Establishment and cellular characteristics of a hepatocyte cell line (OUMS-31) derived from an acatalasemic mouse

Compromised glutathione synthesis results in high susceptibility to acetaminophen hepatotoxicity in acatalasemic mice

Acatalasemia is caused by genetic defect in the catalase gene. Human achatalasemia patients are able to scavenge physiological hydrogen peroxide but are vulnerable to exogenous oxidative stress. In the present study, we used an acetaminophen-induced hepatotoxicity model in acatalasemic mice to explore this vulnerability. Interestingly, the acetaminophen-induced decrease in total glutathione levels was more prolonged in acatalasemic mice. While the subunits of glutamate-cysteine ligase, a glutathione synthase enzyme, were increased by acetaminophen in the liver of wild-type mice, their expression was lower and was further reduced by acetaminophen in acatalasemic mice. This feature was also observed in immortalized hepatocytes derived from the livers of these mice. However, when catalase was knocked down in HepG2 cells, a cultured human liver cell line, the expression of glutamate-cysteine ligase subunits was increased, suggesting that the low expression of glutamate-cysteine ligase subunits in acatalasemia may be due to other mechanism than catalase deficiency. Therefore, when other factors were investigated, it was found that transforming growth factor-β1 was up-regulated by acetaminophen in the liver of acatalasemic mice, which may inhibit the expression of glutamate-cysteine ligase subunits. The results of this study suggest a new toxic mechanism of acetaminophen-induced liver injury in patients with acatalasemia.

Animal model for oxidative stress research-Catalase mutant mice

Catalase-deficient mouse strains was initially established by Feinstein et al. through a large scale screening of the progeny of irradiated C3H mice in 1966. Later, Feinstein provided the mice of catalase mutant strain C3H/AnICs(a)Cs(a) (wild-type), C3H/AnICs(b)Cs(b) and C3H/AnlCs(c)Cs(c) to Okayama University Medical School in Japan. It is known that a point mutation at amino acid 11 (from glutamine to histidine) of acatalasemic mouse catalase and a point mutation at amino acid 439 (from as paragine to serine) of hypocatalasemic mouse catalase are responsible for the catalase deficiency of acatalasemic and hypocatalasemic mice, respectively. Recently, a liver cell line from an acatalasemic mouse andEscherichia coli (E. coli) strains with murine normal, hypocatalasemic, or acatalasemic catalase have been established. The construction of these new systems would be useful for studying the effects of oxidative stress at the cellular level. In this review, we give a brief overview of recent findings of studies in utilizing the catalase-deficient mice and evaluate the possibility of these mouse strains as a candidate animal model for oxidative stress research.

Catalase transgenic mice: characterization and sensitivity to oxidative stress

The role of catalase in the antioxidant defense system was studied using transgenic mice [Tg(CAT)] harboring a human genomic clone containing the entire human CAT gene. Catalase activity was 2-fold higher in the tissues of hemizygous [Tg(CAT)(+/o)] mice and 3- to 4-fold higher in the tissues of homozygous [Tg(CAT)(+/+)] mice compared to wild type mice. The human CAT transgene was expressed in a tissue-specific pattern that was similar to the endogenous catalase gene. The levels of other major antioxidant enzymes were not altered in the tissues of the transgenic mice. Hepatocytes and fibroblasts from the Tg(CAT)(+/+) mice were more resistant to hydrogen peroxide-induced cell death but were more sensitive to paraquat and TNFalpha toxicity. Fibroblasts from the Tg(CAT)(+/+) mice showed reduced growth rate in culture without treatment and reduced colony-forming capability after gamma-irradiation compared to fibroblasts from wild type mice. In addition, the Tg(CAT)(+/+) animals were more sensitive to gamma-irradiation.