Cellular Selenium Status and PGJ2 Metabolism

描述（由申请人提供）：巨噬细胞在免疫中起核心作用，其中从炎症开始到消退的转换对于强大和有益的免疫反应至关重要。然而，在许多疾病状态中，这种开关的不平衡会导致长时间的炎症。这些细胞氧化还原状态的不平衡可能是延迟和/或不成功解决的潜在关键决定因素之一。硒蛋白含有硒（Se），是细胞抗氧化机制的一员，可有效调节氧化还原变化，从而为免疫功能带来营养成分。硒缺乏是吸烟者、艾滋病和乳腺癌患者的特征，其中巨噬细胞激活伴随着促炎细胞因子和前列腺素（PG） E2（一种环氧合酶(COX)-2途径的氧化花生四烯酸产物）的增加。促炎基因的表达受氧化还原敏感转录因子NF-:B和过氧化物酶体增殖物激活受体(PPAR)-3的差异调节影响。有趣的是，巨噬细胞的硒补充导致15d-PGJ2的优先产生，15d-PGJ2共价修饰这两个转录因子。需要验证的具体假设是，硒补充通过COX途径选择性调节花生四烯酸代谢相关的几种酶，从而影响抗炎15d- PGJ2的优先形成，从而通过调节NF-:B和PPAR-3来减弱促炎基因的表达。15d-PGJ2的合成发生在胞内膜-细胞质界面，容易失活，这可能会降低其生物活性。另一个需要验证的补充假设是，微粒体谷胱甘肽s -转移酶（MGSTA1）的表达在缺硒期间上调，这是15d-PGJ2代谢失活的部分原因。这些假设将在缺乏硒（0.01 ppm）、硒充足（0.08 ppm）和硒补充（0.4 ppm）的C57BL/6小鼠以及从这些小鼠中分离的巨噬细胞中进行测试，目的如下：1)研究细胞硒状态通过COX-1和COX-2依赖性途径对PG产生的调节作用；2)研究硒缺乏时微粒体PGE2合成酶和造血PGD2合成酶参与炎症途径的作用和调节；3)阐明MGSTA1在硒缺乏时15d-PGJ2代谢中的作用。我们的研究揭示了细胞硒状态和抗炎轴之间的联系，通过抑制促炎PGE2产生增加的15d-PGJ2。这些研究将开辟新的研究途径，通过饮食干预来抵消NF-: b依赖的促炎基因表达，可能对患有hiv -艾滋病、癌症和动脉粥样硬化的个体有长期的益处和福祉。

DESCRIPTION (provided by applicant): Macrophages play a central role in immunity, where a switch from initiation to resolution of inflammation is crucial for a robust and beneficial immune response. However, an imbalance in this switch culminates in prolonged inflammation that is seen in many disease states. Imbalances in the redox status of these cells could be one of the underlying crucial determinants of delayed and/or unsuccessful resolution. Selenoproteins, which contain selenium (Se), are a member of the cellular antioxidant machinery that effectively regulate the redox changes, and thus, brings in a nutritional component to immune function. Selenium-deficiency is characteristic of cigarette smokers and individuals with AIDS and breast cancer, where macrophage activation is accompanied by increased pro-inflammatory cytokines and prostaglandin (PG) E2, an oxidized arachidonic acid product of the cyclooxygenase (COX)-2 pathway. The pro- inflammatory gene expression is effected by differential modulation of the redox- sensitive transcription factor, NF-:B, and peroxisome proliferator activated receptor (PPAR)-3. Interestingly, Se-supplementation of macrophages leads to the preferential production of 15d-PGJ2 that covalently modifies the two transcription factors. The specific hypothesis to be tested is that Se-supplementation selectively modulates several enzymes associated with the arachidonic acid metabolism via the COX pathway, thereby influencing the preferential formation of anti-inflammatory 15d- PGJ2, which attenuates the expression of pro-inflammatory genes through the modulation of the NF-:B and PPAR-3. Synthesis of 15d-PGJ2, which occurs at the intracellular membrane-cytoplasmic interface, is susceptible to inactivation that potentially blunts its biologic activity. An additional complementary hypothesis to be tested is that the expression of a microsomal glutathione S-transferase (MGSTA1) is up- regulated during Se-deficiency, which is partially responsible for the metabolic inactivation of 15d-PGJ2. The hypotheses will be tested in C57BL/6 mice maintained on Se-deficient (0.01 ppm), Se-adequate (0.08 ppm), and Se-supplemented (0.4 ppm) diets as well as in the macrophages isolated from these mice in the following Specific Aims: 1) to examine the effect of cellular Se status on the regulation of PG production via the COX-1 and COX-2- dependent pathways, 2) to examine the role and regulation of microsomal PGE2 synthase and hematopoietic PGD2 synthase involved in inflammatory pathways during Se-deficiency, and 3) to elucidate the role of MGSTA1 in 15d-PGJ2 metabolism during Se deficiency. Our studies provide insight into a previously unappreciated link between cellular Se status and anti-inflammatory axis, producing increased 15d-PGJ2, by suppressing pro-inflammatory PGE2. The proposed studies will open new avenues of research where dietary interventions to counteracting NF-:B-dependent pro- inflammatory gene expression may be applied for long-term benefits and well-being of individuals suffering from HIV-AIDS, cancer, and atherosclerosis. Project Narrative: Professional phagocytes, such as macrophages, are good sources of cytokines, chemokines, enzymes, and lipid mediators and, thus, play a pivotal role not only in the onset of inflammation, but also in the resolution process. However, it is unclear as to what reprograms the macrophage to switch from pro-inflammatory gene expression networks to anti-inflammatory programs. Based on the preliminary data, we believe that cellular antioxidant status may play an important role in such reprogramming events. The primary objective of this project is to investigate the underlying molecular mechanism of the anti-inflammatory effects of selenium, a micronutrient and antioxidant, in primary macrophages. The proposed studies will delineate a selenium-dependent switch in arachidonic acid metabolism from pro-inflammatory prostaglandin (PG) E2 to an anti-inflammatory 15-deoxy-12,14-PGJ2 (15d-PGJ2) that effects the resolution process of inflammation. Studies proposed here will also unravel the anti-inflammatory mechanism of action of selenium, particularly on the suppression of IKK2/NF-:B- dependent inactivation of pro-inflammatory gene expression via a unique mechanism involving 15d-PGJ2.