Sex hormones and dexamethasone modulate interleukin-5 gene expression in T lymphocytes.

The ability of the sex hormones progesterone, testosterone and estradiol-17 beta and the glucocorticoid dexamethasone to modulate expression of the interleukin-5 (IL-5) gene in T cell lines has been investigated. The T cell lines used show analogous regulation of IL-5 gene expression to that occurring in T-lymphocytes, in that IL-5 mRNA levels are undetectable unless the cells are induced with phorbol myristate acetate (PMA). Progesterone and testosterone were as effective as PMA in inducing IL-5 mRNA levels in the T cell hybrid NIMP-TH1 and induced IL-5, -3 and -2 mRNA accumulation in the T cell lymphoma EL-4. Estradiol-17 beta also induced IL-5 mRNA accumulation but less effectively than testosterone. Nuclear run-on experiments suggested that the effects of progesterone, testosterone and PMA on IL-5 gene expression were mediated at the level of transcription. The presence of the protein synthesis inhibitor cycloheximide completely prevented PMA-induced synthesis of IL-5 mRNA by both NIMP-TH1 and EL-4 cells, indicating that induction of IL-5 mRNA via PMA stimulation requires de novo synthesis of a presumptive trans-acting factor(s). PMA-, testosterone- and progesterone-induced expression of the IL-5 gene was completely blocked by the anti-inflammatory steroid dexamethasone. Stimulation of IL-5 expression by PMA was relatively resistant to the immuno- suppressive drug cyclosporin A although inhibition did occur at very high levels. Testosterone- and progesterone-induced IL-5 gene expression was not inhibited by cyclosporin A. The in vivo significance of these findings are not yet clear but the results show that sex hormones have the potential to regulate cytokine gene expression in cells possessing the appropriate steroid receptors.