miR-29b and autophagy regulate alveolar macrophage function post-BMT

 描述（由申请人提供）：造血干细胞移植（HSCT）用于治疗各种遗传缺陷和恶性肿瘤，但其有效性受到肺部感染的限制。感染并发症可发生在同种异体和自体移植环境中，尽管造血重建，但对感染的易感性仍然升高。为了更好地了解先天性免疫缺陷的特点HSCT，我们开发了一种细菌感染后同基因（syn）骨髓移植（BMT）的小鼠模型。我们以前已经表明，这些小鼠更容易感染铜绿假单胞菌，即使在造血系统重建。我们确定了环氧化酶-2（考克斯-2）的上调和PGE 2的过量产生是这些小鼠先天免疫功能受损的主要因素。我们发现，肺泡巨噬细胞（AM）和中性粒细胞（PMNs）的先天免疫功能，如吞噬功能，细菌杀伤和细胞因子分泌的缺陷。此外，骨髓移植后AM上的清道夫受体谱发生改变，具有胶原结构的巨噬细胞受体（MARCO）丢失，这是识别铜绿假单胞菌的关键受体。我们确定PGE 2通过升高这些AM上的E前列腺素2（EP 2）受体来抑制其功能。重要的是，我们的鼠研究表明，BMT后考克斯-2的药理学或遗传学抑制恢复了肺先天免疫和抗铜绿假单胞菌的AM功能。这些结果令人兴奋，因为它们表明抑制PGE 2信号传导可以是改善移植后宿主防御的治疗方法。然而，存在全身性问题的治疗策略，全面阻断所有前列腺素的合成。因此，该建议的一个方面是测试我们从辉瑞获得的新开发的EP 2拮抗剂（PF-044148948）。我们相信这将是一个更具体和有效的治疗阻断抑制性PGE 2信号。该应用程序还试图深入了解以下未回答的问题。1)为什么骨髓移植后考克斯-2升高导致PGE 2过量产生？2)这些先天性免疫缺陷是否是同种异体BMT的特征？3)骨髓移植后的这些缺陷是否使小鼠更容易感染革兰氏阳性菌（如肺炎链球菌）以及革兰氏阴性菌？4)我们能否确定自噬损伤是否是骨髓移植后杀伤受损的一种机制？5)我们在小鼠模型中发现的缺陷是否也存在于人类HSCT患者中？我们的总体假设是：BMT预处理诱导肺上皮细胞分泌转化生长因子（TGF）β。这增加了miR-29 b的表达以阻断DNA甲基转移酶（DNMT）的合成，从而导致考克斯-2的低甲基化，导致AM中PGE 2过表达。此外，PGE 2-EP 2诱导的自噬改变损害了宿主对铜绿假单胞菌和S.我们推测BMT后宿主防御可以通过使用考克斯抑制剂、EP 2拮抗剂或通过诱导自噬来改善。这些假设将在以下具体目标中加以探讨。目的1）研究同基因和异基因骨髓移植小鼠对铜绿假单胞菌和链球菌的易感性。目的2：确定TGF β 1诱导的miR-29 b是否引起考克斯-2低甲基化以增加BMT后PGE 2的产生目的3：目的3：确定自噬在同基因和异基因BMT AM中是否受损，以确定这是否与PGE 2-EP 2信号传导有关以及自噬对BMT后宿主防御的重要性

 DESCRIPTION (provided by applicant): Hematopoietic stem cell transplantation (HSCT) is used to treat a variety of genetic defects and malignancies, but its usefulness is limited by pulmonary infections. Infectious complications can occur both in allogeneic and autologous transplant settings and susceptibility to infection remains elevated despite hematopoietic reconstitution. To better understand innate immune deficiencies that characterize HSCT, we developed a murine model of bacterial infection post-syngeneic (syn) bone marrow transplant (BMT). We have previously shown that these mice are more susceptible to infection with Pseudomonas aeruginosa even after the hematopoietic system is reconstituted. We identified the upregulation of cyclooxygenase-2 (COX-2) and the overproduction of PGE2 as major contributing factors to the impaired innate immune function in these mice. We identified that alveolar macrophages (AMs) and neutrophils (PMNs) had defects in innate immune functions such as phagocytosis, bacterial killing and cytokine secretion. In addition, the profile of scavenger receptors on AMs were altered post-BMT, with loss of macrophage receptor with collagenous structure (MARCO), a critical receptor for recognition of P. aeurignosa. We determined that PGE2 signaled via elevated E prostanoid 2 (EP2) receptors on these AMs to inhibit their functions. Importantly, our murine studies have shown that pharmacologic or genetic inhibition of COX-2 post-BMT restores lung innate immunity and AM function against P. aeruginosa. These results are exciting because they suggest inhibition of PGE2 signaling can be a therapeutic to improve host defense post-transplant. However, there are systemic problems with a therapeutic strategy that globally blocks all prostaglandin synthesis. Thus, one aspect of this proposal will be to test a newly developed EP2 antagonist (PF-044148948) which we have obtained from Pfizer. We believe this will be a much more specific and effective therapeutic to block the inhibitory PGE2 signaling. The application also seeks to provide insight into the following unanswered questions. 1) Why is COX-2 elevated post-BMT leading to overproduction of PGE2? 2) Do these same innate immune defects characterize allogeneic (allo) BMT? 3) Do these defects post-BMT make mice more susceptible to Gram positive infections (like Streptococcus pneumoniae) as well as Gram negative ones? 4) Can we determine whether impairment of autophagy is one mechanism for impaired killing post-BMT? 5) Are the defects we have noted in our murine model also present in human HSCT patients? Our overall hypothesis is: BMT conditioning induces transforming growth factor (TGF) ß secretion from lung epithelial cells. This augments miR-29b expression to block synthesis of DNA methyltransferases (DNMTs) causing hypomethylation of COX-2 leading to PGE2 overexpression in AMs. Furthermore, PGE2-EP2 induced alterations in autophagy impair host defense against P. aeruginosa and S. pneumoniae post-BMT and we speculate that host defense post-BMT can be improved via treatment with a COX inhibitor, an EP2 antagonist or via induction of autophagy. These hypotheses will be explored in the following specific aims. Aim 1) To determine if syn BMT and allo BMT mice are more susceptible to P. aeruginosa and S. pneumoniae infection and if susceptibility is related to PGE2 signaling via EP2 in mice and man Aim 2: To determine whether TGFß-induced miR-29b causes COX-2 hypomethylation to increase PGE2 production post-BMT Aim 3: Aim 3: To determine if autophagy is impaired in syn and allo BMT AMs, to determine whether this is related to PGE2- EP2 signaling and the importance of autophagy to host defense post-BMT