Antiviral activity of trichothecene mycotoxins (deoxynivalenol, fusarenon-X, and nivalenol) against herpes simplex virus types 1 and 2

Deoxynivalenol Mycotoxin Inhibits Rabies Virus Replication In Vitro

Rabies is a highly fatal disease, and it is vital to find effective ways to manage and control infection. There is a need for new effective antiviral drugs that are particularly effective treatments for rabies. Deoxynivalenol (DON) is known mainly for its toxicity, but at the molecular level, it can inhibit RNA and DNA replication, and there is increasing evidence that different doses of DON have a positive effect on inhibiting virus replication. Based on this, we evaluated the effect of DON on inhibiting the rabies virus in vitro. The inhibitory effect of DON on rabies virus activity was dose- and time-dependent, and 0.25 μg/mL of DON could inhibit 99% of rabies virus activity within 24 h. Furthermore, DON could inhibit the adsorption, entry, replication, and release of rabies virus but could not inactivate the virus. The inhibitory effect of DON on rabies virus may be achieved by promoting apoptosis. Our study provides a new perspective for the study of anti-rabies virus and expands the direction of action of mycotoxins.

A novel toxic effect of foodborne trichothecenes: The exacerbation of genotoxicity

Trichothecenes (TCT) are very common mycotoxins. While the effects of DON, the most prevalent TCT, have been extensively studied, less is known about the effect of other trichothecenes. DON has ribotoxic, pro-inflammatory, and cytotoxic potential and induces multiple toxic effects in humans and animals. Although DON is not genotoxic by itself, it has recently been shown that this toxin exacerbates the genotoxicity induced by model or bacterial genotoxins. Here, we show that five TCT, namely T-2 toxin (T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), fusarenon-X (FX), and the newly discovered NX toxin, also exacerbate the DNA damage inflicted by various genotoxins. The exacerbation was dose dependent and observed with phleomycin, a model genotoxin, captan, a pesticide with genotoxic potential, and colibactin, a bacterial genotoxin produced by the intestinal microbiota. For this newly described effect, the trichothecenes ranked in the following order: T-2>DAS > FX > NIV ≥ DON ≥ NX. The genotoxic exacerbating effect of TCT correlated with their ribotoxic potential, as measured by the inhibition of protein synthesis. In conclusion, our data demonstrate that TCT, which are not genotoxic by themselves, exacerbate DNA damage induced by various genotoxins. Therefore, foodborne TCT could enhance the carcinogenic potential of genotoxins present in the diet or produced by intestinal bacteria.

Simple and rapid high-throughput assay to identify HSV-1 ICP0 transactivation inhibitors

Herpes simplex virus 1 (HSV-1) is a ubiquitous virus that results in lifelong infections due to its ability to cycle between lytic replication and latency. As an obligate intracellular pathogen, HSV-1 exploits host cellular factors to replicate and aid in its life cycle. HSV-1 expresses infected cell protein 0 (ICP0), an immediate-early regulator, to stimulate the transcription of all classes of viral genes via its E3 ubiquitin ligase activity. Here we report an automated, inexpensive, and rapid high-throughput approach to examine the effects of small molecule compounds on ICP0 transactivator function in cells. Two HSV-1 reporter viruses, KOS6β (wt) and dlx3.1-6β (ICP0-null mutant), were used to monitor ICP0 transactivation activity through the HSV-1 ICP6 promoter:lacz expression cassette. A ≥10-fold difference in β-galactosidase activity was observed in cells infected with KOS6β compared to dlx3.1-6β, demonstrating that ICP0 potently transactivates the ICP6 promoter. We established the robustness and reproducibility with a Z'-factor score of ≥0.69, an important criterium for high-throughput analyses. Approximately 19,000 structurally diverse compounds were screened and 76 potential inhibitors of the HSV-1 transactivator ICP0 were identified. We expect this assay will aid in the discovery of novel inhibitors and tools against HSV-1 ICP0. Using well-annotated compounds could identify potential novel factors and pathways that interact with ICP0 to promote HSV-1 gene expression.

Trichothecenes from an Endophytic Fungus Alternaria sp. sb23

Three new (alterchothecenes A - C, 1:  -3: ) and 3 known (4:  -6: ) trichothecenes, along with 9 known compounds (7:  -15: ), were isolated from the culture of Alternaria sp. sb23, an endophytic fungus separated from the root of Schisandra sphenanthera Rehd. et Wils. Their structures were elucidated by spectroscopic analyses, and the absolute configurations of 1: -3: were determined through comparison of the experimental electronic circular dichroism (ECD) spectra and optical rotations with similar analogues. In vitro cytotoxicity tests of compounds 1: -6: against human HT-29 colon carcinoma and human MCF-7 breast cancer cell lines indicated that 4: -6: exhibited significant cytotoxic effects, with IC₅₀ values ranging from 0.89 to 9.38 µM. And the potential of compounds 1: -6: as tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) sensitizers in HT-29 cells was evaluated. The results revealed that combination treatment of TRAIL with compounds 1: -6: synergistically decreased cell viability compared with the sole treatment with those compounds.

An overview of the toxicology and toxicokinetics of fusarenon-X, a type B trichothecene mycotoxin

Fusarenon-X (FX) is a type B trichothecene mycotoxin that is frequently observed along with deoxynivalenol (DON) and nivalenol (NIV) in agricultural commodities. This review aims to give an overview of the literature concerning the toxicology and toxicokinetics of FX. FX is primarily found in cereals grown in temperate regions, but it can also be found worldwide because of the global transport of products. The major toxicity of FX occurs through inhibition of protein synthesis, followed by the disruption of DNA synthesis. Moreover, FX has also been shown to induce apoptosis in in vitro and in vivo studies. The targets of FX are organs containing actively proliferating cells, such as the thymus, spleen, skin, small intestine, testes and bone marrow. FX causes immunosuppression, intestinal malabsorption, developmental toxicity and genotoxicity. In addition, sufficient evidence of carcinogenicity in experimental animals is currently lacking, and the International Agency for Research on Cancer (IARC) classifies it as a group 3 carcinogen.

Antifungal activity of trichothecenes from Fusarium sp. against clinical isolates of Paracoccidioides brasiliensis

Paracoccidioidomycosis (PCM), a human mycosis caused by the dimorphic fungus Paracoccidioides brasiliensis, is a serious public health problem in several countries of Latin America. In our search we found that the crude extract of the endophytic fungus UFMGCB 551 was able to inhibit several clinical strains of P. brasiliensis, and was also active in the bioautographic assay against Cladosporium sphaerospermum. The endophytic fungus UFMGCB 551 was isolated from the plant Piptadenia adiantoides J.F. Macbr (Fabaceae). The fungus was identified as Fusarium sp. based on its macro- and micro-morphology, and on the sequence of the internally transcribed spacer regions (ITS) of its rRNA gene. The chromatographic fractionation of the fungal extract was guided by the bioautographic assay to afford three known trichothecene mycotoxins: T2-toxin (1) and a mixture of 8-n-butyrylneosolaniol (2) and 8-isobutyrylsolaniol (3). The minimal inhibitory concentrations (MIC) of the these compounds against eleven clinical strains of P. brasiliensis were evaluated and found to be in the range between 75 and 640 nmol l(-1) for 1 and 160-640 nmol l(-1) for the mixture of 2 and 3.

Comparison of in vitro cytotoxicity of Fusarium mycotoxins,deoxynivalenol, T-2 toxin and zearalenone on selected human epithelial cell lines

Three human epithelial cell lines (CaCo-2, HEp-2 and HeLa) implicated as potential targets for three Fusarium toxins were tested for the extent of survival on exposure to increasing toxin concentration and incubation periods. Cytotoxicity assay using 3(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) was carried out with deoxynivalenol (DON), T-2 toxins and zearalenone (ZON) on CaCo-2, HEp-2 and HeLa cell lines. Of the three cell lines used, HeLa was the most sensitive, eliciting cell death after 2 days exposure at 100 ng ml(-1)with T-2 toxin. HeLa was the only cell line to exhibit cytotoxicity towards ZON showing cell death at 1000 ng ml(-1)after 2 days which increased to 4 days, showing substantial cell death at 200 ng ml(-1). HEp-2 was sensitive to DON showing cell death after 2 days (100 ng ml(-1)) with complete cell death occurring at 200 ng ml(-1) after 4 days of exposure. Substantial cytoxicity of T-2 towards HEp-2 occurred after 2 days at 1000 ng ml(-1) and complete cell death occurred with 100 ng ml(-1) at day 4. The CaCo-2 cell line was generally resistant to the mycotoxins tested between 100 and 1000 ng ml(-1). This study shows that cytotoxicity of Fusarium toxins to epithelium cell lines is concentration- and time- dependant and results from ZON-HeLa interaction indicate possible cell type-mycotoxin specificity.

Is Fusarium culmorum isotrichodermin-15-hydroxylase different from other fungal species?

Fusarium spp. are ubiquitous fungi infecting cereals and grains, and therefore constitute a major problem for agriculture. Their trichothecene metabolites, and in particular deoxynivalenol and its 3-acetylated derivative, are the mycotoxins involved. The major metabolite produced by Fusarium culmorum is 3-acetyldeoxynivalenol. Studies in vivo with Fusarium culmorum have established that its tricyclic intermediate, isotrichodermin, is a major biosynthetic precursor, which is hydroxylated at position 15 to give 15-deacetylcalonectrin, prior to being converted to the product. In a preliminary in vitro investigation of the cell-free system involved in this transformation, we suggested that cytochrome P450 enzymes are not involved. In this paper, the isotrichodermin-15-hydroxylase from the microsomal fraction of Fusarium culmorum was solubilized and partially purified (60 fold). Our studies with cofactors indicate that this enzyme is a flavoprotein, and the inducers tested highly indicate that indeed the hydroxylase is not attached to cytochrome P450. This is particularly interesting, since the only other enzyme catalyzing the same reaction isolated from Fusarium sporotrichiodes is attached to cytochrome P450.