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INFLAMMATION/IMMUNITY/MEDIATORS
1Environmental and Occupational Health Sciences Institute, Rutgers University and University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854-8020; and 2Pharmaceutical Research Institute, Bristol-Myers Squibb, Princeton, New Jersey 08543
Submitted 12 May 2003 ; accepted in final form 27 June 2003
Tumor necrosis factor (TNF)-
is a macrophage-derived proinflammatory cytokine implicated in hepatotoxicity. In the present studies, p55 TNF receptor 1 (TNFR1) -/- mice were used to assess the role of TNF-
in acetaminophen-induced antioxidant defense. Treatment of wild-type (WT) mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis and increased serum alanine transaminases. This was correlated with a rapid depletion of hepatic glutathione (GSH). Whereas in WT mice GSH levels returned to control after 612 h, in TNFR1-/- mice recovery was delayed for 48 h. Delayed induction of heme oxygenase-1 and reduced expression of CuZn superoxide dismutase were also observed in TNFR1-/- compared with WT mice. This was associated with exaggerated hepatotoxicity. In WT mice, acetaminophen caused a time-dependent increase in activator protein-1 nuclear binding activity and in c-Jun expression. This response was significantly attenuated in TNFR1-/- mice. Constitutive NF-
B binding activity was detectable in livers of both WT and TNFR1-/- mice. A transient decrease in this activity was observed 3 h after acetaminophen in WT mice, followed by an increase that was maximal after 612 h. In contrast, in TNFR1-/- mice, acetaminophen-induced decreases in NF-
B activity were prolonged and did not return to control levels for 24 h. These data indicate that TNF-
signaling through TNFR1 plays an important role in regulating the expression of antioxidants in this model. Reduced generation of antioxidants may contribute to the increased sensitivity of TNFR1-/- mice to acetaminophen.
liver; cytokines; oxidative stress; tissue injury; transcription factors
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