Okadaic Acid Exposure Induced Neural Tube Defects in Chicken (Gallus gallus) Embryos.

Yuhu Jiao,Jiesheng Liu,Weidong Yang,Xuesong Yang,Hongye Li,Guang Wang,Dawei Li

doi:10.3390/md19060322

Abstract

Okadaic acid (OA) is an important liposoluble shellfish toxin distributed worldwide, and is mainly responsible for diarrheic shellfish poisoning in human beings. It has a variety of toxicities, including cytotoxicity, embryonic toxicity, neurotoxicity, and even genotoxicity. However, there is no direct evidence of its developmental toxicity in human offspring. In this study, using the chicken (Gallus gallus) embryo as the animal model, we investigated the effects of OA exposure on neurogenesis and the incidence of neural tube defects (NTDs). We found that OA exposure could cause NTDs and inhibit the neuronal differentiation. Immunofluorescent staining of pHI3 and c-Caspase3 demonstrated that OA exposure could promote cell proliferation and inhibit cell apoptosis on the developing neural tube. Besides, the down-regulation of Nrf2 and increase in reactive oxygen species (ROS) content and superoxide dismutase (SOD) activity in the OA-exposed chicken embryos indicated that OA could result in oxidative stress in early chick embryos, which might enhance the risk of the subsequent NTDs. The inhibition of bone morphogenetic protein 4 (BMP4) and Sonic hedgehog (Shh) expression in the dorsal neural tube suggested that OA could also affect the formation of dorsolateral hinge points, which might ultimately hinder the closure of the neural tube. Transcriptome and qPCR analysis showed the expression of lipopolysaccharide-binding protein (LBP), transcription factor AP-1 (JUN), proto-oncogene protein c-fos (FOS), and C-C motif chemokine 4 (CCL4) in the Toll-like receptor signaling pathway was significantly increased in the OA-exposed embryos, suggesting that the NTDs induced by OA might be associated with the Toll-like receptor signaling pathway. Taken together, our findings could advance the understanding of the embryo–fetal developmental toxicity of OA on human gestation.

Highlights

Okadaic acid (OA), an important marine toxin, is mainly responsible for diarrhetic shellfish poisoning (DSP) in human beings [1,2]
The expresthe OA-treated embryos (Figure 7E’–H’ and I–J). These results suggest that the formation sion of paired box 7 (Pax7) on the dorsal part of cranial and trunk neural tubes was decreased in the OAof neural tube defects (NTDs) might be related to the inhibition of Pax7 and bone morphogenetic protein 4 (BMP4) expression induced by treated embryos (Figure 7E’–H’ and I–J)
These results suggest that the formation of NTDs might be related to the inhibition of Pax7 and BMP4 expression induced by OA exposure

Summary

Introduction

Okadaic acid (OA), an important marine toxin, is mainly responsible for diarrhetic shellfish poisoning (DSP) in human beings [1,2]. OA usually accumulates in the tissues of filter-feeding bivalves, and eventually pose a great threat to human health through the consumption of contaminated shellfish [3]. OA has become a serious concern for the shellfish industry and public health since it is one of the most frequent and globally distributed marine biotoxins [2,4]. Previous studies have proved that OA is a potent and specific inhibitor of serine/threonine protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) [5,6,7]. Studies show that OA has a variety of toxic effects, including cytotoxicity, carcinogenicity, neurotoxicity, as well as embryotoxicity [1,8]. It has been demonstrated that OA can induce spatial memory impairment and neurodegeneration [13] and cause hippocampal cell loss in rats [14]

Results

Discussion

Conclusion