Pharmacological profile and therapeutic potential of BM-573, a combined thromboxane receptor antagonist and synthase inhibitor

The novel thromboxane prostanoid receptor mediates CTGF production to drive human nasal fibroblast self-migration through NF-κB and PKCδ-CREB signaling pathways

Chronic rhinosinusitis without nasal polyp (CRSsNP) is characterized by tissue repair/remodeling and the subepithelial stroma region in whose nasal mucosa has been reported by us to have thromboxane A2 (TXA2) prostanoid (TP) receptor and overexpress connective tissue growth factor (CTGF). Therefore, this study aimed to investigate the relationship between TP receptor activation and CTGF production/function in human CRSsNP nasal mucosa stromal fibroblasts. We found that TP agonists including U46619 and IBOP ([1S-[1α,2α(Z),3β(1E,3 S*),4α]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid) could promote CTGF protein/messenger RNA expression and secretion. The pharmacological intervention and TP activation assay with U46619 identified the possible participation of PKCμ, PKCδ, nuclear factor-κB (NF-κB), and cyclic AMP response element-binding protein (CREB) phosphorylation/activation in the CTGF induction. Moreover, a phorbol ester-phorbol-12-myristate 13-acetate (PMA) exhibited a similar cellular signaling and CTGF production profile to that elicited by TP activation. However, further small interfering RNA interference analysis revealed that only NF-κB and PKCδ-CREB pathways were necessarily required for TP-mediated CTGF production, which could not be completely supported by those findings from PMA. Finally, in a functional assay, although CTGF did not affect fibroblast proliferation, TP-mediated CTGF could drive novel self-migration in fibroblasts both in the scratch/wound healing and transwell apparatus assays. Meanwhile, the overall staining for stress fibers and formation of the lamellipodia and filopodia-like structures was concomitantly increased in the treated migrating cells. Collectively, we provided here that novel TP mediates CTGF production and self-migration in human nasal fibroblasts through NF-κB and PKCδ-CREB signaling pathways. More importantly, we also demonstrated that thromboxane, TP receptor, CTGF, and stromal fibroblasts may act in concert in the tissue remodeling/repair process during CRSsNP development and progression.

Preparation of injectable clopidogrel loaded submicron emulsion for enhancing physicochemical stability and anti-thrombotic efficacy

Due to the superior safety and therapeutic efficacy, clopidogrel (CLP) has been widely used to prevent postoperative thrombosis. However, limitations of delayed absorption and metabolic activation of clopidogrel after oral administration hinder its clinic use for acute thrombosis treatment in percutaneous coronary intervention (PCI). Although clopidogrel aqueous injection systems were designed and developed, chemical instability under physiological condition or vascular irritation remains to be solved. In this study, we aim to prepare an injectable clopidogrel loaded submicron emulsion to overcome the drawbacks of conventional clopidogrel aqueous formulation and improve the antiplatelet aggregation effects. Results showed that this delivery system exerted inspiring features including uniform particle size, higher drug loading capacity and sustained drug release behavior. It can dramatically upgrade the formulation stability and prevent the drug degradation under sterilization or higher pH environments. No remarkable droplet size increase or drug content decrease was observed during storage. Compared to CLP tablet, the peak drug concentration (C_max) and area under the curve (AUC) of CLP emulsion increased by 12.01-fold and 4.69-fold, respectively. Most importantly, it exerted excellent in vivo anti-thrombotic effect on numerous designed animal models. Conclusively, submicron emulsion is a promising delivery system for improving clopidogrel stability and anti-thrombotic efficacy.

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.

Investigation of a Thromboxane A2 Receptor-Based Vaccine for Managing Thrombogenesis

BACKGROUND

Despite the well-established role for the thromboxane A2 receptor (TPR) in the development of thrombotic disorders, none of the antagonists developed to date has been approved for clinical use. To this end, we have previously shown that an antibody targeted against TPR's ligand-binding domain inhibits platelet activation and thrombus formation, without exerting any effects on hemostasis. Thus, the goal of the present studies is to design a novel TPR-based vaccine, demonstrate its ability to trigger an immune response, and characterize its antiplatelet and antithrombotic activity.

METHODS AND RESULTS

We used a mouse keyhole limpet hemocyanin/peptide-based vaccination approach rationalized over the TPR ligand-binding domain (ie, the C-terminus of the second extracellular loop). The biological activity of this vaccine was assessed in the context of platelets and thrombotic diseases, and using a host of in vitro and in vivo platelet function experiments. Our results revealed that the TPR C-terminus of the second extracellular loop vaccine, in mice: (1) triggered an immune response, which resulted in the development of a C-terminus of the second extracellular loop antibody; (2) did not affect expression of major platelet integrins (eg, glycoprotein IIb-IIIa); (3) selectively inhibited TPR-mediated platelet aggregation, platelet-leukocyte aggregation, integrin glycoprotein IIb-IIIa activation, as well as dense and α granule release; (4) significantly prolonged thrombus formation; and (5) did so without impairing physiological hemostasis.

CONCLUSIONS

Collectively, our findings shed light on TPR's structural biological features, and demonstrate that the C-terminus of the second extracellular loop domain may define a new therapeutic target and a TPR vaccine-based approach that should have therapeutic applications.

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.

The thromboxane/endoperoxide receptor (TP): the common villain

The stimulation of thromboxane/endoperoxide receptors (TP) elicits diverse physiological/pathophysiological reactions, including platelet aggregation and contraction of vascular smooth muscle. Furthermore, the activation of endothelial TP promotes the expression of adhesion molecules and favors adhesion and infiltration of monocytes/macrophages. In various cardiovascular diseases, endothelial dysfunction is predominantly the result of the release of endothelium-derived contracting factors that counteract the vasodilator effect of nitric oxide produced by the endothelial nitric oxide synthase. Endothelium-dependent contractions involve the activation of cyclooxygenases, the production of reactive oxygen species along with that of endothelium-derived contracting factors, which diffuse toward the vascular smooth muscle cells and activate their TP. TP antagonists curtail the endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and reduce vascular inflammation. Therefore, TP antagonists, because of this triple activity, may have a unique potential for the treatment of cardiovascular disorders.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

New antithrombotic drugs

Thrombosis, both venous and arterial, is a major cause of morbidity and mortality worldwide. Consequently, there is an ongoing search for new antithrombotic drugs, particularly novel antiplatelet agents and anticoagulants. A better understanding of the biochemical pathways involved in platelet activation and coagulation and of the links between these systems and the impact of thrombosis on inflammation has led to the identification of new targets for antithrombotic drugs. This paper focuses on these new targets and new antiplatelet drugs and anticoagulants and describes the major advances in the continuing search for more potent antithrombotic drugs that have limited effects on hemostasis.

Strategies for antiplatelet targets and agents

Platelets play a key role in thrombosis and haemostasis, which can be either beneficial or deleterious depending on the circumstance. Antiplatelet therapy is the 'cornerstone' in the prevention and treatment of thrombotic diseases. Platelet activation is a complex process known as transmembrane signaling which then serves to activate the platelet via a cascade of biochemical interactions. Currently available strategies of antiplatelet therapy are generally based on the signaling pathway of platelet activation, which possess the characters that mono-agent, mono-target, and mainly irreversible inhibition. Therefore, both established and novel antiplatelet agents have their own pros and cons and such problems as resistance, drug-drug interaction, discontinuation and monitoring, etc. have been appeared. Due to the problems existing in current antiplatelet agents, future new strategies for antiplatelet targets, agent-developing and treatment might probably include three aspects: targeting the factors associated with platelet hyperactivity, developing novel antiplatelet agents with multiple targets, mild and reversible properties from natural products, and keeping healthy lifestyle and emphasizing prevention.

A novel thromboxane receptor antagonist and synthase inhibitor, BM-573, reduces development and progression of atherosclerosis in LDL receptor deficient mice

Atherosclerosis is a chronic inflammatory disease of the vasculature influenced by a variety of mediators. Among them, prostanoids, which include prostacyclin and thromboxane (Tx) A(2), have recently received a lot of attention. Previous studies demonstrated that antagonism or deletion of the receptor for TxA(2) retards early atherogenesis in apolipoprotein E-deficient mice, but no data are available in low-density lipoprotein (LDL) receptor deficient mice. In our study, we tested the effect of a novel TxA(2) receptor (TP) antagonist and synthase inhibitor, BM-573, on atherosclerosis development and progression in LDL receptor deficient mice. To this end, the effect of 12 weeks treatment with BM-573 on early or established aortic atherosclerotic lesions of these mice was assessed. In both treatments, while BM-573 did not affect body weight, systolic blood pressure, total plasma cholesterol or triglycerides levels, it partially reduced TxA(2) but did not affect prostacyclin biosynthesis. Moreover, BM-573 significantly decreased early atherogenesis and prevented progression of established atherosclerotic lesions. These results show for the first time that this dual Tx inhibitor is effective in reducing atherogenesis in the LDL receptor deficient mice. They also demonstrate the novel concept that this therapeutic approach halts the progression of the disease and influences the cellular composition of the atherosclerotic plaques.

Thromboxane receptor blockade improves the antiatherogenic effect of thromboxane A2 suppression in LDLR KO mice

Suppression of thromboxane (Tx) A(2) biosynthesis retards atherogenesis. In this setting, the coincidental presence of nonconventional ligands for the TxA(2) receptor (TP), such as isoprostanes, could still induce a proatherogenic vascular phenotype. However, no data are available on the effect of combining suppression of TxA(2) formation with blockade of TP in atherogenesis. To this end, we tested the effect of a selective COX-1 inhibitor, SC560, a TP antagonist, BM-573, or a combination of both in low-density lipoprotein receptor-deficient mice on a high-fat diet. None of the treatments affected body weight or plasma cholesterol or triglycerides levels. Although SC-560 suppressed TxA(2) biosynthesis, BM-573 reduced its levels by 35%; in contrast, the 2 drugs, alone or in combination, did not significantly affect prostacyclin levels. At the end of the study, SC560 and BM-573 reduced atherogenesis; however, a further significant decrease was observed in mice receiving both drugs. This effect was associated with a further significant reduction of vascular inflammation, a decrease in macrophages, and an increase in the content of collagen and smooth muscle cells of the atherosclerotic lesions. These results show for the first time that the addition of a TP antagonist increases the antiatherogenic effect of COX-1-dependent TxA(2) suppression.