Excessive nitrite affects zebrafish valvulogenesis through yielding too much NO signaling

Exposure to nitrate and nitrite disrupts cardiovascular development through estrogen receptor in zebrafish embryos and larvae

Increasing nitrate concentration on surface and groundwater due to anthropogenic activities is an environmental concern. In this study, Tg(fli1: EGFP) zebrafish embryos were exposed to nitrate (NO3-) and nitrite (NO2-), and their cardiovascular development were investigated. Exposure to 10 mg/L NO3-N and 1 and 10 mg/L NO2-N decreased heart rate at 48-96-h post-fertilization (hpf), ventricular volume, and red blood cell flow rate at 96 hpf. Similar concentrations increased the number of embryos and larvae with pericardial edema and missing intersegmental and parachordal vessels in the caudal region at 48-96 hpf. Addition of ICI 182,720 (ICI) reversed the effects of nitrate and nitrite, suggesting estrogen receptors (ER) are involved. 10 mg/L NO3-N and 1 mg/L NO2-N decreased cardiovascular-related genes, gata4,5,6, hand2, nkx2.5, nkx2.7, tbx2a, tbx2b, and fgf1a. Gene expressions of ovarian aromatase and brain aromatase (cyp19a1a and cyp19a1b, respectively) decreased in the exposed groups, whereas ERs (esr1, esr2a, and esr2b) and nitric oxide synthase 2a (nos2a) increased. The effects on gene expression were also reversed by addition of ICI. Taken together, nitrate and nitrite disrupt cardiovascular system through ER in developing zebrafish, implying that environmental nitrate and nitrite contamination may be harmful to aquatic organisms.

Zebrafish as model organisms for toxicological evaluations in the field of food science

Food safety has long been an area of concern. The selection of stable and efficient model organisms is particularly important for food toxicology studies. Zebrafish (Danio rerio) are small model vertebrates, and 70% of human genes have at least one zebrafish ortholog. Zebrafish have advantages as model organisms due to their short life cycle, strong reproductive ability, easy rearing, and low cost. Zebrafish embryos have the advantage of being sensitive to the breeding environment and thus have been used as biosensors. Zebrafish and their embryos have been widely used for food toxicology assessments. This review provides a systematic and comprehensive summary of food toxicology studies using zebrafish as model organisms. First, we briefly introduce the multidimensional mechanisms and structure-activity relationship studies of food toxicological assessment. Second, we categorize these studies according to eight types of hazards in foods, including mycotoxins, pesticides, antibiotics, heavy metals, endocrine disruptors, food additives, nanoparticles, and other food-related ingredients. Finally, we list the applications of zebrafish in food toxicology studies in line with future research prospects, aiming to provide a valuable reference for researchers in the field of food science.

Partnered Excited-State Intermolecular Proton Transfer Fluorescence (P-ESIPT) Signaling for Nitrate Sensing and High-Resolution Cell-Imaging

Nitrite (NO₂⁻) is a common pollutant and is widely present in the environment and in human bodies. The development of a rapid and accurate method for NO₂⁻ detection is always a very important task. Herein, we synthesized a partnered excited-state intermolecular proton transfer (ESIPT) fluorophore using the “multi-component one pot” method, and used this as a probe (ESIPT-F) for sensing NO₂⁻. ESIPT-F exhibited bimodal emission in different solvents because of the solvent-mediated ESIPT reaction. The addition of NO₂⁻ caused an obvious change in colors and tautomeric fluorescence due to the graft of NO₂⁻ into the ESIPT-F molecules. From this basis, highly sensitive and selective analysis of NO₂⁻ was developed using tautomeric emission signaling, achieving sensitive detection of NO₂⁻ in the concentration range of 0~45 mM with a detection limit of 12.5 nM. More importantly, ESIPT-F showed the ability to anchor proteins and resulted in a recognition-driven “on-off” ESIPT process, enabling it to become a powerful tool for fluorescence imaging of proteins or protein-based subcellular organelles. MTT experimental results revealed that ESIPT-F is low cytotoxic and has good membrane permeability to cells. Thus, ESIPT-F was further employed to image the tunneling nanotube in vitro HEC-1A cells, displaying high-resolution performance.

Association of maternal dietary habits and ADIPOQ gene polymorphisms with the risk of congenital heart defects in offspring: a hospital-based case-control study

OBJECTIVES

To estimate the association of maternal ADIPOQ gene, dietary habits in early pregnancy, and their interactions with the risk of congenital heart defects (CHDs) in offspring.

METHODS

A case-control study of 464 mothers of CHDs children and 504 mothers of healthy children was included. Maternal dietary habits and genetic polymorphisms of ADIPOQ were the main exposure of interest. Their independent effects and interactions in the development of CHDs were analyzed in our study.

RESULTS

The excessive consumption of pickled vegetables (aOR = 1.58, 95%CI: 1.17-2.12), smoked foods (aOR = 1.84, 95%CI:1.34-2.52), barbecued foods (aOR = 1.62, 95%CI: 1.09-2.39), fish and shrimp (aOR = 0.37, 95%CI: 0.27-50), and milk products (aOR = 0.64, 95%CI: 0.51-80) had a significant association with total CHDs risk. The polymorphisms of ADIPOQ gene at rs1501299 (T/T vs G/G: aOR = 0.27, 95%CI: 0.14-50; G/T vs G/G: aOR = 0.67, 95%CI: 0.46-98) and rs2241766 (G/G vs T/T: aOR = 4.35, 95%CI: 2.23-8.51; T/G vs T/T: aOR = 2.23, 95%CI: 1.51-3.28) showed a significant association with total CHDs risk. Likewise, our results found that maternal dietary habits and ADIPOQ genetic variants also were significantly related to the risk of specific CHDs phenotypes. In addition, gene-diet interaction revealed significant associations between the ADIPOQ gene and maternal dietary habits with total CHDs.

CONCLUSIONS

Maternal dietary habits, ADIPOQ gene, and their interactions show a significant association with the risk of CHDs. However, our study has some limitations, thus our findings need to be taken with caution, which highlights that more studies are required to further corroborate our findings.

Cell-Penetrating Delivery of Nitric Oxide by Biocompatible Dinitrosyl Iron Complex and Its Dermato-Physiological Implications

After the discovery of endogenous dinitrosyl iron complexes (DNICs) as a potential biological equivalent of nitric oxide (NO), bioinorganic engineering of [Fe(NO)₂] unit has emerged to develop biomimetic DNICs [(NO)₂Fe(L)₂] as a chemical biology tool for controlled delivery of NO. For example, water-soluble DNIC [Fe₂(μ-SCH₂CH₂OH)₂(NO)₄] (DNIC-1) was explored for oral delivery of NO to the brain and for the activation of hippocampal neurogenesis. However, the kinetics and mechanism for cellular uptake and intracellular release of NO, as well as the biocompatibility of synthetic DNICs, remain elusive. Prompted by the potential application of NO to dermato-physiological regulations, in this study, cellular uptake and intracellular delivery of DNIC [Fe₂(μ-SCH₂CH₂COOH)₂(NO)₄] (DNIC-2) and its regulatory effect/biocompatibility toward epidermal cells were investigated. Upon the treatment of DNIC-2 to human fibroblast cells, cellular uptake of DNIC-2 followed by transformation into protein-bound DNICs occur to trigger the intracellular release of NO with a half-life of 1.8 ± 0.2 h. As opposed to the burst release of extracellular NO from diethylamine NONOate (DEANO), the cell-penetrating nature of DNIC-2 rationalizes its overwhelming efficacy for intracellular delivery of NO. Moreover, NO-delivery DNIC-2 can regulate cell proliferation, accelerate wound healing, and enhance the deposition of collagen in human fibroblast cells. Based on the in vitro and in vivo biocompatibility evaluation, biocompatible DNIC-2 holds the potential to be a novel active ingredient for skincare products.

Association and interaction effect of UCP2 gene polymorphisms and dietary factors with congenital heart diseases in Chinese Han population

Congenital heart diseases (CHDs) are the most common birth defects and the leading cause of non-infectious deaths in infants, with an unknown etiology. We aimed to assess the association of genetic variations in UCP2 gene, dietary factors, and their interactions with the risk of CHDs in offspring. The hospital-based case–control study included 464 mothers of children with CHDs and 504 mothers of healthy children. The exposures of interest were maternal dietary factors in early pregnancy and UCP2 genetic variants. Logistic regression analyses were used to assess the association and interaction of UCP2 gene and dietary factors with CHDs. Our results found that the polymorphisms of UCP2 gene at rs659366 and rs660339, together with maternal dietary factors including excessive intake of pickled vegetables and smoked foods were associated with increased risks of CHDs in offspring. Regular intake of fresh meat, fish and shrimp, and milk products were associated with lower risks of CHDs in offspring. Besides, positive interaction between the dominant model of rs659366 and excessive intake of pickled vegetables was found in the additive interaction model (RERI = 1.19, P = 0.044). These findings provide the theoretical basis for gene screening and a new clue for the prevention of CHDs in offspring.

Axenfeld-Rieger syndrome-associated mutants of the transcription factor FOXC1 abnormally regulate NKX2-5 in model zebrafish embryos

FOXC1 is a member of the forkhead family of transcription factors, and whose function is poorly understood. A variety of FOXC1 mutants have been identified in patients diagnosed with the autosomal dominant disease Axenfeld-Rieger syndrome, which is mainly characterized by abnormal development of the eyes, particularly those who also have accompanying congenital heart defects (CHD). However, the role of FOXC1 in CHD, and how these mutations might impact FOXC1 function, remains elusive. Our previous work provided one clue to possible function, demonstrating that zebrafish foxc1a, an orthologue of human FOXC1 essential for heart development, directly regulates the expression of nkx2.5, encoding a transcriptional regulator of cardiac progenitor cells. Abnormal expression of Nkx2-5 leads to CHD in mice and is also associated with CHD patients. Whether this link extends to the human system, however, requires investigation. In this study, we demonstrate that FOXC1 does regulate human NKX2-5 expression in a dose-dependent manner via direct binding to its proximal promoter. A comparison of FOXC1 mutant function in the rat cardiac cell line H9c2 and zebrafish embryos suggested that the zebrafish embryos might serve as a more representative model system than the H9c2 cells. Finally, we noted that three of the Axenfeld-Rieger syndrome FOXC1 mutations tested increased, whereas a fourth repressed the expression of NKX2-5 These results imply that mutant FOXC1s might play etiological roles in CHD by abnormally regulating NKX2-5 in the patients. And zebrafish embryos can serve as a useful in vivo platform for rapidly evaluating disease-causing roles of mutated genes.

The transcription factor Foxc1a in zebrafish directly regulates expression of nkx2.5, encoding a transcriptional regulator of cardiac progenitor cells

Cardiogenesis is a tightly controlled biological process required for formation of a functional heart. The transcription factor Foxc1 not only plays a crucial role in outflow tract development in mice, but is also involved in cardiac structure formation and normal function in humans. However, the molecular mechanisms by which Foxc1 controls cardiac development remain poorly understood. Previously, we reported that zebrafish embryos deficient in foxc1a, an ortholog of mammalian Foxc1, display pericardial edemas and die 9-10 days postfertilization. To further investigate Foxc1a's role in zebrafish cardiogenesis and identify its downstream target genes during early heart development, we comprehensively analyzed the cardiovascular phenotype of foxc1a-null zebrafish embryos. Our results confirmed that foxc1a-null mutants exhibit disrupted cardiac morphology, structure, and function. Performing transcriptome analysis on the foxc1a mutants, we found that the expression of the cardiac progenitor marker gene nkx2.5 was significantly decreased, but the expression of germ layer-patterning genes was unaffected. Dual-fluorescence in situ hybridization assays revealed that foxc1a and nkx2.5 are co-expressed in the anterior lateral plate mesoderm at the somite stage. Chromatin immunoprecipitation and promoter truncation assays disclosed that Foxc1a regulates nkx2.5 expression via direct binding to two noncanonical binding sites in the proximal nkx2.5 promoter. Moreover, functional rescue experiments revealed that developmental stage-specific nkx2.5 overexpression partially rescues the cardiac defects of the foxc1a-null embryos. Taken together, our results indicate that during zebrafish cardiogenesis, Foxc1a is active directly upstream of nkx2.5.

Developmental toxicity of 2,4-dichlorophenoxyacetic acid in zebrafish embryos

2,4-Dichlorophenoxyacetic acid (2,4-D) is widely used in agriculture as herbicide/pesticide, plant growth regulator and fruit preservative agent. It progressively accumulates in the environment including surface water, air and soil. It could be detected in human food and urine, which poses great risk to the living organisms. In the present study, we investigated the developmental toxicity of 2,4-D on zebrafish (Danio rerio) embryo. 2,4-D exposure significantly decreased both the survival rate (LC₅₀ = 46.71 mg/L) and hatching rate (IC₅₀ = 46.26 mg/L) of zebrafish embryos. The most common developmental defect in 2,4-D treated embryos was pericardial edema. 2,4-D (25 mg/L) upregulated marker genes of cardiac development (vmhc, amhc, hand2, vegf, and gata1) and downregulated marker genes of oxidative stress (cat and gpx1a). Whole mount in situ hybridization confirmed the vmhc and amhc upregulation by 2,4-D treatment. LC/MS/MS showed that the bioaccumulation of 2,4-D in zebrafish embryos were increased in a time-dependent manner after 25 mg/L of 2,4-D treatment. Taken together, our study investigated the toxic effects of 2,4-D on zebrafish embryonic development and its potential molecular mechanisms, gave evidence for the full understanding of 2,4-D toxicity on living organisms and shed light on its environmental impact.

Interplay between cardiac function and heart development

Mechanotransduction refers to the conversion of mechanical forces into biochemical or electrical signals that initiate structural and functional remodeling in cells and tissues. The heart is a kinetic organ whose form changes considerably during development and disease. This requires cardiomyocytes to be mechanically durable and able to mount coordinated responses to a variety of environmental signals on different time scales, including cardiac pressure loading and electrical and hemodynamic forces. During physiological growth, myocytes, endocardial and epicardial cells have to adaptively remodel to these mechanical forces. Here we review some of the recent advances in the understanding of how mechanical forces influence cardiac development, with a focus on fluid flow forces. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Zebrafish as a Model to Assess the Teratogenic Potential of Nitrite

High nitrate levels in the environment may result in congenital defects or miscarriages in humans. Presumably, this is due to the conversion of nitrate to nitrite by gut and salivary bacteria. However, in other mammalian studies, high nitrite levels do not cause birth defects, although they can lead to poor reproductive outcomes. Thus, the teratogenic potential of nitrite is not clear. It would be useful to have a vertebrate model system to easily assess teratogenic effects of nitrite or any other chemical of interest. Here, we demonstrate the utility of zebrafish (Danio rerio) to screen compounds for toxicity and embryonic defects. Zebrafish embryos are fertilized externally and have rapid development, making them a good model for teratogenic studies. We show that increasing the time of exposure to nitrite negatively affects survival. Increasing the concentration of nitrite also adversely affects survival, whereas nitrate does not. For embryos that survive nitrite exposure, various defects can occur, including pericardial and yolk sac edema, swim bladder noninflation, and craniofacial malformation. Our results indicate that the zebrafish is a convenient system for studying the teratogenic potential of nitrite. This approach can easily be adapted to test other chemicals for their effects on early vertebrate development.

Retinoic Acid Signaling Is Essential for Valvulogenesis by Affecting Endocardial Cushions Formation in Zebrafish Embryos

Retinoic acid (RA) plays important roles in many stages of heart morphogenesis. Zebrafish embryos treated with exogenous RA display defective atrio-ventricular canal (AVC) specification. However, whether endogenous RA signaling takes part in cardiac valve formation remains unknown. Herein, we investigated the role of RA signaling in cardiac valve development by knocking down aldh1a2, the gene encoding an enzyme that is mainly responsible for RA synthesis during early development, in zebrafish embryos. The results showed that partially knocking down aldh1a2 caused defective formation of primitive cardiac valve leaflets at 108 hpf (hour post-fertilization). Inhibiting endogenous RA signaling by 4-diethylaminobenzal-dehyde revealed that 16-26 hpf was a key time window when RA signaling affects the valvulogenesis. The aldh1a2 morphants had defective formation of endocardial cushion (EC) at 76 hpf though they had almost normal hemodynamics and cardiac chamber specification at early development. Examining the expression patterns of AVC marker genes including bmp4, bmp2b, nppa, notch1b, and has2, we found the morphants displayed abnormal development of endocardial AVC but almost normal development of myocardial AVC at 50 hpf. Being consistent with the reduced expression of notch1b in endocardial AVC, the VE-cadherin gene cdh5, the downstream gene of Notch signaling, was ectopically expressed in AVC of aldh1a2 morphants at 50 hpf, and overexpression of cdh5 greatly affected the formation of EC in the embryos at 76 hpf. Taken together, our results suggest that RA signaling plays essential roles in zebrafish cardiac valvulogenesis.

Valvular and Mural Endocardiosis in Aging Zebrafish (Danio rerio)

Endocardiosis or myxomatous degeneration of the cardiac valves is a well-described age-related change in humans and dogs. Lesions consist of polypoid nodular proliferations of loose extracellular matrix and valvular interstitial cells, most commonly affecting the mitral valve. This entity has not been previously described in fish. Herein we report the appearance, location, and occurrence of valvular and mural endocardiosis in a retrospective survey of aging laboratory zebrafish. Endocardiosis was present in 59 of 777 fish (7.59%), most commonly affecting the sinoatrial (34 fish; 57.6%) and atrioventricular (33 fish; 55.9%) valves. Lesions were more common in fish raised in recirculating water systems and fed commercial diets (52/230 fish; 22.6%) versus flow-through systems with fish fed semi-purified diets (4/234; 1.71%). Lesions were overrepresented in fish heterozygous for a mutant smoothened allele (34/61 fish, 55.7% vs 17/168, 10.1% wild type). There was no association between endocardiosis and intestinal carcinoids. Valvular endocardiosis is a significant age- and husbandry-related background finding in zebrafish and should be considered in the design and interpretation of research studies.