Glutathione during embryonic development

Calf Fitness Associates with Early Embryo and Recipient Metabolomes and with Calf Epigenetic Marks

We used metadata to explore the metabolic interplay between culture medium from in vitro-produced bovine embryos transferred fresh or frozen, recipient blood plasma, and calf fitness, alongside gene expression and methylation in calf lymphocytes. Principal component (PC) analysis (PCA) identified covariates that were depicted in Debiased Sparse Partial Correlation networks and analyzed as enriched pathways. Four PCs explained 13.77, 9.58, 7.73 and 5.84% variability. PC1 clustered only mother weight and two embryonic metabolites. PC2, PC3 and PC4 associated 10, 17, and 5 calf features with 10, 6, and 16 embryonic and 2, 20, and 5 recipient metabolites, respectively. Subsequently, gene methylation and expression, and calf fitness were analyzed by PCA. Three PCs covered 100% variability. PC1 associated acid-base balance, protein metabolism, Cl-, and Ca2+ with IGF2 and IL1R1 expression, and IL4 and IL12B methylation. PC2 linked H19 expression and methylation with growth and biochemical traits. PC3 clustered growth, hydration, and redox balance, with IGF2, IGF2R, IL1R1 and IL3 methylation, and H19, IGF2, IGF2R and IL12B expression. Gene methylation connected with embryo metabolites through networks via K+, Cl-, HCO3- and TCO2. Calf fitness parallels the early metabolic fingerprints of the embryo and recipient, allowing embryo transfer decision-making based on calf health.

Inferring metabolic objectives and trade-offs in single cells during embryogenesis

While proliferating cells optimize their metabolism to produce biomass, the metabolic objectives of cells that perform non-proliferative tasks are unclear. The opposing requirements for optimizing each objective result in a trade-off that forces single cells to prioritize their metabolic needs and optimally allocate limited resources. Here, we present single-cell optimization objective and trade-off inference (SCOOTI), which infers metabolic objectives and trade-offs in biological systems by integrating bulk and single-cell omics data, using metabolic modeling and machine learning. We validated SCOOTI by identifying essential genes from CRISPR-Cas9 screens in embryonic stem cells, and by inferring the metabolic objectives of quiescent cells, during different cell-cycle phases. Applying this to embryonic cell states, we observed a decrease in metabolic entropy upon development. We further uncovered a trade-off between glutathione and biosynthetic precursors in one-cell zygote, two-cell embryo, and blastocyst cells, potentially representing a trade-off between pluripotency and proliferation. A record of this paper's transparent peer review process is included in the supplemental information.

Formation of multinucleated osteoclasts depends on an oxidized species of cell surface-associated La protein

The bone-resorbing activity of osteoclasts plays a critical role in the life-long remodeling of our bones that is perturbed in many bone loss diseases. Multinucleated osteoclasts are formed by the fusion of precursor cells, and larger cells - generated by an increased number of cell fusion events - have higher resorptive activity. We find that osteoclast fusion and bone resorption are promoted by reactive oxygen species (ROS) signaling and by an unconventional low molecular weight species of La protein, located at the osteoclast surface. Here, we develop the hypothesis that La's unique regulatory role in osteoclast multinucleation and function is controlled by an ROS switch in La trafficking. Using antibodies that recognize reduced or oxidized species of La, we find that differentiating osteoclasts enrich an oxidized species of La at the cell surface, which is distinct from the reduced La species conventionally localized within cell nuclei. ROS signaling triggers the shift from reduced to oxidized La species, its dephosphorylation and delivery to the surface of osteoclasts, where La promotes multinucleation and resorptive activity. Moreover, intracellular ROS signaling in differentiating osteoclasts oxidizes critical cysteine residues in the C-terminal half of La, producing this unconventional La species that promotes osteoclast fusion. Our findings suggest that redox signaling induces changes in the location and function of La and may represent a promising target for novel skeletal therapies.

Environmental high temperature affects pre-implantation embryo development by impairing the DNA repair ability

Environmental high temperature poses a significant threat to human health, however, limited information is available for understanding the relationship between the hot weather and infertility. This study aims to assess the adverse effect of the hot weather to early embryonic cells. Our results indicated that environmental high temperature exposure could cause the decline of early embryo quality and implantation ability. In detail, it led to early embryonic development retardation, embryo degeneration rate increased, the rate of blastocyst and hatching decreased, and reduced the number of implants. And the finding also the impairment of environmental high temperature on early embryonic cells may be due to oxidative damage of DNA caused by ROS, while BER repair ability is decreased, failing to repair oxidative damage of DNA in time, resulting in a large number of early embryonic apoptosis. The work underscored that pregnant women should stay away from high-temperature environments.

Activation of Nrf2 at Critical Windows of Development Alters Tissue-Specific Protein S-Glutathionylation in the Zebrafish (Danio rerio) Embryo

Activation of Nrf2-the master regulator of antioxidative response-at different stages of embryonic development has been shown to result in changes in gene expression, but the tissue-specific and downstream effects of Nrf2 activation during development remain unclear. This work seeks to elucidate the tissue-specific Nrf2 cellular localization and the downstream changes in protein S-glutathionylation during critical windows of zebrafish (Danio rerio) development. Wild-type and mutant zebrafish embryos with a loss-of-function mutation in Nrf2a were treated with two canonical activators, sulforaphane (SFN; 40 µM) or tert-butylhydroquinone (tBHQ; 1 µM), for 6 h at either pharyngula, hatching, or the protruding-mouth stage. Nrf2a protein and S-glutathionylation were visualized in situ using immunohistochemistry. At the hatching stage, Nrf2a protein levels were decreased with SFN, but not tBHQ, exposure. Exposure to both activators, however, decreased downstream S-glutathionylation. Stage- and tissue-specific differences in Nrf2a protein and S-glutathionylation were identified in the pancreatic islet and liver. Protein S-glutathionylation in Nrf2a mutant fish was increased in the liver by both activators, but not the islets, indicating a tissue-specific and Nrf2a-dependent dysregulation. This work demonstrates that critical windows of exposure and Nrf2a activity may influence redox homeostasis and highlights the importance of considering tissue-specific outcomes and sensitivity in developmental redox biology.

The hard life of an octopus embryo is seen through gene expression, energy metabolism, and its ability to neutralize radical oxygen species

The reproductive process in Octopus maya was analyzed to establish the amount of reactive oxygen species that the embryos inherit from females, during yolk synthesis. At the same time, respiratory metabolism, ROS production, and the expression of some genes of the antioxidant system were monitored to understand the ability of embryos to neutralize maternal ROS and those produced during development. The results indicate that carbonylated proteins and peroxidized lipids (LPO) were transferred from females to the embryos, presumably derived from the metabolic processes carried out during yolk synthesis in the ovary. Along with ROS, females also transferred to embryos glutathione (GSH), a key element of the antioxidant defense system, thus facilitating the neutralization of inherited ROS and those produced during development. Embryos are capable of neutralizing ROS thanks to the early expression of genes such as catalase (CAT) and superoxide dismutase (SOD), which give rise to the synthesis of enzymes when the circulatory system is activated. Also, it was observed that the levels of the routine metabolic rate of embryos are almost as high as those of the maximum activity metabolism, which leads, on the one hand, to the elevated production of ROS and suggests that, at this stage of the life cycle in octopuses, energy production is maximum and is physically limited by the biological properties inherent to the structure of embryonic life (oxygen transfer through the chorion, gill surface, pumping capacity, etc.). Due to its role in regulating vascularization, a high expression of HIf-1A during organogenesis suggests that circulatory system development has begun in this phase of embryo development. The results indicate that the routine metabolic rate and the ability of O. maya embryos to neutralize the ROS are probably the maximum possible. Under such circumstances, embryos cannot generate more energy to combat the free radicals produced by their metabolism, even when environmental factors such as high temperatures or contaminants could demand excess energy.

FORMATION OF MULTINUCLEATED OSTEOCLASTS DEPENDS ON AN OXIDIZED SPECIES OF CELL SURFACE ASSOCIATED LA PROTEIN

The bone-resorbing activity of osteoclasts plays a critical role in the life-long remodeling of our bones that is perturbed in many bone loss diseases. Multinucleated osteoclasts are formed by the fusion of precursor cells, and larger cells - generated by an increased number of cell fusion events - have higher resorptive activity. We find that osteoclast fusion and bone-resorption are promoted by reactive oxygen species (ROS) signaling and by an unconventional low molecular weight species of La protein, located at the osteoclast surface. Here, we develop the hypothesis that La's unique regulatory role in osteoclast multinucleation and function is controlled by a ROS switch in La trafficking. Using antibodies that recognize reduced or oxidized species of La, we find that differentiating osteoclasts enrich an oxidized species of La at the cell surface, which is distinct from the reduced La species conventionally localized within cell nuclei. ROS signaling triggers the shift from reduced to oxidized La species, its dephosphorylation and delivery to the surface of osteoclasts, where La promotes multinucleation and resorptive activity. Moreover, intracellular ROS signaling in differentiating osteoclasts oxidizes critical cysteine residues in the C-terminal half of La, producing this unconventional La species that promotes osteoclast fusion. Our findings suggest that redox signaling induces changes in the location and function of La and may represent a promising target for novel skeletal therapies.

Long-term effect of exposure to triethylene glycol dimethacrylate (TEGDMA) on male mouse reproduction

Our study investigated the impact on male mouse fertility and reproduction of long-term (14 weeks) exposure to triethylene glycol dimethacrylate (TEGDMA), a co-monomer of resin-based compounds, at doses of 0.01, 0.1, 1, and 10 ppm. Test and control mice were then paired with sexually mature untreated female mice and their fertility evaluated. Females paired with males exposed to all TEGDMA doses exhibited a significant decline in pregnancy rates, and significant increases in the total embryonic resorption-to-implantation ratio, except for males exposed to 0.01 ppm TEGDMA. Males in the highest dose group (10 ppm) showed significant increases in seminal vesicle and preputial gland weights. They also had significantly higher serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) than the controls, and the 0.01 ppm dosage group for FSH levels. TEGDMA exposure resulted in notable histopathological alterations in the testis, with detachment of germ cells and shedding of germinal epithelium into the tubule lumen. These results strongly indicate that TEGDMA exposure has detrimental consequences on the reproductive abilities and functions in male mice through disruption of the standard hormonal regulation of the reproductive system, leading to changes in spermatogenesis and ultimately leading to decreased fertility.

Valproic Acid Causes Redox-Regulated Post-Translational Protein Modifications That Are Dependent upon P19 Cellular Differentiation States

Valproic acid (VPA) is a common anti-epileptic drug and known neurodevelopmental toxicant. Although the exact mechanism of VPA toxicity remains unknown, recent findings show that VPA disrupts redox signaling in undifferentiated cells but has little effect on fully differentiated neurons. Redox imbalances often alter oxidative post-translational protein modifications and could affect embryogenesis if developmentally critical proteins are targeted. We hypothesize that VPA causes redox-sensitive post-translational protein modifications that are dependent upon cellular differentiation states. Undifferentiated P19 cells and P19-derived neurons were treated with VPA alone or pretreated with D3T, an inducer of the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant pathway, prior to VPA exposure. Undifferentiated cells treated with VPA alone exhibited an oxidized glutathione redox couple and increased overall protein oxidation, whereas differentiated neurons were protected from protein oxidation via increased S-glutathionylation. Pretreatment with D3T prevented the effects of VPA exposure in undifferentiated cells. Taken together, our findings support redox-sensitive post-translational protein alterations in undifferentiated cells as a mechanism of VPA-induced developmental toxicity and propose NRF2 activation as a means to preserve proper neurogenesis.

Direct Activation of Nucleobases with Small Molecules for the Conditional Control of Antisense Function

Conditionally controlled antisense oligonucleotides provide precise interrogation of gene function at different developmental stages in animal models. Only one example of small molecule-induced activation of antisense function exist. This has been restricted to cyclic caged morpholinos that, based on sequence, can have significant background activity in the absence of the trigger. Here, we provide a new approach using azido-caged nucleobases that are site-specifically introduced into antisense morpholinos. The caging group design is a simple azidomethylene (Azm) group that, despite its very small size, efficiently blocks Watson-Crick base pairing in a programmable fashion. Furthermore, it undergoes facile decaging via Staudinger reduction when exposed to a small molecule phosphine, generating the native antisense oligonucleotide under conditions compatible with biological environments. We demonstrated small molecule-induced gene knockdown in mammalian cells, zebrafish embryos, and frog embryos. We validated the general applicability of this approach by targeting three different genes.

Glutathione safeguards TET-dependent DNA demethylation and is critical for the acquisition of totipotency and pluripotency during preimplantation development

During early development, both genome-wide epigenetic reprogramming and metabolic remodeling are hallmark changes of normal embryogenesis. However, little is known about their relationship and developmental functions during the preimplantation window, which is essential for the acquisition of totipotency and pluripotency. Herein, we reported that glutathione (GSH), a ubiquitous intracellular protective antioxidant that maintains mitochondrial function and redox homeostasis, plays a critical role in safeguarding postfertilization DNA demethylation and is essential for establishing developmental potential in preimplantation embryos. By profiling mitochondria-related transcriptome that coupled with different pluripotency, we found GSH is a potential marker that is tightly correlated with full pluripotency, and its beneficial effect on prompting developmental potential was functionally conformed using in vitro fertilized mouse and bovine embryos as the model. Mechanistic study based on preimplantation embryos and embryonic stem cells further revealed that GSH prompts the acquisition of totipotency and pluripotency by facilitating ten-eleven-translocation (TET)-dependent DNA demethylation, and ascorbic acid (AsA)-GSH cycle is implicated in the process. In addition, we also reported that GSH serves as an oviductal paracrine factor that supports development potential of preimplantation embryos. Thus, our results not only advance the current knowledge of functional links between epigenetic reprogramming and metabolic remodeling during preimplantation development but also provided a promising approach for improving current in vitro culture system for assisted reproductive technology.

Redox control of antioxidants, metabolism, immunity, and development at the core of stress adaptation of the oyster Crassostrea gigas to the dynamic intertidal environment

This review uses the marine bivalve Crassostrea gigas to highlight redox reactions and control systems in species living in dynamic intertidal environments. Intertidal species face daily and seasonal environmental variability, including temperature, oxygen, salinity, and nutritional changes. Increasing anthropogenic pressure can bring pollutants and pathogens as additional stressors. Surprisingly, C. gigas demonstrates impressive adaptability to most of these challenges. We explore how ROS production, antioxidant protection, redox signaling, and metabolic adjustments can shed light on how redox biology supports oyster survival in harsh conditions. The review provides (i) a brief summary of shared redox sensing processes in metazoan; (ii) an overview of unique characteristics of the C. gigas intertidal habitat and the suitability of this species as a model organism; (iii) insights into the redox biology of C. gigas, including ROS sources, signaling pathways, ROS-scavenging systems, and thiol-containing proteins; and examples of (iv) hot topics that are underdeveloped in bivalve research linking redox biology with immunometabolism, physioxia, and development. Given its plasticity to environmental changes, C. gigas is a valuable model for studying the role of redox biology in the adaptation to harsh habitats, potentially providing novel insights for basic and applied studies in marine and comparative biochemistry and physiology.

Glutathione: Lights and Shadows in Cancer Patients

In cases of cellular injury, there is an observed increase in the production of reactive oxygen species (ROS). When this production becomes excessive, it can result in various conditions, including cancerogenesis. Glutathione (GSH), the most abundant thiol-containing antioxidant, is fundamental to re-establishing redox homeostasis. In order to evaluate the role of GSH and its antioxi-dant effects in patients affected by cancer, we performed a thorough search on Medline and EMBASE databases for relevant clinical and/or preclinical studies, with particular regard to diet, toxicities, and pharmacological processes. The conjugation of GSH with xenobiotics, including anti-cancer drugs, can result in either of two effects: xenobiotics may lose their harmful effects, or GSH conjugation may enhance their toxicity by inducing bioactivation. While being an interesting weapon against chemotherapy-induced toxicities, GSH may also have a potential protective role for cancer cells. New studies are necessary to better explain the relationship between GSH and cancer. Although self-prescribed glutathione (GSH) implementation is prevalent among cancer patients with the intention of reducing the toxic effects of anticancer treatments and potentially preventing damage to normal tissues, this belief lacks substantial scientific evidence for its efficacy in reducing toxicity, except in the case of cisplatin-related neurotoxicity. Therefore, the use of GSH should only be considered under medical supervision, taking into account the appropriate timing and setting.

Developmental impacts of Nrf2 activation by dimethyl fumarate (DMF) in the developing zebrafish (Danio rerio) embryo

Dimethyl fumarate (DMF) is pharmaceutical activator of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates of many cellular antioxidant response pathways, and has been used to treat inflammatory diseases such as multiple sclerosis. However, DMF has been shown to produce adverse effects on offspring in animal studies and as such is not recommended for use during pregnancy. The goal of this work is to better understand how these adverse effects are initiated and the role of DMF-induced Nrf2 activation during three critical windows of development in embryonic zebrafish (Danio rerio): pharyngula, hatching, and protruding-mouth stages. To evaluate Nrf2 activation, wildtype zebrafish, and mutant zebrafish (nrf2afh318/fh318) embryos with a loss of function mutation in Nrf2a, the co-ortholog to human Nrf2, were treated for 6 h with DMF (0-20 μM) beginning at the pharyngula, hatching, or protruding-mouth stage and assessed for survival and morphology. Nrf2a mutant fish had an increase in survival, however, morphology studies demonstrated Nrf2a mutant fish had more severe deformities occurring with exposures during the hatching stage. To verify Nrf2 cellular localization and downstream impacts on protein-S-glutathionylation in situ, a concentration below the LOAEL was chosen (7 μM) for immunohistochemistry and S-glutathionylation. Embryos were imaged via epifluorescence microscopy studies, the Nrf2a protein in the body tissue was decreased with DMF only when exposed at the hatching stage, while total protein S-glutathionylation was modulated by Nrf2a activity and DMF during the pharyngula and protruding-mouth stage. The pancreatic islet and liver were further analyzed via confocal microscopy. Pancreatic islets and liver also had tissue specific differences with Nrf2a protein expression and protein S-glutathionylation. This work demonstrates how critical windows of exposure and Nrf2a activity may influence toxicity of DMF and highlights tissue-specific changes in Nrf2a protein levels and S-glutathionylation in pancreatic islet and liver during embryonic development.

Effects of paternal methionine supplementation on sperm DNA methylation and embryo transcriptome in sheep

Environmental effects on gene expression and offspring development can be mediated by epigenetic modifications. It is well established that maternal diet influences DNA methylation patterns and phenotypes in the offspring; however, the epigenetic effects of paternal diet on developing offspring warrants further investigation. Here, we examined how a prepubertal methionine-enriched paternal diet affected sperm DNA methylation and its subsequent effects on embryo gene expression. Three treatment and three control rams were bred to seven ewes, and blastocysts were flushed for RNA extraction. Semen was collected from all rams and submitted for reduced representation bisulfite sequencing analysis. In total, 166 differentially methylated cytosines were identified in the sperm from treatment versus control rams. Nine genes were found to be differentially expressed in embryos produced from treatment versus control rams, and seven differentially methylated cytosines in the sperm were found to be highly correlated with gene expression in the embryos. Our results demonstrate that sperm methylation differences induced by diet may influence fetal programming.

Glutathione: A Samsonian life-sustaining small molecule that protects against oxidative stress, ageing and damaging inflammation

Many local and systemic diseases especially diseases that are leading causes of death globally like chronic obstructive pulmonary disease, atherosclerosis with ischemic heart disease and stroke, cancer and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 19 (COVID-19), involve both, (1) oxidative stress with excessive production of reactive oxygen species (ROS) that lower glutathione (GSH) levels, and (2) inflammation. The GSH tripeptide (γ- L-glutamyl-L-cysteinyl-glycine), the most abundant water-soluble non-protein thiol in the cell (1-10 mM) is fundamental for life by (a) sustaining the adequate redox cell signaling needed to maintain physiologic levels of oxidative stress fundamental to control life processes, and (b) limiting excessive oxidative stress that causes cell and tissue damage. GSH activity is facilitated by activation of the Kelch-like ECH-associated protein 1 (Keap1)-Nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) redox regulator pathway, releasing Nrf2 that regulates expression of genes controlling antioxidant, inflammatory and immune system responses. GSH exists in the thiol-reduced (>98% of total GSH) and disulfide-oxidized (GSSG) forms, and the concentrations of GSH and GSSG and their molar ratio are indicators of the functionality of the cell. GSH depletion may play a central role in inflammatory diseases and COVID-19 pathophysiology, host immune response and disease severity and mortality. Therapies enhancing GSH could become a cornerstone to reduce severity and fatal outcomes of inflammatory diseases and COVID-19 and increasing GSH levels may prevent and subdue these diseases. The life value of GSH makes for a paramount research field in biology and medicine and may be key against systemic inflammation and SARS-CoV-2 infection and COVID-19 disease. In this review, we emphasize on (1) GSH depletion as a fundamental risk factor for diseases like chronic obstructive pulmonary disease and atherosclerosis (ischemic heart disease and stroke), (2) importance of oxidative stress and antioxidants in SARS-CoV-2 infection and COVID-19 disease, (3) significance of GSH to counteract persistent damaging inflammation, inflammaging and early (premature) inflammaging associated with cell and tissue damage caused by excessive oxidative stress and lack of adequate antioxidant defenses in younger individuals, and (4) new therapies that include antioxidant defenses restoration.

Exogenous L-Glutathione Improves Vitrification Outcomes in Murine Preimplantation Embryos

Vitrification is an important tool to store surplus embryos in assisted reproductive technology (ART). However, vitrification increases oxidative damage and results in decreased viability. Studies have reported that L-glutathione (GSH) supplementation improves the preimplantation development of murine embryos. Glutathione constitutes the major non-protein sulphydryl compound in mammalian cells, which confers protection against oxidative damage. However, the effect of GSH supplementation on embryonic vitrification outcomes has yet to be reported. This study aims to determine whether GSH supplementation in culture media improves in vitro culture and vitrification outcomes, as observed through embryo morphology and preimplantation development. Female BALB/c mice aged 6−8 weeks were superovulated through an intraperitoneal injection of 10 IU of pregnant mare serum gonadotrophin (PMSG), followed by 10 IU of human chorionic gonadotrophin (hCG) 48 h later. The mated mice were euthanized by cervical dislocation 48 h after hCG to harvest embryos. Two-cell embryos were randomly assigned to be cultured in either Group 1 (GSH-free medium), Group 2 (GSH-free medium with vitrification), Group 3 (0.01 mM GSH-supplemented medium), or Group 4 (0.01 mM GSH-supplemented medium with vitrification). Non-vitrified (Groups 1 and 3) and vitrified (Groups 2 and 4) embryos were observed for morphological quality and preimplantation development at 24, 48, 72, and 96 h. In the non-vitrified groups, there were significant increases in the number of Grade-1 blastocysts in GSH cultures (p < 0.05). Similarly, in the vitrified groups, GSH supplementation was also seen to significantly increase blastocyst formation. Exogenous GSH supplementation resulted in a significant increase in intracellular GSH, a release of cytochrome c from mitochondria, and a parallel decrease in intracellular reactive oxygen species (ROS) levels in vitrified eight-cell embryos (p < 0.05). GSH supplementation was shown to upregulate Bcl2 expression and downregulate Bax expression in the vitrified preimplantation embryo group. The action of exogenous GSH was concomitant with an increase in the relative abundance of Gpx1 and Sod1. In conclusion, our study demonstrated the novel use and practical applicability of GSH supplementation for improving embryonic cryotolerance via a decrease in ROS levels and the inhibition of apoptotic events by improvement in oxidative status.

Comparative transcriptomic analysis revealed dynamic changes of distinct classes of genes during development of the Manila clam (Ruditapes philippinarum)

Background

The Manila clam Ruditapesphilippinarum is one of the most economically important marine shellfish. However, the molecular mechanisms of early development in Manila clams are largely unknown. In this study, we collected samples from 13 stages of early development in Manila clam and compared the mRNA expression pattern between samples by RNA-seq techniques.

Results

We applied RNA-seq technology to 13 embryonic and larval stages of the Manila clam to identify critical genes and pathways involved in their development and biological characteristics. Important genes associated with different morphologies during the early fertilized egg, cell division, cell differentiation, hatching, and metamorphosis stages were identified. We detected the highest number of differentially expressed genes in the comparison of the pediveliger and single pipe juvenile stages, which is a time when biological characteristics greatly change during metamorphosis. Gene Ontology (GO) enrichment analysis showed that expression levels of microtubule protein-related molecules and Rho genes were upregulated and that GO terms such as ribosome, translation, and organelle were enriched in the early development stages of the Manila clam. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the foxo, wnt, and transforming growth factor-beta pathways were significantly enriched during early development. These results provide insights into the molecular mechanisms at work during different periods of early development of Manila clams.

Conclusion

These transcriptomic data provide clues to the molecular mechanisms underlying the development of Manila clam larvae. These results will help to improve Manila clam reproduction and development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08813-0.

Mitochondrial genome undergoes de novo DNA methylation that protects mtDNA against oxidative damage during the peri-implantation window

Mitochondrial remodeling during the peri-implantation stage is the hallmark event essential for normal embryogenesis. Among the changes, enhanced oxidative phosphorylation is critical for supporting high energy demands of postimplantation embryos, but increases mitochondrial oxidative stress, which in turn threatens mitochondrial DNA (mtDNA) stability. However, how mitochondria protect their own histone-lacking mtDNA, during this stage remains unclear. Concurrently, the mitochondrial genome gain DNA methylation by this stage. Its spatiotemporal coincidence with enhanced mitochondrial stress led us to ask if mtDNA methylation has a role in maintaining mitochondrial genome stability. Herein, we report that mitochondrial genome undergoes de novo mtDNA methylation that can protect mtDNA against enhanced oxidative damage during the peri-implantation window. Mitochondrial genome gains extensive mtDNA methylation during transition from blastocysts to postimplantation embryos, thus establishing relatively hypermethylated mtDNA from hypomethylated state in blastocysts. Mechanistic study revealed that DNA methyltransferase 3A (DNMT3A) and DNMT3B enter mitochondria during this process and bind to mtDNA, via their unique mitochondrial targeting sequences. Importantly, loss- and gain-of-function analyses indicated that DNMT3A and DNMT3B are responsible for catalyzing de novo mtDNA methylation, in a synergistic manner. Finally, we proved, in vivo and in vitro, that increased mtDNA methylation functions to protect mitochondrial genome against mtDNA damage induced by increased mitochondrial oxidative stress. Together, we reveal mtDNA methylation dynamics and its underlying mechanism during the critical developmental window. We also provide the functional link between mitochondrial epigenetic remodeling and metabolic changes, which reveals a role for nuclear-mitochondrial crosstalk in establishing mitoepigenetics and maintaining mitochondrial homeostasis.

Oroxin A reduces oxidative stress, apoptosis, and autophagy and improves the developmental competence of porcine embryos in vitro

Oroxin A (OA) is a flavonoid isolated from Oroxylum indicum (L.) Kurz that has various biological activities, including antioxidant activities. This study aimed to examine the viability of using OA in an in vitro culture (IVC) medium for its antioxidant effects and related molecular mechanisms on porcine blastocyst development. In this study, we investigated the effects of OA on early porcine embryo development via terminal deoxynucleotidyl transferase dUTP nick-end labeling, 5-ethynyl-2'-deoxyuridine labeling, quantitative reverse transcription PCR, and immunocytochemistry. Embryos cultured in the IVC medium supplemented with 2.5 μM of OA had an increased blastocyst formation rate, total cell number, and proliferation capacity, along with a low apoptosis rate. OA supplementation decreased reactive oxygen species levels, while increasing glutathione levels. OA-treated embryos exhibited an improved intracellular mitochondrial membrane potential and reduced autophagy. Moreover, levels of pluripotency- and antioxidant-related genes were upregulated, whereas those of apoptosis- and autophagy-related genes were downregulated by OA addition. In conclusion, OA improves preimplantation embryonic development by reducing oxidative stress and enhancing mitochondrial function.

Effect of Passage Number of Conditioned Medium Collected from Equine Amniotic Fluid Mesenchymal Stem Cells: Porcine Oocyte Maturation and Embryo Development

Oocyte in vitro maturation (IVM) is the most important first step in in vitro embryo production. One prerequisite for the success of IVM in oocytes is to provide a rich culture microenvironment that meets the nutritional needs of developing oocytes. We applied different equine amniotic fluid mesenchymal stem cell conditioned medium (eAFMSC-CM) from passages 7, 18, and 27 to porcine oocytes during IVM to determine its effects on oocyte development and subsequent embryo development, specifically. The eAFMSC-CM from passage 7 (eAFMSC-CMp7) has a considerable impact on 9 genes: BAX, BCL2, SOD2, NRF2, TNFAIP6, PTGS2, HAS2, Cx37, and Cx43, which are associated with cumulus cell mediated oocyte maturation. GSH levels and distribution of mitochondrial and cortical granules were significantly increased in oocytes incubated with eAFMSC-CMp7. In addition, catalase and superoxide dismutase activities were high after IVM 44 h with eAFMSC-CMp7. After in vitro fertilization, blastocyst quality was significantly increased in the eAFMSC-CMp7 group compared to control. Lastly, the antioxidant effect of eAFMSC-CMp7 substantially regulated the expression of apoptosis, pluripotency related genes and decreased autophagy activity in blastocysts. Taken together, this study demonstrated that the eAFMSC-CMp7 enhanced the cytoplasmic maturation of oocytes and subsequent embryonic development by generating high antioxidant activity.

Astaxanthin Supplementation Improves the Subsequent Developmental Competence of Vitrified Porcine Zygotes

Cryopreservation of embryos has been confirmed to cause oxidative stress as a factor responsible for impaired developmental competence. Currently, astaxanthin (Ax) raises considerable interest as a strong exogenous antioxidant and for its potential in reproductive biology. The present study aimed to investigate the beneficial effects of Ax supplementation during in vitro culture of vitrified porcine zygotes and the possible underlying mechanisms. First, the parthenogenetic zygotes were submitted to vitrification and then cultured in the medium added with various concentrations of Ax (0, 0.5, 1.5, and 2.5 μM). Supplementation of 1.5 μM Ax achieved the highest blastocyst yield and was considered as the optimal concentration. This concentration also improved the blastocyst formation rate of vitrified cloned zygotes. Moreover, the vitrified parthenogenetic zygotes cultured with Ax exhibited significantly increased mRNA expression of CDX2, SOD2, and GPX4 in their blastocysts. We further analyzed oxidative stress, mitochondrial and lysosomal function in the 4-cell embryos and blastocysts derived from parthenogenetic zygotes. For the 4-cell embryos, vitrification disturbed the levels of reactive oxygen species (ROS) and glutathione (GSH), and the activities of mitochondria, lysosome and cathepsin B, and Ax supplementation could fully or partially rescue these values. The blastocysts obtained from vitrified zygotes showed significantly reduced ATP content and elevated cathepsin B activity, which also was recovered by Ax supplementation. There were no significant differences in other parameters mentioned above for the resultant blastocysts. Furthermore, the addition of Ax significantly enhanced mitochondrial activity and reduced lysosomal activity in resultant blastocysts. In conclusion, these findings revealed that Ax supplementation during the culture period improved subsequent embryonic development and quality of porcine zygotes after vitrification and might be used to ameliorate the recovery culture condition for vitrified embryos.

Glucose-6-Phosphate Dehydrogenase, Redox Homeostasis and Embryogenesis

Normal embryogenesis requires complex regulation and precision, which depends on multiple mechanistic details. Defective embryogenesis can occur by various mechanisms. Maintaining redox homeostasis is of importance during embryogenesis. NADPH, as produced from the action of glucose-6-phosphate dehydrogenase (G6PD), has an important role in redox homeostasis, serving as a cofactor for glutathione reductase in the recycling of glutathione from oxidized glutathione and for NADPH oxidases and nitric oxide synthases in the generation of reactive oxygen (ROS) and nitrogen species (RNS). Oxidative stress differentially influences cell fate and embryogenesis. While low levels of stress (eustress) by ROS and RNS promote cell growth and differentiation, supra-physiological concentrations of ROS and RNS can lead to cell demise and embryonic lethality. G6PD-deficient cells and organisms have been used as models in embryogenesis for determining the role of redox signaling in regulating cell proliferation, differentiation and migration. Embryogenesis is also modulated by anti-oxidant enzymes, transcription factors, microRNAs, growth factors and signaling pathways, which are dependent on redox regulation. Crosstalk among transcription factors, microRNAs and redox signaling is essential for embryogenesis.

Glutathione in Brain Disorders and Aging

Glutathione is a remarkably functional molecule with diverse features, which include being an antioxidant, a regulator of DNA synthesis and repair, a protector of thiol groups in proteins, a stabilizer of cell membranes, and a detoxifier of xenobiotics. Glutathione exists in two states—oxidized and reduced. Under normal physiological conditions of cellular homeostasis, glutathione remains primarily in its reduced form. However, many metabolic pathways involve oxidization of glutathione, resulting in an imbalance in cellular homeostasis. Impairment of glutathione function in the brain is linked to loss of neurons during the aging process or as the result of neurological diseases such as Huntington’s disease, Parkinson’s disease, stroke, and Alzheimer’s disease. The exact mechanisms through which glutathione regulates brain metabolism are not well understood. In this review, we will highlight the common signaling cascades that regulate glutathione in neurons and glia, its functions as a neuronal regulator in homeostasis and metabolism, and finally a mechanistic recapitulation of glutathione signaling. Together, these will put glutathione’s role in normal aging and neurological disorders development into perspective.

β3-Adrenoceptor, a novel player in the round-trip from neonatal diseases to cancer: Suggestive clues from embryo

The role of the β-adrenoceptors (β-ARs) in hypoxia-driven diseases has gained visibility after the demonstration that propranolol promotes the regression of infantile hemangiomas and ameliorates the signs of retinopathy of prematurity (ROP). Besides the role of β2-ARs, preclinical studies in ROP have also revealed that β3-ARs are upregulated by hypoxia and that they are possibly involved in retinal angiogenesis. In a sort of figurative round trip, peculiarities typical of ROP, where hypoxia drives retinal neovascularization, have been then translated to cancer, a disease equally characterized by hypoxia-driven angiogenesis. In this step, investigating the role of β3-ARs has taken advantage of the assumption that cancer growth uses a set of strategies in common with embryo development. The possibility that hypoxic induction of β3-ARs may represent one of the mechanisms through which primarily embryo (and then cancer, as an astute imitator) adapts to grow in an otherwise hostile environment, has grown evidence. In both cancer and embryo, β3-ARs exert similar functions by exploiting a metabolic shift known as the Warburg effect, by acquiring resistance against xenobiotics, and by inducing a local immune tolerance. An additional potential role of β3-AR as a marker of stemness has been suggested by the finding that its antagonism induces cancer cell differentiation evoking that β3-ARs may help cancer to grow in a nonhospital environment, a strategy also exploited by embryos. From cancer, the round trip goes back to neonatal diseases for which new possible interpretative keys and potential pharmacological perspectives have been suggested.

Valproic acid promotes SOD2 acetylation: A potential mechanism of valproic acid-induced oxidative stress in developing systems

Valproic acid (VPA) is an antiepileptic, bipolar and migraine medication, which is associated with embryonic dysmorphology, more specifically neural tube defects (NTDs), if taken while pregnant. One mechanism by which VPA may cause NTDs is through oxidative stress that cause disruption of cell signaling. However, mechanisms of VPA-induced oxidative stress are not fully understood. Since VPA is a deacetylase inhibitor, we propose that VPA promotes mitochondrial superoxide dismutase-2 (SOD2) acetylation, decreasing SOD2 activity and increasing oxidant levels. Using the pluripotent embryonal carcinoma cell line, P19, VPA effects were evaluated in undifferentiated and neurodifferentiated cells. VPA treatments increased oxidant levels, oxidized the glutathione (GSH)/glutathione disulfide (GSSG) redox couple, and decreased total SOD and SOD2 activity in undifferentiated P19 cells but not in differentiated P19 cells. VPA caused a specific increase in mitochondrial oxidants in undifferentiated P19 cells, VPA did not alter respirometry measurements. Immunoblot analyses demonstrated that VPA increased acetylation of SOD2 at lysine⁶⁸ (AcK68 SOD2) in undifferentiated P19 cells but not in differentiated P19 cells. Pretreatments with the Nrf2 inducer, dithiol-3-thione (D3T), in undifferentiated P19 cells prevented increased oxidant levels, GSH/GSSG redox oxidation and restored total SOD and SOD2 activity, correlating with a decrease in AcK68 SOD2 levels. In embryos, VPA decreased total SOD and SOD2 activity and increased levels of AcK68 SOD2, and D3T pretreatments prevented VPA effects, increasing total SOD and SOD2 activity and lowering levels of AcK68 SOD2. These data demonstrate a potential, contributing oxidizing mechanism by which VPA incites teratogenesis in developing systems. Moreover, these data also suggest that Nrf2 interventions may serve as a means to protect developmental signaling and inhibit VPA-induced malformations.

NRF2 activation protects against valproic acid-induced disruption of neurogenesis in P19 cells

Valproic acid (VPA) is a commonly prescribed antiepileptic drug that causes fetal valproate syndrome (FVS) in developing embryos exposed to it. Symptoms of FVS include neural tube defects (NTDs), musculoskeletal abnormalities, and neurodevelopmental difficulties. One proposed mechanism of VPA-induced developmental toxicity is via oxidative stress, defined as the disruption of redox-sensitive cell signaling. We propose that redox imbalances caused by VPA exposure result in improper cellular differentiation that may contribute to FVS. In undifferentiated P19 mouse embryonal carcinoma cells treated with VPA, glutathione disulfide (GSSG) concentrations were higher and the glutathione (GSH)/GSSG redox potential (E_h) was more oxidizing compared to vehicle-treated control cells, both of which are indications of potential intracellular oxidative stress. Interestingly, VPA had no effect on GSH or GSSG levels in differentiated P19 neurons. Undifferentiated cells pretreated with 3H-1,2-dithiole-3-thione (D3T), an inducer of the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant response that combats cellular redox disruption, were protected from VPA-induced alterations to the GSH/GSSG system. To assess differential periods of susceptibility, P19 cells were exposed to VPA at various time points during their neuronal differentiation. Cells exposed to VPA early in the differentiation process did not undergo normal neurogenesis as measured by POU domain, class 5, transcription factor 1 (OCT4) and tubulin beta-3 chain (βIII-tubulin), markers of cell stemness and neuronal differentiation, respectively. Neurogenesis was improved with D3T pretreatments prior to VPA exposure. Furthermore, differentiating P19 cells treated with VPA exhibited increased protein oxidation that was diminished with D3T pretreatment. These findings demonstrate that VPA inhibits neurogenesis and propose NRF2-mediated redox homeostasis as a means to promote normal neuronal differentiation, thereby potentially decreasing the prevalence of FVS outcomes.

Biomarkers of Inflammation and Redox Imbalance in Umbilical Cord in Pregnancies with and without Preeclampsia and Consequent Perinatal Outcomes

OBJECTIVE

To compare redox imbalance and inflammation biomarkers in umbilical cords from pregnancies with and without preeclampsia (PE) and to analyse their relationships with perinatal outcomes.

METHODS

A controlled cross-sectional study was conducted in Maceió, Alagoas, Brazil, that involved pregnant women with PE and a group of women without the disease, through the application of a standardized questionnaire. After delivery, umbilical cord samples were collected to measure antioxidant defense, products from oxidative damage, and inflammation biomarkers such as myeloperoxidase (MPO), interleukin- (IL-) 6, IL-8, IL-10, and tumor necrosis factor-alpha (TNF-α). Statistical analyses were performed using Stata version 13.0 software and IBM Statistical Package for the Social Sciences (SPSS) 20.0, adopting a 95% confidence level (α = 0.05), with the chi-square test, the Wilcoxon-Mann-Whitney test, and the multinomial and Poisson regression tests.

RESULTS

One hundred PE pregnant women and 50 women without the disease were studied. The umbilical cords from PE pregnancies showed higher levels of reduced glutathione (GSH) (p ≤ 0.001), glutathione peroxidase (GPx) (p = 0.016), and malondialdehyde (MDA) (p = 0.028) and lower levels of IL-6 (p = 0.030) and TNF-α (p ≤ 0.001) than the other group, with some associations among these biomarkers with perinatal outcomes.

CONCLUSION

The higher levels of GSH and GPx, in addition to the lower levels of IL-6 and TNF-α, found in the PE umbilical cord, may result from adaptive mechanisms to maintain the oxidative and inflammatory balance; however, despite these changes, the damage to the cell membranes was not minimized, as the MDA level was higher in women with PE than in women without the disease. This implies that a redox imbalance is present, confirming that other physiological and adaptive mechanisms are being activated to preserve foetal health. Therefore, the present work unveils an important role of the umbilical cord in controlling redox imbalance and inflammation in PE pregnancies. Our results reinforce the necessity for continuous research on GSH as a protective compound for the perinatal outcome, especially in PE women.

NRF2 activation inhibits valproic acid-induced neural tube defects in mice

Valproic acid (VPA) is a widely prescribed medication that has traditionally been used to treat epilepsy, yet embryonic exposure to VPA increases the risk of the fetus developing neural tube defects (NTDs). While the mechanism by which VPA causes NTDs is unknown, we hypothesize that VPA causes dysmorphogenesis through the disruption of redox-sensitive signaling pathways that are critical for proper embryonic development, and that protection from the redox disruption may decrease the prevalence of NTDs. Time-bred CD-1 mice were treated with 3H-1,2-dithiole-3-thione (D3T), an inducer of nuclear factor erythroid 2-related factor 2 (NRF2)-a transcription factor that activates the intracellular antioxidant response to prevent redox disruptions. Embryos were then collected for whole embryo culture and subsequently treated with VPA in vitro. The glutathione (GSH)/glutathione disulfide (GSSG) redox potential (E_h), a measure of the intracellular redox environment, was measured in the developing mouse embryos. Embryos treated with VPA exhibited a transiently oxidizing GSH/GSSG E_h, while those that received D3T pretreatment prior to VPA exposure showed no differences compared to controls. Moving to an in utero mouse model, time-bred C57BL/6 J dams were pretreated with or without D3T and then exposed to VPA, after which all embryos were collected for morphological analyses. The prevalence of open neural tubes in embryos treated with VPA significantly decreased with D3T pretreatment, as did the severity of the observed defects evaluated by a morphological assessment. These data show that NRF2 induction via D3T pretreatment protects against VPA-induced redox dysregulation and decreases the prevalence of NTDs in developing mouse embryos.

Ebselen, a multi-target compound: its effects on biological processes and diseases

Ebselen is a well-known synthetic compound mimicking glutathione peroxidase (GPx), which catalyses some vital reactions that protect against oxidative damage. Based on a large number of in vivo and in vitro studies, various mechanisms have been proposed to explain its actions on multiple targets. It targets thiol-related compounds, including cysteine, glutathione, and thiol proteins (e.g., thioredoxin and thioredoxin reductase). Owing to this, ebselen is a unique multifunctional agent with important effects on inflammation, apoptosis, oxidative stress, cell differentiation, immune regulation and neurodegenerative disease, with anti-microbial, detoxifying and anti-tumour activity. This review summarises the current understanding of the multiple biological processes and molecules targeted by ebselen, and its pharmacological applications.

Impaired GSH biosynthesis disrupts eye development, lens morphogenesis and PAX6 function

PURPOSE

The purpose of this study was to elucidate the role and molecular consequences of impaired glutathione (GSH) biosynthesis on eye development.

METHODS

GSH biosynthesis was impaired in surface ectoderm-derived ocular tissues by crossing Gclc^f/f mice with hemizygous Le-Cre transgenic mice to produce Gclc^f/f/Le-Cre^Tg/- (KO) mice. Control mice included Gclc^f/fand Gclc^wt/wt/Le-Cre^Tg/- mice (CRE). Eyes from all mice (at various stages of eye development) were subjected to histological, immunohistochemical, Western blot, RT-qPCR, RNA-seq, and subsequent Gene Ontology, Ingenuity Pathway Analysis and TRANSFAC analyses. PAX6 transactivation activity was studied using a luciferase reporter assay in HEK293T cells depleted of GSH using buthionine sulfoximine (BSO).

RESULTS

Deletion of Gclc diminished GSH levels, increased reactive oxygen species (ROS), and caused an overt microphthalmia phenotype characterized by malformation of the cornea, iris, lens, and retina that is distinct from and much more profound than the one observed in CRE mice. In addition, only the lenses of KO mice displayed reduced crystallin (α, β), PITX3 and Foxe3 expression. RNA-seq analyses at postnatal day 1 revealed 1552 differentially expressed genes (DEGs) in the lenses of KO mice relative to those from Gclc^f/f mice, with Crystallin and lens fiber cell identity genes being downregulated while lens epithelial cell identity and immune response genes were upregulated. Bioinformatic analysis of the DEGs implicated PAX6 as a key upstream regulator. PAX6 transactivation activity was impaired in BSO-treated HEK293T cells.

CONCLUSIONS

These data suggest that impaired ocular GSH biosynthesis may disrupt eye development and PAX6 function.

N-acetyl-cysteine and the control of oxidative stress during in vitro ovarian follicle growth, oocyte maturation, embryo development and cryopreservation

Oxidative stress is generated by an imbalance between reactive oxygen species (ROS) formation and cellular defense mechanisms. To reduce cellular damage caused by ROS in vivo or in vitro, N-acetyl-cysteine (NAC) is converted into metabolites that have the capacity of stimulating synthesis of glutathione (GSH) which functions directly as free radical scavengers. The NAC antioxidant potential evaluated to the greatest extent is the indirect action of NAC, as a precursor of GSH, with glutathione being the primary antioxidant in cells. During long-term preantral follicle culture, NAC has a synergic action with FSH and an important function in sustaining preantral follicle growth and follicle-cell viability in vitro. The NAC inclusion in in vitro maturation medium for cumulus-oocyte complexes (COC) leads to protection of oocytes from damage induced by heat stress, reductions in ROS, and increases in cumulus cell expansion. Developing embryos are susceptable to oxidative stress because of susceptability to cellular structure damage and not having well-developed defense mechanisms. Results from various indicate there are beneficial effects of NAC on embryonic development by increasing GSH biosynthesis and regulating cell proliferation. In addition, NAC is also an effective antioxidant during cryopreservation of ovarian follicles, oocytes and embryos, because inclusion of NAC in preservation medium leads to improvements in mitochondrial function and cell viability, and reductions in ROS and cellular apoptosis. In this review, there is evaluation of mechanisms of action of NAC and beneficial effects during in vitro culture of preantral follicles, as well as oocyte maturation, embryonic development and cryopreservation.

The use of glutathione to reduce oxidative stress status and its potential for modifying the extracellular matrix organization in cleft lip

OBJECTIVE

Cleft lip (CL) is a common congenital anomaly that can be syndromic or non-syndromic. It can be triggered by the mutation of gene or environmental factors. The incidence of CL is about 1 out of 700 live births. Facial development is a complex process, and there is no existing therapy to prevent the disease development. One of the characteristics in this facial malformation is the increased presence of reactive oxygen species (ROS). In this study, we hypothesize that the antioxidant glutathione (GSH) could help to attenuate the oxidative stress in this disease.

METHODS

Bioinformatics network pharmacology was applied to determine pharmacological targets and molecular mechanisms of GSH treatment for CL. Moreover, RNA-sequencing of the POLR1C knockdown osteoblast CL model was applied to validate the in silico data of using GSH in CL.

RESULTS

Twenty-two core targets of GSH and CL were identified via various bioinformatics tools. The GO and KEGG analysis indicated that GSH could modulate two major families (matrix metalloproteinase and integrins), which are related to extracellular matrix modification and composition for facial development in CL. The findings from POLR1C knockdown model further supported the rescue response of GSH in CL.

CONCLUSIONS

The study uncovered the possible pharmacological mechanism of GSH for treating CL. The data helps research group to focus on the specific pathways for understanding the biological action of GSH for treating the CL in the future.

Molecular characteristics of oocytes and somatic cells of follicles at different sizes that influence in vitro oocyte maturation and embryo production

During the last 10 to 15 yr, in vitro research to predict antral follicle growth and oocyte maturation has delivered interesting advances in the knowledge of processes regulating follicle growth and developmental competence of oocytes. This review discusses the contribution of cumulus and mural granulosa cells in the process of oocyte maturation and cumulus expansion in cumulus-oocyte complexes (COCs) from follicles of different sizes and shows that differences in gene expression in oocytes, granulosa, and theca cells of small and large follicles impact the success of in vitro blastocyst development. In addition, the molecular mechanisms by which COC metabolism and antioxidant defense provide oocyte competence are highlighted. Furthermore, new insights and perspectives on molecular and cellular regulation of in vitro oocyte maturation are emphasized.

Severity of prepregnancy diabetes on the fetal malformations and viability associated with early embryos in rats†

Preexisting/pregestational diabetes enhances the risk of birth defects. Several factors have been involved during the implantation process, such as cytokines (granulocyte-macrophage-colony-stimulating factor [GM-CSF]). The objective was to evaluate the effects of two levels of diabetes on the redox status of preimplantation embryos during the implantation process to comprehend how both are involved in embryo and fetal viability against maternal diabetes. Female Sprague-Dawley rats received streptozotocin at birth (mild diabetes [MD]) or at adulthood (severe diabetes [SD]) to obtain two experimental diabetes intensities. After confirming the diabetic status, the nondiabetic and diabetic groups were mated around day 110 of life. At gestational day (GD) 21, fetuses were assessed for viability and malformations and ovaries for embryo loss before implantation. Other pregnant nondiabetic and diabetic rats were sacrificed at GD2-4 for maternal and preimplantation embryo oxidative stress markers, maternal serum insulin, uterine fluid GM-CSF, and preimplantation embryo morphological analysis. MD and SD caused abnormal redox levels, lower GM-CSF and insulin levels during the preimplantation period, and embryonic loss before implantation. SD caused lower fetal viability and higher fetal malformation percentages at GD21. The SD dam-derived preimplantation embryos presented lower glutathione levels and higher thiobarbituric acid reactive substances concentration at GD3 and an increased frequency of abnormal preimplantation embryos at GD4. In conclusion, preexisting diabetes leads to complications in the implantation process. Furthermore, maternal oxidative stress and other metabolic changes alter the redox state and morphological structure of preimplantation embryos, contributing to damaged growth and development in late pregnancy.

Smart Nanocarriers for the Delivery of Nucleic Acid-Based Therapeutics: A Comprehensive Review

Nucleic acid-based therapies are promising therapeutics for the treatment of several systemic disorders, and they offer an exciting opportunity to address emerging biological challenges. The scope of nucleic acid-based therapeutics in the treatment of multiple disease states including cancers has been widened by recent progress in Ribonucleic acids (RNA) biology. However, cascades of systemic and intracellular barriers, including rapid degradation, renal clearance, and poor cellular uptake, hinder the clinical effectiveness of nucleic acid-based therapies. These barriers can be circumvented by utilizing advanced smart nanocarriers that efficiently deliver and release the encapsulated nucleic acids into the target tissues. This review describes the current status of clinical trials on nucleic acid-based therapeutics and highlights representative examples that provide an overview on the current and emerging trends in nucleic acid-based therapies. A better understanding of the design of advanced nanocarriers is essential to promote the translation of therapeutic nucleic acids into a clinical reality.

Metabolic Activity of Human Embryos after Thawing Differs in Atmosphere with Different Oxygen Concentrations

The vitrification of human embryos is more and more frequently being utilized as a method of assisted reproduction. For this technique, gentle treatment of the embryos after thawing is crucial. In this study, the balance of amino acids released to/consumed from the cultivation media surrounding the warmed embryos was observed in the context of a cultivation environment, which was with the atmospheric oxygen concentration ≈20% or with a regulated oxygen level—hysiological (5%). It is the first time that total amino acid turnover in human embryos after their freezing at post compaction stages has been evaluated. During this study, progressive embryos (developed to blastocyst stage) and stagnant embryos (without developmental progression) were analyzed. It was observed that the embryos cultivated in conditions of physiological oxygen levels (5% oxygen) showed a significantly lower consumption of amino acids from the cultivation media. Progressively developing embryos also had significantly lower total amino acid turnovers (consumption and production of amino acids) when cultured in conditions with physiological oxygen levels. Based on these results it seems that a cultivation environment with a reduced oxygen concentration decreases the risk of degenerative changes in the embryos after thawing. Therefore, the cultivation of thawed embryos in an environment with physiological oxygen levels may preclude embryonal stagnation, and can support the further development of human embryos after their thawing.

24-Epibrassinolide protects against ethanol-induced behavioural teratogenesis in zebrafish embryo

Embryonic studies have demonstrated the neurotoxic, teratogenic, and neurobehavioral toxicity of ethanol (EtOH). Although multiple mechanisms may contribute to these effects, oxidative stress has been described as the major damage pathway. In this regard, natural antioxidants have the potential to counteract oxidative stress-induced cellular damage. Therefore, the present study aimed to investigate the potential protective role of 24-epibrassinolide (24-EPI), a natural brassinosteroid with proved antioxidant properties, in EtOH-induced teratogenic effects during early zebrafish development. Embryos (~2 h post-fertilization - hpf) were exposed to 1 % EtOH, co-exposed to 24-EPI (0.01, 0.1 and 1 μM) and to 24-EPI alone (1 μM) for 24 h. Following exposure, biochemical evaluations were made at 26 hpf, developmental analysis was made throughout the embryo-larval period, and behavioural responses were evaluated at 120 hpf. Exposure to 1 % EtOH caused an increase in the number of malformations, which were diminished by 24-EPI. In addition, EtOH induced an accumulation of GSSG and consequent reduction of GSH:GSSG ratio, indicating the involvement of oxidative mechanisms in the EtOH-induced effects. These were reverted by 24-EPI as proved by the GSSG levels and GSH:GSSG ratio that returned to control values. Furthermore, exposure to EtOH resulted in behavioural deficits at 120 hpf as observed by the disrupted response to an aversive stimulus, suggesting the involvement of neurotoxic mechanisms. 24-EPI restored the behavioural deficits observed in a dose-dependent manner. The absence of effects in the embryos exposed solely to 24-EPI showed its safety during the exposure period. In conclusion, EtOH caused developmental teratogenicity and behavioural toxicity by inducing glutathione changes, which were prevented by 24-EPI.

Long Non-Coding RNA and mRNA Profiling in Early-Stage Bovine Embryos Treated with Glutathione

We measured differential expression profiles of genes and long non-coding RNA (lncRNA) using RNA sequencing in bovine embryos with or without glutathione (GSH) treatment. Bovine embryos fertilized in vitro were treated with GSH to blastocyst. Embryos at the 8-16-cell and morula stages were collected, with embryos without GSH treatment as the control. RNA was isolated, amplified, and sequenced. Differentially expressed genes (DEGs) and lncRNAs (DElncRNAs) were identified and bioinformatic analyses carried out. Transcript levels were confirmed using quantitative RT-PCR. A total of 4100 DEGs were identified, of which 3952 were in GSH-treated morulae and 884 in untreated morulae. More gene ontology (GO) terms were associated with GSH treatment than with control conditions. KEGG analysis showed that glutathione metabolism, citrate cycle, and metabolic pathways involving glycine, serine, and threonine were observed only in GSH-treated embryos. Among 4273 DElncRNAs identified, 59 were potentially important in GSH-treated embryo development, including 14 involved in glutathione metabolism. The 59 DElncRNAs co-expressed with protein-coding mRNAs involved similar GO terms and pathways as the DEGs. This appears to be the first comprehensive profiling of DEGs and DElncRNAs in bovine embryos fertilized in vitro with or without GSH, and the first systematic screen of potential lncRNAs in bovine embryos.

The Redox Theory of Development

Significance: The geological record shows that as atmospheric O2 levels increased, it concomitantly coincided with the evolution of metazoans. More complex, higher organisms contain a more cysteine-rich proteome, potentially as a means to regulate homeostatic responses in a more O2-rich environment. Regulation of redox-sensitive processes to control development is likely to be evolutionarily conserved. Recent Advances: During early embryonic development, the conceptus is exposed to varying levels of O2. Oxygen and redox-sensitive elements can be regulated to promote normal development, defined as changes to cellular mass, morphology, biochemistry, and function, suggesting that O2 is a developmental morphogen. During periods of O2 fluctuation, embryos are "reprogrammed," on the genomic and metabolic levels. Reprogramming imparts changes to particular redox couples (nodes) that would support specific post-translational modifications (PTMs), targeting the cysteine proteome to regulate protein function and development. Critical Issues: Major developmental events such as stem cell expansion, proliferation, differentiation, migration, and cell fate decisions are controlled through oxidative PTMs of cysteine-based redox nodes. As such, timely coordinated redox regulation of these events yields normal developmental outcomes and viable species reproduction. Disruption of normal redox signaling can produce adverse developmental outcomes. Future Directions: Furthering our understanding of the redox-sensitive processes/pathways, the nature of the regulatory PTMs involved in development and periods of activation/sensitivity to specific developmental pathways would greatly support the theory of redox regulation of development, and would also provide rationale and direction to more fully comprehend poor developmental outcomes, such as dysmorphogenesis, functional deficits, and preterm embryonic death.

Metabolic Profiling in Blastocoel Fluid and Blood Plasma of Diabetic Rabbits

Metabolic disorders of the mother adversely affect early embryo development, causing changes in maternal metabolism and consequent alterations in the embryo environment in the uterus. The goal of this study was to analyse the biochemical profiles of embryonic fluids and blood plasma of rabbits with and without insulin-dependent diabetes mellitus (DT1), to identify metabolic changes associated with maternal diabetes mellitus in early pregnancy. Insulin-dependent diabetes was induced by alloxan treatment in female rabbits 10 days before mating. On day 6 post-coitum, plasma and blastocoel fluid (BF) were analysed by ultrahigh performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) (Metabolon Inc. Durham, NC, USA). Metabolic datasets comprised a total of 284 and 597 compounds of known identity in BF and plasma, respectively. Diabetes mellitus had profound effects on maternal and embryonic metabolic profiles, with almost half of the metabolites changed. As predicted, we observed an increase in glucose and a decrease in 1,5-anhydroglucitol in diabetic plasma samples. In plasma, fructose, mannose, and sorbitol were elevated in the diabetic group, which may be a way of dealing with excess glucose. In BF, metabolites of the pentose metabolism were especially increased, indicating the need for ribose-based compounds relevant to DNA and RNA metabolism at this very early stage of embryo development. Other changes were more consistent between BF and plasma. Both displayed elevated acylcarnitines, body3-hydroxybutyrate, and multiple compounds within the branched chain amino acid metabolism pathway, suggesting that lipid beta-oxidation is occurring at elevated levels in the diabetic group. This study demonstrates that maternal and embryonic metabolism are closely related. Maternal diabetes mellitus profoundly alters the metabolic profile of the preimplantation embryo with changes in all subclasses of metabolites.

Metabolic Changes of Maternal Uterine Fluid, Uterus, and Plasma during the Peri-implantation Period of Early Pregnancy in Mice

Embryo implantation is a complex process which involves biochemical and physiological interactions between an implantation-competent blastocyst and a receptive uterus. However, the exact biochemical changes of uterine fluid, uterus, and plasma during peri-implantation remain unclear. This study aims to characterize the biochemical and metabolic changes that occur during the peri-implantation period of early pregnancy, using mice as an animal model. Gas chromatography-mass spectrometry was used to analyze the metabolite profiles of the uterus, uterine fluid, and maternal plasma at pre-implantation and implantation. The multivariate analyses, ANOVA and Tukey's HSD test, were applied to detect significant changes in metabolites and metabolic pathways. The metabolic networks were reconstructed in silico based on the identified metabolites and KEGG metabolic framework. Between pre-implantation day 1 and day 4, dramatic metabolic changes were observed in the uterine fluid that could be important for blastocyst development and protection against the harsh uterine environment. Palmitoleic acid, fumaric acid, and glutaric acid changed levels at day 4 in the uterus, suggesting that they may be associated with endometrial receptivity. Both the uterus and maternal plasma showed profound changes in cellular metabolism at the early implantation period, including upregulation of branched-chain amino acids and intermediates of one-carbon metabolism, an upregulation of glyoxylate and dicarboxylate metabolism, and downregulation of aerobic respiration; all of which could be involved in the regulation of the maternal-fetal interface, alternative nutrient utilization, and energy preservation for implantation as well as later placentation and fetal development to ensure successful embryo implantation.

Redox Proteomes in Human Physiology and Disease Mechanisms

Redox proteomics is a field of proteomics that is concerned with the characterization of the oxidation state of proteins to gain information about their modulated structure, function, activity, and involvement in different physiological pathways. Oxidative modifications of proteins have been shown to be implicated in normal physiological processes of cells as well as in pathomechanisms leading to the development of cancer, diabetes, neurodegenerative diseases, and some rare hereditary metabolic diseases, like classic galactosemia. Reactive oxygen species generate a variety of reversible and irreversible modifications in amino acid residue side chains and within the protein backbone. These oxidative post-translational modifications (Ox-PTMs) can participate in the activation of signal transduction pathways and mediate the toxicity of harmful oxidants. Thus the application of advanced redox proteomics technologies is important for gaining insights into molecular mechanisms of diseases. Mass-spectrometry-based proteomics is one of the most powerful methods that can be used to give detailed qualitative and quantitative information on protein modifications and allows us to characterize redox proteomes associated with diseases. This Review illustrates the role and biological consequences of Ox-PTMs under basal and oxidative stress conditions by focusing on protein carbonylation and S-glutathionylation, two abundant modifications with an impact on cellular pathways that have been intensively studied during the past decade.

Catalyst-free Click PEGylation reveals substantial mitochondrial ATP synthase sub-unit alpha oxidation before and after fertilisation

Using non-reducing Western blotting to assess protein thiol redox state is challenging because most reduced and oxidised forms migrate at the same molecular weight and are, therefore, indistinguishable. While copper catalysed Click chemistry can be used to ligate a polyethylene glycol (PEG) moiety termed Click PEGylation to mass shift the reduced or oxidised form as desired, the potential for copper catalysed auto-oxidation is problematic. Here we define a catalyst-free trans-cyclooctene-methyltetrazine (TCO-Tz) inverse electron demand Diels Alder chemistry approach that affords rapid (k ~2000 M-1 s-1), selective and bio-orthogonal Click PEGylation. We used TCO-Tz Click PEGylation to investigate how fertilisation impacts reversible mitochondrial ATP synthase F1-Fo sub-unit alpha (ATP-α-F1) oxidation-an established molecular correlate of impaired enzyme activity-in Xenopus laevis. TCO-Tz Click PEGylation studies reveal substantial (~65%) reversible ATP-α-F1 oxidation at evolutionary conserved cysteine residues (i.e., C244 and C294) before and after fertilisation. A single thiol is, however, preferentially oxidised likely due to greater solvent exposure during the catalytic cycle. Selective reduction experiments show that: S-glutathionylation accounts for ~50-60% of the reversible oxidation observed, making it the dominant oxidative modification type. Intermolecular disulphide bonds may also contribute due to their relative stability. Substantial reversible ATP-α-F1 oxidation before and after fertilisation is biologically meaningful because it implies low mitochondrial F1-Fo ATP synthase activity. Catalyst-free TCO-Tz Click PEGylation is a valuable new tool to interrogate protein thiol redox state in health and disease.

Ceramide: a novel inducer for neural tube defects

BACKGROUND

Circulating plasma ceramides, a class of bioactive sphingolipids, are elevated in metabolic disorders, including obesity. Infants of women with these disorders are at 2- to 3-fold greater risk for developing a neural tube defect (NTD). This study aimed to test the effects of embryonic exposure to C2-ceramides (C2) during neural tube closure. Preliminary data shows an increase in NTDs in chick embryos after C2 exposure, and addresses potential mechanisms.

RESULTS

Cell and embryo models were used to examine redox shifts after ceramide exposure. While undifferentiated P19 cells were resistant to ceramide exposure, neuronally differentiated P19 cells exhibited an oxidizing shift. Consistent with these observations, GSH E _h curves revealed a shift to a more oxidized state in C2 treated embryos without increasing apoptosis or changing Pax3 expression, however cell proliferation was lower. Neural tube defects were observed in 45% of chick embryos exposed to C2, compared to 12% in control embryos.

CONCLUSIONS

C2 exposure during critical developmental stages increased the frequency of NTDs in the avian model. Increased ROS generation in cell culture, along with the more oxidative GSH E _h profiles of C2 exposed cells and embryos, support a model wherein ceramide affects neural tube closure via altered tissue redox environments.

Antioxidant Defence Systems and Oxidative Stress in Poultry Biology: An Update

Poultry in commercial settings are exposed to a range of stressors. A growing body of information clearly indicates that excess ROS/RNS production and oxidative stress are major detrimental consequences of the most common commercial stressors in poultry production. During evolution, antioxidant defence systems were developed in poultry to survive in an oxygenated atmosphere. They include a complex network of internally synthesised (e.g., antioxidant enzymes, (glutathione) GSH, (coenzyme Q) CoQ) and externally supplied (vitamin E, carotenoids, etc.) antioxidants. In fact, all antioxidants in the body work cooperatively as a team to maintain optimal redox balance in the cell/body. This balance is a key element in providing the necessary conditions for cell signalling, a vital process for regulation of the expression of various genes, stress adaptation and homeostasis maintenance in the body. Since ROS/RNS are considered to be important signalling molecules, their concentration is strictly regulated by the antioxidant defence network in conjunction with various transcription factors and vitagenes. In fact, activation of vitagenes via such transcription factors as Nrf2 leads to an additional synthesis of an array of protective molecules which can deal with increased ROS/RNS production. Therefore, it is a challenging task to develop a system of optimal antioxidant supplementation to help growing/productive birds maintain effective antioxidant defences and redox balance in the body. On the one hand, antioxidants, such as vitamin E, or minerals (e.g., Se, Mn, Cu and Zn) are a compulsory part of the commercial pre-mixes for poultry, and, in most cases, are adequate to meet the physiological requirements in these elements. On the other hand, due to the aforementioned commercially relevant stressors, there is a need for additional support for the antioxidant system in poultry. This new direction in improving antioxidant defences for poultry in stress conditions is related to an opportunity to activate a range of vitagenes (via Nrf2-related mechanisms: superoxide dismutase, SOD; heme oxygenase-1, HO-1; GSH and thioredoxin, or other mechanisms: Heat shock protein (HSP)/heat shock factor (HSP), sirtuins, etc.) to maximise internal AO protection and redox balance maintenance. Therefore, the development of vitagene-regulating nutritional supplements is on the agenda of many commercial companies worldwide.

The glutathione degrading enzyme, Chac1, is required for calcium signaling in developing zebrafish: redox as an upstream activator of calcium

Calcium signaling is essential for embryonic development but the signals upstream of calcium are only partially understood. Here, we investigate the role of the intracellular glutathione redox potential in calcium signaling using the Chac1 protein of zebrafish. A member of the γ-glutamylcyclotransferase family of enzymes, the zebrafish Chac1 is a glutathione-degrading enzyme that acts only on reduced glutathione. The zebrafish chac1 expression was seen early in development, and in the latter stages, in the developing muscles, brain and heart. The chac1 knockdown was embryonic lethal, and the developmental defects were seen primarily in the myotome, brain and heart where chac1 was maximally expressed. The phenotypes could be rescued by the WT Chac1 but not by the catalytically inactive Chac1 that was incapable of degrading glutathione. The ability of chac1 to alter the intracellular glutathione redox potential in the live animals was examined using Grx1-roGFP2. The chac1 morphants lacked the increased degree of cellular oxidation seen in the WT zebrafish. As calcium is also known to be critical for the developing myotomes, brain and heart, we further investigated if the chac1 knockdown phenotypes were a consequence of the lack of calcium signals. We observed using GCaMP6s, that calcium transients normally seen in the developing embryos were strongly attenuated in these knockdowns. The study thus identifies Chac1 and the consequent change in intracellular glutathione redox potential as important upstream activators of calcium signaling during development.

Mapping glutathione utilization in the developing zebrafish (Danio rerio) embryo

Glutathione (GSH), the most abundant vertebrate endogenous redox buffer, plays key roles in organogenesis and embryonic development, however, organ-specific GSH utilization during development remains understudied. Monochlorobimane (MCB), a dye conjugated with GSH by glutathione-s-transferase (GST) to form a fluorescent adduct, was used to visualize organ-specific GSH utilization in live developing zebrafish (Danio rerio) embryos. Embryos were incubated in 20 μM MCB for 1 h and imaged on an epifluorescence microscope. GSH conjugation with MCB was high during early organogenesis, decreasing as embryos aged. The heart had fluorescence 21-fold above autofluorescence at 24 hpf, dropping to 8.5-fold by 48 hpf; this increased again by 72 hpf to 23.5-fold, and stayed high till 96 hpf (18-fold). The brain had lower fluorescence (10-fold) at 24 and 48 hpf, steadily increasing to 30-fold by 96 hpf. The sensitivity and specificity of MCB staining was then tested with known GSH modulators. A 10-min treatment at 48 hpf with 750 μM tert-butylhydroperoxide, caused organ-specific reductions in staining, with the heart losing 30% fluorescence, and, the brain ventricle losing 47% fluorescence. A 24 h treatment from 24-48 hpf with 100 μM of N-Acetylcysteine (NAC) resulted in significantly increased fluorescence, with the brain ventricle and heart showing 312% and 240% increases respectively, these were abolished upon co-treatment with 5 μM BSO, an inhibitor of the enzyme that utilizes NAC to synthesize GSH. A 60 min 100 μM treatment with ethacrynic acid, a specific GST inhibitor, caused 30% reduction in fluorescence across all measured structures. MCB staining was then applied to test for GSH disruptions caused by the toxicants perfluorooctanesulfonic acid and mono-(2-ethyl-hexyl)phthalate; MCB fluorescence responded in a dose, structure and age-dependent manner. MCB staining is a robust, sensitive method to detect spatiotemporal changes in GSH utilization, and, can be applied to identify sensitive target tissues of toxicants.