Inflammation can interfere with endometrial receptivity. We examined how interleukin 1b (IL-1b) affects expression of the uterine gap junction protein connexin 43 (Cx43), which is known to be critical for embryonic implantation. We used an in vitro model of human endometrial stromal cells (ESCs), Western blotting, and a combination of validated, selective kinase inhibitors to evaluate five canonical IL-1b signaling pathways. Cx43 and two other markers of ESC differentiation (prolactin and VEGF) were inhibited predominantly via IL-1b-activated ERK1/2 and p38 MAP kinase cascades. The findings were corroborated using small interfering RNA to silence critical genes in either pathway. By contrast, upregulation of endogenous pro-IL-1a and pro-IL-1b following recombinant IL-1b treatment was mediated via the Jun N-terminal kinase pathway. The clinicopharmacological significance of our findings is that multiple signaling cascades may need to be neutralized to reverse deleterious effects of IL-1b on human endometrial function.
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