Disulfiram metabolites permanently inactivate the human multidrug resistance P-glycoprotein

Mol Pharm. 2004 Nov-Dec;1(6):426-33. doi: 10.1021/mp049917l.

Abstract

The human multidrug resistance P-glycoprotein (P-gp) uses ATP to transport a wide variety of structurally unrelated cytotoxic compounds out of the cell. The relatively high expression of P-gp in organs such as the intestine, kidney, blood-brain/testes barrier and in some tumor cells can compromise chemotherapy treatments for patients with cancer or AIDS/HIV. It has been difficult to inhibit P-gp during chemotherapy with noncovalent inhibitors because the relatively high levels of inhibitors have severe side effects. An alternative approach to inhibit P-gp would be to covalently modify cysteine residues within the NBDs. In this study, we tested whether metabolites of disulfiram, a drug currently used to treat chronic alcoholism, could inhibit P-gp. We show that the disulfiram metabolites, S-methyl N,N-diethylthiocarbamate sulfoxide and S-methyl N,N-diethylthiocarbamate sulfone inhibited the verapamil-stimulated ATPase activity of P-gp with IC50 values (concentrations that result in 50% inhibition of activity) of 9 and 4.8 microM, respectively. Similarly, S-methyl N,N-diethylthiocarbamate sulfoxide and S-methyl N,N-diethylthiocarbamate sulfone inhibited the activity of aldehyde dehydrogenase with IC50 values of 3.2 and 1.7 microM, respectively. Inhibition of P-gp by the metabolites was not reversed by addition of the reducing compound, dithiothreitol. We then determined which endogenous cysteine residue was responsible for inhibiting P-gp activity after exposure to the disulfiram metabolites. Treatment of P-gp mutants containing a single cysteine residue showed that inactivation was primarily due to modification of Cys1074 in NBD2. These results indicate that metabolites of disulfiram can covalently inactivate P-gp. Covalent modification of drug transporters could be a useful approach for inhibiting their activities during chemotherapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Adenosine Triphosphatases / antagonists & inhibitors
  • Adenosine Triphosphatases / drug effects
  • Adenosine Triphosphate / metabolism
  • Aldehyde Dehydrogenase / antagonists & inhibitors
  • DNA, Complementary / genetics
  • Ditiocarb / analogs & derivatives*
  • Ditiocarb / metabolism
  • Ditiocarb / pharmacology*
  • Drug Resistance, Multiple*
  • Enzyme Inhibitors / metabolism
  • Enzyme Inhibitors / pharmacology*
  • Gene Expression Regulation
  • Humans
  • Hydrogen-Ion Concentration
  • Models, Biological
  • Mutation
  • Structure-Activity Relationship
  • Verapamil / pharmacology

Substances

  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • DNA, Complementary
  • Enzyme Inhibitors
  • S-methyl N,N-diethylthiocarbamate sulfone
  • S-methyl N,N-diethylthiolcarbamate sulfoxide
  • Adenosine Triphosphate
  • Ditiocarb
  • Verapamil
  • Aldehyde Dehydrogenase
  • Adenosine Triphosphatases