Reactive oxygen species and human spermatozoa. I. Effects on the motility of intact spermatozoa and on sperm axonemes.

TLDR

Mammalian spermatozoa are vulnerable to oxygen‑induced damage via lipid peroxidation of the cell membrane. The study aimed to determine whether reactive oxygen species could also damage sperm axonemes. Exposure of Percoll‑separated sperm to hydrogen peroxide or xanthine/xanthine oxidase progressively lowered flagellar beat frequency until motility ceased, and even after demembranation and MgATP‑mediated reactivation, motility progressively declined to zero within an hour. In 50 % of cases, sperm spontaneously regained motility after 6–24 h of ROS exposure, though at lower beat frequencies; hydrogen peroxide proved most toxic, with superoxide and hydroxyl radicals also contributing, suggesting ROS trigger axonemal damage that endogenous repair can only partially reverse.

Abstract

Mammalian spermatozoa are sensitive to oxygen-induced damages mediated by lipid peroxidation of the cell membrane. The aim of this study was to evaluate whether reactive oxygen species (ROS) could also induce axonemal damage. When Percoll-separated spermatozoa were treated with hydrogen peroxide, or the combination xanthine and xanthine oxidase (X + XO), there was a progressive decrease, leading to a complete arrest, in sperm flagellar beat frequency. Once demembranated in a medium containing magnesium adenosine triphosphate (Mg.ATP), ROS-immobilized spermatozoa still reactivated motility; however, the percentage and duration of motility obtained in these tests gradually decreased to zero in the next hour. In 50% of the cases, motility of intact spermatozoa spontaneously reinitiated after 6 to 24 hours of immobilization due to ROS treatment, although with percentages and beat frequencies lower than those of untreated spermatozoa. Studies using ROS scavengers (such as catalase, superoxide dismutase, and dimethylsulfoxide) indicated that hydrogen peroxide was the most toxic of the ROS involved, but that .O2- and .OH probably also played a role in immobilization of spermatozoa by ROS. The data suggest that ROS induce a chain of events leading to sperm immobilization, that axonemes are affected, and that limited endogenous repair mechanisms exist to reverse these damages.