Unknown,Transcriptomics,Genomics,Proteomics

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Alteration of the expression and 17, 20 lyase activity of cytochrome P450 17-hydroxylase/17, 20 lyase and of the expression of other Leydig cells genes in the rat fetal testis directly exposed to Mono-ethyl hexyl phthalate in culture.

ABSTRACT: This study aimed to investigate the direct mechanism(s) of action ofMono-(Ethyl-Hexyl) phthalate (MEHP) on the rat fetal testis with particular emphasis to Leydig cell steroidogenesis, by means of an in vitro system based on culture for 3 days of fetal testes from 14.5 days post-coïtum old rats. We first confirmed that an exposure to MEHP led to a dose-dependent decrease of testosterone and demonstrated that dihydrotestosterone (DHT) production was also inhibited. We then demonstrated that in 10µM MEHP-exposed testis basal 17alpha-hydroxy-progesterone (17OHP) production was increased (+40%) while androstenedione levels decreased (-55%). Furthermore, the addition of the latter steroid but none of the other precursors rescued testosterone thus establishing further that MEHP specifically blocked steroidogenesis at the level of the 17,20 lyase activity of the P450c17 enzyme (CYP17), which converts 17OHP to androstenedione. Furthermore and accordingly, both levels of testicular CYP17 protein (western blot) and cyp17a1 gene (qPCR, microarrays) were found to decrease under MEHP exposure. The microarray analysis also showed that among the few other testicular genes cyp17a1 whose expression was inhibited by MEHP were the genes encoding for the Leydig cell insulin-like peptid 3 (INSL3), involved in the control of testicular descent, and for inhibin A (INHA), that regulates follicular-stimulating hormone secretion.Under in vitro conditions where MEHP is not metabolized and remains at low intratesticular concentration, our findings show in particular that this phthalate directly inhibits several important Leydig cell factors involved in testis development and function. Transcription profiling of rat fetal testes explants, vehicle or monoethylhexylphthalate (MEHP)-treated (1uM, 10uM) 3 condition experiment, 1-3 biological replicates per treatment. 2 technical replicates per sample.

ORGANISM(S): Rattus norvegicus

SUBMITTER: simon plummer

PROVIDER: E-GEOD-22218 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The purpose of this study is to assess the potential of TOTM to induce testicular maldevelopment in the rat. We studied the effects of TOTM on the expression of genes in pathways involved in steriodogenesis and testes development. Certain phthalate esters have previously been shown to be involved in the induction of rat testicular mal-development (TMD) through effects on the expression of genes in pathways involved in steroidogenesis and testes development. In order to assess the effects of a potential alternate plasticizer, tris(2-ethylhexyl)trimellitate (TOTM), rats were exposed daily, in utero, to TOTM in order to assess the potential of this compound to induce developmental effects on the fetal testes. Pregnant rats were exposed between gestational day 12 and 19 and fetal testes RNA was analysed using whole genome microarrays. The effects of TOTM on the expression of genes in pathways involved in steroidogenesis and testes development were examined. The effects of TOTM were also compared with di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)phthalate (MEHP), an active metabolite of DEHP, and 2-ethylhexanol (2-EH), which were used as positive and negative controls, respectively. MEHP & DEHP (500mg/kg) caused a repression of genes in TMD pathways involved in cholesterol synthesis and transport (HMGCS, HMGCR, StAR, SCARB1, FDFT1, FDPS), steroidogenesis (Cyp11a, HSD3B1, SC4MOL) and testes development (INSL3, INHA). 2-EH caused minor repression of some of the genes in the TMD pathway. This was rationalised on the basis that 2-EH, a DEHP metabolite, is also a weak PPARα agonist. It has been shown that in utero treatment with DBP will repress the genes from fetal testes involved in steroidogenesis and that this effect is associated with direct DBP-mediated binding of PPARα to the promoters of these genes (Plummer et. al. 2010). TOTM did not cause a significant repression of genes in the TMD pathway. Based on these data, it is highly unlikely that TOTM will cause testicular dysgenesis in rats. Rats were exposed to TOTM in utero by the administration of daily oral gavage doses to pregnant dams between gestational day 12 and 19. The foetal testes were obtained by micro-dissection and prepared to facilitate the isolation of RNA, which was subsequently analysed using whole rat genome microarrays.

Dataset Information

Alteration of the expression and 17, 20 lyase activity of cytochrome P450 17-hydroxylase/17, 20 lyase and of the expression of other Leydig cells genes in the rat fetal testis directly exposed to Mono-ethyl hexyl phthalate in culture.

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