Published online before print November 6, 2008
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9-tetrahydrocannabinolDepartment of Pharmacology and Toxicology and Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA
1 Correspondence: Department of Pharmacology and Toxicology, Center for Integrative Toxicology, 315 National Food Safety and Toxicology Building, East Lansing, MI, 48824-1317, USA. E-mail: kamins11{at}msu.edu
ABSTRACT
Inducible costimulator (ICOS), a prototypic T cell costimulator, is induced on activated T cells. ICOS regulates T cell activation and Th cell differentiation and is principally involved in humoral immune responses. Previous work showed that T cell accessory function is modulated by the plant-derived cannabinoid, delta-9-tetrahydrocannabinol (
9-THC). In light of an emerging role by ICOS in T cell-mediated immunity, the objective of this study was to investigate the effect of
9-THC on ICOS in activated mouse T cells. Induction of ICOS mRNA levels by phorbol ester (PMA) plus ionomycin (Io) activation in mouse splenocytes was attenuated by
9-THC in a concentration-related manner. Similar results were obtained in the mouse T cell line, EL4.IL-2. Anti-CD3/CD28 induced ICOS expression on CD4+ splenic T cells, which was suppressed by
9-THC in a time- and concentration-related manner. The PMA/Io-induced icos promoter luciferase reporter activity was also down-regulated by
9-THC, suggesting that the suppression of ICOS expression by
9-THC occurs at the transcriptional level. Moreover, transcriptional activation of the NFAT was also down-regulated by
9-THC as shown by a NFAT luciferase reporter assay, which is consistent with a putative role of NFAT in regulating ICOS expression. Collectively,
9-THC suppresses ICOS expression in activated T cells, and this suppression may be related, in part, to its modulation of NFAT signaling. The emerging role of ICOS in a wide range of immune-related diseases also suggests that it may represent a potential therapeutic target, which could be modulated by cannabinoid compounds.
Key Words: cannabinoid splenocyte NFAT immunomodulation
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