Erythromycin inhibits transcriptional activation of NF-kappa B, but not NFAT, through calcineurin-independent signaling in T cells

The molecular mechanism of the anti-inflammatory effect of erythromycin (EM ) was investigated at the level of transcriptional regulation of cytokine g ene expression in T cells. EM (>10(-6) M) significantly inhibited interleuk in-8 (IL-8) expression but not IL-2 expression from T cells induced with 20 ng of phorbol 12-myristate 13-acetate (PMA) per mi plus 2 mu M calcium ion ophore (P-I). In electrophoretic mobility shift assays EM at 10(-7) to 10(- 5) M concentrations inhibited nuclear factor kappa B (NF-kappa B) DNA-bindi ng activities induced by P-I. Reporter gene assays also showed that EM (10( -5) M) inhibited IL-8 NF-kappa B transcription by 37%. The inhibitory effec ts of EM on transcriptional activation of IL-2 and DNA-binding activity of nuclear factor of activated T cells (NFAT) were not seen in T cells. On the other hand, FK506, which is also a macrolide derivative, inhibited transcr iptional activation of both NF-kappa B and NFAT more strongly than EM did. The mechanism of EM inhibition of transactivation of NF-kappa B was further investigated in transiently transfected T cells that express calcineurin A and B subunits. Expression of calcineurin did not render transactivation o f NF-kappa B in T cells more resistant to EM, while the inhibitory effect o f FK506 on transactivation of NF-kappa B was attenuated. These findings ind icate that EM is capable of inhibiting expression of the IL-8 gene in T cel ls through transcriptional inhibition and that this inhibition is mediated through a non-calcineurin-dependent signaling event in T lymphocytes.