The pathogenic roles of tumor necrosis factor receptor p55 in acetaminophen-induced liver injury in mice

Acetaminophen (APAP) causes a massive production of intrahepatic tumor necrosis factor alpha (TNF-alpha). However, it still remains elusive regarding the roles of TNF-alpha in APAP-induced liver injury. Hence, we examined pathogenic roles of the TNF-alpha-TNF receptor with a molecular weight of 55 kDa (TNF-Rp55) axis in APAP-induced hepatotoxicity using TNF-Rp55-deficient [TNF-Rp55-knockout (KO)] mice. When wild-type (WT) BALB/c and TNF-Rp55-KO mice were intraperitoneally injected with a lethal dose of APAP (750 mg/kg), the mortality of TNF-Rp55-KO mice was marginally but significantly reduced compared with WT mice. Upon treatment with a nonlethal dose (600 mg/kg), WT mice exhibited an increase in serum transaminase levels. Histopathologically, centrilobular hepatic necrosis with leukocyte infiltration was evident at 10 and 24 h after APAP challenge. Moreover, mRNA expression of adhesion molecules, several chemokines, interferon-gamma (IFN-gamma), and inducible nitric oxide synthase (iNOS) was enhanced in the liver. On the contrary, serum transaminase elevation and histopathological changes were attenuated in TNF-Rp55-KO mice injected with APAP (600 mg/kg). The gene expression of all molecules except for IFN-gamma and iNOS was significantly attenuated in TNF-Rp55-KO mice. Moreover, anti-TNF-alpha neutralizing antibodies alleviated liver injury when administered at 2 or 8 h after but not at 1 h before APAP challenge to WT mice. Collectively, the TNF-alpha-TNF-Rp55 axis has pathogenic roles in APAP-induced liver failure.