Effects of single and mixture exposure of cadmium and copper in apoptosis and immune related genes at transcriptional level on the midge Chironomus riparius Meigen (Diptera, Chironomidae)

Antioxidant response fail to rescue growth of Hermetia illucens L. larvae induced by copper accumulated during long-term exposure

Antioxidant indices and hemocytes apoptosis in the 6th instar larvae of Hermetia illucens., and their correlation with larval growth were evaluated by exposing larvae to different concentrations of Cu2+ for 1, 3 and 5 generations. Cu2+ accumulated in larval hemolymph showed significant dose-dependent relationship with Cu2+ concentrations in diets within a generation. Larval growth was only promoted after low concentrations of Cu2+ exposure for 1 generation, while seriously affected after high concentrations of Cu2+ exposure. Though total antioxidant capacity activity in larval hemolymph in treatment groups was all higher than that in control, it was increased at lower levels of Cu2+, while decreased with increasing Cu2+ concentrations at higher levels of Cu2+ exposure. The catalase (CAT) activity and metallothioneins (MTs) levels were also characterized as improved at lower levels of Cu2+, and inhibited at higher levels of Cu2+ exposure. However, CAT activity and MTs levels at higher Cu2+ treatments were significantly lower than that in control. Apoptosis rate of hemocytes was increased with increasing Cu2+ concentrations. Annexin V - fluorescein isothiocyanate (FITC)/ propidium iodide (PI) staining was in accordance with the results exhibited in flow cytometer. Results from transmission electron microscope and comet assay further confirmed that membrane blebbing, nuclear condensation, and DNA fragmentation were gradually apparent with increasing Cu2+ concentration. All parameters in different generation had similar dose-dependent trends, but the effects were strongest in the fifth generation. This study indicated that at some extent growth of H. illucens were associated with antioxidant responses and apoptosis induced by Cu2+.

Toxicity of isolated and mixed metals to a native Amazonian ostracod and ecological risk assessment

In recent decades the Amazonian ecosystem has received large amounts of domestic and industrial effluents, as well as mining-related waste contributing significant quantities of metal to water bodies. Thus, the main objective of the study was to verify the sensitivity of a native Amazonian ostracod (Strandesia rondoniensis) species to isolated and mixed metal salts (CuSO4; ZnCl2; CdCl2 and HgCl2). The sensitivity will be compared to other species using species sensitivity distributions (SSDs) for an ecological risk assessment (ERA). The experiment consisted of simultaneously exposing each metal alone and in mixture, through a factorial design for toxicity with 25 different combinations for 48 h. For the ERA, metal concentrations measured in the water of various aquatic environments in the Amazon basin were considered based on the risk quotient values. The results showed that the metal toxicity gradient was Cd>Hg>Cu>Zn, respectively. The toxicity in the mixture showed that the combination of Cu-Cd and Cu-Zn better fit the model (CA), indicating mainly synergism when copper predominated in the mixture. Meanwhile, the Cu-Hg interaction fit the model better (IA), again indicating synergism when copper was at a higher concentration. The ERA showed a high risk (RQ > 1) for the Cd, Cu, and Hg metals.

Rescue effect of curcumin against copper toxicity

Turmeric has long been used not only as an indispensable part of Asian cuisine but as a medicinal herb for dressing wounds, bites, burns, treating eye infections and acne. Curcuminoids are the active substances and their synthetic derivatives (i.e. diacetylcurcumin (DAC) and metal-curcumin complexes) possess an incredibly wide range of medicinal properties that encompass chelation capacity for multiple heavy metals, antioxidant activity, anti-inflammatory properties, cytotoxicity against cancerous cells, antiviral and antibacterial effects, antihypertensive and insulin sensitizing role, and regulatory role on apoptosis. The aforementioned properties have put curcumin on spotlight as a potential treatment for ailments such as, hepatic diseases, neurodegenerative diseases, metabolic syndrome, dyslipidemia, cardiovascular disease, auto-immune diseases, malignancies and conditions associated with metal overload. Copper is essential for major biological functions, however, an excess causes chronic ailments including neurodegenerative disorders. The fascinating approach of curcumin could alleviate such effect by forming a complex. Thus, this review aims to present available data on the effect of copper-curcumin interaction in various in vitro, ex-vivo in vivo, and clinical studies.

Effects of cadmium and copper mixtures on antibiotic resistance genes in rhizosphere soil

The evolvement and development of antibiotic resistance in microorganisms may be influenced by metals; however, it is still unclear how cadmium (Cd) and copper (Cu) combined affect the distribution and presence of antibiotic-resistance genes (ARGs) in rhizosphere soil. The aims of this research were to (1) compare the distribution patterns of bacterial communities and ARGs in response to the effects of Cd and Cu both separately and combined; (2) explore the possible mechanisms underlying the variation in soil bacterial communities and ARGs in addition to the combined effects of Cd, Cu, and various environmental variables (nutrients, pH, etc.); and (3) provide a reference for assessing the risks of metals (Cd and Cu) and ARGs. The findings showed that the multidrug resistance genes acrA and acrB and the transposon gene intI-1 were present in high relative abundance in bacterial communities. Cadmium and Cu had a substantial interaction effect on the abundance of acrA, whereas Cu had a notable main effect on the abundance of intI-1. According to the network analysis, the strong links between bacterial taxa and specific ARGs revealed that most ARGs were hosted by Proteobacteria, Actinobacteria, and Bacteroidetes. According to structural equation modeling, Cd had a larger effect on ARGs than Cu. Compared to previous analyses of ARGs, bacterial community diversity had little effect on ARGs in this study. Overall, the results may have important consequences for determining the possible hazard of soil metals and extend the understanding of how Cd and Cu co-select ARGs in rhizosphere soils.

Graphene Oxides (GOs) with Different Lateral Dimensions and Thicknesses Affect the Molecular Response in Chironomus riparius

Graphene oxide (GO) materials possess physicochemical properties that facilitate their application in the industrial and medical sectors. The use of graphene may pose a threat to biota, especially aquatic life. In addition, the properties of nanomaterials can differentially affect cell and molecular responses. Therefore, it is essential to study and define the possible genotoxicity of GO materials to aquatic organisms and their ecosystems. In this study, we investigated the changes in the expression of 11 genes in the aquatic organism Chironomus riparius after 96 h of exposure to small GOs (sGO), large GOs (lGO) and monolayer GOs (mlGO) at 50, 500 and 3000 μg/L. Results showed that the different genes encoding heat shock proteins (hsp90, hsp70 and hsp27) were overexpressed after exposure to these nanomaterials. In addition, ATM and NLK-the genes involved in DNA repair mechanisms-were altered at the transcriptional level. DECAY, an apoptotic caspase, was only activated by larger size GO materials, mlGO and lGO. Finally, the gene encoding manganese superoxide dismutase (MnSOD) showed higher expression in the mlG O-treated larvae. The lGO and mlGO treatments indicated high mRNA levels of a developmental gene (FKBP39) and an endocrine pathway-related gene (DRONC). These two genes were only activated by the larger GO materials. The results indicate that larger and thicker GO nanomaterials alter the transcription of genes involved in cellular stress, oxidative stress, DNA damage, apoptosis, endocrine and development in C. riparius. This shows that various cellular processes are modified and affected, providing some of the first evidence for the action mechanisms of GOs in invertebrates. In short, the alterations produced by graphene materials should be further studied to evaluate their effect on the biota to show a more realistic scenario of what is happening at the molecular level.

Impact of single and combined exposure to priority pollutants on gene expression and post-embryonic development in Drosophila melanogaster

Many priority pollutants are concentrated in the environment due to human activity. Most are highly toxic to various organisms, including endocrine disruptors EDCs, aromatic polycyclic hydrocarbons PAHs, pesticides. While the effects of single and binary exposure have been widely explored, several pollutants can be simultaneously present at the same time in the environment, in in more or less polluted matrices. Effective pollution control requires the presence and sources of contamination to be identified. Previously we used Drosophila melanogaster to investigate metal pollution. Here, we re-used Drosophila to identify the biomarkers of pollution, and to determine if they can be used for specific types of pollution. Single and combined exposure of Bis(2-ethylhexyl) phthalate (DEHP), bisphenol A, nonylphenol, benzo(a)pyrene, and glyphosate was investigated. The impact of these pollutants on post-embryonic development and the expression pattern of 38 molecular targets were examined using qPCR. During single exposure, different profiles were observed at the molecular level. In complex mixtures, the expression profile resembled that of bisphenol A. In contrast, relatively specific gene expression profiles were obtained for the effects of each pollutant separately. While direct pollutant-gene profiling remains difficult in mixtures, molecular biology analyses enhance pollution monitoring, and should be incorporated in toxicological studies.

Analysis of Differential Gene Expression of the Aquatic Insect Protohermes costalis (Walker) (Megaloptera: Corydalidae) in Response to Cadmium Exposure

Heavy metal pollution in freshwater ecosystems is a serious threat to aquatic organisms. Species of Megaloptera are important predators of aquatic invertebrates and have been widely used as bioindicators in assessing the quality of freshwater ecosystems. In this study, we determined the differential gene expression profile of Protohermes costalis (Walker) (Megaloptera: Corydalidae) in response to cadmium (Cd) exposure by using transcriptome analysis. A total of 60,627 unigenes were obtained in the transcriptomes of 150 mg/liter (PL), 1,000 mg/liter (PH) CdCl2 treatment, and the no Cd control (PC). Differential expression gene (DEG) analysis by pairwise comparison identified 2,794 DEGs after filtering the noninsect genes and repetitive counts. 606 DEGs were shared in comparisons of PL versus PC and PH versus PC, with 165 DEGs consistently up-regulated and 441 down-regulated by both PL and PH. Six heat shock proteins (HSPs) in the HSP70 family were identified in P. costalis and PcosHSP68 was up-regulated by both PL and PH. Real-time quantitative polymerase chain reaction (RT-qPCR) confirmed that the expression levels of PcosHSP68 in PL and PH were higher than that of PC by 31 and 197%, respectively. These results showed that exposure to Cd altered the gene expression profiles of P. costalis and the transcriptome data presented in this study provide insight into future studying on molecular mechanisms of Cd toxicity to these insects.

Whole genome sequencing and RNA-seq evaluation allowed to detect Cd adaptation footprint in Chironomus riparius

Evolutionary adaptation and phenotypic plasticity are important processes on how organisms respond to pollutant exposure. We dissected here the contribution of both processes to increased tolerance in Chironomus riparius to cadmium (Cd) exposure in a multi-generation experiment and inferred the underlying genomic basis. We simulated environmentally realistic conditions by continuously increasing contaminant concentration in six replicates initiated with 1000 larvae each, three pre-exposed to Cd and three not exposed to Cd (no-Cd) over eight generations. We measured life-cycle traits, transcriptomic responses and genome-wide allele frequency changes from this evolve and resequencing (E&R) experiment. Overall, life cycle tests revealed little phenotypic adaptation to Cd exposure, but a slightly increase in survival in the first larval stage was observed. Population genomic analyses showed a strong genome-wide selective response in all replicates, highlighting two main biological functions involved in development and growth of the chironomids. Emphasizing that laboratory conditions continually exert selective pressure. However, the integration of the transcriptomic to the genomic data allowed to distinguish pathways specifically selected by the Cd exposure related to microtubules and organelles and cellular movement. Those pathways could be functionally related to an excretion of metals. Thus, our results indicate that genetic adaptation to Cd in C. riparius can happen within few generations under an environmentally relevant exposure scenario, but substantial phenotypic tolerance might take more time to arise. With our approach, we introduce an experimental setup to fill the existing gap in evolutionary ecotoxicology to investigate these early signs of genetic adaptation.

Nrf2 signaling pathway in trace metal carcinogenesis: A cross-talk between oxidative stress and angiogenesis

A large number of people worldwide are affected by chronic metal exposure, which is known to be associated with different type of malignancies. The mechanisms of metal carcinogenicity are complex in nature, and excessive reactive oxygen species (ROS) generation induced by chronic metal exposure, among the other factors, has been proposed as one of the major mechanisms involved in that process. In tumor cells, ROS buildup may lead to cell death through intrinsic and extrinsic signaling pathways. Furthermore, ROS-mediated redox signaling has a crucial role in angiogenesis, which is recognized as an essential step in tumor progression. There are several redox-modulating pathways and among them, the nuclear factor erythroid2-related factor2 (Nrf2), as a sensor of oxidative or electrophilic stress, has introduced as a master regulator of cellular response against environmental stresses. Activation of Nrf2 signaling induces expression of wide variety of antioxidant and detoxification enzymes genes. Thus, this transcription factor has recently received much attention as a target for cancer chemoprevention. But meanwhile, constitutive Nrf2 activation in cancerous cells may promote cancer progression and resistance to chemotherapy. The current review describes the major underlying mechanisms involved in carcinogenesis of trace metals: copper, silver, and cadmium, with a special focus on the Nrf2 signaling pathway as a crossroad between oxidative stress and angiogenesis.

Altered gene expression in Chironomus riparius (insecta) in response to tire rubber and polystyrene microplastics

The extent until which plastics are present in our surrounding environment completely exceeds our expectations. Plastic materials in the form of microplastics have been found in terrestrial, freshwater and marine environments and are transported through the atmosphere even to remote locations. However, we are still far from understanding the effects that they may have caused and are causing to biota. In the present study, we investigated the alterations in the expression of twelve genes in the aquatic insect Chironomus riparius after 36 h exposures to polystyrene and tire rubber microplastics at nominal concentrations of 1 and 10 mg L^-1. The results indicated that several genes encoding for heat shock proteins (hsp90, Glycoprotein 93 (Gp93), hsc70, hsp60, hsp40, and the small HSP hsp17) were overexpressed respect to the control. In addition, the genes coding for manganese superoxide dismutase (SOD Mn, related to alleviation of oxidative stress) and for the FK506-binding protein of 39 kDa. (FKBP39, related to development and pupation) showed altered expression. Most of the alterations on gene expression level occurred at a concentration of 10 mg L^-1 of tire rubber microplastics, although specific modifications arose at other concentrations of both rubber and polystyrene. On the contrary, one hsp gene (hsp10) and genes related to biotransformation and detoxification (Cyp9f2, Cyp12a2, and ABCB6) did not alter their expression in any of the treatments. Overall, the results of the gene expression indicated that microplastics (especially tire rubber) or their additives caused cellular stress that led to some alterations in the normal gene expression but did not cause any mortality after 36 h. These results highlight the need for more studies that describe the alterations caused by microplastics at the molecular level. Additionally, it opens questions about the effects caused to aquatic fauna in environmental realistic situations, especially in hot spots of microplastic contamination (e.g., tire rubber released in storm water runoff discharge points).

Exposure to copper induces mitochondria-mediated apoptosis by inhibiting mitophagy and the PINK1/parkin pathway in chicken (Gallus gallus) livers

Copper (Cu), a transition metal with essential cellular functions, exerts toxic effects when present in excess by inducing oxidative stress. However, the Cu-induced crosstalk between mitophagy and apoptosis and the underlying mechanisms are unknown. Here, the mechanism of Cu-induced hepatotoxicity mediated by mitophagy and apoptosis was explored in vivo and in vitro. In in vivo experiments, chickens were fed a diet with various levels of Cu (11, 110, 220, and 330 mg/kg) for 7 weeks, which led to ultrastructural damage, mitophagy, and apoptosis in liver tissue. In vitro experiments on primary chicken hepatocytes showed that Cu treatment for 24 h increased the numbers of mitophagosomes and upregulated PINK1, parkin, and p62 mRNA levels and parkin and p62 protein levels, inducing mitophagy. Moreover, treatment with 3- methyladenine (3-MA) aggravated Cu-induced S-phase arrest in cell cycle; increased the apoptotic rate; increased p53, Bak1, Bax, Cyt C, and Caspase3/cleaved-caspase3 mRNA and protein levels; and decreased Bcl2 mRNA and protein levels. However, rapamycin (Rapa) had the opposite effects on the above factors. In general, the results reveal that Cu exposure can cause mitophagy through the PINK1/Parkin pathway in chicken livers, and that mitophagy might attenuate Cu-induced mitochondrial apoptosis.

A chromosome level genome assembly of Propsilocerus akamusi to understand its response to heavy metal exposure

Chironomidae species are universally used for studying the impact of pollutants in aquatic systems. The nonbiting midge Propsilocerus akamusi is often found in urban streams and is suitable for use as a toxicological bioindicator. However, few studies have previously examined metal stress in this species. We sequenced the genome of this urban midge to address this question. Here, we present the first chromosome-level genome of P. akamusi, obtained from Illumina short-read and PacBio long-read sequences with Hi-C technology. The size of the very small assembled genome was 85.83 Mb with a contig N50 of 6.2 Mb and a scaffold N50 of 26.1 Mb. This assembly revealed significant expansion of haemoglobin (Hb) genes, some of which formed large tandem repeats. Transcriptomic studies for copper tolerance identified four genes in the tandem array that were highly expressed, all of which presented intron loss. This characteristic might highlight the potential role of Hb genes in copper tolerance. Additionally, detoxification genes, chemosensory genes and heat shock protein genes of this midge were identified, some of which are associated with metal stress. The high-quality assembled genome of P. akamusi and the transcriptomic analyses provide new insight into the molecular mechanisms of heavy metal stress. Our comparison of the P. akamusi genome with other dipteran genomes provides valuable resources for understanding the evolutionary history, genetics, and ecology of this species as well as those of other midges.

Transfer of heavy metal along food chain: a mini-review on insect susceptibility to entomopathogenic microorganisms under heavy metal stress

The development and physiological status of pest insects are important factors that affect the effectiveness of biological control. Current knowledge reveals that heavy metals can be transferred to phytophagous insects through food chains and cause various chronic toxicological effects on the growth and physiology of phytophagous insects. These findings potentially attribute heavy metal contamination to an environmental factor governing biocontrol efficiency against pest insects, pointing to an urgent demand to better understand the effects of heavy metal exposure on insect susceptibility to entomopathogenic microorganisms. Here we discuss the transfer characteristics of heavy metals along the food chains to phytophagous insects and conclude that heavy metal exposure may promote insect susceptibility to entomopathogenic microorganisms in the heavy metal-contaminated regions. Furthermore, we propose a 'combined effect' hypothesis that combination of entomopathogenic agent and heavy metal stress can cause a much higher overall insect mortality than does the entomopathogenic agent or the heavy metal stress alone. This is a new and relatively unexplored area in the microbial-based biocontrol research, which might have great potential for future optimization of biocontrol strategies against economically and ecologically important agricultural or forest pests in the heavy metal polluted areas. © 2020 Society of Chemical Industry.

A preliminary gene expression analysis on Paracentrotus lividus embryos exposed to UVB, Cadmium and their combination

Paracentrotus lividus is a Mediterranean and Eastern Atlantic sea urchin species, very sensitive to chemical and physical environmental changes and widely used in eco-toxicological studies. Here, we applied a high throughput screening approach on P. lividus embryos exposed to UVB radiation (UV), Cadmium Chloride (Cd) and their combination (Cd/UV), to deeply characterize the molecular responses adopted by embryos to cope with these stressors. in vitro eco-toxicological assays were performed by exposing embryos to Cd (10-4 M) soon after fertilization, to UV (200 and 400J/m2) at early stage of development, while in co-exposure experiments, Cd-exposed embryos were irradiated with UV at 200 J/m2. By NanoString nCounter technology, custom-made probes were developed and hybridized on total RNA extracted from exposed embryos at 51h after fertilization. By in silico analyses, we selected and retrieved at the NCBI nucleotide database a panel of P. lividus transcripts encoding for many regulatory and structural proteins that we ranked in categories, i.e., Apoptosis, Biomineralization, Defense, Development, Immunity, Signaling and Transcription Factors. The analysis of 127 transcripts highlighted the dysregulation of many genes, some specifically activated to cope with stress agents, others involved in the complex molecular network of genes that regulate embryo development. We revealed the downregulation of Biomineralization and Development genes and the upregulation of Defensive genes in Cd and Cd/UV embryos. Our approach, using sea urchin embryo as an in vivomodel, contributes to advance our knowledge about cellular responses to UV, Cd and their combination.

Ibuprofen as an emerging pollutant on non-target aquatic invertebrates: Effects on Chironomus riparius

The concern about pharmaceuticals has been increased over the last decade due to their burgeoning consumption. Ibuprofen has an extensive presence in surface water with risks for the aquatic biota. This study focuses on the effects of ibuprofen at environmental concentrations on the survival, transcriptional level, and enzymatic activity for 24, 96 h on Chironomus riparius. Ibuprofen developed a substantial effect on survival by all the conditions. mRNA levels of EcR, Dronc, and Met (endocrine system), hsp70, hsp24, and hsp27 (stress response), and Proph and Def (immune system) were modified, joined to increased GST and PO activity. The results confirmed alterations on the development of C. riparius, as well as two essential mechanisms, involved in protection against external toxicological challenge. Ibuprofen poses an incipient risk to C. riparius and could at an organismal level by compromising their survival, development, and ability to respond to adverse conditions on the future populations.

Multi-Level Gene Expression in Response to Environmental Stress in Aquatic Invertebrate Chironomids: Potential Applications in Water Quality Monitoring

In freshwater ecosystems, aquatic invertebrates are influenced continuously by both physical stress and xenobiotics. Chironomids (Diptera; Chironomidae), or non-biting midges, are the most diverse and abundant invertebrates in freshwater habitats. They are a fundamental link in food chains of aquatic ecosystems. Chironomid larvae tolerate stress factors in their environments via various physiological processes. At the molecular level, environmental pollutants induce multi-level gene responses in Chironomus that regulate cellular protection through the activation of defense processes. This paper reviews literature on the transcriptional responses of biomarker genes to environmental stress in chironomids at the molecular level, in studies conducted from 1991 to 2020 (120 selected literatures of 374 results with the keywords "Chironomus and gene expression" by PubMed search tool). According to these studies, transcriptional responses in chironomids vary depending on the type of stress factor and defensive responses associated with antioxidant activity, the endocrine system, detoxification, homeostasis and stress response, energy metabolism, ribosomal machinery, apoptosis, DNA repair, and epigenetics. These data could provide a comprehensive overview of how Chironomus species respond to pollutants in aquatic environments. Furthermore, the transcriptomic data could facilitate the development of genetic tools for water quality and environmental monitoring based on resident chironomid species.

Combined effects of environmentally relevant concentrations of diclofenac and cadmium on Chironomus riparius larvae

The nonsteroidal anti-inflammatory drug diclofenac (DCF) is considered a contaminant of emerging concern. DCF can co-exist with heavy metals in aquatic environments, causing unexpected risks to aquatic organisms. This study aimed to assess the combined effects of DCF and cadmium (Cd) at environmentally relevant concentrations on the bioconcentration and status of oxidative stress and detoxification in Chironomus riparius larvae. The larvae were exposed to DCF (2 and 20 μg L^-1) and Cd (5 and 50 μg L^-1) alone or in mixtures for 48 h. The combined exposure to DCF and Cd was found to reciprocally facilitate the accumulation of each compound in larvae compared with single exposures. As indicated by the antioxidant enzyme activities, reduced glutathione levels, and malondialdehyde contents, the low concentration of the mixture (2 μg L^-1 DCF + 5 μg L^-1 Cd) did not alter the oxidative stress status in larvae, while the high concentration of the mixture (20 μg L^-1 DCF + 50 μg L^-1 Cd) induced stronger oxidative damage to larvae compared with single exposures. The expression levels of eight genes (CuZnSOD, MnSOD, CAT, GSTd3, GSTe1, GSTs4, CYP4G, and CYP9AT2) significantly decreased due to the high concentration of the mixture compared with single exposures in most cases. Overall, the results suggest that the mixture of DCF and Cd might exert greater ecological risks to aquatic insects compared with their individual compounds.