Significance of urinary excretion of 8-hydroxy-2'-deoxyguanosine in healthy subjects and liver disease patients.

BACKGROUND/AIMS: Although the importance of reactive oxygen species (ROS) in the pathogenesis of various diseases is stressed, clinical significance of the markers reflecting DNA oxidation such as 8-hydroxy-2'-deoxyguanosine (8-OHdG) remains to be clarified. METHODOLOGY: To examine clinical usefulness of 8-OHdG in healthy individuals in comparison with liver disease patients, urinary excretion of 8-OHdG was measured in 336 healthy individuals and 110 patients with liver disease. RESULTS: In healthy persons, the 8-OHdG excretion was increased in an age-dependent manner. It was positively correlated with cigarettes smoked a day and negatively correlated with body mass index (BMI) (P < 0.05, each). Age, smoking and BMI were independent predictors of urinary 8-OHdG excretion (P < 0.01, P < 0.01 and P < 0.05, respectively). In liver disease, the excretion of 8-OHdG was not changed, as compared with healthy individuals. However, the liver disease patients under the age of 40 had higher values of 8-OHdG than healthy persons. In addition, the urinary excretion of 8-OHdG was higher in patients with hepatitis C virus (HCV) infection than those with hepatitis B virus (HBV) infection. CONCLUSIONS: The results of the present study suggest that measurement of urinary 8-OHdG excretion is useful in assessing DNA oxidation caused by aging, smoking, body composition and liver disease.

Analyses to clarify rich fractions in hepatic progenitor cells from human umbilical cord blood and cell fusion.

Umbilical cord blood (UCB) is a source of hematopoietic stem cells and other stem cells, and human UCB cells have been reported to contain transplantable hepatic progenitor cells. However, the fractions of UCB cells in which hepatic progenitor cells are rich remain to be clarified. In the present study, first, the fractionated cells by CD34, CD38, and c-kit were transplanted via portal vein of NOD/SCID mice, and albumin mRNA expression was examined in livers at 1 and 3 months posttransplantation. At 1 and 3 months, albumin mRNA expression in CD34+UCB cells-transplanted livers was higher than that in CD34- cells-transplanted livers. Albumin mRNA expression in CD34+CD38+ cells-transplanted livers was higher than that in CD34+CD38- cells-transplanted [corrected] liver at 1 month. However, it was much higher [corrected] in CD34+CD38- cell-transplanted livers at 3 months. Similar expression of albumin mRNA was obtained between CD34+CD38+c-kit+ cells- and CD34+CD38-c-kit- cells-transplanted livers, and between CD34+CD38-c-kit+ cells- and CD34+CD38-c-kit- cells-transplanted livers, respectively. Second, fluorescence in situ hybridization and immunohistochemistry were performed to examine whether UCB cells really transdifferentiated into hepatocytes or they only fused with mouse hepatocytes. In mouse liver sections, of 1.2% cells which had human chromosomes, 0.9% cells were due to cell fusion, whereas 0.3% cells were transdifferentiated into human hepatocytes. These results suggest that CD34+UCB cells are rich fractions in hepatic progenitor cells, and that transdifferentiation from UCB cells into hepatocytes as well as cell fusion simultaneously occur in this situation.

Retinoic acid receptor alpha dominant negative form causes steatohepatitis and liver tumors in transgenic mice.

Although attention has focused on the chemopreventive action of retinoic acid (RA) in hepatocarcinogenesis, the functional role of RA in the liver has yet to be clarified. To explore the role of RA in the liver, we developed transgenic mice expressing RA receptor (RAR) alpha- dominant negative form in hepatocytes using albumin promoter and enhancer. At 4 months of age, the RAR alpha- dominant negative form transgenic mice developed microvesicular steatosis and spotty focal necrosis. Mitochondrial beta-oxidation activity of fatty acids and expression of its related enzymes, including VLCAD, LCAD, and HCD, were down-regulated; on the other hand, peroxisomal beta-oxidation and its related enzymes, including AOX and BFE, were up-regulated. Expression of cytochrome p4504a10, cytochrome p4504a12, and cytochrome p4504a14 was increased, suggesting that omega-oxidation of fatty acids in microsomes was accelerated. In addition, formation of H2O2 and 8-hydroxy-2'-deoxyguanosine was increased. After 12 months of age, these mice developed hepatocellular carcinoma and adenoma of the liver. The incidence of tumor formation increased with age. Expression of beta-catenin and cyclin D1 was enhanced and the TCF-4/beta-catenin complex was increased, whereas the RAR alpha/ beta-catenin complex was decreased. Feeding on a high-RA diet reversed histological and biochemical abnormalities and inhibited the occurrence of liver tumors. These results suggest that hepatic loss of RA function leads to the development of steatohepatitis and liver tumors. In conclusion, RA plays an important role in preventing hepatocarcinogenesis in association with fatty acid metabolism and Wnt signaling.