Changes in microcystin concentration in Lake Taihu, 13 years (2007-2020) after the 2007 drinking water crisis

Bloom-forming planktonic Microcystis and benthic Oscillatoria-induced oxidative stress and inflammatory responses in juvenile silver carp and bighead carp

As global warming and water eutrophication, the multiple proliferation of harmful cyanobacteria can form algal blooms and cause serious ecological problems. In recent years, the large-scale and persistent cyanobacterial blooms occur frequently worldwide and have attracted widespread attention due to the harmful impacts. Among these harmful bloom-forming cyanobacteria, the ecological and toxicological impacts of planktonic cyanobacteria have been extensively studied. However, research on the ecological risks and adverse effects of harmful benthic cyanobacteria is lagging. Filter-feeding fish could suffer from more toxic stimuli than other fish due to their special feeding habits. To investigate and compare the complex toxic effects of different kinds of harmful cyanobacteria on fish, three different-sized (i.e. small, medium, and large) juvenile silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) were exposed to cyanobacterial blooms-related density (1 × 106 cells/mL) of Microcystis aeruginosa (i.e. generating microcystins) and Oscillatoria sp. (i.e. generating cylindrospermopsin) for 3 d, after which biomarkers of oxidative stress and inflammation in the liver of fish were detected. The silver carp and bighead carp can effectively ingest Microcystis cells but cannot effectively ingest Oscillatoria cells through the measurement of the levels of cyanotoxins. Both Microcystis and Oscillatoria cells can induce different levels of oxidative stress and inflammatory responses in the liver of these juvenile filter-feeding fish via altering the biochemical parameters of the antioxidant system (e.g. superoxide dismutase activity) and immune system (e.g. interleukin-1β level). Therefore, our research identified potential data gaps that how the different types of cyanobacteria induce toxic effects in the liver of juvenile filter-feeding fish in a short time. This study contributes to a better understanding of the short-term adverse effects of different cyanobacterial species on juvenile fish, suggesting that the benthic toxic cyanobacteria-induced ecological and health risks require further attention.

Enhanced activity of enzymes encapsulated in spheres metal azolate framework-7 with defects

Developing metal-organic frameworks (MOFs) with specific structures is critical for improving the activity of embedded enzymes, and defects may be one of the effective methods. Several methods have been demonstrated to be effective in creating defects in MOFs, including post-synthetic treatments, the use of acid as a modulator, and the use of ordinary or thermally sensitive linkers. However, these methods necessitate the utilization of additional substances. Metal azolate framework-7 (MAF-7) is a kind of MOF that was formed by the coordination of Zn2+ with 3-methyl-1,2,4-triazole (Hmtz). This paper presents a method for the preparation of defect MAF-7 by changing the sequence of reactants without the introduction of additional substances. The defects were characterized by a range of techniques, including scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and powder X-ray diffraction. The activity of microcystinase A (MlrA) encapsulated in defective MAF-7 (CMlrA@DMAF-7) was found to be significantly increased in comparison to non-porous MAF-7 (NMAF-7), and was largely unaffected by alterations in synthesis conditions. It is also noteworthy that lysozyme (LZ) and horseradish peroxidase (HRP), which are commonly used in industry, also demonstrated enhanced activity when encapsulated in DMAF-7. It was therefore anticipated that modifying the sequence of reactant addition would be a straightforward and simple method of introducing defects into MAF-7, thereby improving enzyme utilization.

Using dredged sediments from Lake Taihu as a plant-growing substrate: Focusing on the impact of microcystins

Using dredged sediment as plant growth substrates is a promising way to deal with large amounts of excavated sediments. However, it is a big challenge to deal with various pollutants in sediments, among which microcystins (MCs) gained limited attention. In this study, sediments collected from Lake Taihu were mixed with agricultural soil at a 1:1 ratio to create various growing substrates for lettuce (Lactuca sativa L. var. ramosa Hort.). Results indicated that fresh weight and leaf area of lettuce increased in some sediment-amended treatments due to additional nutrients, but food quality was negatively affected by sediment amendment as suggested by the soluble sugar and Vitamin C levels. MCs were detected in all lettuce grown in sediment-amended substrates, particularly in treatments with sediments collected during the bloom. The highest MC contents were found in treatment amended with sediments collected from Meiliang Bay in August (88.6 μg kg-1 for MC-LR and 65.6 μg kg-1 for MC-RR). MC accumulation in lettuce and the associated human health risks were significant, especially in treatments with sediments from the bloom period. Ecological risk assessments revealed high RQ values, indicating potential harm to the soil ecosystem. This study underscores the importance of considering MC content in sediments when evaluating their use as growing substrates. The findings contribute to understanding the environmental and health implications of sediment reuse, offering insights for safer agricultural practices and sediment management.

Harmful planktonic Microcystis and benthic Oscillatoria-induced toxicological effects on the Asian clam (Corbicula fluminea): A survey on histopathology, behavior, oxidative stress, apoptosis and inflammation

Cyanobacterial blooms are worldwide distributed and threaten aquatic ecosystems and public health. The current studies mainly focus on the adverse impacts of planktonic cyanobacteria or pure cyanotoxins, while the benthic cyanobacteria-induced ecotoxic effects are relatively lacking. The cyanobacterial cell-induced toxic effects on aquatic organisms might be more serious and complex than the pure cyanotoxins and crude extracts of cyanobacteria. This study explored the chronic effects of toxin-producing planktonic Microcystis aeruginosa (producing microcystin) and benthic Oscillatoria sp. (producing cylindrospermopsin) on the behaviors, tissue structures, oxidative stress, apoptosis, and inflammation of the Asian clams (Corbicula fluminea) under 28-d exposure. The data showed that both M. aeruginosa and Oscillatoria sp. can decrease the behaviors associated with the feeding activity and induce tissue damage (i.e. gill and digestive gland) in clams. Furthermore, two kinds of cyanobacteria can alter the antioxidant enzyme activities and increase antioxidant, lipid oxidation product, and neurotransmitter degrading enzyme levels in clams. Moreover, two kinds of cyanobacteria can activate apoptosis-related enzyme activities and enhance the proinflammatory cytokine levels of clams. In addition, two kinds of cyanobacteria can disturb the transcript levels of genes linked with oxidative stress, apoptosis, and inflammation. These results suggested harmful cyanobacteria can threaten the survival and health of clams, while the benthic cyanobacteria-induced adverse effects deserve more attention. Our finding also indicated that it is necessary to focus on the entire algal cell-induced ecotoxicity when concerning the ecological impacts of cyanobacterial blooms.

Microcystin-RR promote lipid accumulation through CD36 mediated signal pathway and fatty acid uptake in HepG2 cells

Microcystins (MC)-RR is a significant analogue of MC-LR, which has been identified as a hepatotoxin capable of influencing lipid metabolism and promoting the progression of liver-related metabolic diseases. However, the toxicity and biological function of MC-RR are still not well understood. In this study, the toxic effects and its role in lipid metabolism of MC-RR were investigated in hepatoblastoma cells (HepG2cells). The results demonstrated that MC-RR dose-dependently reduced cell viability and induced apoptosis. Additionally, even at low concentrations, MC-RR promoted lipid accumulation through up-regulating levels of triglyceride, total cholesterol, phosphatidylcholines and phosphatidylethaolamine in HepG2 cells, with no impact on cell viability. Proteomics and transcriptomics analysis further revealed significant alterations in the protein and gene expression profiles in HepG2 cells treated with MC-RR. Bioinformatic analysis, along with subsequent validation, indicated the upregulation of CD36 and activation of the AMPK and PI3K/AKT/mTOR in response to MC-RR exposure. Finally, knockdown of CD36 markedly ameliorated MC-RR-induced lipid accumulation in HepG2 cells. These findings collectively suggest that MC-RR promotes lipid accumulation in HepG2 cells through CD36-mediated signal pathway and fatty acid uptake. Our findings provide new insights into the hepatotoxic mechanism of MC-RR.

Biological and Chemical Approaches for Controlling Harmful Microcystis Blooms

The proliferation of harmful cyanobacterial blooms dominated by Microcystis aeruginosa has become an increasingly serious problem in freshwater ecosystems due to climate change and eutrophication. Microcystis-blooms in freshwater generate compounds with unpleasant odors, reduce the levels of dissolved O2, and excrete microcystins into aquatic ecosystems, potentially harming various organisms, including humans. Various chemical and biological approaches have thus been developed to mitigate the impact of the blooms, though issues such as secondary pollution and high economic costs have not been adequately addressed. Red clays and H2O2 are conventional treatment methods that have been employed worldwide for the mitigation of the blooms, while novel approaches, such as the use of plant or microbial metabolites and antagonistic bacteria, have also recently been proposed. Many of these methods rely on the generation of reactive oxygen species, the inhibition of photosynthesis, and/or the disruption of cellular membranes as their mechanisms of action, which may also negatively impact other freshwater microbiota. Nevertheless, the underlying molecular mechanisms of anticyanobacterial chemicals and antagonistic bacteria remain unclear. This review thus discusses both conventional and innovative approaches for the management of M. aeruginosa in freshwater bodies.