The antioxidant system of seminal fluid during in vitro storage of sterlet Acipenser ruthenus sperm

Oxidative stress and cryoresistance of sturgeon sperm: A review

Currently, the majority of sturgeons are relict fishes of high economic value yet endangered with extinction. Cryopreservation of sperm has great potential in fish farming and conservation, but the problem of low cryoresistance of sturgeon sperm has not yet been solved. The goal of this work was to review current literature data on the causes of low tolerance of sturgeon sperm to cryodamage. The influence of cryopreservation on the parameters of physiology and metabolism of sturgeon sperm (morphology and fine ultrastructure, mobility and fertilization ability, integrity of the plasma membrane, protein, lipid and metabolite profiles, antioxidant status, DNA damage), as well as on biomarkers of oxidative stress (lipids peroxidation levels and carbonyl derivatives of proteins) is discussed. Since the development of oxidative stress is an important mechanism of sperm cryodamage induction, the review presents the literature on the role of oxygen-derived species in damage of sturgeon reproductive cells caused by cryopreservation. Particular attention is paid to the system of antioxidant protection of sturgeon seminal plasma and spermatozoa, represented by antioxidant enzymes and low molecular weight antioxidants capable of utilizing various reactive forms of oxygen and nitrogen. The review discusses the results of lipidomic and proteomic studies of sturgeon sperm, which made it possible to obtain new data on the lipid composition of cell membranes, to detect proteins involved in the protection of sturgeon spermatozoa from oxidative damage during cryopreservation. This review presents the use of «omics» technology to elucidate the mechanism of cryodamage in sturgeon sperm. Additionally, the review summarizes information on the unique anatomical, morphological, biochemical, and physiological features of sturgeon sperm, which may be associated with low cryoresistance of sturgeon, in order to establish prospects for further research on improving the methods of the conservation of sperm of these threatened species.

Sperm antioxidant system in ocellate river stingray Potamotrygon motoro at transition from seminal vesicle to cloaca

The importance of reactive oxygen species and the antioxidant system in sperm biology has been recognized for different bony fishes but nothing is known in this regard for chondrichthyans. For the first time for cartilaginous fishes, the enzymatic antioxidant system was shown herein to be present in both fractions of sperm (spermatozoa and seminal fluid) collected from two different places (seminal vesicle and cloaca). In internally fertilizing freshwater ocellate river stingray, Potamotrygon motoro, the activity of superoxide dismutase and glutathione peroxidase was not changed upon sperm transition from the seminal vesicle to the cloaca. The activity of catalase was significantly increased for both sperm fractions at transition from the seminal vesicle to the cloaca (1.6 times for spermatozoa and 1.9 times for seminal fluid). The role of the sperm antioxidant system for different aspects of internal fertilization is discussed. The presented results are the initiatory step in uncovering the biochemical events of internal reproduction in Chondrichthyes.

Melatonin regulates ATP content and fertilising capacity of Onychostoma macrolepis spermatozoa by inhibiting ROS accumulation during semen storage in vitro

Melatonin (MLT) is an efficient antioxidant that protects spermatozoa against damages caused by oxidative stress. In this study, to maintain good function of Onychostoma macrolepis spermatozoa during semen preservation invitro at 4°C, different concentrations of MLT (0.5, 1 and 2μM) were added to the semen. After storage (0, 24, 48 and 72h), 1μM MLT in semen markedly improved sperm quality, as reflected by better plasma membrane integrity, the relative steady level of reactive oxygen species (ROS) and slower rate of decrease in mitochondrial membrane potential. Activated spermatozoa in semen with 1μM MLT had higher kinematic performance (i.e. percentage of motile and progressive spermatozoa and the beat cross frequency; P<0.05) and longer duration of sperm motility (P<0.05) compared with spermatozoa in semen withother MLT concentrations. Furthermore, 1μM MLT maintained higher ATP concentrations in spermatozoa during semen storage and significantly improved the fertilising capacity of spermatozoa after 72h semen storage compared with the other MLT concentrations. To expand wild resources of O. macrolepis, 1μM MLT can be used as a semen additive to maintain better sperm function and enhance sperm fertilising capacity in artificial insemination (AI).

Sperm collection and storage for the sustainable management of amphibian biodiversity

Current rates of biodiversity loss pose an unprecedented challenge to the conservation community, particularly with amphibians and freshwater fish as the most threatened vertebrates. An increasing number of environmental challenges, including habitat loss, pathogens, and global warming, demand a global response toward the sustainable management of ecosystems and their biodiversity. Conservation Breeding Programs (CBPs) are needed for the sustainable management of amphibian species threatened with extinction. CBPs support species survival while increasing public awareness and political influence. Current CBPs only cater for 10% of the almost 500 amphibian species in need. However, the use of sperm storage to increase efficiency and reliability, along with an increased number of CBPs, offer the potential to significantly reduce species loss. The establishment and refinement of techniques over the last two decades, for the collection and storage of amphibian spermatozoa, gives confidence for their use in CBPs and other biotechnical applications. Cryopreserved spermatozoa has produced breeding pairs of frogs and salamanders and the stage is set for Lifecycle Proof of Concept Programs that use cryopreserved sperm in CBPs along with repopulation, supplementation, and translocation programs. The application of cryopreserved sperm in CBPs, is complimentary to but separate from archival gene banking and general cell and tissue storage. However, where appropriate amphibian sperm banking should be integrated into other global biobanking projects, especially those for fish, and those that include the use of cryopreserved material for genomics and other research. Research over a broader range of amphibian species, and more uniformity in experimental methodology, is needed to inform both theory and application. Genomics is revolutionising our understanding of biological processes and increasingly guiding species conservation through the identification of evolutionary significant units as the conservation focus, and through revealing the intimate relationship between evolutionary history and sperm physiology that ultimately affects the amenability of sperm to refrigerated or frozen storage. In the present review we provide a nascent phylogenetic framework for integration with other research lines to further the potential of amphibian sperm banking.

Proteomic and metabolomic insights into the functions of the male reproductive system in fishes

Proteomics and metabolomics are emerging and powerful tools to unravel the complex molecular mechanisms regulating reproduction in male fish. So far, numerous proteins and metabolites have been identified that provide us with valuable information to conduct a comprehensive analysis on seminal plasma and spermatozoa components and their functions. These analyses have allowed a better understanding of the blood-testis barrier functions, the molecular mechanisms underlying spermatogenesis, spermatozoa maturation, motility signaling, and competition as well as the mechanism of cryodamage to sperm structure and functions. To extend, proteins that undergo posttranslational modification, such as phosphorylation and oxidation in response to spermatozoa motility activation and cryopreservation, respectively, have been identified. Proteomic studies resulted in identification of potential proteins that can be used as biomarkers for sperm quality and freezability to enable the control of artificial reproduction, and to improve methods for long-term preservation (cryopreservation) of sperm. The different proteins expressed in the spermatozoa of neomales and normal males can also provide new insights into development of methods for separating X and Y fish sperm, and changes in the protein profiles in haploid and diploid spermatozoa will provide new perspectives to better understand the mechanism of male polyploidy. Overall, the knowledge gained by proteomic and metabolomic studies is important from basic to applied sciences for the development and/or optimisation of techniques in controlled fish reproduction.

Role of Uric Acid in Semen

Since 1963, various research studies and reports have demonstrated the role of uric acid (2,6,8-trihydroxypurine), an end product of adenosine and guanosine catabolism, on semen quality and sperm function. However, this effect has not yet been collectively discussed, even though uric acid has been a well-recognized constituent in semen. Here, we systematically and comprehensively discuss and summarize the role/effect of uric acid in semen quality by searching the main databases for English language articles considering this topic. Additionally, certain significant and relevant papers were considered to support discussions and perceptions. In conclusion, uric acid contributes to maintaining and enhancing sperm motility, viability, and morphology; therefore, protecting sperm function and fertilizing ability. This contribution is performed mainly by neutralizing the damaging effect of oxidizing (e.g., endogenous free radicals and exogenous toxins) and nitrating agents and enhancing certain bioactive enzymes in spermatozoa. In contrast, high levels of uric acid may induce adverse effects to sperm function, at least in part, by reducing the activity of vital enzymes in spermatozoa. However, further research, mainly clinical, is still required to fully explore the role/effect of uric acid in semen.

Malathion-induced spermatozoal oxidative damage and alterations in sperm quality of endangered trout Salmo coruhensis

The use of pesticides has been increased along with increasing the farming activities and has caused environmental impacts deleteriously. In particular, non-target organisms including fish can be affected by toxic effects of pesticides. Therefore, the impacts of malathion (MTN) on oxidative stress and sperm quality were investigated in vitro. The MTN concentrations used on this study were 0 (control), 75, 100, and 125 μg/L. Lipid peroxidation (MDA), non-enzymatic (GSH), and enzymatic (SOD, GSH-Px, and CAT) activities in spermatozoa were examined for determination of oxidative stress status. Our findings showed that motility rate and period of sperm cells significantly decreased with exposure to MTN. Biochemical assays revealed that CAT activity and levels of MDA, GSH increased in spermatozoa based on concentration while activity of GSH-Px and SOD decreased. Consequently, spermatozoa were highly sensitive to MTN exposure. MTN has disruptive effects on sperm quality and caused to oxidative stress in spermatozoa.

Motility and oxidative-antioxidant capacity of Huso huso semen, stored at -80°C

In this study, motility and oxidative-antioxidant capacity (thiobarbituric acid-reactive substance level [TBARS], superoxide dismutase [SOD], catalase [CAT] and glutathione reductase [GR]) of beluga sturgeon (Huso huso) sperm, stored for 6 days at -80°C, were evaluated. After 2 days of storage, sperm motility was significantly decreased (no motile sperm were observed after 6 days of storage; p < .05), while TBARS and SOD values were significantly increased (p < .05). CAT and GR activities did not show significant changes among storage times (p > .05). Furthermore, all investigated parameters showed a significant difference between semen stored at 4°C (control) and -80°C during in vitro storage (p < .05). Data from this work can potentially be useful in sturgeon sperm cryobanking.