Effect of subacute oral doses of nivalenol on immune and metabolic defence systems in miceMarie-Estelle Gouzea, Joëlle Laffittea, Philippe Pintona, Geneviève Dedieuxb, Anne Galinierb, Jean-Paul Thouvenotb, Nicolas Loiseaua, Isabelle P. Oswalda and Pierre Galtiera
a Laboratoire de Pharmacologie-Toxicologie, UR66, INRA, 180 Chemin de Tournefeuille, 31931 Toulouse, France
b Laboratoire de Biochimie Générale et Nutritionnelle, CHU Purpan, Place du Dr Baylac, 31059 Toulouse, France
(Received 21 December 2006; accepted 13 March 2007 ; published online 13 June 2007)
Abstract - Nivalenol (NIV) is a toxic Fusarium secondary trichothecene metabolite occurring naturally in cereal grains. In order to evaluate the no observed adverse effect level (NOAEL), we tested the effects of a large array of oral doses of this toxin for responses on plasma biochemistry, the immune system and hepatic drug metabolism in mice. C57Bl6 mice received oral doses of toxin (0.014, 0.071, 0.355, 1.774 or 8.87 mg/kg bw) 3 days a week for 4 weeks. Only the highest dose of NIV induced an increase in plasma phosphate, decreases in plasma urea and immunoglobulin M and additional changes like increases in plasma alkaline phosphatase and immunoglobulin G. Interleukin 4 production was increased in cultured murine splenocytes. Regarding liver drug metabolising enzymes, the only glutathione transferase activity accepting 1-chloro-2,4-dinitro-benzene as substrate was transiently increased in mice receiving low doses (0.071 and 0.355 mg/kg bw) of NIV. Regarding the cytochrome P450 monooxygenases, no significant change was observed in ethoxyresorufin O-deethylase activity whereas both methoxyresorufin and pentoxyresorufin O-dealkylase activities were decreased by 38-45% for the highest dose (8.87 mg/kg bw) of NIV. However, when analysed by Western blot analysis, the protein expression of mouse P450 1a, 2b, 2c, 3a and 4a subfamilies was unchanged in animals receiving NIV. In conclusion, the NOAEL of this toxin in our study was 1.774 mg/kg bw, corresponding to an exposure to 5 ppm contaminated food. Indeed hepatotoxicity appears in the only mice treated with a five fold higher oral dose of 8.87 mg/kg bw of NIV. Such exposure levels appear to be by far higher than the maximal natural occurrence measured in European cereals, known to range from 0.34 to 1.86 ppm.
Key words: mice / nivalenol / immunotoxicity / biotransformation enzymes
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