title: Inhibition of 17β-estradiol activation by CYP1A1: genotype- and regioselective inhibition by St. John's Wort and several natural polyphenols.
abstract: Several epidemiological studies associate certain CYP1A1 genotypes, alone or in combination, with an increased risk of estrogen-related cancers. Previously we demonstrated that metabolic activation of estrogens by CYP1A1 is a genotype-dependent reaction with the CYP1A1.2 (Ile462Val) variant being the most efficient catalyst (Kisselev et al.). To answer the question whether genotype-dependent inhibition of activation of estrogens by CYP1A1 could also contribute, we studied the inhibition of hydroxylation activity of the most common allelic variants of human CYP1A1 towards 17β-estradiol. We expressed and purified CYP1A1.1 (wild-type), CYP1A1.2 (Ile462Val), and CYP1A1.4 (Thr461Asn) and performed inhibition assays by natural polyphenols of our diet and drugs of NADPH-dependent estradiol hydroxylation in reconstituted CYP1A1 systems. From the polyphenols studied, a St. John's Wort (Hypericum perforatum) extract, some of its main single constituents hypericin, pseudohypericin, and quercetin, as well as the flavonols kaempferol, myricetin and the phytoestrogens resveratrol and tetramethyl-stilbene exhibited strong inhibition. For the St. John's Wort extract and its single constituents hypericin, pseudohypericin, and quercetin, inhibition exhibited a remarkable dependency on the CYP1A1 genotype. Whereas (wild-type) CYP1A1.1 was most inhibited by the whole crude extract, the variant CYP1A1.2 (Ile462Val) was significantly stronger inhibited by the constituents in its pure form: IC₅₀ values for 2-hydroxylation was more than two times lower compared with the wild-type enzyme and the variant CYP1A1.4 (Thr461Asn). Besides this, the inhibition exhibited a remarkable regioselectivity. The data suggest that risk of estrogen-mediated diseases might be not only influenced by CYP1A1 genotype-dependent activation but also its inhibition by natural polyphenols of our diet and drugs.
authors.affiliation: Institute of Clinical Pharmacology and Toxicology, Charité, Campus Mitte, University Medicine Berlin, 10117 Berlin, Germany; Wernigeroder Str. 111, 16341 Panketal, Germany. schwarz.panketal@t-online.de
authors.forename: Dieter
authors.initials: D
authors.lastname: Schwarz
authors.forename: Pyotr
authors.initials: P
authors.lastname: Kisselev
authors.forename: Wolf-Hagen
authors.initials: WH
authors.lastname: Schunck
authors.forename: Ivar
authors.initials: I
authors.lastname: Roots
mesh_terms: D019943:Amino Acid Substitution; D000873:Anthracenes; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D055162:Biocatalysis / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000737:chemistry / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D044948:Flavonols / Q000494:pharmacology; D005838:Genotype; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D020902:Hypericum / Q000737:chemistry*; D010569:Perylene / Q000031:analogs & derivatives / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology*; D059808:Polyphenols; D011794:Quercetin / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D000077185:Resveratrol; D013237:Stereoisomerism; D013267:Stilbenes / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D000873:Anthracenes; D000894:Anti-Inflammatory Agents, Non-Steroidal; D005419:Flavonoids; D044948:Flavonols; D010636:Phenols; D010936:Plant Extracts; D059808:Polyphenols; D011994:Recombinant Proteins; D013267:Stilbenes; D004958:Estradiol; D010569:Perylene; C004965:hypericin; D011794:Quercetin; D019363:Cytochrome P-450 CYP1A1; C056602:pseudohypericin; D000077185:Resveratrol