Cystein, Intestinal Thiols and Goblet Cell Development

描述（由申请人提供）：该建议源于我们的观察，即在新生儿猪经肠外营养的小肠黏膜中，酸黏液蛋白阳性杯状细胞的数量增加了三到四倍，并伴有谷胱甘肽（GSH）的消耗。我们假设肠道半胱氨酸的缺乏是肠外营养上皮所感知到的主要损伤，而这种营养缺乏的功能终点是细胞内氧化还原电位的增加。这种氨基酸作为一种关键营养因子的鉴定是基于(a)饮食中半胱氨酸的首次消耗率高，而肠道对动脉半胱氨酸的利用率低；(b)细胞氧化还原状态是细胞分化的关键决定因素的证据，(c)半胱氨酸在结构和功能上参与细胞内氧化还原状态和粘膜防御，一方面是通过其固有的硫醇缓冲物GSH和硫氧还蛋白（Trx），另一方面是杯状细胞特异性分泌粘蛋白和肠三叶因子（ITF）。我们假设，肠外营养导致粘膜细胞谱系的优先激活以及杯状细胞的选择性保留，导致绒毛与杯状细胞相对于吸收性肠细胞的重新繁殖（以较低的速率）。杯状细胞发育的改变是由半胱氨酸状态受损引起的高氧引起的。换句话说，我们假设杯状细胞是粘膜氧化还原稳态的守护者。我们的假设将在三个具体目标中得到验证：1)确定上皮氧化还原状态和杯状细胞扩张之间是否存在因果关系，独立于tpn相关炎症。2)量化，在杯状细胞培养模型系统中，半胱氨酸用于合成GSH和Trx与ITF和分泌粘蛋白的层次，以及转硫途径在蛋氨酸形成半胱氨酸和硫酸盐中的作用，受半胱氨酸的顶供应量和底供应量的影响，并响应高氧水平的分级。同时，确定用于硫霉素生物合成的硫酸盐的来源（无机或半胱氨酸衍生）和通量是否受到半胱氨酸可用性和高氧胁迫的影响。3)验证位于Cdx2活化结构域的Cysl31和/或Cys165对氧化还原敏感，并通过翻译后修饰改变Cdx2转录调控的特异性的假设。

DESCRIPTION (provided by applicant): The proposal originates from our observations of a three to four fold increase in the number of acidomucin-positive goblet cells accompanied by glutathione (GSH) depletion in the small intestinal mucosa of neonatal pigs being nourished parenterally. We hypothesize that the lack of luminal cysteine is the primary insult perceived by the parenterally nourished epithelium, and that the functional endpoint of this nutritional deficiency is a more oxidized intracellular redox potential The identification of this amino acid as a key nutritional factor is based on (a) the high rate of first-pass consumption of dietary cysteine and the low rate of arterial cysteine utilization by the intestine; (b) evidence that cellular redox status is a key determinant of cellular differentiation, and (c) the fact that cysteine is structurally and functionally involved in both intracellular redox status and mucosal defense via its inherent contribution to the thiol buffers GSH and thioredoxin (Trx) on one hand, and the goblet cell-specific secretory mucins and intestinal trefoil factor (ITF) on the other. We hypothesize that parenteral nutrition results in a preferential activation of the mucous cell lineage as well as selective sparing of goblet cells leading to the repopulation (at a reduced rate) of the villus with goblet cells relative to absorptive enterocytes. The alteration in goblet cell development is initiated by hyperoxia that stems from compromised cysteine status. In other words, we hypothesize that goblet cells are the guardians of mucosal redox homeostasis. Our hypothesis will be tested in three specific aims: 1) Determine if a causal relationship exists between epithelial redox status and goblet cell expansion, independent of TPN-associated inflammation. 2) Quantify, in a goblet cell culture model system, the hierarchy of cysteine usage for the synthesis of GSH and Trx versus ITF and secretory mucins, as well as the role of the transsulfuration pathway in the formation of cysteine and sulfate from methionine, as affected by apical versus basal provision of cysteine, and in response to graded levels of hyperoxia. Simultaneously, determine if the source (inorganic vs. cysteine-derived) and flux of sulfate used for sulfomucin biosynthesis is affected by cysteine availability and hyperoxic stress. 3) Test the hypothesis that Cysl31 and/or Cys165, found within the activation domain of Cdx2, are redox sensitive and upon post-translational modification alter the specificity of Cdx2 transcriptional regulation.