title: Role of tumor necrosis factor receptor 1 (p55) in hepatocyte proliferation during acetaminophen-induced toxicity in mice.
abstract: Hepatocyte proliferation represents an important part of tissue repair. In these studies, TNF receptor 1 (TNFR1) knockout mice were used to analyze the role of TNF-alpha in hepatocyte proliferation during acetaminophen-induced hepatotoxicity. Treatment of wild-type (WT) mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis. This was associated with proliferation of hepatocytes surrounding the damaged areas, which was evident at 24 h. The cell cycle regulatory proteins, cyclin D1 and cyclin A, were also up regulated in hepatocytes. In contrast, in TNFR1-/- mice, which exhibit exaggerated acetaminophen hepatotoxicity, hepatocyte proliferation, and expression of cyclin D1 and cyclin A, as well as the cyclin dependent kinases, Cdk4 and Cdk2, were reduced. The cyclin-dependent kinase inhibitor p21 was also induced in the liver following acetaminophen administration. This was greater in TNFR1-/- mice compared to WT mice. To investigate mechanisms mediating the reduced hepatic proliferative response of TNFR1-/- mice, we analyzed phosphatidyl inositol-3-kinase (PI-3K) signaling. In both WT and TNFR1-/- mice, acetaminophen caused a rapid increase in total PI-3K within 3 h. Acetaminophen also increased phosphorylated PI-3K, but this was delayed 6-12 h in TNFR1-/- mice. Expression of Akt, a downstream target of PI-3K, was increased in both WT and TNFR1-/- mice in response to acetaminophen. However, the increase was greater in WT mice. Acetaminophen-induced expression of phosphorylated STAT3, a key regulator of cytokine-induced hepatocyte proliferation, was also delayed in TNFR1-/- mice relative to WT. These data suggest that TNF-alpha signaling through TNFR1 is important in regulating hepatocyte proliferation following acetaminophen-induced tissue injury. Delayed cytokine signaling may account for reduced hepatocyte proliferation and contribute to exaggerated acetaminophen-induced hepatotoxicity in TNFR1-/- mice.
authors.affiliation: Environmental and Occupational Health Sciences Institute, Rutgers University and University of Medicine and Dentistry of New Jersey--Robert Wood Johnson Medical School, Piscataway, NJ 08854-8020, USA
authors.forename: Hawjyh
authors.initials: H
authors.lastname: Chiu
authors.forename: Carol R
authors.initials: CR
authors.lastname: Gardner
authors.forename: Donna M
authors.initials: DM
authors.lastname: Dambach
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Durham
authors.forename: Jennie A
authors.initials: JA
authors.lastname: Brittingham
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Laskin
authors.forename: Debra L
authors.initials: DL
authors.lastname: Laskin
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D018712:Analgesics, Non-Narcotic / Q000633:toxicity*; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D019925:Cyclin A / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D018124:Receptors, Tumor Necrosis Factor / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D018712:Analgesics, Non-Narcotic; D015703:Antigens, CD; C493957:Cdkn1a protein, mouse; D019925:Cyclin A; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019938:Cyclin D1; D000082:Acetaminophen; D019869:Phosphatidylinositol 3-Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; C495902:Cdk4 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases