脂肪因子CTRP5促动脉粥样硬化发生和机制研究

The relationship between C1q/TNF-related protein (CTRP) family and atherosclerosis remains largely unclear. Our study has shown that CTRP5 levels are significantly increased in atherosclerotic tissue and serum from patients with coronary artery disease, as compared with control vascular tissue and healthy subjects. CTRP5 protein induces lipid uptake and accumulation of lipid peroxidation in endothelial cells. Peritoneal injection of CTRP5 recombinant protein every other day promotes atherogenesis in apoE deficient mice. To decipher the mechanism of CTRP5 pro-atherosclerotic effect, mRNA array has been performed in arterial endothelial cells stimulated by CTRP5. The results show that 12/15-lipoxygenase mRNA level is greatly elevated (52 fold), which is verified by Western blot and RT-realtime PCR. CTRP5-induced effects are significantly attenuated in endothelial cells transfected with siRNA 12/15-lipoxygenase or treated by 12/15-lipoxygenase inhibitor Baicalein. Combining previous literatures and our findings, we speculate that CTRP5 could promote atherogenesis through upregulation of 12/15-lipoxygenase, which leads to robust inflammatory reactions, lipid accumulation and ROS production and eventually results in atherogenesis. In our future experiments, we will test this hypothesis in vitro and in vivo, and clarify the mechanisms behind. CTRP5 effects will be investigated in mice of apoE-KO, CTRP5-KO/apoE-KO, Tg-CTRP5/apoE-KO, and Tg/CTRP5-KO/12/15-lipoxygenase-KO/apoE-KO. Atherosclerosis, inflammation, lipid accumulation, oxidative stress and endothelial function will be analyzed in aorta from above-mentioned mice and also in CTRP5-treated vascular endothelial cells or mouse-derived endothelial cells and monocyte/macrophages. Finally, peritoneal adipose tissue from CTRP5-injection or above-mentioned mice will be transplanted to peri-vascular regions of receiver mice to test the impact of adipose tissue-derived CTRP5.

脂肪因子（C1q/TNF-related protein，CTRP）家族与动脉粥样硬化的关系仍未清楚。我们发现CTRP5在冠心病患者血清和粥样硬化血管组织中水平显著高于对照，与病变严重度有关。CTRP5蛋白增加动脉内皮细胞脂质摄取和脂质过氧化物产生；腹腔注射CTRP5促进apoE-KO小鼠动脉粥样硬化发生。mRNA芯片发现并证实CTRP5上调动脉内皮细胞中脂氧合酶 (12/15-LOX) 52倍。用siRNA和抑制剂Baicalein下调12/15-LOX表达能抑制CTRP5诱导的内皮细胞效应。结合文献推断CTRP5能经上调血管组织12/15-LOX，介导加剧炎症和ROS产生，促进动脉粥样硬化。后续将用CTRP5-KO、Tg-CTRP5、12/15-LOX-KO等小鼠，以腺病毒、siRNA、体内体外分子实验和将上述小鼠腹腔脂肪组织移植到受者小鼠等手段探讨CTRP5促动脉粥样硬化作用和机制。

CTRP（C1q TNF-related protein）5是CTRP家族的重要成员，在脂肪组织含量多，在血管壁组织中也有表达。该脂肪因子家族与炎症、免疫调控关系密切。但CTRP5是否与动脉粥样硬化有关还不清楚。本项目研究结果显示①冠心病患者血清中CTRP5的水平明显高于非冠心病患者，且其水平与病变严重性呈正相关。CTRP5在冠状动脉内膜切除标本中的表达也明显高于非粥样硬化动脉。②免疫荧光结果显示CTRP5主要定位于内皮细胞、斑块浸润的巨噬细胞以及新生内膜中的平滑肌细胞。③体内与体外实验结果显示CTRP5能够增强低密度脂蛋白跨单层内皮细胞的穿胞（transcytosis）作用以及低密度脂蛋白在内皮细胞中的氧化修饰。④在机制方面，我们发现CTRP5可以使12/15-脂氧合（LOX）表达上调。⑤12/15-脂氧合酶是脂质氧化的关键酶，可以通过STAT6通路调节低密度脂蛋白的运输及氧化。通过基因干预或药物阻断12/15-脂氧合酶均可以显著减少氧化低密度脂蛋白在内皮下的沉积并减缓动脉粥样硬化的发展。这些研究结果明确了脂肪因子CTRP5对动脉粥样硬化的重要致病媒介作用。本研究的发现具有原创性，已在本领域主流杂志上发表。