201
|
Doyle PJ, Saeed H, Hermans A, Gleddie SC, Hussack G, Arbabi-Ghahroudi M, Seguin C, Savard ME, MacKenzie CR, Hall JC. Intracellular expression of a single domain antibody reduces cytotoxicity of 15-acetyldeoxynivalenol in yeast. J Biol Chem 2009; 284:35029-39. [PMID: 19783651 PMCID: PMC2787364 DOI: 10.1074/jbc.m109.045047] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/08/2009] [Indexed: 11/06/2022] Open
Abstract
15-Acetyldeoxynivalenol (15-AcDON) is a low molecular weight sesquiterpenoid trichothecene mycotoxin associated with Fusarium ear rot of maize and Fusarium head blight of small grain cereals. The accumulation of mycotoxins such as deoxynivalenol (DON) and 15-AcDON within harvested grain is subject to stringent regulation as both toxins pose dietary health risks to humans and animals. These toxins inhibit peptidyltransferase activity, which in turn limits eukaryotic protein synthesis. To assess the ability of intracellular antibodies (intrabodies) to modulate mycotoxin-specific cytotoxocity, a gene encoding a camelid single domain antibody fragment (V(H)H) with specificity and affinity for 15-AcDON was expressed in the methylotropic yeast Pichia pastoris. Cytotoxicity and V(H)H immunomodulation were assessed by continuous measurement of cellular growth. At equivalent doses, 15-AcDON was significantly more toxic to wild-type P. pastoris than was DON. In turn, DON was orders of magnitude more toxic than 3-acetyldeoxynivalenol. Intracellular expression of a mycotoxin-specific V(H)H within P. pastoris conveyed significant (p = 0.01) resistance to 15-AcDON cytotoxicity at doses ranging from 20 to 100 mug.ml(-1). We also documented a biochemical transformation of DON to 15-AcDON to account for the attenuation of DON cytotoxicity at 100 and 200 mug.ml(-1). The proof of concept established within this eukaryotic system suggests that in planta V(H)H expression may lead to enhanced tolerance to mycotoxins and thereby limit Fusarium infection of commercial agricultural crops.
Collapse
Affiliation(s)
- Patrick J. Doyle
- From the Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1
| | - Hanaa Saeed
- Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, Ontario K1A 0C6, and
| | - Anne Hermans
- Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, Ontario K1A 0C6, and
| | - Steve C. Gleddie
- Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, Ontario K1A 0C6, and
| | - Greg Hussack
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Mehdi Arbabi-Ghahroudi
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Charles Seguin
- Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, Ontario K1A 0C6, and
| | - Marc E. Savard
- Eastern Cereal and Oilseed Research Centre, Agriculture and AgriFood Canada, Ottawa, Ontario K1A 0C6, and
| | - C. Roger MacKenzie
- Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - J. Christopher Hall
- From the Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1
| |
Collapse
|
202
|
A genome-wide screen in Saccharomyces cerevisiae reveals a critical role for the mitochondria in the toxicity of a trichothecene mycotoxin. Proc Natl Acad Sci U S A 2009; 106:21883-8. [PMID: 20007368 DOI: 10.1073/pnas.0909777106] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Trichothecene mycotoxins synthesized by Fusarium species are potent inhibitors of eukaryotic translation. They are encountered in both the environment and in food, posing a threat to human and animal health. They have diverse roles in the cell that are not limited to the inhibition of protein synthesis. To understand the trichothecene mechanism of action, we screened the yeast knockout library to identify genes whose deletion confers resistance to trichothecin (Tcin). The largest group of resistant strains affected mitochondrial function, suggesting a role for fully active mitochondria in trichothecene toxicity. Tcin inhibited mitochondrial translation in the wild-type strain to a greater extent than in the most resistant strains, implicating mitochondrial translation as a previously unrecognized site of action. The Tcin-resistant strains were cross-resistant to anisomycin and chloramphenicol, suggesting that Tcin targets the peptidyltransferase center of mitochondrial ribosomes. Tcin-induced cell death was partially rescued by mutants that regulate mitochondrial fusion and maintenance of the tubular morphology of mitochondria. Treatment of yeast cells with Tcin led to the fragmentation of the tubular mitochondrial network, supporting a role for Tcin in disruption of mitochondrial membrane morphology. These results provide genome-wide insight into the mode of action of trichothecene mycotoxins and uncover a critical role for mitochondrial translation and membrane maintenance in their toxicity.
Collapse
|
203
|
Nielsen C, Casteel M, Didier A, Dietrich R, Märtlbauer E. Trichothecene-induced cytotoxicity on human cell lines. Mycotoxin Res 2009; 25:77-84. [PMID: 23604982 DOI: 10.1007/s12550-009-0011-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Revised: 04/01/2009] [Accepted: 04/17/2009] [Indexed: 11/26/2022]
Abstract
Trichothecene cytotoxicity of type A (T-2 toxin and HT-2 toxin), type B (deoxynivalenol, DON, and nivalenol, NIV), and type D (satratoxins G and H) compounds was determined comparatively by using eight permanent human cell lines (Hep-G2, A549, CaCo-2, HEp-2, A204, U937, RPMI 8226, and Jurkat). Viability of cells was measured by a water-soluble tetrazolium (WST-1) reagent cell proliferation assay assessing mitochondrial metabolic activity. Toxicity was expressed as the toxin concentration inhibiting 50% of cell viability (IC50). Depending on the chemotype of the tested trichothecenes, relative cytotoxic activity differed by a factor of 100-1,000, and the corresponding IC50 values were in the range from 2.2 nmol/l (satratoxin H on Jurkat and U937 cells) to 4,900 nmol/l (deoxynivalenol on HEp-2 cells). In contrast, the specific toxicity of each individual mycotoxin towards different cell lines was within remarkable close limits, and between-cell line differences were much smaller than previously reported. For the cell lines tested, IC50 values were 4.4-10.8 nmol/l for T-2 toxin, 7.5-55.8 mol/l for HT-2 toxin, 600-4,900 nmol/l for DON, 300-2,600 nmol/l for NIV, and 2.2-18.3 nmol/l for satratoxins G/H. In addition, for the first time, the toxic activity of trichothecenes on primary cell culture of human endothelial cells (HUVEC) was tested. The susceptibility of this cell line was comparable to the other cell lines tested, with IC50 values ranging from 16.5 nmol/l (T-2 toxin) to 4,500 nmol/l (DON). The results suggest that the current focus of cytotoxicological studies on trichothecenes on lymphoid cell lines may lead to an underestimate of their potential on other target cell systems.
Collapse
Affiliation(s)
- Carina Nielsen
- Department of Veterinary Sciences, Ludwig Maximilians-Universität München, Schönleutnerstraße 8, 85764, Oberschleißheim, Germany,
| | | | | | | | | |
Collapse
|
204
|
Ansari KI, Hussain I, Das HK, Mandal SS. Overexpression of human histone methylase MLL1 upon exposure to a food contaminant mycotoxin, deoxynivalenol. FEBS J 2009; 276:3299-307. [PMID: 19438726 DOI: 10.1111/j.1742-4658.2009.07055.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Mixed lineage leukemias (MLLs) are histone-methylating enzymes with critical roles in gene expression, epigenetics and cancer. Although MLLs are important gene regulators little is known about their own regulation. Herein, to understand the effects of toxic stress on MLL gene regulation, we treated human cells with a common food contaminant mycotoxin, deoxynivalenol (DON). Our results demonstrate that MLLs and Hox genes are overexpressed upon exposure to DON. Studies using specific inhibitors demonstrated that Src kinase families are involved in upstream events in DON-mediated upregulation of MLL1. Sequence analysis demonstrated that the MLL1 promoter contains multiple Sp1-binding sites and importantly, the binding of Sp1 is enriched in the MLL1 promoter upon exposure to DON. Moreover, antisense-mediated knockdown of Sp1 diminished DON-induced MLL1 upregulation. These results demonstrated that MLL1 gene expression is sensitive to toxic stress and Sp1 plays crucial roles in the stress-induced upregulation of MLL1.
Collapse
Affiliation(s)
- Khairul I Ansari
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, TX 76019, USA
| | | | | | | |
Collapse
|
205
|
Shi Y, Porter K, Parameswaran N, Bae HK, Pestka JJ. Role of GRP78/BiP degradation and ER stress in deoxynivalenol-induced interleukin-6 upregulation in the macrophage. Toxicol Sci 2009; 109:247-55. [PMID: 19336499 DOI: 10.1093/toxsci/kfp060] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The trichothecene mycotoxin deoxynivalenol (DON) induces systemic expression of the interleukin-6 (IL-6) and other proinflammatory cytokines in the mouse. The purpose of this study was to test the hypothesis that DON triggers an endoplasmic reticulum (ER) stress response in murine macrophages capable of driving IL-6 gene expression. DON at concentrations up 5000 ng/ml. was not cytotoxic to peritoneal cells. However, DON markedly decreased protein levels but not the mRNA levels of glucose-regulated protein (GRP) 78 (BiP), a chaperone known to mediate ER stress. Inhibitor studies suggested that DON-induced GRP78 degradation was cathepsin and calpain dependent but was proteosome-independent. RNAi-mediated knockdown of GRP78 resulted in increased IL-6 gene expression indicating a potential downregulatory role for this chaperone. GRP78 is critical to the regulation of the two transcription factors, X-box binding protein 1 (XBP1) and activating transcription factor 6 (ATF6), which bind to cAMP-response element (CRE) and drive expression of CRE-dependent genes such as IL-6. DON exposure was found to increase IRE1alpha protein, its modified products spliced XBP1 mRNA and XBP1 protein as well as ATF6. Knockdown of ATF6 but not XBP1 partially inhibited DON-induced IL-6 expression in the macrophages. Three other trichothecenes (satratoxin G, roridin, T-2 toxin) and the ribosome inhibitory protein ricin were also found to induce GRP78 degradation suggesting that other translation inhibitors might evoke ER stress. Taken together, these data suggest that in the macrophage DON induces GRP78 degradation and evokes an ER stress response that could contribute, in part, to DON-induced IL-6 gene expression.
Collapse
Affiliation(s)
- Yuhui Shi
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA
| | | | | | | | | |
Collapse
|
206
|
Satratoxin G interaction with 40S and 60S ribosomal subunits precedes apoptosis in the macrophage. Toxicol Appl Pharmacol 2009; 237:137-45. [PMID: 19306889 DOI: 10.1016/j.taap.2009.03.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Revised: 03/10/2009] [Accepted: 03/12/2009] [Indexed: 11/24/2022]
Abstract
Satratoxin G (SG) and other macrocyclic trichothecene mycotoxins are potent inhibitors of eukaryotic translation that are potentially immunosuppressive. The purpose of this research was to test the hypothesis that SG-induced apoptosis in the macrophage correlates with binding of this toxin to the ribosome. Exposure of RAW 264.7 murine macrophages to SG at concentrations of 10 to 80 ng/ml induced DNA fragmentation within 4 h that was indicative of apoptosis. To relate these findings to ribosome binding of SG, RAW cells were exposed to different toxin concentrations for various time intervals, ribosomal fractions isolated by sucrose density gradient ultracentrifugation and resultant fractions analyzed for SG by competitive ELISA. SG was found to specifically interact with 40S and 60S ribosomal subunits as early as 5 min and that, at high concentrations or extended incubation times, the toxin induced polysome disaggregation. While co-incubation with the simple Type B trichothecene DON had no effect on SG uptake into cell cytoplasm, it inhibited SG binding to the ribosome, suggesting that the two toxins bound to identical sites and that SG binding was reversible. Although both SG and DON induced mobilization of p38 and JNK 1/2 to the ribosome, phosphorylation of ribosomal bound MAPKs occurred only after DON treatment. SG association with the 40S and 60S subunits was also observed in the PC-12 neuronal cell model which is similarly susceptible to apoptosis. To summarize, SG rapidly binds small and large ribosomal subunits in a concentration- and time-dependent manner that was consistent with induction of apoptosis.
Collapse
|
207
|
Islam Z, Shinozuka J, Harkema JR, Pestka JJ. Purification and comparative neurotoxicity of the trichothecenes satratoxin G and roridin L2 from Stachybotrys chartarum. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2009; 72:1242-1251. [PMID: 20077192 PMCID: PMC2808125 DOI: 10.1080/15287390903129234] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Satratoxin G (SG), a macrocyclic trichothecene produced by Stachybotrys chartarum, induces apoptosis in cultured neuronal cells as well as nasal olfactory sensory neurons (OSN) in the nose and brain of mice exposed intranasally to this toxin. The purposes of this study were to (1) develop a facile method for production and purification of both SG and its putative biosynthetic precursor, roridin L2 (RL2), from S. chartarum cultures and (2) compare their relative neurotoxicity in vitro and in vivo. Stachybotrys chartarum 29-58-17 was cultured in Fernbach flasks on rice (5 x 10(5) spores/250 g rice) for 4 to 6 wk. Following extraction with acetonitrile, the extract was dried, dissolved in dichloromethane, and subjected to Michel-Miller silica-gel chromatography using a stepwise acetonitrile-dichloromethane gradient with SG and RL2 eluting in the 30 and 40% acetonitrile fractions, respectively. Purification of the two compounds was completed by C18 semipreparative reverse-phase liquid chromatography using an acetonitrile-water gradient, and purity was confirmed by electrospray ionization/collision-induced dissociation (ESI-CID) tandem mass spectroscopy. Although viability significantly decreased in PC-12 neuronal cells treated with 10 to 25 ng/ml of SG, RL2 at concentrations up to 1000 ng/ml was not toxic. Flow cytometry and agarose DNA fragmentation assays revealed that SG at 10 to 25 ng/ml induced apoptotic death in the PC-12 cells, while RL2 at concentrations up to 1000 ng/ml was without effect. In a similar fashion, intranasal exposure of mice (female B6C3F1) to SG at 100 microg/kg body weight (bw) induced marked OSN apoptosis and atrophy of the olfactory epithelium, whereas RL2 at the equivalent dose did not exhibit toxicity. Taken together, an optimized protocol for production and isolation of trichothecenes from S. chartarum cultures is described and further demonstrates that while the macrocyclic SG was neurotoxic in vitro and in vivo, its biosynthetic precursor, RL2, was nontoxic.
Collapse
Affiliation(s)
- Zahidul Islam
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing MI 48824, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing MI 48824, USA
- Center for Integrative Toxicology, Michigan State University, East Lansing MI 48824, USA
| | - Junko Shinozuka
- Center for Integrative Toxicology, Michigan State University, East Lansing MI 48824, USA
- Safety Research Laboratory, Mitsubishi Tanabe Pharma Corporation, 2-50, Kawagishi, 2-Chome, Toda, Saitama, 335-8505, JAPAN
| | - Jack R. Harkema
- Center for Integrative Toxicology, Michigan State University, East Lansing MI 48824, USA
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing MI 48824, USA
| | - James J. Pestka
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing MI 48824, USA
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing MI 48824, USA
- Center for Integrative Toxicology, Michigan State University, East Lansing MI 48824, USA
| |
Collapse
|