Modulation of mdr1a and CYP3A gene expression in the intestine and liver as possible cause of changes in the cyclosporin A disposition kinetics by dexamethasone

Biochem Pharmacol. 2002 Feb 15;63(4):777-83. doi: 10.1016/s0006-2952(01)00911-x.


We investigated the effect of dexamethasone (DEX) on the disposition kinetics of cyclosporin A (CyA) and the mechanism of this drug interaction. Rats were treated with DEX (1 or 75mg/kg per day, i.p.) once a day for 1-7 days, and the blood concentration of CyA was measured after an i.v. or p.o. dose of CyA (10mg/kg) at 1.5hr after the last DEX treatment. In rats treated with a low dose of DEX (1mg/kg), the blood concentration of CyA after i.v. administration was unchanged compared with that of untreated rats, whereas the blood concentration after oral administration was significantly decreased, and this decrease was dependent on the duration of DEX administration. The total clearance (CL(tot)) of CyA was unchanged, but the bioavailability was significantly decreased to about one-third of that in DEX-untreated rats after 7 days of DEX treatment. At this time, the expression of mdr1a mRNA and P-gp in the liver and intestine was increased, whereas CYP3A2 was unaffected at both the mRNA and protein levels. In rats treated with a high dose of DEX (75mg/kg), the blood concentration of CyA was significantly decreased after both i.v. and p.o. administrations compared with those of untreated rats. The bioavailability of CyA was decreased, and the CL(tot) was significantly increased. The P-gp and CYP3A2 in the liver and intestine were increased at both the mRNA and protein levels. Our results indicate that the drug interaction between CyA and DEX is a consequence of modulation of P-gp and CYP3A2 gene expression by DEX, with differential dose-dependence.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / genetics*
  • ATP Binding Cassette Transporter, Subfamily B / metabolism
  • ATP-Binding Cassette Transporters / genetics*
  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Aryl Hydrocarbon Hydroxylases*
  • Blotting, Western
  • Cyclosporine / blood
  • Cyclosporine / pharmacokinetics*
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / genetics*
  • Dexamethasone / pharmacology*
  • Drug Interactions
  • Enzyme Inhibitors / blood
  • Enzyme Inhibitors / pharmacology
  • Gene Expression / drug effects*
  • In Vitro Techniques
  • Intestinal Mucosa / metabolism
  • Intestines / drug effects*
  • Kinetics
  • Liver / drug effects*
  • Liver / metabolism
  • Male
  • Oxidoreductases, N-Demethylating / genetics*
  • Rats
  • Rats, Wistar
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors


  • ATP Binding Cassette Transporter, Subfamily B
  • ATP-Binding Cassette Transporters
  • Anti-Inflammatory Agents
  • Enzyme Inhibitors
  • Dexamethasone
  • Cyclosporine
  • Cytochrome P-450 Enzyme System
  • multidrug resistance protein 3
  • Aryl Hydrocarbon Hydroxylases
  • Cytochrome P-450 CYP3A
  • Oxidoreductases, N-Demethylating