Hepatic and extra-hepatic induction of drug metabolizing enzymes and drug transporters by antiretrovirals, in the presence and absence of viral infection.

摘要

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) are important antiretroviral drugs (ARVs) included in the currently used highly active antiretroviral therapy (HAART) regimen. While these agents have significantly improved the morbidity and mortality associated with HIV/AIDS, their clinical use remains fraught with numerous drug-drug interactions (DDIs) including induction of drug clearance pathways. This study represents an attempt to better understand the impact of these agents on key drug-metabolizing enzymes and drug transporters (DMTs) in hepatic and extra-hepatic tissues. In preliminary studies we observed that NNRTI efavirenz, and PIs, nelfinavir and ritonavir, activate the pregnane-X receptor (PXR), a key transcriptional regulator of DMTs. Based on this observation and other published reports, we hypothesized that these agents induce hepatic and extra-hepatic (intestinal and CD4+ T-cells) DMTs, and that the magnitude of induction is modulated by disease state. In Aim 1, employing primary human hepatocytes and LS174T colon carcinoma cell line, a clinically relevant model for intestinal drug metabolism studies, we observed that these drugs have a profound effect on several DMTs. Our studies revealed that efavirenz is potent inducer of CYP3A4, whereas the PIs increase CYP3A4 mRNA levels without a correlative increase in CYP3A4 activity. The three drugs also induced CYP2B6, UGT1A1 and UGT1A6, but only nelfinavir induced UGT2B7. Both PIs markedly induced P-gp. In Aim 2, we evaluated the effect of these drugs on expression and activity of DMTs in CD4+ T-cells. While all three ARVs produced significant increases in the P-gp function in CD4+ T-cells, nelfinavir was the most potent P-gp inducer. In the third Specific Aim, we observed that exposure of nelfinavir-treated CD4+ T-cells to infectious-HIV decreased P-gp activity which corresponded with a reduction in hPXR expression levels. A comparison of the effects on exposed-infected and exposed-uninfected cells revealed a significant decrease of P-gp activity in nelfinavir-treated exposed-infected cells, but an increase in the exposed-uninfected cells. The expression of hPXR was lower in nelfinavir-treated exposed-infected cells than exposed-uninfected cells. Taken together, our studies have provided novel insights into the factors that may increase the potential for drug-drug interactions and alter the intracellular pharmacology of important ARVs.