Dong Wu, Teraoka Hiroki, Tsujimoto Yoshikazu, Stegeman John J, Hiraga Takeo
Department of Toxicology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Japan.
Toxicol Sci. 2004 Jan;77(1):109-16. doi: 10.1093/toxsci/kfh023. Epub 2003 Dec 3.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent and potent developmental toxicant in various animals, with developing fish being the most sensitive organisms. Although the expression of aryl hydrocarbon receptor (AHR) as well as the partner molecule, AHR nuclear translocator (ARNT) in the brain has been reported, the effect of TCDD on the brain remains to be clarified in detail. Previously, we reported local circulation failure and apoptosis in dorsal midbrain caused by TCDD in developing zebrafish. In the present experiments, we investigated the effects of morpholino antisense oligos against aryl hydrocarbon receptor 2 (zfAHR2) (AHR2-MO) on toxicological endpoints caused by TCDD in developing zebrafish. AHR2-MO but not its negative homologue (4mis-AHR2-MO) improved TCDD-evoked circulation failure in mesencephalic vein and reduced the occurrence of apoptosis in dorsal midbrain, with concomitant inhibition of CYP1A induction in vascular endothelium. Injection of bovine serum albumin (BSA) into the general circulation, followed by immunohistochemistry with anti-BSA, showed that TCDD raised vascular permeability to albumin in dorsal midbrain, which was blocked by AHR2-MO and N-acetlycystein. In the absence of TCDD, development of embryos injected with AHR2-MO appeared normal at least until 60 h after fertilization. It is concluded that AHR2 activation in the vascular endothelium of the zebrafish embryo midbrain is involved in the mesencephalic circulation failure and apoptosis elicited by TCDD. This is the further evidence that vascular endothelium is the target of TCDD in relation to local circulation failure and apoptosis in dorsal midbrain.
2,3,7,8-四氯二苯并对二恶英(TCDD)是一种在多种动物体内具有持久性和强发育毒性的物质,发育中的鱼类是最敏感的生物。尽管已有报道称芳烃受体(AHR)以及其伴侣分子AHR核转运蛋白(ARNT)在大脑中有表达,但TCDD对大脑的影响仍有待详细阐明。此前,我们报道了TCDD在发育中的斑马鱼体内导致中脑背侧局部循环衰竭和细胞凋亡。在本实验中,我们研究了针对芳烃受体2(zfAHR2)的吗啉代反义寡核苷酸(AHR2-MO)对TCDD在发育中的斑马鱼体内引起的毒理学终点的影响。AHR2-MO而非其阴性同源物(4mis-AHR2-MO)改善了TCDD诱发的中脑静脉循环衰竭,并减少了中脑背侧细胞凋亡的发生,同时抑制了血管内皮细胞中CYP1A的诱导。将牛血清白蛋白(BSA)注入体循环,随后用抗BSA进行免疫组织化学检测,结果显示TCDD增加了中脑背侧对白蛋白的血管通透性,而AHR2-MO和N-乙酰半胱氨酸可阻断这种增加。在没有TCDD的情况下,注射AHR2-MO的胚胎至少在受精后60小时内发育正常。结论是,斑马鱼胚胎中脑血管内皮细胞中的AHR2激活与TCDD引起的中脑循环衰竭和细胞凋亡有关。这进一步证明血管内皮细胞是TCDD在中脑背侧局部循环衰竭和细胞凋亡方面的作用靶点。