Honing Henk, van den Berg Timo K, van der Pol Susanne M A, Dijkstra Christine D, van der Kammen Rob A, Collard John G, de Vries Helga E
Department of Molecular Cell Biology, VU Medical Center, Amsterdam, The Netherlands.
J Leukoc Biol. 2004 Mar;75(3):523-8. doi: 10.1189/jlb.0203054. Epub 2003 Nov 21.
Monocyte infiltration into inflamed tissue requires the initial arrest of the cells on the endothelium followed by firm adhesion and their subsequent migration. Migration of monocytes and other leukocytes is believed to involve a coordinated remodeling of the actin cytoskeleton. The small GTPases RhoA, Rac1, and Cdc42 are critical regulators of actin reorganization. In this study, we have investigated the role of Rho-like GTPases RhoA, Rac1, and Cdc42 in the adhesion and migration of monocytes across brain endothelial cells by expressing their constitutively active or dominant-negative constructs in NR8383 rat monocytic cells. Monocytes expressing the active form of Cdc42 show a reduced migration, whereas Rac1 expression did not affect adhesion or migration. In contrast, expression of the active form of RhoA in monocytes leads to a dramatic increase in their adhesion and migration across endothelial cells. The effect of RhoA was found to be mediated by its down-stream effector Rho kinase (ROCK), as pretreatment with the selective ROCK inhibitor Y-27632 prevented this enhanced adhesion and migration. These results demonstrate that RhoA activation in monocytes is sufficient to enhance adhesion and migration across monolayers of endothelial cells.
单核细胞浸润到炎症组织中，首先需要细胞在内皮细胞上停滞，随后紧密黏附，接着进行迁移。单核细胞和其他白细胞的迁移被认为涉及肌动蛋白细胞骨架的协同重塑。小GTP酶RhoA、Rac1和Cdc42是肌动蛋白重组的关键调节因子。在本研究中，我们通过在NR8383大鼠单核细胞中表达组成型活性或显性负性构建体，研究了Rho样GTP酶RhoA、Rac1和Cdc42在单核细胞跨脑内皮细胞黏附与迁移中的作用。表达Cdc42活性形式的单核细胞迁移减少，而Rac1的表达不影响黏附或迁移。相反，单核细胞中RhoA活性形式的表达导致其跨内皮细胞的黏附和迁移显著增加。发现RhoA的作用是由其下游效应物Rho激酶（ROCK）介导的，因为用选择性ROCK抑制剂Y-27632预处理可阻止这种增强的黏附和迁移。这些结果表明，单核细胞中RhoA的激活足以增强其跨内皮细胞单层的黏附和迁移。
