Genomic Identification of Potential Risk Factors during Acetaminophen-Induced Liver Disease in Susceptible and Resistant Strains of Mice

Drug-induced liver disease (DILD) continues to cause significant morbidity and mortality and impair new drug development. Mounting evidence suggests that DILD is a complex, multifactorial disease in which no one factor is likely to be an absolute indicator of susceptibility. As an approach to better understand the multifactorial basis of DILD, we recently compared the hepatic proteomes of mice that were resistant (SJL) and susceptible (C57Bl/6) to APAP-induced liver disease (AILD) wherein we identified potential risk factors and mechanistic pathways responsible for DILD. In this study, we have uncovered additional potential risk factors by comparing hepatic mRNA expression profiles of the same two strains of mice with that of SJLxB6-F1 hybrid (F1) mice, which were found to be of intermediate susceptibility to AILD. Global hepatic gene expression profiling over a 24 h period following APAP treatment revealed elevated patterns in the mRNA expression of cytoprotective genes in resistant SJL mice as compared to susceptible B6 mice, while F1 mice had intermediate mRNA expression levels of these genes. One of these genes encoded for heat shock protein (HSP) 70 whose relative protein expression among the three strains of mice was found to parallel that of their mRNA levels, suggesting that this protein had a protective role against AILD. However, there was no difference in the susceptibility of HSP70 knockout (KO) mice to AILD as compared to wild-type (WT) mice. There were also protoxicant genes, such as osteopontin (OPN), with elevated mRNA expression levels in the B6 mice as compared to the SJL mice and with intermediate levels in the F1 mice, suggesting that they may play a role in exacerbating liver injury after APAP treatment. In support of this hypothesis, OPN KO mice were found to be more resistant to AILD than WT mice. Additionally, the results from both the proteomic and the genomic studies were compared. The two approaches were found to be complementary to each other and not simply overlapping. Our findings suggest that comparative gene expression analysis of susceptible and resistant mouse strains may lead to the identification of factors that could have a role in determining the susceptibility of individuals to DILD.

药物性肝损伤（Drug-induced liver disease, DILD）仍是引发显著发病率与死亡率、阻碍新药研发的重要病症。越来越多的证据表明，DILD是一种复杂的多因素疾病，不存在单一因素可作为个体易感性的绝对标志物。为更好地阐明DILD的多因素发病基础，我们近期对比了对乙酰氨基酚诱导的肝损伤（APAP-induced liver disease, AILD）抗性品系SJL小鼠与易感品系C57Bl/6小鼠的肝脏蛋白质组，鉴定出了与DILD相关的潜在危险因素及机制通路。本研究中，我们通过对比上述两种小鼠品系与对AILD呈中等易感性的SJLxB6-F1杂交一代（F1）小鼠的肝脏mRNA表达谱，发现了更多潜在危险因素。对乙酰氨基酚处理后24小时内的全肝脏基因表达谱分析显示，与易感的B6小鼠相比，抗性SJL小鼠的细胞保护基因mRNA表达水平升高，而F1小鼠的此类基因mRNA表达水平处于中间状态。其中一个基因为热休克蛋白（heat shock protein, HSP）70编码，该蛋白在三种小鼠品系中的相对蛋白表达水平与其mRNA水平一致，提示其对AILD具有保护作用。然而，热休克蛋白70基因敲除（HSP70 knockout, KO）小鼠与野生型（wild-type, WT）小鼠对AILD的易感性并无差异。此外还存在骨桥蛋白（osteopontin, OPN）这类前毒性基因，B6小鼠的此类基因mRNA表达水平高于SJL小鼠，而F1小鼠的表达水平处于中间状态，提示其可能在对乙酰氨基酚处理后加重肝损伤。为验证这一假说，我们发现骨桥蛋白基因敲除（OPN KO）小鼠较野生型小鼠对AILD的抗性更强。同时，我们对比了蛋白质组学与基因组学研究的结果，发现两种研究方法互为补充，而非简单重叠。本研究结果表明，对易感与抗性小鼠品系开展比较基因表达分析，有望鉴定出可用于判断个体对DILD易感性的相关因素。