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Biomedical subjects

Nobuo Seki

Publications and source records attributed to Nobuo Seki.

14 recordsLinked to original sources
PubMed2006

Hyperresponsive TH2 cells with enhanced nuclear factor-kappa B activation induce atopic dermatitis-like skin lesions in Nishiki-nezumi Cinnamon/Nagoya mice.

BACKGROUND: Nishiki-nezumi Cinnamon/Nagoya (NC/Nga) mice raised in nonair-controlled conventional circumstances spontaneously develop atopic dermatitis-like skin lesions; however, the underlying mechanisms remain unclear. OBJECTIVE: We wanted to identify the critical intracellular signaling molecules in T cells that induce atopic dermatitis-like skin legions in NC/Nga mice. METHODS: We examined the levels of signal transduction and cytokine production in T cells, particularly those in atopic dermatitis-like lesions induced by the topical injection of mite antigens in NC/Nga mice under specific pathogen-free conditions. RESULTS: In NC/Nga mice maintained under specific pathogen-free conditions, the capability of T(H)1/T(H)2 and T cytotoxic 1/T cytotoxic 2 (Tc1/Tc2) cell differentiation increased significantly. T-cell antigen receptor-mediated activation of the extracellular signal-regulated kinase/mitogen-activated protein kinase cascade and nuclear factor-kappaB (NF-kappaB) signaling were enhanced in NC/Nga T cells. The expression of T(H)2 cytokines (IL-4, IL-13, and IL-5) and that of GATA-binding protein 3 (GATA3), avian musculoaponeurotic fibrosarcoma (c-Maf), NF-kappaB, and activator protein 1 (AP1) selectively increased in draining lymph node T cells of NC/Nga mice. Moreover, the cell transfer of inhibitory NF-kappaB mutant-infected T(H)2 cells reduced ear thickness in the mite antigen-induced skin lesion of NC/Nga mice. CONCLUSION: Hyperresponsive T(H)2 cells with an enhanced activity of NF-kappaB and AP1 play a crucial role in the pathogenesis of atopic dermatitis-like skin lesions in NC/Nga mice. CLINICAL IMPLICATIONS: These results indicate potential therapeutic usefulness of developing selective inhibitors for NF-kappaB in the treatment of human atopic dermatitis.

Animals↗
PubMed2006

Anti-inflammatory activity of non-nucleoside adenosine deaminase inhibitor FR234938.

Adenosine has anti-inflammatory activity. Adenosine deaminase (EC 3.5.4.4) metabolizes extracellular adenosine, resulting in an exacerbation of inflammation. Consequently, it was hypothesized that adenosine deaminase inhibitors produce anti-inflammatory activity by increasing extracellular adenosine concentration. This group recently developed a non-nucleoside adenosine deaminase inhibitor, FR234938, by using rational structure-based drug design. FR234938 inhibits recombinant human adenosine deaminase enzyme competitively. FR234938 inhibits interleukin (IL)-6-dependent immunoglobulin (Ig) M production by SKW6.4 cells, in the presence of adenosine. Inhibitory effect of FR234938/adenosine combination is blocked by an A2a adenosine receptor antagonist. FR234938 also inhibits anti-type II collagen delayed type hypersensitivity (DTH) in a dose-dependent manner, both in the presence and absence of recombinant human adenosine deaminase. Moreover, FR234938 inhibits tumor necrosis factor (TNF)-alpha and IL-10 production in a lipopolysaccharide (LPS)-induced cytokine production model in mice. These results indicate that FR234938 has potential anti-inflammatory activity. Non-nucleoside adenosine deaminase inhibitor FR234938 has good potential as a new type of anti-rheumatic and anti-inflammatory drug, by modulating host-defense concentrations of adenosine.

Adenosine↗
PubMed2005

Structural basis of compound recognition by adenosine deaminase.

Structural snapshots corresponding to various states enable elucidation of the molecular recognition mechanism of enzymes. Adenosine deaminase has two distinct conformations, an open form and a closed form, although it has so far been unclear what factors influence adaptation of the alternative conformations. Herein, we have determined the first nonligated structure as an initial state, which was the open form, and have thereby rationally deduced the molecular recognition mechanism. Inspection of the active site in the nonligated and ligated states indicated that occupancy at one of the water-binding positions in the nonligated state was highly significant in determining alternate conformations. When this position is empty, subsequent movement of Phe65 toward the space induces the closed form. On the other hand, while occupied, the overall conformation remains in the open form. This structural understanding should greatly assist structure-oriented drug design and enable control of the enzymatic activity.

Adenosine Deaminase↗
PubMed2005

Characterization of a transglutaminase from scallop hemocyte and identification of its intracellular substrates.

Scallop hemocytes contain a transglutaminase (TGase) that is electrophoretically different from the TGase in the adductor muscle. The optimum temperature of the hemocyte TGase was lower (about 15 degrees C), compared with the muscle TGase (35-40 degrees C). Other properties, such as the high sodium chloride (NaCl) and CaCl2 concentrations required for activation, instability in salt solutions, and the Km values against monodansylcadaverine (MDC) and succinylated casein, were similar for both enzymes. When hemocyte homogenate was incubated with MDC at 10 degrees C, MDC was incorporated into the 230 k and 100 k proteins of the hemocytes. The 100 k protein was only detected in the supernatant, the 230 k protein was insoluble, and the 210 k protein was detected in both fractions. In the absence of MDC, the 230 k, 210 k, and 100 k proteins were cross-linked by endogenous transglutaminase. The 230 k protein was most quickly cross-linked and formed huge polymers within 5 min. These results suggest that if scallop tissues are injured, hemocyte transglutaminase may be activated, initially cross-linking the insoluble hemocyte 230 k protein, followed by the 210 k and 100 k proteins, to form a cross-linked protein matrix with inter cross-linking of hemocyte sheets, to stop the bleeding.

Animals↗
PubMed2004

Structure-based design, synthesis, and structure-activity relationship studies of novel non-nucleoside adenosine deaminase inhibitors.

We disclose herein optimization efforts around the novel, highly potent non-nucleoside adenosine deaminase (ADA) inhibitor, 1-[(R)-1-hydroxy-4-(6-(3-(1-methylbenzimidazol-2-yl)propionylamino)indol-1-yl)-2-butyl]imidazole-4-carboxamide 1 (K(i)= 7.7 nM), which we recently reported. Structure-based drug design (SBDD) utilizing the crystal structure of the 1/ADA complex was performed in order to obtain structure-activity relationships (SAR) for this type of compound rationally and effectively. To utilize the newly formed hydrophobic space (F2), replacement of the benzimidazole ring of 1 with a n-propyl chain (4b) or a simple phenyl ring (4c) was tolerated in terms of binding activity, and the length of the methylene-spacer was shown to be optimal at two or three. Replacement of an amide with an ether as a linker was also well tolerated in terms of binding activity and moreover improved the oral absorption (6a and 6b). Finally, transformation of indol-1-yl to indol-3-yl resulted in discovery of a novel highly potent and orally bioavailable ADA inhibitor, 1-[(R)-4-(5-(3-(4-chlorophenyl)propoxy)-1-methylindol-3-yl)-1-hydroxy-2-butyl]imidazole-4-carboxamide 8c.

Adenosine Deaminase↗
PubMed2004

Structure-based design and synthesis of non-nucleoside, potent, and orally bioavailable adenosine deaminase inhibitors.

We disclose optimization efforts based on the novel non-nucleoside adenosine deaminase (ADA) inhibitor, 4 (K(i) = 680 nM). Structure-based drug design utilizing the crystal structure of the 4/ADA complex led to discovery of 5 (K(i) = 11 nM, BA = 30% in rats). Furthermore, from metabolic considerations, we discovered two inhibitors with improved oral bioavailability [6 (K(i) = 13 nM, BA = 44%) and 7 (K(i) = 9.8 nM, BA = 42%)]. 6 demonstrated in vivo efficacy in models of inflammation and lymphoma.

Adenosine Deaminase Inhibitors↗
PubMed2004

Transformation of lactulose trihydrate into anhydrous lactulose by fluidized bed drying and its characterization.

Stable anhydrous lactulose was produced from lactulose trihydrate by stepwise heating on a fluidized bed. The processes were performed on stable powder forms. The anhydrous lactulose was characterized by an opaque white appearance, a coarse surface structure with random cracks and indentations, a high degree of crystallization, stability under humid conditions, and by X-ray powder diffraction, differential thermal analysis, and differential thermogravimetry. Those characteristics were different from those of the original trihydrate, which was transparent, had a smooth surface and a higher degree of crystallization, was stable under humid conditions and had different X-ray powder diffraction, differential thermal analysis, and thermogravimetric characteristics. The transformation was enhanced when the inlet temperature was 45-55 degrees C or when the temperature of the fluidized bed was over 40 degrees C. At these cutoff temperatures, both crystalline forms were observed.

Crystallization↗
PubMed2004

CD28 costimulation controls histone hyperacetylation of the interleukin 5 gene locus in developing th2 cells.

Interleukin 5 (IL-5) plays a unique role in allergic inflammatory responses, and the understanding of molecular mechanisms underlying the generation of IL-5-producing cells is crucial for the regulation of allergic disorders. Differentiation of naive CD4 T cells into type-2 helper (Th2) cells is accompanied by chromatin remodeling including hyperacetylation of histones H3 and H4 in the nucleosomes associated with the IL-4, IL-13, and IL-5 genes. Histone hyperacetylation of the IL-5 gene displayed a delayed kinetics compared with that of the IL-4 and IL-13 genes, suggesting a distinct remodeling mechanism for the IL-5-gene locus. Here we studied the role of CD28 costimulation in the generation of IL-5-producing cells and the histone hyperacetylation of the IL-5 gene locus. CD28-costimulation selectively enhanced histone hyperacetylation of the IL-5 gene locus that appeared to be mediated through NF-kappaB activation and subsequent up-regulation of GATA3. The CD28 costimulation-sensitive histone hyperacetylation spanned almost the entire intergenic region between the IL-5 and RAD50 accompanied with intergenic transcript. Thus, this is the first demonstration that CD28 costimulation controls a chromatin-remodeling process during Th2 cell differentiation.

Acetylation↗
PubMed2003

Aspolin, a novel extremely aspartic acid-rich protein in fish muscle, promotes iron-mediated demethylation of trimethylamine-N-oxide.

Trimethylamine-N-oxide (TMAO) is abundant in marine fish. Formaldehyde synthesis by TMAO demethylation during storage markedly deteriorates fish meat. In the present work, we cloned the extremely aspartic acid-rich proteins from skeletal muscle of a commercially important species, walleye pollack, in the course of molecular identification of trimethylamine-N-oxide demethylase (TMAOase). One of the cDNAs, designated as aspolin1, encodes an extremely aspartic acid-rich protein of 228 amino acids which is converted to the TMAOase after processing between Ala42 and Asp43. Mature aspolin1/TMAOase protein contains 179 Asp in 186 total amino acids. The other cDNA, designated as aspolin2, has a common nucleotide sequence with aspolin1 in the 5' part and encodes a protein which has an additional Asp polymer and a C-terminal cysteine-rich region. The amino acid sequence of the C-terminal cysteine-rich region of aspolin2 is highly homologous to the mammalian histidine-rich Ca2+-binding protein. Aspolin1/TMAOase and aspolin2 mRNA was most abundant in the skeletal muscle. A lower level of the mRNA was also detected in kidney, heart, spleen, and brain. Synthetic Asp polymer showed marked TMAOase activity in the presence of Fe2+, whereas a monomer and oligomers did not. Purified TMAOase protein bound to Fe2+ with low affinity, which may be responsible for the catalytic activity. Poly aspartic acid-Fe2+ complex generated after death would be involved in formaldehyde synthesis by the demethylation of TMAO during the storage of fish meat.

Aldehyde-Lyases↗
PubMed2003

Structure-based de novo design of non-nucleoside adenosine deaminase inhibitors.

We searched for non-nucleoside inhibitors of adenosine deaminase by rational structure-based de novo design and succeeded in the discovery of 1-(1-hydroxy-4-phenyl-2-butyl)imidazole-4-carboxamide (FR221647: K(i)=5.9 microM to human ADA) as a novel inhibitor with moderate activity and good pharmacokinetics compared with the known inhibitors pentostatin and EHNA.

Adenine↗
PubMed2003

Essential role of the cryptic epitope SLAYGLR within osteopontin in a murine model of rheumatoid arthritis.

It has been shown that osteopontin (OPN) plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). However, the molecular mechanism of OPN action is yet to be elucidated. Splenic monocytes obtained from arthritic mice exhibited a significant capacity for cell migration toward thrombin-cleaved OPN but not toward full-length OPN. Migratory monocytes expressed alpha9 and alpha4 integrins. Since cleavage of OPN by thrombin exposes the cryptic epitope recognized by alpha9 and alpha4 integrins, we investigated the role of the cryptic epitope SLAYGLR in a murine RA model by using a specific antibody (M5) reacting to SLAYGLR sequence. The M5 antibody could abrogate monocyte migration toward the thrombin-cleaved form of OPN. Importantly, M5 antibody could inhibit the proliferation of synovium, bone erosion, and inflammatory cell infiltration in arthritic joints. Thus, we demonstrated that a cryptic epitope, the SLAYGLR sequence of murine OPN, is critically involved in the pathogenesis of a murine model of RA.

Animals↗
PubMed2003

FR252921, a novel immunosuppressive agent isolated from Pseudomonas fluorescens no. 408813 II. In vitro property and mode of action.

A novel immunosuppressive agent, FR252921 was isolated from the cultured broth of a species of Pseudomonas fluorescens. We have shown that FR252921 inhibited splenic proliferation stimulated with LPS, insensitive to calcinuerin inhibitor. In this study, FR252921 was found to inhibit IL-2 and IL-12 production as well as proliferaion of splenocyte. Analysis of transcription activity revealed that FR252921 inhibited activating protein-1 (AP-1). Exposures of antigen presenting cells (APC) to FR252921 attenuated proliferation supplemented by naïve T cells. Further, FR252921 strongly suppressed splenic dendritic cell proliferation stimulated with LPS and anti-CD40 mAb, while it did not inhibit purified T cell activation, including CD154 expression and IL-2 production. These results suggest that APC is dominant target cell population.

Animals↗
PubMed2002

Quinoline-3-carbothioamides and related compounds as novel immunomodulating agents.

A series of quinoline-3-carbothioamides and their analogues was prepared via four synthetic routes and evaluated for their antinephritic and immunomodulating activities. The optimal compound 9g strongly inhibited the T-cell independent antibody production in mice immunized with TNP-LPS and was highly effective in two nephritis models, namely chronic graft-versus-host disease and autoimmune MRL/l mice.

Adjuvants, Immunologic↗