Abstract
Cultured human hepatocytes are a valuable in vitro system for evaluating new molecular entities as inducers of cytochrome P450 (P450) enzymes. The present study summarizes data obtained from 62 preparations of cultured human hepatocytes that were treated with vehicles (saline or dimethylsulfoxide, 0.1%), β-naphthoflavone (33 μM), phenobarbital (100 or 250 μM), isoniazid (100 μM) and/or rifampin (20 or 50 μM), and examined for the expression of P450 enzymes based on microsomal activity toward marker substrates, or in the case of CYP2C8, the level of immunoreactive protein. The results show that CYP1A2 activity was markedly induced by β-naphthoflavone (on average 13-fold, n = 28 preparations), and weakly induced by phenobarbital (1.9-fold, n = 25) and rifampin (2.3-fold, n = 22); CYP2A6 activity tended to be increased with phenobarbital (n = 7) and rifampin (n = 3) treatments, but the effects were not statistically significant; CYP2B6 was induced by phenobarbital (6.5-fold, n = 13) and rifampin (13-fold,n = 14); CYP2C8 was induced by phenobarbital (4.0-fold, n = 4) and rifampin (5.2-fold,n = 4); CYP2C9 was induced by phenobarbital (1.8-fold, n = 14) and rifampin (3.5-fold,n = 10); CYP2C19 was markedly induced by rifampin (37-fold, n = 10), but relatively modestly by phenobarbital (7-fold, n = 9); CYP2D6 was not significantly induced by phenobarbital (n = 5) or rifampin (n = 5); CYP2E1 was induced by phenobarbital (1.7-fold, n = 5), rifampin (2.2-fold, n = 5), and isoniazid (2.3-fold,n = 5); and, CYP3A4 was induced by phenobarbital (3.3-fold, n = 42) and rifampin (10-fold,n = 61), but not by β-naphthoflavone. Based on these observations, we generalize that β-naphthoflavone induces CYP1A2 and isoniazid induces CYP2E1, whereas rifampin and, to a lesser extent phenobarbital, tend to significantly and consistently induce enzymes of the CYP2A, CYP2B, CYP2C, CYP2E, and CYP3A subfamilies but not the 2D subfamily.
Footnotes
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↵1 Neurocrine Biosciences, 10555 Science Center Dr, San Diego, CA.
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↵2 School of Pharmacy, Division of Pharmaceutics, University of North Carolina-Chapel Hill, NC.
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↵3 Astra Zeneca Pharmaceuticals, 1800 Concord Pike, Wilmington, DE.
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↵4 Millenium Pharmaceuticals, 270 Albany St., Cambridge, MA.
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A preliminary account of this work was presented at the International Society for the Study of Xenobiotics (ISSX) meeting, 2000 June 11–16, St. Andrews, Scotland.
- Abbreviations used are::
- NME
- new molecular entity (also known as NCE, new chemical entity)
- P450
- cytochrome P450
- BCA
- bicinchoninic acid
- ANOVA
- analysis of varience
- EROD
- 7-ethoxyresorufin O-dealkylase
- 7-EFCOD
- 7-ethoxytrifluoromethylcoumarin O-dealkylase
- DMSO
- dimethylsulfoxide
- CAR
- constitutive androstane receptor
- PXR
- pregnane X receptor
- Received September 24, 2002.
- Accepted December 20, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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