Two-stage hydrothermal oxygenation for efficient removal of Cr(VI) by starch-based polyporous carbon: Wastewater application and removal mechanism.

Cr(VI) is of concern because of its high mobility and toxicity. In this work, a two-stage hydrothermal strategy was used to activate the O sites of starch, and by inserting K-ion into the pores, starch-based polyporous carbon (S-PC) adsorption sites was synthesized for removal of Cr(VI). Physicochemical characterization revealed that the O content of the S-PC reached 20.66 % after activation, indicating that S-PC has excellent potential for adsorption of Cr(VI). The S-PC removal rate for 100 mg/L Cr(VI) was 96.29 %, and the adsorption capacity was 883.86 mg/g. Moreover, S-PC showed excellent resistance to interference, and an equal concentration of hetero-ions reduced the activity by less than 5 %. After 8 cycles of factory wastewater treatment, the S-PC maintained 81.15 % of its original activity, which indicated the possibility of practical application. Characterization and model analyses showed that the removal of Cr(VI) from wastewater by the S-PC was due to CC, δ-OH, ν-OH, and C-O-C groups, and the synergistic effect of adsorption and reduction was the key to the performance. This study provides a good solution for treatment of Cr(VI) plant wastewater and provides a technical reference for the use of biological macromolecules such as starch in the treatment of heavy metals.

Activation of estrogen-related receptor: An alternative mechanism of hexafluoropropylene oxide homologs estrogenic effects.

Perfluorooctanoic acid (PFOA) alternatives such as hexafluoropropylene oxide homologs (HFPOs) cause concern due to increased occurrence in the environment as well as potential bioaccumulation and toxicity. HFPOs have been demonstrated to activate the estrogen receptor (ER) pathway. The ER pathway is homologous and connected to the estrogen-related receptor (ERR) pathway, but HFPOs effects on the ERR pathway have not been studied. Hence, we assessed the potential estrogenic effects of HFPOs via ERRγ pathway. In vitro assays revealed that HFPO dimeric, trimeric, and tetrameric acids (HFPO-DA, -TA, and -TeA, respectively), acted as ERRγ agonists, activating the transcription of both human and zebrafish ERRγ at low concentrations, but inhibiting zebrafish ERRγ at high concentrations. We also found that HFPO-TA promoted the human endometrial cancer cells (Ishikawa cells) proliferation via ERRγ/EGF, Cyclin D1 pathway. The HFPO-TA-induced proliferation of Ishikawa cells was inhibited by co-exposure with a specific antagonist of ERRγ, GSK5182. In vivo exposure of female zebrafish to HFPO-TA disturbed sex hormone levels, interfered with the gene expression involved in estrogen synthesis and follicle regulation, and caused histopathological lesions in the ovaries, which were similar to those induced by a known ERRγ agonist GSK4716. Taken together, this study revealed a new mechanism concerning the estrogenic effect of HFPOs via activation of the ERRγ pathway.

Cross-Model Comparison of Transcriptomic Dose-Response of Short-Chain Chlorinated Paraffins.

Short-chain chlorinated paraffins (SCCPs) have attracted attention because of their toxicological potential in humans and wildlife at environmentally relevant doses. However, limited information is available regarding mechanistic differences across species in terms of the biological pathways that are impacted by SCCP exposure. Here, a concentration-dependent reduced human transcriptome (RHT) approach was conducted to evaluate 15 SCCPs in HepG2 cells and compared with our previous results using a reduced zebrafish transcriptome (RZT) approach in zebrafish embryos (ZFEs). Generally, SCCPs induced a broader suite of biological pathways in ZFEs than HepG2 cells, and all of the 15 SCCPs were more potent in HepG2 cells compared to ZFEs. Despite these general differences, the transcriptional potency of SCCPs in both model systems showed a significant linear relationship (p = 0.0017, r2 = 0.57), and the average ratios of transcriptional potency for each SCCP in RZT to that in RHT were ∼100,000. C10H14Cl8 was the most potent SCCP, while C10H17Cl5 was the least potent in both ZFEs and HepG2 cells. An adverse outcome pathway network-based analysis demonstrated model-specific responses, such as xenobiotic metabolism that may be mediated by different nuclear receptor-mediated pathways between HepG2 cells (e.g., CAR and AhR activation) and ZFEs (e.g., PXR activation). Moreover, induced transcriptional changes in ZFEs associated with pathways and molecular initiating events (e.g., activation of nicotinic acetylcholine receptor) suggest that SCCPs may disrupt neural development processes. The cross-model comparison of concentration-dependent transcriptomics represents a promising approach to assess and prioritize SCCPs.

Perfluorooctanoic acid-induced immunotoxicity via NF-kappa B pathway in zebrafish (Danio rerio) kidney.

Perfluorooctanoic acid (PFOA) is widely used in industrial production due to its stable chemical structure and hydrophobic and oleophobic characteristics. PFOA has been frequently detected in environmental media and organisms, leading to increased health risks. There is a lack of information about the immunotoxicity of aquatic organisms induced by PFOA, and the molecular mechanisms remain unclear. In this study, LC-MS analysis proved that PFOA can accumulate in the kidney of zebrafish. In the 0.05 mg/L PFOA treatment group, the accumulation of PFOA in the kidney after 21 days of exposure significantly increased by 79.89%, compared to 14 days of exposure. And a hydropic endoplasmic reticulum, swelling of mitochondria and vacuolization were observed in kidney immune cells of zebrafish. The Toll-like receptor 2 (TLR2)/myeloid differentiation factor 88 (myd88)/NF-κB (P65) pathway was activated when PFOA exerted its effects, which led to regulation of antibody expression; RT-PCR results showed that the mRNA expression level of interleukin-4 (IL-4) decreased in a dose-dependent manner, decreasing to 29.6% of the control level in the 1 mg/L PFOA group after 21 d of exposure. According to triangle plot analysis, immunoglobulin exhibited a notable stress response to PFOA at an early phase; a high concentration of PFOA may disrupt the immune system of zebrafish. Third-order polynomial fitting analysis showed that the high-mRNA-expression regions of IL-4 and antibodies were partially consistent. The results indicated that PFOA could affect antibodies by increasing the concentrations of proinflammatory cytokines. Changes in antibody levels further influenced the expression of other cytokines, which eventually caused disorders in the zebrafish immune system. This study expands the understanding of PFOA-induced immunosuppression and suggests that toxicity mechanisms should be considered for further health risk assessment of emerging pollutants.

Photodegradation of carbon dots cause cytotoxicity.

Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.

A Tiered Approach for Screening and Assessment of Environmental Mixtures by Omics and In Vitro Assays.

New methodology approaches with a broad coverage of the biological effects are urgently needed to evaluate the safety of the universe of environmentally relevant chemicals. Here, we propose a tiered approach incorporating transcriptomics and in vitro bioassays to assess environmental mixtures. The mixture samples and the perturbed biological pathways are prioritized by concentration-dependent transcriptome (CDT) and then used to guide the selection of in vitro bioassays for toxicant identification. To evaluate omics' screening capability, we first applied a CDT technique to test mixture samples by HepG2 and MCF7 cells. The effect recoveries of large-volume solid-phase extraction on the overall bioactivity of the mixture were 48.9% in HepG2 and 58.3% in MCF7. The overall bioactivity potencies obtained by transcriptomics were positively correlated with the panel of 8 bioassays among 14 mixture samples combined with the previous data. Transcriptomics could predict their activation status (AUC = 0.783) and the relative potency (p < 0.05) of bioassays for four of the eight receptors (AhR, ER, AR, and Nrf2). Furthermore, the CDT identified other biological pathways perturbated by mixture samples, such as the pathway related to TP53, CAR, FXR, HIF, THRA, etc. Overall, this study demonstrates the potential of concentration-dependent omics for effect-based water quality assessment.

Early Life Stage Bioactivity Assessment of Short-Chain Chlorinated Paraffins at Environmentally Relevant Concentrations by Concentration-Dependent Transcriptomic Analysis of Zebrafish Embryos.

Short-chain chlorinated paraffins (SCCPs), a class of ubiquitous pollutants, are considered to be embryotoxic and teratogenic. However, little is known regarding the bioactivity and mechanisms at environmentally relevant concentrations at the embryonic period. Here, a concentration-dependent reduced transcriptomic approach was used to evaluate the environmental dose (<100 ppb) effects of nine SCCP congeners and eight commercial mixtures on zebrafish embryos at 8 hpf. After 24 h of exposure, the overall biological potency of all the SCCPs, in terms of interference with 20% of the differentially expressed genes (PODDEG20), in zebrafish embryos ranged from 0.83 to 67.61 ppb. C10H14Cl8 (PODGO20 = 3.80 ppb) and C10-13 51.5% Cl (PODGO20 = 3.31 ppb) exhibited the strongest interference with biological processes compared to other SCCP homologs and mixtures, respectively. The most sensitive early molecular responses induced by SCCPs were associated with pathways of genetic damage, energy metabolite interference, and metal ion binding. Furthermore, the carbon number was positively correlated with the transcriptomic potency (PODGO20) of SCCP congeners (with chlorine content > 60%) (p = 0.038), and the chlorine content of SCCP congeners affected the bioactivity associated with genotoxic pathways. The concentration-dependent reduced transcriptomic approach significantly improved the understanding of the ecological risk of environmental contaminants at early life stages.

A critical review of synthetic chemicals in surface waters of the US, the EU and China.

There is a wide concern that emerging organic pollutants (EOPs) in surface water could adversely affect human health and wildlife. However, the geographic distribution, exposure pattern and ecological risk of emerging organic pollutants are poorly understood at a global scale. This paper provides a comprehensive survey on the exposure level of EOPs in China, the US and the EU based on the published literature. The hazard level of three categories of EOPs, namely pharmaceuticals and personal care products (PPCPs), pesticides and industrial chemicals was further evaluated by adopting a novel Aquatic HazPi index that jointly accounts for the persistence, bioaccumulation, toxicity and bioactivity. Furthermore, a correlation analysis of land use with the surface water exposure status regarding the synthetic chemicals was conducted. According to the published data reported between 2010 and 2016, the concentration of pesticides in the US was higher than in the EU and China. The concentration of PPCPs in the EU was generally lower than in both the US and China, while the concentration of industrial chemicals in China was higher than in the EU and the US. Among the chemicals whose median concentration in surface water was >10 ng/L, the antiretroviral Efavirenz, the pesticide Fipronil, and octocrylene, an industrial chemical and cosmetic ingredient, were found with the highest aquatic HazPi value. Lastly, the spatial distribution and concentration of hazardous EOPs was shown to depend on local landscape and land usages. Our study provides the first broad overview on the geographic distribution, exposure pattern of hazardous EOPs in the three major economic entities: China, the US and the EU.

Application of Environmental DNA Metabarcoding for Predicting Anthropogenic Pollution in Rivers.

Rivers are among the most threatened freshwater ecosystems, and anthropogenic activities are affecting both river structures and water quality. While assessing the organisms can provide a comprehensive measure of a river's ecological status, it is limited by the traditional morphotaxonomy-based biomonitoring. Recent advances in environmental DNA (eDNA) metabarcoding allow to identify prokaryotes and eukaryotes in one sequencing run, and could thus allow unprecedented resolution. Whether such eDNA-based data can be used directly to predict the pollution status of rivers as a complementation of environmental data remains unknown. Here we used eDNA metabarcoding to explore the main stressors of rivers along which community structure changes, and to identify the method's potential for predicting pollution status based on eDNA data. We showed that a broad range of taxa in bacterial, protistan, and metazoan communities could be profiled with eDNA. Nutrients were the main driving stressor affecting communities' structure, alpha diversity, and the ecological network. We specifically observed that the relative abundance of indicative OTUs was significantly correlated with nutrient levels. These OTUs data could be used to predict the nutrient status up to 79% accuracy on testing data sets. Thus, our study gives a novel approach to predicting the pollution status of rivers by eDNA data.

Screening hundreds of emerging organic pollutants (EOPs) in surface water from the Yangtze River Delta (YRD): Occurrence, distribution, ecological risk.

Increased synthetic chemical production and diversification in developing countries caused serious aquatic pollution worldwide with emerging organic pollutants (EOPs) detected in surface water rising health concerns to human and aquatic ecosystem even at low ng/L concentration with long-term exposure. The Yangtze River Delta (YRD) area serves agriculture and industry for people in eastern China. However, the current knowledge on the occurrence and ecological risk of diverse EOPs which are present in the aquatic environment is limited. This study was to investigate the complexity and diversity of EOPs in surface water from 28 sampling sites, which were selected to represent urban, industrial or agriculture areas in the YRD area. In total 484 chemicals were analyze by a target screening approach using liquid chromatography coupled to high-resolution tandem mass spectrometry (LC-HRMS/MS). 181 out of 484 EOPs were detected at least one site in the YRD area, and 44 analytes, mostly industrial chemicals and pesticides, were ubiquitous at all sampling sites. Most EOPs were industrial chemicals with 1H-benzotriazole and organophosphate flame retardants (PFRs) as the chemicals with highest concentrations. For 21 pesticides, mostly herbicides, maximum concentrations of atrazine and isoproturon were above the annual average environmental quality standards of Europe. Amantadine and DEET were the dominant pharmceuticals and personal care products (PPCPs) in the YRD area. Compared to urban areas (mostly in Qinhuai River), chemical profiles from industrial areas were more complex. Industrial activities likely have a strong impact on the composition of chemical mixtures in surface water from the YRD area. ISO E Super, 4-methylbenzylidene camphor and clotrimazole detected in this study are potentially persistent and bioaccumulative chemicals. Furthermore, results of risk assessment showed that hazard quotients of dimethyldioctadecylammonium, didecyldimethylammonium and octocrylene were higher than one and occur frequently, which indicates possibly adverse effects on fish species in the YRD area.

Functional genomics assessment of narcotic and specific acting chemical pollutants using E. coli.

The knowledge of gene-chemical interaction can be used to derive toxicological mechanism of chemical pollutants, therefore, it might be useful to discriminate chemicals with different mechanisms. In this study, three narcotic chemicals (4-chlorophenol (4-CP), 3, 4-dichloroaniline (DCA) and 2, 2, 2-trichloroethanol (TCE)) and three specific acting chemicals (triclosan (TCS), clarithromycin (CLARY), sulfamethoxazole (SMX)) were assessed by Escherichia coli (E. coli) genome-wide knockout screening. 66, 97, 88, 144, 198 and 180 initial robust hits were identified by exposure to 4-CP, DCA, TCE, TCS, CLARY and SMX with two replicates at the concentration of IC50, respectively. The average fold change values of responsive mutants to the three narcotic chemicals were smaller than the three specific acting chemicals. The common gene ontology (GO) term of biological process enriched by the three narcotic chemicals was "response to external stimulus" (GO: 0009605). Other GO terms like "lipopolysaccharide biosynthetic process" (induced by 4-CP) and "purine nucleotide biosynthetic process" (induced by DCA) were also influenced by the narcotic chemicals. The toxic target of three known specific acting chemicals could be validated by GSEA of responsive genes. Four genes (flhC, fliN, fliH and flhD) might serve as potential biomarkers to distinguish narcotic chemicals and specific acting chemicals. The E. coli functional genomic approach presented here has shown great potential not only for the molecular mechanistic screening of chemicals, rather it can discriminate chemicals based on their mode-of-action.

The role of interleukin family in perfluorooctanoic acid (PFOA)-induced immunotoxicity.

Perfluorooctanoic acid (PFOA), a prominent perfluorinated compound (PFC), has been widely detected in natural water bodies worldwide. In this study, zebrafish (Danio rerio) was exposed to nominal concentrations of PFOA (0.05, 0.1, 0.5, and 1 mg/L) for 21 d. After exposure, each fish was decapitated, and the spleen was removed to detect the expression patterns of P65 transcription factor, myeloid differentiation 88, relative interleukins (ILs), and antibody genes. PFOA can stimulate pro-inflammatory cytokine at a low exposure concentration (0.05 mg/L) and can inhibit pro-inflammatory cytokine at higher exposure concentrations (≥ 0.1mg/L). The results of linear correlation analysis indicate that Myd88/NF-κB pathway is one of the important pathways to mediate inflammatory cytokine (IL-1ß and IL-21) in zebrafish spleen. Additionally, the relative mRNA expression level of toll-like receptor 2 (TLR2) at 1mg/L PFOA group was decreased to 56% of its corresponding level in the control. IL secretion disorder is possibly closely related to PFOA-induced TLR2 damage in zebrafish spleen. Furthermore, data show that the trends of PFOA-induced IL secretion have a relationship with Ig-secreting trend. This study demonstrates that PFOA can affect IL expression level through NF-κB, and ILs have an important function in the mediation of Ig secretion.

[Joint effects of apoptosis induced by microcystins and bacterial lipopolysaccharides on grass carp (Ctenopharyngodon idellus) lymphocytes].

In this study, grass carp (Ctenopharyngodon idellus) lymphocytes were used as the vitro test object to demonstrate the joint effects of microcystins (MC-LR) and bacterial lipopolysaccharides (LPS) on fish immune system. The results showed that MC-LR and LPS in the single and combined exposure groups could both induce grass carp lymphocytes apoptosis with typical ladder-like DNA electrophoresis characteristics. However, comparing the apoptosis rate of the combined and single exposure groups, it was suggested that bacterial LPS could cooperate with MC-LR causing a higher rate of fish lymphocytes apoptosis (2.1 and 3.3-fold of that for the single exposure group I (MC-LR) and II (LPS), respectively), and there existed a significant dose-response relationship. The MC-LR cooperating with bacterial LPS decreased the activity of glutathione S-transferase (GST), increased the levels of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA), resulted in DNA damage and cell arrest in G0 phase, which inhibited cell proliferation and accelerated apoptosis. It was proved that MC-LR exacerbated fish immunotoxicity by collaborating with LPS, which had a serious adverse effect on aquaculture industry.

Protective role of oligomeric proanthocyanidin complex against hazardous nodularin-induced oxidative toxicity in Carassius auratus lymphocytes.

Nodularin (NOD) is a hazardous material widely detected in water blooms. Fish immune cells are extremely vulnerable to NOD-induced oxidative stress. Oligomeric proanthocyanidin complex (OPC), extracted from grapeseed, was used as an antioxidant to eliminate reactive oxygen species and prevent apoptotic effects. Carassius auratus lymphocytes were treated with different concentrations (0, 10, 100, and 1,000 µg/L) of OPC and a constant dose (100 µg/L) of NOD for 12h in vitro. OPC inhibited mitosis by decreasing intracellular levels of oxidative stress, regulating antioxidant enzymes (CAT, SOD, GPx, GR, and GST), mediating bcl-2 family proteins, and deactivating caspase-3. Glutathione (GSH) levels in group V (NOD 100 µg/L; OPC 1,000 µg/L) showed a twofold increase compared with corresponding levels in group II (NOD 100 µg/L). Structure parameters of NOD and NOD-GSH were calculated using SYBYL 7.1 software. ClogP and HINK logP values of NOD-GSH decreased by 10.4- and 2.3-fold, respectively, compared with corresponding values of NOD. OPC-stimulated GSH can lower the lipophilicity and polarity of NOD. OPC, as a protective agent, can alleviate NOD-induced toxicity in C. auratus lymphocytes by regulating oxidative stress and inducing NOD-GSH detoxification.

Regulatory effect of quercetin on hazardous microcystin-LR-induced apoptosis of Carassius auratus lymphocytes in vitro.

Microcystins (MCs) are secondary metabolites produced by cyanobacteria. Oxidative stress is considered the major cytotoxic mechanism of microcystin-LR (MCLR). Quercetin (QE) is a flavonoid that can eliminate reactive oxygen species (ROS) and elicit anti-inflammatory and anti-apoptotic effects. This study determined the regulatory effect of QE on the cytotoxicity and oxidative stress of Carassius auratus lymphocytes induced by 1 µg/L MCLR in vitro after 24 h. MCLR-mediated cytotoxicity and ROS formation in fish lymphocytes were suppressed by QE in a concentration-dependent manner. In addition, QE enhanced the endogenous antioxidant defense system and the Bax/Bcl-2 ratio to protect fish lymphocytes against oxidative stress and apoptosis induced by MCLR. Glutathione levels and catalase activities increased by approximately 3.9- and 2-fold, respectively, in the QE treatment group (1000 µg/L) compared with the MCLR treatment group. The percentage of apoptosis in the only MCLR treatment group was 59% whereas that in the control group was 23%. The percentage of apoptosis in the high-dose QE treatment group (1000 µg/L) was 29%, lower by nearly half compared with the only MCLR treatment group. QE (1000 µg/L) effectively inhibited the expression of caspase-3 protein by nearly 43% compared with the only MCLR treatment group. The results obtained clearly indicate that QE can effectively prevent MCLR-induced immunotoxicity by eliminating oxidative stress and blocking the mitochondrial apoptotic pathway in fish lymphocytes.

Oxidative damage and apoptosis induced by microcystin-LR in the liver of Rana nigromaculata in vivo.

Microcystins (MCs) are hepatotoxins with potent inhibitor activity of protein phosphatases PP1 and PP2A. The present study shows that MC-LR can induce severe oxidative damage and apoptosis in the livers of frogs (Rana nigromaculata) exposed to 1µg/L MC-LR for 7 and 14d in vivo. Ultrastructural observation showed the apoptotic morphology of perinuclear chromatin margination and swollen mitochondria, indicating that MC-LR can significantly damage frog liver. Reactive oxygen species (ROS) production and malondialdehyde (MDA) content were positively correlated with exposure time. Meanwhile, reduced glutathione (GSH) content and GSH peroxidase (GPx) activity rapidly decreased after prolonged exposure to 1µg/L MC-LR in a time-dependent manner. These results imply that the antioxidant defense systems of the liver were damaged. Enhanced apoptosis of cells in the livers of MC-treated frogs was detected by terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labeling (TUNEL) associated with up-regulation of the mitochondrial system. MC-LR significantly stimulated the livers to release cytochrome c, which improved the protein expressions of Bax, caspase-3, and caspase-9 (p<0.01) and inhibited the protein expression of Bcl-2 with prolonged exposure (p<0.01) via the mitochondrial pathway. These results imply that the mitochondrial pathway has a key function in toxin-induced liver cell apoptosis. The expression of caspase-8 was induced significantly (p<0.01), which illustrates the mechanism that the death receptor pathway is also involved in apoptosis. The present findings show that MC-LR can induce apoptosis in frog liver, which may be related with the decline of amphibian populations. The World Health Organization-recommended drinking water limit for MC-LR in water may be not safe for amphibians.

Regulation of nodularin-induced apoptosis by epigallocatechin-3-gallate on fish lymphocytes in vitro.

Nodularin is one of the most conspicuous and widespread pollutants that elicit water ecological hazards to fish, causing serious damage on the immune system and physiological functions. Nodularin can cause oxidative stress-induced apoptosis on fish lymphocytes. The regulatory effects of epigallocatechin-3-gallate (EGCG) at 10, 100, and 1000 µg/L levels on the antioxidant defense system and apoptosis of Carassius auratus lymphocytes exposed to a high dose of nodularin (100 µg/L) were quantified in vitro. EGCG reduced nodularin-induced oxidative damage on fish immune cells. This compound significantly increased the activities of superoxide dismutase and catalase and the level of glutathione but decreased the levels of intracellular reactive oxygen species and malondialdehyde. Flow cytometry results showed that the percentages of apoptotic cells after treatment with 10, 100, and 1000 µg/L EGCG for 12 h reached 27.9%, 19.1%, and 13.7%, respectively. By contrast, the nodularin alone-induced group showed a high percentage of apoptosis (44.2%). Western blot analysis showed the increased expression of bcl-2 and the decreased expression of bax and caspase-3 in EGCG-treated fish lymphocytes. EGCG also inhibited the potential collapse of the mitochondrial membrane. Overall, EGCG can inhibit nodularin-induced apoptosis and protect the normal immunity of fish by regulating bax/bcl-2 and blocking the downstream of mitochondrial apoptosis pathway with increased intracellular antioxidant enzyme activity.