Transport of diclofenac by breast cancer resistance protein (ABCG2) and stimulation of multidrug resistance protein 2 (ABCC2)-mediated drug transport by diclofenac and benzbromarone

Diclofenac is an important analgesic and anti-inflammatory drug, widely used for treatment of postoperative pain, rheumatoid arthritis, and chronic pain associated with cancer. Consequently, diclofenac is often used in combination regimens and undesirable drug-drug interactions may occur. Because many drug-drug interactions may occur at the level of drug transporting proteins, we studied interactions of diclofenac with apical ATP-binding cassette (ABC) multidrug efflux transporters. Using Madin-Darby canine kidney (MDCK)-II cells transfected with human P-glycoprotein (P-gp; MDR1/ABCB1), multidrug resistance protein 2 (MRP2/ABCC2), and breast cancer resistance protein (BCRP/ABCG2) and murine Bcrp1, we found that diclofenac was efficiently transported by murine Bcrp1 and moderately by human BCRP but not by P-gp or MRP2. Furthermore, in Sf9-BCRP membrane vesicles diclofenac inhibited transport of methotrexate in a concentration-dependent manner. We next used MDCK-II-MRP2 cells to study interactions of diclofenac with MRP2-mediated drug transport. Diclofenac stimulated paclitaxel, docetaxel, and saquinavir transport at only 50 microM. We further found that the uricosuric drug benzbromarone stimulated MRP2 at an even lower concentration, having maximal stimulatory activity at only 2 microM. Diclofenac and benzbromarone stimulated MRP2-mediated transport of amphipathic lipophilic drugs at 10- and 250-fold lower concentrations, respectively, than reported for other MRP2 stimulators. Because these concentrations are readily achieved in patients, adverse drug-drug interactions may occur, for example, during cancer therapy, in which drug concentrations are often critical and stimulation of elimination via MRP2 may result in suboptimal chemotherapeutic drug concentrations. Moreover, stimulation of MRP2 activity in tumors may lead to increased efflux of chemotherapeutic drugs and thereby drug resistance.     

Role of NADPH-cytochrome P450 reductase and cytochrome-b5/NADH-b5 reductase in variability of CYP3A activity in human liver microsomes

NADPH-cytochrome P450 reductase (CPR) and cytochrome-b(5) (b(5)) together with NADH-b(5) reductase (b(5)R) play important roles in cytochrome P450 3A-mediated drug metabolism via electron transfer. However, it is not clear whether variability in expression of these accessory proteins contributes to the known interindividual variability in CYP3A activity. CPR and b(5) were measured in human liver microsomes (HLMs) by spectrophotometry and immunoblotting. HLMs from elderly (>or=46 years) male donors (n=11) averaged 27% (P=0.034) and 41% (P=0.011) lower CPR levels than young (相似文献   

Dermatological immune restoration syndrome: does it exist?

Dermatological conditions are often an early clue to HIV infection and are common. As the disease progresses patients develop a dominant Th-2 immunological response that may facilitate the development of a number of skin conditions. With antiretroviral therapy the Th-1 response is restored and some skin problems regress. But, paradoxically, some cutaneous conditions may worsen, such as herpes zoster, mucocutaneous herpes, eosinophilic folliculitis and mycobacterial infections. This may be because immune restoration of a host's immunity causes recognition of silent or latent infection and results in development of the condition.