title: Effect of protease inhibitor-containing regimens on lymphocyte multidrug resistance transporter expression.
abstract: BACKGROUND
  Increased expression of multidrug resistance transporters, such as P-glycoprotein (P-gp), has been suggested as a potential mechanism for decreased protease inhibitor (PI) availability at certain intracellular sites and tissue compartments.
  
  
  OBJECTIVE
  To investigate the effect of PIs on the surface lymphocyte expression of P-gp in vitro and in vivo.
  
  
  METHODS
  Peripheral blood mononuclear cells (PBMCs) were isolated from healthy subjects (n = 15) and incubated (72 h) with 10 microM of each PI studied (saquinavir, ritonavir, nelfinavir, indinavir, amprenavir and lopinavir), or dimethyl sulphoxide (DMSO) control. PBMCs were also isolated from HIV-infected subjects (n = 50; viral load <50 copies/mL) on a PI- or a non-PI-containing combination antiretroviral regimen. P-gp expression was analysed by flow cytometry.
  
  
  RESULTS
  No differences in surface P-gp expression on lymphocytes, CD4+ or CD8+ lymphocyte subsets were observed following incubation with 10 microM saquinavir, ritonavir, indinavir, amprenavir or lopinavir in vitro. Nelfinavir, however, increased P-gp expression. In vivo, no difference in P-gp expression on total lymphocytes was observed between patients receiving a PI-containing regimen [saquinavir n = 9, ritonavir n = 6, nelfinavir n = 7, indinavir n = 7 and lopinavir/ritonavir n = 13, and two nucleoside reverse transcriptase inhibitors (NRTIs)] and patients receiving a control regimen of three NRTIs alone (n = 8).
  
  
  CONCLUSIONS
  This study suggests that, of the PIs, only nelfinavir increases P-gp expression in vitro, and in vivo the PI class of antiretrovirals do not increase P-gp expression on lymphocytes. It is clear that factors other than PI induction are important in the inter-individual variability in the lymphocyte expression of P-gp.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Liverpool, 70 Pembroke Place, Block H, First Floor, Liverpool L69 3GF. jford@liv.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Ford
authors.forename: E R
authors.initials: ER
authors.lastname: Meaden
authors.forename: P G
authors.initials: PG
authors.lastname: Hoggard
authors.forename: M
authors.initials: M
authors.lastname: Dalton
authors.forename: P
authors.initials: P
authors.lastname: Newton
authors.forename: I
authors.initials: I
authors.lastname: Williams
authors.forename: S H
authors.initials: SH
authors.lastname: Khoo
authors.forename: D J
authors.initials: DJ
authors.lastname: Back
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics; D000328:Adult; D016516:CD4-CD8 Ratio; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D015658:HIV Infections / Q000378:metabolism; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D018655:Lymphocyte Count; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis* / Q000235:genetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017320:HIV Protease Inhibitors; D027425:ATP-Binding Cassette, Sub-Family C Proteins