Inhibition of hepatic cell nuclear DNA fragmentation by zinc in carbon tetrachloride-treated rats

Background/Aims: The aims of this study were to ascertain: 1) whether hepatic cell DNA fragmentation is increased in rats with early stages of liver disease induced by carbon tetrachloride; 2) whether the inhibition of DNA cleavage is involved in the hepatoprotective effects of zinc; and 3) if relationships exist between DNA fragmentation and the onset of fibrosis in this experimental model. Methods: Twenty-one treated rats and 23 controls were divided into two groups to receive either a standard diet or one supplemented with zinc. All the animals were sacrificed 1 week later for histological and biochemical assessments, which included a DNA fragmentation index, hepatic zinc and metallothionein concentrations, fibrosis measured by hepatic hydroxy-proline concentration and plasma alanine aminotransferase activity. Results: Hepatic cell DNA fragmentation was increased in rats with early hepatic fibrosis and the increase was independent of hepatocytolysis, as measured by alanine aminotransferase activity. Oral zinc administration inhibited hepatic cell DNA fragmentation in the treated rats and was proportional to the hepatic concentration of the metal. The mechanism of the zinc-mediated decrease in DNA cleavage was related to an increase in the hepatic metallothionein concentration. Hepatic cell DNA fragmentation was related to hydroxyproline concentration. Conclusions: Our results suggest that apoptosis may be involved in the early transformations occurring in the liver and which can lead to the initiation of cirrhosis. As such, the potential therapeutic use of zinc supplementation would warrant further investigation.