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和全身性脓毒症或应激损伤的机制。该提案的重点是锌作为氧化应激的信号，氧化应激发生在胃粘膜中，以应对急性炎症后的损伤。我们的初步研究表明，通过细胞质中各种锌转运蛋白、囊泡储存位点和金属结合蛋白的作用，细胞内锌 ([Zn2]i) 浓度维持在极低的水平，其中金属硫蛋白 (MT) 是主要的储存库。我们的研究还表明，接触某些氧化剂会导致胃酸分泌胃腺上皮细胞和分泌粘液/HCO3 的表面上皮细胞中 [Zn2]i 大幅增加。人们对胃粘膜上皮细胞或胃肠道上皮细胞中 Zn2 稳态的调节机制知之甚少。我们假设缺氧损伤和随后的炎症反应导致腺体和表面上皮细胞中 Zn2 的积累。 [Zn2]i 增加的下游后果包括：抑制酸分泌和增强粘膜保护功能，改变第二信使途径（Ca2+、cAMP/PKA、PKC）、抑制糖酵解和线粒体呼吸以及抑制细胞凋亡的内在途径。一般来说，氧化剂诱导的 [Zn2]i 增加被视为具有保护性和抗凋亡作用。然而，我们还假设，[Zn2]i 不受控制的积累可能导致非凋亡、氧化诱导的上皮细胞损伤和坏死。该提案的具体目标是： 1) 利用体外氧化应激模型，确定不稳定的 Zn2 胃腺和表面上皮的摄取、释放和处置机制的改变；评估 Zn2 作为细胞内氧化应激信使的作用，使用胃腺和表面上皮功能的体外和体内模型来监测信号转导和细胞凋亡途径中对氧化剂诱导的细胞内 [Zn2] 信号变化的反应； 3) 探索 Zn2 作为氧化应激细胞外信使的作用，利用体外和体内模型来表征胃粘膜管腔和上皮下空间中氧化剂诱导的 [Zn2] 紊乱及其对粘膜功能和完整性的影响。拟议的研究有望对 Zn2 作为调节胃粘膜上皮功能的细胞内信号的作用提供新的见解。此外，这些研究可能会确定通过氧化应激期间控制 Zn2 稳态而有效的治疗靶点。这种治疗策略不仅适用于胃部损伤，还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.