Decabromodiphenyl ether (BDE-209) exposure to lactating mice perturbs steroidogenesis and spermatogenesis in adult male offspring

Knockdown of type 2 orexin receptor in adult mouse testis potentiates testosterone production and germ cell proliferation

Orexins (OXs) are neuropeptides which regulate various physiological processes. OXs exist in two different forms, mainly orexin A (OXA) and orexin B (OXB) and their effects are mediated via OX1R and OX2R. Presence of OXB and OX2R in mouse testis is also reported. However, the role of OXB/OX2R in the male gonad remains unexplored. Herein we investigated the role of OXB/OX2R system in testicular physiology under in vivo and ex vivo conditions. Adult mice were given a single dose of bilateral intratesticular injection of siRNA targeting OX2R and were sacrificed 96 h post-injection. OX2R-knockdown potentiated serum and intratesticular testosterone levels with up-regulation in the expressions of major steroidogenic proteins. Germ cell proliferation also increased in siRNA-treated mice. Results of the ex vivo experiment also supported the findings of the in vivo study. In conclusion, OX2R may regulate testosterone production and thereby control the fine-tuning between steroidogenesis and germ cell dynamics.

Occurrence and ecotoxicological impacts of polybrominated diphenyl ethers (PBDEs) in electronic waste (e-waste) in Africa: Options for sustainable and eco-friendly management strategies

Polybrominated diphenyl ethers (PBDEs) are persistent contaminants used as flame retardants in electronic products. PBDEs are contaminants of concern due to leaching and recalcitrance conferred by the stable and hydrophobic bromide residues. The near absence of legislatures and conscious initiatives to tackle the challenges of PBDEs in Africa has allowed for the indiscriminate use and consequent environmental degradation. Presently, the incidence, ecotoxicity, and remediation of PBDEs in Africa are poorly elucidated. Here, we present a position on the level of contamination, ecotoxicity, and management strategies for PBDEs with regard to Africa. Our review shows that Africa is inundated with PBDEs from the proliferation of e-waste due to factors like the increasing growth in the IT sector worsened by the procurement of second-hand gadgets. An evaluation of the fate of PBDEs in the African environment reveals that the environment is adequately contaminated, although reported in only a few countries like Nigeria and Ghana. Ultrasound-assisted extraction, microwave-assisted extraction, and Soxhlet extraction coupled with specific chromatographic techniques are used in the detection and quantification of PBDEs. Enormous exposure pathways in humans were highlighted with health implications. In terms of the removal of PBDEs, we found a gap in efforts in this direction, as not much success has been reported in Africa. However, we outline eco-friendly methods used elsewhere, including microbial degradation, zerovalent iron, supercritical fluid, and reduce, reuse, recycle, and recovery methods. The need for Africa to make and implement legislatures against PBDEs holds the key to reduced effect on the continent.

Maternal exposure to DON during lactation induces testicular toxicity in pubertal and adult offspring mice

Deoxynivalenol (DON), a type B trichothecene mycotoxin, commonly occurs in cereal grains, and poses significant health risks to humans and animals. Numerous studies reveal its obvious toxic effects on male reproductive performance as well as its ability to transfer from the lactating mother to the suckling offspring through colostrum and milk. The objective of this study was to evaluate the toxic effect of lactational DON exposure on testicular morphology, hormonal levels, inflammation, apoptosis and proliferation of germ cells, tight junction, and sperm quality in male offspring. Sixty-six male offspring mice from lactating dams exposed to DON were euthanized at PND 21 and PND 70 to investigate the reproductive toxicity. Our results indicated that maternal DON exposure had a significant impact on the weight and volume of the testes, caused testicular histopathology, and reduced testosterone levels by downregulating expressions of StAR, CYP11A1, and CYP17A1 in male offspring. We also found that maternal DON exposure led to testicular inflammation in male offspring, which was attributed to increased levels of inflammatory markers, including IL-1β, IL-6, TNF-α, and IFN-γ. Maternal DON exposure resulted in impaired tight junctions of Sertoli cells in male offspring, as evidenced by decreased expressions of ZO-1, Occludin, and Claudin-3. In addition, maternal DON exposure caused a reduction in the number of Sertoli cells and germ cells, ultimately leading to decreased sperm count and quality in adult male offspring. Collectively, these findings provide compelling evidence that maternal exposure to DON during lactation causes testicular toxicity in both pubertal and adult male offspring.

The role of Sertoli cells-secreted factors in different stages of germ cells development in mice exposed to BDE-209

Decabromodiphenyl ether (BDE-209), a frequently used brominated flame retardant, readily enters the environment and is difficult to degrade with bioaccumulation. BDE-209 could cause male reproductive toxicity, but the regulatory functions of Sertoli cells-secreted factors remain uncertain. In present study, male mice were treated with 75 mg/kg BDE-209 and then stopped exposure for 50 days. Exogenous Glial cell line-derived neurotrophic factor (GDNF), a Sertoli cell-secreted factor, was injected into testes of mice treated with BDE-209 for 50 days to explore the role of GDNF in BDE-209-induced reproductive toxicity. The mouse spermatogonia cell line GC-1 spg was used in vitro to further verify regulatory effects of Sertoli cells-secreted factors on meiotic initiation. The results showed that BDE-209 inhibited expressions of the self-renewal pathway GFRα-1/RAS/ERK1/2 in spermatogonial stem cells (SSCs), and reduced expressions of spermatogonia proliferation-related pathway NRG3/ERBB4 and meiosis initiation factor Stra8. Furthermore, BDE-209 decreased the levels of both GDNF and retinoic acid (RA) secreted by Sertoli cells in testes. Importantly, the alterations of above indicators induced by BDE-209 did not recover after 50-day recovery period. After exogenous GDNF injection, the decreased expression of GFRα-1/RAS/ERK in SSCs was reversed. However, the level of RA and expressions of NRG3/ERBB4/Stra8 were not restored. The in vitro experimental results showed that exogenous RA reversed the reductions in NRG3/ERBB4/Stra8 and ameliorated inhibition of GC-1 spg cells proliferation induced by BDE-209. These results suggested that Sertoli cells-secreted factors play roles in regulating various stages of germ cell development. Specifically, BDE-209 affected the self-renewal of SSCs by decreasing GDNF secretion resulting in the inhibition of GFRα-1/RAS/ERK pathway; BDE-209 hindered the proliferation of spermatogonia and initiation of meiosis by inhibiting the secretion of RA and preventing RA from binding to RARα, resulting in the suppression of NRG3/ERBB4/Stra8 pathway. As a consequence, spermatogenesis was compromised, leading to persistent male reproductive toxicity.

Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (-0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Adverse outcome pathways of PBDEs inducing male reproductive toxicity

Polybrominated diphenyl ethers (PBDEs) are widely used brominated flame retardants, they are easily released into environment and causing adverse effects to the ecosystem and human health. This review aims to summarize the research status of PBDEs-induced male reproductive toxicity and its mechanisms at various levels such as molecular/cellular, tissue/organ and individual/population. The Adverse Outcome Pathways (AOPs) diagram showed that PBDEs-induced reactive oxygen species (ROS) production, disruptions of estrogen receptor-α (ERα) and antagonism of androgen receptor (AR) were defined as critical molecular initiating events (MIEs). They caused key events (KEs) at the molecular and cellular levels, including oxidative stress, increased DNA damage, damaging mitochondria, increased glycolipid levels and apoptosis, depletion of ectoplasmic specialization and decreased Leydig cells numbers. These in turn lead to followed KEs at the tissue or organ levels, such as the impaired spermatogenesis, impaired blood-testis barrier and reduced testosterone synthesis and function. As a result, reproductive system-related adverse outcomes (AOs) were reported, such as the decreased sperm quantity or quality, shorten male anogenital distance and cryptorchidism in individual and reduced reproduction of the population. This review assembled information on the mechanisms of male reproductive toxicity induced by PBDEs, and constructed a causal mechanism relationship diagram from different levels using the an AOP framework to provide theoretical basis for ecological risk assessment and environmental management of PBDEs. The AOP framework makes it possible to develop risk management strategies based on toxicity mechanisms and support for development of Integrated Approach to Testing and Assessment (IATA) which are available for regulatory purposes.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

A comprehensive review on the decabromodiphenyl ether (BDE-209)-induced male reproductive toxicity: Evidences from rodent studies

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants (BFRs), are employed in various manufactured products to prevent fires, slow down their spread and reduce the resulting damages. Decabromodiphenyl ether (BDE-209), an example of PBDEs, accounts for approximately 82 % of the total production of PBDEs. BDE-209 is a thyroid hormone (TH)-disrupting chemical owing to its structural similarity with TH. Currently, increase in the level of BDE-209 in biological samples has become a major issue because of its widespread use. BDE-209 causes male reproductive toxicity mainly via impairment of steroidogenesis, generation of oxidative stress (OS) and interference with germ cell dynamics. Further, exposure to this chemical can affect metabolic status, sperm concentration, epigenetic regulation of various developmental genes and integrity of blood-testis barrier in murine testis. However, the possible adverse effects of BDE-209 and its mechanism of action on the male reproductive health have not yet been critically evaluated. Hence, the present review article, with the help of available literature, aims to elucidate the reproductive toxicity of BDE-209 in relation to thyroid dysfunction in rodents. Further, several crucial pathways have been also highlighted in order to strengthen our knowledge on BDE-209-induced male reproductive toxicity. Data were extracted from scientific articles available in PubMed, Web of Science, and other databases. A thorough understanding of the risk assessment of BDE-209 exposure and mechanisms of its action is crucial for greater awareness of the potential threat of this BFR to preserve male fertility.

Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) impairs Postnatal Testis Development in Mice: The Microtubule Cytoskeleton as a Sensitive Target

Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), a widely used flame retardant, has been frequently detected in various environmental compartments, but its health hazard remains largely unknown. Here, we investigated the adverse effects of TBBPA-BDBPE (50 and 1000 μg/kg/day) on postnatal testis development in CD-1 mice and the underlying mechanism. Following the first week of maternal exposure, neonatal mice in the high-dose group exhibited reduced seminiferous tubule area, fewer Sertoli cells and germ cells, and damaged microtubules in Sertoli cells; even microtubule damage was also observed in the low-dose group. When exposure extended to adulthood, male offspring in the high-dose group presented more remarkable alterations in reproductive parameters, including reduced sperm count; in the low-dose group, microtubule damage was also observable, along with blood-testis barrier impairment. Further molecular docking analysis and tubulin polymerization assay indicated that TBBPA-BDBPE could interact with tubulin and disrupt its polymerization. Moreover, we observed attenuated microtubules in mouse Sertoli cells in vitro (TM4) following TBBPA-BDBPE treatment, suggesting that TBBPA-BDBPE impaired testis development possibly by interfering with tubulin dynamics. This study not only highlights the male reproductive hazard of TBBPA-BDBPE but also greatly improved the understanding of the molecular mechanism for male reproductive toxicity of chemicals.

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.

Endocrine disrupting and carcinogenic effects of decabromodiphenyl ether

Background

Decabromodiphenyl ether (BDE209), an essential industrial flame retardant that is widely used, has recently been reported to be increasing in human serum. Due to the structural similarity between BDE209 and thyroid hormones, its toxic effects on the thyroid are of particular concern.

Methods

Original articles in the PubMed database were collected using the terms "BDE209", "decabromodiphenyl ether", "endocrine disrupting", "thyroid", "carcinogenesis", "polybrominated diphenyl ethers", "PBDEs," and their synonyms from inception up to October of 2022.

Results

Of the 748 studies initially identified, 45 were selected, which emphasized the adverse effects of BDE209 on endocrine system. BDE209 may have a toxic effect not only on thyroid function but also on thyroid cancer tumorigenesis at multiple levels, such as by directly interfering with the TR, hypothalamic-pituitary-thyroid (HPT) axis, enzyme activity, and methylation. However, it is impossible to draw a definitive conclusion on the exact pathway of thyroid toxicity from BDE209.

Conclusions

Although the toxic effects of BDE209 on the thyroid have been well investigated, its tumorigenic effects remain unclear and further research is necessary.

Combined effects of climate change and BDE-209 dietary exposure on the behavioural response of the white seabream, Diplodus sargus

Decabromodiphenyl-ether (BDE-209) is a persistent organic pollutant ubiquitously found in marine environments worldwide. Even though this emerging chemical contaminant is described as highly toxic, bioaccumulative and biomagnifiable, limited studies have addressed the ecotoxicological implications associated with its exposure in non-target marine organisms, particularly from a behavioural standpoint. Alongside, seawater acidification and warming have been intensifying their impacts on marine ecosystems over the years, compromising species welfare and survival. BDE-209 exposure as well as seawater acidification and warming are known to affect fish behaviour, but information regarding their interactive effects is not available. In this study, long-term effects of BDE-209 contamination, seawater acidification and warming were studied on different behavioural traits of Diplodus sargus juveniles. Our results showed that D. sargus exhibited a marked sensitivity in all the behaviour responses after dietary exposure to BDE-209. Fish exposed to BDE-209 alone revealed lower awareness of a risky situation, increased activity, less time spent within the shoal, and reversed lateralization when compared to fish from the Control treatment. However, when acidification and/or warming were added to the equation, behavioural patterns were overall altered. Fish exposed to acidification alone exhibited increased anxiety, being less active, spending more time within the shoal, while presenting a reversed lateralization. Finally, fish exposed to warming alone were more anxious and spent more time within the shoal compared to those of the Control treatment. These novel findings not only confirm the neurotoxicological attributes of brominated flame retardants (like BDE-209), but also highlight the relevance of accounting for the effects of abiotic variables (e.g. pH and seawater temperature) when investigating the impacts of environmental contaminants on marine life.

N-acetylcysteine rescues meiotic arrest during spermatogenesis in mice exposed to BDE-209

Deca-bromodiphenyl ethers (BDE-209) has been widely used in electronic devices and textiles as additives to flame retardants. Growing evidence showed that BDE-209 exposure leads to poorer sperm quality and male reproductive dysfunction. However, the underlying mechanisms of BDE-209 exposure caused a decline in sperm quality remains unclear. This study aimed to evaluate the protective effects of N-acetylcysteine (NAC) on meiotic arrest in spermatocytes and decreased sperm quality in BDE-209-exposed mice. In the study, mice were treated with NAC (150 mg/kg BW) 2 h before administrated with BDE-209 (80 mg/kg BW) for 2 weeks. For the in vitro studies, spermatocyte cell line GC-2spd cells were pretreated with NAC (5 mM) 2 h before treated with BDE-209 (50 μM) for 24 h. We found that pretreatment with NAC attenuated the oxidative stress status induced by BDE-209 in vivo and in vitro. Moreover, pretreatment with NAC rescued the testicular histology impairment and decreased the testicular organ coefficient in BDE-209-exposed mice. In addition, NAC supplement partially promoted meiotic prophase and improved sperm quality in BDE-209-exposed mice. Furthermore, NAC pretreatment effectively improved DNA damage repair by recovering DMC1, RAD51, and MLH1. In conclusion, BDE-209 caused spermatogenesis dysfunction related to the meiotic arrest medicated by oxidative stress, decreasing sperm quality.

BDE-209 disrupted the blood-testis barrier integrity by inhibiting estrogen receptor α signaling pathway in Sprague-Dawley rats

Deca brominated diphenyl ether (BDE-209) is a widely used flame retardant with endocrine-disrupting activity which reportedly caused sperm quality decline and damaged blood-testis barrier (BTB). However, whether BDE-209 exposure led to BTB integrity dysfunction through affecting microtubule cytoskeletal organization and junctions was not well-elucidated. This study aimed to investigate the role of estrogen receptor α (ERα) in BDE-209-mediated perturbation of BTB integrity. Male rats and primary culture Sertoli cells were co-treated with BDE-209 and propylpyrazoletriol (PPT). The data demonstrated that BDE-209 impaired BTB integrity by reducing crucial tight junction-related proteins with ZO-1 and Occludin. Furthermore, the data suggested that BDE-209 diminished the apical ectoplasmic specialization markers with Eps8 and Formin1. In addition, BDE-209 damaged BTB ultrastructure including tight junctions and ectoplasmic specialization structures with broken tight junctions and the absence of actin microfilaments. Further experiments revealed that ERα was triggered in BDE-209-treated Sertoli cells. Unexpectedly, we found that PPT rescued BDE-209-mediated disruption of BTB integrity including tight junction and apical ectoplasmic specialization by activating ERα in Sertoli cells. Taken together, these findings indicated that intratesticular BDE-209 exposure perturbed BTB integrity and destroyed BTB structure by blocking ERα pathway. Our findings provide a new therapeutic target for male reproductive dysfunction.

A comprehensive analysis on the relationship between BDE-209 exposure and erectile dysfunction

Decabromodiphenyl ether (mainly BDE-209) is a commonly used brominated flame retardant in various industrial products. Although its damage to the reproduction system has been established, its effect on erectile function remains unclear. The present study investigated whether BDE-209 induced erectile dysfunction in male SD rats and the underlying mechanisms. Pubertal male rats were exposed to BDE-209 orally (0, 5, 50, and 500 mg/kg/day) for 28 days and the ICP (intracavernous pressure) and MAP (mean arterial pressure) were measured. After the rats were euthanized, the fibrosis and apoptosis levels were evaluated. Additionally, the endothelial function of the rat vascular endothelium cells and the human umbilical vein endothelial cells were impaired after treatment with 50 μM and 100 μM BDE-209. Moreover, the bioinformatics based on CTD database and ChIP-X Enrichment Analysis, version 3 (ChEA3) and molecular docking analysis demonstrated that 5 transcription factors (NFKB1, NR3C1, E2F5, REL, IRF4) might regulate endothelial function by affecting the expression of interactive genes (BCL-2, CAP3, CAT, TNF, MAPK1, and MAPK3). In summary, the present study demonstrated that BDE-209 might affect downstream interactive genes by binding to transcription factors, leading to corpus cavernosum endothelial dysfunction, thus contributing to erectile dysfunction in rats.

Mechanisms of Male Reproductive Toxicity of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDE) are a group of flame retardants used in a variety of artificial materials. Despite being phased out in most industrial countries, they remain in the environment and human tissues due to their persistence, lipophilicity, and bioaccumulation. Populational and experimental studies demonstrate the male reproductive toxicity of PBDEs including increased incidence of genital malformations (hypospadias and cryptorchidism), altered weight of testes and other reproductive tissues, altered testes histology and transcriptome, decreased sperm production and sperm quality, altered epigenetic regulation of developmental genes in spermatozoa, and altered secretion of reproductive hormones. A broad range of mechanistic hypotheses of PBDE reproductive toxicity has been suggested. Among these hypotheses, oxidative stress, the disruption of estrogenic signaling, and mitochondria disruption are affected by PBDE concentrations much higher than concentrations found in human tissues, making them unlikely links between exposures and adverse reproductive outcomes in the general population. Robust evidence suggests that at environmentally relevant doses, PBDEs and their metabolites may affect male reproductive health via mechanisms including AR antagonism and the disruption of a complex network of metabolic signaling.

Vitamin C supplementation rescued meiotic arrest of spermatocytes in Balb/c mice exposed to BDE-209

Deca-brominated diphenyl ether (BDE-209) is a ubiquitous industrial chemical as brominated flame retardant (BFRs). Exposure to BDE-209 has been clearly associated with male reproductive disorders. However, the meiotic arrest mechanism of spermatocytes exposed to BDE-209 is still unclear. The present work aimed to explore the protective effect of vitamin C on BDE-209-induced meiotic arrest of spermatocytes and its possible mechanism. Vitamin C (100 mg/kg BW) was administered to BDE-209-exposed (80 mg/kg BW) male Balb/c mice once daily by intraperitoneal injection for 2 weeks. Our results showed that vitamin C played male reproductive protection effects as showed by attenuated BDE-209-induced testicular damage, and reduced sperm abnormality rate. Vitamin C also attenuated BDE-209-induced increase in SOD and MDA in testes and GC-2 spd cells. Moreover, vitamin C promoted meiotic prophase in BDE-209-induced mice, with suppressed γ-H2AX, restored DMC1, RAD51, and crossover marker MLH1 levels, and prevented BDE-209-induced DNA impairment. In addition, vitamin C supplementation also interfered with BDE-209-induced upregulation of testicular H3K4me3 through inhibition of KDM5s capacity and decreasing ferrous ion concentration. Furthermore, ferrous sulfate pretreatment could partially restore the expression of H3K4me3 via maintaining the concentration of ferrous ions. Taken together, vitamin C exerts a potential therapeutic agent for preventing BDE-209-induced reproductive toxicity with meiotic arrest, which is attributed to its antioxidant and electron donor properties, as well as, modulation of ferrous ion levels and demethylation of H3K4me3.

Effect of Trigonella foenum-graecum L. seed extract on the reproductive system of male mice and possible mechanism of its action on spermatogenesis

Fenugreek seed exhibits antidiabetic, antineoplastic, hepatoprotective, antidepressant and immunomodulatory properties. Fenugreek also causes antifertility effects in rodents. However, the impact of fenugreek seed on male reproduction and the possible mode of its action are not properly evaluated. Herein, we examined the effect of aqueous seed extract of fenugreek (FSE) and the possible mechanism of its action on male reproductive health in mice. Parkes mice were orally administered FSE (600 mg/kg body weight/day) or distilled water for 28 and 56 days, respectively. Various sperm parameters, histopathology, serum testosterone level and fertility indices were assessed. Furthermore, steroidogenic enzymes activities, oxidative status and germ cell dynamics in the testis were evaluated. Toxicological endpoints were also assessed. Treatment with FSE caused degenerative changes in the testis histoarchitecture. The treatment also affected various sperm parameters and concentrations of sialic acid and fructose in the epididymis and seminal vesicle, respectively. Fenugreek treatment also had negative impact on oxidative status and germ cell dynamics in the testis; fertility indices were also affected in female mice impregnated by the extract-treated male mice, though libido of the treated male mice remained unaffected. Results show that treatment with FSE caused adverse effects on the male reproductive health and pregnancy outcome in Parkes mice.

Decabromodiphenyl ether initiates mitochondria-dependent apoptosis by disrupting calcium homeostasis in mice livers

Decabromodiphenyl ether (BDE-209) tends to accumulate in lipid-rich tissues and targets the liver since its high lipophilicity. This study aimed to investigate the effects of BDE-209 on mouse liver and reveal the underlying toxicological mechanisms. Here we firstly confirmed that treatment of BDE-209 could lead to an imbalance of redox and promote apoptosis with a mitochondria-dependent manner in mice livers. Next, the transmission electron microscope (TEM) image revealed BDE-209 induced changes in mitochondrial morphology and increased endoplasmic reticulum (ER) - mitochondrial contact. ER stress was involved in the apoptosis process, which was displayed by the enhancive ER stress makers . Finally, from the increased abundance of cellular pivotal Ca²⁺ signals transducer CaM, activating Ca²⁺ release channel Sig-1R and IP3R1, and the stronger fluorescence density of mitochondria-specifically Ca²⁺ labeled probe Rhod-2 in vitro, we summarized that there was overloaded mitochondrial Ca²⁺ in hepatocytes of BDE-209 treated mice. In conclusion, these results partly illustrated evidence to reveal a potential mechanism of BDE-209-induced hepatoxicity, where oxidative stress-induced-ER stress led to the over-release of Ca²⁺, followed by the overloaded mitochondrial Ca²⁺, and cell apoptosis initiated. Our findings provided a theoretical basis for further studying.

Prenatal exposure to environmentally relevant levels of PBDE-99 leads to testicular dysgenesis with steroidogenesis disorders

Polybrominated diphenyl ethers (PBDEs) are a widely used class of brominated flame retardants. Exposure to PBDEs could induce testicular damage in mammals, but the effects and potential mechanism of action of prenatal exposure to environmentally relevant PBDEs on testicular development remain unclear. For the in vivo study, pregnant ICR mice were exposed to environmentally relevant levels of 2,2',4,4',5-pentabromodiphenyl ether (PBDE-99), a major component of commercial PBDE mixtures. We found that the anogenital index and testicular organ coefficient were significantly decreased, the incidence of cryptorchidism was increased, and testicular histology was disturbed in male offspring. Transcriptomic profiling showed that steroidogenesis disorders were significant in all PBDE-99 exposure groups. The testosterone levels, expressions of testosterone regulators, and the number of CYP11A1-positive and 11β-HSD1-positive Leydig cells were significantly decreased after PBDE-99 exposure. For the in vitro study, TM3 Leydig cells were exposed to PBDE-99 at gradient concentrations. Transcriptomic profiling and validation experiments showed that PBDE-99 upregulated reactive oxygen species, activated the ERK1/2 pathway, inhibited the ubiquitination degradation pathway, and finally induced Leydig cell apoptosis. Cumulatively, these findings revealed that prenatal exposure to environmentally relevant levels of PBDE-99 leads to steroidogenesis disorders by inducing the apoptosis of Leydig cells, causing testicular dysgenesis.

Short- and long-term effects of decabromodiphenyl ether (BDE-209) on sediment denitrification using a semi-continuous microcosm

The widespread use of decabromodiphenyl ether (BDE-209) resulted in its deposition in environmental media and biological matrices. However, to date, few studies focused on the effect of BDE-209 on microorganisms, and those available were investigated via an enclosed system completely cutting off the communication between testing system and its native environment. Herein, 4.0 mg/g BDE-209 acute exposure induced a 20% decline of NO_X-N (the sum of NO₃^--N and NO₂^--N) removal efficiency and a significant accumulation of NO₂^--N and N₂O. These inhibitory effects presented in a BDE-209 concentration-dependent manner. Using a semi-continuous microcosm, the inhibitory effects of BDE-209 on denitrification were observed to be significantly enhanced with the extending of exposure duration. Denitrifying genes assay illustrated that BDE-209 has an insignificant effect on the global abundance of denitrifying bacteria because of microbial exchange with its overlying water. But the utilization of electron donor (carbon substrate), the activity of electron transport system and denitrifying enzymes were significantly inhibited by BDE-209 exposure in a exposure-duration-dependent manner. Finally, insufficient electron donor and lower efficiency of electron transport and utilization on denitrifying enzymes deteriorated the denitrification performance. These results provided a new insight into BDE-209 influence on denitrification in the natural environment.

Highly efficient debromination of 4,4'-dibrominated diphenyl ether by organic palygorskite-supported Pd/Fe nanoparticles

Organic palygorskite (OP)-supported Pd/Fe nanoparticles composite (OP-Pd/Fe) was prepared by stepwise reduction method. The removal capacity of 4,4'-dibrominated diphenyl ether (BDE15) by OP-Pd/Fe was compared with other various materials. For better understanding the possible mechanism, the synthesized and reacted OP-Pd/Fe materials were characterized by TEM, SEM, XRD, and XPS, respectively. The effects of major influencing parameters on the degradation of BDE15 were also studied. Benefit from the synergistic effect of the carrier and bimetallic nanoparticles, BDE15 could be completely debrominated into diphenyl ether (DE) under suitable conditions. A two-stage adsorption/debromination removal mechanism was proposed. The degradation of BDE15 with OP-Pd/Fe was mainly stepwise debromination reaction, and hydrogen transfer mode was assumed as the dominated debromination mechanism. The removal process fitted well to the pseudo first-order kinetic equation. The observed rate constants increased with increasing Pd loading and OP-Pd/Fe dosage while decreased with increasing initial BDE15 concentration, the tetrahydrofuran/water ratio, and the initial pH of the solution. The work provides a new approach for the treatment of PBDEs pollution.