Yoshio Takino

Effect of cisplatin on the activities of enzymes which protect against lipid peroxidation

Increases in lipid peroxide in kidneys of rats treated with cisplatin were examined in relation to decreases in the activities of Cu,Zn-superoxide dismutase (Cu,Zn-SOD), Mn-SOD, glutathione peroxidase (GSHpx), glutathione S-transferase (GST) and catalase. The activities of catalase, GSHpx and GST in the kidney and the liver were significantly decreased after cisplatin administration. The decrease of GST activity in the kidney was 87.3%, this was the largest decrease among these enzymes in the tissues examined. Cu,Zn-SOD activity significantly decreased only in the kidney. In contrast, the activities of these enzymes in the heart and the lung, which showed no increase in lipid peroxide in our previous study, were not significantly decreased. Cisplatin does not directly increase lipid peroxidation in vitro; therefore, the increase of lipid peroxide in the kidneys of these rats treated with cisplatin can be attributed to a decrease in the activities of lipid peroxide-protecting enzymes.

Effect of Adriamycin on the Activities of Superoxide Dismutase, Glutathione Peroxidase and Catalase in Tissues of Mice

The increment of lipid peroxide in the hearts of mice treated with adriamycin (ADR) was examined in relation to the decrease in the activities of Superoxide dismutase (SOD), glutathione peroxidase (GSHpx) and catalase. The natural activities of these enzymes in mouse heart are lower than those in the liver. The biggest decrease in enzyme activity observed in the heart after ADR administration was that of GSHpx. Therefore, the increment of lipid peroxide was attributable to the decrease in the activities of these enzymes, especially GSHpx. Subsequently, the effects of antioxidants on the decreases in activities of SOD, GSHpx and catalase in the hearts of mice treated with ADR were examined. However, the decrease in the activities of the enzymes were not accompanied with any increment of lipid peroxide. This result suggests that active oxygen radicals produced by ADR through the agents redox cycling have no effect on the activities of these enzymes. Therefore, it appears that the decrease in the activities of these enzymes induced by ADR in the mouse results from inhibition of enzyme protein biosynthesis.

Mechanism of caffeine modulation of the antitumor activity of adriamycin

We examined the effects of a combination of adriamycin (ADR) and caffeine on DNA and protein biosynthesis and on the activities of DNA polymerase alpha and beta in normal and tumor tissue. The decrease in DNA and protein biosynthesis in tumor produced by caffeine combined with ADR were 2.5 and 2.4 times greater, respectively, compared with ADR alone. The combination of caffeine and ADR enhanced the decrease in DNA polymerases activities in the tumor which was induced by ADR, the decreases being 1.8 and 1.6 times greater, respectively, than that of ADR alone. In contrast, these ADR-induced changes in normal tissues were not enhanced by the combination with caffeine. The combination with caffeine had no effect on ADR concentration in normal tissues, but in the tumor, it increased the ADR concentration to 2.1 times that of ADR alone. In vitro, ADR efflux from Ehrlich ascites carcinoma cells was significantly inhibited by exposure to caffeine. These findings indicate that the effect of caffeine on ADR concentration in the cell plays an important role in the mechanism by which caffeine enhances ADR antitumor activity.

Effect of Adriamycin on DNA, RNA and Protein Biosyntheses in Mouse Tissues, in Connection with Its Cardiotoxicity

We examined whether the cause of the remarkable decreases in the activities of lipid peroxidationpreventive enzymes in the heart of adriamycin (ADR)‐treated mice might be related to inhibition of DNA, RNA or protein biosynthesis. It was found that biosyntheses of DNA, RNA and protein in the heart, liver and kidney of mice were markedly inhibited by ADR (15 mg/kg, ip). The inhibitory effects of ADR on each type of biosynthesis were particularly marked in the heart among the tissues examined. Strong correlations between the percentage inhibition of DNA and protein biosynthesis by ADR, and the percentage decrease in the activities of lipid peroxidationpreventive enzymes were observed in the heart, liver, kidney and lung, especially for the decrease of glutathione peroxidase activity and the inhibition of DNA and protein biosyntheses. We also found that marked decreases of DNA, RNA and protein biosyntheses in ADR‐treated mice occurred not only in the heart but also in tumor tissues. From these results, we conclude that the increment of cardiac lipid peroxide in ADR‐treated mice, which is closely related to the cardiotoxicity of ADR, results from inhibition of DNA, RNA and protein biosyntheses after the distribution of ADR.