CYTOTOXICITY INDUCED BY NIVALENOL, DEOXYNIVALENOL, AND FUMONISIN B1 IN THE SF-9 INSECT CELL LINE

Nivalenol affects spindle formation and organelle functions during mouse oocyte maturation

Oocyte maturation is essential for fertilization and early embryo development, and proper organelle functions guarantee this process to maintain high-quality oocytes. The type B trichothecene nivalenol (NIV) is a mycotoxin produced by Fusarium oxysporum and is commonly found in contaminated food. NIV intake affect growth, the immune system, and the female reproductive system. Here, we investigated NIV toxicity on mouse oocyte quality. Transcriptome analysis results showed that NIV exposure altered the expression of multiple genes involved in spindle formation and organelle function in mouse oocytes, indicating its toxicity on mouse oocyte maturation. Further analysis indicated that NIV exposure disrupted spindle structure and chromosome alignment, possibly through tubulin acetylation. NIV exposure induced aberrant mitochondria distribution and reduced mitochondria number, mitochondria membrane potential (MMP), and ATP levels. In addition, NIV caused the abnormal distribution of the Golgi apparatus and altered the expression of the vesicle trafficking protein Rab11. ER distribution was also disturbed under NIV exposure, indicating the effects of NIV on protein modification and transport in oocytes. Thus, our results demonstrated that NIV exposure affected spindle structure and organelles function in mouse oocytes.

Deoxynivalenol: Mechanisms of action and its effects on various terrestrial and aquatic species

Deoxynivalenol, a type B trichothecene mycotoxin produced by Fusarium species of fungi, is a ubiquitious contaminant of cereal grains worldwide. Chronic, low dose consumption of feeds contaminated with DON is associated with a wide range of symptoms in terrestrial and aquatic species including decreased feed intake and feed refusal, reduced weight gain, and altered nutritional efficiency. Acute, high dose exposure to DON may be associated with more severe symptoms such as vomiting, diarrhea, intestinal inflammation and gastrointestinal hemorrhage. The toxicity of DON is partly related to its ability to disrupt eukaryotic protein synthesis via binding to the peptidyl transferase site of the ribosome. Moreover, DON exerts its effects at the cellular level by activating mitogen activated protein kinases (MAPK) through a process known as the ribotoxic stress response (RSR). The outcome of DON-associated MAPK activation is dose and duration dependent; acute low dose exposure results in immunostimulation characterized by the upregulation of cytokines, chemokines and other proinflammatory-related proteins, whereas longer term exposure to higher doses generally results in apoptosis, cell cycle arrest, and immunosuppression. The order of decreasing sensitivity to DON is considered to be: swine > rats > mice > poultry ≈ ruminants. However, studies conducted within the past 10 years have demonstrated that some species of fish, such as rainbow trout, are highly sensitive to DON. The aims of this review are to explore the effects of DON on terrestrial and aquatic species as well as its mechanisms of action, metabolism, and interaction with other Fusarium mycotoxins. Notably, a considerable emphasis is placed on reviewing the effects of DON on different species of fish.

Metabolic Depletion of Sphingolipids Does Not Alter Cell Cycle Progression in Chinese Hamster Ovary Cells

The cell cycle is a sequential multi-step process essential for growth and proliferation of cells comprising multicellular organisms. Although a number of proteins are known to modulate the cell cycle, the role of lipids in regulation of cell cycle is still emerging. In our previous work, we monitored the role of cholesterol in cell cycle progression in CHO-K1 cells. Since sphingolipids enjoy a functionally synergistic relationship with membrane cholesterol, in this work, we explored whether sphingolipids could modulate the eukaryotic cell cycle using CHO-K1 cells. Sphingolipids are essential components of eukaryotic cell membranes and are involved in a number of important cellular functions. To comprehensively monitor the role of sphingolipids on cell cycle progression, we carried out metabolic depletion of sphingolipids in CHO-K1 cells using inhibitors (fumonisin B₁, myriocin, and PDMP) that block specific steps of the sphingolipid biosynthetic pathway and examined their effect on individual cell cycle phases. Our results show that metabolic inhibitors led to significant reduction in specific sphingolipids, yet such inhibition in sphingolipid biosynthesis did not show any effect on cell cycle progression in CHO-K1 cells. We speculate that any role of sphingolipids on cell cycle progression could be context and cell-type dependent, and cancer cells could be a better choice for monitoring such regulation, since sphingolipids are differentially modulated in these cells.

The Effect of Simulated Lepidopteran Ear Feeding Injury on Mycotoxin Accumulation in Grain Corn (Poales: Poaceae)

Fusarium graminearum Schwabe (Hypocreales: Nectriaceae) and Fusarium verticillioides (Saccardo) (Hypocreales: Nectriaceae) Nirenberg infection results in accumulation of deoxynivalenol (DON), zearalenone (ZON), and fumonisin (FBs) mycotoxins in infected corn, Zea mays L. Lepidopteran insect feeding may exacerbate fungal infection by providing entry points on the ear resulting in increased mycotoxin contamination of grain. The objective of the current study was to simulate different types and severity levels (extent of injury) of lepidopteran injury to corn ears at different stages of ear development and its effect on mycotoxin accumulation in grain corn. Field experiments were conducted under conditions favorable for F. graminearum development where insect injury was simulated to corn ears and inoculated with F. graminearum. All simulated injury treatments resulted in elevated mycotoxin concentration compared with ears without simulated injury; however, the severity of injury within a treatment had little effect. Injury to kernels on the side of the ear resulted in greater DON and ZON concentration than injury to tip kernels, grazing injury applied at physiological maturity, or when no injury was simulated. Greater FBs was measured when tip kernel injury was simulated at the blister stage or when side kernel injury was simulated at milk and dent stages compared with noninjured ears, silk clipping, tip injury at milk and dent stages, or grazing injury at physiological maturity. The current study confirms that the risk of mycotoxin accumulation in the Great Lakes region is greater in the presence of ear-feeding insect pests and may differ depending on the feeding behavior of pest species.

Induction of Apoptosis and Activation of JNK and p38 MAPK Pathways in Deoxynivalenol-Treated Cell Lines

Deoxynivalenol (DON) is a mycotoxin produced by what are thought to be the most prevalent toxin-producing fungi of the Fusarium genus. Here, we present the results of apoptosis induction, phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs), and expression of the c-Jun protein after DON treatment, in a pre-B lymphocyte REH cell line. In addition, human pre-T lymphocyte Jurkat, hamster kidney-derived BHK21 and mouse hepatoma MH-22a cells were used in comparative experiments in vitro. We found that the DON effect was cell origin-dependent and dose-dependent, with a significant slow-down of cell proliferation and increase of apoptotic cells in blood cell lines. BHK21 and MH-22a cells were less sensitive to the DON effect. In blood-derived REH and Jurkat cells, DON-induced apoptotic changes were preceded by an increase in JNK and p38 MAPKs phosphorylation, as well as in c-Jun expression. However, the activation of JNK phosphorylation and c-Jun expression were transient, but did not coincide with each other. An inhibitor of JNK1/2, SP600125, had a negligible negative effect on REH cell viability after DON treatment, demonstrating that JNK does not contribute to DON-induced apoptosis. In contrast, studies on the role of p38 MAPK revealed that p38 signalling is required for DON-induced apoptosis in REH cells.

Concentration-dependent effect of fumonisin B1 on apoptosis in oesophageal cancer cells

The geographical distribution of oesophageal cancer is linked to the exposure of fumonisin B1 (FB1), a mycotoxin produced by fungi that contaminates staple food worldwide. Non-genotoxic carcinogens like FB1 disturb homeostasis through increased cell proliferation or suppression of apoptosis. This study investigated the involvement of FB1 (0–20 μM) in spindle-shaped N-cadherin (+) CD45 (−) osteoblastic (SNO) cell death. Cell viability and death were assessed using the MTS and Annexin V-Fluos assays, respectively. Caspase activities were determined luminometrically and the comet assay assessed DNA damage. Induction of oxoguanine glycosylase 1 (OGG1) was measured using quantitative Polymerase Chain Reaction (qPCR), while cleaved poly (ADP-ribose) polymerase 1 (PARP-1) and Bax were determined by western blotting. Cell viability and PARP-1 cleavage were not affected by 1.25 μM FB1, but phosphatidylserine externalization, Bax protein expression, caspase activity, comet tail length and OGG1 transcripts were increased. The reduced cell viability in 10 μM FB1-treated cells was accompanied by corresponding increases in externalized phosphatidylserine, Bax, caspase-3/7 activity and cleaved PARP-1. The OGG1 transcripts were not significantly increased, but comet tails were increased. Bax, caspase-3/7 activities and cleaved PARP-1 were inhibited at 20 μM FB1. In addition, the OGG1 transcript levels were decreased ( p < 0.0001) along with comet lengths ( p < 0.0001). This study showed that FB1-induced apoptosis in SNO cells may be caspase-dependent or caspase-independent; the pathway used depends on the exposure concentration.

Individual and combined effects of Aflatoxin B1, Deoxynivalenol and Zearalenone on HepG2 and RAW 264.7 cell lines

To understand the combinatorial toxicity of mycotoxins, we measured the effects of individual, binary and tertiary combinations of Aflatoxin B₁ (AFB₁), Deoxynivalenol (DON) and Zearalenone (ZEN) on the cell viability and cellular perturbations of HepG2 and RAW 264.7 cells. The nature of mycotoxins interactions was assessed using mathematical modeling (Chou-Talalay). Mechanisms of cytotoxicity were studied using high content screening (HCS) that probed cytotoxicity responses, such as changes in intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), intracellular calcium ([Ca²⁺]_i) flux, and cell membrane damage. Our results showed that individual cytotoxicity of mycotoxins in a decreasing order was DON>AFB₁>ZEN. Varying combinations of mycotoxins at differing concentrations showed different types of interactions. Most of the mixtures showed increasing toxic effects-synergism and/or addition while antagonistic effects were observed with combination of AFB₁+ZEN. Generally, combination of mycotoxins showed significantly increased intracellular ROS production and [Ca²⁺]_i flux, and decreased MMP in both cell lines, showing that the synergistic and additive effects of mycotoxin combination originate from perturbations of multiple cellular functions. Additionally, this study demonstrated the applicability of HCS for gaining mechanistic understanding on the toxicity of individual as well as combinatorial mycotoxins, and also provided scientific bases for formulating regulatory policies.

Aphids transform and detoxify the mycotoxin deoxynivalenol via a type II biotransformation mechanism yet unknown in animals

Biotransformation of mycotoxins in animals comprises phase I and phase II metabolisation reactions. For the trichothecene deoxynivalenol (DON), several phase II biotransformation reactions have been described resulting in DON-glutathiones, DON-glucuronides and DON-sulfates made by glutathione-S-transferases, uridine-diphosphoglucuronyl transferases and sulfotransferases, respectively. These metabolites can be easily excreted and are less toxic than their free compounds. Here, we demonstrate for the first time in the animal kingdom the conversion of DON to DON-3-glucoside (DON-3G) via a model system with plant pathogenic aphids. This phase II biotransformation mechanism has only been reported in plants. As the DON-3G metabolite was less toxic for aphids than DON, this conversion is considered a detoxification reaction. Remarkably, English grain aphids (Sitobion avenae) which co-occur with the DON producer Fusarium graminearum on wheat during the development of fusarium symptoms, tolerate DON much better and convert DON to DON-3G more efficiently than pea aphids (Acyrthosiphon pisum), the latter being known to feed on legumes which are no host for F. graminearum. Using a non-targeted high resolution mass spectrometric approach, we detected DON-diglucosides in aphids probably as a result of sequential glucosylation reactions. Data are discussed in the light of an eventual co-evolutionary adaptation of S. avenae to DON.

Toxicokinetics and tissue distribution of nivalenol in broiler chickens

Nivalenol (NIV), a type B trichothecene mycotoxin, is mainly produced by the fungi of Fusarium genus, which naturally occurs in agricultural commodities. Consumers are particularly concerned over the toxicity and safety of NIV in food animal products. To evaluate the toxicokinetics and persistence of residues of NIV, NIV was administered intravenously (iv) or orally (po) to broiler chickens at a dosage of 0.8 mg/kg body weight. The concentration of NIV in the plasma and various tissues was detected using liquid chromatography tandem-mass spectrometry. The plasma concentration of NIV in broilers could be measured up to 24 h and 12 h after iv and po administration, respectively. The value of elimination half-life of NIV was 5.27 ± 0.82 h and 2.51 ± 0.88 h after iv and po administration, respectively. The absolute oral bioavailability was 3.98 ± 0.08%. NIV was detected in the intestine, kidney, muscle, heart and liver after po administration. Regarding tissue residues, largest quantities of NIV were found in the small intestine. These results suggest that NIV is absorbed from the gastrointestinal tract with low bioavailability and it has the ability to diffuse into various tissues of broilers.

Stimulation of the proliferation of human normal esophageal epithelial cells by fumonisin B1 and its mechanism

Previous epidemiological studies have demonstrated a correlation between fumonisin B₁ (FB₁) and human esophageal cancer in China, Iran and South Africa. The purpose of this study was to investigate the effects of FB₁ on the proliferation, cell-cycle and apoptosis of normal human esophageal epithelial cells (HEECs) and to explore the molecular mechanisms of these effects. The proliferation of HEECs treated with FB₁ was assessed using a colorimetric assay, while analyses of the cell cycle and apoptosis were performed using flow cytometry and the measurement of the protein expressions of genes associated with the cell cycle was conducted using western blotting. The results showed that FB₁ stimulated the proliferation of HEECs, decreased the percentage of cells in the G0/G1 phase and reduced apoptosis. The western blotting results showed that FB₁ significantly increased the protein expression of cyclin D1 and significantly decreased the protein expression of cyclin E, p21 and p27. The results indicated that FB₁ stimulated the proliferation of HEECs by affecting the cell cycle and apoptosis. This mechanism was associated with changes in cyclin D1, cyclin E, p21 and p27 expression.

Individual and combined cytotoxic effects of Fusarium toxins (deoxynivalenol, nivalenol, zearalenone and fumonisins B1) on swine jejunal epithelial cells

Fusarium mycotoxins occur worldwide in foods such as cereals and animal forages, leading to acute and chronic exposures in human and animals. Intestinal epithelial cells (IECs) are an important first target site for these dietary toxins. This study investigated the cytotoxicity of four common Fusarium mycotoxins, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA) and fumonisin B1 (FB1) on a normal porcine jejunal epithelial cell line, IPEC-J2. A dose response relationship between individual mycotoxins and cell viability (MTT assay) was initially investigated, and subsequently cytotoxic and non-cytotoxic concentrations were selected to investigate combinations of two, three and all four of the mycotoxins. For individual mycotoxins, a dose response was observed with cell viability, such that the potency ranking was NIV>DON>ZEA>FB1. At cytotoxic doses of individual mycotoxins, all mixtures gave reduced cell viability compared to control. At noncytotoxic concentrations of individual mycotoxins, all mixtures were cytotoxic with DON-NIV, DON-ZEA, DON-NIV-FB1, DON-ZEA-FB1, NIV-ZEA-FB1 and all four mixed causing the greatest loss of cell viability. The latter observation in particular raises concerns over safety margins based on single toxin species, and suggests that the effects of multiple complex mixtures need to be better understood to assess health risks.

Applications of flow cytometry to toxicological mycotoxin effects in cultured mammalian cells: a review

This review gives an overview of flow cytometry applications to toxicological studies of several physiological target sites of mycotoxins on different mammalian cell lines. Mycotoxins are secondary metabolites of fungi that may be present in food, feed, air and water. The increasing presence of mycotoxins in crops, their wide distribution in the food chain, and their potential for toxicity demonstrate the need for further knowledge. Flow cytometry has become a valuable tool in mycotoxin studies in recent years for the rapid analysis of single cells in a mixture. In toxicology, the power of these methods lies in the possibility of determining a wide range of cell parameters, providing valuable information to elucidate cell growth and viability, metabolic activity, mitochondrial membrane potential and membrane integrity mechanisms. There are studies using flow cytometry technique on Alternaria, Aspergillus, Fusarium and Penicillium mycotoxins including information about cell type, assay conditions and functional parameters. Most of the studies collected in the literature are on deoxynivalenol and zearalenone mycotoxins. Cell cycle analysis and apoptosis are the processes more widely investigated.

Mycotoxins in the environment: I. Production and emission from an agricultural test field

Mycotoxins are secondary metabolites that are naturally produced by fungi which infest and contaminate agricultural crops and commodities (e.g., small grain cereals, fruits, vegetables, and organic soil material). Although these compounds have extensively been studied in food and feed, only little is known about their environmental fate. Therefore, we investigated over nearly two years the occurrence of various mycotoxins in a field cropped with winter wheat of the variety Levis, which was artificially inoculated with Fusarium spp., as well as their emission via drainage water. Mycotoxins were regularly quantified in whole wheat plants (0.1-133 mg/kg(dry weight), for deoxynivalenol), and drainage water samples (0.8 ng/L to 1.14 μg/L, for deoxynivalenol). From the mycotoxins quantified in wheat (3-acetyl-deoxynivalenol, deoxynivalenol, fusarenone-X, nivalenol, HT-2 toxin, T-2 toxin, beauvericin, and zearalenone), only the more hydrophilic ones or those prevailing at high concentrations were detected in drainage water. Of the total amounts produced in wheat plants (min: 2.3; max: 292 g/ha/y), 0.5-354 mg/ha/y, i.e. 0.002-0.12%, were emitted via drainage water. Hence, these compounds add to the complex mixture of natural and anthropogenic micropollutants particularly in small rural water bodies, receiving mainly runoff from agricultural areas.

Nivalenol-type populations of Fusarium graminearum and F. asiaticum are prevalent on wheat in southern Louisiana

U.S. populations of the Fusarium graminearum clade cause head blight on wheat and barley and usually contaminate grain with the trichothecene mycotoxin deoxynivalenol (DON). Recently, however, individual nivalenol (NIV)-type isolates from the United States were described that belonged to either the newly described species F. gerlachii or the genetically distinct Gulf Coast population of F. graminearum sensu stricto (s.s.). Here, we describe the discovery of NIV-type F. graminearum s.s. populations that were found in high proportion (79%) among isolates from small-grain-growing regions of Louisiana. We genotyped 237 isolates from Louisiana with newly developed polymerase chain reaction (PCR) restriction fragment length polymorphism markers and multiplex PCR primers that distinguish among the three trichothecene types: the two DON types (15ADON and 3ADON) and NIV. These isolates were compared with 297 isolates from 11 other U.S. states, predominantly from the Midwest. Using Bayesian-model-based clustering, we discovered a southern Louisiana population of F. graminearum s.s. that was genetically distinct from the previously recognized pathogen population in the Midwest (MW15ADON population). Population membership was correlated with trichothecene type. Most isolates from the southern Louisiana population were of the NIV type, while the majority of the isolates from the Midwest were of the 15ADON type. A smaller proportion of isolates from Louisiana belonged to the previously described Gulf Coast population that was mostly of the 3ADON type. The NIV type was also identified in collections from Arkansas (12%), North Carolina (40%), and Missouri (2%), with the collections from Arkansas and North Carolina being small and unrepresentative. F. asiaticum was detected from the two southern Louisiana parishes Acadia and Alexandria. All identified 41 F. asiaticum isolates were of the NIV type. Greenhouse tests indicated that U.S. NIV types accumulated four times less trichothecene toxin than DON types on inoculated wheat. This is the first report of NIV-type populations of F. graminearum s. s. and F. asiaticum in the United States.

Toxicological mechanisms and potential health effects of deoxynivalenol and nivalenol

Produced by the mould genus Fusarium, the type B trichothecenes include deoxynivalenol (DON), nivalenol (NIV) and their acetylated precursors. These mycotoxins often contaminate cereal staples, posing a potential threat to public health that is still incompletely understood. Understanding the mechanistic basis by which these toxins cause toxicity in experimental animal models will improve our ability to predict the specific thresholds for adverse human effects as well as the persistence and reversibility of these effects. Acute exposure to DON and NIV causes emesis in susceptible species such as pigs in a manner similar to that observed for certain bacterial enterotoxins. Chronic exposure to these mycotoxins at low doses causes growth retardation and immunotoxicity whereas much higher doses can interfere with reproduction and development. Pathophysiological events that precede these toxicities include altered neuroendocrine responses, upregulation of proinflammatory gene expression, interference with growth hormone signalling and disruption of gastrointestinal tract permeability. The underlying molecular mechanisms involve deregulation of protein synthesis, aberrant intracellular cell signalling, gene transactivation, mRNA stabilisation and programmed cell death. A fusion of basic and translational research is now needed to validate or refine existing risk assessments and regulatory standards for DON and NIV. From the perspective of human health translation, biomarkers have been identified that potentially make it possible to conduct epidemiological studies relating DON consumption to potential adverse human health effects. Of particular interest will be linkages to growth retardation, gastrointestinal illness and chronic autoimmune diseases. Ultimately, such knowledge can facilitate more precise science-based risk assessment and management strategies that protect consumers without reducing availability of critical food sources.

Influence of deoxynivalenol on NF-kappaB activation and IL-8 secretion in human intestinal Caco-2 cells

Deoxynivalenol (DON) is the most prevalent trichothecene mycotoxin in crops in Europe and North America. In human intestinal Caco-2 cells, DON activates the mitogen-activated protein kinases (MAPKs). We hypothesized a link between DON ingestion and intestinal inflammation, and used Caco-2 cells to assess the effects of DON, at plausible intestinal concentrations (250-10,000 ng/ml), on inflammatory mediators acting downstream the MAPKs cascade i.e. activation of nuclear factor-kappaB (NF-kappaB) and interleukin-8 (IL-8) secretion. In addition, Caco-2 cells were co-exposed to pro-inflammatory stimuli in order to mimic an inflamed intestinal epithelium. Dose-dependent increases in NF-kappaB activity and IL-8 secretion were observed, reaching 1.4- and 7.6-fold, respectively using DON at 10 microg/ml. Phosphorylation of inhibitor-kappaB (IkappaB) increased (1.6-fold) at DON levels <0.5 microg/ml. Exposure of Caco-2 cells to pro-inflammatory agents, i.e. 25 ng/ml interleukin-1beta, 100 ng/ml tumor necrosis factor-alpha or 10 microg/ml lipopolysaccharides, activated NF-kappaB and increased IL-8 secretion. Synergistic interactions between these stimuli and DON were observed. These data show that DON induces NF-kappaB activation and IL-8 secretion dose-dependently in Caco-2 cells, and this effect was accentuated upon pro-inflammatory stimulation, suggesting DON exposure could cause or exacerbate intestinal inflammation.

Cytotoxicity, metabolism and cellular uptake of the mycotoxin deoxynivalenol in human proximal tubule cells and lung fibroblasts in primary culture

At the level of the whole animal, the toxic effects of the mycotoxin deoxynivalenol (DON) range from causing diarrhoea, vomiting, gastro-intestinal inflammation to necrosis of several tissues. It also affects the immune system and leads to kidney lesions. Although DON has been tested in different human and animal cell lines for its cytotoxicity, these tests might be limited due to the disadvantages of cell lines (e.g. immortalization, tumour derivation, longtime cultivation) and do not necessarily reflect the response of normal cells. In order to overcome this problem and to be closer to the human situation, we studied the effect of DON in human kidney epithelial cells (renal proximal tubule epithelial cells, RPTEC) and human lung fibroblasts (normal human lung fibroblast, NHLF) in primary culture. Cell viability, apoptotic and necrotic cell death, collagens I, III and IV as well as fibronectin secretion were determined. It could be demonstrated that DON has a distinct cytotoxic effect on human primary cells. A reduction in viability can be observed in both cell types, with fibroblasts reacting more sensitive. Furthermore, DON caused mainly necrotic cell death in kidney cells whereas mainly apoptotic cell death in fibroblasts. DON had no effect on collagen secretion in RPTEC cells. Collagen secretion was partially decreased in NHLF. In both cells, fibronectin secretion was reduced after 5 days of exposure. We also studied the metabolism and the cellular uptake of DON using LC-MS/MS. DON was neither metabolized by proximal tubule cells nor by fibroblasts. DON is incorporated into the cells whereas the intracellular amount of DON in kidney cells is higher than in fibroblasts. No accumulation of DON occurred in the cells.

A microsatellite based method for quantification of fungi in decomposing plant material elucidates the role of Fusarium graminearum DON production in the saprophytic competition with Trichoderma atroviride in maize tissue microcosms

Common PCR assays for quantification of fungi in living plants cannot be used to study saprophytic colonization of fungi because plant decomposition releases PCR-inhibiting substances and saprophytes degrade the plant DNA which could serve as internal standard. The microsatellite PCR assays presented here overcome these problems by spiking samples prior to DNA extraction with mycelium of a reference strain. PCR with fluorescent primers co-amplifies microsatellite fragments of different length from target and reference strains. These fragments were separated in a capillary sequencer with fluorescence detection. The target/reference ratio of fluorescence signal was used to calculate target biomass in the sample. Such PCR assays were developed for the mycotoxin deoxynivalenol (DON)-producing wheat and maize pathogen Fusarium graminearum and the biocontrol agent Trichoderma atroviride, using new microsatellite markers. In contrast to real-time PCR assays, the novel PCR assays showed reliable fungal biomass quantification in samples with differentially decomposed plant tissue. The PCR assays were used to quantify the two fungi after competitive colonization of autoclaved maize leaf tissue in microcosms. Using a DON-producing F. graminearum wild-type strain and its nontoxigenic mutant we found no evidence for a role of DON production in F. graminearum defense against T. atroviride. The presence of T. atroviride resulted in a 36% lower wild-type DON production per biomass.

Cartap-induced cytotoxicity in mouse C2C12 myoblast cell line and the roles of calcium ion and oxidative stress on the toxic effects

Our previous study has demonstrated that instead of neuromuscular blockage cartap, an organonitrogen insecticide, could cause a marked irreversible Ca2+-dependent contracture in both isolated mouse and rabbit phrenic nerve-diaphragms. We further examined the potential of direct myocytotoxicity of cartap and the possible roles of calcium ion and oxidative stress on cartap-induced muscle cell injury using the mouse myoblast cell line, C2C12. Cartap exerted a dose- and time-dependent cytotoxic effect in C2C12 cells measured by MTT colorimetric assay and trypan blue dye exclusion. The extracellular activities of both creatine kinase (CK) and lactate dehydrogenase (LDH) were elevated in the cartap-treated groups at or greater than 100 microM. The isoenzymatic profiles showed that the elevations were mainly due to CK-3, LDH-3, and LDH-4. Following the addition of 0.5-2.5mM EGTA, a Ca2+ chelator, or 30-100 microM verapamil, an L-type Ca2+ channel blocker, the cartap-induced reduction in MTT metabolic rate of C2C12 cells was significantly restored in a dose-dependent manner in both EGTA and verapamil-treated cells. Furthermore, EGTA could significantly reduce the cartap-induced elevation in the levels of total extracellular CK and LDH activities. Additionally, cartap significantly increased the level of endogenous reactive oxygen species (ROS) in C2C12 cells in a dose- and time-dependent manner. The cartap-induced ROS generation could be significantly inhibited by antioxidants, including Vitamins C and E, catalase, and superoxide dismutase, with catalase the most effective. EGTA could significantly inhibit cartap-induced ROS generation in a dose-dependent manner. The results suggested that cartap could induce ROS generation in C2C12 cells via a Ca2+-dependent mechanism resulting in subsequent cytotoxicity, at least partially, to C2C12 cells. It is speculated that both Ca2+ and Ca2+-induced ROS may also play the central role on the myogenic contracture and myofiber injury of the diaphragm leading to respiratory failure and subsequent death in rabbits exposed ocularly to cartap.

Quantification of endometriotic lesions in a murine model by fluorimetric and morphometric analyses

BACKGROUND

In animal models of endometriosis, the identification and quantification of lesions originating from human endometrium is often hampered by the small size of the implants and their embedding in murine tissue. The purpose of the present study was to develop two new methods of quantifying endometriosis-like lesions in a nude mouse model: fluorimetry and morphometry.

METHODS

Human menstrual endometrium was labelled using a fluorescent tracker, carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE), and transplanted into the pelvic cavity of mice by injection through the peritoneum after performing a cutaneous incision. After 5 days, lesions were recovered by laparotomy. The fluorescence of the recovered endometriotic lesions was measured. Endometrial stroma and glands were immunostained in lesion sections with anti-CD10 and anti-CK22 antibodies, and their surface area was evaluated by morphometric analysis.

RESULTS

Fluorescent labelling allows identification of lesions not visible macroscopically. A good correlation was observed between fluorimetry and morphometry (r=0.88) applied for lesion quantification.

CONCLUSIONS

Fluorimetric evaluation combined with morphometric analysis of endometriosis-like lesions allows objective and reliable recording of endometriosis development in a nude mouse model. This quantification method could therefore be useful for future pharmacological and toxicological studies.

Induction of competing apoptotic and survival signaling pathways in the macrophage by the ribotoxic trichothecene deoxynivalenol

Deoxynivalenol (DON) and other ribotoxic trichothecenes cause immune stimulation and suppression in leukocytes by upregulating gene expression and apoptosis, respectively. The purpose of this study was to test the hypothesis that MAPKs mediate both apoptosis and survival in DON-exposed macrophages. At concentrations which partially inhibit translation, DON induced phosphorylation of p38 and ERK 1/2 mitogen activated protein kinases within 15 min in RAW 264.7 macrophages and these effects lasted up to 3 h. DON-exposed cells exhibited marked caspase 3-dependent DNA fragmentation after 6 h which was suppressed and attenuated by the p38 inhibitor SB203580 and ERK inhibitor PD98059, respectively. DON readily induced the phosphorylation and activity of p53 and this was inhibitable by SB203580. DON exposure evoked BAX translocation to mitochondria and corresponding cytochrome C release but did not alter mitochondrial membrane potential. The p53 inhibitor PFTalpha reduced both DON-induced phosphorylation of p53 and p53 binding activity. Moreover, both PFTalpha and p53 siRNA transfection suppressed DON-induced caspase-3 activity and subsequent DNA fragmentation. Concurrent with p53 activation, DON activated two anti-apoptotic survival pathways as evidenced by both ERK-dependent p90 Rsk and AKT activation. Taken together, the results indicate that DON initiates competing apoptotic (p38/p53/Bax/Mitochondria/Caspase-3) and survival (ERK/AKT/p90Rsk/Bad) pathways in the macrophage.