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  • Title: Unexpected up-regulation of gene expression by cyclosporin A and FK-506 in a T-cell lymphoma: both immunosuppressants augment Ly-6E antigen induction by interferon-gamma in the presence of ionomycin.
    Author: Altmeyer A, Staruch MJ, Fischer PA, Durette PL, Tocci MJ, Sigal NH, Dumont FJ.
    Journal: Int J Immunopharmacol; 1991; 13(8):1187-99. PubMed ID: 1726093.
    Abstract:
    Cyclosporin A (CsA) and FK-506 inhibit lymphokine gene activation in T-cells. In the present study, we investigated the effects of these immunosuppressants on the regulation of a non-lymphokine molecule, the Ly-6E surface antigen, in the YAC-1 T-cell lymphoma. These cells do not normally express Ly-6E mRNA or Ly-6E surface molecules but are induced to do so upon treatment with IFN-gamma. At submicromolar concentrations, CsA or FK-506 did not alter this induction. However, at higher concentrations (1-12 microM), they both increased the induction of Ly-6E mRNA expression. Cyclosporin A or FK-506 also markedly affected Ly-6E induction when the cultures were co-treated with the calcium ionophore, ionomycin. In the absence of CsA or FK-506, ionomycin suppressed Ly-6E induction by IFN-gamma. Both immunosuppressants reversed this inhibitory effect and increased Ly-6E mRNA and Ly-6E surface expression to levels that were 2- to 3-fold higher than in cells induced with IFN-gamma alone. In this system, the two immunosuppressants were active at pharmacologically relevant concentrations, similar to those inhibiting normal T-cell activation, with FK-506 being 30- to 50-fold more potent than CsA. The ability of CsA analogs to enhance Ly-6E induction in the presence of ionomycin also correlated with their immunosuppressive activity. Therefore, through mechanisms apparently related to those involved in their immunosuppressive action, both CsA and FK-506 convert the negative effect of ionomycin on IFN-gamma-mediated Ly-6E induction into an overall positive effect. The YAC-1 cell model, described here, provides a unique example of upregulation of gene expression by these two immunosuppressants.
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