Behaviour of cytokine levels in serum and peritoneal fluid of women with endometriosis

Abstract Endometriosis is a disorder characterised by presence and growth of endometrial tissue outside the uterus, primarily into the peritoneum. The peritoneal fluid (PF) of women with endometriosis undergoes a number of biological changes, including local inflammatory-reparative phenomena and peripheral blood mononuclear cells (PBMC) involvement. These activated cells as well as the endometriotic cells secrete various cytokines with pleiotropic biological activities. Dynamic interplay among cytokines may contribute to realise a favourable microenvironment for the implantation of endometrial cells and the progression of the disease. In the present study, we evaluated the levels of cytokines, such as the tumour necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) in PF and in serum (S) of women with endometriosis to compare their behaviour in both biological fluids. The patients (n = 26) were women of reproductive age attending our observation centre for infertility, diagnosed endometriosis at laparoscopy. Control group (n = 5) consisted of women affected by non-immunologic infertility, diagnosed by explorative laparoscopy. S samples were obtained from peripheral blood before anaesthesia and laparoscopy. PF samples were collected at the time of laparoscopy. Both biological fluids were examined for cytokine by ELISA assays. Our results showed that S and PF levels of TNF-alpha, not dosable in controls, were very high at the early stage and decreased significantly with the severity of the disease (p < 0.001). TGF-beta levels were significantly (p < 0.001) higher than in controls and increased with the severity of the disease (p < 0.001), particularly in the PF. S and PF IL-8 as well as MCP-1 concentrations at all stages were higher than in controls (p < 0.001), yet showed an opposite behaviour in both biological fluids. In fact, S levels of IL-8 and MCP-1 were significantly (p < 0.001) higher at early stages and decreased with the severity of the disease, whereas we observed a significant (p < 0.001) enhancement of these chemokine levels in PF from stage I to stage II and stage III. These observations showed that TNF-alpha and TGF-beta levels were overlapping in S and PF of women with endometriosis. On the contrary, MCP-1 and IL-8 S concentrations decreased with the severity of the disease, whereas PF levels showed markedly increased at severe stages. Taken together the observed changes may be due both to the increased peritoneal macrophage activity and to the larger recruitment of PBMC and autocrine release by endometriotic cells.