Biomedical subjects

Takakazu Furutani

Publications and source records attributed to Takakazu Furutani.

4 recordsLinked to original sources

PubMed2006

Hepatitis C virus core protein inhibits deoxycholic acid-mediated apoptosis despite generating mitochondrial reactive oxygen species.

BACKGROUND: Hepatitis C virus (HCV) core protein is known to cause oxidative stress and alter apoptosis pathways. However, the apoptosis results are inconsistent, and the real significance of oxidative stress is not well known. The aim of this study was twofold. First, we wanted to confirm whether core-induced oxidative stress was really significant enough to cause DNA damage, and whether it induced cellular antioxidant responses. Second, we wanted to evaluate whether this core-induced oxidative stress and the antioxidant response to it was responsible for apoptosis changes. METHODS: HCV core protein was expressed under control of the Tet-Off promoter in Huh-7 cells and HeLa cells. We chose to use deoxycholic acid (DCA) as a model because it is known to produce both reactive oxygen species (ROS) and apoptosis. RESULTS: Core expression uniformly increased ROS and 8-hydroxy-2'-deoxyguanosine (8-OHdG) under basal and DCA-stimulated conditions. Core protein expression also increased manganese superoxide dismutase levels. Core protein inhibited DCA-mediated mitochondrial membrane depolarization and DCA-mediated activation of caspase-9 and caspase-3, despite the increase in ROS by DCA. Core protein inhibited DCA-mediated apoptosis by increasing Bcl-x(L) protein and decreasing Bax protein, without affecting the proportion of Bax between mitochondria and cytosol, resulting in suppression of cytochrome c release from mitochondria into cytoplasm. CONCLUSIONS: HCV core protein induces oxidative DNA damage, whereas it inhibits apoptosis that is accompanied by enhancement of ROS production. Thus, oxidative stress and apoptosis modulation by core protein are independent of each other.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2006

Hepatic iron overload induces hepatocellular carcinoma in transgenic mice expressing the hepatitis C virus polyprotein.

BACKGROUND & AIMS: Despite the evidence of hepatic iron overload in patients with chronic hepatitis C, it remains unknown if iron overload is related to hepatocarcinogenesis in this condition. The aim of this study was to determine whether iron overload contributes to development of hepatocellular carcinoma (HCC) in transgenic mice expressing the hepatitis C virus (HCV) polyprotein. METHODS: Male C57BL/6 transgenic mice expressing the HCV polyprotein and nontransgenic littermates were fed an excess-iron diet or control diet. Mice in each group were assessed for altered liver morphology and function and the development of liver tumors. RESULTS: Hepatic iron concentrations in mice fed the excess-iron diet were comparable to those of patients with chronic hepatitis C. There was no inflammation in transgenic and nontransgenic livers. Compared with mice in 3 other groups, transgenic mice fed the excess-iron diet showed marked hepatic steatosis including the centrilobular microvesicular type, ultrastructural alterations of the mitochondria and decreased degradation activity of fatty acid at 6 months, and greater hepatic content of lipid peroxidation products and 8-hydroxy-2'-deoxyguanosine at 12 months after initiation of feeding. The number of proliferating hepatocytes was significantly increased in mice fed the excess-iron diet but was not different between transgenic and nontransgenic mice. Hepatic tumors including HCC developed in 5 of 11 (45%) transgenic mice fed the excess-iron diet but not in mice in other groups at 12 months after initiation of feeding. CONCLUSIONS: Iron overload induces mitochondrial injury and increases the risk of HCC development in transgenic mice expressing the HCV polyprotein.

Animals↗

PubMed2006

Alpha-tocopherol [corrected] and ascorbic acid attenuates the ribavirin [corrected] induced decrease of eicosapentaenoic acid in erythrocyte membrane in chronic hepatitis C patients.

BACKGROUND: Oxidative damage of the erythrocyte membrane plays an important role in ribavirin-induced anemia. The purpose of the present paper was to assess whether supplementation of alpha-tocopherol and ascorbic acid (vitamins) causes changes in the erythrocyte membrane fatty acid composition during interferon and ribavirin combination therapy for chronic hepatitis C patients. METHODS: Fatty acid compositions in erythrocyte membrane phospholipids were determined by gas chromatography at 0, 2, 4, 8 weeks, and at the end of combination therapy (26 weeks) for interferon with ribavirin in 32 patients with chronic hepatitis C who were randomized to receive vitamins or not (controls). RESULTS: Good compliance with orally administered vitamins and ribavirin were confirmed by their concentrations in erythrocytes or plasma. The hemoglobin level was negatively correlated with the ribavirin concentration at 8 weeks (r = 0.59, P = 0.01) after initiation of therapy in controls, but not in the vitamin group. Among the 26 kinds of fatty acids analyzed, only eicosapentaenoic acid (EPA) significantly decreased at 8 weeks after initiation of therapy (P = 0.03) and at the end of therapy (P = 0.004) in controls. Vitamins did not inhibit ribavirin-induced anemia, but attenuated the decrease of EPA in erythrocytes. The EPA level was negatively correlated with the drop in hemoglobin levels at 8 weeks after initiation of therapy in controls (r = 0.58, P = 0.015), but not in the vitamin group. CONCLUSIONS: Supplementation of alpha-tocopherol and ascorbic acid attenuates the ribavirin-induced decrease of EPA in erythrocyte membrane phospholipids in chronic hepatitis C patients.

Ascorbic Acid↗

PubMed2005

In situ detection of oxidized n-3 polyunsaturated fatty acids in chronic hepatitis C: correlation with hepatic steatosis.

BACKGROUND: Oxidative stress contributes to the pathogenesis of chronic hepatitis C. The aim of this study was to assess the peroxidation of n-3 polyunsaturated fatty acids (PUFAs) in the liver and its relation to hepatic steatosis in chronic hepatitis C. METHODS: We immunohistochemically detected malondialdehyde (MDA)-, 4-hydroxy-2-nonenal (HNE)-, and 4-hydroxy-2-hexenal (HHE)-protein adducts in liver biopsy specimens from 55 patients with chronic hepatitis C. Cells stained positively for HHE-protein adducts were quantified using computer-based image analysis. Fatty-acid composition was determined, by gas chromatography, for the noncancerous portions of resected livers, with or without steatosis, obtained from two patients with hepatitis C virus-associated hepatocellular carcinoma. RESULTS: The detection rate of HHE-protein adducts (63.6%) was significantly higher than that of MDA-protein adducts (21.8%; P < 0.001) or HNE-protein adducts (29.1%; P < 0.001). Areas positively stained for HHE-protein adducts (HHE-positive areas) were significantly larger in 18 patients with steatosis (6.2 +/- 3.6%) than in 17 patients without steatosis (3.4 +/- 2.6%; P = 0.01). Resected liver tissue with steatosis showed a larger HHE-positive area (18.6%) and higher ratio of n-6 PUFA content to n-3 PUFA content (3 : 1) than liver tissue without steatosis (7.2%; 2 : 3). On multivariate analysis, the HHE-positive area (odds ratio, 1.55; 95% confidence interval [CI], 1.08-2.23; P = 0.019) was a factor associated with the presence of hepatic steatosis. CONCLUSIONS: HHE-protein adducts, which are a good marker for oxidative stress, are associated with steatosis in chronic hepatitis C.

Adult↗