Substance P: A central mediator of cardiac fibrosis and diastolic dysfunction

我们最近证实，感觉神经神经肽P物质(SP)是 心肌应激升高，特别是压力超负荷时的心肌纤维化进展 (PO)。由于其定位于投射到冠状动脉的感觉神经，SP可能是最早的 根据冠脉压力/流量的变化而释放介质。我们相信，这将使SP- 一系列促纤维化的级联反应，我们已经确定了SP在 对采购订单的回应。因此，靶向SP具有真正的治疗潜力，然而，解剖这些细胞- 首先需要具体的路径。使SP成为更具吸引力的治疗靶点的是 其受体的两个亚型，神经激肽-1受体(NK-1R)。我们认为全长NK-1R 介导SP的生理作用，而截断的异构体则介导促纤维化作用。因此，它 有可能选择性地针对SP的不利影响，同时保持生理作用不变。 这项建议将研究这些NK-1R亚型在介导SP在细胞特异性活动中的作用。 参与心肌纤维化的多个途径：1)局灶性心肌细胞坏死及随后的 巨噬细胞反应；2)心脏成纤维细胞水平上的SP/ET-1相互作用；以及3)肥大细胞- 特定的蛋白酶。我们的总体假设是，SP通过截短的NK-1R调节细胞特异性 促进心脏纤维化和舒张期功能障碍的分子途径。《特定目标1》将考察 交感神经上NK-1R的SP激活起始局灶性心肌细胞坏死的程度 已知对纤维化有刺激作用。此外，SP激活的巨噬细胞在纤维化中的作用 局灶性坏死也将被检查。具体目标2将研究SP和内皮素-1的协同作用 心脏成纤维细胞表型和功能的研究。这包括调查截短的NK-1R激活 膜型基质金属蛋白酶/转化生长因子-β1途径的体外研究肌成纤维细胞特异性NK-1R缺陷 小鼠将被用来检测在PO条件下肌成纤维细胞特异性NK-1RS在体内的作用。特定的 目标3将确定肥大细胞特异性NK-1Rs在介导肥大细胞来源的释放中的重要性 促纤维化分子包括类胰蛋白酶和乳糜酶。这项建议具有重大意义和创新性，因为它 将建立一种神经肽作为心脏纤维化和舒张期功能障碍的媒介，以及识别 SP促进纤维化的细胞特异性机制。具有重要意义的是两个NK-1R的存在 异构体，我们认为截短的异构体介导了SP的促纤维化作用。因此，这项提议 将确定一种独特的、可操作的舒张期功能障碍的治疗靶点，因为拮抗剂、生物制品或 针对截短的NK-1R的基因治疗方法可能被开发出来。

We recently demonstrated that the sensory nerve neuropeptide substance P (SP) is required for the development of cardiac fibrosis in response to elevations in myocardial stress, specifically pressure overload (PO). Due to its localization to sensory nerves projecting to coronary arteries, SP is likely one of the first mediators released in response to changes in coronary pressure/flow. We believe that this places SP up- stream of multiple pro-fibrotic cascades, and we have identified several cell-specific effects initiated by SP in response to PO. Therefore, targeting SP holds real therapeutic potential, however, dissection of these cell- specific pathways is firstly required. What makes SP an even more attractive therapeutic target is the existence of two isoforms of its receptor, the neurokinin-1 receptor (NK-1R). We believe that the full length NK-1R mediates the physiological actions of SP, while the truncated isoform mediates the pro-fibrotic effects. Thus, it may be possible to selectively target the adverse effects of SP, while leaving the physiological actions intact. This proposal will examine the role of these NK-1R isoforms in mediating the cell-specific actions of SP on multiple pathways involved in cardiac fibrosis: 1) focal cardiomyocyte necrosis and the subsequent macrophage response; 2) SP/endothelin-1 interactions at the level of the cardiac fibroblast; and 3) mast cell- specific proteases. Our overall hypothesis is that SP acts via the truncated NK-1R to modulate cell-specific molecular pathways to promote cardiac fibrosis and diastolic dysfunction. Specific aim 1 will examine the extent to which SP activation of the NK-1R on sympathetic nerves initiates focal cardiomyocyte necrosis, a known stimulus for fibrosis. Further, the contribution to fibrosis of SP activated macrophages in response to focal necrosis will also be examined. Specific aim 2 will examine the synergistic actions of SP and endothelin-1 on cardiac fibroblast phenotype and function. This includes investigating truncated NK-1R activation of the membrane type 1 matrix metalloproteinase/TGF-β1 pathway in vitro. Myofibroblast-specific NK-1R-deficient mice will be used to examine the role of myofibroblast-specific NK-1Rs in vivo under conditions of PO. Specific aim 3 will identify the importance of mast cell-specific NK-1Rs in mediating the release of mast cell-derived pro-fibrotic molecules including tryptase and chymase. This proposal is significant and innovative because it will establish a neuropeptide as a mediator of cardiac fibrosis and diastolic dysfunction, as well as identifying cell-specific mechanisms by which SP promotes fibrosis. Of high significance is the existence of the two NK-1R isoforms, of which we believe the truncated isoform mediates the pro-fibrotic actions of SP. Thus, this proposal will identify a unique, actionable therapeutic target for diastolic dysfunction since antagonists, biologics, or gene therapy approaches specific to the truncated NK-1R could be developed.