A Model for the 3He(\vec d, p)4He Reaction at Intermediate Energies

Polarization correlation coefficients have been measured atRIKEN for the \vec 3He(\vec d,p)4He reaction at intermediate energies. We propose a model for the (\vec d, p) reaction mechanism using the pd elastic scattering amplitude which is rigorously determined by a Faddeev calculation and using modern NN forces. Our theoretical predictions for deuteron polarization observables A_y, A_{yy}, A_{xx} and A_{xz} at E_d=140, 200 and 270 MeV agree qualitatively in shape with the experimental data for the reaction 3He(\vec d,p)4He.Comment: 6 pages, 11 figures, 1 table, reference: http://www.phys.ntu.edu.tw/english/fb16/contribution/topic4/Uesaka_Tomohiro1. ps in Contribution for the XVIth IUPAP International Conference on Few-Body Problems in Physics, (Taipei, Taiwan 6-11, March 2000

Role of platelet-derived growth factor receptor-α and -β in pulmonary fibrosis in mice

Platelet-derived growth factor (PDGF) has been implicated in the pathogenesis of pulmonary fibrosis. Nintedanib, a multi-kinase inhibitor that targets several tyrosine kinases, including PDGF receptor (PDGFR), was recently approved as an anti-fibrotic agent to reduce the deterioration of FVC in patients with idiopathic pulmonary fibrosis (IPF). However, the effects of PDGFR-α or -β on pulmonary fibrosis remain unclear. In an attempt to clarify their effects, we herein used blocking antibodies specific for PDGFR-α (APA5) and -β (APB5) in a bleomycin (BLM)-induced pulmonary fibrosis mouse model. The effects of these treatments on the growth of lung fibroblasts were examined using the 3H-thymidine incorporation assay in vitro. The anti-fibrotic effects of these antibodies were investigated with the Ashcroft score and collagen content of lungs treated with BLM. Their effects on inflammatory cells in the lungs were also analyzed using bronchoalveolar lavage fluid. We investigated damage to epithelial cells and the proliferation of fibroblasts in the lungs. APA5 and APB5 inhibited the phosphorylation of PDGFR-α and -β as well as the proliferation of lung fibroblasts induced by PDGF-AA and BB. The administration of APB5, but not APA5 effectively inhibited BLM-induced pulmonary fibrosis in mice. Apoptosis and the proliferation of epithelial cells and fibroblasts were significantly decreased by the treatment with APB5, but not by APA5. The late treatment with APB5 also ameliorated fibrosis in lungs treated with BLM. These results suggest that PDGFR-α and -β exert different effects on BLM-induced pulmonary fibrosis in mice. A specific approach using the blocking antibody for PDGFR-β may be useful for the treatment of pulmonary fibrosis

Suppression of mutagenesis by 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (7,8-dihydro-8-oxo-2'-deoxyguanosine 5'-triphosphate) by human MTH1, MTH2, and NUDT5

To assess the functions of the three human MutT-type enzymes, MTH1, MTH2, and NUDT5, mutation induction by an oxidized form of dGTP, 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP, 7,8-dihydro-8-oxo-2'-deoxyguanosine 5'-triphosphate), was examined using human 293T cells treated with their specific siRNAs. Shuttle plasmid DNA containing the supF gene was first transfected into the cells, and then 8-OH-dGTP was introduced by means of osmotic pressure. Escherichia coli cells were transformed with the DNAs replicated in the treated cells. The knock-downs of the MTH1, MTH2, and NUDT5 proteins increased the A:T→C:G substitution mutations induced by 8-OH-dGTP. In addition, the increase in the induced mutation frequency was more evident in the triple knock-down cells. These results indicate that all three of the human MTH1, MTH2, and NUDT5 proteins act as a defense against the mutagenesis induced by oxidized dGTP.Normal cellular metabolism produces endogenous reactive oxygen species (ROS). ROS are generated as byproducts of the mitochondrial electron transport chain, and certain cellular enzymes also generate ROS. Moreover, ROS are produced by environmental mutagens/carcinogens, including ionizing radiation and ultraviolet light. The formation of ROS leads to the oxidation of cellular components and disturbs their normal functions. The formation of oxidized DNA lesions is one of the causative factors of mutagenesis, carcinogenesis, neurodegeneration, and aging [1-5]. DNA precursors (2'-deoxyribonucleotides) are also subjected to oxidative damage. The formation of oxidized DNA precursors is a potential source of mutagenesis [6]. 8-Hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP, 7,8-dihydro-8-oxo-2'-deoxyguanosine 5'-triphosphate) is the major oxidation product of dGTP in in vitro oxidation reactions [7]. 8-OH-dGTP was reportedly present at a concentration of 1｡V10% relative to the unmodified dGTP in the mitochondrial nucleotide pool [8]. This oxidized form of dGTP is highly mutagenic in living cells when added exogenously [9-11] and is expected to act as an endogenous mutagen. Nucleotide pool sanitization is an important means by which organisms prevent the mutagenesis caused by damaged DNA precursors [6,12]. The Escherichia coli MutT (NudA) protein, encoded by the mutator gene mutT, was the first enzyme found to degrade an oxidized DNA precursor (8-OH-dGTP) in vitro [13]. Moreover, at least two E. coli MutT-type proteins, Orf135 (NudG) and Orf17 (NudB), in addition to MutT, catalyze the hydrolysis of oxidized DNA precursors in vitro [14,15]. E. coli strains lacking MutT and Orf135 exhibit a mutator phenotype [16-19], indicating the importance of nucleotide pool sanitization to prevent mutagenesis by oxidized DNA precursors. Mammalian cells also possess MutT-type enzymes. The MTH1 (NUDT1) protein catalyzes the hydrolysis of various oxidized DNA precursors, including 8-OH-dGTP, and greater numbers of tumors were formed in the lungs, livers, and stomachs of MTH1-deficient mice than wild-type mice [20,21]. MTH2 (NUDT15) degrades 8-OH-dGTP in vitro, and the expression of the cDNA encoding MTH2 significantly reduced the elevated spontaneous mutation frequency in E. coli mutT cells [22]. The NUDT5 protein is unique, because the hydrolysis of 8-hydroxy-2'-deoxyguanosine 5'-diphosphate (8-OH-dGDP, 7,8-dihydro-8-oxo-2'-deoxyguanosine 5'-diphosphate) by this protein is much more efficient than that of 8-OH-dGTP [23,24]. However, the expression of NUDT5 in mutT-deficient E. coli mutant cells decreases the spontaneous mutation frequency to the normal level, suggesting the importance of its 8-OH-dGDPase activity in nucleotide pool sanitization [23]. Thus, it is quite important to examine whether the three proteins prevent the mutations induced by 8-OH-dGTP in mammalian (human) cells.Recently, we showed that 8-OH-dGTP specifically induced A:T→C:G transversions in live simian and human cells [10,11]. In this study, to assess the contributions of these MutT-type proteins to the prevention of the mutagenesis caused by 8-OH-dGTP in human cells, we suppressed their expression by siRNAs and introduced 8-OH-dGTP into the knocked-down cells. The knock-downs of all of the MutT-type proteins enhanced the A:T→C:G substitution mutations, suggesting their roles as functional nucleotide pool sanitization enzymes

Mutagenic effects of 8-hydroxy-dGTP in live mammalian cells

The mutagenicity of an oxidized form of dGTP, 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP), was examined using COS-7 cells. 8-OH-dGTP and supF shuttle plasmid DNA were cointroduced by means of cationic liposomes, and the DNAs replicated in the cells were recovered and then transfected into Escherichia coli. 8-OH-dGTP induced A:T->C:G substitution mutations in the COS-7 cells. This result agrees with previous observations indicating that DNA polymerases misincorporate 8-OH-dGTP opposite A in vitro, and that the oxidized deoxyribonucleotide induces A:T->C:G transversions in E. coli. These results constitute the first direct evidence to show that 8-OH-dGTP actually induces mutations in living mammalian cells

Involvement of specialized DNA polymerases in mutagenesis by 8-hydroxy-dGTP in human cells

The mutagenicity of an oxidized form of dGTP, 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP), was examined using human 293T cells. Shuttle plasmid DNA containing the supF gene was first transfected into the cells, and then 8-OH-dGTP was introduced by means of osmotic pressure. The DNAs replicated in the cells were recovered and then transfected into Escherichia coli. 8-OH-dGTP induced A:T → C:G substitution mutations in the cells. The knock-downs of DNA polymerases η and ζ, and REV1 by siRNAs reduced the A:T → C:G substitution mutations, suggesting that these DNA polymerases are involved in the misincorporation of 8-OH-dGTP opposite A in human cells. In contrast, the knock-down of DNA polymerase ι did not affect the 8-OH-dGTP-induced mutations. The decrease in the induced mutation frequency was more evident by double knock-downs of DNA pols η plus ζ and REV1 plus DNA pol ζ (but not by that of DNA pol η plus REV1), suggesting that REV1-DNA pol η and DNA pol ζ work in different steps. These results indicate that specialized DNA polymerases are involved in the mutagenesis induced by the oxidized dGTP