Cystein, Intestinal Thiols and Goblet Cell Development

描述（由申请方提供）：该提议源于我们观察到肠外营养新生猪小肠粘膜中酸性粘蛋白阳性杯状细胞数量增加3 - 4倍，伴有谷胱甘肽（GSH）耗竭。我们假设缺乏鲁米那半胱氨酸是肠外营养上皮细胞感受到的主要损伤，并且这种营养缺乏的功能终点是更氧化的细胞内氧化还原电位。将这种氨基酸鉴定为关键营养因子是基于（a）膳食半胱氨酸的高首过消耗率和肠动脉半胱氨酸利用率低;（B）细胞氧化还原状态是细胞分化的关键决定因素的证据，和（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的事实，一方面通过其对巯基缓冲剂GSH和硫氧还蛋白（Trx）的固有贡献，另一方面通过其对杯状细胞特异性分泌粘蛋白和肠三叶因子（ITF）的固有贡献。我们假设肠外营养导致粘液细胞谱系的优先激活以及杯状细胞的选择性保留，导致相对于吸收性肠上皮细胞，具有杯状细胞的绒毛的再增殖（以降低的速率）。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监护人。我们的假设将在三个特定的目标进行测试：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)在杯状细胞培养模型系统中，定量GSH和Trx与ITF和分泌性粘蛋白合成的半胱氨酸使用等级，以及转硫途径在蛋氨酸形成半胱氨酸和硫酸盐中的作用，受顶部与基底半胱氨酸供应的影响，并响应分级的高氧水平。同时，确定用于磺粘蛋白生物合成的硫酸盐的来源（无机与半胱氨酸衍生）和通量是否受半胱氨酸可用性和高氧应激的影响。 3)测试Cdx 2激活结构域中发现的Cysl 31和/或Cysl 65是氧化还原敏感的并且在翻译后修饰时改变Cdx 2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.