title: Tumor necrosis factor-alpha acts as a complete mitogen for primary rat hepatocytes.
abstract: The cytokine tumor necrosis factor (TNF)-alpha has previously been shown to prime hepatocytes to a state of replicative competence, but has not been shown to act as a complete mitogen for these cells. In the present study we have altered our previously described long-term dimethyl sulfoxide culture system to exclude all known hepatocyte mitogens from the culture media and enable us to directly examine the effects of TNF-alpha on primary rat hepatocytes. We have shown that cells maintained under these culture conditions retain the biochemical and morphological features of well-differentiated hepatocytes. Treatment with TNF-alpha induced DNA synthesis relative to control, to a level not significantly different from that induced by the known hepatocyte mitogen, epidermal growth factor (EGF). Maximal DNA synthesis was induced by treatment with 250 U/ml TNF-alpha for 24 hours. Mitotic figures were observed in cultures treated with TNF-alpha or EGF but not in untreated controls. Treatment of cultures with TNF-alpha, but not EGF, induced activation of both nuclear factor-kappaB p50 homodimers and p50/p65 heterodimers. DNA synthesis induced by TNF-alpha was inhibited by treatment with transforming growth factor-beta. Based on the results of our studies, we conclude that TNF-alpha acts as a complete mitogen for rat hepatocytes.
authors.affiliation: Department of Microbiology, Milton S. Hershey Medical Center, The Penn State College of Medicine, Hershey, Pennsylvania 17033, USA.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Iocca
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Isom
mesh_terms: D000818:Animals; D015415:Biomarkers; D048429:Cell Size; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D006801:Humans; D008297:Male; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D015415:Biomarkers; D008934:Mitogens; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D004247:DNA