Role of Hydrogen Peroxide in Sperm Capacitation and Acrosome Reaction1

Abstract

The generation of reactive oxygen species (ROS) has been implicated in the regulation of sperm capacitation and acrosome reaction; however, the mechanisms underlying this regulation remain unclear. To examine the cellular processes involved, we studied the effect of different concentrations of hydrogen peroxide (H(2)O(2)) on protein tyrosine phosphorylation under various conditions. Treatment of spermatozoa with H(2)O(2) in medium without heparin caused a time- and dose-dependent increase in protein tyrosine phosphorylation of at least six proteins in which maximal effect was seen after 2 h of incubation with 50 microM H(2)O(2). At much higher concentrations of H(2)O(2) (0.5 mM), there is significant reduction in the phosphorylation level, and no protein tyrosine phosphorylation is observed at 5 mM H(2)O(2) after 4 h of incubation. Exogenous NADPH enhanced protein tyrosine phosphorylation similarly to H(2)O(2). These two agents, but not heparin, induced Ca(2+)-dependent tyrosine phosphorylation of an 80-kDa protein. Treatment with H(2)O(2) (50 microM) caused approximately a twofold increase in cAMP, which is comparable to the effect of bicarbonate, a known activator of soluble adenylyl cyclase in sperm. This report suggests that relatively low concentrations of H(2)O(2) are beneficial for sperm capacitation, but that too high a concentration inhibits this process. We also conclude that H(2)O(2) activates adenylyl cyclase to produce cAMP, leading to protein kinase A-dependent protein tyrosine phosphorylation.

Physiological and Pathological Roles of Free Radicals in Male Reproduction

“…This process is associated with an increase in tyrosine phosphorylation, and it has been shown that the amount and banding pattern of tyrosine phosphorylation by adding exogenous H 2 O 2 was similar to that observed during endogenous ROS production, providing evidence that H 2 O 2 may be responsible for the enhancement of capacitation [32,57,58]. This hypothesis was further confirmed by Rivlin et al [59] who showed that catalase decreased, while H 2 O 2 increased the tyrosine phosphorylation in a dose-dependent manner, thereby solidifying the involvement of H 2 O 2 in the process of capacitation.…”

“…Both O 2 •− and H 2 O 2 may stimulate different molecules in the biochemical pathways, and depending on the in vitro method used to induce capacitation, specific ROS involved may therefore differ. Several studies have confirmed the lack of molecular specificity in the activation of capacitation and tyrosine phosphorylation, as both SOD and catalase have been shown to negate the positive effect exogenously induced capacitation and hyperactivation [59].…”

“…Of note is also the role of NO • , which is present in the female genital tract. NO • may initiate the acrosome reaction, the effects of which are likely achieved through a complex mechanism involving H 2 O 2 [59,60].…”

“…Catalase activates sperm capacitation induced by nitric oxide [59,60]. Furthermore, it plays an important role in decreasing lipid peroxidation and protecting spermatozoa during genitourinary inflammation [25].…”

Reactive oxygen species production and redox state in parthenogenetic and sperm-mediated bovine oocyte activation

“…On the other hand, some evidence exists demonstrating that ROS are important to spermatozoa in regulating every aspect of sperm function examined, including their movement characteristics, capacitation, sperm-zona interaction, acrosome reaction, and sperm-oocyte fusion (Baker & Aitken 2004, Rivlin et al 2004. Some studies have also documented that the addition of natural antioxidants to oocyte maturation medium failed to modify the percentage of bovine embryos produced in vitro (Blondin et al 1997) or even diminished the rate of embryo production (Dalvit et al 2005b).…”