These findings make plausible the involvement of MMP-9/TIMP-1 imbalance in the invasiveness of the endometrial tissue of patients with endometriosis and the ectopic development of the disease.

Cyclooxygenase (COX) is the rate-limiting enzyme in the metabolic conversion of arachidonic acid to prostaglandins (PGs), including prostaglandin E(2) (PGE(2)), a major mediator of inflammation and angiogenesis. Herein, we report that macrophage migration inhibitory factor (MIF), a potent proinflammatory and growth-promoting factor found at elevated concentrations in the peritoneal fluid of women with endometriosis and active endometriosis lesions, acts directly on ectopic endometrial cells to stimulate the synthesis of COX-2, the inducible form of COX, and the release of PGE(2). MIF treatment strongly activated p38 and ERK MAPK, and specific inhibitors of both pathways completely blocked basal and MIF-induced PGE(2) synthesis. Whereas p38 inhibitors negatively affected the stimulated synthesis of COX-2 and that of PGE(2), ERK inhibitors only decreased the production of PGE(2). These findings show for the first time a direct role for MIF in the up-regulation of COX-2 synthesis and PGE(2) secretion in ectopic endometrial cells. They further indicate that whereas p38 and ERK MAPK signaling pathways both play a significant role in the regulation of basal and MIF-induced synthesis of PGE(2) by ectopic endometrial cells, only p38 kinase is involved in the regulation of COX-2 expression in these cells. This suggests that MIF acts at more than one level to stimulate the synthesis of PGE(2) and triggers the coordinate activation of multiple enzymes in the biosynthesis pathway. Our data provide evidence for a novel mechanism by which MIF can induce a proinflammatory phenotype in ectopic endometrial cells, and favor the establishment of endometriosis and its related clinical symptoms.

Endometriosis, the ectopic development of endometrial tissue, is, particularly in peritoneal endometriosis, believed to result from tubal reflux of menstrual tissue. The release of cytokines and growth factors by refluxed endometrial cells in response to peritoneal inflammatory stimuli may enhance the capability of endometrial cells to implant and grow into the peritoneal host tissue. Herein we report that interleukin 1 (IL1), a major proinflammatory cytokine that is overproduced by endometriosis women-derived peritoneal macrophages and found in elevated concentrations in the peritoneal fluid of patients with endometriosis, stimulates the synthesis and the secretion of macrophage migration inhibitory factor (MIF) by human endometrial stromal cells. IL1B (0.1-100 ng/ml) exerted dose- and time-dependent effects of MIF protein secretion and mRNA synthesis, as shown by ELISA and reverse transcription-polymerase chain reaction, respectively. IL1B appeared to induce MIF gene transcription via the kappaB nuclear transcription factor (NFkappaB), as shown by electrophoretic mobility shift assay and Western blot analysis of IkappaB phosphorylation. Curcumin (10(-8) M), which is known for inhibiting NFkappaB activation, inhibited IL1B-induced MIF secretion as well as NFkappaB nuclear translocation and DNA binding. Taken together, these findings clearly show that IL1B up-regulates the expression of MIF in endometrial stromal cells in vitro and acts via NFkappaB. This may play an important role in the physiology of the human endometrium and the pathophysiology of endometriosis considering the immunomodulatory properties of MIF as well as its role in cell growth, angiogenesis and tissue remodeling.