Glucocorticoid-mediated inhibition of interleukin-2 receptor alpha and -beta subunit expression by human T cells.
To determine the mechanism of glucocorticoid (GC)-mediated inhibition of T cell functions, the effect of dexamethasone (DM) on T cell proliferation and interleukin-2 receptor (IL-2R) generation were studied. Dexamethasone inhibited IL-2-induced T cell proliferation by 30%-88%, relative to its concentration within the cultures. The effect of DM on expression of IL-2R alpha (Tac, p55, CD25) and beta (p75) genes in activated T cells was examined next. In T cells stimulated with purified phytohemagglutinin (PHA-p) and 4 beta-phorbol 12-myristate 13-acetate (PMA) addition of DM to the cultures resulted in a 60% reduction in IL-2R alpha and a 30% reduction in IL-2R beta membrane expression compared to T cells cultured in the absence of DM (p < 0.01). Inhibition of membrane IL-2R alpha and IL-2R beta expression by 10(-6) M DM was partially reversible by recombinant human IL-2 (rhIL-2). By Northern blot analysis, DM caused a comparable decrease in IL-2R alpha and in IL-2R beta mRNA levels to membrane receptor expression in mitogen-stimulated T cells. By in vitro transcription assays, DM regulated IL-2R alpha gene expression at a transcriptional level while transcription of IL-2R beta gene was unaffected by DM. The mechanism of action of DM on IL-2R alpha transcription was examined by determining the mRNA levels of the p50 subunit of nuclear factor kappa B (NF-kappa B), a transcription factor that stimulates IL-2R alpha gene expression. The data indicate that 10(-6) M DM increased T cell p50 NF-kappa B mRNA levels by four-fold compared to the levels obtained in the absence of DM. Further, the level of nuclear proteins capable of binding to the NF-kappa B sites in activated T cells increased in response to DM. In sum, DM regulates T cell membrane expression of IL-2R by more than one molecular mechanism.
Batuman
O A
OA
Hematology Division, SUNY Health Science Center at Brooklyn 11203.
Ferrero
A P
AP
Diaz
A
A
Berger
B
B
Pomerantz
R J
RJ
D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis* / Q000737:chemistry* / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
D016328:NF-kappa B; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D003907:Dexamethasone; D003513:Cycloheximide