Effect of environmental contamination on female and male gametes - A lesson from bovines

Impact of fluazuron on oocyte maturation: May the antiparasitic affect bovine reproduction?

Fluazuron is a novel veterinary pour-on antitick formulation which can be applied simultaneously with bovine reproduction management strategies. Considering the economic importance of the livestock industry in many countries, it is important to know whether antiparasitics such as fluazuron may cause embryonic loss. The aim of this study was to evaluate the toxicological effect of fluazuron on bovine oocytes during in vitro maturation. The best fluazuron concentrations were determined in a preliminary experiment on Chinese hamster ovary (CHO)-K1 cells and further used to compare fluazuron toxicity in both study models. Results of the annexin V and alkaline single cell gel electrophoresis assays demonstrated that fluazuron caused cytotoxicity and genotoxicity in bovine cumulus cells at all the concentrations tested (50, 75 and 100 μg fluazuron/mL). The evaluation of cortical granules and mitochondria distribution showed that cytoplasmic maturation was not affected by fluazuron treatment. However, a decrease in metaphase II + polar body, degenerate oocytes as well as disorganized chromatin in polar body were observed at all concentrations tested. Whereas the fertilization process was not altered by 50 μg/mL fluazuron, the embryo development rate decreased significantly. No significant differences were observed in any of the oxidative stress parameters assessed. This study contributes to a better understanding of fluazuron in bovines, suggesting that the antiparasitic may affect bovine reproduction and might cause embryo loss.

Analysis and remediation of phthalates in aquatic matrices: current perspectives

Phthalic acid esters (PAEs) are high production volume chemicals used extensively as plasticizers, to increase the flexibility of the main polymer. They are reported to leach into their surroundings from plastic products and are now a ubiquitous environmental contaminant. Phthalate levels have been determined in several environmental matrices, especially in water. These levels serve as an indicator of plasticizer abuse and plastic pollution, and also serve as a route of exposure to different species including humans. Reports published on effects of different PAEs on experimental models demonstrate their carcinogenic, teratogenic, reproductive, and endocrine disruptive effects. Therefore, regular monitoring and remediation of environmental water samples is essential to ascertain their hazard quotient and daily exposure levels. This review summarises the extraction and detection techniques available for phthalate analysis in water samples such as chromatography, biosensors, immunoassays, and spectroscopy. Current remediation strategies for phthalate removal such as adsorption, advanced oxidation, and microbial degradation have also been highlighted.

Astaxanthin protects oocyte maturation against cypermethrin-induced defects in pigs

Cypermethrin (CYP), a pyrethroid insecticide, exerts the detrimental effect on the reproductive system, while astaxanthin (AST), a xanthophyll carotenoid, possesses the powerful antioxidant property and can protect oocyte maturation. However, the toxicity of CYP and the protective role of AST against CYP during oocyte maturation remain unclear. Here, porcine oocytes were applied to investigate the potential effects and underlying mechanisms of CYP and AST during oocyte maturation. This work demonstrated that CYP significantly decreased oocyte maturation rate and subsequent embryo development in a dose-dependent manner (P < 0.05). And, CYP obviously induced the overproduction of reactive oxygen species and the reduction of glutathione content by downregulating the expression of redox genes in oocytes (P < 0.05). Moreover, CYP significantly caused oocyte DNA damage and disturbed the function of endoplasmic reticulum by altering the transcription of DNA damage repair and endoplasmic reticulum stress related genes (P < 0.05). Whereas CYP-exposed oocytes were treated with AST, these defects caused by CYP were significantly ameliorated (P < 0.05). In conclusion, this study demonstrated that CYP exerted the toxic effect on porcine oocytes, while AST effectively alleviated CYP-induced defects. This work provides a potential strategy to prevent pesticide toxicity and protect oocyte maturation in mammalian reproduction.

One Health challenges for pig reproduction

The current state of the world challenges pig reproduction as an important part of One Health, which involves interrelationships between animal, human and environmental health. The One Health concept underlines a comparative aspect in reproductive physiology and disease occurrence, bridging knowledge from one species to another. Seasonal changes in the environment affect pig reproduction and climate change may further strengthen those effects. Endocrine-disrupting chemicals (EDCs), and specifically phthalates and heavy metals, interfere with endocrine function, and thereby sexual behavior, fertilization capacity and steroidogenesis. Reproductive infections and extended semen storage are important indications for antimicrobial use. Innovative solutions are needed to explore alternatives to antimicrobials. Efforts to ensure reproductive efficiency have prolonged farrowing as litter size has doubled over the past three decades, compromising immune transfer and welfare. Physiological, metabolic and programming related events around parturition are key areas for future One Health research in pig reproduction. In conclusion, climate change challenges reproductive management and breeding. More resilient pigs that can tolerate harsh environment but maintain high reproductive performance are needed. EDCs continue to grow as an environmental challenge for reproductive management and alternatives to antibiotics will be required.

High doses of GrassOut Max poses reproductive hazard by affecting male reproductive function and early embryogenesis in Swiss albino mice

Clethodim is a widely used and approved class II herbicide, with little information about its impact on the reproductive system. Herein, we investigated the male reproductive toxicity of clethodim using a mouse model. GrassOut Max (26% clethodim-equivalent) or 50 mg kg^-1 body weight analytical grade clethodim (≥90%) were given orally to male mice for 10 d in varying doses. All parameters were assessed at 35 d from the first day of treatment. Significant decrease in testicular weight, decreased germ cell population, elevated DNA damage in testicular cells and lower serum testosterone level was observed post clethodim-equivalent exposure. Epididymal spermatozoa were characterized with significant decrease in motility, elevated DNA damage, abnormal morphology, chromatin immaturity and, decreased acetylated-lysine of sperm proteins. In the testicular cells of clethodim-equivalent treated mice, the expression of Erβ and Gper was significantly higher. Proteomic analysis revealed lower metabolic activity, poor sperm-oocyte binding potential and defective mitochondrial electron transport in spermatozoa of clethodim-equivalent treated mice. Further, fertilizing ability of spermatozoa was compromised and resulted in defective preimplantation embryo development. Together, our data suggest that clethodim exposure risks male reproductive function and early embryogenesis in Swiss albino mice via endocrine disrupting function.

Enhanced autophagy reversed aflatoxin B1-induced decrease in lactate secretion of dairy goat Sertoli cells

The deleterious effects of aflatoxins, especially aflatoxin B1 (AFB1) which are widespread at all stages of food production, on the reproductive system have been widely reported in males. However, it is still far from fully understood about the toxic effect and molecular mechanism after exposure to AFB1 in various testicular cells, especially Sertoli cells (SCs) which provide various energy materials and support to the developing germ cells as nurse cells. In this work, we examined the effects of AFB1 in dairy goat SCs on lactate production and autophagy, and the role of autophagy on AFB1-induced reduction in lactate production. Mechanistically, AFB1 destroyed the energy balance and reduced the secretion of lactate in dairy goat SCs (P < 0.01), resulting in a reduced level of ATP (P < 0.01) and phosphorylation of AMPK (P < 0.01). Subsequently, activated AMPK triggers autophagy by directly phosphorylating ULK1 (P < 0.05). The enhancement of autophagy partially reversed the AFB1-induced decrease in lactate secretion by promoting glucose utilization (P < 0.01) and increasing the expression of proteins related to lactate secretion in dairy goat SCs (P < 0.05) such as GLUT1, GLUT3, LDHA, and MCT4. Collectively, our study suggests that AFB1 inhibits the secretion of lactate which supply for germ cell development by damaging the "Warburg-like" metabolism of dairy goat SCs. Moreover, autophagy contributes to the resistance of glucose metabolism damage induced by AFB1. DATA AVAILABILITY: All data generated or analyzed in this study are available from the corresponding authors upon request.

In vitro adverse effects of amitraz on semen quality: Consequences in bovine embryo development

Veterinary drugs are potential environmental pollutants that interfere with male reproductive function. Infertility has increased, and it is known that environmental toxins contribute to declining sperm parameters. Amitraz {N,N-[(methylamino) dimeth-ylidyne] di-2,4-xylidine} (AMZ) is a formamidine pesticide widely used as an insecticide and an acaricide. The aim of this study was to evaluate the toxicity of AMZ in bovine sperm. Three experiments using frozen-thawed bovine semen incubated with AMZ for 2 h were carried out. Negative and solvent (dimethyl sulfoxide) controls were run simultaneously with treatments. In experiment 1, the AMZ concentrations used were 10, 15 and 25 μg AMZ/ml and the sperm parameters evaluated were viability, mitochondrial activity, acrosomal status, functional membrane integrity and apoptosis. In experiments 2 and 3, 25 μg AMZ/ml was used to evaluate fertilizing capacity, embryo development and blastocyst DNA damage. In experiment 1, 25 μg AMZ/ml decreased sperm viability (P = 0.01), reduced mitochondrial activity (P = 0.03) and induced apoptosis (P < 0.01). Also, 15 and 25 μg AMZ/ml affected functional membrane integrity (P < 0.01). In experiment 2, AMZ did not alter sperm-zona binding (P = 0.40) and pronucleus formation (P = 0.36). In experiment 3, 25 μg AMZ/ml decreased the rate of embryo development (P < 0.01) and increased apoptosis (P = 0.03). These results suggest that AMZ induced alterations in bovine sperm, probably affecting male fertility at concentrations that could be present in the environment.

Environment to embryo: intersections of contaminant exposure and preimplantation embryo development in agricultural animals

Environmental impacts on reproductive function are well documented in humans, yet little information is known about effects on large animals. The interface of environment and reproduction has evolved prudently with a concerted effort to ensure global food sustainability tightly integrated with application of technological advances in agriculture production that include nutrient and resource management. Exposure to environmental toxicants through chemical pesticide application and industry practices have coincided with a decline in cattle and human fertility. The increased adoption of agriculture animals for human biomedical models further emphasizes the importance of understanding the consequences of livestock exposure to environmentally and physiologically relevant levels of contaminants to preimplantation embryo development. In addition, increased awareness of paternal contributions to the early embryo that include both genetic and non-genetic factors support the need to define environmental interactions from gamete to genome. Herein we summarize current knowledge of common environmental contaminants on reproductive function including direct and indirect effects on embryo development success in livestock. Information obtained from a diverse number of species including humans is presented to illustrate gaps in knowledge within livestock directly pertaining to agriculture success, sustainability, clinical practice and biomedical research.

Actions of CSF2 and DKK1 on bovine embryo development and pregnancy outcomes are affected by composition of embryo culture medium

Procedures for in vitro embryo production in cattle have not been optimized. In the current experiment, we utilized a 3 × 3 factorial design to test whether the proportion of embryos becoming blastocysts in culture and the pregnancy rate after embryo transfer are affected by type of serum in the medium [no serum; 3% (v/v) KnockOut Serum Replacement (SR); 3% (v/v) fetal bovine serum (FBS)] and addition of specific embryokines [vehicle; 10 ng/mL colony stimulating factor 2 (CSF2); 100 ng/mL dickkopf related protein 1 (DKK1)] at day 5 of culture. Embryos were produced using abattoir-derived ovaries and Y-sorted semen from two Angus sires. The percent of putative zygotes and cleaved embryos becoming blastocysts was improved by SR and FBS. Pregnancy rate at day 30 was determined for 1426 Nelore recipients and calving rate for 266 recipients. In the absence of CSF2 or DKK1, pregnancy rates were lower for embryos cultured with SR or FBS. CSF2 and DKK1 reduced pregnancy rate for embryos cultured without serum but had no detrimental effect in the SR or FBS groups. Indeed, CSF2 blocked the negative effect of FBS on pregnancy rate. Data on birth weights were available for 67 bull calves. There were no effects of treatment. The sire used to produce embryos had significant and large effects on development to the blastocyst stage, pregnancy rate at day 30, calving rate and pregnancy loss between day 30 and calving. Results indicate that (1) SR and FBS can improve embryonic development in vitro while also compromising competence of embryos to survive after transfer, (2) actions of CSF2 and DKK1 depend upon other characteristics of the embryo production system, and (3) sire can have a large effect on embryonic development before and after transfer.

The Molecular Quality and Mitochondrial Activity of Porcine Cumulus-Oocyte Complexes Are Affected by Their Exposure to Three Endocrine-Active Compounds under 3D In Vitro Maturation Conditions

Thus far, the potential short- and long-term detrimental effects of a variety of environmental chemicals designated as endocrine-active compounds (EACs) have been found to interfere with histo- and anatomo-physiological functions of the reproductive system in humans and wildlife species. For those reasons, this study sought to examine whether selected EACs, which encompass the fungicide vinclozolin (Vnz), the androgenic anabolic steroid nandrolone (Ndn) and the immunosuppressant cyclosporin A (CsA), affect the developmental competence and molecular quality (MQ) of porcine cumulus–oocyte complexes (COCs) subjected to in vitro maturation (IVM) under 3D culture conditions. The COCs underwent 3D-IVM in the presence of Vnz, Ndn or CsA for 48 h. To explore whether the selected EACs induce internucleosomal DNA fragmentation in cumulus cells (CCs), TUNEL-assisted detection of late apoptotic cells was performed. Additionally, for the detailed evaluation of pro- and antiapoptotic pathways in COCs, apoptosis proteome profiler arrays were used. To determine changes in intracellular metabolism in COCs, comprehensive assessments of mitochondrial ultrastructure and activity were carried out. Moreover, the relative abundances (RAs) of mRNAs transcribed from genes that are involved in scavenging reactive oxygen species (ROS), such as SIRT3 and FOXO3, and intramitochondrial bioenergetic balance, such as ATP synthase subunit (ATP5A1), were ascertained. Finally, to investigate the extent of progression of oocyte maturation, the intraooplasmic levels of cAMP and the RAs of mRNA transcripts encoding regulatory and biocatalytic subunits of a heterodimeric meiosis-promoting factor, termed cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2), were also estimated. The obtained results provide, for the first time, strong evidence that both Vnz and Ndn decrease the developmental competence of oocytes and stimulate apoptosis processes in CCs. The present study is also the first to highlight that Vnz accelerates the maturation process in immature oocytes due to both increased ROS production and the augmented RA of the CCNB1 gene. Furthermore, Vnz was proven to trigger proapoptotic events in CCs by prompting the activity of the FOXO3 transcription factor, which regulates the mitochondrial apoptosis pathway. In turn, Ndn was shown to inhibit oocyte maturation by inducing molecular events that ultimately lead to an increase in the intraooplasmic cAMP concentration. However, due to the simultaneous enhancement of the expression of TNF-β and HSP27 proteins in CCs, Ndn might be responsible for the onset of their neoplastic transformation. Finally, our current investigation is the first to clearly demonstrate that although CsA did not interfere with the nuclear and cytoplasmic maturation of oocytes, by inducing mitophagy in CCs, it disrupted oocyte metabolism, consequently attenuating the parameters related to the MQ of COCs. Summing up, Vnz, Ndn and CsA reduced not only the processes of growth and IVM but also the MQ of porcine COCs, which might make them unsuitable for assisted reproductive technologies (ARTs) such as in vitro fertilization by either gamete co-incubation or intracytoplasmic sperm injection (ICSI) and cloning by somatic cell nuclear transfer (SCNT).

Female Germ Cell Development, Functioning and Associated Adversities under Unfavorable Circumstances

In the present era, infertility is one of the major issues which restricts many couples to have their own children. Infertility is the inability to achieve a clinical pregnancy after regular unprotected sexual intercourse for the period of one year or more. Various factors including defective male or female germ cell development, unhealthy and improper lifestyles, diseases like cancer and associated chemo-or-radiation therapies, congenital disorders, etc., may be responsible for infertility. Therefore, it is highly important to understand the basic concepts of germ cell development including primordial germ cell (PGC) formation, specification, migration, entry to genital ridges and their molecular mechanisms, activated pathways, paracrine and autocrine signaling, along with possible alteration which can hamper germ cell development and can cause adversities like cancer progression and infertility. Knowing all these aspects in a proper way can be very much helpful in improving our understanding about gametogenesis and finding possible ways to cure related disorders. Here in this review, various aspects of gametogenesis especially female gametes and relevant factors causing functional impairment have been thoroughly discussed.