PGE2 receptors as therapeutic targets in occlusive and aneurysmal vascular diseas

描述（由申请方提供）：环氧合酶-2（考克斯-2）依赖性前列腺素E2（PGE 2）合成通过诱导巨噬细胞蛋白酶和炎性细胞因子表达加重闭塞性和血管瘤性血管疾病。尽管有这些观察结果，但选择性考克斯-2抑制剂的给药与不良心血管事件的频率增加相关。这种矛盾的效应尚未完全理解;然而，有证据表明，内皮细胞对考克斯-2依赖性PGI 2合成的抑制使血管壁对血栓形成刺激更敏感。尽管如此，阻断PGE 2的病理生理作用仍然是一个重要的治疗目标。在本申请中待测试的总体假设是阻断PGE 2与EP 4前列腺素类受体的结合可抑制血管MMP-9和IL-6表达、动脉粥样硬化病变发展和动脉瘤扩张而不改变血管PGI 2水平。为了支持这一假设，我们报告EP 4拮抗剂或EP 4敲除在阻断巨噬细胞MMP-9表达方面与考克斯-2抑制剂一样有效。此外，EP 4依赖性信号刺激巨噬细胞表达IL-6，其通过正反馈环与考克斯-2和MMP-9表达相关。此外，EP 4依赖性信号通过诱导微粒体PGE合酶-1的表达和抑制降解酶15-羟前列腺素脱氢酶的表达来刺激PGE 2的分泌。最后，抑制PGE 2与EP 4的结合对体外巨噬细胞和内皮细胞产生血栓保护性PGI 2的影响很小。为了验证我们假设的有效性，我们提出了以下具体目标：[1]确定EP 4依赖性信号对调节考克斯-2下游酶的作用，这些酶调节巨噬细胞PGE 2的合成和降解; [2]确定考克斯-2和EP 4依赖性信号对平滑肌细胞MMP-9表达的调节作用;[3]确定阻断PGE 2与EP 4的结合是否减弱ApoE-/-小鼠中动脉粥样硬化病变的发展而不改变血管前列腺素类谱;[4]确定阻断PGE 2与EP 4的结合是否减弱ApoE-/-小鼠中血管紧张素II诱导的动脉瘤的发展而不改变血管前列腺素类谱。如果成功，这些研究将为调节闭塞性和囊性疾病的新治疗策略提供基础。 公共卫生相关性：在美国，动脉粥样硬化和动脉粥样硬化性血管疾病的并发症仍然是发病率和死亡率的主要原因。前列腺素E2（PGE 2）由募集到动脉壁的炎性细胞分泌，触发削弱壁并导致破裂和血栓形成的过程。环氧合酶-2（考克斯-2）是前列腺素E2合成的重要调节因子。人们认为，选择性考克斯-2抑制剂可通过抑制PGE 2合成来减弱血管病变的发展。然而，施用考克斯-2抑制剂令人惊讶地导致心血管并发症的频率增加。这种意想不到的作用尚未完全了解;然而，有证据表明，考克斯-2抑制剂也可阻断血管内衬细胞的PGI 2合成，从而使动脉对损伤更敏感。尽管如此，阻断PGE 2诱导的动脉壁弱化仍然是一个重要的治疗目标。在拟定的研究中，我们试图通过阻断前列腺素受体而不是抑制考克斯-2来绕过考克斯-2抑制对PGI 2合成的不利影响，前列腺素受体介导PGE 2的病理生理作用。如果成功的话，这些研究将为减少动脉粥样硬化和动脉粥样硬化性血管疾病并发症的新治疗策略提供基础。

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.