Sumiko Inoue

Oxidative DNA damage induced by simultaneous generation of nitric oxide and superoxide.

Incubation of calf thymus DNA with 3‐morpholinosydnonimine (SIN‐1), which simultaneously generates nitric oxide (NO) and superoxide (O2 −), induced a significant increase of 8‐hydroxydeoxyguanosine (8‐OH‐dG). Peroxynitrite also increased 8‐OH‐dG in calf thymus DNA. Addition of free hydroxyl radical (•OH) scavengers inhibited the increase of 8‐OH‐dG by SIN‐1 or peroxynitrite. Incubation of 32P‐labeled DNA fragment with SIN‐1 or peroxynitrite caused DNA cleavage at every nucleotide with a little dominance at guanine residues. The results suggest that NO reacts with O2 − to form peroxynitrite and the peroxynitrite induces oxidative DNA damage through an active intermediate of which reactivity is similar to •OH.

Mutations in SLC6A19 , encoding B 0 AT1, cause Hartnup disorder

Hartnup disorder, an autosomal recessive defect named after an English family described in 1956 (ref. 1), results from impaired transport of neutral amino acids across epithelial cells in renal proximal tubules and intestinal mucosa. Symptoms include transient manifestations of pellagra (rashes), cerebellar ataxia and psychosis. Using homozygosity mapping in the original family in whom Hartnup disorder was discovered, we confirmed that the critical region for one causative gene was located on chromosome 5p15 (ref. 3). This region is homologous to the area of mouse chromosome 13 that encodes the sodium-dependent amino acid transporter B0AT1 (ref. 4). We isolated the human homolog of B0AT1, called SLC6A19, and determined its size and molecular organization. We then identified mutations in SLC6A19 in members of the original family in whom Hartnup disorder was discovered and of three Japanese families. The protein product of SLC6A19, the Hartnup transporter, is expressed primarily in intestine and renal proximal tubule and functions as a neutral amino acid transporter.

Autosomal dominant moyamoya disease maps to chromosome 17q25.3.

Background: Moyamoya disease (MMD) is an idiopathic steno-occlusive cerebrovascular disease that represents an important cause of stroke. However, etiology of the disease has remained largely unknown. Methods: We previously showed that the inheritance pattern of MMD is autosomal dominant with incomplete penetrance. Here, we report the genome-wide parametric linkage analysis for MMD in 15 extended Japanese families. We conducted linkage analyses under two diagnostic classifications: narrow and broad. Affected member-only analysis was applied due to incomplete and age-dependent penetrance of the disease. Results: Under both classifications, significant evidence of linkage was only observed on chromosome 17q25.3, with maximum multipoint logarithm of odds (lod) scores of 6.57 (under the narrow classification) and 8.07 (under the broad classification) at D17S704. Haplotype analysis revealed segregation of a disease haplotype in all families but one, and informative crossovers enabled mapping of the MMD locus to a 3.5-Mb region between D17S1806 and the telomere of 17q, encompassing 94 annotated genes. Conclusions: Our data suggest that there is a major gene locus for autosomal dominant moyamoya disease on chromosome 17q25.3.

Superoxide formation and DNA damage induced by a fragrant furanone in the presence of copper(II)

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (2,5-DMHF), a caramel-like fragrant compound found in may processed foodstuff, has been reported to be mutagenic. 4,5-Dimethyl-3-hydroxy-2(5H)-furanone (4,5-DMHF), which is a similar characteristic fragrant compound, has no report concerning its mutagenicity. DNA damage by 2,5-DMHF and 4,5-DMHF was investigated by using DNA fragments obtained from the p53 tumor suppressor gene. 2,5-DMHF induced DNA damage extensively in the presence of Cu(II), but only slightly in the presence of Fe(III). 4,5-DMHF did not cause metal-dependent DNA damage. Bathocuproine, a Cu(I)-specific chelator, and catalase inhibited DNA damage induced by 2,5-DMHF plus Cu(II), whereas free hydroxyl radical scavengers did not. The order of DNA cleavage sites was thymine, cytosine > guanine residues. The site-specific DNA damage and effects of scavengers show that DNA-copper-oxygen complex rather than free .OH are involved in the DNA damage. Formation of 8-oxodeoxyguanosine (8-oxodG) by 2,5-DMHF increased with its concentration in the presence of Cu(II), whereas 8-oxodG formation increased only slightly in the presence of Fe(III). Degradation of 2,5-DMHF was efficiently accelerated by Cu(II), but only slightly accelerated by Fe(III). The degradation of 4,5-DMHF was little even in the presence of metal ions. Examination using cytochrome c suggest that superoxide was generated from 2,5-DMHF. Stoichiometric study of Cu(II) reduction revealed that autoxidation of 2,5-DMHF could offer 4-electron reduction. These results suggest that, at least in vitro and in an acellular system, 2,5-DMHF generates superoxide and subsequently hydrogen peroxide to induce metal-dependent DNA damage.

ESR evidence for superoxide, hydroxyl radicals and singlet oxygen produced from hydrogen peroxide and nickel(II) complex of glycylglycyl-L-histidine.

ESR studies using spin traps, 5,5-dimethylpyrroline-N-oxide and alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone, revealed that hydroxyl radical adducts are produced by the decomposition of hydrogen peroxide in the presence of nickel(II) oligopeptides. Order of catalytic activities of nickel(II) oligopeptides used in the production of hydroxyl radical adducts was tetraglycine greater than pentaglycine greater than triglycine greater than GlyGly, GlyHis. Ni(II) GlyGlyHis plus hydrogen peroxide produced superoxide in addition to hydroxyl radical adduct. Trapping experiments with 2,2,6,6-tetramethyl-4-piperidone suggested that singlet oxygen was generated by the reaction of hydrogen peroxide with Ni(II) GlyGlyHis, but not in the case of tetraglycine, pentaglycine, triglycine, GlyGly or GlyHis.

Genome-Wide Scan for Japanese Familial Intracranial Aneurysms Linkage to Several Chromosomal Regions

Background—Genetic factors have an important role in the pathogenesis of intracranial aneurysm (IA). The results of previous studies have suggested several loci. Methods and Results—From 29 IA families with ≥3 individuals affected by IA, we used nonparametric (model-free) methods for linkage analyses, using GENEHUNTER and Merlin software. Genome-wide linkage analyses revealed 3 regions on chromosomes 17cen (maximum nonparametric logarithm of the odds score [MNS] = 3.00, nominal P=0.001), 19q13 (MNS=2.15, nominal P=0.020), and Xp22 (MNS=2.16, nominal P=0.019). We tested 4 candidate genes in these regions: the microfibril-associated protein 4 gene (MFAP4) and the promoter polymorphism of the inducible nitric oxide synthase gene (NOS2A) on chromosome 17cen, the epsilon genotypes of the apolipoprotein E gene (APOE) on chromosome 19q13, and the angiotensin I converting enzyme 2 gene (ACE2) on chromosome Xp22. Associations of their polymorphisms with IA were evaluated by a case-control study (100 cases: 29 probands from IA families and 71 unrelated subjects with IAs, 100 unrelated control subjects [unaffected members with IAs and absence of family history of IAs]). However, the case-control study showed that none of the polymorphisms of the examined genes had associations with IA. Conclusions—A genome-wide scan in 29 Japanese families with a high degree of familial clustering revealed 1 suggestive linkage region on chromosome 17cen and 2 potentially interesting regions on chromosomes 19q13 and Xp22. These regions were consistent with previous findings in various populations.

Hydroxyl radical and singlet oxygen production and DNA damage induced by carcinogenic metal compounds and hydrogen peroxide

Carcinogenic chromium(VI), iron(III) nitrilotriacetate, cobalt(II), and nickel(II) react with hydrogen peroxide leading to the production of active species including hydroxyl radical and singlet oxygen, which cause DNA damage.

Oxidative DNA Damage and Apoptosis Induced by Metabolites of Butylated Hydroxytoluene

DNA damage by metabolites of a food additive, butylated hydroxytoluene (BHT), was investigated as a potential mechanism of carcinogenicity. The mechanism of DNA damage by 2,6-di-tert-butyl-p-benzoquinone (BHT-quinone), 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHT-OOH), and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) in the presence of metal ions was investigated by using 32P-labeled DNA fragments obtained from the c-Ha-ras-1 proto-oncogene and the p53 tumor suppressor gene. BHT-OOH caused DNA damage in the presence of Cu(II), whereas BHT-quinone and BHT-CHO did not. However, BHT-quinone did induce DNA damage in the presence of NADH and Cu(II). Bathocuproine inhibited Cu(II)-mediated DNA damage, indicating the participation of Cu(I) in the process. Catalase also inhibited DNA damage induced by BHT-quinone, but not that induced by BHT-OOH. The DNA cleavage pattern observed with BHT-quinone plus NADH was different from that seen with BHT-OOH. With BHT-quinone plus NADH, piperidine-labile sites could be generated at nucleotides other than adenine residue. BHT-OOH caused cleavage specifically at guanine residues. Pulsed field gel electrophoresis showed that BHT-OOH and BHT-quinone induced DNA strand breaks in cultured cells, whereas BHT-CHO did not. Both BHT-quinone and BHT-OOH induced internucleosomal DNA fragmentation, which is the characteristic of apoptosis. Furthermore, flow cytometry analysis revealed an increase of peroxides in cultured cells treated with BHT-OOH or BHT-quinone. These results suggest that BHT-OOH participates in oxidative DNA damage directly, whereas BHT-quinone causes DNA damage through H2O2 generation, which leads to internucleosomal DNA fragmentation.

Search on Chromosome 17 Centromere Reveals TNFRSF13B as a Susceptibility Gene for Intracranial Aneurysm A Preliminary Study

Background— Our previous studies have shown a significant linkage of intracranial aneurysms (IAs) to chromosome 17. Methods and Results— Nine genes (TNFRSF13B, M-RIP, COPS3, RAI1, SREBF1, GRAP, MAPK7, MFAP4, and AKAP10) were selected from 108 genes that are located between D17S1857 and D17S1871 by excluding 99 genes that were pseudogenes, hypothetical genes, or well-characterized genes but not likely associated with IA. Direct sequencing of all coding and regulatory regions in 58 cases (29 pedigree probands and 29 unrelated nonpedigree cases) was performed. Deleterious changes were found only in TNFRSF13B, K154X, and c.585 to 586insA in exon4. The association of IA with TNFRSF13B was further studied in 304 unrelated cases and 332 control subjects. Rare nonsynonymous changes, a splicing acceptor site change and a frame shift, were found in unrelated cases (2.3%; 14 of 608) more frequently than in control subjects (0.8%; 5 of 664; P=0.035). The association study using single-nucleotide polymorphisms in an unrelated case-control cohort revealed a protective haplotype (odds ratio 0.69, 95% confidence interval 0.52 to 0.92, P=0.012) compared with the major haplotype after adjustment for covariates. Conclusions— We propose that TNFRSF13B is one of the susceptibility genes for IA.

Metal-mediated DNA damage induced by diabetogenic alloxan in the presence of NADH

Alloxan is known to induce diabetes in experimental animals through destruction of insulin-producing 3-cells of pancreas. The mechanism of DNA damage induced by alloxan was investigated using 32P-labeled human DNA fragments. Cu(II)-dependent DNA damage increased with the concentration of alloxan and NADH. Alloxan induced DNA cleavage frequently at thymine and cytosine residues in the presence of NADH and Cu(II). Catalase and bathocuproine, a Cu(I)-specific chelator, almost completely inhibited DNA damage, suggesting the involvement of H2O2 and Cu(I). Alloxan induced Cu(II)-dependent production of 8-oxodG in calf thymus DNA in the presence of NADH. UV-visible and electron spin resonance (ESR) spectroscopic studies showed that superoxide anion radical and alloxan radical were generated by the reduction of alloxan by NADH, and also by the autoxidation of dialuric acid, the reduced form of alloxan. These results suggest that the copper-oxygen complex derived from the reaction of H2O2 with Cu(I) participates in Cu(II)-dependent DNA damage by alloxan plus NADH and dialuric acid. The mechanism of DNA damage is discussed in relation to diabetogenic action of alloxan.