Yusuke Hiraku

Mie University, Tu, Mie, Japan

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Publications (130)435.6 Total impact

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    ABSTRACT: Circulating microRNAs (miRNAs) are emerging as promising non-invasive biomarkers for human cancer. Head and neck squamous cell carcinoma (HNSCC) is a prevalent malignancy worldwide, but its overall survival has remained unchanged in the past three decades. Biomarkers for evaluating efficacy of cancer therapy are urgently needed. To explore circulating miRNAs as cancer therapy biomarkers, we initially identified that eight miRNAs were distinctly dysregulated in cancerous tissues compared with adjacent non-cancerous counterparts from 16 patients, using microarray and real-time PCR. Based on this discovery, the comparison study was performed between pre- and six months post-operative paired plasma samples on nine patients. MiR-99a, which was down-regulated in cancerous tissues, was significantly increased in plasma after operation. Meanwhile, oncomiR miR-21 and miR-223 that were up-regulated in cancerous tissues, were significantly reduced in post-operative plasma samples. We firstly report the significant changes of miR-99a in plasma of HNSCC patients after surgery. Furthermore, plasma miR-223 was inversely increased in a patient whose cancer relapsed within six months after operation. We conclude that these circulating miRNAs may serve as biomarkers to evaluate the efficacy of therapy and the prognosis of HNSCC.
    Cancer biology & therapy 05/2015; 16(7). DOI:10.1080/15384047.2015.1045692 · 3.07 Impact Factor
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    ABSTRACT: We previously demonstrated that melatonin could be used as a chemopreventive agent for inhibiting cholangiocarcinoma (CCA) development in a hamster model. However, the cytotoxic activity of melatonin in cancer remains unclear. In the present study, we investigated the effect of melatonin on CCA cell lines. Human CCA cell lines (KKU-M055 and KKU-M214) were treated with melatonin at concentrations of 0.5, 1 and 2 mM for 48 h. Melatonin treatment exerted a cytotoxic effect on CCA cells by inhibiting CCA cell viability in a concentration-dependent manner. Treatment with melatonin, especially at 2 mM, increased intracellular reactive oxygen species (ROS) production and in turn led to increased oxidative DNA damage and 8-oxodG formation. Moreover, melatonin treatment enhanced the production of cytochrome c leading to apoptosis in a concentration-dependent manner, as indicated by increased expression of apoptosis-related proteins caspase-3 and caspase-7. In conclusion, melatonin acts as a pro-oxidant by activating ROS-dependent DNA damage and thus leading to the apoptosis of CCA cells.
    Oncology Reports 01/2015; 33(3). DOI:10.3892/or.2015.3738 · 2.30 Impact Factor
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    ABSTRACT: Reactive oxygen and nitrogen species have been implicated in diverse pathophysiological conditions, including inflammation, neurodegenerative diseases and cancer. Accumulating evidence indicates that oxidative damage to biomolecules including lipids, proteins and DNA, contributes to these diseases. Previous studies suggest roles of lipid peroxidation and oxysterols in the development of neurodegenerative diseases and inflammation-related cancer. Our recent studies identifying and characterizing carbonylated proteins reveal oxidative damage to heat shock proteins in neurodegenerative disease models and inflammation-related cancer, suggesting dysfunction in their antioxidative properties. In neurodegenerative diseases, DNA damage may not only play a role in the induction of apoptosis, but also may inhibit cellular division via telomere shortening. Immunohistochemical analyses showed co-localization of oxidative/nitrative DNA lesions and stemness markers in the cells of inflammation-related cancers. Here, we review oxidative stress and its significant roles in neurodegenerative diseases and cancer.
    International Journal of Molecular Sciences 12/2014; 16(1):193-217. DOI:10.3390/ijms16010193 · 2.86 Impact Factor
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    ABSTRACT: Methylene blue (MB) is used for various clinical purposes, including chromoendoscopy and methemoglobinemia treatment. However, MB induces tumors of pancreatic islets and small intestine in experimental animals. This finding raises a possibility that MB induces carcinogenicity in these organs via light-independent mechanisms, although MB is known to cause light-dependent DNA damage. We investigated the mechanism of MB-induced DNA damage using (32)P-5'-end-labeled DNA fragments of human tumor-relevant genes. We investigated the redox reaction of MB by UV-visible spectrometry. MB induced DNA damage at the 5'-ACG-3' sequence, a hot spot of the p53 gene, in the presence of NADH and Cu(II). DNA damage was inhibited by catalase and bathocuproine, a Cu(I)-specific chelator. MB induced DNA damage at every nucleotide in the presence of NADH and Fe(III)-ethylenediaminetetraacetic acid, which was inhibited by •OH scavengers and catalase. MB significantly increased the formation of 8-oxo-7,8-dihydro-2'- deoxyguanosine, an oxidative DNA lesion, in the presence of NADH and metal ions. UV-visible spectrometry revealed that the absorbance of oxidized form of MB at 668nm was decreased by NADH, and the addition of metal ions attenuated the spectral change. MB undergoes NADH-dependent reduction followed by metal ion-mediated reoxidation. Reduced metal ions [Cu(I) and Fe(II)] interact with H2O2, generated during the redox reaction, to produce Cu(I)OOH and •OH that cause DNA damage, respectively. These findings suggest that metal-mediated DNA damage contributes to MB-mediated carcinogenesis. General significance This study would provide an insight into the mechanism of MB-induced carcinogenesis and its safety assurance for clinical use.
    Biochimica et Biophysica Acta 05/2014; 1840(9). DOI:10.1016/j.bbagen.2014.04.020 · 4.66 Impact Factor
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    ABSTRACT: Nasopharyngeal carcinoma (NPC) is one of the most prevalent malignant tumors with poor prognosis in Southern China and Southeast Asia. Angiogenesis-related molecules can be promising therapeutic targets in NPC. To investigate the relationships of cancer-associated fibroblasts (CAFs) and chemokine-related molecules with neoangiogenesis, we compared immunohistochemical analyses of alpha-smooth-muscle actin ( α -SMA), stroma-derived factor-1 (SDF-1), and its receptor CXCR4 in primary NPC specimens and chronic nasopharyngitis tissues. In addition, we examined the expression of vascular endothelial growth factor (VEGF-A), and CD133- and VEGF- receptor-2 (VEGFR-2) double positive cells, as endothelial progenitor cells (EPCs). We also assessed CD34-positive microvessels. Significantly higher expression of α -SMA was observed in fibroblasts in NPC stroma. The immunoreactive intensities of SDF-1 and CXCR4 were significantly higher in NPC cells. CXCR4-positive cells and CD133/VEGFR-2- double positive cells were observed in the stroma surrounding cancer nests, and VEGF was detected in both cancer and stromal cells. Microvessel density was significantly higher in the stroma of NPC tissues compared to chronic nasopharyngitis tissues. Our data suggest that CAFs and NPC tumor cells may enhance neoangiogenesis in a VEGF- and SDF-1-dependent manner by recruiting EPCs from the bone marrow into tumor stroma.
    BioMed Research International 04/2014; 2014(2):507353. DOI:10.1155/2014/507353 · 3.17 Impact Factor
  • Yusuke Hiraku · Shosuke Kawanishi
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    ABSTRACT: This chapter discusses the role of 8-nitroguanine in inflammation-related carcinogenesis caused by representative carcinogenic infectious agents such as parasites and viruses, and physicochemical factors. The staining intensity of 8-nitroguanine in soft tumor tissue was associated with poor patient prognosis. The chapter discusses the role of this DNA lesion in tumor progression. In addition to human papillomavirus (HPV) oncoproteins, epidemiological studies have revealed that chronic inflammation is associated with cervical carcinogenesis. 8-Nitroguanine accumulates during the development of chronic inflammation to cancer as a common mechanism and raises the possibility that the DNA lesion can be used as a promising biomarker to assess the risk of inflammation-mediated carcinogenesis at the precancerous stage and predict the prognosis of cancer patients. Several animal experiments demonstrated that iNOS inhibitors, such as ONO-1714 and 1400W, effectively reduced inflammation-related carcinogenesis. Further study is required to clarify the precise molecular mechanisms of inflammation-related carcinogenesis.
    Cancer and Inflammation Mechanisms, 04/2014: pages 41-59; , ISBN: 9781118160305
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    ABSTRACT: Objectives: Asbestos causes lung cancer and malignant mesothelioma, and chronic inflammation is considered to participate in carcinogenesis. However, biomarkers to evaluate its carcinogenic risk have not been established. Reactive oxygen/nitrogen species are generated in biological systems under inflammatory conditions and may contribute to carcinogenesis by causing DNA damage. In this study, we examined the relationship between the formation of 8-nitroguanine (8-nitroG), a mutagenic DNA lesion formed during inflammation, and asbestos contents in human lung tissues. Methods: We obtained non-tumor lung tissues from patients with (n=15) and without mesothelioma (n=21). The expression of 8-nitroG and related molecules was examined by immunohistochemistry, and their staining intensities were semiquantitatively evaluated. Asbestos contents in lung tissues were analyzed by analytical transmission electron microscopy. Results: In subjects without mesothelioma, staining intensities of 8-nitroG and apurinic/apyrimidinic endonuclease 1 (APE1) were significantly correlated with total asbestos and amphibole contents (p<0.05), but not with chrysotile content. In mesothelioma patients, their staining intensities were not correlated with asbestos contents. The double immunofluorescence technique revealed that APE1 was expressed in 8-nitroG-positive cells, suggesting that abasic sites were formed possibly due to the removal of 8-nitroG. The staining intensities of 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative DNA lesion, and its repair enzyme 8-oxoguanine DNA-glycosylase were correlated with age (p<0.05), but not with asbestos contents in subjects without mesothelioma. Conclusions: This is the first study to demonstrate that 8-nitroG formation is associated with asbestos contents in human lung tissues. This finding raises a possibility that 8-nitroG serves as a biomarker that can be used to evaluate asbestos exposure and carcinogenic risk.
    Journal of Occupational Health 03/2014; 56(3). DOI:10.1539/joh.13-0231-OA · 1.11 Impact Factor
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    ABSTRACT: Nitrative and oxidative DNA damage plays an important role in inflammation-related carcinogenesis. Chronic inflammation such as parasite infection and primary sclerosing cholangitis can be an etiological factor of cholangiocarcinoma. Using a proteomic approach and double-fluorescent staining, we identified high expression and co-localization of albumin and cytokeratin-19 in liver fluke-associated cholangiocarcinoma tissues, compared with normal livers from cholangiocarcinoma patients and cadaveric donors, respectively. Albumin was detected not only in cells of liver stem/progenitor cell origin such as canal of Hering, epithelial cells, ductules and ductular reactions, but also hyperplastic bile ducts and the cancer cells of cholangiocarcinoma, suggesting the involvement of stem/progenitor cells in cholangiocarcinoma development. To clarify the involvement of liver stem/progenitor cells in cholangiocarcinoma, we examined several stem/progenitor cell markers (CD133, CD44, OV6 and Oct3/4) in cholangiocarcinoma tissues analyzed by immunohistochemical staining, and measured 8-oxodG levels by using HPLC-ECD as an inflammation-related DNA lesion. In addition, a stem/progenitor cell factor Bmi1, 8-nitroguanine (formed during nitrative DNA damage), DNA damage response (DDR) proteins (phosphorylated ATM and γ-H2AX) and manganese-SOD (Mn-SOD) were analyzed by immunohistochemistry. Stem/progenitor cell markers (CD133, OV6, CD44 and Oct3/4), were positively stained in 56%, 38%, 47% and 56% of 34 cholangiocarcinoma cases, respectively. Quantitative analysis of 8-oxodG revealed significantly increased levels in CD133- and/or Oct3/4-positive tumor tissues compared to negative tumor tissues, as well as 8-nitroguanine formation detected by immunohistochemistry. In the cases of CD44- and/or OV6-positive, no significant difference was observed. Cholangiocarcinoma patients with CD133- and/or Oct3/4 positive tumor tissues showed significantly lower expression of Mn-SOD and higher DDR protein, γ-H2AX. Moreover, CD133- and/or Oct3/4-positive cholangiocarcinoma patients had significant associations with tumor histology types, tumor stage and poor prognoses. Our results suggest that CD133 and Oct3/4 in cholangiocarcinoma were associated with increased formation of DNA lesions and the DDR protein, which may be involved in genetic instability and lead to cholangiocarcinoma development with aggressive clinical features.
    Free Radical Biology and Medicine 07/2013; 65. DOI:10.1016/j.freeradbiomed.2013.07.034 · 5.74 Impact Factor
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    ABSTRACT: Opisthorchis viverrini infection induces inflammation-mediated oxidative stress and liver injury, which may alter α-tocopherol and lipid metabolism. We investigated plasma α-tocopherol and lipid profiles in hamsters infected with O. viverrini. Levels of α-tocopherol, cholesterol, and low-density lipoprotein increased in the acute phase of infection. In the chronic phase, α-tocopherol decreased, while triglyceride and very low-density lipoprotein increased. Notably, high-density lipoprotein decreased both in the acute and chronic phases. In the liver, cholesteryl oleate, triolein, and oleic acid decreased in the acute phase, and increased in the chronic phase. Such chronological changes were negatively correlated with the plasma α-tocopherol level. The expression of α-tocopherol-related molecules, ATP-binding cassette transporter A1 (ABCA1) and α-tocopherol transfer protein, increased throughout the experiment. These results suggest that O. viverrini infection profoundly affects on lipid and α-tocopherol metabolism in due course of infection.
    Parasitology International 11/2012; 62(2). DOI:10.1016/j.parint.2012.11.002 · 1.86 Impact Factor
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    ABSTRACT: Chronic opisthorchiasis caused by Opisthorchis viverrini infection is characterized by advanced periductal fibrosis leading to hepatobiliary diseases (HBD), including cholangiocarcinoma (CCA). We aimed to determine fibrotic markers to differentiate HBD status including opisthorchiasis, benign biliary disease (BBD) and CCA. Candidate fibrotic markers in plasma of healthy individuals (n = 14) and patients with opisthorchiasis (n = 32, pre- and post-treatment with praziquantel), BBD (n = 31), CCA (n = 37) and other types of tumors (n = 14) were measured by ELISA and zymography. Plasma levels of hydroxyproline (HYP), collagen I, MMP-7 and TIMP2 in opisthorchiasis patients were significantly higher than those in healthy individuals, and MMP9/TIMP2 balance may be associated with tissue resorption after praziquantel treatment. HYP and TIMP-2 levels were significantly correlated with periductal fibrosis status evaluated by ultrasonography. Plasma HYP level of CCA patients was the highest among HBD patients (p < 0.05). ROC curves revealed HYP, MMP-7 and collagen I levels significantly distinguished opisthorchiasis, BBD and CCA (p < 0.001). Odd ratio (OR) analysis demonstrated these markers in opisthorchiasis were predictable for BBD risk (p < 0.05; OR = 28.50, 10.12 and 4.63 for collagen I, MMP-7 and HYP, respectively), and the risk was reduced by praziquantel treatment. Interestingly, only plasma HYP level in BBD was predictable for CCA risk (OR = 3.69; p = 0.020). In conclusion, plasma HYP, collagen I and MMP-7 may be useful as novel predictive markers of opisthorchiasis-related BBD, and HYP may be used as a diagnostic marker for CCA.
    International Journal of Cancer 08/2012; 131(4):E416-24. DOI:10.1002/ijc.26443 · 5.09 Impact Factor
  • Nitric Oxide 07/2012; 27:S40. DOI:10.1016/j.niox.2012.04.143 · 3.52 Impact Factor
  • Feiye Guo · Ning Ma · Shosuke Kawanishi · Mariko Murata · Yusuke Hiraku
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    ABSTRACT: Carbon nanotube (CNT) has the potential for applications in industry because of its unique physicochemical property. However, intraperitoneal administration of CNT was reported to cause mesothelioma in experimental animals. Therefore, there is a concern that nanomaterials may induce carcinogenesis in humans. Chronic inflammation may contribute to carcinogenesis induced by fibrous materials. 8-Nitroguanine is a mutagenic DNA lesion formed during inflammation and may play a role in CNT-induced carcinogenesis. In this study, we examined 8-nitroguanine formation in A549 human alveolar epithelial cell line treated with multi-walled CNT (MWCNT) by fluorescent immunocytochemistry. Both MWCNTs with diameter of 20–30 nm (CNT20) and 40–70 nm (CNT40) induced 8-nitroguanine formation in a dose-dependent manner, which persisted for 24 h. MWCNTs significantly induced the expression of inducible nitric oxide synthase (iNOS) for 24 h (p < 0.05). MWCNTs also significantly increased the level of , a hydrolysis product of oxidized NO, in the culture supernatant at 4 and 8 h (p < 0.05). MWCNT-induced 8-nitroguanine formation and iNOS expression were suppressed by inhibitors of iNOS (1400 W), nuclear factor-kB (Bay11-7082), actin polymerization (cytochalasin D) and caveola- (methyl-b-cyclodextrin, MBCD) and clathrin-mediated endocytosis (monodansylcadaverine, MDC). Electron microscopy revealed that MWCNT was mainly located in vesicular structures in the cytoplasm, and its cellular internalization was largely reduced by MBCD and MDC. These results suggest that MWCNT is internalized into cells via endocytosis, and that internalized particles play the key role in inflammatory reactions, including iNOS expression, and resulting nitrative DNA damage, which may contribute to carcinogenesis.
    Nitric Oxide 07/2012; 27:S39. DOI:10.1016/j.niox.2012.04.140 · 3.52 Impact Factor
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    ABSTRACT: Asbestos causes lung cancer and malignant mesothelioma. Chronic inflammation is considered to play a role in asbestos-induced carcinogenesis. Reactive oxygen/nitrogen species generated under inflammatory conditions may contribute to carcinogenesis by causing DNA damage. 8-Nitroguanine is a mutagenic DNA lesion formed during inflammation. In this study, we examined 8-nitroguanine formation in human lung tissues and the association with asbestos exposure.Methods We obtained autopsy and surgical specimens of non-tumor lung tissues of patients with malignant mesothelioma (n = 15) and subjects without asbestos-associated diseases (n = 21). Fiber contents (chrysotile, amphiboles and non-asbestos fibers) in tissues were analyzed by transmission electron microscopy. We performed immunohistochemistry to examine 8-nitroguanine formation in lung tissues, and analyzed the correlation of the staining intensity with fiber contents. This study was approved by the Ethics Committee of Mie University School of Medicine, Japan.ResultsThe fiber contents of chrysotile and amphiboles in lung tissues were significantly larger in mesothelioma patients than in subjects without asbestos-associated diseases (p < 0.01). 8-Nitroguanine formation was observed in alveolar and bronchial epithelial cells and inflammatory cells. In subjects without asbestos-associated diseases, the staining intensity of 8-nitroguanine was significantly correlated with the content of amphiboles (p < 0.05), but not with those of chrysotile and non-asbestos fibers. 8-Nitroguanine formation in mesothelioma patients was not correlated with asbestos and non-asbestos fiber contents.Conclusion These results suggest that the generation of reactive oxygen/nitrogen species and resulting DNA damage are largely accounted for by amphibole fibers. 8-Nitroguanine can be a potential biomarker to evaluate the asbestos exposure and predict carcinogenic risk.
    Nitric Oxide 07/2012; 27:S40. DOI:10.1016/j.niox.2012.04.144 · 3.52 Impact Factor
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    ABSTRACT: Inflammation may activate stem cells via prostaglandin E2 (PGE2) production mediated by cyclooxygenase-2 (COX-2) expression. We performed an immunohistochemical analysis of the expression of stemness markers (Oct3/4 and CD44v6) and COX-2 in urinary bladder tissues obtained from cystitis and cancer patients with and without Schistosoma haematobium infections. Immunoreactivity to Oct3/4 was significantly higher in S. haematobium-associated cystitis and cancer tissues than in normal tissues. CD44v6 expression was significantly higher in bladder cancer without S. haematobium than in normal tissues. COX-2 was located in the cytoplasmic membrane, cytoplasm, and nucleus of the cancer cells. Interestingly, the nuclear localization of COX-2, which was reported to function as a transcription factor, was significantly associated with the upregulation of Oct3/4 and CD44v6 in bladder cancer tissues with and without S. haematobium infection, respectively. COX-2 activation may be involved in inflammation-mediated stem cell proliferation/differentiation in urinary bladder carcinogenesis.
    Mediators of Inflammation 04/2012; 2012:165879. DOI:10.1155/2012/165879 · 3.24 Impact Factor
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    ABSTRACT: Barrett's esophagus (BE), an inflammatory disease, is a risk factor for Barrett's esophageal adenocarcinoma (BEA). Treatment of BE patients with proton pump inhibitors (PPIs) is expected to reduce the risk of BEA. We performed an immunohistochemical study to examine the formation of nitrative and oxidative DNA lesions, 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxygaunosine (8-oxodG), in normal esophageal, BE with pre- and post-treatment by PPIs and BEA tissues. We also observed the expression of an oxidant-generating enzyme (iNOS) and its transcription factor NF-κB, an antioxidant enzyme (Mn-SOD), its transcription factor (Nrf2) and an Nrf2 inhibitor (Keap1). The immunoreactivity of DNA lesions was significantly higher in the order of BEA>BE>normal tissues. iNOS expression was significantly higher in the order of BEA>BE>normal tissues, while Mn-SOD expression was significantly lower in the order of BEA<BE<normal tissues. Interestingly, Mn-SOD expression and the nuclear localization of Nrf2 were significantly increased, and the formation of DNA lesions was significantly decreased in BE tissues after PPIs treatment for 3-6months. Keap1 and iNOS expression was not significantly changed by the PPIs treatment in BE tissues. These results indicate that 8-nitroguanine and 8-oxodG play a role in BE-derived BEA. Additionally, PPIs treatment may trigger the activation and nuclear translocation of Nrf2 resulting in the expression of antioxidant genes, leading to DNA damage suppression. These DNA lesions can be useful biomarkers to predict both the risk of BEA and the efficacy of PPIs treatment to prevent BEA in BE patients.
    Biochemical and Biophysical Research Communications 04/2012; 421(2):280-5. DOI:10.1016/j.bbrc.2012.03.152 · 2.30 Impact Factor
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    ABSTRACT: Nasopharyngeal carcinoma (NPC) is endemic in southern China. In a genome-wide screen for genes inactivated by promoter hypermethylation, we identified Ras-related associated with diabetes (RRAD). Expression of RRAD was down-regulated in 83.3% (30/36) of the biopsies from NPC patients. RRAD was aberrantly methylated in 74.3% (26/35) of primary tumors, but not in normal nasopharyngeal epithelium. Ectopic RRAD expression in NPC cell lines inhibited the cell growth, colony formation, and cell migration. These results indicate that RRAD might act as a functional tumor suppressor and its epigenetic inactivation may play an important role in NPC development.
    Cancer letters 04/2012; 323(2):147-54. DOI:10.1016/j.canlet.2012.03.042 · 5.62 Impact Factor
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    Biomarker, 03/2012; , ISBN: 978-953-51-0577-0
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    ABSTRACT: Carbonylation is an irreversible and irreparable protein modification induced by oxidative stress. Cholangiocarcinoma (CCA) is associated with chronic inflammation caused by liver fluke infection. To investigate the relationship between protein carbonylation and CCA progression, carbonylated proteins were detected by 2D OxyBlot and identified by MALDI-TOF/TOF analyses in pooled CCA tissues in comparison to adjacent nontumor tissues and normal liver tissues. We identified 14 highly carbonylated proteins in CCA tissues. Immunoprecipitation and Western blot analyses of individual samples confirmed significantly greater carbonylation of serotransferrin, heat shock protein 70-kDa protein 1 (HSP70.1), and α1-antitrypsin (A1AT) in tumor tissues compared to normal tissues. The oxidative modification of these proteins was significantly associated with poor prognoses as determined by the Kaplan-Meier method. LC-MALDI-TOF/TOF mass spectrometry identified R50, K327, and P357 as carbonylated sites in serotransferrin, HSP70.1, and A1AT, respectively. Moreover, iron accumulation was significantly higher in CCA tissues with, compared to those without, carbonylated serotransferrin. We conclude that carbonylated serotransferrin-associated iron accumulation may induce oxidative stress via the Fenton reaction, and the carbonylation of HSP70.1 with antioxidative property and A1AT with protease inhibitory capacity may cause them to become dysfunctional, leading to CCA progression.
    Free Radical Biology and Medicine 02/2012; 52(8):1465-72. DOI:10.1016/j.freeradbiomed.2012.01.018 · 5.74 Impact Factor
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    ABSTRACT: Carbon nanotube (CNT) has a promising usage in the field of material science for industrial purposes because of its unique physicochemical property. However, intraperitoneal administration of CNT was reported to cause mesothelioma in experimental animals. Chronic inflammation may contribute to carcinogenesis induced by fibrous materials. 8-Nitroguanine is a mutagenic DNA lesion formed during inflammation and may play a role in CNT-induced carcinogenesis. In this study, we examined 8-nitroguanine formation in A549 human lung alveolar epithelial cells treated with multi-walled CNT (MWCNT) by fluorescent immunocytochemistry. Both MWCNTs with diameter of 20-30 nm (CNT20) and 40-70 nm (CNT40) significantly induced 8-nitroguanine formation at 5 and 10 μg/ml (p<0.05), which persisted for 24h, although there was no significant difference in DNA-damaging abilities of these MWCNTs. MWCNTs significantly induced the expression of inducible nitric oxide synthase (iNOS) for 24 h (p<0.05). MWCNTs also significantly increased the level of nitrite, a hydrolysis product of oxidized NO, in the culture supernatant at 4 and 8 h (p<0.05). MWCNT-induced 8-nitroguanine formation and iNOS expression were largely suppressed by inhibitors of iNOS (1400 W), nuclear factor-κB (Bay11-7082), actin polymerization (cytochalasin D), caveolae-mediated endocytosis (methyl-β-cyclodextrin, MBCD) and clathrin-mediated endocytosis (monodansylcadaverine, MDC). Electron microscopy revealed that MWCNT was mainly located in vesicular structures in the cytoplasm, and its cellular internalization was reduced by MBCD and MDC. These results suggest that MWCNT is internalized into cells via clathrin- and caveolae-mediated endocytosis, leading to inflammatory reactions including iNOS expression and resulting nitrative DNA damage, which may contribute to carcinogenesis.
    Toxicology and Applied Pharmacology 02/2012; 260(2):183-92. DOI:10.1016/j.taap.2012.02.010 · 3.71 Impact Factor

Publication Stats

4k Citations
435.60 Total Impact Points


  • 2001–2014
    • Mie University
      • • Department of Environmental and Molecular Medicine
      • • School of Medicine
      Tu, Mie, Japan
  • 2012
    • Khon Kaen University
      • Faculty of Medicine
      Kawn Ken, Khon Kaen, Thailand
  • 2005
    • Heart Research Institute
      Newtown, New South Wales, Australia
  • 1997–1998
    • Kyoto University
      • Department of Public Health
      Kioto, Kyōto, Japan