Elucidating epigenetic mechanisms of cellular cadmium toxicity

摘要 镉(Cd)是一种广泛存在的环境污染物，影响着全球数百万人。CD 对人体的接触最常通过CD的许多工业应用，或消费 受污染的食物。由于其极长的生物半衰期，镉在组织中持续存在数十年，主要是 在肝脏和肾脏。镉有许多有害的影响，包括骨骼、生殖、 神经发育、肺部毒性和致癌。肾脏是Cd的主要靶点 毒性，尤其是近端肾小管上皮细胞，损伤会阻碍肾小管的重吸收。尽管 与人体接触Cd有关的许多后遗症，Cd毒性的特定分子机制是 人们对此知之甚少，也没有特定的治疗方法来减轻镉暴露的影响。通过不偏不倚的高 通过筛选，我们确定了一种以前未知的多个化学上不同的组蛋白的能力 脱乙酰酶抑制剂(HDACi)和溴域和末端外基序抑制剂(Beti)抢救急性呼吸窘迫综合征 细胞镉毒性。这些研究的长期目标是阐明细胞和 镉毒性的分子机制。这项应用的目的是：i)评估基因的变化 培养细胞和肾脏对镉暴露的表达和染色质乙酰化(Ac)。 以及通过HDACi或Beti治疗的潜在救治；以及ii)测试HDACi和Beti治疗缓解 镉致小鼠肾毒性。这一应用的中心假设是组蛋白Ac之间的相互作用 在哺乳动物细胞中，线粒体代谢是镉毒性的一个关键功能靶点。其基本原理是 对于这一应用，我们的新的基础数据表明，接触Cd会导致 线粒体功能和组蛋白Ac。至关重要的是，用HDACi和Beti抢救CD导致的缺陷 线粒体呼吸、代谢物水平和细胞活力。这些发现暗示组蛋白Ac和 线粒体功能是镉的重要细胞功能靶点。工作将在以下背景下进行 有两个明确的目标。首先，通过rna-seq和染色质图谱，功能上重要的基因和途径。 CD靶向，HDACi和Beti拯救，将在培养的成纤维细胞中鉴定。第二，救援 将在小鼠体内评估HDACi和Beti对Cd诱导的肾毒性的影响。我们将比较 镉暴露肾脏和成纤维细胞的基因表达特征，以确定核心基因表达程序 推动镉中毒，特别是那些被HDACi和Beti拯救的人。这种方法是创新的，在 镉引起的表观遗传改变与其生物效应之间的机制联系尚未得到证实 最终确定，并使用针对组蛋白ac或表观遗传扰动的小分子 更广泛地说，因为以前没有描述过镉中毒的治疗方法。这项工作意义重大，因为 对镉毒性的改进和机制治疗的需求尚未得到满足。这些研究可能会建立组蛋白 AC作为治疗镉中毒的新靶点。

Abstract Cadmium (Cd) is a widespread environmental pollutant that affects millions of individuals worldwide. Cd exposure in humans occurs most often through Cd’s many industrial applications, or consumption of contaminated food. Due to its extremely extended biological half-life, Cd persists for decades in tissues, primarily in the liver and kidneys. Cd exerts numerous deleterious effects, including bone, reproductive, neurodevelopmental, and pulmonary toxicities, and carcinogenesis. The kidneys are the major target of Cd toxicity, particularly the proximal tubular epithelial cells, injury to which hampers tubular reabsorption. Despite the many sequelae associated with Cd exposure in humans, specific molecular mechanisms of Cd toxicity are poorly understood, and no specific therapies exist to mitigate the effects of Cd exposure. Via unbiased high- throughput screening, we identified a previously unknown ability of multiple chemically distinct histone deacetylase inhibitors (HDACi) and Bromodomain and Extra-Terminal motif inhibitors (BETi) to rescue acute cellular Cd toxicity. The long-term goal of these studies is to elucidate novel aspects of the cellular and molecular mechanisms of Cd toxicity. The objectives of this application are: i) to evaluate changes in gene expression and chromatin acetylation (Ac) occurring in response to Cd exposure in cultured cells and the kidney, and their potential rescue by HDACi or BETi treatment; and ii) to test the ability of HDACi and BETi to mitigate Cd induced nephrotoxicity. The central hypothesis of this application is that the interplay between histone Ac and mitochondrial metabolism represents a key functional target of Cd toxicity in mammalian cells. The rationale for this application is our novel foundational data demonstrating that Cd exposure induces a reduction in mitochondrial function and histone Ac. Crucially, treatment with HDACi and BETi rescue Cd-induced defects in mitochondrial respiration, metabolite levels, and cell viability. These findings implying that histone Ac and mitochondrial function are important functional cellular targets of Cd. The work will take place in the context of two Specific Aims. First, via RNA-seq and chromatin profiling, functionally important genes and pathways targeted by Cd, and rescued by an HDACi and a BETi, will be identified in cultured fibroblasts. Second, rescue of Cd-induced nephrotoxicity by an HDACi and a BETi will be evaluated in vivo in mice. We will compare the gene expression signatures of Cd-exposed kidney and fibroblasts, to identify core gene expression programs driving Cd toxicity, particularly focusing on those rescued by HDACi and BETi. The approach is innovative, in that mechanistic links between epigenetic alterations induced by Cd and its biological effects have yet to be conclusively established, and the use of small molecules directed against histone Ac or epigenetic perturbations more generally as treatments for Cd toxicity has not previously been described. The work is significant, since there is an unmet need for improved, mechanism-treatments for Cd toxicity. These studies may establish histone Ac as a novel therapeutic target for Cd toxicity.