Gastric Injury In Trauma and Surgical Sepsis

描述(由申请人提供)： 该项目的长期目标是在细胞水平上了解胃粘膜保护自身免受创伤、全身脓毒症或应激的损害的机制。这一建议的重点是锌作为氧化应激的信号，发生在胃粘膜损伤后的急性炎症反应中。我们的初步研究表明，在各种锌转运蛋白、囊泡储存部位和细胞质中的金属结合蛋白的作用下，细胞内锌([Zn2]i)的浓度维持在极低的水平，其中金属硫蛋白(MT)是主要的贮存库。我们的研究还表明，暴露于某些氧化剂会导致分泌胃酸的胃腺上皮细胞和分泌粘液/HCO3的表面上皮细胞内[Zn2]i显著增加。胃粘膜上皮细胞或一般的胃肠道上皮细胞中的锌稳态调节机制知之甚少。我们推测，缺氧性损伤和随之而来的炎症反应导致锌在腺体细胞和表面上皮细胞中积聚。[Zn2]i升高的下游后果包括：抑制胃酸分泌和增强粘膜保护功能，改变第二信使通路(钙、cAMP/PKA、PKC)，抑制糖酵解和线粒体呼吸，抑制细胞凋亡的内在途径。一般来说，氧化剂诱导的[Zn2]i增加被视为一种保护和抗细胞凋亡的作用。然而，我们也假设，[Zn2]i的不受控制的积累可能有助于非凋亡性、氧化剂诱导的上皮细胞损伤和坏死。这一建议的具体目的是：1)利用体外氧化应激模型，确定不稳定的胃腺和表面上皮摄取、释放和处置锌的机制的变化；利用体外和体内胃腺和表面上皮功能的模型，评价锌作为氧化应激的细胞内信使的作用，以监测信号转导和细胞内[锌]信号变化对细胞凋亡途径的响应；3)探讨氧化锌作为氧化应激细胞外信使的作用，利用体外和体内模型研究氧化剂引起的胃粘膜管腔和上皮下间隙[锌]的紊乱及其对粘膜功能和完整性的影响。这项拟议的研究有望对锌作为细胞内信号调节胃粘膜上皮功能的作用提供新的见解。此外，这些研究可能通过控制氧化应激期间的锌稳态来确定有效的治疗靶点。这种治疗策略不仅适用于胃损伤，而且适用于受全身应激和急性炎症影响的胃肠道其他区域。

DESCRIPTION (provided by applicant): The long term goal of this project is to understand, at the cellular level, the mechanisms by which gastric mucosa protects itself against damage by trauma and systemic sepsis or stress. This proposal focuses 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 of Zn ([Zn2+]i) 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+]i 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+]i would be viewed as a protective and anti-apoptotic. However, we also hypothesize that uncontrolled accumulation of [Zn2+]i may contribute to non-apoptotic, oxidantinduced epithelial cell injury and necrosis. The Specific Aims of this proposal are: 1) to identify alterations in the mechanisms of uptake, release and disposal of labile Zn2+ 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+] 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. The proposed studies promise novel insights into the role of Zn2+ as an intracellular signal that regulates epithelial function 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 by systemic stress and acute inflammation.