Suppression of HIV-1 Viral Replication by Inhibiting Drug Efflux Transporters in Activated Macrophages

BACKGROUND

Ethanol has been shown to increase oxidative stress, drug efflux transporter expression, and promote HIV progression. Macrophages, which express drug efflux transporters, serve as an essential sanctuary site for HIV. The antiretroviral drug lopinavir, a protease inhibitor, is a substrate of the drug efflux transporters P-glycoprotein and multidrug resistance-associated protein 1. The NF-κB signaling pathway is associated with inflammation and drug efflux transporter expression.

OBJECTIVE

To examine the effects of ethanol on drug efflux transporters and HIV replication of macrophages and develop strategies to increase the efficacy of the protease inhibitor.

METHODS

The expression of PGP and MRP1 was examined with western blot. The NF- κB inhibition was assessed with nuclear western blot. LC-MS/MS and p24 ELISA were used to assess intracellular LPV and viral replication.

RESULTS

Ethanol at 40mM slightly increased drug efflux transporter PGP and MRP1 expression in activated macrophages. IKK-16, an NF- κB inhibitor, counteracted the increased transporter expression caused by ethanol exposure. MK571, an MRP1 inhibitor, and IKK-16 significantly increased intracellular LPV concentration with or without ethanol treatment. MK571 significantly increased LPV efficacy in suppressing viral replication with or without ethanol treatment. A decreasing trend and a significant decrease were observed with IKK-16+LPV treatment compared with LPV alone in the no ethanol treatment and ethanol treatment groups, respectively.

CONCLUSION

In activated macrophages, inhibiting drug efflux transporter MRP1 activity and reducing its expression may represent a promising approach to suppress viral replication by increasing intracellular antiretroviral concentrations. However, different strategies may be required for ethanolrelated vs. untreated groups.

Intracellular Tenofovir and Emtricitabine Concentrations in Younger and Older Women with HIV Receiving Tenofovir Disoproxil Fumarate/Emtricitabine

The altered immune states of aging and HIV infection may affect intracellular metabolism of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC); increased cellular senescence decreases FTC-triphosphate (FTCtp) concentrations. The effects of age and inflammation on the ratio of intracellular metabolites (IMs; tenofovir diphosphate [TFVdp] and FTCtp) to their endogenous nucleotides (ENs; dATP and dCTP), a potential treatment efficacy marker, were assessed among participants of the Women's Interagency HIV Study (WIHS), who ranged from 25 to 75 years. Samples from women receiving TDF-FTC with viral loads of <200 copies/ml were dichotomized by age at collection into two groups (≤45 years and ≥60 years). IM/EN concentrations were measured in peripheral blood mononuclear cell (PBMC) pellets; interleukin-6 (IL-6) and sCD163 were measured in plasma; senescent CD8⁺ T cells were measured in viable PBMCs. The TFVdp:dATP and FTCtp:dCTP ratios had statistically significantly different distributions in older and younger women (log-rank test, P = 0.0023 and P = 0.032, respectively); in general, IM and EN concentrations were higher in the older women. After adjusting for potential confounders, these findings were not significant. In women aged ≤45 years, TFVdp was negatively associated with IL-6 and sCD163, while FTCtp was positively associated with sCD163 and IL-6 in women aged ≥60 years. Body mass index (BMI) was positively associated with IL-6 in both age groups and negatively associated with TFVdp in women aged ≤45 years. After adjustment, age remained significant for sCD163, while black race, BMI, and renal function remained significant for several IMs and ENs, suggesting that factors associated with aging, but not age itself, govern intracellular TDF-FTC pharmacology.

Can We Improve Stavudine's Safety Profile in Children? Pharmacokinetics of Intracellular Stavudine Triphosphate with Reduced Dosing

Stavudine remains a useful replacement option for treatment for HIV⁺ children. WHO reduced the adult dose to 30 mg twice daily, which maintains efficacy and lowers mitochondrial toxicity. We explored intracellular stavudine triphosphate levels in children receiving a reduced dose of 0.5 to 0.75 mg/kg of body weight twice daily to investigate whether a similar dose optimization can safely be made. A population pharmacokinetic model was developed to describe the pharmacokinetics of intracellular stavudine triphosphate in 23 HIV⁺ children and 24 HIV⁺ adults who received stavudine at 0.5 mg/kg and 20 mg twice daily for 7 days, respectively. Simulations were employed to optimize the pediatric dosing regimen to match exposures in adults receiving the current WHO-recommended dose of 30 mg twice daily. A biphasic disposition model with first-order appearance and disappearance described the pharmacokinetics of stavudine triphosphate. The use of allometric scaling with fat-free mass characterized well the pharmacokinetics in both adults and children, and no other significant effect could be detected. Simulations of 30 mg twice daily in adults predicted median (interquartile range [IQR]) stavudine triphosphate minimum drug concentration (C _min) and maximum drug concentration (C _max) values of 13 (10 to 19) and 45 (38 to 53) fmol/10⁶ cells, respectively. Targeting this exposure, simulations in HIV⁺ children were used to identify a suitable weight-band dosing approach (0.5 to 0.75 mg/kg), which was predicted to achieve median (IQR) C _min and C _max values of 13 (9 to 18) and 49 (40 to 58) fmol/10⁶ cells, respectively. Weight-band dosing using a stavudine dose of 0.5 to 0.75 mg/kg is proposed, and it shows comparable exposures to adults receiving the current WHO-recommended dose of 30 mg twice daily. Our pharmacokinetic results suggest that the decreased stavudine dose in children >2 years would have a reduced toxic effect while retaining antiretroviral efficacy.