Microcystin-LR aerosol induces inflammatory responses in healthy human primary airway epithelium

Joint effects of rice straw-derived biochar and microcystin-LR on splenic histopathological injuries, inflammation, and innate immune responses in male zebrafish

Microcystin-LR (MC-LR), a toxin produced by cyanobacterial blooms, poses a significant threat to aquatic animals and humans. Biochar (BC), known for its high adsorption capacity, is increasingly being utilized to remove hazardous pollutants from aquatic environment. In the present study, we conducted a full factorial experiment to investigate the potential immunotoxicity in male zebrafish (Danio rerio) exposed to environmentally relevant levels of MC-LR (0, 1, 5, 25 μg/L) and rice straw-derived BC (0, 100 μg/L) for 30 d. The findings revealed that subchronic MC-LR exposure caused concentration-dependent splenic histopathological injuries, characterized by an augmentation of melano-macrophage centers, edematous mitochondria, and vacuolation. While the presence of BC mitigated the inflammatory response and mitochondrial damage in the combined groups. Furthermore, in contrast to the group solely exposed to 25 μg/L MC-LR, decreased levels of interleukin 1β (IL1β), tumor necrosis factor α (TNFα), and interleukin 6 (IL6) as well as significant downregulation of inflammation and immune-related genes (tlr4a, myd88, p38a, tnfα) were noticed in the corresponding co-exposure group, which confirmed that BC can reduce MC-LR-induced inflammatory response. Concurrently, a significant increase in complement C3 (C3) content, along with higher splenic c3b expression levels, was observed in the MC-LR-co-BC group in relative to the group exposed solely to MC-LR, suggesting that BC alleviated MC-LR-induced innate immune inhibition. Our results also demonstrated that BC can decrease MC-LR contents in both water and spleen, thereby alleviating MC-LR-induced inflammation and innate immune inhibition via the MyD88-dependent toll-like receptor (TLR/MyD88) signaling pathway in male zebrafish. Our results underscore the potential of BC to mitigate the deleterious impacts of MC-LR on aquatic organisms in blooms-contaminated water.

Influence of bloom stage on the effectiveness of algicidal bacteria in controlling harmful cyanobacteria: A microcosm study

Cyanobacterial harmful algae blooms (cyanoHABs) pose significant ecological and public health concerns in freshwater ecosystems worldwide. Understanding the dynamics of phytoplankton communities and the efficacy of mitigation strategies is crucial for managing bloom events. This study investigates the impact of bioaugmentation with algicidal bacteria on Microcystis-dominated blooms through laboratory microcosm experiments. Field-collected samples from MID- and POST-summer bloom stages were treated with Morganella morganii, Exiguobacterium acetylicum, and a bacterial consortium including Bacillus pumilus. Phytoplankton composition, microcystin concentrations and genes related to microbial community dynamics (16S, mcyA, nosZ and amoA) were assessed by microscopy, HPLC and qPCR, respectively. Results showed that M. morganii significantly altered the phytoplankton community structure and promoted diatom proliferation in MID-summer microcosms, though treatments were less effective in POST-summer microcosms representing more mature bloom periods. Additionally, algicidal bacteria influenced microcystin levels, with M. morganii and E. acetylicum reducing toxigenic Microcystis genotypes, as indicated by lower mcyA gene copy numbers. Molecular analyses also revealed that algicidal bacterial treatments contributed to shifts in microbial functional genes, including increased denitrification activity linked to nosZ gene abundance. These findings highlight the intricate interplay between algicidal bacteria and microbial communities, where algicidal activity extends beyond direct cyanobacteria suppression to broader ecosystem-level effects. By rebalancing phytoplankton communities toward eukaryotic dominance and reducing toxigenic cyanobacterial genotypes during intense bloom episodes, bioaugmentation with algicidal bacteria emerges as a promising strategy for bloom management and ecosystem restoration.

Impact of long-term cyanotoxin exposure on cattle: Biochemical, histological, and oxidative stress assessment

Background and Aim

Cyanobacterial blooms, driven by anthropogenic and climatic changes, pose significant ecological and health threats. This study investigates the long-term effects of microcystins (MCs), potent cyanotoxins, on cattle at Lake des Oiseaux, a Ramsar-listed wetland in Algeria. Aligning with the "One Health" framework, the research evaluates the biochemical, histological, and oxidative stress impacts of MCs on livestock as environmental sentinels.

Materials and Methods

A herd of 40 cattle (20 exposed and 20 non-exposed) was studied during the summer bloom period of 2019. Blood and liver samples were analyzed to assess biochemical markers (ALT, AST, ALP, GGT, etc.), histopathological changes, and oxidative stress parameters (GPx, CAT, SOD, LPO and GSH).

Results

Exposed cattle exhibited significant elevations in liver enzymes and oxidative stress markers, indicating hepatic inflammation and redox imbalance. Histological analysis revealed macrovacuolar steatosis, fibrosis, and bile duct dilatation. Antioxidant enzyme activities (GPx, CAT and SOD) were reduced, with notable depletion of GSH levels and increased lipid peroxidation. These findings reflect the cumulative cytotoxic effects of MC exposure. Non-exposed cattle showed no such changes.

Conclusion

Long-term MC exposure disrupts liver function and induces oxidative stress in cattle, implicating significant risks for both animal and human health. The bioaccumulation of cyanotoxins in livestock emphasizes the urgent need for preventive measures, including water monitoring, restricted livestock access to contaminated sites, and farmer education. These strategies are vital to mitigate risks under the "One Health" approach, ensuring sustainable livestock and public health.

The Addition of Transcriptomics to the Bead-Enabled Accelerated Monophasic Multi-Omics Method: A Step toward Universal Sample Preparation

Omics-based measurements enable the study of biomolecules in a high-throughput fashion, leading to the characterization and quantification of biological systems. Multi-omics methods aim to incorporate several omics measurements for a more holistic approach, which is crucial for advancing our understanding of the diversity and redundancy of biological systems. Current multi-omics sample preparation methods have achieved proteomics, lipidomics, and metabolomics from individual samples; however, the bioinformatic tools currently available for interpreting data generated from these omics are limited. Alternately, transcriptomics has a wide arsenal of available bioinformatic tools offering intensive sample characterization but has yet to be incorporated into a unified, multi-omics sample preparation technique. Herein we describe the modified bead-enabled accelerated monophasic multi-omics (mBAMM) method, which incorporates RNA extraction for transcriptomics analysis. mBAMM was shown to enable RNA-seq without compromising the isolation of biomolecules for proteomics, lipidomics, and metabolomics. This methodology greatly improves sample characterization and represents a major innovation toward cohesive insights into biological systems.

Toxicity assessment of microcystin-leucine arginine in planarian Dugesia japonica

Microcystin-leucine arginine (MC-LR), a representative cyanobacterial toxin, poses an increasing and serious threat to aquatic ecosystems. Despite investigating its toxic effects in various organisms and cells, the toxicity to tissue regeneration and stem cells in vivo still needs to be explored. Planarians are ideal regeneration and toxicology research models and have profound implications in ecotoxicology evaluation. This study conducted a systemic toxicity evaluation of MC-LR, including morphological changes, growth, regeneration, and the underlying cellular and molecular changes after MC-LR exposure, which were investigated in planarians. The results showed that exposure to MC-LR led to time- and dose-dependent lethal morphological changes, tissue damage, degrowth, and delayed regeneration in planarians. Furthermore, MC-LR exposure disturbed the activities of antioxidants, including total superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, and total antioxidant capacity, leading to oxidative stress and DNA damage, and then reduced the number of dividing neoblasts and promoted apoptosis. The results demonstrated that oxidative stress and DNA damage induced by MC-LR exposure caused apoptosis. Excessive apoptosis and suppressed neoblast activity led to severe homeostasis imbalance. This study explores the underlying mechanism of MC-LR toxicity in planarians and provides a basis for the toxicity assessment of MC-LR to aquatic organisms and ecological risk evaluation.

Aerosolized Harmful Algal Bloom Toxin Microcystin-LR Induces Type 1/Type 17 Inflammation of Murine Airways

Harmful algal blooms are increasing globally and pose serious health concerns releasing cyanotoxins. Microcystin-LR (MC-LR), one of the most frequently produced cyanotoxins, has recently been detected in aerosols generated by the normal motions of affected bodies of water. MC-LR aerosol exposure has been linked to a pro-inflammatory influence on the airways of mice; however, little is understood about the underlying mechanism or the potential consequences. This study aimed to investigate the pro-inflammatory effects of aerosolized MC-LR on murine airways. C57BL/6 and BALB/c mice were exposed to MC-LR aerosols, as these strains are predisposed to type 1/type 17 and type 2 immune responses, respectively. Exposure to MC-LR induced granulocytic inflammation in C57BL/6 but not BALB/c mice, as observed by increased expression of cytokines MIP-1α, CXCL1, CCL2, and GM-CSF compared with their respective vehicle controls. Furthermore, the upregulation of interleukins IL-17A and IL-12 is consistent with Th1- and Th17-driven type 1/type 17 inflammation. Histological analysis confirmed inflammation in the C57BL/6 lungs, with elevated neutrophils and macrophages in the bronchoalveolar lavage fluid and increased pro-inflammatory and pro-resolving oxidized lipids. In contrast, BALB/c mice showed no significant airway inflammation. These results highlight the ability of aerosolized MC-LR to trigger harmful airway inflammation, requiring further research, particularly into populations with predispositions to type 1/type 17 inflammation.

Aerosolized algal bloom toxins are not inert

Harmful algal blooms (HABs) are projected to become increasingly prevalent, extending over longer periods and wider geographic regions due to the warming surface ocean water and other environmental factors, including but not limited to nutrient concentrations and runoff for marine and freshwater environments. Incidents of respiratory distress linked to the inhalation of marine aerosols containing HAB toxins have been documented, though the risk is typically associated with the original toxins. However, aerosolized toxins in micrometer and submicrometer particles are vulnerable to atmospheric processing. This processing can potentially degrade HAB toxins and produce byproducts with varying potencies compared to the parent toxins. The inhalation of aerosolized HAB toxins, especially in conjunction with co-morbid factors such as exposure to air pollutants from increased commercial activities in ports, may represent a significant exposure pathway for a considerable portion of the global population. Understanding the chemistry behind the transformation of these toxins can enhance public protection by improving the existing HAB alert systems.

Microcystin-LR improves anti-tumor efficacy of oxaliplatin through induction of M1 macrophage polarization

Tumor-associated macrophages within the tumor microenvironment play an immunosuppressive role by promoting tumor growth and immune evasion. Macrophages are highly plastic and can be stimulated to adopt an anti-tumor M1 phenotype. In this study, we used microcystin-LR (MC-LR), a cyclic heptapeptide produced by cyanobacteria, to induce in vitro macrophage innate immunity and transition into the anti-tumor M1 phenotype. MC-LR was also tested in vivo in a mouse model of colorectal cancer. An intraperitoneal injection of MC-LR increased the proportion of CD86⁺ M1 macrophages and triggered the maturation of CD11c⁺ dendritic cells within tumor tissues. MC-LR combined with the chemotherapeutic drug oxaliplatin significantly inhibited tumor growth in vivo. Flow cytometry analysis revealed increased infiltration of activated cytotoxic (CD8⁺, PD-1⁺) T-cells and anti-tumor cytokines (IFNγ and Granzyme B) in the tumor tissues of the combination therapy group, suggesting that this may be the primary mechanism behind the anti-tumor effect of the combination treatment. These findings indicate that MC-LR regulates the immune stimulation of macrophage polarization and dendritic cell maturation, effectively reversing tumor immunosuppression, activating an anti-tumor immune response, and enhancing tumor therapy.

Aerosolized Cyanobacterial Harmful Algal Bloom Toxins: Microcystin Congeners Quantified in the Atmosphere

Cyanobacterial harmful algal blooms (cHABs) have the potential to adversely affect public health through the production of toxins such as microcystins, which consist of numerous molecularly distinct congeners. Microcystins have been observed in the atmosphere after emission from freshwater lakes, but little is known about the health effects of inhaling microcystins and the factors contributing to microcystin aerosolization. This study quantified total microcystin concentrations in water and aerosol samples collected around Grand Lake St. Marys (GLSM), Ohio. Microcystin concentrations in water samples collected on the same day ranged from 13 to 23 μg/L, dominated by the d-Asp3-MC-RR congener. In particulate matter <2.5 μm (PM2.5), microcystin concentrations up to 156 pg/m3 were detected; the microcystins were composed primarily of d-Asp3-MC-RR, with additional congeners (d-Asp3-MC-HtyR and d-Asp3-MC-LR) observed in a sample collected prior to a storm event. The PM size fraction containing the highest aerosolized MC concentration ranged from 0.44 to 2.5 μm. Analysis of total bacteria by qPCR targeting 16S rDNA revealed concentrations up to 9.4 × 104 gc/m3 in aerosol samples (≤3 μm), while a marker specific to cyanobacteria was not detected in any aerosol samples. Concentrations of aerosolized microcystins varied even when concentrations in water were relatively constant, demonstrating the importance of meteorological conditions (wind speed and direction) and aerosol generation mechanism(s) (wave breaking, spillway, and aeration systems) when evaluating inhalation exposure to microcystins and subsequent impacts on human health.

A Case Series of Potential Pediatric Cyanotoxin Exposures Associated with Harmful Algal Blooms in Northwest Ohio

Cyanobacterial harmful algal blooms (CyanoHABs) are increasing in prevalence and severity in the Great Lakes region, as well as both globally and locally. CyanoHABs have the potential to cause adverse effects on human health due to the production of cyanotoxins from cyanobacteria. Common routes of exposure include recreational exposure (swimming, skiing, and boating), ingestion, and aerosolization of contaminated water sources. Cyanotoxins have been shown to adversely affect several major organ systems contributing to hepatotoxicity, gastrointestinal distress, and pulmonary inflammation. We present three pediatric case reports that coincided with CyanoHABs exposure with a focus on presentation of illness, diagnostic work-up, and treatment of CyanoHAB-related illnesses. Potential cyanotoxin exposure occurred while swimming in the Maumee River and Maumee Bay of Lake Erie in Ohio during the summer months with confirmed CyanoHAB activity. Primary symptoms included generalized macular rash, fever, vomiting, diarrhea, and severe respiratory distress. Significant labs included leukocytosis and elevated C-reactive protein. All patients ultimately recovered with supportive care. Symptoms following potential cyanotoxin exposure coincide with multiple disease states representing an urgent need to develop specific diagnostic tests of exposure.

Feedback of lake trophic status via MC-LR fluorescence technique

Eutrophication remains one of the most challenging environmental problems, and microcystin-leucine-arginine (MC-LR) produced in eutrophic waters would cause serious ecological risks. However, the traditional assessment methods of trophic status, such as water quality index (WQI) and trophic status index (TSI), could not directly reflect the existence or concentration of MC-LR in water. Moreover, traditional MC-LR detection methods are costly and time-consuming. Therefore, it remains a challenge to develop a method that can simply and quickly reflect the level of MC-LR. Herein, a novel probe with specific response to MC-LR was proposed to assess the distribution characteristics of MC-LR in water bodies. By combining the response signal of the probe with the filtered water sample and the water quality parameters, a more accurate assessment tool for MC-LR was obtained. This probe can specifically respond to MC-LR in aqueous solution, and its fluorescence signal is enhanced with the increase of MC-LR concentration. More importantly, the fluorescent signal of the probe showed a significant positive correlation with MC-LR concentration in water samples. This visualization tool has practical application potential for the preliminary assessment of MC-LR in eutrophic waters.

Symptom frequency and exposure to a cyanobacteria bloom in Florida

This investigation was undertaken to characterize health effects associated with a major bloom of blue-green algae due to the proliferation Microcystis aeruginosa that occurred in Florida in 2018. Cyanobacteria produce multiple toxins, including the potent hepatotoxic microcystins (MCs), that have been reported to cause illness in exposed persons worldwide. Widespread exposure to toxins released by blue-green algae during the 2018 bloom was shown by the presence of MCs in the nasal passages of 95 percent of the individuals studied previously in south Florida (Schaefer et al., 2020). The current analyses were conducted to determine whether self-reported symptoms were associated with activity patterns, direct contact with water, residential, recreational, and occupational exposure. The 125 persons who participated in the initial study reported an average of 4.94 (± 4.87) symptoms. Those reported most commonly included rhinorrhea, sneezing, headache, sore throat and dry cough. Respiratory symptoms were reported by 74%, ocular symptoms by 62%, and gastrointestinal symptoms by 35% of respondents. Residential and recreational exposures were associated with increased risks of respiratory, gastrointestinal, or ocular symptoms in univariate and adjusted multivariable analyses. Residential exposure was significantly associated with increased reporting of dry cough (p = 0.03), dyspnea (p < 0.01) and wheezy respirations (p = 0.04). Among persons reporting gastrointestinal symptoms, nausea (p = 0.02) and abdominal pain (p < 0.01) were significantly associated with residential exposure. Recreational exposure was significantly associated with sore throat and eye irritation. The findings add to the evidence that exposure to cyanobacteria at concentrations encountered during an algal bloom is associated with a diverse array of symptoms and that inhalation of aerosols constitutes an important exposure pathway.

Harmful algal bloom aerosols and human health

Harmful algal blooms (HABs) are increasing across many locations globally. Toxins from HABs can be incorporated into aerosols and transported inland, where subsequent exposure and inhalation can induce adverse health effects. However, the relationship between HAB aerosols and health outcomes remains unclear despite the potential for population-level exposures. In this review, we synthesized the current state of knowledge and identified evidence gaps in the relationship between HAB aerosols and human health. Aerosols from Karenia brevis, Ostreopsis sp., and cyanobacteria were linked with respiratory outcomes. However, most works did not directly measure aerosol or toxin concentrations and instead relied on proxy metrics of exposure, such as cell concentrations in nearby waterbodies. Furthermore, the number of studies with epidemiological designs was limited. Significant uncertainties remain regarding the health effects of other HAB species; threshold dose and the dose-response relationship; effects of concurrent exposures to mixtures of toxins and other aerosol sources, such as microplastics and metals; the impact of long-term exposures; and disparities in exposures and associated health effects across potentially vulnerable subpopulations. Additional studies employing multifaceted exposure assessment methods and leveraging large health databases could address such gaps and improve our understanding of the public health burden of HABs.

Health risk assessment of lake water contaminated with microcystins for fruit crop irrigation and farm animal drinking

The health risks linked to the consumption of microcystin-accumulating crops have been increasing worldwide in toxic cyanobloom-occurring regions. The bioaccumulation of microcystins (MCs) in agricultural produce at environmentally realistic concentrations is poorly investigated. In this field study, we assessed the health risks of MCs in raw water used for irrigating fruit crops (bioaccumulation) and watering farm animals in the Lalla Takerkoust agricultural region (Marrakesh, Morocco). Thus, MCs were extracted from water and fruit samples and quantified by enzyme-linked immunosorbent assay in order to calculate the health risk indicators. MCs posed a high health-risk level to poultry and horses, with estimated daily intakes (EDI) being 14- and 19-fold higher than the recommended limits (3.1 and 2.3 μg MC-LR L-1), respectively. Furthermore, pomegranate posed the same level of risk, with EDI being 22- and 53-fold higher than the limit dose (0.04 μg MC-LR kg-1) for adults and children, respectively. There was an urgent need for guidelines regarding water use and management in MC-polluted areas, besides the setup of nature-based tools for toxin removal from raw water used in farming practices. Moreover, MCs could contaminate the human food chain, which implies further investigations of their potential accumulation in livestock- and poultry-based food.

Freshwater Cyanobacterial Toxins, Cyanopeptides and Neurodegenerative Diseases

Cyanobacteria produce a wide range of structurally diverse cyanotoxins and bioactive cyanopeptides in freshwater, marine, and terrestrial ecosystems. The health significance of these metabolites, which include genotoxic- and neurotoxic agents, is confirmed by continued associations between the occurrence of animal and human acute toxic events and, in the long term, by associations between cyanobacteria and neurodegenerative diseases. Major mechanisms related to the neurotoxicity of cyanobacteria compounds include (1) blocking of key proteins and channels; (2) inhibition of essential enzymes in mammalian cells such as protein phosphatases and phosphoprotein phosphatases as well as new molecular targets such as toll-like receptors 4 and 8. One of the widely discussed implicated mechanisms includes a misincorporation of cyanobacterial non-proteogenic amino acids. Recent research provides evidence that non-proteinogenic amino acid BMAA produced by cyanobacteria have multiple effects on translation process and bypasses the proof-reading ability of the aminoacyl-tRNA-synthetase. Aberrant proteins generated by non-canonical translation may be a factor in neuronal death and neurodegeneration. We hypothesize that the production of cyanopeptides and non-canonical amino acids is a more general mechanism, leading to mistranslation, affecting protein homeostasis, and targeting mitochondria in eukaryotic cells. It can be evolutionarily ancient and initially developed to control phytoplankton communities during algal blooms. Outcompeting gut symbiotic microorganisms may lead to dysbiosis, increased gut permeability, a shift in blood-brain-barrier functionality, and eventually, mitochondrial dysfunction in high-energy demanding neurons. A better understanding of the interaction between cyanopeptides metabolism and the nervous system will be crucial to target or to prevent neurodegenerative diseases.

Biodegradation of MC-LR and its key bioactive moiety Adda by Sphingopyxis sp. YF1: Comprehensive elucidation of the mechanisms and pathways

Microcystins (MCs) are harmful to the ecology and public health. Some bacteria can degrade MCs into Adda, but few can destroy Adda. Adda is the key bioactive moiety of MCs and mainly contributes to hepatotoxicity. We had previously isolated an indigenous novel bacterial strain named Sphingopyxis sp. YF1 that can efficiently degrade MCs and its key bioactive moiety Adda, but the mechanisms remained unknown. Here, the biodegradation mechanisms and pathways of Adda were systematically investigated using multi-omics analysis, mass spectrometry and heterologous expression. The transcriptomic and metabolomic profiles of strain YF1 during Adda degradation were revealed for the first time. Multi-omics analyses suggested that the fatty acid degradation pathway was enriched. Specifically, the expression of genes encoding aminotransferase, beta oxidation (β-oxidation) enzymes and phenylacetic acid (PAA) degradation enzymes were significantly up-regulated during Adda degradation. These enzymes were further proven to play important roles in the biodegradation of Adda. Simultaneously, some novel potential degradation products of Adda were identified successfully, including 7‑methoxy-4,6-dimethyl-8-phenyloca-2,4-dienoic acid (C₁₇H₂₂O₃), 2-methyl-3‑methoxy-4-phenylbutyric acid (C₁₂H₁₆O₃) and phenylacetic acid (PAA, C₈H₈O₂). In summary, the Adda was converted into PAA through aminotransferase and β-oxidation enzymes, then the PAA was further degraded by PAA degradation enzymes, and finally to CO₂ via the tricarboxylic acid cycle. This study comprehensively elucidated the novel MC-LR biodegradation mechanisms, especially the new enzymatic pathway of Adda degradation. These findings provide a new perspective on the applications of microbes in the MCs polluted environment.