Mamoru Kanda

Endothelium-dependent contraction in intrapulmonary arteries: mediation by endothelial NK1 receptors and TXA2.

1 We have examined whether three natural tachykinins, substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) induce an endothelium‐dependent contraction (EDC) in the rabbit isolated intrapulmonary artery. 2 Removal of the endothelium almost abolished the contraction induced by SP (10−8 m) while it did not attenuate the contraction induced by SP (10−7 m), NKA (10−9‐10−7 m) or NKB (10−9‐10−7 m). 3 The EDC induced by SP (10−8 m) was abolished by NK1 antagonists (FK‐888, CP‐96345, CP‐99994 and SR‐140333) but not by an NK2 antagonist (SR‐48968). 4 The EDC induced by SP was attenuated by cyclo‐oxygenase inhibitors (aspirin and indomethacin), thromboxane A2 (TXA2) synthetase inhibitors (OKY‐046, KY‐234 and KY‐063) and a TXA2 antagonist (S‐1452). 5 The rank order of potency causing endothelium‐independent contraction (EIC) was NKA>NKB>SP. The EIC induced by SP (10−7 m) was attenuated by an NK2 antagonist but not by NK1 antagonists, cyclo‐oxygenase inhibitors, TXA2 synthetase inhibitors or a TXA2 antagonist. 6 In conclusion, SP at 10−8 m induces EDC via endothelial NK1 receptors and TXA2 production, and SP at 10−7 m induces EIC via NK2 receptors in the rabbit intrapulmonary artery.

Novel indoline-based acyl-CoA:cholesterol acyltransferase inhibitor with antiperoxidative activity: improvement of physicochemical properties and biological activities by introduction of carboxylic acid.

A series of novel indoline derivatives with an ionizable moiety were synthesized to find a bioavailable acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor with antiperoxidative activity. [7-(2,2-Dimethylpropanamido)-4,6-dimethyl-1-octylindolin-5-yl]acetic acid hemisulfate (2, pactimibe sulfate) with low lipophilicity and high water solubility showed good oral absorption and inhibitory activity against foam cell formation in THP-1 cells exposed to acetyl-LDL after differentiation (IC50: 0.3 microM) and an antiperoxidative effect in LDL of hypercholesterolemic rabbits (IC50: 1.0 microM). 2 inhibited macrophage, hepatic, and intestinal ACAT activity (IC50: 1.9, 0.7, and 0.7 microM, respectively). Maximal plasma concentration after oral administration of 2 at 10 mg/kg was 0.9 microg/mL in rats, 3.0 microg/mL in rabbits, and 11.2 microg/mL in dogs. Repeated administration of 2 lowered plasma LDL/VLDL cholesterol in hypercholesterolemic rabbits at 1 mg/kg/day, rats and dogs at 3 mg/kg/day, and in normocholesterolemic hamsters at 3 mg/kg/day. 2 is a promising candidate for antihyperlipidemic and antiatherosclerotic drugs.

Inhibitory effects of PGD2, PGJ2 and 15-deoxy-Δ12,14-PGJ2 on iNOS induction in rat mesenteric artery

PGD2 and its metabolites PGJ2 and 15-deoxy-delta12,14-PGJ2 have been reported to inhibit iNOS induction in cultured vascular smooth muscle cells. The present study was undertaken to determine whether these prostanoids inhibit iNOS induction in the isolated rat mesenteric artery. The artery without endothelium was incubated with and without lipopolysaccharide (LPS) at 37 degrees C for 6 hrs, then washed and mounted in an organ bath to measure isometric changes in tension. L-arginine but not D-arginine (10(-6) - 10(-3) M) induced concentration-dependent relaxations only in the artery preincubated with LPS, the relaxations of which were attenuated by L-N(G)-nitroarginine methyl ester (LNAME, 10(-4) M), a non-selective iNOS inhibitor, and 1400W (10(-5) and 10(-4) M), a selective iNOS inhibitor. Co-treatment of cycloheximide (10(-5) M), a protein synthesis inhibitor, or actinomycin D (10(-7) M), an RNA synthesis inhibitor with LPS inhibited the development of relaxing ability in response to L-arginine, indicating iNOS induction by LPS. PGD2, PGJ2 and 15-deoxy-delta12,14-PGJ2 but not PGE2, PGI2 or PGF2alpha also inhibited the development of relaxing ability in response to L-arginine when added during incubation with LPS. Incubation of the artery with LPS at 37 degrees C for 6 hrs markedly increased production of nitric oxide (NO), which was abolished by 15-deoxy-delta12,14-PGJ2 (10(-5) M). An imunohistochemical study using antibody against murine iNOS showed that 15-deoxy-delta12,14-PGJ2 (10(-5) M) inhibited the expression of iNOS protein in isolated rat mesenteric arteries. These results demonstrated that PGD2 and its metabolites inhibit iNOS induction by LPS in isolated rat mesenteric arteries, resulting in reduced relaxing ability in response to L-arginine.

Endothelium-dependent relaxation followed by contraction mediated by NK1 receptors in precontracted rabbit intrapulmonary arteries

In the present study, we examined whether substance P (SP) and SP methyl ester (SPME), a selective NK1 agonist, cause biphasic responses consisting of endothelium‐dependent relaxation (EDR) and contraction (EDC) in precontracted rabbit intrapulmonary arteries. In arteries contracted with PGF2α (2×10−6 M), SP as well as SPME caused only EDR at low concentration (10−9 M) and EDR followed by EDC at higher concentrations, indicating the involvement of NK1 receptors. The SP (10−8 M)‐induced EDR was abolished in arteries moderately contracted by PGF2α (5×10−7 M) and the EDC in arteries maximally contracted by PGF2α (10−5 M), indicating that EDR and EDC are inversely dependent on preexisting tone. Indomethacin (10−8–10−6 M), a cyclo‐oxygenase inhibitor, and ozagrel (10−8–10−6 M), a TXA2 synthetase inhibitor attenuated the EDC in the SPME (10−7 M)‐induced biphasic response and markedly potentiated the EDR. AA‐861 (10−8–10−6 M), a 5‐lipoxygenase inhibitor, did not affect the EDR or EDC. L‐NG‐nitro‐arginine methyl ester (10−5–10−4 M), a nitric oxide synthase inhibitor, attenuated the EDR and slightly potentiated the EDC. CP‐99994 (10−10–10−8 M), an NK1 antagonist, attenuated the EDC and potentiated the EDR in the SPME (10−7 M)‐induced biphasic response, while the NK2 antagonist SR‐48968 (10−9–10−7 M) had no effect. CP‐99994 attenuated the SPME (10−7 M)‐induced EDC under EDR‐blockade to a greater extent than the EDR under EDC‐blockade, indicating that CP‐99994 enhanced the EDR component by preferential inhibition of the EDC component. In conclusion, NK1 agonists caused a biphasic endothelium‐dependent response (EDR and EDC) in submaximally precontracted intrapulmonary arteries. The EDC and EDR mediated by NK1 receptors may play physiological and/or pathophysiological roles in modulation of vascular tone.

Somatostatin-induced contraction mediated by endothelial TXA2 production in canine cerebral arteries

Whether somatostatin causes endothelium-dependent contraction (EDC) in isolated canine basilar arteries was examined. Somatostatin (10(-8)-10(-6) M) caused transient contractions in a dose-dependent manner. These contractions were abolished by removal of the endothelium, while the contractile response to neuropeptide Y occurred even after removal of the endothelium. The EDC induced by somatostatin (10(-7) M) was affected by neither atropine (10(-6) M) nor cyclo-somatostatin (10(-5) M), which suggests that the EDC is not due to release of endogenous acetylcholine and that the endothelial somatostatin receptor is different from hormonal somatostatin receptors. The somatostatin-induced EDC was attenuated by cyclooxygenase inhibitors (aspirin and indomethacin), thromboxane A2 (TXA2) synthetase inhibitors (OKY-064 and RS-5186), and TXA2 antagonists (ONO-3708 and S-145), which suggests that the endothelium-derived contracting factor is TXA2. These findings demonstrate that somatostatin causes EDC via activation of TXA2 synthesis in canine cerebral arteries.

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.

Endothelium-dependent contraction induced by substance P in canine cerebral arteries: involvement of NK1 receptors and thromboxane A2.

We characterized the endothelial responses to substance P (SP) in the isolated canine cerebral artery. SP caused concentration-dependent contraction at 10(-10) - 10(-7) M and relaxation at 10(-10) and 10(-9) M, which were abolished by removal of the endothelium. The SP-induced endothelium-dependent relaxation (EDR) was suppressed, while the endothelium-dependent contraction (EDC) was increased by repeated application. The EDC induced by SP (10(-7) M) was attenuated by SR-140333 (10(-9) - 10(-7) M) and CP-99994 (10(-7) M), both NK1 antagonists, but not by SR-48968 (10(-7) M), an NK2 antagonist, or four antagonistic SP analogues (10(-6) M). The EDC induced by SP (10(-7) M) was attenuated by aspirin (10(-5) M), a cyclooxygenase inhibitor, OKY-046 (10(-5) M), a TXA2 synthetase inhibitor and ONO-3708 (10(-8) M), a TXA2 antagonist. Neurokinin A (10(-7) M) but not neurokinin B (10(-7) M) caused EDC similar to that induced by SP. In conclusion, SP induces EDC via endothelial NK1 receptors and TXA2 production in canine cerebral arteries.

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.

Protective effect of the calcium antagonist NKY-722 against renal and arterial injuries in Dahl salt-sensitive rats.

OBJECTIVE To study the effect of long-term administration of NKY-722 and nicardipine on renal dysfunction and morphological changes in the kidneys and arteries in Dahl salt-sensitive (Dahl-S) rats. DESIGN Vehicle, NKY-722 and nicardipine were administered orally to Dahl-S rats fed a high-salt diet for 6 weeks. METHODS Systolic blood pressure was measured once a week. At the last week blood and urine were collected and an autopsy was carried out. RESULTS NKY-722 (1 mg/kg per day) lowered blood pressure reproducibly for 6 weeks, whereas nicardipine (3 mg/kg per day) showed a similar effect at week 1 only. NKY-722 tended to decrease blood urea-nitrogen, and reduced plasma creatinine and renin activity significantly. NKY-722 increased urine volume, urinary sodium, creatinine and protein excretions, but did not affect urinary N-acetyl-beta-D-glucosaminidase activity significantly. NKY-722 increased the glomerular filtration rate and reduced glomerulosclerosis and renal arterial injury morphologically. Nicardipine did not affect blood or urinary parameters, but reduced glomerular injury significantly. NKY-722 but not nicardipine reduced cerebral arterial injury. A lower dose of NKY-722 (0.3 mg/kg per day) did not affect blood pressure, blood or urinary parameters, but reduced glomerulosclerosis and renal arterial injury significantly. NKY-722 (1 mg/kg per day) and nicardipine (3 mg/kg per day) increased urinary 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and PGE2. NKY-722 but not nicardipine increased the 6-keto-PGF1 alpha:thromboxane B2 ratio in the thoracic aorta. CONCLUSIONS NKY-722 improved the renal dysfunction, and reduced glomerular, renal and cerebral arterial injuries in Dahl-S rats. The effect of NKY-722 on glomerulosclerosis and arterial injuries is, at least partly, independent of blood pressure, and is probably related to the effect on eicosanoid metabolism.

Novel indoline-based acyl-CoA: cholesterol acyltransferase inhibitor: Effects of introducing a methanesulfonamide group on physicochemical properties and biological activities

A novel series of indoline-based acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors with a methanesulfonamide group at the 5-position were synthesized and their lipophilicity and biological activities were evaluated. Hepatic ACAT inhibitory and anti-foam cell formation activity increased dependent on lipophilicity of derivatives with various alkyl chains at the 1-position. The logD(7.0)-biological activity curve of the derivatives with a methanesulfonamide group shifted leftward compared to that of Pactimibe derivatives with a carboxymethyl group, and derivatives with no substituent, suggesting that a methanesulfonamide group plays an important role in the interaction with ACAT protein. Among derivatives, N-(1-ethyl-5-methanesulfonylamino-4,6-dimethylindolin-7-yl)-2,2-dimethylpropanamide (1b) had about twofold lower logD(7.0) than Pactimibe, while it showed twofold higher hepatic ACAT inhibition than and the same anti-foam cell formation as Pactimibe, respectively. The C(max) of 1b (10mg/kg, po) was higher than that of Pactimibe in rats. The plasma protein binding ratio of 1b was lower than that of Pactimibe: 64.8% and 97.9%, respectively. Compound 1b showed greater inhibitory effects on hepatic cholesterol secretion in mice than Pactimibe. In conclusion, the introduction of a methanesulfonamide group is effective to design less lipophilic, more efficacious and more bioavailable indoline-based ACAT inhibitors than previous indoline-based inhibitors.