Nanoplastics cause transgenerational toxicity through inhibiting germline microRNA mir-38 in C. elegans

Amino-modified nanoplastics at predicted environmental concentrations cause transgenerational toxicity through activating germline EGF signal in Caenorhabditis elegans

In the real environment, some chemical functional groups are unavoidably combined on the nanoplastic surface. Reportedly, amino-modified polystyrene nanoparticles (PS-A NPs) exposure in parents can induce severe transgenerational toxicity, but the underlying molecular mechanisms remain largely unclear. Using Caenorhabditis elegans as the animal model, this study was performed to investigate the role of germline epidermal growth factor (EGF) signal on modulating PS-A NPs' transgenerational toxicity. As a result, 1-10 μg/L PS-A NPs exposure transgenerationally enhanced germline EGF ligand/LIN-3 and NSH-1 levels. Germline RNAi of lin-3 and nsh-1 was resistant against PS-A NPs' transgenerational toxicity, implying the involvement of EGF ligand activation in inducing PS-A NPs' transgenerational toxicity. Furthermore, LIN-3 overexpression transgenerationally enhanced EGF receptor/LET-23 expression in the progeny, and let-23 RNAi in F1-generation notably suppressed PS-A NPs' transgenerational toxicity in the exposed worms overexpressing germline LIN-3 at P0 generation. Finally, LET-23 functioned in neurons and intestine for regulating PS-A NPs' transgenerational toxicity. LET-23 acted at the upstream DAF-16/FOXO within the intestine in response to PS-A NPs' transgenerational toxicity. In neurons, LET-23 functioned at the upstream of DAF-7/DBL-1, ligands of TGF-β signals, to mediate PS-A NPs' transgenerational toxicity. Briefly, this work revealed the exposure risk of PS-A NPs' transgenerational toxicity, which was regulated through activating germline EGF signal in organisms.

Polylactic acid microplastics cause transgenerational reproductive toxicity associated with activation of insulin and hedgehog ligands in C. elegans

As a member of biodegradable plastics, exposure risk of polylactic acid microplastic (PLA-MP) has received attention recently. Toxicity of PLA-MP at parental generation (P0-G) has been observed in some organisms; however, its possible transgenerational toxicity and underlying mechanisms remain unclear. In Caenorhabditis elegans, 10 and 100 μg/L PLA-MP resulted in transgenerational inhibition in reproductive capacity and transgenerational damage on gonad development. Meanwhile, transgenerational increase in germline apoptosis was detected after PLA-MP exposure at P0-G, which was associated with transgenerational dysregulation in expressions of genes governing apoptosis (ced-3, ced-4, egl-1, and ced-9) and DNA damage related genes (cep-1, mrt-2, hus-1, and clk-2). Among secreted ligand genes, PLA-MP exposure induced transgenerational increase in expression of ins-39 and wrt-3, and RNAi of ins-39 and wrt-3 inhibited germline apoptosis in PLA-MP exposed nematodes. Additionally, PLA-MP caused transgenerational increase in expression of met-2 and set-6 encoding histone methylation transferases, and germline apoptosis induced by PLA-MP could be suppressed by RNAi of met-2 and set-6. Dysregulated expressions of some apoptosis and DNA damage related genes caused by PLA-MP were reversed by RNAi of ins-39, wrt-3, met-2, and set-6. Moreover, in PLA-MP exposed animals, expression of ins-39 and wrt-3 could be further inhibited by RNAi of met-2 and set-6. Therefore, PLA-MP potentially induced reproductive toxicity across multiple generations, which was under the control of MET-2 and SET-6 activated ligands of INS-39 and WRT-3.

Transgenerational response of germline histone acetyltransferases and deacetylases to nanoplastics at predicted environmental doses in Caenorhabditis elegans

Nanoplastics could cause toxic effects on organism and their offsprings; however, how this transgenerational toxicity is formed remains largely unclear. We here examined potential involvement of germline histone acetylation regulation in modulating transgenerational toxicity of polyetyrene nanoparticle (PS-NP) in Caenorhabditis elegans. At parental generation (P0-G), PS-NP (1-100 μg/L) decreased expressions of germline cbp-1 and taf-1 encoding histone acetyltransferases, as well as germline expressions of sir-2.1 and hda-3 encoding histone deacetylase. Decrease in these 4 germline genes were also observed in the offspring of PS-NP (1-100 μg/L) exposed nematodes. Germline RNAi of cbp-1, taf-1, sir-2.1 and hda-3 resulted in more severe transgenerational PS-NP toxicity on locomotion and brood size. Meanwhile, in PS-NP exposed nematodes, germline RNAi of cbp-1, taf-1, sir-2.1 and hda-3 increased expression of genes encoding insulin, FGF, Wnt, and/or Notch ligands and expressions of their receptor genes in the offspring. Susceptibility to transgenerational PS-NP toxicity in cbp-1(RNAi), taf-1(RNAi), sir-2.1(RNAi), and hda-3 (RNAi) was inhibited by RNAi of these germline ligands genes. Moreover, histone deacetylase inhibition served as molecular initiating event (MIE) leading to transgenerational toxicity in epigenetic adverse outcome pathway (AOP) for nanoplastics. Our data provided evidence that germline histone acetylation regulation functioned as an important mechanism for transgenerational toxicity of nanoplastics at predicted environmental doses (PEDs) by affecting secreted ligands in organisms.

Nanoplastic at environmentally relevant concentrations induces toxicity across multiple generations associated with inhibition in germline G protein-coupled receptor CED-1 in Caenorhabditis elegans

Nanoplastics at environmentally relevant concentrations (ERCs) could cause transgenerational toxicity on organisms. Caenorhabditis elegans is an important model for the study of transgenerational toxicology of pollutants. Nevertheless, the underlying mechanisms for the control of transgenerational nanoplastic toxicity by germline signals remain largely unclear. In C. elegans, exposure to 1-100 μg/L polystyrene nanoparticle (PS-NP) decreased expression of germline ced-1 encoding a G protein-coupled receptor at parental generation (P0-G). After PS-NP exposure at P0-G, transgenerational decrease in germline ced-1 expression could be detected. Meanwhile, the susceptibility to transgenerational PS-NP toxicity was observed in ced-1(RNAi) animals. After PS-NP exposure at P0-G, germline RNAi of ced-1 increased expressions of met-2 and set-6 encoding histone methylation transferases. The susceptibility of ced-1(RNAi) to transgenerational PS-NP toxicity could be inhibited by RNAi of met-2 and set-6. Moreover, in PS-NP exposed met-2(RNAi) and set-6(RNAi) nematodes, expressions of ins-39, wrt-3, and/or efn-3 encoding secreted ligands were decreased. Therefore, our results demonstrated that inhibition in germline CED-1 mediated the toxicity induction of nanoplastics at ERCs across multiple generations in nematodes.

Comparison of Transgenerational Neurotoxicity between Pristine and Amino-Modified Nanoplastics in C. elegans

Increasing evidence has suggested that nanoplastic pollution has become a global concern. More importantly, transgenerational toxicity can be induced by nanoplastics at predicted environmentally relevant doses (ERDs). Considering that amino modification could increase nanoplastic toxicity, we compared transgenerational neurotoxicity between pristine polystyrene nanoparticle (PS-NP) and amino-modified PS-NP (NH2-PS-NP) in Caenorhabditis elegans. At 0.1-10 μg/L, NH2-PS-NP caused more severe transgenerational toxicity on locomotion and neuronal development. Accompanied with a difference in transgenerational neuronal damage, compared to PS-NP (10 μg/L), NH2-PS-NP (10 μg/L) induced more severe transgenerational activation of mec-4, crt-1, itr-1, and tra-3, which are required for the induction of neurodegeneration. Moreover, NH2-PS-NP (10 μg/L) caused more severe transgenerational inhibition in expressions of mpk-1, jnk-1, dbl-1, and daf-7 than PS-NP (10 μg/L), and RNA interference (RNAi) of these genes conferred susceptibility to the toxicity of PS-NP and NH2-PS-NP on locomotion and neuronal development. NH2-PS-NP (10 μg/L) further caused more severe transgenerational activation of germline ligand genes (ins-3, ins-39, daf-28, lin-44, egl-17, efn-3, and lag-2) than PS-NP (10 μg/L), and RNAi of these ligand genes caused resistance to the toxicity of PS-NP and NH2-PS-NP on locomotion and neuronal development. Our results highlighted more severe exposure risk of amino-modified nanoplastics at ERDs in causing transgenerational neurotoxicity in organisms.

Research Progress on Micro (Nano)Plastics Exposure-Induced miRNA-Mediated Biotoxicity

Micro- and nano-plastics (MNPs) are ubiquitously distributed in the environment, infiltrate organisms through multiple pathways, and accumulate, thus posing potential threats to human health. MNP exposure elicits changes in microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), thereby precipitating immune, neurological, and other toxic effects. The investigation of MNP exposure and its effect on miRNA expression has garnered increasing attention. Following MNP exposure, circRNAs serve as miRNA sponges by modulating gene expression, while lncRNAs function as competing endogenous RNAs (ceRNAs) by fine-tuning target gene expression and consequently impacting protein translation and physiological processes in cells. Dysregulated miRNA expression mediates mitochondrial dysfunction, inflammation, and oxidative stress, thereby increasing the risk of neurodegenerative diseases, cardiovascular diseases, and cancer. This tract, blood, urine, feces, placenta, and review delves into the biotoxicity arising from dysregulated miRNA expression due to MNP exposure and addresses the challenges encountered in this field. This study provides novel insights into the connections between MNPs and disease risk.

Transgenerational Response of Germline Nuclear Hormone Receptor Genes to Nanoplastics at Predicted Environmental Doses in Caenorhabditis elegans

Transgenerational nanoplastic toxicity could be detected in Caenorhabditis elegans after exposure at the parental generation (P0-G); however, the underlying mechanisms remain largely unclear. We aimed to examine the role of germline nuclear hormone receptors (NHRs) in controlling the transgenerational toxicity of polystyrene nanoparticles (PS-NPs) based on gene expression screening and functional analysis. Among germline NHR genes, daf-12, nhr-14, and nhr-47 expressions were increased and nhr-12 expression was decreased by PS-NPs (1 and 10 μg/L). Transgenerational alterations in expressions of these four NHR genes were also induced by PS-NPs (1 and 10 μg/L). RNAi of daf-12, nhr-14, and nhr-47 caused resistance, whereas RNAi of nhr-12 conferred susceptibility to transgenerational PS-NP toxicity. After PS-NP exposure, expressions of ins-3, daf-28, and ins-39 encoding insulin ligands, efn-3 encoding Ephrin ligand, and lin-44 encoding Wnt ligand, as well as expressions of their receptor genes (daf-2, vab-1, and/or mig-1), were dysregulated by the RNAi of daf-12, nhr-14, nhr-47, and nhr-12. Therefore, alteration in certain germline NHRs could mediate the induction of transgenerational nanoplastic toxicity by affecting secreted ligands and their receptors in the offspring of exposed organisms.

Polystyrene nanoparticles strengthen high glucose toxicity associated with alteration in insulin signaling pathway in C. elegans

Using Caenorhabditis elegans as animal model, we investigated the effect of exposure to polystyrene nanoparticles (PS-NPs) in the range of μg/L on high glucose toxicity induction. With lifespan and locomotion behavior as endpoints, we observed that PS-NP (10 and 100 μg/L) enhanced toxicity in 50 mM glucose treated animals. In insulin signaling pathway, expressions of genes encoding insulin receptor (daf-2), kinases (age-1 and akt-1/2), and insulin peptides (ins-9, ins-6, and daf-28) were increased, and expressions of daf-16 and its target of sod-3 were decreased in high glucose treated nematodes followed by PS-NP exposure. Toxicity enhancement in high glucose treated nematodes by PS-NP exposure was inhibited by RNAi of daf-2, age-1, akt-2, akt-1, and 3 insulin peptides genes, but increased by RNAi of daf-16 and sod-3. The resistance of animals with RNAi of daf-2 to toxicity in high glucose treated nematodes followed by PS-NP exposure could be suppressed by RNAi of daf-16. Moreover, in high glucose treated animals followed by PS-NP exposure, daf-2 expression was inhibited by RNAi of ins-6, ins-9, and daf-28. Our data demonstrated the risk of PS-NP exposure in enhancing the high glucose toxicity. More importantly, alteration in expression of genes in insulin signaling pathway was associated with the toxicity enhancement in high glucose treated nematodes followed by PS-NP exposure.

Exosomal miRNA analysis provides new insights into exposure to nanoplastics and okadaic acid

As an emerging environmental pollutant, nanoplastics (NPs) have attracted wide attention in terms of their impact on the ecological environment and human health. Currently, researches on the cytotoxicity of NPs mainly focus on oxidative stress, damage to the cell membrane and organelles, induction of immune response and genotoxicity. Okadaic acid (OA) is the main component of diarrheal shellfish toxin. Based on the previous combined toxicity exploration of polystyrene (PS) NPs and (OA) to human gastric adenocarcinoma (AGS) cells, cell-derived exosomes were extracted and exosomal miRNA profiles were analyzed for the first time in this study. The results showed that the composition of miRNAs varied after the exposure of NPs and OA. Specifically, the expression of miR-1-3p in both PS-Exo and PS-OA-Exo was significantly reduced. And the expression of miR-1248 was upregulated most significantly by comparing the DE miRNAs between PS-Exo and PS-OA-Exo. MiR-1-3p and miR-1248 may be the key genes for the combined toxicity of NPs and OA. After analysis, we found that both the decreased expression of miR-1-3p and the increased expression of miR-1248 can increase the expression of FN1 and affect DNA replication, which was surprisingly consistent with the results of our previous cytotoxicity studies. Since exosomal miRNAs are selectively encapsulated by donor cell, we speculate that the changes of exosomal miRNAs may due to the synchronous changes of intracellular environment and the downregulation of intracellular FN1 may be attributed to decreased expression of miR-1-3p and increased expression of miR-1248 in donor cells. Accordingly, we come to the conclusion that the changes of miRNAs in the exosomes derived from AGS cells after environmental stimulation could reflect the biological effects of donor cells.

Four-week repeated exposure to tire-derived 6-PPD quinone causes multiple organ injury in male BALB/c mice

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) is the ozonation product of tire antioxidant 6-PPD. 6-PPDQ can be detected in different environments, such as roadway runoff and dust. Although 6-PPDQ toxicity has been frequently assessed in aquatic organisms, the possible toxic effects of 6-PPDQ on mammals remain largely unclear. We here aimed to perform systematic assessment to evaluate 6-PPDQ toxicity on multiple organs in mice. Male BALB/c mice were intraperitoneally injected with 6-PPDQ for two exposure modes, single intraperitoneal injection and repeated intraperitoneal injection every four days for 28 days. Serum, liver, kidney, lung, spleen, testis, brain, and heart were collected for injury evaluation by organ index, histopathology analysis and biochemical parameters. In 0.4 and 4 mg/kg 6-PPDQ single injected mice, no significant changes in organ indexes and biochemical parameters were detected, and only moderate pathological changes were observed in organs of liver, kidney, lung, and brain. Very different from this, in 0.4 and 4 mg/kg 6-PPDQ repeated injected mice, we observed the obvious increase in organ indexes of liver, kidney, lung, testis, and brain, and the decrease in spleen index. Meanwhile, the significant pathological changes were formed in liver, kidney, lung, spleen, testis, and brain in 0.4 and 4 mg/kg 6-PPDQ repeated injected mice. Biochemical parameters of liver (alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP)) and kidney (urea and creatinine) were all significantly upregulated by repeated injection with 0.4 and 4 mg/kg 6-PPDQ. After repeated exposure, most of 6-PPDQ was accumulated in liver and lung of mice. Therefore, our results suggested the risk of repeated exposure to 6-PPDQ in inducing toxicity on multiple organs in mice.

Long-term exposure to polystyrene nanoparticles at environmentally relevant concentration causes suppression in heme homeostasis signal associated with transgenerational toxicity induction in Caenorhabditis elegans

Heme homeostasis related signaling participates in inducing a protective response when controlling nanopolystyrene toxic effects in parental generation. However, whether the heme homeostasis signal is involved in regulation of transgenerational toxicity of nanopolystyrene toxicity is still unclear. Herein, with the model organism of Caenorhabditis elegans, 0.1-10 μg/L nanopolystyrene particles (PS-NPs) at 20-nm treatment downregulated glb-18, and the decrease was also discovered in the offspring following PS-NPs exposure. Germline glb-18 RNAi induced susceptive property to transgenerational PS-NPs toxicity, suggesting that a decreased GLB-18 level mediated induction of transgenerational toxicity. Importantly, germline GLB-18 transgenerationally activated the function of intestinal HRG-4 in controlling transgenerational PS-NPs toxicity. In transgenerational toxicity control, HRG-1/ATFS-1/HSP-6 was recognized to be the downstream pathway of HRG-4. Briefly, germline GLB-18 in P0 generation can transgenerationally activate the downstream intestinal HRG-4/HRG-1/ATFS-1/HSP-6 pathway among offspring for controlling the transgenerational toxicity of PS-NPs. Findings in the present work strengthens the possible association of heme homeostasis signal changes with transgenerational nanoplastic toxicity within the organisms.

Exposure to 6-PPD quinone enhances lipid accumulation through activating metabolic sensors of SBP-1 and MDT-15 in Caenorhabditis elegans

Although it has been shown that exposure to 6-PPDQ can cause toxicity on environmental organisms, its possible effects on metabolic state remain largely unclear. We here determined the effect of 6-PPDQ exposure on lipid accumulation in Caenorhabditis elegans. We observed increase in triglyceride content, enhancement in lipid accumulation, and increase in size of lipid droplets in 6-PPDQ (1-10 μg/L) exposed nematodes. This detected lipid accumulation was associated with both increase in fatty acid synthesis reflected by increased expressions of fasn-1 and pod-2 and inhibition in mitochondrial and peroxisomal fatty acid β-oxidation indicated by decreased expressions of acs-2, ech-2, acs-1, and ech-3. The observed lipid accumulation in 6-PPDQ (1-10 μg/L) exposed nematodes was also related to the increase in synthesis of monounsaturated fatty acylCoAs reflected by altered expressions of fat-5, fat-6, and fat-7. Exposure to 6-PPDQ (1-10 μg/L) further increased expressions of sbp-1 and mdt-15 encoding two metabolic sensors to initiate the lipid accumulation and to regulate the lipid metabolism. Moreover, the observed increase in triglyceride content, enhancement in lipid accumulation, and alterations in fasn-1, pod-2, acs-2, and fat-5 expressions in 6-PPDQ exposed nematodes were obviously inhibited by sbp-1 and mdt-15 RNAi. Our observations demonstrated the risk of 6-PPDQ at environmentally relevant concentration in affecting lipid metabolic state in organisms.

Long-term exposure to 6-PPD quinone reduces reproductive capacity by enhancing germline apoptosis associated with activation of both DNA damage and cell corpse engulfment in Caenorhabditis elegans

Recently, 6-PPD quinone (6-PPDQ), a derivative of tire antioxidant 6-PPD, was reported to have acute toxicity for organisms. However, the possible reproductive toxicity of 6-PPDQ is still largely unclear. In this study, the reproductive toxicity of 6-PPDQ after long-term exposure was further investigated in Caenorhabditis elegans. Exposure to 1 and 10 μg/L 6-PPDQ reduced the reproductive capacity. Meanwhile, exposure to 1 and 10 μg/L 6-PPDQ enhanced the germline apoptosis, which was accompanied by upregulation of ced-3, ced-4, and egl-1 expressions and downregulation of ced-9 expression. The observed increase in germline apoptosis in 1 and 10 μg/L 6-PPDQ exposed nematodes was associated with the enhancement in DNA damage and increase in expressions of related genes of cep-1, clk-2, hus-1, and mrt-2. The detected enhancement in germline apoptosis in 1 and 10 μg/L 6-PPDQ exposed nematodes was further associated with the increase in expressions of ced-1 and ced-6 governing the cell corpse engulfment process. Molecular docking analysis indicated the binding potentials of 6-PPDQ with three DNA damage checkpoints (CLK-2, HUS-1, and MRT-2) and corpse-recognizing phagocytic receptor CED-1. Therefore, our data suggested the toxicity on reproductive capacity by 6-PPDQ at environmentally relevant concentrations by enhancing DNA damage- and cell corpse engulfment-induced germline apoptosis in organisms.

Combinational exposure to hydroxyatrazine increases neurotoxicity of polystyrene nanoparticles on Caenorhabditis elegans

Using Caenorhabditis elegans as an animal model, we investigated combinational effect between 2-hydroxyatrazine (HA) and polystyrene nanoparticle (PS-NP) on function and development of D-type motor neurons. Exposure to HA (10 and 100 μg/L) alone caused decreases in body bend, head thrash, and forward turn and increase in backward turn. Exposure to 100 μg/L HA also caused neurodegeneration of D-type motor neurons. Moreover, combinational exposure to HA (0.1 and 1 μg/L) induced enhancement in PS-NP (10 μg/L) toxicity in inhibiting body bend, head thrash, and forward turn, and in increasing backward turn. In addition, combinational exposure to HA (1 μg/L) could result in neurodegeneration of D-type motor neurons in PS-NP (10 μg/L) exposed nematodes. Combinational exposure to HA (1 μg/L) and PS-NP (10 μg/L) increased expressions of crt-1, itr-1, mec-4, asp-3, and asp-4, which govern the induction of neurodegeneration. Moreover, combinational exposure to HA (0.1 and 1 μg/L) strengthened PS-NP (10 μg/L)-induced decreases in glb-10, mpk-1, jnk-1, and daf-7 expressions, which encode neuronal signals regulating response to PS-NP. Therefore, our results demonstrated the effect of combinational exposure to HA and nanoplastics at environmentally relevant concentrations in causing toxic effect on nervous system in organisms.

Paeoniflorin mitigates high glucose-induced lifespan reduction by inhibiting insulin signaling in Caenorhabditis elegans

In organisms, high glucose can cause several aspects of toxicity, including the lifespan reduction. Paeoniflorin is the major component of Paeoniaceae plants. Nevertheless, the possible effect of paeoniflorin to suppress high glucose toxicity in reducing lifespan and underlying mechanism are largely unclear. Thus, in this study, we examined the possible effect of paeoniflorin in suppressing high glucose (50 mM)-induced lifespan reduction and the underlying mechanism in Caenorhabditis elegans. Administration with 16-64 mg/L paeoniflorin could prolong the lifespan in glucose treated nematodes. Accompanied with this beneficial effect, in glucose treated nematodes, expressions of daf-2 encoding insulin receptor and its downstream kinase genes (age-1, akt-1, and akt-2) were decreased and expression of daf-16 encoding FOXO transcriptional factor was increased by 16-64 mg/L paeoniflorin administration. Meanwhile, the effect of paeoniflorin in extending lifespan in glucose treated nematodes was enhanced by RNAi of daf-2, age-1, akt-1, and akt-2 and inhibited by RNAi of daf-16. In glucose treated nematodes followed by paeoniflorin administration, the increased lifespan caused by daf-2 RNAi could be suppressed by RNAi of daf-16, suggesting that DAF-2 acted upstream of DAF-16 to regulate pharmacological effect of paeoniflorin. Moreover, in glucose treated nematodes followed by paeoniflorin administration, expression of sod-3 encoding mitochondrial Mn-SOD was inhibited by daf-16 RNAi, and the effect of paeoniflorin in extending lifespan in glucose treated nematodes could be suppressed by sod-3 RNAi. Molecular docking analysis indicated the binding potential of paeoniflorin with DAF-2, AGE-1, AKT-1, and AKT-2. Therefore, our results demonstrated the beneficial effect of paeoniflorin administration in inhibiting glucose-induced lifespan reduction by suppressing signaling cascade of DAF-2-AGE-1-AKT-1/2-DAF-16-SOD-3 in insulin signaling pathway.

Exposure to polystyrene nanoparticles at predicted environmental concentrations enhances toxic effects of Acinetobacter johnsonii AC15 infection on Caenorhabditis elegans

Nanoplastics and microbial pathogens are both widely distributed in the environment; however, their combined toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the possible effect of exposure to polystyrene nanoparticle (PS-NP) in Acinetobacter johnsonii AC15 (a bacterial pathogen) infected animals. Exposure to PS-NP at the concentrations of 0.1-10 μg/L significantly enhanced the toxicity of Acinetobacter johnsonii AC15 infection on lifespan and locomotion behaviors. In addition, after exposure to 0.1-10 μg/L PS-NP, the accumulation of Acinetobacter johnsonii AC15 in body of nematodes was also increased. Meanwhile, the innate immune response indicated by the increase of antimicrobial gene expressions in Acinetobacter johnsonii AC15 infected nematodes was suppressed by exposure to 0.1-10 μg/L PS-NP. Moreover, expressions of egl-1, dbl-1, bar-1, daf-16, pmk-1, and elt-2 governing the bacterial infection and immunity in Acinetobacter johnsonii AC15 infected nematodes were further inhibited by exposure to 0.1-10 μg/L PS-NP. Therefore, our data suggested the possible exposure risk of nanoplastic at predicted environmental concentrations in enhancing the toxic effects of bacterial pathogens on environmental organisms.

Polylactic acid microparticles in the range of μg/L reduce reproductive capacity by affecting the gonad development and the germline apoptosis in Caenorhabditis elegans

Polylactic acid (PLA) accounts for approximately 45% of the global market of biodegradable plastics. Using Caenorhabditis elegans as an animal model, we examined the effect of long-term exposure to PLA microplastic (MP) on reproductive capacity and the underlying mechanism. Brood size, number of fertilized eggs in uterus, and number of hatched eggs were significantly reduced by exposure to 10 and 100 μg/L PLA MP. Number of mitotic cells per gonad, area of gonad arm, and length of gonad arm were further significantly decreased by exposure to 10 and 100 μg/L PLA MP. In addition, exposure to 10 and 100 μg/L PLA MP enhanced germline apoptosis in the gonad. Accompanied with the enhancement in germline apoptosis, exposure to 10 and 100 μg/L PLA MP decreased expression of ced-9 and increased expressions of ced-3, ced-4, and egl-1. Moreover, the induction of germline apoptosis in PLA MP exposed nematodes was suppressed by RNAi of ced-3, ced-4, and egl-1, and strengthened by RNAi of ced-9. Meanwhile, we did not detect the obvious effect of leachate of 10 and 100 μg/L PLA MPs on reproductive capacity, gonad development, germline apoptosis, and expression of apoptosis related genes. Therefore, exposure to 10 and 100 μg/L PLA MPs potentially reduces the reproductive capacity by influencing the gonad development and enhancing the germline apoptosis in nematodes.

Sulfonate-Modified Polystyrene Nanoparticle at Precited Environmental Concentrations Induces Transgenerational Toxicity Associated with Increase in Germline Notch Signal of Caenorhabditis elegans

Recently, the transgenerational toxicity of nanoplastics has received increasing attention. Caenorhabditis elegans is a useful model to assess the transgenerational toxicity of different pollutants. In nematodes, the possibility of early-life exposure to sulfonate-modified polystyrene nanoparticle (PS-S NP) causing transgenerational toxicity and its underlying mechanisms were investigated. After exposure at the L1-larval stage, transgenerational inhibition in both locomotion behavior (body bend and head thrash) and reproductive capacity (number of offspring and fertilized egg number in uterus) was induced by 1-100 μg/L PS-S NP. Meanwhile, after exposure to 1-100 μg/L PS-S NP, the expression of germline lag-2 encoding Notch ligand was increased not only at the parental generation (P0-G) but also in the offspring, and the transgenerational toxicity was inhibited by the germline RNA interference (RNAi) of lag-2. During the transgenerational toxicity formation, the parental LAG-2 activated the corresponding Notch receptor GLP-1 in the offspring, and transgenerational toxicity was also suppressed by glp-1 RNAi. GLP-1 functioned in the germline and the neurons to mediate the PS-S NP toxicity. In PS-S NP-exposed nematodes, germline GLP-1 activated the insulin peptides of INS-39, INS-3, and DAF-28, and neuronal GLP-1 inhibited the DAF-7, DBL-1, and GLB-10. Therefore, the exposure risk in inducing transgenerational toxicity through PS-S NP was suggested, and this transgenerational toxicity was mediated by the activation of germline Notch signal in organisms.

Activation of FGF signal in germline mediates transgenerational toxicity of polystyrene nanoparticles at predicted environmental concentrations in Caenorhabditis elegans

Nanoplastics in the environment could cause the ecological and health risks. Recently, the transgenerational toxicity of nanoplastic has been observed in different animal models. In this study, using Caenorhabditis elegans as an animal model, we aimed to examine the role of alteration in germline fibroblast growth factor (FGF) signal in mediating the transgenerational toxicity of polystyrene nanoparticle (PS-NP). Exposure to 1-100 μg/L PS-NP (20 nm) induced transgenerational increase in expressions of germline FGF ligand/EGL-17 and LRP-1 governing FGF secretion. Germline RNAi of egl-17 and lrp-1 resulted in resistance to transgenerational PS-NP toxicity, indicating the requirement of FGF ligand activation and secretion in formation of transgenerational PS-NP toxicity. Germline overexpression of EGL-17 increased expression of FGF receptor/EGL-15 in the offspring, and RNAi of egl-15 at F1 generation (F1-G) inhibited transgenerational toxicity of PS-NP exposed animals overexpressing germline EGL-17. EGL-15 functions in both the intestine and the neurons to control transgenerational PS-NP toxicity. Intestinal EGL-15 acted upstream of DAF-16 and BAR-1, and neuronal EGL-15 functioned upstream of MPK-1 to control PS-NP toxicity. Our results suggested the important role of activation in germline FGF signal in mediating the induction of transgenerational toxicity in organisms exposed to nanoplastics in the range of μg/L.

Paeoniflorin attenuates polystyrene nanoparticle-induced reduction in reproductive capacity and increase in germline apoptosis through suppressing DNA damage checkpoints in Caenorhabditis elegans

Due to high sensitivity to environmental exposures, Caenorhabditis elegans is helpful for toxicity evaluation and toxicological study of pollutants. Using this animal model, we investigated the reproductive toxicity of 20 nm polystyrene nanoparticle (PS-NP) in the range of μg/L and the following pharmacological intervention of paeoniflorin. After exposure from L1-larvae to young adults, 10-100 μg/L PS-NP could cause the reduction in reproductive capacity reflected by the endpoints of brood size and number of fertilized eggs in uterus. Meanwhile, the enhancements in germline apoptosis analyzed by AO staining and germline DNA damage as shown by alteration in HUS-1::GFP signals were detected in 10-100 μg/L PS-NP exposed nematodes, suggesting the role of DNA damage-induced germline apoptosis in mediating PS-NP toxicity on reproductive capacity. Following the exposure to 100 μg/L PS-NP, posttreatment with 25-100 mg/L paeoniflorin increased the reproductive capacity and inhibited both germline apoptosis and DNA damage. In addition, in 100 μg/L PS-NP exposed nematodes, treatment with 100 mg/L paeoniflorin modulated the expressions of genes governing germline apoptosis as indicated by the decrease in ced-3, ced-4, an egl-1 expressions and the increase in ced-9 expression. After exposure to 100 μg/L PS-NP, treatment with 100 mg/L paeoniflorin also decreased expressions of genes (cep-1, clk-2, hus-1, and mrt-2) governing germline DNA damage. Molecular docking analysis further demonstrated the binding potential of paeoniflorin with three DNA damage checkpoints (CLK-2, HUS-1, and MRT-2). Therefore, our data suggested the toxicity of PS-NP in the range of μg/L on reproductive capacity after exposure from L1-larvae to young adults, which was associated with the enhancement in DNA damage-induced germline apoptosis. More importantly, the PS-NP-induced reproductive toxicity on nematodes could be inhibited by the following paeoniflorin treatment.

Exposure to 6-PPD Quinone at Environmentally Relevant Concentrations Causes Abnormal Locomotion Behaviors and Neurodegeneration in Caenorhabditis elegans

6-PPD quinone (6-PPDQ) can be transformed from 6-PPD through ozonation. Nevertheless, the potential neurotoxicity of 6-PPDQ after long-term exposure and the underlying mechanism are largely unclear. In Caenorhabditis elegans, we here observed that 0.1-10 μg/L of 6-PPDQ caused several forms of abnormal locomotion behaviors. Meanwhile, the neurodegeneration of D-type motor neurons was observed in 10 μg/L of 6-PPDQ-exposed nematodes. The observed neurodegeneration was associated with the activation of the Ca²⁺ channel DEG-3-mediated signaling cascade. In this signaling cascade, expressions of deg-3, unc-68, itr-1, crt-1, clp-1, and tra-3 were increased by 10 μg/L of 6-PPDQ. Moreover, among genes encoding neuronal signals required for the control of stress response, expressions of jnk-1 and dbl-1 were decreased by 0.1-10 μg/L of 6-PPDQ, and expressions of daf-7 and glb-10 were decreased by 10 μg/L of 6-PPDQ. RNAi of jnk-1, dbl-1, daf-7, and glb-10 resulted in the susceptibility to 6-PPDQ toxicity in decreasing locomotory ability and in inducing neurodegeneration, suggesting that JNK-1, DBL-1, DAF-7, and GLB-10 were also required for the induction of 6-PPDQ neurotoxicity. Molecular docking analysis further demonstrated the binding potential of 6-PPDQ to DEG-3, JNK-1, DBL-1, DAF-7, and GLB-10. Together, our data suggested the exposure risk of 6-PPDQ at environmentally relevant concentrations in causing neurotoxicity in organisms.

Treatment with paeoniflorin increases lifespan of Pseudomonas aeruginosa infected Caenorhabditis elegans by inhibiting bacterial accumulation in intestinal lumen and biofilm formation

Paeoniflorin is one of the important components in Paeoniaceae plants. In this study, we used Caenorhabditis elegans as a model host and Pseudomonas aeruginosa as a bacterial pathogen to investigate the possible role of paeoniflorin treatment against P. aeruginosa infection in the host and the underlying mechanisms. Posttreatment with 1.25–10 mg/L paeoniflorin could significantly increase the lifespan of P. aeruginosa infected nematodes. After the infection, the P. aeruginosa colony-forming unit (CFU) and P. aeruginosa accumulation in intestinal lumen were also obviously reduced by 1.25–10 mg/L paeoniflorin treatment. The beneficial effects of paeoniflorin treatment in increasing lifespan in P. aeruginosa infected nematodes and in reducing P. aeruginosa accumulation in intestinal lumen could be inhibited by RNAi of pmk-1, egl-1, and bar-1. In addition, paeoniflorin treatment suppressed the inhibition in expressions of pmk-1, egl-1, and bar-1 caused by P. aeruginosa infection in nematodes, suggesting that paeoniflorin could increase lifespan of P. aeruginosa infected nematode by activating PMK-1, EGL-1, and BAR-1. Moreover, although treatment with 1.25–10 mg/L paeoniflorin did not show obvious anti-P. aeruginosa activity, the P. aeruginosa biofilm formation and expressions of related virulence genes (pelA, pelB, phzA, lasB, lasR, rhlA, and rhlC) were significantly inhibited by paeoniflorin treatment. Treatment with 1.25–10 mg/L paeoniflorin could further decrease the levels of related virulence factors of pyocyanin, elastase, and rhamnolipid. In addition, 2.5–10 mg/L paeoniflorin treatment could inhibit the swimming, swarming, and twitching motility of P. aeruginosa, and treatment with 2.5–10 mg/L paeoniflorin reduced the cyclic-di-GMP (c-di-GMP) level. Therefore, paeoniflorin treatment has the potential to extend lifespan of P. aeruginosa infected hosts by reducing bacterial accumulation in intestinal lumen and inhibiting bacterial biofilm formation.

Exposure to multi-walled carbon nanotubes causes suppression in octopamine signal associated with transgenerational toxicity induction in C.elegans

Multi-walled carbon nanotube (MWCNT), a kind of carbon-based nanomaterials, has been extensively utilized in a variety of fields. In Caenorhabditis elegans, MWCNT exposure can result in toxicity not only at parental generation (P0-G) but also in the offspring. However, the underlying mechanisms remain still largely unknown. DAF-12, a transcriptional factor (TF), was previously found to be activated and involved in transgenerational toxicity control after MWCNT exposure. In this study, we observed that exposure to 0.1-10 μg/L MWCNTs caused the significant decrease in expression of tbh-1 encoding a tyramine beta-hydroxylase with the function to govern the octopamine synthesis, suggesting the inhibition in octopamine signal. After exposure to 0.1 μg/L MWCNT, the decrease in tbh-1 expression could be also detected in F1-G and F2-G. Moreover, in germline cells, the TF DAF-12 regulated transgenerational MWCNT toxicity by suppressing expression and function of TBH-1. Meanwhile, exposure to 0.1-10 μg/L MWCNTs induced the increase in octr-1 expression and the decrease in ser-6 expression. After exposure to 0.1 μg/L MWCNT, the increased octr-1 expression and the decreased ser-6 expression were further observed in F1-G and F2-G. Germline TBH-1 controlled transgenerational MWCNT toxicity by regulating the activity of octopamine receptors (SER-6 and OCTR-1) in offspring. Furthermore, in the offspring, SER-6 and OCTR-1 affected the induction of MWCNT toxicity by upregulating or downregulating the level of ELT-2, a GATA TF. Taken together, these findings suggested possible link between alteration in octopamine related signals and MWCNT toxicity induction in offspring in organisms.

Caenorhabditis elegans as a Prediction Platform for Nanotechnology-Based Strategies: Insights on Analytical Challenges

Nanotechnology-based strategies have played a pivotal role in innovative products in different technological fields, including medicine, agriculture, and engineering. The redesign of the nanometric scale has improved drug targeting and delivery, diagnosis, water treatment, and analytical methods. Although efficiency brings benefits, toxicity in organisms and the environment is a concern, particularly in light of global climate change and plastic disposal in the environment. Therefore, to measure such effects, alternative models enable the assessment of impacts on both functional properties and toxicity. Caenorhabditis elegans is a nematode model that poses valuable advantages such as transparency, sensibility in responding to exogenous compounds, fast response to perturbations besides the possibility to replicate human disease through transgenics. Herein, we discuss the applications of C. elegans to nanomaterial safety and efficacy evaluations from one health perspective. We also highlight the directions for developing appropriate techniques to safely adopt magnetic and organic nanoparticles, and carbon nanosystems. A description was given of the specifics of targeting and treatment, especially for health purposes. Finally, we discuss C. elegans potential for studying the impacts caused by nanopesticides and nanoplastics as emerging contaminants, pointing out gaps in environmental studies related to toxicity, analytical methods, and future directions.

Long-term exposure to tire-derived 6-PPD quinone causes intestinal toxicity by affecting functional state of intestinal barrier in Caenorhabditis elegans

2-((4-Methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione (6-PPDQ) is the ozonation product of 6-PPD, a commonly used tire preservative. Although the 6-PPDQ has been frequently detected in different environmental ecosystems, its long-term effects on organisms remain still largely unknown. We here used Caenorhabditis elegans as an experimental animal to investigate the toxic effect of prolonged exposure to 6-PPDQ (0.1-100 μg/L). After the exposure, we found that 100 μg/L 6-PPDQ caused the lethality. We further selected concentrations of 0.1-10 μg/L to examine the possible intestinal toxicity induced by 6-PPDQ. Although 0.1-10 μg/L 6-PPDQ could not influence intestinal morphology, the intestinal permeability was significantly enhanced by 1-10 μg/L 6-PPDQ as indicated by erioglaucine disodium staining. In addition, the expression of intestinal fatty acid transporter ACS-22 governing functional state of intestinal barrier was decreased by exposure to 1-10 μg/L 6-PPDQ. Meanwhile, intestinal reactive oxygen species (ROS) production was induced by 0.1-10 μg/L 6-PPDQ and lipofuscin accumulation reflected by intestinal autofluorescence was activated by 1-10 μg/L 6-PPDQ. Accompanied with activation of intestinal oxidative stress, expressions of some anti-oxidation related genes (ctl-2, sod-2, sod-3, and sod-4) were significantly increased by 0.1-10 μg/L 6-PPDQ. Moreover, intestinal RNAi of acs-22 strengthened the susceptibility of nematodes to intestinal toxicity of 6-PPDQ. Therefore, considering that the environmentally relevant concentrations of 6-PPDQ were ≤10 μg/L, our data suggested that long-term exposure to 6-PPDQ at environmentally relevant concentrations potentially results in intestinal toxicity by disrupting functional state of intestinal barrier in organisms.

Polystyrene nanoparticles cause dynamic alteration in mitochondrial unfolded protein response from parents to the offspring in C. elegans

The mitochondrial unfolded protein response (mt UPR) is important for organisms against the toxicity from toxicants and stresses. Polystyrene nanoparticle (PS-NP), one of the emerging pollutants, has aroused increasing concern for its toxicity in the offspring. Nevertheless, the molecular basis for this transgenerational toxicity remains largely unclear. In this study, the role of mt UPR in the induction of transgenerational toxicity was determined in Caenorhabditis elegans (C. elegans) after parental exposure to PS-NP. After exposure to PS-NP (1-100 μg/L), the suppression in mt UPR showed the concentration-dependent in nematodes from P0 generation (P0-G) to F2-G. Moreover, the decreased expression of genes required for controlling mt UPR (atfs-1, dve-1, and ubl-5 genes) were observed from P0-G to F2-G after exposure to PS-NP (1 μg/L). The adverse effects on locomotion and reproductive capacity were more severe over generations in nematodes with RNAi of these three genes, indicating that these genes were involved in controlling transgenerational toxicity. After parental PS-NP exposure (1 μg/L), the mt UPR was significantly inhibited by RNAi of atfs-1, dve-1, and ubl-5, indicating the association between the transgenerational PS-NP toxicity and mt UPR suppression. Additionally, during the transgenerational process, RNAi of atfs-1, dve-1, and ubl-5 enhanced the PS-NP toxicity by suppressing mt UPR, while RNAi of daf-2 encoding an insulin receptor inhibited the PS-NP toxicity by increasing mt UPR. Therefore, our data highlighted the role of inhibition in mt UPR in mediating the transgenerational nanoplastic toxicity in nematodes.

Exposure to Nanoplastic Particles Enhances Acinetobacter Survival, Biofilm Formation, and Serum Resistance

The interaction between nanoplastics and bacteria remains still largely unclear. In this study, we determined the effect of nanopolystyrene particle (NP) on a bacterial pathogen of Acinetobacter johnsonii AC15. Scanning electron microscopy (SEM) analysis indicated the aggregation of NPs from 10 μg/L to 100 μg/L on surface of A. johnsonii AC15, suggesting that A. johnsonii AC15 acted as the vector for NPs. Exposure to 100−1000 μg/L NPs increased the growth and colony-forming unit (CFU) of A. johnsonii AC15. In addition, exposure to 100−1000 μg/L NPs enhanced the amount of formed biofilm of A. johnsonii AC15. Alterations in expressions of 3 survival-related (zigA, basD, and zur), 5 biofilm formation-related (ompA, bap, adeG, csuC, and csuD), and 3 serum resistance-related virulence genes (lpxC, lpxL, and pbpG) were observed after exposure to 1000 μg/L NPs. Moreover, both CFU and survival rate of A. johnsonii AC15 in normal human serum (NHS) were significantly increased by 1−1000 μg/L NPs, suggesting the enhancement in serum resistance of Acinetobacter pathogen by NPs. In the NHS, expressions of 3 survival-related (zigA, basD, and zur), 9 biofilm formation-related (ompA, bap, adeF, adeG, csuA/B, csuC, csuD, csuE, and hlyD), and 3 serum resistance-related virulence genes (lpxC, lpxL, and pbpG) were affected by 1000 μg/L NPs. Expressions of 1 survival-related (zigA), 5 biofilm formation-related (bap, adeG, csuC, csuD, and csuE), and 3 serum resistance-related virulence genes (lpxC, lpxL, and pbpG) were also altered by 10 μg/L NPs after the addition of NHS. Therefore, exposure to NPs in the range of μg/L has the potential to enhance bacterial virulence by increasing their growth, biofilm formation, and serum resistance.

Nanoplastic Exposure at Predicted Environmental Concentrations Induces Activation of Germline Ephrin Signal Associated with Toxicity Formation in the Caenorhabditis elegans Offspring

In nematode Caenorhabditis elegans, exposure to polystyrene nanoparticles (PS-NPs) at predicted environmental concentrations can cause induction of transgenerational toxicity. However, the underlying mechanisms for toxicity formation of PS-NP in the offspring remain largely unknown. In this study, based on high-throughput sequencing, Ephrin ligand EFN-3 was identified as a target of KSR-1/2 (two kinase suppressors of Ras) in the germline during the control of transgenerational PS-NP toxicity. At parental generation (P0-G), exposure to 0.1-10 μg/L PS-NP caused the increase in expression of germline efn-3, and this increase in germline efn-3 expression could be further detected in the offspring, such as F1-G and F2-G. Germline RNAi of efn-3 caused a resistance to transgenerational PS-NP toxicity, suggesting that the activation of germline EFN-3 at P0-G mediated transgenerational PS-NP toxicity. In the offspring, Ephrin receptor VAB-1 was further activated by the increased EFN-3 caused by PS-NP exposure at P0-G, and RNAi of vab-1 also resulted in resistance to transgenerational PS-NP toxicity. VAB-1 acted in both the neurons and the germline to control toxicity of PS-NP in the offspring. In the neurons, VAB-1 regulated PS-NP toxicity by suppressing expressions of DBL-1, JNK-1, MPK-1, and GLB-10. In the germline, VAB-1 regulated PS-NP toxicity by increasing NDK-1 and LIN-23 expressions and decreasing EGL-1 expression. Therefore, germline Ephrin ligand EFN-3 and its receptor VAB-1 acted together to mediate the formation of transgenerational PS-NP toxicity. Our data highlight the important role of activation in germline Ephrin signals in mediating transgenerational toxicity of nanoplastics at predicted environmental concentrations in organisms.

Alteration in Wnt signaling mediates induction of transgenerational toxicity of polystyrene nanoplastics in C. elegans

Polystyrene nanoparticles (PS-NPs) have a potential toxicity on offspring after the exposure. However, the molecular basis for PS-NP in inducing transgenerational toxicity remains largely unknown. In this study, the role and the underlying mechanism of germline Wnt signaling in regulating transgenerational toxicity of PS-NPs were determined using an in vivo animal model of Caenorhabditis elegans. Exposure to PS-NP (1-100 μg/L) increased expression of Wnt ligand LIN-44 and decreased expression of Wnt receptor MIG-1. After the exposure, the transgenerational PS-NP toxicity on locomotion behavior and brood size were inhibited in lin-44(RNAi) nematodes, while enhanced in mig-1(RNAi) nematodes. The resistance to transgenerational PS-NP toxicity induced by RNAi of lin-44 in P0 generation (P0-G) was inhibited by RNAi of mig-1 in F1-G. In addition, after PS-NP exposure, germline RNAi of lin-44 at P0-G could increase the mig-1 expression in F1-G. Exposure to PS-NP (1-100 μg/L) further decreased expressions of Dishevelled proteins of DSH-1/2, increased APC complex component APR-1, and decreased expression of BAR-1/β-catenin. Meanwhile, transgenerational PS-NP toxicity was enhanced by RNAi of dsh-1, dsh-2, or bar-1 and inhibited by RNAi of apr-1, suggesting that the DSH-1/2-APR-1-BAR-1 signaling cascade acted downstream of Wnt receptor MIG-1 to control transgenerational PS-NP toxicity. Moreover, BAR-1 acted upstream of DVE-1 to activate mitochondrial unfolded protein response (mt UPR) against the transgenerational PS-NP toxicity. Our data highlights the potential link between alteration in germline Wnt signaling and induction of transgenerational nanoplastic toxicity in organisms.

Induction of transgenerational toxicity is associated with the activated germline insulin signals in nematodes exposed to nanoplastic at predicted environmental concentrations

Exposure to nanoplastics can induce toxicity on organisms at both parental generation (P0-G) and the offspring. However, the underlying mechanism remains unknown. Using Caenorhabditis elegans as a model organism, exposure to 20-nm polystyrene nanoparticle (PS-NP) (1-100 μg/L) upregulated the expressions of insulin ligands (INS-39, INS-3, and DAF-28), and this increase could be further detected in the offspring after PS-NP exposure. Germline ins-39, ins-3, and daf-28 RNAi induced resistance to transgenerational toxicity of PS-NP, indicating that increase in expression of these three insulin ligands mediated induction of transgenerational toxicity. These three insulin ligands transgenerationally activated function of insulin receptor DAF-2 to control transgenerational toxicity of PS-NP. Exposure to 1-100 μg/L PS-NP further upregulated DAF-2, AGE-1, and AKT-1 expressions and downregulated DAF-16 expression. During transgenerational toxicity control, DAF-16/AKT-1/AGE-1 was identified as downstream signaling cascade of DAF-2. Moreover, transcriptional factor DAF-16 activated two downstream targets of HSP-6 (a mitochondrial UPR marker) and SOD-3 (a mitochondrial SOD) to modulate transgenerational toxicity of PS-NP. Our findings indicate a crucial link between activation of insulin signaling and induction of transgenerational toxicity of nanoplastics at low concentrations in organisms.