Diterpene quinone tanshinone IIA selectively inhibits mouse and human cytochrome p4501A2.
1. Tanshinone IIA is the main active diterpene quinone in the herbal medicine Salvia miltiorrhiza. In untreated mouse liver microsomes, tanshinone IIA selectively inhibited 7-ethoxyresorufin O-deethylation (EROD) and 7-methoxyresorufin O-demethylation (MROD) activities without affecting the oxidation of benzo(a)pyrene, tolbutamide, N-nitrosodimethylamine and nifedipine. Tanshinone IIA was a competitive inhibitor of MROD activity with a K(i) of 7.2 +/- 0.7 nM. 2. In 3-methylcholanthrene-treated mouse liver microsomes, tanshinone IIA and two minor tanshinones, tanshinone I and cryptotanshinone, inhibited liver microsomal MROD activity without affecting EROD and benzo(a)pyrene hydroxylation activities at the concentrations up to 1 microM. Tanshinone IIA induced a type I binding spectrum with a spectral dissociation constant K(s) of 2.3 +/-0.8 microM without cooperativity. 3. In human liver microsomes, tanshinone IIA decreased EROD and MROD activities without affecting the oxidation of benzo(a)pyrene, tolbutamide, chlorzoxazone and nifedipine. 4. In Escherichia coli membranes expressing bicistronic human CYP1A enzymes, tanshinone IIA inhibited EROD activity of CYP1A1 with an IC(50) 48 times higher than that for CYP1A2. Tanshinone I and cryptotanshinone had the same IC(50) ratio (1A1/1A2) of 4. 5. The results indicate that tanshinone represents a new group of CYP1A inhibitors, and tanshinone IIA had the highest selectivity in inhibition of CYP1A2.
Ueng
Yune-Fang
YF
National Research Institute of Chinese Medicine, Taipei 112, Taiwan, ROC. ueng@cma23.nricm.edu.tw
Kuo
Ya-Hui
YH
Peng
Hsiao-Chi
HC
Chen
Ta-Liang
TL
Jan
Woan-Ching
WC
Peter Guengerich
F
F
Lin
Yun-Lian
YL
D045784:Abietanes; D000465:Algorithms; D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D004224:Diterpenes / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010084:Oxidation-Reduction; D010616:Phenanthrenes / Q000302:isolation & purification / Q000494:pharmacology*; D027544:Salvia / Q000737:chemistry
D045784:Abietanes; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D004224:Diterpenes; D004791:Enzyme Inhibitors; D010616:Phenanthrenes; C021751:tanshinone; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2