Biology of Reproduction, 2017, 97(4), 577–585 doi:10.1093/biolre/iox104 Review Advance Access Publication Date: 13 September 2017 Review Reactive oxygen species and protein modifications in spermatozoa† ∗ Cristian O’Flaherty1,2,3, and David Matsushita-Fournier2,3 Downloaded from https://academic.oup.com/biolreprod/article/97/4/577/4157784 by guest on 01 October 2021 1Department of Surgery (Urology Division), McGill University, Montreal,´ Quebec,´ Canada; 2Pharmacology and Therapeutics, Faculty of Medicine, McGill University, Montreal,´ Quebec,´ Canada and 3The Research Institute, McGill University Health Centre, Montreal,´ Quebec,´ Canada ∗Correspondence: The Research Insitute, McGill University Health Centre, room EM03212, 1001 Decarie Boulevard, Montreal,´ QC H4A 3J1, Canada. Fax: +514-933-4149; E-mail: cristian.ofl[email protected] †Grant support: This work was supported by a grant from the Canadian Institutes of Health Research (MOP 133661 to C.O.). CO is the recipient of the Chercher Boursier Junior 2 salary award from the Fonds de la Recherche en SanteduQu´ ebec´ (33158). Received 2 June 2017; Revised 1 August 2017; Accepted 11 September 2017 Abstract Cellular response to reactive oxygen species (ROS) includes both reversible redox signaling and irreversible nonenzymatic reactions which depend on the nature and concentration of the ROS involved. Changes in thiol/disulfide pairs affect protein conformation, enzymatic activity, ligand binding, and protein–protein interactions. During spermatogenesis and epididymal maturation, there are ROS-dependent modifications of the sperm chromatin and flagellar proteins.The sperma- tozoon is regulated by redox mechanisms to acquire fertilizing ability. For this purpose, controlled amounts of ROS are necessary to assure sperm activation (motility and capacitation). Modifica- tions of the thiol groups redox status of sperm proteins are needed for spermatozoon to achieve fertilizing ability. However, when ROS are produced at high concentrations, the established ox- idative stress promotes pathological changes affecting sperm function and leading to infertility. Sperm proteins are sensitive to high levels of ROS and suffer modifications that impact on motility, capacitation, and the ability of the spermatozoon to recognize and bind to the zona pellucida and damage of sperm DNA. Thiol oxidation, tyrosine nitration, and S-glutathionylation are highlighted in this review as significant redox-dependent protein modifications associated with impairment of sperm function and alteration of paternal genome leading to infertility. Peroxiredoxins, the primary antioxidant protection in spermatozoa, are affected by most of the protein modifications described in this review. They play a significant role in both physiological and pathological processes in mammalian spermatozoa. Summary Sentence Reactive oxygen species promote redox-dependent protein modifications that lead to impairment of sperm function. Key words: reactive oxygen species, oxidative stress, redox signaling, spermatozoa, sperm activation, sperm motility, sperm capacitation. Introduction that includes enzymes such as superoxide dismutase (SOD), cata- lase (CAT), glutathione peroxidases (GPXs), thioredoxins (TRXs), Reactive oxygen species (ROS) are obligatory metabolic products of and peroxiredoxins (PRDXs), and other molecules with scavenging aerobic cells. They are kept at low levels by an antioxidant system properties such as glutathione (GSH), ubiquinol, vitamins C and E, C The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. 577 For permissions, please e-mail: [email protected] 578 C. O’Flaherty and D. Matsushita-Fournier, 2017, Vol. 97, No. 4 Ta b l e 1 . Redox-dependent protein modifications associated with physiological processes in spermatozoa. Modification Physiological processes Species Reference Thiol oxidation Binding of spermatozoon with oviductal epithelium Bovine [142,143] Sperm motility Hamster, human, rat [144–147] Sperm capacitation Human, bovine [120,123,143,148] Sperm chromatin remodeling Human, mouse, equine, rabbit, rat [36,37,39,149–151] S-Nitrosylation Sperm motility Human [76,152] Tyrosine nitration Sperm capacitation Human [83,153] Ta b l e 2 . Redox-dependent protein modifications associated with deleterious effects in spermatozoa. Modification Associated outcome Species Reference Thiol oxidation Male infertility Human [38,39,42] Downloaded from https://academic.oup.com/biolreprod/article/97/4/577/4157784 by guest on 01 October 2021 Impairment of sperm motility Hamster, human, rat [42,154,155] Blockage of sperm-egg fusion Mouse [156,157] 4-HNE protein adducts Impairment of sperm motility Human, equine [62,158,159] S-Glutathionylation Impairment of sperm motility Human [34] Impairment of sperm capacitation Human [34] Tyrosine nitration Impairment of sperm motility Human [34,80] Impairment of sperm capacitation Human [34] Sulfonation Impairment of sperm motility Human, rat [42,60,154] Impairment of epididymal maturation Rat [154] andsoon[1]. However, when the antioxidant system is dysregu- (Tables 1 and 2). Some of these modifications are reversible, thus lated, and the production of ROS is exacerbated, then these active allowing a tight regulation of cellular processes involved in redox molecules become harmful by-products of cellular metabolism [1]. signaling [29,30]. A schematic representation of the major redox- Mammalian spermatozoar are sensitive to ROS, such as the super-r protein modifications is shown in Figure 1. − oxide anion (O2r ), hydrogen peroxide (H2O2), nitric oxide (NO ), − hydroxyl (HO ), and peroxynitrite anion (ONOO ). When ROS Thiol oxidation levels are increased, sperm function is affected leading to infertil- Cysteine, a sulfur-containing amino acid, is a potent nucleophile un- ity [2–6]. This increase in ROS levels is denominated oxidative stress der physiological conditions. This remarkable reactivity is due to and is the result of an excessive production of ROS and/or a decrease the thiol (-SH) group. The formation of disulfide bridges (-SS-) by in the antioxidant defense system [7,8]. The oxidative damage tar- thiol oxidation is a common strategy to fold a protein generating gets all cell components, reducing sperm motility and mitochondrial a structure to assure, for instance, enzymatic activity or interaction activity [5,9,10]. The first evidence of a relationship between oxida- with receptors, plasma membrane components, etc. A specific ratio tive damage and male infertility was demonstrated by the pioneering -SS-/–SH within a protein molecule is essential to assure its function, work of Thaddeus Mann and Bayard Storey [11,12]. and this rate can be affected by ROS. An oxidative stress will oxidize The infertile population has been increasing over the past few free -SH, thus preventing the formation of -SS- where and when it decades [13]. However, treatment efficiency is poor because the is needed during a physiological process and will translate in the cause is unknown in 40%–50% of cases [14]. Several factors are impairment of protein function. A good example of this situation is related to infertility such as exposure to environmental pollutants, the effects of high levels of ROS on the ATP production by human chemicals, drugs, smoke, toxins, radiation, and even diseases [15– spermatozoa. It was observed that elevated levels of ROS, gener- 18]. A common feature of the above is the production of oxidative ated by direct addition of H2O2r or by adding xanthine-xanthine stress. In such conditions, vital cell components (proteins, lipids, and − oxidase system (generator of O2 and of H2O2) to the incubation DNA) are oxidized compromising cell function and survival [8,19]. medium, reduce human sperm motility in a dose- and time-dependent In at least 25% of cases, elevated levels of ROS are detected in both manner [31]. This reduction was correlated with a decrease in the semen and spermatozoa from infertile patients [2–5]. In some cases ATP production by the spermatozoon [32], thus suggesting that the of male infertility, the antioxidant system present in semen [20,21]is impairment of sperm motility was a depletion of energy. Human not sufficient to protect spermatozoa from ROS-dependent damages. spermatozoa depend on aerobic oxidation of glucose accomplish by Spermatozoa from infertile patients have peroxidation of membrane the conjunction of glycolysis, Krebs cycle, and the oxidative phos- lipids [22], DNA fragmentation and oxidation of bases [23,24], low phorylation by the electron transport chain. In 1992, de Lamirande mitochondrial membrane potential [25,26], and inactivation of en- and Gagnon [32] suggested that one possible target of ROS could zymes associated with motility [27,28]. be the glyceraldehyde 3-phosphate dehydrogenase, which is linked to the fiber sheath explaining the drop in ATP production observed Protein modifications in spermatozoa due to reactive in ROS-treated spermatozoa. Recently, it was demonstrated that the oxygen species glyceraldehyde 3-phosphate dehydrogenase, a key enzyme of the gly- Sperm proteins are the target of redox-dependent modifications that colytic pathway, can be inactivated by oxidation of the –SH in its will lead, depending on the levels of ROS, to either the activa- active site by exogenous H2O2 [33]. tion/inactivation of signaling pathways important for sperm phys- An appropriate level of thiol oxidation in proteins is necessary for iology or to oxidative damage and impairment