Endometrial interleukin-6 in vitro is not regulated directly by female steroid hormones, but by pro-inflammatory cytokines and hypoxia.
Endometrial interleukin-6 (IL-6) mRNA has been reported to be suppressed in the mid-secretory phase in patients with recurrent early spontaneous abortions. This prompted our study concerning the regulation of endometrial IL-6 in cell culture models of endometrial epithelial and stromal cells. Steroid-dependent secretion of IL-6 was analysed by 17beta-estradiol (10(-8) mol/l) or progesterone (10(-6) mol/l) treatment and withdrawal (n = 8). Regulation by pro-inflammatory cytokines was studied in co-cultures of endometrial cells with human blood peripheral mononuclear cells (PBMC; n = 5) and by stimulation with IL-1beta, IL-6 and tumour necrosis factor alpha (TNFalpha), secreted by PBMCs at high concentrations. Regulation by hypoxia was assessed by culture of endometrial cells in 2% oxygen for 6 and 24 h (n = 5). IL-6 mRNA and protein levels were analysed by RT-PCR and enzyme-linked immunosorbent assays respectively. Endometrial IL-6 was not directly affected by 17beta-estradiol and/or progesterone. Co-culturing endometrial cells with PBMCs led to an increase of stromal but not epithelial IL-6 mRNA levels. In stromal cells, IL-6 secretion increased 2-10-fold if stimulated with 10 ng/ml recombinant IL-1beta or TNFalpha (P < 0.05). Hypoxia stimulated IL-6 secretion in epithelial cells up to 2-fold and in stromal cells up to 48-fold (P < 0.05). In conclusion, IL-6 expression in stromal and epithelial cells in vitro is regulated differently by pro-inflammatory cytokines and hypoxia. These results suggest a tight and specific network of control for this important cytokine within different endometrial compartments.
von Wolff
M
M
Department of Endocrinology and Reproductive Medicine, Universitätsklinikum Heidelberg, Vossstrasse 9, 69115 Heidelberg, Germany. michael.von.wolff@med.uni-heidelberg.de
Stieger
S
S
Lumpp
K
K
Bücking
J
J
Strowitzki
T
T
Thaler
C J
CJ
D018929:Cell Culture Techniques; D002460:Cell Line; D018920:Coculture Techniques; D016207:Cytokines / Q000378:metabolism*; D004717:Endometrium / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism*; D007378:Interleukins / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D015850:Interleukin-6; D007378:Interleukins; D014409:Tumor Necrosis Factor-alpha; D011374:Progesterone; D004958:Estradiol