Biomedical subjects

Yoshiki Takahashi

Publications and source records attributed to Yoshiki Takahashi.

15 recordsLinked to original sources

PubMed2006

Involvement of ionotropic purinergic receptors in the histamine-induced enhancement of the cough reflex sensitivity in guinea pigs.

We examined the effect of inhaled histamine on citric acid-induced coughs and clarified the role of ionotropic purinergic receptors in the resulting changes. Although the inhalation of 0.1 M citric acid by itself produced only a few coughs in guinea pigs, exposure to histamine, at concentrations of 0.3 to 1 mM, for 2 min concentration dependently increased the number of citric acid-induced coughs. This histamine-induced increase in the number of citric acid-induced coughs was dose dependently and significantly reduced when animals were pretreated with fexofenadine, a histamine H1 receptor antagonist. The histamine-induced increase in the number of citric acid-induced coughs was completely reduced when animals were co-pretreated with 2',3'-O-(2,4,6-trinitrophenyl) adenosine 5-triphosphate (TNP-ATP, 50 microM), a P2X receptor antagonist, and reactive blue 2, a P2Y receptor antagonist, for 2 min. Furthermore, the ATP-induced increase in the number of citric acid-induced coughs was dose dependently and significantly decreased when animals were pretreated with fexofenadine, at doses of 0.3, 1 and 3 mg/kg, p.o. These results suggest that histamine enhances the excitability of rapidly adapting receptors to tussive stimuli via modulation of ATP release in the airways. Furthermore, ATP might act not only on P2X receptors to directly activate rapidly adapting receptors, but also on P2Y receptors to increase histamine release, indirectly increasing the cough reflex sensitivity.

Adenosine Triphosphate↗

PubMed2005

Involvement of P2X receptor subtypes in ATP-induced enhancement of the cough reflex sensitivity.

We examined the effect of inhaled ATP on the chemical irritant-induced coughs to clarify the roles of ionotropic purinergic receptors in these modulations. Although inhalation of 0.1 M citric acid by itself produced only a few coughs in guinea pigs, exposure to ATP, at concentrations of 3-10 microM, for 2 min concentration-dependently increased the number of 0.1 M citric acid-induced coughs. ATP-induced enhancement of the number of citric acid-induced coughs was abolished when animals were pretreated with 2',3'-O-(2,4,6-trinitrophenyl) adenosine 5-triphosphate (TNP-ATP), an antagonist of P2X receptor subtypes P2X1-4, at a concentration of 50 microM, for 2 min. However, exposure to pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), an antagonist of P2X receptor subtypes P2X1,2,3,5,7, but not of P2X4 receptors, at a concentration of 50 microM, for 2 min, had no effect on the ATP-induced enhancement of the number of citric acid-induced coughs. Furthermore, exposure to reactive blue 2 (RB2, 30 microM, 2 min), an antagonist of P2Y receptors, had no effect on the ATP-induced enhancement of the number of citric acid-induced coughs. Exposure to ATP, at a concentration of 10 microM, for 2 min significantly increased the number of citric acid-induced coughs in capsaicin-pretreated guinea pigs. Furthermore, ATP had no effect on the number of capsaicin-induced coughs in naive animals. These results suggest that although ATP, by itself, does not elicit spontaneous coughs, it likely enhances the cough reflex sensitivity. Furthermore, stimulation of P2X receptors, especially P2X4 receptors, on rapidly adapting receptors may be required for the ATP-induced enhancement of the cough reflex sensitivity.

Adenosine Triphosphate↗

PubMed2005

Novel gender-related regulation of CYP2C12 gene expression in rats.

The expression of CYP2C12 by GH occurs in female but not in male rat livers. Direct injection of the CYP2C12 promoter-luciferase gene into male rat livers showed that the CYP2C12 promoter was active in both male and female rats. Thus, to further examine one or more factors that regulate the gender-related expression of CYP2C12, male rats were treated with trichostatin A, a specific inhibitor of histone deacetylase capable of condensing the chromatin structure. Interestingly, the expression of CYP2C12 by GH was seen even in the livers of male rats, indicating that histone deacetylase contributes to the suppression of CYP2C12 expression in male rats. Deoxyribonuclease I hypersensitive assay using nuclei from the livers of male or female rats revealed that the chromatin structure of the CYP2C12 gene was gender specific: a hypersensitive site at a position -4.2 kb containing GH-responsive element that bound to signal transducer and activator of transcription 5 (STAT5), termed as HS (hypersensitive site) 1, was specific for female rat livers, whereas a hypersensitive site at a position -3 kb, designated as HSm (male-specific hypersensitive site), was characteristic of male rat livers. A -3425/-3275 region within HSm functioned as a negative regulatory region, when the region was inserted in front of simian virus 40 promoter. Gel shift assay demonstrated that both CCAAT/enhancer-binding protein alpha and beta bound to the -3425/-3275 region. Based on these results, we conclude that the gender-related expression of the CYP2C12 gene results from the inaccessibility of to STAT5 to the GH-responsive element by chromatin condensation seen in male rat livers, and from the presence of the male-specific HSm that acts as a silencer.

5' Flanking Region↗

PubMed2004

Aryl hydrocarbon receptor-mediated suppression of GH receptor and Janus kinase 2 expression in mice.

Differential mRNA display revealed that a cDNA encoding the major urinary protein 2 (MUP2) that belongs to the lipocalin superfamily was absent in livers of mice treated with 3-methylcholanthrene (MC). The expression of MUP2 is known to be stimulated by growth hormone (GH), through the GH receptor (GHR), Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) signal transduction pathway. Since MC is an aryl hydrocarbon receptor (AhR) ligand, the effects of MC treatment on the expression of GHR, JAK2 or STAT5 in the livers of wild-type or AhR-null mice were examined. The result indicated that the expression of GHR and JAK2 mRNA was greatly decreased by MC in wild-type mice but not in AhR-null mice. In addition, the binding activity of STAT5 bound to STAT5-binding element was reduced after MC treatment in wild-type mice but not in AhR-null mice. Based on these results, we conclude that the suppression of MUP2 mRNA expression by MC is caused by the AhR-mediated disruption of the GH signaling pathway. Possible mechanism(s) by which exposure to aromatic hydrocarbons causes a decrease in the body weight of mice, which has been referred to as wasting syndrome, will also be discussed.

Animals↗

PubMed2004

Inverted L-shape sternotomy as a minimally invasive approach: re-do cardiac surgery for papillary muscle rupture.

We report a successful treatment of the complete papillary muscle rupture occurring 16 months after coronary artery bypass grafting (CABG). A 57-year-old man was admitted for the sudden onset of chest pain and cardiogenic shock. Emergency cardiac catheterization revealed severe mitral regurgitation and total occlusion in the right coronary artery, which was successfully revascularized by percutaneous coronary intervention under intra-aortic balloon pumping. The right internal thoracic artery grafted to the left anterior descending artery in the previous CABG was functioning well. An echocardiogram distinctly indicated the ruptured head of the papillary muscle. Since an emergency operation revealed complete rupture of the posterior papillary muscle, mitral valve replacement was carried out through an inverted L-shape sternotomy with T-shape left atriotomy. Our case indicates that the inverted L-shape sternotomy was a useful approach to preserve the function of grafts, and that T-shape left atriotomy offered a good exposure of the mitral valve in the limited surgical field.

Coronary Artery Bypass↗

PubMed2004

Identification of a novel polymorphic enhancer of the human CYP3A4 gene.

CYP3A4, the most abundant form of cytochrome P450 in the human adult liver, shows wide interindividual variation in its activity. This variability is thought to be caused largely by transcriptional and genetic factors, yet the underlying mechanisms are poorly understood. The purpose of this study was to clarify the mechanisms controlling the CYP3A4 gene transcription and to search for genetic polymorphisms in the 5'-flanking region of the CYP3A4 gene. Transient transfection of human hepatoma HepG2 cells and of normal human hepatocytes with a series of CYP3A4 promoter-luciferase reporter plasmids revealed that a region from -11.4 to -10.5 kilobases, designated the constitutive liver enhancer module of CYP3A4 (CLEM4), was important for the constitutive activation of the CYP3A4 gene. Gel shift assay using nuclear extracts prepared from HepG2 cells showed that HNF-1alpha, HNF-4alpha, USF1, and AP-1 interacted with CLEM4. Furthermore, the introduction of mutations into their binding sites demonstrated that essentially all sites were required for the maximal enhancer activity. Screening for genetic polymorphisms within CLEM4 in genomic DNA from French persons, we identified the novel variant, TGT insertion between -11,129 and -11,128 (-11,129_-11,128insTGT), whose allele frequency was 3.1%. The -11,129_-11,128insTGT resulted in the disruption of USF1 binding and a 36% reduction of the enhancer activity. These results suggest that CLEM4 is a constitutive enhancer of the CYP3A4 gene in the liver and that -11,129_-11,128insTGT may at least partly contribute to the interindividual variability of CYP3A4 expression.

5' Flanking Region↗

PubMed2004

[Antibiotic treatment for traumatic brain injury patients without positive bacterial cultures].

Prophylactic administration of antibiotics is prevalent for traumatic patients including head injury, when the patients have contaminated wounds, CSF leakage, and multiple injuries. In cases with prolonged fever and inflammatory signs, other antibiotics must be selected without confirming the infections by cultures. Usually, 1st or 2nd generation cefalosporins are selected as empiric therapy for traumatic patients, but, successive antibiotics are usually selected according to the situation. In this study, we analyzed 60 cases of head injured patients with Glasgow Coma Scale under 12, in terms of the selection of antibiotics and the reasons for the antibiotic selections. CEZ > PIPC > FMOX were used for initial treatment without any culture results. The second selection was made without any positive culture results in 85.7%, and tertiary selection without culture results in 50% of the patients. CPR > CFSL > FMOX > PAPM/BP were mainly used as second selection, and IPM/CS > CPR = PIPC were mainly used as tertiary selection. In cases with traumatic brain injuries, it is important to prevent antibiotic resistances. 1) by selecting appropriate antibiotics, 2) by using antibiotics after excluding catheter related infections, 3) by not using antibiotics and performing frequent cultures when no apparent infection focuses are detected.

Adolescent↗

PubMed2003

A novel transcriptional element which regulates expression of the CYP2D4 gene by Oct-1 and YY-1 binding.

We first identified the transcriptional regulatory element of the CYP2D4 gene. CYP2D4 is of interest in brain pharmacology and physiology because this enzyme can be involved in the metabolism of endogenous and exogenous compounds, which act on the central nervous system. Transfection studies using a series of the CYP2D4 promoter luciferase constructs identified the transcriptional element of CYP2D4 in the sequence between nucleotides -116 and -90 (named the neural expression regulatory element, NERE). The nucleotide sequence of NERE was specific for the CYP2D4 gene. Within this region, two nuclear factor-binding sequences, Oct-1 and YY-1, were present. Oct-1 acts as the activator of the CYP2D4. The core sequence of the YY-1 binding motif partially overlapped that of the Oct-1 binding motif. YY-1 may act as the repressor of CYP2D4, which interferes with Oct-1 activation by its binding to NERE. We concluded that a novel transcriptional regulatory element NERE specifically regulates the expression of the CYP2D4. This regulation system may be involved in the unique distribution of this isoform, such as the expression in the brain.

Amino Acid Sequence↗

PubMed2003

Hepatocyte nuclear factor-4 alpha/gamma and hepatocyte nuclear factor-1 alpha as causal factors of interindividual difference in the expression of human dihydrodiol dehydrogenase 4 mRNA in human livers.

Human dihydrodiol dehydrogenase (DD) catalyses the oxidation of trans-dihydrodiols of polycyclic aromatic hydrocarbons and the reduction of several ketone-containing drugs. About 40-fold interindividual difference in DD activities has been noted. Recently, we found that transcriptional factors, hepatocyte nuclear factor (HNF)-1 alpha, HNF-4 alpha and HNF-4 gamma were essential for the expression of DD4 mRNA, which is a major form of DDs. Thus, to clarify a possible mechanism(s) underlying the interindividual difference in DD activities, we investigated the sequences of genes and the expression levels of mRNA for DD4 and HNFs in human livers. We found no clear relationship between the genotypes of DD4 and HNF genes and the expression levels of DD4 mRNA in the subjects. The expression level of DD4 mRNA significantly correlated with that of HNF-1 alpha, HNF-4 alpha or HNF-4 gamma. These results suggest that the expression level of DD4 mRNA is cooperatively regulated by the amounts of HNF-1 alpha, HNF-4 alpha and HNF-4 gamma.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗

PubMed2003

Pigmented squamous cell carcinoma of the uterine cervix.

A 57-year-old female presented with an abnormal Pap smear. Colposcopic examination of the cervix revealed white mucosa with erosion and several areas of black pigmentation. After a colposcopically directed biopsy and loop conization, radical hysterectomy and bilateral salpingo-oophorectomy with pelvic and paraaortic lymphadenectomy were performed. Pathological examination disclosed an invasive squamous cell carcinoma admixed with many dendritic melanocytes. Melanin granules were present within the melanocytes and tumor cells. Although similar tumors have been reported in other sites, this is the first report to our knowledge of a pigmented squamous cell carcinoma of the uterine cervix.

Biopsy↗

PubMed2003

Aryl hydrocarbon hydroxylase represents CYP1B1, and not CYP1A1, in human freshly isolated white cells: trimodal distribution of Japanese population according to induction of CYP1B1 mRNA by environmental dioxins.

The expression level of mRNAs for cytochrome P450 (CYP) 1A1 and 1B1 in freshly prepared white cells from 72 subjects exposed to dioxins at waste incinerators was investigated. The amounts of CYP1B1 mRNA ranged from 0.16 to 671 molecules/10(7) molecules of 18S rRNA, whereas the amounts of CYP1A1 mRNA were <6 molecules/10 ng total RNA, indicating that CYP1A1 was not induced to a detectable level by environmentally exposed dioxins. The inducibility of CYP1B1 mRNA in leukocytes, defined as the ratio of CYP1B1 mRNA to the plasma concentration of dioxins, varied among the subjects. It was found that the subjects showed trimodal distribution according to inducibility: 39 (54.2%), 25 (34.7%), and 8 (11.1%) of 72 subjects were judged as poor, intermediate, and high responders to environmental dioxins, respectively. The amounts of CYP1B1 mRNA in leukocytes of the intermediate and high responders were highly correlated with the plasma concentrations of dioxins (P < 0.05 and <0.01). These results suggest that CYP1B1 with polymorphic inducibility by dioxins is involved in aromatic hydrocarbon hydroxylase activities in human lymphocytes.

Aryl Hydrocarbon Hydroxylases↗

PubMed2002

Hepatocyte nuclear factor (HNF)-4 alpha/gamma, HNF-1 alpha, and vHNF-1 regulate the cell-specific expression of the human dihydrodiol dehydrogenase (DD)4/AKR1C4 gene.

Recently, we found a region A (a hepatocyte nuclear factor (HNF)-4-binding site from nucleotides -701 to -684) and a region B (an HNF-1-binding site from nucleotides -682 to -666) as cis-acting elements necessary for the transcriptional activation of the human dihydrodiol dehydrogenase (DD)4 gene in human hepatoblastoma HepG2 cells, which express DD4 mRNA. Thus, to investigate the mechanism(s) responsible for the cell-type-specific expression of DD4 mRNA, we constructed a reporter plasmid, pDD4 Foot A+B: -95/+28, in which regions A and B were linked to the human DD4 minimal promoter (-95 to +28) fused to the luciferase gene. The luciferase activity was detectable in HepG2 cells but not in human renal adenocarcinoma ACHN cells transfected with the pDD4 Foot A+B: -95/+28, which do not express DD4 mRNA. A supershift assay using antibodies to HNF-4 alpha, -4 gamma, -1 alpha, or valiant HNF (vHNF)-1 revealed that HNF-4 alpha, -4 gamma, and -1 alpha recognized regions A and B in HepG2 cells and that only vHNF-1 bound to regions A and B in ACHN cells. Semiquantitative reverse-transcribed polymerase chain reaction showed that a large amount of vHNF-1-C, which lacked transcriptional activation domain, was expressed in ACHN cells. Transfection of ACHN cells with an expression plasmid of vHNF-1-C did not activate the pDD4 Foot A+B: -95/+28 reporter gene. Taken together, we conclude that the cell-type-specific expression of DD4 mRNA is regulated by vHNF-1-C.

Adenocarcinoma↗

PubMed2002

A novel mutant allele of the CYP2A6 gene (CYP2A6*11 ) found in a cancer patient who showed poor metabolic phenotype towards tegafur.

In a clinical study, a newly developed anticancer drug, TS-1 capsule, which contained tegafur (FT) and 5-chloro-2,4-dihydroxypyridine, an inhibitor of dihydropyrimidine dehydrogenase, was orally administered to five gastric cancer patients (patients 1-5). The total area under the plasma FT concentration-time curve in patient 1 was four-fold higher than in other patients. Since cytochrome P450 2A6 (CYP2A6) has been reported to metabolize FT to yield 5-fluorouracil (5-FU), it was postulated that the poor metabolic phenotype of patient 1 was caused by mutations of the CYP2A6 gene. Thus, alleles for the CYP2A6 genes derived from patient 1 were completely sequenced. It was found that one allele was CYP2A6*4C, which was a whole deleted allele for the human CYP2A6 gene. The other allele was a novel mutant allele (CYP2A6*11) in which thymine at nucleotide 670 was changed to cytosine. The nucleotide change caused an amino acid change from serine at residue 224 to proline. To examine whether or not the amino acid change affected CYP2A6 activity, we expressed an intact or mutant CYP2A6 together with NADPH-P450 oxidoreductase in Escherichia coli, and compared the capacity of the wild and mutant enzymes to metabolize FT to 5-FU. The Vmax value for FT metabolism by the mutant CYP2A6 was approximately one-half of the value of the intact CYP2A6, although the Km values were nearly the same. From these results, we conclude that the poor metabolic phenotype of patient 1 was caused by the existence of the two mutant alleles, CYP2A6*4C and the new variant CYP2A6*11.

Administration, Oral↗

PubMed2002

Hepatocyte nuclear factor-1alpha is a causal factor responsible for interindividual differences in the expression of UDP-glucuronosyltransferase 2B7 mRNA in human livers.

UDP-glucuronosyltransferase (UGT) 2B7 is one of the most important UGT isozymes expressed in human livers. This enzyme is reported to show more than 10-fold interindividual differences in its enzyme activities. Thus, the amounts of UGT2B7 mRNA in 12 human livers were quantified by quantitative reverse transcription-polymerase chain reaction. The amounts of UGT2B7 mRNA in the subjects ranged from 0.22 to 2.63 copies/10(3) copies of beta-actin. A novel point mutation (-253G to A) found in this study did not affect the level of UGT2B7 mRNA in the subjects. To clarify a causal factor(s) determining the expression level of UGT2B7 mRNA, we examined the correlation between the amounts of mRNAs for UGT2B7 and hepatocyte nuclear factor (HNF)-1alpha, which regulates the expression of UGT2B7 gene. HNF-1alpha mRNA was expressed at a level ranging from 2.99 to 24.76 copies/10(6) copies of beta-actin in the subjects. The amounts of mRNAs for UGT2B7 expressed in these individual liver samples were highly associated with the amount of mRNA for HNF-1alpha (r = 0.786, p = 0.002), suggesting that HNF-1alpha is a factor limiting the expression of UGT2B7 mRNA and a causal factor responsible for an interindividual difference in human livers.

DNA-Binding Proteins↗

PubMed2002

A major genotype in UDP-glucuronosyltransferase 2B15.

A novel single nucleotide polymorphism (SNP) was found in exon 6 of the UDP-glucuronosyltransferase (UGT) 2B15 gene from healthy Japanese populations. The SNP was as follows: SNP, 020228Toide001; GENE NAME, UGT2B15; ACCESSION NUMBER, U08854, AF180322, and NM_001078; LENGTH, 25 base; 5'-AGCTTGCCAAAAC/AAGGAAAGAAGAA-3'. This SNP was expected to cause a change of an amino acid residue at the position 523 (Thr to Lys) located in a putative co-factor binding region. The allele frequency of this SNP was 79% in Japanese, suggesting this polymorphism to be a major genotype in Japanese people.

Journal Article↗