ABSTRACT
BACKGROUND: Antiretroviral therapy has considerably reduced HIV disease progression, but complete eradication of HIV cannot actually be achieved. Moreover, prolonged use of protease inhibitors (PIs) causes profound changes in lipid metabolism with an increased risk of cardiovascular diseases. P-glycoprotein (P-gp) is expressed on many cell types, playing an important role in the efflux of drugs including PIs, limiting their intracellular concentration. Furthermore, several studies showed that P-gp is involved in lipid homeostasis and its activity is regulated by cholesterol. METHODS: THP-1 monocytes were used to study: (i) the influence of low-density lipoprotein (LDL) on P-gp expression and function, assessed by flow cytometry and quantitative real-time PCR analysis and measuring ritonavir and rhodamine-123 dye efflux, respectively; and (ii) the influence of ritonavir on cholesterol mobilization. The intracellular levels of ritonavir or cholesterol were measured by HPLC-UV and filipin staining, respectively. RESULTS: In THP-1 cells, LDL was able to yield an increase in both P-gp expression and activity. THP-1 cells treated with LDL showed a decrease in the intracellular ritonavir concentration in a dose-dependent manner. Notably, ritonavir induced reduced cholesterol mobilization in THP-1 cells, probably due to its inhibitory action on P-gp activity. CONCLUSIONS: Our data indicate a potential interplay between LDL and ritonavir mediated by P-gp. This interaction could influence both therapy effectiveness and cellular lipid metabolism, with important implications in the management of HIV patients treated with boosted PIs.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Anti-HIV Agents/metabolism , Anti-HIV Agents/pharmacokinetics , Lipoproteins, LDL/metabolism , Ritonavir/metabolism , Ritonavir/pharmacokinetics , Cell Line , Chromatography, High Pressure Liquid , Cytosol/chemistry , Flow Cytometry , Gene Expression Profiling , Humans , Monocytes , Protein Binding , Real-Time Polymerase Chain Reaction , Spectrophotometry, UltravioletABSTRACT
The rate of HIV-positive patients that fails to reach or to maintain a durable virological suppression under anti-retroviral (ARV) therapy might be as high as 50%, therefore new tools to improve ARV drug efficacy are urgently needed. Among others, therapeutic drug monitoring (TDM) is a strategy by which the dosing regimen for a patient is guided by measurement of plasma drug levels, enabling physicians to optimize ARV drug efficacy and to avoid drug-related toxicity. The most used analytical methods to determine plasma levels of ARV drugs are HPLC-UV and HPLC-MS(/MS), recently MALDI-based methods and enzyme immunoassay (EIA) technologies have been also employed. The wide inter-patient variability in ARV drug pharmacokinetic supports the application of TDM to the clinical management of HIV-infected patients. Drug-drug and drug-food interactions, drug binding to plasma proteins, drug sequestering by erythrocytes, hepatic impairment, sex, age, pregnancy, and host genetic factors are sources of inter-patient variability affecting ARV drug pharmacokinetics. Combining the information of TDM and resistance tests in genotypic inhibitory quotient (GIQ) is likely to be of great clinical utility. Indeed, only two clinical trials on GIQ, both conducted using ARV drugs not more commonly in use, have shown clinical benefits. The design of new trials with long follow-up and sample size representative of the current HIV prevalence is urgently needed to give indications for GIQ as an early predictor of virological response. Here, the basic principles and the available methods for TDM in the management of HIV-infected patients are reviewed.
