; Epoprostenol; Glyburide; Iloprost; Imidazoles; Male; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Oxazoles; Phenoxyacetates; Phosphodiesterase Inhibitors; Prostaglandins, Synthetic; Rats; Rats, Sprague-Dawley; Receptors, Prostaglandin

[3H]PGE2 and [3H]PGF2 alpha were shown to bind with similar binding capacity and dissociation constants to bovine aorta endothelial cells. The similarity in the binding parameters suggests that both agonists may bind to the same binding site. Displacement of [3H]PGE2 performed with PGE2, PGF2 alpha or U-46619, a thromboxane agonist, shows that all three prostanoids displaced the bound [3H]PGE2 with comparable potency (IC50 = 10(-7) M). These results indicated that the three different prostanoids, which serve as specific agonists to different prostanoid receptors, also compete for the same binding site in bovine endothelial cells with similar affinity. Comparison of the displacement of [3H]PGE2 or [3H]PGF2 alpha by a number of prostaglandin agonists and antagonists further supports the notion that the natural prostanoids bind with similar affinities to the same binding site. Thus, sulprostone, an EP1/EP3 agonist, displaced bound [3H]PGE2 and [3H]PGF2 alpha with IC50 of about 10(-7) M. On the other hand, thromboxane antagonists (BAY u-3405 and GR-32191B), EP1 specific antagonist (SC-19220) EP1/DP antagonist (AH-6809) and iloprost, a stable prostacyclin agonist, failed to displace bound [3H]PGE2 or [3H]PGF2 alpha at a concentration range of 10(-9)-10(-6) M. Gradual increase of sodium fluoride (NaF), a general activator of G binding proteins, or incubation of permeabilized cells with GTP gamma S resulted in a decrease in [3H]PGE2 binding, suggesting that the binding site represents a low-affinity common prostanoid receptor which, similar to other prostanoid receptors, is probably coupled with G binding proteins.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aorta; Binding Sites; Biphenyl Compounds; Carbazoles; Cattle; Cells, Cultured; Dibenz(b,f)(1,4)oxazepine-10(11H)-carboxylic acid, 8-chloro-, 2-acetylhydrazide; Dinoprostone; Endothelium, Vascular; Epoprostenol; Heptanoic Acids; Iloprost; Prostaglandin Endoperoxides, Synthetic; Prostaglandins; Sulfonamides; Thromboxane A2; Thromboxanes; Xanthenes; Xanthones

We have investigated the regulatory role of PGI2 and its stable analogs, i.e., iloprost and cicaprost, on 12(S)-HETE- and TPA-enhanced tumor cell integrin expression and adhesion. Walker 256 carcinosarcoma cells express alpha IIb beta 3 integrin receptors, which mediate their adhesion to endothelium, subendothelial matrix and fibronectin. Adhesion is enhanced by treatment with exogenous 12(S)-HETE but not 12(R)-HETE or other lipoxygenase-derived hydroxy fatty acids, as well as by TPA. Both 12(S)-HETE and TPA enhanced alpha IIb beta 3 expression on W256 cells. PGI2 iloprost and cicaprost inhibited both 12(S)-HETE- and TPA-enhanced adhesion to endothelium and subendothelial matrix as well as alpha IIb beta 3 expression on W256 cells. The mechanism responsible for the effect of PGI2 was explored. Prostacyclin treatment of W256 cells resulted in an enhanced production of cAMP in a time- and dose-dependent manner. Pre-treatment of tumor cells with increasing concentrations of adenosine resulted in a dose-dependent decrease in the PGI2 effect on TPA or 12(S)-HETE-enhanced adhesion, suggesting that the PGI2 effect is mediated through PKA. Dibutyryl cAMP also blocked the 12(S)-HETE- or TPA-enhanced adhesion, and adenosine pre-treatment did not result in an inhibition of the dibutyryl cAMP effect. Collectively, our results suggest that the cyclooxygenase metabolite PGI2 can antagonize the lipoxygenase metabolite 12(S)-HETE- and TPA-enhanced alpha IIb beta 3 expression and tumor cell adhesion via activation of adenylate cyclase and elevation of intracellular levels of cAMP.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Adenylyl Cyclases; Animals; Antineoplastic Agents; Cell Adhesion; Cyclic AMP; Epoprostenol; Hydroxyeicosatetraenoic Acids; Iloprost; In Vitro Techniques; Integrins; Rats; Rats, Sprague-Dawley; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

The group of prostaglandin (PG) E2- and prostacyclin receptors consists of different subtypes, which exhibit different affinities for prostaglandins and synthetic analogues. PGE2 activities the E-type PG receptor subtypes EP1, EP2 and EP3, whereas the PGE2 analogue, sulprostone, binds only to the EP1 and EP3 receptor subtypes. The stable PGI2 analogues, iloprost and cicaprost, both activate the PGI2 receptor (IP) and iloprost, additionally, bind to the EP1 subtype. Using these subtype-selective PG receptor agonists, we studied the interaction of PG receptor subtypes with Gs and Gi-type heterotrimeric guanine nucleotide-binding proteins (G proteins) in membranes from the human erythroleukaemia cell line, HEL. Sulprostone stimulated high-affinity GTPase in HEL membranes in a pertussis toxin (PTX)-sensitive manner. In contrast, the stimulations induced by PGE2, iloprost and cicaprost were only partially inhibited by PTX. PGE2, sulprostone, iloprost and cicaprost stimulated cholera toxin-catalysed ADP-ribosylation as well as labelling with GTP azidoanilide of membrane proteins comigrating with immunologically identified Gi protein alpha subunits. Furthermore, PGE2, iloprost and cicaprost enhanced GTP azidoanilide-labelling of Gs protein alpha subunits, whereas sulprostone did not. We suggest that in HEL cells (1) EP1 and EP3 receptor subtypes activate G1 proteins, that (2) the EP2 receptor subtype activates Gs proteins and that (3) the IP receptor activates both Gi and Gs proteins.

Topics: Cell Membrane; Dinoprostone; Epoprostenol; GTP-Binding Proteins; Humans; Iloprost; Leukemia, Erythroblastic, Acute; Prostaglandins E; Receptors, Epoprostenol; Receptors, Prostaglandin; Receptors, Prostaglandin E; Signal Transduction; Tumor Cells, Cultured

A new method is introduced admitting of direct quantification of collagen-induced platelet trapping in the rat lung. The synthetic PG1(2)-mimetics, Iloprost and Cicaprost, are capable of inhibiting the trapping of platelets induced by collagen. The described method has proved to be suited for performing both pharmacodynamic and effectkinetic investigations with inhibitors of collagen-induced platelet trapping.

Topics: Administration, Oral; Animals; Blood Platelets; Collagen; Epoprostenol; Female; Iloprost; Lung; Male; Platelet Aggregation; Rats; Rats, Wistar; Thrombosis

Previous studies have shown that prostacyclin analogs can inhibit the expression of tissue factor (TF) procoagulant activity by human monocytes. The present studies have investigated this phenomenon further, by using a plasma coagulation assay to measure cellular TF activity, an immunoassay to measure TF antigen and reverse transcription/polymerase chain reaction with appropriate oligomer primers to measure TF mRNA. Iloprost and cicaprost inhibited lipopolysaccharide-induced increases in TF activity, antigen and mRNA (50% inhibition, 2-8 nM), with no apparent effect on TF mRNA stability. These agents therefore act at or before the level of transcription of the TF gene. The analogs were more potent inhibitors of tumor necrosis factor-alpha synthesis (50% inhibition at 334 +/- 40 pM cicaprost or 846 +/- 182 pM iloprost) and extraordinarily potent when combined with a phosphodiesterase inhibitor (50% inhibition at 101 +/- 31 pM iloprost in the presence of 20 microM isobutylmethylxanthine). Iloprost and cicaprost were less potent in inhibiting the synthesis of interleukin-1 beta (50% inhibition, 50-100 nM). Cicaprost inhibited lipopolysaccharide-induced increases in mRNA levels for TF, tumor necrosis factor-alpha and interleukin-1 beta; differential potency was again observed. We conclude that these three important monocyte functions can be down-regulated by prostacyclin analogs, and with differential sensitivity. Furthermore, the extreme sensitivity of tumor necrosis factor-alpha synthesis to inhibition suggests that such inhibition may be a major physiological function of prostacyclin itself.

Topics: 1-Methyl-3-isobutylxanthine; Base Sequence; Cyclic AMP; Epoprostenol; Humans; Iloprost; Interleukin-1; Molecular Sequence Data; Monocytes; RNA, Messenger; Thromboplastin; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

Cica-, eptalo- and iloprost are chemically and metabolically stabilized derivatives of prostacyclin which maintain the pharmacodynamic profile of the endogenous precursor. While iloprost is still subject to beta-oxidative degradation of the upper side chain, cicaprost is highly metabolically stable. Eptaloprost was synthesized to realize the pro-drug concept in PGI2-mimetics and was designed to be activated to cicaprost by single beta-oxidation. All three prostacyclin-mimetics were studied in various animal species (mouse, rat, rabbit, monkey, dog and pig) and in man to determine their pharmacokinetic profiles. Based upon this data, it was of interest whether an inter-species extrapolation of pharmacokinetic parameters can be performed to show the predictive value of animal experimentation. Allometric inter-species extrapolation is performed by modelling pharmacokinetic data (Y) as exponential functions (x) of species characteristics (e.g. body weight, W) as: Y = .aWx. For total clearance and volumes of distribution at steady state, a clear-cut correlation with x-values of 0.6-0.8 and 1.0-1.1 could be shown for all three compounds. For cicaprost, which was excreted unchanged in several species, renal and non-renal clearance was also mathematically scalable. Due to the use of different compartment models to describe plasma disposition, different sets of half-life data were obtained and could not be extrapolated reasonably. However, mean residence time showed a dependency on body weight with 0.25 as power function. In case of cicaprost, only the dog, which extensively metabolizes the compound, could not be enrolled in inter-species extrapolation. Excretion half-lives or residence times did not show a significant correlation to body weight or maximum life time potential. The present inter-species extrapolation showed a dependency from species body weight for model-independent pharmacokinetic data, e.g. clearance, volume of distribution at steady state and correspondingly mean residence time. The disposition profile of these compounds can therefore be predicted. Preliminary information on bio-degradation is an additional prerequisite for extrapolation. These data demonstrate that basic physiologically determined processes, which show some evolutionary allometric dependency, also influence the disposition of prostacyclin-mimetics. An extrapolation of data from animal to man could easily be realized giving additional justification for animal studies in pharmaco

Topics: Animals; Dogs; Epoprostenol; Half-Life; Haplorhini; Humans; Iloprost; Mice; Molecular Mimicry; Rabbits; Rats; Species Specificity; Swine

Free flap transplantations and replantations of extremities are threatened by venous occlusion in the postoperative course. In rats, free autogenous groin flaps were transplanted to the neck using microsurgical techniques. On the first postoperative day, the draining vein of the flap was temporarily clamped. In the control group there was always a total loss of the flaps by haemorrhagic necrosis. The intraarterial flap perfusion by iloprost during the clamping was able to diminish the ischaemic effects; 80% of the flaps survived. The systemic application of iloprost by intravenous infusion reduced the ischaemic effects in a similar way. Serious complications such as intraabdominal bleeding or bleeding in the donor area were seen after intravenous administration. Cicaprost had a similar protective effect on flap ischaemia after intravenous infusion. Flap survival was comparable to iloprost. Severe complications seemed to be less. Prostacyclin analogues were able to diminish damage of secondary ischaemia caused by venous occlusion.

Topics: Animals; Epoprostenol; Iloprost; Ischemia; Microsurgery; Rats; Surgical Flaps; Tissue Survival; Transplantation, Autologous

Interleukin-6 (IL-6) is a cytokine involved in the differentiation of B-cells to antibody secreting plasma cells, the activation of T-cells, and the stimulation of hepatocyte production of acute phase proteins. Because of the pro-inflammatory effects of this cytokine, we investigated the ability of the fatty acid arachidonic acid (AA) to regulate the release of IL-6 from rat resident peritoneal macrophages (M phi) in vitro. AA (0.5-16 microM) stimulated IL-6 release during a 4 h incubation period in a biphasic manner, with 4 microM AA generating a peak of IL-6 release (3-5-fold). AA (0.5-16 microM) also induced an increasing release of the AA metabolite thromboxane B2 (TXB2). The AA-induced release of IL-6 occurred within 1-2 h of incubation, whereas TXB2 concentrations were elevated within 5 min of AA treatment. The TX synthetase inhibitor CGS 12970 (4.0 microM and 40.0 microM) effectively blocked the generation of TXB2, but increased prostacyclin (PGI2) generation and potentiated the release of IL-6. In addition, PGI2, as well as the PGI2 agonists iloprost and cicaprost, stimulated IL-6 release from M phi by greater than 5-fold over vehicle-treated basal levels. These data suggest that PGI2 (but not TXA2) is involved in AA-induced IL-6 release from peritoneal M phi.

Topics: Animals; Arachidonic Acid; Epoprostenol; Iloprost; In Vitro Techniques; Interleukin-6; Kinetics; Macrophages, Peritoneal; Male; Prostaglandins, Synthetic; Pyridines; Rats; Thromboxane A2; Thromboxane-A Synthase

Eptaloprost is a novel concept PGI2-mimetic, which is designed to be activated to the pharmacologically potent cicaprost via beta-oxidation. By pro-drug formation advantages in terms of sustained delivery of prostacyclin-mimetic activity were envisaged. The active metabolite is known to be metabolically stable and highly pharmacologically potent. In the present set of experiments the pharmacokinetics of eptaloprost was studied in rat, monkey and man by i.v. and ig administration of tritiated compound. Eptaloprost was completely and rapidly absorbed in all three species. Peak plasma levels of the parent compound were observed within 30 min postdose. Total clearance of the pro-drug accounted for 170, 62 and 66 ml/min/kg in rat, monkey and man. Disposition of eptaloprost exhibited half-lives of 0.1 to 0.5 h and mean residence times accounted for 0.15, 0.4 and 0.6 h in the three species. The active metabolite cicaprost was present in the central compartment with a slight delay as compared to eptaloprost. Its peak plasma levels were found within 0.25 to 0.5 h postdose. Disposition of radiolabel in plasma and 3H-excretion with the urine and feces was determined by the pharmacokinetic behaviour of cicaprost. In rats excretion was mainly biliary while monkeys and man excreted almost unchanged cicaprost in equal portions with urine and feces. Half-lives of renal excretion were in the range of terminal half-lives in the central compartment. Neither in animals nor in man eptaloprost administration resulted in an advantageous systemic profile of cicaprost. On the contrary the bioavailable dose fraction of cicaprost was lower as compared to cicaprost administration. A delay or an extension of cicaprost plasma levels was not observed. The present pharmacokinetic data of eptaloprost studied in three species demonstrated that a pro-drug concept based on simple beta-oxidative bioactivation could be successfully realized for a special PGI2-mimetic. An advantage resulting from oral pro-drug administration as compared to direct treatment with the active metabolite could not be shown. For long-lasting plasma levels of cicaprost a chemically determined retardation might require a more sophisticated pro-drug concept or alternatively pharmaceutical technology is required.

Topics: Absorption; Aged; Animals; Biotransformation; Epoprostenol; Feces; Female; Half-Life; Humans; Iloprost; Kinetics; Macaca fascicularis; Male; Middle Aged; Rats; Rats, Wistar; Species Specificity; Tritium

In the human erythroleukemia cell line, HEL, prostaglandin E2 (PGE2) and the stable prostacyclin analogue, iloprost, increase cytosolic Ca2+ concentration ([Ca2+]i) via pertussis toxin-sensitive and -insensitive pathways. Unlike iloprost, the stable prostacyclin analogue cicaprost (ZK 96480), is devoid of agonistic properties at prostaglandin E2 receptors. We compared the effects of cicaprost, iloprost and PGE2 on [Ca2+]i in HEL cells. Cicaprost, iloprost and PGE2 were similarly potent to increase [Ca2+]i in HEL cells. However, unlike the effects of PGE2, those of the prostacyclin analogues were not inhibited by pertussis toxin. The prostaglandins studied increased [Ca2+]i through both mobilization from internal stores and Ca2+ influx from the extracellular space. Prostacyclin analogue- and PGE2-induced rises in [Ca2+]i were desensitized in a homologous manner. Additionally, there was cross-desensitization between cicaprost and iloprost, but not between the prostacyclin analogues and PGE2. Our data suggest that in HEL cells (i) cicaprost and iloprost act through prostacyclin receptors and (ii) that these receptors couple to pertussis toxin-insensitive heterotrimeric regulatory guanine nucleotide-binding proteins, (iii) resulting in an increase in [Ca2+]i by Ca2+ mobilization from internal stores and sustained influx.

Topics: Calcium; Cytosol; Dinoprostone; Epoprostenol; GTP-Binding Proteins; Humans; Iloprost; Kinetics; Leukemia, Erythroblastic, Acute; Pertussis Toxin; Tumor Cells, Cultured; Virulence Factors, Bordetella

Iloprost and cicaprost are two PGI2-mimetics, which are chemically stable and highly pharmacologically potent. Both compounds differ by their susceptibility to metabolic degradation. While iloprost contains a pentanoic acid upper side chain, which is subject to beta-oxidative degradation, cicaprost is metabolically stabilized by the introduction of an oxygen atom at position 3 of the pentanoic acid chain, preventing beta-oxidation. Both compounds have been characterized concerning their pharmacological and pharmacokinetic profile in a number of animal species and in man. In the present set of experiments both drugs were characterized in terms of pharmacokinetics in mice, an animal species quite routinely used in long-term toxicity studies on cancerogenicity, by iv and ig administration of 0.2 mg/kg (iloprost) and 0.01 mg/kg (cicaprost) using tritiated substances. Iloprost was rapidly inactivated after iv dosing with plasma levels declining from 247 to 0.27 ng/ml within 60 min. Disposition half-lives were 3 and 14 min. Total clerance accounted for 152 ml/min/kg. Total radiolabel exhibited a clearance of 35 ml/min/kg, its AUC in plasma was 146 ng-equiv.h/ml. After ig administration Iloprost peak plasma levels of 9.2 ng/ml occurred after 5 min. Bioavailability was 10%. AUC of total radiolabel was 152 ng-equiv.h/ml, showing complete absorption. Excretion of 3H-label was 41%/57% of dose (iv) and 36%/47% o.d. (ig) with the urine and 32%/18% o.d. (iv) and 36%/25% o.d. (ig) in male/female animals and proceeded for > 90% of dose fraction recovered with half-lives of 0.2-0.3 d. Metabolic patterns revealed the known profile consisting of unchanged drug, dinor- and tetranor-metabolites in plasma and mainly, tetranor-products in urine and feces. After iv dosing of cicaprost total radiolabel plasma levels declined biphasically with half-lives of approx. 0.05 h and 0.31 h. Extrapolated AUC was 1.6 ng-equiv. h/ml and total clearance accounted for 108 ml/min/kg. After ig treatment peak radioactivity plasma levels of 0.7 and 1 ng-equiv./ml were observed at 0.16 and 1 h postdose, probably due to differences between animal groups. Extrapolated AUC was 1 ng-equiv.h/ml. Excretion of 3H-label was mainly biliary: With the feces 83%/89% o.d. (iv) and 93%/92% o.d. (ig) were excreted by male/female animals, while 8.3%/5.7% o.d. (iv) and 2.6%/5.5% were recovered in the urine. More than 90% of the excreted radiolabel was found in samples collected up to 24 h postdose. Metabolic patte

Topics: Animals; Biological Availability; Epoprostenol; Female; Iloprost; Male; Metabolic Clearance Rate; Mice; Mice, Inbred Strains; Rats; Species Specificity

Increased expression of tissue factor procoagulant by peripheral blood monocytes has been implicated in a number of thrombotic disorders. The present studies were undertaken to determine whether stable analogues of prostacyclin, a potent endothelium-derived platelet inhibitor and vasodilator, could inhibit tissue factor expression by human monocytic cells. Exposure of monocytic tumor THP-1 cells to 100 ng/ml endotoxin, 2 units/ml interleukin-1 beta, or 5 ng/ml tumor necrosis factor-alpha for 4 hours led to increased tissue factor procoagulant activity. Preincubation for 30 minutes with iloprost, ciprostene, and carbacyclin led to a dose-dependent inhibition of tissue factor expression induced by all three challenging agents. Iloprost was the most potent: 50% inhibition occurred at 5 nM, a concentration close to the reported dissociation constant for iloprost binding to the platelet prostacyclin receptor. An orally active analogue, cicaprost, was equally effective against endotoxin-induced tissue factor expression. Carbacyclin and ciprostene were 100 times less potent. Iloprost prevented the endotoxin-induced expression of tissue factor antigen on the surface of THP-1 cells, as determined by flow cytometry. Iloprost (500 pM-50 nM) increased intracellular levels of cyclic AMP. This effect was potentiated by isobutylmethylxanthine, an inhibitor of phosphodiesterase. The inhibitory effects of iloprost on tissue factor expression were also potentiated by isobutylmethylxanthine and mimicked by forskolin and dibutyryl cyclic AMP but not dibutyryl cyclic GMP. These results suggest that prostacyclin may play a role in downregulating tissue factor expression in monocytes, at least in part via elevation of intracellular levels of cyclic AMP.

Topics: 1-Methyl-3-isobutylxanthine; Bucladesine; Colforsin; Cyclic AMP; Endotoxins; Epoprostenol; Fluorescent Antibody Technique; Humans; Iloprost; Interleukin-1; Monocytes; Prostaglandins, Synthetic; Thromboplastin; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

We have compared the effects of prostacyclin (PGI2) and its stable analogs, Iloprost and Cicaprost, on cyclic AMP metabolism in intact platelets. All three compounds show similar but not identical patterns of prostaglandin concentration-dependent cyclic AMP formation. All three compounds apparently stimulate and inhibit cyclic AMP formation with different concentration dependencies, indicating the presence of distinct stimulatory and inhibitory receptors. Differences in response can be accounted for by slight differences in affinity of stimulatory and inhibitory receptors for the prostaglandins, by the fact that Iloprost contains almost 50% of a relatively inactive isomer, and by the fact that PGI2 is labile in aqueous solution, with a half-life on the order of a few minutes. We conclude 1) stimulation and inhibition of adenylate cyclase is not due to separate effects of 16S- and 16R-stereoisomers of Iloprost because similar patterns were obtained with a single isomeric form of Cicaprost and with authentic PGI2; 2) prostaglandin induced inhibition of adenylate cyclase is readily reversible because inhibition disappears when PGI2 concentration decays below saturation of the inhibitory receptor; 3) the potency of prostaglandins in stimulating platelet adenylate cyclase must be viewed in terms of their effects on both stimulatory and inhibitory receptors.

Topics: Blood Platelets; Cyclic AMP; Epoprostenol; Humans; Iloprost

Topics: Animals; Antineoplastic Agents; Epoprostenol; Female; Iloprost; Mice; Neoplasm Metastasis; Platelet Aggregation

Topics: Alprostadil; Blood Platelets; Cell Separation; Epoprostenol; Humans; Iloprost; In Vitro Techniques; Platelet Aggregation; Platelet-Derived Growth Factor; Prostaglandin D2; Prostaglandins

Transient incomplete cerebral ischemia (oligemia) has been obtained in rats by associating mild systemic hypotension with bilateral carotid artery occlusion for 60 min. Continuous i.v drug administration for 3 days, performed with Alzet osmotic minipumps so that to deliver 167 ng.kg-1.min-1 Iloprost, 5 ng.kg-1.min-1 ZK 96480 or their respective vehicle, started 1 hour post-oligemia. Both compounds which are stable prostacyclin analogues reduced the edematous reaction and the post-oligemic accumulation of calcium in the brain tissue but above all they improved, mainly ZK 96480, the learning capacity of injured animals. These results indicate that regarding its therapeutic effect toward early consequences of a transient cerebral oligemia, ZK 96480 has the same profile as Iloprost at a dose 20-fold lower. Thus, these data encourage further clinical studies, in ischemic stroke, in which PGI2 and Iloprost have been shown promising.

Topics: Animals; Brain; Calcium; Epoprostenol; Iloprost; Ischemic Attack, Transient; Learning; Male; Memory; Potassium; Prostaglandins, Synthetic; Rats; Rats, Inbred Strains; Vasodilator Agents; Water

The effects of PGI2 and two analogs Iloprost and ZK 96480 were examined on isolated human pulmonary muscle preparations. High concentrations of these agents reduced the basal tone in all types of preparations. In addition, they relaxed tissues which had been maximally contracted with histamine (50 microM). PGI2 was more potent on pulmonary arterial muscle preparations (pD2 value: 6.33, n = 3) than on bronchial muscles. The relaxations induced by PGI2 in bronchial preparations were quite variable, that is, some tissues relaxed while others did not. The analogs also relaxed arterial preparations and the pD2 values were approximately the same (Iloprost: 7.42, n = 4 and ZK 96480: 7.48, n = 4). The isolated human pulmonary vascular preparations were approximately 10-fold more sensitive to the analogs than bronchial muscle preparations. In bronchial tissues we noted that the PGI2 relaxant effect was spontaneously reversed with time, an activity not observed with both analogs. A pretreatment of the bronchial tissues with indomethacin (1.7 microM) did not reduce the variations observed with PGI2 nor modify the transient relaxation observed with this agent. These data demonstrate that vascular tissues from the human lung are considerably more sensitive to these relaxant agonists than bronchial preparations.

Topics: Bronchi; Epoprostenol; Histamine; Humans; Iloprost; Indomethacin; Lung; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Pulmonary Artery; Pulmonary Veins; Serotonin

Topics: Administration, Oral; Animals; Binding, Competitive; Blood Pressure; Epoprostenol; Heart Rate; Humans; Iloprost; In Vitro Techniques; Platelet Aggregation; Rats; Receptors, Epoprostenol; Receptors, Prostaglandin

The agonist activities of a range of prostaglandin analogues on smooth muscle preparations sensitive to prostaglandin E2 (PGE2) have been investigated. When necessary thromboxane-like activity was eliminated using the thromboxane receptor antagonists EP 045 and EP 092. On the bullock iris sphincter, rat stomach fundus and guinea-pig trachea, (+/-) omega-tetranor-16-p-chlorophenoxy PGE2 (ICI 80205) and 16,16-dimethyl PGE2 were more active contractile agents than PGE2, whereas for relaxant activity on the cat trachea, guinea-pig trachea and dog hind limb arterial vessels in vivo the order of potency was reversed. 11-Deoxy PGE1 exhibited greater relaxant than contractile activity when compared to PGE2. Iloprost and 6a-carba-delta 6,6aPGI1 (potent mimetics of PGI2) showed high contractile activity on the PGE-sensitive preparations. PGI2 was less active and another potent PGI2 mimetic, ZK 96480, showed only very weak activity. When tested, the dibenzoxazepines SC 19220 and SC 25191 blocked the contractile actions of iloprost and 6a-carba-delta 6,6aPGI1 and those of PGE2 and 16,16-dimethyl PGE2 to similar extents. Each of the PGI2 analogues showed weak activity on the relaxant systems. On the proximal portion of the ascending colon of the rat, PGI2, iloprost, 6a-carba-delta 6,6aPGI1 and ZK 96480 always inhibited spontaneous activity at nanomolar concentrations. PGE2 and PGE1 showed weak contractile activity. The distal portion of the ascending colon was more responsive to the contractile action of PGE analogues: both iloprost and 6a-carba-delta 6,6aPGI1 showed evidence of contractile activity, whereas PGI2 and ZK 96480 always inhibited spontaneous activity. Evidence was obtained that the rat stomach fundus also contains a PGF receptor; (+/-) omega-tetranor-16-m-trifluoromethylphenoxy PGF2 alpha (ICI 81008) acted as a specific agonist. PGF2 alpha and its omega-tetranor-16-p-fluorophenoxy analogue produced a higher maximum response that ICI 81008 probably due to their additional agonist action at the PGE receptor. The data support the hypothesis that there are two subtypes of the PGE receptor. ZK 96480 has minimal activity on both receptor subtypes and appears to be a highly specific PGI2 mimetic.

Topics: Animals; Cats; Colon; Dibenz(b,f)(1,4)oxazepine-10(11H)-carboxylic acid, 8-chloro-, 2-acetylhydrazide; Dogs; Dose-Response Relationship, Drug; Epoprostenol; Female; Gastric Fundus; Guinea Pigs; Hindlimb; Iloprost; In Vitro Techniques; Iris; Male; Muscle Contraction; Muscle, Smooth; Prostaglandins E; Prostaglandins F; Prostaglandins F, Synthetic; Prostaglandins, Synthetic; Rats; Receptors, Cell Surface; Receptors, Prostaglandin; Trachea

Iloprost (ILO) and ZK 96 480 (96 480) are stable prostacyclin (PGI2) analogues with platelet aggregation-inhibiting and hypotensive activities equal or superior to PGI2 which in contrast to PGI2 show longlasting pharmacological effects also after oral application. PGI2 as well as ILO and 96 480 with i.v. infusion at equihypotensive doses in rats after coronary artery ligation reduce ventricular ectopic beats, markedly reduce or abolish the periods of ventricular tachycardia and entirely prevent ventricular fibrilloflutter. Even nonhypotensive doses of the prostanoids attenuate postligation arrhythmias. Catecholamine depletion by reserpine pretreatment also markedly reduced the incidence of arrhythmias. As PGI2 and ILO have previously been shown by others to preserve noradrenaline content of sympathetic nerve terminals in ischemic myocardium, prevention of excessive catecholamine loss from hypoxically compromised sympathetic nerve terminals might be involved in the antiarrhythmic action of PGI2, ILO and 96 480.

Topics: Adenosine Diphosphate; Animals; Arrhythmias, Cardiac; Blood Pressure; Cardiovascular Agents; Epoprostenol; Iloprost; Lidocaine; Platelet Aggregation; Rats; Rats, Inbred SHR; Reserpine