The effect of aspartame on rat brain xenobiotic-metabolizing enzymes.

This study demonstrates that chronic aspartame (ASP) consumption leads to an increase of phase I metabolizing enzymes (cytochrome P450 (CYP)) in rat brain. Wistar rats were treated by gavage with ASP at daily doses of 75 and 125 mg/kg body weight for 30 days. Cerebrum and cerebellum were used to obtain microsomal fractions to analyse activity and protein levels of seven cytochrome P450 enzymes. Increases in activity were consistently found with the 75 mg/kg dose both in cerebrum and cerebellum for all seven enzymes, although not at the same levels: CYP 2E1-associated 4-nitrophenol hydroxylase (4-NPH) activity was increased 1.5-fold in cerebrum and 25-fold in cerebellum; likewise, CYP2B1-associated penthoxyresorufin O-dealkylase (PROD) activity increased 2.9- and 1.7-fold respectively, CYP2B2-associated benzyloxyresorufin O-dealkylase (BROD) 4.5- and 1.1-fold, CYP3A-associated erythromycin N-demethylase (END) 1.4- and 3.3-fold, CYP1A1-associated ethoxyresorufin O-deethylase (EROD) 5.5- and 2.8-fold, and CYP1A2-associated methoxyresorufin O-demethylase (MROD) 3.7- and 1.3-fold. Furthermore, the pattern of induction of CYP immunoreactive proteins by ASP paralleled that of 4-NHP-, PROD-, BROD-, END-, EROD- and MROD-related activities only in the cerebellum. Conversely, no differences in CYP concentration and activity were detected in hepatic microsomes of treated animals with respect to the controls, suggesting a brain-specific response to ASP treatment.

Cytochrome P450 expression in rat gastric epithelium with intestinal metaplasia induced by high dietary NaCl levels.

Drug metabolizing enzymes like cytochrome P450 (CYP) play an important role in determining the susceptibility of organs or tissue to the toxic effects of drugs or other xenobiotics. There is some evidence indicating that individual isoforms of CYPs are over-expressed in different types of malignant tumors including that of oesophagus, pancreas, breast, lung, colon and stomach. Nevertheless, it is not clear if this change in expression is previous or after the appearance of malignancy. This is important in order to clarify the possible role of xenobiotics in the development of gastric cancer. On the other hand, it has been reported that a high salt ingestion leads to histological changes in rat stomach mucosa including enhanced cell proliferation, lipid peroxidation and intestinal metaplasia. The aim of this study is to explore the expression and activity of CYP families involved in the metabolism of carcinogens in normal rat stomach mucosa and intestinal metaplasia induced by high NaCl ingestion. Male Wistar rats were exposed to diets containing different NaCl concentrations (0.6% control group, 6%, 12%, 18% and 24%) for 12 weeks and histological changes as well as CYP modulation were monitored in gastric mucosa. Chronic gastritis, regenerative hyperplasia and focal metaplasia were noted in animals receiving the 12%, 18% and 24% NaCl diets. In the same groups, induction of CYP1A1 and CYP3A2 was produced, mainly in areas of metaplasia. The expression of xenobiotic metabolizing enzymes in the gastric mucosa might contribute to chemical activation in the stomach, metabolizing both exogenous and endogenous compounds implicated in the development of gastric cancer.

Induction of cytochrome P450 enzymes by albendazole treatment in the rat.

The anthelmintic drug albendazole (ABZ), methyl(5-(propylthio)-1H-benzimidazol-2-yl)carbamate, is a benzimidazole highly efficient in the treatment of neurocysticercosis. The effects of ABZ treatment (i.p. and p.o. administration) on the expression of several cytochrome P450 (CYP) enzymes were evaluated in rat liver in order to characterize the spectrum of altered CYP enzymes involved in the metabolism of environmental mutagens and carcinogens, after drug intake. Intraperitoneal administration of ABZ (50 mg/kg body weight/day/three days in corn oil) to rats, caused an induction of hepatic activities of CYP1A1-associated ethoxyresorufin O-deethylase (EROD) 65 fold, CYP1A2-associated methoxyresorufin O-demethylase (MROD) 6 fold, CYP2B1-associated penthoxyresorufin O-dealkylase (PROD) 4 fold, CYP2B2-associated benzyloxyresorufin O-dealkylase (BROD) 14 fold, as well as a partial reduction of CYP2E1-associated 4-nitrophenol hydroxylase (4-NPH) activity. CYP3A-associated erythromycin N-demethylase (END) activity was not modified under the same treatment conditions. Western blot analysis was conducted to explore if the increased catalytic activity was a result of an increased protein content; only CYP1A1/2 showed a visible increase in protein concentration after ABZ inoculation, therefore, the increased PROD and BROD activities could be attributed to the induction of CYP1A1/2. Results with the two main metabolites of ABZ (15 mg/kg body weight/day/three days, i.p.) indicated that ABZ sulfoxide (ABZSO) but not ABZ sulfone (ABZSO(2)) displayed the same pattern of CYP induction than ABZ. Oral administration of ABZ at the human therapeutic dose of 20 mg/kg body weight/day/three days, produced an increase in CYP1A1/2 protein content 24 h after the first intake. The protein level remained high during the treatment, and up to 72 h after the last administration; basal protein levels were almost recovered 48 h later.