硒蛋白K-钙流-钙蛋白酶环路对动脉粥样硬化血管炎症巨噬细胞的双向调控作用与分子机制研究

We have shown previously that selenoprotein K (SelK) is an endoplasmic reticulum transmembrane protein expressed at high levels in macrophages (Mø). It is important for promoting effective Ca2+ flux, and regulating Ca2+-dependent proliferation, migration, and oxidative burst in macrophages. Additionally, SelK is important for Ca2+-dependent lipid transport function of CD36 in macrophages during inflammation, thereby contributing to foam cell formation and atherogenesis. Moreover, we identified SelK as a novel target of calpain (CAPN), which mediated cleavage of SelK was detected in resting macrophages and, when activated through Toll-like receptors (TLRs), was inhibited due to TLR-induced up-regulation of the CAPN inhibitor, calpastatin (CAST). Considering CAPNs/CAST system proteolytically modulate cellular function and have been implicated in inflammatory diseases, we have revealed recently that CAST plays a central role in regulating macrophage activation and limiting pathology during inflammatory disorders of IBD. These data taken together indicate that a SelK/Ca2+/CAPN feedback loop exists in macrophages, and its dynamic changes during activation of macrophages might be essential to foam cell formation and atherosclerosis (AS). To investigate the daul role of SelK/Ca2+/CAPN pathway in regulating macrophages mediated inflammation in AS, mouse models of AS will be performed in ApoE-/- mice coupled with SelK-/-, m-CAPN-/-, CAST-/- and CASTtg. To further determine precise mechanisms by which SelK/Ca2+/CAPN loop regulates Mø phenotypes, inflammation limitation and foam cell formation, cellular and molecular biology protocols also will be conducted for cell models of mouse bone marrow derived macrophage (BMDM) and human monocyte derived macrophage (HMDM) as well as RAW264.7 and THP-1 derived macrophages with specific gene depletion of SelK, m-CAPN, and CAST. The specific aims are as follows: 1) To determine the role of SelK/Ca2+/CAPN loop in the development of AS; 2) To determine the role of SelK/Ca2+/CAPN loop during foam cell formation by affecting LDL uptake and transporting. To determine the mechanisms by which the levels and timing of SelK-Ca2+, m-CAPN and CAST affect the activation of human and mouse Mø, we focus on the OxLDL stimulated TLRs/NFkB signaling pathway. To determine the modulating role of CAST in foam cell formation, we focus on the scavenger receptors (SRs) and ABC transporters A1 and G1 pathway in response to lipid homeostasis. This project will define the daul role of SelK/Ca2+/CAPN feedback loop in regulating the initiation and progression of chronic inflammation and foam cell formation during AS. Uncovering these mechanisms are critical for understanding how impairments in SelK/Ca2+/CAPN loop driven the dysfunction, and the new insights from this work will guide the use of inhibitors targeting to Ca2+ flux and CAPN or other therapeutic interventions that target SelK and CAST in the treatment of AS related diseases.

我们发现巨噬细胞高表达内质网跨膜硒蛋白K(SelK)，它通过调控钙流对巨噬细胞活化及炎症反应产生重要影响，并参与泡沫细胞(FC)形成和动脉粥样硬化(AS)病生过程，另发现钙蛋白酶(CAPN)及其主要内源抑制蛋白(CAST) 通过剪切NFkB/IkB和SelK，对巨噬细胞发挥重要调控作用，据此提出SelK/Ca2+/CAPN环路对AS炎症巨噬细胞的双向调控作用与分子机制研究课题。拟利用ApoE-/-、SelK-/-、CAPN-/-、CAST-/-小鼠及共敲除或嵌合模型，及其骨髓来源巨噬细胞，研究SelK/Ca2+/CAPN反馈环路对AS血管巨噬细胞极化和炎症反应的影响，阐明该环路在氧化低密度脂蛋白胆固醇活化的炎症信号通路、脂代谢转运途径及FC形成过程中的双向调控作用，发现对AS发生进展起重要作用的新靶点分子，为利用SelK、钙流和CAPN抑制剂开展AS血管病变的干预治疗提供理论和实验依据。

项目背景：我们发现炎症巨噬细胞高表达内质网跨膜硒蛋白K(selenoprotein K，SelK)，SelK通过调控钙流对巨噬细胞活化及炎症反应产生重要影响，并参与泡沫细胞(FC)形成和动脉粥样硬化(AS)发生过程。还发现钙蛋白酶(calpain，CAPN)及其主要内源抑制蛋白(calpastatin，CAST) 通过剪切调控SelK及IkB，影响NFkB炎症信号，对巨噬细胞功能发挥重要调节作用。.研究内容：聚焦SelK-钙流-钙蛋白酶环路对AS炎症巨噬细胞的双向调控作用与分子机制，主要开展的研究内容包括：利用ApoE、SelK、CAPN、CAST基因敲除小鼠构建共敲除或嵌合模型，及其骨髓来源巨噬细胞，研究SelK/Ca2+/CAPN反馈环路对AS血管巨噬细胞极化和炎症反应的影响，阐明该环路在氧化低密度脂蛋白胆固醇活化的炎症信号通路、脂代谢转运途径及FC形成过程中的双向调控作用，发现对AS发生进展起重要作用的新靶点分子，为利用SelK、钙流和CAPN抑制剂开展AS血管病变的干预治疗提供理论和实验依据。.重要结果及科学意义：发现环境应激（砷暴露）触发血管内皮钙信号迅速响应，引起CAPN-1活化及膜转位水平增加，进而造成内皮粘附分子VE-cadherin的剪切，使内皮细胞间完整性受损，对氧化低密度脂蛋白（ox-LDL）渗漏和人外周血单核细胞招募增加，这可能是环境应激导致AS发生的重要机制，提示CAPN-1抑制剂在维持血管稳态和抗AS发生中的潜在应用价值。进一步利用单细胞分析技术研究发现血管内皮在应激条件下硒蛋白组成员表达水平变化，SelK表达水平上调为内皮细胞钙流响应所必需，其一方面参与CAPN活化，并作为CAPN底物发生剪切；另一方面通过介导巨噬细胞CD36棕榈酰化促LDL内流，在FC形成和AS发生中起作用；这些结果表明SelK功能多重性，其适度表达水平对维持血管稳态是有益的。