Chronic exposure of nanomolar MC-LR caused oxidative stress and inflammatory responses in HepG2 cells

Microcystin-LR and its health impacts: Chemistry, transmission routes, mechanisms of toxicity and target organs

Microcystin-LR, a hepatotoxin produced by cyanobacteria, poses significant health risks to humans and other animals through various routes of exposure. This review comprehensively explores the chemistry, transmission pathways, mechanisms of toxicity, and target organs affected by MC-LR to provide a detailed understanding of its health impacts on animals and humans. MC-LR exposure occurs through different transmission routes, including ingesting contaminated water and food, algal dietary supplements, direct body contact with harmful algal blooms, and inhalation of aerosolized toxins. In this review, we explored that the toxic effects of MC-LR are mediated through multiple complex mechanisms. A key mechanism of its toxicity is the inhibition of protein phosphatases PP1 and PP2A which results in abnormal cellular signalling pathways. Additionally, MC-LR induces oxidative stress and disrupts cellular homeostasis. The findings suggest that MC-LR modulates the activity of various antioxidant enzymes and also activates apoptosis pathways by different mechanisms. It also induces cytoskeletal disruption, ultimately compromising cellular integrity and function. MC-LR also induces activation of oncogenes such as Gankyrin, PI3K/AKT, HIF-1α, RAC1/JNK and NEK2 pathway and upregulates the inflammatory molecules such as NF-κβ, and TNF-α, hence leading to carcinogenesis. MC-LR has toxicological effects on multiple organs. The liver is the primary target, where MC-LR accumulates and causes hepatotoxicity, but other organs are affected as well. MC-LR shows neurotoxicity, nephrotoxicity, cardiotoxicity and reproductive toxicity.

Oxidative stress and mitochondrial dysfunctions induced by cyanobacterial microcystin-LR in primary grass carp hepatocytes

Microcystin-LR (MC-LR), a cyclic heptapeptide produced by freshwater cyanobacteria, induces a range of liver injuries. However, the mechanisms underlying MC-LR toxicity in primary hepatocytes of aquatic organisms remains poorly understood. In this study, we investigated the effects of MC-LR on oxidative stress and mitochondrial function using primarily cultured grass carp hepatocytes. The results revealed that IC50 of MC-LR on grass carp primary liver cells for 24 hours was 2.40 μmol/L. Based on 24h-IC50, concentrations of 0, 0.30, 0.60, and 1.20 μmol/L were used in subsequent experiments. MC-LR exposure led to a significant reduction in cell viability, induced abnormal cell morphology, and caused plasma membrane rupture, as indicated by elevated LDH activity in a concentration-dependent manner. Additionally, MC-LR exposure induced oxidative stress, resulting in increased ROS levels and downregulation of genes associated with oxidative stress, including keap1, nrf2, cat, sod1, gpx, gst, and gr (P<0.05). Furthermore, the electron microscopy results showed that MC-LR caused damage to the ultrastructure of primary hepatocytes, including mitochondrial membrane rupture, vacuolation, and induction of mitochondrial autophagy. Moreover, MC-LR exposure elevated intracellular Ca2+ concentration, reduced MMP and ATP levels, and inhibited mitochondrial respiratory chain complex I activity (P<0.05). qRT-PCR analysis demonstrated that MC-LR treatment significantly decreased the transcriptional levels of genes related to mitochondrial quality control including pgc-1α, tfam, nrf1, drp1, opa1, mfn1, and mfn2 (P<0.05). Collectively, our findings highlight that MC-LR causes oxidative stress and impairs mitochondrial function, leading to further hepatocyte damage, which provides insights into the mechanisms of MC-LR-induced hepatotoxicity and offers valuable references for further investigations.

Exposure to MC-LR activates the RAF/ERK signaling pathway, leading to renal inflammation and tissue damage in mice

Exposure to microcysatin-LR (MC-LR) is known to result in kidney damage, however the underlying mechanisms involved in MC-LR-initiated renal injury are not known. Thus, the aim of this study was to examine the effects of exposure to MC-LR on human embryo kidney (HEK 293) cell in vitro and male C57BL/6 in vivo. In the in vitro study, HEK 293 cells were incubated with MC-LR (20 µM) for 24 hr. Treatment with MC-LR significantly increased the protein expression of RAF and ERK as well as mRNA expression levels of inflammatory cytokines TNF-α, IL-6, and IL-1β. These findings were confirmed when HEK 293 cells were co-incubated with ERK inhibitor U0126 and MC-LR demonstrating a decrease in protein expression of RAF, ERK, and mRNA levels of pro-inflammatory cytokines. Male C57BL/6 mice were intraperitoneally (ip) injected with MC-LR (20 µg/kg) daily for 21 days. Histopathological analysis demonstrated significant glomerular and tubular damage with inflammatory infiltration. The expression levels of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β were significantly elevated following MC-LR treatment. Administration of MC-LR asignificantly enhanced the protein phosphorylation levels of RAF and ERK. Data demonstrated that exposure to MC-LR induced morphological tissue damage and renal inflammatory reactions by activating the RAF/ERK signaling pathway.

Microcystins Exposure and the Risk of Metabolic Syndrome: A Cross-Sectional Study in Central China

A growing body of evidence indicates that microcystins (MCs) exposure may cause metabolic diseases. However, studies exploring the effects of MCs exposure on the risk of metabolic syndrome (MetS) in humans are currently lacking, and the underlying mechanisms remain unclear. Here, we conducted a cross-sectional study in central China to explore the effect of serum MCs on MetS, and assessed the mediation effects of the inflammation biomarker, white blood cell (WBC) level, in this relationship. The relationships among MCs and WBC level and risk of MetS were assessed using binary logistic and linear regression. Mediation analysis was used to explore possible mechanisms underlying those associations by employing R software (version 4.3.1). Compared to the lowest quartile of MCs, the highest quartile had an increased risk of MetS (odds ratio [OR] = 2.10, 95% confidence interval [CI]: 1.19, 3.70), with a dose-response relationship (p for trend < 0.05). WBCs mediated 11.14% of the association between serum MCs and triglyceride (TG) levels, but did not mediate the association of MCs exposure with MetS. This study firstly reveals that MCs exposure is an independent risk factor for MetS in a dose-response manner, and suggests that WBC level could partially mediate the association of MCs exposure with TG levels.

Role of cyanotoxins in the development and promotion of cancer

Cyanotoxins are primarily produced by different species of cyanobacteria, also known as blue-green algae, and have appeared to be environmental poisons that have various toxic effects on animal health, including humans. Cyanotoxins have been linked to the development and promotion of multiple cancers in recent studies. Important cyanotoxins, such as microcystins, nodularins, and cylindrospermopsin, have been found to play significant roles in developing and promoting various cancers. These toxins are generally responsible for oxidative stress, DNA damage, and disrupt cellular signaling pathways thus the development of cancers in various cells. Cancer is a multistep process caused by multiple mutations in normal cells. Microcystin-LR inhibits protein phosphatases (PP1 and PP2A), which leads to abnormal cell proliferation and tumor development. Similar inhibition of PP1 and PP2A is shown by nodularin, and in fact, their mechanism of carcinogenesis is the same as that of microcystins to some extent. Cylindrospermopsin inhibits protein synthesis and thus has genotoxic effects and may promote the development of cancer. Anatoxin-a and saxitoxins are well-known neurotoxins but, are thought to have indirect carcinogenic effects based on the fact that they can induce oxidative stress and DNA damage in cells by producing reactive oxygen species, thus further studies are needed to fully elucidate their role in the development and promotion of cancer. This review provides a detailed account of how different cyanotoxins play a role in the development and promotion of cancer.

The effect and mechanism of combined exposure of MC-LR and NaNO2 on liver lipid metabolism

Microcystin-LR (MC-LR) and sodium nitrite (NaNO2) co-exist in the environment and are hepatotoxic. The liver has the function of lipid metabolism, but the impacts and mechanisms of MC-LR and NaNO2 on liver lipid metabolism are unclear. Therefore, we established a chronic exposure model of Balb/c mice and used LO2 cells for in vitro verification to investigate the effects and mechanisms of liver lipid metabolism caused by MC-LR and NaNO2. The results showed that after 6 months of exposure to MC-LR and NaNO2, the lipid droplets content was increased, and the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were raised in the liver (P < 0.05). Moreover, MC-LR and NaNO2 synergistically induced hepatic oxidative stress by decreasing total superoxide dismutase (T-SOD) activity and glutathione (GSH) levels and increasing malondialdehyde (MDA) content levels. In addition, the levels of Nrf2, HO-1, NQO1 and P-AMPK was decreased and Keap1 was increased in the Nrf2/HO-1 pathway. The key factors of lipid metabolism, SREBP-1c, FASN and ACC, were up-regulated in the liver. More importantly, there was a combined effect on lipid deposition of MC-LR and NaNO2 co-exposure. In vitro experiments, MC-LR and NaNO2-induced lipid deposition and changes in lipid metabolism-related changes were mitigated after activation of the Nrf2/HO-1 signaling pathway by the Nrf2 activator tertiary butylhydroquinone (TBHQ). Additionally, TBHQ alleviated the rise of reactive oxygen species (ROS) in LO2 cells induced by MC-LR and NaNO2. Overall, our findings indicated that MC-LR and NaNO2 can cause abnormal liver lipid metabolism, and the combined effects were observed after MC-LR and NaNO2 co-exposure. The Nrf2/HO-1 signal pathway may be a potential target for prevention and control of liver toxicity caused by MC-LR and NaNO2.

CXCL1/IGHG1 signaling enhances crosstalk between tumor cells and tumor-associated macrophages to promote MC-LR-induced colorectal cancer progression

Microcystin-leucine arginine (MC-LR) is a common cyantotoxin produced by hazardous cyanobacterial blooms, and eutrophication is increasing the contamination level of MC-LR in drinking water supplies and aquatic foods. MC-LR has been linked to colorectal cancer (CRC) progression associated with tumor microenvironment, however, the underlying mechanism is not clearly understood. In present study, by using GEO, KEGG, GESA and ImmPort database, MC-LR related differentially expressed genes (DEGs) and pathway- and gene set-enrichment analysis were performed. Of the three identified DEGs (CXCL1, GUCA2A and GDF15), CXCL1 was shown a positive association with tumor infiltration, and was validated to have a dominantly higher upregulation in MC-LR-treated tumor-associated macrophages (TAMs) rather than in MC-LR-treated CRC cells. Both CRC cell/macrophage co-culture and xenograft mouse models indicated that MC-LR stimulated TAMs to secrete CXCL1 resulting in promoted proliferation, migration, and invasion capability of CRC cells. Furtherly, IP-MS assay found that interaction between TAMs-derived CXCL1 and CRC cell-derived IGHG1 may enhance CRC cell proliferation and migration after MC-LR treatment, and this effect can be attenuated by silencing IGHG1 in CRC cell. In addition, molecular docking analysis, co-immunoprecipitation and immunofluorescence further proved the interactions between CXCL1 and IGHG1. In conclusion, CXCL1 secreted by TAMs can trigger IGHG1 expression in CRC cells, which provides a new clue in elucidating the mechanism of MC-LR-mediated CRC progression.

The cytotoxicity of microcystin-LR: ultrastructural and functional damage of cells

Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria, which is widely distributed in eutrophic water bodies and has multi-organ toxicity. Previous cytotoxicity studies have mostly elucidated the effects of MC-LR on intracellular-related factors, proteins, and DNA at the molecular level. However, there have been few studies on the adverse effects of MC-LR on cell ultrastructure and function. Therefore, research on the cytotoxicity of MC-LR in recent years was collected and summarized. It was found that MC-LR can induce a series of cytotoxic effects, including decreased cell viability, induced autophagy, apoptosis and necrosis, altered cell cycle, altered cell morphology, abnormal cell migration and invasion as well as leading to genetic damage. The above cytotoxic effects were related to the damage of various ultrastructure and functions such as cell membranes and mitochondria. Furthermore, MC-LR can disrupt cell ultrastructure and function by inducing oxidative stress and inhibiting protein phosphatase activity. In addition, the combined toxic effects of MC-LR and other environmental pollutants were investigated. This review explored the toxic targets of MC-LR at the subcellular level, which will provide new ideas for the prevention and treatment of multi-organ toxicity caused by MC-LR.

Toxic cyanobacteria induce coupled changes in gut microbiota and co-metabolite of freshwater gastropods

Frequent outbreaks of harmful cyanobacterial blooms and the microcystins (MCs) they produce seriously affect the survival of aquatic organisms. Interactions between gut microbiota and hosts often play crucial roles in driving the adaptation of aquatic organisms to environmental changes. In this study, we investigated the phenotypic indicators of the freshwater gastropod Bellamya aeruginosa, after uptake of Microcystis aeruginosa and explored its gut microbial composition and gut metabolites in response to toxic cyanobacterial stress. Results showed that the MCs concentration in the hepatopancreas of snails fed with toxic cyanobacteria decreased from 2.64 ± 0.14 μg·g-1 on day 7 to 1.16 ± 0.10 μg·g-1 on day 14. The compositions of the intestinal microbiota of snails fed with different algae significantly differed, and the relative abundance of gut microbes such as Lactobacillus and Sphingobium significantly increased after feeding toxic cyanobacteria. Significant differences also existed in intestinal metabolites, the relative abundance of the following metabolites significantly increased: l-proline, 5,6-DHET, stachyose, raffinose, and 3-isopropylmalate. Sankey network diagrams showing links between gut microbes and gut metabolites. The association of Lactobacillus and Sphingobium with amino acids may be related to host tolerance to toxicity, and the linkages of gut microbes with metabolites such as levan, imidazolepropionic acid, and eicosanoids may be associated with involvement in host immune responses. The association of microbes with stachyose and raffinose can help the host to regulate energy homeostasis. These results reveal the underlying mechanisms of gut microbes in the snail adaptation to toxic cyanobacterial stress. This study could be great important for gaining new insights into toxic cyanobacteria-induced changes in snail gut microbes and metabolites and their roles in snail adaptation to toxic cyanobacterial stress, and may provide important insights into the use of freshwater gastropods for the prevention and control of cyanobacterial blooms.

Microcystin-leucine-arginine impairs bone microstructure and biomechanics by activating osteoimmune response and inhibiting osteoblasts maturation in developing rats

Microcystin-LR (MC-LR) affects bone health in adult mice via osteo-immunomodulation. However, its effect on osteoblasts and bone development is unclear. This study investigated the effect of MC-LR on bone osteoimmune and osteoblasts in the developing period. 18 Four-week-old male Sprague Dawley rats were divided into two groups (n = 9 per group) and exposed to 0 (control) and 1 μg/kg b.w. MC-LR (exposure) by intraperitoneal injection for four weeks. The heart blood was collected for serological examination, and the femur for morphological, histopathological, and biomechanical analysis. MC-LR exposure significantly weakened bone microstructures (bone volume, bone volume/total volume, bone trabecular number, connectivity density) and biomechanics (maximum loads and maximum deflection) (P < 0.05). Besides, MC-LR decreased serum procollagen type І car-boxy-terminal propeptide, osteocalcin, bone morphogenetic protein-2, osteoprotegerin, and receptor activator of nuclear factor κB ligand, while elevating osteoclasts number, matrix metalloproteinase-9, β-catenin, Runt-related transcription factor 2, and osterix in bone, and bone alkaline phosphate, C-terminal cross-linked telopeptide of type-I collagen, tartrate-resistant acid phosphatase-5b in serum (P < 0.05). Moreover, MC-LR increased CD4+ T-cells, CD4+/CD8+, M1 and M2 macrophages, and cells apoptosis in the bone marrow, interleukin-6, interleukin-17, and tumor necrosis factor-α in serum, decreased serum interleukin-10 (P < 0.05). Overall, MC-LR can promote bone resorption by activating osteoclasts via osteoimmunology, which may involve macrophages besides lymphocytes. MC-LR may inhibit bone formation by stopping the osteoblasts at an immature stage. Thus, MC-LR weakened bone microstructure and biomechanics in developing period. Its risk on bone development needs further study.

Cyanotoxins Increase Cytotoxicity and Promote Nonalcoholic Fatty Liver Disease Progression by Enhancing Cell Steatosis

Freshwater prokaryotic cyanobacteria within harmful algal blooms produce cyanotoxins which are considered major pollutants in the aquatic system. Direct exposure to cyanotoxins through inhalation, skin contact, or ingestion of contaminated drinking water can target the liver and may cause hepatotoxicity. In the current study, we investigated the effect of low concentrations of cyanotoxins on cytotoxicity, inflammation, modulation of unfolded protein response (UPR), steatosis, and fibrosis signaling in human hepatocytes and liver cell models. Exposure to low concentrations of microcystin-LR (MC-LR), microcystin-RR (MC-RR), nodularin (NOD), and cylindrospermopsin (CYN) in human bipotent progenitor cell line HepaRG and hepatocellular carcinoma (HCC) cell lines HepG2 and SK-Hep1 resulted in increased cell toxicity. MC-LR, NOD, and CYN differentially regulated inflammatory signaling, activated UPR signaling and lipogenic gene expression, and induced cellular steatosis and fibrotic signaling in HCC cells. MC-LR, NOD, and CYN also regulated AKT/mTOR signaling and inhibited autophagy. Chronic exposure to MC-LR, NOD, and CYN upregulated the expression of lipogenic and fibrosis biomarkers. Moreover, RNA sequencing (RNA seq) data suggested that exposure of human hepatocytes, HepaRG, and HCC HepG2 cells to MC-LR and CYN modulated expression levels of several genes that regulate non-alcoholic fatty liver disease (NAFLD). Our data suggest that low concentrations of cyanotoxins can cause hepatotoxicity and cell steatosis and promote NAFLD progression.

A meta-analysis on the toxicity of microcystin-LR to fish and mammals

Microcystin-leucine arginine (MC-LR), the most prevalent and dangerous microcystin, poses high risks to living organisms, especially fish and mammals. Although many studies have focused on the toxic effect on fish and mammals exposed to MC-LR, works that incorporate published data into a comprehensive comparison and analysis are still limited. Here, the adverse effects of oxidative stress markers, health, functional traits, and performance traits in fish and mammals were systematically verified by collecting data from 67 studies for the first time. Notably, we first found that the activities of malondialdehyde (MDA) (p < 0.05) and lactoperoxidase (LPO) always showed increases, whereas the growth (performance traits) always had a significant decrease (p < 0.001) under all variables of MC-LR exposure, i.e., exposure time, exposure concentration, exposure route, and even life stage. Additionally, our study first verified that the activities of MDA and LPO can be employed as oxidative stress indicators of MC-LR effects in fish and mammals instead of other biomarkers of oxidative stress, such as superoxide dismutase (SOD) and catalase (CAT), considered by previous studies. Growth may be regarded as a highly sensitive indicator of MC-LR toxicity in mammals and fish. At the same time, we first found that the impact of MC-LR exposure concentration on LPO, MDA, and growth is higher than that of exposure time, exposure route, and different life stages using the random forest (RF) model. In short, this work sheds light on the potential biochemical and individual toxicity of MC-LR exposure in fish and mammals.

Saikosaponin A and Its Epimers Alleviate LPS-Induced Acute Lung Injury in Mice

The purpose of this work was to illustrate the effect of processing with vinegar on saikosaponins of Bupleurum chinense DC. (BC) and the protective effects of saikosaponin A (SSA), saikosaponin b1 (SSb1), saikosaponin b2 (SSb2), and saikosaponin D (SSD) in lipopolysaccharide (LPS)-induced acute lung injury (ALI) mice. We comprehensively evaluated the anti-inflammatory effects and potential mechanisms of SSA, SSb1, SSb2, and SSD through an LPS-induced ALI model using intratracheal injection. The results showed that SSA, SSb1, SSb2, and SSD significantly decreased pulmonary edema; reduced the levels of IL-6, TNF-α, and IL-1β in serum and lung tissues; alleviated pulmonary pathological damage; and decreased the levels of the IL-6, TNF-α, and IL-1β genes and the expression of NF-κB/TLR4-related proteins. Interestingly, they were similar in structure, but SSb2 had a better anti-inflammatory effect at the same dose, according to a principal component analysis. These findings indicated that it may not have been comprehensive to only use SSA and SSD as indicators to evaluate the quality of BC, especially as the contents of SSb1 and SSb2 in vinegar-processed BC were significantly increased.

miR-146a-5p Promotes the Inflammatory Response in PBMCs Induced by Microcystin-Leucine-Arginine

Background

Microcystin-leucine-arginine (MC-LR) is the most abundant and most toxic variant of microcystin isomers. Various experiments have clearly shown that MC-LR has hepatotoxicity and carcinogenicity, but there are relatively few studies on its immune damage effect. In addition, numerous studies have shown that microRNAs (miRNAs) are involved in a wide range of biological processes. Do miRNAs also play a role in inflammatory response caused by microcystin exposure? This is the question to be answered in this study. Moreover, this study can also provides experimental evidence for the significance of miRNA applications.

Objective

To investigate the effect of MC-LR on the expressions of miR-146a and pro/anti-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs) and to further explore the role of miR-146a in the inflammatory responses caused by MC-LR.

Methods

Serum samples from 1789 medical examiners were collected and detect the concentrations of MCs, and 30 serum samples with concentrations of MCs around P₂₅, P₅₀, and p₇₅ were randomly selected for the detection of inflammatory factors. PBMCs from fresh peripheral blood extracted from these 90 medical examiners were subsequently tested for relative miR-146a expression. In vitro, the MC-LR were exposed to the PBMCs to detect the levels of inflammatory factors as well as the relative expression of miR-146a-5p. Then, a miRNA transfection assay was performed to verify the regulation of inflammatory factors by miR-146a-5p.

Results

In population samples, the expression of inflammatory factors and miR-146a-5p increased with increasing MCs concentration. In vitro experiments showed that the expression of inflammatory factors and miR-146a-5p in PBMCs increased with MC-LR exposure time or exposure dose too. In addition, inhibiting the expression of miR-146a-5p in PBMCs reduced inflammatory factor levels.

Conclusion

miR-146a-5p exerts a promoting effect on the MC-LR-induced inflammatory response by positively regulating inflammatory factor levels.

The Abnormal Proliferation of Hepatocytes is Associated with MC-LR and C-Terminal Truncated HBX Synergistic Disturbance of the Redox Balance

Background

Microcystin-LR (MC-LR) and hepatitis B virus (HBV) are associated with hepatocellular carcinoma (HCC). However, the concentrations of MC-LR in drinking water and the synergistic effect of MC-LR and HBV on hepatocellular carcinogenesis through their disturbance of redox balance have not been fully elucidated.

Methods

We measured the MC-LR concentrations in 168 drinking water samples of areas with a high incidence of HCC. The relationships between MC-LR and both redox status and liver diseases in 177 local residents were analyzed. The hepatoma cell line HepG2 transfected with C-terminal truncated hepatitis B virus X gene (Ct-HBX) were treated with MC-LR. Reactive oxygen species (ROS), superoxide dismutase (SOD), glutathione (GSH) and malondialdehyde (MDA) were measured. Cell proliferation, migration, invasion, and apoptosis were assessed with cell activity assays, scratch and transwell assays, and flow cytometry, respectively. The mRNA and protein expression-related redox status genes were analyzed with qPCR and Western blotting.

Results

The average concentration of MC-LR in well water, river water and reservoir water were 57.55 ng/L, 76.74 ng/L and 132.86 ng/L respectively, and the differences were statistically significant (P < 0.05). The MC-LR levels in drinking water were correlated with liver health status, including hepatitis, clonorchiasis, glutamic pyruvic transaminase abnormalities and hepatitis B surface antigen carriage (all P values < 0.05). The serum MDA increased in subjects who drank reservoir water and were infected with HBV (P < 0.05). In the cell experiment, ROS increased when Ct-HBX-transfected HepG2 cells were treated with MC-LR, followed by a decrease in SOD and GSH and an increase in MDA. MC-LR combined with Ct-HBX promoted the proliferation, migration and invasion of HepG2 cells, upregulated the mRNA and protein expression of MAOA gene, and downregulated UCP2 and GPX1 genes.

Conclusion

MC-LR and HBV may synergistically affect redox status and play an important role in hepatocarcinoma genesis.

Microcystin-LR in Primary Liver Cancers: An Overview

The cyanobacterial blooms produced by eutrophic water bodies have become a serious environmental issue around the world. After cellular lysing or algaecide treatment, microcystins (MCs), which are regarded as the most frequently encountered cyanobacterial toxins in fresh water, are released into water. Among all the variants of MCs, MC-LR has been widely studied due to its severe hepatotoxicity. Since 1992, various studies have identified the important roles of MC-LR in the origin and progression of primary liver cancers (PLCs), although few reviews have focused on it. Therefore, this review aims to summarize the major achievements and shortcomings observed in the past few years. Based on the available literature, the mechanisms of how MC-LR induces or promotes PLCs are elucidated in this review. This review aims to enhance our understanding of the role that MC-LR plays in PLCs and provides a rational approach for future applications.

MicroRNA-122 overexpression promotes apoptosis and tumor suppressor gene expression induced by microcystin-leucine arginine in mouse liver

Microcystin-leucine arginine (MC-LR), an important hepatoxin, has the effect of promoting hepatocarcinogenesis. MicroRNA-122 (miR-122), an important tumor suppressor in liver, plays an important role in promoting cell apoptosis. Previous studies found that the expression of miR-122 was reduced after MC-LR exposure in liver. In this study, C57BL/6 mice were exposed to saline, negative control agomir, and MC-LR with or without miR-122 agomir transfection. The results indicated that MC-LR promoted the expressions of tumor suppressor genes and decreased the expressions of anti-apoptotic proteins B cell lymphoma-2 (Bcl-2) and Bcl-2-like 2 (Bcl-w), causing hepatocyte apoptosis. Under MC-LR exposure, miR-122 agomir transfection could further increase the expressions of tumor suppressor genes and the release of cytochrome-c (Cyt-c) and decrease the expressions of Bcl-2 and Bcl-w. In conclusion, miR-122 reduction can mitigate MC-LR-induced apoptosis to a certain extent, which in turn, it is likely to have contributed to MC-LR-induced hepatocarcinogenesis.

Microcystin-LR induces apoptosis in Juvenile Eriocheir sinensis via the mitochondrial pathway

Microcystin-LR (MC-LR), the toxic substance of cyanobacteria secondary metabolism, widely exists in water environments and poses great risks to living organisms. Some toxicological assessments of MC-LR have performed at physiological and biochemical levels. However, plenty of blanks about the potential mechanism in aquatic crustacean remains. In this study, we firstly assessed the exposure toxicity of MC-LR to juvenile E. sinensis and clarified that the 96 h LD50 of MC-LR was 73.23 μg/kg. Then, hepatopancreas transcriptome profiles of MC-LR stressed crabs were constructed at 6 h post-injection and 37 differential expressed genes (DEGs) were identified. These DEGs were enriched in cytoskeleton, peroxisome and apoptosis pathways. To further reveal the toxicity of MC-LR, oxidative stress parameters (SOD, CAT, GSH-px and MDA), apoptosis genes (caspase 3, bcl-2 and bax) and apoptotic cells were detected. Significant accumulated MDA and rise-fall enzyme activities verified the oxidative stress caused by MC-LR. It is noteworthy that quantitative real-time PCR and TUNEL assay indicated that MC-LR stress-induced apoptosis via the mitochondrial pathway. Interestingly, activator protein-1 may play a crucial role in mediating the hepatotoxicity of MC-LR by regulating apoptosis and oxidative stress. Taken together, our study investigated the toxic effects and the potential molecular mechanisms of MC-LR on juvenile E. sinensis. It provided useful data for exploring the toxicity of MC-LR to aquatic crustaceans at molecular levels.

CRISPR-Cas12a-Based Aptasensor for On-Site and Highly Sensitive Detection of Microcystin-LR in Freshwater

On-site monitoring of trace organic pollutants with facile methods is critical to environmental pollutant prevention and control. Herein, we proposed a CRISPR-Cas12a-based aptasensor platform (named as MC-LR-Casor) for on-site and sensitive detection of microcystin-LR (MC-LR). After hybridization with blocker DNA, the MC-LR aptamers were conjugated to magnetic beads (MBs) to get the MB aptasensor. In the presence of MC-LR, their interactions with aptamers were triggered and the specific binding caused the release of blocker DNA. Using the programmability of the CRISPR-Cas system, the released blocker DNA was designed to activate a Cas12a-crRNA complex. Single strand DNA reporters were rapidly cleaved by the complex. Signal readout could be achieved by fluorometer or lateral flow strips, which were positively correlated to MC-LR concentration. Benefiting from the CRISPR-Cas12a amplification system, the proposed sensing platform exhibited high sensitivity and reached the limit of detection of ∼3 × 10^-6 μg/L (fluorescence method) or 1 × 10^-3 μg/L (lateral flow assay). In addition, the MC-LR-Casor showed excellent selectivity and good recovery rates, demonstrating their good applicability for real water sample analysis. During the whole assay, only two steps of incubation at a constant temperature were required and the results could be visualized when employing flow strips. Therefore, the proposed assay offered a simple and convenient alternative for in situ MC-LR monitoring, which may hold great promise for future environmental surveillance.

Chinese Tea Alleviates CCl4-Induced Liver Injury through the NF-κBorNrf2Signaling Pathway in C57BL-6J Mice

Liver injury is a life-threatening condition that is usually caused by excessive alcohol consumption, improperdiet, and stressful lifestyle and can even progress to liver cancer. Tea is a popular beverage with proven health benefits and is known to exert a protective effect on the liver, intestines, and stomach. In this study, we analyzed the therapeutic effects of six kinds of tea on carbon tetrachloride (CCl₄)-induced liver injury in a mouse model. The mice were injected with 10 mL/kg 5% CCl₄ to induce liver injury and then given oral gavage of green tea, yellow tea, oolong tea, white tea, black tea, and dark tea, respectively. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured, and the expression levels of inflammation and oxidative stress-related proteins in the liver tissues were quantified. All six kinds of tea partly reduced the liver index, restored the size of the enlarged liver in the CCl₄ model, and decreased the serum levels of ALT and AST. Furthermore, the highly fermented dark tea significantly reduced the expression levels of NF-κB and the downstream inflammatory factors, whereas the unfermented green tea inhibited oxidative stress by activating the antioxidant Nrf2 pathway. Taken together, tea can protect against liver inflammation, and unfermented tea can improve antioxidant levels. Further studies are needed on the bioactive components of tea to develop drugs against liver injury.

Negative impacts of microcystin-LR and glyphosate on zebrafish intestine: Linked with gut microbiota and microRNAs?

Microcystin-LR (MC-LR) and glyphosate (GLY) have been classified as a Group 2B and Group 2A carcinogens for humans, respectively, and frequently found in aquatic ecosystems. However, data on the potential hazard of MC-LR and GLY exposure to the fish gut are relatively scarce. In the current study, a subacute toxicity test of zebrafish exposed to MC-LR (35 μg L-1) and GLY (3.5 mg L-1), either alone or in combination was performed for 21 d. The results showed that MC-LR or/and GLY treatment reduced the mRNA levels of tight junction genes (claudin-5, occludin, and zonula occludens-1) and altered the levels of diamine oxidase and D-lactic, indicating increased intestinal permeability in zebrafish. Furthermore, MC-LR and/or GLY treatment remarkably increased the levels of intestinal IL-1β and IL-8 but decreased the levels of IL-10 and TGF-β, indicating that MC-LR and/or GLY exposure induced an inflammatory response in the fish gut. MC-LR and/or GLY exposure also activated superoxide dismutase and catalase, generally upregulated the levels of p53, bax, bcl-2, caspase-3, and caspase-9, downregulated the levels of caspase-8 and caused notable histological injury in the fish gut. Moreover, MC-LR and/or GLY exposure also significantly altered the microbial community in the zebrafish gut and the expression of miRNAs (miR-146a, miR-155, miR-16, miR-21, and miR-223). Chronic exposure to MC-LR and/or GLY can induce intestinal damage in zebrafish, and this study is the first to demonstrate an altered gut microbiome and miRNAs in the zebrafish gut after MC-LR and GLY exposure.

Microcystin-LR inhibits testosterone synthesis via reactive oxygen species-mediated GCN2/eIF2α pathway in mouse testes

Previous studies demonstrated that microcystin-leucine-arginine (MC-LR) disrupted testosterone (T) synthesis, but the underlying mechanisms are not entirely elucidated. This study aims to explore the role of reactive oxygen species (ROS)-mediated GCN2/eIF2α activation on MC-LR-induced disruption of testicular T synthesis. Male mice were intraperitoneally injected with MC-LR (0 or 20 μg/kg) daily for 5 weeks. Serum T was decreased in MC-LR-exposed mice (0.626 ± 0.122 vs 24.565 ± 8.486 ng/ml, P < 0.01), so did testicular T (0.667 ± 0.15 vs 8.317 ± 1.387 ng/mg protein, P < 0.01). Steroidogenic proteins including StAR, CYP11A1 and CYP17A1 were downregulated in MC-LR-exposed mouse testes and TM3 cells. Mechanistically, p-GCN2 and p-eIF2α were elevated in MC-LR-exposed TM3 cells. GCN2iB attenuated MC-LR-induced GCN2 and eIF2α phosphorylation in TM3 cells. Moreover, GCN2iB attenuated MC-LR-induced downregulation of steroidogenic proteins in TM3 cells. Further analysis found that cellular ROS were elevated and HO-1 was upregulated in MC-LR-exposed TM3 cells. PBN rescued MC-LR-induced activation of GCN2/eIF2α signaling in TM3 cells. Additionally, pretreatment with PBN attenuated MC-LR induced downregulation of steroidogenic proteins and synthases in TM3 cells. These results suggest that ROS-mediated GCN2/eIF2α activation contributes partially to MC-LR-caused downregulation of steroidogenic proteins and synthases. The present study provides a new clue for understanding the mechanism of MC-LR-induced endocrine disruption.

Neither microcystin, nor nodularin, nor cylindrospermopsin directly interact with human toll-like receptors

Various stressors including temperature, environmental chemicals, and toxins can have profound impacts on immunity to pathogens. Increased eutrophication near rivers and lakes coupled with climate change are predicted to lead to increased algal blooms. Currently, the effects of cyanobacterial toxins on disease resistance in mammals is a largely unexplored area of research. Recent studies have suggested that freshwater cyanotoxins can elicit immunomodulation through interaction with specific components of innate immunity, thus potentially altering disease susceptibility parameters for fish, wildlife, and human health owing to the conserved nature of the vertebrate immune system. In this study, we investigated the effects of three microcystin congeners (LR, LA, and RR), nodularin-R, and cylindrospermopsin for their ability to directly interact with nine different human Toll-like receptors (TLRs)-key pathogen recognition receptors for innate immunity. Toxin concentrations were verified by LC/MS/MS prior to use. Using an established HEK293-hTLR NF-κB reporter assay, we concluded that none of the tested toxins (29-90 nM final concentration) directly interacted with human TLRs in either an agonistic or antagonistic manner. These results suggest that earlier reports of cyanotoxin-induced NF-κB responses likely occur through different surface receptors to mediate inflammation.

A novel therapeutic strategy for hepatocellular carcinoma: Immunomodulatory mechanisms of selenium and/or selenoproteins on a shift towards anti-cancer

Selenium (Se) is an essential trace chemical element that is widely distributed worldwide. Se exerts its immunomodulatory and nutritional activities in the human body in the form of selenoproteins. Se has increasingly appeared as a potential trace element associated with many human diseases, including hepatocellular carcinoma (HCC). Recently, increasing evidence has suggested that Se and selenoproteins exert their immunomodulatory effects on HCC by regulating the molecules of oxidative stress, inflammation, immune response, cell proliferation and growth, angiogenesis, signaling pathways, apoptosis, and other processes in vitro cell studies and in vivo animal studies. Se concentrations are generally low in tissues of patients with HCC, such as blood, serum, scalp hair, and toenail. However, Se concentrations were higher in HCC patient tissues after Se supplementation than before supplementation. This review summarizes the significant relationship between Se and HCC, and details the role of Se as a novel immunomodulatory or immunotherapeutic approach against HCC.

MC-LR-induced interaction between M2 macrophage and biliary epithelial cell promotes biliary epithelial cell proliferation and migration through regulating STAT3

Microcystin-leucine-arginine (MC-LR) was produced by toxic cyanobacteria, which has been shown to have potent hepatotoxicity. Our previous study has proved that MC-LR were able to promote intrahepatic biliary epithelial cell excessive proliferation. However, the underlying mechanism is not yet entirely clarified. Herein, mice were fed with different concentrations (1, 7.5, 15, or 30 μg/L) of MC-LR by drinking water for 6 months. As the concentration of MC-LR increased, a growing number of macrophages were evaluated in the portal area of the mouse liver. Next, we built a co-culture system to explore the interaction between macrophages (THP-1 cells) and human intrahepatic biliary epithelial cells (HiBECs) in the presence of MC-LR. Under the exposure of MC-LR, HiBECs secreted a large amount of inflammatory factors (IL-6, IL-8, IL-1β, COX-2, XCL-1) and chemokine (MCP-1), which produced a huge chemotactic effect on THP-1 cells and induced elevation of the surface M2-subtype biomarkers (IL-10, CD163, CCL22, and Arg-1). In turn, high content of IL-6 in the medium activated JAK2/STAT3, MEK/ERK, and PI3K/AKT pathways in HiBECs, inducing HiBEC abnormal proliferation and migration. Together, these results suggested that MC-LR-mediated interaction between HiBECs and macrophages induced the M2-type polarization of macrophages, and activated IL-6/JAK2/STAT3, MEK/ERK, and PI3K/AKT pathways in HiBECs, further enhanced cell proliferation, improved cell migration, and hindered cell apoptosis by activating p-STAT3. MC-LR stimulates HiBECs to produce various inflammatory factors, recruiting a large number of macrophages and promoting the differentiation of macrophages into M2-type. In turn, the M2 macrophages could also produce amounts of IL-6 and activate STAT3 through JAK2/STAT3, MEK/ERK, and PI3K/AKT pathways in HiBECs, resulting in the promotion of cell proliferation, inhibition of apoptosis, and enhancement of migration.

Synergistic Effect of MC-LR and C-Terminal Truncated HBx on HepG2 Cells and Their Effects on PP2A Mediated Downstream Target of MAPK Signaling Pathway

C-terminally truncated hepatitis B virus (HBV) X (ctHBx) infection and exposure to microcystins-LR (MC-LR) can lead to human hepatitis and liver cancer, but the mechanism associated with their synergistically effects not been fully elucidated. The ctHBx (HBxΔ4 and HBxΔ32) lentivirus were constructed and transfected into the HepG2 cells. Then we investigated the function of MC-LR and ctHBx using the molecular biology approaches, including enzyme-linked immunosorbent assay, clone formation assay, scratch wound testing, transwell assays, carried out flow cytometry respectively to examine cell cycle and apoptosis in each group, and detected the related proteins of HBx, MEK/ERK/JNK/p38 in mitogen-activated protein kinase (MAPK) pathway and the downstream proteins such as cdc2, cdc25C, and p53 by western blotting. We found that the protein phosphorylase 2A (PP2A) enzyme activity in MC-LR and HBxΔ32/HBxΔ4 groups decreased more than in MC-LR and HBx group at the same time point and MC-LR concentration (P < 0.05). Meanwhile the proliferation, migration, invasion and colony formation capability of HepG2 cells were significantly enhanced in MC-LR and ctHBx groups (P < 0.05). In addition the proportion of S stage cells in the MC-LR-treated HBxΔ32/HBxΔ4 groups was significantly greater than that in the untreated groups (P < 0.05). Furthermore, the protein expression of MAPK signaling pathway including phospho-MEK1/2, ERKl/2, p38, and JNK were up-regulated by MC-LR and HBxΔ32, and the expression of cyclin-related proteins, including p53, cdc25C, and cdc2 were also activated (P < 0.05). Taken together, our findings revealed the essential significance of the MC-LR and ctHBx on the PP2A/MAPK/p53, cdc25C and cdc2 axis in the formation and development of HCC and identified MC-LR and ctHBx as potential causal cofactors of hepatocarcinogenesis.

Vitamin C Protects Porcine Oocytes From Microcystin-LR Toxicity During Maturation

Microcystin-leucine arginine (MC-LR) is the most toxic cyanotoxin found in water bodies. Microcystins are produced as secondary products of cyanobacteria metabolism. They have a stable structure, and can bioaccumulate in living organisms. Humans and livestock who drink fresh water containing MC-LR can be poisoned. However, few studies have reported the effects of MC-LR exposure on livestock or human reproduction. In this study, we used porcine oocytes as a model to explore the effects of MC-LR on oocyte maturation, and studied the impact of vitamin C (VC) administration on MC-LR-induced meiosis defects. Exposure to MC-LR significantly restricted cumulus cell expansion and decreased first polar body extrusion. Further studies showed that MC-LR exposure led to meiosis arrest by disturbing cytoskeleton dynamics with MC-LR exposed oocytes displaying aberrant spindle organization, low levels of acetylate α-tubulin, and disturbed actin polymerization. Additionally, MC-LR exposure impaired cytoplasmic maturation by inducing mitochondria dysfunction. Moreover, MC-LR also produced abnormal epigenetic modifications, and induced high levels of oxidative stress, caused DNA damage and early apoptosis. The administration of VC provided partial protection from all of the defects observed in oocytes exposed to MC-LR. These results demonstrate that MC-LR has a toxic effect on oocyte meiosis through mitochondrial dysfunction-induced ROS, DNA damage and early apoptosis. Supplementation of VC is able to protect against MC-LR-induced oocyte damage and represents a potential therapeutic strategy to improve the quality of MC-LR-exposed oocytes.

Low-dose microcystin-LR antagonizes aflatoxin B1 induced hepatocarcinogenesis through decreasing cytochrome P450 1A2 expression and aflatoxin B1-DNA adduct generation

Aflatoxin B1 (AFB1) and microcystin-LR (MC-LR) co-existed in food and water, and were associated with hepatocellular carcinoma (HCC). AFB1 induced HCC by activating oxidative stress and generating AFB1-DNA adducts, while MC-LR could promote HCC progression. However, whether they have co-effects in HCC progression remains uncertain. In this study, we found the antagonistic effects of MC-LR on AFB1 induced HCC when they were exposed simultaneously. Compared with single exposure to AFB1, co-exposed to MC-LR significantly repressed the AFB1 induced malignant transformation of human hepatic cells and the glutathione S-transferase Pi positive foci formation in rat livers. MC-LR inhibited AFB1 induced upregulation of cytochrome P450 family 1 subfamily A member 2 (CYP1A2) and reduced the AFB1-DNA adducts generation in both human hepatic cells and rat livers. These results suggest that when co-exposure with AFB1, MC-LR might repress hepatocarcinogenicity of AFB1, which might be associated with its repression on AFB1 induced CYP1A2 upregulation and activation.

Mechanical Changes and Microfilament Reorganization Involved in Microcystin-LR-Promoted Cell Invasion in DU145 and WPMY Cells

Microcystin-leucine arginine (MC-LR) is a potent tumor initiator that can induce malignant cell transformation. Cellular mechanical characteristics are pivotal parameters that are closely related to cell invasion. The aim of this study is to determine the effect of MC-LR on mechanical parameters, microfilament, and cell invasion in DU145 and WPMY cells. Firstly, 10 μM MC-LR was selected as the appropriate concentration via cell viability assay. Subsequently, after MC-LR treatment, the cellular deformability and viscoelastic parameters were tested using the micropipette aspiration technique. The results showed that MC-LR increased the cellular deformability, reduced the cellular viscoelastic parameter values, and caused the cells to become softer. Furthermore, microfilament and microfilament-associated proteins were examined by immunofluorescence and Western blot, respectively. Our results showed that MC-LR induced microfilament reorganization and increased the expression of p-VASP and p-ezrin. Finally, the impact of MC-LR on cell invasion was evaluated. The results revealed that MC-LR promoted cell invasion. Taken together, our results suggested that mechanical changes and microfilament reorganization were involved in MC-LR-promoted cell invasion in DU145 and WPMY cells. Our data provide novel information to explain the toxicological mechanism of MC-LR.

Parental Transfer of Microcystin-LR-Induced Innate Immune Dysfunction of Zebrafish: A Cross-Generational Study

Transgenerational effects of microcystin-LR (MC-LR) released by cyanobacterial blooms have become a hot topic. In the present study, adult zebrafish pairs were exposed to 0, 0.4, 2, and 10 μg/L MC-LR for 60 days and the embryos (F1 generation) were hatched without or with continued MC-LR exposures at the same concentrations until 5 days postfertilization (dpf). The results showed the existence of MC-LR both in F0 gonads and in F1 embryos and indicated that MC-LR could be transferred directly from the F0 adult fish to F1 offspring. The adverse effects on sex hormone levels, sexual development, and fecundity in F0 generation along with abnormal development in F1 offspring were observed. Furthermore, downregulation of antioxidant genes (cat, mn-sod, gpx1a) and upregulation of innate immune-related genes (tlr4a, myd88, tnfα, il1β) as well as increased proinflammation cytokine contents (TNF-α, IL-1β, IL-6) were noticed in F1 offspring without/with continued MC-LR exposures. In addition, significant differences between the two F1 embryo treatments demonstrated that continuous MC-LR exposure could result in a higher degree of inflammatory response compared to those without MC-LR exposure. Our findings revealed that MC-LR could exert cross-generational effects of immunotoxicity by inhibiting the antioxidant system and activating an inflammatory response.

Effects of spinetoram on the developmental toxicity and immunotoxicity of zebrafish

Our study investigated the effects of spinetoram on the developmental toxicity and immunotoxicity of zebrafish. 10 h post-fertilization (hpf) zebrafish embryos were exposed to several concentrations of spinetoram (0, 5.0 mg/L, 7.5 mg/L, 10 mg/L) for up to 96 hpf, and their mortality, heart rate, number of innate and adaptive immune cells, oxidative stress, apoptosis and gene expression were detected. Studies indicated that the spinetoram exposed zebrafish embryos showed yolk sac edema, slow growth, decreased heart rate, decreased number of immune cells, delayed thymic development and cell apoptosis. In addition, there were also significant changes in oxidative stress related indicators in zebrafish, the content of ROS and MDA and the activity of CAT and SOD increased with the increase of spinetoram concentration. Moreover, we detected the expression of TLR4 related genes including TLR4, MYD88 and NF-κB p65 which were significantly up-regulated in the treated groups. Meanwhile, we also found that pro-inflammatory factors IL-6, IL-8, IFN-γ and CXCL-c1c were up-regulated, but anti-inflammatory factor IL-10 was down-regulated in the treated groups. Briefly, our results show that spinetoram induces the developmental toxicity and immunotoxicity of zebrafish to a certain extent, providing basis for the further research on the molecular mechanism of spinetoram exposure to aquatic ecosystems.

Synthesis of magnetic core–shell Fe3O4@PDA@Cu-MOFs composites for enrichment of microcystin-LR by MALDI-TOF MS analysis

The synthetic route of the Fe₃O₄@PDA@Cu-MOFs microspheres and enrichment process of MC-LR.

Blood-brain barrier disruption and inflammation reaction in mice after chronic exposure to Microcystin-LR

Microcystin-leucine-arginine (MC-LR), which produced by toxic cyanobacteria and widely present in eutrophic waters, has been shown to have potent acute hepatotoxicity. MC-LR has been revealed to inflict damage to brain, while the neurotoxicity of chronic exposure to MC-LR and mechanisms underlying it are still confusing. Here, the mice were exposed to MC-LR dissolved in drinking water at dose of 1, 7.5, 15, and 30 μg/L for consecutive 180 days. MC-LR accumulated in mouse brains and impaired the blood-brain barrier by inducing the expression of matrix metalloproteinase-8 (MMP-8), which was regulated by NF-κB, c-Fos and c-Jun. Furthermore, MC-LR exposure induced microglial and astrocyte activation and resultant neuroinflammatory response. This study highlights the risks to human health of the current microcystin exposure.

Responses of pro- and anti-inflammatory cytokines in zebrafish liver exposed to sublethal doses of Aphanizomenon flosaquae DC-1 aphantoxins

Blooms of the dominant cyanobacterium Aphanizomenon flosaquae are frequently encountered in natural waters, and their secretion of neurotoxic paralytic shellfish toxins called aphantoxins threatens environmental safety and human health worldwide. The liver is the primary detoxification organ in animals, and its pro- and anti-inflammatory responses are important functions in the detoxification of toxins. Therefore, we investigated the response of these inflammatory factors to aphantoxins in the liver of zebrafish (Danio rerio). A. flosaquae DC-1 was sampled during blooms in Dianchi Lake, China and cultured, and the toxin was extracted and analyzed using high performance liquid chromatography. The primary constituents were gonyautoxins 1 (34.04%) and 5 (21.28%) and neosaxitoxin (12.77%). Zebrafish were injected intraperitoneally with 5.3 μg (low dose) or 7.61 μg (high dose) of saxitoxin equivalents [equivalents (eq.)]/kg body weight of A. flosaquae DC-1 aphantoxins. Hyperemia, the hepatosomatic index (HSI), and physiological and molecular responses of pro- and anti-inflammatory cytokines in the zebrafish liver were investigated at different time points 1-24 h post-exposure. Aphantoxins significantly enhanced hepatic hyperemia and altered the HSI 3-24 h post-exposure, suggesting that inflammation caused morphological changes. Subsequent investigations using the enzyme-linked immunosorbent assay showed that the pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β (IL-1β), IL-6, and IL-8 and anti-inflammatory cytokines IL-10 and transforming growth factor β were higher in the liver of zebrafish exposed to aphantoxins, which indicated physiological inflammatory responses. Further analysis by real-time fluorescence quantitative polymerase chain reaction demonstrated upregulated mRNA expression of these cytokines, suggesting molecular inflammatory responses in the zebrafish liver. These changes showed dose- and time-dependent patterns. These results indicated that aphantoxins induced hyperemia and altered the HSI, and subsequently increased the levels of proinflammatory cytokines TNF-α, IL-1β, IL-6 and IL-8 to induce physiological inflammatory responses. These changes activated the anti-inflammatory cytokines IL-10 and TGF-β to suppress inflammatory damage. The induced changes were the result of upregulated mRNA expression of these inflammatory cytokines caused by aphantoxins. Aphantoxins resulted in hepatic immunotoxicity and response by inducing pro-inflammatory cytokines. Zebrafish liver in turn suppressed the inflammatory damage by upregulating the activities of anti-inflammatory cytokines. In the future, these pro- and anti-inflammatory cytokines in the zebrafish liver may be prove to be useful biomarkers of aphantoxins and blooms in nature.

Chronic Low Dose Oral Exposure to Microcystin-LR Exacerbates Hepatic Injury in a Murine Model of Non-Alcoholic Fatty Liver Disease

Microcystins are potent hepatotoxins that have become a global health concern in recent years. Their actions in at-risk populations with pre-existing liver disease is unknown. We tested the hypothesis that the No Observed Adverse Effect Level (NOAEL) of Microcystin-LR (MC-LR) established in healthy mice would cause exacerbation of hepatic injury in a murine model (Lepr^db/J) of Non-alcoholic Fatty Liver Disease (NAFLD). Ten-week-old male Lepr^db/J mice were gavaged with 50 μg/kg, 100 μg/kg MC-LR or vehicle every 48 h for 4 weeks (n = 15–17 mice/group). Early mortality was observed in both the 50 μg/kg (1/17, 6%), and 100 μg/kg (3/17, 18%) MC-LR exposed mice. MC-LR exposure resulted in significant increases in circulating alkaline phosphatase levels, and histopathological markers of hepatic injury as well as significant upregulation of genes associated with hepatotoxicity, necrosis, nongenotoxic hepatocarcinogenicity and oxidative stress response. In addition, we observed exposure dependent changes in protein phosphorylation sites in pathways involved in inflammation, immune function, and response to oxidative stress. These results demonstrate that exposure to MC-LR at levels that are below the NOAEL established in healthy animals results in significant exacerbation of hepatic injury that is accompanied by genetic and phosphoproteomic dysregulation in key signaling pathways in the livers of NAFLD mice.

Exposure to the Harmful Algal Bloom (HAB) Toxin Microcystin-LR (MC-LR) Prolongs and Increases Severity of Dextran Sulfate Sodium (DSS)-Induced Colitis

Inflammatory Bowel Disease (IBD) represents a collection of gastrointestinal disorders resulting from genetic and environmental factors. Microcystin-leucine arginine (MC-LR) is a toxin produced by cyanobacteria during algal blooms and demonstrates bioaccumulation in the intestinal tract following ingestion. Little is known about the impact of MC-LR ingestion in individuals with IBD. In this study, we sought to investigate MC-LR’s effects in a dextran sulfate sodium (DSS)-induced colitis model. Mice were separated into four groups: (a) water only (control), (b) DSS followed by water (DSS), (c) water followed by MC-LR (MC-LR), and (d) DSS followed by MC-LR (DSS + MC-LR). DSS resulted in weight loss, splenomegaly, and severe colitis marked by transmural acute inflammation, ulceration, shortened colon length, and bloody stools. DSS + MC-LR mice experienced prolonged weight loss and bloody stools, increased ulceration of colonic mucosa, and shorter colon length as compared with DSS mice. DSS + MC-LR also resulted in greater increases in pro-inflammatory transcripts within colonic tissue (TNF-α, IL-1β, CD40, MCP-1) and the pro-fibrotic marker, PAI-1, as compared to DSS-only ingestion. These findings demonstrate that MC-LR exposure not only prolongs, but also worsens the severity of pre-existing colitis, strengthening evidence of MC-LR as an under-recognized environmental toxin in vulnerable populations, such as those with IBD.

Chronic exposure to the ionic liquid [C8mim]Br induces inflammation in silver carp spleen: Involvement of oxidative stress-mediated p38MAPK/NF-κB signalling and microRNAs

The present study aimed to determine the chronic toxicity of 1-methyl-3-octylimidazolium bromide ([C₈mim]Br) on the silver carp to further reveal the toxicological mechanisms of ionic liquids. Chronic exposure of silver carp to [C₈mim]Br at concentrations of 1.095 and 4.380 mg/L for 60 d was conducted under laboratory conditions. The results revealed that chronic exposure to [C₈mim]Br inhibited the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and reduced glutathione (GSH) levels while markedly increasing malondialdehyde (MDA) and protein carbonyl (PC) levels in fish spleen, indicating that [C₈mim]Br treatment induced oxidative stress. Additionally, long-term exposure to [C₈mim]Br markedly upregulated the expressions of nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), IL-6, tumour necrosis factor-α (TNF-α), and interferon-γ (IFN-γ); altered the levels of transforming growth factor-β (TGF-β); and increased the mRNA levels of p38MAPK, c-fos, c-jun, and c-myc, suggesting that long-term exposure to [C₈mim]Br might promote the inflammatory response in fish spleen and that p38MAPK/NF-κB signalling may potentially be involved in this process. Moreover, [C₈mim]Br-exposure altered lysozyme activity and complement 3 (C3) and immunoglobulin M (IgM) content, indicating that chronic [C₈mim]Br exposure also has immunotoxic effects on silver carp. Furthermore, we also found that [C₈mim]Br exposure reduced miR-125b levels, altered miR-143 levels, and upregulated miR-155 and miR-21 levels, suggesting that these miRNAs may be involved in the [C₈mim]Br-induced inflammatory response in fish spleen. In summary, the present study indicates that chronic exposure to [C₈mim]Br induces inflammation in fish spleen and that oxidative stress-mediated p38MAPK/NF-κB signalling and miRNAs may play a key role in this process.

Negative impact of the imidazolium-based ionic liquid [C8mim]Br on silver carp (Hypophthalmichthys molitrix): Long-term and low-level exposure

This study aimed to determine the chronic toxicity of the ionic liquid (IL) 1-methyl-3-octylimidazolium bromide ([C₈mim]Br) on silver carp to further study the toxicological mechanism of ILs. For this purpose, 60-d chronic exposure at concentrations of 1.09 or 4.38 mg L^-1 [C₈mim]Br in silver carp was conducted. The results of biochemical assays revealed that [C₈mim]Br-treatment remarkably promoted serum lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities, indicating that [C₈mim]Br-exposure caused fish organ damage. Long-term exposure of [C₈mim]Br also altered the activities of superoxide dismutase (SOD) and catalase (CAT) and the glutathione (GSH) level but increased malondialdehyde (MDA) levels in fish brain, gill, intestine, kidney, liver, and muscle, suggesting that [C₈mim]Br-treatment may cause oxidative stress in fish organs. Further work revealed that [C₈mim]Br-treatment increased the activities of erythromycin-N-demethylase (ERND) and glutathione S-transferases (GST), which may participate in the metabolism of [C₈mim]Br in fish liver. Moreover, chronic [C₈mim]Br-exposure remarkably promoted the expression of inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α), and nuclear factor-κB (NF-κB) and altered the levels of transforming growth factor-β (TGF-β), suggesting that long-term exposure of [C₈mim]Br might promote the inflammatory response in fish liver. Additionally, [C₈mim]Br-exposure altered succinate dehydrogenase (SDH) activity and promoted caspase-9 and caspase-3 activities in fish liver, suggesting that chronic [C₈mim]Br-exposure also induces hepatocellular apoptosis via the mitochondrial pathway. The results presented here may be helpful to illuminate the chronic toxicity mechanism of imidazolium-based ILs and safe use of ILs in the future.

MC-LR induces dysregulation of iron homeostasis by inhibiting hepcidin expression: A preliminary study

The liver is an important iron storage site and a primary MC-LR target. C57BL/6 and Hfe^-/- mice were used to investigate effects and mechanisms of MC-LR on systematic iron homeostasis. Body weight, tissue iron content, hematological and serological indexes, and histopathological were evaluated. Ultrastructure and iron metabolism-related genes and proteins were analyzed. MC-LR induced dose-dependent increases in red blood cells, hemoglobin, and hematocrit. In contrast MC-LR-induced dose-dependent decreases in mean corpuscular volume, hemoglobin, and hemoglobin concentration were observed both C57BL/6 and Hfe^-/- mice. In both mouse species, serological indexes increased. Aggravated liver and spleen iron were observed in C57BL/6 mice, consistent with Perls' Prussian blue staining. However, an opposite trend was observed in Hfe^-/- mice. C57BL/6 mice had lower Hamp1 (Hepcidn), Bmp6, Il-6, and Tmprss6. Significant increased Hjv, Hif-1α and Hif-2α were observed in both C57BL/6 and Hfe^-/- mice. MC-LR-induced pathological lesions were dose-dependent increase in C57BL/6 mice. More severe pathological injuries in MC-LR groups (25 μg/kg) were observed in Hfe^-/- mice than in C57BL/6 mice. In Hfe^-/- mice, upon exposure to 25 μg/kg MC-LR, mitochondrial membranes were damaged and mitochondrial counts increased with significant swelling. These results indicated that MC-LR can induce the accumulation of iron in C57BL/6 mice with the occurrence of anemia, similar to thalassemia. Moreover, dysregulation of iron homeostasis may be due to MC-LR-induced Hamp1 downregulation, possibly mediated by hypoxia or the IL6-STAT3 and BMP-SMAD signaling pathways.

Insight into the negative impact of ionic liquid: A cytotoxicity mechanism of 1-methyl-3-octylimidazolium bromide

Ionic liquids (ILs) as a green replacement for volatile organic solvents are increasingly used in large-scale commercial applications. A good understanding of the toxic mechanisms and environmental impact of ILs is neede to reduce the risk for human health and the environment. For this purpose, we aimed to evaluate the possible impacts of 1-methyl-3-octylimidazolium bromide ([C₈mim]Br) exposure on human hepatocellular carcinoma (HepG2) cells as to elucidate the cytotoxic mechanism of [C₈mim]Br. Biochemical assays revealed that [C₈mim]Br exposure altered the protein levels of heat shock protein 70 (HSP70) and HSP90, generally inhibiting total antioxidative capacity (T-AOC), depleting heme oxygenase-1 (HO-1) and increasing transcription and activity of inducible nitric oxide synthase (iNOS) in HepG2 cells. These results indicated that [C₈mim]Br may induce biochemical disturbances and cause oxidative stress in HepG2 cells. Moreover, increased phosphorylation of p53, mitochondrial membrane disruption, cyclooxygenase-2 activation, Bcl-2 family protein modulation, cytochrome c and Smac/DIABLO release, and inhibition of apoptosis inhibitory protein-2 (c-IAP2) and survivin were also observed in [C₈mim]Br-treated cells, suggesting that [C₈mim]Br-induced apoptosis might be mediated by the mitochondrial pathway. Further research showed that [C₈mim]Br exposure increased tumour necrosis factor α (TNF-α) transcription and content and promoted the expression of Fas and FasL, indicating that TNF-α and Fas/FasL are involved in the apoptosis induced by [C₈mim]Br. Additionally, [C₈mim]Br cytotoxicity was partly inhibited by N-acetyl-cysteine (NAC), and NAC reversed [C₈mim]Br-mediated mitochondrial dysfunction and blocked apoptotic events by inhibiting the generation of reactive oxygen species (ROS). This work first demonstrated that the ROS-mediated mitochondrial and death receptor-initiated apoptotic pathway is involved in [C₈mim]Br-induced HepG2 cell apoptosis.

Gastrointestinal toxicity induced by microcystins

Microcystins (MCs) are produced by certain bloom-forming cyanobacteria that can induce toxicity in various organs, including renal toxicity, reproductive toxicity, cardiotoxicity, and immunosuppressive effects. It has been a significant global environmental issue due to its harm to the aquatic environment and human health. Numerous investigators have demonstrated that MC exposure can induce a widespread epidemic of enterogastritis with symptoms similar to food poisoning in areas close to lakes. Both in vivo and in vitro studies have provided evidence of positive associations between MC exposure and gastrointestinal toxicity. The toxicity of MCs on the gastrointestinal tract is multidimensional. MCs can affect gastrointestinal barrier function and shift the structure of gut microbiota in different gut regions. Furthermore, MCs can inhibit the secretion of gastrointestinal digestive enzymes and the release of inflammatory cytokines, which affects the expression of immune-related genes in the intestine. The damage of the intestine is closely correlated to MC exposure because the intestine is the main site for the digestion and absorption of nutrients. The damage to the gastrointestinal tract due to MCs was summarized from different aspects, which can be used as a foundation for further exploration of molecular damage mechanisms.

Polyphenols in Liubao Tea Can Prevent CCl₄-Induced Hepatic Damage in Mice through Its Antioxidant Capacities

The present study investigated the preventive effect of polyphenols in Liubao tea (PLT) on carbon tetrachloride (CCl₄)-induced liver injury in mice. The mice were initially treated with PLT, followed by induction of liver injury using 10 mL/kg CCl₄. Then liver and serum indices, as well as the expression levels of related messenger RNAs (mRNAs) and proteins in liver tissues were measured. The results showed that PLT reduces the liver quality and indices of mice with liver injury. PLT also downregulates aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides (TGs), and malondialdehyde (MDA), and upregulates superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the sera of mice with liver injury. PLT also reduces serum levels of interleukin-6 (IL-6), interleukin-12 (IL-12), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) cytokines in mice with liver injury. Pathological morphological observation also shows that PLT reduces CCl₄-induced central venous differentiation of liver tissues and liver cell damage. Furthermore, qPCR and Western blot also confirm that PLT upregulates the mRNA and protein expressions of Gu/Zn-SOD, Mn-SOD, catalase (CAT), GSH-Px, and nuclear factor of κ-light polypeptide gene enhancer in B-cells inhibitor-α (IκB-α) in liver tissues, and downregulates the expression of cyclooxygenase 2 (COX-2) and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). Meanwhile, PLT also raised the phosphorylated (p)-NF-κB p65 and cytochrome P450 reductase protein expression in liver injury mice. The components of PLT include gallic acid, catechin, caffeine, epicatechin (EC), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), and epicatechin gallate (ECG), which possibly have a wide range of biological activities. Thus, PLT imparts preventive effects against CCl₄-induced liver injury, which is similar to silymarin.

Microcystis bloom containing microcystin-LR induces type 2 diabetes mellitus

Epidemiological data from Lake Taihu showed significantly higher incidences of type 2 diabetes mellitus (T2DM) than in other areas of China. This may be related to the occurrence of a Microcystis bloom in Lake Taihu in the summer and autumn every year. The objective of this study is to investigate whether the contaminated water from the Microcystis bloom and the derivative pollutant microcystin-LR (MC-LR) can explain the higher incidences of T2DM. Healthy male mice were fed with water from different regions of Lake Taihu, and were either acutely or chronically exposed to MC-LR through oral administration or intraperitoneal injection. Serum lipid profiles were determined, and the effects on T2DM-related gene expression and insulin receptor signaling pathway were investigated. Intraperitoneal glucose tolerance (IPGTT) and insulin resistance (IRT) tests were implemented, and the functions of pancreatic islet and β-cell were also evaluated. The results showed that both water sampled from the region with a Microcysis bloom and those containing MC-LR altered the serum glucide and lipid profiles in mice after exposure. The exposure to a Microcysis bloom water affected the expression T2DM-related genes: up-regulated the mRNA levels of FASn, ACACA, G6pc, LPL, and Insig2, and down-regulated the mRNA level of PEPCK and Gsk-3β. Both acute and chronic exposure of MC-LR, even at very low concentrations (1 μg/L), impaired the insulin receptor signalling pathway and induced hyperinsulinemia and insulin resistance in mice. In this study, the most important intracellular target of MC-LR was found to be hetapocellular mitochondria. Thus, exposure to Microcystis bloom water containing microcystin-LR can induce the incidence of T2DM, by impairing the function of mitochondria by microcystin-LR. The study suggests a review of the risk assessment concerning 1 μg/L MC-LR as the reference dose in surface water.