Faculty Profiles - TOYOKUNI Shinya

Radiation-induced kidney injury: a role for chronic oxidative stress?

Target genes in fenton reaction-induced carcinogenisis: A novel concept International journal

Toyokuni, S, Hiroyasu, M, Ozeki, M, Hiai, H

FREE RADICAL BIOLOGY AND MEDICINE Vol. 33 page： S177 - S177 2002

Target genes in Fenton reaction-induced carcinogenesis: A novel concept International journal

Toyokuni, S, Hiroyasu, M, Ozeki, M, Hiai, H

XI BIENNIAL MEETING OF THE SOCIETY FOR FREE RADICAL RESEARCH INTERNATIONAL page： 459 - 462 2002

Robbins ME, Zhao W, Davis CS, Toyokuni S, Bonsib SM

Micron (Oxford, England : 1993) Vol. 33 ( 2 ) page： 133 - 41 2002

Language：English Publishing type：Research paper (scientific journal) Publisher：Micron

Kidney irradiation clearly leads to a progressive reduction in function associated with concomitant glomerulosclerosis and/or tubulointerstitial fibrosis. However, the particular cell types, mediators and/or mechanisms involved in the development and progression of radiation nephropathy remain ill defined. Angiotensin II (Ang II) plays a major pathogenic role; administration of Ang II blockers markedly abrogates the severity of radiation nephropathy in experimental models. Both ionizing radiation and Ang II signal via generation of reactive oxygen species (ROS). Thus, we hypothesized that localized kidney irradiation might lead to a chronic oxidative stress. In view of the difficulty in measuring ROS in vivo we adopted an indirect immunohistochemical approach in which we used a monoclonal antibody specific for 8hydroxy-2′-deoxyguanosine (8-OHdG), one of the most commonly used markers of DNA oxidation. The right kidney of 7-8 week-old male Sprague-Dawley rats was removed. Five to 6 weeks later the remaining hypertrophied kidney was irradiated with single doses of 0-20.0 Gy X-rays. Groups of rats, three per dose, were killed at 4, 8, 16 and 24 weeks post-irradiation, their kidneys fixed, and sections stained with the 8-OHdG-specific antibody N45.1. For quantitation of glomerular DNA oxidation with the N45.1 antibody stained sections, 50 glomeruli/animal were counted. The presence of any intensely stained nuclei within the glomerular tuft was scored as positive. Quantitation of tubular DNA oxidation employed a 10 × 10 point ocular grid. Sections were examined at 400 magnification; 250 tubular profiles were counted. All tubules with any nuclear staining were scored as positive. Sham-irradiated kidneys showed little evidence of DNA oxidation over the experimental period. In contrast, localized kidney irradiation led to a marked, dose-independent increase in glomerular and tubular cell nuclear DNA oxidation. This increase was evident at the first time point studied, i.e. 4 weeks after irradiation, and persisted for up to 24 weeks postirradiation. DNA oxidation in the irradiated kidney was only seen in apparently viable glomerular and tubular cells. Thus, while from 16 to 24 weeks post-irradiation structural alterations had progressed to glomerular sclerosis and tubular atrophy, positive staining for 8-OHdG was not observed in severely atrophic tubules. Similarly, fewer positive staining cells were noted in glomeruli undergoing sclerosis, while none were seen in totally sclerotic glomeruli. These data support the hypothesis that renal irradiation is associated with a chronic and persistent oxidative stress. © 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/s0968-4328(01)00006-3

Radiation-induced kidney injury: a role for chronic oxidative stress? International journal

Mike E Robbins, Weiling Zhao, Charles S Davis, Shinya Toyokuni, Stephen M Bonsib

Micron (Oxford, England : 1993) Vol. 33 ( 2 ) page： 133 - 41 2002

Language：English Publishing type：Research paper (scientific journal)

Kidney irradiation clearly leads to a progressive reduction in function associated with concomitant glomerulosclerosis and/or tubulointerstitial fibrosis. However, the particular cell types, mediators and/or mechanisms involved in the development and progression of radiation nephropathy remain ill defined. Angiotensin II (Ang II) plays a major pathogenic role; administration of Ang II blockers markedly abrogates the severity of radiation nephropathy in experimental models. Both ionizing radiation and Ang II signal via generation of reactive oxygen species (ROS). Thus, we hypothesized that localized kidney irradiation might lead to a chronic oxidative stress. In view of the difficulty in measuring ROS in vivo we adopted an indirect immunohistochemical approach in which we used a monoclonal antibody specific for 8-hydroxy-2'-deoxyguanosine (8-OHdG), one of the most commonly used markers of DNA oxidation. The right kidney of 7-8 week-old male Sprague-Dawley rats was removed. Five to 6 weeks later the remaining hypertrophied kidney was irradiated with single doses of 0-20.0 Gy X-rays. Groups of rats, three per dose, were killed at 4, 8, 16 and 24 weeks post-irradiation, their kidneys fixed, and sections stained with the 8-OHdG-specific antibody N45.1. For quantitation of glomerular DNA oxidation with the N45.1 antibody stained sections, 50 glomeruli/animal were counted. The presence of any intensely stained nuclei within the glomerular tuft was scored as positive. Quantitation of tubular DNA oxidation employed a 10 x 10 point ocular grid. Sections were examined at 400 magnification; 250 tubular profiles were counted. All tubules with any nuclear staining were scored as positive.Sham-irradiated kidneys showed little evidence of DNA oxidation over the experimental period. In contrast, localized kidney irradiation led to a marked, dose-independent increase in glomerular and tubular cell nuclear DNA oxidation. This increase was evident at the first time point studied, i.e. 4 weeks after irradiation, and persisted for up to 24 weeks postirradiation. DNA oxidation in the irradiated kidney was only seen in apparently viable glomerular and tubular cells. Thus, while from 16 to 24 weeks post-irradiation structural alterations had progressed to glomerular sclerosis and tubular atrophy, positive staining for 8-OHdG was not observed in severely atrophic tubules. Similarly, fewer positive staining cells were noted in glomeruli undergoing sclerosis, while none were seen in totally sclerotic glomeruli. These data support the hypothesis that renal irradiation is associated with a chronic and persistent oxidative stress.

Comparison between high-performance liquid chromatography and enzyme-linked immunosorbent assay for the determination of 8-hydroxy-2′-deoxyguanosine in human urine Reviewed International journal

Shimoi K., Kasai H., Yokota N., Toyokuni S., Kinae N.

Cancer Epidemiology Biomarkers and Prevention Vol. 11 ( 8 ) page： 767 - 770 2002

Language：English Publishing type：Research paper (scientific journal) Publisher：Cancer Epidemiology Biomarkers and Prevention

8-Hydroxy-2′-deoxyguanosine (8-OH-dG), which has been regarded as a potential marker of oxidative DNA damage induced by reactive oxygen species, was measured in human urine by a commercial ELISA using a monoclonal antibody N45.1 and by high-performance liquid chromatography (HPLC) coupled to an electrochemical detector (HPLCECD) to evaluate whether the ELISA system is applicable to human monitoring studies. The urine samples were collected from 120 healthy men ages 18-58 in a steel-manufacturing company. A good correlation (r = 0.833; P < 0.0001) was observed between the two methods on HPLC-purified 8- OH-dG fractions from 23 urine samples. The mean value (±SD) of 8-OH-dG (μg/g creatinine) was 5.47 (±2.97) by HPLC-ECD assay and 5.50 (±2.36) by ELISA. However, the correlation (r) between the two methods on 120 original urine samples was 0.460 [P < 0.001; mean value (±SD) of 8-OH-dG (μg/g creatinine) was 4.46 (±2.03) by the HPLC assay and 9.33 (±3.23) by ELISA]. ELISA estimates were about 2-fold higher than the HPLC estimates on original urine. For an unknown reason, 10% of the urine samples showed more than a 4-fold increase in value by ELISA. It is suggested that the ELISA system is applicable for comparative human monitoring studies. Prepurification of 'samples is required to determine the absolute value of 8-OH-dG in individual urine samples by ELISA.

Amelioration of cisplatin toxicity by a fermented grain food product.

Birth of offspring transplantation of cryopreserved immature testicular pieces and in-vitro microinsemination

Shinohara, T, Inoue, K, Ogonuki, N, Kanatsu-Shinohara, M, Miki, H, Nakata, K, Kurome, M, Nagashima, H, Toyokuni, S, Kogishi, K, Honjo, T, Ogura, A

Human Reproduction Vol. 17 page： 3039-3045 - 3045 2002

Minamiyama Y, Takemura S, Toyokuni S, Nishino Y, Yamasaki K, Hai S, Yamamoto S, Okada S

BioFactors (Oxford, England) Vol. 16 ( 3-4 ) page： 105 - 15 2002

Language：English Publishing type：Research paper (scientific journal) Publisher：BioFactors

The most noticeable hypothesis regarding the pathogenesis of cisplatin toxicity, seen mainly in kidney and intestine, is oxidative stress, an imbalance between free-radical generating cisplatin and radical scavenging systems. This paper describes the role of the antioxidant system in cisplatin-induced toxicity and the protective effect by a processed grain food (Antioxidant Biofactor: AOB®), which has been shown to exhibit strong antioxidant activity. Male Fischer 344 rats were used. They were pre-fed either a basal diet (control, 15 g/day) or the diet supplemented with AOB® to provide 6.5% or 20% of total diet throughout the experiment. Cisplatin (5 mg/kg, i.v.) was administered at the start of the experiment, and the animals were sacrificed 5 days later. Blood urea nitrogen (BUN) and plasma creatinine, NO2- and NO3- (NOx) were determined from the plasma. The levels of 4-hydroxy-2-nonenal (a lipid peroxidation product), 8-hydroxy-deoxyguanosine (8-OHdG, an oxidatively modified DNA adduct) and nitrotyrosine were histologically analyzed. The cisplatin administration resulted in a loss of body weight and elevations of BUN, serum creatinine and NOx levels, whereas AOB supplement reversed these effects. The severe morphological damages induced in the kidney and intestine by the cisplatin administration were markedly improved in the AOB group. The levels of lipid peroxidation, 8-OHdG, and nitrotyrosine all paralleled the morphological damage. The AOB effect was dose dependent. In conclusion, the present study suggests that certain food additives like AOB may be of benefit against the side effects of cisplatin.

DOI： 10.1002/biof.5520160306

Amelioration of cisplatin toxicity by a fermented grain food product. Reviewed International journal

Yukiko Minamiyama, Shigekazu Takemura, Shinya Toyokuni, Yoshihiro Nishino, Keiichi Yamasaki, Seikan Hai, Satoshi Yamamoto, Shigeru Okada

BioFactors (Oxford, England) Vol. 16 ( 3-4 ) page： 105 - 15 2002

Language：English Publishing type：Research paper (scientific journal)

The most noticeable hypothesis regarding the pathogenesis of cisplatin toxicity, seen mainly in kidney and intestine, is oxidative stress, an imbalance between free-radical generating cisplatin and radical scavenging systems. This paper describes the role of the antioxidant system in cisplatin-induced toxicity and the protective effect by a processed grain food (Antioxidant Biofactor: AOB), which has been shown to exhibit strong antioxidant activity. Male Fischer 344 rats were used. They were pre-fed either a basal diet (control, 15 g/day) or the diet supplemented with AOB to provide 6.5% or 20% of total diet throughout the experiment. Cisplatin (5 mg/kg, i.v.) was administered at the start of the experiment, and the animals were sacrificed 5 days later. Blood urea nitrogen (BUN) and plasma creatinine, NO2(-) and NO3(-) (NOx) were determined from the plasma. The levels of 4-hydroxy-2-nonenal (a lipid peroxidation product), 8-hydroxy-deoxyguanosine (8-OHdG, an oxidatively modified DNA adduct) and nitrotyrosine were histologically analyzed. The cisplatin administration resulted in a loss of body weight and elevations of BUN, serum creatinine and NOx levels, whereas AOB supplement reversed these effects. The severe morphological damages induced in the kidney and intestine by the cisplatin administration were markedly improved in the AOB group. The levels of lipid peroxidation, 8-OHdG, and nitrotyrosine all paralleled the morphological damage. The AOB effect was dose dependent. In conclusion, the present study suggests that certain food additives like AOB may be of benefit against the side effects of cisplatin.

Target genes in oxystress-induced carcinogenesis and its molecular mechanisms

TOYOKUNI Shinya

Environmental mutagen research communications Vol. 23 ( 3 ) page： 177 - 182 2001.12

Language：Japanese Publishing type：Research paper (scientific journal)

Oxidative stress has been associated with carcinogenesis. In 1982, our laboratory established an oxys-tress-induced carcinogenesis model of rodent kidney by the use of an iron chelate, ferric nitrilotriacetate. This model is unique in that 1) only carcinoma, not sarcoma, is induced, 2) the induced tumor is of high malignant potential to kill the animal by pulmonary metastasis, peritoneal invasion or rupture of the primary tumor, and, 3) increase in a variety of covalently modified products including 8-oxoguanine, thymine-tyrosine cross-link, 4-hydroxy-2-nonenal and its modified proteins are demonstrated in its early stage. Since in general free radicals are not considered to react with specific target molecules in contrast with immune reaction, we undertook to answer the question whether there is any specific target gene (s) in this carcinogenesis model. By genetically analyzing F_1 hybrid rats, we found two chromosomal areas that showed a high incidence of loss of heterozygosity, which lead to a finding that p15^<INK4B>/p16^<INK4A> tumor suppressor genes are one of the major pathways responsible for this oxystress-induced cancer. Furthermore, by screening 84,000 transcripts by differential display techniques, we found that at least 15 genes associated with stress-response or cellular proliferation are differentially expressed in this model. We believe that not only genetic changes but also epigenetic changes play a role in oxidative stress-induced carcinogenesis.

CiNii Research

Target genes in oxystress-induced carcinogenesis and its molecular mechanisms

TOYOKUNI Shinya

Environmental mutagen research communications Vol. 23 ( 3 ) page： 177 - 182 2001.12

Language：Japanese Publishing type：Research paper (scientific journal)

Activation of lectin-like oxidized low-density lipoprotein receptor-1 induces apoptosis in cultured neonatal rat cardiac myocytes

Iwai-Kanai E., Hasegawa K., Sawamura T., Fujita M., Yanazume T., Toyokuni S., Adachi S., Kihara Y., Sasayama S.

Circulation Vol. 104 ( 24 ) page： 2948 - 2954 2001.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Circulation

Background - Lectin-like oxidized LDL receptor-1 (LOX-1) was originally identified as a receptor expressed predominantly in endothelial cells. LOX-1 can also be expressed in other cell types, and the activation of the LOX-1 pathway has been implicated in apoptosis. There have been no reports, however, about LOX-1 expression in cardiac myocytes or regulation of myocardial cell apoptosis by LOX-1. Methods and Results - In primary cardiac myocytes from neonatal rats, immunohistochemical analyses using a specific monoclonal antibody against LOX-1 demonstrated that LOX-1 expression was markedly induced by stimulation with norepinephrine and endothelin-1. LOX-1 expression was upregulated in cardiac myocytes as well as in vessel walls of failing rat hearts in vivo. In the presence of a low concentration of oxidized LDL that did not induce apoptosis by itself, artificial overexpression of LOX-1 in cardiac myocytes in culture resulted in apoptosis. LOX-1 overexpression induced activation of p38 mitogen-activated protein kinase (MAPK) and oxidative stress in cardiac myocytes, as demonstrated by an increase in positive immunostaining for 8-hydroxy-2′-deoxyguanosine. Inhibition of p38 MAPK by cotransfection of a dominant-negative form of MKK6 as well as by administration of a specific inhibitor, SB203580 or FR167653, almost completely blocked the induction of apoptosis by LOX-1 activation. Antioxidant catalase also blocked LOX-1-induced apoptosis as well as activation of p38 MAPK. Conclusions - These findings demonstrate that LOX-1 expression in cardiac myocytes is induced by neurohormonal factors activated in heart failure and that LOX-1-dependent apoptosis in these cells requires p38 MAPK, a component of oxidant stress-sensitive signaling pathways.

DOI： 10.1161/hc4901.100381