New mycotoxins and their toxicological mechanisms of action (AKATOX)

“Application of modern molecular techniques to investigate the mode of action of highly prevalent Fusarium avenaceum mycotoxins enniatin B and moniliformin.”

Summary:

Red mould Fusarium spp. infections in crops and particularly in cereals, cause  substantial economic losses globally by spoiling the crop.  Fusarium not only cause toxicity in  the hostplant, but also producea secondary metabolic products, mycotoxins. More than 300 different mycotoxins have been isolated, some of which have highly adverse or even death-inducing effects on humans and animals. Hence, the European Community has set  limits for the maximum daily intake of the most harmful mycotoxins in 2006 (Regulation 2005/856/EC). Nevertheless, a group of prevalent but less known Fusarium mycotoxins,  whose health effects are still not  known, such as enniatin (ENN), moniliformin (MON) and beauvericin (BEA), remains outside the scope of legislation. These mycotoxins have not caused large-scale epidemics in humans or animals but have been shown to cause symptoms and even death in test animals or to have toxicity in vitro.

The mycotoxins produced by  Fusarium species often have a polycyclic structure and are biologically active. They can be divided into three main groups: tricotesens, fumonisins and zearalenone, and furthermore a group of other less known mycotoxins, among which are MON, ENN and BEA. The toxicity and mode of action of ENN and MON are not yet fully known. ENN is a cyclic depsipeptide proposed to  act as a   ionofor, forming an ion channel in the cell membranes of cells and hence affecting the ion balance in cells. Moniliformin is a hydrocyclobutenedione,with the  structure resembling  puryvate, a molecule essential to the energy production in  cells.It has been proposed  that MON would  replace puryvate in the citric acid cycle and hence stop the cellular energy production.

F. avenaceum, commonly found in Northern Europe, , mainly produces ENN, BEA and MON. In Finland and Norway, repeated low concentrations of MON and ENN in grain have been reported. Of grain samples collected in Finland during 2001-2002, ENN was found in 100 per cent and MON in 74 per cent of the samples (Jestoi,M., 2005). Despite the prevalence of MON and ENN, not many in vivo studies to determine the acute toxicity or the health effects of low, frequent doses of these two mycotoxins have been conducted.

The Akatox project, financed by the Academy of Finland and coordinated by professor Kimmo Peltonen (Finnish Food Safety Authority EVIRA), was launched in 2008. The objective  is to to study  the acute and subacute toxicity of the Fusarium mycotoxins MON and ENN in vivo, in accordance with the OECD guidelines, and  to study the in vitro toxicity as well as  the mode  of action  by molecular  methods and gene expression studies.  Furthermore, he metabolism  and metabolic products of the toxins are examined ,by mass spectrometric measurements from urine and faecal samples of test animals , and by in silico computer modelling.

Results:

In vivo tests conducted on moniliformin showed MON to cause acute toxicity in rats, the LD 50 value being at the same level with the most toxic Fusarium mycotoxins, T-2 and HT-2.   Pathological investigations revealed mainly cardiotoxic effects. By mass spectrometric analyses of urine samples moniliformin was shown to be rapidly excreted into urine.  Metabolic studies are still in progress. Long-term effects have been studied in accordance with the OECD guideline 407, by conducting  a subacute toxicity test, the results of which have not yet been published. Enniatin has not been shown to be particularly toxic in acute, oral toxicitystudies. The results of in vitro studies and geneexpression studies are currently being processed and will be published during the year  2014.

Keywords:

Fusarium, Mycotoxins, Moniliformin, Enniatin  

Responsible project leader:

Peltonen, Kimmo, Professor, Chemistry and Toxicology Research Unit

In cooperation with:

Evira;
University of Turku:  Department of Biochemistry and Food Chemistry;
University of Helsinki: Laboratory of Organic Chemistry;
University of Helsinki: Division of Pharmaceutical Chemistry;
University of Helsinki: Department of Equine and Small Animal Medicine (pharmacology and toxicology);
University of Eastern Finland: School of Pharmacy (foreign substance metabolism, Kuopio);
National Veterinary Institute, Oslo

Project status:

Previous

Year of commencement:

2008

Year of completion:

2015

Publications:

Jonsson,M., Jestoi,M.,Nathanail,A.V., Kokkonen, U-M.,Anttila, M:, Koivisto,P.,Karhunen,P., Peltonen, K.  Application of OECD Guideline 423 in assessing the acute oral toxicity of moniliformin. Food and Chemical Toxicology 53 (2013) 27-32. 

Project financed by:

Academy of Finland (121724)

Project code:

8701