17β-estradiol modifies human spermatozoa mitochondrial function in vitro

BACKGROUND: It is assumed that spermatozoa are target cells for estrogens however, the mechanism of their action is not fully understood. The aim of this study was to investigate the influence of 17β-estradiol (E2) on the human spermatozoa mitochondrial function. METHODS: The effects on spermatozoa of E2 at final concentrations of 10(−10), 10(−8) and 10(−6) M were studied regarding the following phenomena: (1) kinetics of intracellular free calcium ions changes (using Fluo-3), (2) mitochondrial membrane potential ΔΨ(m) (using JC-1 fluorochrome), (3) production of superoxide anion in mitochondria (using MitoSOX RED dye), (4) spermatozoa vitality (propidium iodide staining) and (5) phosphatidylserine membrane translocation (staining with annexin V marked with fluorescein). RESULTS: E2 initiated rapid (within a few seconds) dose dependent increase of intracellular free calcium ions concentration. E2 was changing the mitochondrial membrane potential: 10(−8) M initiated significant increase of percentage of high ΔΨ(m) spermatozoa while the 10(−6) M induced significant decrease of high ΔΨm cells. In spermatozoa stimulated with E2 10(−6) M a significant increase of mitochondrial superoxide anion level was observed. 2 h incubation of spermatozoa with E2 did not alter cells vitality nor stimulated phosphatidylserine membrane translocation, for all three doses. CONCLUSIONS: 17β-estradiol affected the human spermatozoa mitochondrial function. E2 in low concentration improved while in high concentration might deteriorate mitochondrial function.