F 16915 prevents heart failure-induced atrial fibrillation: a promising new drug as upstream therapy.

Atrial fibrillation (AF) is a common complication of heart failure. The aim of the present study was to investigate the effects of a new pure docosahexaenoic acid derivative called F 16915 in experimental models of heart failure-induced atria dysfunction. The atrial dysfunction-induced AF was investigated (1) in a dog model of tachypacing-induced congestive heart failure and (2) in a rat model of heart failure induced by occlusion of left descending coronary artery and 2 months reperfusion. F 16915 (5 g/day for 4 weeks) significantly reduced the mean duration of AF induced by burst pacing in the dog model (989 ± 111 s in the vehicle group to 79 ± 59 s with F 16915, P < 0.01). This dose of F 16915 also significantly reduced the incidence of sustained AF (5/5 dogs in the vehicle group versus 1/5 with F 16915, P < 0.05). In the rat model, the percentage of shortening fraction in the F 16915 group (100 mg/kg p.o. daily) was significantly restored after 2 months (32.6 ± 7.4 %, n = 9 vs 17.6 ± 3.4 %, n = 9 in the vehicle group, P < 0.01). F 16915 also reduced the de-phosphorylation of connexin43 from atria tissue. The present results show that treatment with F 16915 reduced the heart dilation, resynchronized the gap junction activity, and reduced the AF duration in models of heart failure. Thus, F 16915 constitutes a promising new drug as upstream therapy for the treatment of AF in patients with heart failure.

Protease-activated receptor-1 antagonist F 16618 reduces arterial restenosis by down-regulation of tumor necrosis factor α and matrix metalloproteinase 7 expression, migration, and proliferation of vascular smooth muscle cells.

Wound healing after angioplasty or stenting is associated with increased production of thrombin and the activation of protease-activated receptor 1 (PAR1). The aim of the present study was to examine the effects of a new selective PAR1 antagonist, 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)-penta-1,3-dienyl]-benzonitrile (F 16618), in restenosis and vascular smooth muscle cell (SMC) proliferation and migration using both in vivo and in vitro approaches. Daily oral administration of F 16618 inhibited the restenosis induced by balloon angioplasty on rat carotid artery in a dose-dependent manner. Furthermore, single intravenous administration of F 16618 during the angioplasty procedure was sufficient to protect the carotid artery against restenosis. In vitro, F 16618 inhibited the growth of human aortic SMCs in a concentration-dependent manner with maximal effects at 10 µM. At that concentration, F 16618 also prevented thrombin-mediated SMC migration. In vivo, oral and intravenous F 16618 treatments reduced by 30 and 50% the expression of the inflammatory cytokine tumor necrosis factor α (TNFα) 24 h after angioplasty. However, only acute intravenous administration prevented the induction of matrix metalloproteinase 7 expression. In contrast, F 16618 treatments had no effect on early SMC de-differentiation and transcription of monocyte chemoattractant protein-1 and interleukin-6 and late re-endothelialization of injured arteries. Furthermore, F 16618 compensated for the carotid endothelium loss by inhibiting PAR1-mediated contraction. Altogether, these data demonstrate that PAR1 antagonists such as F 16618 are a highly effective treatment of restenosis after vascular injury, by inhibition of TNFα, matrix metalloproteinase 7, and SMC migration and proliferation in addition to an antithrombotic effect.

Protease-activated receptor 1 antagonists prevent platelet aggregation and adhesion without affecting thrombin time.

The aim of this study was to investigate the in vitro antithrombotic effects of two PAR1 antagonists, ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation and on the thrombin time in human and guinea-pig platelets. ER121958 inhibited SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 1.73nM and 2.91nM, respectively and SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 2.74nM and 11.9nM, respectively. Similarly, SCH203099 exhibited a non competitive profile of inhibition on both SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 93nM and 127nM, respectively or SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 1.74microM and 2.36microM, respectively. These two antagonists failed to prolong the thrombin time. Altogether, these results highlighted the potent anti-platelets properties of both ER121958 and SCH203099 in an in vitro model of aggregation as well as in a static model of adhesion without any effect on the last step of coagulation cascade. Moreover, this work emphasized that guinea-pig is a suitable animal model to study the role of PAR1 antagonists since the magnitude of the effects of ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation were similar in both species.

Antithrombotic activity of F 16618, a new PAR1 antagonist evaluated in extracorporeal arterio-venous shunt in the rat.

The purpose of the present work was the evaluation of the antithrombotic activity of a new PAR1 antagonist, F 16618 in arterio-venous shunt in the rat. Arterial thrombosis was induced by insertion of a silk thread (thrombogenic substrate) into an extracorporeal shunt. F 16618 was administered either by intravenous route (0.63-2.5mg/kg) or by oral route (20-80mg/kg). Oral activity of F 16618 was compared to that of aspirin (20-80mg/kg) and clopidogrel (0.63-10mg/kg). Finally, F 16618 was associated to aspirin and/or clopidogrel to test for possible antithrombotic activity and its effects on bleeding time. SFLLR-induced human platelet aggregation was evaluated in the presence of F 16618, demonstrating the anti-aggregant activity of this compound. F 16618 (1.25mg/kg) significantly delayed the time leading to occlusion by 52+/-17%, without affecting bleeding time and in absence of hemodynamic effects. F 16618 given orally dose-dependently increased the time to occlusion. The maximal effect was observed at 40mg/kg (984+/-95s versus 644+/-17s in vehicle group). Aspirin and clopidogrel also dose-dependently lengthened time to occlusion, but this effect was associated with an increase of bleeding time. F 16618 (20mg/kg) orally associated with either aspirin (40mg/kg) or with clopidogrel (1.25mg/kg) potentiated the antithrombotic effects of both compounds without further increasing of bleeding time. In conclusion, F 16618 exerted a potent antithrombotic activity by intravenous and oral routes, without affecting bleeding time. Furthermore, the antithrombotic activity was potentiated when combined with aspirin or clopidogrel.

Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo.

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.

Myocardial protection by F 15845, a persistent sodium current blocker, in an ischemia-reperfusion model in the pig.

The specific persistent sodium current blocker F 15845 was tested in two myocardial ischemia-reperfusion models in the pig in order to evaluate its cardioprotective effects. In the first protocol, the left circumflex coronary artery was ligated for 60-min and then reperfused for 48-h. F 15845 (2.5+2.5 and 5+5mg/kg) was administered by i.v. infusion, starting before ischemia to the beginning of reperfusion. The second protocol attempted to evaluate F 15845 (5+5mg/kg) response in a more pathological state of the heart. To this end, a non necrotic ligation of the left circumflex coronary artery was applied for 15 min one week before the actual 60 min occlusion. For both protocols, infarct size was determined at the end of the reperfusion period and was assessed by histochemistry (tetrazolium staining). Plasma levels of biochemical markers (myoglobin and troponin I) were also evaluated. In protocol 1, F 15845 significantly reduced the infarct size by 27+/-3 and 43+/-5% at 2.5+2.5 and 5+5mg/kg, respectively. At 5+5mg/kg, F 15845 decreased plasma levels of myoglobin and cardiac troponin I. In protocol 2, F 15845 (5+5mg/kg) significantly reduced myocardial infarct size by 54+/-15% and lowered the plasma myoglobin and troponin I levels relative to vehicle-treated animals. In conclusion, the highly effective persistent sodium current blocker F 15845 exerts remarkable cardioprotective activities. It reduces both myocardial infarct size and the release of biochemical markers in healthy pigs as well in pigs previously exposed to an ischemic episode.

Na+ currents in cardioprotection: better to be late.

We report the discovery of a selective, potent inhibitor of the late current mediated by the cardiac isoform of the sodium channel (Na(V)1.5). The compound, 3,4-dihydro-N-[(2S)-3-[(2-hydroxy-3-methylphenyl)thio]-2-methylpropyl]-2H-(3R)-1,5-benzoxathiepin-3-amine (2d) (F 15741), blocks the late component of the Na(+) currents and greatly reduces veratridine- or ischemia-induced contracture in isolated tissue and whole heart. The cardioprotective action of 2d was further established in a model of myocardial infarction in the pig in which 2d prevents ischemia-reperfusion damage after 60 min of coronary occlusion and 48 h reperfusion. Under these experimental conditions, only 2d and cariporide reduce infarct size. Remarkably, myocardial protection afforded by 2d occurs in the absence of hemodynamic effects. These data expand the therapeutic potential of late I(Na) blockers and suggest that 2d could be useful in pathologies for which pharmacological treatments are not yet available.

3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5-benzoxathiepine bromhydrate (F 15845) prevents ischemia-induced heart remodeling by reduction of the intracellular Na+ overload.

The present study investigates whether 3-(R)-[3-(2-methoxyphenylthio-2-(S)-methylpropyl]amino-3,4-dihydro-2H-1,5-benzoxathiepine bromhydrate (F 15845), a new, persistent sodium current blocker, can reduce the ischemic Na(+) accumulation and exert short- and long-term cardioprotection after myocardial infarction. First, F 15845 concentration-dependently reduced veratrine-induced diastolic contracture (IC(50) = 0.14 microM) in isolated atria. Second, F 15845 from 1 microM preserved viability in 54.2 +/- 12.5% of isolated cardiomyocytes exposed to lysophosphatidylcholine. Third, the effect of F 15845 on intracellular Na(+) of isolated hearts from control and diabetic db/db mice was monitored using (23)Na-nuclear magnetic resonance spectroscopy. F 15845 (0.3 microM) significantly counteracted [Na(+)](i) increase during no-flow ischemia in control mouse hearts. In diabetic db/db mouse hearts, the reduction in [Na(+)](i) was delayed relative to control. However, it was more marked and maintained upon reperfusion. The cardioprotective properties after myocardial infarction associated with short- (24-h) and long-term (14-day) reperfusion were measured in anesthetized rats. After 24-h reperfusion, F 15845 (5 mg/kg) significantly reduced infarct size (32.4 +/- 1.7% with vehicle and 24.2 +/- 3.4% with F 15845; P < 0.05) and decrease of troponin I levels (524 +/- 93 microg/l with vehicle versus 271 +/- 63 microg/l with F 15845; P < 0.05). It is important that F 15845 limits the long-term expansion of infarct size (35.2 +/- 2.6%, n = 19 versus 46.7 +/- 1.6%, n = 27 in the vehicle group; P < 0.001). Overall, F 15845 attenuates [Na(+)](i) and prevents (or reverses) contractile and biochemical dysfunction in ischemic and remodeling heart. F 15845 constitutes a new generation of cardioprotective agent.

Effects of a new PAR1 antagonist, F 16618, on smooth muscle cell contraction.

This study evaluated the effects of two PAR1 antagonists on vessels contracted by SFLLR. ER 121958 antagonized the SFLLR-induced contraction on rat denuded superior mesenteric artery and pig coronary artery in a non-competitive manner (IC(50) values were 22 [7.5-43.6] nM and 2.9 [2.09-4.02] nM, respectively). F 16618 inhibited the SFLLR-induced superior mesenteric arteries and coronary arteries contraction in a competitive manner (pA(2) values of 7.3 and 6.2, respectively). PAR1 antagonists do not affect vessel resting tension or haemodynamic parameters in anaesthetized rats. Thus, PAR1 antagonists could have beneficial effects against vasospasm due to vessel injury.

Sodium late current blockers in ischemia reperfusion: is the bullet magic?

We describe the discovery of the first selective, potent, and voltage-dependent inhibitor of the late current mediated by the cardiac sodium channel Na V1.5. The compound 3,4-dihydro- N-[(2 S)-3-[(2-methoxyphenyl)thio]-2-methylpropyl]-2 H-(3 R)-1,5-benzoxathiepin-3-amine, 2a (F 15845), was identified from a novel family of 3-amino-1,5-benzoxathiepine derivatives. The late sodium current inhibition and antiischemic effects of 2a were studied in various models in vitro and in vivo. In a rabbit model of ischemia-reperfusion, 2a exhibited more potent antiischemic effects than reference compounds KC 12291, ranolazine, and ivabradine. Thus, after a single administration, 2a almost abolished ST segment elevation in response to a transient coronary occlusion. Further, the antiischemic activity of 2a is maintained over a wide range of doses and is not associated with any hemodynamic changes, contrary to conventional antiischemic agents. The unique pharmacological profile of 2a opens new and promising opportunities for the treatment of ischemic heart diseases.

Effects of SM-20550 against myocardial infarction-induced arrhythmias, late infarct expansion, and left ventricular dysfunction.

The aim of the study was to evaluate the cardioprotective and antiarrhythmic effects of intravenous Na+/H+ blockers (cariporide and SM-20550) in a rat model of ischemia and a long period reperfusion (14 days). This model allowed study of the role of Na+/H+ exchanger against late myocardial infarct expansion and left ventricular dysfunction. Each compound was administered 5 min before ischemia. Cariporide (from 0.16 mg/kg) and SM-20550 (from 0.04 mg/kg) significantly and dose-dependently reduced the number of ventricular premature beats during ischemia. The duration of ventricular tachycardia was importantly shortened in the presence of cariporide (0.63 mg/kg) and SM-20550 (0.16 mg/kg). Furthermore, cariporide (0.63 mg/kg) and SM-20550 (from 0.04 mg/kg) significantly reduced the infarct expansion: 43 +/- 2% in the cariporide group and 42 +/- 2% at 0.16 mg/kg SM-20550 versus 48 +/- 1% in the vehicle group. Cariporide and SM-20550 significantly prevented the left ventricular free wall thinning associated with the thickness ratio, suggesting a significant reduction of the ventricular dilation. Cariporide and SM-20550 significantly improved the negative dP/dtmax, suggesting a partial restoration of the cardiac relaxation. Collectively, Na+/H+ blockers administered before ischemia reduced arrhythmias and also prevented the remodeling process of the heart during postinfarction.

Cardioprotection of cariporide evaluated by plasma myoglobin and troponin I in myocardial infarction in pigs.

The cardioprotective effects of cariporide were investigated against myoglobin and troponin I elevation in a model of myocardial infarction in pig, and the possible relationship between these markers and myocardial infarct size. The left circumflex coronary artery was ligated for 60-min and then reperfused for 48-h. Plasma levels of myoglobin and troponin I were quantified during reperfusion. Vehicle or cariporide (2.5 mg/kg) were administered i.v. before ischaemia and infused throughout ischaemia and for the beginning of reperfusion. In vehicle-treated pigs, the infarct size represented 26% +/- 3% of the area at risk. Cariporide significantly decreased the infarct size by 66% +/- 9%, and significantly reduced plasma levels of myoglobin and troponin I. A strongly correlated linear relationship between myocardial necrosis and plasma levels of myoglobin (R = 0.966, P < 0.0001) or troponin I (R = 0.855, P < 0.0001) was clearly identified. In conclusion, in our porcine model of myocardial infarction, even with small infarcts (in the presence of cariporide), plasma levels of myoglobin and troponin I are predictive of the presence of necrosis and its extent.

Pharmacological characterisation of sodium channels in sinoatrial node pacemaking in the rat heart.

Blockade of sodium channels located in the sinoatrial node can slow diastolic depolarisation rate, recorded in vitro. The objective was therefore to determine whether these blockers could slow heart rate in vivo. The heart rate was firstly measured in spontaneously beating, isolated rat heart atria in the presence of different voltage gated sodium channel blockers. Tetrodotoxin and lidocaine slightly reduced heart rate whereas KC 12291 and R 56865, which mainly interact with the persistent component of the sodium current, concentration dependently and potently induced bradycardia. In the pithed rat, tetrodotoxin induced statistically significant decreases heart rate, maximal effects were: -32.2+/-6.1 beat per min. KC 12291 and R 56865 dose-dependently induced bradycardia (Delta heart rate obtained, -55.1+/-5.2 beat per min, P<0.05, and -71.9+/-8.5 bpm, P<0.05, respectively). In conclusion, voltage gated sodium channel blockers rather selective for the persistent current, exert a potent bradycardic effect in the rat.

Donitriptan decreases jugular venous oxygen saturation in rats in the absence of cranial vasoconstriction: an overlooked mechanism of antimigraine action?

The aim of the present study was to determine whether donitriptan and sumatriptan decreased jugular venous oxygen saturation and increased carbon dioxide partial pressure in venous blood. However, previous studies conducted with these compounds cannot discriminate whether the decrease of venous oxygen saturation is dependent of cranial vasoconstrictor. In the present study, vehicle (n = 10), donitriptan (2.5, 10, and 40 microg/kg; n = 8) or sumatriptan (630 microg/kg; n = 8) were infused into the carotid artery in the anesthetized rat. Regional blood flows were evaluated in the presence of donitriptan (10 microg/kg; n = 6) or vehicle (n = 6). Jugular venous oxygen saturation was significantly decreased by donitriptan (from 10 microg/kg) with maximal changes of -32.9 +/- 8.0%. Jugular carbon dioxide partial pressure was increased by donitriptan, reaching maximal changes of 17.7 +/- 4.6% (P < 0.05 versus vehicle). Similarly, sumatriptan significantly decreased venous oxygen saturation and increased jugular carbon dioxide partial pressure. These changes induced by donitriptan are abolished by the 5-hydroxytryptamine (5-HT)(1B/1D) receptor antagonist GR 127935 (N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2-[-methyl-4(5-methyl-1,2,4)-oxadiazol-3-yl]-(1,1 biphenyl)-4-carboxamide dihydrochloride). In addition, donitriptan was devoid of significant effects on systemic arterial pressure, heart rate, or regional blood flows, including systemic arterial-jugular venous anastomotic, systemic, or cranial. The results demonstrate that donitriptan increases cerebral oxygen consumption by 5-HT(1B/1D) receptor activation in the absence of cranial vasoconstriction.

KC 12291: an atypical sodium channel blocker with myocardial antiischemic properties.

KC 12291 was designed as a voltage-gated sodium channel (VGSC) blocker with cardioprotective properties. KC 12291 has moderate inhibitory effects on peak (or rapid) Na+ current, and markedly reduces sustained (or slowly or non-inactivating) Na+ current. This distinguishes KC 12291 from conventional VGSC blockers such as local anesthetics or antiarrhythmics, which have little or no cardioprotective properties. Since VGSCs represent the main pathway for ischemic Na+ loading by failing to inactivate fully, KC 12291 exerts pronounced antiischemic activity principally by reducing the amplitude of sustained Na+ current. In isolated atria and Langendorff-perfused hearts, KC 12291 inhibits diastolic contracture, renowned for its resistance to pharmacological inhibition, reduces ischemic Na+ loading and preserves cardiac energy status. KC 12291 exerts oral antiischemic activity in vivo in the absence of major hemodynamic effects. Cardiac VGSC blockers such as KC 12291, which block cardiac VGSCs in atypical fashion by effectively inhibiting the sustained component of Na+ current, represent, therefore, promising potential antiischemic and cardioprotective drugs.

Investigation of the effects of naratriptan, rizatriptan, and sumatriptan on jugular venous oxygen saturation in anesthetized pigs: implications for their mechanism of acute antimigraine action.

The effects of naratriptan, rizatriptan, and sumatriptan on arteriovenous oxygen saturation difference and carotid hemodynamics were compared in the anesthetized pig. Oxygen and carbon dioxide partial pressures in systemic arterial and jugular venous blood as well as hemoglobin oxygen saturation were determined by conventional blood gas analysis. Vehicle (n = 19) or naratriptan, rizatriptan, or sumatriptan (0.63, 2.5, 10, 40, 160, 630, and 2,500 microg/kg i.v.; n = 7/group) were infused cumulatively. In naratriptan-, rizatriptan-, and sumatriptan-treated animals, jugular venous oxygen saturation decreased dose dependently (geometric mean ED50 values of 3.1, 17.9, and 16.0 microg/kg, respectively) concomitantly with increases in carotid vascular resistance. Rizatriptan significantly and dose dependently, from 160 microg/kg, increased PvCO2 (P < 0.05 versus vehicle). Naratriptan and sumatriptan also tended to increase PvCO2 albeit nonstatistically significantly. All three triptans consistently evoked quantitatively similar carotid vasoconstriction, whereas decreases in jugular venous oxygen saturation (VOS) and increases in PvCO2 had different magnitudes and occurred only in around one-half of the animals studied. Maximal variations in PvCO2 were found to correlate highly with those in PvO2 (P = 0.002), but maximal variations in carotid resistance failed to correlate with those in PvCO2 (P = 0.76) or PvO2 (P = 0.28). The results demonstrate that the triptans investigated robustly produced carotid vasoconstriction, but elicited less consistent decreases in VOS and increases in jugular PvCO2, possibly suggestive of distinct mechanisms. Collectively, the data suggest that triptan-induced increases in arteriovenous oxygen saturation difference and carbon dioxide partial pressure in venous blood draining the head are class effects.

Donitriptan selectively decreases jugular venous oxygen saturation in the anesthetized pig: further insights into its mechanism of action relevant to headache relief.

The effects of donitriptan on systemic arterial-jugular venous oxygen saturation difference were evaluated in pentobarbitone-anesthetized pigs. Oxygen and carbon dioxide partial pressures in systemic arterial and jugular venous blood as well as hemoglobin oxygen saturation were determined by conventional blood gas analysis. Vehicle (40% polyethyleneglycol in saline, n = 9) or donitriptan (0.01, 0.04, 0.16, 0.63, 2.5, 10, and 40 microg/kg, n = 7) were cumulatively infused over 15 min/dose. The involvement of 5-hydroxytryptamine(1B) (5-HT(1B)) receptors was assessed in the presence of the 5-HT(1B/1D) receptor antagonist, GR 127935. Donitriptan decreased markedly and dose dependently jugular venous oxygen saturation [ED(50) 0.5 (0.3-1.1) microg/kg], in parallel with increases in carotid vascular resistance [ED(50) 0.9 (0.7-1.1) microg/kg]. Since arterial oxygen saturation and partial pressure remained unchanged, donitriptan significantly increased arteriovenous oxygen saturation difference from 0.63 microg/kg (maximal variation: 57 +/- 18%, P < 0.05 compared with vehicle). Unexpectedly, donitriptan from 2.5 microg/kg induced marked and significant increases in carbon dioxide partial pressure (pVCO(2)) in venous blood (maximal increase 18.8 +/- 5.7%; P < 0.05 compared with vehicle). Pretreatment with GR 127935 (0.63 mg/kg, n = 5) abolished the fall in venous oxygen saturation and the increase in carotid vascular resistance and reduced the increases in pVCO(2) induced by donitriptan. The results demonstrate that donitriptan, via 5-HT(1B) receptor activation, decreases the oxygen saturation of venous blood draining the head, concomitantly with cranial vasoconstriction. Since donitriptan also increased pVCO(2), an effect upon cerebral oxygen consumption and metabolism is suggested in addition to cranial vasoconstriction, which may be relevant to its headache-relieving effects.