Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
Mutagenesis. 2012 Jan;27(1):59-66. doi: 10.1093/mutage/ger060. Epub 2011 Oct 4.
Pyrrolizidine alkaloids (PAs) are the most common plant constituents that poison livestock, wildlife and humans. Riddelliine is a prototype genotoxic PA and has been nominated to be classified as a reasonably anticipated human carcinogen by the US National Toxicology Program (NTP) in the 12th Report on Carcinogens. Riddelliine's nomination is due to the high incidence of liver tumours that were observed in both mice and rats in the NTP tumourigenicity bioassay study. In this current study, we explored whether riddelliine treatment could alter microRNA (miRNA) expression in rat liver and whether the possible deregulation of miRNA was related to mutagenicity and carcinogenicity of riddelliine. Groups of six rats were administered riddelliine at a mutagenic dose of 1 mg/kg body weight or with control vehicle 5 days a week for 12 weeks. A group of six rats treated with aristolochic acid, a renal carcinogen, was used as a tissue-specific negative control. The animals were sacrificed 1 day after the last treatment and the livers were isolated for miRNA expression analysis using miRNA microarrays. miRNA expression was significantly altered by riddelliine treatment. Principal component analysis and hierarchical clustering analysis showed that the miRNA expression profiles were clearly classified into two groups, riddelliine treatment versus other samples. Forty-seven miRNAs were significantly dysregulated by riddelliine treatment, among which 38 were up-regulated and 9 were down-regulated. Functional analysis of these differentially expressed miRNAs by riddelliine revealed that these miRNAs were involved in liver carcinogenicity and toxicity, such as liver proliferation, liver necrosis/cell death, hepatocellular carcinoma, liver hepatomegaly, liver inflammation and liver fibrosis. These results suggest that miRNAs actively respond to a mutagenic dose of riddelliine and the pattern of miRNA expression has the potential to be used as a biomarker of genotoxicity and carcinogenicity for riddelliine and possibly other PAs.
吡咯里西啶生物碱（PAs）是最常见的毒害家畜、野生动物和人类的植物成分。里德利碱是一种原型遗传毒性 PA，已被美国国家毒理学计划（NTP）提名为第 12 届致癌物报告中的“合理预期人类致癌物”。里德利碱的提名是由于在 NTP 肿瘤发生生物测定研究中，无论是在小鼠还是大鼠中都观察到了高发生率的肝脏肿瘤。在本研究中，我们探讨了里德利碱处理是否会改变大鼠肝脏中的 microRNA（miRNA）表达，以及 miRNA 的可能失调是否与里德利碱的致突变性和致癌性有关。六组大鼠每周 5 天，以 1mg/kg 体重的致突变剂量或对照载体给予里德利碱处理 12 周。一组六只大鼠用马兜铃酸处理，作为组织特异性阴性对照。最后一次处理后 1 天，处死动物并分离肝脏，用于 miRNA 表达分析的 miRNA 微阵列。里德利碱处理显著改变了 miRNA 的表达。主成分分析和层次聚类分析表明，miRNA 表达谱明显分为两组，一组是里德利碱处理组，另一组是其他样本。里德利碱处理显著下调了 47 个 miRNA，其中 38 个上调，9 个下调。通过里德利碱处理对这些差异表达的 miRNA 进行功能分析表明，这些 miRNA 参与了肝脏致癌性和毒性，如肝增殖、肝坏死/细胞死亡、肝细胞癌、肝肿大、肝炎症和肝纤维化。这些结果表明，miRNA 积极响应致突变剂量的里德利碱，miRNA 表达模式有可能成为里德利碱和可能其他 PA 的遗传毒性和致癌性的生物标志物。
