A new human hepatoma cell line to study repeated cell toxicity.

Early toxicity screening of new drugs is performed to select candidates for development. Many cell models are used to assess basic cytotoxicity and to show a good correlation with acute toxicity. However, their correlation with chronic in vivo exposure is inadequate. The new hepatoma cell line (HBG BC2) possesses the capacities of being reversibly differentiated in vitro, and of maintaining a relatively higher metabolic rate when in the differentiated phase (3 weeks) as compared to Hep G2 cells. MTT reduction was used to evaluate the toxicity of propranolol, perhexiline, aspirin and paracetamol, after both single and repeated treatments (three times a week for 2 weeks). Under conditions of repeated treatment, cytotoxicity was observed at lower doses when compared with single administration. Moreover, the first non-toxic doses were in the same range as plasma concentrations measured in humans during therapeutic use. Our results suggest that the new human hepatoma HBG BC2 cell line may be of interest for the evaluation of cell toxicity under repeated treatment conditions.

Histopathological and molecular changes during apoptosis produced by 7H-dibenzo[c,g]-carbazole in mouse liver.

The topical administration of 7H-dibenzo[c,g]carbazole (7H-DBC) at very low but repeated doses causes genotoxic effects such as DNA adduct formation and produces hepatocellular apoptosis in mouse liver. The purpose of this work was to investigate the alterations in gene expression and protein levels of biomarkers associated with the p53 pathway in mouse liver after exposure to cumulative low doses of 7H-DBC by skin paint applications. The compound was administered topically at the dose of 13.35 microg per animal every 2 days to give either 6, 8, 10, or 12 applications. Animals were sacrificed 48 hours after the different treatments. The apoptotic index increased with the number of applications, with a major proportion of apoptotic cells in the periportal areas. A significant increase of Bax mRNA and protein expression was observed after the 8th application whereas the expression of mRNA levels of Fas and p53 did not show significant differences between treated and control animals. Nuclear staining of p53 was detected in hepatocyte nuclei showing the activation of this protein. Later in the apoptosis process we observed the up-regulation of TGF-beta1 in parenchymal cells. In addition to the induction of the p53 apoptosis pathway in vivo by 7H-DBC, we have observed molecular changes related to cell proliferation such as the overexpression of the antiapoptotic gene Bcl-2.