Recent evidence suggests that a deficiency in one or more hepatoprotective regulatory mechanisms may contribute to determining susceptibility in drug-induced liver disease. In the present study, we investigated the role of interleukin (IL)-13 in acetaminophen (APAP)-induced liver disease (AILD). Following APAP (200 mg/kg) administration to male C57BL/6 wild-type (WT) mice, hepatotoxicity developed up to 24 h post-APAP, with a concomitant increase in serum IL-13 concentration. Pretreatment of these mice with an IL-13-neutralizing antibody exacerbated liver injury, as did APAP administration to IL-13 knockout (KO) mice in comparison to WT mice. No difference was observed in either overall APAP-protein adduct formation or liver glutathione levels between KO and WT mice following APAP administration, suggesting that the increased susceptibility of IL-13 KO mice to AILD was not due to enhanced APAP bioactivation but rather injurious downstream events. In this regard, multiplex antibody arrays were used to identify potential IL-13-regulated biomarkers, including various cytokines and chemokines, as well as nitric oxide (NO), associated with AILD that were present at higher concentrations in the sera of APAP-treated IL-13 KO mice than in WT mice. Subsequent inhibition studies determined interferon-gamma, NO, neutrophils, natural killer cells, and natural killer cells with T-cell receptors had pathologic roles in AILD in IL-13 KO mice. Taken together, these results suggest that IL-13 is a critical hepatoprotective factor modulating the susceptibility to AILD and may provide hepatoprotection, in part, by down-regulating protoxicant factors and cells associated with the innate immune system.

Bacterial endotoxin (lipopolysaccharide; LPS) given to animals in large doses results in pronounced, midzonal liver injury. Exposure to smaller, non-injurious doses of LPS augments the toxicity of certain hepatotoxicants. This study was conducted to delineate the development of injury in a rat model of augmentation of aflatoxin B(1) (AFB(1)) hepatotoxicity by LPS. At large doses (i.e., > 1 mg/kg, ip), AFB(1) administration resulted in pronounced injury to the periportal regions of the liver. Male, Sprague-Dawley rats (250-350 g) were treated with 1 mg AFB(1)/kg, ip or its vehicle (0.5% DMSO/saline) and 4 h later with either E. coli LPS (7.4 x 106 EU/kg, iv) or its saline vehicle. Liver injury was assessed 6, 12, 24, 48, 72, or 96 h after AFB(1) administration. Hepatic parenchymal cell injury was evaluated as increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in serum and from histologic examination of liver sections. Biliary tract alterations were evaluated as increased concentration of serum bile acids and activities of gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), and 5'-nucleotidase (5'-ND) in serum. At all times and for all markers, injury in rats treated with either AFB(1) or LPS alone was absent or modest. In the AFB(1)/LPS cotreated group, hepatic parenchymal cell injury was pronounced by 24 h and had returned to control values by 72 h. The injury began in the periportal region and spread midzonally with time. Furthermore, changes in serum markers indicative of biliary tract alterations were evident by 12 h and had returned to control values by 72 h. Thus, the nature of the hepatic lesions suggested that LPS potentiated the effects of AFB(1) on both parenchymal and bile duct epithelial cells.

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Recent studies in mice suggest that stress-activated c-Jun N-terminal protein kinase 2 (JNK2) plays a pathologic role in acetaminophen (APAP)-induced liver injury (AILI), a major cause of acute liver failure (ALF). In contrast, we present evidence that JNK2 can have a protective role against AILI. When male C57BL/6J wild type (WT) and JNK2 −/− mice were treated with 300mg APAP/kg, 90% of JNK2 −/− mice died of ALF compared to 20% of WT mice within 48 h. The high susceptibility of JNK2 −/− mice to AILI appears to be due in part to deficiencies in hepatocyte proliferation and repair. Therefore, our findings are consistent with JNK2 signaling playing a protective role in AILI and further suggest that the use of JNK inhibitors as a potential treatment for AILI, as has been recommended by other investigators, should be reconsidered. KeywordsAcetaminophen; Cyclin D1; Hepatoprotection; c-Jun N-terminal kinase 2; JNK2; Liver injury; Proliferating cell nuclear antigen; Repair Overdose of APAP, a popular antipyretic and analgesic, is a leading cause of ALF resulting in approximately 1,800 deaths per year in the United States [1]. Although the initiating events in AILI have been attributed to reactive metabolite and protein adduct formation as well as glutathione depletion [2][3][4], the downstream signaling pathways controlling or promoting the severity of AILI have become of a great interest to many researchers [5][6][7][8][9][10][11][12][13][14]. One of these pathways involves JNK, which when activated is known to influence important cellular events, including alterations in gene expression [15], cell death [16], cellular proliferation and survival [17][18][19][20].Recent studies involving AILI in JNK2 −/− mice have led to conflicting results where JNK2 −/− mice were found to be either less susceptible [21] Animals and APAP treatmentSeven to 9 week-old male WT, JNK1 −/− and JNK2 −/− mice on a C57BL/6J background were purchased from Jackson Laboratories (Bar Harbor, ME). Mice were acclimated for at least 1 week to a 12-h light/dark cycle in a humidity and temperature-controlled, specific-pathogenfree environment in microisolator autoclaved cages. Mice were allowed autoclaved food and water ad libitum until experimental use. Before each study, mice were fasted overnight (14-16h; free access to water) to uniformly deplete hepatic GSH stores [23]. Food supplies were restored after intraperitoneal administration of APAP (300mg/kg in warm saline; 20ml/kg) or saline vehicle (20ml/kg). All maintenance of animals conformed to the guidelines for humane treatment set by the Association for Assessment and Accreditation for Laboratory Animal Care International's Guide for the Care and Use of Laboratory Animals and by the National Institutes of Health. Sera and tissue collectionBlood samples were collected and allowed to clot in microtainer serum separator tubes (Becton Dickinson and Co., Franklin Lakes, NJ) for approximately 2h at room temperature and then centrifuged. Serum was separated and used for ALT measurements. A por...