Regulation of a Novel Intestinal NHE Isoform (NHE8)

新型肠道 NHE 亚型 (NHE8) 的调节

• 批准号: 7268715
• 负责人: Fayez Khalaf Ghishan
• 金额: $ 30.06万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7268715
• 关键词: 1 year old; Acid-Base Imbalance; Acids; Acute; Apical; Calcium; Cell membrane; Cells; Chronic; Colon; Complex; Condition; Cyclic AMP; Cyclic GMP; Cyclic Nucleotides; Daily; Data; Development; Diarrhea; Digestive Physiology; Disease; EGF gene; Electrolyte Balance; Electrolytes; Elevation; Endotoxemia; Epithelial Cells; Feces; Gastric Parietal Cells; Gastrointestinal tract structure; Gene Expression; Gene Proteins; Genes; Genus Cola; Glucocorticoids; Goals; Golgi Apparatus; Growth; Guanylate Cyclase; Homeostasis; Infant; Inflammation; Inflammatory; Intestines; Knock-out; Knockout Mice; Life; Liquid substance; Localized; Mediating; Modeling; Molecular; NHE2; Neonatal; Nutrient; Output; Pattern; Personal Satisfaction; Phenotype; Phorbol Esters; Physiological; Play; Property; Protein Isoforms; Protein Kinase C; Proteins; Rattus; Recovery; Regulation; Research Design; Research Personnel; Role; Second Messenger Systems; Small Intestines; Sodium-Hydrogen Antiporter; Staging; Stimulus; Testing; Transcriptional Regulation; Villus; Weaning; absorption; adenylate; apical membrane; brush border membrane; day; design; follow-up; intestinal epithelium; mouse model; multicatalytic endopeptidase complex; novel; polyclonal antibody; programs; protein expression; renal epithelium; second messenger; vector

DESCRIPTION (provided by applicant): The gastrointestinal tract undergoes significant morphological and functional changes during maturation to meet the increasing demands for nutrient transport. The major function of the gastrointestinal tract is to transport nutrients and fluids to maintain adequate electrolyte homeostasis. The gastrointestinal tract of a 1- year-old infant handles approximately 3 liters of fluid per day, resulting in only 50 grams of daily stool output, indicating the complex transport capacity of the gastrointestinal tract during early life. Our previous studies have shown that expression of the intestinal sodium/hydrogen exchangers (NHE2 and NHE3) is low during early life, and increases significantly with maturation. Moreover, the phenotypes of knockout mouse models of NHE2 and NHE3 show minimal perturbations in fluid and electrolyte balance, indicating the presence of another NHE(s) during this period of maturation. Our study demonstrates that NHE8 is expressed in the apical membrane of epithelial cells in the gastrointestinal tract, at high levels during early life, and decreasing into adulthood. This localization is similar to the finding that NHE8 is expressed apically in the renal epithelium. Therefore, the proposed studies are designed to test the hypothesis that NHE8 represents a unique, novel NHE, which is important in electrolyte homeostasis during the suckling and weaning periods of development. We plan to explore five specific aims to determine the physiological role of NHE8 and its regulation in physiological and pathological conditions. Specific Aim 1 is designed to characterize functional and pharmacological properties of NHE8. Our second Specific Aim is designed to determine NHE8 expression along the cephalo-caudal and crypt-villus axes in the rat intestine and in NHE2/3 knock-out mice. We will also seek to further strengthen our supposition that NHE8 is expressed on the brush-border membrane of intestinal epithelial cells. In Specific Aim 3, we plan to investigate the transcriptional mechanisms of NHE8 regulation under basal conditions and as regulated by EGF and glucocorticoids. Our preliminary data show that NHE8 gene expression is regulated by these physiological effectors. EGF and glucocorticoids are important for functional maturation of the gastrointestinal tract, and have been shown to regulate intestinal NHEs. Furthermore, known intestinal NHEs are regulated during inflammation and we plan to follow up on our preliminary observation that NHE8 is regulated during endotoxemia (e.g. LPS administration) and by TNFa exposure. Therefore our Specific Aim 4 is designed to determine the mechanism responsible for acute and chronic effects of TNFa on NHES protein and gene expression. Specific Aim 5 is designed to define the mechanisms involved in the acute regulation of NHES by second messengers (cyclic nucleotides and intracellular calcium). Overall, the proposed studies are likely to have a significant impact on our understanding of the molecular mechanisms controlling electroneutral NaCI absorption in early life and its relationship to various perturbations of intestinal homeostasis.

描述（由申请人提供）：胃肠道在成熟过程中经历了显着的形态和功能变化，以满足对营养转运的日益增长的需求。胃肠道的主要功能是运输养分和液体以维持足够的电解质稳态。一个1岁婴儿的胃肠道每天处理约3升的液体，仅导致50克的每日粪便输出，表明早期胃肠道的复杂运输能力。我们先前的研究表明，肠道钠/氢交换器（NHE2和NHE3）在早期生命时很低，并且随着成熟而显着增加。此外，NHE2和NHE3的基因敲除小鼠模型的表型显示出流体和电解质平衡的极少扰动，表明在此成熟期间存在另一种NHE（S）。我们的研究表明，NHE8在胃肠道的上皮细胞的顶膜中表达，在早期生命中高水平，并降低到成年。该定位类似于以下发现，即NHE8在肾上皮中以顶端表达。因此，拟议的研究旨在检验以下假设：NHE8代表了独特的新型NHE，在哺乳和断奶的发育时期对电解质体内平衡很重要。我们计划探索五个具体目标，以确定NHE8的生理作用及其在生理和病理条件下的调节。特定目标1旨在表征NHE8的功能和药理特性。我们的第二个特定目的旨在确定大鼠肠和NHE2/3敲除小鼠中的头孢鼠尾声和隐窝villus轴的NHE8表达。我们还将寻求进一步加强我们在肠上皮细胞的刷子膜上表达NHE8的假设。在特定目标3中，我们计划研究基础条件下NHE8调控的转录机制，并由EGF和糖皮质激素调节。我们的初步数据表明，NHE8基因表达受这些生理效应子的调节。 EGF和糖皮质激素对于胃肠道的功能成熟至关重要，并且已证明可以调节肠道NHES。此外，在炎症期间调节已知的肠NES，我们计划跟进我们的初步观察，即NHE8在内毒素血症期间受到调节（例如LPS给药）和TNFA暴露。因此，我们的特定目标4旨在确定负责TNFA对NHES蛋白和基因表达的急性和慢性作用的机制。特定的目标5旨在定义第二个使者（环状核苷酸和细胞内钙）急性调节NHES的机制。总体而言，拟议的研究可能会对我们对早期生命中电击NACI吸收的分子机制的理解产生重大影响，及其与肠内稳态的各种扰动的关系。