Nanoparticles Induced Oxidative Damage in Reproductive System and Role of Antioxidants on the Induced Toxicity

Nanotechnology is used in a variety of scientific, medical, and research domains. It is significant to mention that there are negative and severe repercussions of nanotechnology on both individuals and the environment. The toxic effect of nanoparticles exerted on living beings is termed as nanotoxicity. Nanoparticles are synthesized by various methods such as chemical, biological, physical, etc. These nanoparticles’ nanotoxicity has been observed to vary depending on the synthesis process, precursors, size of the particles, etc. Nanoparticles can enter the cell in different ways and can cause cytotoxic effects. In this review, the toxicity caused in the reproductive system and the role of the antioxidants against the nanotoxicity are briefly explained.

Integrating multi-omics and regular analyses identifies the molecular responses of zebrafish brains to graphene oxide: Perspectives in environmental criteria

With the broad application of nanoparticles, nanotoxicology has attracted substantial attention in environmental science. However, the methods for detecting few and targeted genes or proteins, even single omics approaches, may miss other responses, including the major responses induced by nanoparticles. To determine the actual toxicological mechanisms of zebrafish brains induced by graphene oxide (GO, a popular carbon-based nanomaterial applied in various fields) at nonlethal concentrations, multi-omics and regular analyses were combined. The biomolecule responses were remarkable, although GO was not obviously observed in brain tissues. The trends for gene and protein changes were the same and accounted for 3.53% and 5.36% of all changes in the genome and proteome, respectively, suggesting a limitation of single omics analysis. Transcriptomics and proteomics analyses indicated that GO affected the functions or pathways of the troponin complex, actin cytoskeleton, monosaccharide transmembrane transporter activity, oxidoreductase activity and focal adhesion. Both metabolomics and proteomics revealed mitochondrial dysfunction and disruption of the citric acid cycle. The integrated analysis of omics, transmission electron microscopy and immunostaining confirmed that GO induced energy disruptions and mitochondrial damage by downregulating tubulin. The combination of multi-omics and regular analyses provides insights into the actual and highly influential mechanisms underlying nanotoxicity.

Combinational effect of titanium dioxide nanoparticles and nanopolystyrene particles at environmentally relevant concentrations on nematode Caenorhabditis elegans

The possible adverse effects of nanoplastics have received the great attention recently; however, their effects at environmentally relevant concentration on organisms are still largely unclear. We here employed Caenorhabditis elegans to investigate the combinational effects of titanium dioxide nanoparticles (TiO₂-NPs) and nanopolystyrene particles at environmentally relevant concentrations on organisms. In wild-type nematodes, prolonged exposure to nanopolystyrene particles (1 μg/L) could enhance the toxicity of TiO₂-NPs (1 μg/L) in decreasing locomotion behavior and in inducing intestinal reactive oxygen species (ROS) production. Meanwhile, combinational exposure to TiO₂-NPs (1 μg/L) and nanopolystyrene particles (1 μg/L) altered the molecular basis for oxidative stress in wild-type nematodes. Moreover, prolonged exposure to nanopolystyrene particles (0.1 μg/L) could further enhance the toxicity of TiO₂-NPs (1 μg/L) in decreasing locomotion behavior and in inducing intestinal ROS production in sod-3 mutant nematodes. Our data suggest the potential role of nanopolystyrene particles at environmentally relevant concentrations in enhancing the toxicity of ENMs in the environment.

Developmental basis for intestinal barrier against the toxicity of graphene oxide

BACKGROUND

Intestinal barrier is crucial for animals against translocation of engineered nanomaterials (ENMs) into secondary targeted organs. However, the molecular mechanisms for the role of intestinal barrier against ENMs toxicity are still largely unclear. The intestine of Caenorhabditis elegans is a powerful in vivo experimental system for the study on intestinal function. In this study, we investigated the molecular basis for intestinal barrier against toxicity and translocation of graphene oxide (GO) using C. elegans as a model animal.

RESULTS

Based on the genetic screen of genes required for the control of intestinal development at different aspects using intestine-specific RNA interference (RNAi) technique, we identified four genes (erm-1, pkc-3, hmp-2 and act-5) required for the function of intestinal barrier against GO toxicity. Under normal conditions, mutation of any of these genes altered the intestinal permeability. With the focus on PKC-3, an atypical protein kinase C, we identified an intestinal signaling cascade of PKC-3-SEC-8-WTS-1, which implies that PKC-3 might regulate intestinal permeability and GO toxicity by affecting the function of SEC-8-mediated exocyst complex and the role of WTS-1 in maintaining integrity of apical intestinal membrane. ISP-1 and SOD-3, two proteins required for the control of oxidative stress, were also identified as downstream targets for PKC-3, and functioned in parallel with WTS-1 in the regulation of GO toxicity.

CONCLUSIONS

Using C. elegans as an in vivo assay system, we found that several developmental genes required for the control of intestinal development regulated both the intestinal permeability and the GO toxicity. With the focus on PKC-3, we raised two intestinal signaling cascades, PKC-3-SEC-8-WTS-1 and PKC-3-ISP-1/SOD-3. Our results will strengthen our understanding the molecular basis for developmental machinery of intestinal barrier against GO toxicity and translocation in animals.

Toxicity evaluation of Wanzhou watershed of Yangtze Three Gorges Reservior in the flood season in Caenorhabditis elegans

Three Gorges Reservoir (TGR) in the upper stream of Yangtze River in China is a reservoir with the largest and the longest yearly water-level drop. Considering the fact that most of safety assessments of water samples collected from TGR region were based on chemical analysis, we here employed Caenorhabditis elegans to perform in vivo safety assessment of original surface water samples collected from TGR region in the flood season in Wanzhou, Chongqing. Among the examined five original surface water samples, only exposure to original surface water sample collected from backwater area could induce the significant intestinal ROS production, enhance the intestinal permeability, and decrease the locomotion behavior. Additionally, exposure to original surface water sample collected from backwater area altered the expressions of sod-2, sod-5, clk-1, and mev-1. Moreover, mutation of sod-2 or sod-5 was susceptible to the potential toxicity of original surface water sample collected from backwater area on nematodes. Together, our results imply that exposure to surface water sample from the backwater area may at least cause the adverse effects on intestinal function and locomotion behavior in nematodes.

Identification of interneurons required for the aversive response of Caenorhabditis elegans to graphene oxide

BACKGROUND

So far, how the animals evade the environmental nanomaterials is still largely unclear. In this study, we employed in vivo assay system of Caenorhabditis elegans to investigate the aversive behavior of nematodes to graphene oxide (GO) and the underlying neuronal basis.

RESULTS

In this assay model, we detected the significant aversive behavior of nematodes to GO at concentrations more than 50 mg/L. Loss-of-function mutation of nlg-1 encoding a neuroligin with the function in connecting pre- and post-synaptic neurons suppressed the aversive behavior of nematodes to GO. Moreover, based on the neuron-specific activity assay, we found that the NLG-1 activity in AIY or AIB interneurons was required for the regulation of aversive behavior to GO. The neuron-specific activities of NLG-1 in AIY or AIB interneurons were also required for the regulation of GO toxicity.

CONCLUSIONS

Using nlg-1 mutant as a genetic tool, we identified the AIY and AIB interneurons required for the regulation of aversive behavior to GO. Our results provide an important neuronal basis for the aversive response of animals to environmental nanomaterials.

Long-term exposure to thiolated graphene oxide in the range of μg/L induces toxicity in nematode Caenorhabditis elegans

The in vivo toxicity and translocation of thiolated graphene oxide (GO-SH) are still largely unclear. We hypothesized that long-term exposure to GO-SH may cause the adverse effects on environmental organisms. We here employed in vivo assay system of Caenorhabditis elegans to investigate the possible toxicity and translocation of GO-SH after long-term exposure. In wild-type nematodes, we observed that prolonged exposure to GO-SH at concentrations>100μg/L resulted in the toxicity on functions of both primary targeted organs such as the intestine and secondary targeted organs such as the neurons and the reproductive organs. The severe accumulation of GO-SH was further detected in the body of wild-type nematodes. The translocation of GO-SH into secondary targeted organs such as reproductive organs through intestinal barrier might be associated with the enhancement in intestinal permeability in GO-SH exposed wild-type nematodes. Prolonged exposure to GO-SH (100μg/L) decreased the expression of gas-1 encoding a subunit of mitochondrial complex I, and mutation of gas-1 caused the formation of GO-SH toxicity at concentration>10μg/L and more severe accumulation of GO-SH in the body of animals. Therefore, our results confirm the possibility for prolonged exposure to GO-SH in inducing adverse effects on nematodes. Our data highlight the potential adverse effects of GO-SH in the range of μg/L on environmental organisms after long-term exposure.

Molecular basis for oxidative stress induced by simulated microgravity in nematode Caenorhabditis elegans

Caenorhabditis elegans is an important in vivo assay system for toxicological studies. Herein, we investigated the role of oxidative stress and the underlying molecular mechanism for induced adverse effects of simulated microgravity. In nematodes, simulated microgravity treatment induced a significant induction of oxidative stress. Genes (mev-1, gas-1, and isp-1) encoding a molecular machinery for the control of oxidative stress were found to be dysregulated in simulated microgravity treated nematodes. Meanwhile, genes (sod-2, sod-3, sod-4, sod-5, aak-2, skn-1, and gst-4) encoding certain antioxidant defense systems were increased in simulated microgravity treated nematodes. Mutation of mev-1, gas-1, sod-2, sod-3, aak-2, skn-1, or gst-4 enhanced susceptibility to oxidative stress induced by simulated microgravity, whereas mutation of isp-1 induced a resistance to oxidative stress induced by simulated microgravity. Mutation of sod-2, sod-3, or aak-2 further suppressed the recovery effect of simulated microgravity toxicity in nematodes after simulated microgravity treatment for 1h. Moreover, administration of ascorbate could inhibit the adverse effects including the induction of oxidative stress in simulated microgravity treated nematodes. Mutation of any of the genes encoding metallothioneins or the genes of hsp-16.1, hsp-16.2 and hsp-16.48 encoding heat-shock proteins did not affect the induction of oxidative stress in simulated microgravity treated nematodes. Our results provide a molecular basis for the induction of oxidative stress in simulated microgravity treated organisms.

The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles

The exponential increase in the usage of engineered nanoparticles (ENPs) has raised global concerns due to their potential toxicity and environmental impacts. Nano-TiO₂ and nano-ZnO have been extensively used in various applications. Thus, there is a need for determining the toxic potentials of ENPs as well as, to develop the possible attenuation method for ENPs toxicity. Both in the in vitro and in vivo systems, exposure to the majority of ENPs have shown Reactive Oxygen Species (ROS) generation, which leads to oxidative stress mediated inflammation, genotoxicity, and cytotoxicity. Hence, with the rationale of determining easy and economical protection against ENPs exposure, the amelioration effect of the antioxidants (curcumin and vitamin-C) against the nano-TiO₂ and nano-ZnO induced ROS and lethality were investigated in Caenorhabditis elegans. We not only employed pre-treatment and along with treatment approach, but also determined the effect of antioxidants at different time points of treatment. Our study revealed that both the antioxidants efficiently ameliorate nanoparticles induced ROS as well as lethality in worms. Further, the pretreatment approach was more effective than the along with treatment. Therefore, our study indicates the possibility of evading the nanotoxicity by incorporating curcumin and vitamin-C in everyday diet.

Reproductive toxicity induced by nickel nanoparticles in Caenorhabditis elegans

To investigate the reproductive toxicity and underlying mechanism of nickel nanoparticles (Ni NPs), Caenorhabditis elegans (C. elegans) were treated with/without 1.0, 2.5, and 5.0 μg cm^-2 of Ni NPs or nickel microparticles (Ni MPs). Generation time, fertilized egg numbers, spermatide activation and motility were detected. Results indicated, under the same treatment doses, that Ni NPs induced higher reproductive toxicity to C. elegans than Ni MPs. Reproductive toxicities observed in C. elegans included a decrease in brood size, fertilized egg and spermatide activation, but an increase in generation time and out-of-round spermatids. The reproductive toxicity of Ni NPs on C. elegans may be induced by oxidative stress. The reproductive toxicity in C. elegans induced by Ni NPs is consistent with our previous results in the rats. Therefore, C. elegans can be used as an alternative model to detect the early reproductive toxicity of Ni NPs exposure. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1530-1538, 2017.

Antioxidant enzymes and their role in phoxim and carbaryl stress in Caenorhabditis elegans

Pesticide exposure can induce oxidative stress and cause changes to antioxidant enzymes in living organisms. In the present study, the effects of phoxim (an organophosphorus insecticide) and carbaryl (a carbamate insecticide) on antioxidant enzyme activity and gene expression were investigated in the model organism Caenorhabditis elegans. The results show that phoxim exposure can induce superoxide dismutase (SOD) and catalase (CAT) activities and decrease glutathione peroxidase (GPx) activity at lower concentrations. The expression levels of sod-3, sod-5, ctl-1, gpx-6, and gpx-8 were up-regulated after treatment with phoxim. The mRNA expression levels of sod-5, ctl-1 and gpx-6 were increased approximately 70-, 170- and 130-fold, respectively, in the 0.25mM treatment group compared to the control group. Carbaryl exposure decreased SOD activity and induced CAT and GPx activities. The addition of carbaryl up-regulated the expression of sod-5, ctl-1, ctl-3 and gpx-8. Specifically, ctl-1 expression increased approximately 10-fold, and gpx-8 expression increased <30-fold in the 0.5mM treatment group relative to the control group. The transcript level of sod-5 increased >20-fold, and ctl-3 increased approximately 10-fold in the 1mM treatment group. The functions of the antioxidant enzymes during oxidative stress caused by the two insecticides were investigated using deletion mutants. The LC₅₀ values phoxim for the of sod-3 (tm760), sod-5 (tm1146), ctl-1 (ok1242), ctl-3 (ok2042) and gpx-8 (tm2108) mutant strains were lower than those observed for the N2 strain. The LC₅₀ values of carbaryl for the ctl-1 (ok1242), ctl-3 (ok2042) and gpx-6 (tm2535) deletion mutant strains decreased in comparison to the N2 strain. The results suggest that these two insecticides caused oxidative stress and changed altered the antioxidant enzyme activities and their gene expressions in C. elegans. The sod-3, sod-5, ctl-1, ctl-3, gpx-6, and gpx-8 encoding enzymes may play roles in defending cells from oxidative stress caused by these two insecticides.

Neuronal ERK signaling in response to graphene oxide in nematode Caenorhabditis elegans

ERK signaling is one of the important mitogen-activated protein kinases (MAPKs). However, the role of ERK signaling in the regulation of response to engineered nanomaterial exposure is still largely unclear. In this study, using in vivo assay system of Caenorhabditis elegans, we investigated the function of ERK signaling in response to graphene oxide (GO) exposure and the underlying molecular mechanism. GO exposure increased the expression of MEK-2/MEK and MPK-1/ERK in the ERK signaling pathway. Mutation of mek-2 or mpk-1 resulted in a susceptibility to GO toxicity. Both the MEK-2 and the MPK-1 acted in neurons to regulate the response to GO exposure, and the neuronal expression of MEK-2 or MPK-1 caused a resistance to GO toxicity. In the neurons, SKN-1b/Nrf acted downstream of the MPK-1, and AEX-3, a guanine exchange factor for GTPase, further acted downstream of the SKN-1b to regulate the response to GO exposure. Therefore, a signaling cascade of MEK-2-MPK-1-SKN-1b/-AEX-3 was identified in the neurons required for the regulation of response to GO exposure. Moreover, genetic interaction assay demonstrated that the neuronal ERK signaling-mediated signaling pathway and the intestinal p38 MAPK-mediated signaling pathway functioned synergistically in the regulation of response to GO exposure. Our results highlight the crucial function of the neuronal ERK signaling in the regulation of response to nanomaterial exposure in organisms.

Biological effects, translocation, and metabolism of quantum dots in the nematode Caenorhabditis elegans

Quantum dots (QDs), semiconductor nanomaterials with tiny light-emitting particles, act as important alternatives to conventional fluorescent dyes for biomedical imaging. With the increased tendency towards QD applications, concerns about the likelihood of adverse health impacts from exposure to QDs have also received attention. The nematode Caenorhabditis elegans is an important non-mammalian alternative model for the toxicological study of environmental toxicants including engineered nanomaterials. In this review, we summarize recent progress on the biological effects, translocation, and metabolism of QDs in the in vivo assay system of C. elegans. Moreover, certain perspectives or suggestions are further raised for the future toxicological study of QDs in nematodes.

Lactic Acid Bacteria Protects Caenorhabditis elegans from Toxicity of Graphene Oxide by Maintaining Normal Intestinal Permeability under different Genetic Backgrounds

Lactic acid bacteria (LAB) is safe and useful for food and feed fermentation. We employed Caenorhabditis elegans to investigate the possible beneficial effect of LAB (Lactobacillus bulgaricus) pretreatment against toxicity of graphene oxide (GO) and the underlying mechanisms. LAB prevented GO toxicity on the functions of both primary and secondary targeted organs in wild-type nematodes. LAB blocked translocation of GO into secondary targeted organs through intestinal barrier by maintaining normal intestinal permeability in wild-type nematodes. Moreover, LAB prevented GO damage on the functions of both primary and secondary targeted organs in exposed nematodes with mutations of susceptible genes (sod-2, sod-3, gas-1, and aak-2) to GO toxicity by sustaining normal intestinal permeability. LAB also sustained the normal defecation behavior in both wild-type nematodes and nematodes with mutations of susceptible genes. Therefore, the beneficial role of LAB against GO toxicity under different genetic backgrounds may be due to the combinational effects on intestinal permeability and defecation behavior. Moreover, the beneficial effects of LAB against GO toxicity was dependent on the function of ACS-22, homologous to mammalian FATP4 to mammalian FATP4. Our study provides highlight on establishment of pharmacological strategy to protect intestinal barrier from toxicity of GO.