Effects of Nrf2-Keap1 signaling pathway on antioxidant defense system and oxidative damage in the clams Ruditapes philippinarum exposure to PAHs

Urinary Metabolites of Polycyclic Aromatic Hydrocarbons of Rural Population in Northwestern China: Oxidative Stress and Health Risk Assessment

Polycyclic aromatic hydrocarbon (PAH) exposure is suspected to be linked to oxidative damage. Herein, ten PAH human exposure biomarkers [hydroxylated PAH metabolites (OH-PAHs)] and five oxidative stress biomarkers (OSBs) were detected in urine samples collected from participants living in a rural area (n = 181) in Northwestern China. The median molar concentration of ΣOH-PAHs in urine was 47.0 pmol mL-1. The 2-hydroxynaphthalene (2-OHNap; median: 2.21 ng mL-1) was the dominant OH-PAH. The risk assessment of PAH exposure found that hazard index (HI) values were <1, indicating that the PAH exposure of rural people in Jingyuan would not generate significant cumulative risks. Smokers (median: 0.033) obtained higher HI values than nonsmokers (median: 0.015, p < 0.01), suggesting that smokers face a higher health risk from PAH exposure than nonsmokers. Pearson correlation and multivariate linear regression analysis revealed that ΣOH-PAH concentrations were significant factors in increasing the oxidative damage to deoxyribonucleic acid (DNA) (8-hydroxy-2'-deoxyguanosine, 8-OHdG), ribonucleic acid (RNA) (8-oxo-7,8-dihydroguanine, 8-oxoGua), and protein (o, o'-dityrosine, diY) (p < 0.05). Among all PAH metabolites, only 1-hydroxypyrene (1-OHPyr) could positively affect the expression of all five OSBs (p < 0.05), suggesting that urinary 1-OHPyr might be a reliable biomarker for PAH exposure and a useful indicator for assessing the impacts of PAH exposure on oxidative stress. This study is focused on the relation between PAH exposure and oxidative damage and lays a foundation for the study of the health effect mechanism of PAHs.

JNK regulates the Nrf2/NQO1-ARE pathway against Microcystins-Induced oxidative stress in freshwater mussel Cristaria plicata

In response to stress, cells can utilize several processes, such as the activation of the Nrf2/Keap1 pathway as a critical regulator of oxidative stress to protect against oxidative damage. C-Jun N-terminal kinase (JNK), a member of the mitogen-activated protein kinase (MAPK) family, is involved in regulating the NF-E2-related nuclear factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway. NAD(P)H quinone redox enzyme-1 (NQO1), a downstream target gene of the Nrf2 pathway, plays a vital role in removing peroxide and providing resistance to oxidative injury. We found that microcystins (MCs) stimulated CpNrf2 to express and increase anti-oxidative enzyme activities in a previous experiment. In our current study, the full-length cDNAs of JNK and NQO1 from Cristaria plicata (designated CpJNK and CpNQO1) were cloned. The relative levels of CpJNK and CpNQO1 were high in hepatopancreas. Upon MCs induction, the relative level of CpNQO1 was increased, whereas that of CpJNK was decreased significantly. In contrast, CpNrf2 knockdown upregulated the expression of CpJNK mRNA and phosphorylation of CpJNK protein (Cpp-JNK), but inhibited CpNQO1 expression. Additionally, we found that JNK inhibitor SP600125 stimulated expression of CpNQO1 and CpNrf2 upon exposure to MCs, and we further confirmed that CpNrf2 protein combined with the ARE element in CpNQO1 gene promoter in vitro, and increased CpNQO1-ARE-luciferase activity in a CpNrf2-dependent manner. These findings indicated C. plicata effectively alleviated MC-induced oxidative injury through JNK participated in regulating the Nrf2/NQO1-ARE pathway.

ChIP-seq identifies McSLC35E2 as a novel target gene of McNrf2 in Mytilus coruscus, highlighting its role in the regulation of oxidative stress response in marine mollusks

NF-E2-related factor 2 (Nrf2) plays a crucial role in the oxidative regulatory process, which could trigger hundreds of antioxidant elements to confront xenobiotics. In the previous study, we identified Nrf2 from the marine mussel Mytilus coruscus, and the findings demonstrated that McNrf2 effectively protected the mussels against oxidative stress induced by benzopyrene (Bap). In order to delve deeper into the underlying mechanism, we utilized Chromatin Immunoprecipitation followed by sequencing (ChIP-seq) technology to systematically identify potential novel target genes of McNrf2. A total of 3,465 potential target genes were screened, of which 219 owned binding sites located within the promoter region. During subsequent experimental verification, it was found that McSLC35E2, a candidate target gene of McNrf2, exhibited negative regulation by McNrf2, as confirmed through dual luciferase and qRT-PCR detection. Further, the enzyme activity tests demonstrated that McNrf2 could counteract Bap induced oxidative stress by inhibiting McSLC35E2. The current study provides valuable insights into the application of ChIP-seq technology in the research of marine mollusks, advancing our understanding of the key role of Nrf2 in antioxidant defense mechanisms, and highlighting the significance of SLC35E2 in the highly sophisticated regulation of oxidative stress response in marine invertebrates.

Different effects of continuous and pulsed Benzo[a]pyrene exposure on metabolism and antioxidant defense of large yellow croaker: Depend on exposure duration

This study aims to compare differential effects of continuous and pulsed BaP exposures on metabolism and antioxidant defense in the liver of large yellow croaker. Fish were subjected to BaP for 4 days and 36 days in three exposure regimes with the same time-averaged concentration of BaP: 4 μg/L BaP continuously, 8 μg/L BaP for 24 h every other day or 16 μg/L BaP for 24 h every 4 days. Our results showed that compared to pulsed BaP exposures, continuous BaP exposure reduced BaP metabolism (CYP1A, CYP3A and AHR transcriptional expressions, GSH content, GSH/GSSG ratio, EROD and GST activities) and antioxidant defense (T-SOD activity) on day 4, resulting to the increases in MDA and PC contents, indicating that continuous BaP exposure induced more severe oxidative damage during the early stage of exposure. But continuous BaP exposure reduced MDA and PC contents by improving BaP metabolism and antioxidant defense during the late stage of exposure. CYP1B transcriptional expression and CAT activity were unsuitable biomarkers of both continuous and pulsed BaP exposures. In conclusion, our results demonstrated differential effects of continuous and pulsed exposures on BaP metabolism and antioxidant responses, which were depend on exposure duration.

The role of Nrf2 in protection against electrostatic field-induced oxidative stress and learning and memory decline in mice

The intensity of static electric field (SEF) in the surrounding environment of transmission lines has been greatly increased with the rapid development of ultra-high-voltage direct-current transmission. Therefore, the potential health effects of SEF have stimulated great public attention. It has been proven that SEF exposure can cause reversible damage to the nervous system through oxidative stress; however, the mechanism of its recovery is unclear. This study focused on nuclear factor erythroid 2-related factor 2 (Nrf2), a vital regulator of oxidative stress, and has been identified to notably impact the protection of organisms against many external stimuli. Herein, it was found that 56.3 kV/m SEF exposure for 7 days and 14 days significantly improved the expression levels of Nrf2 protein in the cytoplasm and nucleus of mice' hippocampus, as well as antioxidant genes, superoxide dismutase 2, and glutathione peroxidase 1. No significant difference in the expression level of the Nrf2 gene was found. The results indicated that the body could activate the Nrf2 signalling under SEF exposure by means other than up-regulation of Nrf2 gene expression. Inhibiting Nrf2 signalling by isoniazid could block SEF-induced gene transcription and protein expression, resulting in a decrease in antioxidant capacity, an increase in the level of lipid peroxide product, and irretrievability of learning and memory damage. These results demonstrated that the Nrf2 signalling pathway exhibited a protective role in SEF-induced oxidative damage and decline in learning and memory ability, which provides a potential strategy for preventing and treating SEF-related neurotoxicity.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. Methods: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. Results: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. Conclusions: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.