Role for S1P2 in the Arterial Injury Response

描述(申请人提供)：内膜增生是由内膜平滑肌细胞(SMCs)的增殖和迁移引起的，并有助于动脉重建后的再狭窄(血管的再闭塞)。这项建议调查了发生内膜生长的可能性，因为通常抑制损伤后SMC过度增殖的途径被抑制。我们发现，在缺乏鞘氨醇-1-磷酸(S1P2)2型受体(S1P2)的小鼠的颈动脉损伤中，但在野生型对应的小鼠中，颈动脉损伤会导致大的新生内膜的形成。由于S1P2基因缺陷小鼠发育正常，不表现出任何血管表型，S1P2显然在血管系统的发育中不起关键作用。我们的总体假设是S1P是在损伤后产生的，并与S1P2结合，导致肌钙蛋白样蛋白家族的血清反应因子及其辅助因子的激活。这种转录因子复合体是已知的调节SMC特异性基因的表达，我们假设这些基因抑制SMC的增殖。这一抑制途径在S1P2基因敲除小鼠中缺失，这可能是这些动物在动脉损伤时发生大型内膜损伤的原因。这一建议的目的是检验这一假说，并提出了四个具体目标。在目标1中，我们将检测SMC特异性基因在野生型和S1P缺陷小鼠损伤动脉中的表达。在目标2中，我们将确定在SMC中表达的所有三种S1P受体在调节SRF依赖基因中的作用。在目标3中，我们将描述由S1P2激活并调节SMC特异性基因表达的转录复合体。在目标4中，我们将利用微阵列技术在血管壁中寻找受S1P2直接调控的损伤反应新基因。公共卫生相关性：再狭窄是动脉修复的一种严重且昂贵的并发症，约30%的患者会发生这种并发症。S1P2表达水平和信号的变化可能决定是否发生内膜病变。因此，S1P2途径中的蛋白质可能成为药物控制血管内膜生长的新靶点。

DESCRIPTION (provided by applicant): Intimal hyperplasia is caused by proliferation and migration of intimal smooth muscle cells (SMCs) and contributes to restenosis (the re-occlusion of vessels) after arterial reconstruction. This proposal investigates the possibility that intimal growth occurs because a pathway that normally inhibits excessive proliferation of SMCs after injury is suppressed. We have found that carotid injury in a mouse lacking the type-2 receptor for sphingosine-1-phosphate (S1P2), but not in their wild-type counterpart, results in the formation of a large neointima. Because S1P2-deficient mice develop normally and do not exhibit any vascular phenotype, S1P2 does apparently not play a critical role in the development of the vasculature. Our overall hypothesis is that S1P is generated after injury and binds to S1P2, which causes activation of serum-response factor and its cofactor of the myocardin-like protein family. This transcription factor complex is known to regulate expression of SMC-specific genes, and we hypothesize that these genes inhibit SMC proliferation. This inhibitory pathway is absent in the S1P2 knock-out mouse, and this might be the reason that these animals develop large intimal lesions in response to arterial injury. The goal of this proposal is to test this hypothesis, and four specific aims are proposed. In aim 1, we will measure expression of SMC- specific genes in injured arteries of wild-type and S1P-deficient mice. In aim 2, we will define a role for all three S1P receptors expressed in SMCs in the regulation of SRF- dependent genes. In aim 3, we will characterize the transcriptional complex that is activated by S1P2 and regulates the expression of SMC-specific genes. In aim 4, we will use micro array technology to identify novel genes in the vessel wall that are directly controlled by S1P2 in response to injury. PUBLIC HEALTH RELEVANCE: Restenosis is a serious and costly complication of arterial repair which occurs in ca. 30% of patients. Variations in S1P2 expression levels and signaling might determine if intimal lesions develop. Thus, proteins in the S1P2 pathway may constitute promising novel targets to pharmacological control of intimal growth.