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Author Notes:

Correspondence: Dr. Robert Swerlick, Emory University Dept of Dermatology, 101 Woodruff Circle, WMB 5001, Atlanta, GA 30322; Tel: 404-727-3669; Fax: 404-727-5878; Email: rswerli@emory.edu

Disclosures: The authors have no conflict of interest to declare

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Research Funding:

This work was supported by NIH/NIAMS (T32 AR007587) and VA Merit Award.

Hypoxia and hypoxia mimetics inhibit TNF-dependent VCAM1 induction in the 5A32 endothelial cell line via a hypoxia inducible factor dependent mechanism

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Journal Title:

Journal of Dermatological Science

Volume:

Volume 65, Number 2

Publisher:

, Pages 86-94

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Background We previously reported that iron chelators inhibit TNFα-mediated induction of VCAM-1 in human dermal microvascular endothelial cells. We hypothesized that iron chelators mediate inhibition of VCAM-1 via inhibition of iron-dependent enzymes such as those involved with oxygen sensing and that similar inhibition may be observed with agents which simulate hypoxia. Objective We proposed to examine whether non-metal binding hypoxia mimetics inhibit TNFα-mediated VCAM-1 induction and define the mechanisms by which they mediate their effects on VCAM-1 expression. Methods These studies were undertaken in vitro using immortalized dermal endothelial cells, western blot analysis, ELISA, immunofluorescence microscopy, quantitative real-time PCR, and chromatin immunoprecipitation. Results Hypoxia and the non-iron binding hypoxia mimetic dimethyl oxallyl glycine (DMOG) inhibited TNFα-mediated induction of VCAM-1. DMOG inhibition of VCAM-1 was dose-dependent, targeted VCAM-1 gene transcription independent of NF-κB nuclear translocation, and blocked TNFα-mediated chromatin modifications of relevant elements of the VCAM-1 promoter. Combined gene silencing of both HIF-1α and HIF-2α using siRNA led to a partial rescue of VCAM expression in hypoxia mimetic-treated cells. Conclusion Iron chelators, non-metal binding hypoxia mimetics, and hypoxia all inhibit TNFα-mediated VCAM-1 expression. Inhibition is mediated independent of nuclear translocation of NF-kB, appears to target TNFα-mediated chromatin modifications, and is at least partially dependent upon HIF expression. The absence of complete VCAM-1 expression rescue with HIF silencing implies an important regulatory role for an Fe(II)/α-ketoglutarate dioxygenase distinct from the prolyl and asparagyl hydroxylases that control HIF function. Identification of this dioxygenase may provide a valuable target for modulating inflammation in human tissues.

Copyright information:

© 2012, Elsevier

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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