Folic acid supplement rescues ethanol-induced developmental defects in the zebrafish embryos

The Role of One-Carbon Metabolism and Methyl Donors in Medically Assisted Reproduction: A Narrative Review of the Literature

One-carbon (1-C) metabolic deficiency impairs homeostasis, driving disease development, including infertility. It is of importance to summarize the current evidence regarding the clinical utility of 1-C metabolism-related biomolecules and methyl donors, namely, folate, betaine, choline, vitamin B12, homocysteine (Hcy), and zinc, as potential biomarkers, dietary supplements, and culture media supplements in the context of medically assisted reproduction (MAR). A narrative review of the literature was conducted in the PubMed/Medline database. Diet, ageing, and the endocrine milieu of individuals affect both 1-C metabolism and fertility status. In vitro fertilization (IVF) techniques, and culture conditions in particular, have a direct impact on 1-C metabolic activity in gametes and embryos. Critical analysis indicated that zinc supplementation in cryopreservation media may be a promising approach to reducing oxidative damage, while female serum homocysteine levels may be employed as a possible biomarker for predicting IVF outcomes. Nonetheless, the level of evidence is low, and future studies are needed to verify these data. One-carbon metabolism-related processes, including redox defense and epigenetic regulation, may be compromised in IVF-derived embryos. The study of 1-C metabolism may lead the way towards improving MAR efficiency and safety and ensuring the lifelong health of MAR infants.

A perspective on psychedelic teratogenicity: the utility of zebrafish models

Psychedelic drugs have experienced an unprecedented surge in recreational use within the past few years. Among recreational users, the risks of psychedelic use by pregnant and breastfeeding women are severely understudied and there is little information on the potential teratogenic effects of these drugs. We provide an overview of the previous data on psychedelic teratogenicity from rodent studies and human surveys, discuss their limitations, and propose the utility of the zebrafish as a potential effective model for investigating psychedelic teratogenicity. Recent years have validated the use of zebrafish in the study of fetal exposure and developmental biology; we highlight these properties of the zebrafish for its suitability in psychedelic toxicity research.

Retinoic acid signaling pathway perturbation impacts mesodermal-tissue development in the zebrafish embryo: Biomarker candidate identification using transcriptomics

The zebrafish embryo (ZE) model provides a developmental model well conserved throughout vertebrate embryogenesis, with relevance for early human embryo development. It was employed to search for gene expression biomarkers of compound-induced disruption of mesodermal development. We were particularly interested in the expression of genes related to the retinoic acid signaling pathway (RA-SP), as a major morphogenetic regulating mechanism. We exposed ZE to teratogenic concentrations of valproic acid (VPA) and all-trans retinoic acid (ATRA), using folic acid (FA) as a non-teratogenic control compound shortly after fertilization for 4 h, and performed gene expression analysis by RNA sequencing. We identified 248 genes specifically regulated by both teratogens but not by FA. Further analysis of this gene set revealed 54 GO-terms related to the development of mesodermal tissues, distributed along the paraxial, intermediate, and lateral plate sections of the mesoderm. Gene expression regulation was specific to tissues and was observed for somites, striated muscle, bone, kidney, circulatory system, and blood. Stitch analysis revealed 47 regulated genes related to the RA-SP, which were differentially expressed in the various mesodermal tissues. These genes provide potential molecular biomarkers of mesodermal tissue and organ (mal)formation in the early vertebrate embryo.

Nervous system development related gene expression regulation in the zebrafish embryo after exposure to valproic acid and retinoic acid: A genome wide approach

The evaluation of chemical and pharmaceutical safety for humans is moving from animal studies to New Approach Methodologies (NAM), reducing animal use and focusing on mechanism of action, whilst enhancing human relevance. In developmental toxicology, the mechanistic approach is facilitated by the assessment of predictive biomarkers, which allow mechanistic pathways perturbation monitoring at the basis of human hazard assessment. In our search for biomarkers of maldevelopment, we focused on chemically-induced perturbation of the retinoic acid signaling pathway (RA-SP), a major pathway implicated in a plethora of developmental processes. A genome-wide expression screening was performed on zebrafish embryos treated with two teratogens, all-trans retinoic acid (ATRA) and valproic acid (VPA), and a non-teratogen reference compound, folic acid (FA). Each compound was found to have a specific mRNA expression profile with 248 genes commonly dysregulated by both teratogenic compounds but not by FA. These genes were implicated in several developmental processes (e.g., the circulatory and nervous system). Given the prominent response of neurodevelopmental gene sets, and the crucial need to better understand developmental neurotoxicity, our study then focused on nervous system development. We found 62 genes that are potential early neurodevelopmental toxicity biomarker candidates. These results advance NAM-based safety assessment evaluation by highlighting the usefulness of the RA-SP in providing early toxicity biomarker candidates.

Epigenetics and Neuroinflammation Associated With Neurodevelopmental Disorders: A Microglial Perspective

Neuroinflammation is a cause of neurodevelopmental disorders such as autism spectrum disorders, fetal alcohol syndrome, and cerebral palsy. Converging lines of evidence from basic and clinical sciences suggest that dysregulation of the epigenetic landscape, including DNA methylation and miRNA expression, is associated with neuroinflammation. Genetic and environmental factors can affect the interaction between epigenetics and neuroinflammation, which may cause neurodevelopmental disorders. In this minireview, we focus on neuroinflammation that might be mediated by epigenetic dysregulation in microglia, and compare studies using mammals and zebrafish.

The effect of combined exposure of zinc and nickel on the development of zebrafish

Excessive accumulation of Zn²⁺ or Ni²⁺ can cause various problems to aquatic animals. In this study, the developmental toxicity induced by individual or combined exposure of Zn²⁺ and Ni²⁺ to zebrafish embryos and larvae were evaluated to better understand the interaction between Zn²⁺ and Ni²⁺ . Both of individual and combined exposure of Zn²⁺ and Ni²⁺ could cause obvious developmental toxicity, which mainly occurred after hatching, at a concentration-dependent manner. The calculated 168-h LC₅₀ were 2.79 mg/L for Zn²⁺ and 7.44 mg/L for Ni²⁺ . The interaction of Zn²⁺ and Ni²⁺ based on mortality was found to be an antagonism. Various malformations, including tail curving, spinal curvature, pericardial edema, and yolk sac edema, were observed with significant effects on body length and heartbeat rates after exposure of Zn²⁺ and Ni²⁺ . Meanwhile, some genes related to cardiovascular development and bone formation were mainly down-regulated by the individual and combined exposure of Zn²⁺ and Ni²⁺ . The individual exposure was more toxic than combined exposure because the interaction of Zn²⁺ and Ni²⁺ was determined to be an antagonism. The down-regulation of genes related to cardiovascular development and bone formation may contribute to the observed malformation and decreases of body length and heartbeat rates.

Glutathione Protects the Developing Heart from Defects and Global DNA Hypomethylation Induced by Prenatal Alcohol Exposure

BACKGROUND

Fetal alcohol spectrum disorder (FASD) is caused by prenatal alcohol exposure (PAE), the intake of ethanol (C₂ H₅ OH) during pregnancy. Features of FASD cover a range of structural and functional defects including congenital heart defects (CHDs). Folic acid and choline, contributors of methyl groups to one-carbon metabolism (OCM), prevent CHDs in humans. Using our avian model of FASD, we have previously reported that betaine, another methyl donor downstream of choline, prevents CHDs. The CHD preventions are substantial but incomplete. Ethanol causes oxidative stress as well as depleting methyl groups for OCM to support DNA methylation and other epigenetic alterations. To identify more compounds that can safely and effectively prevent CHDs and other effects of PAE, we tested glutathione (GSH), a compound that regulates OCM and is known as a "master antioxidant."

METHODS/RESULTS

Quail embryos injected with a single dose of ethanol at gastrulation exhibited congenital defects including CHDs similar to those identified in FASD individuals. GSH injected simultaneously with ethanol not only prevented CHDs, but also improved survival and prevented other PAE-induced defects. Assays of hearts at 8 days (HH stage 34) of quail development, when the heart normally has developed 4-chambers, showed that this single dose of PAE reduced global DNA methylation. GSH supplementation concurrent with PAE normalized global DNA methylation levels. The same assays performed on quail hearts at 3 days (HH stage 19-20) of development, showed no difference in global DNA methylation between controls, ethanol-treated, GSH alone, and GSH plus ethanol-treated cohorts.

CONCLUSIONS

GSH supplementation shows promise to inhibit effects of PAE by improving survival, reducing the incidence of morphological defects including CHDs, and preventing global hypomethylation of DNA in heart tissues.

Zebrafish Models of Craniofacial Malformations: Interactions of Environmental Factors

The zebrafish is an appealing model organism for investigating the genetic (G) and environmental (E) factors, as well as their interactions (GxE), which contribute to craniofacial malformations. Here, we review zebrafish studies on environmental factors involved in the etiology of craniofacial malformations in humans including maternal smoking, alcohol consumption, nutrition and drug use. As an example, we focus on the (cleft) palate, for which the zebrafish ethmoid plate is a good model. This review highlights the importance of investigating ExE interactions and discusses the variable effects of exposure to environmental factors on craniofacial development depending on dosage, exposure time and developmental stage. Zebrafish also promise to be a good tool to study novel craniofacial teratogens and toxin mixtures. Lastly, we discuss the handful of studies on gene–alcohol interactions using mutant sensitivity screens and reverse genetic techniques. We expect that studies addressing complex interactions (ExE and GxE) in craniofacial malformations will increase in the coming years. These are likely to uncover currently unknown mechanisms with implications for the prevention of craniofacial malformations. The zebrafish appears to be an excellent complementary model with high translational value to study these complex interactions.

Cellular and molecular mechanisms in the development of a cleft lip and/or cleft palate; insights from zebrafish (Danio rerio)

Human cleft lip and/or palate (CLP) are immediately recognizable congenital abnormalities of the face. Lip and palate develop from facial primordia through the coordinated activities of ectodermal epithelium and neural crest cells (NCCs) derived from ectomesenchyme tissue. Subtle changes in the regulatory mechanisms of NCC or ectodermal epithelial cells can result in CLP. Genetic and environmental contributions or a combination of both play a significant role in the progression of CLP. Model organisms provide us with a wealth of information in understanding the pathophysiology and genetic etiology of this complex disease. Small teleost, zebrafish (Danio rerio) is one of the popular model in craniofacial developmental biology. The short generation time and large number of optically transparent, easily manipulated embryos increase the value of zebrafish to identify novel candidate genes and gene regulatory networks underlying craniofacial development. In addition, it is widely used to identify the mechanisms of environmental teratogens and in therapeutic drug screening. Here, we discuss the value of zebrafish as a model to understand epithelial and NCC induced ectomesenchymal cell activities during early palate morphogenesis and robustness of the zebrafish in modern research on identifying the genetic and environmental etiological factors of CLP.

[Effect of dhfr gene overexpression on ethanol-induced abnormal cardiovascular development in zebrafish embryos]

OBJECTIVE

To study the effect of dhfr gene overexpression on ethanol-induced abnormal cardiac and vascular development in zebrafish embryos and underlying mechanisms.

METHODS

dhfr mRNA was transcribed in vitro and microinjected into zebrafish fertilized eggs to induce the overexpression of dhfr gene, and the efficiency of overexpression was verified. Wild-type zebrafish were divided into a control group, an ethanol group, and an ethanol+dhfr overexpression group (microinjection of 6 nL dhfr mRNA). The embryonic development was observed for each group. The transgenic zebrafish Tg (cmlc2:mcherry) with heart-specific red fluorescence was used to observe atrial and ventricular development. Fluorescence microscopy was performed to observe the development of cardiac outflow tract and blood vessels. Heart rate and ventricular shortening fraction were used to assess cardiac function. Gene probes were constructed, and embryo in situ hybridization and real-time PCR were used to measure the expression of nkx2.5, tbx1, and flk-1 in the embryo.

RESULTS

Compared with the ethanol group, the ethanol+dhfr overexpression group had a significant reduction in the percentage of abnormal embryonic development and a significant increase in the percentage of embryonic survival (P<0.05), with significant improvements in the abnormalities of the atrium, ventricle, outflow tract, and blood vessels and cardiac function. Compared with the control group, the ethanol group had significant reductions in the expression of nkx2.5, tbx1, and flk-1 (P<0.05), and compared with the ethanol group, the ethanol+dhfr overexpression group had significant increases in the expression of nkx2.5, tbx1, and flk-1 (P<0.05), which were still lower than their expression in the control group.

CONCLUSIONS

The overexpression of the dhfr gene can partially improve the abnormal development of embryonic heart and blood vessels induced by ethanol, possibly by upregulating the decreased expression of nkx2.5, tbx1, and flk-1 caused by ethanol.