Kujigamberol Inhibits IFN-γ and IL-2 mRNA Expression and NFATc2 Binding to Their Promoters in Response to a Phorbol Ester and Ionomycin Stimulation

Kujigamberol, a dinorlabdane compound isolated from Kuji amber, exerts multiple biological effects, including anti-allergic and anti-inflammatory activities. The present study demonstrated that kujigamberol inhibited cytokine production by T cells. In response to a phorbol 12-myristate 13-acetate (PMA) and ionomycin (IM) stimulation, kujigamberol suppressed interferon-γ (IFN-γ) and interleukin-2 (IL-2) mRNA expression in murine T-cell lymphoma BW5147 cells stably transfected with the T-box transcription factor eomesodermin. IL-4 and Fas ligand mRNA expression was also inhibited by kujigamberol. In the murine cytotoxic T-cell line CTLL-2, kujigamberol more strongly decreased IFN-γ mRNA expression induced by IM alone than that induced by the combination of PMA and IM. A luciferase reporter assay showed that kujigamberol preferentially reduced nuclear factor of activated T cell (NFAT)-dependent transcription in human embryonic kidney 293T cells. Unlike the calcineurin inhibitor FK506, kujigamberol did not markedly affect NFATc2 protein levels in BW5147 cells but interfered with the binding of NFATc2 to the IFN-γ and IL-2 promoters. These results indicate that kujigamberol inhibited IFN-γ and IL-2 mRNA expression by preventing the binding of NFATc2 to their promoters; therefore, it has potential as an immunosuppressive agent.