title: Naturally occurring coumarins inhibit 7,12-dimethylbenz[a]anthracene DNA adduct formation in mouse mammary gland.
abstract: Naturally occurring coumarins (NOCs) are anti-carcinogenic in the mouse skin model. To characterize the chemopreventive potential of NOCs against breast cancer, we first examined their effects on 7,12-dimethylbenz[a]anthracene (DMBA)-DNA adduct formation in mouse mammary gland. We hypothesized that those NOCs that both inhibited cytochrome P450 1A1/1B1 and induced hepatic glutathione S-transferases (GSTs) would be the most effective in blocking DMBA-DNA adduct formation in mouse mammary gland. To address this hypothesis, simple coumarins (e.g. coumarin and limettin, which induced mouse hepatic GSTs but had little effect on P4501A1/1B1) and linear furanocoumarins (e.g. imperatorin and isopimpinellin, which induced hepatic GSTs and were potent inhibitors of P4501A1/1B1) were compared. Mice were pretreated with NOCs (150 mg/kg body wt, by gavage) prior to either a single dose of DMBA (50 microg) or multiple doses of DMBA (20 microg daily for 3 and 6 weeks). Mammary DMBA-DNA adduct formation was quantitated by the nuclease P1-enhanced 32P-postlabeling assay. With the single dose of DMBA, coumarin, limettin, imperatorin and isopimpinellin inhibited DMBA-DNA adduct formation by 50, 41, 79 and 88%, respectively. Coumarin, limettin and imperatorin blocked DMBA-DNA adduct formation by 36, 60, and 66% at 3 weeks, and by 0, 49 and 55% at 6 weeks of DMBA dosing, respectively. In a 6 week dose-response study of select NOCs and 7,8-benzoflavone (a potent P4501 inhibitor that had little effect on GSTs), DMBA-DNA adduct formation was inhibited by 0, 43 and 24% in the limettin groups; by 26, 26 and 69% in the isopimpinellin groups; and by 80, 96 and 97% in the 7,8- benzoflavone groups at 35, 70 and 150 mg/kg, respectively. Taken together, these results suggest that linear furanocoumarins had a greater inhibitory effect on DMBA-DNA adduct formation in mouse mammary glands compared with simple coumarins, and that the predominant effect may be P4501 inhibition.
authors.affiliation: Department of Pharmacology, Toxicology & Neuroscience Louisiana State University-Health Sciences Center, Shreveport, LA, USA.
authors.forename: Misty
authors.initials: M
authors.lastname: Prince
authors.forename: Cheryl T
authors.initials: CT
authors.lastname: Campbell
authors.forename: Taylor A
authors.initials: TA
authors.lastname: Robertson
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Wells
authors.forename: Heather E
authors.initials: HE
authors.lastname: Kleiner
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002273:Carcinogens / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003374:Coumarins / Q000737:chemistry / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D005260:Female; D005982:Glutathione Transferase / Q000378:metabolism; D020128:Inhibitory Concentration 50; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D008956:Models, Chemical; D009153:Mutagens
chemical_list: C059444:7,12-dimethylbenz(a)anthracene-DNA adduct; D002273:Carcinogens; D003374:Coumarins; D018736:DNA Adducts; D009153:Mutagens; D015127:9,10-Dimethyl-1,2-benzanthracene; C030123:coumarin; D005982:Glutathione Transferase