Biomedical subjects

Ryuji Kato

Publications and source records attributed to Ryuji Kato.

10 recordsLinked to original sources

PubMed2006

High-throughput screening of cell death inducible short peptides from TNF-related apoptosis-inducing ligand sequence.

Therapeutic peptides and small molecules, rationally designed to trigger cell death have attracted strong attention. Cell death inducible peptides were screened from amino acid sequence of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Using Fmoc solid phase synthesis, cellulose membrane-bound octameric peptide library of TRAIL scan was prepared and cell viability assay was directly performed on peptide disk with Jurkat cells. Six peptide sequences that could induce cell death were found. Peptide sequence with RNSCWSKD (TRAIL(227-234)) that exist in the zinc-binding site revealed high cell death inducible activity. Apoptotic cell death was observed when cells were treated with soluble synthesized peptide.

Amino Acid Sequence↗

PubMed2006

Peptide array-based interaction assay of solid-bound peptides and anchorage-dependant cells and its effectiveness in cell-adhesive peptide design.

Peptide array, the designable peptide library covalently synthesized on cellulose support, was applied to assay peptide-cell interaction, between solid-bound peptides and anchorage-dependant cells, to study objective peptide design. As a model case, cell-adhesive peptides that could enhance cell growth as tissue engineering scaffold material, was studied. On the peptide array, the relative cell-adhesion ratio of NIH/3T3 cells was 2.5-fold higher on the RGDS (Arg-Gly-Asp-Ser) peptide spot as compared to the spot with no peptide, thus indicating integrin-mediated peptide-cell interaction. Such strong cell adhesion mediated by the RGDS peptide was easily disrupted by single residue substitution on the peptide array, thus indicating that the sequence recognition accuracy of cells was strictly conserved in our optimized scheme. The observed cellular morphological extension with active actin stress-fiber on the RGD motif-containing peptide supported our strategy that peptide array-based interaction assay of solid-bound peptide and anchorage-dependant cells (PIASPAC) could provide quantitative data on biological peptide-cell interaction. The analysis of 180 peptides obtained from fibronectin type III domain (no. 1447-1629) yielded 18 novel cell-adhesive peptides without the RGD motif. Taken together with the novel candidates, representative rules of ineffective amino acid usage were obtained from non-effective candidate sequences for the effective designing of cell-adhesive peptides. On comparing the amino acid usage of the top 20 and last 20 peptides from the 180 peptides, the following four brief design rules were indicated: (i) Arg or Lys of positively charged amino acids (except His) could enhance cell adhesion, (ii) small hydrophilic amino acids are favored in cell-adhesion peptides, (iii) negatively charged amino acids and small amino acids (except Gly) could reduce cell adhesion, and (iv) Cys and Met could be excluded from the sequence combination since they have less influence on the peptide design. Such rules that are indicative of the nature of the functional peptide sequence can be obtained only by the mass comparison analysis of PIASPAC using peptide array. By following such indicative rules, numerous amino acid combinations can be effectively screened for further examination of novel peptide design.

Amino Acid Sequence↗

PubMed2006

Effect of amiodarone on the serum concentration/dose ratio of metoprolol in patients with cardiac arrhythmia.

Amiodarone has pharmacokinetic interactions with a number of therapeutic drugs, including warfarin, phenytoin, flecainide, and cyclosporine. Metoprolol is mainly metabolized by CYP2D6, and desethylamiodarone, a metabolite of amiodarone, has a markedly greater inhibitory effect on CYP2D6 than amiodarone. Therefore, the goal of this study was to evaluate the effect of amiodarone and desethylamiodarone on the serum concentration/dose ratio (C/D) of metoprolol in 120 inpatients with cardiac arrhythmias that received either metoprolol and amiodarone (MET+AMD group, n=30) or metoprolol alone (MET group, n=90). The ratio of administered metoprolol was compared between the MET and the MET+AMD groups. The dose of metoprolol and patient age were significantly higher in the MET group when compared with the MET+AMD group (1.00+/-0.480 versus 0.767+/-0.418 mg/kg/day, p<0.050; 68.6+/-10.6 versus 57.6+/-14.1 years, p<0.001, respectively), but the C/D ratio was significantly lower in the MET group than in the MET+AMD group (90.8+/-64.0 versus 136+/-97.8, p<0.01). Furthermore, a significant correlation was found between the C/D ratio and desethylamiodarone concentration (n=30, r=0.371, p<0.01). The results suggest that there is a significant interaction between amiodarone and metoprolol via desethylamiodarone-induced inhibition of CYP2D6. Therefore, careful monitoring of metoprolol concentrations/bioactivity of CYP2D6 is required in the context of co-administration of amiodarone and metoprolol.

Adult↗

PubMed2005

Novel strategy for protein exploration: high-throughput screening assisted with fuzzy neural network.

To engineer proteins with desirable characteristics from a naturally occurring protein, high-throughput screening (HTS) combined with directed evolutional approach is the essential technology. However, most HTS techniques are simple positive screenings. The information obtained from the positive candidates is used only as results but rarely as clues for understanding the structural rules, which may explain the protein activity. In here, we have attempted to establish a novel strategy for exploring functional proteins associated with computational analysis. As a model case, we explored lipases with inverted enantioselectivity for a substrate p-nitrophenyl 3-phenylbutyrate from the wild-type lipase of Burkhorderia cepacia KWI-56, which is originally selective for (S)-configuration of the substrate. Data from our previous work on (R)-enantioselective lipase screening were applied to fuzzy neural network (FNN), bioinformatic algorithm, to extract guidelines for screening and engineering processes to be followed. FNN has an advantageous feature of extracting hidden rules that lie between sequences of variants and their enzyme activity to gain high prediction accuracy. Without any prior knowledge, FNN predicted a rule indicating that "size at position L167," among four positions (L17, F119, L167, and L266) in the substrate binding core region, is the most influential factor for obtaining lipase with inverted (R)-enantioselectivity. Based on the guidelines obtained, newly engineered novel variants, which were not found in the actual screening, were experimentally proven to gain high (R)-enantioselectivity by engineering the size at position L167. We also designed and assayed two novel variants, namely FIGV (L17F, F119I, L167G, and L266V) and FFGI (L17F, L167G, and L266I), which were compatible with the guideline obtained from FNN analysis, and confirmed that these designed lipases could acquire high inverted enantioselectivity. The results have shown that with the aid of bioinformatic analysis, high-throughput screening can expand its potential for exploring vast combinatorial sequence spaces of proteins.

Fuzzy Logic↗

PubMed2004

Angiotensin II inhibitory peptide found in the receptor sequence using peptide array.

Peptide array consisting of hundreds of peptides spatially addressed and synthesized on a cellulose membrane support was used to screen ligand-inhibitory peptides. As a model, angiotensin II (Ang II), a significant peptide related to the treatment of cardiovascular diseases, was chosen as the target ligand. Peptide arrays covering the Ang II receptor type 1 sequence were prepared, and peptide domains with high affinity to the Ang II fluorescein conjugate were investigated. The peptide (VVIVIY) within the first transmembrane region exhibited the highest affinity to Ang II. The synthesized soluble VVIVIY peptide had an 84% inhibitory effect on Ang II-induced aorta contraction. These results indicate that our screening strategy utilizing peptide array is an effective approach for the peptide drug development.

Amino Acid Sequence↗

PubMed2003

[A case in which tofisopam was effective for treatment of paroxysmal supraventricular tachycardia].

Paroxysmal supraventricular tachycardia (PSVT) is a reentrant tachycardia, and the autonomic nervous system influences the paroxysms of PSVT. Tofisopam (Grandaxin) is a derivative of benzodiazepines. It is reported that heart rate variability (HRV) reveals the function of the autonomic nervous system and is used as an index of the effects of the autonomic nervous system on the heart rhythm. In previous studies, it was reported that tofisopam improved HRV. In this case report, the frequency of PSVT was significantly decreased and subjective symptoms of arrhythmia were eliminated after the administration of tofisopam. R-R interval variability and high-frequency power (HF; 0.15-0.40 Hz) were increased, and [low-frequency power (LF; 0.04-0.15 Hz)]/HF was decreased after administration of tofisopam. These results suggest that tofisopam overcame the existing imbalance of the sympathetic and vagus nervous system. In this case report, it is suggested that tofisopam is effective for the treatment of PSVT.

Adult↗

PubMed2002

Impairment of ciprofloxacin absorption by calcium polycarbophil.

The effect of calcium polycarbophil on the absorption of ciprofloxacin, a broad-spectrum antibacterial agent, was evaluated in an in vitro and in vivo study. In the in vitro study, the release of ciprofloxacin from the cellulose membrane in the presence or absence of metal cations was measured using the dissolution test procedure. In the in vivo study, male ST Wistar rats and male volunteers were employed. First, 20 mg/kg of ciprofloxacin alone (Rat Study 1) or 20 mg/kg of ciprofloxacin in combination with 64 mg/kg of calcium chloride (Rat Study 2) was administered orally to 3 rats. Second, a volunteer study was employed and a randomized crossover design with twophases was used. In onephase, volunteers received 400 mg of ciprofloxacin alone (Study 1); in the other phase, they received 400 mg of ciprofloxacin and 1200 mg of fine calcium polycarbophil granules concomitantly (Study 2). The plasma and serum concentrations of ciprofloxacin were measured by high-performance liquid chromatography. The release of ciprofloxacin from the cellulose membrane in the presence of aluminum, calcium, or iron ions was slower than that in the absence of these metal ions. The AUC0-4 and Cmax in Rat Study 2 were lower than those respective values in Rat Study 1. AUC0-4 was approximately 60% lower in Rat Study 2 than Rat Study 1. In the volunteer study, the AUC0-12 and Cmax in Study 2 were lower than those respective values in Study 1. In particular, AUC0-12 was approximately 50% lowerin Study 2 than in Study 1. These findings suggest that when ciprofloxacin and calcium polycarbophil were coadministered concomitantly, a decrease of ciprofloxacin absorption was observed, and this action was caused by the formation of chelate complexes. Therefore, it seems clear that we should avoid the concomitant administration of ciprofloxacin and calcium polycarbophil.

Absorption↗

PubMed2002

Impairment of mycophenolate mofetil absorption by calcium polycarbophil.

The effect of calcium polycarbophil on the absorption of mycophenolate mofetil, an immunosuppressive agent, was evaluated in healthy subjects. In vitro studies were performed to further evaluate the mechanism of the potential interaction. In the in vitro study, the release of mycophenolate mofetil from a cellulose membrane in the presence or absence of metal cations was measured using the dissolution test procedure. In the in vivo study, a randomized crossover design with two phases was used. In one phase, 6 male healthy volunteers received 1000 mg of mycophenolate mofetil alone (treatment 1); in the other phase, they received 1000 mg of mycophenolate mofetil and 2400 mg of calcium polycarbophil fine granules concomitantly (treatment 2). They received 30 mg of lansoprazole for 5 days and, on the 6th day, received mycophenolate mofetil and 2400 mg of calcium polycarbophil fine granules concomitantly (treatment 3). The serum concentration of mycophenolic acid was measured by high-performance liquid chromatography. In the in vitro study, the release from a cellulose membrane in the presence of calcium or iron ions was slower than that in the absence of these metal ions. In the in vivo study, the AUC0-12 and C(max) in treatment 2 were less than those in treatment 1. About 50% and 25% decreases in AUC0-12 in treatment 2 and treatment 3 were observed compared with those in treatment 1, respectively. These findings suggest that when mycophenolate mofetil and calcium polycarbophil were coadministered concomitantly, a decrease in mycophenolate mofetil absorption was observed. Therefore, it appears clear that the concomitant administration of mycophenolate mofetil and calcium polycarbophil should be avoided.

Absorption↗

PubMed2002

Hidden Markov model-based prediction of antigenic peptides that interact with MHC class II molecules.

Elucidating the interaction between major histocompatibility complex (MHC) molecules and antigenic peptides is fundamental to better understanding of the processes involved in immune responses and for the development of innovative immunotherapies. In the present study, hidden Markov models (HMM) were combined with the successive state splitting (SSS) algorithm for optimization of the HMM structure, to predict peptide binders to the human MHC class II molecule HLA-DRB1*0101. The predictive performance of our model (S-HMM) was compared with fully connected HMM and artificial neural network (ANN) methods using the relative operating characteristic (ROC) analysis. The S-HMM predictions had values of ROC > or = 0.85 which was at least as good, or better than the comparison methods. In addition, S-HMM is trained on positive data only and does not require exhaustive data preprocessing, such as peptide alignment. Our results demonstrated that S-HMM combines the high accuracy of predictions with the simplicity of implementation and is therefore useful for analyzing MHC class II binding peptides. In particular the S-HMM may be trained using only positive data and, the preprocessing of training data, such as peptide alignment and the selection of binding cores, is not required in this method.

Journal Article↗

PubMed2002

Lack of interaction between cefdinir and calcium polycarbophil: in vitro and in vivo studies.

The effect of calcium polycarbophil on the absorption of cefdinir, cephalosporin derivative, was evaluated in both in vitro and in vivo studies. In the in vitro study, the release of cefdinir from a cellulose membrane in the presence or absence of metal cations was measured using the dissolution test procedure. In the in vivo study, volunteers and a randomized crossover design with two phases were used. In the first phase, the volunteers received 200 mg of cefdinir alone (Study 1); in the other phase, they received 200 mg of cefdinir and 1200 mg of fine calcium polycarbophil granules concomitantly (Study 2). The cefdinir concentrations in the samples or serum were measured by an UV-VIS spectrophotometer or high-performance liquid chromatography. Release in the presence of iron ions was slower than that in the absence of metal ions, however no difference was observed between release in the presence of calcium ions and that in the absence of metal ions. No difference was observed in AUC(0-10), C(max) and t(max) between Study 1 and Study 2. The absorption of cefdinir was not affected by co-administration of calcium polycarbophil. Moreover, the in vitro study on the release of drugs from a cellulose membrane may predict the absorption of a drug caused by the formation of chelate complexes between the drug and metal ions.

Clinical Trial↗