2,4-dichlorophenol exposure induces lipid accumulation and reactive oxygen species formation in zebrafish embryos

Effects of 2,4-dichlorophenol on non-specific immunity, histopathological lesions, and redox balance in African Catfish, clarias gariepinus (Burchell, 1822)

The toxic effects of 2, 4-dichlorophenol (2, 4-DCP) on aquatic organisms are well-established; however, the details regarding the mechanisms underlying the toxicity, especially immunotoxicity are poorly understood. Consequently, the aim of this study was to investigate the histopathologic, oxidative stress and immunotoxic effects attributed to exposure to sublethal concentrations of 2,4-DCP in the African catfish, Clarias gariepinus. Juvenile C. gariepinus were exposed to 0.4, 0.8, or 1.6 mg/L 2, 4-DCP for 28 days after which blood and head kidney were extracted for the determination of various nonspecific innate immune parameters while the liver was excised for histopathology examination and measurement of oxidative stress biomarkers. Control fish were maintained in water spiked 10 µL/L ethanol, representing the solvent control. A significant increase was noted in the activities of lactate dehydrogenase and superoxide dismutase as well as in levels of lipid peroxidation and DNA fragmentation in a dose-dependent manner, with higher adverse effects observed at the highest concentration tested (1.6 mg/L). The total white blood cells (WBC) count was significantly elevated in fish exposed to 2,4-DCP compared to control. Myeloperoxidase content was decreased significantly in fish exposed to 2,4-DCP especially at the highest concentration (1.6 mg/L) compared to controls. The respiratory burst activity did not differ markedly amongst groups. Histopathological lesions noted included edema, leucocyte infiltration, and depletion of hemopoietic tissue in the head kidney of exposed fish. There was significant upregulation in the mRNA expression of tumor necrosis factor (TNF-α) and heat shock protein 70 (HSP 70) but downregulation of major histocompatibility complex 2 (MHC 2) in exposed fish. Data demonstrated that exposure to 2,4-DCP resulted in histopathological lesions, oxidative stress, and compromised immune system in C. gariepinus.

Changes in the Transcription of Proliferation- and Apoptosis-Related Genes in Embryos in Women of Different Ages under the Influence of Extracellular Vesicles from Donor Follicular Fluid In Vitro

We studied the influence of extracellular vesicles from the follicular fluid of a young donor on gene expression (MKI67, MYBL2, CCNB1, CCND1, CCNE1, CALM2, BAX, NDRG1, TP53I3, VEGF, VCAN, HAS2, CTSL2, PIBF1, RPL37, PFKP, GPX3, and AQP3) in embryos of women of different ages. According to nanoparticle tracking analysis data, the concentration of extracellular vesicles was 3.75±0.47×1011 particles/ml and the mean particle size was 138.78±9.90 nm. During co-culturing of the follicular fluid extracellular vesicles with blastocysts of young women, we observed significantly increased expression of mRNA for genes CTSL2, CCND1, CCNE1, VEGF and reduced expression of BAX gene mRNA in comparison with embryos in women of late reproductive age. We hypothesized that addition of extracellular vesicles of the oocyte follicular fluid from a young donor to the culture medium of embryos could slow down apoptosis process typical of blastocyst cells in women above 36 years.

Metagenomic insights into the diversity of 2,4-dichlorophenol degraders and the cooperation patterns in a bacterial consortium

2,4-Dichlorophenol, which is largely employed in herbicides and industrial production, is frequently detected in ecosystems and poses risks to human health and environmental safety. Microbial communities are thought to perform better than individual strains in the complete degradation of organic contaminants. However, the synergistic degradation mechanisms of the microbial consortia involved in 2,4-dichlorophenol degradation are still not widely understood. In this study, a bacterial consortium named DCP-2 that is capable of degrading 2,4-dichlorophenol was obtained. Metagenomic analysis, cultivation-dependent functional verification, and co-occurrence network analysis were combined to reveal the primary 2,4-dichlorophenol degraders and the cooperation patterns in the consortium DCP-2. Metagenomic analysis showed that Pseudomonas, Achromobacter, and Pigmentiphaga were the primary degraders for the complete degradation of 2,4-dichlorophenol. Thirty-nine phylogenetically diverse bacterial genera, such as Brucella, Acinetobacter, Aeromonas, Allochromatium and Bosea, were identified as keystone taxa for 2,4-dichlorophenol degradation by keystone taxa analysis of the co-occurrence networks. In addition, a stable synthetic consortium of isolates from DCP-2 was constructed, consisting of Pseudomonas sp. DD-13 and Brucella sp. FZ-1; this synthetic consortium showed superior degradation capability for 2,4-dichlorophenol in both mineral salt medium and wastewater compared with monoculture. The findings provide valuable insights into the practical bioremediation of 2,4-dichlorophenol-contaminated sites.

Associations of dichlorophenol with metabolic syndrome based on multivariate-adjusted logistic regression: a U.S. nationwide population-based study 2003-2016

BACKGROUND

Para-dichlorobenzene (p-DCB) exposure associated with oxidative stress has indeed raised public concerns. However, whether p-DCB is linked with metabolic syndrome (MetS) remains unclear. We hypothesized that higher exposure to p-DCB would be linked with a higher risk of MetS in the U.S population. This study aimed to examine the associations of exposure to p-DCB with MetS prevalence.

METHODS

We included 10,428 participants (5,084 men and 5,344 women), aged ≥ 20 years, from the National Health and Nutrition Examination Survey (2003-2016). The cases of MetS were diagnosed by NCEP/ATPIII. Logistic regression models were conducted to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of MetS prevalence. Moreover, the mix associations of p-DCB metabolites were assessed using quantile sum (WQS) regression and quantile g-computation (qgcomp) methods.

RESULTS

We documented 2,861 (27.1%) MetS cases. After adjustment for the potential risk factors, the ORs (95% CI) of MetS prevalence across the quartile of urinary 2,5-dichlorophenol (2,5-DCP) were 1.09 (0.93-1.28), 1.22 (1.00-1.49), and 1.34 (1.04-1.73). Moreover, 2,5 DCP is significantly associated with a higher prevalence of abdominal obesity [ORQ4vsQ1 (95% CI): 1.23 (1.03-1.48)]. The WQS and qgcomp index also showed significant associations between p-DCB metabolites and MetS. Moreover, we further examined that 2,5 DCP was correlated with higher systolic blood pressure (r = 0.022, P = 0.027), waist circumference (r = 0.099, P < 0.001), and glycohemoglobin (r = 0.027, P = 0.008) and a lower high density cholesterol (r = -0.059, P < 0.001). In addition, the significant positive associations between 2,5 DCP and MetS were robust in the subgroup and sensitivity analyses.

CONCLUSION

These findings indicated that increased urinary p-DCB concentration, especially 2,5 DCP, had a higher MetS prevalence. These results should be interpreted cautiously and further research is warranted to validate our findings.

Cyanobacterial degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D): Its response to the oxidative stress induced by the primary degradation product 2,4-dichlorophenol (2,4-DCP)

Excessive use of herbicides in agricultural fields has become a major environmental concern due to the negative effects on the ecosystem. Microbial degradation has been well-known as an effective approach for combating such non-natural substances in soil. In the present study, the degradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) as a result of metabolic activities of a cyanobacterium Nostoc muscorum Meg 1 was investigated using GC-MS analysis. After seven days of 2,4-D exposure, the main residue obtained was 2,4-dichlorophenol (2,4-DCP) at RT: 8.334 (confirmed using NIST library). The effects of 2,4-DCP were studied in a cyanobacterium Nostoc muscorum Meg 1 isolated from a rice field where 2,4-D is commonly used. Exposure to 2,4-DCP at 20, 40, and 80 ppm significantly increased ROS production in the cyanobacterium by 74, 107, and 211 % (p < 0.001). With rising 2,4-DCP concentrations in the surroundings, lipid peroxidation and protein oxidation in the organism correspondingly increased, indicating cellular injury. The mRNA and protein contents, and also the activities of different oxidant neutralizing enzymes such as CAT, SOD, GR, and GPx and the non-enzymatic antioxidants (proline, GSH, thiol and phytochelatin content) were found augmented in 20 ppm 2,4-DCP exposed cultures. However, in the presence of 40 and 80 ppm 2,4-DCP, most enzymatic and non-enzymatic antioxidants were severely compromised. At higher exposures, the organism's attempt to mitigate the oxidants was still visible, as both proline and TSH levels increased. SEM and TEM analysis aided in visualizing the effects of 2,4-DCP on the morphology and ultrastructures of the organism.

Incorporating Primer Amplification Efficiencies in Quantitative Reverse Transcription Polymerase Chain Reaction Experiments; Considerations for Differential Gene Expression Analyses in Zebrafish

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) is commonly used to measure the mRNA expression of target genes in zebrafish. Gene expression values from RT-qPCR are typically reported as relative fold-changes, and relative quantification of RT-qPCR data incorporates primer amplification efficiency values for each target gene. We describe the influence of the primer amplification efficiency analysis method on RT-qPCR gene expression fold-change calculations. This report describes (1) a sample analysis demonstrating incorporation of primer amplification efficiency into RT-qPCR analysis for comparing gene expression of a gene of interest between two groups when normalized to multiple reference genes, (2) the influence of differences in primer amplification efficiencies between measured genes on gene expression differences calculated from theoretical delta-Cq (dCq) values, and (3) an empirical comparison of the influence of three methods of defining primer amplification efficiency in gene expression analyses (delta-delta-Cq [ddCq], standard curve, LinRegPCR) using mRNA measurements of a set of genes in zebrafish embryonic development. Given the need to account for the influence of primer amplification efficiency along with the simplicity of using software programs (LinRegPCR) to measure primer amplification efficiency from RT-qPCR data, we encourage using empirical measurements of primer amplification efficiency for RT-qPCR analysis of differential gene expression in zebrafish.

Perfluorohexanesulfonic acid (PFHxS) induces oxidative stress and causes developmental toxicities in zebrafish embryos

Perfluorohexanesulfonic acid (PFHxS) is a short-chain perfluoroalkyl substance widely used to replace the banned perfluorooctanesulfonic acid (PFOS) in different industrial and household products. It has currently been identified in the environment and human bodies; nonetheless, the possible toxicities are not well-known. Zebrafish have been used as a toxicant screening model due to their fast and transparent developmental processes. In this study, zebrafish embryos were exposed to PFHxS for five days, and various experiments were performed to monitor the developmental and cellular processes. Liquid chromatography-mass spectrometry (LC/MS) analysis confirmed that PFHxS was absorbed and accumulated in the zebrafish embryos. We reported that 2.5 µM or higher PFHxS exposure induced phenotypic abnormalities, marked by developmental delay in the mid-hind brain boundary and yolk sac edema. Additionally, larvae exposed to PFHxS displayed facial malformation due to the reduction of neural crest cell expression. RNA sequencing analysis further identified 4643 differentiated expressed transcripts in 5 µM PFHxS-exposed 5-days post fertilization (5-dpf) larvae. Bioinformatics analysis revealed that glucose metabolism, lipid metabolism, as well as oxidative stress were enriched in the PFHxS-exposed larvae. To validate these findings, a series of biological experiments were conducted. PFHxS exposure led to a nearly 4-fold increase in reactive oxygen species, possibly due to hyperglycemia and impaired glutathione balance. The Oil Red O' staining and qPCR analysis strengthens the notions that lipid metabolism was disrupted, leading to lipid accumulation, lipid peroxidation, and malondialdehyde formation. All these alterations ultimately affected cell cycle events, resulting in S and G2/M cell cycle arrest. In conclusion, our study demonstrated that PFHxS could accumulate and induce various developmental toxicities in aquatic life, and such data might assist the government to accelerate the regulatory policy on PFHxS usage.

Messenger roles of extracellular vesicles during fertilization of gametes, development and implantation: Recent advances

Extracellular vesicles (EVs) have become a research hotspot in recent years because they act as messengers between cells in the physiological and pathological processes of the human body. It can be produced by the follicle, prostate, embryo, uterus, and oviduct in the reproductive field and exists in the extracellular environment as follicular fluid, semen, uterine cavity fluid, and oviduct fluid. Because extracellular vesicles are more stable at transmitting information, it allows all cells involved in the physiological processes of embryo formation, development, and implantation to communicate with one another. Extracellular vesicles carried miRNAs and proteins as mail, and when the messenger delivers the mail to the recipient cell, the recipient cell undergoes a series of changes. Current research begins with intercepting and decoding the information carried by extracellular vesicles. This information may help us gain a better understanding of the secrets of reproduction, as well as assist reproductive technology as an emerging marker and treatment.

2,4-Dichlorophenol Increases Primordial Germ Cell Numbers via ESR2a-Dependent Pathway in Zebrafish Larvae

Previous studies have reported the feminizing effects of 2,4-dichlorophenol (2,4-DCP) on zebrafish (Danio rerio). However, the effect of 2,4-DCP on the number of primordial germ cells (PGCs), an indicator for early sex differentiation, remains elusive. In the present study, Tg (piwil1:egfp-UTR nanos3) zebrafish (GFP-labeled PGCs) were treated with 2,4-DCP (10, 20, and 40 μg/L) from 5 to 15 days postfertilization to explore the effect on PGC numbers and to elucidate associated molecular mechanisms. The results showed that 2,4-DCP exposure increased PGC numbers, as evidenced by larger GFP fluorescent areas, upregulated expressions of PGC marker genes (vasa and dnd), and raised the female ratio. Notably, the mRNA level of estrogen receptor 2a (esr2a) was also increased subsequently. Moreover, docking studies revealed stable 2,4-DCP interactions with ESR2a, speculating a role of ESR2a signaling pathway in 2,4-DCP toxicity. Furthermore, in esr2a knockout (esr2a^-/-) zebrafish, the effects of 2,4-DCP were considerably minimized, proving the involvement of the ESR2a signaling pathway in the 2,4-DCP-mediated increase in PGC numbers. Dual-luciferase reporter gene assay and point mutation studies demonstrated that 2,4-DCP-stimulated promoter activity was mediated by estrogen response element (ERE) located in -686/-674 of the vasa promoter and -731/-719 of the dnd promoter. Overall, 2,4-DCP can potentially enhance the expression of vasa and dnd by binding to zebrafish ESR2a, thus leading to increased PGC numbers and subsequent female-biased sex differentiation.