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Biomedical subjects

Shigeo Ohta

Publications and source records attributed to Shigeo Ohta.

At least 37 records · Page 2Linked to original sources
PubMed2004

Mitochondrial ALDH2 deficiency as an oxidative stress.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a major role in ethanol metabolism. It is involved in acetaldehyde detoxification. A polymorphism of the ALDH2 gene is specific to North-East Asians. Sensitivity to ethanol is highly associated with this polymorphism (ALDH2(*)2 allele), which is responsible for a deficiency of ALDH2 activity. We first show that this deficiency influences the risk for late-onset Alzheimer's disease (LOAD) by a case-control study in a Japanese population. In a comparison of 447 patients with sex, age, and region-matched non-demented controls, the genotype frequency for the ALDH2(*)2 allele was significantly higher in the patients than in the controls (P=0.001). Next, we examined the combined effect of the ALDH2(*)2 and the apolipoprotein E4 allele (APOE-epsilon4), which has been confirmed to be a risk factor for LOAD. The ALDH2(*)2 allele more significantly affected frequency and age at onset in patients with APOE-epsilon4 than in those without it. These results indicate that the ALDH2 deficiency is a risk factor for LOAD, acting synergistically with the APOE-epsilon allele. Next, to elucidate the molecular mechanism involved, we obtained ALDH2-deficient cell lines by introducing mouse mutant ALDH2 cDNA into PC12 cells. We speculate that ALDH2 may act to oxidize toxic aldehyde derivatives. Then, we found that the ALDH2-deficient transfectants were highly vulnerable to exogenous 4-hydroxy-2-nonenal, an aldehyde derivative generated from peroxidized fatty acids. In addition, the ALDH2-deficient transfectants were sensitive to oxidative insult induced by antimycin A, accompanied by an accumulation of proteins modified with 4-hydroxy-2-nonenal. Mitochondrial ALDH2 functions as a protector against oxidative stress.

Aldehyde Dehydrogenase↗
PubMed2004

ALDH2/ADH2 polymorphism associated with vasculopathy and neuropathy in type 2 diabetes.

In the history of diabetes, chlorpropamide alcohol flushing test (CPAF) was a big topic in the 1970s to 1980s. Alcohol tolerance after chlorpropamide has prognostic significance, with the intolerant group (CPAF-positive group) being less prone to develop vascular complication than the tolerant group (CPAF-negative group). A mechanism of CPAF has been regarded as the inhibition of aldehyde dehydrogenase 2 (ALDH2) by an N-alkyl-substituted derivative of chlorpropamide, and the expression of these mutations of ALDH2 and alcohol dehydrogenase 2 (ADH2) could determine the alcohol tolerance among the Japanese population. Therefore, we hypothesized that expression of different ALDH2 and ADH2 polymorphisms may induce differences in vascular complications in diabetes and conducted two studies. The first study (study 1) was to determine the association of ALDH2/AHD2 polymorphism with diabetic complications. To know the association of ALDH2/AHD2 polymorphism with diabetic vasculopathy and neuropathy, a total of 158 patients with type 2 diabetes were divided into four groups on the basis of ALDH2 "activity" and ADH2 "superactivity." The frequency of proteinuria and the percentage of proliferative retinopathy among the patients with retinopathy was higher in those with active ALDH2 and superactive ADH2. We speculated that protein kinase C isoforms up-regulated by 4-hydroxynonenal that was detoxified by ALDH2 and ADH2 may account for the long-term development of diabetic nephropathy and severe retinopathy. As for neuropathy, the frequency of symptomatic neuropathy was higher in patients with inactive ALDH2 and usual ADH2. We speculate that increased tissue levels of toxic aldehyde could result from inactive ALDH2 and usual ADH2 expression, which results in the increased level of reactive aldehyde in sensory neuron pathway, thereby causing symptomatic polyneuropathy.

Adolescent↗
PubMed2004

Mitochondrial genome variation in eastern Asia and the peopling of Japan.

To construct an East Asia mitochondrial DNA (mtDNA) phylogeny, we sequenced the complete mitochondrial genomes of 672 Japanese individuals (http://www.giib.or.jp/mtsnp/index_e.html). This allowed us to perform a phylogenetic analysis with a pool of 942 Asiatic sequences. New clades and subclades emerged from the Japanese data. On the basis of this unequivocal phylogeny, we classified 4713 Asian partial mitochondrial sequences, with <10% ambiguity. Applying population and phylogeographic methods, we used these sequences to shed light on the controversial issue of the peopling of Japan. Population-based comparisons confirmed that present-day Japanese have their closest genetic affinity to northern Asian populations, especially to Koreans, which finding is congruent with the proposed Continental gene flow to Japan after the Yayoi period. This phylogeographic approach unraveled a high degree of differentiation in Paleolithic Japanese. Ancient southern and northern migrations were detected based on the existence of basic M and N lineages in Ryukyuans and Ainu. Direct connections with Tibet, parallel to those found for the Y-chromosome, were also apparent. Furthermore, the highest diversity found in Japan for some derived clades suggests that Japan could be included in an area of migratory expansion to Continental Asia. All the theories that have been proposed up to now to explain the peopling of Japan seem insufficient to accommodate fully this complex picture.

DNA, Mitochondrial↗
PubMed2004

Endurance exercise training inhibits activity of plasma GOT and liver caspase-3 of mice [correction of rats] exposed to stress by induction of heat shock protein 70.

A single bout of exercise increases production of heat shock protein 70 (HSP70), which protects cells against various stresses. In this study, we investigated whether endurance exercise training enhances liver level of HSP70 and, if so, whether HSP70 contributes to hepatic protection against stress in vivo. Mice of an exercise-training group performed 60 min of treadmill running 5 days/wk for 4 wk. The resting level of liver HSP70 was 4.5 times higher in the trained than in sedentary mice. After 4 wk of exercise training, both groups of mice were exposed to the following stresses: 1) heat stress, 2) cold stress, 3) oxidative stress, 4) ethanol stress, and 5) exercise stress by compelling the mice to run on a treadmill until exhausted. After exposure to the stresses, the liver was immediately isolated. Elevation of liver HSP70 in the trained mice was evident, whereas no elevation was found in the sedentary mice. On exposure to heat, diethyldithiocarbamate and ethanol, activities of glutanic oxalacetic transaminase in plasma, and liver caspase-3, a key enzyme of apoptotic processing, were elevated in the sedentary mice but not in the trained mice. These results suggest that exercise training enhanced the resting level of liver HSP70 and hepatic protection against various stresses, at least partly attributing to the suppression of caspase-3 activity by the increase in HSP70.

Adaptation, Physiological↗
PubMed2004

Detection of urine survivin in 40 patients with bladder cancer.

PURPOSE: We investigated whether urine survivin, an inhibitor of the apoptosis protein, is useful for diagnosing bladder tumor. METHOD: We measured urine survivin levels in 40 patients with bladder tumors and 9 healthy volunteers. RESULTS: The average urine survivin levels in the 40 patients and 9 healthy controls were not significantly different (3.802+/-8.669 and 1.127+/-1.529, respectively (p=0.3646) ). However, significantly high urine survivin levels were observed in 3 of the 40 patients, but not in healthy volunteers. Urine Cyfra 21-1 was not elevated (1.3 ng/ml) in one patient with a significantly elevated urine survivin level (33.54 ng/ml), while in two patients with elevated Cyfra (320 ng/ml and 240 ng/ml), the urine survivin level was not detectable. CONCLUSION: With improvements in the sensitivity of our Elisa system for urine survivin and combined use of urine Cyfra 21-1, it is possible that urine survivin will be a useful tumor marker in detecting both new-onset and recurrent bladder tumors.

Adult↗
PubMed2003

Genetic deficiency of a mitochondrial aldehyde dehydrogenase increases serum lipid peroxides in community-dwelling females.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a major role in acetaldehyde detoxification. The alcohol sensitivity is associated with a genetic deficiency of ALDH2. We and others have previously reported that such a deficiency influences the risk for late-onset Alzheimer's disease (LOAD), hypertension, and myocardial infarction. Then we tried to find phenotypes to which the ALDH2 polymorphism contributes by conducting several evaluations including biochemical and functional analyses of various tissues in a community-dwelling population. Several serum proteins, lipids, and lipid peroxides (LPO) levels showed differences between the nondefective (ALDH2*1/1) and defective (ALDH2*1/2 and ALDH2*2/2) ALDH2 individuals. However, alcohol-drinking behavior is known to affect these evaluations. Thus, we excluded the effects of alcohol-drinking behavior from the association with the ALDH2-deficient genotype through correction and found that the concentration of LPO was significantly lower in the nondefective ALDH2 females than the defective females. The effect of frequent alcohol-drinking behavior in males seems to override the phenotype of the high serum LPO level. These results indicate that the ALDH2 deficiency may enhance oxidative stress in vivo. Thus, these findings suggest that ALDH2 functions as a protector against oxidative stress and the decrease in protection may influence the onset of AD, hypertension, and myocardial infarction.

Adult↗
PubMed2003

Truncated product of the bifunctional DLST gene involved in biogenesis of the respiratory chain.

Dihydrolipoamide succinyltransferase (DLST) is a subunit enzyme of the alpha-ketoglutarate dehydrogenase complex of the Krebs cycle. While studying how the DLST genotype contributes to the pathogenesis of Alzheimer's disease (AD), we found a novel mRNA that is transcribed starting from intron 7 in the DLST gene. The novel mRNA level in the brain of AD patients was significantly lower than that of controls. The truncated gene product (designated MIRTD) localized to the intermembrane space of mitochondria. To investigate the function of MIRTD, we established human neuroblastoma SH-SY5Y cells expressing a maxizyme, a kind of ribozyme, that specifically digests the MIRTD mRNA. The expression of the maxizyme specifically eliminated the MIRTD protein and the resultant MIRTD-deficient cells exhibited a marked decrease in the amounts of subunits of complexes I and IV of the mitochondrial respiratory chain, resulting in a decline of activity. A pulse-label experiment revealed that the loss of the subunits is a post-translational event. Thus, the DLST gene is bifunctional and MIRTD transcribed from the gene contributes to the biogenesis of the mitochondrial respiratory complexes.

Acyltransferases↗
PubMed2003

N-terminal deletion augments the cell-death-inducing activity of BAX in adenoviral gene delivery to nonsmall cell lung cancers.

Therapeutic modalities that overcome the antiapoptotic function of Bcl-2 that is often overexpressed in cancer cells are expected to be a novel strategy for cancer treatment. We previously reported that the leukemic cell death induced by an N-terminally truncated Bax (deltaN Bax: corresponding to amino acid 112-192 of full-length Bax) was not blocked by Bcl-2 or Bcl-x(L) owing to the lack of the BH3 domain needed to interact with the antiapoptotic Bcl-2 family molecules. In this study, we used the Cre-loxP system that allowed us to propagate adenoviruses expressing deltaN Bax, and investigated the effects of the deltaN Bax gene transfer into A549 and NCI-H1299 nonsmall cell lung cancer cell lines. deltaN Bax showed more cell-death-inducing activity in both cells than did the full-length Bax in vitro. It was found that the deltaN Bax-induced cell death was not inhibited by the pan-caspase inhibitor z-VAD-fmk, suggesting that deltaN Bax induces cell death through a caspase-independent mechanism. Intratumoral injection of adenoviruses expressing deltaN Bax into A549 tumors in Balb/c nude mice showed a significantly stronger suppression of tumor growth (74%) than full-length Bax (25%) compared to the control. Our results suggest that deltaN Bax may provide a better alternative than currently used cytotoxic genes in cancer gene therapy trials.

Adenoviridae↗
PubMed2003

Expression of Bcl-2 on leukocytes in prostatic fluid from patients with acute and chronic prostatitis.

In our continuing investigation to clarify the significance of leukocytosis and its prolongation in prostatic fluid (PF) from prostatitis patients, we investigated whether expression of the antiapoptotic gene Bcl-2 on leukocytes in prostatic fluid has any relation with prolonged leukocytosis in prostatitis. The subjects were eight patients with acute bacterial prostatitis (ABP) and eight with nonbacterial prostatitis (NBP) with a history of more than 2 years. Twelve micrograms of protein obtained from leukocytes in PF were subjected to Western blot analysis. Bcl-2 was expressed in seven of eight (87.5%) and six of eight (75.0%) patients with NBP and ABP, respectively. Quantitative density analysis of the Bcl-2 band did not show any statistically significant differences between patients with NBP and those with ABP. These results suggest that the expression of antiapoptotic Bcl-2 on leukocytes in PF is not a cause of leukocyte longevity in long-term prostatitis.

Acute Disease↗
PubMed2003

Continuous culture of novel mitochondrial cells lacking nuclei.

We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin-eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus.

Journal Article↗
PubMed2003

Deficiency in a mitochondrial aldehyde dehydrogenase increases vulnerability to oxidative stress in PC12 cells.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a major role in acetaldehyde detoxification. The alcohol sensitivity is associated with a genetic deficiency of ALDH2. We have previously reported that this deficiency influences the risk for late-onset Alzheimer's disease. However, the biological effects of the deficiency on neuronal cells are poorly understood. Thus, we obtained ALDH2-deficient cell lines by introducing mouse mutant Aldh2 cDNA into PC12 cells. The mutant ALDH2 repressed mitochondrial ALDH activity in a dominant negative fashion, but not cytosolic activity. The resultant ALDH2-deficient transfectants were highly vulnerable to exogenous 4-hydroxy-2-nonenal, an aldehyde derivative generated by the reaction of superoxide with unsaturated fatty acid. In addition, the ALDH2-deficient transfectants were sensitive to oxidative insult induced by antimycin A, accompanied by an accumulation of proteins modified with 4-hydroxy-2-nonenal. Thus, these findings suggest that mitochondrial ALDH2 functions as a protector against oxidative stress.

Aldehyde Dehydrogenase↗
PubMed2003

[Development of the protein therapeutics using the super anti-cell death factor FNK].

A powerful artificial anti-apoptotic factor will be useful for the reproductive therapies for many diseases by prolonging survival of stem cells. For constructing it, we designed the super anti-apoptotic factor by disturbing three intramolecular polar interactions among alpha-helix structures of Bcl-xL. The resultant mutant Bcl-xL, named FNK, was expected to make the pore-forming domain more mobile and flexible than the wild-type. When overexpressed in Jurkat cells, FNK was markedly more potent in prolonging survival following apoptosis-inducing treatment with a kind of cell death cytokines (anti-Fas), a protein kinase inhibitor (staurosporine), cell cycle inhibitors (TN-16, camptothecin, hydroxyurea and trichostatin A) or oxidative stress (hydrogen peroxide and paraquat) than wild-type Bcl-xL. Furthermore, the transfectants of FNK became more resistant against a calcium ionophore and even a heat treatment than wild-type Bcl-xL. In addition, FNK showed marked anti-apoptotic activity in CHO and Jurkat cells deprived of serum. Thus, FNK may be the first mutant generated by site-directed mutagenesis of Bcl-xL with an enhance gain-of-function phenotype. Next, we tried to transduce the FNK protein into cells. Protein therapeutics has the advantage of delivering proteins in a short period of time. We have engineered the anti-apoptotic bcl-x gene to generate the super anti-apoptotic factor, FNK, with a more powerful cytoprotective activity. In this study, we fused the protein transduction domain (PTD) of the HIV/Tat protein to FNK, and used the construct in an animal model of ischemic brain injury. When added into culture media of human neuroblastoma cells and rat neocortical neurons, PTD-FNK rapidly transduced into cells and localized to mitochondria within 1 hr. It protected the neuroblastomas and neurons against staurosporine-induced apoptosis and glutamate-induced excitotoxicity, respectively. The cytoprotective activity of PTD-FNK was found at concentrations as low as 0.3 pM. Additionally, PTD-FNK affected the cytosolic movement of calcium ions, which may relate to its neuroprotective action. Immunohistochemical analysis revealed that myc-tagged PTD-FNK (PTD-myc-FNK) injected intraperitoneally into mice can have access into brain neurons. When injected intraperitoneally into gerbils, PTD-FNK prevented delayed neuronal death in the hippocampus caused by transient global ischemia. These results suggest that PTD-FNK has a potential for clinical utility as a novel protein therapeutic strategy to prevent cell death in the brain. Thus, the protein delivery system will be useful to make cells survived for a long time during the differentiation of stem cells in the reproductive therapies.

Animals↗
PubMed2003

A multi-functional organelle mitochondrion is involved in cell death, proliferation and disease.

The mitochondrion, long considered an organelle specific to energy metabolism, is in fact multi-functional and involved in many diseases. Mitochondrial DNA accumulates somatic mutations during aging, the progression of cancer and diabetes. Most cancer cells contain homoplasmic mutations in the mitochondrial genome. Although little is known about the contributions of mutations to carcinogenesis, some mutations in the nuclear genes encoding mitochondrial proteins have been identified as responsible for certain familial cancers. Mitochondria play an essential role in generating the germ line by releasing mitochondrial ribosomal RNAs, by which the germ line transfers the genetic information necessary for life to the next generation. Collaboration between mitochondria and the cytosol occurs in several metabolic pathways. Many enzymes involved in synthesizing uridine, heme and steroids and in the urea cycle are located inside mitochondria. Notably, a reaction involved in the synthesis of UMP is coupled with the energized state of mitochondria. Thus, the synthesis of DNA and RNA should be indirectly coupled with the energized state of mitochondria. Additionally, storing calcium is an important role of mitochondria. Calcium functions as a second messenger in signal transduction, however, it also activates several proteinases or lipases to induce damage. The mitochondrion plays a significant role in necrosis and is a center for apoptosis, determining its initiation, regulation and execution. Thus, the mitochondrion is widely involved in cell proliferation, cell death and disease.

Animals↗