PROSTAGLANDIN E-2 DIFFERENTIALLY MODULATES IL-5 GENE-EXPRESSION IN ACTIVATED HUMAN T-LYMPHOCYTES DEPENDING ON THE COSTIMULATORY SIGNAL

Background: Protein kinase A (PKA) activation is documented to be inhi bitory for T helper cell (T-H1)-like cytokines (IL-2, IFN-gamma), wher eas T-H2-like cytokines (IL-4, IL-5) are not affected or upregulated. We have recently shown that IL-4 gene expression can be inhibited by P KA activation but depends on the mode of T-cell activation. For IL-5 g ene expression, we hypothesized that the mode of T-cell activation als o determines the ultimate effect of simultaneous PKA activation. Objec tives: The objective of this study was the examination of IL-5 gene ex pression in healthy T cells activated with various mitogenic stimuli a fter simultaneous activation of PKA by dibutyryl-cAMP or prostaglandin E-2 (PGE(2)). Methods: IL-5 mRNA was measured by semiquantitative rev erse transcription-polymerase chain reaction or Northern analysis. IL- 5 protein was measured by ELISA. Transcriptional mechanisms involved i n IL-5 gene expression were determined by nuclear run-on experiments a nd electrophoretic mobility shift assays. Posttranscriptional mechanis ms were determined by actinomycin D chase studies. Results: Anti-CD2-, anti-CD3-, and anti-CD3 plus anti-CD28-induced IL-5 mRNA were complet ely inhibited by dibutyryl cyclic AMP (10(-3) mol/L) and PGE(2) (10(-5 ) mol/L), whereas concanavalin A-induced IL-5 mRNA was partially reduc ed. The effect of PGE(2) was accomplished at the transcriptional level , probably as the result of inhibition of DNA binding of nuclear facto r-kappa B. Anti-CD3 plus anti-CD28-induced IL-5 protein (504 +/- 56 pg /ml) was significantly reduced by PGE(2) (122 +/- 42 pg/ml, p < 0.001) . Addition of cytokines that use the IL-2 receptor gamma(C) chain (IL- 2, IL-7, IL-15) abrogated the PGE(2)-induced inhibition of IL-5 protei n. In contrast, concanavalin A plus PMA-induced IL-5 protein (75 +/- 8 pg/ml) was significantly upregulated by the simultaneous addition of PGE(2) (128 +/- 17 pg/ml, p < 0.03). Conclusions: PKA activation diffe rentially modulates IL-5 gene expression and depends on the mode of T- cell activation.