Regulation of Intestinal Iron Transfer

铁是人体内含量最丰富的过渡金属，也是人体必需的营养物质。当细胞内的游离铁催化形成破坏性的自由基时，就会产生毒性。衰老、动脉粥样硬化、关节炎是越来越多的人类疾病之一，在这些疾病中，铁催化产生的自由基被怀疑是导致组织损伤的原因。为了将毒性降到最低，身体中的铁含量严格控制着十二指肠上皮对铁的吸收。这一应用的中心假设是，对十二指肠铁输出的控制主要是转录的，这种转录控制独立于十二指肠上皮细胞的铁含量。这一假说是基于来自我的实验室的强有力的初步证据，即a)铁对MTP1的调节与其他含有5‘IRE的基因(如铁蛋白)的调节相反，b)MTP1在十二指肠上皮的表达与上皮细胞本身的铁含量无关。我计划验证这一假设，并通过完成以下具体目标来实现这项赠款提案的目标：1.测量正常、MK、SLA和HPX小鼠的十二指肠切片中MTP1的mRNA和蛋白质水平以及转录速率。2.测定缺铁诱导的十二指肠上皮细胞MTP1mRNA 5‘端非编码区的结构。3.研究MTP1基因5‘端非编码区IRE在铁依赖的基因调控中的作用。这一方法预计将产生以下结果：a)确定十二指肠中铁对MTP1的调节模式。B)鉴定MTP1不同的5‘UTRs在铁依赖的基因调控中的作用。识别铁对铁吸收的调节机制将有助于更好地了解铁的整体代谢，并将导致更好的治疗策略，以限制铁源性自由基继发的细胞损伤。

Iron is the most abundant transition metal in the human body and an essential nutrient. Toxicity results when cellular free iron catalyzes the formation of destructive free radicals. Aging, atherosclerosis, arthritis, are some of the increasing list of human conditions in which iron catalyzed generation of free radicals is suspected to contribute to tissue injury. To minimize toxicity, the iron content of the body tightly regulates uptake of iron through the duodenal epithelium. The central hypothesis of this application is that the control of duodenal iron export is primarily transcriptional and that this transcriptional control is independent of duodenal epithelial cell iron content. This hypothesis has been formulated on the basis of strong preliminary evidence from my laboratory that a) the regulation of MTP1 by iron is the opposite of the regulation observed with other 5' IRE containing genes, such as ferritin, b) the duodenal epithelial expression of MTP1 is independent of iron content of the epithelial cell itself. I plan to test the hypothesis and accomplish the objectives of this grant proposal by completing the following specific aims: 1. Measure MTP1 mRNA and protein levels and transcription rates in duodenal sections of normal, mk, sla and hpx mice with varying amounts of total body iron. 2. Determine the structure of the 5' UTR of the MTP1 mRNA induced with iron deprivation in duodenal epithelial cells. 3. Characterize the role of the 5' UTR IRE of MTP1 in the iron dependent regulation of the gene. This approach is expected to yield the following results: a) Identification of the mode of regulation of MTP1 by iron in the duodenum. b) Characterization of the role of the differing 5' UTRs of MTP1 in the iron dependent regulation of the gene. Identification of the mechanisms of the regulation by iron of components responsible for iron absorption will result in a better understanding of overall iron metabolism and will lead to better therapeutic strategies for limiting cellular damage secondary to iron derived free radicals.