17β-estradiol and xenoestrogens reveal synergistic effect on mitochondria of human sperm

Objectives: The aim of the study was to investigate the influence of 17 beta-estradiol (main endogenous estrogen) and selected xenoestrogens (genistein, bisphenol-A), individually and in combination, on the mitochondrial function of human spermatozoa. In natural environment, human beings are exposed to multiple xenoestrogens, so their impact is combined with endogenous steroids. Material and methods: The effects of ligands on human spermatozoa were assessed regarding the following phenomena: spermatozoa vitality (propidium iodide staining), phosphatidylserine membrane translocation (staining with annexin V marked with fluorescein), mitochondrial membrane potential (using JC-1 fluorochrome), and production of superoxide anion in mitochondria (using MitoSOX RED dye). Results: Two-hour incubation of spermatozoa with 17 beta-estradiol, genistein, and bisphenol-A neither altered cell vitality nor stimulated phosphatidylserine membrane translocation. Incubation of spermatozoa with 17 beta-estradiol or bisphenol-A separately, as well as incubation with the three ligands simultaneously, resulted in altered mitochondrial membrane potential. Spermatozoa incubation with the three ligands significantly increased the mitochondrial superoxide anion level. Conclusions: It seems safe to conclude that human spermatozoa mitochondria are target cell structures for both, 17 beta-estradiol and xenoestrogens. The reaction to the 17 beta-estradiol and xenoestrogens mixture suggests a synergistic mechanism of action. Xenoestrogens may increase the sensitivity of spermatozoa to 17 beta-estradiol.