Effect of JNK inhibition on VE-cadherin phosphorylation, intercellular gap formation and monolayer permeability. (A) TNF-induced tyrosine phosphorylation of VE-cadherin was examined after transfection with vector, LNCX (control), or DN-JNK1. The dominant-negative JNK mutant prevented TNF-induced tyrosine phosphorylation of VE-cadherin (top panel). (B) Confluent HUVEC monolayers were exposed to vehicle or saline in the presence or absence of the JNK inhibitor SP600125. The JNK inhibitor prevented TNF-induced FITC–dextran transmonolayer flux. *P < .05; n > 6 per group. (C-F) Dominant-negative JNK1 prevents TNF-induced junctional disassembly, intercellular gap formation, and VE-cadherin redistribution. HUVECs were cotransfected with full-length VE-cadherin GFP and either LNCX (C-D) or dominant-negative JNK1 (E-F) and were examined by confocal microscopy in the presence of vehicle (C, E) or TNF (D, F). As did nontransfected cells, VE-cadherin GFP localized to adherens junctions (C, solid arrow). In cells transfected with LNCX, TNF caused junctional disassembly and intercellular gap formation (D, open arrow). This was accompanied by redistribution of VE-cadherin GFP from adherens junctions. Transfection with dominant-negative JNK1 prevented TNF-induced junctional disassembly, gap formation, and VE-cadherin redistribution (F). This effect of dominant-negative JNK1 was present for up to 30 minutes of TNF exposure.