Interleukin (IL)-1 beta regulation of IL-1 beta and IL-1 receptor antagonist expression in cultured human endometrial stromal cells

The interleukin (IL)-1 system is a major regulator of local cellular intera ctions during embryonic implantation. Because IL-1 beta and IL receptor ant agonist (IL-1ra) are both expressed in human endometrium, we hypothesized t hat an appropriate ratio of IL-1 beta to IL-1ra might favor the process of embryo implantation. Therefore, we investigated IL-1 regulation of the quan titative ratio of IL-1 beta /IL-1ra messenger RNA (mRNA) expression in huma n endometrial stromal cells using quantitative competitive PCR, as well as intracellular protein expression after stromal cell solubilization. Conflue nt stromal cell cultures were stimulated with human IL-1 beta (0-1000 IU/mL ) for 24 h. After 24 h, total RNA was extracted, reverse transcribed, and c oamplified by PCR with a defined amount of internal standard. The quantitat ive ratio was determined by the density of target to the internal standard. After culture with IL-1 beta for 24 and 48 h, stromal cells were solubiliz ed, and the intracellular protein levels of IL-1 beta and IL-1ra were measu red by enzyme-linked immunosorbent assay. The IL-1 beta and IL-1ra mRNA wer e both up-regulated, and IL-1R tI mRNA was down-regulated, by IL-1 beta in a dose-dependent manner. The quantitative ratio of IL-1 beta to IL-1ra mRNA was constant with the presence of increasing concentrations of IL-1 beta ( 1-1000 IU/mL). IL-1 beta and IL-1ra protein was not detected in conditioned media of cultures before addition of IL-1 beta. IL-1 beta and IL-1ra prote in levels increased with increasing amounts of IL-1 beta after solubilizati on of stromal cells. The IL-1 beta was detectable after 12 h of culture, in comparison with IL-1ra, which was detectable after 24 h of IL-1 beta stimu lation. These results suggest that IL-1 may play a crucial role in embryo-m aternal interaction by regulating stromal cell expression of IL-1 beta and IL-1ra, resulting in an appropriate ratio during the process of embryonic i mplantation.