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No description available.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13490号 / 論医博第2258号 / 新制||医||1059(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 渡邉 大, 教授 稲垣 暢也, 教授 長船 健二 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

In chronic myelogenous leukemia (CML), activation of BCR-ABL, the product of the bcr-abl chimeric gene, leads to constitutive activation of pathways that increase genomic instability through endogenous production of reactive oxygen species (ROS) that cause oxidative DNA damage and inactivate the function of repair proteins leading to unfaithful DNA repair. If misrepaired, oxidative DNA damage, such as 8-oxoguanine (8-oxoG), may result in point mutations and/or DNA double-strand breaks (DSBs) leading to drug resistance to the BCR-ABL kinase inhibitor imatinib mesylate (IM) and accumulation of chromosomal aberrations associated with malignant CML progression from a benign chronic phase (CP) to a fatal blast phase (BP). To determine which population of CML-CP cells, leukemia stem cells (LSCs) and/or leukemia progenitor cells (LPCs), displays elevated levels of ROS and oxidative DNA damage, and whether these elevated levels of ROS and oxidative DNA damage in CML-CP subpopulations result in the accumulation of genomic instability, we employed the tetracycline-inducible SCLtTA/BCR-ABL transgenic mouse model. We showed that LSCs, including the quiescent subpopulation, but not LPCs, displayed elevated levels of ROS and oxidative DNA damage, perhaps due to deregulated expression of genes involved in ROS metabolism, resulting in genomic instability manifested by both point mutations and genetic alterations. We also examined the effect of IM on ROS, oxidative DNA damage and genomic instability displayed by CML-CP subpopulations, and determined that elevated ROS and oxidative DNA damage were not inhibited by IM in quiescent LSCs, nor was genomic instability and deregulated gene expression prevented. To explore underlying mechanisms, i.e. BCR-ABL expression levels, by which CML-CP cells accumulate genomic instability, we examined the effect of low and high BCR-ABL expression on ROS and oxidative DNA damage in BCR-ABL-transduced human CD34+ cells. We detected elevated ROS and oxidative DNA damage in high BCR-ABL-expressing CD34+ cells compared to low BCR-ABL-expressing cells. Furthermore, BCR-ABL exerted a kinase-dependent effect on ROS-dependent DNA damage. These data support the hypothesis that genomic instability may originate from LSCs, but do not exclude the potential role of LPCs, and may have important clinical implications for CML treatment since additional genetic aberrations that encode primary resistance may protect LSCs, including the quiescent subpopulation, from eradication by tyrosine kinase inhibitors (TKIs), and the continuous accumulation of genetic errors may trigger disease relapse and progression. / Microbiology and Immunology

No / Age is characterized by deficits in synaptic function identified by decreased performance of aged animals in spatial learning tasks and reduced ability of animals to sustain long-term potentiation (LTP). Several cellular and molecular events are correlated with these deficits, many of which are indicative of cell stress. Thus there is evidence of age-related neuroinflammatory stress and oxidative stress and these have been linked with microglial activation which is likely to be primarily responsible for the age-related increase in production of proinflammatory cytokines and reactive oxygen species. It is significant that agents which decrease microglial activation are commonly associated with restoration of function. We set out to examine whether the n-3 polyunsaturated fatty acid docosapentaenoic acid (DPA), which is a metabolite of eicosapentaenoic acid (EPA), could modulate the age-related increase in microglial activation and the associated increase in oxidative changes and therefore impact on synaptic function in aged rats. We demonstrate that DPA possesses neurorestorative effects and is capable of downregulating microglial activation. The data show that it also decreases the coupled activation of sphingomyelinase and caspase 3, probably as a result of its ability to decrease age-related oxidative changes, and consequently attenuates the age-related decrease in spatial learning and LTP.

Syngeneic graft-versus-host disease (SGVHD) is induced by reconstituting lethally irradiated mice with syngeneic BM cells followed by a 21 day treatment with the immunosuppressive agent cyclosporine A (CsA). Clinical symptoms of the disease appear 2-3 weeks following cessation of CsA therapy and disease-associated inflammation occurs primarily in the colon and liver. The development of SGVHD is a complex process resulting from the cooperative interaction of multiple effector cell populations including NK cells, T cells and macrophages. TH1 cytokines (IL-12, TNF-α, IFN- γ), produced by these effector cells, serve as inflammatory mediators contributing to the pathogenesis of SGVHD. The SGVHD conditioning agents, irradiation and CsA, are both required for the development of disease and contribute to the production of oxidative stress. Time course studies revealed increased reactive oxygen and nitrogen species (ROS/RNS), as well as, increased colon mRNA levels for TNF-α and iNOS in CsA-treated versus control BMT animals. Since ROS/RNS are known to mediate CsA toxicity, studies were undertaken to determine the effect of oxidative stress on the induction of SGVHD. In vivo treatment with the antioxidant MnTBAP caused a reduction in colon mRNA levels for iNOS and TNF-α, as well as delayed disease development, suggesting a role for oxidative stress in the development of SGVHD. In addition, CD4+ T cells have been shown to play an important role in the inflammatory response observed in the gut of SGVHD mice. Time course studies revealed significant increases in the migration of CD4+ T cells as early as day 14 post- BMT into the colon of CsA mice as well as significant elevated mRNA levels of cell adhesion molecules. Homing studies revealed that a labeled CD4+ T cell line, generated from SGVHD mice, migrated in larger numbers into the gut of CsA-treated mice compared to control animals. This study demonstrated that CD4+ T cells responsible for the pathogenesis observed in murine SGVHD are present early after BMT in colons of CsA-treated mice, suggesting that during the 21 days of immunosuppression therapy functional mechanisms are in place that result in increased homing of effector cells to colons of CsA-treated mice.

No description available.

Lung cancer is one of the leading causes of cancer deaths in the United States. Radiation and chemotherapy are conventional treatments, but they result in serious side effects and the probability of tumor recurrence remains high. Therefore, there is an increasing need to enhance the efficacy of conventional treatments. Magnetic nanoparticles have been previously studied for a variety of applications such as magnetic resonance imaging contrast agents, anemia treatment, magnetic cell sorting and magnetically mediated hyperthermia (MMH). In this work, dextran coated iron oxide nanoparticles were developed and functionalized with peptides to target the nanoparticles to either the extracellular matrix (ECM) of tumor tissue or to localize the nanoparticles in subcellular regions after cell uptake. The magnetic nanoparticles were utilized for a variety of applications. First, heating properties of the nanoparticles were utilized to administer hyperthermia treatments combined with chemotherapy. The nanoparticles were functionalized with peptides to target fibrinogen in the ECM and extensively characterized for their physicochemical properties, and MMH combined with chemotherapy was able to enhance the toxicity of chemotherapy. The second application of the nanoparticles was magnetically mediated energy delivery. This treatment does not result in a bulk temperature rise upon actuation of the nanoparticles by an alternating magnetic field (AMF) but rather results in intracellular damage via friction from Brownian rotation or nanoscale heating effects from Neél relaxations. The nanoparticles were functionalized with a cell penetrating peptide to facilitate cell uptake and lysosomal escape. The intracellular effects of the internalized nanoparticles alone and with activation by an AMF were evaluated. Iron concentrations in vivo are highly regulated as excess iron can catalyze the formation of the hydroxyl radical through Fenton chemistry. Although often a concern of using iron oxide nanoparticles for therapeutic applications, these inherent toxicities were harnessed and utilized to enhance radiation therapy. Therefore, the third application of magnetic nanoparticles was their ability to catalyze reactive oxygen species formation and increase efficacy of radiation. Overall, iron oxide nanoparticles have a variety of cancer therapy applications and are a promising class of materials for increasing efficacy and reducing the side effects of conventional cancer treatments.

[NiFe] hydrogenases are metalloenzymes that act as highly efficient molecular electrocatalysts for the interconversion of protons and molecular hydrogen. Unlike any other known molecular electrocatalyst, the members of a subgroup of respiratory membrane-bound [NiFe] hydrogenases are able to maintain H₂ catalysis in the sustained presence of O₂. This O₂-tolerance depends on the ability to respond to oxidative inactivation by O₂ by exclusively forming rapidly reactivated active site states, thus implying a catalytic cycle in which O₂ acts as a competing substrate to H₂. Using isotope ratio mass spectrometry it is proven that the O2-tolerant Escherichia coli Hydrogenase 1 responds to O₂ attack by acting as a four-electron oxidoreductase, catalysing the reaction 2 H₂ + O₂ → 2 H₂O, equivalent to hydrogen combustion. Special features of the enzyme’s electron relay system enable delivery of the required electrons. A small fraction of the H₂O produced arises from side reactions proceeding via reactive oxygen species, an unavoidable consequence of the presence of low-potential relay centres that release electrons from H₂ oxidation. While the ability to fully reduce O₂ to harmless H₂O at the active site to generate the rapidly reactivated state Ni-B, determines if a hydrogenase is O₂-tolerant, the ratio of oxidative inactivation to reductive reactivation rates determines how tolerant the enzyme is. It is shown by protein film electrochemistry that the (αβ)₂ dimeric assembly of Hyd-1 plays an important role in O₂-tolerance by aiding reactivation of one catalytic unit through electron transfer from the other. The teamwork between two redundant partners implicates a new role for dimerisation and represents a new example of cooperativity in biology. Finally, the non-natural amino acid p-azido-L-phenylalanine was synthesised and incorporated into Hyd-1, testing the possibility of introducing labels at specific sites.

Phosphodiesterase Type 5 (PDE5) inhibitors are cardioprotective against ischemia/reperfusion (I/R) injury. However, it remains uncertain if I/R affects PDE5. We hypothesized that generation of reactive oxygen species (ROS) during I/R leads to upregulation of PDE5, which contributes to pathological changes following acute myocardial infarction (AMI). Adult male ICR mice were subjected to 30 minutes of in vivo or ex vivo I/R. To examine the role of ROS, a subset of hearts were perfused with 100 µM hydrogen peroxide (H2O2). Expression and activity of PDE5, pPDE5, and cGMP-dependent protein kinase (PKG) were measured by Western blots and spectrophotometric assay. The results show that ischemia and I/R significantly increased expression of PDE5. H2O2 had no effect on PDE5 expression and activity but significantly increased PKG activity. We conclude that acute cardiac ischemia or I/R upregulate PDE5 independent of oxidant stress in the heart.