Effect of endothelin-1 and endothelin receptor blockade on the release of microparticles.
BACKGROUND
Increased levels of endothelial cell microparticles (EMP) are known to reflect endothelial dysfunction (ED). In diabetes mellitus type 2 (T2DM), the expression of endothelin (ET)-1 is increased. As treatment with an ET-1 antagonist significantly inhibited atherosclerosis in animal models, we sought to investigate whether treatment with ET-1 antagonists affects EMP levels in vitro and in vivo in patients with T2DM.


METHODS
In vitro study: Human umbilical vein endothelial cells (HUVEC) were stimulated with ET-1 alone and ET-1 in combination with a dual ET-A and ET-B endothelin receptor blocker. In vivo study: Patients with T2DM were randomized to treatment with the ET receptor antagonist bosentan or placebo. After 4 weeks, the patients were re-examined and blood samples were obtained. EMP counts in supernatants and plasma samples were determined using flow cytometry.


RESULTS
In vitro study: In supernatants of ET-1-stimulated HUVECs, the increased release of EMP was reduced significantly by co-incubation with an ET-1 receptor antagonist (e.g. CD31+/CD42b-EMP decreased from 37·1% ± 2·8 to 31·5% ± 2·8 SEM, P = 0·0078). In vivo study: No changes in EMP levels in blood samples of patients with T2DM were found after 4 weeks of bosentan treatment (n = 36, P = ns).


CONCLUSIONS
Our in vitro results suggest that ET-1 stimulates the release of EMP from HUVECs via a receptor-dependent mechanism. Co-incubation with an endothelin receptor blocker abolished ET-1-dependent EMP release. However, treatment with bosentan for 4 weeks failed to alter EMP levels in patients with T2DM. Other factors seem to have influenced EMP release in patients with T2DM independent of ET-1 receptor-mediated mechanisms.
Division of Cardiology, Pulmonology, and Vascular Medicine, Medical Faculty, University Duesseldorf, Duesseldorf, Germany.|Division of Cardiology, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Christian
C
Jung
Clinic of Internal Medicine II, Department of Cardiology, Paracelsus Medical University of Salzburg, Salzburg, Austria.
Michael
M
Lichtenauer
Clinic of Internal Medicine II, Department of Cardiology, Paracelsus Medical University of Salzburg, Salzburg, Austria.
Bernhard
B
Wernly
Universitätsherzzentrum Thüringen, Clinic of Internal Medicine I, Department of Cardiology, Friedrich Schiller University Jena, Jena, Germany.
Marcus
M
Franz
Universitätsherzzentrum Thüringen, Clinic of Internal Medicine I, Department of Cardiology, Friedrich Schiller University Jena, Jena, Germany.
Bjoern
B
Goebel
Division of Cardiology, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Arnar
A
Rafnsson
Universitätsherzzentrum Thüringen, Clinic of Internal Medicine I, Department of Cardiology, Friedrich Schiller University Jena, Jena, Germany.
Hans-Reiner
HR
Figulla
Division of Cardiology, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
John
J
Pernow
D000077300:Bosentan; D055252:Cell-Derived Microparticles / Q000187:drug effects*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D004311:Double-Blind Method; D065130:Endothelin A Receptor Antagonists / Q000494:pharmacology*; D065128:Endothelin Receptor Antagonists / Q000627:therapeutic use; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D044022:Receptor, Endothelin A / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology
D065130:Endothelin A Receptor Antagonists; D065128:Endothelin Receptor Antagonists; D044022:Receptor, Endothelin A; D013449:Sulfonamides; D000077300:Bosentan
Diabetes; endothelial cells; endothelial microparticles; endothelin