Purpose: The production of epithelial neutrophil activating peptide-78 (NA-78) and the interleukins IL-8 and IL-6 by endometrial stromal cells is stimulated by pro-inflammatory interleukin-1 (IL-1) and tumour necrosis factor-α (TNF-α). IL-8 is suggested to play a role in the pathogenesis of endometriosis, and in these women the peritoneal fluid concentrations of ENA-78 and IL-8 are increased. TNF-α has been tested together with interferon-γ because of their cooperative stimulation of IL-6. The release of IL-8, however, is inhibited with increasing interferon levels. The aim of the study was the analysis of the production of ENA-78, IL-6 and IL-8 by cultured human endometrial stromal cells in the presence of varying concentrations of IL-1β, TNF-α, and interferon-γ.
Methods: Eutopic endometrial tissue was obtained from seven cycling, endometriosis-free women undergoing laparoscopy for reasons of infertility or pain. The release of ENA-78, IL-8 and IL-6 by the isolated and monolayer cultured stromal cell fraction in the presence of IL-1β (0.08 to 50 ng/mL), TNF-α, and interferon-γ (both 20 to 500 ng/mL) was determined.
Results: IL-1β stimulated the production of IL-8, IL-6, and ENA-78 dose dependently from 0.08 to 2.0 ng/mL (ENA-78) or to 10 ng/mL (IL-8, IL-6); at 50 ng/mL a decrease in release was observed for IL-8 and IL-6. TNF-α stimulation yielded a plateau between 20 and 100 ng/mL. Interferon-γ stimulated IL-6 and inhibited IL-8 production above 20 ng/mL. ENA-78 release was largely unaffected by interferon-γ.
Conclusions: IL-1β and TNF-α stimulate stromal cytokine production cumulatively with different dose-response curves. The presence of interferon-γ has opposite effects on IL-8 and IL-6. TNF-α and interferon-γ should be investigated separately in future in vitro studies with endometrial cells and explants.