PGE2 receptors as therapeutic targets in occlusive and aneurysmal vascular diseas

描述（由申请人提供）：环氧化酶-2 （COX-2）依赖的前列腺素E2 （PGE2）合成通过诱导巨噬细胞蛋白酶和炎症细胞因子的表达，加重闭塞性和动脉瘤性血管疾病。尽管有这些观察结果，选择性COX-2抑制剂的使用与不良心血管事件的频率增加有关。这种矛盾的效应还没有被完全理解；然而，有证据表明，内皮细胞抑制cox -2依赖性PGI2的合成会使血管壁对血栓形成的刺激更加敏感。尽管如此，阻断PGE2的病理生理作用仍然是一个重要的治疗目标。在本应用中要验证的总体假设是，阻断PGE2与EP4前列腺素受体的结合可以抑制血管MMP-9和IL-6的表达、动脉粥样硬化病变的发展和动脉瘤的扩张，而不改变血管PGI2的水平。为了支持这一假设，我们报道了EP4拮抗剂或EP4敲低在阻断巨噬细胞MMP-9表达方面与COX-2抑制一样有效。此外，ep4依赖性信号通路刺激巨噬细胞IL-6的表达，而IL-6与COX-2和MMP-9的表达通过正反馈回路相关联。此外，ep4依赖性信号通过诱导微粒体PGE合成酶-1的表达和抑制降解酶15-羟基前列腺素脱氢酶的表达来刺激PGE2的分泌。最后，在体外实验中，抑制PGE2与EP4结合对巨噬细胞和内皮细胞产生血小板保护性PGI2的影响不大。为了验证我们假设的有效性，我们提出了以下具体目标：b[1]确定EP4依赖性信号在巨噬细胞调节PGE2合成和降解的COX-2下游酶的调控中的作用；确定COX-2和ep4依赖性信号在平滑肌细胞MMP-9表达调控中的作用；确定阻断PGE2与EP4的结合是否能在不改变血管前列腺素谱的情况下减弱ApoE-/-小鼠动脉粥样硬化病变的发展；确定阻断PGE2与EP4的结合是否能在不改变血管前列腺素谱的情况下减轻ApoE-/-小鼠血管紧张素ii诱导的动脉瘤的发展。如果成功，这些研究将为一种新的治疗策略提供基础，以调节闭塞性和动脉瘤性疾病。

DESCRIPTION (provided by applicant): Cyclooxygenase-2 (COX-2)-dependent prostaglandin E2 (PGE2) synthesis exacerbates occlusive and aneurysmal vascular disease by inducing macrophage proteinase and inflammatory cytokine expression. Despite these observations, administration of selective COX-2 inhibitors is associated with an increased frequency of adverse cardiovascular events. This paradoxical effect is not fully understood; however evidence suggests that suppression of COX-2-dependent PGI2 synthesis by endothelium renders the vascular wall more sensitive to thrombotic stimuli. Nonetheless, blocking the pathophysiologic actions of PGE2 remains an important therapeutic goal. The overall hypothesis to be tested in this application is that blocking PGE2 binding to the EP4 prostanoid receptor can inhibit vascular MMP-9 and IL-6 expression, atherosclerotic lesion development and aneurysmal dilation without altering levels of vascular PGI2. In support of this hypothesis, we report that an EP4 antagonist or EP4 knockdown is as effective as COX-2 inhibition in blocking macrophage MMP-9 expression. Moreover, EP4-dependent signaling stimulates macrophage expression of IL-6, which is linked to COX-2 and MMP-9 expression by a positive feedback loop. Also, EP4-dependent signaling stimulates secretion of PGE2 by inducing expression of microsomal PGE synthase-1 and inhibiting expression of the degradative enzyme 15-hydoxyprostaglandin dehydrogenase. Finally, inhibiting PGE2 binding to EP4 has little impact on the generation of thromboprotective PGI2 by macrophages and endothelial cells in vitro. To test the validity of our hypothesis, we propose the following specific aims: [1] Determine the role of EP4- dependent signaling on the regulation of enzymes downstream of COX-2 that regulate PGE2 synthesis and degradation by macrophages; [2] Determine the role of COX-2 and EP4-dependent signaling on the regulation of smooth muscle cell MMP-9 expression; [3] Determine whether blocking PGE2 binding to EP4 attenuates atherosclerotic lesion development in ApoE-/- mice without altering vascular prostanoid profiles; and [4] Determine whether blocking PGE2 binding to EP4 attenuates the development of angiotensin II-induced aneurysms in ApoE-/- mice without altering vascular prostanoid profiles. If successful, these studies will provide the basis for a novel therapeutic strategy to modulate occlusive and aneurysmal disease. PUBLIC HEALTH RELEVANCE: Complications of atherosclerotic and aneurysmal vascular diseases remain a major cause of morbidity and mortality in the United States. Prostaglandin E2 (PGE2), secreted by inflammatory cells recruited to the arterial wall, triggers processes that weaken the wall and lead to rupture and thrombosis. Cyclooxygenase-2 (COX-2) is an important regulator of PGE2 synthesis. It was thought that selective COX-2 inhibitors would attenuate vascular lesion development by inhibiting PGE2 synthesis. However, administration of COX-2 inhibitors surprisingly caused an increased frequency of cardiovascular complications. This unexpected effect is not fully understood; however evidence suggests that COX-2 inhibitors also block PGI2 synthesis by cells lining blood vessels, which renders the artery more sensitive to injury. Nonetheless, blocking PGE2-induced weakening of the arterial wall remains an important therapeutic goal. In proposed studies, we are attempting to bypass the unwanted effect of COX-2 inhibition on PGI2 synthesis by blocking the prostanoid receptor that mediates the pathophysiologic actions of PGE2 rather than inhibiting COX-2. If successful, these studies will provide the basis for novel therapeutic strategies to reduce the complications of atherosclerotic and aneurysmal vascular diseases.