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Abstract
THE INHIBITORY EFFECTS OF THE HIV PROTEASE INHIBITORS AND HIV-1 ON P-GLYCOPROTEIN IN VITRO
B. Chandler, D. Back
University of Liverpool, Liverpool, United Kingdom
OBJECT OF STUDY: In HIV infection, both viral and cellular resistance mechanisms may lead to therapeutic failure. P-glycoprotein (P-gp) is a transport protein expressed in lymphocytes and other tissues for which the PIs have been shown to act as substrates and inhibitors, raising the possibility that P-gp mediated efflux may contribute to sub-therapeutic drug levels and treatment failure. There is also evidence to suggest that elevated expression of P-gp may decrease a cell’s sensitivity to HIV infection although the mechanism of such interaction is unknown. The aim of this study was to investigate the ability of PIs and HIV-1 to potentiate toxicity of vinblastine, a well characterised P-gp substrate, in a P-gp over-expressing cell line (CEMVBL) compared to the low P-gp expressing parental cell line (CEM). METHODS: CEMVBL were generated by stepwise selection of CEM cells with vinblastine. Control conditions consisted of 0.5 ( 106 CEM or VBL resuspended in a range of vinblastine concentrations (5-1000ng/ml) and incubated (37(C, 72h). Test conditions were included either 10(M PI, ritonavir (RTV), saquinavir (SQV), nelfinavir (NFV), lopinavir (LPV), indinavir (IDV) or amprenavir (APV), HIV-IIIB (MOI 0.001) or, as a positive control, verapamil, a know P-gp inhibitor (n=4 for all conditions). Vinblastine cytotoxicity was evaluated using the MTT formazan formation assay and expressed as mean EC50 ( sd . RESULTS: A significant decrease in the vinblastine EC50 was observed in CEM cells in the presence of each of the PIs but not in the presence of either verapamil or HIV IIIB. However, much greater decreases in EC50 were observed in CEMVBL cells in the presence of the PIs RTV (239 ( 33, p=0.02), NFV (40 ( 12, p<0.0001), LPV (123 ( 83, p<0.0001) and APV (248 ( 47 p=0.007) compared to VBL treated with vinblastine alone (542 ( 120), verapamil also caused a decrease in EC50 (27 ( 7, p<0.001). HIV-IIIB had no effect on the vinblastine EC50 in CEMVBL cells. CONCLUSIONS: These findings confirm that the HIV PIs are capable of inhibiting the efflux action of P-glycoprotein to varying extents (NFV>LPV>RTV=APV>SQV=IDV), thus potentiating toxicity of other substrates. HIV did not have such an effect, indicating that any interaction occurring between the transport protein and virus does not interfere with substrate binding and transport by P-gp.
The 2nd IAS Conference on HIV Pathogenesis and Treatment
Abstract no.
871
Suggested Citation
" B. Chandler, et al.
THE INHIBITORY EFFECTS OF THE HIV PROTEASE INHIBITORS AND HIV-1 ON P-GLYCOPROTEIN IN VITRO.
Poster:
The 2nd IAS Conference on HIV Pathogenesis and Treatment:
Abstract no.
871"
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