Catecholestradiol Activation of Adrenergic Receptors Induces Endometrial Cell Survival via p38 MAPK Signaling

Context: Enhanced levels of catecholestradiols, 2-hydroxyestradiol (2-OHE2) or 4-hydroxyestradiol (4-OHE2), are reported in endometriosis. During gestation, catecholestradiol activation of adrenergic receptors (AR) elevates Estrogen Receptor (ER)-independent proliferation of uterine arterial endothelial cells.

Objective: To investigate β-AR-mediated catecholestradiol effects on human endometrial stromal cell (HESC) and epithelial cell survival in endometriosis.

Design: β-AR immunostaining of eutopic and ectopic endometria (n = 9). Assays for cell viability, 5-bromo-2'-deoxyuridine proliferation, Apoptosis, quantitative PCR, and estrogenicity (Alkaline Phosphatase activity), as well as siRNA β-AR silencing and immunoblot analyses of cultured HESCs or Ishikawa cells treated with control or 2-OHE2 or 4-OHE2 ±β-AR antagonist or ±p38 MAPK inhibitor.

Setting: University research institution.

Patients: Women with or without endometriosis.

Interventions: None.

Main outcome measures: β-AR expression in eutopic vs ectopic endometria and regulation of HESC survival by 2-OHE2 and 4-OHE2.

Results: Eutopic and ectopic endometrial stromal and epithelial cells displayed β2-AR immunoreactivity with increased staining in the functionalis vs basalis layer (P < 0.05). Both 2-OHE2 and 4-OHE2 enhanced HESC and Ishikawa cell survival (P < 0.05), an effect abrogated by β-AR antagonist propranolol, but not ER antagonist ICI182,780. 2-OHE2 or 4-OHE2 failed to induce cell survival and estrogenic activity in ADRB2-silenced HESCs and in Ishikawa cells, respectively. Although 2-OHE2 inhibited Apoptosis and Bax mRNA expression, 4-OHE2 induced proliferation and decreased Apoptosis (P < 0.05). Both catecholestradiols elevated phospho-p38 MAPK levels (P < 0.05), which was blocked by propranolol, and p38 MAPK Inhibitor reversed catecholestradiol-enhanced HESC survival.

Conclusions: Catecholestradiols increase endometrial cell survival by an ER-independent β-AR-mediated p38 MAPK activation, suggesting that agents blocking β-AR (e.g., propranolol) or inhibiting 2-OHE2- or 4-OHE2-generating enzymes (i.e., CYP1A1/B1) could treat endometriosis.