Gastric Injury In Trauma and Surgical Sepsis

本项目的长期目标是在细胞水平上了解胃粘膜细胞凋亡的机制， 保护自身免受创伤和全身性脓毒症或压力的损害。这个建议把锌作为一个信号 氧化应激是胃粘膜对急性炎症后损伤的反应。我们 初步研究表明，细胞内Zn（[Zn 2 *]^）浓度维持在非常高的水平， 低水平的各种锌转运蛋白，囊泡储存网站，和金属结合蛋白的作用， 细胞质，其中金属硫蛋白（MT）是一个主要的水库。我们的研究还表明， 氧化剂导致胃酸分泌腺上皮细胞中[Zn 2 +] i的显著增加， 粘液/HCO3分泌表面上皮。关于锌稳态的调控机制，目前还知之甚少。 胃粘膜上皮细胞或一般在胃肠道中。我们假设缺氧 损伤和随后的炎症反应导致Zn 2+在腺体细胞中的积累， 表面上皮[Zn2 +] t增加的下游后果包括：抑制酸分泌 和粘膜保护功能的增强，第二信使途径（Ca 2+，cAMP/PKA， 蛋白激酶C），糖酵解和线粒体呼吸的抑制，以及内源性代谢途径的遏制。 凋亡一般来说，氧化剂诱导的[Zn 2 +] i增加将被视为保护性和抗凋亡。 然而，我们也假设[Zn 2 +] i的不受控制的积累可能有助于非凋亡，氧化- 诱导上皮细胞损伤和坏死。本建议的具体目标是：1）确定 不稳定Z <$2+胃腺和表面上皮细胞的摄取、释放和处置机制， 氧化应激模型;评估锌2+作为细胞内的氧化应激信使，使用在体外和在体内， 胃腺和表面上皮功能的体内模型，以监测信号转导中的反应， 细胞内[Zn2 +]信号对氧化剂诱导的变化的响应的凋亡途径;以及3）探索 利用体外和体内模型研究了Zn 2 * 作为氧化应激的细胞外信使的作用， 表征胃粘膜内腔和上皮下空间中氧化剂诱导的[Zn 2 *]紊乱 以及它们对粘膜功能和完整性的影响。这些研究提出了新的见解， Zn~（2+）是调节胃粘膜上皮细胞功能的细胞内信号此外，这些研究 可以鉴定通过在氧化应激期间控制Zn 2+稳态而有效的治疗靶点。 这种治疗策略不仅适用于胃损伤，也适用于胃肠道的其他区域 受全身性应激和急性炎症影响的道。

The long term goal of thisproject is to understand, at the cellular level, the mechanisms bywhich gastric mucosa protects itself against damage by trauma and systemic sepsis or stress. This proposalfocuses on Zinc as a signal of oxidative stress that occurs in gastric mucosa in response to injury followed by acute inflammation. Our preliminary studies suggest that the intracellular concentration ofZn ([Zn2*]^ is maintained at extraordinarily low levels by the actions of various zinc transporters, vesicular storage sites, and metal binding proteins in the cytoplasm, of which metallothionein (MT) is a major reservoir. Our studies also indicate that exposure to some oxidants leads to substantial increases in [Zn2+]i in epithelial cells of the acid-secreting gastric glands and mucus/HCO3-secreting surface epithelium. Little is known of the mechanisms regulating Zn2* homeostasis in epithelial cells of the gastric mucosa¿ or in the gastrointestinal tract generally. We hypothesize that hypoxic injury and the ensuing inflammatory response lead to accumulation of Zn2+, in cells of the glands and of the surface epithelium. The downstream consequences of increases in [Zn2+]t include: suppression of acid secretion and enhancement of mucosal protective functions, alterations in second messenger pathways (Ca2+, cAMP/PKA, PKC), restraint of glycolysis and mitochondrial respiration, and containment of the intrinsic pathway of apoptosis. In general, oxidant-induced increases in [Zn2+Ji would be viewed as a protective and anti-apoptotic. However, we also hypothesize that uncontrolled accumulation of[Zn2+]i maycontribute to non-apoptotic, oxidant- induced epithelial cell injury and necrosis. TheSpecific Aims of thisproposal are: 1) to identify alterations in the mechanisms of uptake, release and disposal of labile Z¿2+ gastric glands and surface epithelium, using in vitro models of oxidative stress; to evaluate Zn2+ as an intra-cellular messenger of oxidative stress, using in vitro and in vivo models of gastric gland and surface epithelial function to monitor responses in signal transduction and apoptosis pathways in response to oxidant-induced alterations in intracellular [Zn2+J signals; and 3) to explore the role of Zn2* as an extra-cellular messenger of oxidative stress, using both in vitro and in vivo models to characterize oxidant-induced disturbances in [Zn2*] in the the lumen and subepithelial spaces of gastric mucosa and their effects on mucosal function and integrity. Theproposed studies promise novel insights into the role of Zn2* as an intracellular signal that regulates epithelialfunction in the gastric mucosa. In addition, these studies may identify therapeutic targets that are effective through control of Zn2+ homeostasis during oxidative stress. Such therapeutic strategies would be applicable not only to injury in the stomach, but to other regions of the GI tract affected bysystemic stress and acute inflammation.