Bhattacharya Nandini, Dufour Jannette M, Vo My-Nuong, Okita Janice, Okita Richard, Kim Kwan Hee
School of Molecular Biosciences, Center for Reproductive Biology, Washington State University, Pullman, Washington 99164, USA.
Biol Reprod. 2005 Mar;72(3):745-54. doi: 10.1095/biolreprod.104.031583. Epub 2004 Nov 24.
Phthalates have been shown to elicit contrasting effects on the testis and the liver, causing testicular degeneration and promoting abnormal hepatocyte proliferation and carcinogenesis. In the present study, we compared the effects of phthalates on testicular and liver cells to better understand the mechanisms by which phthalates cause testicular degeneration. In vivo treatment of rats with di-(2-ethylhexyl) phthalate (DEHP) caused a threefold increase of germ cell apoptosis in the testis, whereas apoptosis was not changed significantly in livers from the same animals. Western blot analyses revealed that peroxisome proliferator-activated receptor (PPAR) alpha is equally abundant in the liver and the testis, whereas PPAR gamma and retinoic acid receptor (RAR) alpha are expressed more in the testis. To determine whether the principal metabolite of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), or a strong peroxisome proliferator, 4-chloro-6(2,3-xylindino)-2-pyrimidinylthioacetic acid (Wy-14,643), have a differential effect in Sertoli and liver cells by altering the function of RAR alpha and PPARs, their nuclear trafficking patterns were compared in Sertoli and liver cells after treatment. Both MEHP and Wy-14,643 increased the nuclear localization of PPAR alpha and PPAR gamma in Sertoli cells, but they decreased the nuclear localization of RAR alpha, as previously shown. Both PPAR alpha and PPAR gamma were in the nucleus and cytoplasm of liver cells, but RAR alpha was predominant in the cytoplasm, regardless of the treatment. At the molecular level, MEHP and Wy-14,643 reduced the amount of phosphorylated mitogen-activated protein kinase (activated MAPK) in Sertoli cells. In comparison, both MEHP and Wy-14,643 increased phosphorylated MAPK in liver cells. These results suggest that phthalates may cause contrasting effects on the testis and the liver by differential activation of the MAPK pathway, RAR alpha, PPAR alpha, and PPAR gamma in these organs.
邻苯二甲酸酯已被证明对睾丸和肝脏产生相反的影响，导致睾丸退化，并促进异常的肝细胞增殖和致癌作用。在本研究中，我们比较了邻苯二甲酸酯对睾丸和肝细胞的影响，以更好地理解邻苯二甲酸酯导致睾丸退化的机制。用邻苯二甲酸二（2-乙基己基）酯（DEHP）对大鼠进行体内治疗，导致睾丸中生精细胞凋亡增加了三倍，而同一动物肝脏中的凋亡没有明显变化。蛋白质免疫印迹分析显示，过氧化物酶体增殖物激活受体（PPAR）α在肝脏和睾丸中的含量相同，而PPARγ和视黄酸受体（RAR）α在睾丸中的表达更多。为了确定DEHP的主要代谢产物单（2-乙基己基）邻苯二甲酸酯（MEHP）或一种强效过氧化物酶体增殖剂4-氯-6（2,3-二氯苄基）-2-嘧啶硫代乙酸（Wy-14,643）是否通过改变RARα和PPARs的功能而对支持细胞和肝细胞产生不同的影响，在处理后比较了它们在支持细胞和肝细胞中的核转运模式。MEHP和Wy-14,643都增加了支持细胞中PPARα和PPARγ的核定位，但正如先前所示，它们降低了RARα的核定位。PPARα和PPARγ都存在于肝细胞的细胞核和细胞质中，但无论是否处理，RARα在细胞质中占主导地位。在分子水平上，MEHP和Wy-14,643减少了支持细胞中磷酸化丝裂原活化蛋白激酶（活化的MAPK）的量。相比之下，MEHP和Wy-14,643都增加了肝细胞中磷酸化的MAPK。这些结果表明，邻苯二甲酸酯可能通过这些器官中MAPK途径、RARα、PPARα和PPARγ的差异激活，对睾丸和肝脏产生相反的影响。
