Mechano-Sensitive Hypoxia-Inducible Factor-MMP Pathway in Venous Insufficiency

描述（由申请人提供）：慢性静脉功能不全（CVI）是一种常见且昂贵的疾病，其特征是静脉过度扩张和静脉曲张。CVI通常发生在下肢，提示静脉压力和静脉壁拉伸的作用。此外，CVI患者血浆和静脉组织中基质金属蛋白酶（MMPs）水平升高，表明MMPs在静脉扩张中发挥作用。我们已经发现，大鼠静脉的延长拉伸与收缩减少和MMP-2和-9的表达增加有关。此外，与对照隐静脉相比，曲张静脉的静脉曲张段表现出减少的收缩。这些新的发现使得研究静脉壁伸展和MMPs在静脉曲张相关的静脉扩张中的联系，并确定所涉及的上游和下游机制变得重要。我们的数据表明，延长静脉拉伸与缺氧诱导因子（HIF）的表达增加。此外，MMP- 2和-9诱导静脉节段的松弛，即使在没有可检测的细胞外基质（ECM）降解，表明抑制静脉平滑肌（VSM）收缩机制。该提案的目的是检验中心假设，即静脉压增加和静脉壁伸展延长与机械敏感性HIF-MMP途径的上调相关，这反过来又导致VSM收缩机制的下游抑制和ECM蛋白的降解增加，导致过度静脉扩张。因此，下调HIF-MMP途径应改善静脉长期拉伸和静脉曲张的反应性。将在大鼠股静脉压升高模型以及离体髂静脉和股静脉中进行机制研究。虽然大鼠是一种四足动物，但大鼠是一种一致的品种，避免了人类年龄，性别和其他混淆因素的变化。为了增强平移方面，将在人静脉曲张上进行实验，与邻近的近端和远端静脉以及对照隐静脉进行比较。具体目的是确定：1）静脉压/静脉壁拉伸增加是否与静脉收缩减少和HIF/MMP途径上调相关。2)HIF/MMP活性的增加通过下游抑制VSM收缩机制（包括[Ca 2 +]i、蛋白激酶C和Rho-激酶活性）和增加ECM降解来促进静脉扩张。3)曲张静脉中增加的静脉扩张是由于HIF/MMP的上调而发生的，因此使用HIF或MMP抑制剂和siRNA下调HIF或MMP应将静脉曲张节段中的收缩改善至接近在相邻近端或远端静脉或对照隐静脉中观察到的水平。这些研究将阐明静脉压升高/静脉壁伸展、HIF/MMP表达/活性、VSM收缩机制降低和静脉过度扩张之间的关系。这些结果将突出HIF和MMPs特异性抑制剂作为预防静脉曲张进展和复发的新策略的益处。

DESCRIPTION (provided by applicant): Chronic venous insufficiency (CVI) is a common and costly disease characterized by excessive vein dilation and varicose veins. CVI commonly occurs in the lower extremity, suggesting a role of venous pressure and vein wall stretch. Also, the plasma and venous tissue levels of matrix metalloproteinases (MMPs) are elevated in CVI, suggesting a role for MMPs in vein dilation. We have found that prolonged stretch of rat veins is associated with decreased contraction and increased expression of MMP-2 and -9. Also, varix segments of varicose veins demonstrate reduced contraction as compared to control saphenous vein. These novel findings make it important to investigate the link between vein wall stretch and MMPs in the venous dilation associated with varicose veins, and to identify the upstream and downstream mechanisms involved. Our data suggest that prolonged vein stretch is associated with increased expression of hypoxia-inducible factors (HIF). Also, MMP- 2 and -9 induce relaxation of vein segments even in the absence of detectable extracellular matrix (ECM) degradation, suggesting inhibition of venous smooth muscle (VSM) contraction mechanisms. The objective of this proposal is to test the central hypothesis that increased venous pressure and prolonged vein wall stretch are associated with upregulation of a mechano-sensitive HIF-MMP pathway, which in turn causes downstream inhibition of VSM contraction mechanisms and increased degradation of ECM proteins, leading to excessive venous dilation. Consequently, downregulation of the HIF-MMP pathway should improve reactivity in veins subjected to prolonged stretch and in varicose veins. Mechanistic studies will be conducted in a rat model of increased femoral venous pressure, and on isolated iliac and femoral veins. Although the rat is a four-legged animal, the rat is a consistent breed that avoids the variability in age, sex and other confounding factors in humans. To enhance the translational aspects, experiments will be conducted on human varix veins as compared to adjacent proximal and distal veins, and control saphenous veins. The specific aims are to determine whether: 1) Increased venous pressure/vein wall stretch is associated with decreased vein contraction and upregulation of HIF/MMP pathway. 2) Increases in HIF/MMP activity promote venous dilation by downstream inhibition of the mechanisms of VSM contraction including [Ca2+]i, protein kinase C and Rho- kinase activity, and increased ECM degradation. 3) The increased venous dilation in varicose veins occurs as a result of upregulation of HIF/MMPs, and therefore downregulation of HIF or MMPs using HIF or MMP inhibitors and siRNA should improve contraction in varix segments to levels approaching those observed in the adjacent proximal or distal veins, or in control saphenous vein. These studies would elucidate the relation between increased venous pressure/vein wall stretch, HIF/MMP expression/activity, reduced mechanisms of VSM contraction, and excessive venous dilation. The results would highlight the benefits of specific inhibitors of HIF and MMPs as a new strategy to prevent the progression and recurrence of varicose veins.