prepared from either control or 3-methylcholanthrene-pretreated mice inhibited benzo(a)pyrene binding to calf thymus DNA by 63-64, 38-43,. 36-37, and ...
[CANCER RESEARCH 47, 767-773, February 1, 1987]
Inhibition of Polycyclic Aromatic Hydrocarbon-DNA Adduct Formation in Epidermis and Lungs of SENCAR Mice by Naturally Occurring Plant Phenols1 Mukul Das,2 Wasiuddin A. Khan, Parthasarathy
Asokan, David R. Bickers, and Hasan Mukhtar3
Departments of Dermatology, University Hospitals of Cleveland, Case Western Reserve University, and Veterans Administration Medical Center, Cleveland, Ohio 44106
ABSTRACT
This stereospecificity was also observed in a two stage skin tumorigenicity assay, in which the (+)-awf/'-enantiomer was
Naturally occurring plant phenols such as tannic acid, quercetin, myricetin, and anthraflavic acid are known to inhibit the mutagenicity of several bay-region diol-epoxides of polycyclic aromatic hydrocarbons (PAHs). The binding of bay-region diol-epoxides of PAHs to target
found to be 60-fold more potent than the other 3 enantiomers as a tumor initiator in CD-I and SENCAR mice (11). Similarly, the (+)-anti isomer was at least 59 times more potent than the (-)-anti isomer in its stereospecific binding to DNA and RNA in mouse skin (6, 8), human colon expiants (12), hamster embryo cells (13, 14), and hamster epidermal cells (7) exposed to BP. A positive correlation exists between the DNA binding of bay-region diol-epoxides of PAHs such as BP in mouse skin and lung and their carcinogenic potency (6, 8, 15). Following topical application of BP to mouse skin in vivo or treatment of cells or organ expiants in tissue culture, the major DNA adduct formed is BPDE-I bound through a trans-addition to the exocyclic amino group of deoxyguanosine (16). Prior studies from our laboratory have shown that ellagic acid, a naturally occurring plant phenol, is a potent inhibitor of epidermal microsomal aryl hydrocarbon hydroxylase activity and of the enzyme-mediated binding of BP to both calf thymus DNA in vitro and epidermal DNA in vivo (17). Ellagic acid was also shown to inhibit the covalent binding of BP to mouse epidermal DNA in organ culture (18). Dixit et al. (19) have shown that ellagic acid inhibits the metablic activation and the binding of BP and BP-7,8-diol to DNA in cultured mouse lung. Furthermore, we have shown that ellagic acid is a potent inhibitor of BP metabolism and its subsequent glucuronidation, sulfation, and covalent binding to DNA in cultured BALB/c mouse keratinocytes (20). It is also known that topical appli cation of ellagic acid to skin of BALB/c mice affords protection against MCA-induced skin carcinogenesis (21). Lesea (22) has shown that parenteral administration of ferrulic, chlorogenic, and ellagic acid inhibits BP-induced lung tumor formation in A/J mice. Using a standard two stage (initiation and promo tion) skin carcinogenesis experimental protocol in which DMBA was used as a carcinogen, Lesea (22) has also shown that topically applied ellagic acid inhibits skin tumor formation in CD-I mice. Recently, ellagic acid has also been found to protect mice against skin carcinogenesis induced by topically applied BP-diol-epoxide (23). In a recent publication we have shown that tannic acid, quercetin, myricetin, and anthraflavic acid are potent inhibitors of epidermal cytochrome P-450dependent monooxygenases including aryl hydrocarbon hy droxylase in SENCAR mice (24). In this study we have analyzed the capacity of these plant phenols to inhibit PAH-DNA adduct formation in the skin and lungs of SENCAR mice.
tissue DNA is thought to be essential for the initiation of cancer by these compounds. In this study we investigated the effect of these plant phenols on PAH-DNA adduct formation in the epidermis and lung of SENCAR mice. In vitro addition of tannic acid, quercetin, myricetin, and anthrafla vic acid (25 ¿IM) to an incubation system containing epidermal microsomes prepared from either control or 3-methylcholanthrene-pretreated mice inhibited benzo(a)pyrene binding to calf thymus DNA by 63-64, 38-43, 36-37, and 27-33%, respectively. A single topical application of tannic acid, quercetin, myricetin, and anthraflavic acid at a dose of 400 nmol/ kg body weight resulted in the inhibition of |'I I|hcn/o(u)p\rene binding to epidermal DNA (48-73%)
and protein (51-63%).
The same dose of
these plant phenols (400 /tmol/kg) caused even greater inhibition of (±> [3H]-7/3,8a-dihydroxy-7,8-dihydrobenzo(a)pyrene and |3H]-7,12-dimethylbenz(
