Effect of Heme on mRNA and miRNA Profiles

描述（申请人提供）：血红素[铁原卟啉]是一种原始大环化合物，地球上几乎所有的生命都依赖于它。它具有多种已知的功能和不同的性质。血红素代谢的正常途径和调节的重要性被其中存在血红素稳态缺陷的疾病的严重性所强调。例如，卟啉症是一组其中存在正常血红素合成缺陷的疾病，这主要是由于产生正常卟啉和血红素合成的酶的活性缺陷的先天性代谢缺陷。在血红素代谢中特别重要的基因及其产物分别是ALA合成酶1 [ALAS 1]和血红素加氧酶1 [HMOX 1]，它们是血红素合成和催化血红素的速率控制酶。羟甲基胆烷合酶（HMBS）是血红素生物合成途径的第三种酶，在急性间歇性卟啉症（最严重的急性卟啉症）中缺乏。最近，我们报道了miRNAs-122、-196和-let 7对HMOX 1及其关键阻遏物BACH 1表达的重要新作用，我们最近发现了蛋白酶体和其他蛋白酶途径在调节ALAS 1、BACH 1和HMOX 1水平方面的新的和迄今为止意想不到的作用。我们还发现了血红素过量与血红素缺乏对人肝细胞中miRNAs和mRNAs相互表达的影响。血红素，这是治疗急性卟啉病发作和预防的选择，可能会对肝脏和其他组织和器官产生有害影响，特别是重复使用。我们最近在人类Huh-7细胞中的微阵列结果揭示了血红素过量与血红素缺乏对几个基因和途径的新影响。现在重要的是评估体外模型中miRNA和mRNA谱改变的潜在生理重要性，以及在体内、AIP动物模型和急性卟啉症患者中是否以及在何种程度上发生类似变化。我们假设血红素和其他金属卟啉通过改变选定的microRNA和mRNA谱来调节ALAS 1、HMBS和HMOX 1的表达。我们的具体目标如下：目的#1：描述选定的microRNA调节ALAS 1、HMBS和HMOX 1和/或它们在人肝细胞中的关键调节因子的表达的作用和机制。目的#2描述选定的生理相关剂量的血红素对具有类似于人类AIP中所见突变的小鼠的肝脏、肾脏、脾脏和骨髓以及对接受血红素治疗的AIP患者的外周血单核细胞的影响。这些研究的结果将为血红素在健康和疾病中的多方面和关键功能提供重要的新见解，并在我们的基础和临床水平上有所了解。

DESCRIPTION (provided by applicant): Heme [iron protoporphyrin] is a primordial macrocycle upon which nearly all life on earth depends. It has manifold known functions and diverse properties. The importance of a normal pathway and regulation of heme metabolism is underscored by the seriousness of diseases in which there are defects in heme homeostasis. For example, the porphyrias are a group of diseases in which there are defects in normal heme synthesis, due mainly to inborn errors of metabolism that produce deficient activities of the enzymes of normal porphyrin and heme synthesis. Genes and their products of particular importance in heme metabolism are ALA synthase 1 [ALAS1] and heme oxygenase 1 [HMOX1], respectively, the rate-controlling enzymes of heme synthesis and catabolism. Hydroxymethylbilane synthase [HMBS], the third enzyme of the heme biosynthetic pathway, is deficient in acute intermittent porphyria, the most severe of the acute porphyrias. Recently, we reported important novel effects of miRNAs-122, -196, and -let 7 on expression of HMOX1 and its key repressor BACH1, and we recently discovered new and heretofore unexpected roles of proteasomal and other protease pathways that regulate levels of ALAS1, BACH1, and HMOX1. We also have discovered changes caused by heme excess vs heme deficiency on reciprocal expression of miRNAs and mRNAs in human hepatocytes. Heme, which is the treatment of choice for acute porphyric attacks and for their prevention, may have deleterious effects on the liver and other tissues and organs, especially with repeated use. Our recent microarray results in human Huh-7 cells have unveiled novel effects of heme excess vs heme deficiency on several genes and pathways. It is important now to assess the potential physiological importance of alterations in miRNA and mRNA profiles in in vitro models and whether and to what extent similar changes occur in vivo, in animal models of AIP and in humans with acute porphyrias. We hypothesize that heme and other metalloporphyrins regulate ALAS1, HMBS and HMOX1 expression by altering selected microRNAs and mRNA profiles Our specific aims are as follows: Aim #1: To delineate effects and mechanisms whereby selected microRNAs modulate expression of ALAS1, HMBS, and HMOX1 and/or their key regulators in human hepatocytes. Aim #2 To characterize the effects of selected, physiologically relevant doses of heme on the livers, kidneys, spleens, and bone marrows of mice with mutations that resemble those seen in human AIP and on peripheral blood mononuclear cells of patients with AIP who are receiving heme as therapy. Results of these studies will provide important new insights into the manifold and critical functions of heme in health and disease, and in our understanding at both the basic and clinical level.