Increased estrogen-dependent expression of calcineurin in female SLE T cells is regulated by multiple mechanisms

Calcineurin is a key mediator of T cell activation. Previous studies in our laboratory showed a dose-dependent and hormone-specific increase in calcineurin expression in the T cells from females with systemic lupus erythematosus (SLE). This study investigates whether the estrogen-dependent increase in calcineurin expression is due to stabilization of the messenger RNA (mRNA).

T cells from female patients with SLE and controls were cultured for 18 hours in a serum-free medium with and without estradiol-17 beta (10(-7) M). Some T cells were activated by further culture on anti-CD3-coated plates. Actinomycin D (25 micrograms/mL) was added to some cultures to inhibit new mRNA synthesis. Calcineurin mRNA stability was assessed by reverse-transcription polymerase chain amplification.

Resting SLE (n = 9, P = .59) and normal (n = 5, P = .90) T cells showed no significant differences in mRNA stability in response to estradiol. Calcineurin mRNA was not significantly stabilized in activated SLE (n = 10, P = .12) or activated normal (n = 8, P = .09) T cells in response to estradiol. However, the amount of calcineurin mRNA stabilized in activated normal T cells (n = 8) was significantly greater (P = .02) compared with SLE T cells (n = 10) only after culture in medium without estradiol.

These findings highlight the complex gene regulatory mechanisms underlying the differential action of estrogen on SLE T cells. Furthermore, the data indicate that increased calcineurin expression in SLE T cells is not due solely to estrogen-dependent stabilization of the message, and probably involves additional transcriptional regulatory mechanisms.