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R Yanoshita

Publications and source records attributed to R Yanoshita.

15 recordsLinked to original sources
PubMed2000

cDNA cloning of bradykinin-potentiating peptides-C-type natriuretic peptide precursor, and characterization of the novel peptide Leu3-blomhotin from the venom of Agkistrodon blomhoffi.

A cDNA clone, 1.8 kb long, was isolated from a venom gland cDNA library of Agkistrodon blomhoffi that encodes a large plurifunctional precursor composed of 263 amino-acid residues. Nucleotide sequence analysis of this clone revealed that sequences which code for blomhotin and a novel peptide Leu3-blomhotin are located in the N-terminal region of the precursor polypeptide, followed by four tandemly aligned sequences which code for three types of bradykinin-potentiating peptide. In the C-terminal region, the sequence for the C-type natriuretic peptide was located along with a preceding processing signal. The deduced amino-acid sequences for the four bradykinin-potentiating peptides coincided exactly with previously known sequences for potentiator B, potentiator C and potentiator E. The actual Leu3-blomhotin peptide was subsequently isolated from the venom of A. blomhoffi and characterized. Leu3-blomhotin possesses contractile activity in isolated rat stomach fundus smooth muscle in the same manner as blomhotin. Furthermore, it was shown that blomhotin and Leu3-blomhotin retained activity to inhibit the angiotensin-converting enzyme.

Amino Acid Sequence↗
PubMed2000

Structure-activity studies of analogues of blomhotin mediating contraction of rat fundus.

Blomhotin is a novel peptide (pGlu1-Gly2-Arg3-Pro4-Pro5-Gly6-Pro7-Pro8-Ile9-Pro10-Arg11) which has been isolated from the venom of Agkistrodon halys blomhoffii and exhibits contractile activity on rat stomach fundus. We carried out a structure-activity study of blomhotin and its related peptides, and the findings suggested that the N-terminal portion of blomhotin is mainly responsible for affinity for the blomhotin receptor, whereas the C-terminal portion of blomhotin, Pro-Ile-Pro-Arg, is responsible for complete activation of the blomhotin receptor in the rat stomach fundus. In particular, the amino acids at positions 9 and 11 of blomhotin appear to be essential for binding and intrinsic activity. Using knowledge gained from this structure-activity analysis, we have identified photoactive blomhotin analogues that have sufficient biological activity to probe the target molecule of blomhotin.

Animals↗
PubMed1999

Blomhotin: a novel peptide with smooth muscle contractile activity identified in the venom of Agkistrodon halys blomhoffii.

A novel peptide has been isolated from the venom of Agkistrodon halys blomhoffii using a bioassay that monitors the stimulant effect on rat stomach fundus. The 11-amino acid peptide, named blomhotin, was purified to homogeneity by gel-filtration column chromatography and reverse-phase HPLC. The amino acid sequence of blomhotin was determined to be pGlu-Gly-Arg-Pro-Pro-Gly-Pro-Pro-Ile-Pro-Arg, which is similar to that of bradykinin-potentiating peptides which themselves cause no contraction of smooth muscle. The contraction induced by blomhotin showed homologous desensitization, implicating the involvement of a blomhotin-specific site in the response.

Amino Acid Sequence↗
PubMed1999

Inhibition of lysoPAF acetyltransferase activity by components of licorice root.

Licorice root traditionally used as an anti-inflammatory drug exhibited an inhibitory effect on lysoPAF (platelet-activating factor) acetyltransferase in vitro: the ether soluble fraction of the crude drug produced a 27.3% inhibition at a concentration 10 microg/ml. From this fraction, licoricidin (1), 1-methoxyphaseollin (2), 6,8-diprenylgenistein (3) and 1-methoxyphaseollidin (4) were isolated as active components, whose IC50 values were 7.7, 57, 19 and 48 microM, respectively. Licoricidin (1) seems to be one of the most potent compounds of plant origin isolated so far.

Acetyltransferases↗
PubMed1998

Mechanisms of non-drowsiness after oral administration of TMK688, a novel antiallergic drug.

The mechanisms of non-drowsiness after oral administration of TMK688 (1- [[5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadienoyl ] aminoethyl]-4-diphenylmethoxypiperidine, CAS 110501-66-1) were investigated using mice. TMK688 inhibited the histamine-induced vascular permeability at oral doses of 3.2-10 mg/kg with an ID50 value of 5.4 mg/kg. More than 100 times higher doses were needed to prolong the hexobarbital-induced sleeping. Pyrilamine, a typical antihistamine agent, showed little difference among these doses and antiallergic drugs having antihistamine activity, i.e., terfenadine, azelastine and ketotifen, had effects between TMK688 and pyrilamine. The inhibitory activity of orally administered TMK688 against ex vivo [3H]-pyrilamine binding to mouse cerebral histamine receptors appeared at the same doses as its potentiating activity against hexobarbital-induced sleeping. When given orally, TMK688 was hydrolyzed to TMK777 (CAS 101619-11-8), then conjugated with glucuronic acid to TMK777-glucuronide. No TMK688 was detected in the blood. The main metabolite TMK777-glucuronide could hardly penetrate the blood-brain barrier because of its polarity. Although the plasma concentrations of TMK777 were far lower than those of TMK777-glucuronide, TMK777 was penetrable into the brain and the cerebral concentrations of TMK777 increased in parallel with the plasma concentrations of the drug. Since intracerebroventricularly-injected TMK777 prolonged the sleeping time, and since the threshold concentration of TMK777 in the cerebral cortex to potentiate the hexobarbital-induced sleeping was consistent despite different administration routes, the drowsiness elicited by markedly high doses of TMK688 is though to be caused by intracerebral TMK777. In other words, TMK688 does not seem to cause drowsiness at effective doses because of the poor prenetrability of its main metabolites into the brain.

Administration, Oral↗
PubMed1997

Activated mast cells release extracellular type platelet-activating factor acetylhydrolase that contributes to autocrine inactivation of platelet-activating factor.

IgE-dependent and -independent activation of mouse bone marrow-derived mast cells (BMMC) elicited rapid and transient production of platelet-activating factor (PAF), which reached a maximal level by 2-5 min and was then degraded rapidly, returning to base-line levels by 10-20 min. Inactivation of PAF was preceded by the release of PAF acetylhydrolase (PAF-AH) activity, which reached a plateau by 3-5 min and paralleled the release of beta-hexosaminidase, a marker of mast cell exocytosis. Immunochemical and molecular biological studies revealed that the PAF-AH released from activated mast cells was identical to the plasma-type isoform. In support of the autocrine action of exocytosed PAF-AH, adding exogenous recombinant plasma-type PAF-AH markedly reduced PAF accumulation in activated BMMC. Furthermore, culture of BMMC with a combination of c-kit ligand, interleukin-1beta and interleukin-10 for > 24 h led to an increase in plasma-type PAF-AH expression, accompanied by a reduction in stimulus-initiated PAF production. Collectively, these results suggest that plasma-type PAF-AH released from activated mast cells sequesters proinflammatory PAF produced by these cells, thereby revealing an intriguing anti-inflammatory aspect of mast cells.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1996

Inhibition of lysoPAF acetyltransferase activity by flavonoids.

OBJECTIVE AND DESIGN: Several kinds of flavonoids, widely distributed natural products of the vegetable kingdom which possess anti-inflammatory activity, were examined for inhibitory effects on the acetyl-CoA: 1-alkyl-2-lyso-sn-glycero-3-phosphocholine (lysoPAF) acetyltransferase activity. METHODS: Acetyl-CoA:lysoPAF acetyltransferase activity was determined using homogenates of a rat mucosal-type mastocytoma cell line, RBL-2H3 as an enzyme source. The production of platelet-activating factor (PAF) in rat peripheral white blood cells stimulated with the calcium ionophore A23187 was studied. RESULTS: Of the flavonoids tested, luteolin and quercetin exhibited significant inhibitory effects (IC50, 45 microM and 80 microM, respectively), whereas other structurally-related flavonoids failed to affect the lysoPAF acetyltransferase activity. Luteolin did not suppress the activity of choline acetyltransferase, suggesting that the inhibition observed here was specific. Luteolin also inhibited the production of PAF in rat peripheral white blood cells. CONCLUSIONS: These results indicate that luteolin could become a leading compound for developing a novel type of anti-inflammatory, anti-allergic drugs that target lysoPAF acetyltransferase.

Acetyltransferases↗
PubMed1993

Preferential hydrolysis of phosphatidylethanolamine in rat ischemic heart homogenates during in vitro incubation.

Phospholipid-hydrolyzing activities were examined in rat hearts with ischemia induced by occlusion of the left main coronary artery. When homogenates of ischemic heart were incubated in vitro at 37 degrees C, a significant amount of phosphatidylethanolamine (PE) was degraded, whereas the contents of other phospholipids did not change significantly. During the incubation, a stoichiometrical amount of lysoPE was concomitantly formed. The lysoPE formed had mainly saturated fatty acids and its composition resembled that of fatty acids detected at the sn-1 position in the glycerol backbone of heart PE. No appreciable PE degradation was observed in homogenates prepared from nonischemic rat heart. No difference in phospholipase activities was found between ischemic and nonischemic heart homogenates when exogenous radioactive phospholipids were used as substrates. Rabbit anti-rat 14-kDa type II phospholipase A2 antibody suppressed the degradation of PE observed in ischemic heart homogenates. These findings indicate that the type II phospholipase A2 activity may be involved in the breakdown of endogenous PE in ischemic heart homogenates.

Animals↗
PubMed1993

Suppression of tumourigenicity in human colon carcinoma cells by introduction of normal chromosome 1p36 region.

Development of colon carcinomas appears to be associated with inactivation of multiple tumour suppressor genes. Cytogenetic and DNA analyses of colon carcinomas have detected a high frequency of chromosome 1p deletion, which suggests the presence of a tumour suppressor gene. We therefore introduced normal human chromosome 1 into colon carcinoma COKFu cells, through microcell hybridization. Six clones of hybrid cells containing normal chromosome 1 were obtained, four of which had a small fragment of the introduced chromosome 1, including 1p36-34. The morphology of hybrid cells with chromosome 1 markedly altered to a flat shape. The cloning efficiency of all six hybrid cells in soft agar was significantly reduced, and the tumourigenicity in athymic nude mice was completely suppressed. Hybrid cells containing only the region of 1p36-34, as well as those containing intact chromosome 1, showed suppressed transformed phenotype. Furthermore, several tumourigenic revertant cells were obtained from the hybrid cells. These revertant cells had a morphology similar to that of COKFu cells, and were found to have lost the 1p36 region from the introduced chromosome 1. These results indicate that a normal chromosome 1p36 carries a tumour suppressor gene for colon carcinogenesis.

Adenocarcinoma↗
PubMed1991

Guinea pig bone marrow cells treated with platelet-activating factor generate factor(s) which affects their DNA synthesis and microbicidal activity.

We have previously reported that platelet-activating factor (PAF) induces proliferation and microbicidal activity of guinea pig bone marrow cells. In the present study, we have found that the conditioned medium of PAF- or nonmetabolizable PAF agonist-treated guinea pig bone marrow cells augmented DNA synthesis and induced microbicial activity of bone marrow cells. A PAF specific antagonist, CV-6209, inhibited generation of the active conditioned medium by PAF. Addition of the PAF antagonist only partially suppressed the augmentative effect of the active conditioned medium on DNA synthesis; this is consistent with the fact that, because of the rapid breakdown, no appreciable amount of PAF remained in the conditioned medium of PAF-treated cells. Although mouse bone marrow cells did not respond to PAF unlike guinea pig cells, their DNA synthesis was significantly enhanced by the conditioned medium of PAF-treated guinea pig bone marrow cells. Thus, some newly generated factor(s) distinct from the originally inoculated PAF seemed to modulate the bioactions of PAF on bone marrow cells. An appreciable amount of PAF was produced by calcium ionophore-treated guinea pig bone marrow cells. These findings indicate that PAF synthesized in guinea pig bone marrow cells induces generation in the cells of some factor(s) which affects proliferation or microbicidal activity.

Animals↗
PubMed1988

Hydrolysis of platelet activating factor and its methylated analogs by acetylhydrolases.

We examined the substrate specificity of PAF-degrading enzymes from various sources using platelet activating factor (PAF) and its synthetic analogs. The results were as follows: 1) Tissue-originated acetylhydrolases, such as rat kidney soluble enzyme, deacetylated 1S-methyl-1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (1S-Me-PAF) slightly more rapidly than PAF, whereas plasma acetylhydrolase hydrolyzed PAF more effectively than 1S-Me-PAF. 2) Rat polymorphonuclear leukocytes, monocytes, and lymphocytes homogenates showed an appreciable acetylhydrolase activity, the substrate specificity of which resembled that of the plasma enzyme. 3) Pleural exudates in an experimental pleurisy induced in rats by carrageenan contained an acetylhydrolase activity, the properties of which were similar to those of the plasma enzyme. 4) An extracellular phospholipase A2 activity, which was also observed in the pleural exudate and required Ca2+ ion for maximum activity, seemed not to participate in the deacetylation of PAF, since addition of EDTA did not affect the PAF deacetylation catalyzed by the pleural exudate. These findings indicate that the inactivation reaction of PAF present in the extracellular space is mainly catalyzed by plasma acetylhydrolase, which yields lysoPAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1987

Antitumor activity of synthetic alkylphospholipids with or without PAF activity.

1-O-Octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-OMe) has been reported to possess definite antitumor activity in vivo. Twenty-two alkyl lysophospholipid analogs were chemically synthesized, and their antitumor activity against mouse experimental tumors (Sarcoma 180, MM46, P388) was examined. Among them, 1-O-octadecyl-2-O-acetoacetyl-rac-glycero-3-phosphocholine was found to show antitumor activity similar to ET-18-OMe with less acute toxicity. Intravenous injection of the ET-18-OMe with sn-3 configuration retarded the subcutaneous growth of Sarcoma 180 cells effectively, while the growth inhibition by the sn-1 isomer was much less effective. This stereospecificity was similar to that observed in their activities as platelet-activating factor (PAF) agonists. The acetoacetyl compound, another PAF agonist, showed similar stereospecific antitumor action in vivo. These findings suggest that some alkyl lysophospholipids may activate host cells to a cytostatic stage against tumor cells in vivo through binding to a PAF receptor. Our preliminary results indicated that the responsible cells under these conditions might be primarily immature macrophages present in the bone marrow. No appreciable or even adverse stereospecificity was observed in the different sets of experiments where the activity of ET-18-OMe against MM46 tumor cells in vivo or the direct cytotoxicity against human promyelocytic leukemia HL-60 cells in vitro was examined. Under some conditions, the antitumor activity of ET-18-OMe in vivo may be revealed through direct cytotoxicity and/or modulation of the host defense system by "nonspecific" mechanisms. Some alkylphospholipids without PAF activity may also show antitumor activity through similar "nonspecific" mechanisms.

Animals↗