Effect of azole fungicides on testicular steroidogenesis in vivo and ex vivo in zebrafish (Danio rerio)
Résumé
The occurrence of several azole fungicides in aquatic environment has been recently reported but their endocrine effects in fish are poorly studied. The aim of the present study was to assess the effect of clotrimazole, a pharmaceutical fungicide, on expression of key target genes (StaR, cyp17a1, cyp11b2) involved in testicular steroidogenesis as well as on 11- ketotestosterone (11KT) biosynthesis. For that purpose, we first exposed adult male zebrafish to a wide range of clotrimazole concentrations(from 0.01 uM to 0.3 uM) for 7 days. In vivo exposure to clotrimazole resulted in an increase of cyp17a1 and cyp11b2 gene expressions in testis. To gain further information about the mechanism of action of clotrimazole, zebrafish testicular explants were exposed to similar concentrations of clotrimazole, with or without forskolin (FSK), an activator of the cAMP pathway that stimulates steroidogenesis. FSK (1 uM) strongly up-regulated cyp17a1 and cyp11b2 gene expressions and increased 11KT release in the culture medium. Clotrimazole (0.2, 1, and 5 uM), alone or in combination with FSK (1 uM), did not change basal or FSK-induced expression of cyp17a1 and cyp11b2. However, it inhibited both basal and FSK-induced 11KT release ex vivo, suggesting it acted as an inhibitor of steroidogenic enzymes. In order to determine whether other compounds belonging to the azole family are able to elicit similar effect on testicular steroidogenesis as clotrimazole, two other azole fungicides known to contaminate aquatic environment were tested, fenbuconazole and propiconazole. We showed that exposure of male zebrafish for 7 days to fenbuconazole and propiconazole had no significant effects on steroidogenic gene expressions while ex vivo both azoles was able to inhibit the 11KT release. Overall, our results show for the first time that the pharmaceutical fungicide clotrimazole is able to affect key steroidogenic genes expressions in a fish testis. However, the marked differences observed between in vivo and ex vivo experiments suggest that clotrimazole does not act directly on testes to regulate cyp17a1and cyp11b2 transcription. Whatever, using the testis tissue explants model, we demonstrate a direct action of clotrimazole, and to a lesser extent propiconazole and fenbuconazole, on the gonad which results in inhibition of 11KT synthesis. These original data deserve further studies on the effect of these compounds on fish reproduction