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Akt1 promotes stimuli-induced endothelial-barrier protection through FoxO-mediated tight-junction protein turnover.

ABSTRACT: Vascular permeability regulated by the vascular endothelial growth factor (VEGF) through endothelial-barrier junctions is essential for inflammation. Mechanisms regulating vascular permeability remain elusive. Although 'Akt' and 'Src' have been implicated in the endothelial-barrier regulation, it is puzzling how both agents that protect and disrupt the endothelial-barrier activate these kinases to reciprocally regulate vascular permeability. To delineate the role of Akt1 in endothelial-barrier regulation, we created endothelial-specific, tamoxifen-inducible Akt1 knockout mice and stable ShRNA-mediated Akt1 knockdown in human microvascular endothelial cells. Akt1 loss leads to decreased basal and angiopoietin1-induced endothelial-barrier resistance, and enhanced VEGF-induced endothelial-barrier breakdown. Endothelial Akt1 deficiency resulted in enhanced VEGF-induced vascular leakage in mice ears, which was rescued upon re-expression with Adeno-myrAkt1. Furthermore, co-treatment with angiopoietin1 reversed VEGF-induced vascular leakage in an Akt1-dependent manner. Mechanistically, our study revealed that while VEGF-induced short-term vascular permeability is independent of Akt1, its recovery is reliant on Akt1 and FoxO-mediated claudin expression. Pharmacological inhibition of FoxO transcription factors rescued the defective endothelial barrier due to Akt1 deficiency. Here we provide novel insights on the endothelial-barrier protective role of VEGF in the long term and the importance of Akt1-FoxO signaling on tight-junction stabilization and prevention of vascular leakage through claudin expression.

SUBMITTER: Gao F

PROVIDER: S-EPMC5023469 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Akt1 promotes stimuli-induced endothelial-barrier protection through FoxO-mediated tight-junction protein turnover.

Gao Fei F Artham Sandeep S Sabbineni Harika H Al-Azayzih Ahmad A Peng Xiao-Ding XD Hay Nissim N Adams Ralf H RH Byzova Tatiana V TV Somanath Payaningal R PR

Cellular and molecular life sciences : CMLS 20160425 20

Vascular permeability regulated by the vascular endothelial growth factor (VEGF) through endothelial-barrier junctions is essential for inflammation. Mechanisms regulating vascular permeability remain elusive. Although 'Akt' and 'Src' have been implicated in the endothelial-barrier regulation, it is puzzling how both agents that protect and disrupt the endothelial-barrier activate these kinases to reciprocally regulate vascular permeability. To delineate the role of Akt1 in endothelial-barrier r ...[more]

PMID: 27113546

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Project description:Rationale: Endothelial cells (ECs) line the inner surface of continuous capillaries and form a permselective barrier between blood and tissues to limit paracellular fluid and solute flux. The capillary barrier is maintained by intercellular tight junctions (TJs) which are regulated, in part, by differential activity of small GTPases. Tumor necrosis factor (TNF) causes TJ disassembly in a process dependent upon NF-κB-mediated gene expression. Activated (GTP-bound) RhoB has been identified as a downstream effector of TNF-induced leak both through Rho-associated coiled-coil kinase-mediated phosphorylation of RelA, enhancing TNF-induced NF-κB-mediated gene activation, and through sequestration of Rac1 away from the cell junction, preventing barrier restoration. To date, no TNF-induced, RhoB-selective GTP exchange factor (GEF) has been identified in ECs. Objective: Identify a TNF-induced RhoB specific GEF in capillary ECs. Method and Results: human dermal microvascular ECs (HDMECs) were used because they form TJs. Candidate GEFs were identified by whole transcriptome profiling of HDMECs with or without TNF stimulation. Fifty-seven of 73 known GEFs were expressed in HDMECs and 17 were significantly upregulated by TNF. Functional impact of each of the latter group was assessed by measuring the effects of depletion by short interfering RNA knockdown on TNF-induced reduction of trans-endothelial electrical resistance (TEER) of HDMEC monolayers. Depletions of ArhGEF10 or RhoB or double depletion of ArhGEF10/RhoB similarly decreased TNF-mediated reduction of TEER. ArhGEF10 knockdown prevented TNF-induced disruption of TJ proteins assessed by confocal microscopy. TNF-induced increases in the levels of activated RhoB in HDMEC lysates were markedly reduced with only minimal alterations in RhoA or RhoC activation. Finally, immunoisolated ArhGEF10 selectively catalyzed GTP exchange for GDP in RhoB, but not RhoA or RhoC, in vitro. Conclusion: ArhGEF10 is a TNF-induced RhoB-selective GEF for RhoB in cultured human capillary ECs that contributes to TJ disruption.

Dataset Information

Akt1 promotes stimuli-induced endothelial-barrier protection through FoxO-mediated tight-junction protein turnover.

Publications

Akt1 promotes stimuli-induced endothelial-barrier protection through FoxO-mediated tight-junction protein turnover.

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