Effect of ASP6432, a Novel Type 1 Lysophosphatidic Acid Receptor Antagonist, on Urethral Function and Prostate Cell Proliferation.

Current pharmacotherapies for lower urinary tract symptoms associated with benign prostate hyperplasia (LUTS/BPH) are in need of improvement. Lysophosphatidic acid (LPA) is a phospholipid with various biologic functions. However, its exact role in the lower urinary tract and its target receptor subtype have not been fully elucidated. We investigated the role of LPA and the type 1 LPA receptor (LPA1) in urethral/prostatic contractile function and prostate cell proliferation by pharmacologically characterizing ASP6432 (potassium 1-(2-{[3,5-dimethoxy-4-methyl-N-(3-phenylpropyl)benzamido]methyl}-1,3-thiazole-4-carbonyl)-3-ethyl-2,2-dioxo-2λ6-diazathian-1-ide), a novel LPA1 antagonist. ASP6432 exhibited potent and selective antagonistic activity against LPA1 in cells expressing LPA receptor subtypes. In isolated rat tissue strips and anesthetized rats, ASP6432 concentration-/dose-dependently inhibited LPA-induced urethra and prostate contractions. In addition, in anesthetized rats, ASP6432 maximally decreased the urethral perfusion pressure (UPP) in the absence of exogenous LPA stimulation by 43% from baseline, whereas tamsulosin, an α1-adrenoceptor antagonist, reduced UPP by 22%. Further, in human prostate stromal cells, ASP6432 significantly and concentration-dependently suppressed LPA-induced bromodeoxyuridine incorporation. These results demonstrate a pivotal role for LPA and LPA1 in the regulation of urethral tonus and prostate cell proliferation. The potent urethral relaxation and inhibition of prostatic stromal cell growth indicate the potential of ASP6432 as a novel therapeutic agent for LUTS/BPH.

Antiemetic effect of a potent and selective neurokinin-1 receptor antagonist, FK886, on cisplatin-induced acute and delayed emesis in ferrets.

The antiemetic effect of a potent and selective neurokinin-1 (NK1) receptor antagonist, FK886 ([3,5-bis(trifluoromethyl)phenyl][(2R)-2-(3-hydroxy-4-methylbenzyl)-4-{2-[(2S)-2-(methoxymethyl)morpholin-4-yl]ethyl}piperazin-1-yl]methanone dihydrochloride), on cisplatin-induced acute and delayed emesis in ferrets was studied. Intravenous administration of FK886 dose-dependently inhibited cisplatin (10 mg/kg)-induced acute emesis with a minimum effective dose (MED) of 0.32 mg/kg. In the same study, oral FK886 administered 8 h prior to cisplatin also dose-dependently inhibited the acute emesis during the 4-h observation period with an MED of 3.2 mg/kg. Further, when given by repeated oral administration of ≥1.6 mg/kg at 12-h intervals, the first dose being administered 1 min before cisplatin, FK886 significantly decreased the number of emetic responses in cisplatin (5 mg/kg)-induced delayed emesis. In the same study, oral FK886 (3.2 mg/kg) repeatedly administrated at 12-h intervals, the first dose being administered 36 h post cisplatin, also significantly attenuated the delayed emesis. Pharmacokinetic data in ferrets showed that plasma FK886 reached a maximum concentration within 0.5 h of administration, suggesting rapid oral absorption. In addition, rapid brain penetration of FK886 was suggested by complete and near complete inhibition of GR73632- and copper sulfate-induced emesis, respectively, by low-dose intravenous FK886 administered shortly before the emetogens. These results suggest that FK886 is an orally available NK1 receptor antagonist which is effective against both the acute and delayed emesis induced by cisplatin. Because of its therapeutic efficacy on the delayed emesis and rapid brain distribution after oral administration, FK886 may have potential as an antiemetic agent that can be used for interventional treatment of chemotherapy-induced delayed emesis.

Antiemetic effects of a potent and selective neurokinin-1 receptor antagonist, FK886, on cisplatin- and apomorphine-induced emesis in dogs.

The antiemetic properties of a novel neurokinin-1 (NK1) receptor antagonist, FK886 ([3,5-bis(trifluoromethyl)phenyl][(2R)-2-(3-hydroxy-4-methylbenzyl)-4-{2-[(2S)-2-(methoxymethyl)morpholin-4-yl]ethyl}piperazin-1-yl]methanone dihydrochloride), were studied in dog models of cisplatin- and apomorphine-induced emesis. Intravenously administered FK886 (0.32-1 mg/kg) significantly inhibited cisplatin-induced acute emesis during the 5-h observation period. Nearly complete inhibition was observed at 1 mg/kg. At an equivalent dose range, orally administered FK886 also significantly inhibited emesis, indicating good oral absorption. Similarly, FK886 inhibited apomorphine-induced emetic responses effectively following both intravenous and oral administration. The effects were long lasting, with 1.6 mg/kg of FK886 completely blocking apomorphine-induced retching and vomiting after a 12-h pretreatment period. Furthermore, FK886 showed rapid onset of antiemetic activity after oral administration. At doses of 0.32 mg/kg or more, a pretreatment time of 0.5 h was sufficient for complete inhibition of apomorphine-induced emetic responses. This fast onset after oral administration was supported by pharmacokinetic data, which demonstrated plasma levels of FK886 after oral administration reached levels similar to those 30 min after intravenous administration. These results suggest that FK886 has excellent antiemetic properties in dogs, and that its rapid-onset and long-lasting properties might make it a promising antiemetic agent.

Pharmacological properties of FK886, a new, centrally active neurokinin-1 receptor antagonist.

The pharmacological properties of the novel neurokinin-1 (NK(1)) receptor antagonist FK886, ([3,5-bis(trifluoromethyl)phenyl][(2R)-2-(3-hydroxy-4-methylbenzyl)-4-{2-[(2S)-2-(methoxymethyl)morpholin-4-yl]ethyl}piperazin-1-yl]methanone dihydrochloride), were studied. FK886 potently inhibited the binding of [(125)I]Bolton-Hunter-labeled substance P ([(125)I]BH-SP; 100 pM) to human NK(1) receptors expressed in Chinese hamster ovary (CHO) cells (IC(50)=0.70 nM). It also possessed high affinities for dog, ferret, gerbil and guinea pig NK(1) receptors, but not for rat NK(1) receptor. FK886 was highly selective for the NK(1) receptor, with 250- and >20000-fold selectivity for human NK(1) over NK(2) and NK(3), respectively. Further, it did not inhibit radioligand binding at 54 different sites, including receptors, ion channels and transporters. FK886 inhibited substance P (3.2 nM)-induced inositol phosphate formation in human NK(1) receptor-expressing CHO cells (IC(50)=1.4 nM) without stimulating NK(1) receptors. The antagonism exerted by FK886 against human NK(1) receptor was insurmountable in saturation binding experiments, with both the affinity and B(max) of [(125)I]BH-SP being significantly reduced. After intravenous administration, FK886 (0.01-0.1 mg/kg) dose-dependently inhibited the foot-tapping behavior induced by intracerebroventricular administration of a selective NK(1) receptor agonist, GR73632 (10 pmol), in gerbils, with significant inhibition being observed at doses of 0.032-0.1 mg/kg, indicating excellent brain penetration. The brain penetration of FK886 was further demonstrated by the cerebral distribution of radioactivity after intravenous injection of radiolabeled FK886. Taken together, these results demonstrate that FK886 is a potent, highly selective and centrally active, insurmountable antagonist of the NK(1) receptor, and suggest that FK886 antagonizes various NK(1) receptor-mediated biological effects in the central nervous system.

Inhibitory effect of zacopride on Cisplatin-induced delayed emesis in ferrets.

We evaluated the antiemetic effect of zacopride, a potent 5-HT3-receptor antagonist with 5-HT4-receptor agonist properties, on delayed emesis caused by cisplatin (5 mg/kg, i.p.) in ferrets, compared with granisetron, a selective 5-HT3-receptor antagonist. Multiple intravenous injections of zacopride at 1 mg/kg, a dose that completely inhibited acute emesis caused bycisplatin (10 mg/kg, i.v.), significantly reduced delayed emesis. Granisetron (3.2 mg/kg) also reduced delayed emesis but this failed to reach statistical significance. The present study suggests that a combined 5-HT3-receptor antagonist/5-HT4-receptor agonist, like zacopride, may be useful against both acute and delayed emesis induced by cancer chemotherapy.

Antiemetic activity of FK1052, a 5-HT3- and 5-HT4-receptor antagonist, in Suncus murinus and ferrets.

We investigated the effect of FK1052 [(+)-8,9-dihydro-10-methyl-7-[(5-methyl-1H-imidazol-4-yl)methyl]pyrido[1,2-a]indol-6(7H)-one hydrochloride], a 5-HT3- and 5-HT4-receptor antagonist, on the emesis induced by motion stimuli, copper sulfate, or cisplatin in either Suncus murinus or ferrets and also clarified the role of the 5-HT3 and 5-HT4 receptors in these models. In Suncus murinus, oral administration of FK1052 (100 microg/kg) completely prevented emesis induced by cisplatin (18 mg/kg, i.p.). Intraperitoneal injection of scopolamine (10 mg/kg) and promethazine (32 mg/kg), but not FK1052 (1 mg/kg), significantly reduced the emetic responses by motion stimuli. In ferrets, copper sulfate (40 mg/kg, p.o.)-induced emesis was moderately prevented by FK1052 (3.2 mg/kg), but not by granisetron (3.2 mg/kg). Cisplatin-induced acute (10 mg/kg, i.v.) and delayed (5 mg/kg, i.p.) emesis were significantly reduced by single and multiple intravenous injection of both FK1052 (3.2 mg/kg) and granisetron (3.2 mg/kg), respectively. The present study suggests that FK1052 may be useful against both acute and delayed emesis induced by cancer chemotherapy. Moreover, it is suggested that blockades of 5-HT3 and 5-HT4 receptors are not relevant to the control of motion sickness; and furthermore, it suggested that blocking 5-HT4 receptors in addition to 5-HT3 receptors does not have an additional effect on the control of cisplatin-induced emesis, but that 5-HT4 receptors are at least partly involved in the mechanism of emesis induced by copper sulfate.

Diphenidol has no actual broad antiemetic activity in dogs and ferrets.

Previous studies showed that diphenidol was effective on emetogens-induced pica, eating of non-nutritive substances, in rats, a model analogous to emesis in other species. We evaluated the actual antiemetic activity of diphenidol against four emetic stimuli in the dog and ferret, animals that possess an emetic reflex. In dogs, emetic responses to apomorphine were significantly prevented by diphenidol (3.2 mg/kg, i.v.), whereas diphenidol (3.2 mg/kg, i.v. x 2) showed a weak inhibition to the vomiting evoked by cisplatin. In ferrets, diphenidol (10 mg/kg, i.p.) exhibited a weak antiemetic activity on the emesis induced by copper sulfate and had no activity on emesis by loperamide. On the other hand, CP-122,721, a NK1-receptor antagonist, significantly reduced the emetic episodes to all four stimuli. These results suggest that the prediction of antiemetic activity of compounds in animals lacking an emetic reflex does not always correspond with actual antiemetic activity.

Kainic acid induces leukemia inhibitory factor mRNA expression in the rat brain: differences in the time course of mRNA expression between the dentate gyrus and hippocampal CA1/CA3 subfields.

Leukemia inhibitory factor (LIF) is a pluripotent cytokine which affects the survival and differentiation of various types of cells both in the hematopoietic and nervous systems. In this study, the time course and localization of LIF mRNA expression following kainic acid-induced seizures were examined by northern blot analyses and in situ hybridization. Northern blot analyses demonstrated that intraperitoneal injection of kainic acid at a convulsive dose induced LIF mRNA expression intensely in the hippocampus and moderately to weakly in the cerebral cortex, thalamus and hypothalamus. The expression peaked at 8-24 h after the injection in the hippocampus and cerebral cortex and at 8 h in the thalamus and hypothalamus. In situ hybridization revealed different time courses of LIF mRNA expression depending on the area of the hippocampus; that is, the expression peaked at 10 h in the granule cell layer of the dentate gyrus, then at 12 h in the polymorph and molecular layers of the dentate gyrus, and finally at 12-24 h in the strata oriens and radiatum of the CA1 and CA3 subfields. It is worth noting that the expression of LIF mRNA was intense in the dentate gyrus, the region where neurogenesis and aberrant network reorganization have been shown to be induced by seizures. The upregulation of LIF mRNA expression in the dentate granule cell layer followed by that in the dentate polymorph and molecular layers may be involved in activity-dependent neurogenesis in the granule cell layer and ectopic migration of granule cells to the polymorph and molecular layers in the dentate gyrus.

ATP induces leukemia inhibitory factor mRNA in cultured rat astrocytes.

Leukemia inhibitory factor (LIF) is a cytokine involved in the survival and differentiation of the neural cells in the central and peripheral nervous systems. In the present study, we examined the effects of various neurotransmitter receptor agonists on LIF mRNA expression in cultured rat astrocytes, microglia and neurons to elucidate the cell types producing LIF and to clarify the neurotransmitter(s) regulating the mRNA expression. The results demonstrated that the expression of LIF mRNA was intensely induced by ATP in the cultured astrocytes. Experiments using ATP, UTP and related compounds showed the involvement of P2Y2 and P2Y4 purinoceptors in the expression induced by ATP.

Resiniferatoxin antagonizes cisplatin-induced emesis in dogs and ferrets.

We evaluated the antiemetic activity of resiniferatoxin, an ultrapotent capsaicin analogue, on cisplatin- and apomorphine-induced emesis in dogs, and on cisplatin-induced acute and delayed emesis in ferrets. In the dog, resiniferatoxin (10 microg/kg, s.c.) 30 min before the injection of cisplatin markedly prevented acute emesis induced by cisplatin. When animals were given resiniferatoxin (10 microg/kg, s.c.) 24 h prior to cisplatin, the emesis was still inhibited, but not significantly. Resiniferatoxin (10 microg/kg, s.c.) 30 min before the administration of apomorphine also significantly reduced the emetic responses induced by apomorphine in dogs. In the ferret, resiniferatoxin (10 microg/kg, s.c.) 30 min prior to cisplatin completely inhibited acute emesis caused by cisplatin (10 mg/kg, i.p.). When ferrets were given resiniferatoxin (10 microg/kg, s.c.) 16 h prior to cisplatin, the emesis was still significantly inhibited. Cisplatin (5 mg/kg, i.p.) induced both acute (0-24 h) and delayed (24-72 h) phase emesis, and a single injection of resiniferatoxin (10 microg/kg, s.c.) at 36 h after cisplatin significantly reduced subsequent emetic responses during the 36-72 h period. These results suggest that resiniferatoxin-related vanilloids may be useful drugs against both acute and delayed emesis induced by cancer chemotherapy.