RESUMEN
To investigate the relationship between fenofibrate (FF) and oxidative stress, enzymatic, histopathological, and molecular biological analyses were performed in the liver of male F344 rats fed 2 doses of FF (Experiment 1; 0 and 6000 ppm) for 3 weeks and 3 doses (Experiment 2; 0, 3000, and 6000 ppm) for 9 weeks. FF treatment increased the activity of enzymes such as carnitine acetyltransferase, carnitine palmitoyltransferase, fatty acyl-CoA oxidizing system, and catalase in the liver. However, it decreased those of superoxide dismutase in the liver in both experiments. Increased 8-hydroxy-2'-deoxyguanosine levels in liver DNA and lipofuscin accumulation were observed in the treated rats of Experiment 2. In vitro measurement of reactive oxygen species (ROS) in rat liver microsomes revealed a dose-dependent increase due to FF treatment. Microarray (only Experiment 1) or real-time reverse transcription-polymerase chain reaction analyses revealed that the expression levels of metabolism and DNA repair-related genes such as Aco, Cyp4a1, Cat, Yc2, Gpx2, Apex1, Xrcc5, Mgmt, Mlh1, Gadd45a, and Nbn were increased in FF-treated rats. These results provide evidence of a direct or indirect relationship between oxidative stress and FF treatment. In addition, increases in the expression levels of cell cycle-related genes such as Chek1, Cdc25a, and Ccdn1; increases in the expression levels of cell proliferation-related genes such as Hdgfrp3 and Vegfb; and fluctuations in the expression levels of apoptosis-related genes such as Casp11 and Trp53inp1 were observed in these rats. This suggests that cell proliferation induction, apoptosis suppression, and DNA damage due to oxidative stresses are probably involved in the mechanism of hepatocarcinogenesis due to FF in rats.
Asunto(s)
Apoptosis/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Transformación Celular Neoplásica/efectos de los fármacos , Daño del ADN , Fenofibrato/toxicidad , Hígado/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Proliferadores de Peroxisomas/toxicidad , 8-Hidroxi-2'-Desoxicoguanosina , Animales , Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Biotransformación/genética , Catalasa/metabolismo , Proteínas de Ciclo Celular/metabolismo , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Enzimas Reparadoras del ADN/metabolismo , Desoxiguanosina/análogos & derivados , Desoxiguanosina/metabolismo , Relación Dosis-Respuesta a Droga , Perfilación de la Expresión Génica/métodos , Antígeno Ki-67/metabolismo , Metabolismo de los Lípidos/efectos de los fármacos , Hígado/enzimología , Hígado/patología , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas F344 , Especies Reactivas de Oxígeno/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Superóxido Dismutasa/metabolismo , Factores de TiempoRESUMEN
Our previous study suggested the possibilities that dicyclanil (DC), a nongenotoxic carcinogen, produces oxidative stress in the liver of the two-stage hepatocarcinogenesis model of mice and the stress induced probably causes secondary oxidative DNA damage. However, clear evidences demonstrating the relationship between DC-induced hepatocarcinogenesis, oxidative stress, and oxidative DNA damage have not been obtained. To clarify the relationship, further investigations were performed in the liver of the partially hepatectomized (PH) mice maintained on diet containing 1,500 ppm of DC for 13 and 26 weeks after intraperitoneal injection of dimethylnitrosamine (DMN). Significant increases in mRNA expressions of some metabolism- and oxidative stress-related genes with a formation of gamma-glutamyltranspeptidase (GGT) positive foci were observed in the DMN + DC + PH group by the treatment of DC for 13 and 26 weeks. The levels of 8-hydroxy-deoxyguanosine (8-OHdG) in the liver DNA also significantly increased in mice of the DMN + DC + PH group at weeks 13 and 26 and mice given DC alone for 26 weeks. The in vitro measurement of reactive oxygen species (ROS) generation from the mouse liver microsomes showed a significant increase of ROS production in the presence of DC. These results suggest that DC induces oxidative stress which is probably derived from its metabolic pathway, partly, and support our previous speculation that oxidative stress plays one of the important roles in the DC-induced hepatocarcinogenesis in mice.