1. Arsenite alters the expression of aryl hydrocarbon receptor (AhR)-regulated genes in extrahepatic tissues; yet, the effect of organic arsenicals still unknown. Therefore, C57BL/6 mice received trimethylarsine oxide (TMAO; 13 mg/kg i.p.) with or without 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 15 μg/kg), and euthanized at 6 or 24 h. 2. Our results demonstrated that TMAO increased Cyp1a1 and Cyp1b1 mRNA, protein and activity in the lung. TMAO potentiated the TCDD-mediated induction of Cyp1a1 and Cyp1a2 mRNA, protein and activity in the lung. In the kidney, TMAO increased Cyp1b1 mRNA and protein. TMAO potentiated the TCDD-mediated induction of Cyp1a1 and Cyp1b1 mRNA, protein and activity. In the heart, TMAO potentiated the TCDD-mediated induction of Cyp1a1 and Cyp1b1 mRNA. 3. Moreover, TMAO induced Nqo1 mRNA in the lung, kidney and heart, with subsequent increase in Nqo1 protein and activity in the lung. TMAO increased Gsta mRNA in the heart; and increased Gsta protein and activity in the lung and kidney. TMAO increased Nqo1 mRNA as compared to TCDD in the kidney and heart, and potentiated the TCDD-mediated induction of Gsta protein and activity in the kidney. 4. In conclusion, TMAO modulates AhR-regulated genes in a tissue- and enzyme-specific manner.
Keywords: AhR; TMAO; arsenic; carcinogen activating enzymes.