Skip to main content
ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #163992
Title: EXPOSING FERRETS TO CIGARETTE SMOKE AND A PHARMACOLOGICAL DOSE OF BETA-CAROTENE SUPPLEMENTATION ENHANCE IN VITRO RETINOIC ACID CATABOLISM IN LUNG VIA INDUCTION OF CYTOCHROME P450 ENZYMES

Author
item LIU, CHUN - TUFTS-HNRCA
item RUSSELL, ROBERT - TUFTS-HNRCA
item WANG, XIANG-DONG - TUFTS-HNRCA

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2003
Publication Date: 1/15/2003
Citation: LIU, C., RUSSELL, R.M., WANG, X. EXPOSING FERRETS TO CIGARETTE SMOKE AND A PHARMACOLOGICAL DOSE OF BETA-CAROTENE SUPPLEMENTATION ENHANCE IN VITRO RETINOIC ACID CATABOLISM IN LUNG VIA INDUCTION OF CYTOCHROME P450 ENZYMES. JOURNAL OF NUTRITION. 2003;133:173-9.

Interpretive Summary: In our previous studies, we found lower levels of retinoic acid, the most active form of vitamin A, in the lungs of ferrets exposed to cigarette smoke and/or high dose of ß-carotene. To determine whether this is involved in excessive degradation of retinoic acid via cytochrome P450 (CYP) enzymes induction, we carried out in vitro incubations of retinoic acid with the lung microsomal fractions of ferrets with or without CYP inhibitors and antibodies against CYPs. We observed that the incubation of retinoic acid with the lung microsomal fraction from ferrets exposed to cigarette smoke, high dose of beta-carotene, and their combination resulted in increased amounts of polar metabolites of retinoic acid in a dose-dependant manner as compared with the control ferrets. Furthermore, this enhanced retinoic acid catabolism was partially inhibited by resveratrol (CYP1A1 inhibitor), alpha-naphthoflavone (CYP1A2 inhibitor) and antibodies against CYP1A1 and CYP1A2. These findings suggest that low levels of retinoic acid in the lung of ferrets exposed to cigarette smoke and/or high dose of beta-carotene may be caused by the enhanced retinoic acid catabolism via induction of CYPs, CYP1A1 and CYP1A2 in particular, which provides a possible explanation for enhanced lung carcinogenesis seen with high dose of beta-carotene supplementation in cigarette smokers.

Technical Abstract: In our previous studies, we found lower levels of retinoic acid (RA) in the lungs of ferrets exposed to cigarette smoke and/or pharmacological dose of beta-carotene. To determine whether this is involved in excessive catabolism of RA via cytochrome P450 (CYP) induction, we carried out in vitro incubations of RA with the lung microsomal fractions of ferrets with or without CYP inhibitors and antibodies against CYPs. The polar metabolites (4-oxo-RA and 18-hydroxy-RA) of RA metabolism after the incubation were analyzed by HPLC. Expressions of CYPs (1A1, 1A2, 2E1 and 3A1) were examined using Western blot analysis. Incubation of RA with the lung microsomal fraction from ferrets exposed to cigarette smoke, pharmacological dose of beta-carotene, and their combination resulted in increased amounts of 4-oxo-RA and 18-hydroxy-RA in a dose-dependant manner as compared with the control ferrets; this increase was the greatest in the combined treatment group. Furthermore, this enhanced RA catabolism was substantially (~80%) inhibited by non-specific CYPs inhibitors (disulfiram and liarozole), but were partially (~50%) inhibited by resveratrol (CYP1A1 inhibitor), alpha-naphthoflavone (CYP1A2 inhibitor) and antibodies against CYP1A1 and CYP1A2. Cigarette smoke-exposure and/or pharmacological dose of beta-carotene increased levels of CYP1A1 and 1A2 by 3 to 6 folds but not levels of 2E1 and 3A1 in ferret lung tissue. These findings suggest that low levels of RA in the lung of ferrets exposed to cigarette smoke and/or pharmacological dose of beta-carotene may be caused by the enhanced RA catabolism via induction of CYPs, CYP1A1 and CYP1A2 in particular, which provides a possible explanation for enhanced lung carcinogenesis seen with pharmacological dose of beta-carotene supplementation in cigarette smokers.