A one-factor analysis of variance was used for intergroup comparisons and significance
within individual study groups determined with a Fisher’s protected least significant difference test (Fisher’s PSLD). A forward stepwise regression test was Apoptosis inhibitor used for correlations between pSTAT3 and growth factors/cytokines in stained tissues. For all, a P value of <0.05 was considered significant. Data was analyzed using Statcel (OMS Publishing Inc., Saitama, Japan). Estrogen17 and IL-6 are known to influence BEC physiology,9 and estrogens regulate IL-6 expression in other cell types. Therefore, we tested whether increasing concentrations of estradiol affected BEC IL-6 mRNA and protein expression, and whether male and female BECs responded differently. The estrogen concentrations used correspond roughly to those in normal male or postmenopausal female (2 pg/mL), normal premenopausal female (200 pg/mL), and pregnant female (20,000 pg/mL). Treatment of male mBECs with increasing concentrations Antiinfection Compound Library of 17β-estradiol for 48 hours either caused no significant change or inhibited IL-6 mRNA and protein expression compared to the vehicle control (Fig. 1). In contrast, the same treatment of female mBECs resulted in significantly increased IL-6 mRNA and protein expression with maximum induction
at 200 pg/mL. Media containing forskolin (C-SFM), which stimulates BEC IL-6 production, was used as a positive control (Fig. 1B). Consistent with previous studies,10 estrogen treatment of male and female peritoneal macrophages inhibited LPS-induced IL-6 expression, as expected (Fig.
1C). We next examined expression of another well-known estrogen-responsive gene, trefoil family factor 1 (TFF1), to determine whether the sex difference in mBEC estrogen responsiveness was specific for IL-6 production (Fig. 1D). Because TFF1 expression can also be induced by IL-6, we used IL-6−/− mBECs. The results show that estradiol increased TFF1 mRNA expression in female, but not in male, IL-6−/− mBECs. This shows that male mBECs also respond differently than female mBECs to estrogen stimulation when another estrogen-responsive gene is used as the read-out. After ligand binding, ERα and ERβ form homodimers or heterodimers, interact with basal medchemexpress transcription factors and numerous coactivators, and bind to estrogen-responsive elements to influence transcription.16, 26 ERs can also modulate target gene expression by interacting indirectly with activator protein 1 (AP-1), Sp1, or cyclic AMP responsive element (CRE) to modulate expression in a tissue-specific manner. The IL-6 promoter has CRE and AP-1 binding sites.27 When expressed together, ERβ generally inhibits gene activation by ERα.16, 26 We hypothesized, therefore, that differential ERα and ERβ expression between male and female mBECs might account for the sex differential regulation of IL-6 expression by estrogens.