Transcriptomic Analysis of Thalidomide Challenged Chick Embryo Suggests Possible Link between Impaired Vasculogenesis and Defective Organogenesis

System-wide health risk prediction for 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene(MBP), a major active metabolite of environmental pollutant and food contaminant - Bisphenol A

Human exposure to plastic contaminated foods and environmental micro/nano plastic derived chemicals necessitates system-wide health risk assessment. Hence, current study intend to explore the mode of action (MoA) based adverse outcome pathways of 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), the major active metabolite of bisphenol A (BPA). The computational study employed broad range of target prediction, systems biology tools and molecular docking protocols. Further, validation of MBP targets was done using protein-ligand fluorescence quenching assay, endothelial cell culture and chicken embryo vascular angiogenesis models. Interestingly, the current results illustrate that various physiological signaling pathways (MAPK and VEGF related angiogenesis signaling) and disease progression pathways (hypertension, cancer and endocrine disorders) were enriched as potential targets of MBP. Further, docking studies highlights the possible binding mechanism of MBP with important targets including endothelial nitric oxide synthase (eNOS) and serum albumin (BSA). In addition, the validation studies on MBP-BSA interaction (fluorescence quenching), eNOS derived nitric oxide (NOx) generation in endothelial cells and chicken embryo angiogenesis support the system-wide impacts of MBP with highlights on cardiovascular pathogenesis. Thus, the current observation provides novel insights into the system wide impacts of MBP for the futuristic health risk assessment of plastic derived chemicals.

Al2O3 nanoparticles trigger the embryonic hepatotoxic response and potentiate TNF-α-induced apoptosis-modulatory effect of p38 MAPK and JNK inhibitors

Recent evidences illustrated that the release of aluminum oxide nanoparticles (Al₂O₃-NPs) into the biosphere may pose risk to the environment and cause adverse effects on living organisms including humans. The current study assessed the hepatotoxic effects of Al₂O₃-NPs on developing chicken embryo and cell culture models. Results demonstrated that Al₂O₃-NPs exposure causes histological abnormalities and increased the level of tissue damage markers (ALP, AST, and ALT) in the embryonic liver. Furthermore, increased oxidative stress (TBARS) and impaired function of antioxidant enzymes (SOD, CAT, and GPx) were also observed. Moreover, it adversely affects red blood cells (RBC) morphology, liver metabolism, and stress response gene expression (HO-1 and NQO-1). Dose-dependent ROS generation and cytotoxic response in addition to potentiating effect on tumor necrosis factor alpha (TNF-α)-induced apoptosis (caspase-3 activity) were also observed. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK) pathways modulates Al₂O₃-NPs-induced apoptosis in HepG2 cells. Novel mechanisms behind embryonic hepatotoxicity, cytotoxic potentiating effects, and possible prevention strategies have been explored.

Neuronal and cardiac toxicity of pharmacological compounds identified through transcriptomic analysis of human pluripotent stem cell-derived embryoid bodies

Concurrent with the '3R' principle, the embryonic stem cell test (EST) using mouse embryonic stem cells, developed in 2000, remains the solely accepted in vitro method for embryotoxicity testing. However, the scope and implementation of EST for embryotoxicity screening, compliant with regulatory requirements, are limited. This is due to its technical complexity, long testing period, labor-intensive methodology, and limited endpoint data, leading to misclassification of embryotoxic potential. In this study, we used human induced pluripotent stem cell (hiPSC)-derived embryoid bodies (EB) as an in vitro model to investigate the embryotoxic effects of a carefully selected set of pharmacological compounds. Morphology, viability, and differentiation potential were investigated after exposing EBs to folic acid, all-trans-retinoic acid, dexamethasone, and valproic acid for 15 days. The results showed that the compounds differentially repressed cell growth, compromised morphology, and triggered apoptosis in the EBs. Further, transcriptomics was employed to compare subtle temporal changes between treated and untreated cultures. Gene ontology and pathway analysis revealed that dysregulation of a large number of genes strongly correlated with impaired neuroectoderm and cardiac mesoderm formation. This aberrant gene expression pattern was associated with several disorders of the brain like mental retardation, multiple sclerosis, stroke and of the heart like dilated cardiomyopathy, ventricular tachycardia, and ventricular arrhythmia. Lastly, these in vitro findings were validated using in ovo chick embryo model. Taken together, pharmacological compound or drug-induced defective EB development from hiPSCs could potentially be used as a suitable in vitro platform for embryotoxicity screening.

Ectopic release of nitric oxide modulates the onset of cardiac development in avian model

Heart development is one of the earliest developmental events, and its pumping action is directly linked to the intensity of development of other organs. Heart contractions mediate the circulation of the nutrients and signalling molecules to the focal points of developing embryos. In the present study, we used in vivo, ex vivo, in vitro, and in silico methods for chick embryo model to characterize and identify molecular targets under the influence of ectopic nitric oxide in reference to cardiogenesis. Spermine NONOate (SpNO) treatment of 10 μM increased the percentage of chick embryos having beating heart at 40th h of incubation by 2.2-fold (p < 0.001). In an ex vivo chick embryo culture, SpNO increased the percentage of embryos having beats by 1.56-fold (p < 0.05) compared with control after 2 h of treatment. Total body weight of SpNO-treated chick embryos at the Hamburger and Hamilton (HH) stage 29 was increased by 1.22-fold (p < 0.005). Cardiac field potential (FP) recordings of chick embryo at HH29 showed 2.5-fold (p < 0.001) increased in the amplitude, 3.2-fold (p < 0.001) increased in frequency of SpNO-treated embryos over that of the control group, whereas FP duration was unaffected. In cultured cardiac progenitors cells (CPCs), SpNO treatment decreased apoptosis and cell death by twofold (p < 0.001) and 1.7-fold (p < 0.001), respectively. Transcriptome analysis of chick embryonic heart isolated from HH15 stage pre-treated with SpNO at HH8 stage showed upregulation of genes involved in heart morphogenesis, heart contraction, cardiac cell development, calcium signalling, structure, and development whereas downregulated genes were enriched under the terms extracellular matrix, wnt pathway, and BMP pathway. The key upstream molecules predicted to be activated were p38 MAPK, MEF2C, TBX5, and GATA4 while KDM5α, DNMT3A, and HNF1α were predicted to be inhibited. This study suggests that the ectopic nitric oxide modulates the onset of cardiac development.

Recent advances in the molecular mechanism of thalidomide teratogenicity

Thalidomide was first marketed in 1957 but soon withdrawn because of its notorious teratogenicity. Studies on the mechanism of action of thalidomide revealed the pleiotropic properties of this class of drugs, including their anti-inflammatory, antiangiogenic and immunomodulatory activities. Based on their notable activities, thalidomide and its analogues, lenalidomide and pomalidomide, have been repurposed to treat erythema nodosum leprosum, multiple myeloma and other haematological malignancies. Thalidomide analogues were recently found to hijack CRL4^CRBN ubiquitin ligase to target a number of cellular proteins for ubiquitination and proteasomal degradation. Thalidomide-mediated degradation of SALL4 and p63, transcription factors essential for embryonic development, very likely plays a critical role in thalidomide embryopathy. In this review, we provide a brief retrospective summary of thalidomide-induced teratogenesis, the mechanism of thalidomide activity, and the latest advances in the molecular mechanism of thalidomide-induced birth malformations.

Thalidomide leads to mandible hypoplasia through inhibiting angiogenesis and secondary hemorrhage in the fetal craniofacial region in rabbits

The effect of thalidomide on mandibular development is unclear. In this study, thalidomide was delivered to pregnant rabbits from the 8th to 14th day of gestation. Then, embryos were harvested for examination on the 16th day (GD16), 20th day (GD20) and 24th day (GD24) of gestation. The results showed obvious hemorrhage and hematoma on one side of the craniofacial region in 50 % of the thalidomide-treated embryos and obvious hemorrhage and hematoma on both sides of the craniofacial region in 50 % of the thalidomide-treated embryos at GD16. Histological examination showed soft tissues and mandible defects on the affected side of the maxillofacial region. The expression of Vegf-α, Ki67 and Sox9 on the affected side was significantly down-regulated in comparison to their expression on the unaffected side at GD20. There was also an obvious defect in the affected mandible, and the density of the skull and mandible was decreased compared to the unaffected side or the control group at GD24. These findings demonstrated that thalidomide may lead to hemorrhage and hematoma in the craniofacial region by inhibiting angiogenesis, resulting in the abnormal development of cranial neural crest cells that are involved in the normal development of the mandible in rabbits.

A proof of concept study demonstrating that environmental levels of carbamazepine impair early stages of chick embryonic development

Carbamazepine (CBZ) is an anticonvulsant drug used for epilepsy and other disorders. Prescription of CBZ during pregnancy increases the risk for congenital malformations. CBZ is ubiquitous in effluents and persistent during wastewater treatment. Thus, it is re-introduced into agricultural ecosystems upon irrigation with reclaimed wastewater. People consuming produce irrigated with reclaimed wastewater were found to be exposed to CBZ. However, environmental concentrations of CBZ (μgL^-1) are magnitudes lower than its therapeutic levels (μgml^-1), raising the question of whether and how environmental levels of CBZ affect embryonic development. The chick embryo is a powerful and highly sensitive amniotic model system that enables to assess environmental contaminants in the living organism. Since the chick embryonic development is highly similar to mammalians, yet, it develops in an egg, toxic effects can be directly analyzed in a well-controlled system without maternal influences. This research utilized the chick embryo to test whether CBZ is embryo-toxic by using morphological, cellular, molecular and imaging strategies. Three key embryonic stages were monitored: after blastulation (st.1HH), gastrulation/neurulation (st.8HH) and organogenesis (st.15HH). Here we demonstrate that environmental relevant concentrations of CBZ impair morphogenesis in a dose- and stage- dependent manner. Effects on gastrulation, neural tube closure, differentiation and proliferation were exhibited in early stages by exposing embryos to CBZ dose as low as 0.1μgL^-1. Quantification of developmental progression revealed a significant difference in the total score obtained by CBZ-treated embryos compared to controls (up to 5-fold difference, p<0.05). Yet, defects were unnoticed as embryos passed gastrulation/neurulation. This study provides the first evidence for teratogenic effect of environmental-relevant concentrations of CBZ in amniotic embryos that impair early but not late stages of development. These findings call for in-depth risk analysis to ensure that the environmental presence of CBZ and other drugs is not causing irreversible ecological and public-health damages.

Thalidomide and Its Analogs Differentially Target Fibroblast Growth Factor Receptors: Thalidomide Suppresses FGFR Gene Expression while Pomalidomide Dampens FGFR2 Activity

Thalidomide is an infamous teratogen and it is continuously being explored for its anticancer properties. Fibroblast growth factor receptors (FGFRs) are implicated in embryo development and cancer pathophysiology. With striking similarities observed between FGFR implicated conditions and thalidomide embryopathy, we hypothesized thalidomide targets FGFRs. We utilized three different cell lines and chicken embryo model to investigate the effects of thalidomide and analogs on FGFR expression. We performed molecular docking, KINOMEscan analysis, and kinase activity assays to study the drug-protein interactions. The expression of FGFR1 and FGFR2 was differentially regulated by all the three drugs in cells as well as in developing organs. Transcriptome analysis of thalidomide-treated chick embryo strongly suggests the modulation of FGFR signaling and key transcription factors. Corroboration with previous studies suggests that thalidomide might affect FGFR expression through the transcription factor, E2F1. At the protein level, molecular docking predicted all three analogs to interact with lysine residue at 517th and 508th positions of FGFR2 and FGFR3, respectively. This lysine coordinates the ATP binding site of FGFR, thus hinting at the possible perturbation of FGFR activity by thalidomide. Kinome analysis revealed that kinase activities of FGFR2 and FGFR3 (G697C) reduced by 31% and 65%, respectively, in the presence of 10 μM thalidomide. Further, we checked and confirmed that the analogs inhibited the FGFR2 kinase activity in a dose-dependent manner. This study suggests that FGFRs could be potential targets of thalidomide and the two analogs, and also endorses the link between the teratogenicity and antitumor activities of the drugs.

Thalidomide remodels developing heart in chick embryo: discovery of a thalidomide mediated hematoma in heart muscle

Despite of medical disaster caused by thalidomide in 1960s, the drug came to clinical use again for the treatment of erythema nodosum leprosum (ENL) and multiple myeloma. Recently, a new generation of children affected by thalidomide intake by their mothers during pregnancy has been identified in Brazil. In the past few years, there is the great enhancement in our understanding of the molecular mechanisms and targets of thalidomide with the help of modern OMICS technologies. However, understanding of cardiac-specific anomalies in fetus due to thalidomide intake by the respective mother has not been explored fully. At organ level, thalidomide causes congenital heart diseases, limb deformities in addition to ocular, and neural and ear abnormalities. The period of morning sickness and cardiogenesis is synchronized in pregnant women. Therefore, thalidomide intake during the first trimester could affect cardiogenesis severely. Thalidomide intake in pregnant women either causes miscarriage or heart abnormalities such as patent ductus arteriosus, ventricular septal defect (VSD), atrial septal defect (ASD), and pulmonary stenosis in survivors. In the present study, we identified a novel morphological defect (lump) in the heart of thalidomide-treated chick embryos. We characterized the lump at morphological, histo-pathological, oxidative stress, electro-physiological, and gene expression level. To our knowledge, here, we report the very first electrophysiological characterization of embryonic heart affected by thalidomide treatment.