Role of nuclear factor of activated T-cells and activator protein-1 in theinhibition of interleukin-2 gene transcription by cannabinol in EL4 T-cells

We previously reported that immunosuppressive cannabinoids inhibited interl eukin (IL)-2 steady-state mRNA expression and secretion by phorbol-12-myris tate-13-acetate plus ionomycin-activated mouse splenocytes and EL4 murine T -cells. Here we show that inhibition of IL-2 production by cannabinol, a mo dest central nervous system-active cannabinoid, is mediated through the inh ibition of IL-2 gene transcription. Moreover, electrophoretic mobility shif t assays demonstrated that cannabinol markedly inhibited the DNA binding ac tivity of nuclear factor of activated T-cells (NF-AT) and activator protein -1 (AP-1) in a time- and concentration-dependent manner in activated EL4 ce lls. The inhibitory effects produced by cannabinol on AP-1 DNA binding were quite transient, showing partial recovery by 240 min after cell activation and no effect on the activity of a reporter gene under the control of AP-1 . Conversely, cannabinol-mediated inhibition of NF-AT was robust and sustai ned as demonstrated by an NF-AT-regulated reporter gene. Collectively, thes e results suggest that decreased IL-2 production by cannabinol in EL4 cells is due to the inhibition of transcriptional activation of the IL-2 gene an d is mediated, at least in part, through a transient inhibition of AP-1 and a sustained inhibition of NF-AT.