Research progress in the functionalization of microcystin-LR based on interdisciplinary technologies

The biological functions of microcystins

Microcystins are potent hepatotoxins predominantly produced by bloom-forming freshwater cyanobacteria (e.g., Microcystis, Planktothrix, Dolichospermum). Microcystin biosynthesis involves large multienzyme complexes and tailoring enzymes encoded by the mcy gene cluster. Mutation, recombination, and deletion events have shaped the mcy gene cluster in the course of evolution, resulting in a large diversity of microcystin congeners and the natural coexistence of toxic and non-toxic strains. The biological functions of microcystins and their association with algal bloom formation have been extensively investigated over the past decades. This review synthesizes recent advances in decoding the biological role of microcystins in carbon/nitrogen metabolism, antioxidation, colony formation, and cell-to-cell communication. Microcystins appear to adopt multifunctional roles in cyanobacteria that reflect the adaptive plasticity of toxic cyanobacteria to changing environments.

Mechanisms of harmful effects of Microcystis aeruginosa on a brackish water organism Moina mongolica based on physiological and transcriptomic responses

To investigate the detrimental impacts of cyanobacterial bloom, specifically Microcystis aeruginosa, on brackish water ecosystems, the study used Moina mongolica, a cladoceran species, as the test organism. In a chronic toxicology experiment, the survival and reproductive rates of M. mongolica were assessed under M. aeruginosa stress. It was observed that the survival rate of M. mongolica fed with M. aeruginosa significantly decreased with time and their reproduction rate dropped to zero, while the control group remained maintained stable and normal reproduction. To further explore the underlying molecular mechanisms of the effects of M. aeruginosa on M. mongolica, we conducted a transcriptomic analysis on newly hatched M. mongolica cultured under different food conditions for 24 h. The results revealed significant expression differences in 572 genes, with 233 genes significantly up-regulated and 339 genes significantly down-regulated. Functional analysis of these differentially expressed genes identified six categories of physiological functional changes, including nutrition and metabolism, oxidative phosphorylation, neuroimmunology, cuticle and molting, reproduction, and programmed cell death. Based on these findings, we outlined the basic mechanisms of microcystin toxicity. The discovery provides critical insights into the mechanisms of Microcystis toxicity on organisms and explores the response mechanisms of cladocerans under the stress of Microcystis.

Mediation of association between semen microcystin exposure and semen quality by sex hormones in Chinese men

Numerous studies have shown microcystins (MCs) inducing male reproductive toxicity, but the underlying mechanisms in humans are unclear. Therefore, this study aimed to evaluate the mediating role of serum sex hormones in the association between MC exposure and semen quality. In this study, we measured the levels of semen MCs and serum sex hormones in Chinese men [sample 1 (n = 649); sample 2 (n = 924)]. The results showed that there was a non-significant dose-dependent relationship between semen MCs and semen volume reduction (p for trend = 0.079) in sample 1, and semen MCs were significantly negatively associated with total motility, progressive motility, curvilinear velocity, mean angular displacement and acrosome integrity (p < 0.05) in sample 2. We also found that semen MCs were significantly positively associated with serum follicle stimulating hormone (FSH) (β = 0.151; 95% CI: 0.065, 0.236), but negatively associated with serum inhibin B (INHB) (β = -0.605; 95% CI: -0.944, -0.265), and these linear associations were confirmed in restricted cubic spline (RCS) models (all pnon-linearity > 0.1). Furthermore, mediation analysis revealed that serum INHB mediated 19.86% of the adverse effect of MC exposure on acrosome integrity. In conclusion, this study reveals the mediating roles of serum sex hormones in the relationship between MC exposure and decreased semen quality in men.

Introducing fluorescent probe technology for detecting microcystin-LR in the water and cells

BACKGROUND

For a long time, the environment hazards caused by cyanobacteria bloom and associated microcystins have attracted attention worldwide. Microcystin-LR (MC-LR) is the most widely distributed and most toxic toxin. At present, numerous MC-LR detection methods exist many drawbacks. Therefore, a quick and accurate method for identifying and detecting MC-LR is crucial and necessary. In this work, we strived to introduce a novel fluorescence assay to detect MC-LR in the water and cells.

RESULTS

According to the special spatial configuration and physicochemical properties of MC-LR, we designed and constructed six fluorescent probes. The design concepts of the probes were exhaustively elaborated. MC-YdTPA, MC-YdTPE, MC-RdTPA, and MC-RdTPE could show significant fluorescence enhancement in MC-LR solution. Significantly, MC-YdTPA, MC-YdTPE, and MC-RdTPA could also response well in the cells treated with MC-LR, demonstrating these fluorescent probes' values. The recognition mechanism between probes and MC-LR were also deeply explored: (1) The polyphenylene ring structure of probes may have nested or hydrogen bond weak interaction with the ring structure of MC-LR. (2) The probes can generate a reaction to the hydrogen ions ionized by MC-LR.

SIGNIFICANCE

We proposed the novel ideas for designing MC-LR probes. This research can provide valuable experiences and important assistance in synthesizing MC-LR fluorescent probes. We expect that this work may bring new ideas to develop fluorescent probes for researching MC-LR in vivo and in vitro.

Immunotoxicity of cynobacterial toxin Microcystin-LR is mitigated by Quercitin and himalaya tonic Liv52

Microcystin-LR (MC-LR) has received worldwide concern for its hepatotoxicity with maximum acceptable daily intake of 0.0015 mg/L (1.5 μg/L) [Federal-Provinicial-Territorial-Committee-on-drinking-water-2002]. Comprehensive immunotoxicity data is still deficient with MC-LR. To curb the menace of MC-LR, Quercitin (QE), himalaya made hepatotonic Liv52 were studied. To investigate the immunotoxic properties of MC-LR, QE and Liv52, primary splenocyte cells prepared, cultured, and immunoproliferation assay with mitogens lipopolysaccharide (LPS) or concanavalin A, (Con A) was done for, immunophenotyping, cell cycle and apoptotic studies. In current study, we have divided the splenocytes into 4 groups, i.e., Group I: Normal saline, Group II: MC-LR (0.1 μM), Group III: MC-LR (0.1 μM) + QE (20 μM), and Group IV: MC-LR (0.1 μM) + Liv52 (25 μg/ml) and treated with maximum < CC50 concentration. MC-LR enhanced proliferation of Con A and LPS stirred splenocytes at 24 h, whereas QE and Liv52 both act as antimitogenic. With combined mixture of MC-LR + QE, a significant increase in proliferation compared to mitogen or MC-LR was observed. MC-LR down-regulated expression of CD19+, CD3e+, CD4+, CD8+, (1.05%), (18.9%), (8.9%), and (7.8%) respectively in comparison to Group I. Down-regulation of 10% and 28% is observed in CD19+ and CD4+ populations with MC-LR and QE. The Liv52 addition concealed MC-LR adverse properties in most effective way. MC-LR induced G1-phase significant declined cell cycle arrest at S phase (9.26%) and G2/M phase (26.31%) was observed. QE and Liv52 mask the activity of MC-LR. Further apoptotic study revealed that MC-LR treatment decreases late apoptotic cells compared to control with no significant change in live and early apoptotic cells. Although QE increased live cells and Liv52 significantly increased late apoptotic cells, these results suggest that a Collapse

Key Words

• Cynobacterial toxin
• FACS analysis
• Immunomodulation
• Immunophenotyping
• MC-LR

Collapse

MESH Headings

• Lipopolysaccharides
• Microcystins/toxicity
• Cell Cycle

Collapse

Grants Collapse

Affiliation(s)

Kriti Shrinet School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, 221005, India; School of Biotechnology, IFTM University, Moradabad, Uttar Pradesh, 244102, India
Arvind Kumar School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, 221005, India.

Collapse

Visualization Tools for Detecting Microcystin-LR in the Biological System via Near-Infrared Fluorescent Probes

Numerous toxicological and epidemiological studies have shown that microcystin-LR (MC-LR) could cause a variety of toxicity to humans and animals. However, the absence of effective methods to trace MC-LR in biological systems has hindered the in-depth understanding of the mechanism of MC-LR toxicity. Near-infrared (NIR) fluorescent probes are crucial tools for accurate visualization and in-depth study of specific molecules in biological systems. Due to the lack of effective design strategies, NIR fluorescent probes for imaging MC-LR specifically in biological systems have not been reported yet. In order to address this pressing issue, herein, we have introduced a new and facile strategy to improve MC-LR detection and imaging in biological systems, and based on this design strategy, three NIR fluorescence probes (MC-RdTPA1, MC-RdTPA2, and MC-RdTPE1) have been constructed. These probes have several advantages: (i) have long emission wavelength and large Stokes shifts, which have great potential in vivo imaging applications; (ii) could selectively visualize MC-LR in cells; and (iii) showed stable fluorescence intensity in the pH range of 5.0-7.0. This work may provide a new avenue for the detection of MC-LR in biological systems and new tool to advance our knowledge of the mechanism of MC-LR toxicity.

Dual-amplification system based on CRISPR-Cas12a and horseradish peroxidase-tethered magnetic microspheres for colorimetric detection of microcystin-LR

A novel dual-amplification system based on CRISPR-Cas12a and horseradish peroxidase (HRP) was developed for colorimetric determination of MC-LR. This dual-amplification was accomplished by combining the nuclease activity of CRISPR-Cas12a with the redox activity of HRP. HRP linked to magnetic beads through an ssDNA (MB-ssDNA-HRP) was used to induce a color change of the 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ chromogenic substrate solution. Specific binding of MC-LR with its aptamer initiated the release of a complementary DNA (cDNA), which was designed to activate the trans-cleavage activity of CRISPR-Cas12a. Upon activation, Cas12a cut the ssDNA linker in MB-ssDNA-HRP, causing a reduction of HRP on the magnetic beads. Consequently, the UV-Vis absorbance of the HRP-catalyzed reaction was decreased. The dual-signal amplification facilitated by CRISPR-Cas12a and HRP enabled the colorimetric detection of MC-LR in the range 0.01 to 50 ng·mL^-1 with a limit of detection (LOD) of 4.53 pg·mL^-1. The practicability of the developed colorimetric method was demonstrated by detecting different levels of MC-LR in spiked real water samples. The recoveries ranged from 86.2 to 118.5% and the relative standard deviation (RSD) was 8.4 to 17.6%. This work provides new inspiration for the construction of effective signal amplification platforms and demonstrates a simple and user-friendly colorimetric method for determination of trace MC-LR.

Integrated analysis of mRNA and microRNA expression profiles in hepatopancreas of Litopenaeus vannamei under acute exposure to MC-LR

Intensive shrimp farming is often threatened by microcystins Hepatopancreas is the primary target organ of MCs in shrimp. To investigate the response of hepatopancreas to acute MC-LR exposure, the expression profiles of RNA-seq and miRNA-seq in the hepatopancreas of L. vannamei were determined, and data integration analysis was performed at 72 h after MC-LR injection. The expression of 5 DEGs and three DEMs were detected by Quantitative PCR (qPCR). The results showed that the cumulative mortality rate of shrimp in MC-LR treatment group was 41.1%. A total of 1229 differentially expressed genes (844 up- and 385 down-regulated) and 86 differentially expressed miRNAs (40 up- and 46 down-regulated) were identified after MC-LR exposure. Functional analysis indicated that DEGs is mainly involved in the oxidative activity process in molecular functional categories, and proteasome was the most enriched KEGG pathway for mRNAs profile. According to the functional annotation of target genes of DEMs, protein binding was the most important term in the GO category, and protein processing in endoplasmic reticulum (ER) was the most enriched KEGG pathway. The regulatory network of miRNAs and DEGs involved in the pathway related to protein degradation in endoplasmic reticulum was constructed, and miR-181-5p regulated many genes in this pathway. The results of qPCR showed that there were significant differences in the expression of five DEGs and three DEMs, which might play an important role in the toxicity and hepatopancreas detoxification of MC-LR in shrimp. The results revealed that MC-LR exposure affected the degradation pathway of misfolded protein in ER of L. vannamei hepatopancreas, and miR-181-5p might play an important role in the effect of MC-LR on the degradation pathway of misfolded protein.

Excluding interference and detecting Microcystin-LR in the natural lakes and cells based a unique fluorescence method

Cyanobacteria blooms that cause the death of aquatic and terrestrial organisms have attracted considerable attention since the 19th century. The most typical toxin in cyanobacteria blooms is cyanobacteria toxin, particularly microcystin-LR (MC-LR). Therefore, a simple and highly efficient method for detecting MC-LR plays a role in studying the ecological toxicology of MC-LR. However, as MC-LR itself is located in a complex environment, traditional techniques present complex and false-positive defects. To address the above issues, novel technologies should be explored and discovered. Herein, we describe the development of MC-BDKZ as the first paradigm of probes that can concurrently report MC-LR in natural lakes and cells. This novel material shows large Stokes Shift and possesses good photostability and high sensitivity. Considering the properties mentioned above, MC-BDKZ not only achieves the detection of MC-LR in the lake water samples, but also completes the imaging of exogenous MC-LR in cells. Moreover, the interference of many factors in the lake and cells is excluded completely in the process of MC-LR detection. We comprehensively analyzed the response principle and potential application of MC-BDKZ in the process of MC-LR detection. Compared with the conventional MC-LR detection technologies, fluorescence probe technology shows better convenience and greatly reduces distance from the practical application in vitro and in vivo. We envisioned that the development of this visual research tool could provide crucial clues for exploring the pathogenesis of MC-LR in body.

Chronic exposure to low concentration of MC-LR caused hepatic lipid metabolism disorder

Microcystin-LR (MC-LR), a potent hepatotoxin can cause liver damages. However, research on hepatic lipid metabolism caused by long-term exposure to environmental concentrations MC-LR is limited. In the current study, mice were exposed to various low concentrations of MC-LR (0, 1, 30, 60, 90, 120 μg/L in the drinking water) for 9 months. The general parameters, serum and liver lipids, liver tissue pathology, lipid metabolism-related genes and proteins of liver were investigated. The results show that chronic MC-LR exposure had increased the levels of triglyceride (TG) and total cholesterol (TC) in serum and liver. In addition, histological observation revealed that hepatic lobules were disordered with obvious inflammatory cell infiltration and lipid droplets. More importantly, the mRNA and proteins expression levels of lipid synthesis-related nuclear sterol regulatory element binding protein-1c (nSREBP-1c), SREBP-1c, cluster of differentiation 36 (CD36), acetyl-CoA-carboxylase1 (ACC1), stearoyl-CoA desaturase1 (SCD1) and fatty acid synthase (FASN) were increased in MC-LR treated groups, the expression levels of fatty acids β-oxidation related genes peroxisomal acyl-coenzyme A oxidase 1 (ACOX1) was decreased after exposure to 60-120 μg/L MC-LR. Furthermore, the inflammatory factors interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) were higher than that in the control group. All the findings indicated that mice were exposed to chronic low concentrations MC-LR caused liver inflammation and hepatic lipid metabolism disorder .

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.

Hepatotoxic shellfish poisoning: Accumulation of microcystins in Eastern oysters (Crassostrea virginica) and Asian clams (Corbicula fluminea) exposed to wild and cultured populations of the harmful cyanobacteria, Microcystis

The Asian clam (Corbicula fluminea) and eastern oyster (Crassostrea virginica) are important resource bivalves found in and downstream of waterways afflicted with cyanobacterial harmful algae blooms (CHABs), respectively. This study examined the potential for C. fluminea and C. virginica to become vectors of the hepatotoxin, microcystin, from the CHAB Microcystis. Laboratory experiments were performed to quantify clearance rates, particle selection, and accumulation of the hepatotoxin, microcystin, using a microcystin-producing Microcystis culture isolated from Lake Erie (strain LE-3) and field experiments were performed with water from Microcystis blooms in Lake Agawam, NY, USA. Clearance rates of Microcystis were faster (p<0.05) than those of Raphidocelis for C. fluminea, while C. virginica cleared Microcystis and Tisochrysis at similar rates. For both bivalves, clearance rates of bloom water were slower than cultures and clams displayed significantly greater electivity for green algae compared to wild populations of cyanobacteria in field experiments while oysters did not. In experiments with cultured Microcystis comprised of single and double cells, both bivalves accumulated >3 µg microcystins g ^- 1 (wet weight) in 24 - 72 h, several orders of magnitude beyond California guidance value (10 ng g ^- 1) but accumulated only up to 2 ng microcystins g ^- 1 when fed bloom water dominated by large Microcystis colonies for four days. For Asian clams, clearance rates and tissue microcystin content decreased when exposed to toxic Microcystis for 3 - 4 days. In contrast, eastern oysters did not depurate microcystin over 3 - 4-day exposures and accumulated an order of magnitude more microcystin than clams. This contrast suggests Asian clams are likely to accumulate minor amounts of microcystin by reducing clearance rates during blooms of Microcystis, selectively feeding on green algae, and depurating microcystin whereas oysters are more likely to accumulate microcystins and thus are more likely to be a vector for hepatotoxic shellfish poisoning in estuaries downstream of Microcystis blooms.

Land-Use Driven Changes in Soil Microbial Community Composition and Soil Fertility in the Dry-Hot Valley Region of Southwestern China

The Dry-Hot Valley is a unique geographical region in southwestern China, where steep-slope cultivation and accelerating changes in land-use have resulted in land degradation and have aggravated soil erosion, with profound impacts on soil fertility. Soil microbes play a key role in soil fertility, but the impact of land-use changes on soil microbes in the Dry-Hot Valley is not well known. Here, we compared characteristics and drivers of soil microbial community composition and soil fertility in typical Dry-Hot Valley land uses of sugarcane land (SL), forest land (FL), barren land (BL) converted from former maize land (ML), and ML control. Our results showed that BL and SL had reduced soil organic carbon (SOC), total nitrogen (TN), and total potassium (TK) compared to ML and FL. This indicated that conversion of ML to SL and abandonment of ML had the potential to decrease soil fertility. We also found that fungal phyla Zoopagomycota and Blastocladiomycota were absent in SL and BL, respectively, indicating that land-use change from ML to SL decreased the diversity of the bacterial community. Redundancy analysis indicated that the relative abundance of bacterial phyla was positively correlated with TN, SOC, and available potassium (AK) content, and that fungal phyla were positively correlated with AK. Land-use indirectly affected the relative abundance of bacterial phyla through effects on soil moisture, clay, and AK contents, and that of fungal phyla through effects on clay and AK contents. In addition, land-use effects on bacteria were greater than those on fungi, indicating that bacterial communities were more sensitive to land-use changes. Management regimes that incorporate soil carbon conservation, potassium addition, and judicious irrigation are expected to benefit the stability of the plant–soil system in the Dry-Hot Valley.

The presence of polystyrene nanoplastics enhances the MCLR uptake in zebrafish leading to the exacerbation of oxidative liver damage

The accumulation of diminutive plastic waste in the environment, including microplastics and nanoplastics, has threatened the health of multiple species. Nanoplastics can adsorb the pollutants from the immediate environment, and may be used as carriers for pollutants to enter organisms and bring serious ecological risk. To evaluate the toxic effects of microcystin-LR (MCLR) on the liver of adult zebrafish (Danio rerio) in the presence of 70 nm polystyrene nanoplastics (PSNPs), zebrafish were exposed to MCLR alone (0, 0.9, 4.5 and 22.5 μg/L) and a mixture of MCLR + PSNPs (100 μg/L) for three months. The results indicated that groups with combined exposure to MCLR and PSNPs further enhanced the accumulation of MCLR in the liver when compared to groups only exposed to MCLR. Cellular swelling, fat vacuolation, and cytoarchitectonic damage were observed in zebrafish livers after exposure to MCLR, and the presence of PSNPs exacerbated these adverse effects. The results of biochemical tests showed the combined effect of MCLR + PSNPs enhanced MCLR-induced hepatotoxicity, which could be attributed to the altered levels of reactive oxygen species, malondialdehyde and glutathione, and activities of catalase. The expression of genes related to antioxidant responses (p38a, p38b, ERK2, ERK3, Nrf2, HO-1, cat1, sod1, gax, JINK1, and gstr1) was further performed to study the mechanisms of MCLR combined with PSNPs aggravated oxidative stress of zebrafish. The results showed that PSNPs could improve the bioavailability of MCLR in the zebrafish liver by acting as a carrier and accelerate MCLR-induced oxidative stress by regulating the levels of corresponding enzymes and genes.

Immunoassay technology: Research progress in microcystin-LR detection in water samples

Increasing global warming and eutrophication have led to frequent outbreaks of cyanobacteria blooms in freshwater. Cyanobacteria blooms cause the death of aquatic and terrestrial organisms and have attracted considerable attention since the 19th century. Microcystin-LR (MC-LR) is one of the most typical cyanobacterial toxins. Therefore, the fast, sensitive, and accurate determination of MC-LR plays an important role in the health of humans and animals. Immunoassay refers to a method that uses the principle of immunology to determine the content of the tested substance in a sample using the tested substance as an antigen or antibody. In analytical applications, the immunoassay technology could use the specific recognition of antibodies for MC-LR detection. In this review, we firstly highlight the immunoassay detection of MC-LR over the past two decades, including classical enzyme-link immunosorbent assay (ELISA), modern immunoassay with optical signal, and modern immunoassay with electrical signal. Among these detection methods, the water environment was used as the main detection system. The advantages and disadvantages of the different detection methods were compared and analyzed, and the principles and applications of immunoassays in water samples were elaborated. Furthermore, the current challenges and developmental trends in immunoassay were systematically introduced to enhance MC-LR detection performance, and some critical points were given to deal with current challenges. This review provides novel insight into MC-LR detection based on immunoassay method.

Spirulina platensis protects against microcystin-LR-induced toxicity in rats

Microcystis aeruginosa produces an abundant cyanotoxin (microcystins (MCs) in freshwater supplies. MCs have adverse health hazards to animals and humans. Microcystin-leucine-arginine (microcystin-LR or MC-LR) is the most studied among these MCs due to their high toxicity. So, this study was designed to evaluate the possible therapeutic role of the natural algal food supplement, Spirulina platensis (SP), against MC-LR-induced toxic effects in male Wistar rats. Forty rats were randomly divided into five groups. Control and SP groups orally administered distilled water and SP (1000 mg/kg/daily), respectively, for 21 days. MC-LR group was intraperitoneally injected with MC-LR (10 μg/kg/day) for 14 days. MC-LR-SP₅₀₀ and MC-LR-SP₁₀₀₀ groups were orally treated with SP (500 and 1000 mg/kg, respectively) for 7 days and concomitantly with MC-LR for 14 days. MC-LR induced oxidative hepatorenal damage, cardiotoxicity, and neurotoxicity greatly, which was represented by reduction of reduced glutathione content and the activities of glutathione peroxidase, catalase, and superoxide dismutase and elevation of concentrations of nitric oxide and malondialdehyde in renal, hepatic, brain, and heart tissues. In addition, it increased serum levels of urea, creatinine, tumor necrosis factor-alfa, interleukin-1beta and interleukin-6 and serum activities of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase, and creatine kinase-MB. However, S. platensis restored normal levels of measured serum parameters, ameliorated MC-LR-induced oxidative damage, and normalized tissue antioxidant biomarkers. In conclusion, SP alleviated MC-induced organ toxicities by mitigating oxidative and nitrosative stress and lipid peroxidation.

Microcystin-leucine arginine exposure induced intestinal lipid accumulation and MC-LR efflux disorder in Lithobates catesbeianus tadpoles

Few studies exist on the toxic effects of chronic exposure to microcystins (MCs) on amphibian intestines, and the toxicity mechanisms are unclear. Here, we evaluated the impact of subchronic exposure (30 days) to environmentally realistic microcystin-leucine arginine (MC-LR) concentrations (0 μg/L, 0.5 μg/L and 2 μg/L) on tadpole (Lithobates catesbeianus) intestines by analyzing the histopathological and subcellular microstructural damage, the antioxidative and oxidative enzyme activities, and the transcriptome levels. Histopathological results showed severe damage accompanied by inflammation to the intestinal tissues as the MC-LR exposure concentration increased from 0.5 μg/L to 2 μg/L. RNA-sequencing analysis identified 634 and 1,147 differentially expressed genes (DEGs) after exposure to 0.5 μg/L and 2 μg/L MC-LR, respectively, compared with those of the control group (0 μg/L). Biosynthesis of unsaturated fatty acids and the peroxisome proliferator-activated receptor (PPAR) signaling pathway were upregulated in the intestinal tissues of the exposed groups, with many lipid droplets being observed on transmission electron microscopy, implying that MC-LR may induce lipid accumulation in frog intestines. Moreover, 2 μg/L of MC-LR exposure inhibited the xenobiotic and toxicant biodegradation related to detoxification, implying that the tadpoles' intestinal detoxification ability was weakened after exposure to 2 μg/L MC-LR, which may aggravate intestinal toxicity. Lipid accumulation and toxin efflux disorder may be caused by MC-LR-induced endoplasmic reticular stress. This study presents new evidence that MC-LR harms amphibians by impairing intestinal lipid metabolism and toxin efflux, providing a theoretical basis for evaluating the health risks of MC-LR to amphibians.

Metal-organic frameworks-assisted nonenzymatic cascade amplification multiplexed strategy for sensing acute myocardial infarction related microRNAs

Amplification strategies for multiple microRNAs (miRNAs) detection are pivotal for acute myocardial infarction (AMI). Herein, we rationally developed a metal-organic frameworks-assisted nonenzymatic cascade amplification strategy for simultaneous quantification of three AMI-related miRNAs (miR-21, miR-499 and miR-133a). The fluorescence of the elaborately designed DNA molecular beacons with the respective modification of FAM, TAMRA and Cy5 in the terminal was quenched by a metal-organic framework named Fe-MIL-88. When targets miRNA appeared, they hybridized with the corresponding DNA molecular beacons, and the catalyzed hairpin assembly (CHA) reaction would be triggered, producing "Y" shaped three-branched duplex nanostructure with the targets released, and initiating subsequent another cycle. The "Y" shaped nanostructures could not be adsorbed onto the surface of Fe-MIL-88 due to the weaker affinity between Fe-MIL-88 and "Y" shaped nanostructures. Therefore, the fluorescence of "Y" shaped nanostructures could not be quenched by Fe-MIL-88. In this way, three AMI-related miRNAs were simultaneously detected in the respective ranges of 0.05-30 nM, 0.08-30 nM and 0.1-20 nM with respective limits of detection down to 13, 25 and 40 pM. Furthermore, the method was successfully employed to determine three AMI-related miRNAs in human serum. The strategy offered great opportunity for ultrasensitive detecting multiple AMI-related miRNAs and substantially improving the accuracy of clinical early AMI diagnosis.

Chronic exposure to MC-LR increases the risks of microcytic anemia: Evidence from human and mice

Microcystins (MCs) produced by cyanobacteria are potent toxins to humans that cannot be ignored. However, the toxicity of MCs to humans remains largely unknown. The study explored the role of MCs in the development of hematological parameters through human observations and a chronic mouse model to explore related mechanisms. The adjusted odds ratio of MC-LR to the risk of anemia was 4.954 (95 % CI, 2.423-10.131) in a case-control study in Nanjing. An inverse correlation between serum MC-LR and hemoglobin (HGB), hematocrit (HCT), mean corpuscular volume (MCV), and red blood cell count (RBC) was observed. MC-LR in the serum of the population was an independent risk factor for microcytic anemia. Animal experiments demonstrated that MC-LR resulted in microcytic anemia, which is associated with inflammation, dysregulation of iron homeostasis, and erythropoiesis. We first identified the possible signaling pathway of MC-LR-induced anemia that MC-LR significantly upregulated the levels of hepcidin via EPO/EPOR signaling pathway and the decreased levels of Twsg1 and Gdf15, thereby resulting in the decreased levels of Hbb and Fpn, and the increased expression of Fth1, and Tf in a chronic mouse model. Our study first identified that prolonged environmental exposure to MCs probably contribute to the occurrence of microcytic anemia in humans, which provides new insights into the toxicity of MCs for public health.

Microcystin-LR induces ferroptosis in intestine of common carp (Cyprinus carpio)

Previous studies provide comprehensive evidence of the environmental hazards and intestinal toxicity of microcystin-LR (MC-LR) exposure. However, little is known about the mechanisms underlying the injury of intestine exposed to MC-LR. Juvenile common carp (Cyprinus carpio) were exposed to MC-LR (0 and 10 μg/L) for 15 days. The results suggest that organic anion-transporting polypeptides 3a1, 4a1, 2b1, and 1d1 mediate MC-LR entry into intestinal tissues. Lesion morphological features (vacuolization, deformation and dilation of the endoplasmic reticulum [ER], absence of mitochondrial cristae in mid-intestine), up-regulated mRNA expressions of ER stress (eukaryotic translation initiation factor 2-alpha kinase 3, endoplasmic reticulum to nucleus signaling 1, activating transcription factor [ATF] 6, ATF4, DNA damage-inducible transcript 3), iron accumulation, and down-regulated activity of glutathione peroxidase (GPx) and glutathione (GSH) content were all typical characteristics of ferroptosis in intestinal tissue following MC-LR exposure. GSH levels in intestinal tissue corroborated as the most influential GSH/GPx 4- related metabolic pathway in response to MC-LR exposure. Verrucomicrobiota, Planctomycetes, Bdellovibrionota, Firmicutes and Cyanobacteria were correlated with the ferroptosis-related GSH following MC-LR exposure. These findings provide new perspectives of the ferroptosis mechanism of MC-LR-induced intestinal injury in the common carp.

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.

Allium sativum mitigates oxidative damages induced by Microcystin-LR in heart and liver tissues of mice

Microcystins (MCs) are hepatotoxic cyanotoxins implicated in several incidents of human and animal toxicity. Microcystin-(Lysine, Arginine) or MC-LR is the most toxic and encountered variant of MCs where oxidative stress plays a key role in its toxicity. This study investigated the oxidative damages induced in the liver and heart of Balb/C mice by an intraperitoneal injected acute dose of MC-LR. Thereafter, the potential protective effect of garlic (Allium sativum) extract supplementation against such damages was assessed through the evaluation of oxidative stress and cytotoxicity markers. Lipid peroxidation (LPO), carbonyl content (CC), glutathione content (GSH), alkaline phosphatase activity (ALP), lactate dehydrogenase (LDH) and sorbitol dehydrogenase (SDH) activities were measured. Results showed important oxidative damages in hepatic and cardiac cells of mice injected with the toxin. However, these damages have been significantly reduced in mice supplemented with garlic extract. Thus, this study demonstrated for the first time the effective use of garlic as an antioxidant agent against oxidative damages induced by MC-LR. As well, this study supports the use of garlic as a potential remedy against pathologies related to toxic agents.

A single small molecule fluorescent probe for imaging RNA distribution and detecting endogenous SO2 through distinct fluorescence channels

Herein, we developed a novel small molecule fluorescent probe for imaging the distribution of RNA and detecting endogenous SO2 through distinct fluorescence channels in cells.