title: Cultured CD4T cells and primary human lymphocytes express hOATPs: intracellular accumulation of saquinavir and lopinavir.
abstract: OBJECTIVE
  Drug efflux tranporters (P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP)) limit the cellular uptake of human immunodeficiency virus protease inhibitors but the contribution of influx transporters in cells that (over)express P-gp or MRP is less clear. Here, we studied the expression of one influx transporter system, human organic anion-transporting polypeptide (hOATP), in some T-cell lines (CEM, CEM(VBL), CEM(E1000)) and in peripheral blood mononuclear cells (PBMCs) and examined the effects of manipulation of influx/efflux transporters on the uptake of saquinavir and lopinavir.
  
  
  METHODS
  The expression of hOATPs was studied by PCR. We used hOATP substrate or inhibitor (estrone-3-sulphate (E-3-S) or montelukast, respectively) and inhibitors of P-gp (XR9576) and MRP (MK571 and frusemide) to study functional interactions between influx and efflux transporters in the uptake of saquinavir and lopinavir. Lipophilicity of the drugs was measured by octanol/saline partition coefficient.
  
  
  RESULTS
  CEM cells, their variants and PBMCs express various hOATP isoforms, with OATP3A1 detected in all of the cells. MK571, XR9576 and frusemide increased the uptake of saquinavir and lopinavir. E-3-S and montelukast reduced the uptake of saquinavir and lopinavir in some, but not all, of the cells. Pretreatment of the cells with MK571, XR9576 or frusemide, followed by E-3-S co-incubation reduced the cellular accumulation of saquinavir and lopinavir. Lopinavir is much more lipophilic than saquinavir.
  
  
  CONCLUSIONS
  Human OATPs, MRP, P-gp and lipophilicity determine the cellular uptake and retention of saquinavir and lopinavir. These data may have important implications for drug-drug interactions, drug safety and efficacy.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, County Londonderry, UK. o.janneh@ulster.ac.uk
authors.forename: O
authors.initials: O
authors.lastname: Janneh
authors.forename: R C
authors.initials: RC
authors.lastname: Hartkoorn
authors.forename: E
authors.initials: E
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Owen
authors.forename: S A
authors.initials: SA
authors.lastname: Ward
authors.forename: R
authors.initials: R
authors.lastname: Davey
authors.forename: D J
authors.initials: DJ
authors.lastname: Back
authors.forename: S H
authors.initials: SH
authors.lastname: Khoo
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D002478:Cells, Cultured; D017320:HIV Protease Inhibitors / Q000378:metabolism; D006801:Humans; D061466:Lopinavir; D008214:Lymphocytes / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D011744:Pyrimidinones / Q000378:metabolism*; D019258:Saquinavir / Q000378:metabolism*
chemical_list: D017320:HIV Protease Inhibitors; D061466:Lopinavir; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011744:Pyrimidinones; D019258:Saquinavir