Meyer Joel N, Wassenberg Deena M, Karchner Sibel I, Hahn Mark E, Di Giulio Richard T
Nicholas School of the Environment and Earth Sciences and Integrated Toxicology Program, Duke University, Durham, North Carolina 27708-0328, USA.
Environ Toxicol Chem. 2003 Oct;22(10):2337-43. doi: 10.1897/02-495.
Wildcaught killifish from a contaminated site on the Elizabeth River (VA, USA) are refractory to induction of cytochrome P4501A (CYP1A, measured as catalytic activity and immunodetectable CYP1A protein) after exposure to typical aryl hydrocarbon receptor (AHR) agonists, as has been reported for fish from other sites highly contaminated with these compounds. In an attempt to understand the molecular basis for the lack of inducibility of CYP1A protein expression and activity in Elizabeth River killifish, we analyzed the expression of CYP1A and four other members of the AHR signal transduction pathway: AHR1, AHR2, AHR repressor (AHRR), and AHR nuclear translocator (ARNT). Gene expression was measured by cycle-optimized reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of messenger ribonucleic acid (mRNA) extracted from livers of killifish from the Elizabeth River and King's Creek (VA, USA) (reference site), 36 h after injection with beta-naphthoflavone (BNF, an AHR agonist) or corn oil (carrier control). Hepatic CYP1A mRNA was inducible in King's Creek killifish. However, in Elizabeth River killifish, no induction of CYP1A mRNA was observed, confirming and extending previous results showing no induction of CYP1A protein or catalytic activity in this population. Similarly, AHRR and AHR2 mRNA levels were induced by BNF in King's Creek but not Elizabeth River killifish. No population or treatment-related differences were observed in expression of AHR1 or ARNT mRNAs. The results reveal in Elizabeth River killifish a consistent lack of inducibility of genes that are normally inducible by AHR agonists (CYP1A, AHRR, AHR2). However, the expression of AHR1, AHR2, and AHRR in vehicle-treated fish did not differ between Elizabeth River and King's Creek killifish, suggesting that altered constitutive expression of AHRs or AHRR does not underlie the refractory CYP1A phenotype in Elizabeth River killifish.
从美国弗吉尼亚州伊丽莎白河一个受污染地点捕获的野生鳉鱼，在暴露于典型的芳烃受体（AHR）激动剂后，对细胞色素P4501A（CYP1A，以催化活性和免疫可检测的CYP1A蛋白衡量）的诱导具有抗性，正如其他受这些化合物高度污染地点的鱼类所报道的那样。为了理解伊丽莎白河鳉鱼中CYP1A蛋白表达和活性缺乏诱导性的分子基础，我们分析了CYP1A以及AHR信号转导途径的其他四个成员的表达：AHR1、AHR2、AHR阻遏物（AHRR）和AHR核转运蛋白（ARNT）。通过对从美国弗吉尼亚州伊丽莎白河和国王溪（参考地点）的鳉鱼肝脏中提取的信使核糖核酸（mRNA）进行循环优化逆转录聚合酶链反应（RT-PCR）分析，在注射β-萘黄酮（BNF，一种AHR激动剂）或玉米油（载体对照）36小时后测量基因表达。肝CYP1A mRNA在国王溪鳉鱼中可诱导。然而，在伊丽莎白河鳉鱼中，未观察到CYP1A mRNA的诱导，证实并扩展了先前的结果，即该种群中未诱导出CYP1A蛋白或催化活性。同样，BNF诱导了国王溪鳉鱼中AHRR和AHR2 mRNA水平，但未诱导伊丽莎白河鳉鱼中的水平。在AHR1或ARNT mRNA的表达中未观察到种群或处理相关差异。结果表明，在伊丽莎白河鳉鱼中，通常由AHR激动剂诱导的基因（CYP1A、AHRR、AHR2）始终缺乏诱导性。然而，在接受载体处理的鱼中，伊丽莎白河鳉鱼和国王溪鳉鱼之间AHR1、AHR2和AHRR的表达没有差异，这表明AHR或AHRR组成型表达的改变并非伊丽莎白河鳉鱼中CYP1A抗性表型的基础。
