The roles of thioredoxin and thioredoxin-binding protein-2 in endometriosis.

BACKGROUND Oxidative stress is considered to be involved in the establishment and development of endometriosis. Thioredoxin (TRX) is an endogenous redox regulator that protects cells against oxidative stress, and TRX-binding protein-2 (TBP-2) is a negative regulator of TRX in the biological function and expression. The aim of this study was to investigate the roles of TRX and TBP-2 in the pathophysiology of endometriosis. METHODS A total of 35 patients with histologically confirmed endometriosis and 31 patients without endometriosis participated in this study. Real-time polymerase chain reaction was used to quantify TRX and TBP-2 mRNA levels, and immunohistochemistry (IHC) was used to assess TRX and TBP-2 protein localization in the endometrium. Serum and peritoneal fluid levels of TRX and TBP-2 were measured using a specific commercial ELISA. RESULTS There were no significant differences in TRX mRNA levels in the endometrium of patients with endometriosis and the control groups. However, TBP-2 mRNA levels in the endometrium were lower, and the TRX to TBP-2 ratio was higher in patients with endometriosis than in the control group. In particular, the TRX to TBP-2 ratio was significantly higher during late secretory and menstrual phase in patients with endometriosis compared with the control group. IHC studies also showed the decreased TBP-2 immunoreactivity in patients with endometriosis compared with the control group. There was no correlation between TRX and TBP-2 mRNA levels in patients with endometriosis, whereas TRX mRNA levels were positively correlated with TBP-2 mRNA levels in the control group. There were no significant differences between the two groups in TRX and TBP-2 levels in serum or peritoneal fluid. CONCLUSIONS Aberrant expression of TRX and TBP-2 in the endometrium may be associated with the establishment of endometriosis.