R(+)-methanandamide-induced cyclooxygenase-2 expression in H4 human neuroglioma cells: possible involvement of membrane lipid rafts |
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Authors: | Hinz Burkhard Ramer Robert Eichele Karin Weinzierl Ulrike Brune Kay |
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Affiliation: | Department of Experimental and Clinical Pharmacology and Toxicology, Friedrich Alexander University Erlangen-Nürnberg, Fahrstrasse 17, D-91054 Erlangen, Germany. hinz@pharmakologie.uni-erlangen.de |
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Abstract: | Cannabinoids induce the expression of the cyclooxygenase-2 (COX-2) isoenzyme in H4 human neuroglioma cells via a pathway independent of cannabinoid- or vanilloid receptor activation. The underlying mechanism was recently shown to involve increased synthesis of ceramide, which in turn leads to activation of p38 and p42/44 mitogen-activated protein kinases (MAPKs). The present study investigates a possible contribution of membrane lipid rafts to cannabinoid-induced COX-2 expression. To address this issue, we tested the influence of methyl-beta-cyclodextrin (MCD), a membrane cholesterol depletor, on COX-2 expression by the endocannabinoid analogue R(+)-methanandamide (R(+)-MA). Incubation of H4 cells with MCD was associated with a loss of lipid raft integrity and a substantial inhibition of R(+)-MA-induced COX-2 expression and subsequent formation of prostaglandin E2. Moreover, MCD was shown to suppress signal transduction steps upstream to COX-2 induction by R(+)-MA. Accordingly, the cholesterol depletor suppressed R(+)-MA-induced formation of ceramide as well as phosphorylation of p38 and p42/44 MAPKs. Together, our results suggest that R(+)-MA induces COX-2 expression in human neuroglioma cells via a pathway linked to lipid raft microdomains. |
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Keywords: | Cannabinoids R(+)-methanandamide Non-cannabinoid receptor-mediated effects Membrane lipid rafts Cyclooxygenase-2 Human neuroglioma cells Mitogen-activated protein kinases |
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