Molecular Mechanisms Involved in the Estrogen-Dependent Regulation of Calcineurin in Systemic Lupus Erythematosus T Cells

Previous experiments in our laboratory indicated that calcineurin expression and PP2B phosphatase activity increased when estrogen was cultured with SLE T cells but not with T cells from normal women. In this report we extended our findings to show that estrogen receptor (ER) antagonism by ICI 182,780 inhibited the estrogen-dependent increase in calcineurin mRNA and phosphatase PP2B activity indicating that estrogen action was mediated through the ER. Inhibition of de novo protein synthesis with cycloheximide suggested that the estrogen-dependent increase in T cell calcineurin mRNA was a direct effect of the ER and new protein synthesis was not required. Estrogen increased calcineurin mRNA in systemic lupus erythematosus (SLE) T cells at 6 h after the start of culture correlating with increased phosphatase activity at this same time. Phosphatase activity increased significantly (P < 0.02) in lupus T cells cultured for 8 h in estradiol-containing medium. Reverse transcription and polymerase chain amplification revealed that ER-β and ER-α were expressed in female and male T cells from SLE patients and normal controls. However, calcineurin steady-state mRNA levels were unaffected by estradiol in cultured T cells from male SLE patients and normal male and female controls. These data indicate that estrogen, bound to the ER, evokes a direct increase in calcineurin expression in T cells from female lupus patients. This gender-specific response suggests that ER function is altered in women with the female predominant autoimmune disease, SLE.