BLOCKADE OF T-CELL ACTIVATION BY DITHIOCARBAMATES INVOLVES NOVEL MECHANISMS OF INHIBITION OF NUCLEAR FACTOR OF ACTIVATED T-CELLS

Dithiocarbamates (DTCs) have recently been reported as powerful inhibi tors of NF-kappa B activation in a number of cell types. Given the rol e of this transcription factor an the regulation of gene expression in the inflammatory response, NF-kappa B inhibitors have been suggested as potential therapeutic drugs for inflammatory diseases. We show here that DTCs inhibited both interleukin 2 (IL-2) synthesis and membrane expression of antigens which are induced during T-cell activation. Thi s inhibition, which occurred with a parallel activation of c-Jun trans activating functions and expression, was reflected by transfection exp eriments at the IL-2 promoter level, and involved not only the inhibit ion of NF-kappa B-driven reporter activation but also that of nuclear factor of activated T cells (NFAT). Accordingly, electrophoretic mobil ity shift assays (EMSAs) indicated that pyrrolidine DTC (PDTC) prevent ed NF-kappa B, and NFAT DNA-binding activity in T cells stimulated wit h either phorbol myristate acetate plus ionophore or antibodies agains t the CD3-T-cell receptor complex and simultaneously activated the bin ding of AP-1. Furthermore, PDTC differentially targeted both NFATp and NFATc family members, inhibiting the transactivation functions of NFA Tp and mRNA induction of NFATc. Strikingly, Western blotting and immun ocytochemical experiments indicated that PDTC promoted a transient and rapid shuttling of NFATp and NFATc, leading to their accelerated expo rt from the nucleus of activated T cells. We propose that the activati on of an NFAT kinase by PDTC could be responsible for the rapid shuttl ing of the NFAT, therefore transiently converting the sustained transa ctivation of this transcription factor that occurs during lymphocyte a ctivation, and show that c-Jun NH2-terminal kinase (JNK) can act by di rectly phosphorylating NFATp. In addition, the combined inhibitory eff ects on NFAT and NF-kappa B support a potential use of DTCs as immunos uppressants.