Disturbance of the Dlk1-Dio3 imprinted domain may underlie placental Dio3 suppression and extracellular thyroid hormone disturbance in placenta-derived JEG-3 cells following decabromodiphenyl ether (BDE209) exposure

Distribution of polybrominated diphenyl ethers (PBDEs) in placental tissues of maternal and fetal origin in exposed Wistar rats and associations with thyroid hormone levels

In utero exposure to polybrominated diphenyl ethers (PBDEs) is linked to adverse pregnancy and fetal health outcomes, including altered thyroid hormone (TH) levels. Despite their phase-out, PBDEs are still commonly detected in newborn cord blood. While PBDEs can cross the placenta, few studies have separately assessed PBDEs or THs in the maternal and fetal placental tissues. Additionally, no studies have separately assessed THs in these tissues across mid- and late gestation, during the onset of fetal TH synthesis. To address these gaps, we conducted a study with Wistar rats and examined PBDE accumulation in the maternal and fetal placenta. Pregnant dams were exposed daily to sesame oil vehicle, a low dose, or high dose PBDE mixture. At GD15 and 20, dams were sacrificed and placental tissues were collected. Tissues were analyzed for PBDEs, T3, rT3, and T4 using mass spectrometry. BDE-47, -99, -100, and -209 were frequently detected in both the fetal and maternal placenta. At GD15, higher concentrations of BDE-99, -100, and -209 were measured in the fetal placenta; however, this trend reversed by GD20, with higher maternal placental concentrations. Placental T3 and T4 were significantly impacted by exposure, tissue, and exposure × tissue at GD15, with significant reductions in both THs following low-dose exposure in the maternal placenta. By GD20, maternal placental T3 was only significantly reduced in the high exposure groups and there was no effect on placental T4. Overall, these results highlight the rapid developmental changes that occur throughout gestation between the maternal and fetal placenta, and the differential impacts of gestational PBDE exposure on placental T3 and T4 across mid- and late gestation.

A critical review on BDE-209: Source, distribution, influencing factors, toxicity, and degradation

As the most widely used polybrominated diphenyl ether, BDE-209 is commonly used in polymer-based commercial and household products. Due to its unique physicochemical properties, BDE-209 is ubiquitous in a variety of environmental compartments and can be exposed to organisms in various ways and cause toxic effects. The present review outlines the current state of knowledge on the occurrence of BDE-209 in the environment, influencing factors, toxicity, and degradation. BDE-209 has been detected in various environmental matrices including air, soil, water, and sediment. Additionally, environmental factors such as organic matter, total suspended particulate, hydrodynamic, wind, and temperature affecting BDE-209 are specifically discussed. Toxicity studies suggest BDE-209 may cause systemic toxic effects on living organisms, reproductive toxicity, embryo-fetal toxicity, genetic toxicity, endocrine toxicity, neurotoxicity, immunotoxicity, and developmental toxicity, or even be carcinogenic. BDE-209 has toxic effects on organisms mainly through epigenetic regulation and induction of oxidative stress. Evidence regarding the degradation of BDE-209, including biodegradation, photodegradation, Fenton degradation, zero-valent iron degradation, chemical oxidative degradation, and microwave radiation degradation is summarized. This review may contribute to assessing the environmental risks of BDE-209 to help develop rational management plans.

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants used in plastics, textiles, polyurethane foam, and other materials. They contain two halogenated aromatic rings bonded by an ester bond and are classified according to the number and position of bromine atoms. Due to their widespread use, PBDEs have been detected in soil, air, water, dust, and animal tissues. Besides, PBDEs have been found in various tissues, including liver, kidney, adipose, brain, breast milk and plasma. The continued accumulation of PBDEs has raised concerns about their potential toxicity, including hepatotoxicity, kidney toxicity, gut toxicity, thyroid toxicity, embryotoxicity, reproductive toxicity, neurotoxicity, and immunotoxicity. Previous studies have suggested that there may be various mechanisms contributing to PBDEs toxicity. The present study aimed to outline PBDEs' toxic effects and mechanisms on different organ systems. Given PBDEs' bioaccumulation and adverse impacts on human health and other living organisms, we summarize PBDEs' effects and potential toxicity mechanisms and tend to broaden the horizons to facilitate the design of new prevention strategies for PBDEs-induced toxicity.

BDE209-promoted Dio2 degradation in H4 glioma cells through the autophagy pathway, resulting in hypothyroidism and leading to neurotoxicity

Decabromodiphenyl ether (BDE209), the homologue with the highest number of brominates in polybrominated diphenyl ethers (PBDEs), is one of the most widespread environmental persistent organic pollutants (POPs) due to its mass production and extensive application in recent decades. BDE209 is neurotoxic, possibly related to its interference with the thyroid hormone (TH) system. However, the underlying molecular mechanisms of BDE209-induced TH interference and neurobehavioral disorders remains unknown. Here, we explored how BDE209 manipulated the major enzyme, human type II iodothyronine deiodinase (Dio2), that is most important in regulating local cerebral TH equilibrium by neuroglial cells, using an in vitro model of human glioma H4 cells. Clonogenic cell survival assay and LC/MS/MS analysis showed that BDE209 could induce chronic neurotoxicity by inducing TH interference. Co-IP assay, RT-qPCR and confocal assay identified that BDE209 destroyed the stability of Dio2 without affecting its expression, and promoted its binding to p62, thereby enhancing its autophagic degradation, thus causing TH metabolism disorder and neurotoxicity. Furthermore, molecular docking studies predicted that BDE209 could effectively suppress Dio2 activity by competing with tetraiodothyronine (T4). Collectively, our study demonstrates that BDE209-induced Dio2 degradation and loss of its enzymatic activity in neuroglial cells are the fundamental pathogenic basis for BDE209-mediated cerebral TH disequilibrium and neurotoxicity, providing a target of interest for further investigation using glial/neuronal cell co-culture system and in vivo models.

Intravenous As2O3 as a promising treatment for psoriasis - an experimental study in psoriasis-like mouse model

OBJECTIVE

To evaluate the efficacy and mechanistic bases of the intravenous injection of arsenic trioxide at clinical-relevant doses for treating an imiquimod-induced psoriasis-like mouse model.

METHODS

After inducing psoriasis-like skin lesions on the back of mice with imiquimod, mice in each group were injected with a clinical dose of arsenic trioxide through the tail vein. The changes in the gene expression, protein expression and distribution of relevant inflammatory factors were evaluated in the inflicted skin area, for mechanisms underlying the efficacy of intravenous As₂O₃ intervention. HaCaT cells were used to establish an in vitro psoriasis model and pcDNA3.1-NF-κB overexpression plasmid was transfected into cells to overexpress P65, which further confirmed the role of the NF-κB signaling pathway in the effectiveness of As₂O₃.

RESULTS

Clinical dose of As₂O₃ can significantly improve abnormal symptoms and pathological changes in psoriasis-like skin lesions induced by IMQ in mice. While IMQ induced abnormal expression and distribution of inflammatory factors in the RIG-I pathway and the microRNA-31 (miR-31) pathway in psoriatic skin tissues, intravenous As₂O₃ can effectively regulate and restore the normality. The leading role of NF-κB signaling was evidenced in vivo and validated in vitro using the NF-κB-overexpressed HaCaT cell model.

CONCLUSION

Clinical dosage of As₂O₃ may achieve effective treatment of IMQ-induced psoriatic skin lesions by modulating the NF-κB signaling pathway which regulates both the RIG-I and the miR-31 lines of action. Our data provided strong evidence supporting the claim that systemic As₂O₃ administration of clinical doses can be a promising treatment for psoriasis patients.

Thyroid hormones: Metabolism and transportation in the fetoplacental unit

The thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3), are of vital importance for fetal development. The concentration of THs in fetal circulation varies throughout gestation and differs from the concentration in the maternal serum, indicating the presence of maternal-fetal thyroid homeostasis regulatory mechanisms in the placenta. The passage of THs from maternal circulation to fetal circulation is modulated by plasma membrane transporters, enzymes, and carrier proteins. Monocarboxylate transporter 8, iodothyronine deiodinases (DIO2 and DIO3), and transthyretin are especially involved in this maternal-fetal thyroid modulation, shown by a greater expression in the placenta. THs also play a role in placental development and as expected, abnormal variations in TH levels are associated with pregnancy complications and can result in damage to the fetus. Although new evidence regarding TH regulation during pregnancy and its effects in the mother, placenta, and fetus has been published, many aspects of these interactions are still poorly understood. The objective of this review is to provide an evidence-based update, drawn from current data, on the metabolism and transport of THs in the placenta and their vital role in the maternal-fetal relationship.