Abstract
The members of Rho family of GTPases, RhoA and Rac1 regulate endothelial cytoskeleton dynamics and hence barrier integrity. The spatial activities of these GTPases are regulated by post-translational prenylation. In the present study, we investigated the effect of prenylation inhibition on the endothelial cytoskeleton and barrier properties. The study was carried out in human umbilical vein endothelial cells (HUVEC) and protein prenylation is manipulated with various pharmacological inhibitors. Inhibition of either complete prenylation using statins or specifically geranylgeranylation but not farnesylation has a biphasic effect on HUVEC cytoskeleton and permeability. Short-term treatment inhibits the spatial activity of RhoA/Rho kinase (Rock) to actin cytoskeleton resulting in adherens junctions (AJ) stabilization and ameliorates thrombin-induced barrier disruption whereas long-term inhibition results in collapse of endothelial cytoskeleton leading to increased basal permeability. These effects are reversed by supplementing the cells with geranylgeranyl but not farnesyl pyrophosphate. Moreover, long-term inhibition of protein prenylation results in basal hyper activation of RhoA/Rock signaling that is antagonized by a specific Rock inhibitor or an activation of cAMP signaling. In conclusion, inhibition of geranylgeranylation in endothelial cells (ECs) exerts biphasic effect on endothelial barrier properties. Short-term inhibition stabilizes AJs and hence barrier function whereas long-term treatment results in disruption of barrier properties.
Highlights
The integrity of the vascular endothelial (VE) barrier is maintained by the equilibrium of competing contractile and adhesive forces generated by the acto-myosin-based endothelial cell (EC) contractile machinery and adhesive molecules located at cell–cell and cell–matrix contacts, respectively [1]
When the cells were pretreated with statins for 16 h, this transient effect of thrombin on EC permeability was lost and thrombin-induced hyperpermeability persisted during whole period of measurement and it did not return to the initial basal state (Figure 1C)
The group of van Hinsbergh investigated the effect of simvastatin on human umbilical vein endothelial cells (HUVEC) permeability
Summary
The integrity of the vascular endothelial (VE) barrier is maintained by the equilibrium of competing contractile and adhesive forces generated by the acto-myosin-based endothelial cell (EC) contractile machinery and adhesive molecules located at cell–cell and cell–matrix contacts, respectively [1]. Overexpression of a constitutively active form of Rac showed a strong junctional staining of VE-cadherin and abolished H/R-induced loss of cell–cell contacts [4]. Unlike RhoA and Rac, overexpression of a constitutively active or inactive form of Cdc had no significant effect on endothelial barrier integrity [4,6,7,8]. These GTPases act as molecular switches and their activation is primarily regulated by shuttling between the GDP- (inactive) or the GTP-bound (active) form [9]. The prenylation of GTPases can be blocked by HMG-CoA reductase inhibitors (statins) leading to reduced production of the substrate or downstream enzymes responsible for the addition of these moieties to the GTPases [11]
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