Fontijn Ruud D, Rohlena Jakub, van Marle Jan, Pannekoek Hans, Horrevoets Anton J G
Department of Medical Biochemistry, University of Amsterdam, Academic Medical Center K1-114, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
Eur J Cell Biol. 2006 Nov;85(11):1131-44. doi: 10.1016/j.ejcb.2006.07.005. Epub 2006 Sep 7.
Members of the claudin family are involved in formation of barriers that control access to the paracellular space of epithelia. Likewise, endothelium-specific claudin-5 is involved in the function of the blood-brain barrier (BBB). Here, we assessed the role of claudin-5 in non-BBB endothelial barriers using lentiviral-driven overexpression and silencing of claudin-5 in its native environment of primary vascular endothelial cells. Effects were monitored using macromolecular tracers between 342Da and 40kDa. Measurements were made both in absence and presence of transmigrating leukocytes. Freeze-fracture preparations were analyzed for effects at the ultrastructural level. We show that overexpression of claudin-5 leads to formation of elaborate networks of junction strands, which are absent in untransduced endothelial cells. Concomitantly, a modest, non-size-selective enhancement of the barrier function was observed. In contrast, silencing of endogenous claudin-5 does not influence barrier function. The efficient sealing of the endothelium during diapedesis of monocytes or granulocytes is also claudin-5 independent. Collectively, these data provide evidence for a limited contribution of claudin-5 to the barrier function of human umbilical vein endothelial cells (HUVEC), implying that, unlike selective barriers in epithelia, the barrier of non-BBB endothelium seems largely independent of claudin-directed tight junction structures.
claudin家族成员参与形成控制上皮细胞旁细胞间隙通路的屏障。同样，内皮细胞特异性的claudin-5参与血脑屏障（BBB）的功能。在此，我们在原代血管内皮细胞的天然环境中使用慢病毒驱动的claudin-5过表达和沉默，评估了claudin-5在非血脑屏障内皮屏障中的作用。使用342Da至40kDa之间的大分子示踪剂监测效果。在不存在和存在迁移白细胞的情况下均进行测量。分析冷冻断裂制剂在超微结构水平的影响。我们表明，claudin-5的过表达导致形成复杂的连接链网络，而未转导的内皮细胞中不存在这种网络。同时，观察到屏障功能有适度的、非大小选择性的增强。相比之下，内源性claudin-5的沉默不影响屏障功能。单核细胞或粒细胞渗出过程中内皮细胞的有效封闭也不依赖于claudin-5。总体而言，这些数据证明claudin-5对人脐静脉内皮细胞（HUVEC）的屏障功能贡献有限，这意味着与上皮细胞中的选择性屏障不同，非血脑屏障内皮的屏障似乎在很大程度上独立于claudin导向的紧密连接结构。
