DHA attenuates Inflammatory Responses Through Altering RAGE Signaling

描述（由申请人提供）：二十二碳六烯酸（DHA）是一种长链脂肪酸，具有抗炎和免疫调节特性。虽然所涉及的机制尚不完全清楚，但长链脂肪酸的抗炎特性被认为包括对导致基因转录修饰的信号通路的影响。迄今为止，DHA的特异性高亲和力受体尚未被确定，但DHA介导的细胞因子和趋化因子产生的减少可能是由于受体相关机制。晚期糖基化终产物受体（RAGE）是一种“损伤相关分子模式”受体，因此，它能够利用三级结构与不相关的分子进行配体识别。RAGE在肺中高表达；特别是上皮I型细胞、内皮细胞和肺泡巨噬细胞。暴露于高氧环境下的小鼠肺部RAGE蛋白表达增加，且与损伤的严重程度有关。此外，RAGE基因敲除小鼠可以免受高氧性肺损伤，这表明RAGE介导的事件在肺损伤的发展中发挥了作用。DHA优先由妊娠晚期的人类胎儿增加，以帮助神经组织的成熟。极度早产的婴儿在这种增加之前出生，并且通常没有在肠外营养中提供“预先形成的”DHA，或者从母乳库中接受低水平的母乳。此外，早产婴儿通常需要维持生命的治疗，包括呼吸机支持和高浓度氧气，并有发生与高氧性肺损伤相关的炎症的风险。支气管肺发育不良（BPD）是最常见的早产儿疾病之一，与母婴炎症反应密切相关。诊断为BPD的婴儿肺泡化减少，通常需要长时间的呼吸支持。此外，患有BPD的婴儿往往表现出神经发育迟缓，并有进一步损害其整体健康的其他医学问题的风险。中心假设是DHA通过改变RAGE表达和信号通路，通过降低白细胞趋化性来减轻高氧诱导的肺损伤。目的1将验证DHA补充剂通过调节可溶性RAGE （sRAGE）水平和活性来减少炎症的假设。sRAGE是由膜结合RAGE （mRAGE）的胞外结构域的蛋白水解裂解产生的。sRAGE可以增强趋化性，促进单核细胞的成熟和分化。这一目的将研究在高氧暴露的情况下DHA降低sRAGE水平的机制。目的2将验证DHA补充改变rage介导的信号通路的假设。DHA可以通过直接结合配体结构域或影响配体结合或激活受体的能力来传播或拮抗受体介导的信号。这一目的将探讨DHA减少细胞内促炎信号的机制。目的3将验证一个假设，即哺乳期妇女补充DHA将为早产儿提供DHA，并导致母亲和婴儿的sRAGE表达和炎症反应减少。这些研究将调查在早产的背景下DHA对sRAGE水平的影响。本提案中概述的研究将结合已建立的高氧暴露和肺部发育停滞的新生小鼠模型，以及早产儿的临床研究，以研究DHA减少炎症和改善肺部生长的机制。

DESCRIPTION (provided by applicant): Docosahexaenoic acid (DHA) is a long chain fatty acid that exhibits anti-inflammatory and immuno-modulating properties. Although the mechanisms involved are not completely understood, the anti-inflammatory properties of long chain fatty acids are thought to include effects on signaling pathways resulting in modified gene transcription. To date, a specific high affinity receptor for DHA has not been identified however DHA-mediated decreases in cytokine and chemokine production are likely due to receptor related mechanisms. Receptor for Advanced Glycation End Products (RAGE) is a "Damage Associated Molecular Pattern" receptor and, as such, is able to engage classes of unrelated molecules using tertiary structure for ligand recognition. RAGE is highly expressed in lung; specifically epithelial type I cells, endothelial cells, and alveolar macrophages. RAGE protein expression is increased in the lungs of mice exposed to hyperoxia, and the increase is related to the severity of injury. Furthermore, RAGE knockout mice are protected from hyperoxic lung injury, indicating that RAGE-mediated events play a role in the development of lung injury. DHA is preferentially accreted by the third trimester human fetus to aid the maturation of neurological tissues. Extremely preterm infants are born prior to this accretion and are often not provided "pre-formed" DHA in parenteral nutrition or receive low levels in milk from human milk banks. In addition, prematurely born infants often require life-sustaining therapies, including ventilatory support and high concentrations of oxygen and are at risk for inflammation associated with hyperoxic lung injury. Bronchopulmonary Dysplasia (BPD) is one of the most common diseases of prematurity and is closely linked to both maternal and infant inflammatory responses. Infants diagnosed with BPD have decreased lung alveolarization and often require respiratory support for a prolonged period of time. Furthermore, infants with BPD often exhibit delayed neurological development and are at risk for other medical problems that further impair their overall health. The central hypothesis is that DHA attenuates hyperoxia- induced lung injury by decreasing leukocyte chemotaxis, through altering RAGE expression and signaling pathways. Aim 1 will test the hypothesis that DHA supplementation decreases inflammation through the modulation of soluble RAGE (sRAGE) levels and activity. sRAGE is generated by proteolytic cleavage of the extracellular domain of membrane-bound RAGE (mRAGE). sRAGE can enhance chemotaxis and promote maturation and differentiation of monocytes. This aim will investigate the mechanisms by which DHA decreases sRAGE levels in the context of hyperoxia exposure. Aim 2 will test the hypothesis that DHA supplementation alters RAGE-mediated signaling pathways. DHA can propagate or antagonize receptor- mediated signaling by either directly binding to the ligand domain or influencing the ability of ligand to bind or activate the receptor. This aim will investigate the mechanisms by which DHA diminishes intracellular pro- inflammatory signaling. Aim 3 will test the hypothesis that DHA supplementation to lactating women will provide DHA to preterm infants and result in decreased sRAGE expression and inflammatory responses in both the mother and the infant. These studies will investigate the influence of DHA on sRAGE levels in the context of preterm birth. The studies outlined in this proposal will combine an established newborn mouse model of hyperoxia exposure and arrested lung development with clinical investigations in preterm human infants to investigate the mechanisms by which DHA decreases inflammation and improves lung growth. PUBLIC HEALTH RELEVANCE: Long chain fatty acids are efficacious in reducing inflammation in many diseases however the mechanisms of action are poorly understood. Preterm birth is associated with inflammation and the use of long chain fatty acids, such as docosahexeanoic acid (DHA), as an anti-inflammatory therapy has not been explored. The ultimate goal of this study is to identify mechanisms associated with the anti-inflammatory properties of DHA in the context of hyperoxic lung injury and preterm birth.