title: Inhibition of P-glycoprotein and multidrug resistance-associated proteins modulates the intracellular concentration of lopinavir in cultured CD4 T cells and primary human lymphocytes.
abstract: BACKGROUND
  HIV protease inhibitors (HPIs) are an important component of highly active antiretroviral therapy. However, the activity of drug efflux transporters, such as P-glycoprotein (P-gp) and multidrug resistance-associated proteins (MRP1/MRP2), may limit intracellular drug accumulation. Drugs that inhibit the activity of drug efflux proteins may, in combination with HPIs, enhance the clinical efficacy of the drugs.
  
  
  METHODS
  The transport of [(14)C]lopinavir was evaluated in peripheral blood mononuclear cells (PBMCs) in the absence or presence of known inhibitors: tariquidar (P-gp), MK571 (MRP), frusemide (MRP1/2), dipyridamole (MRP1/P-gp) and probenecid (MRP2/OATP). The effects of ritonavir, amprenavir and atazanavir on the accumulation of lopinavir were also evaluated in cultured CD4(+) T-lymphoblastoid cells [CEM (parental), CEM(VBL) (P-gp-overexpressing) and CEM(E1000) (MRP1-overexpressing)] and PBMCs. The relative expression of the drug efflux proteins on the PBMCs was assessed by flow cytometric and real-time PCR methods.
  
  
  RESULTS
  Tariquidar, MK571, frusemide and dipyridamole all significantly increased the intracellular accumulation of lopinavir in the PBMCs, whereas probenecid decreased it. The cellular accumulation ratio (CAR) of lopinavir was also increased by ritonavir, amprenavir and atazanavir in a concentration-dependent manner in both cell types. The expression of P-gp, MRP1 and MRP2 mRNA were variable and individually did not correlate with CARs of lopinavir.
  
  
  CONCLUSIONS
  We provide evidence that lopinavir is a substrate of P-gp, MRP1 and MRP2. The intracellular concentration of lopinavir is increased when co-incubated with ritonavir, amprenavir and atazanavir in PBMCs. Manipulation of drug efflux transporters may be a useful strategy for increasing the intracellular concentration and thereby enhancing the clinical efficacy of lopinavir.
authors: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Co., Londonderry BT52 1SA, UK. o.janneh@ulster.ac.uk
authors: Omar
authors: O
authors: Janneh
authors: Elizabeth
authors: E
authors: Jones
authors: Becky
authors: B
authors: Chandler
authors: Andrew
authors: A
authors: Owen
authors: Saye H
authors: SH
authors: Khoo
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D024921:Drug Resistance, Multiple, Viral; D005786:Gene Expression Regulation; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D061466:Lopinavir; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011744:Pyrimidinones / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D019380:Anti-HIV Agents; D061466:Lopinavir; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011744:Pyrimidinones; D012333:RNA, Messenger; C000715087:ABCC2 protein, human; C421109:multidrug resistance-associated protein 1