Biomedical subjects

Hiroyuki Mizuguchi

Publications and source records attributed to Hiroyuki Mizuguchi.

At least 19 recordsLinked to original sources

PubMed2026

Evaluation of transduction properties and vaccine efficacy of a simian adenovirus type 25-based vector.

Although human adenovirus serotype 5 (Ad5) is widely used as a vaccine vector for infectious diseases due to its high transduction efficiency, pre-existing immunity to Ad5 in many people reduces vaccine efficacy. To address this limitation, simian Ad vectors, such as ChAdOx1 and ChAdOx2, have been explored as alternative vaccine platforms. ChAdOx2 is based on simian Ad25 (SAd25), but the fundamental characteristics of gene transduction by SAd25-based vectors have not been fully elucidated. This study aimed to characterize the gene transduction efficiency, tissue distribution, and immunogenicity of an SAd25-based vector in comparison with those of the Ad5 vector following various routes of administration. Compared with intravenous administration of the Ad5 vector, intravenous administration of the SAd25 vector showed distinct biodistribution patterns, including reduced liver accumulation and predominant expression in the lung. Transduction by the SAd25 vector was not inhibited by human serum, whereas transduction by the Ad5 vector was inhibited, indicating that the SAd25 vector, but not the Ad5 vector, can evade pre-existing Ad immunity. Although intramuscular administration of the SAd25 vector induced lower transgene product-specific antibody production than intramuscular administration of the Ad5 vector, gene expression and Ad genome distribution mediated by the SAd25 vector, but not the Ad5 vector, were localized only to the muscle at the administration site. Intranasal administration of the SAd25 vector induced an antigen-specific antibody response in serum more rapidly than intranasal administration of the Ad5 vector. The SAd25 vector induced antigen-specific antibody production in bronchoalveolar lavage fluid (BALF) that was comparable to that induced by the Ad5 vector. These findings provide essential insights into the biological characteristics of the SAd25 vector, supporting its potential as a safe and effective vaccine vector.

Animals↗

PubMed2005

Immunological properties and vaccine efficacy of murine dendritic cells simultaneously expressing melanoma-associated antigen and interleukin-12.

Interleukin (IL)-12 is a key factor for inducing cellular immune responses, which play a central role in the eradication of cancer. In the present study, in order to create a dendritic cell (DC)-based vaccine capable of positively skewing immune response toward a cellular immunity-dominant state, we analyzed immunological characteristics and vaccine efficacy of DCs cotransduced with melanoma-associated antigen (gp100) and IL-12 gene (gp100+IL12/DCs) by using RGD fiber-mutant adenovirus vector (AdRGD), which enables highly efficient gene transduction into DCs. gp100+IL12/DCs could simultaneously express cytoplasmic gp100 and secretory IL-12 at levels comparable to DCs transduced with each gene alone. In comparison with DCs transduced with gp100 alone (gp100/DCs), upregulation of major histocompatibility complex class I, CD40, and CD86 molecules on the cell surface and more potent T-cell-stimulating ability for proliferation and interferon-gamma secretion were observed as characteristic changes in gp100+IL12/DCs. In addition, administration of gp100+IL12/DCs, which were prepared by a relatively low dose of AdRGD-IL12, could induce more potent tumor-specific cellular immunity in the murine B16BL6 melanoma model than vaccination with gp100/DCs. However, antitumor effect and B16BL6-specific cytotoxic T-lymphocyte activity in mice vaccinated with gp100+IL12/DCs diminished with increasing AdRGD-IL12 dose during gene transduction, and paralleled the decrease in presentation levels via MHC class I molecules for antigen transduced with another AdRGD. Collectively, our results suggested that optimization of combined vector dose was required for development of a more efficacious DC-based vaccine for cancer immunotherapy, which relied on genetic engineering to simultaneously express tumor-associated antigen and IL-12.

Adenoviridae↗

PubMed2004

Simultaneous imaging of initiator/effector caspase activity and mitochondrial membrane potential during cell death in living HeLa cells.

A family of cystein proteases, the caspases, plays a central role in mediating cell death. In this study, we measured the activation of the initiator and effector caspase in real time, and studied the relationship between caspase activity and mitochondrial membrane potential in living cells by means of bioimaging. We also designed and developed a fluorescence resonance energy transfer (FRET)-based genetically encoded fluorescent indicator, which consisted of yellow fluorescent protein (YFP), a peptide sequence which can be cleaved by specific caspases, and cyan fluorescent protein (CFP). Two peptide sequences which could be cleaved by initiator caspases and effector caspases, respectively, were used. Simultaneous real-time measurements of the caspase activity and mitochondrial membrane potential in the cells treated with TNF-alpha and staurosporine revealed that dying cells showed caspase activation and mitochondrial depolarization, and that these events, however, were not firmly linked. Although it takes anywhere from 1 to over 10 h after the addition of the cell death inducer for the caspases to begin to be activated, initiator caspases and effector caspases are activated within a short period of time at the last stage in the entire process leading to cell death.

Amino Acid Sequence↗

PubMed2004

Anti-tumor activity of chemokine is affected by both kinds of tumors and the activation state of the host's immune system: implications for chemokine-based cancer immunotherapy.

In this study, we screened the anti-tumor activity of murine chemokines including CCL17, CCL19, CCL20, CCL21, CCL22, CCL27, XCL1, and CX3CL1 by inoculating murine B16BL6, CT26, or OV-HM tumor cells, all of which were transfected with chemokine-expressing fiber-mutant adenovirus vector, into immunocompetent mice. A tumor-suppressive effect was observed in mice inoculated with CCL19/B16BL6 and XCL1/B16BL6, and CCL22/OV-HM showed considerable retardation in tumor growth. In the cured mice inoculated with CCL22/OV-HM, a long-term specific immune protection against parental tumor was developed. However, we were unable to identify the chemokine that had a suppressive activity common to all three tumor models. Furthermore, an experiment using chemokine-transfected B16BL6 cells was also performed on mice sensitized with melanoma-associated antigen. A drastic enhancement of the frequency of complete rejection was observed in mice inoculated with CCL17-, CCL19-, CCL22-, and CCL27-transfected B16BL6. Altogether, our results suggest that the tumor-suppressive activity of chemokine-gene immunotherapy is greatly influenced by the kind of tumor and the activation state of the host's immune system.

Adenoviridae↗

PubMed2004

RNA interfering approach for clarifying the PPARgamma pathway using lentiviral vector expressing short hairpin RNA.

Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a central role in adipocyte differentiation and insulin sensitivity. Although PPARgamma also appears to regulate diverse cellular processes in other cell types such as lymphocytes, the detailed mechanisms remain unclear. In this study, we established a lentivirus-mediated short hairpin RNA expression system and identified a potent short hairpin RNA which suppresses PPARgamma expression, resulting in marked inhibition of preadipocyte-to-adipocyte differentiation in 3T3-L1 cells. Our PPARgamma-knockdown method will serve to clarify the PPARgamma pathway in various cell types in vivo and in vitro, and will facilitate the development of therapeutic applications for a variety of diseases.

3T3-L1 Cells↗

PubMed2004

Optimization of antitumor efficacy and safety of in vivo cytokine gene therapy using RGD fiber-mutant adenovirus vector for preexisting murine melanoma.

We previously reported that RGD fiber-mutant adenovirus vector (AdRGD) was a very useful vector system for in vivo cytokine gene therapy for established murine B16BL6 melanoma. However, intratumoral administration of AdRGD expressing tumor necrosis factor alpha (AdRGD-TNFalpha) at high dose revealed not only the dramatic reinforcement of anti-tumor effect but also serious adverse effects, such as body weight reduction and sudden death, caused by high-level TNF-alpha leakage from the tumor into circulation. These results strongly suggested that the determination of 'limiting dose', which demonstrated therapeutic effectiveness without adverse effect, against each vector was important for the development of appropriate cytokine gene therapy. In the present study, we investigated the efficacy and the safety of AdRGD expressing interleukin-12 (AdRGD-IL12) in murine melanoma model, and determined its limiting dose. Moreover, we demonstrated that combination therapy using AdRGD-IL12 and AdRGD-TNFalpha at limiting doses or less could achieve more effective tumor regression without adverse effects. Therefore, we conclude that a combination of multiple AdRGD expressing cytokines having distinct anti-tumor mechanisms can contribute to the establishment of in vivo cytokine gene therapy for melanoma, which possesses both excellent efficacy and high safety.

Adenoviridae↗

PubMed2004

Antibody-targeted cell fusion.

Membrane fusion has many potential applications in biotechnology. Here we show that antibody-targeted cell fusion can be achieved by engineering a fusogenic viral membrane glycoprotein complex. Three different single-chain antibodies were displayed at the extracellular C terminus of the measles hemagglutinin (H) protein, and combinations of point mutations were introduced to ablate its ability to trigger fusion through the native viral receptors CD46 and SLAM. When coexpressed with the measles fusion (F) protein, using plasmid cotransfection or bicistronic adenoviral vectors, the retargeted H proteins could mediate antibody-targeted cell fusion of receptor-negative or receptor-positive index cells with receptor-positive target cells. Adenoviral expression vectors mediating human epidermal growth factor receptor (EGFR)-targeted cell fusion were potently cytotoxic against EGFR-positive tumor cell lines and showed superior antitumor potency against EGFR-positive tumor xenografts as compared with control adenoviruses expressing native (untargeted) or CD38-targeted H proteins.

Animals↗

PubMed2004

Crystal structures of glutamine:phenylpyruvate aminotransferase from Thermus thermophilus HB8: induced fit and substrate recognition.

The following three-dimensional structures of three forms of glutamine:phenylpyruvate aminotransferase from Thermus thermophilus HB8 have been determined and represent the first x-ray analysis of the enzyme: the unliganded pyridoxal 5'-phosphate form at 1.9 A resolution and two complexes with 3-phenylpropionate and alpha-keto-gamma-methylthiobutyrate at 2.35 and 2.6 A resolution, respectively. The enzyme shows high activity toward phenylalanine, tyrosine, tryptophan, kynurenine, methionine, and glutamine. The enzyme is a homodimer, and each subunit is divided into an N-terminal arm and small and large domains. Based on its folding, the enzyme belongs to fold type I, aminotransferase subclass Ib. The subclass I aminotransferases whose structures have so far been determined exhibit a large movement of the small domain region upon binding of a substrate. Similarly, the glutamine:phenylpyruvate aminotransferase undergoes a large movement in part of the small domain to close the active site. The active-site pocket has a shape and size suitable to enclose the side chain of an aromatic amino acid or that of methionine. The inner side of the pocket is mostly hydrophobic, but also has polar sites. The kynurenine complex generated by computer modeling fits the pocket of the enzyme and its hydrophilic groups interact with the polar sites of the pocket.

Protein Conformation↗

PubMed2004

Adenovirus vector-mediated doxycycline-inducible RNA interference.

RNA interference (RNAi) is a powerful tool for the knockdown of gene expression. Here, we report on the development of an adenovirus (Ad) vector-mediated doxycycline (Dox)-inducible small interfering RNA (siRNA) expression system. We used this siRNA system to control the expression of p53 and c-Myc in human cancer cells. Coinfection of Ad vectors containing the siRNA expression system under the control of the Dox-inducible H1 promoter and Ad vectors expressing a tetracycline repressor inhibited the expression levels of p53 and c-Myc in a dose-dependent manner with both Dox and viral dose. Regulated silencing of p53 and c-Myc expression was obtained. Because an Ad vector-mediated inducible RNAi system can efficiently transduce a variety of cell types in vitro and in vivo, and the degree of loss of gene expression can be modulated according to the dose of Dox, this expression system should be a useful tool for both basic research on the analysis of gene function and therapeutic applications of RNAi.

Adenoviridae↗

PubMed2004

Neutralizing antibody evasion ability of adenovirus vector induced by the bioconjugation of methoxypolyethylene glycol succinimidyl propionate (MPEG-SPA).

Although adenovirus vectors (Ad) which possesses high transduction efficiency are widely used for gene therapy in animal models, clinical use is very limited. One of the main reason is that nearly 80% of human beings possess anti-Ad antibodies. In this study, we tried to modify Ad with methoxypolyethylene glycol (MPEG) activated by succinimidyl propionate, and, the neutralizing antibody evasion ability of PEGylated Ad was evaluated. The results demonstrated that PEG-Ad showed stronger protection ability against anti-Ad neutralizing antibody compared to that with unmodified-Ad. Considering there are many people carrying neutralizing antibody against Ad and readministration of Ad was necessary for treating chronic diseases, this strategy, which was also applicable to other vectors, can be used for developing improved vectors.

Adenoviruses, Human↗

PubMed2003

Overexpression of constitutively activated glutamate dehydrogenase induces insulin secretion through enhanced glutamate oxidation.

Glutamate dehydrogenase (GDH) catalyzes reversible oxidative deamination of l-glutamate to alpha-ketoglutarate. Enzyme activity is regulated by several allosteric effectors. Recognition of a new form of hyperinsulinemic hypoglycemia, hyperinsulinism/hyperammonemia (HI/HA) syndrome, which is caused by gain-of-function mutations in GDH, highlighted the importance of GDH in glucose homeostasis. GDH266C is a constitutively activated mutant enzyme we identified in a patient with HI/HA syndrome. By overexpressing GDH266C in MIN6 mouse insulinoma cells, we previously demonstrated unregulated elevation of GDH activity to render the cells responsive to glutamine in insulin secretion. Interestingly, at low glucose concentrations, basal insulin secretion was exaggerated in such cells. Herein, to clarify the role of GDH in the regulation of insulin secretion, we studied cellular glutamate metabolism using MIN6 cells overexpressing GDH266C (MIN6-GDH266C). Glutamine-stimulated insulin secretion was associated with increased glutamine oxidation and decreased intracellular glutamate content. Similarly, at 5 mmol/l glucose without glutamine, glutamine oxidation also increased, and glutamate content decreased with exaggerated insulin secretion. Glucose oxidation was not altered. Insulin secretion profiles from GDH266C-overexpressing isolated rat pancreatic islets were similar to those from MIN6-GDH266C, suggesting observation in MIN6 cells to be relevant in native beta-cells. These results demonstrate that, upon activation, GDH oxidizes glutamate to alpha-ketoglutarate, thereby stimulating insulin secretion by providing the TCA cycle with a substrate. No evidence was obtained supporting the hypothesis that activated GDH produced glutamate, a recently proposed second messenger of insulin secretion, by the reverse reaction, to stimulate insulin secretion.

Animals↗

PubMed2003

Crystal structures of threonine synthase from Thermus thermophilus HB8: conformational change, substrate recognition, and mechanism.

Threonine synthase, which is a PLP-dependent enzyme, catalyzes the beta,gamma-replacement reaction of l-homoserine phosphate to yield threonine and inorganic phosphate. The three-dimensional structures of the enzyme from Thermus thermophilus HB8 in its unliganded form and complexed with the substrate analogue 2-amino-5-phosphonopentanoic acid have been determined at 2.15 and 2.0 A resolution, respectively. The complexed form, assigned as an enamine, uncovered the interactions of the cofactor-analogue conjugate with the active site residues. The binding of the substrate analogue induces a large conformational change at the domain level. The small domain rotates by about 25 degrees and approaches the large domain to close the active site. The complicated catalytic process of the enzyme has been elucidated based on the complex structure to reveal the stereochemistry of the reaction and to present the released inorganic phosphate as a possible catalyst to carry a proton to the Cgamma atom of the substrate.

Binding Sites↗

PubMed2003

Tight positive regulation of transgene expression by a single adenovirus vector containing the rtTA and tTS expression cassettes in separate genome regions.

We previously developed single adenovirus (Ad) vectors that contained the components for a tetracycline-regulatable gene-expression system in the E1 and E3 deletion regions, and showed that the Ad vectors containing the tet-on system exhibit a much inferior regulation of transgene expression than those containing the tet-off system. In many cases, the tet-on system may be preferable because of its positive regulation of transgene expression. To this end, in the present study, by introducing the latest generation reverse tetracycline-responsive transcriptional activator (rtTA2s-M2 or rtTA2s-S2) and the tetracycline-controlled transcriptional silencer (tTS) into the original tet-on system, we constructed various modified Ad-mediated tet-on systems. Among them, the novel single Ad vector, which contained three heterologous gene-expression cassettes of the gene of interest, rtTA2s-S2, and tTS in the E1 deletion region, the E3 deletion region, and the region between E4 and 3'ITR, respectively, displayed vastly improved doxycycline-inducible gene expression in terms of low basal expression, high induced expression, and high responsiveness to doxycycline both in vitro and in vivo. These results also suggest that the low responsiveness to doxycycline may explain why the original tet-on system in the context of the Ad vector is not effective in vivo. This is the first report describing the cloning of three heterologous gene-expression cassettes into three separate regions of the E1/E3-deleted Ad genome. This improved Ad-mediated tet-on system might be useful for gene therapy and greatly facilitate the analyses of gene function.

Adenoviridae↗

PubMed2003

Antitumor effect by interleukin-11 receptor alpha-locus chemokine/CCL27, introduced into tumor cells through a recombinant adenovirus vector.

In this study, we examined antitumor activity of a mouse CC chemokine ILC/CCL27 and a mouse CX(3)C chemokine fractalkine/CX(3)CL1 in vivo. We generated recombinant adenovirus vectors with a fiber mutation, encoding mILC (Ad-RGD-mILC) and mFKN (Ad-RGD-mFKN). We confirmed tumor cells infected with Ad-RGD-mILC and Ad-RGD-mFKN to express and release these chemokines. Tumor rejection experiments in vivo were carried out by inoculating OV-HM cells infected with Ad-RGD-mILC or Ad-RGD-mFKN into immunocompetent mice. mILC significantly suppressed the tumor growth, whereas no such significant effect was observed by mFKN. The antitumor activity induced by mILC was T cell dependent, involving both CD4(+) and CD8(+) T cells. Immunohistochemical analysis revealed accumulation of both CD3(+) lymphocytes and NK cells in the tumor tissue transduced with mILC and mFKN. However, there was a significant difference in the distribution of infiltrating cells. Furthermore, mFKN appeared to have an angiogenic activity, which might have masked its tumor suppressive activity. Collectively, ILC/CCL27 may be a good candidate molecule for cancer gene therapy.

Adenoviridae↗

PubMed2003

Woodchuck hepatitis virus post-transcriptional regulation element enhances transgene expression from adenovirus vectors.

In studies of both gene therapy and gene function, transgene expression can be modulated at both the transcriptional and post-transcriptional levels. In a previous study, we optimized the transcriptional regulatory elements for adenovirus (Ad) vectors to mediate efficient transgene expression, including promoter, enhancer, intron, and poly(A) sequence. In the present study, we systematically investigated the ability of the Woodchuck hepatitis virus post-transcriptional regulation element (WPRE) to enhance the expression of the luciferase gene, as a model gene, in the context of Ad vectors. We found that the WPRE in the sense orientation cloned between the luciferase gene and the poly(A) sequence stimulated 2- to 7-fold more luciferase expression in vitro and 2- to 50-fold more in the liver, kidney and lung of mouse than occurred without the use of the WPRE. The most efficient Ad vector in this study, which contained the improved CMV promoter (the conventional CMV promoter with the intron A) and the WPRE, showed more than 700-fold luciferase expression in mouse liver than did the Ad vector containing the conventional CMV promoter but no WPRE. These results indicate that inclusion of the WPRE, combined with the optimization of transcriptional regulatory elements in Ad vectors, will permit a given therapeutic goal to be achieved with substantially fewer viral particles. This information would be helpful for the construction of adenovirus vectors for studies regarding both gene therapy and gene function.

Adenoviridae↗

PubMed2003

Regulated gene expression from adenovirus vectors: a systematic comparison of various inducible systems.

Positively and tightly regulated gene expression is essential for gene function and gene therapy research. The currently-used inducible gene expression systems include tetracycline (Tet-on and T-REx), ecdysone, antiprogestin and dimerizer-based systems. Adenovirus (Ad) vectors play an important role in gene function and gene therapy research for their various advantages over other vector systems. Previously, we reported the inferiority of the Tet-on system as an inducible gene expression system in the context of Ad vectors in comparison with the Tet-off system. In this study, to identify an optimal system for regulated gene expression from Ad vectors, we made a rigorous direct comparison of these five inducible gene expression systems in three cell lines using the luciferase reporter gene. The highest sensitivity to the respective inducer was that of the dimerizer system, followed by the antiprogestin system. The lowest basal expression and the highest induction factor were both characteristic of the dimerizer system. Furthermore, the dimerizer and T-REx systems exhibited much higher induced expression levels than the other three systems. The elucidation of the characteristic features of each system should provide important information for widespread and feasible application of these systems. Overall, these results suggest the most appropriate inducible gene expression system in the context of Ad vectors to be the dimerizer system.

Adenoviridae↗

PubMed2003

Postinfarction treatment with an adenoviral vector expressing hepatocyte growth factor relieves chronic left ventricular remodeling and dysfunction in mice.

BACKGROUND: Hepatocyte growth factor (HGF) is implicated in tissue regeneration, angiogenesis, and antiapoptosis. However, its chronic effects are undetermined on postinfarction left ventricular (LV) remodeling and heart failure. METHODS AND RESULTS: In mice, on day 3 after myocardial infarction (MI), adenovirus encoding human HGF (Ad.CAG-HGF) was injected into the hindlimb muscles (n=13). As a control (n=15), LacZ gene was used. A persistent increase in plasma human HGF was confirmed in the treated mice: 1.0+/-0.2 ng/mL 4 weeks later. At 4 weeks after MI, the HGF-treated mice showed improved LV remodeling and dysfunction compared with controls, as indicated by the smaller LV cavity and heart/body weight ratio, greater % fractional shortening and LV +/-dP/dt, and lower LV end-diastolic pressure. The cardiomyocytes near MI, including the papillary muscles and trabeculae, were greatly hypertrophied in the treated mice. The old infarct size was similar between the groups, but the infarct wall was thicker in the treated mice, where the density of noncardiomyocyte cells, including vessels, was greater. Fibrosis of the ventricular wall was significantly reduced in them. Examination of 10-day-old MI revealed no proliferation or apoptosis but showed augmented expression of c-Met/HGF receptor in cardiomyocytes near MI, whereas a greater proliferating activity and smaller apoptotic rate of granulation tissue cells in the HGF-treated hearts was observed compared with controls. CONCLUSIONS: Postinfarction HGF gene therapy improved LV remodeling and dysfunction through hypertrophy of cardiomyocytes, infarct wall thickening, preservation of vessels, and antifibrosis. These findings imply a novel therapeutic approach against postinfarction heart failure.

Adenoviridae↗

PubMed2003

Strain and catalysis in aspartate aminotransferase.

The notion of "ground-state destabilization" has been well documented in enzymology. It is the unfavourable interaction (strain) in the enzyme-substrate complex, and increases the k(cat) value without changing the k(cat)/K(m) value. During the course of the investigation on the reaction mechanism of aspartate aminotransferase (AAT), we found another type of strain that is crucial for catalysis: the strain of the distorted internal aldimine in the unliganded enzyme. This strain raises the energy level of the starting state (E+S), thereby reducing the energy gap between E+S and ES(++) and increasing the k(cat)/K(m) value. Further analysis on the reaction intermediates showed that the Michaelis complex of AAT with aspartate contains strain energy due to an unfavourable interaction between the main chain carbonyl oxygen and the Tyr225-aldimine hydrogen-bonding network. This belongs to the classical type of strain. In each case, the strain is reflected in the pK(a) value of the internal aldimine. In the historical explanation of the reaction mechanism of AAT, the shifts in the aldimine pK(a) have been considered to be the driving forces for the proton transfer during catalysis. However, the above findings indicate that the true driving forces are the strain energy inherent to the respective intermediates. We describe here how these strain energies are generated and are used for catalysis, and show that variations in the aldimine pK(a) during catalysis are no more than phenomenological results of adjusting the energy levels of the reaction intermediates for efficient catalysis.

Aspartate Aminotransferases↗