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Arterioscler Thromb Vasc Biol. 2007 May;27(5):1184-90. Epub 2007 Mar 8.

EXP3179 inhibits collagen-dependent platelet activation via glycoprotein receptor-VI independent of AT1-receptor antagonism: potential impact on atherothrombosis.

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1
Abt. fuer Kardiologie und Angiologie, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.

Abstract

OBJECTIVE:

Thrombus formation after atherosclerotic plaque rupture critically involves the platelet collagen receptor glycoprotein (GP) VI. We investigated the impact of EXP3179, an active metabolite of the angiotensin II type 1 (AT1)-receptor antagonist Losartan (LOS) on GPVI-dependent platelet activation.

METHODS AND RESULTS:

EXP3179 and LOS but not EXP3174--the major AT1-receptor blocking metabolite of LOS--dose-dependently inhibited collagen-I (P<0.01) and GPVI-dependent platelet aggregation (P<0.01) analyzed by optical aggregometry. Platelet activation was further determined by flow cytometry measuring the expression of platelet PAC-1, an epitope of the activated fibrinogen-receptor complex. EXP3179 and LOS inhibited collagen-I (P<0.01) and GPVI-dependent PAC-1 expression (P<0.01). EXP3179 and LOS but not EXP3174 decreased the adhesion of GPVI-receptor expressing Chinese hamster ovarian cells on collagen-I under arterial shear conditions determined by flow chamber analysis (P<0.01 and P<0.05). EXP3179 also reduced human atherosclerotic plaque material-induced platelet aggregation (P<0.01) in vitro and murine platelet adhesion after acute vessel injury in vivo as determined by intravital microscopy (P<0.01).

CONCLUSION:

EXP3179 acts as a specific inhibitor of the platelet collagen receptor GPVI independent of AT1-receptor antagonism. Further investigations may clarify its individual potential as a novel pharmacological approach to specifically inhibit atherothrombotic events by GPVI-receptor blockade.

PMID:
17347483
DOI:
10.1161/ATVBAHA.106.138693
[Indexed for MEDLINE]
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