Effect of IL-15 on APAP Hepatitis Figure 7. The hepatic HO-1 induction was suppressed in Il152/2 than WT mice with APAP challenge. (A) Time course of hepatic HO-1 induction after APAP injection in WT mice. HO-1 (B) mRNAs at 0, 2 and 8 hr and (C) proteins-representative and quantitative data at 8 hr post-APAP treatment. HO-1 (D) mRNA levels and (E) protein-representative and quantitative data of hepatocytes at 8 hr with APAP challenge. #P,0.05, compared with WT 0 hr; *P,0.05; **P,0.01; ***P,0.001. Data are mean 6 SEM from 3,6 mice per group in (A) and 6,8 mice per group in (B,E). doi:10.1371/journal.pone.0044880.g007 the mispairing C57BL/6 controls of genetically engineered mice could lead to confounding results in AILI [43]. Moreover, this study showed the C57BL/6J substrains, which carried the nicotinamide nucleotide transhydrogenase (Nnt) mutation, were less susceptible to AILI than Nnt intact C57BL/6NJ (Nnt+/+) counterparts [43]. We also found that C57BL/6J but not C57BL/ 6NTac/Il152/2 mice carried Nnt mutation by DNA genotyping assay (Figure S4A). Therefore, C57BL/6NTac/Il152/2 mice were backcrossed to C57BL/6J substrains for 4 generations prior to further analysis of IL-15 effect on AILI. Similarly, we confirmed C57BL/6J (Nnt2/2) mice were less susceptible to APAP-hepatitis than C57BL/6NTac (Nnt+/+) counterparts, based on the 8-hr post- challenge serum ALT levels. Furthermore, C57BL/6NTac/Il152/2 or C57BL/6J/Il152/2 mice showed similarly higher susceptibility to APAP than their control counterparts (Figure S4B). Thus, Nnt or contamination of non-C57BL/6J substrain might not be involved in heightened APAP hepatotoxicity in Il152/2 mice of our study. The efficacy of APAP metabolism (Figure 3) and the expressions of hepatic Nrf2-related and ROS detoxification genes (Figure 4) were similar in WT and Il152/2 mice. Therefore, the increased sensitivity of Il152/2 mice might not depend on liver parenchymal cells at the earlier stage of APAP toxicity. Indeed, after APAP challenge, we found productions of pro-inflammatory cytokines IL-1b, TNFa and IFNc, as well as vascular adherence molecules and chemokines [6,39], were greater in Il152/2 than WT mice PLOS ONE | www.plosone.org 9 September 2012 | Volume 7 | Issue 9 | e44880