title: Celecoxib enhances the detoxification of diethylnitrosamine in rat liver cancer.
abstract: OBJECTIVE
  To study the effect of celecoxib (CXB) on diethylnitrosamine activation through the regulation of cytochrome P450 in a hepatocarcinogenesis model.
  
  
  METHODS
  Six-week-old male Sprague-Dawley rats were randomly divided into five groups, a non-treated group (NT), a diethylnitrosamine-treated group (DEN), a DEN+CXB-treated group (DEN+CXB), and CXB 8 d-treated and CXB 32 d-treated groups. The effects of celecoxib on the enzymatic activities of CYP1A1, 2A, 2B1/2, and 2E1 were assessed in hepatic microsomes 24 h after DEN administration. Changes in CYP1A1 and CYP2B1/2 protein expression were also evaluated. The rate of DEN metabolism was measured by the production of the deethylation metabolite acetaldehyde, and the denitrosation metabolite nitrite.
  
  
  RESULTS
  DEN+CXB administration produced a significant increase in the enzymatic activities of CYP2B1/2 and 1A1, whereas it did not change the activities of CYP2A and 2E1, compared to that of the DEN group. CXB treatment for eight days did not produce a significant effect on enzymatic activity when compared to the NT group; however, when it was administered for prolonged times (CXB 32 d group), the enzymatic activities were increased in a similar pattern to those in the DEN+CXB group. The observed increase in the enzymatic activities in the DEN+CXB group was accompanied by an increase in the CYP2B1/2 protein levels; no changes were observed in the levels of CYP1A1. In vitro, CXB increased the denitrosation of DEN, a pathway of metabolic detoxification. The addition of SKF-525A, a preferential inhibitor of CYP2B, abrogated the denitrosation of DEN.
  
  
  CONCLUSIONS
  These results suggest that the mechanism of action of CXB involves enhancement of the detoxification of DEN by an increasing denitrosation via CYP2B1/2.
authors.affiliation: Department of Cell Biology, Center of Research and Advanced Studies, National Politechnic Institute, Av. IPN No. 2508 Col. San Pedro Zacatenco, Mexico, DF, México.
authors.forename: Martha Estela
authors.initials: ME
authors.lastname: Salcido-Neyoy
authors.forename: Adolfo
authors.initials: A
authors.lastname: Sierra-Santoyo
authors.forename: Olga
authors.initials: O
authors.lastname: Beltrán-Ramírez
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Macías-Pérez
authors.forename: Saúl
authors.initials: S
authors.lastname: Villa-Treviño
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D000068579:Celecoxib; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D004052:Diethylnitrosamine / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D011720:Pyrazoles / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D016861:Cyclooxygenase Inhibitors; D011720:Pyrazoles; D013449:Sulfonamides; D004052:Diethylnitrosamine; D001189:Aryl Hydrocarbon Hydroxylases; D000068579:Celecoxib