Related Experiment Videos
Interactions of HIV protease inhibitors with a human organic cation transporter in a mammalian expression system
L Zhang1, W Gorset, C B Washington
1Department of Biopharmaceutical Sciences, University of California, San Francisco, California 94143-0446, USA.
Abstract:
Recently, we cloned a human organic cation transporter, hOCT1, which is expressed primarily in the liver. hOCT1 plays an important role in the cellular uptake and elimination of various xenobiotics including therapeutically important drugs. HIV protease inhibitors are a new class of therapeutic agents. The purpose of this study was to elucidate the interactions of HIV protease inhibitors with hOCT1 and to determine whether hOCT1 is involved in the elimination of these compounds. We studied the interactions of HIV protease inhibitors with hOCT1 in a transiently transfected human cell line, HeLa. Uptake studies were carried out 40 h post-transfection using the radiolabeled model organic cation, [(14)C]tetraethylammonium (TEA), under different experimental conditions. In cis-inhibition studies, all of the HIV protease inhibitors tested, i.e., indinavir (IC(50) of 62 microM), nelfinavir (IC(50) of 22 microM), ritonavir (IC(50) of 5.2 microM), and saquinavir (IC(50) of 8.3 microM) inhibited TEA uptake in HeLa cells expressing hOCT1. However, none of the HIV protease inhibitors trans-stimulated [(14)C]TEA uptake, suggesting that they are poorly translocated by hOCT1. Nelfinavir, ritonavir, and saquinavir demonstrated an apparent "trans-inhibition" effect. No enhanced uptake of [(14)C]saquinavir was observed in hOCT1 DNA-transfected cells versus empty vector-transfected cells. These data suggest that HIV protease inhibitors are potent inhibitors, but poor substrates, of hOCT1. Some HIV protease inhibitors may potently inhibit the uptake and elimination of cationic drugs that are substrates for hOCT1, leading to potential drug-drug interactions. Other transporters, e.g., MDR1 and MRP1, in HIV-targeted cells may control the intracellular concentrations of HIV protease inhibitors.
Insights
HIV protease inhibitors strongly inhibit the human organic cation transporter 1 (hOCT1), but are poorly transported by it. This interaction may cause drug-drug interactions with other hOCT1 substrates.
Area of Science:
- Pharmacology
- Biochemistry
- Drug Metabolism
Background:
- The human organic cation transporter 1 (hOCT1) is crucial for liver uptake and elimination of xenobiotics.
- HIV protease inhibitors are key therapeutic agents for HIV treatment.
- Understanding transporter interactions is vital for predicting drug efficacy and safety.
Purpose of the Study:
- To investigate the interaction between HIV protease inhibitors and hOCT1.
- To determine if hOCT1 mediates the elimination of HIV protease inhibitors.
Main Methods:
- Utilized a HeLa cell line transiently transfected with hOCT1.
- Performed [(14)C]tetraethylammonium (TEA) uptake studies.
- Conducted cis-inhibition and trans-stimulation experiments with various HIV protease inhibitors.
Main Results:
- All tested HIV protease inhibitors (indinavir, nelfinavir, ritonavir, saquinavir) inhibited TEA uptake by hOCT1.
- HIV protease inhibitors showed minimal trans-stimulation of TEA uptake, indicating poor substrate translocation.
- Nelfinavir, ritonavir, and saquinavir exhibited a trans-inhibition effect.
Conclusions:
- HIV protease inhibitors act as potent inhibitors but poor substrates of hOCT1.
- Potential for drug-drug interactions exists if HIV protease inhibitors interfere with cationic drugs cleared by hOCT1.
- Other transporters like MDR1 and MRP1 may influence intracellular HIV protease inhibitor concentrations.