Orosomucoid has a cAMP-dependent effect on human endothelial cells and inhibits the action of histamine.
The plasma protein orosomucoid (alpha(1)-acid glycoprotein) has previously been shown to constitute a critical component of the capillary barrier. The protein has also been suggested to act as an anti-inflammatory mediator in a diversity of experimental situations. Recently we reported that orosomucoid is synthesized by the microvascular endothelial cells per se. In the present study, the effects of orosomucoid on primary cultures of human umbilical vein endothelial cells (HUVEC) were studied using the Cytosensor microphysiometer. We found that 1) orosomucoid (0.01 g/l) increased the metabolic activity of HUVEC as reflected by the increased acidification rate of +14 +/- 1%; 2) pretreatment with 0.5 mM 8-bromo-cAMP for 20 min markedly and reversibly inhibited the effect of orosomucoid, whereas 8-bromo-cGMP did not; 3) histamine elicited a dose-dependent response that was abolished by pretreatment with either cAMP or cGMP; and finally, 4) pretreatment of HUVEC for 6 min with orosomucoid (0.01 g/l) inhibited the action of histamine. In summary, this is the first report demonstrating that orosomucoid affects human endothelial cells and that it does so by using cAMP as a second messenger. This provides an explanation for previous findings of anti-inflammatory effects of the protein and shows that orosomucoid affects the endothelium during both normal and pathophysiological conditions.
Sörensson
J
J
Department of Physiology, Göteborg University, SE-405 30 Göteborg, Sweden. jenny.sorensson@fysiologi.gu.se
Ohlson
M
M
Björnson
A
A
Haraldsson
B
B
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000143:Acids / Q000032:analysis / Q000378:metabolism; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006632:Histamine / Q000378:metabolism; D006633:Histamine Antagonists / Q000494:pharmacology*; D006801:Humans; D009961:Orosomucoid / Q000494:pharmacology*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D015290:Second Messenger Systems / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013268:Stimulation, Chemical; D014470:Umbilical Cord; D014841:von Willebrand Factor / Q000096:biosynthesis
D000143:Acids; D017077:Culture Media, Conditioned; D006633:Histamine Antagonists; D009961:Orosomucoid; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D014841:von Willebrand Factor; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D006632:Histamine; D000242:Cyclic AMP; D006152:Cyclic GMP; D019297:2,4-Dinitrophenol