PGE2 Regulation of Host Defense post-BMT

描述(由申请人提供)：骨髓移植(BMT)是许多恶性肿瘤和特定遗传性疾病的首选治疗方法。不幸的是，即使在植入后，也经常发生像铜绿假单胞菌这样的感染。关于骨髓移植患者肺部感染风险增加的机制，人们知之甚少。我们已经证明，尽管供者白细胞完全重建，但接受同基因骨髓移植的小鼠比未移植的小鼠更容易感染铜绿假单胞菌。我们发现BMT小鼠的肺泡巨噬细胞(AM)和中性粒细胞(PMN)吞噬和/或杀灭细菌和释放肿瘤坏死因子-a(TNFa)的能力存在缺陷。此外，骨髓移植小鼠的AM和PMN产生的前列腺素E2(PGE2)是对照小鼠细胞的125倍。PGE2通过与E前列腺素2(EP2)受体相互作用，抑制AM的吞噬作用，限制AM和PMN的杀菌作用。因此，PGE2是一个有吸引力的候选基因，在骨髓移植小鼠AM和PMN功能失调的活动中发挥核心作用。体内证实来自我们的研究，药物阻断PGE2的产生(使用吲哚美辛)恢复肺宿主对BMT后铜绿假单胞菌的防御。这些数据导致了我们的假设，即BMT后肺内PGE2的过度产生通过EP2受体信号作用，抑制肺吞噬细胞功能，导致肺宿主对铜绿假单胞菌的防御能力受损。我们目前的研究将确定骨髓移植后粒细胞-巨噬细胞集落刺激因子(GM-CSF)的增加是否会导致PGE2的产生增加，以及肺吞噬细胞的供体来源与宿主来源或骨髓移植条件下的肺环境是否有助于削弱宿主防御。最后，我们将探讨十号染色体上的磷酸酶和张力蛋白同源物(PTEN)和IL-1受体相关激酶(IRAK)-M在PGE2诱导的抑制中所起的中介作用。我们将利用分子、细胞和动物模拟策略，解决以下目标：目的1)确定GM-CSF升高在确定骨髓移植后PGE2升高和宿主防御受损中的作用；目的2)确定AM的来源(供体和宿主)是否决定骨髓移植后的功能；目的3)确定骨髓移植后肺微环境是否对AM功能具有抑制作用；目的4)确定PTEN激活和/或IRAK-M升高在介导PGE2诱导的骨髓移植后免疫抑制中的作用。这项工作提供了对骨髓移植后持续免疫抑制的机械性见解，并为开发新的治疗策略(中和GM-CSF、抑制PGE2合成/信号和药物抑制PTEN激活)提供了概念证明，这些策略可能会导致有效的新疗法来预防干细胞移植后患者的肺部感染。

DESCRIPTION (provided by applicant): Bone marrow (BM) transplantation (BMT) is the treatment of choice for many malignancies and specific inherited disorders. Unfortunately, infections such as Pseudomonas aeruginosa (P. aeruginosa) occur frequently even post-engraftment. Little is known about the mechanisms responsible for the increased risk of lung infections in BMT patients. We have shown that mice undergoing syngeneic BMT are more susceptible to pulmonary infection with P. aeruginosa than are non-transplanted mice despite complete donor leukocyte reconstitution. We found defects in the ability of alveolar macrophages (AMs) and polymorphonuclear leukocytes (PMNs) from BMT mice to phagocytose and/or kill bacteria and release tumor necrosis factor-a (TNFa). In addition, AMs and PMNs from BMT mice produce up to 125-times more prostaglandin E2 (PGE2) than cells from control mice. PGE2 is able to limit AM phagocytosis and to limit AM and PMN bacterial killing via interactions with the E prostanoid 2 (EP2) receptor. Thus, PGE2 is an attractive candidate to play a central role in the dysfunctional activity of AMs and PMNs from BMT mice. In vivo confirmation comes from our studies where pharmacologic blockade of PGE2 production (using indomethacin) restores lung host defense against P. aeruginosa post-BMT. These data have led to our hypothesis that over-production of PGE2 in the lung post-BMT, acting via EP2 receptor signaling, suppresses lung phagocyte function leading to impaired pulmonary host defense against P. aeruginosa. Our current studies will determine whether increased production of granulocyte-macrophage colony-stimulating factor (GM-CSF) post-BMT leads to increased production of PGE2 and whether the donor vs. host origin of the lung phagocytes or the BMT-conditioned lung environment contributes to impaired host defense. Finally, we will explore the role that the phosphatase and tensin homolog on chromosome ten (PTEN) and IL-1 receptor-associated kinase (IRAK)-M play as mediators of the PGE2-induced suppression. Using molecular, cellular and animal modeling strategies, we will address the following aims: Aim 1) To determine the role of increased GM-CSF in determining PGE2 elevation and impaired host-defense post- BMT; Aim 2) To determine whether the origin of the AMs (donor vs. host) dictates function post-BM; Aim 3 To determine whether the BMT lung microenvironment is inhibitory to AM function; Aim 4) To determine the roles that PTEN activation and/or IRAK-M elevation play in mediating the PGE2-induced immunosuppression post-BMT. This work provides mechanistic insight into the persistent immunosuppression seen post-BMT and provides a proof of concept for the development of new therapeutic strategies (neutralization of GM- CSF, inhibition of PGE2 synthesis/signaling and pharmacologic inhibition of PTEN activation) which may result in effective new treatments to prevent pulmonary infections in patients post-stem cell transplant.