Hypoxia and Epigenetic Mechanisms for Toxicity

描述(申请人提供)：接触类铁金属会导致多种毒性终点，包括肺和红细胞生成异常，以及癌症。人们提出了许多不同的机制来解释黑色金属的毒性。我们的初步数据和最近的文献表明，低氧信号系统可能在金属诱导的损伤中发挥作用。感知和应对低氧压或低氧的能力对正常生理和一些病理情况至关重要。生物体已经形成了一种应对缺氧的机制，而这一过程的核心是缺氧诱导因子(HIF)。HIF是一种可诱导的转录因子，可以调节一系列基因的表达，这些基因是处理低氧环境所必需的。这些低氧反应基因也会受到类铁金属的影响，如钴和镍。最近，一类作为缺氧诱导因子蛋白氧感受器的脯氨酸羟化酶家族被鉴定出来。这些酶可以被类铁金属抑制，并在缺氧和金属暴露之间提供了联系。这一交叉导致了以下假设：HIF介导的转录对于接触类铁金属引起的细胞损伤和肺毒性是必要的。为了解决这一假设，提出了五个具体目标：1)建立和鉴定Arnt缺陷细胞。2)研究HIF信号在HIF缺陷细胞系金属毒性中的作用。3)确定金属诱导的毒性是否依赖于抑制Pro对HIFs的稳定作用。羟化作用。4)利用RNAi技术确定HIF调控基因在介导金属毒性中的作用。5)利用HIF1-n和Arnt条件性缺失小鼠，确定HIF介导的信号转导是否在金属诱导的肺毒性中是必需的。这项拟议研究的完成将增加我们对黑色金属所使用的信号机制的理解。这些研究将把类铁金属与低氧反应途径及其下游靶基因联系起来。该提案将创建一系列细胞系，这些细胞系将在几个领域产生广泛兴趣，包括肿瘤学、毒理学和药理学。此外，我们对缺氧和HIF介导的信号转导的了解将对发育和癌症生物学有所裨益。最后，这些研究将阐明低氧信号在体内和体外金属毒性中的作用。

DESCRIPTION (provided by applicant): Exposure to ferrous-like metals lead to multiple toxic endpoints, including lung and erythropoietic abnormalities, and cancer. Many different mechanisms have been proposed to explain the toxicity of ferrous-like metals. Our preliminary data and recent publications suggest that the hypoxia signaling system may play a role in metal induced injury. The ability to sense and cope with low oxygen tension, or hypoxia, is critical to normal physiology and several pathological conditions. Organisms have developed a mechanism of coping with hypoxia and central to this process are the hypoxia inducible factors (HIFs). HIFs are inducible transcription factors that regulate the expression of a battery of genes essential to dealing with a hypoxic environment. These hypoxia responsive genes are also affected by ferrous-like metals, such as cobalt and nickel. Recently, a family of prolyl hydroxylases was identified that act as oxygen sensors for the HIF proteins. These enzymes can be inhibited by ferrous-like metals and offer a link between hypoxia and metal exposure. This intersection has led us to the following hypothesis: HIF mediated transcription is necessary for cellular damage and lung toxicity caused by exposure to ferrous-like metals. To address this hypothesis five specific aims are proposed: 1) Create and characterize ARNT deficient cells. 2) Characterize the role of HIF signaling in metal induced toxicity with HIF deficient cell lines. 3) Determine whether metal induced toxicity is dependent upon stabilization of the HIFs through inhibition of prolyl. hydroxylation. 4) Determine the role of HIF regulated genes in mediating metal induced toxicity using RNAi. 5) Determine whether HIF mediated signaling is necessary for metal induced lung toxicity using HIF1 n and ARNT conditional null mice. The completion of the proposed research will increase our understanding of the signaling mechanism used by ferrous-like metals. The studies will link ferrous-like metals to the hypoxia response pathway and its down-stream target genes. The proposal will create a set of cell lines that will have broad interest in several fields, including oncology, toxicology, and pharmacology. In addition, the understanding we gain about hypoxia and HIF mediated signaling will have benefits to developmental and cancer biology. Finally, these studies will elucidate the role of hypoxia signaling in metal induced toxicity in vitro and in vivo.