Immunosuppressant FK506 induces interleukin-6 production through the activation of transcription factor nuclear factor (NF)-kappa B - Implications for FK506 nephropathy

FK506 is a powerful immunosuppressive drug currently in use that inhibits the activation of several transcription factors (nuclear factor (NF)-AT and NF-kappa B) critical for T cell activation. We show here that, contrary to the situation in T cells, FK506 activates transcription factor NF-kappa B in non-lymphoid cells such as fibroblasts and renal mesangial cells. We further show that FK506 induces NF-kappa B-regulated IL-6 production in vitro and in vivo, in particular in kidney. IL-6 has been shown previously to produce renal abnormalities in vivo, such as mesangioproliferative glomerulonephritis. Similar renal abnormalities were also observed in FK506-treated animals. These results thus suggest a causal relationship between FK506-induced NF-kappa B activation/IL-6 production and some of FK506-induced renal abnormalities.