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

Abstract

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-saquinavir (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 microM) or MK-571 (12.5-50 microM) 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.

Viral surface glycoproteins, gp120 and gp41, as potential drug targets against HIV-1: Brief overview one quarter of a century past the approval of zidovudine, the first anti-retroviral drug

“…Why? Anti-HIV drugs that must enter cells to exert their action can be efficiently neutralized by some cells, using primitive and innate self-defense mechanisms such as "efflux pumps" [95], which sense toxins and eject them outside of the cell. Many experts believe that this situation could be an important reason for the viral persistence and evolution in patients on ostensibly potent combination therapies.…”

Pharmacogenomics Dictate Pharmacokinetics: Polymorphisms in Drug-Metabolizing Enzymes and Drug-Transporters

“…2005;Tiwari AK, 2011). Recent studies by us, and others, have also shown that several anti-HIV-1 drugs, especially HIV protease inhibitors (HPIs) and nucleoside analog reverse transcriptase inhibitors (NRTIs) are substrates of ABC-transporters (Choo EF, 2000;Roy U, 2009) and their expression on both lymphocytes and BBB endothelial cells (ECs) can suppress drug entry into the cellular and anatomical reservoirs of HIV-1 (Eilers M, 2008;Tarbell JM. 2010;Shen S, 2010).…”

“…probenecid), and the leukotrienes (LT) receptor antagonist (e.g. MK-571), are known inhibitors of MRPs (Eilers M, 2008). A number of preclinical and clinical trials are also being carried out to discover new and more effective efflux pump inhibitors (EPIs).…”

“…BCRP is also referred to as a half transporter since it has one transmembrane domain and functions as a dimer to www.intechopen.com transport a variety of drugs. The immunosuppressant cyclosporine-A and verapamil, a calcium channel antagonist, are competitive inhibitors of MDR-1 mediated efflux (also referred to as MDR-modulators) and have often been used in the laboratory to determine MDR-1 specific drug-efflux (Eilers M, 2008;Roy U, 2009). A newly discovered group of ABC transporters is the MDR associated proteins (MRPs) also referred to as the ABCC family of transporters (Gradhand U, 2008).…”

Pharmacokinetic–pharmacodynamic relationship of NRTIs and its connection to viral escape: An example based on zidovudine

“…Most anti-HIV drugs act on intracellular targets (Owen and Khoo, 2004), and a high percentage of these drugs are substrates of some efflux transporters (Eilers et al, 2008;Janneh et al, 2005Janneh et al, , 2007Weiss et al, 2007;Hayashi et al, 2006). For the class of nucleoside reverse transcriptase inhibitors (NRTI), the current backbone of HAART, their pharmacological penetration into the target tissue/cells depends not only on the presence of transporters, but also on a cascade of intracellular activation (Painter et al, 2004).…”