Received for publication October 26, 2007.
Revised December 20, 2007.
Accepted for publication December 21, 2007.

Analysis of Promoter Regions Regulating Basal and Interleukin-4-inducible Expression of the Human CB1 Receptor Gene in T Lymphocytes

Abstract

The majority of effects of cannabinoids are mediated by the two receptors CB1 and CB2. In addition to neuronal cells, CB1 receptors are expressed in T lymphocytes, where they are involved in cannabinoid-induced T helper cell biasing. Although basally expressed only weakly in T cells, CB1 receptors are up-regulated in these cells by stimuli such as cannabinoids themselves. This effect is mediated by interleukin-4. In this study, we investigated basal and interleukin-4-inducible expression of the CB1 gene in T lymphocytes. In a promoter analysis, two regions (nts -3086 to -2490 and nts -1950 to -1653) were identified, which suppress basal transcription of the gene in Jurkat T cells, while the region between nts -648 and -559 enhanced basal CB1 transcription. Interleukin-4 markedly induced transcription of CB1 in Jurkat cells and primary human T cells. Experiments using transcription factor decoy oligonucleotides demonstrated that STAT6 mediates regulation of the gene by interleukin-4. Using reporter gene assays and the transcription factor decoy oligonucleotide approach, a binding site for STAT6 was identified at nt -2769 on the human CB1 gene promoter. Interleukin-4 also caused up-regulation of functional CB1 receptor proteins. In interleukin-4 pretreated, but not in naive Jurkat cells, the CB1 agonist R(+)-methanandamide caused a significant inhibition of forskolin-induced cAMP formation. This effect was blocked by the CB1-selective antogonists AM251 and AM281. Taking together, these data show that CB1 receptors are expressed and up-regulated by interleukin-4 in T lymphocytes, which enables CB1-mediated communication to cells of other systems as for example neuronal cells.

Key words: Cannabinoid, Interleukins, Stat activated transcriptional events, DNA binding sites, Promoter analysis, Regulation of gene expression