1,721,225 research outputs found
Mixture effect of two antifungal triazoles (triadimefon and cyproconazole) in rat and Amphibian embryos cultured in vitro
No full textThe present work aims to evaluate the teratogenic potential of
two triazole-derived fungicides (triadimefon, FON, cyproconazole,
CYPRO) alone, as well as their action in a mixed solution on Amphibian
(Xenopus laevis) and rat embryos cultured in vitro. On the basis
of the morphological and molecular interclasses similarities at the
phylotypic stage, low vertebrate animal models have been proposed
as alternative to mammals in assessing the developmental
toxicity of xenobiotics. Triazole derivatives represent a large class
of molecules with antifungal properties, used in agriculture and
human-veterinary therapy. Experimental studies indicate all the
tested triazoles as teratogenic in rodents, rabbits, amphibians and
tunicates, and neurulation as the most sensitive period for inducing
craniofacial defects thus affecting the organization of embryonic
transient structures (branchial arches). Rat embryos were exposed
during the whole culture period (from early neurulation till phylotypic
stage) to 7.8–250Mof two agrochemical triazoles (FON and
CYPRO) alone, or to their mixture (MIX1: FON 7.8M plus CYPRO
7.8M). At the end of the culture period embryos were morphologically
examined and immunostained to evaluate neural crest cell
migration. X. laevis embryos were exposed during early neurulation
stages to FON and CYPRO alone (3.9-250M), to MIX1, and
to MIX2 (FON 3.9M plus CYPRO 3.9M). At the end of the exposures,
embryos were washed and allowed to reach the phylotypic
stage or the larval stage 47 to evaluate neural crest cell migration
and craniofacial morphology. The obtained results confirmFONand
CYPRO as teratogenic and showed a clear mixture effect in both
species. This suggests that the teratogenic mechanism is common
for the two molecules and that it is able to act in different Vertebrate
species, indicating X. laevis as an adequate alternative animal model
for teratogenic screening of mixtures obtained from molecules of
this chemical class
Citral, an inhibitor of retinoic acid synthesis, attenuates the frequency and severity of branchial arch abnormalities induced by triazole-derivative fluconazole in rat embryos cultured in vitro
No full textThe clinically used antimycotic fluconazole (fluco) is teratogenic in rodents. Exposure in vitro to fluco, other investigated azoles (triadimefon, triadimenol, flusilazole, ketoconazole and imazalil) or retinoic acid (RA), is correlated to branchial arch abnormalities. Inhibition of RA degradation has been suggested as the azole-related mechanism. Citral is a RA synthesis inhibitor. E9.5 rat embryos were cultured for 48 h in normal serum or exposed in vitro to fluco 125 microM, citral 200 microM or co-exposed to the two molecules to test the hypothesis that citral attenuates fluco-related teratogenic effects. Some embryos were cultured for 12 extra hours, and cranial nerves immunodetected. Fluco induced typical abnormalities, including branchial arch and cranial nerve defects. The co-exposure to fluco+citral was significantly effective in reducing branchial arch and cranial nerve defects, supporting the hypothesis that citral balances the fluco-induced RA concentration increase. However, other fluco-related effects were unalterated by citral
Postulated pathogenic pathway in triazole fungicide induced dysmorphogenic effects
No full textTriazole fungicides are used in medicine as well as in agricultural treatment of mycoses. The pharmacological mechanism is related to the inhibition of CYP enzymes involved in the formation of the fungal walls. A similar inhibition of human CYP enzymes has been suggested as the cause of triazole side effects in humans. An importent role of some CYP isoforms (CYP26 isoforms) expressed during mammalian development is the catabolism of retinoic acid, a known morphogen in vertebrates and invertebrates. The adverse effects on morphogenesis, observed after exposure of mammalian, anfibian and ascidiacea, are compared to the reported effects of triazole in humans. The possible pathogenic pathway in triazole-related teratogenesis is discussed on the basis of different experimental approaches
Inhibition of histone deacetylase as a new mechanism of teratogenesis
No full textHistone deacetylases (HDACs) are nuclear and cytoplasmic enzymes that deacetylate a number of substrates, of which histones are the best known and described in the literature. HDACs are present in eukaryotic and bacteria cells, and are fundamental for a number of cellular functions, including correct gene expression. Surprisingly, only up to 20% of the whole genome is controlled by HDACs, but key processes for survival, proliferation, and differentiation have been strictly linked to HDAC enzyme functioning. The use of HDAC inhibitors (HDACi) has been proposed for the treatment of neoplastic diseases. Their effectiveness has been suggested for a number of liquid and solid tumors, particularly acute promyelocytic leukemia (APL). The role of HDACs in embryo development is currently under investigation. Published data indicate knockout phenotype analysis to be of particular interest, in which a number of HDACs play a key role during development. Little data have been published on the effects of HDACi on embryonic development, although for valproic acid (VPA), literature from the 1980s described its teratogenic effects in experimental animals and humans. To date, all tested HDACi have shown teratogenic effects similar to those described for VPA when tested in zebrafish, Xenopus laevis, and mice. HDACs were also able to alter embryo development in invertebrates and plants. A model, similar to that proposed in APL, involving retinoic acid receptors (RAR) and tissue specific Hox gene expression, is suggested to explain the HDAC effects on embryo development
VPA-related axial skeletal defects and apoptosis: a proposed event cascade
No full textVPA axial malformations are related to embryonic somitic histone hyperacetylation. In cancer, histone hyperacetylation activates apoptosis. To verify if apoptosis is involved in somitic abnormalities, VPA-exposed embryos were evaluated for DNA fragmentation and for pro- (p53, acetylated p53, caspase 3) and anti-apoptotic (Sirt 1) protein expression.
Pregnant mice were i.p. dosed on day 8 with VPA 400 mg/kg or TSA (16 mg/kg). Embryos, collected 3, 5, 9 or 24 h after treatment, were examined and processed for apoptosis or protein analysis.
An event cascade has been observed at the level of somites and proposed as related to VPA-induced axial skeletal defects: increased p53 (3 h), DNA fragmentation (9 h), abnormalities (24 h). TSA, used as alternative HDAC inhibitor, induced apoptosis and somitic abnormalities, strengthening our hypothesized link between HDAC inhibition and axial defects
Pathogenic pathways in fluconazole-induced branchial arch malformations
No full textBACKGROUND: A widely-used antimycotic agent, bis-triazole fluconazole (FLUCO), is able to produce abnormalities to the branchial apparatus (hypoplasia, agenesis, and fusion) in postimplantation rodent embryos cultured in vitro. The branchial apparatus is a complex and transient structure in vertebrate embryos and is essential for the development of the face skeleton. Branchial arch mesenchyme is formed by two different cellular populations: paraxial mesenchyme and ectomesenchyme, which originate from rhombencephalic neural crest cell (NCC) migration. We investigated the possible pathogenic pathways involved in FLUCO-related branchial arch abnormalities. Perturbations in physiological apoptosis, cell proliferation, NCC migration and branchial mesenchyme induction have been considered. METHODS: Rat embryos (9.5-day postcoitum; 1-3 somites) were exposed in vitro to 0 or 500 microM FLUCO. After 24, 36, or 48 hr of culture, embryos were examined for apoptosis (acridine orange method) and cell proliferation (BrdU incorporation and detection method). Rhombencephalic NCC migration was analyzed using immunostaining of NCC (using anti-CRABP antibodies) and the extracellular matrix (using anti-fibronectin antibodies). The differentiative capability of the branchial mesenchymes was investigated using anti-endothelin and anti-endothelin-receptor antibodies. RESULTS: During the whole culture period, no alterations in physiological apoptosis, cell proliferation, and mesenchymal cell induction were observed in FLUCO-exposed embryos in comparison to controls. On the contrary, severe alterations in NCC migration pathways were observed in FLUCO-exposed embryos. CONCLUSIONS: The findings suggest that FLUCO produces teratogenic effects by interfering with the cellular and molecular mechanisms that control NCC migration
Antifungal triazole derivative triadimefon induces ectopic maxillary cartilage by altering the morphogenesis of the first branchial arch
No full textBACKGROUND: The triazole derivative, triadimefon (FON), induces branchial arch abnormalities in post-implantation rat embryos cultured in vitro, and cranio-facial malformations in mouse fetuses. Ectopic maxillary cartilage has been also described as a typical FON-related malformation. This work studies the morphogenesis of the ectopic cartilage in rat embryos and fetuses exposed in vivo to FON during the early postimplantation period. METHODS: Pregnant rats were treated with 0, 250, and 500 mg/kg FON on Day 9.5 of pregnancy (D9.5) and sacrificed at term (D20), during the early fetal period (D17) or at different embryogenetic periods (D10, D11, D12). The skeleton was examined after stain of bone and cartilage or of cartilage alone respectively at term or at D17. The neural crest cell (NCC) migration and compaction was investigated at D10 and D11 and the cranial nerve organization described at D12. RESULTS: Triadimefon is teratogenic in rats under the chosen experimental conditions. The malformations were at the level of the cranio-facial and axial skeleton at term and of the hindbrain nerves in embryos. A NCC abnormal migration and compaction was observed at the level of the first branchial arch: in FON-exposed embryos NCC were detected at the level of both maxillary and mandibular processes, whereas control embryos showed the immunostained tissue only at the level of the mandibular bud. CONCLUSIONS: The pathogenic pathway, proposed to explain the ectopic cartilage, is the displacement of part of the NCC-derived tissues at the maxillary region of the first branchial arch
Dysmorphogenic effects of some fungicides derived from the imidazole on rat embryos cultured in vitro
No full textLike triazole-derivs., imidazole-derivs. exert their antifungal and toxicol. properties by inhibiting P 450 enzymes (Cyps). At the embryonic level, Cyp enzymes are involved also in the catabolism of the retinoic acid. Specific effects of triazole-derivs. have been reported on developing rodent embryos, and were correlated to an imbalance of the retinoid homeostasis. The aim of this work was to investigate if imidazole-derivs. are able to induce specific malformations similar to those obsd. after triazole-deriv. exposure. Post implantation rat embryos were exposed in vitro to 1000 mM Imidazole and to 5-100 mM of the imidazole-derivs. Ketoconazole and Enilconazole. After 48 h in culture, the embryos exposed to the imidazole-derivs. showed specific malformations, quite similar to those obsd. after triazole-deriv. exposure. The common dysmorphogenic effects of the azole-derivs. of the two classes could be due to the inhibition of retinoid catabolism. From this point of view, the contemporaneous exposure to these substances or their therapeutic use could be considered as potentially dangerous for human conceptuses. [on SciFinder (R)
Chemical-induced facial dismorphogenesis: A modeling approach to help understanding the mode-of-action
No full textMixture effect of two agrochemical antifungal triazoles (triadimefon and cyproconazole) in two different alternative developmental animal models (WEC and FETAX)
No full textAzole fungicides are described as teratogenic in different animal models, inducing cranio-facial defects. The aim of the present work is to evaluate the teratogenic potential of two triazole-derived fungicides (triadimefon, FON, cyproconazole, CYPRO) alone or in a mixed solution by using two different alternative animal models (rat postimplantation Whole Embryo Culture- WEC and Frog Embryo Teratogenesis Assay: Xenopus- FETAX). On the basis of the morphological and molecular interclasses similarities at the phylotypic stage, low vertebrate animal models have been proposed as alternative to mammals in assessing the developmental toxicity of xenobiotics. Rat embryos were exposed during the whole culture period (from early neurulation till phylotypic stage) to 7.8-250μM of two agrochemical triazoles (FON and CYPRO) alone, or to their mixture (FON 7.8μM plus CYPRO 7.8μM). At the end of the culture period, embryos were morphologically examined and immunostained to evaluate neural crest cell (NCC) migration. Xenopus laevis embryos were exposed during early neurulation stages to FON and CYPRO alone (3.9-250μM), or to their mixtures (FON 3.9μM plus CYPRO 3.9μM). At the end of the exposure period, embryos were washed and allowed to reach the phylotypic stage (to evaluate neural crest cell migration) or the tadpole stage (to evaluate the craniofacial morphology). In both animal models, FON and CYPRO were teratogenic and showed a clear mixture effect (the mixture of no effect levels resulted effective in inducing teratogenic effects, suggesting that the teratogenic mechanism is common for the two molecules). The evidence that similar results were obtained both in rat and X. laevis embryos, indicates X. laevis as an adequate alternative animal model for teratogenic screening of mixtures of xenobiotics
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