Study on the reproductive toxicity and mechanism of tri-n-butyl phosphate (TnBP) in Caenorhabditis elegans

Bioactivity assessment of organophosphate flame retardants via a dose-dependent yeast functional genomics approach

Organophosphate flame retardants (OPFRs) have been widely detected in multiple environment media and have many adverse effects with complex toxicity mechanisms. However, the early molecular responses to OPFRs have not been fully elucidated, thereby making it difficult to assess their risks accurately. In this work, we systematically explored the point of departure (POD) of biological pathways at genome-wide level perturbed by 14 OPFRs with three substituents (alkyl, halogen, and aryl) using a dose-dependent functional genomics approach in Saccharomyces cerevisiae at 24 h exposure. Firstly, our results demonstrated that the overall biological potency at gene level (PODDRG20) ranged from 0.013 to 35.079 μM for 14 OPFRs, especially the tributyl phosphate (TnBP) exhibited the strongest biological potency with the least PODDRG20. Secondly, we found that structural characteristics of carbon number and logKow were significantly negatively correlated with POD, and carbon number and logKow also significantly affected lipid metabolism associated processes. Thirdly, these early biological pathways of OPFRs toxification were found to be involved in lipid metabolism, oxidative stress, DNA damage, MAPK signaling pathway, and amino acid and carbohydrate metabolism, among which the lipid metabolism was the most sensitive molecular response perturbed by most OPFRs. More importantly, we identified one resistant mutant strain with knockout of ERG2 (YMR202W) gene participated in steroid biosynthesis pathway, which can serve as a key yeast strain of OPFRs toxification. Overall, our study demonstrated an effective platform for accurately assessing OPFRs risks and provided a basis for further green OPFRs development.

Viral inactivation for pH-sensitive antibody formats such as multi-specific antibodies

Recently developed multi-specific antibody formats enable new therapeutic concepts. Conveniently, formats with an Fc domain allow purification in well-established mAb platform processes. However, due to the structural complexity of the formats, the assembled molecules may be sensitive to extreme pH commonly used for viral inactivation. An alternative to low pH incubation for virus inactivation is the use of a mixture of tri-n-butyl phosphate (TnBP, solvent) and Polysorbate 80 (PS80, detergent). While TnBP is toxic, this combination has a long history of use in the manufacturing of human plasma-derived products that are sensitive to low or high pH incubation. Data are provided demonstrating that the solvent/detergent (S/D) treatment using TnBP and PS80 can be successfully used for pH-sensitive, multi-specific antibody formats in the clarified cell culture fluid (CCCF). A different placement of the S/D within the purification process, namely during the capture by Protein A (PA), has been evaluated. This alternative placement allows effective viral inactivation by S/D while preserving the viral reduction and viral inactivation achieved through the PA step itself, enabling the cumulation of these effects. Furthermore, the process alternative simplifies the liquid handling by reducing the added volumes of the required S/D liquids, thus reducing the amount of toxic TnBP to a minimum. Data are shown demonstrating a complete removal of TnBP and PS80 in the process.

Cadmium-induced reproductive toxicity combined with a correlation to the oogenesis process and competing endogenous RNA networks based on a Caenorhabditis elegans model

Accumulation of the heavy metal Cadmium (Cd) in the ovaries and placenta can affect the structure and function of these organs and induce female reproductive toxicity. This toxicity may be due to Cd's similarity to estrogen and its ability to disrupt endocrine systems. However, the exact molecular mechanism by which Cd causes reproductive toxicity at the transcriptome level remains poorly understood. Hence, this study aimed to observe Cd-induced reproductive damage at the gene level, scrutinize the repercussions of Cd exposure on oogenesis, and explicate the putative pathogenesis of Cd-induced oogenesis based on Caenorhabditis elegans (C. elegans) as an in vivo model. The results showed that Cd exposure significantly decreased the number of offspring and prolonged the reproductive span of C. elegans. Cd exposure also reduced the number of cells in mitosis and the pachytene and diakinesis stages of meiosis, thereby disrupting oogenesis. Combined with transcriptional sequencing and bioinformatics analysis, a total of 3167 DEmRNAs were identified. Regarding gene expression, cul-6, mum-2, and vang-1 were found to be related to Cd-induced reproductive toxicity, and their competing endogenous RNA networks were constructed. We observed that mutations of mom-2 and vang-1 in the Wnt pathway could induce susceptibility to Cd-caused meiosis injury. In conclusion, the results indicated that Cd could impair the oogenesis of C. elegans and the Wnt pathway might serve as a protective mechanism against Cd reproductive toxicity. These findings contribute to a better understanding of the damaging effects and molecular biological mechanisms of Cd on the human reproductive system.

Effects of tri-n-butyl phosphate (TnBP) on neurobehavior of Caenorhabditis elegans

As an emerging flame retardant, organic phosphate flame retardants have been extensively used worldwide. The aim of this study is to determine the effects of TnBP on neurobehavior of Caenorhabditis elegans (C. elegans) and its mechanisms. L1 larvae of wild-type nematodes (N2) were exposed to TnBP of 0, 0.1, 1, 10, and 20 mg/L for 72 hours. Then, we observed that the body length and body width were inhibited, the head swings were increased, the pump contractions and chemical trend index were reduced, the production of reactive oxygen species (ROS) was increased, and the expression of mitochondrial oxidative stress related genes (mev-1 and gas-1) and P38 MAPK signal pathway-related genes (pmk-1, sek-1, and nsy-1) was altered. After reporter gene strains BZ555, DA1240, and EG1285 were exposed to TnBP of 0, 0.1, 1, 10, and 20 mg/L for 72 hours, the synthesis of dopamine, glutamate, and Gamma-Amino Butyric Acid (GABA) was increased. In addition, the pmk-1 mutants (KU25) led to the sensitivity of C. elegans to TnBP in terms of head swings. The results showed that TnBP had harmful effects on the neurobehavior of C. elegans, oxidative stress might be one of the mechanisms of its neurotoxicity, and P38 MAPK signal pathway might play an important regulatory role in this process. The results revealed the potential adverse effects of TnBP on the neurobehavior of C. elegans.

Maternal exposure to organophosphate flame retardants and neonatal anthropometric measures

BACKGROUND

Organophosphate flame retardants (OPFRs) are widely used as flame retardants and plasticizers. Laboratory evidence has suggested that maternal OPFR exposure may adversely affect fetal growth, but the epidemiological data are limited.

OBJECTIVES

To investigate the association of maternal OPFR exposure with neonatal anthropometric measures.

METHODS

This study included 354 mother-newborn pairs from the Laizhou Wan Birth Cohort (LWBC), China. Ten OPFR metabolites were measured in maternal urine samples collected before delivery. Neonatal anthropometric data was collected from medical records and standardized into z-scores using the WHO standards (2007), including the weight-for-age (WAZ), length-for-age (LAZ), body mass index-for-age (BMIZ), weight-for-length (WLZ), and head circumference-for-age z-score (HCZ). Multiple linear regression and weighted quantile sum (WQS) regression were used to estimate the associations of individual OPFR metabolites and their mixtures with neonatal anthropometrics, respectively. Stratified analysis by sex was performed.

RESULTS

The detection rates of BCEP, DPHP, BCIPP, BDCIPP, BBOEP, DnBP and DiBP were above 60%, with median concentrations ranging from 0.14 to 3.60 μg/g creatinine. Most OPFR metabolites (i.e., BCIPP, BDCIPP, DiBP, DnBP, or BBOEP) were associated with decreased offspring WAZ and HCZ. When using WQS analysis, the OPFR metabolite mixture was inversely associated with the WAZ, BMIZ and HCZ, whereas DnBP had the highest weights. After stratified by gender, the negative associations were more pronounced among males.

CONCLUSIONS

Maternal OPFR exposure was negatively associated with offspring WAZ, BMIZ, and HCZ, and males seemed to be more vulnerable to the developmental toxicity of certain OPFRs.

Multi-generation reproductive toxicity of RDX and the involved signal pathways in Caenorhabditis elegans

As one of the most frequently used explosives, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) can cause persistent pollution in the environment, leading to the potential ecological threat crossing the generations. In this study, we employed Caenorhabditis elegans to explore the toxic effects of RDX on the parental and offspring worms and the involved signaling pathways. Exposure up to 1000 ng/mL of RDX produced a significant increase in reactive oxygen species (ROS) production, germ cell apoptosis, and decrease in eggs laid. Various mutants were used to demonstrate the RDX-induced apoptosis signaling pathway, and the metabolism of RDX in the nematodes was found related to cytochrome P450 and GST through RNA sequencing. Exposure of parental worms to RDX produced significant reproductive toxicity in F1 and F2, but was recovered in F3 and F4. The transgenerational effects were associated with the decreased expression of met-2, spr-5, and set-2. Our findings revealed the signaling pathways related to the reproductive toxicity caused by RDX in C. elegans and their future generations, which provided the basis for further exploration of the ecological risks of energetic compounds in the environment.

Exposure to environmentally relevant concentrations of TnBP results in tissue-specific bio-accumulation and inhibits growth of silver carp (Hypophthalmichthys molitrix)

Tri-n-butyl phosphate (TnBP) is commonly used as flame retardant and rubber plasticizer, and has been widely detected in aquatic organisms and natural waters. However, the potential toxicity of TnBP in fish remains unclear. In the present study, silver carp (Hypophthalmichthys molitrix) larvae were treated with environmentally relevant concentrations (100 or 1000 ng/L) of TnBP for 60 d and then they were depurated in clean water for 15 d, and the accumulation and depuration of the chemical in six tissues of silver carp were measured. Furthermore, effects on growth were evaluated and potential molecular mechanisms were explored. Results indicated that TnBP could be rapidly accumulated and depurated in silver carp tissues. In addition, the bio-accumulation of TnBP displayed tissue-specificity, where intestine contained the greatest and vertebra had the smallest level of TnBP. Furthermore, exposure to environmentally relevant concentrations of TnBP led to time- and concentration-dependent growth inhibition of silver carp, even though TnBP was completely depurated in tissues. Mechanistic studies suggested that exposure to TnBP up- and down-regulated the expression of ghr and igf1 in liver, respectively, and increased GH contents in plasma of silver carp. TnBP exposure also up-regulated the expression of ugt1ab and dio2 in liver, as well as decreased T4 contents in plasma of silver carp. Our findings provide direct evidence of health hazards of TnBP to fish in natural waters, calling for more attention of environmental risks of TnBP in aquatic environment.

Human exposure to organophosphate esters in water and packed beverages

Drinks are an essential part of human diet, which makes them a source of human exposure to plasticizers such as organophosphate esters (OPEs). The current study provides new information about sixteen OPE levels in 75 different samples (tap water, packed water, cola drinks, juice, wine and hot drinks). Tap water mean levels (40.9 ng/L) were statistically higher than packed water mean levels (4.82 ng/L), mainly due to the contribution of tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2-butoxyethyl) phosphate (TBOEP) that may come from PVC water pipes. Over 90% of samples presented at least one OPE, where regular cola drinks had the highest mean concentrations (2876 ng/L). There was a significantly higher presence of OPEs in added sugar beverages than sugar free drinks, especially for 2-ethylhexyl diphenyl phosphate (EHDPP), which might be related not only to packaging materials but to the added sugar content. Estimated daily intakes (EDIs) in normal and high-exposure scenarios were 2.52 ng/kg bw/day and 7.43 ng/kg bw/day, respectively. Human risk associated with beverages ingestion showed regular cola drinks, juice and tap water as the groups with the highest hazard quotients (HQs). Although OPE exposure was below to safety limits, it should be noted that EHDPP values for regular cola group must be cause of concern, and other routes of exposure such as food ingestion or air inhalation should be also considered.

Transgenerational reproductive toxicity of 2,4,6-trinitrotoluene (TNT) and its metabolite 4-ADNT in Caenorhabditis elegans

2,4,6-trinitrotoluene (TNT) as an energetic compound widely used in military applications has aroused great concerns in recent years due to its large-scale contamination in soil and water; however, its toxicity is still largely unknown. In this study, we investigated the reproductive toxicity and the transgenerational effects of TNT on Caenorhabditis elegans (C. elegans). Our data showed that exposure to TNT at concentrations ranging from 10 to 100 ng/mL resulted in decreasing the lifespan, brood size, number of oocytes and eggs in uterus, while increasing the number of germ cell apoptosis in C. elegans. The apoptotic effects of TNT were blocked in mutants of cep-1 (w40), egl-1 (n487), and hus-1 (op241), indicating conserved genotoxic response genes was involved in mediating TNT-induced germ cell apoptosis. Parental exposure to TNT significantly increased the germ cell apoptosis from P0 to F2 generation, but the toxicity faded away in F3 and F4 generations. Furthermore, TNT was rapidly metabolized in P0, and the accumulation of 4-aminodinitrotoluene (4-ADNT), the main metabolite of TNT in C. elegans, showed a significant decrease from P0 to F1 and a slow decrease in the subsequent generations. Our results demonstrated that ingested TNT can cause severe transgenerational reproductive toxicity and be rapidly converted to 4-ADNT in the nematodes. These data provided basis for future studies on the effects of energetic compounds across generations.