Thromboxane A2 Synthetase Inhibitor Research Articles

Phase I Trial of Pyragrel, a Novel Thromboxane Synthetase Inhibitor, to Evaluate the Safety, Tolerability, and Pharmacokinetics in Healthy Volunteers.

Background and Objective: Inhibition of thrombosis and platelet aggregation through a thromboxane synthetase inhibitor proved to be an effective and promising treatment for cardiovascular and/or cerebrovascular disease (CCVD) patients. This phase I study evaluated the safety, tolerability, and pharmacokinetics of sodium pyragrel, a novel thromboxane A2 synthetase inhibitor, in healthy volunteers. Methods: A total of 84 healthy Chinese volunteers were enrolled in the study and randomized into one of five dosing regimens of intravenous pyragrel, which were single ascending dose (30 to 300 mg), multiple doses (pyragrel 180 mg once daily on Day 1 and Day 6, twice daily from Day 2 to Day 5), 3×3 Latin square crossover (60, 120, 240 mg), and a continuous dose (360 mg in 24 h), respectively. Plasma concentrations were determined using HPLC-MS/MS. Pharmacokinetics parameters were calculated with non-compartment analysis. Results: The maximum plasma concentrations of pyragrel were essentially reached at the end of the 3 h infusion. The pharmacokinetic process of pyragrel and two main metabolites (BBS and BJS) is linear over the 30–300 mg dose range, with no significant accumulation on multiple doses. The urinary excretion of pyragrel accounted for more than 70% of the total drug amount. Preliminary pharmacodynamic results demonstrated that the production of urinary 11-D-HTXB2 was time- and dose-dependently inhibited by single i.v. dose of pyragrel. Conclusions: Pyragrel was well tolerated after single ascending doses up to 300 mg, multiple doses of 180 mg, and continuous administration of 360 mg within 24 h. No drug-related, serious adverse drug reactions occurred during the five-part study. The most common pyragrel-related adverse events (AEs) were total bilirubin (TB)/direct bilirubin (DB) elevations with a relatively low incidence rate and seemed to be dose independent. Given the acceptable safety and appropriate pharmacokinetic properties of sodium pyragrel proven in this study, continued clinical development is warranted. The study was registered at http://www.chictr.org.cn (ChiCTR-IID-16010159).

Simultaneous determination of Pyragrel, a novel anti-thrombotic agent, and its two primary metabolites in plasma by HPLC–MS/MS

Pyragrel is a novel thromboxane A2-synthetase inhibitor for the treatment of cerebral infarction, and it is currently being investigated in phase I clinical trials. This paper reports the first reliable LC–MS/MS method for the simultaneous determination of Pyragrel and its two main metabolites, M1 and M2, in human plasma. All analytes were extracted from human serum using liquid-phase extraction and separated on a Zorbax EcLipse XDB C18 column using isocratic elution with a mobile phase composed of methanol, water and formic acid (65:35:0.1, v/v/v). Determination of the analytes was achieved by tandem-mass spectrometry with positive electrospray ionization. The multiple reaction monitoring transitions under positive electrospray ionization were performed at m/z 329.0 → m/z 135.9 for Pyragrel, m/z 303.1 → m/z 135.0 for M1, m/z 331.2 → m/z 135.0 for M2, and 482.2 → m/z 258.0 for IS, respectively. The following parameters were validated: specificity, recovery, matrix effects, carry-over, linearity, sample stability under a variety of storage and handling conditions, and stock solution stability. The validated method has been successfully applied to an initial pharmacokinetic study in healthy volunteers following intravenous administrations of 60 mg of Pyragrel, and this method will facilitate further studies involving more comprehensive identification of the metabolic profile of Pyragrel and the appropriate dosage regimen.

Poly(hydroxamic acid) palladium catalyst for heck reactions and its application in the synthesis of Ozagrel

Bio-waste corn-cob cellulose supported poly(hydroxamic acid) palladium complex was synthesized and it is characterized using some different techniques such as FTIR, FESEM, HRTEM, EDX, XPS, UV–vis, TGA and ICP-AES analyses. The cellulose supported heterogeneous palladium complex showed high stability and catalytic activity toward Mizoroki-Heck reaction of aryl/heteroaryl halides and arenediazonium tetrafluoroborate with a variety of olefins to give the corresponding coupling products in up to 97% yield. The palladium complex was also applied to the synthesis of Ozagrel a thromboxane A2-synthetase inhibitor with excellent yield. The complex was separated from the reaction mixture by simple filtration and repeatedly used up to seven times without significant loss of its catalytic performance.

Effect of Ozagrel, a Selective Thromboxane A2-Synthetase Inhibitor, on Cerebral Infarction in Rats

The effects of ozagrel (CAS 82571-53-7), a thromboxane A2-synthetase inhibitor, and norphenazone (CAS 89-25-8), a free-radical scavenger, on cerebral infarction were assessed using the suture-induced middle cerebral artery occlusion (MCAO) model and a microthrombosis model. In the former model, the middle cerebral artery was occluded for 2 h, and the infarction area and volume were evaluated 24 h after the start of reperfusion. In the latter model, microthrombosis were induced by two injections of sodium laurate (interval, 2 days) into the internal carotid artery, and the neurologic deficits were evaluated on the day afer the 2nd injection. Ozagrel at 3 mg/kg decreased both the area and volume of the cortical infarction after ischemia-reperfusion of the middle cerebral artery. Ozagrel also had suppressive effects on the neurologic deficits in the microthrombosis model. Norphenazone at 1 and 3 mg/kg had no clear effects in either model. Since the suture-induced MCAO model and the microthrombosis model are models for occlusion-reperfusion of the major cerebral arteries and lacunar infarction, respectively, these results suggest a highly beneficial effect of ozagrel in the clinical therapy for stroke.

Thromboxane A2 Synthetase Inhibitor Plus Low Dose Aspirin : Can It Be a Salvage Treatment in Acute Stroke Beyond Thrombolytic Time Window

There is no proven regimen to reduce the severity of stroke in patients with acute cerebral infarction presenting beyond the thrombolytic time window. Ozagrel sodium, a selective thromboxane A2 synthetase inhibitor, has been known to suppress the development of infarction. The antiplatelet effect is improved when aspirin is used together with a thromboxane synthetase inhibitor. Patients with non-cardiogenic acute ischemic stroke who were not eligible for thrombolysis were randomly assigned to two groups; one group received ozagrel sodium plus 100 mg of aspirin (group 1, n=43) and the other 100 mg of aspirin alone (group 2, n=43). Demographic data, cardiovascular risk factors, initial stroke severity [National Institute of Health Stroke Scale (NIHSS) and motor strength scale] and stroke subtypes were analyzed in each group. Clinical outcomes were analyzed by NIHSS and motor strength scale at 14 days after the onset of stroke. There were no significant differences in the mean age, gender proportion, the prevalence of cardiovascular risk factors, stroke subtypes, and baseline neurological severity between the two groups. However, the clinical outcome for group 1 was much better at 14 days after the onset of stroke compared to group 2 (NIHSS score, p=0.007, Motor strength scale score, p<0.001). There was one case of hemorrhagic transformation in group 1, but there was no statistically significant difference in bleeding tendency between two groups. In this preliminary study, thromboxane A2 synthetase inhibitor plus a low dose of aspirin seems to be safe and has a favorable outcome compared to aspirin alone in patients with acute ischemic stroke who presented beyond the thrombolytic time window.

The effect of leukotriene C4/D4 receptor antagonist (ONO-1078) and thromboxane A2 synthetase inhibitor (OKY-046) on airway hyperresponsiveness induced by ozone exposure in guinea pigs

To clarify the mechanisms of ozone-induced airway hyperresponsiveness, we studied the effect of leukotriene C4/D4 receptor antagonist (ONO-1078) and thromboxane A2 synthetase inhibitor (OKY-046) on airway hyperresponsiveness induced by ozone exposure in guinea pigs. Airway responsiveness to inhaled methacholine was determined in artificially ventilated guinea pigs using a modification of the Konzett-Rössler technique. After the methacholine challenge, bronchoalveolar lavage (BAL) was performed. After 1 hour following ozone exposure (2.9 ppm, 30 min), airway responsiveness increased significantly. There was no cellular change in the bronchoalveolar lavage fluid (BALF). Pretreatment with ONO-1078 (30 mg/kg, i.p.) or OKY-046 (20 mg/kg, i.p.) caused no effect on airway responsiveness before ozone exposure, and inhibited the increase of airway responsiveness induced by ozone exposure. These results suggest that leukotriene and thromboxane play an important role in the development of airway hyperresponsiveness induced by ozone exposure in guinea pigs.

Effects of thromboxane A2 synthetase inhibitor, DP-1904 on the action of vasoactive substances in rabbit blood vessel smooth muscle preparations

Thromboxane A2 (TxA2) is a potent platelet aggregator as well as a vascular and bronchial constrictor. DP-1904, a newly synthesized imidazol TxA2 synthetase inhibitor, is a potent and long-acting agent. The present investigation was conducted to explore the effect of DP-1904 on the contractile responses in rabbit pulmonary artery and descending aorta strips induced by various vasoactive substances. Fourteen Japanese albino rabbits, weighing about 3 kg, were sacrificed. Rabbit pulmonary artery and descending aorta were removed, cut spirally, set up in bioassay glass jackets and superfused with Krebs-Henseleit solution at 37 degrees C, saturated with oxygen and carbon dioxide. Contraction of tissues was detected by an isotonic transducer and displayed on a polyrecorder. Arachidonic acid-induced contractile responses in rabbit pulmonary artery and descending aorta strips were attenuated significantly by the continuous infusion of DP-1904 in a dose-dependent fashion. Prostaglandin F2 alpha-induced contractile responses in rabbit pulmonary artery and descending aorta strips were attenuated significantly by the continuous infusion of DP-1904, dose-dependently. Angiotensin II-induced contractile responses in rabbit pulmonary artery and descending aorta strips were attenuated significantly by the continuous infusion of DP-1904, dose-dependently. Norepinephrine-induced contractile responses in rabbit pulmonary artery and descending aorta strips were attenuated significantly by the continuous infusion of DP-1904, dose-dependently. The above results suggest that DP-1904 might be a useful therapeutic agent for treatment of pulmonary hypertension in patients with chronic obstructive lung diseases.

Pharmacological interventions versus no pharmacological intervention for ischaemia reperfusion injury in liver resection surgery performed under vascular control

Vascular occlusion to reduce blood loss is used during elective liver resection but results in significant ischaemia reperfusion injury. This, in turn, might lead to significant postoperative liver dysfunction and morbidity. Various pharmacological drugs have been used with an intention to ameliorate the ischaemia reperfusion injury in liver resections. To assess the benefits and harms of different pharmacological agents versus no pharmacological interventions to decrease ischaemia reperfusion injury during liver resections where vascular occlusion was performed during the surgery. We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until January 2009. We included randomised clinical trials, irrespective of language or publication status, comparing any pharmacological agent versus placebo or no pharmacological agent during elective liver resections with vascular occlusion. Two authors independently identified trials for inclusion and independently extracted the data. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. We calculated the risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI) based on intention-to-treat analysis or available case analysis. We identified a total of 15 randomised trials evaluating 11 different pharmacological interventions (methylprednisolone, multivitamin antioxidant infusion, vitamin E infusion, amrinone, prostaglandin E1, pentoxifylline, mannitol, trimetazidine, dextrose, allopurinol, and OKY 046 (a thromboxane A2 synthetase inhibitor)). All trials had high risk of bias. There were no significant differences between the groups in mortality, liver failure, or perioperative morbidity. The trimetazidine group had a significantly shorter hospital stay than control (MD -3.00 days; 95% CI -3.57 to -2.43). There were no significant differences in any of the clinically relevant outcomes in the remaining comparisons. Methylprednisolone improved the enzyme markers of liver function and trimetazidine, methylprednisolone, and dextrose reduced the enzyme markers of liver injury compared with controls. However, there is a high risk of type I and type II errors because of the few trials included, the small sample size in each trial, and the risk of bias. Trimetazidine, methylprednisolone, and dextrose may protect against ischaemia reperfusion injury in elective liver resections performed under vascular occlusion, but this is shown in trials with small sample sizes and high risk of bias. The use of these drugs should be restricted to well-designed randomised clinical trials before implementing them in clinical practice.

Impairment of endothelium-dependent ACh-induced relaxation in aorta of diabetic db/db mice—possible dysfunction of receptor and/or receptor–G protein coupling

Diabetes is a risk factor of ischemic heart disease, cerebral ischemia, and atherosclerosis, in which endothelial dysfunction plays a role in the pathogenesis. We examined vascular responses in the aorta of pre-diabetic db/db mice with normoglycemia, hyperlipidemia, and hyperinsulinemia (6 weeks old), and diabetic db/db mice with hyperglycemia, hyperlipidemia, and hyperinsulinemia (11 weeks old) in comparison with age-matched non-diabetic db/+ mice. Prostaglandin F2alpha (PGF2alpha)-induced contraction was significantly enhanced in the aorta of diabetic but not pre-diabetic db/db mice compared to age-matched non-diabetic db/+ mice. Acetylcholine (ACh), adenosine-5'-diphosphate (ADP), NaF, a G protein activator and A-23187, a Ca-ionophore, caused endothelium-dependent and nitric oxide (NO)-mediated relaxation, and sodium nitroprusside (SNP), an NO donor, caused endothelium-independent relaxation in the pre-contracted aorta of db/db mice. Maximal endothelium-dependent ACh-induced relaxation was reduced in diabetic but not pre-diabetic db/db mice compared to age-matched db/+ mice, while maximal SNP-induced relaxation was not different between diabetic and non-diabetic mice. ACh-induced relaxation in diabetic db/db mice was not affected by ozagrel, a thromboxane A2 (TXA2) synthetase inhibitor, or acetylsalicylic acid (aspirin), a cyclooxygenase inhibitor, suggesting no involvement of endogenous TXA2 or prostanoids in the reduction of relaxation. Maximal endothelium-dependent ADP-, A-23187-, and NaF-induced relaxation was not reduced in diabetic db/db mice. EC50 values for ACh- and SNP-induced relaxation were increased in diabetic but not pre-diabetic db/db mice, suggesting decreases in sensitivity to NO in diabetic mice. Two-week treatment with KV-5070, a PPARgamma agonist, lowered plasma glucose, triglyceride (TG), and insulin but not cholesterol, and reversed the reduced ACh-induced relaxation. In conclusion, ACh-induced endothelium-dependent relaxation is impaired in diabetic db/db mice, probably due to the dysfunction of ACh receptors and/or receptor-G protein coupling. Endothelial dysfunction was not genetic and was considered to be initiated primarily by hyperglycemia, and was improved by anti-diabetic treatment with a PPARgamma agonist.

Effect of a selective thromboxane A2 synthetase inhibitor on the systemic changes induced by circulating pancreatic phospholipase A2

In acute pancreatitis, pancreatic phospholipase A(2) (PLA2) in the circulating blood hydrolyzes phospholipids contained in plasma lipoproteins, liberating eicosanoid precursors that are subsequently converted to various eicosanoids. The pathophysiological significance of eicosanoid synthesis via this pathway is unknown. The aim of this study was to clarify the role of thromboxane A(2) (TXA(2)) synthesis by circulating pancreatic PLA(2) in the pathogenesis of the systemic complications of acute pancreatitis. Guinea pigs were divided into two groups: a control group and an ozagrel group, which received intravenous administration of ozagrel, a selective TXA(2) synthetase inhibitor. Pancreatic PLA(2) was infused intravenously in both groups for 30 min, and systemic changes during the infusion were examined. In the control group, there was an increase in plasma thromboxane B(2) (TXB(2)) concentration, a decrease in mean arterial pressure and heart rate, a decrease in arterial base excess (BE), bicarbonate concentration (HCO(3) (-)), and pH, a decrease in platelet count and plasma fibrinogen concentration, and a shortened prothrombin time during the infusion of pancreatic PLA(2). In the ozagrel-treated group, changes in plasma TXB(2) concentration, BE, HCO(3) (-), and platelet count were significantly inhibited. TXA(2) synthesis by circulating pancreatic PLA(2) contributes to metabolic acidosis and thrombocytopenia during acute pancreatitis.

INVOLVEMENT OF ENDOTHELIAL CYCLO‐OXYGENASE METABOLITES IN NORADRENALINE‐INDUCED CONTRACTION OF RAT CORONARY ARTERY

1. Noradrenaline (NA; 0.3 micromol/L) caused a contraction of the rat coronary artery that markedly increased in the presence of the nitric oxide synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME; 100 micromol/L) and arachidonic acid (1 micromol/L; P < 0.05). 2. The present experiments attempted to elucidate the endothelium dependency of the contraction and to pharmacologically characterize the factors involved in the contraction induced by NA (0.3 micromol/L) in the presence of L-NAME and arachidonic acid in ring preparations of the rat coronary artery. 3. The NA (0.3 micromol/L)-induced contraction was attenuated by a chemical remover of the endothelium (saponin at concentrations of 0.1 and 0.4 mg/mL) in a concentration-dependent manner (P < 0.05). 4. The cyclo-oxygenase (COX)-1 inhibitor flurbiprofen (0.01-1 micromol/L) and the COX-2 inhibitor nimesulide (0.01-1 micromol/L) attenuated the NA-induced contraction in a concentration-dependent manner and the inhibitory effect of flurbiprofen was significantly more potent than that of nimesulide (P < 0.05). The 5-lipoxigenase inhibitor ZM-230487 (1 micromol/L) did not affect the NA-induced contraction. 5. The thromboxane A2 (TXA2) synthetase inhibitor OKY-046 (30 micromol/L) and the TXA2 antagonist S-1452 (0.1-10 micromol/L) did not attenuate the NA-induced contraction. 6. These results indicate that the contraction induced by NA in the rat coronary artery in the presence of L-NAME and arachidonic acid is endothelium dependent and is due to endothelial COX metabolites of arachidonic acid.

Noradrenaline-induced contraction mediated by endothelial COX-1 metabolites in the rat coronary artery.

Noradrenaline-induced contraction of the rat coronary arteries was significantly augmented by the presence of NG-nitro-L-arginine methyl ester (L-NAME) and arachidonic acid. The experiments in the study presented here were undertaken to characterize pharmacologically the augmented noradrenaline-induced contraction in ring preparations of rat coronary arteries. The contraction was stopped by a chemical remover of endothelium (saponin). Oxygen radical scavengers, superoxide dismutase and catalase, significantly attenuated the contraction. Cyclooxygenase-1 inhibitors (flurbiprofen, 10(-7) M) attenuated the noradrenaline-induced contraction and cyclooxygenase-2 (nimesulide, 10(-7) M) slightly attenuated the contraction. A thromboxane A2 (TXA2) synthetase inhibitor (OKY-046) and a TXA2 receptor antagonist (S-1452) did not affect the contraction. Based on these results, it was suggested that the contraction induced by noradrenaline in the rat coronary artery in the presence of L-NAME and arachidonic acid is endothelium-dependent, and that it involves reactive oxygen species and endothelial cyclooxygenase-1 metabolites of arachidonic acid.

Effect of TTC-909 in a middle cerebral artery thrombosis model in stroke-prone spontaneously hypertensive rats

We investigated the effect of TTC-909, a preparation of the stable prostaglandin I2 analogue clinprost (isocarbacyclin methylester; methyl 5-{(1S,5S,6R,7R)-7-hydroxy-6-[(E)-(S)-3-hydroxy-1-octenyl] bicyclo[3.3.0]oct-2-en-3-yl} pentanoate) incorporated into lipid microspheres, on infarct volume 24 h after photochemically induced thrombotic occlusion of the middle cerebral artery in stroke-prone spontaneously hypertensive rats (SHR). Under anesthesia, the photosensitizing dye rose bengal (20 mg/kg) was administered intravenously and photoirradiation with green light (wavelength 540 nm) on the middle cerebral artery above the rhinal fissure was achieved using a xenon lamp for 10 min. Infarct volume 24 h after the photochemically induced thrombotic occlusion of the middle cerebral artery was significantly larger in stroke-prone SHR than in Wistar rats. When TTC-909 in doses of 100, 300 and 900 ng/kg/h was intravenously infused for 3 h, starting immediately after the end of the 10-min photoirradiation, the infarct volume was dose-dependently reduced and was statistically significant at a dose of 900 ng/kg/h (p<0.05). Ozagrel, a thromboxane A2 synthetase inhibitor, significantly reduced the infarct volume. The model of photochemically induced thrombotic occlusion of the middle cerebral artery in stroke-prone SHR is very useful, because the cerebral infarction is large enough and reproducible. TTC-909 may be effective for the treatment of acute ischemic stroke.

Semiquantitative dynamic computed tomography to predict response to anti-platelet therapy in acute cerebral infarction.

We investigated whether dynamic computed tomography (CT) in patients with acute cerebral infarction could identify patients likely to respond to anti-platelet therapy. Seventy patients underwent semiquantitative dynamic CT within 6 h as well as cerebral angiography. All then received anti-platelet therapy with a thromboxane A2 synthetase inhibitor. Peak value (pv) and time-to-peak (tp) (time-density curves) for the Sylvian fissure were extracted from dynamic CT data and standardizing interpatient data, two indices, PV/TP index and TP index, were prepared following a standard semiquantitative manner. Both PV/TP index and TP index were effective in discriminating between 48 responders (modified Rankin scale (mRS): 0 to 2) and 22 non-responders (mRS: 3 to 5, or death: 6; both P<0.0001). High PV/TP index (>or=0.8) was a strong indicator of favorable response. Most of these patients maintained regional cerebral blood flow (rCBF) via anterograde flow or collaterals, with a TP index <or=1.1. Low PV/TP index (<or=0.4) predicted non-response associated with increased TP index (>1.1) and non-compensated rCBF. Intermediate PV/TP values could not predict outcome. Dynamic CT prior to therapy can identify patients with acute cerebral infarction who are treatable with anti-platelet therapy alone.

Minimally invasive hepatectomy: Modulation of systemic reactions to operation or laparoscopic approach?

A new concept of surgical stress has been proposed that consists of both aggressiveness of operation and systemic reactions to an operation. We have investigated a possible modulation of such systemic reactions to operation and have demonstrated the following 3 points: (1) coagulation and fibrinolytic systems are independently activated during hepatectomy and such activation can be modulated by protease inhibitors such as nafamostat mesilate and antithrombin III; (2) elevated thromboxane A2 during hepatectomy is characterized in the prostanoid system, the elevation of thromboxane A2 is inhibited by thromboxane A2 synthetase inhibitor, and postoperative liver injury is reduced; (3) cytokine response induced by hepatectomy is modulated by preoperative administration of methylprednisolone, leading to possible prevention of bacterial translocation. Therefore, modulating systemic reactions to hepatectomy may be important for successful minimally invasive hepatectomy. Another important option for minimally invasive hepatectomy is the use of operative procedures such as laparoscope or thoracoscope. We have investigated the usefulness of a laparoscopic hepatectomy from the standpoints of early and long-term outcome after hepatectomy. Laparoscopic hepatectomy, which is a difficult and dangerous procedure, can be a feasible option and can result in better short-term outcome and a similar long-term outcome after hepatectomy when compared with conventional open hepatectomy. Therefore, the laparoscopic approach is also a viable option for minimally invasive hepatectomy. Modulation of systemic reactions to the operation itself and laparoscopic hepatectomy may be new strategies for performing minimally invasive hepatectomy.

Nicotine-induced contraction in the rat coronary artery: possible involvement of the endothelium, reactive oxygen species and COX-1 metabolites.

Nicotine caused a contraction of the rat coronary artery in the presence of Nomega-nitro-L-arginine methyl ester (L-NAME) and arachidonic acid, and did not in the absence of these agents. The present experiments were undertaken to pharmacologically characterize the nicotine-induced contraction in ring preparations of the rat coronary artery. The contraction was abolished by chemical removal of endothelium saponin. Oxygen radical scavengers, superoxide dismutase and catalase, significantly attenuated the contraction. Cyclooxygenase-1 (COX-1) inhibitors (flurbiprofen, ketoprofen and ketrolack) attenuated the nicotine-induced contraction in a concentration-dependent manner, and cyclooxygenase-2 (COX-2) inhibitors at high concentrations (nimesulide and NS-389) slightly attenuated the contraction. A TXA2 synthetase inhibitor (OKY-046) attenuated the contraction to a small extent only at high concentrations. A TXA2 receptor antagonist (S-1452) attenuated the contraction in a concentration-dependent manner. A nicotinic receptor antagonist (hexamethonium) attenuated the contraction in part and an alpha-adrenoceptor antagonist (prazosin) nearly abolished the contraction. From these results, it was suggested that the contraction induced by nicotine in the rat coronary artery in the presence of L-NAME and arachidonic acid is endothelium dependent, and involves reactive oxygen species and endothelial COX-1 metabolites of arachidonic acid. Part of the contraction is probably due to release of norepinephrine.

The combined use of prostaglandin I2 analogue (OP-2507) and thromboxane A2 synthetase inhibitor (OKY-046) strongly inhibits atherosclerosis of aortic allografts in rats

Background. Atherosclerosis is the main lesion in allografts undergoing chronic rejection. We investigated the effect of OP-2507 (prostaglandin I2 analogue) and OKY-046 (thromboxane A2 synthetase inhibitor) on graft atherosclerosis morphologically and the production of eicosanoids in grafts in a rat aortic allograft model. Methods. Abdominal aortic allografts of Lewis (RT-1l) rats were transplanted orthotopically into fully major histocompatibility complex mismatched Wistar King A/Qdj (RT-1u) rats that were subcutaneously administered OP-2507 (0.1 mg/kg/d) or OKY-046 (125 mg/kg/d), or both, with an osmotic pump. Four, 8, or 12 weeks later, the grafts were harvested and examined histologically, and the concentration of eicosanoids in the grafts were analyzed. Results. Lewis aortic allografts in Wistar King A recipients with no treatment displayed atherosclerosis, which involved gradual intimal thickening and medial thinning with continuous inflammation in adventitia. Neither OP-2507 nor OKY-046 treatment affected the intensity of adventitial inflammation. Although inhibition of medial thinning or a decrease in medial nuclear density was not observed, OKY-046 administration alone significantly inhibited an increase in intimal thickness. OP-2507 administration alone significantly inhibited a decrease in medial nuclear density and intimal thickening. Combined treatment with OP-2507 and OKY-046 further decreased the alteration of media and intima. The ratio of thromboxane B2 and 6-keto-prostaglandin F1α in the grafts was significantly reduced by OKY-046 but not by OP-2507 alone. Conclusions. We have demonstrated that atherosclerosis in aortic allografts is inhibited by the continuous administration of either OP-2507 or OKY-046, and a combination of both agents strongly increases this inhibitory effect. Amelioration of balance in eicosanoid production in the grafts by the use of thromboxane A2 synthetase inhibitor and the simultaneous usage of stable prostaglandin I2 analogue may be a strategy for preventing atherosclerosis that results from chronic rejection. (Surgery 2001;129:595-605.)

L-Arginine improves endothelial function in renal artery of hypertensive Dahl rats.

To clarify whether endothelium-derived contracting factor (EDCF) is developed in renal artery of hypertensive Dahl rats and whether prolonged oral L-arginine treatments prevent development of EDCF and hypertension. The effect of prolonged salt treatment with or without L-arginine on the renal artery was examined. Dahl salt-sensitive and -resistant rats were fed a 0.4 or an 8% NaCl diet for 4 weeks. High sodium intake increased arterial pressure in Dahl salt-sensitive rats. The rings of renal arteries were suspended for isometric tension recording. Only in the hypertensive rats, more than 1 micromol/l acetylcholine induced an endothelium-dependent contraction response. The contraction was completely inhibited by indomethacin or ONO-3708 [prostaglandin H2 (PGH2)/thromboxane A2 (TXA2) receptor antagonist], and partially inhibited by OKY-046 (TXA2 synthetase inhibitor). Acetylcholine-induced relaxation was significantly depressed in hypertensive rats, which was partially improved by SQ29548 (PGH2/TXA2 receptor antagonist). Oral L-arginine, but not ONO-8809 (orally active PGH2/TXA2 receptor antagonist) treatment, inhibited the contraction and amended the relaxation. The endothelium-independent contraction to TXA2 receptor agonist U46619 and relaxation to nitroprusside were not altered by L-arginine treatment The L-Arginine treatment reduced blood pressure and sodium retention with increases in urinary NO2-/NO3- and cGMP excretion. Hydralazine treatment also inhibited development of EDCF. The present results suggest that impaired endothelium-dependent relaxation to acetylcholine is caused in part by induction of EDCF synthesis/release in renal arteries of hypertensive Dahl rats. L-arginine can attenuate sodium retention and development of hypertension, which lead to a decrease in EDCF synthesis in renal arteries.

A novel series of thromboxane A2 synthetase inhibitors with free radical scavenging and anti-peroxidative activities.

A novel series of indoline derivatives with imidazole and carboxyl moieties were synthesized and evaluated for their thromboxane A2 (TXA2) synthetase inhibiting, radical scavenging and anti-peroxidative activities. Among the compounds synthesized, 3-[5-substituted-3-[2-(imidazol-1-yl)ethyl]indolin-1-yl]propionic acids showed free radical scavenging activity and inhibitory effects on lipid-peroxidation of rat brain homogenate and on arachidonate-induced TXA2-dependent aggregation of rabbit platelets. The anti-platelet and anti-peroxidative activities were related to the lipophilicity of the 5-substituent. The 5-hexyloxy derivative (13) showed about 35-fold higher inhibitory activity on TXA2 synthesis than that of ozagrel and about 100-fold higher activity on lipid peroxidation than that of alpha-tocopherol. Compound 13 showed in vivo anti-thrombotic effect in mice and ex vivo anti-peroxidative activity in rats.

A phase II study of the 5-lipoxygenase inhibitor, CV6504, in advanced pancreatic cancer: Correlation of clinical data with pharmacokinetic and pharmacodynamic endpoints

Primary objective was to determine response rate of patients with advanced pancreatic cancer to a novel lipoxygenase and thromboxane A2 synthetase inhibitor (CV6504); secondary objectives included estimation of pharmacokinetics of CV6504, target-enzyme inhibition, safety and tolerance, quality of life and survival. Thirty-one patients with advanced pancreatic cancer were planned to receive CV6504, 100 mg TDS, orally for three months, at which point CT scans were performed to assess therapeutic response rates. Steady state concentrations of CV6504 and thromboxane B2 (an indirect measure of thromboxane A2 synthetase (TA2S) inhibition) were made. Of the 31 patients entered into the study, 23 were considered fully evaluable for response. The drug was well tolerated with few side effects; no partial or complete responses were seen, but 10 patients had stable disease at 3 months; quality of life was maintained during therapy; mean CV6504 steady state plasma concentrations of 14 +/- 6 ng/ml resulting in 75 +/- 18% inhibition of TA2S were achieved; median-survival time for all patients considered eligible for assessment of efficacy was 36.6 weeks after the initial dose of study medication. The actuarial one-year survival was approximately 25%. CV6504 inhibits its target enzyme in vivo, maintains stable disease in 32% of evaluable patients and is well tolerated.