Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island 02912.
Division of Natural Sciences, College of Mount Saint Vincent, Riverdale, New York 10471.
Toxicol Sci. 2019 Mar 1;168(1):149-159. doi: 10.1093/toxsci/kfy283.
Humans are universally exposed to low levels of phthalate esters (phthalates), which are used to plasticize polyvinyl chloride. Phthalates exert adverse effects on the development of seminiferous cords in the fetal testis through unknown toxicity pathways. To investigate the hypothesis that phthalates alter seminiferous cord development by disrupting retinoic acid (RA) signaling in the fetal testis, gestational day 15 fetal rat testes were exposed for 1-3 days to 10-6 M all-trans retinoic acid (ATRA) alone or in combination with 10-6-10-4 M mono-(2-ethylhexyl) phthalate (MEHP) in ex vivo culture. As previously reported, exogenous ATRA reduced seminiferous cord number. This effect was attenuated in a concentration-dependent fashion by MEHP co-exposure. ATRA and MEHP-exposed testes were depleted of DDX4-positive germ cells but not Sertoli cells. MEHP alone enhanced the expression of the RA receptor target Rbp1 and the ovary development-associated genes Wnt4 and Nr0b1, and suppressed expression of the Leydig cell marker, Star, and the germ cell markers, Ddx4 and Pou5f1. In co-exposures, MEHP predominantly enhanced the gene expression effects of ATRA, but the Wnt4 and Nr0b1 concentration-responses were nonlinear. Similarly, ATRA increased the number of cells expressing the granulosa cell marker FOXL2 in testis cultures, but this induction was attenuated by addition of MEHP. These results indicate that MEHP can both enhance and inhibit actions of ATRA during fetal testis development and provide evidence that RA signaling is a target for phthalate toxicity in the fetal testis.
人类普遍接触到低水平的邻苯二甲酸酯（邻苯二甲酸盐），这些物质被用于聚氯乙烯的增塑。邻苯二甲酸盐通过未知的毒性途径对胎儿睾丸中的精曲小管发育产生不良影响。为了研究邻苯二甲酸盐通过破坏胎儿睾丸中的视黄酸（RA）信号来改变精曲小管发育的假说，将妊娠第 15 天的胎鼠睾丸在离体培养中暴露于 10-6 M 全反式视黄酸（ATRA）中 1-3 天，或与 10-6-10-4 M 单-（2-乙基己基）邻苯二甲酸酯（MEHP）联合暴露。如前所述，外源性 ATRA 减少了精曲小管的数量。这种作用在 MEHP 共暴露时呈浓度依赖性减弱。ATRA 和 MEHP 暴露的睾丸耗尽了 DDX4 阳性生殖细胞，但 Sertoli 细胞不受影响。MEHP 单独增强了 RA 受体靶基因 Rbp1 和卵巢发育相关基因 Wnt4 和 Nr0b1 的表达，并抑制了 Leydig 细胞标记物 Star 和生殖细胞标记物 Ddx4 和 Pou5f1 的表达。在共暴露中，MEHP 主要增强了 ATRA 的基因表达作用，但 Wnt4 和 Nr0b1 的浓度反应是非线性的。同样，ATRA 增加了睾丸培养物中表达颗粒细胞标记物 FOXL2 的细胞数量，但 MEHP 的加入减弱了这种诱导作用。这些结果表明，MEHP 可以增强和抑制 ATRA 在胎儿睾丸发育过程中的作用，并提供证据表明 RA 信号是胎儿睾丸中邻苯二甲酸盐毒性的靶标。
