Threat assessment of mycotoxins as weapons: molecular mechanisms of acute toxicity

Degradation of ochratoxins A and B by lipases: A kinetic study unraveled by molecular modeling

Mycotoxins are toxic substances produced by fungi and, frequently, different mycotoxins cooccur in food commodities. Ochratoxin A (OTA) and Ochratoxin B (OTB) may co-occur in a variety of foods, like red wines and wheat, presenting a significant risk of population exposure. In this study, we investigated the potential of five lipases (Candida rugosa Lipase, Candida antarctica B Lipase, Thermomyces lanuginosus Lipase, Amano Lipase A from Aspergillus niger (ANL) and Porcine Pancreas Lipase (PPL)) to hydrolyze OTA and OTB into non-hazardous products. Only ANL and PPL degraded both substrates, however, with varying degrees of efficiency. PPL completely degraded OTB (9 h), but only 43% of OTA (25 h). Molecular simulations indicated a high binding energy of OTA to PPL, that can be explained by the impact of the chlorine group, impairing hydrolysis. ANL was able to completely degrade both mycotoxins, OTA in 3 h and OTB in 10 h. The ANL enzyme showed also high specificity to OTA, however, the activity of this enzyme is not affected by chlorine and hydrolyzes OTA faster than OTB. These two enzymes were found to be able to detoxify co-occurring ochratoxins A and B, making isolated enzymes an alternative to the direct use of microorganisms for mycotoxin mitigation in food.

Fluorescence spectroscopy and multispectral imaging for fingerprinting of aflatoxin-B1 contaminated (Zea mays L.) seeds: a preliminary study

Cereal seeds safety may be compromised by the presence of toxic contaminants, such as aflatoxins. Besides being carcinogenic, they have other adverse health effects on humans and animals. In this preliminary study, we used two non-invasive optical techniques, optical fiber fluorescence spectroscopy and multispectral imaging (MSI), for discrimination of maize seeds naturally contaminated with aflatoxin B₁ (AFB₁) from the uncontaminated seeds. The AFB₁-contaminated seeds exhibited a red shift of the emission maximum position compared to the control samples. Using linear discrimination analysis to analyse fluorescence data, classification accuracy of 100% was obtained to discriminate uncontaminated and AFB₁-contaminated seeds. The MSI analysis combined with a normalized canonical discriminant analysis, provided spectral and spatial patterns of the analysed seeds. The AFB₁-contaminated seeds showed a 7.9 to 9.6-fold increase in the seed reflectance in the VIS region, and 10.4 and 12.2-fold increase in the NIR spectral region, compared with the uncontaminated seeds. Thus the MSI method classified successfully contaminated from uncontaminated seeds with high accuracy. The results may have an impact on development of spectroscopic non-invasive methods for detection of AFs presence in seeds, providing valuable information for the assessment of seed adulteration in the field of food forensics and food safety.

Extrapolating from acute to chronic toxicity in vitro

Chemical safety assessment requires information on both chronic and acute effects of toxicants. Traditionally, such information has been provided by a set of animal studies conducted over different durations, ranging from a single dose with observation of effects over a few days, to repeat daily dosing and observations made over many months. With the advent of modern mechanistic approaches to toxicology, the role of in vitro studies within alternative approaches has never been more prominent. Typical in vitro experiments are conducted over short durations with measurements of response at a single time point, with a focus on providing effect and concentration-response information as input to hazard and risk assessment. This limits the usefulness of such data since potential chronic effects that cumulate over time are not usually considered. To address this, an experimental design is presented to characterise the toxicodynamics of a response not only in terms of concentration, but also as a function of time. Generation of concentration-time-effect responses allows both the extrapolation of points of departure from an acute to chronic exposure, and the determination of a chronicity index that provides a quantitative measure of a chemical's potential to cause cumulative effects over time. In addition, the approach provides a means to characterise the dynamics of key event relationships for the development of quantitative adverse outcome pathways.

Differential effects of route of T-2 toxin exposure on hepatic oxidative damage in mice

T-2 toxin is the most toxic among mycotoxins and poses a potential health hazard for both humans and animals. At high doses, T-2 toxin can cause shock-like syndrome that can result in death. We evaluated the effect of time course and route of exposure on hepatic oxidative damage in mice and it is only such study so far to compare the effects of dermal and subcutaneous exposure of T-2 toxin. Mice were exposed to 1 LD50 of T-2 toxin either by percutaneous (5.94 mg/kg body weight) or subcutaneous (1.54 mg/kg body weight) route and sacrificed at 0, 1, 3, and 7 days postexposure. Analysis of a number of serum biochemical variables, antioxidant enzymes activity, gene and protein expression by immunoblot assay showed time and route dependent effects of T-2 induced hepatic oxidative damage. Time dependent increase in protein carbonyl content and protein oxidation was seen in serum and liver. Results of our study may provide possible mechanism for developing medical countermeasures against T-2 toxin.

Producers and important dietary sources of ochratoxin A and citrinin

Ochratoxin A (OTA) is a very important mycotoxin, and its research is focused right now on the new findings of OTA, like being a complete carcinogen, information about OTA producers and new exposure sources of OTA. Citrinin (CIT) is another important mycotoxin, too, and its research turns towards nephrotoxicity. Both additive and synergistic effects have been described in combination with OTA. OTA is produced in foodstuffs by Aspergillus Section Circumdati (Aspergillus ochraceus, A. westerdijkiae, A. steynii) and Aspergillus Section Nigri (Aspergillus carbonarius, A. foetidus, A. lacticoffeatus, A. niger, A. sclerotioniger, A. tubingensis), mostly in subtropical and tropical areas. OTA is produced in foodstuffs by Penicillium verrucosum and P. nordicum, notably in temperate and colder zones. CIT is produced in foodstuffs by Monascus species (Monascus purpureus, M. ruber) and Penicillium species (Penicillium citrinum, P. expansum, P. radicicola, P. verrucosum). OTA was frequently found in foodstuffs of both plant origin (e.g., cereal products, coffee, vegetable, liquorice, raisins, wine) and animal origin (e.g., pork/poultry). CIT was also found in foodstuffs of vegetable origin (e.g., cereals, pomaceous fruits, black olive, roasted nuts, spices), food supplements based on rice fermented with red microfungi Monascus purpureus and in foodstuffs of animal origin (e.g., cheese).

Medical aspects of bio-terrorism

INTRODUCTION

Bioterrorism is a terrorist action involving the intentional release or dissemination of a biological warfare agent (BWA), which includes some bacteria, viruses, rickettsiae, fungi or biological toxins. BWA is a naturally occurring or human-modified form that may kill or incapacitate humans, animals or plants as an act of war or terrorism. BWA is a weapon of choice for mass destruction and terrorism, because of the incubation period, less effective amount than chemical warfare agents, easily distribution, odorless, colorless, difficult to detect, no need of specialized equipment for production and naturally distribution which can easily be obtained. BWA may be disseminating as an aerosol, spray, explosive device, and by food or water.

CLASSIFICATION

Based on the risk for human health, BWAs have been prioritized into three categories of A, B and C. Category A includes microorganisms or toxins that easily spread, leading to intoxication with high death rates such as Anthrax, Botulism, Plague, Smallpox, Tularemia and Viral hemorrhagic fevers. Category B has lower toxicity with wider range, including Staphylococcal Entrotoxin type B (SEB), Epsilon toxin of Clostridium perfringens, Ricin, Saxotoxins, Abrin and Trichothecene mycotoxins. The C category includes emerging pathogens that could also be engineered for mass spread such as Hanta viruses, multidrug-resistant tuberculosis, Nipah virus, the tick-borne encephalitis viruses, hemorrhagic fever viruses and yellow fever. CLINICAL MANIFESTATIONS OF BIOTOXINS IN HUMAN: Clinical features and severity of intoxication depend on the agent and exposed dose, route of entry, individual variation and environmental factors. Onset of symptoms varies from 2-24 h in Ricin to 24-96 h in Botulism. Clinical manifestations also vary from irritation of the eyes, skin and mucus membranes in T2 toxin to an acute flaccid paralysis of bilateral cranial nerve impairment of descending manner in botulism. Most of the pyrogenic toxins such as SEB produce the same signs and symptoms as toxic shock syndrome including a rapid drop in blood pressure, elevated temperature, and multiple organ failure.

MANAGEMENT

There is no specific antidote or effective treatment for most of the biotoxins. The clinical management is thus more supportive and symptomatic. Fortunately vaccines are now available for most of BWA. Therefore, immunization of personnel at risk of exposure is recommended.

CONCLUSION

Biotoxins are very wide and bioterrorism is a heath and security threat that may induce national and international problems. Therefore, the security authorities, health professional and even public should be aware of bioterrorism.

Evaluation of protective efficacy of CC-2 formulation against topical lethal dose of T-2 toxin in mice

T-2 toxin is the type-A trichothecene and a common contaminant of food and cereals, produced by Fusarium species. T-2 toxin easily penetrates skin due to its lipophilic nature and causes skin irritation and blisters in humans. Physical protection of the skin and airway is the only proven effective method of protection. To date, no chemical antidotes are available to prevent T-2 induced lethality. In the present study, we evaluated the protective efficacy of 20% N,N'-dichloro-bis(2,4,6-trichlorophenyl) urea (CC-2) formulation against lethal topical exposure dose of T-2 toxin in mice. None of the animals exposed to only T-2 toxin at lethal dose of 2 and 4 LD50 (11.8 and 23.76 mg/kg body weight) survived beyond 36 and 16 h, respectively. CC-2 application at 5 and 15 min post-exposure protected mice 100% from lethality at 2 LD50. Survival rate was 100% and 50% at 4LD50 dose if CC-2 was applied dermally within 5 and 15 min post-exposure. Recovery profile of surviving animals after 2LD50 T-2 toxin exposure at 1, 3, 7, and 14 days was assessed in terms of hepatic GSH, lipid peroxidation, serum ALP, ALT and AST. Hepatic lipid peroxidation significantly increased in all groups exposed to T-2 toxin by 3 day but normalized by day 7. A delayed GSH depletion was noted in surviving animals on day 7 but recovered by day 14. ALT and AST levels were elevated in all CC-2 protected mice on day 1 and normalized by day 3. ALP level decreased till day 7 in all protected groups. The biochemical variables recovered to control values by 14th day. GC-MS analysis after in vitro interaction of CC-2 formulation with T-2 toxin had shown that nearly 86% of T-2 toxin is decontaminated in 5 min but 8-10% of T-2 toxin was still present even after 60 min of interaction. Results of our study suggest that CC-2 may be an effective dermal decontaminant against lethal topical exposure of T-2 toxin.

Functionalized gold nanoparticle supported sensory mechanisms applied in detection of chemical and biological threat agents: a review

There is a great necessity for development of novel sensory concepts supportive of smart sensing capabilities in defense and homeland security applications for detection of chemical and biological threat agents. A smart sensor is a detection device that can exhibit important features such as speed, sensitivity, selectivity, portability, and more importantly, simplicity in identifying a target analyte. Emerging nanomaterial based sensors, particularly those developed by utilizing functionalized gold nanoparticles (GNPs) as a sensing component potentially offer many desirable features needed for threat agent detection. The sensitiveness of physical properties expressed by GNPs, e.g. color, surface plasmon resonance, electrical conductivity and binding affinity are significantly enhanced when they are subjected to functionalization with an appropriate metal, organic or biomolecular functional groups. This sensitive nature of functionalized GNPs can be potentially exploited in the design of threat agent detection devices with smart sensing capabilities. In the presence of a target analyte (i.e., a chemical or biological threat agent) a change proportional to concentration of the analyte is observed, which can be measured either by colorimetric, fluorimetric, electrochemical or spectroscopic means. This article provides a review of how functionally modified gold colloids are applied in the detection of a broad range of threat agents, including radioactive substances, explosive compounds, chemical warfare agents, biotoxins, and biothreat pathogens through any of the four sensory means mentioned previously.

Some food-associated mycotoxins as potential risk factors in humans predisposed to chronic intestinal inflammatory diseases

Mycotoxins are fungal metabolites able to affect the functions of numerous tissues and organs in animals and humans, including intestinal and immune systems. However, the potential link between exposure to some mycotoxins and human chronic intestinal inflammatory diseases, such as celiac and Crohn's diseases or ulcerative colitis, has not been investigated. Instead, several theories based on bacterial, immunological or neurological events have been elaborated to explain the etiology of these pathologies. Here we reviewed the literature on mycotoxin-induced intestinal dysfunctions and compared these perturbations to the impairments of intestinal functions typically observed in human chronic intestinal inflammatory diseases. Converging evidence based on various cellular and animal studies show that several mycotoxins induce intestinal alterations that are similar to those observed at the onset and during the progression of inflammatory bowel diseases. Although epidemiologic evidence is still required, existing data are sufficient to suspect a role of some food-associated mycotoxins in the induction and/or persistence of human chronic intestinal inflammatory diseases in genetically predisposed patients.

Microbial transformation of trichothecene mycotoxins

Trichothecene mycotoxins produced by the Fusarium genus are highly toxic to humans and animals. They are commonly found in cereals worldwide, which is not only a concern for food safety, but also highly relevant to the livestock industry. Controlling trichothecenes in food and feed has been a challenge since the toxins are markedly stable under different environmental conditions. Thermal processing is usually ineffective, and chemical treatments generally are expensive and often result in side effects. Previous studies on innovative biological approaches, such as the use of microorganisms and enzymes, to convert the toxins into non or less toxic compounds have shown promise. This review will briefly describe the chemical structures and toxicity of trichothecenes, and examine the microorganisms, including both bacteria and fungi, from various natural sources that are able to detoxify the toxins as either mixed cultures or a pure culture of single isolates. Finally, challenges and innovative strategies in the development of technology to detoxify trichothecenes by microorganisms are described.

Mycotoxin assays using biosensor technology: a review

Toxic fungal metabolites - mycotoxins - cause poisonings after consumption of contaminated food commodities. The most probable intoxications are connected with eating poorly stored food or inhaling of moldy dust. One of the effective ways to protect people against mycotoxins is timely detection. Several methods such as affinity chromatography and enzyme-linked immunosorbent assay are commercially available for this purpose. Nevertheless, fast, sensitive, simple, portable, and low-cost devices are difficult to find. Application of biosensors appears to be a possible method to meet this need for mycotoxins assay.

Unusual But Potential Agents of Terrorists

Emergency personnel are tasked with the daunting job of being the first to evaluate and manage victims of a terrorist attack. Numerous potential chemical agents could be used by terrorists. The challenge for first responders and local hospital emergency personnel is to prepare for a terrorist event that might use one or more of these agents. As part of that preparation, emergency physicians should have a basic understanding of potential chemical terrorist agents. It is beyond the scope of this article to review all potential terrorist agents. Rather, four potential agents have been chosen for review: sodium monofluoroacetate, trichothecene mycotoxins, vomiting agents, and saxitoxin.

Fungi and fungal toxins as weapons

Recent aggressive attacks on innocent citizens have resulted in governments increasing security. However, there is a good case for prevention rather than reaction. Bioweapons, mycotoxins, fungal biocontrol agents (FBCA), and even pharmaceuticals contain, or are, toxins and need to be considered in the context of the new paradigm. Is it desirable to discuss such issues? None of the fungi are (a) as toxic as botulinum toxin from Clostridium botulinum, and (b) as dangerous as nuclear weapons. One toxin may be defined as a pharmaceutical and vice versa simply by a small change in concentration or a moiety. Mycotoxins are defined as naturally occurring toxic compounds obtained from fungi. They are the biggest chronic health risk when incorporated into the diet. The current list of fungal toxins as biochemical weapons is small, although awareness is growing of the threats they may pose. T-2 toxin is perhaps the biggest concern. A clear distinction is required between the biological (fungus) and chemical (toxin) aspects of the issue. There is an obvious requirement to be able to trace these fungi and compounds in the environment and to know when concentrations are abnormal. Many FBCA, produce toxins. This paper indicates how to treat mycotoxicosis and decontaminate mycotoxins. There is considerable confusion and inconsistency surrounding this topic which requires assessment in an impartial and scientific manner.