GroEL1, from <em>Chlamydia pneumoniae</em>, Induces Vascular Adhesion Molecule 1 Expression by p37^AUF1 in Endothelial Cells and Hypercholesterolemic Rabbit

The expression of vascular adhesion molecule-1 (VCAM-1) by endothelial cells may play a major role in atherogenesis. The actual mechanisms of chlamydia pneumoniae (C. pneumoniae) relate to atherogenesis are unclear. We investigate the influence of VCAM-1 expression in the GroEL1 from C. pneumoniae-administered human coronary artery endothelial cells (HCAECs) and hypercholesterolemic rabbits. In this study, we constructed the recombinant GroEL1 from C. pneumoniae. The HCAECs/THP-1 adhesion assay, tube formation assay, western blotting, enzyme-linked immunosorbent assay, actinomycin D chase experiment, luciferase reporter assay, and immunohistochemical stainings were performed. The results show that GroEL1 increased both VCAM-1expression and THP-1 cell adhesives, and impaired tube-formation capacity in the HCAECs. GroEL1 significantly increased the VCAM-1 mRNA stability and cytosolic AU-binding factor 1 (AUF1) level. Overexpression of the p37AUF1 significantly increased VCAM-1 gene expression in GroEL1-induced bovine aortic endothelial cells (BAECs). GroEL1 prolonged the stability of VCAM-1 mRNA by increasing both p37AUF1 and the regulation of the 5′ untranslated region (UTR) of the VCAM-1 mRNA in BAECs. In hypercholesterolemic rabbits, GroEL1 administration enhanced fatty-streak and macrophage infiltration in atherosclerotic lesions, which may be mediated by elevated VCAM-1 expression. In conclusion, GroEL1 induces VCAM-1 expression by p37AUF1 in endothelial cells and enhances atherogenesis in hypercholesterolemic rabbits.内皮细胞表达的血管细胞黏附分子-1（vascular adhesion molecule-1, VCAM-1）可能在动脉粥样硬化形成中发挥核心作用。目前肺炎衣原体（chlamydia pneumoniae, C. pneumoniae）参与动脉粥样硬化形成的具体机制尚未阐明。本研究探讨了肺炎衣原体来源的GroEL1对人冠状动脉内皮细胞（human coronary artery endothelial cells, HCAECs）以及高胆固醇血症兔体内VCAM-1表达的影响。本研究构建了肺炎衣原体重组GroEL1蛋白，实验采用了HCAEC/THP-1黏附实验、管腔形成实验、蛋白质印迹法、酶联免疫吸附试验、放线菌素D追踪实验、荧光素酶报告基因实验以及免疫组织化学染色。结果显示，GroEL1可同时上调VCAM-1表达并增强THP-1细胞黏附作用，且损害HCAEC的管腔形成能力。GroEL1可显著提高VCAM-1 mRNA的稳定性以及胞质AU结合蛋白1（cytosolic AU-binding factor 1, AUF1）的水平。过表达p37AUF1可显著增强GroEL1诱导的牛主动脉内皮细胞（bovine aortic endothelial cells, BAECs）中VCAM-1基因的表达。在BAECs中，GroEL1通过上调p37AUF1以及调控VCAM-1 mRNA的5'非翻译区（5′ untranslated region, UTR），延长了VCAM-1 mRNA的稳定性。在高胆固醇血症兔体内，给予GroEL1可增强动脉粥样硬化病变中的脂纹形成与巨噬细胞浸润，这一效应可能由VCAM-1表达上调所介导。综上，GroEL1可通过p37AUF1在内皮细胞中诱导VCAM-1表达，并促进高胆固醇血症兔的动脉粥样硬化形成。