Misexpression of BRE gene in the developing chick neural tube affects neurulation and somitogenesis

Effect of aripiprazole on neural tube development in early chick embryos

INTRODUCTION

Aripiprazole (ARI) is a recently developed antipsychotic medication that belongs to the second generation of antipsychotics. The literature has contradictory information regarding ARI, which has been classified as pregnant use category C by the FDA.

METHODS

125 pathogen-free fertilized eggs were incubated for 28 h and divided into five groups of 25 eggs each (including the control group), and 18 eggs with intact integrity were selected from each group. After the experimental groups were divided, ARI was administered subblastodermally with a Hamilton micro-injector at 4 different doses (1 mg/kg, 5 mg/kg, 10 mg/kg, 20 mg/kg). At the 48th hour of incubation, all eggs were hatched and embryos were removed from the embryonic membranes. And then morphologic (position of the neural tube (open or closed), crown-rump length, number of somites, embryological development status), histopathologic (apoptosis (caspase 3), cell proliferation (PCNA), in situ recognition of DNA breaks (tunnel)), genetic (BRE gene expression) analyzes were performed.

RESULTS

According to the results of the morphological analysis, when the frequency of neural tube patency was evaluated among the experimental groups, a statistically significant difference was determined between the control group and all groups (p < 0.001). In addition, the mean crown-rump length and somite number of the embryos decreased in a dose-dependent manner compared to the control group. It was determined that mRNA levels of the BRE gene decreased in embryos exposed to ARI compared to the control group (p < 0.001).

CONCLUSION

Morphologically, histopathologically, and genetically, aripiprazole exposure delayed neurogenesis and development in early chick embryos. These findings suggest its use in pregnant women may be teratogenic. We note that these results are preliminary for pregnant women, but they should be expanded and studied with additional and other samples.

Effect of post-gastrulation exposure to acrylamide on chick embryonic development

The critical developmental stages of the embryo are strongly influenced by the dietary composition of the mother. Acrylamide is a food contaminant that can form in carbohydrate-rich foods that are heat-treated. The aim of this study was to investigate the toxicity of a relatively low dose of acrylamide on the development of the neural tube in the early stage chick embryos. Specific pathogen-free fertilized eggs (n = 100) were treated with acrylamide (0.1, 0.5, 2.5, 12.5 mg/kg) between 28-30th hours of incubation and dissected at 48th hours. In addition to morphological and histopathological examinations, proliferating cell nuclear antigen (PCNA) and caspase 3 were analyzed immunohistochemically. The brain and reproductive expression gene (BRE) was analyzed by RT-PCR. Acrylamide exposure had a negative effect on neural tube status even at a very low dose (0.1 mg/kg) (p < 0.05). Doses of 0.5 mg/kg and above caused a delay in neural tube development (p < 0.05). Crown-rump length and somite count decreased dose-dependently, while this decrease was not significant in the very low dose group (p > 0.05), which was most pronounced at doses of 2.5 and 12.5 mg/kg (p < 0.001). Acrylamide exposure dose-dependently decreased PCNA and increased caspase 3, with this change being significant at doses of 0.5 mg/kg and above (p < 0.001). BRE was downregulated at all acrylamide exposures except in the very low dose group (0.1 mg/kg). In conclusion, we find that acrylamide exposure (at 0.5 mg/kg and above) in post-gastrulation delays neural tube closure in chicken embryos by suppressing proliferation and apoptosis induction and downregulating BRE gene expression.

Mycotoxin Fumonisin B1 Interferes Sphingolipid Metabolisms and Neural Tube Closure during Early Embryogenesis in Brown Tsaiya Ducks

Fumonisin B₁ (FB₁) is among the most common contaminants produced by Fusarium spp. fungus from corns and animal feeds. Although FB₁ has been known to cause physical or functional defects of embryos in humans and several animal species such as Syrian hamsters, rabbits, and rodents, little is known about the precise toxicity to the embryos and the underlying mechanisms have not been fully addressed. The present study aimed to investigate its developmental toxicity and potential mechanisms of action on sphingolipid metabolism in Brown Tsaiya Ducks (BTDs) embryos. We examined the effect of various FB₁ dosages (0, 10, 20 and 40 µg/embryo) on BTD embryogenesis 72 h post-incubation. The sphingomyelin content of duck embryos decreased (p < 0.05) in the highest FB₁-treated group (40 µg). Failure of neural tube closure was observed in treated embryos and the expression levels of a neurulation-related gene, sonic hedgehog (Shh) was abnormally decreased. The sphingolipid metabolism-related genes including N-acylsphingosine amidohydrolase 1 (ASAH1), and ceramide synthase 6 (CERS6) expressions were altered in the treated embryos compared to those in the control embryos. Apparently, FB₁ have interfered sphingolipid metabolisms by inhibiting the functions of ceramide synthase and folate transporters. In conclusion, FB₁-caused developmental retardation and abnormalities, such as neural tube defects in Brown Tsaiya Duck embryos, as well as are partly mediated by the disruption of sphingolipid metabolisms.

Effect of Pethidine Hydrochloride on the Development of Neural Tube: A Genetic Analysis Study in a Chick Embryo Model

BACKGROUND

Neural tube defects are among the most frequent congenital abnormalities of the central nervous system. Progression of neural tube deficits is affected by hereditary predilection and environmental determinants. Pethidine (meperidine) is a fast and powerful opioid analgesic in U.S. Food and Drug Administration category C. There are reports about developmental anomalies due to this medication. The aim of this study was to investigate the effects of different doses of pethidine hydrochloride on neural tube development in a chick embryo model resembling the first month of vertebral growth in mammals.

METHODS

Seventy-five specific pathogen-free eggs were incubated for 28 hours and divided into 5 groups (including the control group), each consisting of 15 eggs. Pethidine hydrochloride was administered sub-blastodermically with a Hamilton microinjector in 4 different doses. Incubation was continued until the end of the 48th hour. Subsequently, all eggs were opened, and embryos were cut from the embryonic membranes and evaluated morphologically, genetically, and histopathologically.

RESULTS

Crown-rump length, somite numbers, and silver-stained nucleolar organizer region (AgNOR) number averages, and total AgNOR/nuclear area ratios decreased in a dose-dependent manner. Examination of neural tube closure revealed statistically significant differences in all experimental groups (P<0.05). Messenger RNA levels of the BRE gene were decreased in pethidine hydrochloride-exposed embryos compared with the control group. Although this downregulation was not statistically significant, this decrease was striking with a 0.422-fold change in the fifth group.

CONCLUSIONS

We demonstrated that pethidine hydrochloride affects neuronal development in chicken embryos. The teratogenic mechanism of pethidine hydrochloride is unclear; therefore, further investigation is required.

Retinoic Acid Signaling Plays a Crucial Role in Excessive Caffeine Intake-Disturbed Apoptosis and Differentiation of Myogenic Progenitors

Whether or not the process of somitogenesis and myogenesis is affected by excessive caffeine intake still remains ambiguous. In this study, we first showed that caffeine treatment results in chest wall deformities and simultaneously reduced mRNA expressions of genes involved in myogenesis in the developing chicken embryos. We then used embryo cultures to assess in further detail how caffeine exposure affects the earliest steps of myogenesis, and we demonstrated that the caffeine treatment suppressed somitogenesis of chicken embryos by interfering with the expressions of crucial genes modulating apoptosis, proliferation, and differentiation of myogenic progenitors in differentiating somites. These phenotypes were abrogated by a retinoic acid (RA) antagonist in embryo cultures, even at low caffeine doses in C2C12 cells, implying that excess RA levels are responsible for these phenotypes in cells and possibly in vivo. These findings highlight that excessive caffeine exposure is negatively involved in regulating the development of myogenic progenitors through interfering with RA signaling. The RA somitogenesis/myogenesis pathway might be directly impacted by caffeine signaling rather than reflecting an indirect effect of the toxicity of excess caffeine dosage.

Zinc oxide nanoparticles exposure-induced oxidative stress restricts cranial neural crest development during chicken embryogenesis

Zinc oxide Nanoparticles (ZnO NPs) are widely used as emerging materials in agricultural and food-related fields, which exists potential safety hazards to public health and environment while bringing an added level of convenience to our original life. It has been proved that ZnO NPs could be taken up by pregnant women and passed through human placental barrier. However, the toxic potential for embryo development remains largely unanswered. In this study, we discovered that ZnO NPs caused the cytotoxicity in vitro. Inhibition of free Zn²⁺ ions in solution by EDTA or inhibition of Zn²⁺ ions absorption by CaCl₂ could partially eliminate ZnO NPs-mediated cell toxicity, though not redeem completely. This indicated that both nanoparticles and the release of Zn²⁺ ions were involved in ZnO NPs-mediated cytotoxicity. In addition, we also found that both nanoparticles and Zn²⁺ ion release triggered reactive oxygen species (ROS) production, which further induced cell toxicity, inflammation and apoptosis, which are mediated by NF-κB signaling cascades and the mitochondria dysfunction, respectively. Eventually, these events lead to the suppressed production and migration of cranial neural crest cells (CNCCs), which subsequently prompts the craniofacial defects in chicken embryos. The application of the antioxidant N-Acetyl-L-cysteine (NAC) rescued the ZnO NPs-induced cell toxicity and malformation of the CNCCs, which further verified our hypothesis. Our results revealed the relevant mechanism of ZnO NPs exposure-inhibited the development of CNCCs, which absolutely contribute to assess the risk of nanoparticles application.

Roles of chitinase 3-like 1 in the development of cancer, neurodegenerative diseases, and inflammatory diseases

Chitinase 3-like 1 (CHI3L1) is a secreted glycoprotein that mediates inflammation, macrophage polarization, apoptosis, and carcinogenesis. The expression of CHI3L1 is strongly increased by various inflammatory and immunological conditions, including rheumatoid arthritis, multiple sclerosis, Alzheimer's disease, and several cancers. However, its physiological and pathophysiological roles in the development of cancer and neurodegenerative and inflammatory diseases remain unclear. Several studies have reported that CHI3L1 promotes cancer proliferation, inflammatory cytokine production, and microglial activation, and that multiple receptors, such as advanced glycation end product, syndecan-1/αVβ3, and IL-13Rα2, are involved. In addition, the pro-inflammatory action of CHI3L1 may be mediated via the protein kinase B and phosphoinositide-3 signaling pathways and responses to various pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ. Therefore, CHI3L1 could contribute to a vast array of inflammatory diseases. In this article, we review recent findings regarding the roles of CHI3L1 and suggest therapeutic approaches targeting CHI3L1 in the development of cancers, neurodegenerative diseases, and inflammatory diseases.

Role of FGF signalling in neural crest cell migration during early chick embryo development

Fibroblast growth factor (FGF) signalling acts as one of modulators that control neural crest cell (NCC) migration, but how this is achieved is still unclear. In this study, we investigated the effects of FGF signalling on NCC migration by blocking this process. Constructs that were capable of inducing Sprouty2 (Spry2) or dominant-negative FGFR1 (Dn-FGFR1) expression were transfected into the cells making up the neural tubes. Our results revealed that blocking FGF signalling at stage HH10 (neurulation stage) could enhance NCC migration at both the cranial and trunk levels in the developing embryos. It was established that FGF-mediated NCC migration was not due to altering the expression of N-cadherin in the neural tube. Instead, we determined that cyclin D1 was overexpressed in the cranial and trunk levels when Sprouty2 was upregulated in the dorsal neural tube. These results imply that the cell cycle was a target of FGF signalling through which it regulates NCC migration at the neurulation stage.

Atg7-Mediated Autophagy Is Involved in the Neural Crest Cell Generation in Chick Embryo

Autophagy plays a very important role in numerous physiological and pathological events. However, it still remains unclear whether Atg7-induced autophagy is involved in the regulation of neural crest cell production. In this study, we found the co-location of Atg7 and Pax7⁺ neural crest cells in early chick embryo development. Upregulation of Atg7 with unilateral transfection of full-length Atg7 increased Pax7⁺ and HNK-1⁺ cephalic and trunk neural crest cell numbers compared to either Control-GFP transfection or opposite neural tubes, suggesting that Atg7 over-expression in neural tubes could enhance the production of neural crest cells. BMP4 in situ hybridization and p-Smad1/5/8 immunofluorescent staining demonstrated that upregulation of Atg7 in neural tubes suppressed the BMP4/Smad signaling, which is considered to promote the delamination of neural crest cells. Interestingly, upregulation of Atg7 in neural tubes could significantly accelerate cell progression into the S phase, implying that Atg7 modulates cell cycle progression. However, β-catenin expression was not significantly altered. Finally, we demonstrated that upregulation of the Atg7 gene could activate autophagy as did Atg8. We have also observed that similar phenotypes, such as more HNK-1⁺ neural crest cells in the unilateral Atg8 transfection side of neural tubes, and the transfection with full-length Atg8-GFP certainly promote the numbers of BrdU⁺ neural crest cells in comparison to the GFP control. Taken together, we reveal that Atg7-induced autophagy is involved in regulating the production of neural crest cells in early chick embryos through the modification of the cell cycle.

High glucose environment inhibits cranial neural crest survival by activating excessive autophagy in the chick embryo

High glucose levels induced by maternal diabetes could lead to defects in neural crest development during embryogenesis, but the cellular mechanism is still not understood. In this study, we observed a defect in chick cranial skeleton, especially parietal bone development in the presence of high glucose levels, which is derived from cranial neural crest cells (CNCC). In early chick embryo, we found that inducing high glucose levels could inhibit the development of CNCC, however, cell proliferation was not significantly involved. Nevertheless, apoptotic CNCC increased in the presence of high levels of glucose. In addition, the expression of apoptosis and autophagy relevant genes were elevated by high glucose treatment. Next, the application of beads soaked in either an autophagy stimulator (Tunicamycin) or inhibitor (Hydroxychloroquine) functionally proved that autophagy was involved in regulating the production of CNCC in the presence of high glucose levels. Our observations suggest that the ERK pathway, rather than the mTOR pathway, most likely participates in mediating the autophagy induced by high glucose. Taken together, our observations indicated that exposure to high levels of glucose could inhibit the survival of CNCC by affecting cell apoptosis, which might result from the dysregulation of the autophagic process.