Regulation of Intestinal Iron Transfer

铁是人体中含量最丰富的过渡金属，也是人体必需的营养素。 当细胞内游离铁催化破坏性自由基的形成时，就会产生毒性。衰老、动脉粥样硬化、关节炎是其中铁催化的自由基生成被怀疑有助于组织损伤的人类病症的增加列表中的一些。 为了使毒性最小化，体内的铁含量严格调节通过十二指肠上皮细胞的铁摄取。 本申请的中心假设是十二指肠铁输出的控制主要是转录的，并且这种转录控制独立于十二指肠上皮细胞铁含量。 这一假设是基于我实验室的初步有力证据而提出的，即a）铁对MTP 1的调节与用其它含5' IRE的基因如铁蛋白观察到的调节相反，B）MTP 1的十二指肠上皮表达不依赖于上皮细胞本身的铁含量。 我计划通过完成以下具体目标来测试假设并实现本资助提案的目标：1.测定不同铁摄入量的正常小鼠、Wistar小鼠、SLA小鼠和hpx小鼠十二指肠组织中MTP1 mRNA和蛋白水平以及转录率。 2.确定十二指肠上皮细胞中铁剥夺诱导的MTP1 mRNA的5' UTR结构。3. 表征MTP1的5' UTR IRE在该基因的铁依赖性调控中的作用。 这种方法预计将产生以下结果：a）鉴定铁在十二指肠中对MTP 1的调节模式。B）MTP 1的不同5'UTR在基因的铁依赖性调节中的作用的表征。 鉴定铁对负责铁吸收的组分的调节机制将导致更好地理解整体铁代谢，并将导致更好的治疗策略，用于限制继发于铁衍生自由基的细胞损伤。

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.