Reactive oxygen-induced reactive oxygen formation during human sperm capacitation (original) (raw)
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Control of superoxide and nitric oxide formation during human sperm capacitation
Free Radical Biology and Medicine, 2009
We studied the modulation of superoxide anion (O 2 · − ) and nitric oxide (NO·) generation during human sperm capacitation (changes needed for the acquisition of fertility). The production of NO· (diaminofluorescein-2 fluorescence assay), but not that of O 2 · − (luminescence assay), related to sperm capacitation was blocked by inhibitors of protein kinase C, Akt, protein tyrosine kinase, etc., but not by those of protein kinase A. Extracellular calcium (Ca 2+ ) controlled O 2 · − synthesis but extra-and intracellular Ca 2+ regulated NO· formation. Zinc inhibited capacitation and formation of O 2 · − and NO·. Zinc chelators (TPEN and EDTA) and sulfhydryl-targeted compounds (diamide and N-ethylmaleimide) stimulated capacitation and formation of O 2 · − and NO·; superoxide dismutase (SOD) and nitric oxide synthase inhibitor (L-NMMA) prevented these events. Diphenyliodonium (flavoenzyme inhibitor) blocked capacitation and related O 2 · − synthesis but promoted NO· formation, an effect canceled by SOD and L-NMMA. NADPH induced capacitation and NO· (but not O 2 · − ) synthesis and these events were blocked by L-NMMA and not by SOD. Integration of these data on O 2 · − and NO· production during capacitation reinforces the concept that a complex, but flexible, network of factors is involved and probably is associated with rescue mechanisms, so that spermatozoa can achieve successful fertilization.
Human Reproduction, 2011
Generation of controlled amounts of reactive oxygen species (ROS) and phosphorylation of protein tyrosine residues (Tyr) are two closely related changes involved in sperm capacitation. This study investigated the effect of altered endogenous ROS production on Tyr-phosphorylation (Tyr-P), acrosome reaction (AR) and cell viability during sperm capacitation. The possible origin of the altered ROS production was also evaluated by apocynin (APO) or oligomycin (Oligo) addition. A total of 63 samples of purified sperm were analysed for ROS production by enhanced chemiluminescence, Tyr-P pattern by immunocytochemistry, and AR and viability by fluorochrome fluorescein isothiocyanate (FITC)-labelled peanut (Arachis hypogaea) agglutinin and propidium iodide positivity, respectively. Samples were divided into four categories depending on the ability of sperm to produce ROS, expressed as Relative Luminescence Units (RLU), in capacitating conditions: low ROS production (LRP), range about 0.0-0.05 RLU; normal (NRP), 0.05-0.1 RLU; high (HRP), 0.1-0.4 RLU; very high (VHRP) 0.4-2.0 RLU. In NRP sperm heads, capacitation induced Tyr-P in 87.9 ± 4.3%, and the AR occurred in 62.5 ± 5.4% of cells; in LRP, HRP and VHRP Tyr-P labelling rarely spread over the head, acrosome-reacted cells only accounted for a small number of sperm, and the non-viable cells (NVC) were increased. The addition of APO, but not Oligo, drastically decreased ROS production in analysed samples. This study proposes the optimal threshold for endogenous ROS production for correct sperm viability and functioning, and indicates the direct involvement of APO-sensitive NADPH oxidase in ROS production.
Human Reproduction, 1995
Reactive oxygen species (ROS) have beneficial or detrimental effects on sperm functions depending on the nature and the concentration of the ROS involved, as well as the moment and the location of exposure. Excessive generation of ROS in semen, mainly by neutrophils but also by abnormal spermatozoa, could be a cause for infertility. Hydrogen peroxide is the primary toxic ROS for human spermatozoa. Low concentrations of this ROS do not affect sperm viability but cause sperm immobilization mostly via depletion of intracellular ATP and the subsequent decrease in the phosphorylation of axonemal proteins. High concentrations of hydrogen peroxide induce lipid peroxidation and result in cell death. On the other hand, the superoxide anion appears to play a major role in the development of hyperactivation and capacitation. The observations that: (i) exogenously generated superoxide anions induce hyperactivation and capacitation; (ii) capacitating spermatozoa themselves produce elevated concentrations of superoxide anion over prolonged periods of time; and (iii) removal of this ROS by superoxide dismutase prevents sperm hyperactivation and capacitation induced by various biological fluids, stress the importance of the superoxide anion in these processes.
Reactive oxygen species and sperm physiology
2000
Although high concentrations of reactive oxygen species (ROS) cause sperm pathology (ATP de- pletion leading to insufficient axonemal phosphorylation, lipid peroxidation and loss of motility and viability), recent evidence demonstrates that low and controlled concentrations of these ROS play an important role in sperm physiology. Reactive oxygen species, such as the super- oxide anion, hydrogen peroxide and nitric oxide, induce
Contemporary evidence on the physiological role of reactive oxygen species in human sperm function
Journal of assisted reproduction and genetics, 2015
Reactive oxygen species (ROS) play an important role in male fertility. Overproduction of reactive oxygen species (ROS) has been associated with a variety of male fertility complications, including leukocytospermia, varicocele and idiopathic infertility. The subsequent oxidative insult to spermatozoa can manifest as insufficient energy metabolism, lipid peroxidation and DNA damage, leading to loss of motility and viability. However, various studies have demonstrated that physiological amounts of ROS play important roles in the processes of spermatozoa maturation, capacitation, hyperactivation and acrosome reaction. It is therefore crucial to define and understand the delicate oxidative balance in male reproductive cells and tissues for a better understanding of both positive as well as negative impact of ROS production on the fertilizing ability. This review will discuss the specific physiological roles, mechanisms of action and effects that ROS have on the acquisition of structural...
Free Radical Biology and Medicine, 2006
The role of reactive oxygen species (ROS) as signal transduction elements in physiological phenomena is a recent concept that changes the paradigm of these active species as harmful molecules that promote deleterious effects and even cell death. Capacitation is a term used to define a complex and not well-characterized process that allows spermatozoa to complete their preparation to fertilize oocytes. Spermatozoa from many species incubated under specific conditions have the ability to produce small amounts of ROS without harming cell function and rather promoting signal transduction pathways associated with capacitation. This review summarizes the findings regarding the role of ROS during mammalian sperm capacitation, specifically as physiological mediators that trigger phosphorylation events. The role of ROS as regulators of protein tyrosine phosphorylation has been known for a decade but other novel phosphorylations, such as those of PKA substrates, of MEK-like proteins, and of proteins with the threonine-glutamine-tyrosine motif, were recently evidenced. Here we stress the involvement of PKA and the ERK pathway as two signal mechanisms acting independently that contribute to the modulation of protein tyrosine phosphorylation required for spermatozoa to achieve capacitation. Moreover, integration of all these data reinforces the concept that although some phosphorylation events are independent of the others, cross talk is also needed among the various pathways involved.
Human sperm hyperactivation and capacitation as parts of an oxidative process☆
Free Radical Biology and Medicine, 1993
Capacitation of spermatozoa is essential for fertilization and is visually characterized by hyperactivated motility. Previous reports have shown that foetal cord serum (FCS) and superoxide anion, 02, can trigger human sperm hyperactivation (HA) and capacitation and that superoxide dismutase (SOD) could prevent these processes. We investigated further the role of 02-and FCS components in human sperm HA and capacitation. Percoll-washed spermatozoa were incubated, at 37°C, in Ham's F-l0 medium with 7.5% of FCS, dialyzed FCS (> 12 kD), ultrafiltrate from FCS (FCSu; < 3 kD), or xanthine + xanthine oxidase + catalase (X + XO + cat). Spermatozoa incubated with FCSu were also supplemented with catalase to prevent the loss of motility often observed after 2-3 h of incubation. FCS and dialyzed FCS induced significant levels of HA (10 +_ 1% and 7.7 _+ 0.7%, respectively) that were, however, lower than those observed with FCSu (19 +_ 1%) or X + XO + cat (16 _+ 2%). Similar results were obtained when the lysophosphatidylcholine-induced acrosome reaction (LPC-AR, a measure of sperm capacitation) was evaluated. The presence of SOD in the incubation medium blocked the induction of HA and capacitation by FCS, FCSu, X + XO + cat, as well as the spontaneous HA and capacitation. The enzymatic activity of SOD was needed for the prevention of these processes. Desferrioxamine, up to 100 t~M, had no effect on HA and LPC-AR induced by FCSu and X + XO + cat. Addition of SOD to already hyperactivated spermatozoa reversed the HA. These data suggest that spermatozoa need a sustained O~-generation to maintain HA and proceed to capacitation. We hypothesize that FCSu or the O~-generated by X + XO + cat activate enzymes, possibly a reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase at the level of sperm membrane.
Biochemical entities involved in reactive oxygen species generation by human spermatozoa
Protoplasma, 2003
Spermatozoa were the first cell type suggested to generate reactive oxygen species. However, a lack of standardization in sperm preparation techniques and the obfuscating impact of contaminating cell types in human ejaculates have made it difficult to confirm that mammalian germ cells do, in fact, make such reactive metabolites. By identifying, on a molecular level, those entities involved in reactive oxygen species generation and demonstrating their presence in spermatozoa, the role of redox chemistry in the control of sperm function can be elucidated. Two major proteins have apparently been identified in this context, namely, NOX5, a calcium-activated NADPH oxidase, and nitric oxide synthase. Understanding the involvement of these enzymes in sperm physiology is essential if we are to understand the causes of oxidative stress in the male germ line.