Systemic anthrax disease is characterized by vascular leakage pathologies. We previously reported that anthrax lethal toxin (LT) induces human endothelial barrier dysfunction in a cell death-independent manner with actin stress fiber formation and disruption of adherens junctions (AJs). In the present study, we further characterize the molecular changes in the AJ complex and investigate whether AJ structure and barrier function can be preserved by modulating key cytoskeletal signaling pathways. Here, we show that LT reduces total VE-cadherin protein and gene expression but the expression of the key linker protein beta-catenin remained unchanged. The changes in VE-cadherin expression correlated temporally with the appearance of actin stress fibers and a two-fold increase in phosphorylation of the stress fiber-associated protein myosin light chain (p-MLC) and cleavage of Rho-associated kinase-1 (ROCK-1). Co-treatment with ROCK inhibitors (H-1152 and Y27632), but not an inhibitor of MLC kinase (ML-7), blocked LT-induced p-MLC enhancement and stress fiber formation. This was accompanied by the restoration of VE-cadherin expression and membrane localization, and attenuation of the LT-induced increase in monolayer permeability to albumin. Together, these findings suggest the ROCK pathway may be a relevant target for countering LT-mediated endothelial barrier dysfunction.
Keywords: anthrax lethal toxin; actin stress fibers; adherens junction; barrier function; cadherin; vascular endothelium.