Identification of vasodilator‐stimulated phosphoprotein (VASP) as an HIF‐regulated tissue permeability factor during hypoxia

Abstract

Increased tissue permeability is commonly associated with hypoxia of many origins. Since hypoxia-inducible factor (HIF) represents a predominant hypoxia signaling mechanism, we compared hypoxia-elicited changes in tissue barrier function in mice conditionally lacking intestinal epithelial hypoxia-inducible factor-1alpha (hif1a). Somewhat surprisingly, these studies revealed that mutant hif1a mice were protected from hypoxia-induced increases in intestinal permeability in vivo. Guided by microarray analysis of tissues derived from these mutant hif1a mice, we identified HIF-1-dependent repression of vasodilator-stimulated phosphoprotein (VASP), a molecule known to be important in the control of cytoskeletal dynamics, including barrier function. Studies at the mRNA and protein level confirmed hypoxia-elicited repression of VASP in murine tissue, cultured epithelia and endothelia, as well as human saphenous vein ex vivo. Targeted repression of VASP by siRNA recapitulated our findings with hypoxia and directed overexpression of VASP abolished hypoxia-induced barrier dysfunction. Studies in the cloned human VASP promoter revealed hypoxia-dependent transcriptional repression, and functional studies by chromatin immunoprecipitation (ChIP) and site-directed mutagenesis revealed hypoxia-dependent binding of HIF-1alpha to the human VASP promoter. These studies identify HIF-1-dependent repression of VASP as a control point for hypoxia-regulated barrier dysfunction.

Role of vasodilator-stimulated phosphoprotein in cGMP-mediated protection of human pulmonary artery endothelial barrier function

“…There was no basal Ser 239 VASP phosphorylation in any of these monolayers (data not shown), suggesting a phosphorylation-independent PKG I -VASP interaction that served to enhance basal endothelial barrier function. Similar increases in basal permeability in systemic microvascular endothelial cells were reported in monolayers treated with VASP siRNA (28) or derived from VASP knockout mice (29), but PKG I expression was not measured.…”

Hypoxia/Reoxygenation Inhibits P2Y11 Receptor Expression and Its Immunosuppressive Activity in Human Dendritic Cells

“…Additionally, HIF-1a has been implicated in downregulation of several genes that may involve the HIF-1a/Myc pathway (51). Several studies reported that HIF-1a can directly repress gene transcription by binding to response elements present within the gene promoters (52)(53)(54). In this study, we have shown that HIF-1a regulates P2Y11 mRNA expression in human DCs during hypoxia.…”

Differential VASP phosphorylation controls remodeling of the actin cytoskeleton

“…The study correlates defined VASP phosphorylation patterns with distinct functions in endothelial and HEK293 cells. The phospho-VASP-mediated regulation of actin dynamics appears to be of general importance and has been observed in endothelial cells (Benz et al, 2008;Price and Brindle, 2000;Rentsendorj et al, 2008;Rosenberger et al, 2007), leukocytes (Lawrence and Pryzwansky, 2001), platelets and fibroblasts (Grosse et al, 2003), and in glioma (Zhuang et al, 2004), smooth muscle ) and epithelial cells (Lindsay et al, 2007).…”

“…In the endothelium, VASP is involved in sealing cell-cell contacts and permeability regulation (Benz et al, 2008;Furman et al, 2007;Rentsendorj et al, 2008;Rosenberger et al, 2007;Schlegel et al, 2008). S157-P or pseudophosphorylated VASP was enriched at lamellipodia and focal adhesions in spreading cells (Figs 2, 3 and Table 1).…”