Effect of 17β-estradiol on tumor necrosis factor-α-induced cytotoxicity in the human peripheral T lymphocytes

We determined the effect of 17beta-estradiol on tumor necrosis factor alpha (TNF-alpha)-induced cytotoxicity in human peripheral T lymphocytes (T cells) using lactate dehydrogenase assay. Treatment with 17beta-estradiol (1-100 nM) for 24 h showed dose-dependent reduction of TNF-alpha-induced cytotoxicity in T cells. To further evaluate the mechanism of 17beta-estradiol on TNF-alpha-induced cytotoxicity in T cells, we identified estrogen receptor (ER) protein in T cells using immunocytochemistry and used the pure ER antagonist ICI 172,780. ERalpha immunoreactivity was clearly observed in T cells. ERbeta immunoreactivity was also detected in some T cells. ICI 172,780 (10(-7) M) alone did not affect cytotoxicity in T cells, however, ICI 172,780 (10(-7) M) completely abolished 17beta-estradiol cytoprotective effects in T cells. TNF-alpha tended to increase nuclear factor kappaB (NF-kappaB) protein levels in nuclear extracts but it did not reach statistical significance by Western blotting. In contrast, NF-kappaB protein levels in nuclear extracts followed by TNF-alpha, with 17beta-estradiol treatment were significantly increased compared with NF-kappaB protein levels in untreated group. NF-kappaB blocker pyrrolidinedithiocarbamate (PDTC) (10(-4) M) alone did not affect cytotoxicity in T cells. In contrast, PDTC (10(-4) M) completely abolished 17beta-estradiol cytoprotective effects in T cells. Caspase -3/-7 activity was significantly increased followed by TNF-alpha, and 17beta-estradiol treatment significantly reduced the increment. The present studies suggest the protective effect of 17beta-estradiol on TNF-alpha-induced cytotoxicity through ERs in T cells and that NF-kappaB activation and caspase suppression may be involved in the mechanism.