A regulatory role of prolactin, growth hormone, and corticosteroids for human T-cell production of cytokines

The release of the pituitary hormones, prolactin and growth hormone (GH), and of adrenal corticosteroids is subject to a profound regulation by sleep. In addition these hormones are known to be involved in the regulation of the immune response. Here, we examined their role for in vitro production of T-cell cytokines. Specifically, we hypothesized that increased concentrations of prolactin and GH as well as a decrease in cortisol, i.e., hormonal changes characterizing early nocturnal sleep, could be responsible for a shift towards T helper 1 (Th1) cytokines during this time. Whole blood was sampled from 15 healthy humans in the morning after regular sleep and was activated in vitro with ionomycin and two concentrations of phorbol myrestate acetate (PMA, 8 and 25ng/ml) in the absence or presence of prolactin, prolactin antibody, GH, glucocorticoid receptor (GR) antagonist RU-486, or mineralocorticoid receptor (MR) antagonist spironolactone. Hormones were examined at physiological concentrations. Production of T-cell derived cytokines was measured at the single cell level using multiparametric flow cytometry. Generally, effects were more pronounced after stimulation with 8 rather than 25ng/ml PMA. The following changes reached significance (p<.05): prolactin (versus prolactin antibody) increased tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) producing CD4+ and CD8+ cells and interleukin-2 (IL-2) producing CD8+ cells. Compared with control, prolactin antibody decreased, whereas GH increased IFN-γ+CD4+ cells. RU-486 increased TNF-α, IFN-γ, and IL-2 producing CD4+ and CD8+ cells. Surprisingly strong effects were found after MR blocking with spironolactone which increased TNF-α, IFN-γ, and IL-2 producing CD4+ and CD8+ cells. No effects on IL-4+CD4+ cells were observed, while the IFN-γ/IL-4 ratio shifted towards Th1 after spironolactone and after RU-486 plus GH. Results suggest that enhanced prolactin and GH concentrations as well as low cortisol levels during early nocturnal sleep synergistically act to enhance Th1 cytokine activity.