Proteomic changes in uterine flushings after levonorgestrel treatment and effects on sperm function

Abstract

When levonorgestrel (LNG) is given for emergency contraception during the follicular phase inhibits or delays ovulation, but also induces changes in endometrial secretions that modulate sperm functionality. In order to characterize the female reproductive tract secreted molecules that may affect human spermatozoa, we analyzed changes in the protein content of uterine flushings obtained from women during the periovulatory phase of a control and a LNG-treated menstrual cycle. Lectin affinity analysis and two-dimensional gel electrophoresis of uterine samples showed changes in protein glycosylation pattern and the presence of 31 differentially expressed proteins (8 up- and 23 down-regulated). Mass spectrometry and Western blot analyses of the differential expressed proteins showed lactotransferrin (LTF) as one of the up-regulated molecules by LNG. In this study, LTF exhibited significant dose-related effects on sperm functionality, particularly a decrease of calcium ionophore-induced acrosome reaction and protein tyrosine phosphorylation. Overall, the results indicated that LNG promoted changes in the proteome of uterine secretions that might compromise human sperm capacitation. These data further support the participation of other mechanisms of action of LNG as emergency contraceptive, in addition to those on ovulation.