Toxic effects of Fusarium mycotoxin butenolide on rat myocardium and primary culture of cardiac myocytes

The Role of Nitrogen Fertilization on the Occurrence of Regulated, Modified and Emerging Mycotoxins and Fungal Metabolites in Maize Kernels

The European Food Safety Authority is currently evaluating the risks related to the presence of emerging mycotoxins in food and feeds. The aim of this study was to investigate the role of soil fertility, resulting from different nitrogen fertilization rates, on the contamination of regulated mycotoxins and emerging fungal metabolites in maize grains. The trial was carried out in the 2012–2013 growing seasons as part of a long-term (20-year) experimental platform area in North-West Italy, where five different N rates, ranging from 0 to 400 kg N ha−1, were applied to maize each year. Maize samples were analyzed by means of a dilute-and-shoot multi-mycotoxin LC-MS/MS method, and more than 25 of the most abundant mycotoxins and fungal metabolites were detected. Contamination by fumonisins and other fungal metabolites produced by Fusarium spp. of the section Liseola was observed to have increased in soils that showed a poor fertility status. On the other hand, an overload of nitrogen fertilization was generally associated with higher deoxynivalenol and zearalenone contamination in maize kernels, as well as a higher risk of other fungal metabolites produced by Fusarium spp. sections Discolor and Roseum. A balanced application of N fertilizer, in accordance with maize uptake, generally appears to be the best solution to guarantee an overall lower contamination by regulated mycotoxins and emerging fungal metabolites.

Relevant Fusarium Mycotoxins in Malt and Beer

Mycotoxins are secondary fungal metabolites of high concern in the food and feed industry. Their presence in many cereal-based products has been numerously reported. Beer is the most consumed alcoholic beverage worldwide, and Fusarium mycotoxins originating from the malted and unmalted cereals might reach the final product. This review aims to describe the possible Fusarium fungi that could infect the cereals used in beer production, the transfer of mycotoxins throughout malting and brewing as well as an insight into the incidence of mycotoxins in the craft beer segment of the industry. Studies show that germination is the malting step that can lead to a significant increase in the level of all Fusarium mycotoxins. The first step of mashing (45 °C) has been proved to possess the most significant impact in the transfer of hydrophilic toxins from the grist into the wort. However, during fermentation, a slight reduction of deoxynivalenol, and especially of zearalenone, is achieved. This review also highlights the limited research available on craft beer and the occurrence of mycotoxins in these products.

Fate of regulated, masked, emerging mycotoxins and secondary fungal metabolites during different large-scale maize dry-milling processes

The use of maize in the food chain could be mainly limited due to its contamination by mycotoxins. As scarce information is available, the current study is aimed at collecting new data on the co-occurrence and the fate of the most frequent masked, modified and emerging mycotoxins and other second fungal metabolites in maize food products and by-products. Three maize lots, obtained in different growing seasons, were processed using two different degermination processes, a dry-degermination system or a tempering-degermination one, in order to compare the interaction between mycotoxins and the dry-milling management system. Whole grain before and after cleaning, and all the products and the by-products were sampled twice for each lot and were subjected to a multi-mycotoxin LC-MS/MS analysis. More than 30 mycotoxins and other fungal metabolites, including masked or modified forms, co-occurred in all the maize milling fractions. Grain cleaning reduced all the detected fungal metabolites by 1.2-2 times, compared to the grain before cleaning. Animal feed flour showed the highest content of almost all the mycotoxins and fungal metabolites, with a consequent negative impact on animal health. Considering that for all the mycotoxins and fungal metabolites an inverse relationship with particle size was observed, flaking grits represented the healthiest maize products with the least contamination level, while the abatement was always lower for maize flour. Furthermore, the metabolites were variably redistributed in the maize fractions. The total aflatoxins, kojic acid, deoxynivalenol and its modified form, culmorin, and its associated forms, butenolide, fusaproliferin, fusaric acid, fusarinolic acid and, in some cases, zearalenone and its modified forms, and fusarin C were found to be concentrated significantly in the germ. Some of them also had a greater permanence in the maize food fractions and a weaker decontamination, both of which point to a higher risk of exposure for the end consumers. The co-occurrence of a such a high number of mycotoxins and fungal metabolites and their different fates during the dry-milling process have never been described before.

Keshan Disease: A Potentially Fatal Endemic Cardiomyopathy in Remote Mountains of China

Keshan disease (KD) as an endemic, highly lethal cardiomyopathy, first reported in northeast China's Keshan County in 1935. The clinical manifestations of patients with KD include primarily congestive heart failure, acute heart failure, and cardiac arrhythmia. Even though some possible etiologies, such as viral infection, fungal infection, microelement deficiency, and malnutrition, have been reported, the exact causes of KD remain poorly known. The endemic areas where KD is found are remote and rural, and many are poor and mountainous places where people are the most socioeconomically disadvantaged in terms of housing, income, education, transportation, and utilization of health services. To date, KD is a huge burden to and severely restricts the economic development of the local residents and health systems of the endemic areas. Although efforts have been made by the government to control, treat, and interrupt disease transmission, the cure for or complete eradication of KD still requires global attention. For this reason, in this review, we systematically describe the etiological hypothesis, clinical manifestations, incidence characteristics, and treatment of KD, to facilitate the better understanding of and draw more attention to this non-representative cardiovascular disease, with the aim of accelerating its elimination.

Suppression of Trichothecene-Mediated Immune Response by the Fusarium Secondary Metabolite Butenolide in Human Colon Epithelial Cells

Butenolide (BUT, 4-acetamido-4-hydroxy-2-butenoic acid gamma-lactone) is a secondary metabolite produced by several Fusarium species and is co-produced with the major trichothecene mycotoxin deoxynivalenol (DON) on cereal grains throughout the world. BUT has low acute toxicity and only very limited occurrence and exposure data are available. The intestinal epithelium represents the first physiological barrier against food contaminants. We aimed to elucidate the intestinal inflammatory response of the human, non-cancer epithelial HCEC-1CT cells to BUT and to characterize potential combinatory interactions with co-occurring trichothecenes, such as DON and NX-3. Using a reporter gene approach, BUT (≥5 μM, 20 h) was found to decrease lipopolysaccharide (LPS; 10 ng/mL) induced nuclear factor kappa B (NF-κB) activation in a dose-dependent manner, and in combinatory treatments BUT represses trichothecene-induced enhancement of this important inflammatory pathway. Analysis of transcription and secretion levels of NF-κB-dependent, pro-inflammatory cytokines, revealed a significant down-regulation of IL-1β, IL-6, and TNF-α in IL-1β-stimulated (25 ng/mL) HCEC-1CT cells after BUT exposure (10 μM). Trichothecene-induced expression of pro-inflammatory cytokines by the presence of 1 μM DON or NX-3 was substantially suppressed in the presence of 10 μM BUT. The emerging mycotoxin BUT has the ability to suppress NF-κB-induced intestinal inflammatory response mechanisms and to modulate substantially the immune responsiveness of HCEC-1CT cells after trichothecene treatment. Our results suggest that BUT, present in naturally occurring mixtures of Fusarium fungal metabolites, should be increasingly monitored, and the mechanism of inhibition of NF-κB that might affect the pathogenesis or progression of intestinal inflammatory disorders, should be further investigated.

Dynamic network inference and association computation discover gene modules regulating virulence, mycotoxin and sexual reproduction in Fusarium graminearum

Background

The filamentous fungus Fusarium graminearum causes devastating crop diseases and produces harmful mycotoxins worldwide. Understanding the complex F. graminearum transcriptional regulatory networks (TRNs) is vital for effective disease management. Reconstructing F. graminearum dynamic TRNs, an NP (non-deterministic polynomial) -hard problem, remains unsolved using commonly adopted reductionist or co-expression based approaches. Multi-omic data such as fungal genomic, transcriptomic data and phenomic data are vital to but so far have been largely isolated and untapped for unraveling phenotype-specific TRNs.

Results

Here for the first time, we harnessed these resources to infer global TRNs for F. graminearum using a Bayesian network based algorithm called “Module Networks”. The inferred TRNs contain 49 regulatory modules that show condition-specific gene regulation. Through a thorough validation based on prior biological knowledge including functional annotations and TF binding site enrichment, our network prediction displayed high accuracy and concordance with existing knowledge. One regulatory module was partially validated using network perturbations caused by Tri6 and Tri10 gene disruptions, as well as using Tri6 Chip-seq data. We then developed a novel computational method to calculate the associations between modules and phenotypes, and identified major module groups regulating different phenotypes. As a result, we identified TRN subnetworks responsible for F. graminearum virulence, sexual reproduction and mycotoxin production, pinpointing phenotype-associated modules and key regulators. Finally, we found a clear compartmentalization of TRN modules in core and lineage-specific genomic regions in F. graminearum, reflecting the evolution of the TRNs in fungal speciation.

Conclusions

This system-level reconstruction of filamentous fungal TRNs provides novel insights into the intricate networks of gene regulation that underlie key processes in F. graminearum pathobiology and offers promise for the development of improved disease control strategies.

Impact of glutathione modulation on the toxicity of the Fusarium mycotoxins deoxynivalenol (DON), NX-3 and butenolide in human liver cells

DON, NX-3 and butenolide (BUT) are secondary metabolites formed by Fusarium graminearum. Evidence for formation of DON-glutathione adducts exists in plants, and also in human liver (HepG2) cells mass spectrometric evidence for GSH-adduct formation was reported. NX-3 is a DON derivative lacking structural features for Thiol-Michael addition, while BUT has the structural requirements (conjugated double bond and keto group). In the present study, we addressed whether these structural differences affect levels of intracellular reactive oxygen species in HepG2 cells, and if intracellular GSH levels influence toxic effects induced by DON, NX-3 and BUT. Pre-treatment with an inhibitor of GSH bio-synthesis, L-buthionine-[S,R]-sulfoximine, aggravated substantially BUT-induced cytotoxicity (≥50 μM, 24 h), but only marginally affected the cytotoxicity of DON and NX-3 indicating that GSH-mediated detoxification is of minor importance in HepG2 cells. We further investigated whether BUT, a compound inducing alone low oral toxicity, might affect the toxicity of DON. Under different experimental designs with respect to pre- and/or co-incubations, BUT was found to contribute to the combinatorial cytotoxicity, exceeding the toxic effect of DON alone. The observed combinatorial effects underline the potential contribution of secondary metabolites like BUT, considered to be alone of low toxicological relevance, to the toxicity of DON or structurally related trichothecenes, arguing for further studies on the toxicological relevance of naturally occurring mixtures.

Emerging Mycotoxins: Beyond Traditionally Determined Food Contaminants

Modern analytical techniques can determine a multitude of fungal metabolites contaminating food and feed. In addition to known mycotoxins, for which maximum levels in food are enforced, also currently unregulated, so-called "emerging mycotoxins" were shown to occur frequently in agricultural products. The aim of this review is to critically discuss the relevance of selected emerging mycotoxins to food and feed safety. Acute and chronic toxicity as well as occurrence data are presented for enniatins, beauvericin, moniliformin, fusaproliferin, fusaric acid, culmorin, butenolide, sterigmatocystin, emodin, mycophenolic acid, alternariol, alternariol monomethyl ether, and tenuazonic acid. By far not all of the detected compounds are toxicologically relevant at their naturally occurring levels and are therefore of little or no health concern to consumers. Still, gaps in knowledge have been identified for several compounds. These gaps should be closed by the scientific community in the coming years to allow a proper risk assessment.

Zinc-induced metallothionein overexpression prevents doxorubicin toxicity in cardiomyocytes by regulating the peroxiredoxins

1. Cardiotoxicity is an important factor that limits the clinical use of doxorubicin (Dox). Metallothionein (MT) can antagonize the Dox-induced cardiotoxicity. Using a proteomics approach we have detected that major peroxiredoxins (Prxs) may be involved in this process. In the present study, we further investigate the mechanisms of the MT effects against Dox-induced cytotoxicity and the interactions between MT and Prxs. 2. We have established a primary cardiomyocyte culture system from MT-I/II null (MT(-/-)) and corresponding wild type (MT(+/+)) neonatal mice, and pretreated the MT(+/+) cardiomyocytes with ZnCl2 to establish the MT overexpression cardiomyocyte model. 3. Based on the results, in MT(+/+) cardiomyocytes, ZnCl2 pretreatment significantly increased the cardiomyocytes MT levels and inhibited the cardiotoxicity of Dox; it can resist LDH leakage, cardiomyocyte apoptosis, DNA damage, ROS accumulation and inhibit the decrease in activity of antioxidant enzymes induced by Dox. Moreover, ZnCl2 enhanced the expression of Prx-2, -3, -5 and -6, it can inhibit the expression of Prxs decrease in MT(+/+) cardiomyocytes induced by Dox, but had no effect in MT(-/-) cardiomyocytes. 4. Therefore, the present study suggests that ZnCl2 can protect the cardiomyocytes from the Dox-induced oxidative injury and can inhibit the changes in Prxs expression through induced MT overexpression.

Enhanced toxicity and ROS generation by doxorubicin in primary cultures of cardiomyocytes from neonatal metallothionein-I/II null mice

The clinical use of doxorubicin (Dox), a potent anticancer drug, is limited by its concurrent dose-dependent cardiotoxicity. We previously found that metallothionein-I/II (MT-I/II) null mice are more vulnerable to Dox-induced cardiomyopathy, but it is unknown whether depletion of MT would sensitize cardiomyocytes to Dox toxicity in vitro since the protective effect of MT still remains controversial. In the present study, a primary culture system of cardiomyocytes from neonatal MT-I/II null (MT(-/-)) and corresponding wild type (MT(+/+)) mice was established to unequivocally determine the effect of MT deficiency on Dox-induced toxicity. MT concentrations in the MT(-/-) cardiomyocytes were about 2.5-fold lower than those in MT(+/+) cardiomyocytes. MT(-/-) cardiomyocytes were more sensitive to Dox-induced cytotoxicity than MT(+/+) cardiomyocytes as measured by morphological alterations, lactate dehydrogenase leakage, cell viability, and apoptosis. Dox time- and concentration-dependently increased reactive oxygen species (ROS) formation in MT(+/+) cardiomyocytes, and this effect was exaggerated in MT(-/-) cardiomyocytes. Antioxidant N-acetylcysteine (NAC) and glutathione (GSH) significantly rescued MT(+/+) but not MT(-/-)cardiomyocytes from Dox-induced cell death and ROS generation. These findings suggest that basal MT provide protection against Dox-induced toxicity in cardiomyocytes, particularly highlight the important role of MT as a cellular antioxidant on scavenging ROS.

The African Fusarium/maize disease

There is a general but rather vague feeling that the use of maize (corn) as a staple foodstuff by black rural Africans is somehow a factor in, or is linked to, chronic disease found in these populations. An attempt is made in this review to consider the evidence for this connection and to identify what is actually the root of the problem. The main thrust of the argument to explain this perception is that maize is routinely contaminated with fungi and of these Fusarium verticillioides is found in maize throughout the world. Evidence is presented to this effect and, further, of the mycotoxins found in maize, the fumonisins are the most common and at the highest levels. Various animal chronic diseases arising from the consumption of contaminated maize are reviewed and possible human conditions listed, in some cases related to the known animal ones. A brief overview of the complicated cellular mechanisms of fumonisin B1 is given and it is concluded that the prime suspect in what might be called "the maize disease" can be attributed to the ingestion of this mycotoxin, sometimes in combination with other synergist mycotoxins and other disease factors, such as smoking and drinking.