Two classes of anti-platelet drugs reduce anatomical infarct size in monkey hearts.

Background: Recent studies in rabbits have demonstrated that platelet P2Y12 receptor antagonists are cardioprotective, and that the mechanism is surprisingly not related to blockade of platelet aggregation but rather to triggering of the same signal transduction pathway seen in pre- and postconditioning. We wanted to determine whether this same cardioprotection could be documented in a primate model and whether the protection was limited to P2Y12 receptor antagonists or was a class effect.

Methods: Thirty-one macaque monkeys underwent 90-min LAD occlusion/4-h reperfusion.

Platelet P2Y₁₂ blockers confer direct postconditioning-like protection in reperfused rabbit hearts.

Background: Blockade of platelet activation during primary percutaneous intervention for acute myocardial infarction is standard care to minimize stent thrombosis. To determine whether antiplatelet agents offer any direct cardioprotective effect, we tested whether they could modify infarction in a rabbit model of ischemia/reperfusion caused by reversible ligation of a coronary artery.

Methods And Results: The P2Y₁₂ (adenosine diphosphate) receptor blocker cangrelor administered shortly before reperfusion in rabbits undergoing 30-minute regional ischemia/3-hour reperfusion reduced infarction from 38% of ischemic zone in control hearts to only 19%.

Therapeutic potential of phosphodiesterase inhibitors in parasitic diseases.

Protozoan parasites of the order kinetoplastida are the causative agents of three of the world's most important neglected human diseases: African trypanosomiasis, American trypanosomiasis, and leishmaniasis. Current therapies are limited, with some treatments having serious and sometimes lethal side effects. The growing number of cases that are refractory to treatment is also of concern.

Phosphodiesterases as targets for intermittent claudication.

Intermittent claudication (IC) is one of the most frequent forms of lower extremity peripheral arterial disease (PAD) and is most commonly caused by arterial atherosclerosis. Its clinical manifestation includes fatigue, discomfort, or pain occurring in limb muscles due to exercise-induced ischemia, thus limiting the ability of IC patients to walk and exercise. In addition to lifestyle changes (diet, exercise, and smoking cessation), pharmacological treatments are needed.

Thrombocytogenesis by megakaryocyte; Interpretation by protoplatelet hypothesis.

Serial transmission electron microscopy of human megakaryocytes (MKs) revealed their polyploidization and gradual maturation through consecutive transition in characteristics of various organelles and others. At the beginning of differentiation, MK with ploidy 32N, e.g.

Aripiprazole protects cortical neurons from glutamate toxicity.

Neurodegeneration is thought to be a component of schizophrenia pathology, and some antipsychotics appear to slow degenerative changes in patients. Aripiprazole, the first partial dopamine D(2) receptor agonist approved for the treatment of schizophrenia, is suggested to be neuroprotective based on non-clinical studies using transformed cell lines and in vivo stress and lesion paradigms. However, aripiprazole-induced neuroprotection has not been studied in a neuronal glutamate toxicity assay, which may model aspects of neurodegeneration occurring in schizophrenia.

Cilostazol increases tissue blood flow in contracting rabbit gastrocnemius muscle.

Background: The mechanisms underlying the ability of cilostazol to improve walking distance in patients with intermittent claudication (IC) are not fully understood, but may be related to its phosphodiesterase type 3 (PDE3) and adenosine uptake inhibition. In the present study the effect of cilostazol on blood flow and interstitial adenosine concentration was compared with that of the PDE3 inhibitor, milrinone, and the adenosine uptake inhibitor, draflazine.

Methods And Results: Rabbit gastrocnemius muscle blood flow was measured under resting, contracting and ischemic conditions.

Involvement of an alternatively spliced mitochondrial oxodicarboxylate carrier in adipogenesis in 3T3-L1 cells.

Background: Adipogenesis is a complex process that involves many genes/proteins at different stages of differentiation. In order to identify genes critical for adipogenesis, we took a novel approach based on phenotype change of individual cell, to search for genes with regulatory roles in adipogenesis genome-wide in 3T3-L1 cells.

Methods: Lentivirus-based inducible random homologous knockdown was used for the screening of functional gene that altered lipid formation in the adipocyte during differentiation.

Attenuation of infarction in cynomolgus monkeys: preconditioning and postconditioning.

Ischemic pre- (IPC) and post- (IPOC) conditioning are very protective in laboratory animals, but it has not been possible to measure their anti-infarct potency in human hearts. Non-human primates are genetically closer to humans than other laboratory animals, but until now there have been no studies of IPC or IPOC in any primate species. Accordingly the left anterior descending coronary artery of cynomolgus monkeys was occluded for 90 min and reperfused for 4 h.

Inhibition of collagen-induced platelet aggregation by anopheline antiplatelet protein, a saliva protein from a malaria vector mosquito.

During blood feeding, mosquitoes inject saliva containing a mixture of molecules that inactivate or inhibit various components of the hemostatic response to the bite injury as well as the inflammatory reactions produced by the bite, to facilitate the ingestion of blood. However, the molecular functions of the individual saliva components remain largely unknown. Here, we describe anopheline antiplatelet protein (AAPP) isolated from the saliva of Anopheles stephensi, a human malaria vector mosquito.

Role of phosphodiesterase type 3A and 3B in regulating platelet and cardiac function using subtype-selective knockout mice.

Phosphodiesterase type 3 (PDE3) is an important regulator of cAMP-mediated responses within the cardiovascular system. PDE3 exists as two subtypes: PDE3A and PDE3B, with distinct cellular and subcellular locations. Due to the lack of subtype-specific pharmacological tools, the definitive role of each subtype in regulating cardiovascular function has not been determined.

The Fab fragment of a novel anti-GPVI monoclonal antibody, OM4, reduces in vivo thrombosis without bleeding risk in rats.

Background: Inhibition of GPVI has been proposed as a useful antithrombotic strategy; however, in vivo proof-of-concept animal studies targeting GPVI are lacking. We evaluated a novel anti-human GPVI monoclonal antibody OM4 Fab in rats.

Methods And Results: OM4 Fab specifically inhibited collagen-induced aggregation of rat platelets in vitro with an IC50 of 20 to 30 microg/mL but not ADP and AA-induced platelet aggregation.

In vitro functional characteristics of dopamine D2 receptor partial agonists in second and third messenger-based assays of cloned human dopamine D2Long receptor signalling.

Aripiprazole, (+)terguride, OPC-4392 and (-)3-PPP have been classified as dopamine D(2) receptor partial agonists based largely on their activity in second messenger-based assays of dopamine D(2) receptor signalling. Nevertheless, signal transduction amplification might result in these compounds behaving as dopamine D(2) receptor full agonists at a more downstream level of signalling. We compared the intrinsic activity (E(max), expressed as a percentage of the maximal effect of dopamine) of aripiprazole, (+)terguride, OPC-4392 and (-)3-PPP using second (calcium (Ca(2+)) mobilization) and third (extracellular signal-regulated kinase 2 (ERK2) phosphoprotein expression) messenger readouts of cloned human dopamine D(2long) (hD(2L)) receptor signalling in CHO cells.

Dopamine D2 receptor partial agonists display differential or contrasting characteristics in membrane and cell-based assays of dopamine D2 receptor signaling.

Clinical evidence suggests that dopamine D(2) receptor partial agonists must have a sufficiently low intrinsic activity to be effective as antipsychotics. Here, we used dopamine D(2) receptor signaling assays to compare the in vitro functional characteristics of the antipsychotic aripiprazole with other dopamine D(2) receptor partial agonists (7-{3-[4-(2,3-dimethylphenyl)-piperazinyl]propoxy}-2(1H)-quinolinone [OPC-4392], (-)-3-(3-hydroxy-phenyl)-N-n-propylpiperidine [(-)3-PPP] and (+)terguride) and dopamine D(2) receptor antagonists. Aripiprazole and OPC-4392 were inactive in a guanosine-5'-O-(3-[(35)S]thio)-triphosphate ([(35)S]GTPgammaS) binding assay using Chinese Hamster Ovary (CHO) cell membranes expressing cloned human dopamine D(2Long) (hD(2L)) receptors, whereas (-)3-PPP and (+)terguride displayed low intrinsic activity.

Ex vivo evaluation of anti-GPVI antibody in cynomolgus monkeys: dissociation between anti-platelet aggregatory effect and bleeding time.

Recent progress in the understanding of thrombus formation has suggested an important role of glycoprotein (GP)VI. In contrast to its pivotal role in collagen-induced platelet activation, it has been suggested that its blockade does not induce massive bleeding tendency. To demonstrate the dissociation between inhibitory effect on platelet aggregation and bleeding by GPVI blockade, we examined the effects of Fab fragment of OM2, an anti-human GPVI monoclonal antibody on ex vivo collagen-induced platelet aggregation and skin bleeding time after intravenous injection in cynomolgus monkeys.

In vitro biochemical evidence that the psychotomimetics phencyclidine, ketamine and dizocilpine (MK-801) are inactive at cloned human and rat dopamine D2 receptors.

Dopamine potently increased calcium mobilization in Chinese hamster ovary cells expressing human dopamine D2Long receptors (CHO-D2L cells), and increased guanosine-5'-O-(3-[35S]thio)-triphosphate binding to CHO-D2L cell and rat striatal membranes. These effects of dopamine were blocked by the dopamine D2 receptor antagonist (-)raclopride. In contrast to the findings of a recent controversial study, phencyclidine, ketamine and dizocilpine (MK-801) lacked dopamine D2 receptor full agonist, partial agonist and antagonist activity in these assays, suggesting their psychotomimetic effects, and activity in rodent models of schizophrenia, are associated with N-methyl-d-aspartate receptor blockade rather than a direct interaction with dopamine D2 receptors.

Highly potent anti-human GPVI monoclonal antibodies derived from GPVI knockout mouse immunization.

Recent progress in the understanding of thrombus formation has suggested an important role for glycoprotein (GP) VI in this process. To clarify the exact role in detail, it is necessary to use specific, high affinity inhibitory antibodies. However, possibly due to the conserved structure of GPVI among species, it has been difficult to obtain potent antibodies.

GPVI-deficient mice lack collagen responses and are protected against experimentally induced pulmonary thromboembolism.

Platelet glycoprotein VI (GPVI) is now considered to be a major player in platelet-collagen adhesive interactions leading to thrombus formation. GPVI blockade, or its depletion, has been shown in mice to result in complete protection against arterial thrombosis, without significant prolongation of bleeding time. GPVI may therefore represent a useful antithrombotic target.

Antiplatelet and antithrombotic activity of cilostazol is potentiated by dipyridamole in rabbits and dissociated from bleeding time prolongation.

Purpose: To determine the antiplatelet effect of cilostazol (Pletal) and its interaction with dipyridamole in in vitro and in vivo rabbit models, and to see if it can be dissociated from bleeding time prolongation.

Methods: In vitro collagen-induced platelet aggregation was measured by an impedance-based aggregometer. The in vivo antithrombotic effect was evaluated in a rabbit carotid artery cyclic flow reduction (CFR) model, in which repetitive thrombosis was induced by mechanical injuries of the artery and stenosis.

Efficacy and tolerability of a selective alpha(2C)-adrenergic receptor blocker in recovery from cold-induced vasospasm in scleroderma patients: a single-center, double-blind, placebo-controlled, randomized crossover study.

Objective: OPC-28326 is a selective alpha-adrenergic antagonist with preferential binding to the alpha(2C)-adrenergic receptor (alpha(2C)-AR) subtype. This study observed the effect of OPC-28326 on skin temperature and digital blood flow following an acute cold challenge in patients with Raynaud's phenomenon secondary to scleroderma.

Methods: The study was designed as a single-center, double-blind, placebo-controlled, randomized, 3-period crossover study of OPC-28326 (oral doses of 10 mg or 40 mg) or placebo.

Cilostazol and dipyridamole synergistically inhibit human platelet aggregation.

It has been previously shown that cilostazol (Pletal), a drug for relief of symptoms of intermittent claudication, potently inhibits cyclic nucleotide phosphodiesterase type 3 (PDE3) and moderately inhibits adenosine uptake. It elevates extracellular adenosine concentration, by inhibiting adenosine uptake, and combines with PDE3 inhibition to augment inhibition of platelet aggregation and vasodilation while attenuating positive chronotropic and inotropic effects on the heart. In the present study, we tested the hypothesis that cilostazol combined with a more potent adenosine uptake inhibitor, dipyridamole, synergistically inhibited platelet aggregation in human blood.

Cilostazol as a unique antithrombotic agent.

Cilostazol (CLZ) was originally developed as a selective inhibitor of cyclic nucleotide phosphodiesterase 3 (PDE3). PDE3 inhibition in platelets and vascular smooth muscle cells (VSMC) was expected to provide an antiplatelet effect and vasodilation. Recent preclinical studies have demonstrated that CLZ also possesses the ability to inhibit adenosine uptake by various cells, a property that distinguishes CLZ from other PDE3 inhibitors, such as milrinone.

Expression of glycoprotein VI in vascular endothelial cells.

Glycoprotein (GP) VI, a collagen receptor, plays a important role in collagen-mediated platelet aggregation and adhesion. To date, GPVI expression has been found only in platelets and megakaryocytes. In the present studies, we have demonstrated that GPVI was also expressed in cultured human umbilical vein endothelial cells (HUVEC) at both transcript and protein levels.

Vasopressin V2-receptor blockade with tolvaptan in patients with chronic heart failure: results from a double-blind, randomized trial.

Background: In this study, we evaluated the effects of tolvaptan (OPC-41061), a novel, oral, nonpeptide vasopressin V2-receptor antagonist in patients with chronic heart failure (CHF).

Methods And Results: This was a double-blind study investigating the effects of three doses of tolvaptan and placebo in patients with CHF. After a run-in period, 254 patients were randomly assigned to placebo (n=63) or tolvaptan [30 mg (n=64), 45 mg (n=64), or 60 mg (n=63)] once daily for 25 days.