Intergenerational toxicity of nonylphenol ethoxylate (NP-9) in Caenorhabditis elegans

Behavioral and molecular neurotoxicity of thermally degraded polystyrene in Caenorhabditis elegans

Microplastics are pervasive environmental contaminants found across diverse ecosystems, inducing toxic effects in a wide range of organisms. However, the neurotoxic effects of thermally degraded polystyrene (T-PS) and its underlying mechanisms remain poorly unexplored. In this study, Caenorhabditis elegans was exposed to environmentally relevant concentrations of T-PS (0.1-100 μg/L), and endpoints including locomotion behaviors, neuronal development, neurotransmitter levels, and gene expression were assessed. Significant alterations in morphology, crystallinity, elemental composition, and functional groups were observed in T-PS compared to virgin polystyrene (V-PS), indicating that thermal degradation modifies the physicochemical properties of V-PS. Exposure to 10-100 μg/L T-PS resulted in a more pronounced decrease in head thrashes, body bends, forward turns, and backward turns compared to V-PS. In transgenic nematodes, T-PS exposure significantly impacted fluorescence intensity and the percentage of worms exhibiting neurodegeneration in serotonergic, cholinergic, dopaminergic, and γ-aminobutyric acid (GABA) neurons. Correspondingly, marked reductions were observed in the levels of dopamine, serotonin, GABA, and choline neurotransmitters, alongside significant declines in neurotransmitter-related gene expression (e.g., dat-1, tph-1, unc-30, and cha-1). Pearson's correlation analysis revealed a significant positive association between these genes and locomotion behaviors. Furthermore, the absence of locomotion behavior impairment in dat-1 (ok157), tph-1 (mg280), unc-30 (e191), and cha-1 (e1152) mutants highlights the pivotal roles of these genes in mediating T-PS-induced neurotoxicity in C. elegans. This study enhances our understanding of the neurotoxic mechanisms of T-PS at environmental concentrations, providing valuable insights into its potential environmental health risks.

Microbiological and toxicity analyses of the synthetic polymer polyhexamethylene guanidine hydrochloride against endodontic microorganisms

Failures in endodontic treatments are common due to microbial resistance in the pulp canal. The study evaluated the in vitro activity of polyhexamethylene guanidine hydrochloride (PHMGH) against endodontic strains, as well as in vivo toxicity. Using minimum inhibitory concentration and minimum bactericidal concentration techniques, PHMGH was effective against all microorganisms, even at low concentrations. At 50.0 µg/mL, it inhibited Enterococcus faecalis; furthermore, when compared to chlorhexidine (CLX), it demonstrated values 19 times lower against Candida albicans. The polymer's activity was also determined by agar diffusion, evaluating products A (calcium hydroxide - Ca(OH)2, as a reference), B (Ca(OH)2 combined with physiological solution, reference with a vehicle), C (PHMGH 6.25%), D (PHMGH 3.125%), E (PHMGH 1.5625%), F (PHMGH 0.78125%), G (PHMGH 6.25% and Ca(OH)2), H (PHMGH 3.125% and Ca(OH)2), I (PHMGH 1.5625% and Ca(OH)2), J (PHMGH 0.78125% and Ca(OH)2), and K (positive control, CLX 0.12%). Products containing PHMGH were more effective than the references against all strains, and C, D, and G were more effective than CLX against Peptostreptococcus anaerobius, Actinomyces naeslundii, and Actinomyces viscosus. According to the fractional inhibitory concentration index, the combination of PHMGH and CLX showed indifference for Peptostreptococcus anaerobius, Actinomyces naeslundii, Actinomyces viscosus and Escherichia coli, antagonism for Candida albicans, and synergy for Enterococcus faecalis. The toxicity of PHMGH at different concentrations was tested in Caenorhabditis elegans and did not show lethality in nematodes, with the LC50 observed only at the highest concentration (100 µg/mL) after two days of exposure. It is suggested that PHMGH exhibited antimicrobial activity against endodontic strains and low toxicity, raising expectations for new preventive and therapeutic products in endodontics.

Meloidogyne incognita genes involved in the repellent behavior in response to ascr#9

Meloidogyne incognita is one of the globally serious plant parasitic nematodes. New control measure is urgently needed to replace the common chemical control method. Ascarosides are pheromones regulating the nematodes' aggregation, avoidance, mating, dispersal and dauer recovery and formation. Ascr#9, one of the ascarosides, exhibits the potential to repel M. incognita. However, the nematode genes involved in the perception of ascr# 9 signal are totally unknown. In this study, the transcriptome of ascr#9-treated second stage M. incognita juveniles (J2s) was analyzed, 44 pathways were significantly affected, multiple ligand-receptor and mucin type O-glycan were induced, and olfactory transduction was disturbed. A total of 11 highly differentially expressed genes involved in neuroactive ligand-receptor interaction and FMRFamide-like peptide related process were identified and knocked down by RNAi. The dispersal rates of M. incognita with three knocked-down genes (flp-14, mgl-1 and ADOR-1) significantly decreased, respectively, when ascr#9 was present. The results demonstrate that flp-14, mgl-1, and ADOR-1 are involved in the dispersal behavior of M. incognita nematodes responding to ascr#9, which promotes the interaction study between ascarosides and M. incognita, and provides new ideas for the prevention and control of M. incognita by using pheromone ascarosides.

Neurotoxicity of tetrabromobisphenol-A-bis(2,3-dibromopropyl ether) through the GABAergic and serotonergic neurotransmission in Caenorhabditis elegans

Tetrabromobisphenol-A-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), a novel additive brominated flame retardant, is being developed for use in polyolefin and copolymers. Despite its emerging application, the neurotoxicity and mechanisms of action of TBBPA-BDBPE remain unexplored. Caenorhabditis elegans was utilized as the model organism to study the neurotoxic effects of TBBPA-BDBPE across environmental concentrations ranging from 0 to 100 μg/L. This investigation focused on various toxicological endpoints such as locomotive behavior, neuronal injury, neurotransmitter transmission, and the regulation of nervous system-related gene expression. Acute exposure to TBBPA-BDBPE at concentrations of 10-100 μg/L significantly impaired nematode movement, indicating potential neurotoxicity. In transgenic nematodes, this exposure also caused damage to γ-aminobutyric acid (GABAergic) and serotonergic neurons, along with notable changes in the levels of GABAergic and serotonergic neurotransmitters. Further molecular studies indicated alterations in neurotransmission-related genes (cat-4, mod-1, unc-25, and unc-47). Molecular docking analysis confirmed the binding affinity of TBBPA-BDBPE to key neurotransmission proteins-CAT-4, MOD-1, UNC-25, and UNC-47. These findings demonstrate that TBBPA-BDBPE exerts neurotoxic effects by impacting GABAergic and serotonergic neurotransmission in nematodes. This study provides new insights into the potential environmental risks of TBBPA-BDBPE.

Photoaged Nanopolystyrene Affects Neurotransmission to Induce Transgenerational Neurotoxicity in Caenorhabditis elegans

Nanopolystyrene (NPS), a frequently employed nanoplastic, is an emerging environmental contaminant known to cause neurotoxicity in various organisms. However, the potential for transgenerational neurotoxic effects, especially from photoaged NPS (P-NPS), remains underexplored. This study investigated the aging of virgin NPS (V-NPS) under a xenon lamp to simulate natural sunlight exposure, which altered the physicochemical characteristics of the NPS. The parental generation (P0) of Caenorhabditis elegans was exposed to environmental concentrations (0.1-100 μg/L) of V-NPS and P-NPS, with subsequent offspring (F1-F4 generations) cultured under NPS-free conditions. Exposure to 100 μg/L P-NPS resulted in more pronounced deterioration in locomotion behavior in the P0 generation compared to V-NPS; this deterioration persisted into the F1-F2 generations but returned to normal in the F3-F4 generations. Additionally, maternal exposure to P-NPS damaged dopaminergic, glutamatergic, and serotonergic neurons in subsequent generations. Correspondingly, there was a significant decrease in the levels of dopamine, glutamate, and serotonin, associated with reduced expression of neurotransmission-related genes dat-1, eat-4, and tph-1 in the P0 and F1-F2 generations. Further analysis showed that the effects of P-NPS on locomotion behavior were absent in subsequent generations of eat-4(ad572), tph-1(mg280), and dat-1(ok157) mutants, highlighting the pivotal roles of these genes in mediating P-NPS-induced transgenerational neurotoxicity. These findings emphasize the crucial role of neurotransmission in the transgenerational effects of P-NPS on locomotion behavior, providing new insights into the environmental risks associated with exposure to photoaged nanoplastics.

Identification of endocrine-disrupting chemicals targeting key DCM-associated genes via bioinformatics and machine learning

Dilated cardiomyopathy (DCM) is a primary cause of heart failure (HF), with the incidence of HF increasing consistently in recent years. DCM pathogenesis involves a combination of inherited predisposition and environmental factors. Endocrine-disrupting chemicals (EDCs) are exogenous chemicals that interfere with endogenous hormone action and are capable of targeting various organs, including the heart. However, the impact of these disruptors on heart disease through their effects on genes remains underexplored. In this study, we aimed to explore key DCM-related genes using machine learning (ML) and the construction of a predictive model. Using the Gene Expression Omnibus (GEO) database, we screened differentially expressed genes (DEGs) and performed enrichment analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to DCM. Through ML techniques combining maximum relevance minimum redundancy (mRMR) and least absolute shrinkage and selection operator (LASSO) logistic regression, we identified key genes for predicting DCM (IL1RL1, SEZ6L, SFRP4, COL22A1, RNASE2, HB). Based on these key genes, 79 EDCs with the potential to affect DCM were identified, among which 4 (3,4-dichloroaniline, fenitrothion, pyrene, and isoproturon) have not been previously associated with DCM. These findings establish a novel relationship between the EDCs mediated by key genes and the development of DCM.

Toxicity of Three Optical Brighteners: Potential Pharmacological Targets and Effects on Caenorhabditis elegans

Optical brighteners (OBs) have become an integral part of our daily lives and culture, with a growing number of applications in various fields. Most industrially produced OBs are derived from stilbene, which has been found in environmental matrices. The main objectives for this work are as follows: first, to identify protein targets for DAST, FB-28, and FB-71, and second, to assess their effects in some behaviors physiologic of Caenorhabditis elegans. To achieve the first objective, each OB was tested against a total of 844 human proteins through molecular docking using AutoDock Vina, and affinities were employed as the main criteria to identify potential target proteins for the OB. Molecular dynamics simulations took and validated the best 25 docking results from two protein databases. The highest affinity was obtained for the Hsp70-1/DAST, CD40 ligand/FB-71, and CD40 ligand/FB-28 complexes. The possible toxic effects that OBs could cause were evaluated using the nematode C. elegans. The lethality, body length, locomotion, and reproduction were investigated in larval stage L1 or L4 of the wild-type strain N2. In addition, transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. The effects on the inhibition of growth, locomotion, and reproduction of C. elegans nematodes exposed to DAST, FB-71, and FB-28 OBs were more noticeable with respect to lethality. Moreover, an interesting aspect in OB was increased the expression of gpx-4 and sod-4 genes associated with oxidative stress indicating a toxic response related to the generation of reactive oxygen species (ROS). In all cases, a clear concentration-response relationship was observed. It is of special attention that the use of OBs is increasing, and their different sources, such as detergents, textiles, plastics, and paper products, must also be investigated to characterize the primary emissions of OBs to the environment and to develop an adequate regulatory framework.

Environmentally persistent free radicals on photoaged nanopolystyrene induce neurotoxicity by affecting dopamine, glutamate, serotonin and GABA in Caenorhabditis elegans

Microplastics are widely detected in the environment and induce toxic effects in various organisms. However, the properties and toxicity associated with environmentally persistent free radicals (EPFRs) in photoaged nanopolystyrene (NPS) remain largely unknown. We investigated the generation of EPFRs on photoaged NPS and their neurotoxicity and underlying mechanism in Caenorhabditis elegans. The results suggested that photoaging induces the generation of EPFRs and reactive oxygen species (O2•-, •OH, and 1O2), which altered the physicochemical properties (morphology, crystallinity, and functional groups) of NPS. Acute exposure to 1 μg/L of NPS-60 (NPS with light irradiation time of 60 d) significantly decreased locomotion behaviors and neurotransmitter contents (e.g., glutamate, serotonin, dopamine, and γ-aminobutyric acid). Treatment with N-acetyl-L-cysteine (NAC) by radical quenching test significantly reduced EPFRs levels on the aged NPS, and the toxicity of NAC-quenching NPS was decreased in nematodes compared to those in photoaged NPS. EPFRs also caused dysfunction of neurotransmission-related gene expression in C. elegans. Thus, EPFRs generated on photoaged NPS contributed to neurotoxicity by affecting dopamine, glutamate, serotonin, and γ-aminobutyric acid neurotransmission. The study highlights the potential risks of photoaged NPS and the contributions of EPFRs to toxicity.

Studies of Endocrine Disruptors: Nonylphenol and Isomers in Biological Models

Certain emerging pollutants are among the most widely used chemicals globally, causing widespread concern in relation to their use in products devoted to cleaniness and asepsis. Nonylphenol ethoxylate (NPEOn) is one such contaminant, along with its degradation product, nonylphenol, an active ingredient presents in nonionic surfactants used as herbicides, cosmetics, paints, plastics, disinfectants, and detergents. These chemicals and their metabolites are commonly found in environmental matrices. Nonylphenol and NPEOn, used, are particularly concerning, given their role as endocrine disruptors chemical and possible neurotoxic effects recorded in several biological models, primarily aquatic organisms. Limiting and detecting these compounds remain of paramount importance. The objective of the present review was to evaluate the toxic effects of nonylphenol and NPEOn in different biological models. Environ Toxicol Chem 2023;00:1-12. © 2023 SETAC.

Introduction of Flavor Chemical Eugenol Attenuating the Synergistic Toxicological Interactions of Flavor Mixtures

The flavor chemicals benzyl alcohol (BEA), phenylethanol (PHA), and cinnamaldehyde (CID) and their binary mixtures have high toxicity sensitivity to the lethal endpoint of Caenorhabditis elegans. Some binary flavor mixtures even have synergistic toxicological interactions. Eugenol (EUG) is closely related to human life and has many special nonlethal effects on organisms. The effect of its introduction on the combined toxicities of flavor mixtures is worth studying. We introduced EUG into three binary (BEA-PHA, BEA-CID, and PHA-CID) and one ternary (BEA-PHA-CID) flavor mixture systems. Five representative mixture rays were selected from each of the four mixture systems using the uniform design ray (UD-Ray) method. The lethal toxicity of each mixture ray to C. elegans was measured at three different exposure volumes (100, 200, and 400 μL), and a dose-effect model was established. The new parameter iSPAN was used to quantitatively characterize the toxicity sensitivity of each chemical and mixture ray. The toxicological interaction of each mixture was evaluated by the toxicological interaction heatmap based on the combination index (CI). It can be seen that all flavor chemicals and their ternary and quaternary mixture rays have high iSPANs, and the highest value is 16.160 (BEA-PHA-CID-EUG-R1 at 400 μL). According to the heatmap and CI, the introduction of EUG attenuates the synergistic toxicological interactions of flavor mixtures, leading to the transformation ofsynergistic interactions in flavor mixtures into additive action and even antagonistic interaction, and the CI value of the antagonistic interaction is up to 1.8494 (BEA-CID-EUG-R4 at 400 μL).

Study on the Combined Toxicities and Quantitative Characterization of Toxicity Sensitivities of Three Flavor Chemicals and Their Mixtures to Caenorhabditis elegans

It was shown that flavor chemicals with high toxicity sensitivities mean that small changes in their effective concentrations can lead to significant changes in toxicity. Flavors are widely used in personal care products. However, our study demonstrated that some flavor chemicals and their mixture rays have high toxicity sensitivities to Caenorhabditis elegans (C. elegans), which may have an impact on human health. In this paper, three flavor chemicals (benzyl alcohol, phenethyl alcohol, and cinnamaldehyde) were used as components of the mixture, and three binary mixture systems were constructed, respectively. Five mixture rays were designed for each mixture system by a direct equipartition ray design method. The lethal toxicities of the three flavor chemicals and mixture rays to C. elegans at three exposure volumes were determined. A new concept (inverse of the negative logarithmic concentration span (iSPAN)) was introduced to quantitatively evaluate the toxicity sensitivity of chemicals or mixture rays, and the combination index (CI) was employed to identify the toxicological interactions in the mixtures. It was shown that the three flavor chemicals as well as the binary mixture rays have a significant concentration-response relationship on the lethality of C. elegans. The iSPAN values of the three flavor chemicals and their mixture rays were larger than 3.000, showing very strong toxicity sensitivity to C. elegans. In mixture systems, the toxicity sensitivities of mixture rays with different mixture ratios were also different at different exposure volumes. In addition, it can be seen from the CI heat map that the toxicological interaction not only shows the mixture ratio dependence but also changes with the different exposure volumes, which implies that the mixtures consisting of flavor chemicals with high toxicity sensitivity have complex toxicological interactions. Therefore, in environmental risk assessment, special attention should be paid to chemicals with high toxicity sensitivities.

Chronic exposure to UV-aged microplastics induces neurotoxicity by affecting dopamine, glutamate, and serotonin neurotransmission in Caenorhabditis elegans

Microplastics are ubiquitous in all environments and exert toxic effects in various organisms. However, the neurotoxicity and underlying mechanisms of long-term exposure to MPs aged under UV radiation remain largely unclear. In this study, Caenorhabditis elegans was treated with 0.1-100 μg/L virgin and aged polystyrene microplastics (PS-MPs) for 10 d, with locomotion behavior, neuronal development, neurotransmitter content, and neurotransmission-related to gene expression as endpoints. Using locomotion behavior as an endpoint, chronic exposure to aged PS-MPs at low concentrations (1 μg/L) caused more severe neurotoxicity than that to virgin PS-MPs. In transgenic nematodes, exposure to 10-100 μg/L aged PS-MPs significantly influenced the fluorescence intensity and percentage of worms with neurodegeneration of dopaminergic, glutamatergic, and serotonergic neurons compared with control. Further investigations showed that the content of glutamate, serotonin, and dopamine was significantly influenced in nematodes chronically exposed to 100 μg/L of aged PS-MPs. Similarly, neurotransmission-related gene (e.g., eat-4, dat-1, and tph-1) expression was also altered in nematodes. These results indicate that aged PS-MPs exert neurotoxicity owing to their effects on dopamine, glutamate, and serotonin neurotransmission. This study provides insights into the underlying mechanisms and potential risks of PS-MPs after UV radiation.

The aqueous extract of Fridericia chica grown in northern Colombia ameliorates toxicity induced by Tergitol on Caenorhabditis elegans

The aqueous extract of fallen leaves from Fridericia chica (Bonpl.) L.G. Lohmann is utilized as a remedy in communities at northern Colombia. Traditional uses include wound healing, gastrointestinal inflammation, leukemia and psoriasis, among others. The aims of this research were to evaluate the potential of the aqueous extract of fallen leaves of F. chica (AEFchica) to inhibit ethoxylated nonylphenol (Tergitol)-induced toxicity in Caenorhabditis elegans; and to identify its main components. The pharmacological properties of AEFchica was evaluated using a Tergitol-induced toxicity model in Caenorhabditis elegans. Lethality, locomotion, reproduction, and DAF-16 nuclear translocation were quantified. The chemical composition of AEFchica was carried out using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. AEFchica induced very little lethality on C. elegans (5.6%) even at high concentrations (10,000 μg/mL). The extract had no effect on locomotion impairing induced by ethoxylated nonylphenol. However, AEFchica (1000 μg/mL) abrogated Tergitol-induced mortality, recovering up to 53.3% of the nematodes from lethality induced by 10 mM Tergitol. Similarly, it also blocked Tergitol-dependent reproduction inhibition (82.1% recovery), as well as DAF-16 nuclear translocation (>95%), suggesting a prominent role on oxidative stress control. The chemical analysis indicated the presence of a great variety of molecules with known antioxidant, metabolic and immune modulator properties, such as hydroxylated methoxy flavones, N-methyl-1-deoxynojirimycin, and rehmaionoside A. In short, the aqueous extract of F. chica protects C. elegans from the deleterious effects of Tergitol on lethality, reproduction and oxidative stress involving DAF-16-mediated pathway. This extract is a promising source of bioactive phytochemicals for multi-target pharmacological purposes.