Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky, United States of America.
PLoS One. 2012;7(6):e38713. doi: 10.1371/journal.pone.0038713. Epub 2012 Jun 15.
The mechanisms by which environmental toxicants alter developmental processes predisposing individuals to adult onset chronic disease are not well-understood. Transplacental arsenic exposure promotes atherogenesis in apolipoprotein E-knockout (ApoE(-/-)) mice. Because the liver plays a central role in atherosclerosis, diabetes and metabolic syndrome, we hypothesized that accelerated atherosclerosis may be linked to altered hepatic development. This hypothesis was tested in ApoE(-/-) mice exposed to 49 ppm arsenic in utero from gestational day (GD) 8 to term. GD18 hepatic arsenic was 1.2 µg/g in dams and 350 ng/g in fetuses. The hepatic transcriptome was evaluated by microarray analysis to assess mRNA and microRNA abundance in control and exposed pups at postnatal day (PND) 1 and PND70. Arsenic exposure altered postnatal developmental trajectory of mRNA and microRNA profiles. We identified an arsenic exposure related 51-gene signature at PND1 and PND70 with several hubs of interaction (Hspa8, IgM and Hnf4a). Gene ontology (GO) annotation analyses indicated that pathways for gluconeogenesis and glycolysis were suppressed in exposed pups at PND1, and pathways for protein export, ribosome, antigen processing and presentation, and complement and coagulation cascades were induced by PND70. Promoter analysis of differentially-expressed transcripts identified enriched transcription factor binding sites and clustering to common regulatory sites. SREBP1 binding sites were identified in about 16% of PND70 differentially-expressed genes. Western blot analysis confirmed changes in the liver at PND70 that included increases of heat shock protein 70 (Hspa8) and active SREBP1. Plasma AST and ALT levels were increased at PND70. These results suggest that transplacental arsenic exposure alters developmental programming in fetal liver, leading to an enduring stress and proinflammatory response postnatally that may contribute to early onset of atherosclerosis. Genes containing SREBP1 binding sites also suggest pathways for diabetes mellitus and rheumatoid arthritis, both diseases that contribute to increased cardiovascular disease in humans.
环境毒物通过何种机制改变了导致个体成年后罹患慢性疾病的发育过程尚不清楚。胎盘中砷暴露会促进载脂蛋白 E 基因敲除（ApoE(-/-)）小鼠的动脉粥样硬化形成。由于肝脏在动脉粥样硬化、糖尿病和代谢综合征中起着核心作用，我们假设加速的动脉粥样硬化可能与肝发育改变有关。本研究在宫内暴露于 49ppm 砷（从妊娠第 8 天到足月）的 ApoE(-/-)小鼠中检验了这一假说。妊娠第 18 天，母鼠肝脏中的砷含量为 1.2μg/g，胎鼠肝脏中的砷含量为 350ng/g。通过微阵列分析评估肝转录组，以评估对照组和暴露组在出生后第 1 天（PND1）和第 70 天（PND70）的新生仔鼠的 mRNA 和 microRNA 丰度。砷暴露改变了新生仔鼠出生后的 mRNA 和 microRNA 谱的发育轨迹。我们在 PND1 和 PND70 时鉴定了一个与砷暴露相关的 51 个基因特征，其中有几个相互作用的中心（Hspa8、IgM 和 Hnf4a）。基因本体（GO）注释分析表明，暴露组在 PND1 时的糖异生和糖酵解途径受到抑制，而 PND70 时的蛋白质输出、核糖体、抗原处理和呈递以及补体和凝血级联途径被激活。差异表达转录物的启动子分析确定了丰富的转录因子结合位点和聚类到常见的调节位点。PND70 时差异表达基因中约有 16%含有 SREBP1 结合位点。Western blot 分析证实，PND70 时肝脏发生变化，包括热休克蛋白 70（Hspa8）和活性 SREBP1 的增加。PND70 时血浆天冬氨酸氨基转移酶（AST）和丙氨酸氨基转移酶（ALT）水平升高。这些结果表明，胎盘中砷暴露改变了胎儿肝脏的发育编程，导致出生后持久的应激和炎症反应，这可能导致动脉粥样硬化的早期发生。含有 SREBP1 结合位点的基因也提示了糖尿病和类风湿关节炎的途径，这两种疾病都会增加人类心血管疾病的风险。
