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Biomedical subjects

M Asano

Publications and source records attributed to M Asano.

At least 109 records · Page 6Linked to original sources

Specificity of mutations induced by riboflavin mediated photosensitization in the supF gene of Escherichia coli.

Riboflavin-mediated photosensitization has been shown to produce 8-hydroxyguanine (oh8Gua) in DNA. We investigated the specificity of mutation of photosensitized supF gene induced in Escherichia coli. The oh8Gua repair deficient E. coli mutant mutM and mutY were transformed with plasmid pUB3 carrying the supF gene irradiated with white light in the presence of riboflavin. Under these conditions, riboflavin photosensitization increased the amounts of oh8Gua in pUB3 DNA. Three types of a single base substitution occurring at G:C pairs were detected in both wild-type and mutM mutant strains. Almost all base substitutions were transversions to T:A or C:G pairs occurring at a similar extent in both wild-type and mutM strains. Mutations derived from mutY strain transformed with photosensitized DNA were only G:C to T:A transversions. These G:C to T:A transversions observed in the mutY strain were suggested to be the result of mispairing of oh8Gua with adenine. Riboflavin-mediated photosensitization may also produce lesions on DNA causing G:C to C:G changes by unknown mechanisms.

Base Sequence↗

A novel class of orally active non-peptide bradykinin B2 receptor antagonists. 4. Discovery of novel frameworks mimicking the active conformation.

In recent articles we reported the identification of a series of 8-[[2, 6-dichloro-3-[N-methyl-N-[(E)-(substituted)acryloylglycyl]amino]++ +benzy l]oxy]-2-methylimidazo[1,2-a]pyridines as the first orally active non-peptide bradykinin (BK) B2 receptor antagonists. Optimization of the terminal glycine part and the imidazo[1,2-a]pyridine moiety led to the discovery of a clinical candidate (5, FR173657). With the aim of completion of the structure-activity relationship (SAR) study, we next investigated the roles of the substituents on the central phenyl ring. The results suggested that the 2,6-dichloro or 2, 6-dimethyl groups may play important roles in regulating the conformations of the 1- and 3-substituents and also may interact with hydrophobic pockets of the B2 receptors. Furthermore, according to the results of a molecular modeling study reported in part 1 of this series, we designed and synthesized a series of sterically constrained analogues by replacing the N-methylamide group with cis-amide-like rigid moieties. We discovered several bioisosteres and chemically proved that the N-methylamide moiety adopts the cis-amide form in the active conformation. Extensive chemical modification led to the identification of a novel class of highly potent and orally active non-peptide B2 antagonists represented by a pyrrole derivative (52a, FR193517). Compound 52a inhibited the specific binding of [3H]BK to recombinant human B2 receptors expressed in Chinese hamster ovary (CHO) cells and guinea pig ileum membrane preparations expressing B2 receptors with IC50s of 0.37 and 0.56 nM, respectively. This compound also displayed excellent in vivo functional antagonistic activity against BK-induced bronchoconstriction in guinea pigs at 1 mg/kg by oral administration.

Administration, Oral↗

A novel class of orally active non-peptide bradykinin B2 receptor antagonists. 2. Overcoming the species difference between guinea pig and man.

Recently we reported the identification of a series of 8-[[3-(N-acylglycyl-N-methylamino)-2, 6-dichlorobenzyl]oxy]-3-halo-2-methylimidazo[1,2-a]pyridines as the first orally active non-peptide bradykinin (BK) B2 receptor antagonists (1-3). These compounds inhibited the specific binding of [3H]BK to guinea pig ileum membrane preparations expressing B2 receptors with nanomolar IC50's and also displayed in vivo functional antagonistic activities against BK-induced bronchoconstriction in guinea pigs at 1 mg/kg by oral administration. However, it was found that their affinities for the B2 receptors in human A-431 cells (human epidermoid carcinoma) were much lower. Intensive modifications of the terminal substituents at the glycine moiety elucidated the structure-activity relationships (SAR) for human B2 receptors, leading to an extended basic framework which incorporated a novel key pharmacophore. Thus, we overcame the species difference and identified the first clinical candidate 18c (FR167344) with IC50's of 0.66 and 1.4 nM for guinea pig ileum and human A-431 cells, respectively. This compound displayed in vivo functional antagonistic activity against BK-induced bronchoconstriction in guinea pigs with an ED50 value of 0.17 mg/kg by oral administration. This novel non-peptide B2 antagonist is extremely potent both in vitro and in vivo by oral administration and is expected to be the first member of a new class of drug for the treatment of various inflammatory diseases.

Administration, Oral↗

A novel class of orally active non-peptide bradykinin B2 receptor antagonists. 3. Discovering bioisosteres of the imidazo[1,2-a] pyridine moiety.

Recently we reported on overcoming the species difference of our first orally active non-peptide bradykinin (BK) B2 receptor antagonists, incorporating an 8-[[3-(N-acylglycyl-N-methylamino)-2, 6-dichlorobenzyl]oxy]-3-halo-2-methylimidazo[1,2-a]pyridine skeleton, leading to identification of the first clinical candidate 4a (FR167344). With this potent new lead compound in hand, we then investigated further refinement of the basic framework by replacement of the imidazo[1,2-a]pyridine moiety and discovered several bioisosteric heterocycles. Extensive optimization of these new heteroaromatic derivatives revealed the detailed structure-activity relationships (SAR) around the imidazo[1, 2-a]pyridine ring and the 2,6-dichlorobenzyl moiety, leading to the discovery of our second clinical candidate 87b (FR173657) which inhibited the specific binding of [3H]BK to recombinant human B2 receptors expressed in Chinese hamster ovary (CHO) cells and guinea pig ileum membrane preparations expressing B2 receptors with IC50's of 1.4 and 0.46 nM, respectively. This compound also displayed excellent in vivo functional antagonistic activity against BK-induced bronchoconstriction in guinea pigs with an ED50 value of 0.075 mg/kg by oral administration. Further modifications of the terminal substituents on the pyridine moiety led to a novel pharmacophore and resulted in the identification of 99 (FR184280), whose IC50 value for human B2 receptors (0.51 nM) was comparable to that of the second-generation peptide B2 antagonist Icatibant.

Administration, Oral↗

Anti-tumor and anti-metastatic effects of human-vascular-endothelial-growth-factor-neutralizing antibody on human colon and gastric carcinoma xenotransplanted orthotopically into nude mice.

In order to determine whether the inhibition of vascular-endothelial-growth-factor (VEGF) activity by administration of an immunoneutralizing antibody could suppress tumor growth and metastasis in spontaneous metastatic models of human colon and gastric carcinoma, 4 human carcinoma xenografts, 2 human colon carcinomas (TK4 and TK 13) and 2 gastric carcinomas (MT2 and MT5) were transplanted orthotopically into nude mice. The anti-VEGF antibody (MV833, 100 microg/mouse) or the same volume of saline was administered i.p. on alternative days from day 10 after transplantation. With each of the 4 xenografts, administration of MV833 significantly inhibited not only primary tumor growth but also macroscopic liver metastasis, although the growth rate varied. The inhibitory effect of MV833 on primary tumor growth appeared to have no correlation with the level of VEGF in tumor. Body-weight gain in each treated group was comparable with that in the control group. No toxicity of the antibody was observed. These results suggest that an anti-VEGF antibody can be effective against a wide variety of cancers, and that VEGF may be a possible target for cancer therapy.

Adenocarcinoma↗

Omega-3 polyunsaturated fatty acids--modulation of voltage-dependent L-type Ca2+ current in guinea-pig tracheal smooth muscle cells.

Omega-3 polyunsaturated fatty acids have been reported to be associated with favorable changes in the respiratory system. To determine one of the mechanisms for this effect, membrane currents were recorded in guinea-pig tracheal myocytes by using the whole-cell voltage clamp technique. Without EGTA in the patch pipette containing the Cs-internal solution, command voltage pulses positive to +0 mV from a holding potential of -60 mV elicited a voltage-dependent L-type Ca2+ current (I(Ca x L)) and a subsequent outward current. Upon repolarization, slowly decaying inward tail currents were recorded. The outward currents and the inward tail current were enhanced by methyl-1,4,-dihydro-2,6-dimethyl-3-nitro-4-(2-trigluromethylphenyl )-pyridine-5-carboxylate, and blocked by Cd2+ or nifedipine. Inclusion of EGTA (5 mM) in the patch pipette also abolished these currents, indicating that they were Ca2+-dependent. When [Cl-]o or [Cl-]i was changed, the reversal potential of these currents shifted, thus behaving like a Cl(-)-sensitive ion channel. 4,4'-Diisothiocyanatostilbene-2,2'-disulphonic acid. a Cl- channel blocker, inhibited the currents. The omega-3 polyunsaturated fatty acids eicosapentaenoic acid (3-30 microM) and docosahexaenoic acid (30 microM) suppressed I(Ca x L) and then inhibited I(Ca x Cl) in a reversible manner. Similar inhibitory effects of eicosapentaenoic acid on I(Ca x L) were observed with 5 mM EGTA in the patch pipette. Neurokinin A (1 microM) and caffeine (10 mM) also transiently activated I(Cl x Ca), probably due to Ca2+ release from Ca2+ storage sites. Pretreatment of the cells with eicosapentaenoic acid markedly suppressed the activation of I(Cl x Ca) by neurokinin A or caffeine. These results suggest that omega-3 polyunsaturated fatty acids inhibit voltage-dependent L-type Ca2+ currents and also Ca2+-activated Cl- currents in tracheal smooth muscle cells from the guinea-pig, which may play a role in modulation of tracheal smooth muscle tone.

Animals↗

Possible mechanism underlying the potent vasoconstrictor actions of cyclopiazonic acid on dog cerebral arteries.

A sustained Ca2+ influx via L-type Ca2+ channels has been shown in the resting state of dog cerebral arteries. Sarcoplasmic reticulum is now recognized to serve as a buffer barrier to Ca2+ entry in vascular smooth muscle cells. To clarify whether sarcoplasmic reticulum of the cerebral arteries can buffer the sustained Ca2+ influx, effects of cyclopiazonic acid (CPA), an inhibitor of sarcoplasmic reticulum Ca2+-ATPase, were determined in endothelium-denuded strips of the cerebral (basilar, posterior communicating, middle cerebral), mesenteric and coronary arteries of the dog. The addition of CPA (0.1-10 microM) during the resting state of the strips caused a concentration-dependent contraction in the three cerebral arteries. The CPA-induced contraction was extremely small in the mesenteric or coronary artery. The CPA-induced contractions in the cerebral arteries were inhibited concentration-dependently by nifedipine (1-100 nM). Nifedipine itself induced relaxation from the resting state of cerebral arteries, suggesting a maintenance of basal tone. The CPA-induced potent contraction seen in the cerebral arteries could be mimicked in the mesenteric artery by elevating the extracellular K+ concentration (14.9 mM) or adding Bay K 8644 [methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyr idine-5-carboxylate] (100 nM) to produce an increase in Ca2+ influx via L-type Ca2+ channels. We conclude that, in the resting state of dog cerebral arteries, (1) the greater part of the sustained Ca2+ influx is buffered by Ca2+ uptake into the sarcoplasmic reticulum, (2) therefore, the inhibition of sarcoplasmic reticulum Ca2+-ATPase by CPA causes a potent contraction, and (3) the maintenance of basal tone suggests that some Ca2+ that entered via L-type Ca2+ channels always reaches the myofilaments in the resting state.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

Demonstration of receptors specific for connective tissue growth factor on a human chondrocytic cell line (HCS-2/8).

The presence of receptors specific for connective tissue growth factor (CTGF) was demonstrated on a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8. The binding of 125I-labeled recombinant CTGF to HCS-2/8 cells was inhibited by unlabeled CTGF but not by PDGF-BB or bFGF. Scatchard analysis revealed the presence of two classes of binding sites with Kd values of 18.6 and 259 nM on cells. A cross-linking study revealed the formation of 125I-CTGF-receptor complex with an apparent molecular weight of 280 kDa. The 125I-CTGF-receptor complex disappeared almost completely on the addition of unlabeled CTGF but not PDGF-BB or bFGF. In addition, the 125I-CTGF-receptor complex was immunoprecipitated with anti-CTGF antiserum but not with anti-PDGF receptor antiserum. These findings suggest that CTGF directly binds to specific receptor molecules on HCS-2/8 cells.

Binding Sites↗

Production of mice deficient in genes for interleukin (IL)-1alpha, IL-1beta, IL-1alpha/beta, and IL-1 receptor antagonist shows that IL-1beta is crucial in turpentine-induced fever development and glucocorticoid secretion.

Interleukin (IL)-1 is a major mediator of inflammation and exerts pleiotropic effects on the neuro-immuno-endocrine system. To elucidate pathophysiological roles of IL-1, we have first produced IL-1alpha/beta doubly deficient (KO) mice together with mice deficient in either the IL-1alpha, IL-1beta, or IL-1 receptor antagonist (IL-1ra) genes. These mice were born healthy, and their growth was normal except for IL-1ra KO mice, which showed growth retardation after weaning. Fever development upon injection with turpentine was suppressed in IL-1beta as well as IL-1alpha/beta KO mice, but not in IL-1alpha KO mice, whereas IL-1ra KO mice showed an elevated response. At this time, expression of IL-1beta mRNA in the diencephalon decreased 1.5-fold in IL-1alpha KO mice, whereas expression of IL-1alpha mRNA decreased >30-fold in IL-1beta KO mice, suggesting mutual induction between IL-1alpha and IL-1beta. This mutual induction was also suggested in peritoneal macrophages stimulated with lipopolysaccharide in vitro. In IL-1beta KO mice treated with turpentine, the induction of cyclooxygenase-2 (EC 1.14.99.1) in the diencephalon was suppressed, whereas it was enhanced in IL-1ra KO mice. We also found that glucocorticoid induction 8 h after turpentine treatment was suppressed in IL-1beta but not IL-1alpha KO mice. These observations suggest that IL-1beta but not IL-1alpha is crucial in febrile and neuro-immuno-endocrine responses, and that this is because IL-1alpha expression in the brain is dependent on IL-1beta. The importance of IL-1ra both in normal physiology and under stress is also suggested.

Animals↗

Molecular maturation and functional expression of mouse polymeric immunoglobulin receptor.

Mouse polymeric immunoglobulin receptor (pIgR) cDNA was stably introduced into a hamster-derived fibroblastic cell line, Chinese hamster ovary (CHO) cell, by the calcium phosphate method. Surface expression of pIgR was detected by immunostaining and FACS analysis. The immunoprecipitated products of cell lysates revealed that the molecular mass of the most mature form of pIgR was approximately 120 kDa. Western blotting and metabolic labeling experiments followed by immunoprecipitation with an anti-mouse secretory component (SC) Ab demonstrated the existence of a 110 kDa immature form of pIgR. The reason for the existence of two forms of pIgR molecule was examined by conducting pulse-chase experiments which revealed the pIgR underwent molecular maturation. During this process, the 110 kDa form of pIgR was converted into a 120 kDa form by glycosylation. Moreover, tunicamycin treatment revealed the core form of pIgR had a molecular mass of approximately 100 kDa. The pIgR expressed on the surface of the transfectant could specifically bind and take up mouse polymeric IgA (MOPC 315), suggesting that, at least in this mouse system, cell type-specific molecules are not necessary for surface pIgR expression and polymeric immunoglobulin (pIg) binding and uptake.

Animals↗

Presence of polysialic acid and HNK-1 carbohydrate on brain glycoproteins from beta-1,4-galactosyltransferase-knockout mice.

Polysialic acid and HNK-1 carbohydrate are expressed on Gal beta 1-->4GlcNAc outer chains of N-linked sugar chain of neural cell recognition molecules at certain developmental stages and involved in neural tissue formation. Targeted inactivation of the mouse beta-1,4-galactosyltransferase (beta-1,4-GalT) gene resulted in short life of the mice which supposedly do not have such carbohydrate antigens but have no defects in neural tissue formation. Analysis of the mutant mouse brain glycoproteins revealed that polysialic acid and HNK-1 carbohydrate are normally expressed in an age-dependent manner. In support of this, protein bands reacted with Ricinus communis agglutinin-I, which interacts with oligosaccharides terminated with the Gal beta 1-->4GlcNAc group, and beta-1,4-GalT activity toward GlcNAc beta-S-pNP were detected in the mutant mouse brain, indicating that brain contains another functional beta-1,4-GalT important for the expression of the carbohydrate antigens.

Animals↗

A novel class of orally active non-peptide bradykinin B2 receptor antagonists. 1. Construction of the basic framework.

A novel class of potent, selective, and orally active non-peptide bradykinin (BK) B2 receptor antagonists were designed and synthesized starting from 8-benzyloxyimidazo[1,2-a]pyridine derivative 2. The unique screening lead (2) was discovered by a two-step intentional random screening process, involving recognition of the relationship between BK and angiotensin II (Ang II) and the common structural features. Systematic chemical modification of 2 elucidated the structural requirements essential for B2 binding affinity leading to the identification of 8-[[3-(N-acylglycyl-N-methylamino)-2,6-dichlorobenzyl]oxy]-3-halo- 2- methylimidazo[1,2-a]pyridine skeleton as the basic framework of this new series of B2 antagonists. A molecular modeling study suggested the key role of the N-methylanilide moiety at the 3-position of the 2,6-dichlorobenzene ring to allow these compounds to adopt the characteristic active conformation. The representative lead compounds inhibited the specific binding of [3H]BK to guinea pig ileum membrane preparations expressing B2 receptors, with nanomolar IC50S and also displayed in vivo functional antagonistic activities against BK-induced bronchoconstriction in guinea pigs at an oral dose of 1 mg/kg. Pharmacokinetic studies of compounds 47c and 50b in rats highlighted their excellent oral bioavailabilities, indicating that they represent the first orally active non-peptide B2 antagonists reported to date.

Administration, Oral↗

Elevated plasma nitrate in patients with crush syndrome caused by the Kobe earthquake.

We investigated the nitric oxide profile in the plasma of ten healthy controls and 29 patients hurt by the Kobe Earthquake. The levels of nitrite (NO2-) and nitrate (NO3-) were measured simultaneously by high-performance liquid chromatography (HPLC) with UV detection using the Griess reaction after the reduction of nitrate to nitrite. Arginine consumed in food or diet-derived nitrite had no effect on the plasma nitrite and nitrate contents of the healthy volunteers. Plasma nitrate was elevated in the crush syndrome patients; whereas neither nitrite nor nitrate was increased in patients with normal renal function. This finding suggests increased nitric oxide synthesis, decreased excretion of nitric oxide in the crush syndrome or both.

Adult↗

GTP-binding protein gamma12 subunit phosphorylation by protein kinase C--identification of the phosphorylation site and factors involved in cultured cells and rat tissues in vivo.

We have demonstrated previously that the GTP-binding protein gamma12 subunit is a selective substrate for phosphorylation by protein kinase C among various gamma subunits in vitro, and that a serine residue in the N-terminal region is involved. In the present study, we first determined that the site of phosphorylation was Ser1 with antibodies developed against two N-terminal peptides containing phosphorylated Ser1 and Ser2, respectively. Using an antibody recognizing phosphorylated gamma12 and Swiss 3T3 cells rich in this protein, gamma12 was found to be phosphorylated by stimulation of quiescent cells with various reagents, such as phorbol 12-myristate 13-acetate (PMA), NaF, fetal calf serum, lysophosphatidic acid, endothelin, and growth factors. Pertussis toxin completely and partially prevented phosphorylation of gamma12 induced by lysophosphatidic acid and fetal calf serum and by endothelin, respectively, suggesting a contribution of G(i/o). Phosphorylation of gamma12 was limited when cells were stimulated by a single reagent, even with PMA, a strong activator of protein kinase C, whereas simultaneous stimulation with lysophosphatidic acid and either PMA or platelet-derived growth factor induced a synergistic increase of phosphorylation, suggesting physiological roles for GTP-binding proteins and protein kinase C in combination. Phosphorylated gamma12 was also detected in various tissues of untreated rats. Its decrease by pertussis toxin treatment also suggested the involvement of G(i/o) in vivo.

3T3 Cells↗

Rectal cancer associated with acquired hypertrichosis lanuginosa as a possible cutaneous marker of internal malignancy.

We report a case of acquired hypertrichosis lanuginosa associated with rectal cancer and discuss the cutaneous symptoms as a marker of malignancy. A 75-year-old man had noticed increasing growth of hair over his entire body 4 months before he was admitted to our hospital because of bloody stools. Advanced rectal cancer was diagnosed, and he underwent sigmoidocolostomy. After the operation, levels of serum adrenocorticotrophic hormone and cortisone were normal, as were urinary levels of 17-ketosteroids and 17-hydroxycorticosteroids. Levels of carcinoembryonic antigen and carbohydrate antigen 19-9 were slightly elevated. The patient died 5 months after the operation because of peritonitis carcinomatosa. We suggest that hypertrichosis lanuginosa is a marker of internal malignant tumors.

Aged↗

Chemiluminescent determination of cholesterol hydroperoxides in human erythrocyte membrane.

A method for separating, detecting, and quantifying cholesterol hydroperoxide (Ch-OOH) based on extraction, purification by solid-phase extraction cartridge, high-performance liquid chromatography with chemiluminescent detection (HPLC-CL), and liquid chromatography-mass spectrometry has been developed for human erythrocyte membrane. We prepared standard compounds of the cholesterol 5alpha-, 7alpha-, and 7beta-hydroperoxides (Ch 5alpha-OOH, Ch 7alpha-OOH, and Ch 7beta-OOH). An octyl silica column with methanol/water/acetonitrile 89:9:2 (by vol) as eluent was used to determine Ch-OOH. HPLC-CL that incorporated cytochrome c and luminol as the post-column luminescent reagent was used. We also investigated the optimal assay conditions and how to prevent formation of artifact Ch-OOH. Analysis of erythrocyte membranes from seven healthy volunteers identified Ch 7alpha-OOH and Ch 7beta-OOH, but not Ch 5alpha-OOH, as commonly occurring components. The respective mean concentrations of Ch 7alpha-OOH and Ch 7beta-OOH were 2.5+/-1.6 and 5.4+/-3.5 pmol/mL blood.

Antioxidants↗

Influence of cellular incorporation of n-3 eicosapentaenoic acid on intracellular Ca2+ concentration and membrane potential in vascular smooth muscle cells.

Long-term treatment with n-3 eicosapentaenoic acid (EPA) has been shown to exert hypotensive effects and have beneficial effects on atherosclerosis. To elucidate one of the underlying mechanisms of these effects, intracellular calcium concentration [Ca2+]i, and resting membrane potential were measured in rat vascular smooth muscle cells (A7r5 cell) treated with EPA, using Ca2+-sensitive dye fura-2 AM and the patch clamp technique. The alterations in fatty acid compositions of phospholipids and cell migration after treatment with EPA (30 microM) for 6 h-7 days were also examined. After treating cells with EPA, the EPA and DPA (docosapentaenoic acid) content of the phospholipid fraction (mol.%) increased in a time-dependent manner. Alternatively, arachidonic acid (AA) decreased, and then the ratio of EPA and AA (EPA/AA) increased significantly. The resting [Ca2+]i decreased from 170 +/- 46 nM (n = 16) in control cells to 123 +/- 29 nM (n = 16) in cells treated with EPA (30 microM) for 7 days. Vasopressin (100 nM), endothelin-1 (100 nM) and platelet-derived growth factor (PDGF 5 ng/ml) evoked an initial peak of [Ca2+]i, followed by a smaller sustained rise of [Ca2+]i in the presence of extracellular Ca2+. In EPA-treated cells, both the peak and the sustained rise of [Ca2+]i induced by these agonists decreased in comparison to the control cells. EPA treatment also decreased the transient [Ca2+]i rise evoked by these agonists in the absence of extracellular Ca2+. Under the current clamp condition, resting membrane potential was significantly higher in EPA-treated cells (-49.8 +/- 10.4 mV, n = 41) than in control cells (-44.6 +/- 7.4 mV, n = 41, P < 0.05), and the input resistance of the cell was lower in EPA-treated cells, while cell size and capacitance were not statistically different. In addition, long-term treatment with EPA for 7 days significantly inhibited PDGF-induced cell migration. These results suggest that cellular incorporation of n-3 eicosapentaenoic acid attenuates intracellular mechanisms related to changes of [Ca2+]i and affects membrane potential, thereby inhibiting migration of vascular smooth muscle cells. These actions of EPA may contribute to its vasorelaxant and antiatherosclerotic effects.

Animals↗