Protein oxidative stress markers in peritoneal fluids of women with deep infiltrating endometriosis are increased

STUDY QUESTION Are protein oxidative stress markers [thiols, advanced oxidation protein products (AOPP), protein carbonyls and nitrates/nitrites] in perioperative peritoneal fluid higher in women with histologically proven endometriosis when compared with endometriosis-free controls? SUMMARY ANSWER Protein oxidative stress markers are significantly increased in peritoneal fluids from women with deep infiltrating endometriosis with intestinal involvement when compared with endometriosis-free controls. WHAT IS KNOWN ALREADY Endometriosis is a common gynaecologic condition characterized by an important inflammatory process. Various source of evidence support the role of oxidative stress in the development of endometriosis. STUDY DESIGN, SIZE, DURATION We conducted a prospective laboratory study in a tertiary-care university hospital between January 2011 and December 2012, and included 235 non-pregnant women, younger than 42 year old, undergoing surgery for a benign gynaecological condition. PARTICIPANTS/MATERIALS, SETTING, METHODS After complete surgical exploration of the abdomino-pelvic cavity, 150 women with histologically proven endometriosis and 85 endometriosis-free controls women were enrolled. Women with endometriosis were staged according to a surgical classification in three different phenotypes of endometriosis: superficial peritoneal endometriosis (SUP), ovarian endometrioma (OMA) and deeply infiltrating endometriosis (DIE). Perioperative peritoneal fluids samples were obtained from all study participants. Thiols, AOPP, protein carbonyls and nitrates/nitrites were assayed in all peritoneal samples. MAIN RESULTS AND THE ROLE OF CHANCE Concentrations of peritoneal AOPP were significantly higher in endometriosis patients than in the control group (median, 128.9 µmol/l; range, 0.3–1180.1 versus median, 77.8 µmol/l; range, 0.8–616.1; P < 0.001). In a similar manner concentrations of peritoneal nitrates/nitrites were higher in endometriosis patients than in the control group (median, 24.8 µmol/l; range, 1.6–681.6 versus median, 18.5 µmol/l; range, 1.6–184.5; P < 0.05). According to the surgical classification, peritoneal fluids protein AOPP and nitrates/nitrites were significantly increased only in DIE samples when compared with controls (P < 0.001 and P < 0.05; respectively), whereas the others forms of endometriosis (SUP and OMA) showed non-statistically significant increases. We found positive correlations between peritoneal fluids AOPP concentration