Apoptosis induced by transforming growth factor-beta in fetal hepatocyte primary cultures: involvement of reactive oxygen intermediates

• Published in: The Journal of biological chemistry Vol. 271; no. 13; p. 7416
• Main Authors: Sánchez, A, Alvarez, A M, Benito, M, Fabregat, I
• Format: Journal Article
• Language: English
• Published: United States 29.03.1996
• Subjects: Animals; Apoptosis - drug effects; Ascorbic Acid - pharmacology; Blotting, Northern; Cell Division - drug effects; Cell Nucleus - drug effects; Cells, Cultured; DNA - drug effects; DNA - metabolism; DNA Probes; Dose-Response Relationship, Drug; Epidermal Growth Factor - pharmacology; Fetus; Flow Cytometry; Free Radical Scavengers - pharmacology; Gene Expression - drug effects; Genes, fos; Glutathione - metabolism; Kinetics; Liver - cytology; Liver - drug effects; Liver - physiology; Mice; Oxidative Stress; Proto-Oncogene Proteins c-fos - biosynthesis; Rats; Rats, Wistar; Reactive Oxygen Species - metabolism; RNA, Messenger - biosynthesis; Transforming Growth Factor beta - pharmacology
• ISSN: 0021-9258
• DOI: 10.1074/jbc.271.13.7416

Transforming growth factor-beta (TGF-beta), a growth regulator of fetal hepatocytes in primary culture, also regulates death of these cells. Dose-response analysis showed that the TGF-beta concentration needed to induce hepatocyte death (2.5 ng/ml) was 5 times that needed to inhibit growth in these cells (0.5 ng/ml). In response to TGF-beta, hepatocytes induced DNA fragmentation and the appearance of nuclei with a DNA content lower than 2C (diploid content), typical of a programmed cell death model. TGF-beta-induced apoptosis in fetal hepatocytes was preceded by an induction of reactive oxygen species production and a decrease in the glutathione intracellular content, indicating that this factor induces oxidative stress in fetal hepatocytes. Studies performed to analyze levels of c-fos mRNA, a gene whose expression is modulated by redox state, demonstrated that only high, apoptotic concentrations of TGF-beta (2.5 ng/ml) produced an increase in the mRNA levels of this gene, the level of induction being similar to that found when cells were incubated in the presence of tert-butyl hydroperoxide. Gel mobility shift assays showed that the c-fos-induced expression was coincident with an increase in AP-1 activity. Finally, cell death induced by TGF-beta in fetal hepatocytes was partially blocked by radical scavengers, which decreased the percentage of apoptotic cells, whereas these agents did not modify the growth-inhibitory effect elicited by TGF-beta in these cells. In summary, the results presented in this paper provide evidence for the involvement of an oxidative process in the apoptosis elicited by TGF-beta in fetal hepatocytes.