tretinoin and triadimefon

Although some central effects of triadimefon, a triazole fungicide, have been reported, its effects on spatial memory have not been examined. In this study, we used the Morris water maze to study the effect of triadimefon on spatial learning and memory in rats. To elucidate the mechanism of this effect, we also measured the retinoic acid concentration in the hippocampus by high-performance liquid chromatography. Our data showed that triadimefon inhibited spatial learning and impaired spatial reference memory, and decreased hippocampal retinoic acid concentration. There is evidence that triadimefon can regulate the metabolism of retinoic acid, which serves a critical function in the development and maintenance of spatial memory. Therefore, we speculate that the reduction in hippocampal retinoic acid concentration induced by triadimefon might be responsible for its suppressive effect on spatial learning and reference memory.

Topics: Animals; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Fungicides, Industrial; Hippocampus; Male; Maze Learning; Memory; Rats; Rats, Sprague-Dawley; Tretinoin; Triazoles

The use of nonmammal models in teratological studies is a matter of debate and seems to be justified if the embryotoxic mechanism involves conserved processes. Published data on mammals and Xenopus laevis suggest that azoles are teratogenic by altering the endogenous concentration of retinoic acid (RA). The expression of some genes (Shh, Ptch-1, Gsc, and Msx2) controlled by retinoic acid is downregulated in rat embryos exposed at the phylotypic stage to the triazole triadimefon (FON). In order to propose X. laevis as a model for gene-based comparative teratology, this work evaluates the expression of Shh, Ptch-1, Gsc, and Msx2 in FON-exposed X. laevis embryos.. Embryos, exposed to a high concentration level (500 µM) of FON from stage 13 till 17, were examined at stages 17, 27, and 47. Stage 17 and 27 embryos were processed to perform quantitative RT-PCR.. The developmental rate was never affected by FON at any considered stage. FON-exposed stage 47 larvae showed the typical craniofacial malformations. A significant downregulation of Gsc was observed in FON-exposed stage 17 embryos. Shh, Ptch-1, Msx2 showed a high fluctuation of expression both in control and in FON-exposed samples both at stages 17 and 27.. The downregulation of Gsc mimics the effects of FON on rat embryos, showing for this gene a common effect of FON in the two vertebrate classes. The high fluctuation observed in the gene expression of the other genes, however, suggests that X. laevis at this stage has limited utility for gene-based comparative teratology.

Topics: Animals; Embryo, Nonmammalian; Gene Expression Regulation, Developmental; Models, Animal; Teratology; Tretinoin; Triazoles; Xenopus laevis; Xenopus Proteins

Conazoles are fungicides used in agriculture and as pharmaceuticals. In a previous toxicogenomic study of triazole-containing conazoles we found gene expression changes consistent with the alteration of the metabolism of all trans-retinoic acid (atRA), a vitamin A metabolite with cancer-preventative properties (Ward et al., Toxicol. Pathol. 2006; 34:863-78). The goals of this study were to examine effects of propiconazole, triadimefon, and myclobutanil, three triazole-containing conazoles, on the microsomal metabolism of atRA, the associated hepatic cytochrome P450 (P450) enzyme(s) involved in atRA metabolism, and their effects on hepatic atRA levels in vivo. The in vitro metabolism of atRA was quantitatively measured in liver microsomes from male CD-1 mice following four daily intraperitoneal injections of propiconazole (210 mg/kg/d), triadimefon (257 mg/kg/d) or myclobutanil (270 mg/kg/d). The formation of both 4-hydroxy-atRA and 4-oxo-atRA were significantly increased by all three conazoles. Propiconazole-induced microsomes possessed slightly greater metabolizing activities compared to myclobutanil-induced microsomes. Both propiconazole and triadimefon treatment induced greater formation of 4-hydroxy-atRA compared to myclobutanil treatment. Chemical and immuno-inhibition metabolism studies suggested that Cyp26a1, Cyp2b, and Cyp3a, but not Cyp1a1 proteins were involved in atRA metabolism. Cyp2b10/20 and Cyp3a11 genes were significantly over-expressed in the livers of both triadimefon- and propiconazole-treated mice while Cyp26a1, Cyp2c65 and Cyp1a2 genes were over-expressed in the livers of either triadimefon- or propiconazole-treated mice, and Cyp2b10/20 and Cyp3a13 genes were over-expressed in the livers of myclobutanil-treated mice. Western blot analyses indicated conazole induced-increases in Cyp2b and Cyp3a proteins. All three conazoles decreased hepatic atRA tissue levels ranging from 45-67%. The possible implications of these changes in hepatic atRA levels on cell proliferation in the mouse tumorigenesis process are discussed.

Topics: Animals; Blotting, Western; Body Weight; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Fungicides, Industrial; Gene Expression Profiling; Liver; Male; Mice; Microsomes, Liver; Nitriles; Organ Size; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Spectrometry, Mass, Electrospray Ionization; Tretinoin; Triazoles

The triazole derivative Triadimefon (FON) is a systemic fungicide used to control powdery mildews, rusts, and other fungal pests. Some data have already been published about the teratogenic activity of this compound: craniofacial malformations were found in mouse, rat, and Xenopus laevis embryos exposed to FON. These alterations were correlated to defective branchial arch development possibly caused by abnormal neural crest cell (NCC) migration into the branchial mesenchyme. As the migration of NCCs is controlled by the HOX code and by an anteroposterior retinoic acid (RA) gradient, we analyzed the expression of CYP26, a key enzyme in RA metabolism, following FON exposure. The increased expression of this gene and the ability of citral (a RA inhibitor) to reduce the teratogenic effects of the fungicide support the notion that endogenous RA is involved in the mechanism of action of FON. Moreover, by in situ hybridization, we studied the effects of FON exposure at gastrula stage on the expression of some genes involved in craniofacial development, hindbrain patterning, and NCC migration. We observed abnormal localization of xCRABP, Hoxa2 and Xbap signal expression at the level of migrating NCC domains, whereas in the hindbrain, we did not find any alteration in Krox20 and Hoxa2 expression.

Topics: Animals; Cell Movement; Cytochrome P-450 Enzyme System; Fungicides, Industrial; Gastrula; Gene Expression Regulation, Developmental; Homeodomain Proteins; In Situ Hybridization; Neural Crest; Receptors, Retinoic Acid; Retinoic Acid 4-Hydroxylase; Teratogens; Transcription Factors; Tretinoin; Triazoles; Xenopus laevis; Xenopus Proteins

Triadimefon and triadimenol, fungicides used in agriculture, are suspected of producing craniofacial malformations. As the results of FETAX analysis showed that Triadimefon was highly teratogenic, we studied the action of these triazoles on the development of the branchial apparatus in Xenopus, using early molecular markers and analysis of the cartilaginous-muscular elements of tadpoles. Teratogenic effects were observed, after exposure at the neurula stage, at the level of cartilages and muscles of the 1st and 2nd branchial arches. By in situ hybridization, we observed that in exposed specimens the territories of the branchial arches are perturbed. From these results, we considered the craniofacial malformations related to the influence of triazoles on the differentiation of branchial arches. Comparing the anomalies caused by triazoles and by retinoic acid (RA) led us to the conclusion that triazoles can affect endogenous RA content, as has been shown for mammals.

Topics: Animals; Branchial Region; Craniofacial Abnormalities; Fungicides, Industrial; Histological Techniques; Immunohistochemistry; In Situ Hybridization; Tretinoin; Triazoles; Xenopus laevis