title: Effect of hypoxia on integrin-mediated adhesion of endothelial progenitor cells.
abstract: Homing of endothelial progenitor cells (EPCs) is crucial for neoangiogenesis, which might be negatively affected by hypoxia. We investigated the influence of hypoxia on fibronectin binding integrins for migration and cell-matrix-adhesion. AMP-activated kinase (AMPK) and integrin-linked kinase (ILK) were examined as possible effectors of hypoxia. Human EPCs were expanded on fibronectin (FN) and integrin expression was profiled by flow cytometry. Cell-matrix-adhesion- and migration-assays on FN were performed to examine the influence of hypoxia and AMPK-activation. Regulation of AMPK and ILK was shown by Western blot analysis. We demonstrate the presence of integrin β(1), β(2) and α(5) on EPCs. Adhesion to FN is reduced by blocking β(1) and α(5) (49% and 2% of control, P < 0.05) whereas α(4)-blockade has no effect. Corresponding effects were shown for migration. Hypoxia and AMPK-activation decrease adhesion on FN. Although total AMPK-expression remains unchanged, phospho-AMPK increases eightfold. The EPCs require α(5) for adhesion on FN. Hypoxia and AMPK-activation decrease adhesion. As α(5) is the major adhesive factor for EPCs on FN, this suggests a link between AMPK and α(5)-integrins. We found novel evidence for a connection between hypoxia, AMPK-activity and integrin activity. This might affect the fate of EPCs in ischaemic tissue.
authors.affiliation: Klinik für Innere Medizin V (Pneumologie), Universitätsklinikum des Saarlandes, Homburg/Saar, Germany. ralfkaiser@gmx.net
authors.forename: Ralf
authors.initials: R
authors.lastname: Kaiser
authors.forename: Denise
authors.initials: D
authors.lastname: Friedrich
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Chavakis
authors.forename: Michael
authors.initials: M
authors.lastname: Böhm
authors.forename: Erik B
authors.initials: EB
authors.lastname: Friedrich
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D002448:Cell Adhesion; D015687:Cell Hypoxia; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology*; D005353:Fibronectins / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D036102:Peripheral Blood Stem Cell Transplantation; D010766:Phosphorylation; D013234:Stem Cells / Q000166:cytology*
chemical_list: D005353:Fibronectins; D016023:Integrins; D055372:AMP-Activated Protein Kinases