Pxr- and Nrf2- mediated induction of ABC transporters by heavy metal ions in zebrafish embryos

Co-exposure to UV-aged microplastics and cadmium induces intestinal toxicity and metabolic responses in earthworms

Aged microplastics (MPs) alter the interaction with heavy metals due to changes in surface properties. However, the combined toxicological effects of aged MPs on heavy metals in soil remain poorly understood. In this study, earthworms were employed as model animals to investigate the effects of aged MPs on the biotoxicity of cadmium (Cd) by simulating the exposure patterns of original and UV-aged MPs (polylactic acid (PLA) and polyethylene (PE)) with Cd. The results showed that UV-aging decreased the zeta potential and increased the specific surface area of the MPs, which enhanced the bioaccumulation of Cd and caused more severe oxidative stress to earthworms. Meanwhile, the earthworm intestines exhibited increased tissue damage, including chloragogenous tissue congestion lesions, and typhlosole damage. Furthermore, the combined exposure to UV-aged MPs and Cd enhanced the complexity of the microbial network in the earthworm gut and interfered with endocrine disruption, membrane structure, and energy metabolic pathways in earthworms. The results emphasized the need to consider the degradation of MPs in the environment. Hence, we recommend that future toxicological studies use aged MPs that are more representative of the actual environmental conditions, with the results being important for the risk assessment and management of MPs.

Elucidating the roles of Cr(VI)-Cu(II) Co-pollution in the stress of aniline degradation stress: Insights into metabolic pathways and functional genes

In order to examine the impact of Cu(II)-Cr(VI) co-pollution in printing and dyeing wastewater on the aniline biodegradation system (ABS), loading experiments were conducted on ABS at varying concentrations of Cu(II)-Cr(VI). The synergistic stress imposed by Cu(II)-Cr(VI) accelerated the deterioration of the systems, with only the C2-3 (2 mg/L Cr(VI)-3 mg/L Cu(II)) sustaining stable operation for 42 days. However, its nitrogen removal performance remained significantly impaired, resulting in a total nitrogen (TN) removal rate below 40%. High-throughput sequencing analysis revealed a stronger correlation between Cr(VI) and microbial diversity compared to Cu(II). Metagenomic sequencing results demonstrated that Cu(II) emerged as the dominant factor influencing the distribution of dominant bacteria in C2-3, as well as its contribution to contaminant degradation. The complex co-pollution systems hindered aniline degradation and nitrogen metabolism through the combined bio-toxicity of heavy metals and aniline, thereby disrupting the transport chain within the systems matrix.

ABC transporter-mediated MXR mechanism in fish embryos and its potential role in the efflux of nanoparticles

ATP-binding cassette (ABC) transporters are believed to protect aquatic organisms by pumping xenobiotics out, and recent investigation has suggested their involvement in the detoxification and efflux of nanoparticles (NPs), but their roles in fish embryos are poorly understood. In this regard, this paper summarizes the recent advances in research pertaining to the development of ABC transporter-mediated multi-xenobiotic resistance (MXR) mechanism in fish embryos and the potential interaction between ABC transporters and NPs. The paper focuses on: (1) Expression, function, and modulation mechanism of ABC proteins in fish embryos; (2) Potential interaction between ABC transporters and NPs in cell models and fish embryos. ABC transporters could be maternally transferred to fish embryos and thus play an important role in the detoxification of various chemical pollutants and NPs. There is a need to understand the specific mechanism to benefit the protection of aquatic resources.

Recombinant Technologies Facilitate Drug Metabolism, Pharmacokinetics, and General Biomedical Research

The development of safe and effective medications requires a profound understanding of their pharmacokinetic (PK) and pharmacodynamic properties. PK studies have been built through investigation of enzymes and transporters that drive drug absorption, distribution, metabolism, and excretion (ADME). Like many other disciplines, the study of ADME gene products and their functions has been revolutionized through the invention and widespread adoption of recombinant DNA technologies. Recombinant DNA technologies use expression vectors such as plasmids to achieve heterologous expression of a desired transgene in a specified host organism. This has enabled the purification of recombinant ADME gene products for functional and structural characterization, allowing investigators to elucidate their roles in drug metabolism and disposition. This strategy has also been used to offer recombinant or bioengineered RNA (BioRNA) agents to investigate the posttranscriptional regulation of ADME genes. Conventional research with small noncoding RNAs such as microRNAs (miRNAs) and small interfering RNAs has been dependent on synthetic RNA analogs that are known to carry a range of chemical modifications expected to improve stability and PK properties. Indeed, a novel transfer RNA fused pre-miRNA carrier-based bioengineering platform technology has been established to offer consistent and high-yield production of unparalleled BioRNA molecules from Escherichia coli fermentation. These BioRNAs are produced and processed inside living cells to better recapitulate the properties of natural RNAs, representing superior research tools to investigate regulatory mechanisms behind ADME. SIGNIFICANCE STATEMENT: This review article summarizes recombinant DNA technologies that have been an incredible boon in the study of drug metabolism and PK, providing investigators with powerful tools to express nearly any ADME gene products for functional and structural studies. It further overviews novel recombinant RNA technologies and discusses the utilities of bioengineered RNA agents for the investigation of ADME gene regulation and general biomedical research.

The critical role of nanoparticle sizes in the interactions between gold nanoparticles and ABC transporters in zebrafish embryos

Despite the increasing evidences for adenosine triphosphate-binding cassette (ABC transporters)-mediated efflux of nanoparticles, the universality of these phenomena and the determining factors for the process remained to be clarified. This paper aimed to systemically investigate the role of nanoparticle size in the interactions between adenosine triphosphate-binding cassette (ABC transporters) and gold nanoparticles (AuNPs, 3 nm, 19 nm, and 84 nm, named as Au-3, Au-19, and Au-84) in zebrafish embryos. The results showed that all the three AuNPs induced significant toxicity as reflected by delayed hatching of embryos, decreased glutathione (GSH) contents, and increased reactive oxygen species (ROS) levels. Under the hindrance of embryo chorions, smaller AuNPs could more easily accumulate in the embryos, causing higher toxicity. Addition of transporter inhibitors enhanced the accumulation and toxicity of Au-3 and Au-19, and these nanoparticles induced the expressions of abcc2 and abcb4, indicating a fact that Au-3 and Au-19 were the potential substrates of ABC transporters, but these phenomena were barely found for Au-84. On the contrary, Au-84 suppressed the gene expressions of various ABC transporters like abcc1, abcg5, and abcg8. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (Nrf2) and pregnane X receptor (Pxr) were found to be important in the induction of ABC transporters by AuNPs. After all, these results revealed a vital role of nanoparticle sizes in the interactions between ABC transporters and AuNPs in zebrafish embryos, and the critical size could be around 19 nm. Such information would be beneficial in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants.

Combined effects of S-metolachlor and benoxacor on embryo development in zebrafish (Danio rerio)

It is necessary to study the combined toxicity of an herbicide and its safener because the two are often used in combination. S-metolachlor and its safener benoxacor have been detected in aquatic environments and can individually damage the oxidative stress system in zebrafish embryos (Danio rerio). However, only their separate toxicity in zebrafish (Danio rerio) embryo development has been reported. This study assessed the combined toxicity of benoxacor and S-metolachlor in zebrafish embryo development, including acute toxicity, developmental toxicity, oxidative damage, and cell apoptosis. The 96-h LC₅₀ values were higher in mixtures of benoxacor and S-metolachlor than in benoxacor alone. The treatments included S-metolachlor, Mix-1 (0.1 mg/L benoxacor + 0.1 mg/L S-metolachlor), Mix-2 (0.1 mg/L benoxacor + 0.3 mg/L S-metolachlor) and benoxacor alone. Embryos exposed to Mix-1 and Mix-2 had lower developmental toxicities, superoxide dismutase (SOD) activity, osx and cat expression levels than those exposed to benoxacor alone. Moreover, glutathione S-transferase (GST), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) activities, and the expressions of tbx16, nrf2, bcl2, and caspase9 were higher in the mixtures than in the benoxacor group. High-throughput RNA sequencing revealed that benoxacor had a greater effect on gene regulation than Mix-1 and Mix-2. The malformation rate, different enrichment gene numbers, and gene expression levels of hatched embryos were higher in Mix-1 than in Mix-2. The results indicate that a mixture of S-metolachlor and benoxacor has antagonistic effects in the early stage of embryo development. The mixtures can break the reactive oxygen species balance, causing abnormal cell apoptosis and developmental malformation in embryos. Besides investigating the combined toxicity of benoxacor and S-metolachlor in zebrafish embryo development, this study provides a risk assessment basis for a herbicide combined with its safener.

Oxidative stress-mediated up-regulation of ABC transporters in lung cancer cells

This paper aimed to evaluate the role of oxidative stress in the regulation of ABC transporters in human lung cancer (A549) cells facing substrate (doxorubicin, DOX) and non-substrate (ethanol, ETH and hydrogen peroxide, HP) chemicals. After 24-h treatment, all the chemicals caused significant cytotoxicity as reflected by the reduction in cell viability and the increase in reactive oxygen species (ROS) levels. Depending on the rescuing effects of ROS scavenger including glutathione (GSH) and Vitamin C (VC), the toxicity dependence on oxidative stress were found to be HP>ETH>DOX. Addition of transporter inhibitors significantly enhanced the ROS levels and death-inducing effects of chemicals, indicating the universal detoxification function of ABC transporters. At moderate ROS levels (about 3-4 folds of control levels, caused by 10 μM DOX, 400 mM ETH, and 400 μM HP), all the three chemicals induced the gene expressions and activities of ABC transporters, but these values decreased at too high ROS levels (8.36 folds of control levels) caused by HP at LC₅₀ (800 μM). Such induction could be attenuated by GSH and KCZ, and was completely abolished by 50 μM KCZ, indicating an important role of oxidative stress and pregnane X receptor (PXR) in the induction of ABC transporters. After all, this paper revealed a critical role of oxidative stress in the modulation of ABC transporters by either substrate or non-substrate chemicals during 24-h treatment. Such information should be beneficial for overcoming ABC transporter-mediated multidrug resistance (MDR). This article is protected by copyright. All rights reserved.

Interactions of Environmental Chemicals and Natural Products With ABC and SLC Transporters in the Digestive System of Aquatic Organisms

An organism’s diet is a major route of exposure to both beneficial nutrients and toxic environmental chemicals and natural products. The uptake of dietary xenobiotics in the intestine is prevented by transporters of the Solute Carrier (SLC) and ATP Binding Cassette (ABC) family. Several environmental chemicals and natural toxins have been identified to induce expression of these defense transporters in fish and aquatic invertebrates, indicating that they are substrates and can be eliminated. However, certain environmental chemicals, termed Transporter-Interfering Chemicals or TICs, have recently been shown to bind to and inhibit fish and mammalian P-glycoprotein (ABCB1), thereby sensitizing cells to toxic chemical accumulation. If and to what extent other xenobiotic defense or nutrient uptake transporters can also be inhibited by dietary TICs is still unknown. To date, most chemical-transporter interaction studies in aquatic organisms have focused on ABC-type transporters, while molecular interactions of xenobiotics with SLC-type transporters are poorly understood. In this perspective, we summarize current advances in the identification, localization, and functional analysis of protective MXR transporters and nutrient uptake systems in the digestive system of fish and aquatic invertebrates. We collate the existing literature data on chemically induced transporter gene expression and summarize the molecular interactions of xenobiotics with these transport systems. Our review emphasizes the need for standardized assays in a broader panel of commercially important fish and seafood species to better evaluate the effects of TIC and other xenobiotic interactions with physiological substrates and MXR transporters across the aquatic ecosystem and predict possible transfer to humans through consumption.

Role of nuclear pregnane X receptor in Cu-induced lipid metabolism and xenobiotic responses in largemouth bass (Micropterus salmoides)

The pregnane X receptor (PXR) is a master xenobiotic-sensing receptor in response to toxic byproducts, as well as a key regulator in intermediary lipid metabolism. Therefore, the present study was conducted to investigate the potential role of PXR in mediating the lipid dysregulation and xenobiotic responses under Cu-induced stress in largemouth bass (Micropterus salmoides). Four groups of largemouth bass (52.66 ± 0.03 g) were treated with control, Cu waterborne (9.44 μmol/L), Cu+RIF (Rifampicin, 100 mg/kg, PXR activator), and Cu+KET (Ketoconazole, 20 mg/kg, PXR inhibitor) for 48 h. Results showed that Cu exposure significantly elevated the plasma stress indicators and triggered antioxidant systems to counteract Cu-induced oxidative stress. Acute Cu exposure caused liver steatosis, as indicated by the significantly higher levels of plasma triglycerides (TG), lipid droplets, and mRNA levels of lipogenesis genes in the liver. Liver injuries were detected, as shown by hepatocyte vacuolization and severe apoptotic signals after Cu exposure. Importantly, Cu exposure significantly stimulated mRNA levels of PXR, suggesting the response of this regulator in the xenobiotic response. The pharmacological intervention of PXR by the agonist and antagonist significantly altered hepatic mRNA levels of PXR, implying that RIF and KET were effective agents of PXR in largemouth bass. Administration of RIF significantly exacerbated liver steatosis, and such alterations were dependent on the regulations on pparγ and cd36 rather than srebp1 signaling, which suggested that PXR-PPARγ might be another pathway for Cu-induced lipid deposition in fish. Whereas, KET administration showed reverse effects on lipid metabolism as indicated by the lower hepatic TG levels, suppressed mRNA levels of pparγ and cd36. Activation of PXR stimulated autophagy and inhibited apoptosis, leading to lower hepatic vacuolization; while inhibition of PXR showed higher apoptotic signals, inhibition of autophagic genes and stimulation of apoptotic genes. Taken together, PXR played a cytoprotective role in Cu-induced hepatotoxicity through regulations on autophagy and apoptosis. Overall, our data has demonstrated for the first time on the dual roles of PXR as a co-regulator in mediating xenobiotic responses and lipid metabolism in fish, which implying the potential of PXR as a therapy target for xenobiotics-induced lipid dysregulation and hepatotoxicity.

Nanoplastics aggravate the toxicity of arsenic to AGS cells by disrupting ABC transporter and cytoskeleton

The coexistence of nanoplastics (NPs) and pollutants such as arsenic (As) has become an unignorable environmental problem. However, there is still a considerable knowledge gap about the impact of NPs and pollutants on human health risks. In this study, the human gastric adenocarcinoma (AGS) cells were used as a model to investigate the toxicity of NPs with different particle sizes and As by MTT assay, western blotting, immunofluorescence and so on. The results showed that 20 nm (8 μg/mL), 50 nm (128 μg/mL), 200 nm (128 μg/mL), 500 nm (128 μg/mL), 1000 nm (128 μg/mL) polystyrene (PS) did not affect cell viability, ROS, intracellular calcium and activate apoptosis pathway in AGS cells. However, noncytotoxic concentration of NPs enhanced the cytotoxicity and intracellular accumulation of As. NPs destroys the fluidity of cell membrane and cytoskeleton, inhibits the activity of ABC transporter, and leads to the accumulation of As in cells. This work highlights that the damage caused by NPs, especially at the level of noncytotoxicity, joint with As cannot be ignored and provides a specific toxicological mechanism of NPs accompanied by exposure to As.

Effects of Long-Term Exposure to Copper on the Keap1/Nrf2 Signaling Pathway and Msr-Related Redox Status in the Kidneys of Rats

The objective of the present study was to examine the effects of long-term exposure on oxidative damage, Keap1/Nrf2 signaling pathway, and Msr-related redox status in the kidneys of rats. Therefore, in this experimental study, a total of 32 CD-1 rats were randomized into 4 groups and treated with 30-, 60-, and 120-mg/kg Cu for 24 weeks. Different serum biomarkers suggestive of renal functions, pathological changes, and oxidative stress were analyzed in kidney tissues. Moreover, the levels of the Keap1/Nrf2 signaling pathway and redox status-related gene mRNA and proteins were also detected. The results indicated that Cu exposure dramatically increased the contents of creatinine and carbamide. Furthermore, histopathological alterations and mitochondrial damage in kidneys of rats of different Cu-treated groups were obviously observed. In addition, Cu exposure markedly changed the levels of glutathione, catalase, and total antioxidant capacity, and upregulated the contents of protein carbonyl, nitric oxide, and malondialdehyde. Moreover, higher levels of Cu treatments significantly increased the expression of Keap1/Nrf2 signaling pathway and redox status-related genes (NQO1, SOD-1, TRX, MsrA, MsrB1, MsrB2, MsrB3). Simultaneously, the mRNA expression levels of Nrf2, HO-1, and CAT were upregulated in rats exposed to 30- and 60-mg/kg Cu, but downregulated in the 120-mg/kg Cu group compared with the control group. Moreover, the Keap1/Nrf2 signaling pathway and redox status-related protein expression levels (HO-1, SOD-1, TRX, MsrA, MsrB1, MsrB2) were significantly increased in treated rats. In summary, it is suggested that the Keap1/Nrf2 signaling pathway and activation of Msr prevent Cu-induced nephrotoxicity and attenuate oxidative damage.

Comprehensive Interrogation of Metabolic and Bioenergetic Responses of Early-Staged Zebrafish (Danio rerio) to a Commercial Copper Hydroxide Nanopesticide

The use of copper hydroxide nanopesticide can pose exposure risks to aquatic organisms. In this study, the toxicity of a copper hydroxide nanopesticide, compared to conventional copper sulfate at environmentally relevant doses, was evaluated using metabolomics and bioenergetic assays in embryonic zebrafish. At a copper concentration of 100 μg/L, the nanopesticide caused higher mortality and deformity compared to copper ions alone; despite higher copper accumulation, increased metallothionein and elevated ATP-binding cassette (ABC) transporter activity in zebrafish exposed to copper ions were observed. Both nanopesticide and copper ions reduced the abundance of metabolites of glycolysis and induced energetic stress in zebrafish. The nanopesticide also increased concentrations of several organic acids involved in the tricarboxylic acid (TCA) cycle and elevated the activity of isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, suggesting enhanced TCA cycle activity. Nanopesticide exposure depleted both glutamate and glutamine parallel to the upregulation of the TCA cycle. In addition, zebrafish exposed to the nanopesticide appeared to shift metabolism toward amino acid catabolism and lipid accumulation based upon altered expression profiles of glutaminase, glutamate dehydrogenase, fatty acid synthase, and acetyl-CoA carboxylase. Lastly, the ability of the ions to increase oxidative phosphorylation to alleviate energetic stress was reduced in the case of the nanopesticide. We hypothesize that, unlike copper ions alone, the nanopesticide induces higher toxicity to zebrafish because of increased protein catabolism. This study provides a comprehensive understanding of the risks of copper hydroxide nanopesticide exposure in relation to metabolic activity and mitochondrial function.

Nrf2 signaling promotes cancer stemness, migration, and expression of ABC transporter genes in sorafenib-resistant hepatocellular carcinoma cells

Background and aim

As a multiple tyrosine kinase inhibitor, sorafenib is widely used to treat hepatocellular carcinoma (HCC), but patients frequently face resistance problems. Because the mechanism controlling sorafenib-resistance is not well understood, this study focused on the connection between tumor characteristics and the Nrf2 signaling pathway in a sorafenib-resistant HCC cell line.

Methods

A sorafenib-resistant HCC cell line (Huh7) was developed by increasing the dose of sorafenib in the culture medium until the target concentration was reached. Cell morphology, migration/invasion rates, and expression of stemness-related and ATP-binding cassette (ABC) transporter genes were compared between sorafenib-resistant Huh7 cells and parental Huh7 cells. Next, a small interfering RNA was used to knock down Nrf2 expression in sorafenib-resistant Huh7 cells, after which cell viability, stemness, migration, and ABC transporter gene expression were examined again.

Results

Proliferation, migration, and invasion rates of sorafenib-resistant Huh7 cells were significantly increased relative to the parental cells with or without sorafenib added to the medium. The expression levels of stemness markers and ABC transporter genes were up-regulated in sorafenib-resistant cells. After Nrf2 was knocked down in sorafenib-resistant cells, cell migration and invasion rates were reduced, and expression levels of stemness markers and ABC transporter genes were reduced.

Conclusion

Nrf2 signaling promotes cancer stemness, migration, and expression of ABC transporter genes in sorafenib-resistant HCC cells.

Genetic variation and urine cadmium levels: ABCC1 effects in the Strong Heart Family Study

Genetic effects are suspected to influence cadmium internal dose. Our objective was to assess genetic determinants of urine cadmium in American Indian adults participating in the Strong Heart Family Study (SHFS). Urine cadmium levels and genotyped short tandem repeat (STR) markers were available on 1936 SHFS participants. We investigated heritability, including gene-by-sex and smoking interactions, and STR-based quantitative trait locus (QTL) linkage, using a variance-component decomposition approach, which incorporates the genetic information contained in the pedigrees. We also used available single nucleotide polymorphisms (SNPs) from Illumina's Metabochip and custom panel to assess whether promising QTLs associated regions could be attributed to SNPs annotated to specific genes. Median urine cadmium levels were 0.44 μg/g creatinine. The heritability of urine cadmium concentrations was 28%, with no evidence of gene-by-sex or -smoking interaction. We found strong statistical evidence for a genetic locus at chromosome 16 determining urine cadmium concentrations (Logarithm of odds score [LOD] = 3.8). Among the top 20 associated SNPs in this locus, 17 were annotated to ABCC1 (p-values from 0.0002 to 0.02), and attenuated the maximum linkage peak by a ∼40%. Suggestive QTL signals (LOD>1.9) in chromosomes 2, 6, 11, 14, and 19, showed associated SNPs in the genes NDUFA10, PDE10A, PLEKHA7, BAZ1A and CHAF1A, respectively. Our findings support that urinary cadmium levels are heritable and influenced by a QTL on chromosome 16, which was explained by genetic variation in ABCC1. Studies with extended sets of genome-wide markers are needed to confirm these findings and to identify additional metabolism and toxicity pathways for cadmium.

Characterization of cadmium-responsive transcription factors in wolf spider Pardosa pseudoannulata

Transcription factors (TFs) act on the regulation of gene expression, which is prevalent in all organisms, and their characterization may provide important clues for understanding the regulatory mechanism of gene expression. In this research, inhibited growth (delayed developmental time and decreased body weight) and increased activities of antioxidant enzymes (peroxidase, superoxide dismutase, and catalase) were recorded in Pardosa pseudoannulata in response to cadmium burden. Expression profiles of TFs were analyzed based on the transcriptome profiling of P. pseudoannulata, and 1711 TFs genes were differentially expressed with 995 up-regulated and 716 down-regulated. Most of the differentially expressed TFs belonged to zf-C2H2, ZBTB, Homeobox, and bHLH families. Interestingly, hub genes smads, TCF7L2, EGR1, and GATA5 were identified to be the candidate Cd-responsive TFs related to growth of spider. The expression level of Sod2 (superoxide dismutase) was regulated by the up-regulated TF foxo3, implying its important role in the antioxidant defense of spider. Moreover, sequence analysis demonstrated that smads and foxo3 were conserved among spiders and insects. This study revealed for the first time the role of TFs in molecular response of P. pseudoannulata to Cd stress, providing the basis for the protection of tarantula under Cd stress.

Involvement of ABC transporters in the detoxification of non-substrate nanoparticles in lung and cervical cancer cells

This paper aimed to systemically investigate the role of adenosine triphosphate-binding cassette (ABC transporters) in the detoxification of non-substrate nanoparticles including titanium dioxide (n-TiO₂, 5-10 nm) and gold (AuNPs, 3 nm, 15 nm, and 80 nm, named as Au-3, Au-15 and Au-80) in human lung cancer (A549) and human cervical cancer (HeLa) cells. All these nanoparticles were of larger hydrophilic diameters than the channel sizes of ABC transporters, thus should not be the substrates of membrane proteins. After 24-h treatment, they induced significant cytotoxicity as reflected by the reduction in cell viability and glutathione (GSH) contents, as well as the increase in reactive oxygen species (ROS) level. At median-lethal concentrations (10 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for A549 cells; 20 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for Hela cells), all the nanoparticles significantly induced the gene expressions and activities of ABC transporters including P-glycoprotein (PGP) and multidrug resistance associated protein 1 (MRP1). Addition of transporter inhibitors enhanced the ROS levels produced by nanoparticles, but didn't alter their death-inducing effects and intracellular accumulations. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (NRF2) and pregnane X receptor (PXR) were proved to be important in the induction of ABC transporters by nanoparticles. After all, this paper revealed a damage-dependent modulation of ABC transporters by non-substrate nanoparticles. The up-regulated ABC transporters could help in reducing the oxidative stress produced by nanoparticles. Such information should be useful in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants or drugs.

The role of Nrf2 in mitigating cadmium-induced oxidative stress of Marsupenaeus japonicus

Nuclear factor-erythroid 2-related factor-2 (Nrf2) is an important modulator of cellular responses against Cd in mammalian cells. However, whether such modulation is conserved in Marsupenaeus japonicas remains unknown.In our study, the shrimps were injected with dsRNA targeting Nrf2 at 4 μg g^-1 body weight (b.w.) or sulforaphane (SFN) at 5 μg g^-1 b.w., and then were exposed to 40 mg L^-1 CdCl₂ for 48 h. After Nrf2 knockdown, the Cd content increased, but decreased in the SFN group. This suggested that Nrf2 could promote Cd excretion. A terminal deoxynulceotidyl transferase nick-end-labeling (TUNEL) assay revealed that the Nrf2 knockdown increased the number of apoptotic cells in M. japonicas, while SFN decreased the number of apoptotic cells. After Nrf2 knockdown, the total antioxidant capacity (T-AOC), superoxide dismutase (Sod) activity, and related gene expression decreased significantly, while the malondialdehyde (MDA) content increased remarkably. By contrast, SFN injection alleviated the oxidative stress, as evidenced by increased T-AOC, Sod activity, sod mRNA expression and a reduced MDA content. Similarly, detoxification related enzyme activities (ethoxyresorufin O-deethylase and glutathione-S-transferase (GST)) and their corresponding gene expressions (cyp3a (cytochrome P450 family 3 subfamily A) and gst) were suppressed in the ds-Nrf2 injection group, while they were elevated in the SFN group. In addition, ds-Nrf2 activated mitochondrial apoptotic pathway, as evidenced the mRNA and protein levels of caspase-3, Bcl2 associated X protein (Bax), and p53, while SFN treatment suppressed them. These results displayed that in M. japonicus Cd-induced cellular oxidative damage probably acts via the Nrf2 pathway.