Francesca Di Renzo

Antifungal triazoles induce malformations in vitro

Triazole-derivatives are antimycotics used in agriculture as well as in clinical and veterinary therapy. The aim of the present work is the in vitro comparative study of the teratogenic activity of triazole (the parental compound), flusilazole (an agricultural triazole mono-derivative fungicide), and fluconazole (a clinically used bis-triazole derivative). Rat embryos, 9.5 days old (1 to 3 somites) were exposed in vitro to triazole 500 to 5000 microM, flusilazole 3.125 to 250 microM, or fluconazole 62.5 to 500 microM. After 48 h in culture, the embryos were morphologically examined and processed for histologic and biochemical analysis. Flusilazole and fluconazole showed similar teratogenic effects (abnormalities at the branchial apparatus level and cell death at the level of the branchial mesenchyme) at concentration levels of 6.25 microM and higher for flusilazole and of 125 microM and higher for fluconazole. By contrast, only slight developmental retardation and blood discoloration were observed at the highest concentrations of triazole, suggesting no teratogenic activity for the triazole group.

In vitro teratogenic potential of two antifungal triazoles: Triadimefon and triadimenol

SummaryThe teratogenic potential of two antifungal triazoles (Triadimefon and Triadimenol) has been investigated in vitro by the rat postimplantation whole embryo culture method. Rat embryos 9.5 d old were cultured for 48 h in rat serum with Triadimefon (12.5–250 μM) or Triadimenol (6.25–125 μM) and then examined. Some embryos exposed to Triadimenol (6.25–125 μM) were cultured for 12 extra hours in control serum to improve their developmental degree and then immunostain cranial nerves and ganglia. The exposure to the highest doses of triazoles only moderately reduced some morphometrical developmental parameters. By contrast, 25–250 μM Triadimefon and 25–125 μM Triadimenol induced specific concentration-related teratogenic effects at the level of first and second branchial arches. After immunostaining, embryos exposed to 12.5–125 μM Triadimenol showed specific cranial nerve and ganglia abnormalities. The possible implication of neural crest cell alterations on triazole-related abnormalities is discussed.

Comparative study of sodium valproate-induced skeletal malformations using single or double staining methods

The teratogenic activity of xenobiotics is usually investigated by examining visceral and skeletal abnormalities of term fetuses. Although the rodent fetal skeleton is only partially ossified, the single stain for bone is the most commonly used method in routine teratology testing, while the double stain for evaluation of both bone and cartilage is often used only in basic research. The present work compares data obtained from rat fetuses using the two methods after exposure to the teratogenic agent sodium valproate at specific embryonic stages of development. Pregnant rats were treated with 400mg/kg sodium valproate and sacrificed at term of pregnancy. Even if both methods were able to identify sodium valproate as a teratogenic molecule, correct and complete interpretation of data was possible only by using the double stain. Our results show the inability of the single stain to correctly discriminate between major and minor abnormalities.

The Inhibition of Embryonic Histone Deacetylases as the Possible Mechanism Accounting for Axial Skeletal Malformations Induced by Sodium Salicylate

In spite of the large use of salicylates, introduced into clinical practice more than 100 years ago, their anti-inflammatory and cancer preventive mechanisms are still under study. Teratogenic effects of salicylates have been reported in experimental animals since 1959 but the pathogenic pathways and the mechanisms of action were never described until now. The aim of this work is to verify if the inhibition of embryonic histone deacetylase (HDAC) enzymes and the consequent tissue hyperacetylation could be the mechanism responsible for axial skeletal defects described after the exposure of pregnant rodents to sodium salicylate (SAL). E8 pregnant CD-1 mice were intraperitoneally treated with SAL 0-150-300-450 mg/kg and sacrificed at 1, 3, 5 h after treatment or at term of gestation (E18). E8 embryos were processed for Western blotting and immunostaining analyses, while skeletons of E18 fetuses were double stained for bone and cartilage. A group of control E8 embryos were used to prepare embryonic nuclear extract for the HDAC enzyme assay. A significant SAL dose-related HDAC inhibition activity, compatible with a mixed-type partial inhibition mechanism, was detected. A clear dose-related hyperacetylation of histones was observed in embryos exposed in utero to SAL, with a peak at 3 h after treatment of dams. The most hyperacetylated organs were somites and the heart. Histone hyperacetylation is suggested to be the mechanism accounting for SAL-related axial skeletal and cardiovascular defects and is proposed as the mechanism responsible for other biological effects of salicylates.

The agrochemical fungicide triadimefon induces abnormalities in Xenopus laevis embryos.

The dysmorphogenic activity of the triazole fungicide triadimefon (FON) has been evaluated using Xenopus laevis development. Embryos, exposed to 500 μM FON during early neurulation phases (stages 13-17, Nieuwkoop and Faber), were allowed to develop until stage 47. Larvae revealed serious craniofacial defects, bent forebrain, and abnormal hindbrain segmentation. CRABP and CYP26 (markers related to retinoic acid homeostasis) gene and protein expression and protein distribution have been evaluated at stage 17 and at the end of the branchial arch morphogenesis (stage 27) by real-time PCR, western blot and whole-mount immunostaining. A significant increase of CYP26 transcript has been observed at both embryonic stages. A co-localization of the two markers has been observed at the cephalic region. Embryos exposed to FON showed abnormal distribution of positive tissues. Due to the strict similarity of these results with those previously described in rodents, a FON-related alteration of mechanism conserved during vertebrate evolution is suggested.

EFFECTS OF EXCESS AND DEPRIVATION OF SEROTONIN ON IN VITRO NEURONAL DIFFERENTIATION

SummaryThe neutrotransmitter serotonin (5HT) possesses developmental functions in vertebrates and invertebrates. Rodent embryos express 5HT receptors even before neural development, but the role of this neurochemical seems to be particularly important during axonal morphogenesis and differentiation and in neural crest cell migration. Moreover, 5HT inhibitors are teratogenic in mammals, inducing brain and heart abnormalities. The aim of this study was to investigate the effects of nonphysiological concentrations of 5HT (5HT excess as well as deprivation) on developing rat neural cells using the micromass method. This simple and rapid micromass method allows the culture of mesencephalic cells capable of achieving and maintaining a significant degree of differentiation. Mesencephalic cells from 13 d post coitum (pc) rat were cultured and exposed to exogenous 5HT (1, 10, 50, or 100 μM) or to the specific 5HT2 receptor inhibitor mianserin (0.5, 5, 25, or 50 μM) during the whole culture period (5 d). The micromass morphology, the cytoskeletal organization, the pathological apoptosis, and the differentiative capability of cultured mesencephalic cells have been analyzed. The results show that 10–100 μM 5HT and 0.5–50 μM mianserin are able to disrupt the normal micromass morphology; 5HT and mianserin are unable to interfere with the cytoskeletal structures; mianserin (but not 5HT) induces pathological apoptosis on micromass cells at concentration levels of 0.5–50 μM; 5HT (but not mianserin) alters the neural differentiation at concentration levels of 10–100 μM. In conclusion, our results demonstrate that an excess of 5HT inhibits the capability of mesencephalic neurons to differentiate as shown by the alterations of the expression of the neuronal differentiative proteins glial-derived neurotrophic factor and Neu-N; on the other hand, the blocking of 5HT2 receptors induces apoptosis in differentiating neurons.

Is the amphibian X. laevis WEC a good alternative method to rodent WEC teratogenicity assay? The example of the three triazole derivative fungicides Triadimefon, Tebuconazole, Cyproconazole

The aim of the present work is the assessment of teratogenic effects of three triazole-derived fungicides (Triadimefon, FON, Tebuconazole, TEBU, Cyproconazole, CYPRO) on rat and Xenopus laevis embryos cultured in vitro. Rat embryos, exposed to FON 31.25-250μM, CYPRO 31.25-62.5μM and to TEBU 62.5-250μM, showed specific malformations (fusions) at the level of the first and second branchial arches, with a concentration-dependent increase of severity of malformative pictures. After immunostaining, the ectomesenchyme has been identified as the target tissue. X. laevis larvae showed, at the same concentrations, specific malformations at the level of cartilaginous element derived from the first and second branchial arch ectomesenchyme. This work indicates the three tested triazoles as teratogenic both in rodents and in amphibian, inducing ectomesenchymal abnormalities, and suggests, at least for this class of molecules, the X. laevis method as adequate alternative model for teratogenic screening.

VPA-related axial skeletal defects and apoptosis: A proposed event cascade

VPA 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 400mg/kg or TSA (16 mg/kg). Embryos, collected 3, 5, 9 or 24h 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 (3h), DNA fragmentation (9h), abnormalities (24h). TSA, used as alternative HDAC inhibitor, induced apoptosis and somitic abnormalities, strengthening our hypothesized link between HDAC inhibition and axial defects.

Early genetic control of craniofacial development is affected by the in vitro exposure of rat embryos to the fungicide triadimefon

BACKGROUND Previous published experiments reported that in vitro exposure of postimplantation rat embryos to the triazole fungicide triadimefon (FON) resulted in specific abnormalities at the branchial apparatus and that the sensitive period is restricted to the first 24 hr of culture and is associated with the abnormal expression of TGF family genes (some of a large panel of genes regulated by retinoic acid (RA) and involved in branchial arch morphogenesis). The aim of this study is the determination of the sensitive window to FON-induced abnormalities during in vitro development and the evaluation of the expression of some genes controlled by RA and involved in early branchial arch morphogenesis (Gsc, Msx1, Msx2, Dlx1, Dlx2, Shh, Patched (the main Shh receptor)). METHODS Rat embryos were exposed in vitro to the FON under condition known to be able to induce 100% of abnormal embryos (250  µM) at different stages and examined after 48 hr of culture. The sensitive window for FON-induced abnormalities was during the hours E9 h8.00 PM-E10 h8.00 AM. To evaluate the expression of selected genes, embryos exposed during the sensitive stages were processed to perform quantitative PCR after 18 and 24 hr of culture. RESULTS FON was able to affect the expression of some genes in a stage-specific manner: earlier embryos were characterized by the downregulation of Msx2 and Gsc, later embryos showed the downregulation of Gsc, Shh, and Patched. The obtained data suggest that FON-induced abnormalities are mediated, at least in part, through the imbalance of the expression of RA-related signals.

Stage-dependent abnormalities induced by the fungicide triadimefon in the mouse ☆

Aim of this work is the study of abnormalities induced by the triazole triadimefon (FON) administered to pregnant mice at E8, E9, E10, E11 or E12. Pregnant CD-1 mouse were gavaged with FON 500 mg/kg at the selected stages and sacrificed at term and fetuses morphologically examined and processed for visceral and skeletal analysis. Administration of FON on E8, E10-E12 resulted in fetuses with cleft palate (E8 39% and E12 24% representing the peak of sensitivity, in E8 fetuses associated to severe skull basis abnormalities). Other cranial malformations (fusions abnormalities or agenesis of bones) were observed in E8-E10 groups (E8 the most sensitive with 96% of malformed fetuses). Cardiovascular abnormalities were observed in a stage dependent manner at E8-E10 (22.2, 3.8, 7.8%). As far as craniofacial malformation is concerned, we propose that FON acts on two different stages, involved in early and late craniofacial formation.