Differential expression of upstream stimulatory factor (USF) 2 variants in eutopic endometria from women with endometriosis: estradiol regulation

BACKGROUND: Endometriosis, pro-inflammatory and invasive benign disease estrogen dependent, abnormally express in endometria the enzyme P(450)Arom, positively regulated by steroid factor-1 (SF-1). Our objective was to study the nuclear protein contents of upstream stimulating factor 2 (USF2a and USF2b), a positive regulator of SF-1, throughout the menstrual cycle in eutopic endometria from women with and without (control) endometriosis and the involvement of nuclear estrogen receptors (ER) and G-coupled protein estrogen receptor (GPER)-1. RESULTS: Upstream stimulating factor 2 protein contents were higher in mid (USF2b) and late (USF2a and USF2b) secretory phase in eutopic endometria from endometriosis than control (p < 0.05). In isolated control epithelial cells incubated with E(2) and PGE(2), to resemble the endometriosis condition, the data showed: (a) significant increase of USF2a and USF2b nuclear protein contents when treated with E(2), PPT (specific agonist for ERα) or G1 (specific agonist for GPER1); (b) no increase in USF2 binding to SF-1 E-Box/DNA consensus sequence in E(2)-treated cells; (c) USF2 variants protein contents were not modified by PGE(2); (d) SF-1 nuclear protein content was significantly higher than basal when treated with PGE(2), E(2) or G1, stimulation unaffected by ICI (nuclear ER antagonist); and (e) increased (p < 0.05) cytosolic protein contents of P(450)Arom when treated with PGE(2), E(2), PPT or G1 compared to basal, effect that was additive with E(2) + PGE(2) together. Nevertheless, in endometriosis cells, the high USF2, SF-1 and P(450)Arom protein contents in basal condition were unmodified. CONCLUSION: These data strongly suggest that USF2 variants and P(450)Arom are regulated by E(2) through ERα and GPER1, whereas SF-1 through GPER1, visualized by the response of the cells obtained from control endometria, being unaffected the endogenously stimulated cells from endometriosis origin. The lack of E(2) stimulation on USF2/SF-1 E-Box/DNA-sequence binding and the absence of PGE(2) effect on USF2 variants opposite to the strong induction that they exert on SF1 and P450 proteins suggest different mechanisms and indirect regulations. The sustained USF2 variants protein expression during the secretory phase in eutopic endometria from women with endometriosis may participate in the pathophysiology of this disease strongly associated with infertility and its characteristic endometrial invasion to ectopic sites in the pelvic cavity.