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(The FASEB Journal. 1998;12:1035-1044.)
© 1998 FASEB
RESEARCH COMMUNICATION
Platelet- and macrophage-derived endogenous cannabinoids are involved in endotoxin-induced hypotension
Károly Vargaa, Jens A. Wagnera, D. Troy Bridgena, and George Kunosa a Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Virginia 23298, USA
Macrophages are the primary cellular targets of bacterial lipopolysaccharide (LPS), but the role of macrophage-derived cytokines in LPS-induced septic shock is uncertain. Recent evidence indicates that activation of peripheral CB1 cannabinoid receptors contributes to hemorrhagic hypotension and that macrophage-derived anandamide as well as unidentified platelet-derived substances may be contributing factors. Here we demonstrate that rat platelets contain the endogenous cannabinoid 2-arachidonyl glyceride (2-AG), as identified by reverse phase high-performance liquid chromatography, gas chromatography, and mass spectrometry, and that in vitro exposure of platelets to LPS (200 µg/ml) markedly increases 2-AG levels. LPS-stimulated, but not control, macrophages contain anandamide, which is undetectable in either control or LPS-stimulated platelets. Prolonged hypotension and tachycardia are elicited in urethane-anesthetized rats treated 1) with LPS (15 mg/kg i.v.); 2) with macrophages plus platelets isolated from 3 ml of blood from an LPS-treated donor rat; or 3) with rat macrophages or 4) platelets preincubated in vitro with LPS (200 µg/ml). In all four cases, the hypotension but not the tachycardia is prevented by pretreatment of the recipient rat with the CB1 receptor antagonist SR141716A (3 mg/kg i.v.), which also inhibits the hypotensive response to anandamide or 2-AG. The hypotension elicited by LPS-treated macrophages or platelets remains unchanged in the absence of sympathetic tone or after blockade of nitric oxide synthase. These findings indicate that platelets and macrophages generate different endogenous cannabinoids, and that both 2-AG and anandamide may be paracrine mediators of endotoxin-induced hypotension via activation of vascular CB1 receptors.—Varga, K., Wagner, J. A., Bridgen, D. T., Kunos, G. Platelet- and macrophage-derived endogenous cannabinoids are involved in endotoxin-induced hypotension. FASEB J. 12, 1035–1044 (1998)
Key Words: anandamide • 2-arachidonyl glyceride • CB1 cannabinoid receptors • vasodilation
Copyright © 1998 by the The Federation of American Societies for Experimental Biology.
varga-01.pdf
file size: 343.34KB (351585 bytes)