Cyclic strain-mediated regulation of vascular endothelial occludin and ZO-1: influence on intercellular tight junction assembly and function.
OBJECTIVE
The vascular endothelium constitutes a highly effective fluid/solute barrier through the regulated apposition of intercellular tight junction complexes. Because endothelium-mediated functions and pathology are driven by hemodynamic forces (cyclic strain and shear stress), we hypothesized a dynamic regulatory link between endothelial tight junction assembly/function and hemodynamic stimuli. We, therefore, examined the effects of cyclic strain on the expression, modification, and function of 2 pivotal endothelial tight junction components, occludin and ZO-1.


RESULTS
For these studies, bovine aortic endothelial cells were subjected to physiological levels of equibiaxial cyclic strain (5% strain, 60 cycles/min, 24 hours). In response to strain, both occludin and ZO-1 protein expression increased by 2.3+/-0.1-fold and 2.0+/-0.3-fold, respectively, concomitant with a strain-dependent increase in occludin (but not ZO-1) mRNA levels. These changes were accompanied by reduced occludin tyrosine phosphorylation (75.7+/-8%) and increased ZO-1 serine/threonine phosphorylation (51.7+/-9% and 82.7+/-25%, respectively), modifications that could be completely blocked with tyrosine phosphatase and protein kinase C inhibitors (dephostatin and rottlerin, respectively). In addition, there was a significant strain-dependent increase in endothelial occludin/ZO-1 association (2.0+/-0.1-fold) in parallel with increased localization of both occludin and ZO-1 to the cell-cell border. These events could be completely blocked by dephostatin and rottlerin, and they correlated with a strain-dependent reduction in transendothelial permeability to FITC-dextran.


CONCLUSIONS
Overall, these findings indicate that cyclic strain modulates both the expression and phosphorylation state of occludin and ZO-1 in vascular endothelial cells, with putative consequences for endothelial tight junction assembly and barrier integrity.
Collins
Nora T
NT
Vascular Health Research Centre, Faculty of Science and Health, Dublin City University, Glasnevin, Dublin 9, Ireland.
Cummins
Philip M
PM
Colgan
Olga C
OC
Ferguson
Gail
G
Birney
Yvonne A
YA
Murphy
Ronan P
RP
Meade
Gerardene
G
Cahill
Paul A
PA
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology; D001578:Benzopyrans / Q000494:pharmacology; D002199:Capillary Permeability / Q000502:physiology; D002417:Cattle; D003911:Dextrans / Q000493:pharmacokinetics; D042783:Endothelial Cells / Q000166:cytology* / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D015870:Gene Expression / Q000502:physiology; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D062793:Occludin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013314:Stress, Mechanical; D019108:Tight Junctions / Q000378:metabolism / Q000502:physiology*; D062826:Zonula Occludens-1 Protein
D000098:Acetophenones; D001578:Benzopyrans; D003911:Dextrans; D004791:Enzyme Inhibitors; D006873:Hydroquinones; D008565:Membrane Proteins; D062793:Occludin; D010750:Phosphoproteins; D012333:RNA, Messenger; D062826:Zonula Occludens-1 Protein; C015219:fluorescein isothiocyanate dextran; C084037:dephostatin; C085746:rottlerin; D011493:Protein Kinase C; D017027:Protein Tyrosine Phosphatases; D016650:Fluorescein-5-isothiocyanate