Fusaric acid and modification of the subchronic toxicity to rats of fumonisins in F. moniliforme culture material

Fusaric acid inhibits proliferation and induces apoptosis through triggering endoplasmic reticulum stress in MCF-7 human breast cancer cells

Breast cancer has replaced lung cancer to be the leading cancer in the world. Currently, chemotherapy is still the major method for breast cancer therapy, but its overall effect remains unsatisfactory. Fusaric acid (FSA), a mycotoxin derived from fusarium species, has shown potency against the proliferation of several types of cancer cells, but its effect on breast cancer cells has not been examined. Therefore, we explored the possible effect of FSA on the proliferation of MCF-7 human breast cancer cells and uncovered the underlying mechanism in the present study. Our results showed that FSA has a strong anti-proliferative effect on MCF-7 cells through inducing ROS production, apoptosis and arresting cell cycle at G2/M transition phase. Additionally, FSA triggers endoplasmic reticulum (ER) stress in the cells. Notably, the cell cycle arrest and apoptosis inducing effect of FSA can be attenuated by ER stress inhibitor, tauroursodeoxycholic acid. Our study provide evidence that FSA is a potent proliferation inhibition and apoptosis inducing agent against human breast cancer cells, and the possible mechanism involves the activation of ER stress signaling pathways. Our study may highlight that FSA is promising for the future in vivo study and development of potential agent for breast cancer therapy.

Production and characterization of a broad-spectrum antimicrobial 5-butyl-2-pyridine carboxylic acid from Aspergillus fumigatus nHF-01

The present study aims at the production optimization, purification, and characterization of a potent broad-spectrum antimicrobial compound (AMC) produced by Aspergillus fumigatus nHF-01 (GenBank Ac. No. MN190286). The culture conditions were optimized for a higher amount of AMC. The AMC was solvent extracted and characterized by UV–Vis, FT–IR, ESI–MS, and ¹H-NMR spectroscopy. The MIC, MBC and mode of action were determined against a set of Gram-positive and Gram-negative human pathogenic bacteria. Its antibiofilm, synergistic and cytotoxic effects were also tested. The putative target site of action was evaluated through in silico molecular docking study. The stain A. fumigatus nHF-01 produced the maximum AMC (5-butyl-2-pyridine carboxylic acid) in 2% MEB (w/v) and 4% YE (w/v) at pH 6.0 and 20 °C temperature with 100 rpm agitation for ten days. It caused complete lethality of the Gram-positive and Gram-negative human pathogenic bacteria at a 129 µg/mL dose by rupture and entire dissolution of cell integrity. It showed moderate antibiofilm activity and had a synergistic activity with streptomycin and additive effects with ciprofloxacin and vancomycin. It targets a respiratory enzyme, Quinol-Fumarate Reductase (1l0v), with the highest binding affinities. It had cytotoxicity against human lung carcinoma A549 cell line and was stable up to 100 °C. Thus, the study revealed that the strain A. fumigatus nHF-01 produces a potent broad-spectrum AMC 5-butyl-2-pyridine carboxylic acid that could be used against human food and topical pathogenic bacteria. This is the first report of such a compound produced from the A. fumigatus.

Evaluation of the cytotoxic and genotoxic effects of mycotoxin fusaric acid

Fusaric acid (FA) is produced by several Fusarium species and is commonly found in grains. This investigation was performed to evaluate the cytotoxic and genotoxic effects of FA either in human cervix carcinoma (HeLa) cell line using 3-(4,5-dimethylthiazolyl-2)-2,5 diphenyltetrazolium bromide (MTT) assay and in human lymphocytes using chromosome aberrations (CAs), sister chromatid exchanges (SCEs), micronuclei (MN) as well as comet assay in vitro. The cells were treated with 0.78, 1.56, 3.125, 6.25, 12.50, 25, 50, 100, 200, and 400 µg/mL concentrations of FA. It has potent cytotoxic effect on HeLa cell line measured by MTT assay especially at higher concentrations (200, 400 µg/mL). The half of inhibitory concentration (IC₅₀) evidenced by FA in the HeLa cells was 200 μg/mL at 24 h and between 200 and 400 μg/mL at 48 h. It was also observed that FA produced a significant decrease in mitotic index (MI) at 12.50 µg/mL compared to solvent control. Furthermore, it indicated a cytotoxic effect at the concentrations ranging from 25 to 400 μg/mL in human lymphocytes. The results of this research point out that being exposed to FA at high concentrations show cytotoxicity. Besides FA induced comet tail intensity at 3.125, 6.25, and 12.50 µg/mL concentrations in isolated human lymphocytes. On the other hand, no genotoxic effects were seen in human lymphocytes in vitro using CA, SCE and MN assays.

Fusaric Acid Induces DNA Damage and Post-Translational Modifications of p53 in Human Hepatocellular Carcinoma (HepG2 ) Cells

Fusaric acid (FA), a common fungal contaminant of maize, is known to mediate toxicity in plants and animals; however, its mechanism of action is unclear. p53 is a tumor suppressor protein that is activated in response to cellular stress. The function of p53 is regulated by post-translational modifications-ubiquitination, phosphorylation, and acetylation. This study investigated a possible mechanism of FA induced toxicity in the human hepatocellular carcinoma (HepG₂ ) cell line. The effect of FA on DNA integrity and post-translational modifications of p53 were investigated. Methods included: (a) culture and treatment of HepG₂ cells with FA (IC₅₀ : 580.32 μM, 24 h); (b) comet assay (DNA damage); (c) Western blots (protein expression of p53, MDM2, p-Ser-15-p53, a-K382-p53, a-CBP (K1535)/p300 (K1499), HDAC1 and p-Ser-47-Sirt1); and (d) Hoechst 33342 assay (apoptosis analysis). FA caused DNA damage in HepG₂ cells relative to the control (P < 0.0001). FA decreased the protein expression of p53 (0.24-fold, P = 0.0004) and increased the expression of p-Ser-15-p53 (12.74-fold, P = 0.0126) and a-K382-p53 (2.24-fold, P = 0.0096). This occurred despite the significant decrease in the histone acetyltransferase, a-CBP (K1535)/p300 (K1499) (0.42-fold, P = 0.0023) and increase in the histone deacetylase, p-Ser-47-Sirt1 (1.22-fold, P = 0.0020). The expression of MDM2, a negative regulator of p53, was elevated in the FA treatment compared to the control (1.83-fold, P < 0.0001). FA also inhibited cell proliferation and induced apoptosis in HepG₂ cells as evidenced by the Hoechst assay. Together, these results indicate that FA is genotoxic and post-translationally modified p53 leading to HepG₂ cell death. J. Cell. Biochem. 118: 3866-3874, 2017. © 2017 Wiley Periodicals, Inc.

Fusaric acid induces oxidative stress and apoptosis in human cancerous oesophageal SNO cells

Oesophageal cancer (OC) is a global problem incrementally incident among black South African males. The high incidence of OC may be due to the consumption of corn as a staple, often contaminated with mycotoxins. Fusaric acid (FA), a neglected mycotoxin, is known to disrupt mitochondrial energy metabolism, chelates divalent metal cations and induces cell death in plants. This study investigated FA-induced cytotoxicity and apoptotic induction in the SNO OC cell line. Cells were treated with FA (IC₅₀ = 78.81 μg/mL; 24 h; MTT assay) and assayed for oxidative stress and membrane damage (TBARS, LDH cytotoxicity and glutathione), apoptotic induction (ATP levels, caspase-8, -9, -3/7 activities) (Luminometry), single strand DNA and nuclear fragmentation (Comet and Hoechst assay). Additionally, relative expression of pro- and anti-apoptotic proteins were determined (Western Blotting). Significant antioxidant depletion was consistent with a concomitant increase in ROS-induced lipid peroxidation and extracellular LDH levels. FA induced apoptosis by significantly increasing Bax expression and caspase-8, -9 and -3/7 activities whilst decreasing ATP levels and Bcl-2 expression. Further, FA significantly increased comet tail lengths, PARP-1 expression and late stage apoptotic body formation in SNO cells. This study shows that FA is cytotoxic and induces increased apoptosis in SNO cells.

A Rapid Method with UPLC for the Determination of Fusaric Acid in Fusarium Strains and Commercial Food and Feed Products

A rapid, sensitive and validated method for the determination of fusaric acid (FA) in several Fusarium strains and different commercial food and feed products is reported based on ultra-performance liquid chromatography. This method requires only crude sample by a simple extraction with methanol, and requires a very short time of 8 min for completion. Separation of FA was performed at injection volume of 1 μl with a 20:80 (v/v) water/acetonitrile mobile phase containing 0.1 % formic acid at a flow rate of 0.05 ml/min and detected with UV at 220 nm. Nice linearity and good correlation coefficient (R² > 0.99) were obtained in the concentration range of 1-200 μg/ml. Validation was demonstrated using blank samples spiked at three different concentrations with standard solution, and the method yielded more than 98.2 % recovery efficiencies and below 2.56 % R.S.D. when applied in the analysis of FA produced by Fusarium verticillioides and a set of transgenic strains of this fungus. Satisfactory recoveries in the range of 79.1-105.8 % and R.S.D lower than 10 % were also obtained for the tested commercial food and feed products. The concentration FA detection in the transgenic strains ranged from 9.65 to 135 μg/kg (0.29-4.05 μg per gram of biomass). However, FA was not detected in most of the commercial products with the exception of niblet, oatmeal, red kidney bean and soybean, for which the concentrations of FA ranged from 2.5 to 18 μg/kg (below the permitted maximum). These results show that the proposed method has a great potential application to analyze FA from different sources rapidly.

Fusaric acid: A novel agent and mechanism to treat HNSCC

OBJECTIVE: A new class of carboxylic acids has tumoricidal activity for head and neck squamous cell cancer (HNSCC). Fusaric acid (FA) can chelate divalent cations, especially zinc, and inactivate zinc finger proteins involved in DNA repair and protein synthesis.

METHODS: 2 squamous carcinoma lines were utilized for in vitro and in vivo portions of this study. Cell counting and flow cytometry were used to analyze cells in culture in treatment and control groups over 96 hours. HNSCC subcutaneous implants were created in treatment and control groups of BALB-c nude mice (N = 30).

RESULTS: In vitro studies demonstrated significant changes in cell numbers and cell cycle. In vivo studies of daily intralesional therapy for 1 month also showed reduced onset of growth and overall growth compared to controls.

CONCLUSION: FA appears to have a tumoristatic/tumoricidal effect on HNSCC. Further nude mice studies are needed to optimize dosing and administration regimens for FA in anticipation of clinical trials.

Mycotoxins in animal and human patients

The majority of human food and animal feed production occurs in a highly managed agroecosystem. Management decisions include variety grown, tillage and irrigation methods and practices, fertilization, pest and disease control, harvesting methods, and storage and transportation practices. This system is generally managed for optimum returns to labor and capital investments. The spores of toxigenic fungi have ubiquitous distribution and toxigenic fungi exploit food sources when conditions of moisture and temperature are above minimums for growth. The safety margins in the agroecosystem are close and are influenced by extrinsic factors such as climatic events. Control of fungal growth is important in management of raw feedstuffs, foodstuffs, condiments-spices, botanicals, and other consumable substances as they are grown, harvested, stored, and transported. The risk factors for mycotoxin production are weather conditions during crop growth and when the crop is mature, damage to seeds before, during, and after harvest, how commodities are physically handled, the presence of weed seeds and other foreign material in grain, and how commodity moisture and temperature are managed during storage and transportation. Diversion of commodities and by-products from human consumption to animal feedstuffs can increase the risk of mycotoxicoses in animals. The toxicology of selected toxigenic fungi and the mycotoxins they produce are reviewed.

Chronic toxicity of fumonisins in turkeys

Fumonisins are mycotoxins that are found worldwide. They are mainly produced by Fusarium verticillioides during its development on corn. The main toxic effects of these molecules have been well characterized in poultry in the case of acute exposure, but the subclinical and economic effects of chronic exposure are less known. Whereas the latest European recommendations suggest that maximal levels of fumonisins in corn could reach 60 mg/kg and the maximal contamination of poultry feeds could reach 20 mg/kg, no study is available at this level in turkeys. The aim of the present work was thus to characterize the effects of exposure to fumonisins (concentrations of 0, 5, 10, and 20 mg of fumonisin B1 + fumonisin B2/kg of feed) on feed consumption and growth in turkeys over a period of 9 wk. Main biochemical parameters of the liver and alteration of sphingolipid metabolism were investigated in plasma, liver, and kidney. The main results showed no effect on feed consumption and growth in exposed turkeys. Moreover, no effect was observed on the weight of tissues and markers of liver injury. By contrast, a disruption of sphingolipid metabolism was clear at a level of exposure of 10 and 20 mg of fumonisin B1 + fumonisin B2 mg/kg of feed. Both hepatic and kidney concentrations of sphinganine increased gradually throughout the exposure period. These results reveal that disruption of sphingolipid metabolism is an early and sensitive biomarker of fumonisins exposure in turkeys; the consequences on these alterations remain to be established.

The effect of single agent oral fusaric acid (FA) on the growth of subcuta neously xenografted SCC-1 cells in a nude mouse model

OBJECTIVE

To determine whether oral administration of fusaric acid (FA) inhibits tumor growth in an animal model of head and neck cancer (HNSCC).

DESIGN

In vivo murine model, two arm controlled study.

METHODS

Thirty-eight (38) 5-week-old athymic nude mice were randomly assigned to a fusaric acid treatment group (1 mg/mL) (n = 19) or a sterile saline group (n = 19). A left, lateral flank subcutaneous injection of 2.0 x 10(6) UM-SCC-1 cells were administered to all mice on day 1. Both groups were gavaged daily with either 0.25 mLs of oral FA or sterile saline throughout the experiment (32 days). Latency to a measurable tumor (> or =65 mm3), and tumor volumes were recorded after tumor xenografting. Tumor weights were recorded at the conclusion of the experiment. Tumor volume growth curves were modeled as polynomial functions of time with treatment interaction effects. Survivorship functions for time to measurable tumor were estimated using the Kaplan-Meier product limit estimator.

RESULTS

Survival analysis showed mice treated with FA developed measurable tumors after a significantly longer interval post-xenografting than control mice (p = 0.00451). By Day 9, all mice in the control group had developed measurable tumors in comparison to only 78% of mice in the FA group. Likewise, estimated growth curves for both groups suggested that mice receiving FA demonstrated significantly slower tumor growth rates throughout the entire study period (p < 0.0001). At the conclusion of the experiment, tumor weights from both the control and FA groups were also significantly different (p = 0.0142).

CONCLUSIONS

Single agent oral fusaric acid (1 mg/mL) is an inhibitor of UM-SCC-1 in a murine model. As an orally active agent, it may have a potential role in the treatment of human squamous cell carcinoma of the head and neck.

Chronic effects of fumonisin B1 on ducks

Partially purified fumonisin B1 (FB1) was orally administrated for 77 d to 5 groups of 8 mule ducks starting at 7 d of age; the concentrations corresponded to 5 diets containing 0, 2, 8, 32, and 128 mg of FB1/kg of feed. No mortality was observed, and no effects on feed consumption and body weight gain were observed at the end of the treatment period. But, surprisingly, FB1 ingested at 32 and 128 mg/kg led to decreased body weight from d 28 to 63 and from d 7 to 63, respectively. FB1 had no effect on the relative weight of heart and breast muscle, whereas a significant increases in the relative weights of gizzard, spleen, and liver were measured in ducks receiving 32 and 128 mg of FB1/kg of feed without evidence of detectable microscopic modification of these organs. FB1 had no significant effect of the serum aspartate aminotransferase and gamma-glutamyltransferase levels but increased serum total protein, cholesterol, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase levels when 128 mg of FB1/kg of feed was given. Serum, liver, and kidney sphinganine to sphingosine ratio was significantly increased in ducks fed 8 to 128 mg of FB1/kg of feed. The biggest increase was observed in kidneys, suggesting that this organ is the most sensitive to detect FB1-induced disruption of sphingolipid metabolism.

Fusaric acid-producing strains of Fusarium oxysporum alter 2,4-diacetylphloroglucinol biosynthetic gene expression in Pseudomonas fluorescens CHA0 in vitro and in the rhizosphere of wheat

The phytotoxic pathogenicity factor fusaric acid (FA) represses the production of 2,4-diacetylphloroglucinol (DAPG), a key factor in the antimicrobial activity of the biocontrol strain Pseudomonas fluorescens CHA0. FA production by 12 Fusarium oxysporum strains varied substantially. We measured the effect of FA production on expression of the phlACBDE biosynthetic operon of strain CHA0 in culture media and in the wheat rhizosphere by using a translational phlA'-'lacZ fusion. Only FA-producing F. oxysporum strains could suppress DAPG production in strain CHA0, and the FA concentration was strongly correlated with the degree of phlA repression. The repressing effect of FA on phlA'-'lacZ expression was abolished in a mutant that lacked the DAPG pathway-specific repressor PhlF. One FA-producing strain (798) and one nonproducing strain (242) of F. oxysporum were tested for their influence on phlA expression in CHA0 in the rhizosphere of wheat in a gnotobiotic system containing a sand and clay mineral-based artificial soil. F. oxysporum strain 798 (FA(+)) repressed phlA expression in CHA0 significantly, whereas strain 242 (FA(-)) did not. In the phlF mutant CHA638, phlA expression was not altered by the presence of either F. oxysporum strain 242 or 798. phlA expression levels were seven to eight times higher in strain CHA638 than in the wild-type CHA0, indicating that PhlF limits phlA expression in the wheat rhizosphere.

An overview of rodent toxicities: liver and kidney effects of fumonisins and Fusarium moniliforme

Fumonisins are produced by Fusarium moniliforme F. verticillioides) and other Fusarium that grow on corn worldwide. They cause fatal toxicoses of horses and swine. Their effects in humans are unclear, but epidemiologic evidence suggests that consumption of fumonisin-contaminated corn contributes to human esophageal cancer in southern Africa and China. Much has been learned from rodent studies about fumonisin B1(FB1), the most common homologue. FB1 is poorly absorbed and rapidly eliminated in feces. Minor amounts are retained in liver and kidneys. Unlike other mycotoxins, fumonisins cause the same liver cancer promotion and subchronic (studies (3/4) 90 days) liver and kidney effects as (italic)F. moniliforme. FB 1 induces apoptosis of hepatocytes and of proximal tubule epithelial cells. More advanced lesions in both organs are characterized by simultaneous cell loss (apoptosis and necrosis) and proliferation (mitosis). Microscopic and other findings suggest that an imbalance between cell loss and replacement develops, a condition favorable for carcinogenesis. On the molecular level, fumonisins inhibit ceramide synthase, and disrupt sphingolipid metabolism and, theoretically, sphingolipid-mediated regulatory processes that influence apoptosis and mitosis. Liver sphingolipid effects and toxicity are correlated, and ceramide synthase inhibition occurs in liver and kidney at doses below their respective no-observed-effect levels. FB1 does not cross the placenta and is not teratogenic in vivoin rats, mice, or rabbits, but is embryotoxic at high, maternally toxic doses. These data have contributed to preliminary risk evaluation and to protocol development for carcinogenicity and chronic toxicity studies of FB1 in rats and mice.