PROSTAGLANDIN E(2) STIMULATES AROMATASE EXPRESSION IN ENDOMETRIOSIS-DERIVED STROMAL CELLS

C-19 steroids are converted to estrogens by aromatase P450 (P450arom). Aromatase expression in humans is regulated by use of tissue-specific promoters in the placenta (promoter I.1), adipose tissue (promoters 1 .4, I.3, and II), and gonads (promoter II). The use of each promoter g ives rise to a population of P450arom messenger ribonucleic acid (mRNA ) species with a unique untranslated 5'-terminus. Aromatase is not exp ressed in the endometrium of disease-free women. We demonstrated, howe ver, the presence of P450arom mRNA in pelvic endometriotic implants an d eutopic endometrial curettings of women with endometriosis. In the c urrent report, aromatase activity and P450arom gene expression were in vestigated in cultured stromal cells derived from eutopic endometrium and ovarian endometriomas of women with pelvic endometriosis. We also investigated the hormonal regulation of aromatase expression and alter native promoter use in these cells. The effects of interleukin-1 beta (IL-1 beta), IL-2, IL-6, IL-11, oncostatin M, IL-15, tumor necrosis fa ctor-alpha, PGE(2), estradiol, R5020, dexamethasone, and dibutyryl cAM P (Bt(2)cAMP) on aromatase activity in endometriosis-derived stromal c ells were assessed. We chose treatments with PGs and ILs because of th e inflammatory nature of endometriosis. PGE(2) stimulated aromatase ac tivity in endometriosis-derived stromal cells by 19- to 44-fold (37-22 1 pmol/mg protein . 4 h), whereas Bt(2)cAMP induction was 26- to 60-fo ld the baseline level. No stimulation was observed by estradiol or R50 20 or by IL-1 beta, IL-2, IL-6, IL-11, IL-15, or TNF alpha in the pres ence or absence of glucocorticoids. A modest induction of aromatase ac tivity (2-fold) was observed in dexamethasone-plus oncostatin M-treate d cells. These changes in aromatase activity were accompanied by compa rable changes in the levels of P450arom mRNA levels, determined by a q uantitative reverse transcription-PCR method. Promoter-specific 5'-end s of P450arom transcripts in total RNA from endometriosis-derived stro mal cells treated with PGE(2) and Bt(2)cAMP were amplified employing a novel modified rapid amplification of cDNA5'-ends/Southern hybridizat ion method using exon-specificoligo- nucleotide probes. The majority o f P450arom transcripts in these cells contained the gonadal-type promo ter II-specific sequences, whereas very few transcripts contained adip ose-type promoter 1.3- and I.4-specific sequences. PGE(2) appears to b e the most potent known stimulator of aromatase in endometriosis. Arom atase expression in PGE(2)-stimulated stromal cells of endometriosis i s regulated primarily by the classically located promoter II, which, i n turn, is regulated by cAMP. As PGE(2) is known to increase intracell ular cAMP levels, estrogen biosynthesis in endometriosis may be primar ily regulated by PGE(2) that is locally produced. Consequent local est rogen production may promote the growth of endometriotic implants.