Regulation of Intestinal Iron Transfer

铁是人体中含量最多的过渡金属，是人体必需的营养物质。当细胞中的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、关节炎是越来越多的人类疾病中的一些，在这些疾病中，铁催化自由基的产生被怀疑会导致组织损伤。为了减少毒性，体内的铁含量通过十二指肠上皮严格调节铁的摄取。本应用的中心假设是，十二指肠铁输出的控制主要是转录的，并且这种转录控制与十二指肠上皮细胞铁含量无关。这一假设是基于我实验室强有力的初步证据得出的：a)铁对MTP1的调控与其他含5' IRE基因（如铁蛋白）的调控相反；b)十二指肠上皮细胞中MTP1的表达与上皮细胞本身的铁含量无关。我计划通过完成以下具体目标来验证这个假设并实现这个拨款提案的目标：1。测量不同总铁量的正常、mk、sla和hpx小鼠十二指肠切片MTP1 mRNA和蛋白水平及转录率。2. 测定十二指肠上皮细胞铁剥夺诱导的MTP1 mRNA的5' UTR的结构。3. 表征MTP1的5' UTR IRE在该基因的铁依赖性调节中的作用。该方法有望产生以下结果：a)确定铁在十二指肠中调节MTP1的模式。b)表征MTP1不同的5' utr在该基因铁依赖性调控中的作用。确定铁对铁吸收成分的调节机制将有助于更好地了解整体铁代谢，并将为限制铁自由基引起的细胞损伤提供更好的治疗策略。

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.