Roles of Rho/ROCK and MLCK in TNF‐α‐induced changes in endothelial morphology and permeability

Abstract

Tumor necrosis factor‐α (TNF‐α) is known to induce changes in endothelial cell morphology and permeability, but the mechanisms have not been extensively characterized. TNF‐α rapidly induced RhoA activation and myosin light chain phosphorylation, but caused only small changes to cortical F‐actin, without significantly increasing paracellular permeability up to 30 min after stimulation. TNF‐α subsequently caused a progressive increase in permeability and in stress fiber reorganization, cell elongation, and intercellular gap formation over 8–24 h. Consistent with the increased permeability, Occludin and JAM‐A were removed from tight junctions and ZO‐1 was partially redistributed. Rho/ROCK but not MLCK inhibition prevented the long‐term TNF‐α‐induced changes in F‐actin and cell morphology, but ROCK inhibition did not affect permeability. These results suggest that the gradual increase in permeability induced by TNF‐α does not reflect contractile mechanisms mediated by Rho, ROCK, and MLCK, but involves long‐term reorganization of tight junction proteins. J. Cell. Physiol. 213: 221–228, 2007. © 2007 Wiley‐Liss, Inc.