Modulation of brain steroidogenesis by affecting transcriptional changes of steroidogenic acute regulatory (StAR) protein and cholesterol side chain cleavage (P450scc) in juvenile Atlantic salmon (Salmo salar) is a novel aspect of nonylphenol toxicity.
Gene expression patterns for key brain steroidogenic (StAR, P450scc, CYP11beta) and xenobiotic- and steroid-metabolizing enzymes (CYP1A1 and CYP3A) have been investigated in waterborne nonylphenol (5, 15, and 50 microg/ L) treated juvenile Atlantic salmon (Salmo salar), in addition to carrier vehicle (ethanol) exposed fish, sampled at different time intervals (0, 3, and 7 days) after exposure. Gene expression patterns were studied using the quantitative polymerase chain reaction (real-time PCR). Treatment of juvenile salmon with nonylphenol caused significant induction of steroidogenic acute regulatory (StAR) protein mRNA at day 7 postexposure in the group receiving 15 microg of nonylphenol/L. P450scc was first induced in the group treated with 5 microg of nonylphenol/L at day 7; thereafter, an apparent nonylphenol-concentration-dependent decrease in P450scc mRNA was observed. CYP11beta mRNA was significantly induced at day 3 after exposure to 5 betag of nonylphenol/L; thereafter, CYP11beta mRNA levels were inhibited below control levels in the 15 and 50 microg of nonylphenol/L groups at day 3. At day 7, significant induction of CYP11beta mRNA was observed only in the group exposed to 15 microg of nonylphenol/L. For CYP1A1 mRNA, apparent nonylphenol-concentration-dependent decreases were observed at day 7 postexposure. CYP3A mRNA was significantly induced by all nonylphenol exposure concentrations at day 7. When exposed groups were compared, CYP3A transcript was significantly induced between 5 and 15 microg of nonylphenol/ L, and decreased between 15 and 50 microg of nonylphenol/ L. The ethanol control showed a significant reduction of CYP3A mRNA at day 3 postexposure. The present study has demonstrated variations in three key steroidogenic proteins and xenobiotic- and steroid-metabolizing CYP isoenzyme gene transcripts in the brain of nonylphenol-exposed juvenile salmon. Therefore, the present study represents a novel aspect of neuroendocrine effects of nonylphenol in fish not previously demonstrated and should be studied in more detail.
Arukwe
Augustine
A
Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, 7491 Trondheim, Norway. arukwe@bio.ntnu.no
D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000187:drug effects* / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D010636:Phenols / Q000633:toxicity*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D020317:Salmo salar; D014158:Transcription, Genetic / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D000098682:Steroidogenic Acute Regulatory Protein
D010636:Phenols; D010750:Phosphoproteins; D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; D000098682:Steroidogenic Acute Regulatory Protein; C025256:nonylphenol; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A; D002786:Cholesterol Side-Chain Cleavage Enzyme