The role of cGMP in the anti-aggregating properties of BY-1949, a novel dibenzoxazepine derivative

A One-Pot Synthesis of Oxazepine-Quinazolinone bis-Heterocyclic Scaffolds via Isocyanide-Based Three-Component Reactions

A novel, efficient and environmentally friendly approach has been developed for the synthesis of biologically important bis-heterocyclic oxazepine-quinazolinone derivatives. The structurally interesting compounds of high purity were synthesized by a one-pot three-component reaction of 2-(2-formylphenoxy) acetic acid and 2-aminobenzamide as bifunctional reagents and an isocyanide without using any catalyst, with excellent overall yields.

Role of the recombinant protein of the platelet receptor for type I collagen in the release of nitric oxide during platelet aggregation

Nitric oxide plays an important role in platelet function and platelets possess the endothelial isoform of nitric oxide synthase. Several reports have indicated that nitric oxide is released upon exposure of platelets to collagen. We have reported that a non-integrin platelet protein of 65 kDa is a receptor for type I collagen. By direct measurement of NO release from washed human platelets suspended in Tyrode buffer with a ISO-NO Mark II, World Precision Instruments, Sarasota, FL, USA, p30 sensor, type I collagen, but not ADP and epinephrine, induces the release of NO in a time-dependent manner. The production of NO is inhibited either by preincubation of type I collagen with the platelet type I collagen receptor recombinant protein or by preincubation of platelets with the antibody to the receptor protein, the anti-65 antibody. However, preincubation of platelets with anti-P-selectin and anti-glycoprotein IIb/IIIa did not affect the release of NO by platelets. These results suggest that the 65 kDa platelet receptor for type I collagen is specifically linked to the generation of NO, and that the 65 kDa platelet receptor for type I collagen plays an important new role in platelet function.

Endogenous mediators and thrombophilia

Platelets are one of the most important components of primary haemostasis. Since they lack a nucleus, their functional characteristics are determined at the time of production. The role of platelets in thrombosis is further modified by the interaction with vascular mediators that are endogenously produced in response to a variety of stimuli. This chapter discusses the factors that influence platelet production, the interaction with endogenous mediators, and the potential therapeutic benefits achieved by modifying this interaction in the clinical setting.

Endogenous mediators and thrombophilia

Platelet function is a balance between factors determined at thrombopoiesis and prothrombotic and antithrombotic mediators from the vascular wall. Nitric oxide is a crucial vasodilator and inhibitor of platelet activation synthesized constitutively by the vascular endothelium. In some pathological states this synthesis may be impaired leading to a prothrombotic state. In other situations, synthesis may be increased by a second inducible enzyme. Nitric oxide synergizes with other antithrombotic vasodilators such as prostacyclin and is opposed by prothrombotic vasoconstrictor mediators such as thromboxane. Platelets are anucleate and their reactivity is partly determined at thrombopoiesis by their progenitor cell, the megakaryocyte. In thrombotic states, such as myocardial infarction, larger, more reactive platelets from larger megakaryocytes are observed.

BY-1949 elicits vasodilation via preferential elevation of cyclic GMP levels within the cerebral artery: possible involvement of endothelium-mediated mechanisms

The pharmacological mechanisms by which BY-1949, a novel dibenzoxazepine derivative, increases in regional cerebral blood flow, were investigated using the canine basilar artery in vitro. BY-1949 inhibited contractions elicited by serotonin (5-HT), prostaglandin (PG) F2 alpha, endothelin and phorbol-12,13-diacetate (PDA), respectively, to the same extent. In addition, pretreatment of the artery with methylene blue significantly suppressed the vasodilating effect of BY-1949. BY-1949 also dose dependently suppressed contractions of the basilar artery induced by CaCl2 (Ca2+) in a non-competitive manner. Biochemical studies disclosed that BY-1949 significantly increased cyclic GMP without causing any apparent change in cyclic AMP. These increases in cyclic GMP were virtually abolished after the endothelial cells were removed. These results strongly suggest that the increased regional cerebral blood flow induced by BY-1949 is explicable, at least partly, in terms of a preferential elevation of cyclic GMP within the cerebral vasculature, where the endothelium plays a pivotal role.

Neurochemical correlates of selective neuronal loss following cerebral ischemia: role of decreased Na+,K(+)-ATPase activity

In order to investigate the role of Na+,K(+)-ATPase in the development of neuronal necrosis following cerebral ischemia, ischemia was induced in gerbils by occluding the common carotid artery unilaterally for 10 min. A time-course analysis revealed that significant reductions of the Na+,K(+)-ATPase activity in the cerebral cortex and hippocampus were manifested at 15 min, 30 min, and 1 h, and returned to the control level one day following recirculation. No apparent alterations of the Mg(2+)-ATPase activity, on the other hand, were obtained throughout the experimental period. Furthermore, Scatchard analyses of [3H]ouabain binding to the cerebral cortex membranes disclosed that the Bmax values invariably decreased without any change of Kd values following ischemia. It has also been shown that treatment of the animals with an agent known to mitigate ischemic neuronal necrosis, i.e. BY-1949, significantly reversed such derangements. These results suggest that the recovery of decreased Na+,K(+)-ATPase activity shortly after ischemia exerts a protective effect against ischemic brain damage.

An Activation of Synaptosomal Na+, K+-ATPase by a Novel Dibenzoxazepine Derivative (BY-1949) in the Rat Brain: Its Functional Role in the Neurotransmitter Uptake Systems

In search of factors mitigating the final outcome of ischemic and epileptic brain damage, we tested a novel dibenzoxazepine derivative (BY-1949), as the compound has been shown to be effective under these two conditions. First, using rat brain, we assessed whether or not BY-1949 affects the Na+,K(+)-ATPase activity. Although in vitro applications of either BY-1949 or its three major metabolites did not cause any apparent effects, both acute and chronic oral administrations of the compound (10 mg/kg) invariably increased the Na+,K(+)-ATPase activity in the synaptosomal plasma membranes by increasing Vmax values. Second, it was shown by this study that the drug treatment caused marked increases in the uptake of both glutamic acid and gamma-aminobutyric acid into the synaptosomes. These results suggest that the activity against ischemic/epileptic brain damage by BY-1949 is explicable, at least partly, in terms of improvement of ionic derangements across the neural membranes via Na+,K(+)-ATPase activation.