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Atsushi Kato

Publications and source records attributed to Atsushi Kato.

At least 19 recordsLinked to original sources
PubMed2007

Importance of the anti-interferon capacity of Sendai virus C protein for pathogenicity in mice.

The Sendai virus (SeV) C protein blocks signal transduction of interferon (IFN), thereby counteracting the antiviral actions of IFN. Using HeLa cell lines expressing truncated or mutated SeV C proteins, we found that the C-terminal half has anti-IFN capacity, and that K(151)A, E(153)A, and R(154)A substitutions in the C protein eliminated this capacity. Here, we further created the mutant virus SeV Cm*, in which K(151)A, E(153)K, and R(157)L substitutions in the C protein were introduced without changing the amino acid sequence of overlapped P, V, and W proteins. SeV Cm* was found to lack anti-IFN capacity, as expected. While the growth rate and final yield of SeV Cm* were inferior to those of the wild-type SeV in IFN-responsive, STAT1-positive 2fTGH cells, SeV Cm* grew equivalently to the wild-type SeV in IFN-nonresponsive, STAT1-deficient U3A cells. SeV Cm* was thus shown to maintain multiplication capacity, except that it lacked anti-IFN capacity. Intranasally inoculated SeV Cm* could propagate in the lungs of STAT1(-/-) mice but was cleared from those of STAT1(+/+) mice without propagation. It was found that the anti-IFN capacity of the SeV C protein was indispensable for pathogenicity in mice. Conversely, the results show that the innate immunity contributed to elimination of SeV in early stages of infection in the absence of anti-IFN capacity.

Animals↗
PubMed2007

Mutational analysis of protein solubility enhancement using short peptide tags.

Protein aggregation is a common phenomenon. The preparation of highly concentrated protein samples, typically required for biophysical measurements, often involves a time consuming and tedious testing of solvent conditions for improving protein solubility. Here, in a systematic analysis, we have determined the increase in solubility upon the addition of SEP-tags (solubility enhancement peptide tags) containing, one, three, and five lysines or arginines (or six arginines) to either the N or C terminus of our low solubility model protein, bovine pancreatic trypsin inhibitor variant, BPTI-22 (a BPTI variant containing 22 alanines). As anticipated, the BPTI-22 solubility increased in direct relation to the number of charged residues contained in the SEP-tag, and without altering either the activity or the structure of the protein. The largest solubility increases were of 4.2-, 4.8-, and 6.2-folds produced by the addition, at the C terminus, of five lysine (BPTI-22-C5K), five and six arginine residues (BPTI-22-C5R and BPTI-22-C6R), respectively. The increased solubility of the tagged BPTI-22 yielded higher quality NMR spectra (hetero single quantum correlation HSQC spectra; with respect of the signal-to-noise and line shapes) in a much shorter time than for the untagged BPTI-22. Furthermore, tagged samples remained soluble for over ten days, as observed by their HSQC spectra. We believe that lysine- and arginine-based SEP-tags may provide an effective and versatile method for enhancing protein solubility.

Amino Acid Sequence↗
PubMed2006

Airway epithelial cells produce B cell-activating factor of TNF family by an IFN-beta-dependent mechanism.

Activation of B cells in the airways is now believed to be of great importance in immunity to pathogens, and it participates in the pathogenesis of airway diseases. However, little is known about the mechanisms of local activation of B cells in airway mucosa. We investigated the expression of members of the B cell-activating TNF superfamily (B cell-activating factor of TNF family (BAFF) and a proliferation-inducing ligand (APRIL)) in resting and TLR ligand-treated BEAS-2B cells and primary human bronchial epithelial cells (PBEC). In unstimulated cells, expression of BAFF and APRIL was minimal. However, BAFF mRNA was significantly up-regulated by TLR3 ligand (dsRNA), but not by other TLR ligands, in both BEAS-2B cells (376-fold) and PBEC (224-fold). APRIL mRNA was up-regulated by dsRNA in PBEC (7-fold), but not in BEAS-2B cells. Membrane-bound BAFF protein was detectable after stimulation with dsRNA. Soluble BAFF protein was also induced by dsRNA (> 200 pg/ml). The biological activity of the epithelial cell-produced BAFF was verified using a B cell survival assay. BAFF was also strongly induced by IFN-beta, a cytokine induced by dsRNA. Induction of BAFF by dsRNA was dependent upon protein synthesis and IFN-alphabeta receptor-JAK-STAT signaling, as indicated by studies with cycloheximide, the JAK inhibitor I, and small interfering RNA against STAT1 and IFN-alphabeta receptor 2. These results suggest that BAFF is induced by dsRNA in airway epithelial cells and that the response results via an autocrine pathway involving IFN-beta. The production of BAFF and APRIL by epithelial cells may contribute to local accumulation, activation, class switch recombination, and Ig synthesis by B cells in the airways.

B-Cell Activating Factor↗
PubMed2006

Paramyxovirus Sendai virus V protein counteracts innate virus clearance through IRF-3 activation, but not via interferon, in mice.

The present study was undertaken to clarify the role of Sendai virus (SeV) V protein, which has been shown to downregulate IFN-beta induction through inhibition of IRF-3 activation, in viral pathogenesis. Mice infected with rSeV mutants, deficient in V expression or expressing V lacking the C-terminus, had several-fold higher IFN activity levels in the lungs than those in wild-type virus-infected mice, and the mutant viruses were rapidly excluded from the lung from the early phase of infection before induction of acquired immunity. In addition, the unique early clearance of the mutants did not occur in IRF-3 knockout (KO) mice. However, high titers of IFN were detected even in the infected KO mice. Furthermore, early clearance of the mutant viruses was also observed in IFN signaling-deficient mice, IFN-alpha/beta receptor KO mice and STAT1 KO mice. These results indicate that SeV V protein counteracts IRF-3-mediated innate antiviral immunity for efficient virus replication and pathogenesis in mice, but it is not IFN.

Animals↗
PubMed2006

Secondary and tertiary isoquinoline alkaloids from Xylopia parviflora.

From the secondary and tertiary alkaloidal fractions of the root and the bark of Xylopia parviflora (Annonaceae), the isoquinoline alkaloids, 10,11-dihydroxy-1,2-dimethoxynoraporphine and parvinine were isolated, along with 39 known alkaloids. Their structures were determined on the basis of analysis of spectroscopic data.

Alkaloids↗
PubMed2006

Inhibitory effects of Zingiber officinale Roscoe derived components on aldose reductase activity in vitro and in vivo.

Ginger (Zingiber officinale Roscoe) continues to be used as an important cooking spice and herbal medicine around the world. Scientific research has gradually verified the antidiabetic effects of ginger. Especially gingerols, which are the major components of ginger, are known to improve diabetes including the effect of enhancement against insulin-sensitivity. Aldose reductase inhibitors have considerable potential for the treatment of diabetes, without increased risk of hypoglycemia. The assay for aldose reductase inhibitors in ginger led to the isolation of five active compounds including 2-(4-hydroxy-3-methoxyphenyl)ethanol (2) and 2-(4-hydroxy-3-methoxyphenyl)ethanoic acid (3). Compounds 2 and 3 were good inhibitors of recombinant human aldose reductase, with IC50 values of 19.2 +/- 1.9 and 18.5 +/- 1.1 microM, respectively. Furthermore, these compounds significantly suppressed not only sorbitol accumulation in human erythrocytes but also lens galactitol accumulation in 30% of galactose-fed cataract rat model. A structure-activity relationship study revealed that the applicable side alkyl chain length and the presence of a C3 OCH3 group in the aromatic ring are essential features for enzyme recognition and binding. These results suggested that it would contribute to the protection against or improvement of diabetic complications for a dietary supplement of ginger or its extract containing aldose reductase inhibitors.

Aldehyde Reductase↗
PubMed2006

Alpha-1-C-octyl-1-deoxynojirimycin as a pharmacological chaperone for Gaucher disease.

The most common lysosomal storage disorder, Gaucher disease, is caused by inefficient folding and trafficking of certain variants of lysosomal beta-glucosidase (beta-Glu, also known as beta-glucocerebrosidase). Recently, Sawker et al. reported that the addition of subinhibitory concentrations (10 microM) of the pharmacological chaperone N-nonyl-1-deoxynojirimycin (NN-DNJ) (10) to Gaucher patient-derived cells leads to a 2-fold increase in activity of mutant (N370S) enzyme [Proc. Natl. Acad. Sci. U.S.A.2002, 99, 15428]. However, we found that the addition of NN-DNJ at 10 microM lowered the lysosomal alpha-glucosidase (alpha-Glu) activity by 50% throughout the assay period in spite of the excellent chaperoning activity in N370S fibroblasts. Hence, we prepared a series of DNJ derivatives with an alkyl chain at the C-1alpha position and evaluated their in vitro inhibitory activity and potential as pharmacological chaperones for Gaucher cell lines. Among them, alpha-1-C-octyl-DNJ (CO-DNJ) (15) showed 460-fold stronger in vitro inhibitory activity than DNJ toward beta-Glu, while NN-DNJ enhanced in vitro inhibitory activity by 360-fold. Treatment with CO-DNJ (20 microM) for 4 days maximally increased intracellular beta-Glu activity by 1.7-fold in Gaucher N370 cell line (GM0037) and by 2.0-fold in another N370 cell line (GM00852). The addition of 20 microM CO-DNJ to the N370S (GM00372) culture medium for 10 days led to 1.9-fold increase in the beta-Glu activity without affecting the intracellular alpha-Glu activity for 10 days. Only CO-DNJ showed a weak beta-Glu chaperoning activity in the L444P type 2 variant, with 1.2-fold increase at 5-20 microM, and furthermore maximally increased the alpha-Glu activity by 1.3-fold at 20 microM. These experimental results suggest that CO-DNJ is a significant pharmacological chaperone for N370S Gaucher variants, minimizing the potential for undesirable side effects such as alpha-Glu inhibition.

1-Deoxynojirimycin↗
PubMed2006

Biosynthesis of Dictyostelium discoideum differentiation-inducing factor by a hybrid type I fatty acid-type III polyketide synthase.

Differentiation-inducing factors (DIFs) are well known to modulate formation of distinct communal cell types from identical Dictyostelium discoideum amoebas, but DIF biosynthesis remains obscure. We report complimentary in vivo and in vitro experiments identifying one of two approximately 3,000-residue D. discoideum proteins, termed 'steely', as responsible for biosynthesis of the DIF acylphloroglucinol scaffold. Steely proteins possess six catalytic domains homologous to metazoan type I fatty acid synthases (FASs) but feature an iterative type III polyketide synthase (PKS) in place of the expected FAS C-terminal thioesterase used to off load fatty acid products. This new domain arrangement likely facilitates covalent transfer of steely N-terminal acyl products directly to the C-terminal type III PKS active sites, which catalyze both iterative polyketide extension and cyclization. The crystal structure of a steely C-terminal domain confirms conservation of the homodimeric type III PKS fold. These findings suggest new bioengineering strategies for expanding the scope of fatty acid and polyketide biosynthesis.

Acyltransferases↗
PubMed2006

CpG oligodeoxynucleotide prolongs eosinophil survival through activation of contaminating B cells and plasmacytoid dendritic cells in vitro.

BACKGROUND: In our previous study, oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODNs) significantly prolonged eosinophil survival without inducing active release of eosinophil-derived neurotoxin or interleukin 8. In addition, this survival-promoting activity was nuclear factor-kappaB dependent. However, some eosinophil preparations from different donors hardly responded to CpG ODNs at all. To clarify why CpG ODN-induced nuclear factor-kB activation in eosinophils does not cause eosinophil-derived neurotoxin or interleukin 8 release and why the survival-promoting activity of CpG ODNs was not found in some eosinophil preparations, we determined the effect of extensive removal of contaminating B cells and plasmacytoid dendritic cells from human eosinophil preparations. METHODS: Eosinophils were purified from the peripheral blood of healthy or slightly allergic donors by gradient sedimentation and negative selection with anti-CD16 alone or a combination of anti-CD16, anti-CD19 and anti-blood dendritic cell antigen 4 (BDCA4) immunomagnetic beads. Eosinophil survival was measured with FITC-conjugated annexin V and propidium iodide by FACS after incubation with synthetic CpG 2006(CpG-B), CpG 2216 (CpG-A) or their GpC control ODNs for 24 h. RESULTS: The addition of anti-CD19 and anti-BDCA4 immunomagnetic beads reduced the number of contaminating CD19+ cells and CD123+ BDCA2+ cells in eosinophil preparations. CpG 2006 and CpG 2216, but not their GpC control ODNs, significantly prolonged survival of eosinophils purified with anti-CD16 immunomagnetic beads alone but not eosinophils purified with a combination of anti-CD16, anti-CD19 and anti-BDCA4 beads. CONCLUSIONS: These results strongly suggest that contaminating B cells or plasmacytoid dendritic cells in eosinophil preparations critically regulate CpG ODN-mediated prolongation of eosinophil survival and that CpG ODNs do not activate eosinophils directly.

Adjuvants, Immunologic↗
PubMed2006

Changes in growth factor and cytokine expression in biliary obstructed rat liver and their relationship with delayed liver regeneration after partial hepatectomy.

AIM: To study the effects of obstructive jaundice on liver regeneration after partial hepatectomy. METHODS: Hepatocyte growth factor (HGF), its receptor, c-Met, vascular endothelial growth factor (VEGF) and transforming growth factor-beta1 (TGF-beta1) mRNA expression in both liver tissue and isolated liver cells were investigated after biliary obstruction (BO) by quantitative reverse-transcription polymerase chain reaction (RT-PCR) using a LightCycler. Immunohistochemical staining for desmin and alpha-smooth muscle actin (alpha-SMA) was also studied. Regenerating liver weight and proliferating cell nuclear antigen (PCNA) labeling index, and growth factor expression were then evaluated after 70% hepatectomy with concomitant internal biliary drainage in BO rats or sham-operated rats. RESULTS: Hepatic TGF-beta1 mRNA levels increased significantly 14 days after BO, and further increased with duration of cholestasis. Meanwhile, HGF and VEGF tended to increase, but was not significant. In cell isolates, TGF-beta1 mRNA was found mainly in the hepatic stellate cell (HSC) fraction. Immunohistochemical studies revealed an increased number of HSCs (desmin-positive cells) and activated HSCs (alpha-SMA-positive cells) in portal areas after BO. In a hepatectomy model, liver regeneration was delayed in BO rats, as compared to sham-operated rats. TGF-beta1 mRNA was significantly up-regulated up to 48 h after hepatectomy, and the earlier HGF mRNA peak was lost in BO rats. CONCLUSION: BO induces HSCs proliferation and activation, leading to up-regulation of TGF-beta1 mRNA and suppression of HGF mRNA in livers. These altered expression patterns may be strongly involved in delayed liver regeneration after hepatectomy with obstructive jaundice.

Actins↗
PubMed2006

Computer-aided NMR assay for detecting natively folded structural domains.

Structural genomics projects require strategies for rapidly recognizing protein sequences appropriate for routine structure determination. For large proteins, this strategy includes the dissection of proteins into structural domains that form stable native structures. However, protein dissection essentially remains an empirical and often a tedious process. Here, we describe a simple strategy for rapidly identifying structural domains and assessing their structures. This approach combines the computational prediction of sequence regions corresponding to putative domains with an experimental assessment of their structures and stabilities by NMR and biochemical methods. We tested this approach with nine putative domains predicted from a set of 108 Thermus thermophilus HB8 sequences using PASS, a domain prediction program we previously reported. To facilitate the experimental assessment of the domain structures, we developed a generic 6-hour His-tag-based purification protocol, which enables the sample quality evaluation of a putative structural domain in a single day. As a result, we observed that half of the predicted structural domains were indeed natively folded, as judged by their HSQC spectra. Furthermore, two of the natively folded domains were novel, without related sequences classified in the Pfam and SMART databases, which is a significant result with regard to the ability of structural genomics projects to uniformly cover the protein fold space.

Computational Biology↗
PubMed2006

Identification of new differentiation inducing factors from Dictyostelium discoideum.

Developing Dictyostelium discoideum amoebae form a stalked fruiting body in which individual cells differentiate into either stalk cells or spores. The major known inducer of stalk cell differentiation is the chlorinated polyketide DIF-1 (1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)hexan-1-one); however a mutant blocked in the terminal step of DIF-1 biosynthesis still produces one of the prestalk cell subtypes - the pstA cells - as well as some mature stalk cells. We therefore searched for additional stalk cell-inducing factors in the medium supporting development of this mutant. These factors were purified by solvent extraction and HPLC and identified by mass spectroscopy and NMR. The mutant lacked detectable DIF-2 and DIF-3 (the pentanone and deschloro homologues of DIF-1) but four major stalk cell-inducing activities were detected, of which three were identified. Two compounds were predicted intermediates in DIF-1 biosynthesis: the desmethyl, and desmethyl-monochloro analogues of DIF-1 (dM-DIF-1 and Cl-THPH, respectively), supporting the previously proposed pathway of DIF-1 biosynthesis. The third compound was a novel factor and was identified as 4-methyl-5-pentylbenzene-1,3-diol (MPBD) with the structure confirmed by chemical synthesis. To investigate the potential roles of these compounds as signal molecules, their effects on morphological stalk and spore differentiation were examined in cell culture. All three induced morphological stalk cell differentiation. We found that synthetic MPBD also stimulated spore cell differentiation. Now that these factors are known to be produced and released during development, their biological roles can be pursued further.

Animals↗
PubMed2006

Circulating cytokines, chemokines, and stress hormones are increased in patients with organ dysfunction following liver resection.

BACKGROUND: Humoral mediators are potentially involved in the pathogenesis of postoperative complications following surgery. The aim of the present study is to evaluate the postoperative responses of circulating cytokines, chemokines, and stress hormones following liver resection, and their effects on postoperative infectious complications and organ dysfunction. PATIENTS AND METHODS: Perioperative plasma concentrations of interleukin (IL)-6, IL-10, IL-4, IL-8, macrophage chemoattractant protein (MCP)-1, cortisol, macrophage migration inhibitory factor (MIF), and leptin were measured by immunoassays in 128 consecutive patients undergoing liver resection. RESULTS: Forty-three patients had postoperative infection and 11 had infection-related organ dysfunction. Plasma levels of all mediators except for IL-4 increased postoperatively. Postoperative levels of IL-6, IL-10, IL-8, MCP-1, cortisol, and leptin were significantly higher in patients with organ dysfunction than in those without organ dysfunction (P < 0.05). However, postoperative MIF levels were not affected by postoperative infection or organ dysfunction. Plasma levels of IL-6, IL-10, IL-8, and MCP-1 were positively correlated with operation time (P < 0.0001) or blood loss (P < 0.0001), and higher in patients with jaundiced liver (P < 0.05). In univariate logistic regression analyses, elevated IL-6, IL-10, IL-8, and MCP-1, advanced age, large volume of blood loss, long operation time, long hepatic ischemia time, and major liver resection were significantly correlated with postoperative infection (P < 0.05). In multivariate analyses, IL-6 and IL-10 were significant predisposing factors for postoperative infection (P < 0.05), and blood loss and IL-6 for organ dysfunction (P < 0.01). CONCLUSIONS: These results suggest that IL-6, IL-10, IL-8, MCP-1, cortisol, and leptin are released after liver resection in response to surgical stress and correlated with postoperative infection and organ dysfunction, and that of these circulating mediators, IL-6 and IL-10, have a close relationship to the complications.

Adult↗
PubMed2006

Novel mucosal insulin delivery systems based on fusogenic liposomes.

PURPOSE: Fusogenic liposomes (FLs) are unique delivery vehicles capable of introducing their contents directly into the cytoplasm with the aid of envelope glycoproteins of Sendai virus (SeV). The objective of this study was to evaluate the potential of FL to improve the mucosal absorption of insulin from rat intestinal membranes. METHOD: The FLs containing insulin were prepared by fusing insulin-loaded liposomes with inactivated SeV particles and were administered directly into the ileal, the colonic, and the rectal loops (10 IU/kg). RESULTS: The FL successfully enhanced the insulin absorption and induced a significant hypoglycemic effect following the colonic and the rectal administration without detectable mucosal damage. This enhancing effect of insulin absorption was further improved by increasing the amount of insulin loaded in the FL and by coencapsulating insulin-degrading enzyme inhibitor. In contrast, the insulin absorption was not increased by the ileal administration of FL because the mucous/glycocalyx layers overlaid on the ileal epithelium impede the fusion of FL to the intestinal mucosa. CONCLUSION: Our results indicated that FL is a useful carrier for improving the absorption of poorly absorbable drugs, such as insulin, via the intestinal tract.

Animals↗
PubMed2006

Increased plasma levels of IL-6 and IL-8 are associated with surgical site infection after pancreaticoduodenectomy.

OBJECTIVES: Cytokines and chemokines potentially modulate postoperative immune response. Association of circulating cytokines and chemokines with postoperative infectious complications after pancreaticoduodenectomy was evaluated. METHODS: Plasma concentrations of interleukin (IL) 6, IL-10, IL-8, macrophage chemoattractant protein 1, heat shock protein 70, and amylase, as well as amylase levels in peritoneal exudative fluid, were measured perioperatively in 60 consecutive patients who underwent pancreaticoduodenectomy. RESULTS: Of the 60 patients, 27 patients had surgical site infection (SSI), including peritoneal infection in all, intra-abdominal abscess in 14, and radiologically visualized pancreatic leakage in 6. Postoperative plasma levels of IL-6, IL-8, and macrophage chemoattractant protein 1, as well as peritoneal amylase levels, were significantly higher in patients with SSI than in those without SSI (P < 0.05). Nonpancreatic cancer as a histopathologic diagnosis, high pancreatic juice flow, and increased levels of IL-6 and IL-8 were independently associated with SSI (P < 0.05) in multiple logistic regression analysis. Plasma levels of IL-6 and IL-10 among patients with SSI were significantly higher in those with pancreatic leakage than in those without leakage. CONCLUSIONS: These results suggest that, in addition to pancreatic exocrine function, IL-6 and IL-8 are associated with postoperative SSI, including pancreatic leakage after pancreaticoduodenectomy.

Adult↗
PubMed2006

Sendai virus-mediated gene delivery into hepatocytes via isolated hepatic perfusion.

The recombinant Sendai virus vector is a promising tool for human gene therapy, capable of inducing high-level expression of therapeutic genes in tissue cells in situ. The target tissues include airway epithelium, blood vessels, skeletal muscle, retina and the central nervous system, but application to hepatic tissues has not yet been achieved, because direct intraportal injection of the vector is not feasible. We report an efficient and harmless procedure of gene delivery by recombinant Sendai virus into rat parenchymal hepatocytes, based on isolated hepatic perfusion with controlled inflow. Critical parameters for successful hepatic gene delivery are a brief preperfusion period (25 degrees C, 5 min); appropriate vector concentration in the perfusate (10(7) pfu/ml); moderate portal vein pressure (12 mmHg) and a brief hyperthermic postperfusion period (42 degrees C, 5 min). Under these optimized conditions, marker genes were expressed in most parenchymal hepatocytes without significant damage to hepatic tissues. Furthermore, expression of the marker genes was undetectable in nonhepatic tissues, including the gonads, indicating that this approach strictly targets hepatic tissues and thus offers good clinical potential for human gene therapy.

Animals↗
PubMed2006

[The anti-tumoral effect of PI3K inhibitor and MEK inhibitor combined with STI571 on chronic myeloid leukemia cells in a bone marrow stromal cell co-culture system].

The goal of this study was to elucidate the functional roles of PI3K/AKT and MEK/ERK signaling on the proliferation and apoptosis of STI571-sensitive and -resistant CML cell lines in a co-culture system with human marrow stromal cells (MSCs), mimicking the bone marrow microenvironment. The phosphorylation of AKT and ERK was enhanced by co-culture with MSCs in both STI571-sensitive KBM-5 and STI571-resistant KBM-5/STI cells. In KBM-5 cells, the STI571 and PI3K inhibitor LY294002 combination was effective on apoptosis induction in the MSC co-culture system. In KBM-5/STI cells, treatment with LY294002 or PD98059 alone resulted in massive apoptosis, which was enhanced by co-culture with MSCs. These results provide a rationale for multi-molecular target therapy approaches based on a combination of signal transduction inhibitors with STI571 in CML.

Antineoplastic Agents↗