CANNABINOID INHIBITION OF ADENYLATE CYCLASE-MEDIATED SIGNAL-TRANSDUCTION AND INTERLEUKIN-2 (IL-2) EXPRESSION IN THE MURINE T-CELL LINE, EL4.IL-2

Cannabinoid receptors negatively regulate adenylate cyclase through a pertussis toxin-sensitive GTP-binding protein. In the present studies, signaling via the adenylate cyclase/cAMP pathway was investigated in the murine thymoma-derived T-cell line, EL4.IL-2. Northern analysis of EL4.IL-2 cells identified the presence of 4-kilobase CB2 but not CB1 receptor-subtype mRNA transcripts. Southern analysis of genomic DNA di gests for the CB2 receptor demonstrated identical banding patterns for EL4.IL-2 cells and mouse-derived DNA, both of which were dissimilar t o DNA isolated from rat, Treatment of EL4.IL-2 cells with either canna binol or Delta(9)-THC disrupted the adenylate cyclase signaling cascad e by inhibiting forskolin-stimulated cAMP accumulation which consequen tly led to a decrease in protein kinase A activity and the binding of transcription factors to a CRE consensus sequence. Likewise, an inhibi tion of phorbol 12-myristate 13-acetate (PMA)/ionomycin-induced interl eukin 2 (IL-2) protein secretion, which correlated to decreased IL-2 g ene transcription, was induced by both cannabinol and Delta(9)-THC. Fu rther, cannabinoid treatment also decreased PMA/ionomycin-induced nucl ear factor binding to the AP-1 proximal site of the IL-2 promoter. Con versely, forskolin enhanced PMA/ionomycin-induced AP-1 binding. These findings suggest that inhibition of signal transduction via the adenyl ate cyclase/cAMP pathway induces T-cell dysfunction which leads to a d iminution in IL-2 gene transcription.