Oxidative stress activates the Nrf2-mediated antioxidant response and P38 MAPK pathway: A possible apoptotic mechanism induced by BDE-47 in rainbow trout (Oncorhynchus mykiss) gonadal RTG-2 cells

Toxicity of methylmercury in aquatic organisms and interaction with environmental factors and coexisting pollutants: A review

Mercury is a hazardous heavy metal that is distributed worldwide in aquatic ecosystems. Methylmercury (MeHg) poses significant toxicity risks to aquatic organisms, primarily through bioaccumulation and biomagnification, due to its strong affinity for protein thiol groups, which results in negative effects even at low concentrations. MeHg exposure can cause various physiological changes, oxidative stress, neurotoxicity, metabolic disorders, genetic damage, and immunotoxicity. To assess the risks of MeHg contamination in actual aquatic ecosystems, it is important to understand how MeHg interacts with environmental factors such as temperature, pH, dissolved organic matter, salinity, and other pollutants such as microplastics and organic compounds. Complex environmental conditions can cause potential toxicity, such as synergistic, antagonistic, and unchanged effects, of MeHg in aquatic organisms. This review focuses on demonstrating the toxic effects of single MeHg exposure and the interactive relationships between MeHg and surrounding environmental factors or pollutants on aquatic organisms. Our review also recommends further research on biological and molecular responses in aquatic organisms to better understand the potential toxicity of combinational exposure.

Protective Effects of Isoliquiritigenin and Licochalcone B on the Immunotoxicity of BDE-47: Antioxidant Effects Based on the Activation of the Nrf2 Pathway and Inhibition of the NF-κB Pathway

2,2',4,4'-Tetrabrominated biphenyl ether (BDE-47) is a polybrominated diphenyl ether (PBDE) homologue that is ubiquitous in biological samples and highly toxic to humans and other organisms. Prior research has confirmed that BDE-47 can induce oxidative damage in RAW264.7 cells, resulting in apoptosis and impaired immune function. The current study mainly focused on how Isoliquiritigenin (ISL) and Licochalcone B (LCB) might protect against BDE-47's immunotoxic effects on RAW264.7 cells. The results show that ISL and LCB could increase phagocytosis, increase the production of MHC-II, and decrease the production of inflammatory factors (TNF-α, IL-6, and IL-1β) and co-stimulatory factors (CD40, CD80, and CD86), alleviating the immune function impairment caused by BDE-47. Secondly, both ISL and LCB could reduce the expressions of the proteins Bax and Caspase-3, promote the expression of the protein Bcl-2, and reduce the apoptotic rate, alleviating the apoptosis initiated by BDE-47. Additionally, ISL and LCB could increase the levels of antioxidant substances (SOD, CAT, and GSH) and decrease the production of reactive oxygen species (ROS), thereby counteracting the oxidative stress induced by BDE-47. Ultimately, ISL and LCB suppress the NF-κB pathway by down-regulating IKBKB and up-regulating IκB-Alpha in addition to activating the Nrf2 pathway and promoting the production of HO-1 and NQO1. To summarize, BDE-47 causes oxidative damage that can be mitigated by ISL and LCB through the activation of the Nrf2 pathway and inhibition of the NF-κB pathway, which in turn prevents immune function impairment and apoptosis. These findings enrich the current understanding of the toxicological molecular mechanism of BDE-47 and the detoxification mechanism of licorice.

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

Pathway-dependent toxic interaction between polystyrene microbeads and methylmercury on the brackish water flea Diaphanosoma celebensis: Based on mercury bioaccumulation, cytotoxicity, and transcriptomic analysis

Given their worldwide distribution and toxicity to aquatic organisms, methylmercury (MeHg) and microplastics (MP) are major pollutants in marine ecosystems. Although they commonly co-exist in the ocean, information on their toxicological interactions is limited. Therefore, to understand the toxicological interactions between MeHg and MP (6-μm polystyrene), we investigated the bioaccumulation of MeHg, its cytotoxicity, and transcriptomic modulation in the brackish water flea Diaphanosoma celebensis following single and combined exposure to MeHg and MP. After single exposure to MeHg for 48-h, D. celebensis showed high Hg accumulation (34.83 ± 0.40 μg/g dw biota) and cytotoxicity, which was reduced upon co-exposure to MP. After transcriptomic analysis, 2, 253, and 159 differentially expressed genes were detected in the groups exposed to MP, MeHg, and MeHg+MP, respectively. Genes related to metabolic pathways and the immune system were significantly affected after MeHg exposure, but the effect of MeHg on these pathways was alleviated by MP co-exposure. However, MeHg and MP exhibited synergistic effects on the expression of gene related to DNA replication. These findings suggest that MP can reduce the toxicity of MeHg but that their toxicological interactions differ depending on the molecular pathway.

Effect of Glutamine on the Growth Performance, Oxidative Stress, and Nrf2/p38 MAPK Expression in the Livers of Heat-Stressed Broilers

The purpose of this work was to study the effects of glutamine (Gln) on the growth performance, oxidative stress, Nrf2, and p38 MAPK pathway in the livers of heat-stressed broilers. In total, 300 broilers were divided into five groups, including a normal temperature (NT, without dietary Gln) group and four cyclic high temperature groups (HT, GHT1, GHT2, and GHT3) fed with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. High temperature conditions increased (p < 0.05) liver malonaldehyde (MDA) concentration, but decreased (p < 0.05), body weight gain (BWG), feed intake (FI), liver superoxide dismutase (SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione (GSH) levels in broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were lower (p < 0.05) in the NT group than that in the HT group. However, dietary 1.5% Gln decreased (p < 0.05) liver MDA concentration, but increased (p < 0.05) BWG, FI, liver SOD, T-AOC, GSH-Px, GST, and GSH levels in heat-stressed broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were higher (p < 0.05) in the GHT3 group than that in the HT group. In summary, Gln improved oxidative damage through the activation of Nrf2 and p38 MAPK expression in the livers of heat-stressed broilers.

DBDPE and ZnO NPs synergistically induce neurotoxicity of SK-N-SH cells and activate mitochondrial apoptosis signaling pathway and Nrf2-mediated antioxidant pathway

Decabromodiphenyl ethane (DBDPE), a new brominated flame retardant, could negatively affect neurobehavior and pose health risks to humans. Humans are also exposed to widely used nanomaterials. This study investigated the combined toxic effects and action types of DBDPE and Zinc oxide nanoparticles (ZnO NPs) on human neuroblastoma SK-N-SH cells and the toxicity mechanisms. DBDPE inhibited the viability of SK-N-SH cells by 21.87% at 25 mg/L. ZnO NPs synergistically exacerbated the toxic effects of DBDPE. DBDPE and ZnO NPs caused excessive ROS production and inhibition of antioxidant enzyme (SOD and GSH) activity in cells, thus causing oxidative cellular damage. Moreover, DBDPE and ZnO NPs caused apoptosis by disrupting mitochondrial kinetic homeostasis, reducing mitochondrial membrane potential (MMP), increasing cytochrome C release and regulating Bax/Bcl-2 and Caspase-3 mRNA and protein expression. DBDPE and ZnO NPs increased the mRNA expression of nuclear factor erythroid 2- related factor (Nrf2) and its downstream genes. The molecular mechanisms revealed that oxidative stress, apoptosis and mitochondrial dysfunction were the critical factors in combined cytotoxicity. The bioinformatics analysis further indicated that co-exposure affected Nrf2 activation, apoptotic factors expression and mitochondrial fusion. The findings enrich the risk perception of neurotoxicity caused by DBDPE and ZnO NPs.

Thiram induces myocardial oxidative damage and apoptosis in broilers via interfering their cardiac metabolism

Thiram is a dithiocarbamate pesticide extensively used as a fungicide to preserve crops and seeds. Long-term exposure to thiram causes potential harm to the health of human beings and animals. So far, most of the researches on thiram focused on erythrocyte toxicity, immune system, kidney damage, and tibial dyschondroplasia; however, there is less data on cardiac toxicity. In this study, we examined cardiac histopathology, inflammatory factors, oxidative stress indicators, and apoptosis markers in the heart of broilers that were exposed to thiram. According to our findings, the continuous exposure to thiram caused pathological changes and abnormal function of myocardial tissues with increased level of inducible nitric oxide synthase (iNOS), inflammatory factors (IL-6, IL-8, TNF-α and NF-κB), and decreased level of anti-inflammatory factor (IL-10). In addition, thiram significantly upregulated the protein expression of cleaved-caspase 3, cleaved-PARP, and caused cardiomyocyte apoptosis. Meanwhile, the expression of heat shock proteins (HSP60, HSP70, HSP90) markedly decreased in the thiram-treated groups. An excessive accumulation of peroxidation products (MDA, H₂O₂), a decrease in T-AOC, and antioxidant activity enzymes (T-SOD, GST and GPX) were also noticed, all of which led to oxidative stress and activation of Nrf2 signal pathway by up-regulating key target genes (HO-1 and SODs). Thiram-induced metabolites were further identified via non-targeted metabonomic analysis. Correlation analysis revealed eighteen differentially expressed metabolites, closely related to cardiac injury. Importantly, thiram primarily affected the taurine and hypotaurine metabolism, pyrimidine metabolism as well as glycerol metabolism. Collectively, our study suggests that thiram could cause cardiotoxicity by interfering with taurine and hypotaurine metabolism, pyrimidine metabolism, and glycerolipid metabolism, which further induce oxidative stress via triggering Nrf2 signal pathway. This study may provide new evidence for the molecular mechanism of cardiotoxicity caused by thiram and resonate the alarm for animals and workers who have been exposed to thiram for a long time.

Prophylactic role of olive fruit extract against cigarette smoke-induced oxidative stress in Sprague-Dawley rats

Cigarette smoke exposure increases the production of free radicals leading to initiation of several pathological conditions by triggering the oxidative stress and inflammatory cascade. Olive fruit owing to its unique phytochemical composition possesses antioxidant, immune modulatory, and anti-inflammatory potential. Considering the compositional alterations in olive fruits during ripening, the current experimental trail was designed to investigate the prophylactic role of green and black olives against the oxidative stress induced by cigarette smoke exposure in rats. Purposely, rats were divided into five different groups: NC (negative control; normal diet), PC [positive control; normal diet + smoke exposure (SE)], drug (normal diet + SE + citalopram), GO (normal diet + SE + green olive extract), and BO (normal diet + SE + black olive extract). Rats of all groups were exposed to cigarette smoke except "NC" and were sacrificed for collection of blood and organs after 28 days of experimental trial. The percent reduction in total oxidative stress by citalopram and green and black olive extracts in serum was 29.72, 58.69, and 57.97%, respectively, while the total antioxidant capacity increased by 30.78, 53.94, and 43.98%, accordingly in comparison to PC. Moreover, malondialdehyde (MDA) was reduced by 29.63, 42.59, and 45.70% in drug, GO, and BO groups, respectively. Likewise, green and black olive extracts reduced the leakage of hepatic enzymes in sera, alkaline phosphatase (ALP) by 23.44 and 25.80% and 35.62 and 37.61%, alanine transaminase (ALT) by 42.68 and 24.39% and 51.04 and 35.41%, and aspartate transaminase (AST) by 31.51 and 16.07% and 40.50 and 27.09% from PC and drug group, respectively. Additionally, olive extracts also maintained the antioxidant pool, i.e., superoxide dismutase, catalase, and glutathione in serum. Furthermore, histological examination revealed that olive extracts prevented the cigarette smoke-induced necrosis, pyknotic alterations, and congestion in the lung, hepatic, and renal parenchyma. Besides, gene expression analysis revealed that olive extracts and citalopram decreased the brain and lung damage caused by stress-induced upregulation of NRF-2 and MAPK signaling pathways. Hence, it can be concluded that olives (both green and black) can act as promising antioxidant in alleviating the cigarette smoke-induced oxidative stress.

Taxifolin Modulates Transcriptomic Response to Heat Stress in Rainbow Trout, Oncorhynchus mykiss

Taxifolin is a natural flavonoid known for its antioxidant, anti-inflammatory, and antiproliferative effects on animals. In this work, we have studied the effect of this compound on rainbow trout, Oncorhynchus mykiss, a major object of aquaculture, under slowly increasing ambient temperature and Gyrodactylus flatworm infection. Transcriptomic profiling of liver samples performed by using the Illumina HiSeq 2500 sequencing platform shows that a combined taxifolin/heat treatment, unlike heat treatment alone, downregulates the production of isopentenyl diphosphate, likely affecting the production of cholesterol and other sterols. Taxifolin treatment also modulates multiple apoptosis regulators and affects the expression of HSPs in response to increasing temperature. On the other hand, the expression of antioxidant enzymes in response to heat is not significantly affected by taxifolin. As for the Gyrodactylus infection, the parasite load is not affected by taxifolin treatment, although it was lower in the high-temperature group. Parasite load also did not induce a statistically significant transcriptomic response within the no heat/no taxifolin group.

Transcriptome and biochemical analyses of rainbow trout (Oncorhynchus mykiss) RTG-2 gonadal cells in response to BDE-47 stress indicates effects on cell proliferation

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is a biotoxin of polybrominated diphenyl ether (PBDEs) frequently detected in the environment. Apoptosis and cell cycle arrest are important toxic phenomena of xenobiotics that inhibit cell proliferation. In this study, we investigated the effects of BDE-47 (5 μM, 10 μM, 20 μM, 40 μM) on cell viability, morphology, cell cycle and apoptosis. BDE-47 significantly decreased cell viability, and morphological alterations were observed. The significant increase in cells at G1 phase indicated the occurrence of G1 phase cell cycle arrest in RTG-2 cells. An acridine orange and ethidium bromide (AO/EB) staining assay was employed and revealed the induction of apoptosis in RTG-2 cells. The results indicated that BDE-47 exposure inhibits cell proliferation. Transcriptome analysis was applied for further evidence. A total of 1300 differentially expressed genes (DEGs) were identified in RTG-2 cells, among which 26 DEGs were associated with the cell cycle and apoptosis. Western blotting and qPCR analyses also showed the expression of cell cycle- and apoptosis-related proteins and genes. Mapping the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, p53, Tumor necrosis factor (TNF), Mitogen-activated protein kinase (MAPK), phosphatidylinositide 3-kinase-AKT (PI3K-AKT), and reaction oxygen species (ROS)-mediated signaling pathways were determined to be the major pathways involved in modulating the cell cycle and apoptosis. Since we demonstrated simultaneous ROS overproduction during BDE-47 exposure in a previous study, we speculated a possible explanation for the observation: BDE-47-induced ROS overproduction was the initiating signal, which activated cell cycle arrest and apoptosis and finally inhibited cell proliferation.

Exploring the molecular mechanisms of the inhibition of acrolein-induced BEAS-2B cytotoxicity by luteolin using network pharmacology and cell biology technology

Acrolein is a highly reactive unsaturated hazardous air pollutant, which is extremely irritating to the respiratory tract. Luteolin, an active flavonoid compound, possesses multiple biological activities. The purpose of this study was to evaluate the mechanism of the inhibition of acrolein-induced human bronchial epithelial (BEAS-2B) cells cytotoxicity by luteolin using network pharmacology and cell biology technology. Firstly, network pharmacology results indicated that oxidative stress processes might play an important role in luteolin inhibiting lung injury. Next, it was verified at the cellular level. Reactive oxygen species (ROS) generation increased, glutathione (GSH) level decreased after exposure to acrolein. MAPK signaling pathways were activated, which activated downstream IκBα/NF-κB signaling pathways. Meanwhile, acrolein caused oxidative DNA damage and double-strand breaks, induced DNA damage response (DDR) and apoptosis. These adverse effects were significantly reversed by luteolin, which inhibited the activation of MAPK/IκBα/NF-κB and DDR pathways, and reduced the ratio of Bax/Bcl-2. Moreover, luteolin also had a similar effect to antioxidant N-acetyl cysteine (NAC) in the regulation of signaling transduction mechanisms, which indicated that the regulation of oxidative stress played an important role in the process. These results provide an experimental basis for elucidating the molecular mechanisms of the inhibition of acrolein-induced BEAS-2B cytotoxicity with luteolin.

Targeting Mechanosensitive Piezo1 Alleviated Renal Fibrosis Through p38MAPK-YAP Pathway

Renal fibrosis is the most common pathological manifestation of a wide variety of chronic kidney disease. Increased extracellular matrix (ECM) secretion and enhanced microenvironment stiffening aggravate the progression of renal fibrosis. However, the related mechanisms remain unclear. Here, we evaluated the mechanism by which ECM stiffness aggravates renal fibrosis. In the present study, renal mesangial cells (MCs) were cultured on polyacrylamide hydrogels with different stiffness accurately detected by atomic force microscope (AFM), simulating the in vivo growth microenvironment of MCs in normal kidney and renal fibrosis. A series of in vitro knockdown and activation experiments were performed to establish the signaling pathway responsible for mechanics-induced MCs activation. In addition, an animal model of renal fibrosis was established in mice induced by unilateral ureteral obstruction (UUO). Lentiviral particles containing short hairpin RNA (sh RNA) targeting Piezo1 were used to explore the effect of Piezo1 knockdown on matrix stiffness-induced MCs activation and UUO-induced renal fibrosis. An in vitro experiment demonstrated that elevated ECM stiffness triggered the activation of Piezo1, which increased YAP nuclear translocation through the p38MAPK, and consequently led to increased ECM secretion. Furthermore, these consequences have been verified in the animal model of renal fibrosis induced by UUO and Piezo1 knockdown could alleviate UUO-induced fibrosis and improve renal function in vivo. Collectively, our results for the first time demonstrate enhanced matrix stiffness aggravates the progression of renal fibrosis through the Piezo1-p38MAPK-YAP pathway. Targeting mechanosensitive Piezo1 might be a potential therapeutic strategy for delaying the progression of renal fibrosis.