In vitro and in vivo pharmacological characterization of BM-613 [N-n-pentyl-N'-[2-(4'-methylphenylamino)-5-nitrobenzenesulfonyl]urea], a novel dual thromboxane synthase inhibitor and thromboxane receptor antagonist

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Structure-activity relationship studies for multitarget antithrombotic drugs

Thrombosis is a complex process involving multiple pathways. Currently, therapy relies on the combination of two or more antithrombotic drugs, showing that inhibiting more than one target provides benefits in the prevention and treatment of thrombosis. This review focuses on structure-activity relationship studies of molecules possessing multiple actions against thrombosis, namely, dual inhibitors of coagulation, dual inhibitors of coagulation and platelet aggregation, and also dual inhibitors of platelet aggregation. EP217609 has just entered clinical trials, which raise the expectations on the multitarget strategy to prevent or treat thrombosis.

In silico design of a dual TPR/TxS inhibitor for venous thromboembolism and related cardiovascular diseases

In recent years, many research efforts have been directed towards preventing vasoconstrictor and platelet aggregatory properties of TxA2related to the prostaglandin cycle, as TxA2has been implicated directly or indirectly in pathologies such as cardiovascular diseases, venous thromboembolism, and pulmonary embolism. The TxA2antagonists and TxS inhibitors undergoing clinical trials have not shown the expected clinical efficacy. This molecular modeling and docking study explains how efficacy may be enhanced by a careful design of multitarget drugs producing synergistic effects simultaneously at different targets. A dual TPR/TxS inhibition strategy is expected to give better clinical efficacy. This study also emphasizes the importance of designing efforts based on detailed analysis of drug−receptor interactions at both targets. Ab initio HF/6-31G(d) and B3LYP/6-31G(d) molecular orbital calculations coupled with flexible ligand docking studies have led to the design of a dual TPR/TxS inhibitor starting from a naturally occurring compound bromelain, derived from pineapple extract with some known pharmacological advantages. A designed lead compound may prove to be a fruitful starting point for the development of clinically efficient drugs for venous thromboembolism and related cardiovascular diseases.

Dietary spinach saponin-enriched lipophilic fraction inhibits platelet aggregation and blood coagulation

In this study, we investigated the effect of spinach saponin-enriched lipophilic fraction (SSEF) on collagen (10 μg/mL)-stimulated platelet aggregation in vivo. Dietary SSEF dose-dependently inhibited collagen-induced platelet aggregation by decreasing thromboxane A₂ production and intracellular Ca²⁺ agonist activity as an aggregation-inducing autacoidal molecule. In addition, SSEF significantly increased the formation of cyclic AMP and cyclic GMP, intracellular Ca²⁺ antagonists that are aggregation-inhibiting molecules in collagen-stimulated platelets. These results suggest that SSEF is a potent inhibitor of collagen-stimulated platelet aggregation in vivo. Prothrombin time and activated partial thromboplastin time, indicators of blood coagulation, were potently prolonged by dietary SSEF in vivo. These findings suggest that SSEF prolongs the interval time between the conversion of fibrinogen to fibrin. Dietary SSEF also inhibited 0.4 M sucrose-induced hemolysis. Accordingly, our data demonstrate that SSEF might be a useful tool for inhibiting platelet activation and blood coagulation in thrombotic diseases.

Enhanced airway smooth muscle cell thromboxane receptor signaling via activation of JNK MAPK and extracellular calcium influx

Thromboxane is a key inflammatory mediator and potent airway constrictor. It acts on thromboxane A(2) (TP) receptors and contributes to airway inflammation and airway hyperresponsiveness that is the characteristic feature of asthma. The present study was designed to study TP receptor signaling in airway smooth muscle cells by using an organ culture model and a set of selective pharmacological inhibitors for mitogen-activated protein kinase (MAPK) and calcium signal pathways. Western-blot, immunohistochemistry, myograph and a selective TP receptor agonist U46619 were used for examining TP receptor signal proteins and function. Organ culture of rat bronchial segments for up to 48 h induces a time-dependently increased airway contractile response to U46619. This indicates that organ culture increases TP receptor signaling in the airway smooth muscle cells. The enhanced bronchial contraction was attenuated by the inhibition of c-Jun N-terminal kinase (JNK) MAPK activity, chelation of extracellular calcium and calcium channel blocker nifedipine, suggesting that JNK MAPK activity and elevated intracellular calcium level are required for the TP receptor signaling. In conclusion, airway smooth muscle cell TP receptor signaling occurs via JNK MAPK activity and the elevation of extracellular calcium influx, which may provide knowledge for understanding the signaling pathway responsible for the modulation of TP receptor mediated airway hyperresponsiveness to thromboxane.

Adventures in vascular biology: a tale of two mediators

I would like to thank the Royal Society for inviting me to deliver the Croonian Lecture. In so doing, the Society is adding my name to a list of very distinguished scientists who, since 1738, have preceded me in this task. This is, indeed, a great honour. For most of my research career my main interest has been the understanding of the normal functioning of the blood vessel wall and the way this is affected in pathology. During this time, our knowledge of these subjects has grown to such an extent that many people now believe that the conquering of vascular disease is a real possibility in the foreseeable future. My lecture concerns the discovery of two substances, prostacyclin and nitric oxide. I would like to describe the moments of insight and some of the critical experiments that contributed significantly to the uncovering of their roles in vascular biology. The process was often adventurous, hence the title of this lecture. It is the excitement of the adventure that I would like to convey in the text that follows.

Synthesis and Pharmacological Evaluation of Novel Nitrobenzenic Thromboxane Modulators as Antiplatelet Agents Acting on Both the Alpha and Beta Isoforms of the Human Thromboxane Receptor

Thromboxane A(2) (TXA(2)) is an arachidonic acid metabolite involved in pathologies such as stroke, myocardial infarction, and atherosclerosis. Consequently, the design of TXA(2) receptor (TP) antagonists remains of great interest in cardiovascular medicine. The actions of TXA(2) are mediated by its specific G-protein coupled receptor of which two alternative spliced isoforms, TPalpha and TPbeta, have been described in humans. In this study, we report the synthesis of a series of original N-alkyl-N'-[2-(cycloalkyl, alkylaryl)-5-nitrobenzenesulfonyl]urea and N-alkyl-N'-[2-(alkylaryl)-5-nitrobenzenesulfonyl]-N' '-cyanoguanidines and outline their pharmacological evaluation using the individual TPalpha and TPbeta isoforms. Among compounds analyzed, several of them exhibited greater affinity and/or functional activity for either TPalpha or TPbeta. The most promising molecules were also found to be antiplatelet agents. From the present results, structural features involved in isoform selectivity can be proposed, and thereby several lead compounds have been identified for the further development of selective TP isoform antagonists.

Pharmacological characterization of 2NTX-99 [4-methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a potential antiatherothrombotic agent with antithromboxane and nitric oxide donor activity in platelet and vascular preparations

Thromboxane (TX) A(2), prostacyclin (PGI(2)), and nitric oxide (NO) regulate platelet function and interaction with the vessel wall. Inhibition of TXA(2), implemented synthesis of PGI(2), and supply of exogenous NO may afford therapeutic benefit. 2NTX-99 [4-methoxy-N(1)-(4-trans-nitrooxycyclohexyl)-N(3)-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a new chemical entity related to picotamide, showed antithromboxane activity and NO donor properties. 2NTX-99 relaxed rabbit aortic rings precontracted with norepinephrine or U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid; EC(50), 7.9 and 17.1 microM, respectively), an effect abolished by 10 microM 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). 2NTX-99 inhibited arachidonic acid (AA)-induced washed platelet aggregation (EC(50), 9.8 microM) and TXB(2) formation (-71% at 10 microM), and its potency increased in the presence of aortic rings (EC(50), 1.4 microM). In whole rabbit aorta incubated with homologous platelets, AA caused contraction and TXA(2) formation, reduced by 2NTX-99 (10-40 microM): contraction, -28 and -47%, TXA(2) formation, -37 and -75.4%, respectively, with concomitant increase in PGI(2). 2NTX-99 (20-40 microM) inhibited U46619-induced aggregation in rabbit platelet-rich plasma (PRP) (-74 +/- 6.7 and -96 +/- 2.4%, respectively) and inhibited collagen-induced aggregation in human PRP (-48.2 +/- 10 and -79.2 +/- 6%), whereas ozagrel was ineffective. In human embryonic kidney 293 cells transfected with the TXA(2) receptor isophorm alpha receptor, 2NTX-99 did not compete with the ligand, [(3)H]SQ29,548 ([(3)H][1S-[1alpha,2beta(5Z),3beta,4alpha]]-7-[3-[[2-(phenylamino)-carbonyl]hydrazino]methyl]-7-oxabicyclo[2,2,1]-hept-2-yl]-5-heptanoic acid), or prevent inositol phosphate accumulation. After oral administration (50-250 mg/kg), 2NTX-99 inhibited TXA(2) production in rat clotting blood (-71 and -91%); at 250 mg/kg, an area under the curve, 0 to 16 h, of 149.5 h/microg/ml and a t(1/2) of 6 h were calculated, with a C(max) value of 31.8 +/- 8.2 microg/ml. An excellent correlation between plasma concentrations and TXA(2) inhibition occurs. 2NTX-99 controls platelet function and vessel wall interaction by multifactorial mechanisms and possesses therapeutic potential.

Eicosanoids and the vascular endothelium

Cyclooxygenase (COX) enzymes catalyse the biotransformation of arachidonic acid to prostaglandins which subserve important functions in cardiovascular homeostasis. Prostacyclin (PGI2) and prostaglandin (PG)E2, dominant products of COX activityin macro- and microvascular endothelial cells, respectively, in vitro, modulate the interaction of blood cells with the vasculature and contribute to the regulation of blood pressure. COXs are the target for inhibition by nonsteroidal anti-inflammatory drugs (NSAIDs--which include those selective for COX-2) and for aspirin. Modulation of the interaction between COX products of the vasculature and platelets underlies both the cardioprotection afforded by aspirin and the cardiovascular hazard which characterises specific inhibitors of COX-2.