The effect of in utero exposure to 2,3,7,8-Tetrachlorodibenzo-p-Dioxin on male reproductive organ development in a murine model

Abstract

[한글]

내분비계장애물질인 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD)은 음식을 통해 주로 인체에 노출되며 기형발생과 암발생 등을 유발시킨다고 알려져 있다. 실험동물에서 TCDD에 노출되었을 경우 웅성생식기관 발달에 있어 항문-외부생식기 길이 감소, 정자수 감소, 생식기관 무게 감소와 발달 저하 들의 이상이 나타남이 보고되었다. TCDD에 의한 이러한 변화가 어떠한 작용으로 인해 야기되는지 알아보고자 C57BL/6 마우스를 사용하여 임신 15일에 TCDD를 1 µg/kg 농도로 투여하여 차산자를 생후 30일과 60일에 희생하여 웅성생식기관 발달 변화를 살펴보았다.

TCDD에 의해 차산자의 항문-외부생식기 길이와 생식기관 무게가 감소하였다. 정낭의 크기와 발달이 저하되었고 전립선에 있어 관 형성 발달이 줄어들었음이 관찰되었다. 안드로젠 수용체의 발현이 정낭과 정소에서 낮게 나타났고 이는 생식기관의 유지와 발달에 중요한 역할을 하는 안드로젠 발현 변화가 생식기관 발달 이상을 가져올 수 있음을 시사한다. 고환에서는 생식세포의 사멸이 증가되었고 반면 세포 분열은 감소 되었다. 이러한 기전이 고환의 무게 감소에 영향을 미쳤을 것이라 여겨진다. 생식기관에 있어 MAPK의 활성화는 고환조직에서 TCDD에 의하여 과도한 활성화를 보이며 TCDD가 MAPK 경로에도 영향을 끼친다는 것을 나타낸다.

[영문]2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an endocrine disruptors, is the most toxic congener of a class of polyhalogenated aromatic hydrocarbons. The toxic effects of TCDD are well known in carcinogenicity, teratogenecity, and hepatotoxicity in animals and humans. To evaluate the effects of in utero TCDD exposure on male reproductive development, pregnant C57BL/6 mice were given a single intraperitoneally (i.p.) injection of TCDD (1 µg TCDD/ kg body weight) on Gestation Day (GD) 15. Offspring were examined on Postnatal Day (PND) 30, ‘the immature stage’, and Postnatal Day (PND) 60, ‘the mature stage’. Body weight, body length and anogenital distance of male offspring were measured. Male reproductive organs, testes and epididymides, prostate, and seminal vesicles were excised and weighed. Androgen receptor immunoexpression in reproductive organs was performed by immunohistochemistry, and apoptosis and cell proliferation were measured by counting cells as revealed by TUNEL and PCNA (proliferating cell nuclear antigen) positive in seminiferous tubules in the testis. The effect of TCDD on MAPK activity was observed in testis, prostate, and seminal vesicle by immunoblotting for ERK. Body weights and lengths of male offspring were not affected by TCDD exposure, but anogenital distance in TCDD exposed offspring on PND 30 was significantly decreased. All organ weights were reduced by TCDD exposure; the weights of testes on PND 60 and the weights of prostates on both PND 30 and PND 60 were significantly reduced by TCDD treatment. TCDD induced apoptosis and reduced cell proliferation in testis. Prostate and seminal vesicle exhibited low androgen receptor immunoreactivity. In addition, epithelial branches in seminal vesicle and canalized epithelium in prostate of TCDD exposed offspring were decreased. Expression of phospho-ERK1/2 was affected by TCDD exposure in reproductive organs. Androgens are known to regulate prostate and seminal vesicle growth, development and maintenance. Therefore, this alternation of androgen receptor expression could be involved in prostate and seminal vesicle impairment. In addition, the MAPK cascade could be involved in TCDD-medicated alternation in reproductive organs.