Tomohiro Miike

Novel (S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids: Peroxisome proliferator-activated receptor γ selective agonists with protein-tyrosine phosphatase 1B inhibition

A novel series of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and (S)-2-[(2E,4E)-hexadienoyl]-7-(2-{5-methyl-2-[(1E)-5-methylhexen-1-yl]oxazol-4-yl}ethoxy)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14i) was identified as a potent human peroxisome proliferator-activated receptor γ (PPARγ) selective agonist (EC(50)=0.03 μM) and human protein-tyrosine phosphatase 1B (PTP-1B) inhibitor (IC(50)=1.18 μM). C(max) after oral administration of 14i at 10mg/kg was 2.2 μg/ml (4.5 μM) in male SD rats. Repeated administration of 14i and rosiglitazone for 14 days dose-dependently decreased plasma glucose levels, ED(50)=4.3 and 23 mg/kg/day, respectively, in male KK-A(y) mice. In female SD rats, repeated administration of 14i at 12.5-100mg/kg/day for 28 days had no effect on the hematocrit value (Ht) and red blood cell count (RBC), while rosiglitazone significantly decreased them from 25mg/kg/day. In conclusion, 14i showed about a fivefold stronger hypoglycemic effect and fourfold or more weaker hemodilution effect than rosiglitazone, indicating that 14i is 20-fold or more safer than rosiglitazone. Compound 14i is a promising candidate for an efficacious and safe anti-diabetic drug targeting PPARγ and PTP-1B.

Regional heterogeneity of substance P-induced endothelium-dependent contraction, relaxation, and -independent contraction in rabbit pulmonary arteries

AIMS The present study examined whether substance P (SP)-induced endothelium-dependent TXA(2)-mediated contraction (EDC), nitric oxide (NO)-mediated relaxation (EDR), and endothelium-independent contraction (EIC) are different between the rabbit proximal and distal intrapulmonary arteries. MAIN METHODS The helically cut strips of isolated proximal and distal arteries were fixed vertically between hooks in organ bath, and changes in isometric tension were measured. KEY FINDINGS SP-induced EDC was greater in the distal than proximal arteries, and EDR was greater in the proximal than distal arteries. However, under the complete blockade of NK(2) receptors and NO production, SP (10(-9)-3x10(-7) M)-induced EDC did not differ between proximal and distal arteries. Under the complete blockade of NK(2) receptors and TXA(2) production, SP (3x10(-10)-3x10(-8) M)-induced EDR was greater in the proximal than distal arteries. Neither contraction induced by U-46619, a TXA(2) agonist, nor relaxation by sodium nitroprusside, an NO donor, was different between both portions of the arteries. Both ionomycin (10(-8) M)- and l-arginine (1 mM)-induced EDRs were also significantly greater in the proximal than distal arteries. Under the blockade of NK(1) receptors and NO and TXA(2) production, SP (10(-7) M)-induced EIC was greater in the distal than proximal arteries. In summary, the capacity for NO production is higher in the proximal than distal arteries, resulting in SP-induced higher EDR and lower EDC in the proximal arteries. SIGNIFICANCE These regional differences in responses to SP may play important roles in maintaining the homogenous distribution of blood flow in the lung.

Lipopolysaccharide-induced impairment of nitric oxide-mediated vasorelaxation and protective effects of nitric oxide synthesis inhibitors in isolated rat mesenteric arteries

Isolated rat mesenteric arteries were incubated with lipopolysaccharide (LPS) for 6 h and then mounted in an organ bath to investigate their responses to various relaxants. Exposure to LPS moderately reduced acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), and markedly reduced sodium nitroprusside (SNP)-induced endothelium-independent relaxation (EIR). It did not affect ACh-induced EDR under treatment with a nitric oxide synthase (NOS) inhibitor, which is mediated by an endothelium-derived hyperpolarizing factor (EDHF), and forskolin-induced EIR. N-(3-(Aminomethyl)benzyl)acetamidine (1400 W), an inducible nitric oxide synthase (iNOS) inhibitor, actinomycin D, an RNA polymerase inhibitor, cycloheximide, a protein synthesis inhibitor, and dexamethazone reduced the nitric oxide (NO) production and reversed the reduced ACh-induced EDR and SNP-induced EIR. In LPS-treated mesenteric artery, L-arginine-induced relaxation was not affected by removal of endothelium, indicating muscular inducible nitric oxide synthase (iNOS) induction. Pre-exposure to SNP (NO donor) also moderately reduced ACh-induced EDR and markedly reduced SNP-induced EIR with little effect on ACh-induced EDHF-mediated EDR. In conclusion, in vitro exposure to LPS desensitized vascular smooth muscle cells to endogenous and exogenous NO by overproduction of muscular iNOS-derived NO, and an iNOS inhibitor and iNOS induction inhibitors prevented the LPS-induced desensitization.

NK1, receptor-mediated endothelium-dependent relaxation and contraction with different sensitivity to post-receptor signaling in pulmonary arteries

In rabbit intrapulmonary arteries, substance P (SP) has been reported to induce endothelium-dependent relaxation (EDR) and endothelium-dependent contraction (EDC) via tachykinin NK(1) receptors, and endothelium-independent contraction (EIC) via tachykinin NK(2) receptors. The present study pharmacologically examined whether these opposite responses (EDR and EDC) are mediated by the same NK(1) receptor. Five tachykinin agonists, including septide, a reportedly atypical NK(1) agonist, caused concentration-dependent EDR in the presence of NK2 antagonist (SR-48968) + TXA2 synthetase inhibitor (ozagrel), which blocked EIC and EDC, in pre-contracted arteries, and concentration-dependent EDC in the presence of NK2 antagonist (SR-48968) + nitric oxide synthase inhibitor (l-N(G)-nitro-arginine methyl ester), which blocked EIC and EDR, in non-contracted arteries. The EC(50) values of these agonists for EDR were smaller than those for EDC, indicating that the affinities of NK(1) agonists to NK(1) receptors are different between EDR and EDC. However, the rank order of their potency for EDR and EDC was the same: SP = septide > SP methyl ester (SPME) > neurokinin A > neurokinin B. [Ala(5), beta-Ala(8)]-alpha-neurokinin fragment 4-10 (NK2 agonist) and senktide (NK3 agonist) caused no responses. Two structurally different NK(1) antagonists, CP-99994 and SR-140333, shifted the concentration-EDC and -EDR curves of SPME, a selective NK(1) agonist, and septide rightward and suppressed their maximal responses in a similar concentration-dependent manner, indicating that the affinities of NK(1) antagonists to NK1 receptors are similar between EDR and EDC. U-73122, a phospholipase C inhibitor, and thapsigargin, 2,5-di-tert-butylhydroquinone, and ruthenium red, all intracellular Ca2+ release blockers, inhibited SP-induced EDR and EDC. Effective concentrations of ionomycin (Ca2+ ionophore) causing EDR were also lower than those causing EDC. Taken together, SP-induced EDR and EDC are mediated by activation of the same NK1 receptor followed by an increase in intracellular Ca2+, and sensitivity to Ca2+ may be higher in the EDR than EDC pathway.

Relationships between lipophilicity and biological activities in a series of indoline-based anti-oxidative acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors.

A novel series of 1-alkyl-7-amido-indoline-based anti-oxidative acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors have been reported and are expected to lower plasma cholesterol levels due to the inhibition of intestinal and hepatic ACAT, and to inhibit cholesterol accumulation in macrophages due to the inhibition of low density lipoprotein (LDL) oxidation. In the present study, relationships between lipophilicity and biological activities were examined in 13 derivatives. Lipophilicity (logP) increased and water solubility decreased with dependence on the number of carbons in the 1-alkyl chain. Inhibitory activity against both in vitro intestinal ACAT and LDL oxidation positively correlated with logP; however, the optimum logP, at which the level of activity is maximal, differed between these two effects. Inhibitory activity against in vitro plasma oxidation was weakly dependent on logP. Plasma concentrations of the derivatives after oral administration at 10 mg/kg correlated negatively with logP and positively with water solubility. Hypocholesterolemic activity in rats fed a high-cholesterol diet, and the ratio of Cmax and IC50 values for ACAT inhibition, an index of effective plasma concentration, positively and highly correlated with logP, while ex vivo inhibitory activity against plasma oxidation in rats, and the ratio of Cmax and IC50 values for the inhibition of plasma oxidation negatively correlated with logP. In conclusion, in vitro ACAT inhibitory and anti-oxidative activity were differently dependent on logP, and intestinal absorption was inversely dependent on lipophilicity in indoline-based anti-oxidative ACAT inhibitors. The hypocholesterolemic effect positively correlated and the ex vivo anti-oxidative effect negatively correlated with lipophilicity. Optimum logP as a bioavailable dual inhibitor against in vivo ACAT and lipid peroxidation was estimated to be 3.8 (1-pentyl and 1-isopentyl derivatives) in the present series of derivatives.