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Toxins, Volume 12, Issue 4 (April 2020) – 69 articles

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Cover Story (view full-size image) Bacillus thuringiensis cytolytic toxin (Cyt) directly interacts with membrane lipids resulting in [...] Read more.
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Open AccessArticle
Molecular Identification and Mycotoxin Production by Alternaria Species Occurring on Durum Wheat, Showing Black Point Symptoms
Toxins 2020, 12(4), 275; https://doi.org/10.3390/toxins12040275 - 23 Apr 2020
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Abstract
Black point is a fungal disease of wheat, mainly associated with mycotoxigenic Alternaria species. Affected wheat kernels are characterized by dark brown discolouration of the embryo region and reduction of grain quality. Potential risk is the possible accumulation of Alternaria mycotoxins, alternariol (AOH), [...] Read more.
Black point is a fungal disease of wheat, mainly associated with mycotoxigenic Alternaria species. Affected wheat kernels are characterized by dark brown discolouration of the embryo region and reduction of grain quality. Potential risk is the possible accumulation of Alternaria mycotoxins, alternariol (AOH), alternariol-monomethyl ether (AME), tenuazonic acid (TA), and altenuene (ALT), provided by haemato-toxic, genotoxic, and mutagenic activities. One hundred and twenty durum wheat samples belonging to 30 different genotypes grown in Bologna and Modena areas, in Italy, showing black point symptoms, were analyzed for Alternaria species and their mycotoxin contamination. Alternariol was selected as an indicator of the capability of the Alternaria species to produce mycotoxin in vivo in field conditions. The data showed that Alternaria species occurred in 118 out of 120 wheat kernels samples, with the incidence of infected kernels ranging between 1% and 26%. Moreover, AOH was detected by using a HPLC with a diode array detector (LC-DAD) in 98 out of 120 samples with values ranging between 24 and 262 µg Kg−1. Ninety-two Alternaria representative strains, previously identified morphologically, were identified at species/section level using gene sequencing, and therefore were analyzed for their mycotoxin profiles. Eighty-four strains, phylogenetically grouped in the Alternaria section, produced AOH, AME, and TA with values up to 8064, 14,341, and 3683 µg g−1, respectively, analyzed by using a LC-DAD. On the other hand, eight Alternaria strains, included in Infectoriae Section, showed a very low or no capability to produce mycotoxins. Full article
(This article belongs to the Special Issue Mycotoxins in Food: Origin and Management of Risk)
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Open AccessArticle
Oligomer Formation and Insecticidal Activity of Bacillus thuringiensis Vip3Aa Toxin
Toxins 2020, 12(4), 274; https://doi.org/10.3390/toxins12040274 - 23 Apr 2020
Viewed by 348
Abstract
Bacillus thuringiensis (Bt) Vip3A proteins are important insecticidal proteins used for control of lepidopteran insects. However, the mode of action of Vip3A toxin is still unclear. In this study, the amino acid residue S164 in Vip3Aa was identified to be critical for the [...] Read more.
Bacillus thuringiensis (Bt) Vip3A proteins are important insecticidal proteins used for control of lepidopteran insects. However, the mode of action of Vip3A toxin is still unclear. In this study, the amino acid residue S164 in Vip3Aa was identified to be critical for the toxicity in Spodoptera litura. Results from substitution mutations of the S164 indicate that the insecticidal activity of Vip3Aa correlated with the formation of a >240 kDa complex of the toxin upon proteolytic activation. The >240 kDa complex was found to be composed of the 19 kDa and the 65 kDa fragments of Vip3Aa. Substitution of the S164 in Vip3Aa protein with Ala or Pro resulted in loss of the >240 kDa complex and loss of toxicity in Spodoptera litura. In contrast, substitution of S164 with Thr did not affect the >240 kDa complex formation, and the toxicity of the mutant was only reduced by 35%. Therefore, the results from this study indicated that formation of the >240 kDa complex correlates with the toxicity of Vip3Aa in insects and the residue S164 is important for the formation of the complex. Full article
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Open AccessArticle
Change of Amino Acid Residues in Idiotypic Nanobodies Enhanced the Sensitivity of Competitive Enzyme Immunoassay for Mycotoxin Ochratoxin A in Cereals
Toxins 2020, 12(4), 273; https://doi.org/10.3390/toxins12040273 - 23 Apr 2020
Viewed by 334
Abstract
Anti-idiotypic nanobodies, usually expressed by gene engineering protocol, has been shown as a nontoxic coating antigen for toxic compound immunoassays. We here focused on how to increase immunoassay sensitivity by changing the nanobody’s primary sequence. In the experiments, two anti-idiotype nanobodies against monoclonal [...] Read more.
Anti-idiotypic nanobodies, usually expressed by gene engineering protocol, has been shown as a nontoxic coating antigen for toxic compound immunoassays. We here focused on how to increase immunoassay sensitivity by changing the nanobody’s primary sequence. In the experiments, two anti-idiotype nanobodies against monoclonal antibody 1H2, which is specific to ochratoxin A, were obtained and named as nontoxic coating antigen 1 (NCA1) and nontoxic coating antigen 2 (NCA2). Three differences between the nanobodies were discovered. First, there are six amino acid residues (AAR) of changes in the complementarity determining region (CDR), which compose the antigen-binding site. One of them locates in CDR1 (I–L), two of them in CDR2 (G–D, E–K), and three of them in CDR3 (Y–H, Y–W). Second, the affinity constant of NCA1 was tested as 1.20 × 108 L mol−1, which is about 4 times lower than that of NCA2 (5.36 × 108 L mol−1). Third, the sensitivity (50% inhibition concentration) of NCA1 for OTA was shown as 0.052 ng mL−1, which was 3.5 times lower than that of nontoxic coating antigen 2 (0.015 ng mL−1). The results indicate that the AAR changes in CDR of the anti-idiotypic nanobodies, from nonpolar to polar, increasing the affinity constant may enhance the immunoassay sensitivity. In addition, by using the nontoxic coating antigen 2 to substitute the routine synthetic toxic antigen, we established an eco-friendly and green enzyme-linked immunosorbent assay (ELISA) method for rapid detection of ochratoxin A in cereals. The half-maximal inhibitory concentration (IC50) of optimized ELISA was 0.017 ng mL−1 with a limit of detection (LOD) of 0.003 ng mL−1. The optimized immunoassay showed that the average recoveries of spiked corn, rice, and wheat were between 80% and 114.8%, with the relative standard deviation (RSD) ranging from 3.1–12.3%. Therefore, we provided not only basic knowledge on how to improve the structure of anti-idiotype nanobody for increasing assay sensitivity, but also an available eco-friendly ELISA for ochratoxin A in cereals. Full article
(This article belongs to the collection Biorecognition Assays for Mycotoxins)
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Open AccessEditorial
Application of LC–MS/MS in the Mycotoxins Studies
Toxins 2020, 12(4), 272; https://doi.org/10.3390/toxins12040272 - 23 Apr 2020
Viewed by 385
Abstract
Mycotoxins are secondary metabolites produced by fungi of different species (mainly Aspergillus, Fusarium, and Penicillium) with toxic effects for humans and animals that can contaminate food and feed [...] Full article
(This article belongs to the Special Issue Application of LC-MS/MS in the Mycotoxins Studies)
Open AccessArticle
The bZIP Transcription Factor AflRsmA Regulates Aflatoxin B1 Biosynthesis, Oxidative Stress Response and Sclerotium Formation in Aspergillus flavus
Toxins 2020, 12(4), 271; https://doi.org/10.3390/toxins12040271 - 23 Apr 2020
Viewed by 349
Abstract
Fungal secondary metabolites play important roles not only in fungal ecology but also in humans living as beneficial medicine or harmful toxins. In filamentous fungi, bZIP-type transcription factors (TFs) are associated with the proteins involved in oxidative stress response and secondary metabolism. In [...] Read more.
Fungal secondary metabolites play important roles not only in fungal ecology but also in humans living as beneficial medicine or harmful toxins. In filamentous fungi, bZIP-type transcription factors (TFs) are associated with the proteins involved in oxidative stress response and secondary metabolism. In this study, a connection between a bZIP TF and oxidative stress induction of secondary metabolism is uncovered in an opportunistic pathogen Aspergillus flavus, which produces carcinogenic and mutagenic aflatoxins. The bZIP transcription factor AflRsmA was identified by a homology research of A. flavus genome with the bZIP protein RsmA, involved in secondary metabolites production in Aspergillus nidulans. The AflrsmA deletion strain (ΔAflrsmA) displayed less sensitivity to the oxidative reagents tert-Butyl hydroperoxide (tBOOH) in comparison with wild type (WT) and AflrsmA overexpression strain (AflrsmAOE), while AflrsmAOE strain increased sensitivity to the oxidative reagents menadione sodium bisulfite (MSB) compared to WT and ΔAflrsmA strains. Without oxidative treatment, aflatoxin B1 (AFB1) production of ΔAflrsmA strains was consistent with that of WT, but AflrsmAOE strain produced more AFB1 than WT; tBOOH and MSB treatment decreased AFB1 production of ΔAflrsmA compared to WT. Besides, relative to WT, ΔAflrsmA strain decreased sclerotia, while AflrsmAOE strain increased sclerotia. The decrease of AFB1 by ΔAflrsmA but increase of AFB1 by AflrsmAOE was on corn. Our results suggest that AFB1 biosynthesis is regulated by AflRsmA by oxidative stress pathways and provide insights into a possible function of AflRsmA in mediating AFB1 biosynthesis response host defense in pathogen A. flavus. Full article
(This article belongs to the Section Mycotoxins)
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Open AccessArticle
Critical Comparison of Analytical Performances of Two Immunoassay Methods for Rapid Detection of Aflatoxin M1 in Milk
Toxins 2020, 12(4), 270; https://doi.org/10.3390/toxins12040270 - 22 Apr 2020
Viewed by 440
Abstract
Aflatoxin B1 (AFB1) is a secondary metabolite produced by some Aspergillus spp. fungi affecting many crops and feed materials. Aflatoxin M1 (AFM1), the 4-hydroxylated metabolite of AFB1, is the main AFB1-related compound present [...] Read more.
Aflatoxin B1 (AFB1) is a secondary metabolite produced by some Aspergillus spp. fungi affecting many crops and feed materials. Aflatoxin M1 (AFM1), the 4-hydroxylated metabolite of AFB1, is the main AFB1-related compound present in milk, and it is categorized by the International Agency for Research on Cancer (IARC) as a “group 1 human carcinogen”. The aim of this work was to evaluate and compare the analytical performances of two commercial immunoassays widely applied for the detection of AFM1 in milk, namely strip test immunoassay and enzyme linked immunosorbent assay (ELISA). Assay validation included samples at AFM1 levels of 25, 50, 75 ng/kg and blank samples (AFM1 < 0.5 ng/kg). With respect to a screening target concentration (STC) of 50 ng/kg the two assays showed cut-off values of 37.7 ng/kg and 47.5 ng/kg for strip test and ELISA, respectively, a false suspect rate for blanks <0.1% (for both assays) and a false negative rate for samples containing AFM1 at levels higher than STC, of 0.4% (for both assays). The intermediate precision (RSDip) was <32% for the strip test and <15% for the ELISA. Method verification through long-term intra-laboratory quality control (QC) measurements confirmed the results from the validation study. Furthermore, a satisfactory correlation of the results obtained with both immunoassays and the AOAC Official Method 2000.08 was obtained for the analysis of cow milk samples naturally contaminated with AFM1 at levels within “not detected” (< 0.5 ng/kg) and 50 ng/kg. Finally, the extension of the scope of the strip test method to goat and sheep milk was evaluated by applying the experimental design foreseen in the EU regulation. Full article
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Open AccessReview
Treatment of Blepharospasm and Oromandibular Dystonia with Botulinum Toxins
Toxins 2020, 12(4), 269; https://doi.org/10.3390/toxins12040269 - 22 Apr 2020
Viewed by 407
Abstract
Blepharospasm and oromandibular dystonia are focal dystonias characterized by involuntary and often patterned, repetitive muscle contractions. There is a long history of medical and surgical therapies, with the current first-line therapy, botulinum neurotoxin (BoNT), becoming standard of care in 1989. This comprehensive review [...] Read more.
Blepharospasm and oromandibular dystonia are focal dystonias characterized by involuntary and often patterned, repetitive muscle contractions. There is a long history of medical and surgical therapies, with the current first-line therapy, botulinum neurotoxin (BoNT), becoming standard of care in 1989. This comprehensive review utilized MEDLINE and PubMed and provides an overview of the history of these focal dystonias, BoNT, and the use of toxin to treat them. We present the levels of clinical evidence for each toxin for both, focal dystonias and offer guidance for muscle and site selection as well as dosing. Full article
(This article belongs to the Special Issue Treatment of Dystonia with Botulinum Toxins)
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Open AccessReview
A Mini Review on Microcystins and Bacterial Degradation
Toxins 2020, 12(4), 268; https://doi.org/10.3390/toxins12040268 - 21 Apr 2020
Viewed by 468
Abstract
Microcystins (MCs) classified as hepatotoxic and carcinogenic are the most commonly reported cyanobacterial toxins found in the environment. Microcystis sp. possessing a series of MC synthesis genes (mcyA-mcyJ) are well documented for their excessive abundance, numerous bloom occurrences and MC producing capacity. About [...] Read more.
Microcystins (MCs) classified as hepatotoxic and carcinogenic are the most commonly reported cyanobacterial toxins found in the environment. Microcystis sp. possessing a series of MC synthesis genes (mcyA-mcyJ) are well documented for their excessive abundance, numerous bloom occurrences and MC producing capacity. About 246 variants of MC which exert severe animal and human health hazards through the inhibition of protein phosphatases (PP1 and PP2A) have been characterized. To minimize and prevent MC health consequences, the World Health Organization proposed 1 µg/L MC guidelines for safe drinking water quality. Further the utilization of bacteria that represent a promising biological treatment approach to degrade and remove MC from water bodies without harming the environment has gained global attention. Thus the present review described toxic effects and bacterial degradation of MCs. Full article
(This article belongs to the Special Issue Cyanobacterial Toxins: Their Occurrence, Detection and Removal)
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Open AccessCommunication
Liquid Chromatography Coupled to High-Resolution Mass Spectrometry for the Confirmation of Caribbean Ciguatoxin-1 as the Main Toxin Responsible for Ciguatera Poisoning Caused by Fish from European Atlantic Coasts
Toxins 2020, 12(4), 267; https://doi.org/10.3390/toxins12040267 - 21 Apr 2020
Viewed by 512
Abstract
Ciguatera poisoning (CP) is a common seafood intoxication mainly caused by the consumption of fish contaminated by ciguatoxins. Recent studies showed that Caribbean ciguatoxin-1 (C-CTX1) is the main toxin causing CP through fish caught in the Northeast Atlantic, e.g., Canary Islands (Spain) and [...] Read more.
Ciguatera poisoning (CP) is a common seafood intoxication mainly caused by the consumption of fish contaminated by ciguatoxins. Recent studies showed that Caribbean ciguatoxin-1 (C-CTX1) is the main toxin causing CP through fish caught in the Northeast Atlantic, e.g., Canary Islands (Spain) and Madeira (Portugal). The use of liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) combined with neuroblastoma cell assay (N2a) allowed the initial confirmation of the presence of C-CTX1 in contaminated fish samples from the abovementioned areas, nevertheless the lack of commercially available reference materials for these particular ciguatoxin (CTX) analogues has been a major limitation to progress research. The EuroCigua project allowed the preparation of C-CTX1 laboratory reference material (LRM) from fish species (Seriola fasciata) from the Madeira archipelago (Portugal). This reference material was used to implement a liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) for the detection of C-CTX1, acquisition of full-scan as well as collision-induced mass spectra of this particular analogue. Fragmentation pathways were proposed based on fragments obtained. The optimized LC-HRMS method was then applied to confirm C-CTX1 in fish (Bodianus scrofa) caught in the Selvagens Islands (Portugal). Full article
(This article belongs to the Special Issue Ciguatoxins)
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Open AccessArticle
APETx-Like Peptides from the Sea Anemone Heteractis crispa, Diverse in Their Effect on ASIC1a and ASIC3 Ion Channels
Toxins 2020, 12(4), 266; https://doi.org/10.3390/toxins12040266 - 20 Apr 2020
Viewed by 518
Abstract
Currently, five peptide modulators of acid-sensing ion channels (ASICs) attributed to structural class 1b of sea anemone toxins have been described. The APETx2 toxin is the first and most potent ASIC3 inhibitor, so its homologs from sea anemones are known as the APETx-like [...] Read more.
Currently, five peptide modulators of acid-sensing ion channels (ASICs) attributed to structural class 1b of sea anemone toxins have been described. The APETx2 toxin is the first and most potent ASIC3 inhibitor, so its homologs from sea anemones are known as the APETx-like peptides. We have discovered that two APETx-like peptides from the sea anemone Heteractis crispa, Hcr 1b-3 and Hcr 1b-4, demonstrate different effects on rASIC1a and rASIC3 currents. While Hcr 1b-3 inhibits both investigated ASIC subtypes with IC50 4.95 ± 0.19 μM for rASIC1a and 17 ± 5.8 μM for rASIC3, Hcr 1b-4 has been found to be the first potentiator of ASIC3, simultaneously inhibiting rASIC1a at similar concentrations: EC50 1.53 ± 0.07 μM and IC50 1.25 ± 0.04 μM. The closest homologs, APETx2, Hcr 1b-1, and Hcr 1b-2, previously demonstrated the ability to inhibit hASIC3 with IC50 63 nM, 5.5, and 15.9 μM, respectively, while Hcr 1b-2 also inhibited rASIC1a with IC50 4.8 ± 0.3 μM. Computer modeling allowed us to describe the peculiarities of Hcr 1b-2 and Hcr 1b-4 interfaces with the rASIC1a channel and the stabilization of the expanded acidic pocket resulting from peptides binding which traps the rASIC1a channel in the closed state. Full article
(This article belongs to the Special Issue Sea Anemone Venom)
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Open AccessArticle
Enzyme Immunoassay for Measuring Aflatoxin B1 in Legal Cannabis
Toxins 2020, 12(4), 265; https://doi.org/10.3390/toxins12040265 - 20 Apr 2020
Viewed by 431
Abstract
The diffusion of the legalization of cannabis for recreational, medicinal and nutraceutical uses requires the development of adequate analytical methods to assure the safety and security of such products. In particular, aflatoxins are considered to pose a major risk for the health of [...] Read more.
The diffusion of the legalization of cannabis for recreational, medicinal and nutraceutical uses requires the development of adequate analytical methods to assure the safety and security of such products. In particular, aflatoxins are considered to pose a major risk for the health of cannabis consumers. Among analytical methods that allows for adequate monitoring of food safety, immunoassays play a major role thanks to their cost-effectiveness, high-throughput capacity, simplicity and limited requirement for equipment and skilled operators. Therefore, a rapid and sensitive enzyme immunoassay has been adapted to measure the most hazardous aflatoxin B1 in cannabis products. The assay was acceptably accurate (recovery rate: 78–136%), reproducible (intra- and inter-assay means coefficients of variation 11.8% and 13.8%, respectively), and sensitive (limit of detection and range of quantification: 0.35 ng mL−1 and 0.4–2 ng mL−1, respectively corresponding to 7 ng g−1 and 8–40 ng g−1 ng g−1 in the plant) and provided results which agreed with a HPLC-MS/MS method for the direct analysis of aflatoxin B1 in cannabis inflorescence and leaves. In addition, the carcinogenic aflatoxin B1 was detected in 50% of the cannabis products analyzed (14 samples collected from small retails) at levels exceeding those admitted by the European Union in commodities intended for direct human consumption, thus envisaging the need for effective surveillance of aflatoxin contamination in legal cannabis. Full article
(This article belongs to the Section Mycotoxins)
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Open AccessArticle
Enzymatic Synthesis of Modified Alternaria Mycotoxins Using a Whole-Cell Biotransformation System
Toxins 2020, 12(4), 264; https://doi.org/10.3390/toxins12040264 - 20 Apr 2020
Viewed by 312
Abstract
Reference standards for Alternaria mycotoxins are rarely available, especially the modified mycotoxins alternariol-3-glucoside (AOH-3-G), alternariol-9-glucoside (AOH-9-G), and alternariol monomethylether-3-glucoside (AME-3-G). To obtain these three glucosides as analytical standards for method development and method validation, alternariol and alternariol monomethylether were enzymatically glycosylated in a [...] Read more.
Reference standards for Alternaria mycotoxins are rarely available, especially the modified mycotoxins alternariol-3-glucoside (AOH-3-G), alternariol-9-glucoside (AOH-9-G), and alternariol monomethylether-3-glucoside (AME-3-G). To obtain these three glucosides as analytical standards for method development and method validation, alternariol and alternariol monomethylether were enzymatically glycosylated in a whole-cell biotransformation system using a glycosyltransferase from strawberry (Fragaria x ananassa), namely UGT71A44, expressed in Escherichia coli (E. coli). The formed glucosides were isolated, purified, and structurally characterized. The exact amount of the isolated compounds was determined using high-performance liquid chromatography with UV-detection (HPLC-UV) and quantitative nuclear resonance spectroscopy (qNMR). This method has proved to be highly effective with biotransformation rates of 58% for AOH-3-G, 5% for AOH-9-G, and 24% for AME-3-G. Full article
(This article belongs to the Section Mycotoxins)
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Open AccessArticle
Development and Application of Extraction Methods for LC-MS Quantification of Microcystins in Liver Tissue
Toxins 2020, 12(4), 263; https://doi.org/10.3390/toxins12040263 - 19 Apr 2020
Viewed by 428
Abstract
A method was developed to extract and quantify microcystins (MCs) from mouse liver with limits of quantification (LOQs) lower than previously reported. MCs were extracted from 40-mg liver samples using 85:15 (v:v) CH3CN:H2O containing 200 mM ZnSO4 and [...] Read more.
A method was developed to extract and quantify microcystins (MCs) from mouse liver with limits of quantification (LOQs) lower than previously reported. MCs were extracted from 40-mg liver samples using 85:15 (v:v) CH3CN:H2O containing 200 mM ZnSO4 and 1% formic acid. Solid-phase extraction with a C18 cartridge was used for sample cleanup. MCs were detected and quantified using HPLC-orbitrap-MS with simultaneous MS/MS detection of the 135.08 m/z fragment from the conserved Adda amino acid for structural confirmation. The method was used to extract six MCs (MC-LR, MC-RR, MC-YR, MC-LA, MC-LF, and MC-LW) from spiked liver tissue and the MC-LR cysteine adduct (MC-LR-Cys) created by the glutathione detoxification pathway. Matrix-matched internal standard calibration curves were constructed for each MC (R2 ≥ 0.993), with LOQs between 0.25 ng per g of liver tissue (ng/g) and 0.75 ng/g for MC-LR, MC-RR, MC-YR, MC-LA, and MC-LR-Cys, and 2.5 ng/g for MC-LF and MC-LW. The protocol was applied to extract and quantify MC-LR and MC-LR-Cys from the liver of mice that had been gavaged with 50 µg or 100 µg of MC-LR per kg bodyweight and were euthanized 2 h, 4 h, or 48 h after final gavage. C57Bl/6J (wild type, control) and Leprdb/J (experiment) mice were used as a model to study non-alcoholic fatty liver disease. The Leprdb/J mice were relatively inefficient in metabolizing MC-LR into MC-LR-Cys, which is an important defense mechanism against MC-LR exposure. Trends were also observed as a function of MC-LR gavage amount and time between final MC-LR gavage and euthanasia/organ harvest. Full article
(This article belongs to the Special Issue Cyanobacterial Toxins: Their Occurrence, Detection and Removal)
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Open AccessArticle
Status of Asp29 and Asp40 in the Interaction of Naja atra Cardiotoxins with Lipid Bilayers
Toxins 2020, 12(4), 262; https://doi.org/10.3390/toxins12040262 - 18 Apr 2020
Viewed by 407
Abstract
It is widely accepted that snake venom cardiotoxins (CTXs) target the plasma membranes of cells. In the present study, we investigated the role of Asp residues in the interaction of Naja atra cardiotoxin 1 (CTX1) and cardiotoxin 3 (CTX3) with phospholipid bilayers using [...] Read more.
It is widely accepted that snake venom cardiotoxins (CTXs) target the plasma membranes of cells. In the present study, we investigated the role of Asp residues in the interaction of Naja atra cardiotoxin 1 (CTX1) and cardiotoxin 3 (CTX3) with phospholipid bilayers using chemical modification. CTX1 contains three Asp residues at positions 29, 40, and 57; CTX3 contains two Asp residues at positions 40 and 57. Compared to Asp29 and Asp40, Asp57 was sparingly modified with semi-carbazide, as revealed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass and mass/mass analyses. Thus, semi-carbazide-modified CTX1 (SEM-CTX1) mainly contained modified Asp29 and Asp40, while SEM-CTX3 contained modified Asp40. Compared to that of native toxins, trifluoroethanol easily induced structural transition of SEM-CTX1 and SEM-CTX3, suggesting that the structural flexibility of CTXs was constrained by Asp40. Modification of Asp29 and Asp40 markedly promoted the ability of CTX1 to induce permeability of cell membranes and lipid vesicles; CTX3 and SEM-CTX3 showed similar membrane-damaging activity. Modification of Asp residues did not affect the membrane-binding capability of CTXs. Circular dichroism spectra of SEM-CTX3 and CTX3 were similar, while the gross conformation of SEM-CTX1 was distinct from that of CTX1. The interaction of CTX1 with membrane was distinctly changed by Asp modification. Collectively, our data suggest that Asp29 of CTX1 suppresses the optimization of membrane-bound conformation to a fully active state and that the function of Asp40 in the structural constraints of CTX1 and CTX3 is not important for the manifestation of membrane-perturbing activity. Full article
(This article belongs to the Section Animal Venoms)
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Open AccessArticle
Neuroprotective and Anti—Neuroinflammatory Effects of a Poisonous Plant Croton tiglium Linn. Extract
Toxins 2020, 12(4), 261; https://doi.org/10.3390/toxins12040261 - 17 Apr 2020
Viewed by 304
Abstract
Neuroinflammation is involved in various neurological diseases. Activated microglia secrete many pro-inflammatory factors and induce neuronal cell death. Thus, the inhibition of excessive proinflammatory activity of microglia leads to a therapeutic effect that alleviates the progression of neuronal degeneration. In this study, we [...] Read more.
Neuroinflammation is involved in various neurological diseases. Activated microglia secrete many pro-inflammatory factors and induce neuronal cell death. Thus, the inhibition of excessive proinflammatory activity of microglia leads to a therapeutic effect that alleviates the progression of neuronal degeneration. In this study, we investigated the effect of Croton tiglium (C. tiglium) Linn. extract (CTE) on the production of pro- and anti-inflammatory mediators in microglia and astrocytes via RT-PCR, Western blot, and nitric oxide assay. Neurotoxicity was measured by cell viability assay and GFP image analysis. Phagocytosis of microglia was measured using fluorescent zymosan particles. CTE significantly inhibited the production of neurotoxic inflammatory factors, including nitric oxide and tumor necrosis factor-α. In addition, CTE increased the production of the neurotrophic factor, brain-derived neurotrophic factor, and the M2 phenotype of microglia. The culture medium retained after CTE treatment increased the survival of neurons, thereby indicating the neuroprotective effect of CTE. Our findings indicated that CTE inhibited pro-inflammatory response and increased the neuroprotective ability of microglia. In conclusion, although CTE is known to be a poisonous plant and listed on the FDA poisonous plant database, it can be used as a medicine if the amount is properly controlled. Our results suggested the potential benefits of CTE as a therapeutic agent for different neurodegenerative disorders involving neuroinflammation. Full article
(This article belongs to the Special Issue Plant Toxins and Related Proteins: Pharmacology and Toxicology)
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Open AccessArticle
Defensive Venoms: Is Pain Sufficient for Predator Deterrence?
Toxins 2020, 12(4), 260; https://doi.org/10.3390/toxins12040260 - 17 Apr 2020
Viewed by 841
Abstract
Pain, though unpleasant, is adaptive in calling an animal’s attention to potential tissue damage. A long list of animals representing diverse taxa possess venom-mediated, pain-inducing bites or stings that work by co-opting the pain-sensing pathways of potential enemies. Typically, such venoms include toxins [...] Read more.
Pain, though unpleasant, is adaptive in calling an animal’s attention to potential tissue damage. A long list of animals representing diverse taxa possess venom-mediated, pain-inducing bites or stings that work by co-opting the pain-sensing pathways of potential enemies. Typically, such venoms include toxins that cause tissue damage or disrupt neuronal activity, rendering painful stings honest indicators of harm. But could pain alone be sufficient for deterring a hungry predator? Some venomologists have argued “no”; predators, in the absence of injury, would “see through” the bluff of a painful but otherwise benign sting or bite. Because most algogenic venoms are also toxic (although not vice versa), it has been difficult to disentangle the relative contributions of each component to predator deterrence. Southern grasshopper mice (Onychomys torridus) are voracious predators of arthropods, feeding on a diversity of scorpion species whose stings vary in painfulness, including painful Arizona bark scorpions (Centruroides sculpturatus) and essentially painless stripe-tailed scorpions (Paravaejovis spinigerus). Moreover, southern grasshopper mice have evolved resistance to the lethal toxins in bark scorpion venom, rendering a sting from these scorpions painful but harmless. Results from a series of laboratory experiments demonstrate that painful stings matter. Grasshopper mice preferred to prey on stripe-tailed scorpions rather than bark scorpions when both species could sting; the preference disappeared when each species had their stingers blocked. A painful sting therefore appears necessary for a scorpion to deter a hungry grasshopper mouse, but it may not always be sufficient: after first attacking and consuming a painless stripe-tailed scorpion, many grasshopper mice went on to attack, kill, and eat a bark scorpion even when the scorpion was capable of stinging. Defensive venoms that result in tissue damage or neurological dysfunction may, thus, be required to condition greater aversion than venoms causing pain alone. Full article
(This article belongs to the Special Issue The Behavioral Ecology of Venom)
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Open AccessArticle
The Importance of Allelopathic Picocyanobacterium Synechococcus sp. on the Abundance, Biomass Formation, and Structure of Phytoplankton Assemblages in Three Freshwater Lakes
Toxins 2020, 12(4), 259; https://doi.org/10.3390/toxins12040259 - 16 Apr 2020
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Abstract
The contribution of picocyanobacteria to summer phytoplankton blooms, accompanied by an ecological crisis, is a new phenomenon in Europe. This issue requires careful investigation. We studied allelopathic activity of freshwater picocyanobacterium Synechococcus sp. on phytoplankton assemblages from three freshwater lakes. In this study, [...] Read more.
The contribution of picocyanobacteria to summer phytoplankton blooms, accompanied by an ecological crisis, is a new phenomenon in Europe. This issue requires careful investigation. We studied allelopathic activity of freshwater picocyanobacterium Synechococcus sp. on phytoplankton assemblages from three freshwater lakes. In this study, the allelopathic activity of the Synechococcus sp. on the total abundance, biomass, as well as structure of the phytoplankton assemblages were investigated. Our results indicated that addition of exudates obtained from Synechococcus sp. affected the number of cells and biomass of the phytoplankton communities; the degree of inhibition or stimulation was different for each species, causing a change in the phytoplankton abundance and dominance during the experiment. We observed that some group of organisms (especially cyanobacteria from the genus Aphanothece, Limnothrix, Microcystis, and Synechococcus) showed tolerance for allelopathic compounds produced and released by Synechococcus sp. It is also worth noting that in some samples, Bacillariophyceae (e.g., Amphora pediculus, Navicula pygmaea, and Nitzschia paleacea) were completely eliminated in the experimental treatments, while present in the controls. This work demonstrated that the allelopathic activity exhibited by the Synechococcus sp. is probably one of the major competitive strategies affecting some of the coexisting phytoplankton species in freshwater ecosystems. To our best knowledge this is the first report of the allelopathic activity of Synechococcus sp. in the freshwater reservoirs, and one of the few published works showing allelopathic properties of freshwater picocyanobacteria on coexisting phytoplankton species. Full article
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Open AccessArticle
An In Silico Target Fishing Approach to Identify Novel Ochratoxin A Hydrolyzing Enzyme
Toxins 2020, 12(4), 258; https://doi.org/10.3390/toxins12040258 - 16 Apr 2020
Viewed by 375
Abstract
Ochratoxin A (OTA), a mycotoxin that is of utmost concern in food and feed safety, is produced by fungal species that mainly belong to the Aspergillus and Penicillium genera. The development of mitigation strategies to reduce OTA content along the supply chains is [...] Read more.
Ochratoxin A (OTA), a mycotoxin that is of utmost concern in food and feed safety, is produced by fungal species that mainly belong to the Aspergillus and Penicillium genera. The development of mitigation strategies to reduce OTA content along the supply chains is key to ensuring safer production of food and feed. Enzyme-based strategies are among the most promising methods due to their specificity, efficacy, and multi-situ applicability. In particular, some enzymes are already known for hydrolyzing OTA into ochratoxin alpha (OTα) and phenylalanine (Phe), eventually resulting in detoxification action. Therefore, the discovery of novel OTA hydrolyzing enzymes, along with the advancement of an innovative approach for their identification, could provide a broader basis to develop more effective mitigating strategies in the future. In the present study, a hybrid in silico/in vitro workflow coupling virtual screening with enzymatic assays was applied in order to identify novel OTA hydrolyzing enzymes. Among the various hits, porcine carboxypeptidase B was identified for the first time as an effective OTA hydrolyzing enzyme. The successful experimental endorsement of findings of the workflow confirms that the presented strategy is suitable for identifying novel OTA hydrolyzing enzymes, and it might be relevant for the discovery of other mycotoxin- mitigating enzymes. Full article
(This article belongs to the Special Issue Mycotoxins in Food: Origin and Management of Risk)
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Open AccessArticle
Loxoscelism: Advances and Challenges in the Design of Antibody Fragments with Therapeutic Potential
Toxins 2020, 12(4), 256; https://doi.org/10.3390/toxins12040256 - 16 Apr 2020
Viewed by 491
Abstract
Envenoming due to Loxosceles spider bites still remains a neglected disease of particular medical concern in the Americas. To date, there is no consensus for the treatment of envenomed patients, yet horse polyclonal antivenoms are usually infused to patients with identified severe medical [...] Read more.
Envenoming due to Loxosceles spider bites still remains a neglected disease of particular medical concern in the Americas. To date, there is no consensus for the treatment of envenomed patients, yet horse polyclonal antivenoms are usually infused to patients with identified severe medical conditions. It is widely known that venom proteins in the 30–35 kDa range with sphingomyelinase D (SMasesD) activity, reproduce most of the toxic effects observed in loxoscelism. Hence, we believe that monoclonal antibody fragments targeting such toxins might pose an alternative safe and effective treatment. In the present study, starting from the monoclonal antibody LimAb7, previously shown to target SMasesD from the venom of L. intermedia and neutralize its dermonecrotic activity, we designed humanized antibody V-domains, then produced and purified as recombinant single-chain antibody fragments (scFvs). These molecules were characterized in terms of humanness, structural stability, antigen-binding activity, and venom-neutralizing potential. Throughout this process, we identified some blocking points that can impact the Abs antigen-binding activity and neutralizing capacity. In silico analysis of the antigen/antibody amino acid interactions also contributed to a better understanding of the antibody’s neutralization mechanism and led to reformatting the humanized antibody fragment which, ultimately, recovered the functional characteristics for efficient in vitro venom neutralization. Full article
(This article belongs to the Section Animal Venoms)
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Open AccessArticle
Blooms of Toxic Cyanobacterium Nodularia spumigena in Norwegian Fjords During Holocene Warm Periods
Toxins 2020, 12(4), 257; https://doi.org/10.3390/toxins12040257 - 15 Apr 2020
Viewed by 380
Abstract
In paleoecological studies, molecular markers are being used increasingly often to reconstruct community structures, environmental conditions and ecosystem changes. In this work, nodularin, anabaenopeptins and selected DNA sequences were applied as Nodularia spumigena markers to reconstruct the history of the cyanobacterium in the [...] Read more.
In paleoecological studies, molecular markers are being used increasingly often to reconstruct community structures, environmental conditions and ecosystem changes. In this work, nodularin, anabaenopeptins and selected DNA sequences were applied as Nodularia spumigena markers to reconstruct the history of the cyanobacterium in the Norwegian fjords. For the purpose of this study, three sediment cores collected in Oslofjorden, Trondheimsfjorden and Balsfjorden were analyzed. The lack of nodularin in most recent sediments is consistent with the fact that only one report on the sporadic occurrence and low amounts of the cyanobacterium in Norwegian Fjords in 1976 has been published. However, analyses of species-specific chemical markers in deep sediments showed that thousands of years ago, N. spumigena constituted an important component of the phytoplankton community. The content of the markers in the cores indicated that the biomass of the cyanobacterium increased during the warmer Holocene periods. The analyses of genetic markers were less conclusive; they showed the occurrence of microcystin/nodularin producing cyanobacteria of Nostocales order, but they did not allow for the identification of the organisms at a species level. Full article
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Open AccessReview
Hitchhiking with Nature: Snake Venom Peptides to Fight Cancer and Superbugs
Toxins 2020, 12(4), 255; https://doi.org/10.3390/toxins12040255 - 15 Apr 2020
Cited by 1 | Viewed by 507
Abstract
For decades, natural products in general and snake venoms (SV) in particular have been a rich source of bioactive compounds for drug discovery, and they remain a promising substrate for therapeutic development. Currently, a handful of SV-based drugs for diagnosis and treatment of [...] Read more.
For decades, natural products in general and snake venoms (SV) in particular have been a rich source of bioactive compounds for drug discovery, and they remain a promising substrate for therapeutic development. Currently, a handful of SV-based drugs for diagnosis and treatment of various cardiovascular disorders and blood abnormalities are on the market. Likewise, far more SV compounds and their mimetics are under investigation today for diverse therapeutic applications, including antibiotic-resistant bacteria and cancer. In this review, we analyze the state of the art regarding SV-derived compounds with therapeutic potential, focusing on the development of antimicrobial and anticancer drugs. Specifically, information about SV peptides experimentally validated or predicted to act as antimicrobial and anticancer peptides (AMPs and ACPs, respectively) has been collected and analyzed. Their principal activities both in vitro and in vivo, structures, mechanisms of action, and attempts at sequence optimization are discussed in order to highlight their potential as drug leads. Full article
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Open AccessArticle
Predicting Virulence of Fusarium oxysporum f. sp. Cubense Based on the Production of Mycotoxin Using a Linear Regression Model
Toxins 2020, 12(4), 254; https://doi.org/10.3390/toxins12040254 - 14 Apr 2020
Viewed by 392
Abstract
Fusarium wilt caused by Fusarium oxysporum f.sp. cubense (Foc) is one of the most destructive diseases for banana. For their risk assessment and hazard characterization, it is vital to quickly determine the virulence of Foc isolates. However, this usually takes weeks [...] Read more.
Fusarium wilt caused by Fusarium oxysporum f.sp. cubense (Foc) is one of the most destructive diseases for banana. For their risk assessment and hazard characterization, it is vital to quickly determine the virulence of Foc isolates. However, this usually takes weeks or months using banana plant assays, which demands a better approach to speed up the process with reliable results. Foc produces various mycotoxins, such as fusaric acid (FSA), beauvericin (BEA), and enniatins (ENs) to facilitate their infection. In this study, we developed a linear regression model to predict Foc virulence using the production levels of the three mycotoxins. We collected data of 40 Foc isolates from 20 vegetative compatibility groups (VCGs), including their mycotoxin profiles (LC-MS) and their plant disease index (PDI) values on Pisang Awak plantlets in greenhouse. A linear regression model was trained from the collected data using FSA, BEA and ENs as predictor variables and PDI values as the response variable. Linearity test statistics showed this model meets all linearity assumptions. We used all data to predict PDI with high fitness of the model (coefficient of determination (R2 = 0.906) and adjust coefficient (R2adj = 0.898)) indicating a strong predictive power of the model. In summary, we developed a linear regression model useful for the prediction of Foc virulence on banana plants from the quantification of mycotoxins in Foc strains, which will facilitate quick determination of virulence in newly isolated Foc emerging Fusarium wilt of banana epidemics threatening banana plantations worldwide. Full article
(This article belongs to the Section Mycotoxins)
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Open AccessArticle
Simultaneous Determination of Multiple Mycotoxins in Swine, Poultry and Dairy Feeds Using Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry
Toxins 2020, 12(4), 253; https://doi.org/10.3390/toxins12040253 - 13 Apr 2020
Viewed by 544
Abstract
A reliable, sensitive and accurate multiple mycotoxin method was developed for the simultaneous determination of 17 mycotoxins in swine, poultry and dairy feeds using stable isotope dilution (13C-ISTD) and (ultra)-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A simple QuEChERS-based method (quick, [...] Read more.
A reliable, sensitive and accurate multiple mycotoxin method was developed for the simultaneous determination of 17 mycotoxins in swine, poultry and dairy feeds using stable isotope dilution (13C-ISTD) and (ultra)-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A simple QuEChERS-based method (quick, easy, cheap, effective, rugged and safe) was developed consisting of soaking with a solution of 1% formic acid followed by extraction with acetonitrile, clean-up with C18 sorbent and finally adding 13C-ISTD before the UHPLC-MS/MS analysis. The chromatographic condition was optimized for separation and detection of the 17 mycotoxins using gradient elution. The method’s performance complied with the SANTE/11813/2017 standard and had mean recovery accuracies in the range 70%–120% and precision testing of % relative standard deviation (RSD) ≤ 20%. The limit of detection and limit of quantification values ranged from 0.25 to 40.0 ng/g and 0.5 to 100.0 ng/g, respectively. Finally, the method was applied to analyze feed samples, with the results showing that fumonisins, zearalenone, aflatoxin B1 and deoxynivalenol were the most prevalent mycotoxins contaminating the feed samples. Full article
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Open AccessArticle
A Bacillus thuringiensis Chitin-Binding Protein is Involved in Insect Peritrophic Matrix Adhesion and Takes Part in the Infection Process
Toxins 2020, 12(4), 252; https://doi.org/10.3390/toxins12040252 - 13 Apr 2020
Viewed by 401
Abstract
Bacillus thuringiensis (Bt) is used for insect pest control, and its larvicidal activity is primarily attributed to Cry toxins. Other factors participate in infection, and limited information is available regarding factors acting on the peritrophic matrix (PM). This study aimed to investigate the [...] Read more.
Bacillus thuringiensis (Bt) is used for insect pest control, and its larvicidal activity is primarily attributed to Cry toxins. Other factors participate in infection, and limited information is available regarding factors acting on the peritrophic matrix (PM). This study aimed to investigate the role of a Bt chitin-binding protein (CBPA) that had been previously shown to be expressed at pH 9 in vitro and could therefore be expressed in the alkaline gut of lepidopteron larvae. A ∆cbpA mutant was generated that was 10-fold less virulent than wild-type Bt HD73 towards Ostrinia furnacalis neonate larvae, indicating its important role in infection. Purified recombinant Escherichia coli CBPA was shown to have a chitin affinity, thus indicating a possible interaction with the chitin-rich PM. A translational GFP–CBPA fusion elucidated the localization of CBPA on the bacterial surface, and the transcriptional activity of the promoter PcbpA was immediately induced and confirmed at pH 9. Next, in order to connect surface expression and possible in vivo gut activity, last instar Galleria mellonella (Gm) larvae (not susceptible to Bt HD-73) were used as a model to follow CBPA in gut expression, bacterial transit, and PM adhesion. CBPA-GFP was quickly expressed in the Gm gut lumen, and more Bt HD73 strain bacteria adhered to the PM than those of the ∆cbpA mutant strain. Therefore, CBPA may help to retain the bacteria, via the PM binding, close to the gut surface and thus takes part in the early steps of Bt gut interactions. Full article
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Open AccessArticle
Comparative Effectiveness of Botulinum Toxin Injection for Chronic Shoulder Pain: A Meta-Analysis of Randomized Controlled Trials
Toxins 2020, 12(4), 251; https://doi.org/10.3390/toxins12040251 - 12 Apr 2020
Viewed by 636
Abstract
Botulinum toxin (BoNT) injection is regarded as a promising treatment for musculoskeletal pain. However, its efficacy for treating chronic shoulder pain remains unclear. We investigated the effectiveness of BoNT injections for chronic shoulder pain by conducting a systematic search of electronic databases up [...] Read more.
Botulinum toxin (BoNT) injection is regarded as a promising treatment for musculoskeletal pain. However, its efficacy for treating chronic shoulder pain remains unclear. We investigated the effectiveness of BoNT injections for chronic shoulder pain by conducting a systematic search of electronic databases up to March 2020 for randomized control trials (RCTs) that used BoNT injections for chronic shoulder pain treatment. The primary outcome was the between-group comparison of pain reduction, quantified by the standardized mean difference (SMD). Nine RCTs comprising 666 patients were included and divided into two groups: one group with shoulder joint pain (n = 182) and the other group with shoulder myofascial pain (n = 484). Regarding shoulder joint pain, the efficacy of BoNT injections was similar to that of the reference treatment (SMD: −0.605, 95% confidence level [CI]: −1.242 to 0.032 versus saline; SMD: −0.180, 95% CI: −0.514 to 0.153 versus corticosteroids) at one month post-intervention, and was superior (SMD: −0.648, 95% CI: −0.1071 to −0.225 versus corticosteroids) between one and three months. Likewise, in terms of shoulder myofascial pain, the effectiveness of BoNT injections did not differ from the reference treatment (SMD: −0.212, 95% CI: −0.551 to 0.127 versus saline; SMD: 0.665, 95% CI: −0.260 to 1.590 versus dry needling and SMD: 1.093; 95% CI: 0.128 to 2.058 versus lidocaine) at one month post- intervention, and appeared superior (SMD: −0.314, 95% CI: −0.516 to −0.111 versus saline) between one and three months. Our meta-analysis revealed that BoNT injections could be a safe and effective alternative for patients with chronic shoulder pain. Full article
(This article belongs to the Special Issue Botulinum Neurotoxin Injection)
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Open AccessArticle
Neurotoxin Merging: A Strategy Deployed by the Venom of the Spider Cupiennius salei to Potentiate Toxicity on Insects
Toxins 2020, 12(4), 250; https://doi.org/10.3390/toxins12040250 - 12 Apr 2020
Viewed by 502
Abstract
The venom of Cupiennius salei is composed of dozens of neurotoxins, with most of them supposed to act on ion channels. Some insecticidal monomeric neurotoxins contain an α-helical part besides their inhibitor cystine knot (ICK) motif (type 1). Other neurotoxins have, besides the [...] Read more.
The venom of Cupiennius salei is composed of dozens of neurotoxins, with most of them supposed to act on ion channels. Some insecticidal monomeric neurotoxins contain an α-helical part besides their inhibitor cystine knot (ICK) motif (type 1). Other neurotoxins have, besides the ICK motif, an α-helical part of an open loop, resulting in a heterodimeric structure (type 2). Due to their low toxicity, it is difficult to understand the existence of type 2 peptides. Here, we show with the voltage clamp technique in oocytes of Xenopus laevis that a combined application of structural type 1 and type 2 neurotoxins has a much more pronounced cytolytic effect than each of the toxins alone. In biotests with Drosophila melanogaster, the combined effect of both neurotoxins was enhanced by 2 to 3 log units when compared to the components alone. Electrophysiological measurements of a type 2 peptide at 18 ion channel types, expressed in Xenopus laevis oocytes, showed no effect. Microscale thermophoresis data indicate a monomeric/heterodimeric peptide complex formation, thus a direct interaction between type 1 and type 2 peptides, leading to cell death. In conclusion, peptide mergers between both neurotoxins are the main cause for the high cytolytic activity of Cupiennius salei venom. Full article
(This article belongs to the Special Issue Animal Venoms and Their Components: Molecular Mechanisms of Action)
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Open AccessArticle
Ochratoxin A in Beers Marketed in Portugal: Occurrence and Human Risk Assessment
Toxins 2020, 12(4), 249; https://doi.org/10.3390/toxins12040249 - 12 Apr 2020
Viewed by 440
Abstract
Ochratoxin A (OTA) is produced by fungi present in several agricultural products with much relevance to food safety. Since this mycotoxin is widely found in cereals, beer has a potential contamination risk. Therefore, it was deemed essential to quantify, for the first time, [...] Read more.
Ochratoxin A (OTA) is produced by fungi present in several agricultural products with much relevance to food safety. Since this mycotoxin is widely found in cereals, beer has a potential contamination risk. Therefore, it was deemed essential to quantify, for the first time, the levels of OTA in beer, a cereal-based product that is marketed in Portugal, as well as to calculate the human estimated weekly intake (EWI) and risk assessment. A total of 85 samples were analyzed through immunoaffinity clean-up, followed by liquid chromatography-fluorescence detection (LC-FD). This analytical methodology allowed a limit of quantification (LOQ) of 0.43 µg/L. The results showed that 10.6% were contaminated at levels ranging between <LOQ and 11.25 µg/L, with an average of 3.14 ± 4.09 µg/L. Samples of industrial production presented lower incidence and contamination levels than homemade and craft beers. On what concerns human risk, the calculated EWI was significantly lower than the tolerable weekly intake (TWI). However, in the worst case scenario, based on a high concentration, the rate EWI/TWI was 138.01%. Full article
(This article belongs to the Special Issue Mycotoxins Study: Toxicology, Identification and Control)
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Open AccessArticle
Phylogenomic Analysis of Secondary Metabolism in the Toxic Cyanobacterial Genera Anabaena, Dolichospermum and Aphanizomenon
Toxins 2020, 12(4), 248; https://doi.org/10.3390/toxins12040248 - 11 Apr 2020
Viewed by 551
Abstract
Cyanobacteria produce an array of toxins that pose serious health risks to humans and animals. The closely related diazotrophic genera, Anabaena, Dolichospermum and Aphanizomenon, frequently form poisonous blooms in lakes and brackish waters around the world. These genera form a complex [...] Read more.
Cyanobacteria produce an array of toxins that pose serious health risks to humans and animals. The closely related diazotrophic genera, Anabaena, Dolichospermum and Aphanizomenon, frequently form poisonous blooms in lakes and brackish waters around the world. These genera form a complex now termed the Anabaena, Dolichospermum and Aphanizomenon (ADA) clade and produce a greater array of toxins than any other cyanobacteria group. However, taxonomic confusion masks the distribution of toxin biosynthetic pathways in cyanobacteria. Here we obtained 11 new draft genomes to improve the understanding of toxin production in these genera. Comparison of secondary metabolite pathways in all available 31 genomes for these three genera suggests that the ability to produce microcystin, anatoxin-a, and saxitoxin is associated with specific subgroups. Each toxin gene cluster was concentrated or even limited to a certain subgroup within the ADA clade. Our results indicate that members of the ADA clade encode a variety of secondary metabolites following the phylogenetic clustering of constituent species. The newly sequenced members of the ADA clade show that phylogenetic separation of planktonic Dolichospermum and benthic Anabaena is not complete. This underscores the importance of taxonomic revision of Anabaena, Dolichospermum and Aphanizomenon genera to reflect current phylogenomic understanding. Full article
(This article belongs to the Section Marine and Freshwater Toxins)
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Open AccessArticle
Ultra-Trace Analysis of Cyanotoxins by Liquid Chromatography Coupled to High-Resolution Mass Spectrometry
Toxins 2020, 12(4), 247; https://doi.org/10.3390/toxins12040247 - 11 Apr 2020
Viewed by 608
Abstract
The increasing frequency of episodes of harmful algal blooms of cyanobacterial origin is a risk to ecosystems and human health. The main human hazard may arise from drinking water supply and recreational water use. For this reason, efficient multiclass analytical methods are needed [...] Read more.
The increasing frequency of episodes of harmful algal blooms of cyanobacterial origin is a risk to ecosystems and human health. The main human hazard may arise from drinking water supply and recreational water use. For this reason, efficient multiclass analytical methods are needed to assess the level of cyanotoxins in water reservoirs and tackle these problems. This work describes the development of a fast, sensitive, and robust analytical method for multiclass cyanotoxins determination based on dual solid-phase extraction (SPE) procedure using a polymeric cartridge, Oasis HLB (Waters Corporation, Milford, MA, USA), and a graphitized non-porous carbon cartridge, SupelcleanTM ENVI-CarbTM (Sigma-Aldrich, St. Louis, MO, USA), followed by ultra-high-performance liquid chromatography high-resolution mass spectrometry (SPE-UHPLC-HRMS). This method enabled the analysis of cylindrospermopsin, anatoxin-a, nodularin, and seven microcystins (MC-LR, MC-RR, MC-YR, MC-LA, MC-LY, MC-LW, MC-LF). The method limits of detection (MLOD) of the validated approach were between 4 and 150 pg/L. The analytical method was applied to assess the presence of the selected toxins in 21 samples collected in three natural water reservoirs in the Ter River in Catalonia (NE of Spain) used to produce drinking water for Barcelona city (Spain). Full article
(This article belongs to the Special Issue Cyanobacterial Toxins: Their Occurrence, Detection and Removal)
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Open AccessArticle
CRISPR-Mediated Knockout of the ABCC2 Gene in Ostrinia furnacalis Confers High-Level Resistance to the Bacillus thuringiensis Cry1Fa Toxin
Toxins 2020, 12(4), 246; https://doi.org/10.3390/toxins12040246 - 11 Apr 2020
Cited by 1 | Viewed by 543
Abstract
The adoption of transgenic crops expressing Bacillus thuringiensis (Bt) insecticidal crystalline (Cry) proteins has reduced insecticide application, increased yields, and contributed to food safety worldwide. However, the efficacy of transgenic Bt crops is put at risk by the adaptive resistance evolution of target [...] Read more.
The adoption of transgenic crops expressing Bacillus thuringiensis (Bt) insecticidal crystalline (Cry) proteins has reduced insecticide application, increased yields, and contributed to food safety worldwide. However, the efficacy of transgenic Bt crops is put at risk by the adaptive resistance evolution of target pests. Previous studies indicate that resistance to Bacillus thuringiensis Cry1A and Cry1F toxins was genetically linked with mutations of ATP-binding cassette (ABC) transporter subfamily C gene ABCC2 in at least seven lepidopteran insects. Several strains selected in the laboratory of the Asian corn borer, Ostrinia furnacalis, a destructive pest of corn in Asian Western Pacific countries, developed high levels of resistance to Cry1A and Cry1F toxins. The causality between the O. furnacalis ABCC2 (OfABCC2) gene and resistance to Cry1A and Cry1F toxins remains unknown. Here, we successfully generated a homozygous strain (OfC2-KO) of O. furnacalis with an 8-bp deletion mutation of ABCC2 by the CRISPR/Cas9 approach. The 8-bp deletion mutation results in a frame shift in the open reading frame of transcripts, which produced a predicted protein truncated in the TM4-TM5 loop region. The knockout strain OfC2-KO showed much more than a 300-fold resistance to Cry1Fa, and low levels of resistance to Cry1Ab and Cry1Ac (<10-fold), but no significant effects on the toxicities of Cry1Aa and two chemical insecticides (abamectin and chlorantraniliprole), compared to the background NJ-S strain. Furthermore, we found that the Cry1Fa resistance was autosomal, recessive, and significantly linked with the 8-bp deletion mutation of OfABCC2 in the OfC2-KO strain. In conclusion, in vivo functional investigation demonstrates the causality of the OfABCC2 truncating mutation with high-level resistance to the Cry1Fa toxin in O. furnacalis. Our results suggest that the OfABCC2 protein might be a functional receptor for Cry1Fa and reinforces the association of this gene to the mode of action of the Cry1Fa toxin. Full article
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