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M Hiramoto

Publications and source records attributed to M Hiramoto.

At least 37 records · Page 2Linked to original sources
PubMed1998

A mutation in plasma platelet-activating factor acetylhydrolase (Val279Phe) is a genetic risk factor for cerebral hemorrhage but not for hypertension.

Platelet-activating factor (PAF) acetylhydrolase is an enzyme that inactivates PAF. Deficiency of this enzyme is caused by a missense mutation in the gene. We previously found a higher prevalence of this mutation in patients with ischemic stroke. This fact suggests that the mutation might enhance the risk for stroke through its association with hypertension. We have addressed this hypothesis by analyzing the prevalence of the mutation in hypertension. We studied 138 patients with essential hypertension, 99 patients with brain hemorrhage, and 270 healthy controls. Genomic DNA was analyzed for the mutant allele by the polymerase-chain reaction. The prevalence of the mutation was 29.3% (27.4% heterozygotes and 1.9% homozygotes) in controls and 36.2% in hypertensives and the difference was not significant. The prevalence in patients with brain hemorrhage was significantly higher than the control: 32.6% heterozygotes and 6.1% homozygotes (p <0.05). PAF acetylhydrolase deficiency may be a genetic risk factor for vascular diseases.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1997

A mutation in plasma platelet-activating factor acetylhydrolase (Val279-->Phe) is a genetic risk factor for stroke.

BACKGROUND AND PURPOSE: Platelet-activating factor (PAF) is a phospholipid with multiple actions that include thrombosis and inflammation. It is inactivated by a plasma enzyme, PAF acetylhydrolase. Deficiency of this enzyme in plasma is caused by a missense mutation in the gene (Val279-->Phe). We have studied a possible association of this mutation with the risk of stroke. SUBJECTS AND METHODS: We studied 120 consecutive patients with cerebral thrombosis. The control group consisted of 134 patients matched for age and sex with minor complaints but without stroke. Genomic DNA was analyzed for the mutant allele by a specific polymerase-chain reaction. Plasma PAF acetylhydrolase activity was determined by the method of Stafforini et al. RESULTS: The prevalence of the mutant gene was 43.4% in stroke patients (39.2% heterozygotes and 4.2% homozygotes), which was significantly higher than the 25.4% in control subjects (22.4% heterozygotes and 3.0% homozygotes) (chi 2 = 9.22, P < .01). The prevalence was slightly higher in stroke patients without hypertension than those with hypertension, but the difference was not significant. The patients with family histories of stroke had a slightly higher but not a significant prevalence of the mutant gene as compared with those without family histories of stroke. Plasma PAF acetylhydrolase activity was higher in patients than in control subjects, in normal subjects, or patients with a heterozygous genotype. CONCLUSIONS: These results suggest that plasma PAF acetylhydrolase deficiency may be a risk factor for stroke. This may explain the relatively high prevalence of stroke in Japan, as the mutation is more common among Japanese than Caucasians.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1996

Copurification of casein kinase II with transcription factor ATF/E4TF3.

We have developed a simple method to purify sequence-specific DNA-binding proteins directly from crude cell extracts by using DNA affinity latex beads. The method enabled us to purify not only DNA-binding proteins, but also their associated proteins. Using beads bearing the ATF/E4TF3 site from the adenovirus E4 gene promoter, a protein kinase activity was copurified with the ATF/E4TF3 family. We found that the kinase interacted with ATF1 in vitro efficiently. The kinase did not bind directly to DNA. The kinase mainly phosphorylated ATF1 on serine 36, which was one of target amino acids for casein kinase (CK) II. Biological features of the kinase were the same as those of CKII and an anti-CKII serum reacted with the kinase, indicating that the kinase was CKII. Moreover, it was clearly shown that one of CKII subunits, the CKII alpha protein bound to glutathione-S-transferase (GST) fusion ATF1 but not GST in vitro. It has been reported that a specific CKII inhibitor, 5,6-dichloro-1-beta-D-ribo-furanosylbenzimidazole (DRB) inhibits transcription by RNA polymerase II [Zandomeni et al., (1986) J. Biol. Chem. 261, 3414-3419]. Taken together, these results suggest that ATF/E4TF3 may recruit the CKII activity to a transcription initiation machinery and stimulate transcription.

Activating Transcription Factors↗
PubMed1996

Deficiency of plasma platelet-activating factor acetylhydrolase: roles of blood cells.

Platelet-activating factor (PAF), a potent mediator of inflammation and circulatory shock, is inactivated by the enzyme PAF acetylhydrolase. Plasma PAF acetylhydrolase deficiency occurs even in healthy subjects. We hypothesized that erythrocyte PAF acetylhydrolase could play a supplementary role in this plasma acetylhydrolase deficiency. We examined 1,030 subjects who participated in mass checkups, and assayed plasma and erythrocyte PAF acetylhydrolase. We also investigated the degradation of exogenous PAF by erythrocytes or other blood cells obtained from subjects who exhibited the plasma enzyme deficiency. The incidence of the plasma enzyme deficiency in this general Japanese population was 4.7% (48/1,030). None of the subjects with the deficiency had a history of allergy, circulatory shock, or chronic inflammatory diseases. The mean values for erythrocyte cytosolic PAF acetylhydrolase activity in the normal and deficient subjects were 0.51 +/- 0.15 (SD) and 0.71 +/- 0.28 nkat (nmol/s)/g protein, respectively, and the difference was significant (P < 0.001, Mann-Whitney U-test). The half-life of 10 nmol/l [3H]PAF in plasma from normal subjects was about 5 min, and the half-life in whole blood or erythrocyte suspension in autologous plasma was almost the same as that in plasma. In plasma from deficient subjects, unchanged PAF virtually remained and the degradation in whole blood or erythrocyte suspension was a little faster than in plasma. We conclude that erythrocytes contribute only little to PAF metabolism in normal blood but they account for almost all of the slow PAF degradation in blood from subjects deficient in plasma PAF acetylhydrolase.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1996

Induction of the transcription factor AP-1 in cultured human colon adenocarcinoma cells following exposure to bile acids.

We studied the effects of bile acids on inducibility of the transcription factor AP-1 in human colon carcinoma LoVo cells. Firstly, cells were treated with chenodeoxycholic acid and the nuclear extracts from those cells were processed by electrophoretic mobility shift assays to analyze nuclear AP-1 DNA-binding activity. We demonstrated that chenodeoxycholic acid induced AP-1 DNA-binding activity in a dose- and time-dependent fashion. Antibody supershift experiments clearly revealed that the majority of protein components in induced AP-1 DNA-binding activity were the products of oncogenes c-fos and c-jun. On the other hand, DNA-binding activity in the nuclear extracts for either NF kappa B, Sp1, or ATF/CREB was not affected by bile acids, suggesting that the effect of bile acids was rather specific for AP-1. Transient transfection experiments supported this notion: expression of the AP-1-luciferase reporter construct was induced by bile acids in a dose-dependent manner, and expression of either reporter construct for NF kappa B, Sp1, or ATF/CREB was not influenced by treatment of the cells with bile acids. We also demonstrated that those bile acids efficiently activated AP-1-dependent promoter in DLD-1 cells, which (as well as LoVo cells), are derived from colon adenocarcinoma, but not in COLO320DM cells which are from colon carcinoid tumor. Thus, we may indicate that bile acids exclusively induce nuclear AP-1 activity in colon adenocarcinoma cells.

Activating Transcription Factor 1↗
PubMed1995

Potentiation of glucocorticoid-mediated gene expression by the novel benzoquinone derivative (2E)-3-[5-(2,3-dimethoxy-o-methyl-1, 4-benzoquinoyl)]-2-nonyl-2-propenoic acid (E3330).

We examined the effects of the novel benzoquinone derivative (2E)-3-[5-(2,3-dimethoxy-o-methyl-1,4-benzoquinoyl)]-2-nonyl -2-propenoic acid, E3330, on the functional activity of the glucocorticoid receptors. For that purpose we used a cloned CHOpMTGR cells, in which human glucocorticoid receptor cDNA was stably transfected and glucocorticoid receptor was expressed at high levels. After treatment of CHOpMTGR cells with E3330, neither the ligand binding activity nor immunoreactivity of the glucocorticoid receptor was affected. Moreover, E3330 did not affect the sequence-specific DNA binding activity of partially-purified glucocorticoid receptor in vitro. However, a glucocorticoid-inducible promoter was activated by E3330 in a dose-dependent fashion in the presence of the synthetic ligand dexamethasone. Interestingly, E3330 increased nuclear translocation of the glucocorticoid receptor in a ligand-independent fashion, indicating that E3330, through facilitation of the translocation of the glucocorticoid receptor, augments glucocorticoid-mediated gene transcription.

Animals↗
PubMed1994

Density-associated changes in platelet-activating factor acetylhydrolase activity and membrane fluidity of human erythrocytes.

Platelet-activating factor acetylhydrolase is known to degrade oxidatively fragmented phospholipids which are similar in structure to platelet-activating factor. We examined changes of acetylhydrolase activity during in vivo aging of human erythrocytes and tried to assess its role in maintaining the membrane properties of erythrocytes. Higher-density erythrocytes are enriched with older cells. Erythrocytes obtained from seven healthy colleagues were separated into four density fractions by centrifugation in discontinuous Percoll density gradients. Both membrane and cytosolic acetylhydrolase decreased with increasing erythrocyte density. Membrane and cytosolic acetylhydrolase activities in the lightest fraction were 2.0 +/- 1.0 (SD) nkat/g protein and 362 +/- 58 pkat/g protein, respectively, and these values were significantly higher than those in the densest fraction: 1.3 +/- 0.7 nkat/g protein and 286 +/- 70 pkat/g protein, respectively. Membrane acyltransferase activity also decreased with red cell density and the average values in the lightest and densest fractions were 51.2 +/- 23.6 and 27.0 +/- 20.2 mukat/g protein, respectively. Generation of thiobarbituric acid-reactive substances induced by t-butyl hydroperoxide treatment decreased with increasing cell density, and the inhibition of acetylhydrolase with diisopropylfluorophosphate resulted in enhanced peroxide-induced lipid oxidation, particularly in lower-density fractions. There was no significant change in basal levels of thiobarbituric acid-reactive substances in red cell membrane. Membrane fluidity was evaluated by fluorescence recovery after photo-bleaching and it decreased as erythrocyte density increased. We conclude that the activity of the deacylation/reacylation cycle maintained by acetylhydrolase and acyltransferase is gradually reduced during in vivo aging of erythrocytes. This may be connected with decreases of polyunsaturated fatty acids and membrane fluidity in old erythrocytes.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1994

Pyrazolopyridine derivative acts as a novel cyclooxygenase inhibitor: antiplatelet effect in aged patients with ischemic stroke.

OBJECTIVE: To examine the antiplatelet effect of a novel pyrazolopyridine derivative (KC-764) in geriatric patients with ischemic stroke. DESIGN: Randomized clinical trial of three graded dose levels. SETTING: A geriatric clinic attached to a nursing home. PATIENTS: Fifteen patients with a history of cerebral infarction with a mean age of 75 +/- 5 years (range, 65-83). Patients were divided into three groups and administered 10, 20, or 40 mg/day KC-764 for 8 weeks. MEASUREMENTS: Platelet aggregation induced by arachidonate, ADP, collagen and platelet-activating factor. Plasma or serum levels of thromboxane B2 and 6-ketoprostaglandin F1 alpha. MAIN RESULTS: Platelet aggregation was inhibited by KC-764 administration and returned to the control level after discontinuation. Although plasma thromboxane B2 levels were markedly decreased, plasma 6-ketoprostaglandin F1 alpha was not affected. However, the dose of 10 mg/day was not sufficient to maintain an effective plasma level of KC-764. There were no side effects or changes in laboratory findings. CONCLUSIONS: We confirmed that KC-764 at a dose of 20 to 40 mg/day is an effective antiplatelet agent and a good candidate for a trial to see if it is feasible for long-term use for the prevention of ischemic stroke in high-risk patients.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Direct purification of multiple ATF/E4TF3 polypeptides from HeLa cell crude nuclear extracts using DNA affinity latex particles.

We developed a method using affinity latex particles to rapidly and efficiently purify DNA-binding proteins directly from crude cell extracts. The particles are composed of a styrene core and a polyglycidyl methacrylate surface, to which DNA oligomers were immobilized by means of epoxy groups. Multiple polypeptides were copurified, which bound to the ATF/E4TF3-binding site from crude nuclear extracts of HeLa cells, within a few hours. Affinity-purified polypeptides stimulated transcription in vitro from a promoter in which ATF/E4TF3-binding sites were present. At least eight polypeptides with molecular masses of 116, 80, 65, 60, 55, 47, 45, and 43 kDa were copurified. About 2 micrograms of the 43-kDa protein was purified directly from 8 mg of crude nuclear extracts. All the polypeptides directly bound to the same DNA sequence and were thought to form a family. The results indicated that the particles are useful for quickly purifying various DNA-binding proteins directly from crude cell extracts.

Activating Transcription Factors↗
PubMed1992

Increased levels of blood platelet-activating factor (PAF) and PAF-like lipids in patients with ischemic stroke.

Levels of platelet-activating factor (PAF) in blood from patients with ischemic stroke were determined by radioimmunoassay (RIA). Using 2 ml of blood as a starting material, PAF was detected in 11 out of 17 stroke patients and 3 of 25 age-matched healthy controls. This implies that blood level of PAF is higher in stroke patients than in controls. Plasma levels of PAF-like lipid(s) (PAF-LL) were also estimated in the same subjects by a bioassay based on aggregation of human polymorphonuclear neutrophils. PAF-LL was detected in plasma samples of all subjects and the average values in patients and controls were 294 +/- 211 pg/ml and 140 +/- 122 pg/ml, respectively. There was a statistically significant difference between these two values (p less than 0.01). Separation of plasma lipids by HPLC gave a single peak in bioassay, which had the same elution volume as authentic PAF. When each fraction was subjected to RIA, the fractions corresponded to phosphatidylcholine (PC) or lysoPC also showed the immunoreactivity, however, the purification procedure using an octadecylsilica gel cartridge eliminated such cross-reacting compounds. We conclude that blood PAF is higher in patients with ischemic stroke than in healthy subjects. Besides, there may be bioactive phospholipid molecules other than PAF, which level in plasma is also higher in stroke patients.

Aged↗
PubMed1992

Platelet-activating factor acetylhydrolase activity in red blood cell-stroma from patients with cerebral thrombosis.

Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) is a bioactive phospholipid and inactivated by a specific enzyme, PAF acetylhydrolase (PAF-AH). We have measured PAF-AH activity in red blood cells (RBCs) from patients with a history of cerebral thrombosis and age-matched healthy controls. The activities in 34 patients and 34 controls were 1.29 +/- 0.28 and 1.64 +/- 0.26 nmol/10(9) RBCs/min (or, 30.0 +/- 5.8 and 35.1 +/- 4.7 nmol/g protein/min) (mean +/- SD), respectively, and the difference was significant (p less than 0.001). In patients, RBC PAF-AH activity correlated positively with RBC filterability, an index of RBC deformability (r = +0.501, p less than 0.05). The RBC activity may play a role in scavenging oxidation products of membrane phospholipids. Lower RBC PAF-AH activity may predispose to ischemic diseases by disturbing microcirculatory behavior of the RBCs.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1992

Participation of serum albumin and LDL-cholesterol in impaired blood cell-filterability affected by white blood cells in patients with cerebral thrombosis.

We examined the effect of white blood cells (WBCs) on the red blood cell (RBC)-filterability, and the influence of plasma components on their interaction of their microcirculatory behaviour in cerebral thrombosis patients. Subjects studied were 20 patients with a history of cerebral thrombosis (60 +/- 4.7 years old) (mean +/- SD) and 28 healthy controls (59 +/- 5.4 years old). Filterability indices of RBC suspension (RFI) and suspension with RBCs plus WBCs (RWFI) were measured by the method of Nuclepore filtration. The values of RFI in patients and controls were 0.44 +/- 0.12 and 0.56 +/- 0.16 ml min-1 (mean +/- SD), and RWFIs were 0.33 +/- 0.092 and 0.40 +/- 0.11 ml min-1, respectively. The differences in both of these values between patients and controls were significant (p < or = 0.01 for RFI and p < or = 0.05 for RWFI, based on Student's t test, respectively). Both RFI and RWFI in bed-ridden patients were lower than those in the more active counterparts (p < or = 0.05, based on Student's t test). In patients, RFI and RWFI correlated positively with serum albumin (r = +0.515, p < 0.05; r = +0.533, p < 0.05, based on Student's t test, respectively). The net lowering effect of WBCs on RFI (RFI-RWFI) correlated positively with serum LDL-cholesterol in patients (r = +0.574, p < 0.01, based on Student's t test). WBCs play a significant role in reducing RFI, and its effect is related to the pathemas of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol, LDL↗
PubMed1991

Effect of cigarette smoking on the levels of platelet-activating factor-like lipid(s) in plasma lipoproteins.

The effect of cigarette smoking on the levels of platelet-activating factor-like lipid(s) (PAF-LL) in plasma lipoproteins was studied. The subjects were 10 healthy male non-smokers (24 +/- 1.4 years old) and 13 healthy male habitual smokers (23 +/- 1.3 years old). Fasting venous blood was obtained and basal levels of PAF-LL in plasma lipoproteins were estimated. The acute effect of cigarette smoking was also studied in smokers. Plasma lipoproteins were separated by ultracentrifugation. Lipids were extracted and separated by thin-layer chromatography. The fraction with the same migration as authentic PAF was recovered and was shown to cause aggregation of human polymorphonuclear neutrophils. This activity was identified as PAF-LL because it was inactivated by phospholipase A2 and was blocked by CV-3988, an antagonist of the PAF receptor. PAF-LL was detected in LDL and HDL, but not in VLDL or in lipoprotein-deficient plasma. The levels of PAF-LL in LDL in non-smokers, and in smokers before and after smoking were 13 +/- 7.5, 16 +/- 14.9 and 190 +/- 179.0 pg/ml, and those in HDL were 12 +/- 5.2, 40 +/- 40.0 and 235 +/- 205.1 pg/ml, respectively. The values in both LDL and HDL in smokers increased significantly after smoking (P less than 0.05). After 30 min, the levels had returned almost to the pre-smoking levels. We conclude that cigarette smoking induces an increase in the levels of PAF or closely related lipid(s) in LDL and HDL, which may be related to smoking-induced atherosclerosis.

Adult↗
PubMed1991

Plasma 11-dehydrothromboxane B2: a reliable indicator of platelet hyperfunction in patients with ischemic stroke.

The plasma level of 11-dehydrothromboxane B2 (11-dehydroTXB2) is free from artifactual increase during blood sampling, and it can be reliable indicator of TXA2 production in vivo. We have estimated plasma 11-dehydroTXB2 in patients with ischemic stroke. Subjects studied were 29 patients with cerebral thrombosis (62 +/- 9 years old) and 41 healthy controls (61 +/- 7 years old). Plasma 11-dehydroTXB2 and TXB2 were determined by radioimmunoassay. Plasma 11-dehydroTXB2 levels in patients and controls were 5.4 +/- 2.5 and 1.8 +/- 0.9 pg ml, respectively, and the difference was significant (p less than 0.001). Plasma TXB2 also was higher in patients than in controls: 401 +/- 61 vs 311 +/- 51 pg/ml (p less than 0.05). However, the 11-dehydroTXB2 was found to be a more effective parameter to distinguish between stroke patients and controls. Estimation of plasma 11-dehydroTXB2 levels is a reliable method to detect platelet hyperfunction in stroke patients.

Aged↗
PubMed1991

Platelet-activating factor (PAF) stimulates the production of PAF acetylhydrolase by the human hepatoma cell line, HepG2.

The human hepatoma cell line, HepG2, secreted an activity that degrades platelet-activating factor (PAF) by the hydrolysis of the sn-2 acetyl group. This activity was Ca++ independent, inhibited by diisopropylfluorophosphate but not by p-bromophenacyl bromide, and resistant to treatment with trypsin or pronase. Separation of HepG2-conditioned medium by gel filtration disclosed that the activity was associated with lipoproteins. An antiserum against PAF acetylhydrolase immunoprecipitated this activity. It was not recognized by an antibody against lecithin:cholesterol acyltransferase (LCAT), which also is secreted by HepG2 cells. Therefore the phospholipase A2 activity of LCAT was excluded as a source of the observed activity. PAF added to the culture medium stimulated the secretion of the PAF-degrading activity by HepG2 cells, while lyso-PAF was inactive. Maximal stimulation was observed with 5 ng/ml PAF, which induced a fivefold increase. The presence of 5 ng/ml PAF, enhanced the secretion of [35S]methionine-labeled PAF acetylhydrolase and cycloheximide inhibited both the basal and PAF-stimulated secretion of the labeled enzyme. We conclude that HepG2 cells produce PAF acetylhydrolase. The liver may be a major source of plasma PAF acetylhydrolase, and PAF may induce the production of its inactivating enzyme by the liver.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1990

Activity of platelet-activating factor (PAF) acetylhydrolase in plasma from healthy habitual cigarette smokers.

The activity of platelet-activating factor acetylhydrolase, a specific metabolizing enzyme of platelet-activating factor (PAF), in plasma of 39 male subjects was determined radiochemically by the method of Stafforini et al., (1987) J Biol Chem 262: 4223-4230, to clarify to what extent PAF affects atherosclerotic disorders induced by habitual smoking. The subjects examined included 18 habitual smokers (mean age: 62 +/- 10.6 years) and 21 age-matched nonsmokers. Plasma PAF acetylhydrolase activity was higher in the smokers than in the nonsmokers. There was no difference between smokers and nonsmokers in platelet aggregability in response to PAF or ADP. A higher apoprotein B/apoprotein A-I ratio in smokers as compared to nonsmokers was the only manifestation of abnormal lipoprotein metabolism in the former group. In the smokers, plasma PAF acetylhydrolase activity was directly proportional to total cholesterol, LDL-cholesterol, triglyceride, apoprotein B, LDL-cholesterol/HDL-cholesterol or apoprotein B/apoprotein A-I, and inversely proportional to HDL-cholesterol or apoprotein A-I. The results obtained suggest that alterations in PAF acetylhydrolase levels result from a slightly abnormal lipoprotein metabolism. Determination of plasma PAF acetylhydrolase activity is useful to study the role of PAF in atherosclerotic changes induced by smoking.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗