Interleukin-6 causes endothelial barrier dysfunction via the protein kinase C pathway.
BACKGROUND
Elevated levels of interleukin-6 (IL-6) have been identified in a variety of systemic inflammatory states that are associated with endothelial barrier dysfunction, but the specific effect of IL-6 on endothelial permeability and the mechanism of action have not been fully examined. The current study evaluated the effect of IL-6 on endothelial permeability and on the distribution of the tight junctional protein ZO-1 and cytoskeletal actin. We also assessed the role of protein kinase C (PKC) in this process.


METHODS
Confluent monolayers of human umbilical vein endothelial cells (n = 6) were exposed to IL-6 (50-500 ng/ml) in the presence or absence of the PKC inhibitor Gö6976 (0.1 microM). Transendothelial electrical resistance (TEER) was measured at the onset of exposure and at 6-h intervals and compared with that of control cells using ANOVA with a Bonferroni multiple comparison test. Additional monolayers were exposed to IL-6, stained for ZO-1 and F-actin, and evaluated via fluorescence microscopy.


RESULTS
Interleukin-6 increased endothelial permeability as measured by TEER in a dose- and time-dependent manner. In the presence of PKC inhibitor, the IL-6-mediated increase in permeability was attenuated (18-h TEER 73% of control with IL-6 exposure vs 95% of control with IL-6 + Gö6976 inhibitor, P < 0.01). Microscopy revealed that permeability changes were accompanied by a redistribution of the tight junctional protein ZO-1 and cytoskeletal actin, increased cell contraction, and disorganization of the intercellular borders. Conclusions. The inflammatory cytokine IL-6 is an important mediator of increased endothelial permeability via alterations in the ultrastructural distribution of tight junctions and morphologic changes in cell shape. PKC is a critical intracellular messenger in these IL-6-mediated changes. A better understanding of this mechanism should allow the determination of rational treatment strategies for endothelial barrier dysfunction which occurs in inflammatory states.
Desai
Tina R
TR
Department of Surgery, University of Chicago, Chicago, Illinois 60637, USA. tdesai@surgery.bsd.uchicago.edu
Leeper
Nicholas J
NJ
Hynes
Karen L
KL
Gewertz
Bruce L
BL
D000199:Actins / Q000032:analysis; D002199:Capillary Permeability; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000503:physiopathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D008565:Membrane Proteins / Q000032:analysis; D010446:Peptide Fragments / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D014471:Umbilical Veins; D062826:Zonula Occludens-1 Protein
D000199:Actins; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D015850:Interleukin-6; D008565:Membrane Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; C073885:protein kinase C (19-31); C081021:Go 6976; D011493:Protein Kinase C