Cyclic Strain–Mediated Regulation of Vascular Endothelial Occludin and ZO-1

Abstract

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. Methods and 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 2.3Ϯ0.1-fold and 2.0Ϯ0.3-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 (75.7Ϯ8%) and increased ZO-1 serine/threonine phosphorylation (51.7Ϯ9% and 82.7Ϯ25%, 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 (2.0Ϯ0.1-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. Key Words: occludin Ⅲ ZO-1 Ⅲ endothelium Ⅲ cyclic strain Ⅲ permeability T he vascular endothelial monolayer or endothelium is a dynamic cellular interface between the vessel wall and bloodstream. In addition to regulating the physiological effects of humoral and mechanical stimuli on blood vessel tone and remodeling, the endothelium participates in immune and inflammatory reactions and presents a nonthrombogenic surface for blood flow. 1,2 Moreover, the vascular endothelium constitutes a highly effective barrier, which regulates fluid and solute balance in addition to movement of molecular/ cellular components between bloodstream and tissues. [3][4][5] As such, regulation of endothelial barrier integrity (or permeability) is crucial for vascular homeostasis and is a central pathophysiologic mechanism of many vascular processes, including wound healing, angiogenesis, and vascular diseases. [5][6][7] Barrier function is maintained by the regulated apposition of tight junction and adherens protein complexes between adjacent endothelial cells. The organization of these protein complexes is controlled by a number of physiolog...

12/15-Lipoxygenase Mediates High-fat Diet-induced Endothelial Tight Junction Disruption and Monocyte Transmigration

“…The role of phosphorylation of TJ proteins in the regulation of endothelial TJ integrity has not been studied in detail. In this aspect, some studies showed that tyrosine phosphorylation of endothelial TJ proteins leads to loss of its barrier function (36). In the present study, we, for the first time, report that Src-Pyk2-mediated phosphorylation of ZO-2 results in TJ disassembly and enhances EC permeability in response to 15(S)-HETE.…”

“…1B). Several kinases and phosphatases were reported to regulate the assembly and/or disassembly of TJs via modulation of the phosphorylation state of TJ proteins in epithelial cells as well as ECs (33)(34)(35)(36)(37). Therefore, we next studied the phosphorylation of TJ proteins.…”

Ascorbic Acid Prevents Blood–Brain Barrier Disruption and Sensory Deficit Caused by Sustained Compression of Primary Somatosensory Cortex

“…In our model, despite no ischemic signs, cortical compression significantly reduced the size of the cortical microvessels. This may cause the alteration of the blood flow-associated hemodynamic forces such as shear stress and cyclic strain on the vascular endothelium, which have been evidenced to activate integrin and Rac1, to decrease the occludin tyrosine phosphorylation and increase the ZO-1 serine/threonine phosphorylation, and to modulate the expression, association, and distribution of occludin and ZO-1 (Colgan et al, 2007;Collins et al, 2006;Tzima et al, 2002). Moreover, increasing evidences have suggested that the BBB permeability is strictly regulated by the redistribution of tight junction proteins between the cell membrane and the cytoplasmic fraction of endothelial cells, and the underlying mechanism involves the phosphorylation of tyrosine, serine, or threonine in the tight junction proteins (Andras et al, 2007;Elias et al, 2009).…”

Cyclic strain-mediated matrix metalloproteinase regulation within the vascular endothelium: a force to be reckoned with

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“…Both models reveal that cyclic strain has a profound impact on endothelial metabolism and can induce qualitative and quantitative changes in gene expression leading to changes in cell fate, with consequences for endothelial phenotype and vessel wall homeostasis (17,111,146). In addition to affecting the expression and/or activation of numerous signaling molecules associated with mechanotransduction, cyclic strain has been shown to regulate the expression and/or activation of several classes of effector genes (and gene products) in vascular ECs, including those regulating 1) vessel diameter: NO, nitric oxide synthase (NOS), cyclooxygenase-2 (COX-2), endothelin (ET)-1, and thimet oligopeptidase (16,20,22,74); 2) proliferation: platelet-derived growth factor (PDGF) and vascular endothelial growth factor (140,169); 3) migration/angiogenesis: Arg-Gly-Asp (RGD)-dependent integrins, urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor (PAI)-1, monocyte chemotactic protein (MCP)-1, MMP-2, MMP-9, and membrane type 1 MMP (MT1-MMP, MMP-14) (150, 152-155, 162, 164); and 4) cell-cell communication/barrier function: intercellular adhesion molecule (ICAM)-1, zonula occludens (ZO)-1, and occludin (21,117).…”