Mineralocorticoid receptor signaling reduces numbers of circulating human naïve T cells and increases their CD62L, CCR7, and CXCR4 expression

Abstract

The role of mineralocorticoid receptors (MRs) in human T-cell migration is not yet understood. We have recently shown that the MR antagonist spironolactone selectively increases the numbers of circulating naïve and central memory T cells during early sleep, which is the time period in the 24 h cycle hallmarked by predominant MR activation. To investigate whether this effect is specific to spironolactone's blockade of MRs and to study the underlying molecular mechanisms, healthy humans were given the selective MR-agonist fludrocortisone or placebo and numbers of eight T-cell subsets and their CD62L and CXCR4 expression were analyzed. Fludrocortisone selectively reduced counts of naïve CD4(+) , central memory CD4(+), and naïve CD8(+) T cells and increased CXCR4 expression on the naïve subsets. In complementing in vitro studies, fludrocortisone enhanced CXCR4 and CD62L expression, which was counteracted by spironolactone. Incubation of naïve T cells with spironolactone alone reduced CD62L and CCR7 expression. Our results indicate a regulatory influence of MR signaling on human T-cell migration and suggest a role for endogenous aldosterone in the redistribution of T-cell subsets to lymph nodes, involving CD62L, CCR7, and CXCR4. Facilitation of T-cell homing following sleep-dependent aldosterone release might thus essentially contribute to sleep's well-known role in supporting adaptive immunity.

Keywords: CD62L; CXCR4; Mineralocorticoid receptor; Naïve T cells; Sleep.

Figure 1

Changes in the numbers of circulating CD4⁺ and CD8⁺ T cells after fludrocortisone administration. Naive (CD45RA⁺CD62L⁺), central memory (CD45RA⁻CD62L⁺), effector memory (CD45RA⁻CD62L⁻) and effector (CD45RA⁺CD62L⁻) CD4⁺ (left) and CD8⁺ (right) T-cell counts were determined in whole blood by flow cytometry before (−1.5 and 0 h) and between 1.5 and 8.25 h after oral administration of fludrocortisone (0.2 mg) or placebo. Values for the fludrocortisone condition are indicated as difference from the placebo condition to eliminate the well-known strong circadian variation in T-cell numbers. Data are expressed as mean ± SEM of 13 healthy male subjects. All values are adjusted to baseline measures (i.e., the first two samples before drug administration) based on covariance analyses. *p < 0.05, **p < 0.01, for pairwise comparisons between the effects of fludrocortisone and placebo at single time points (paired t-tests). See text for ANOVA results.

Figure 2

Changes in CXCR4 expression on circulating CD4⁺ and CD8⁺ T-cell subsets after fludrocortisone administration. CXCR4 expression was assessed by flow cytometry on naïve (CD45RA⁺CD62L⁺), central memory (CD45RA⁻CD62L⁺), effector memory (CD45RA⁻CD62L⁻) and effector (CD45RA⁺CD62L⁻) CD4⁺ (left) and CD8⁺ (right) T cells before (−1.5 and 0 h) and between 1.5 and 8.25 h after oral administration of fludrocortisone (0.2 mg) or placebo. Values for the fludrocortisone condition are indicated as difference from the placebo condition. All values are adjusted to baseline measures (i.e., the first two samples before drug administration) based on covariance analyses and are expressed as mean ± SEM of median fluorescence intensity (MFI) of 13 healthy male subjects. *p < 0.05, **p < 0.01, for pairwise comparisons between the effects of fludrocortisone and placebo at single time points (paired t-tests). See text for ANOVA results.

Figure 3

Changes in cortisol concentration after fludrocortisone administration. Serum cortisol concentration was measured before (−1.5 and 0 h) and between 1.5 and 8.25 h after oral administration of fludrocortisone (0.2 mg) or placebo. Values for the fludrocortisone condition are indicated as difference from the placebo condition to eliminate the well-known strong circadian variation in cortisol levels. Values shown as mean ± SEM of 13 healthy male subjects are adjusted to baseline measures (i.e., the first two samples before drug administration) based on covariance analyses. *p < 0.05, **p < 0.01, for pairwise comparisons between the effects of fludrocortisone and placebo at single time points (paired t-tests). See text for ANOVA results.

Figure 4

Changes in CD62L and CCR7 expression on naïve and central memory CD4⁺ and CD8⁺ T cells after incubation with spironolactone and fludrocortisone. Blood was sampled during sleep at 03:30 h and was then incubated for 2 or 4 h either with spironolactone (Spi), fludrocortisone (FC), fludrocortisone plus spironolactone (FC + Spi) or PBS as control. Expression of CD62L (top) and CCR7 (bottom) were assessed by flow cytometry on naïve (CD45RA⁺CD62L⁺) and central memory (CD45RA⁻CD62L⁺) CD4⁺ (left) and CD8⁺ (right) T cells and are shown as mean ± SEM of median fluorescence intensity (MFI) of 13 healthy male subjects. Data are expressed as difference from the PBS control. *p < 0.05, **p < 0.01, for pairwise comparisons between effects of the active agent(s) and PBS (paired t-tests).

Figure 5

Changes in CXCR4 expression on CD4⁺ and CD8⁺ T-cell subsets after incubation with spironolactone and fludrocortisone. Blood was sampled during sleep at 03:30 h and was then incubated for 2 or 4 h either with spironolactone (Spi), fludrocortisone (FC), fludrocortisone plus spironolactone (FC + Spi) or PBS as control. Expression of CXCR4 was assessed by flow cytometry on naïve (CD45RA⁺CD62L⁺), central memory (CD45RA⁻CD62L⁺), effector memory (CD45RA⁻CD62L⁻) and effector (CD45RA⁺CD62L⁻) CD4⁺ (left) and CD8⁺ (right) T cells and is shown as mean ± SEM of median fluorescence intensity (MFI) of 13 healthy male subjects. Data are expressed as difference from the PBS control. *p < 0.05, **p < 0.01, for pairwise comparisons between effects of the active agent(s) and PBS (paired t-tests).

Figure 6

Concept: Nocturnal sleep facilitates T-cell homing to lymph nodes via aldosterone release, whereas cortisol facilitates migration to bone marrow during daytime wakefulness. Sleep induces an increase in aldosterone levels, which activates mineralocorticoid receptors (MRs) on naïve T cells (left). This leads to an increase in the expression of CCR7 and CD62L, the most important lymph node-homing receptors on T cells, as well as of CXCR4. As a consequence, migration to lymph nodes is facilitated. This concept could explain the beneficial effect of sleep on mounting an adaptive immune response. During daytime, the circadian peak in cortisol release leads to an activation of glucocorticoid receptors (GRs) on T cells, which diminishes lymph node homing (right). The further increase in CXCR4 expression leads to a preferential recruitment of these cells to the bone marrow, which produces high levels of the CXCR4 ligand CXCL12 during daytime wakefulness.