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  • Title: Effect of protease inhibitor-containing regimens on lymphocyte multidrug resistance transporter expression.
    Author: Ford J, Meaden ER, Hoggard PG, Dalton M, Newton P, Williams I, Khoo SH, Back DJ.
    Journal: J Antimicrob Chemother; 2003 Sep; 52(3):354-8. PubMed ID: 12917239.
    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. OBJECTIVES: To investigate the effect of PIs on the surface lymphocyte expression of P-gp in vitro and in vivo. PATIENTS AND 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). CONCLUSION: 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.
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