Kumiko Noda

A Long-Acting and Highly Selective Prostacyclin Receptor Agonist Prodrug, 2-{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304), Ameliorates Rat Pulmonary Hypertension with Unique Relaxant Responses of Its Active Form, {4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic Acid (MRE-269), on Rat Pulmonary Artery

2-{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304) is an orally available, long-acting nonprostanoid prostacyclin receptor (IP receptor) agonist prodrug. In a rat model of pulmonary hypertension induced by monocrotaline (MCT), NS-304 ameliorated vascular endothelial dysfunction, pulmonary arterial wall hypertrophy, and right ventricular hypertrophy, and it elevated right ventricular systolic pressure and improved survival. {4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid (MRE-269), the active form of NS-304, is much more selective for the IP receptor than are the prostacyclin analogs beraprost and iloprost, which also have high affinity for the EP3 receptor. To investigate the effect of receptor selectivity on vasodilation of the pulmonary artery, we assessed the relaxant response to these IP agonists in rats. MRE-269 induced vasodilation equally in large pulmonary arteries (LPA) and small pulmonary arteries (SPA), whereas beraprost and iloprost induced less vasodilation in SPA than in LPA. An EP3 agonist, sulprostone, induced SPA and LPA vasoconstriction, and an EP3 antagonist attenuated the vasoconstriction. Beraprost showed EP3 agonism and induced LPA and SPA vasoconstriction, whereas the EP3 antagonist inhibited this vasoconstriction and enhanced beraprost- and iloprost-induced SPA vasodilation. These findings suggest that the EP3 agonism of beraprost and iloprost interfered with the SPA vasodilation resulting from their IP receptor agonism. Endothelium removal markedly attenuated the vasodilation induced by beraprost, but not that induced by MRE-269 or iloprost. Moreover, the vasodilation induced by beraprost and iloprost, but not that induced by MRE-269, was more strongly attenuated in LPA from MCT-treated rats than from normal rats. NS-304 is a promising alternative medication for pulmonary arterial hypertension with prospects for good patient compliance.

A long-acting and highly selective prostacyclin receptor agonist prodrug, NS-304, ameliorates rat pulmonary hypertension with unique relaxant responses of its active form, MRE-269, on rat pulmonary artery

2-{4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide (NS-304) is an orally available, long-acting nonprostanoid prostacyclin receptor (IP receptor) agonist prodrug. In a rat model of pulmonary hypertension induced by monocrotaline (MCT), NS-304 ameliorated vascular endothelial dysfunction, pulmonary arterial wall hypertrophy, and right ventricular hypertrophy, and it elevated right ventricular systolic pressure and improved survival. {4-[(5,6-Diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid (MRE-269), the active form of NS-304, is much more selective for the IP receptor than are the prostacyclin analogs beraprost and iloprost, which also have high affinity for the EP3 receptor. To investigate the effect of receptor selectivity on vasodilation of the pulmonary artery, we assessed the relaxant response to these IP agonists in rats. MRE-269 induced vasodilation equally in large pulmonary arteries (LPA) and small pulmonary arteries (SPA), whereas beraprost and iloprost induced less vasodilation in SPA than in LPA. An EP3 agonist, sulprostone, induced SPA and LPA vasoconstriction, and an EP3 antagonist attenuated the vasoconstriction. Beraprost showed EP3 agonism and induced LPA and SPA vasoconstriction, whereas the EP3 antagonist inhibited this vasoconstriction and enhanced beraprost- and iloprost-induced SPA vasodilation. These findings suggest that the EP3 agonism of beraprost and iloprost interfered with the SPA vasodilation resulting from their IP receptor agonism. Endothelium removal markedly attenuated the vasodilation induced by beraprost, but not that induced by MRE-269 or iloprost. Moreover, the vasodilation induced by beraprost and iloprost, but not that induced by MRE-269, was more strongly attenuated in LPA from MCT-treated rats than from normal rats. NS-304 is a promising alternative medication for pulmonary arterial hypertension with prospects for good patient compliance.

Inhibitions of urinary oxidative stress and renal calcium level by an extract of Quercus salicina Blume/Quercus stenophylla Makino in a rat calcium oxalate urolithiasis model.

Objectives:  To clarify the mechanism of Urocalun, an extract of Quercus salicina Blume/Quercus stenophylla Makino (QS), in the treatment of urolithiasis.

Release of endothelial nitric oxide in coronary arteries by celiprolol, a β1-adrenoceptor antagonist: possible clinical relevance

Mechanisms underlying celiprolol-induced vasodilatation were analyzed in isolated porcine coronary arteries. Celiprolol induced dose-related relaxation of the artery rings with endothelium, an effect which was suppressed by N(G)-nitro-L-arginine methylester (L-NAME), nitric oxide (NO) scavenger, guanylate cyclase inhibitor, endothelium denudation, and removal of Ca(2+). L-NAME contracted, and superoxide dismutase relaxed, the arteries only when the endothelium was preserved. Neither superoxide dismutase nor beta-adrenoceptor antagonists changed celiprolol-induced relaxations. Celiprolol increased the cyclic GMP content in the tissue. The release of NO from endothelium, estimated by the extracellular production of cyclic GMP in arteries incubated in medium containing guanylate cyclase and GTP, was augmented by celiprolol, and L-NAME abolished this action of celiprolol. It is concluded that celiprolol elicits relaxation by acting on sites other than beta-adrenoceptors in the endothelium and by releasing NO, which activates soluble guanylate cyclase in smooth muscle and produces cyclic GMP. Scavenging of superoxide anions from the endothelium does not seem to account for the induced relaxation.

Modifications by sumatriptan and acetylcholine of nitric oxide-mediated neurogenic dilatation in dog cerebral arteries

Canine cerebral arterial strips denuded of endothelium responded to nicotine and transmural electrical stimulation with relaxations, which were abolished by NG-nitro-L-arginine and methylene blue. Magnitudes of relaxation did not differ in the arteries contracted with prostaglandin F2alpha and sumatriptan, an effective therapeutic of migraine. Sumatriptan concentration-dependently contracted the arteries responding to 2 Hz stimulation with persistent relaxations, and the concentration of this 5-HT1B/1D/1F receptor agonist to overcome the relaxation averaged 1.06 x 10(-7) M. Acetylcholine inhibited the response to nerve stimulation due possibly to its action on prejunctional nitroxidergic nerves; the inhibition did not differ in the arteries contracted with prostaglandin F2alpha and K+. It appears that sumatriptan does not interfere with the release of nitric oxide from nerves but counteracts the neurogenic relaxation by functional antagonistic action on smooth muscle. Prejunctional inhibition by muscarinic receptor activation is unlikely associated with opening of neuronal K+ channels.

Functional role of inhibitory and excitatory nerves in the porcine lower urinary tract

In the trigone (three portions) and proximal urethra isolated from castrated male pigs, transmural electrical stimulation (0.5-10 Hz) induced no or slight contractions followed by frequency-related relaxations. Atropine suppressed the contraction and potentiated the relaxation. N(G)-nitro-L-arginine methylester (L-NAME), a nitric oxide (NO) synthase inhibitor, depressed or abolished the relaxation induced by low frequency stimulation, but only slightly attenuated the response to high frequency stimulation. L-Arginine reversed the inhibitory effect. L-NAME-sensitive relaxation by 1 Hz stimulation was abolished by 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor. Release of NO by nerve stimulation to trigonal strips was determined by increased formation of cyclic GMP in the incubation media containing guanylate cyclase and GTP. L-NAME-resistant relaxation by 10 Hz stimulation was not impaired by ODQ, capsaicin, chymotrypsin, K(+) channel inhibitors and beta-adrenoceptor antagonists. Similar results were obtained in the trigone and urethra from normal male and female pigs. Detrusor muscle responded to nerve stimulation with contraction followed by slight relaxation. Relaxations at 1 and 10 Hz stimulation under treatment with atropine and alpha,beta-methylene ATP were partially attenuated by L-NAME. It is concluded that there is no significant difference in the inhibitory responses, sensitive and resistant to L-NAME, to nerve stimulation in the trigone and proximal urethra from castrated and non-castrated male and female pigs. Relaxations to stimulation at 1 Hz seem to be mediated exclusively by neurogenic NO and cyclic GMP generation, whereas those to 10 Hz stimulation is mainly associated with non-NO relaxing factor(s), peptides, K(+) channel openers and beta-adrenoceptor agonist being unlikely involved.

Blockade of voltage-gated calcium channel Cav1.2 and α1-adrenoceptors increases vertebral artery blood flow induced by the antivertigo agent difenidol

Difenidol (1,1-diphenyl-4-piperidino-1-butanol hydrochloride) is an effective drug for the treatment of vertigo and dizziness. This drug is known to improve the blood flow in vertebral arteries, though the precise mechanism underlying this action remains unclear. In the present study, we investigated the effect of difenidol on voltage-gated calcium channel Ca(v)1.2 and α(1)-adrenoceptor subtypes that regulate the intracellular calcium concentration ([Ca(2+)](i)), as well as their possible involvement in the action of difenidol on vertebral artery relaxation and blood flow in dogs. In vitro binding assays demonstrated that difenidol at micromolar concentrations bound to the α(1A)-, α(1B)- and α(1D)-adrenoceptor subtypes. Difenidol inhibited the phenylephrine-induced increase in [Ca(2+)](i) in Chinese hamster ovary cells expressing human α(1A)-, α(1B)- or α(1D)-adrenoceptor subtypes with similar IC(50) values in the low micromolar range. In an electrophysiological assay, difenidol inhibited L-type calcium channel (Ca(v)1.2 subunit). In dogs, i.v. difenidol preferentially enhanced vertebral over femoral arterial blood flow. Phenylephrine and potassium induced contraction of dog vertebral arterial rings, and difenidol inhibited this action. Inhibition of phenylephrine-induced contraction by difenidol was mimicked by the α(1)-adrenoceptor antagonist phentolamine, the α(1A)-adrenoceptor antagonist RS 17,053 (N-[2-(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-α,α-dimethyl-1H-indole-3-ethanamine hydrochloride) and the α(1D)-adrenoceptor antagonist BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione dihydrochloride). In addition, the L-type calcium channel blocker nifedipine, like difenidol, attenuated the potassium-induced contraction. These findings suggest that the difenidol-induced increase in vertebral arterial blood flow may be due to vascular relaxation mediated by mixed blocking actions at α(1)-adrenoceptors and voltage-gated calcium channel Ca(v)1.2.