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ORIGINAL RESEARCH ARTICLE

MRP (ABCC) Transporters-Mediated Efflux of Anti-HIV Drugs, Saquinavir and Zidovudine, from Human Endothelial Cells

Department of Pharmacology, Tulane University Health Sciences Center, New Orleans, Louisiana 70112

To whom requests for reprints should be addressed at ¹ Department of Pharmacology, Tulane University Health Sciences Center, 1430 Tulane Avenue, SL-83, New Orleans, LA 70112. E-mail: dmondal{at}tulane.edu

The constituents of highly active anti-retroviral therapy (HAART) include HIV-1 protease inhibitors (HPIs) and nucleoside reverse transcriptase inhibitors (NRTIs). Endothelial cell (EC) barriers, especially the blood-brain-barrier (BBB) suppresses the entry of HAART drugs to subendothelial HIV-1 reservoirs. The ATP binding cassette (ABC) transporter family members, multidrug resistant-1 (MDR-1) and multidrug resistance-associated proteins (MRPs) can efflux both HPIs and NRTIs from intracellular compartments. Using brain derived ECs from non-human sources, previous studies suggested a dominant role for MDR-1 in HAART efflux from the BBB. However, due to species variations in ABC-transporter expression, drug-efflux functions using human brain ECs need to be investigated. Furthermore, roles of ABC-transporters in drug-efflux from systemic EC barriers need to be studied. We monitored the expression of ABC-transporters in primary human ECs obtained from brain (HBMVECs), aorta (HAECs), pulmonary-artery (HPAECs), dermal-microvessel (HDMVECs) and umbilical vein (HUVECs). Gene expression for MDR-1 and MRPs (MRP-1 to MRP-5) were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). Drug efflux functions were determined by calcein retention assays. Intracellular accumulation of both ³H-saqui-navir (an HPI) and ³H-zidovudine (an NRTI) were also monitored in HAECs and HBMVECs. Both assays were carried out in presence of verapamil (20–60 µM) or MK-571 (12.5–50 µM) inhibitors of MDR-1 and MRPs, respectively in presence of verapamil or MK-571. The HBMVECs expressed higher levels of MRPs than MDR-1 and only MK-571 significantly (P < 0.01) suppressed calcein efflux from these cells. However, both HAECs and HPAECs showed MDR-1 and MRP expression and calcein efflux was inhibited by both verapamil and MK-571. Both inhibitors suppressed ³H-saqubinavir efflux from HAECs, but only MK-571 suppressed saquinavir efflux from HBMVECs. In both ECs, ³H-zidovudine efflux was only suppressed by MK-571. Thus, primary human ECs, especially brain derived ECs, predominantly express MRPs and their specific inhibition may enhance HAART efficacy in subendothelial HIV-1 reservoirs.

Key Words: HIV-1 • brain reservoirs • anti-retroviral drugs • MDR-1 • MRP • human endothelial cells