Biomedical subjects

Takahisa Noma

Publications and source records attributed to Takahisa Noma.

At least 19 recordsLinked to original sources

PubMed2007

In silico panning for a non-competitive peptide inhibitor.

BACKGROUND: Peptide ligands have tremendous therapeutic potential as efficacious drugs. Currently, more than 40 peptides are available in the market for a drug. However, since costly and time-consuming synthesis procedures represent a problem for high-throughput screening, novel procedures to reduce the time and labor involved in screening peptide ligands are required. We propose the novel approach of 'in silico panning' which consists of a two-stage screening, involving affinity selection by docking simulation and evolution of the peptide ligand using genetic algorithms (GAs). In silico panning was successfully applied to the selection of peptide inhibitor for water-soluble quinoprotein glucose dehydrogenase (PQQGDH). RESULTS: The evolution of peptide ligands for a target enzyme was achieved by combining a docking simulation with evolution of the peptide ligand using genetic algorithms (GAs), which mimic Darwinian evolution. Designation of the target area as next to the substrate-binding site of the enzyme in the docking simulation enabled the selection of a non-competitive inhibitor. In all, four rounds of selection were carried out on the computer; the distribution of the docking energy decreased gradually for each generation and improvements in the docking energy were observed over the four rounds of selection. One of the top three selected peptides with the lowest docking energy, 'SERG' showed an inhibitory effect with Ki value of 20 microM. PQQGDH activity, in terms of the Vmax value, was 3-fold lower than that of the wild-type enzyme in the presence of this peptide. The mechanism of the SERG blockage of the enzyme was identified as non-competitive inhibition. We confirmed the specific binding of the peptide, and its equilibrium dissociation constant (KD) value was calculated as 60 microM by surface plasmon resonance (SPR) analysis. CONCLUSION: We demonstrate an effective methodology of in silico panning for the selection of a non-competitive peptide inhibitor from small virtual peptide library. This study is the first to demonstrate the usefulness of in silico evolution using experimental data. Our study highlights the usefulness of this strategy for structure-based screening of enzyme inhibitors.

Acinetobacter calcoaceticus↗

PubMed2006

Analysis of the evolution of the thrombin-inhibiting DNA aptamers using a genetic algorithm.

We previously identified a thrombin-inhibiting DNA aptamer that was presumed to form a G-quartet structure with a duplex. To investigate the importance of the sequences in the duplex region and to obtain aptamers with higher inhibitory activities, we randomized the sequences of the duplex region of this aptamer and carried out selection based on inhibitory activity using a genetic algorithm. This method consisted of selection via an inhibition assay, crossover, and mutation in silico. After two cycles, we obtained ligands with greater inhibitory activities than that of the original aptamer. In addition, the duplex sequences were found to contribute to the inhibitory activities of aptamers.

Algorithms↗

PubMed2006

Characterization and application of aptamers for Taq DNA polymerase selected using an evolution-mimicking algorithm.

Using an evolution-mimicking algorithm (EMA), we have recently identified DNA aptamers that inhibit Taq DNA polymerase. In the present study, we have attempted to improve further the inhibitory activities of aptamers, as well as to characterize those aptamers with the most potent inhibitory activities. To characterize the most potent aptamer and demonstrate its applicability, the abilities to inhibit Tth DNA polymerase and to modulate specific amplification in PCR were investigated. This aptamer inhibited both Tth DNA polymerase and Taq DNA polymerase and improved the specificity of detection of a low-copy-number target gene in PCR using these DNA polymerases.

Algorithms↗

PubMed2006

A screening method for DNA aptamers that bind to a specific, unidentified protein in tissue samples.

Aptamers are oligonucleotide ligands with a high affinity to, and specificity for, various target molecules and they are expected to be powerful tools for proteomic analysis. To select aptamers that bind to a specific unidentified protein in tissues for protein analysis, a screening method was developed using chicken skeletal muscle as a model. Target proteins in the target mixture were separated by electrophoresis and transferred to a membrane, and a DNA library was added onto it. The aptamers that bound to the target protein were visualized by chemiluminescence and collected by cutting out the visualized band. The specific aptamers to the target protein were selected by only one round of selection using this screening, suggesting this screening method might be useful for selecting aptamers for proteome analysis.

Animals↗

PubMed2006

Aptamer selection based on inhibitory activity using an evolution-mimicking algorithm.

In order to efficiently select aptamers that bind to and inhibit proteins, we developed a method that involves screening DNA aptamers based on their inhibitory activities using an evolution-mimicking algorithm after the pre-selection by SELEX. The value of this method was demonstrated by the identification of an inhibitor of Taq DNA polymerase in a unique single-stranded DNA library, which was expected to form a G-quartet structure. This method consists of selection via an inhibition assay, sequence shuffling, and mutation in silico. After six rounds of selection, the inhibitory activities of the aptamers had evolved significantly. This demonstrates the utility of this strategy for screening aptamers based on their inhibitory actions.

Algorithms↗

PubMed2006

Competitive displacement of phosphoinositide 3-kinase from beta-adrenergic receptor kinase-1 improves postinfarction adverse myocardial remodeling.

Adverse remodeling after myocardial infarction (MI) determines the progression of heart failure. Failing hearts are characterized by downregulation of beta-adrenergic receptor (beta-AR) signaling in part because of increased beta-AR kinase 1 activity. Our previous studies have shown that overexpression of the phosphoinositide kinase (PIK) domain of phosphoinositide 3-kinase (PI3K), prevents beta-AR downregulation and enhances adrenergic agonist responsiveness by inhibiting the targeting of PI3K to the beta-AR complex. To investigate whether preventing beta-AR downregulation in the heart ameliorates cardiac function post-MI, transgenic mice with cardiac-specific overexpression of the PIK domain peptide (TgPIK) underwent left coronary artery ligation and were subsequently followed by serial echocardiography at 4, 8, 12, 16, and 20 wk. Despite having similar infarction sizes, TgPIK mice showed better systolic function, less cardiac dilatation, and improved hemodynamic response to dobutamine compared with littermate controls after MI. To test that displacement of PI3K from the beta-AR complex, but not the total loss of PI3K-gamma, is critical for amelioration of cardiac function, mice lacking the PI3K-gamma (PI3K-gamma-KO) underwent MI, and their cardiac function was assessed 20 wk post-MI. Serial echocardiographic measurements showed severe reduction in contractile performance in PI3K-gamma-KO compared with TgPIK mice. Furthermore, significant beta-AR downregulation and desensitization were only seen in infarcted wild-type and PI3K-gamma-KO mice and not in TgPIK mice. Together, these results demonstrate that adverse remodeling of the ventricle after MI can be attenuated by a strategy that prevents recruitment of PI3K to the plasma membrane and restores normal beta-AR function.

Animals↗

PubMed2006

An antioxidant treatment potentially protects myocardial energy metabolism by regulating uncoupling protein 2 expression in a chronic beta-adrenergic stimulation rat model.

Excessive beta-adrenergic stimulation causes cardiac toxicity, which also contributes to cardiac oxidative stress. Although uncoupling protein 2 (UCP2), a member of the mitochondrial inner membrane carrier family, can regulate energy efficiency and oxidative stress in mitochondria, little data exist regarding interactions between UCP2 expression and beta-adrenergic stimulation induced cardiac oxidative damage. We investigated whether chronic beta-adrenergic stimulation induces myocardial energy metabolism abnormality via oxidative stress, including any role of UCP2. We also examined whether 3-methyl-1-phenyl-2-pyrazolin-5-one (MIC-186; edaravone), a potent free radical scavenger, has cardioprotective effects against beta-adrenergic stimulation. Male Sprague-Dawley rats received isoproterenol (1.2 mg/kg/day) subcutaneously or/and edaravone (30 mg/kg/day) orally. Isoproterenol increased the heart/body weight ratio, accompanied by an increase in the level of myocardial thiobarbituric acid reactive substances (TBARS) and a decreased phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio. Isoproterenol also markedly increased expressions of UCP2 mRNA (1.74 fold vs. non-isoproterenol) and protein (1.93 fold vs. non-isoproterenol). Edaravone had no apparent effect in hypertrophic responses, but significantly prevented both increases in TBARS and decreases in the PCr/ATP ratio. Edaravone also prevented increases in UCP2 mRNA (0.76 fold vs. isoproterenol) and protein (0.62 fold vs. isoproterenol) expressions against isoproterenol administration. Our results suggest that chronic beta-adrenergic stimulation induces myocardial energy inefficiency via excessive oxidative stress. The antioxidant effect of edaravone has potential to improve energy metabolism abnormalities against beta-adrenergic stimulation. Adequate regulation of UCP2 expression through artificial reduction of oxidative stress may play an important role in protection of the myocardial energy metabolism.

Adrenergic beta-Agonists↗

PubMed2006

Contribution of reactive oxygen species to the pathogenesis of left ventricular failure in Dahl salt-sensitive hypertensive rats: effects of angiotensin II blockade.

OBJECTIVE: We investigated the contribution of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) generation to the pathogenesis of diastolic heart failure (DHF) in Dahl salt-sensitive (DS) hypertensive rats, with the aim of testing our hypothesis that the cardioprotective effects of angiotensin II (Ang II) blockade are provided by the suppression of this pathway. METHODS: DS rats were maintained on high (H: 8.0% NaCl) or low (L: 0.3% NaCl) salt diets from age 7 to 17 weeks. DS/H rats were also treated with candesartan cilexetil (10 mg/kg per day, orally) or a superoxide dismutase mimetic, tempol (3 mmol/l in drinking water) from age 7 to 17 weeks. RESULTS: DS/H rats represented hypertension, left ventricular (LV) relaxation abnormality and myocardial stiffening with preserved systolic heart function. As compared with DS/L rats, DS/H rats showed higher levels of transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF), p22phox and gp91phox mRNA expression, NADPH oxidase activity and thiobarbituric acid-reactive substance (TBARS) contents in LV tissues. Gene expression of uncoupling protein-2 (UCP-2), an inner mitochondrial membrane proton transporter, was also 2.8 +/- 0.5-fold higher. In DS/H rats, treatment with candesartan did not alter blood pressure, but resulted in a marked improvement of the hemodynamic deterioration; these therapeutic effects were accompanied by decreases in myocardial NADPH oxidase activity, TBARS contents and the expression of TGF-beta, CTGF, p22phox, gp91phox and UCP-2. Similar therapeutic effects were provided by treatment with tempol in DS/H rats. CONCLUSIONS: Our data suggest that NADPH oxidase-mediated ROS production contributes to the pathogenesis of DHF in DS hypertensive rats, and that the cardioprotective effects of AngII blockade are, at least partially, mediated through the suppression of this pathway.

Angiotensin II↗

PubMed2006

Intermittent pressure overload triggers hypertrophy-independent cardiac dysfunction and vascular rarefaction.

For over a century, there has been intense debate as to the reason why some cardiac stresses are pathological and others are physiological. One long-standing theory is that physiological overloads such as exercise are intermittent, while pathological overloads such as hypertension are chronic. In this study, we hypothesized that the nature of the stress on the heart, rather than its duration, is the key determinant of the maladaptive phenotype. To test this, we applied intermittent pressure overload on the hearts of mice and tested the roles of duration and nature of the stress on the development of cardiac failure. Despite a mild hypertrophic response, preserved systolic function, and a favorable fetal gene expression profile, hearts exposed to intermittent pressure overload displayed pathological features. Importantly, intermittent pressure overload caused diastolic dysfunction, altered beta-adrenergic receptor (betaAR) function, and vascular rarefaction before the development of cardiac hypertrophy, which were largely normalized by preventing the recruitment of PI3K by betaAR kinase 1 to ligand-activated receptors. Thus stress-induced activation of pathogenic signaling pathways, not the duration of stress or the hypertrophic growth per se, is the molecular trigger of cardiac dysfunction.

Adrenergic beta-Antagonists↗

PubMed2005

Association of uncoupling protein-2 expression with increased reactive oxygen species in residual myocardium of the enlarged left ventricle after myocardial infarction.

Left ventricular (LV) dilatation following myocardial infarction (MI) is a major determinant of the patient's prognosis, and myocardial energy metabolism may play a key role in LV remodeling. We aimed to investigate the relative timing of LV dilatation to LV function, myocardial energy regulation by uncoupling protein (UCP)-2, and cellular damage in the noninfarct zone. Myocardial infarction was produced in Sprague-Dawley rats by ligation of the coronary artery. The LV end-diastolic dimension (mm) increased (8.9+/-0.3 vs 6.8+/-0.8 in sham-operated rats, P<0.01) in association with elevation of the LV end-diastolic pressure (mmHg) (18+/-5 vs 6+/-2 in sham-operated rats) at 1 week following the ligation. At 4 weeks, the UCP-2 expression (180% of that in sham-operated rats) and LV end-diastolic dimension increased further (11.1+/-0.5, P<0.01) but there was no change in the LV end-diastolic pressure. The mechanisms for LV dilatation were quite different between the early and late stages after MI. In the late stage, augmentation of UCP-2 expression in the noninfarct zone may be related to the LV dilatation. Further examinations regarding the possibility of the protective role of UCP-2 are needed.

Animals↗

PubMed2005

Screening of DNA aptamers against multiple proteins in tissue.

We report the development of a novel screening method for DNA aptamers against multiple proteins in the target tissue. Although a purified single protein is generally used in screening of aptamers at present, such a simultaneous selection would be very advantageous in efficiency and selectivity. We first carried out the screening in situ and it was suggested that aptamers against particular target proteins were enriched. We also developed another novel screening method named Aptamer Blotting based on protein separation by PAGE and its visualization with fluorescein labeled aptamers and it was demonstrated that this method allowed the simultaneous selection of specific aptamers against multiple proteins.

Animals↗

PubMed2004

Treatment of acute myocardial infarction by hepatocyte growth factor gene transfer: the first demonstration of myocardial transfer of a "functional" gene using ultrasonic microbubble destruction.

OBJECTIVES: We examined whether ultrasonic microbubble destruction (US/MB) enables therapeutic myocardial gene transfer of hepatocyte growth factor (HGF) for acute myocardial infarction (MI). BACKGROUND: Hepatocyte growth factor gene transfer provides cardioprotective effects in MI, which requires direct intramyocardial injection or special vectors. Although US/MB was used in myocardial gene transfer, its feasibility in transfer of a therapeutic gene with non-viral vector remains unknown. METHODS: In a rat model of acute MI, naked plasmid (pVaxl) encoding human HGF (1,500 microg) was infused into the left ventricular (LV) chamber during US/MB (HGF-US/MB) or insonation only (HGF-US) or alone (HGF-alone), while control MI rats received empty pVaxl during US/MB (pVaxl-US/MB). For US/MB, transthoracic intermittent insonation with a diagnostic transducer (1.3 MHz) was performed for 2 min at a peak negative pressure of -2,160 kPa during intravenous 20% Optison. RESULTS: Baseline risk area was comparable among the groups. Immunohistology seven days after treatment revealed significant myocardial expression of HGF protein only in HGF-US/MB. At three weeks, LV weight in HGF-US/MB (0.89 +/- 0.03 g) was significantly lower than those in HGF-alone (1.09 +/- 0.08 g), HGF-US (1.04 +/- 0.07 g), and pVaxl-US/MB (1.04 +/- 0.05 g). Moreover, scar size was significantly smaller (16 +/- 6% vs. 39 +/- 5%, 41 +/- 6%, and 40 +/- 4% of total myocardial circumferential length, respectively), while capillary density (49 +/- 8 vs. 34 +/- 5, 37 +/- 6, and 36 +/- 4 capillaries/high-power field, respectively) and arterial density (37 +/- 7 vs. 15 +/- 9, 18 +/- 4, and 14 +/- 11 arterioles/high-power field, respectively) in the risk area were higher in HGF-US/MB than the other groups. CONCLUSIONS: Ultrasound-mediated microbubble destruction may enable myocardial HGF gene transfer with systemic administration of naked plasmid, which enhances angiogenesis, limits infarction size, and prevents LV remodeling after MI.

Animals↗

PubMed2004

Development of a novel DNA sensing system using DNA aptamer that inhibits enzymatic activity 2.

We have developed novel DNA sensor system using the DNA aptamers for thrombin. We modified original thrombin aptamer by addition of the target DNA complementary strands to the 5' end or 3' end of aptamer. Inhibitory activity of this modified aptamer increased in the presence of target DNA. We were able to detect the target DNA by measuring thrombin activity using this aptamer without the separation of bound and free separation.

Aptamers, Nucleotide↗

PubMed2003

Screening of DNA aptamers inhibiting Taq DNA polymerase using algorithm mimicking evolution.

We have developed a novel method for screening DNA aptamers by an algorithm mimicking evolution, which have enabled selection by not affinity but inhibitory activity of aptamers. Using this method, we have successfully obtained DNA aptamers that inhibit Taq DNA polymerase in a few hundred-nanomolar range. This result shows this method would be useful for screening aptamers as an enzyme inhibitor.

Algorithms↗

PubMed2002

Correlation of functional and structural alterations of the coronary arterioles during development of type II diabetes mellitus in rats.

OBJECTIVE: Cardiac complications in diabetes mellitus (DM) are frequently ascribed to microangiopathy. Therefore, we sought to directly correlate the serial changes in coronary arterial function with the extent of coronary arteriolar remodeling in a model spontaneously developing type II DM. METHODS: Otsuka Long-Evans Tokushima Fatty (OLETF) rats and control Long-Evans Tokushima Otsuka (LETO) rats were used. At 5, 15 and 30 weeks of age, ten rats in each group were subjected to systemic and coronary hemodynamic measurements using the colored microsphere technique before and during maximal coronary hyperemia and histological assessment with Azan-Mallory stain of the coronary arterioles. RESULTS: As early as 15 weeks of age, at which time fasting plasma glucose concentration remained normal, OLETF rats exhibited a lower coronary flow reserve and a greater coronary vascular resistance during hyperemia than did LETO rats. On histomorphometry, OLETF rats exhibited a greater wall-to-lumen ratio and a greater degree of perivascular fibrosis of arterioles at 15 weeks of age and thereafter, both of which exhibited a significant correlation with the minimal coronary vascular resistance. CONCLUSIONS: The degree of functional deterioration in coronary circulation was directly correlated with the severity of coronary arteriolar structural remodeling during the development of microangiopathy in early stage of DM.

Animals↗

PubMed2002

Improvement of aortic wall distensibility and reduction of oxidative stress by pioglitazone in pre-diabetic stage of Otsuka Long-Evans Tokushima fatty rats.

We tested the hypothesis that pioglitazone (insulin sensitizer) reduces oxidative stress and improves aortic wall distensibility in the pre-diabetic stage of Otsuka Long-Evans Tokushima Fatty rats, type 2 diabetes mellitus (DM) model. 20 DM and 9 nonDM male rats were divided into 3 groups: treated-DM, untreated-DM, and untreated-nonDM. Pioglitazone (0.01%) was mixed in chow in the treated group from 15 to 20 weeks of age. At baseline and 20 weeks, plasma malondialdehyde (MDA) was measured. At 20 weeks, intravascular ultrasound images and aortic pressure were simultaneously recorded. Stiffness parameter beta was calculated from the cyclic variations of aortic diameter and pressure. From an excised thoracic aorta, aortic wall collagen was measured, and the morphology was histopathologically evaluated by hematoxylin-eosin staining. At 20 weeks, MDA (nmol/ml) in treated-DM (2.3 +/- 0.3) was lower than in untreated-DM (3.2 +/- 0.6, p < 0.0001). beta in treated-DM (0.53 +/- 0.21) was smaller than that in untreated-DM (0.88 +/- 0.26, p = 0.0067). Aortic wall collagen (mg/100 mg dry weight) did not decrease in treated-DM (22.3 +/- 3.2 vs untreated-DM : 19.6 +/- 4.7). Lumen/medial area ratio (L/M) increased in treated-DM (2.79 +/- 0.40 vs untreated-DM : 2.22 +/- 0.20, p = 0.0041, untreated-nonDM : 2.25 +/- 0.55, p = 0.0075). MDA was significantly correlated with beta (r = 0.65, p = 0.0005) or L/M (r = -0.60, p = 0.0008). Pioglitazone may reduce oxidative stress and contribute to improvement of aortic wall stiffness without decrease in collagen content at an early prediabetic stage of type 2 DM.

Age Factors↗

PubMed2002

Pioglitazone: cardiovascular effects in prediabetic patients.

Pioglitazone is the second thiazolidine derivative used clinically in the type 2 diabetes mellitus (DM). In the prediabetic stage, hyperinsulinemia or insulin resistance has been suggested to be closely associated with the oxidative stress. The first thiazolidine derivative used to treat DM, troglitazone, is chemically related to alpha-tocopherol, a known antioxidant. Troglitazone prevents tissue damage, but has been reported to produce hepatotoxicity. Pioglitazone strongly increases insulin sensitivity, improves glucose and lipid metabolism and showed no evidence of hepatotoxicity. The mechanism of the antidiabetic action of pioglitazone involves activation of insulin receptors and/or high affinity for peroxisome proliferator-activated receptor gamma (PPARgamma). Hydroxylation of the phenyl and pyridine rings in the chemical structure of pioglitazone may facilitate the scavenging of hydroxyl radicals. The direct antioxidant effect of pioglitazone may contribute to its effect on insulin resistance. The hypoglycemic and hypolipidemic effects of pioglitazone are likely to reduce the expression of TNFalpha. The reduction in the oxidative stress may lead to the suppression of TGFbeta and of collagen accumulation. A decrease in collagen content is likely to improve left ventricular diastolic function and distensibility of the aortic wall. Reduction in the oxidative stress may prevent the proliferation of vascular smooth muscle cells and contribute to the decrease in the aortic wall stiffness.

Animals↗

PubMed2002

Perindopril effect on uncoupling protein and energy metabolism in failing rat hearts.

Uncoupling proteins, inner mitochondrial membrane proton transporters, are important for regulating myocardial energy efficiency. We investigated the effects of the ACE inhibitor perindopril on cardiac performance, myocardial energy efficiency, and uncoupling protein expression in an aortic regurgitation rat model. Twenty male Sprague-Dawley rats, in which aortic regurgitation was produced, were divided into untreated and perindopril-treated (5 mg x kg(-1) x d(-1)) rats. The treatments were initiated 3 days after operation. Ten control rats were sham-operated. Measurements of blood pressure and echocardiography were repeated before and 100 days after operation (endpoint). Left ventricular uncoupling protein-2 expression, creatine phosphate, and adenosine triphosphate were measured at endpoint. In perindopril-treated rats, systolic and diastolic blood pressure decreased after treatment (92+/-4/65+/-2 mm Hg). At endpoint, left ventricular end-diastolic dimension in untreated (10.7+/-0.2 mm) and treated rats (9.2+/-0.2 mm) was increased, and fractional shortening was reduced in untreated rats (28+/-1%) but did not change in treated rats (36+/-2%). Uncoupling protein-2 mRNA expression increased in untreated rats (3.7-fold) and was suppressed by perindopril (1.5-fold). The creatine phosphate was reduced in untreated rats (10.6+/-0.7 micro mol/g) but not in treated rats (15.9+/-2.0 micro mol/g). In the chronic stage of aortic regurgitation, perindopril improved cardiac performance and myocardial energy efficiency, in which the suppression of uncoupling protein-2 may play an important role.

Adenosine Triphosphate↗