Advances in investigating microcystin-induced liver toxicity and underlying mechanisms

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.

Microcystin-LR Induces Lipid Metabolism Disorder in Pelophylax nigromaculatus Tadpoles via the Gut-Liver Axis

Disruption of lipid homeostasis in aquatic animals poses serious health risks, including tissue damage and systemic metabolic dysfunction. The precise mechanisms by which microcystin-LR, a potent cyanotoxin, disrupts lipid metabolism in amphibian tadpoles remain unclear. In this study, tadpoles (Pelophylax nigromaculatus) were exposed to MC-LR and fecal microbiota transplantation (FMT) experiments were performed to investigate whether or how MC-LR at environmental concentrations interfered with tadpole lipid metabolism from the perspective of the gut microbiota-gut-liver axis. Following exposure, the liver exhibited significant inflammation, hypertrophy, and fibrosis, accompanied by elevated serum lipid levels. Furthermore, the expression levels of the farnesoid X receptor (FXR), a nuclear receptor, were significantly downregulated. Molecular docking and molecular dynamics simulations indicated a strong and stable binding between FXR and MC-LR. Moreover, MC-LR suppressed liver FXR expression or activity, triggering: (1) upregulation of sterol regulatory element-binding protein 1 (SREBP1)-mediated triglyceride (TG) synthesis, (2) inhibition of free fatty acid (FFA) β-oxidation, and (3) activation of SREBP2-dependent bile acid biosynthesis. Moreover, MC-LR altered the composition of gut microbiota and specific bile acid levels (e.g., taurocholic acid and glycochenodeoxycholic acid) in the gut, thereby interfering with hepatic lipid metabolism, as evidenced by FMT-induced hepatic lipid accumulation in recipient tadpoles. These findings identify FXR as a potentially key molecular target for MC-LR and suggest that changes in bile acid levels of intestinal microbiota metabolism also may be an important pathway driving hepatic lipid dysregulation in amphibians exposed to environmental concentrations of MC-LR.

Microcystin-LR induces lung injury in mice through the NF-κB/NLRP3 pathway

Microcystin-LR (MC-LR) a cyclic toxin produced by cyanobacterial species is known to exert detrimental effects on various organs, including lung. Several investigators demonstrated that MC-LR exerts pulmonary toxicity, but the underlying mechanisms remain unclear. This study aimed to investigate whether exposure to MC-LR-induced lung inflammation and examine the underlying mechanisms. Thirty specific pathogen-free (SPF) male mice were allocated into control and MC-LR treatment groups. Mice were intraperitoneally injected with physiological saline or MC-LR (20 μg/kg) daily for a total of 21 days. Our findings indicated that exposure to MC-LR-produced histopathological changes in lung tissue, including thickening of alveolar walls and inflammatory infiltration. MC-LR was found to upregulate mRNA expression levels of pro-inflammatory cytokines TNFα, IL-6, IL-1β, and IL-18. Further, MC-LR significantly elevated the expression levels of proteins associated with the NF-κB/NLRP3 pathway p-NF-κB, NLRP3, Caspase-1, ASC. The activation of NF-κB/NLRP3 pathway further promoted the release of inflammatory cytokine IL-1β and cleavage of pyroptosis-associated GSDMD protein. These findings indicate that MC-LR may induce lung inflammation by promoting cell pyroptosis via the activation of the NF-κB/NLRP3 pathway.

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.

Sensing technology empowering food safety: research progress of SERS-assisted multimodal biosensing toward food hazard factors

Food is the main source of human energy and nutrition, but once it is contaminated with hazardous factors, such as biotoxins, pesticide residues, etc., it will seriously damage health. This paper reviews the research progress of biosensors based on surface-enhanced Raman scattering (SERS) in the detection of food hazard factors. First, the basic principle, substrate and assay mode of SERS technology, as well as related design and sensing strategy mechanisms, are introduced. Then, the design idea of multimodal biosensors combining SERS with microfluidic, fluorescence, colorimetric, electrochemical (EC), molecular imprinting and other technologies is expounded to improve the analysis accuracy and specificity. Then the application results of multimodal biosensors based on SERS sensing toward food hazard factors are discussed, and the necessity of its development is illustrated. Finally, the future development direction of this field is prospected, which provides a reference for promoting the research and application of multimodal biosensors based on SERS.

Destruction of the intestinal microbiota and gut-liver axis homeostasis by microcystin-LR-induced inflammation in the common carp (Cyprinus carpio)

Water eutrophication leads to the frequent occurrence of cyanobacterial blooms, which pose a serious threat to the health and survival of fish, the top consumer in freshwater ecosystems. The hepatotoxicity induced by microcystin-LR (MC-LR) has been well studied; however, its impact on the intestinal flora and the gut-liver axis has rarely been reported. This study aimed to investigate the harmful effects of acute oral (303.89 µg/kg.bw) and intraperitoneal (i.p., 101.3 µg/kg.bw) exposure to MC-LR on the intestine and liver and the gut-liver axis of common carp. The results showed that the transaminase activity and levels of proinflammatory factors increased significantly, and histological abnormalities were observed, indicating that MC-LR induced a hepatoenteric inflammatory response. The levels of gram-negative bacteria increased, but the expression levels of bile acid (BA)-related genes (cyp7a1, cyp8b1, cyp27a1, and fxr) and the short-chain fatty acid (SCFA) content decreased as the LPS level increased. These results suggest that MC-LR exposure induces liver inflammation and impairs BA synthesis, weakening intestinal defences and promoting LPS-related hepatic inflammation. Additionally, increased intestinal permeability and reduced SCFA synthesis can further compromise intestinal epithelium protection. The inflammation induced by MC-LR was significantly more severe in the liver than in the intestine, and the recovery of the liver was slower. This study enhances the understanding of the environmental risks posed by cyanobacteria.

Activation of gut FXR improves the metabolism of bile acids, intestinal barrier, and microbiota under cholestatic condition caused by GCDCA in mice

Abnormal bile acid (BA) metabolism is involved in liver fibrosis. In a previous study, we discovered that the hydrophobic BA glycochenodeoxycholate (GCDCA) induced liver fibrosis and that GW4064, an agonist of farnesoid X receptor (FXR), alleviated liver fibrosis caused by GCDCA. However, the impacts of GCDCA on liver BAs, gut BAs, the intestinal barrier, and the gut microbiota are unclear, and obtaining this information would provide additional information into the role of GCDCA in the development of liver fibrosis. In the present study, ultra-performance liquid chromatography‒tandem mass spectrometry revealed that mice administered GCDCA by gavage had higher levels of total and primary liver BAs than those in the control group, and a significant reduction in primary liver BAs was observed in the GCDCA + GW4064 group compared with those in the GCDCA group. Compared with those in the control group, the mice administered GCDCA by gavage had greater levels of total and primary BAs in the gut, especially T-alpha-MCA and T-beta-MCA, and no significant differences in the terminal ileum were observed between the GCDCA and GCDCA + GW4064 groups. Immunohistochemistry indicated that GCDCA administration inhibited gut FXR and FGF15 expression, whereas GW4064 activated gut FXR and promoted FGF15 expression. Moreover, immunohistochemistry revealed that GCDCA administration decreased mucin2, claudin-1, occludin, and ZO-1 expression, whereas GW4064 restored their expression. 16S rDNA sequencing revealed that the alpha diversity of the microbiota did not significantly differ among the three groups, but differences in the beta diversity of the microbiota were observed among the three groups. At the phylum level, GCDCA significantly disturbed the gut microbiota, as indicated by reductions in Desulfobacterota, Bacteroidota, and Actinobacteria in the GCDCA group compared with those in the control group. However, significantly increased abundances of Proteobacteria, Cyanobacteria, and Patescibacteria were noted in the GCDCA group compared with the control group. GW4064 administration significantly improved the microbiota structure at the phylum level. The efficacy of GW4064 was also observed at the genus level. Correlation analyses revealed fewer relationships between the gut microbiota and gut BAs, whereas the gut microbiota was more closely related to liver BAs in the GCDCA and GW4064 intervention groups. Together, GCDCA induced cholestasis and disturbed BA metabolism in the gut and liver, as well as the intestinal barrier and structure of the gut microbiota. Activation of gut FXR improved intestinal barrier injury and alleviated BA metabolism dysfunction and dysbacteriosis caused by GCDCA under cholestatic conditions.

IMPORTANCE

Glycochenodeoxycholate (GCDCA) is a hydrophobic bile acid (BA) in humans and is highly increased in the serum and stool of liver fibrosis patients. However, the effects of GCDCA were not comprehensively investigated in the process of liver bile acid metabolism, gut microbiota, and intestinal barrier. It was reported that GCDCA can promote liver fibrosis via the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome pathway in mice, and gut farnesoid X receptor activation alleviated the fibrosis caused by GCDCA in our previous study. Gut microbiota is also responsible for BA metabolism; meanwhile, BA metabolism may also exert an effect on the intestinal barrier. Nowadays, the comprehensive understanding of gut microbiota and intestinal barrier in relation to BA disorder was still insufficient. Current study further investigated the role of GCDCA in BA metabolism, gut microbiota, and intestinal barrier to help understand the effects of GCDCA in liver fibrosis, which may provide intervention methods for liver fibrosis caused by dysregulation of BA metabolism.

Environmental Pollutants, Occupational Exposures, and Liver Disease

Environmental pollutants significantly impact liver disease development, progression, and outcomes. This review examines the complex relationship between environmental exposures and liver pathology, from malignant conditions like hepatocellular carcinoma to steatotic and cholestatic liver diseases. Key environmental factors include air pollutants, volatile organic compounds, persistent organic pollutants, heavy metals, and per- and polyfluoroalkyl substances. These compounds can act through multiple mechanisms, including endocrine disruption, metabolic perturbation, oxidative stress, and direct hepatotoxicity. The impact of these exposures is often modified by factors such as sex, diet, and genetic predisposition. Recent research has revealed that even low-level exposures to certain chemicals can significantly affect liver health, particularly when combined with other risk factors. The emergence of exposomics as a research tool promises to enhance our understanding of how environmental factors influence liver disease. Importantly, exposure effects can vary by demographic and socioeconomic factors, highlighting environmental justice concerns. Implementation of this knowledge in clinical practice requires new diagnostic approaches, healthcare system adaptations, and increased awareness among medical professionals. In conclusion, this review provides a comprehensive examination of current evidence linking environmental exposures to liver disease and discusses implications for clinical practice and public health policy.

Algae removal and degradation of microcystins by UV-C system: A review

Harmful algal blooms (HABs), driven by eutrophication, are a growing ecological threat, compromising water quality and ecosystem health through the release of toxic microcystins (MCs). These toxins pose significant risks to both aquatic life and human health. Among the emerging solutions, UV-C technology has gained attention for its efficiency in inhibiting algal growth and degrading MCs, offering a cost-effective and environmentally friendly approach with minimal secondary pollution. However, existing studies often overlook key aspects, including the variability in algae sensitivity to UV-C wavelengths, the stability of treatment across diverse aquatic conditions, and the toxicity of degradation byproducts. This review highlights the mechanisms underlying UV-C-based algae removal, explores its potential limitation, such as algal resistance, and compares its efficacy with other remediation methods. Notably, the lack of comprehensive research on wavelength-specific sensitivity and real-world application efficacy represents a significant knowledge gap. Further investigation into these areas is essential to optimize UV-C technology for mitigating HABs and improving water safety in eutrophic environments. PRACTITIONER POINTS: The choice of UV band should be adjusted to the algae species. The UV-C system, with limited studies and applications in natural water bodies, demonstrates instability. Combining UV-C with other technologies substantially enhances the efficiency of algal control. Future research should emphasize strategies to prevent the rapid release of microcystins (MCs) from this system due to cell lysis and extracellular release within a short time frame.

Advances in environmental pollutant detection techniques: Enhancing public health monitoring and risk assessment

Accurate detection and monitoring of environmental pollutants are of paramount importance for disease prevention and public health. In recent years, the ever-expanding human activities and industrial production have given rise to a sharp increase in the complexity and variety of these pollutants, which pose significant threats to human well - being. Environmental pollutants stem from multiple sources, such as heavy metals, persistent organic pollutants, inorganic non - metallic pollutants, emerging pollutants, and biological contaminants. Traditional detection technologies, though valuable for their sensitivity and accuracy, are constrained by complex sample preparation, poor selectivity, and the absence of standardized detection methods. On the other hand, emerging technologies, including nanotechnology, molecular detection methods, biosensors, Surface-Enhanced Raman Spectroscopy (SERS), multi-omics, and big data analysis, offer promising solutions for rapid and sensitive pollutant detection. The establishment of environmental monitoring networks and data - sharing platforms further enhances real - time pollutant monitoring and provides solid data support for public health initiatives. Nonetheless, challenges persist, including data integration, exposure assessment, and the development of cost-effective and portable detection solutions. Future progress in interdisciplinary approaches and technology integration will be crucial for advancing environmental pollutant detection and facilitating comprehensive disease prevention. This review systematically classifies environmental pollutants and showcases the latest advancements in detection technologies, offering critical insights for environmental monitoring and public health protection.

Simultaneous determination of twelve microcystins in algal supplements on the Chinese market and possible risks to exposed populations

Algae supplements are widely recognized for their nutritional benefits and are commonly marketed as natural health products. However, concerns regarding contamination with cyanobacterial toxins have been raised. Moreover, there is very little data regarding the potential contamination of algal supplements on the Chinese market by these toxins. In this study, we employed a validated solid-phase extraction ultra-high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) method to analyze algal supplements available in China. Therefore, this study optimized the extraction conditions for twelve microcystins (MCs) simultaneously using response surface methodology (RSM) and analyzed via UHPLC-MS/MS. Method validation was conducted in four supplement matrices (capsule, liquid, powder, and tablet) to ensure the method's accuracy, sensitivity, and reproducibility. Analysis of nineteen commercial algae products available in China using the validated method revealed the presence of four MCs: microcystin-LF (MC-LF), microcystin-LR (MC-LR), microcystin-LA (MC-LA), and microcystin-YR (MC-YR). Furthermore, seven products were found to contain one or more of the MCs, with two products exceeding the 1 μg/g MC limit. These findings underscore the effectiveness of the validated method in assessing MC contamination of algae supplements and consequently identifying consumers expected to be at risk from prolonged exposure to recommended daily algal supplements.

Chronic exposure to low-dose MC-LR induces ileal inflammation in mice through the PI3K/AKT/mTOR pathway

The global phenomenon of cyanobacterial bloom pollution is spreading globally due to climate change and eutrophication. It is well established that harmful cyanobacteria produce a wide range of toxins including microcystin-LR (MC-LR), a cyclic heptapeptide toxin known to damage various organs. The intestinal tract is the main site of MC-LR absorption and one of the targets susceptible to toxicity. Currently, studies on the enterotoxic effects of MC-LR predominantly focused on the colorectum, with limited investigations addressing the impact of microcystins on the small intestine. Therefore, the aim of our study was to examine the impact of chronic 9-month exposure of mice to low-dose 120 μg/L MC-LR in drinking water on ileal inflammation and potential mechanisms underlying these effects. Our findings showed that in mice chronically administered with low-dose MC-LR disorganized intestinal epithelial cells, lymphocytic infiltration and disturbed crypt arrangement were detected. The results of qPCR and Western blot demonstrated that, in comparison to control, the mRNA expression levels of pro-inflammatory factors IL-6, IL-17, IL-18, and IFN-γ were markedly elevated in the ileal tissue of mice treated with MC-LR, associated with significant increases in protein expression levels of p-PI3K, p-AKT, and p-mTOR. Taken together, evidence indicates that MC-LR induces ileal inflammation and histopathological damage involved activation of the PI3K/AKT/mTOR signaling pathway.

Liver Lesions in Estuarine Dolphins in the Indian River Lagoon, Florida: Does Microcystin Play a Role?

Microcystin (MC), a hepatotoxin produced by cyanobacteria, was introduced into the Indian River Lagoon (IRL), Florida, in 2005 through freshwater outflows. Since then, MC has been detected in humans, domestic animals, and wildlife in the lagoon. Potential public health effects associated with MC exposure along the IRL include an increased risk of non-alcoholic liver disease among area residents. Yet, there are limited studies characterizing liver disease, as well as the potential role of MC, in humans and animals in this region. Thus, histopathology reports (n = 133) were reviewed in the stranded common bottlenose dolphin (Tursiops truncatus truncatus) (n = 156, 2005-2024) to describe liver lesions in this important IRL sentinel. Liver and fecal samples (n = 161) from stranded individuals were screened for MC via an enzyme immunoassay (ELISA). These samples were then confirmed via the 2-methyl-3-methoxy-4-phenylbutyric acid technique (MMPB) to evaluate whether liver histopathologic lesions were linked to MC exposure. Minimally invasive MC screening methods were also assessed using respiratory swabs and vapor. Inflammation (24%, n = 32), fibrosis (23%, n = 31), lipidosis/vacuolation (11%, n = 15), and necrosis (11%, n = 14) were the most common liver anomalies observed. These non-specific lesions have been reported to be associated with MC exposure in numerous species in the peer-reviewed literature. Ten bottlenose dolphins tested positive for the toxin via ELISA, including two individuals with hepatic lipidosis, but none were confirmed by MMPB. Thus, this study did not provide evidence for MC-induced liver disease in IRL bottlenose dolphins. Other causes should be considered for the lesions observed (e.g., heavy metals, metabolic disease, and endoparasites). Respiratory swabs require further validation as a pre-mortem MC screening tool in free-ranging wildlife.

Hepatocyte apoptosis is triggered by hepatic inflammation in common carp acutely exposed to microcystin-LR or chronically exposed to Microcystis

Cyanobacterial blooms pose a serious threat to the survival of fish because of the hepatotoxicity of microcystins produced by toxic cyanobacteria such as Microcystis. Many studies have investigated the hepatotoxicity of microcystins in common carp, a freshwater fish distributed worldwide, but the hepatotoxicity mechanism has not been fully clarified. The present study aimed to investigate the mechanism underlying the hepatic inflammatory response and hepatocyte apoptosis induced by acute microcystin-LR exposure via intraperitoneal injection (71 μg/kg and 119 μg/kg) or gavage (357.08 μg/kg) and chronic exposure to toxic Microcystis blooms. The results of acute exposure revealed that microcystin-LR caused an increase in serum transaminase activity and increased the levels of inflammatory factors and inflammatory mediators, inducing a significant inflammatory response in the liver of common carp. Moreover, biochemical detection revealed that hepatocyte apoptosis occurred in the fish. Moreover, chronic toxic Microcystis exposure also caused hepatic inflammation and subsequent apoptosis mediated by the tumour necrosis factor-α (TNF-α) pathway and the mitochondrial pathway similar to acute exposure. Therefore, our study suggests that the inflammatory response induced by microcystin-LR exacerbates apoptosis, likely mediated by TNF-α. In summary, both acute microcystin-LR exposure and chronic toxic Microcystis exposure can cause inflammation in the liver of common carp, which subsequently triggers hepatocyte apoptosis mediated by the TNF-α pathway and the mitochondrial pathway. This study helps elucidate the mechanism of liver damage induced by cyanobacterial blooms in natural water.

Therapeutic Potential of Lactiplantibacillus plantarum FB091 in Alleviating Alcohol-Induced Liver Disease through Gut-Liver Axis

Alcoholic liver disease (ALD) poses a significant global health burden, often requiring liver transplantation and resulting in fatalities. Current treatments, like corticosteroids, effectively reduce inflammation but carry significant immunosuppressive risks. This study evaluates Lactiplantibacillus plantarum FB091, a newly isolated probiotic strain, as a safer alternative for ALD treatment. Using an in vivo mouse model, we assessed the effects of L. plantarum FB091 on alcohol-induced liver damage and gut microbiota composition. Alcohol and probiotics administration did not significantly impact water/feed intake or body weight. Histopathological analysis showed that L. plantarum FB091 reduced hepatocellular ballooning and inflammatory cell infiltration in liver tissues and mitigated structural damage in colon tissues, demonstrating protective effects against alcohol-induced damage. Biomarker analysis indicated that L. plantarum FB091 decreased aspartate aminotransferase levels, suggesting reduced liver damage, and increased alcohol dehydrogenase activity, indicating enhanced alcohol metabolism. Additionally, cytokine assays revealed a reduction in pro-inflammatory TNF-α and an increase in anti-inflammatory IL-10 levels in colon tissues of the L. plantarum FB091 group, suggesting an anti-inflammatory effect. Gut microbiota analysis showed changes in the L. plantarum FB091 group, including a reduction in Cyanobacteria and an increase in beneficial bacteria such as Akkermansia and Lactobacillus. These changes correlated with the recovery and protection of liver and colon health. Overall, L. plantarum FB091 shows potential as a therapeutic probiotic for managing ALD through its protective effects on liver and colon tissues, enhancement of alcohol metabolism, and beneficial modulation of gut microbiota. Further clinical studies are warranted to confirm these findings in humans.

Microcystin-LR induces histopathological injury and cell apoptosis in the hepatopancreas of white shrimp, Litopenaeus vannamei

Microcystin-LR (MC-LR), a common hepatotoxin produced by bloom-forming cyanobacteria, presents a serious threat to the health of aquatic animals. In this study, we studied the impact of MC-LR on hepatopancreas histopathology, enzyme activity, transcriptome, and apoptosis of Litopenaeus vannamei. Thus, shrimp postlarvae (1.63 ± 0.5 g) exposed to MC-LR at 500 μg/kg caused morphological lesions in the histology of the shrimp hepatopancreas, which exhibited swollen, lighter coloration and unclear edges. Moreover, MC-LR significantly altered the hepatopancreas enzyme activities such as the levels of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (AKP) and lysozyme (LZM), including the state of apoptosis in hepatopancreas. From the RNA-seq analysis of the hepatopancreas, a total of 728 differentially expressed genes (DEGs) were identified, and their functions in MC-LR treatment group were involved in cellular processes, metabolic processes, biological regulation, cellular components, catalytic activity and binding. The metabolic pathways primarily associated with the DEGs included reactive oxygen species, glycerophospholipid metabolism and the phospholipase D signaling pathway. Overall, q-PCR results indicated that MC-LR led to significant changes in multiple apoptosis genes of shrimp hepatopancreas. This study expand the understanding of the effect of microcystin-LR on commercially farmed crustaceans.

Potential (co-)contamination of dairy milk with AFM1 and MC-LR and their synergistic interaction in inducing mitochondrial dysfunction in HepG2 cells

Several toxic metabolites, such as aflatoxin M1 (AFM1), are known to contaminate dairy milk. However, as mentioned in an external EFSA report, there is a knowledge gap regarding the carry-over of certain emerging toxins such as microcystin-LR (MC-LR). Therefore, this work aimed to develop an LC-MS/MS method for MC-LR quantification in dairy milk. Also, the method included AFM1 as a common fungal metabolite and applied to analyze 113 dairy milk samples collected directly after the end of the summer peak. Both toxins were below their LODs, keeping the question on MC-LR carry-over still unanswered. Moreover, an in silico analysis, using a 3D molecular modeling was performed, pointing to a possible interaction between MC-LR and milk proteins, especially β-lactoglobulin. Since AFM1 and MC-LR are hepatotoxic, their interaction in inducing mitochondrial dysfunction in HepG2 cells was investigated at low (subcytotoxic) concentrations. Live cell imaging-based assays showed an inhibition in cell viability, without involvement of caspase-3/7, and a hyperpolarization in the mitochondrial membrane potential after the exposure to a mixture of 100 ng mL-1 AFM1 and 1000 ng mL-1 MC-LR for 48h. Extracellular flux analysis revealed inhibitions of several key parameters of mitochondrial function (basal respiration, ATP-linked respiration, and spare respiratory capacity).

Contaminant Exposure and Liver and Kidney Lesions in North American River Otters in the Indian River Lagoon, Florida

The harmful algal bloom (HAB) liver toxin microcystin (MC) and trace element biomagnification were previously detected in organisms in the Indian River Lagoon (IRL), Florida. Since there are no routine screening programs for these contaminants, liver tissue from North American river otters (Lontra canadensis), an important sentinel species in the IRL, was screened for MC via enzyme-linked immunoassay (ELISA), followed by confirmatory analyses via liquid-chromatography/mass spectrometry methods (LC-MS/MS). Liver and kidney samples were evaluated for trace element (As, Cd, Co, Cu, Fe, Hg, Mn, Mo, Pb, Se, Tl, and Zn) bioaccumulation via inductively coupled plasma mass spectrometry (ICP-MS). Histopathologic evaluation of the liver and kidney was conducted to assess possible correlation with toxic insults. Forty-three river otters were evaluated (2016-2022). Microcystin was not detected in any river otter sample (n = 37). Of those tested for trace element bioaccumulation (n = 22), no sample measured above provided reference ranges or estimated toxic thresholds for this species. There were no statistically significant patterns observed based on season, year, or age class, but sex had a small influence on trace element levels in the kidney. One individual had a kidney Cu level (52 μg/g dry weight) higher than any previously reported for this species. Trace elements were detected at presumed background levels providing baselines for future monitoring. For otters with available histopathologic evaluation (n = 28), anomalies indicative of contaminant exposure (non-specific inflammation, necrosis, and/or lipidosis) were present in the liver and kidney of 18% and 4% of individuals, respectively. However, since these lesions were not linked to abnormal trace element bioaccumulation or MC exposure, other causes (e.g., infectious disease) should be considered.

Ion‐Specific Hydrogel Microcarriers with Biomimetic Niches for Bioartifical Liver System

Bioartificial livers have showcased significant value in the treatment of acute liver failure (ALF). Current efforts are directed toward overcoming challenges in the development of microcarriers, with a specific emphasis on integrating higher‐density liver cells to enhance detoxification capabilities. Here, inspired by the radial filtration model in hepatic lobules, ion‐specific silk fibroin microcarriers are proposed with biomimetic niches for cultivating functional liver cells at high density. These biomimetic microcarriers are generated by capillary microfluidic device with controllable adjustments of ion type or concentration within the aqueous phase. When cultivating human induced pluripotent stem cell ‐differentiated mature liver cells on these recrystallized microcarriers, notably enhanced cell proliferation activity, as well as increased metabolic and secretory functionality is observed. Based on these features, the microcarrier‐integrated bioreactor can effectively reduce hepatic transaminase levels and significantly improve urea, albumin production, and survival rate in rabbit ALF models is demonstrated. Thus, it is believed that the biomimetic microcarriers and their derived bioreactor may hold potential for clinical applications in managing ALF and other liver diseases.

Cyanobacterial Cyclic Peptides Can Disrupt Cytoskeleton Organization in Human Astrocytes-A Contribution to the Understanding of the Systemic Toxicity of Cyanotoxins

The systemic toxicity of cyclic peptides produced by cyanobacteria (CCPs) is not yet completely understood. Apart from the most known damages to the liver and kidneys, symptoms of their neurotoxicity have also been reported. Hepatotoxic CCPs, like microcystins, as well as non-hepatotoxic anabaenopeptins and planktopeptins, all exhibit cytotoxic and cytostatic effects on mammalian cells. However, responses of different cell types to CCPs depend on their specific modes of interaction with cell membranes. This study demonstrates that non-hepatotoxic planktopeptin BL1125 and anabaenopeptins B and F, at concentrations up to 10 µM, affect normal and tumor human astrocytes (NHA and U87-GM) in vitro by their almost immediate insertion into the lipid monolayer. Like microcystin-LR (up to 1 µM), they inhibit Ser/Thr phosphatases and reorganize cytoskeletal elements, with modest effects on their gene expression. Based on the observed effects on intermediate filaments and intermediate filament linkage elements, their direct or indirect influence on tubulin cytoskeletons via post-translational modifications, we conclude that the basic mechanism of CCP toxicities is the induction of inter- and intracellular communication failure. The assessed inhibitory activity on Ser/Thr phosphatases is also crucial since the signal transduction cascades are modulated by phosphorylation/dephosphorylation processes.

Histology and transcriptomic analysis reveal the inflammation and affected pathways under 2-methylisoborneol (2-MIB) exposure on grass carp

2-Methylisoborneol (2-MIB) is a common and widely distributed off-flavor compound in water. However, the toxic mechanisms of 2-MIB on aquatic organisms remain largely unexplored. In this study, grass carp larvae were exposed to different concentrations (0, 5, and 20 μg L-1) of 2-MIB for 96 h. The accumulation of 2-MIB in the dorsal muscle was measured. Histological analysis, ultrastructure observations, and transcriptomic sequencing were conducted on the liver tissues. The results showed that 2-MIB accumulated significantly in the fish muscle, with the accumulation increasing as the exposure concentration increased through gas chromatography-mass spectrometry (GC-MS) detection. Histological and ultrastructure observations indicated that 2-MIB caused concentration-dependent inflammatory infiltration and mitochondrial damage in the liver. Transcriptomic analysis revealed lipid metabolism disorders induced by exposure to 2-MIB in grass carp. Additionally, 5 μg L-1 2-MIB affected the neurodevelopment and cardiovascular system of grass carp larvae through extracellular matrix (ECM)-receptor interaction and focal adhesion pathway. Furthermore, several pathways related to the digestive system were significantly enriched, implying that 2-MIB may impact pancreatic secretion function, protein digestion and absorption processes. These findings provide new insights into the potential toxicological mechanisms of 2-MIB.

Increased Prorenin Expression in the Kidneys May Be Involved in the Abnormal Renal Function Caused by Prolonged Environmental Exposure to Microcystin-LR

Toxic algae in eutrophic lakes produce cyanotoxic microcystins. Prior research on the effect of microcystin-LR in the kidney utilized intraperitoneal injections, which did not reflect natural exposure. Oral microcystin-LR research has focused on renal function and histopathology without examining the molecular mechanisms. The present study aimed to evaluate the mechanism of microcystin-LR in the kidneys via oral administration in WKAH/HkmSlc rats over 7 weeks, alongside stimulation of the proximal tubular cells. Although there were no differences in the concentrations of plasma albumin, blood urea nitrogen, and creatinine, which are parameters of renal function, between the control and microcystin-LR-administrated rats, prorenin expression was significantly increased in the renal cortex of the rats administered microcystin-LR and the microcystin-LR-treated proximal tubular cells. The expression levels of (pro)renin receptor (PRR), transforming growth factor-β1 (TGFβ1), and α-smooth muscle actin (α-SMA) in the renal cortex did not differ significantly between the control and microcystin-LR-administered rats. However, the expression levels of prorenin were significantly positively correlated with those of PRR, TGFβ1, and α-SMA in the renal cortex of rats administered microcystin-LR. Additionally, a significant positive correlation was observed between the expression levels of TGFβ1 and α-SMA. Collectively, increased prorenin expression caused by the long-term consumption of microcystin-LR may initiate a process that influences renal fibrosis and abnormal renal function by regulating the expression levels of PRR, TGFβ1, and α-SMA.

Magnetic recyclable visible light-driven Bi2WO6/Fe3O4/RGO for photocatalytic degradation of Microcystin-LR: Mechanism, pathway, and influencing factors

Photocatalysis was an attractive strategy that had potential to tackle the Microcystin-LR (MC-LR) contamination of aquatic ecosystems. Herein, magnetic photocatalyst Fe3O4/Bi2WO6/Reduced graphene oxide composites (Bi2WO6/Fe3O4/RGO) were employed to degrade MC-LR. The removal efficiency and kinetic constant of the optimized Bi2WO6/Fe3O4/RGO (Bi2WO6/Fe3O4-40%/RGO) was 1.8 and 2.3 times stronger than the pure Bi2WO6. The improved activity of Bi2WO6/Fe3O4-40%/RGO was corresponded to the expanded visible light adsorption ability and reduction of photogenerated carrier recombination efficiency through the integration of Bi2WO6 and Fe3O4-40%/RGO. The MC-LR removal efficiency exhibited a positive tendency to the initial density of algae cells, fulvic acid, and the concentration of MC-LR decreased. The existed anions (Cl-, CO3-2, NO3-, H2PO4-) reduced MC-LR removal efficiency of Bi2WO6/Fe3O4-40%/RGO. The Bi2WO6/Fe3O4-40%/RGO could degrade 79.3% of MC-LR at pH = 7 after 180 min reaction process. The trapping experiments and ESR tests confirmed that the h+, ∙OH, and ∙O2- played a significant role in MC-LR degradation. The LC-MS/MS result revealed the intermediates and possible degradation pathways.

Transgenerational effects of extracts containing Microcystin-LR exposure on reproductive toxicity and offspring growth inhibition in a model organism zebrafish

Cyanobacteria cell lysates release numerous toxic substances (e.g., cyanotoxins) into the water, posing a serious threat to human health and aquatic ecosystems. Microcystins (MCs) are among the most abundant cyanotoxins in the cell lysates, with microcystin-LR (MC-LR) being one of the most common and highly toxic congeners. In this study, zebrafish (Danio rerio) were exposed to different levels MC-LR that from extracts of Microcystis aeruginosa. Changes in the MC-LR accumulations, organ coefficients, and antioxidant enzyme activities in the zebrafish were analyzed. Transgenerational reproductive toxicity of MC-LR in the maternal and paternal generations was further investigated, as well as the influences of extracts containing MC-LR exposures of the F1 on the growth of zebrafish. The study found that high levels of MC-LR could be detected in the major organs of adult zebrafish, particularly in spleen. Notably, concentration of MC-LR in the spermary was significantly higher than that in the ovarium. MC-LR could induce oxidative damage by affecting the activities of catalase and superoxide dismutase. Inherited from F0, MC-LR led to impaired development in the F1 generation. Difference in offspring survival rates could be observed in the groups with different MC-LR levels of maternal and paternal exposures. This study reveals transgenerational effects of MC-LR on the reproductive toxicity and offspring growth inhibition to the aquatic organisms, which should be emphasized in the future ecological risk assessment.