Exposing endothelial cells to tumor necrosis factor-alpha and peripheral blood mononuclear cells damage endothelial integrity via interleukin-1 beta by degradation of vascular endothelial-cadherin

Background and purpose. We demonstrated previously that the administration of tumor necrosis factor alpha (TNF-alpha) for the treatment of solid tumors enhanced the respon'se to chemotherapy by augmenting intratumoral drug accumulation. TNF-alpha changes the integrity of the endothelial cell monolayer in combination with interferon gamma (IFN-gamma), which is further enhanced by the addition of peripheral blood mononuclear cells (PBMCs). The improved effect of PBMG5 was mostly induced by the endogenous production of interleukin-1beta (IL-1 beta) after TNF-alpha stimulation. In the current study, we demonstrate that exposing endothelial cells to TNF-alpha and PBMCs mediates the loss of vascular endothelial (VE)-cadherin, an important adherens junction, protein for maintaining endothelial'integrity, through endogenous IL-1 beta. This loss increases permeability of the endothelial layer, thereby explaining the augmented passage of chemotherapeutics into the tumor. Methods. Human umbilical vein endothelial cells were exposed to TNF-alpha, PBMCs, or IL-1 beta, and the effects on the endothelial integrity were assessed by morphological changes and permeability changes with the use of fluorescein isothiocyanate-labeled bovine serum albumin flux. The loss of VE-cadherin was assessed using immunofluorescence, western blotting, and polymerase chain reaction. Results. Incubating endothelial cells with TNF-alpha, and PBMCs increased cell elongation, gap formation, and subsequently the permeability of fluorescein isothiooyanate-labeled bovine serum albumin compared with control or TNF-alpha and HATT treated cells (P < .05). When PBMCs were replaced with IL-1 beta, identical changes were observed. These changes in integrity were associated with a loss of VE-cadherin at the membrane. Conclusion. We conclude that VE-cadherin is lost at the membrane when endothelial cells are exposed to TNF-alpha, IFIV-gamma, and PBMCs, which results in loss of integrity. IL-1 beta can mimic the effects of PBMCs, indicating a dominant role of endogenously produced IL-1 beta in this process.