Hajime Tamaki

A new thromboxane receptor antagonist, Z-335, ameliorates experimental thrombosis without prolonging the rat tail bleeding time.

We investigated the antithrombotic activity of Z-335, a new thromboxane A2 receptor antagonist, using experimental thrombosis models, and also tested its effect on the rat tail bleeding time. Z-335 (0.1, 0.3, and 1 mg/kg, p.o.) dose-dependently prevented the occurrence of arachidonic acid-induced pulmonary thromboembolism in mice. During photochemically induced thrombosis in the femoral artery of guinea pigs, Z-335 (0.3, 1, and 3 mg/kg, i.v.) dose-dependently prolonged the time required to form thrombi. Moreover, Z-335 (10 mg/kg/day, p.o.) strongly suppressed lauric acid-induced hind limb injury in rats. Z-335 (0.3, 3, 30, and 300 mg/kg, p.o.) did not prolong the tail bleeding time in rats. These results strongly suggest that Z-335 ameliorates experimental thrombosis without prolonging the rat tail bleeding time, and may therefore be a useful antithrombotic drug.

Relationship between gastroprotective effect of locally acting antiulcer agent ecabet sodium and its binding to gastric mucosa in rats. Comparison with sucralfate.

The present study was designed to examine the relationship between the gastroprotective efficacy of the locally acting antiulcer drug ecabet sodium (ecabet) against ethanol-induced gastric lesions and the amount of the drug bound to the mucosa in comparison with sucralfate in rats. Oral administration of ecabet (25–100 mg/kg) and sucralfate (25–400 mg/kg) dose dependently prevented the formation of ethanol-induced gastric lesions, and dose dependently increased the amount of each drug bound to the gastric mucosa. Pretreatment with the antisecretory agent cimetidine (200 mg/kg, per os) significantly reduced the gastroprotective effect of sucralfate in proportion to a decrease in its binding to the mucosa. The same pretreatment tended to reduce both gastroprotection by ecabet and its binding to the mucosa. In anin vitro study using an everted stomach sac, the binding of sucralfate to the mucosa was more markedly decreased than that of ecabet on increasing the pH. These findings indicate that ecabet and sucralfate protect the gastric mucosa against ethanol in proportion to the amount of each drug bound to the gastric mucosa and that the binding of these drugs to the mucosa is under the influence of intraluminal pH. However, the gastroprotective effect of ecabet seems to be less dependent on intraluminal acidity than that of sucralfate.

Antiplatelet effect of Z-335, a new orally active and long-lasting thromboxane receptor antagonist

We investigated the pharmacological characteristics of Z-335 ((+/-)-sodium[2-[4-(chlorophenylsulfonylaminomethyl)indan-5-yl]ace tate monohydrate), a new indan derivative. Z-335 inhibited the specific binding of [3H]SQ-29548 to human platelets and guinea pig platelet membranes. The IC50 values of Z-335 for human platelets and guinea pig platelet membranes were 29.9 +/- 3.1 nM with a slope of 1.09 +/- 0.05 and 32.5 +/- 1.7 nM with a slope of 1.07 +/- 0.02, respectively. Z-335 inhibited thromboxane A2 receptor-mediated human and guinea pig platelet aggregation in vitro and oral administration of this drug to guinea pigs inhibited U-46619- and collagen-induced platelet aggregation for 24 h. Z-335 dose-dependently prevented the occurrence of U-46619-induced pulmonary thromboembolism in mice and the protective effect of this drug (0.3 and 3 mg/kg, p.o.) lasted for 24 h. These results strongly suggest that Z-335 is a potent, orally active and long-lasting thromboxane A2 receptor antagonist, which may be useful as an antiplatelet drug.

Possible Mechanism of Increase in Gastric Mucosal PGE2 and PGI2 Generation Induced by Ecabet Sodium, a Novel Gastroprotective Agent

The gastroprotective agent ecabet sodium(ecabet, 12-sulfodehydroabietic acid monosodium salt)increases the formation of prostaglandin (PG)E2 and I2 by gastric mucosa. Inthe present study, we examined the effect of ecabet on metabolism ofarachidonic acid (AA) in rat gastric mucosal cells.Ecabet (0.1-10 mM) concentration- and time-dependentlypotentiated the release of [14C]AA fromgastric mucosal cells prelabeled with [14C]AA andsimultaneously increased the production ofPGE2 and PGI2. The ecabet-mediatedincreases in [14C]AA release andPGE2 production were both partly depressed bymepacrine (30 and 100 μM) and Ca2+ chelation.Ecabet, however, showed no effect on gastricphospholipase A2 (PLA2) activityand [Ca2+]i in the gastric mucosalcells. Ecabet and other dehydroabietic acid derivatives, 12-carboxydehydroabietic acid monosodium saltand mono[16-(12-sulfodehydroabietyl)]succinic acidmonosodium salt, which potentiated the liberation of[14C]AA, increased the membrane fluidity ofgastric mucosal cells assessed by usingdiphenylhexatrienepropionic acid (DPH-PA) as the probe,while 12-sulfamoyldehydroabietic acid showed no effecton either the AA liberation or the membrane fluidity.Ecabet (0.1-10 mM) increased the membrane fluidityconcentration- and time-dependently in accordance withits facilitating effect on AA release. In conclusion,ecabet increases the synthesis of PGE2 andPGI2 by gastric mucosal cells through promoting the release ofAA, which is partly dependent on PLA2 andCa2+. The ecabet-induced increase in membranefluidity may be involved in part 2 in the liberation ofAA from the gastric mucosal cells.

Antisecretory and antiulcer effect of T-330, a novel reversible proton pump inhibitor, in rats

The antisecretory and antiulcer effects of T-330 (2-[(2-dimethylaminobenzyl)sulfinyl]-1-(3-methylpyridine-2-yl)imidazole) , a novel reversible proton pump inhibitor, were studied in rats. T-330 suppressed dibutyryl cyclic AMP-stimulated acid formation in isolated rat gastric mucosal cells with the IC50 value of 0.57 microM. In chronic fistula rats, intravenous, intraduodenal and oral administration of T-330 inhibited pentagastrin-stimulated gastric acid secretion; the ED50 values calculated from the peak inhibition were 0.36, 0.43 and 0.73 mg/kg, respectively. T-330 also reduced dimaprit-stimulated gastric acid secretion following its intraduodenal injection (ED50 0.85 mg/kg). The antisecretory activities of T-330 following its intraduodenal and oral administration were 3-6- and 4-10-times more potent than those of omeprazole and ranitidine, respectively, while the duration of action of T-330 was apparently shorter than that of omeprazole and was almost equal to that of ranitidine. Oral or duodenal administration of T-330 inhibited the development of acid-related damage (water-immersion- and aspirin-induced gastric lesions, cysteamine-induced duodenal ulcers and reflux esophagitis) with equal or higher potency than omeprazole or ranitidine. Furthermore, T-330 prevented ethanol-induced gastric lesions. These findings indicate that T-330 exerts its antiulcer effect mainly via its potent antisecretory action and partly via its gastroprotective action.

Z-350, a new chimera compound possessing α1-adrenoceptor antagonistic and steroid 5α-reductase inhibitory actions

Abstract The effects of Z-350, (S)-4-[3-(4-{1-(4-methylphenyl)-3-[4-(2-methoxyphenyl)piperazine-1-yl]propoxy} benzoyl)indole-1-yl]butyric acid hydrochloride, a newly synthesized compound possessing α1-adrenoceptor antagonistic and steroid 5α-reductase inhibitory actions, were studied in vitro. In functional experiments, Z-350 shifted the concentration/response curve for the phenylephrine-induced contraction of rabbit prostate, urethra and aorta to the right with pA2 values of 8.04, 7.57 and 7.13, respectively. The binding affinity of Z-350 for α1-adrenoceptors in rabbit prostate, urethra and aorta were estimated by the displacement of [3H]prazosin. The pKi values for this action of Z-350 were 7.53, 7.95 and 7.62 for the prostate, urethra and aorta, respectively. α1-Adrenoceptor subtype selectivities were studied in the submaxillary gland (α1A) and liver (α1B) of rat. Z-350 inhibited the specific binding of [3H]prazosin to α1A and α1B-adrenoceptors with pKi values of 7.82 and 7.29, respectively. Z-350 inhibited rat prostatic steroid 5α-reductase non-competitively with a pIC50 of 8.42. These results indicate that Z-350 is a α1-adrenoceptor antagonist and is a steroid 5α-reductase inhibitor. It is expected that Z-350 will be a candidate drug for the treatment of benign prostatic hyperplasia.

Nanodisc-to-Nanofiber Transition of Noncovalent Peptide–Phospholipid Assemblies

We report a novel molecular architecture of peptide–phospholipid coassemblies. The amphiphilic peptide Ac-18A-NH2 (18A), which was designed to mimic apolipoprotein α-helices, has been shown to form nanodisc structures with phospholipid bilayers. We show that an 18A peptide cysteine substitution at residue 11, 18A[A11C], forms fibrous assemblies with 1-palmitoyl-2-oleoyl-phosphatidylcholine at a lipid-to-peptide (L/P) molar ratio of 1, a fiber diameter of 10–20 nm, and a length of more than 1 μm. Furthermore, 18A[A11C] can form nanodiscs with these lipid bilayers at L/P ratios of 4–6. The peptide adopts α-helical structures in both the nanodisc and nanofiber assemblies, although the α-helical bundle structures were evident only in the nanofibers, and the phospholipids of the nanofibers were not lamellar. Fluorescence spectroscopic analysis revealed that the peptide and lipid molecules in the nanofibers exhibited different solvent accessibility and hydrophobicity from those of the nanodiscs. Furthermore, the cysteine substitution at residue 11 did not result in disulfide bond formation, although it was responsible for the nanofiber formation, suggesting that this free sulfhydryl group has an important functional role. Alternatively, the disulfide dimer of 18A[A11C] preferentially formed nanodiscs, even at an L/P ratio of 1. Interconversions of these discoidal and fibrous assemblies were induced by the stepwise addition of free 18A[A11C] or liposomes into the solution. Furthermore, these structural transitions could also be induced by the introduction of oxidative and reductive stresses to the assemblies. Our results demonstrate that heteromolecular lipid–peptide complexes represent a novel approach to the construction of controllable and functional nanoscale assemblies.

Effects of anti-rheumatic drugs on rhIL-1.BETA.-induced nitric oxide production in rat synovial fibroblast-like cells.

Effects of anti-rheumatic drugs, gold sodium thiomalate (GST), methotrexate (MTX), D-penicillamine (D-P) and bucillamine (BU), on rhIL-1β-induced nitric oxide (NO) production in rat synovial fibroblast-like cells (SFC) cultured in vitro were investigated. The SFC (passage 4) were cultured for 48hrs in Dulbeccos modified Eagles medium containing an NO inducer, LPS or rhIL-1β. NO production by SFC was assessed by using Griess reagent. RhIL-1β but not LPS, induced a significant increase in NO production in SFC. The rhIL-1β-induced NO production was inhibited by the presence of GST in a dose dependent manner, whereas MTX (100 ng/ml) had no effect. In contrast, both D-P (10 μg/ml) and BU (3 μg/ml) significantly stimulated rhIL-1β-induced NO production in SFC. This effect of SH-containing antirheumatic drugs was completely abolished by the presence of NO inhibitors, aminoguanidine (AG : 1 mM) and cycloheximide (CH : 2 μM) . AG but not CH, added at a later stage of culture (24-48hrs) abolished rhiL 1β induced NO production, indicating that these SH-compounds stimulate NO synthase activity in SFC.The present study suggests that SH-anti-rheumatic drugs stimulate rhIL-1β-induced NO production in SFC, and that the increase in NO may partly inhibit the bone destruction in rheumatoid arthritis.