Parental Exposure to Environmentally Relevant Concentrations of Bisphenol-A Bis(diphenyl phosphate) Impairs Vascular Development in Offspring through DNA/RNA Methylation-Dependent Transmission

Bisphenol C Induces Cardiac Developmental Defects by Disrupting m6A Homeostasis

Bisphenol A (BPA) is a commonly used plastic additive. Since BPA has been banned in maternal and infant food containers in many countries, BPA substitutes have been widely introduced to replace it. By systematically assessing the potential developmental toxicity of BPA substitutes, we observed that the 41-150 nM in vivo BPC exposure (around the reported concentration detected in infant urine: 6-186 nM) induced cardiac defects in zebrafish. Mechanistically, BPC disrupted m6A homeostasis by downregulation of the key m6A methyltransferase, Mettl3, thereby causing the m6A reader, Igf2bp2b, to fail in recognizing and stabilizing the inefficiently m6A-modified acox1 and tnnt2d mRNA. Then, downregulation of Acox1 (a regulator in cardiac fatty acid metabolism) and Tnnt2d (a component of cardiac troponin for muscle contraction) led to cardiac defects. Indeed, the dual cardiac functional axes regulated by the same m6A reader in response to BPC provided new insight into the regulatory mechanisms of epitranscriptomics and cardiac development. Collectively, our study not only presented evidence showing that the internal exposure levels of BPC in humans could lead to cardiac developmental defects but also demonstrated the underlying mechanism of BPC-mediated defects by disrupting the Mettl3-m6A-Igf2bp2b-Acox1/Tnnt2d pathways, which provided potential molecular markers associated with BPC exposure.

Highly sensitive response to the toxicity of environmental chemicals in transparent casper zebrafish

The response sensitivity to toxic substances is the most concerned performance of animal model in chemical risk assessment. Casper (mitfaw2/w2;mpv17a9/a9), a transparent zebrafish mutant, is a useful in vivo model for toxicological assessment. However, the ability of casper to respond to the toxicity of exogenous chemicals is unknown. In this study, zebrafish embryos were exposed to five environmental chemicals, chlorpyrifos, lindane, α-endosulfan, bisphenol A, tetrabromobisphenol A (TBBPA), and an antiepileptic drug valproic acid. The half-lethal concentration (LC50) values of these chemicals in casper embryos were 62-87 % of that in the wild-type. After TBBPA exposure, the occurrence of developmental defects in the posterior blood island of casper embryos was increased by 67-77 % in relative to the wild-type, and the half-maximal effective concentration (EC50) in casper was 73 % of that in the wild-type. Moreover, the casper genetic background significantly increased the hyperlocomotion caused by chlorpyrifos and lindane exposure compared with the wild-type. These results demonstrated that casper had greater susceptibility to toxicity than wild-type zebrafish in acute toxicity, developmental toxicity and neurobehavioral toxicity assessments. Our data will inform future toxicological studies in casper and accelerate the development of efficient approaches and strategies for toxicity assessment via the use of casper.

Aggravating Pollution of Emerging Aryl Organophosphate Esters in Urban Estuarine Sediments of South China

Emerging aryl organophosphate esters (aryl-OPEs) have been employed as substitutes for organohalogen flame retardants in recent years; however, their environmental occurrence and associated impacts in urban estuarine sediments have not been adequately investigated, impeding regulatory decision-making. Herein, field-based investigations and modeling based on surface sediment and sediment core analysis were employed to uncover the historical pollution and current environmental impacts of aryl-OPEs in the Pearl River Estuary, South China. Our results revealed a substantial increase in aryl-OPE emission, particularly emerging aryl-OPEs, through sediment transport to the estuary since the 2000s. The emerging aryl-OPEs comprised 83% of the total annual input in the past decade, with an average annual input of 155,000 g. Additionally, the emerging-to-traditional aryl-OPE concentration ratios increased with decreasing distance from the shore, peaking in the highly urbanized riverine outlets. These findings indicate that inventories of emerging aryl-OPEs are likely increasing in estuarine sediments and their emissions are surpassing those of traditional aryl-OPEs. Our risk-based priority screening approach indicates that some emerging aryl-OPEs, particularly bisphenol A bis(diphenyl phosphate), can pose a higher environmental risk than traditional aryl-OPEs in estuarine sediments. Overall, our study highlights the importance of recognizing the environmental impacts of emerging aryl-OPEs.

Universal occurrence of organophosphate tri-esters and di-esters in marine sediments: Evidence from the Okinawa Trough in the East China Sea

Despite numerous data on organophosphate tri-esters (tri-OPEs) in the environment, literatures on organophosphate di-esters (di-OPEs) in field environment, especially marine sediments remain scarce. This study addresses this gap by analyzing 35 abyssal sediment samples from the middle Okinawa Trough in the East China Sea. A total of 25 tri-OPEs and 10 di-OPEs were determined, but 13 tri-OPEs and 2 di-OPEs were nondetectable in any of these sediment samples. The concentrations of ∑12tri-OPE and ∑8di-OPE were 0.108-32.2 ng/g (median 1.11 ng/g) and 0.548-15.0 ng/g (median 2.74 ng/g). Chlorinated (Cl) tri-OPEs were the dominant tri-esters, accounting for 47.5 % of total tri-OPEs on average, whereas chlorinated di-OPEs represented only 19.2 % of total di-OPEs. This discrepancy between the relatively higher percentage of Cl-tri-OPEs and lower abundance of Cl-di-OPEs may be ascribed to the stronger environmental persistence of chlorinated tri-OPEs. Source assessment suggested that di-OPEs were primarily originated from the degradation of tri-OPEs rather than industrial production. Long range waterborne transport facilitated by oceanic currents was an important input pathway for OPEs in sediments from the Okinawa Trough. These findings enhance the understanding of the sources and transport of OPEs in marine sediments, particularly in the Okinawa Trough.

Regulatory role of m6A epitranscriptomic modifications in normal development and congenital malformations during embryogenesis

The discovery of N6-methyladenosine (m6A) methylation and its role in translation has led to the emergence of a new field of research. Despite accumulating evidence suggesting that m6A methylation is essential for the pathogenesis of cancers and aging diseases by influencing RNA stability, localization, transformation, and translation efficiency, its role in normal and abnormal embryonic development remains unclear. An increasing number of studies are addressing the development of the nervous and gonadal systems during embryonic development, but only few are assessing that of the immune, hematopoietic, urinary, and respiratory systems. Additionally, these studies are limited by the requirement for reliable embryonic animal models and the difficulty in collecting tissue samples of fetuses during development. Multiple studies on the function of m6A methylation have used suitable cell lines to mimic the complex biological processes of fetal development or the early postnatal phase; hence, the research is still in the primary stage. Herein, we discuss current advances in the extensive biological functions of m6A methylation in the development and maldevelopment of embryos/fetuses and conclude that m6A modification occurs extensively during fetal development. Aberrant expression of m6A regulators is probably correlated with single or multiple defects in organogenesis during the intrauterine life. This comprehensive review will enhance our understanding of the pivotal role of m6A modifications involved in fetal development and examine future research directions in embryogenesis.