Hypoxia enhances stimulus-dependent induction of E-selectin on aortic endothelial cells.
In many diseases, tissue hypoxia occurs in conjunction with other inflammatory processes. Since previous studies have demonstrated a role for leukocytes in ischemia/reperfusion injury, we hypothesized that endothelial hypoxia may "superinduce" expression of an important leukocyte adhesion molecule, E-selectin (ELAM-1, CD62E). Bovine aortic endothelial monolayers were exposed to hypoxia in the presence or absence of tumor-necrosis factor alpha (TNF-alpha) or lipopolysaccharide (LPS). Cell surface E-selectin was quantitated by whole cell ELISA or by immunoprecipitation using polyclonal anti-E-selectin sera. Endothelial mRNA levels were assessed using ribonuclease protection assays. Hypoxia alone did not induce endothelial E-selectin expression. However, enhanced induction of E-selectin was observed with the combination of hypoxia and TNF-alpha (270% increase over normoxia and TNF-alpha) or hypoxia and LPS (190% increase over normoxia and LPS). These studies revealed that a mechanism for such enhancement may be hypoxia-elicited decrements in endothelial intracellular levels of cAMP (<50% compared with normoxia). Addition of forskolin and isobutyl-methyl-xanthine during hypoxia resulted in reversal of cAMP decreases and a loss of enhanced E-selectin surface expression with the combination of TNF-alpha and hypoxia. We conclude that endothelial hypoxia may provide a novel signal for superinduction of E-selectin during states of inflammation.
Zünd
G
G
Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesia, Brigham and Women's Hospital, Boston, MA 02115, USA.
Nelson
D P
DP
Neufeld
E J
EJ
Dzus
A L
AL
Bischoff
J
J
Mayer
J E
JE
Colgan
S P
SP
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D015153:Blotting, Western; D002417:Cattle; D015687:Cell Hypoxia; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D019040:E-Selectin / Q000096:biosynthesis*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D013873:Thionucleotides / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D019040:E-Selectin; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D013873:Thionucleotides; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; C016957:adenosine-3',5'-cyclic phosphorothioate; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine