Macrophages serve as vehicles for the carriage and delivery of polymer-coated nanoformulated antiretroviral therapy (nanoART). Although superior to native drug, high drug concentrations are required for viral inhibition. Herein, folate-modified atazanavir/ritonavir (ATV/r)-encased polymers facilitated macrophage receptor targeting for optimizing drug dosing. Folate coating of nanoART ATV/r significantly enhanced cell uptake, retention and antiretroviral activities without altering cell viability. Enhanced retentions of folate-coated nanoART within recycling endosomes provided a stable subcellular drug depot. Importantly, five-fold enhanced plasma and tissue drug levels followed folate-coated formulation injection in mice. Folate polymer encased ATV/r improves nanoART pharmacokinetics bringing the technology one step closer to human use.
Nanoformulations of crystalline indinavir, ritonavir, atazanavir, and efavirenz were manufactured by wet milling, homogenization or sonication with a variety of excipients. The chemical, biological, immune, virological, and toxicological properties of these formulations were compared using an established monocyte-derived macrophage scoring indicator system. Measurements of drug uptake, retention, release, and antiretroviral activity demonstrated differences amongst preparation methods. Interestingly, for drug cell targeting and antiretroviral responses the most significant difference among the particles was the drug itself. We posit that the choice of drug and formulation composition may ultimately affect clinical utility.
Our laboratory has pioneered the development of long-acting nanoformulations of antiretroviral therapy (nanoART). NanoART serves to improve drug compliance, toxicities, and access to viral reservoirs. These all function to improve treatment of human immunodeficiency virus (HIV) infection. Formulations are designed to harness the carrying capacities of mononuclear phagocytes (MP; monocytes and macrophages) and to use these cells as Trojan horses for drug delivery. Such a drug distribution system limits ART metabolism and excretion while facilitating access to viral reservoirs. Our prior works demonstrated a high degree of nanoART sequestration in macrophage recycling endosomes with broad and sustained drug tissue biodistribution and depots with limited untoward systemic toxicities. Despite such benefits, the effects of particle carriage on the cells’ functional capacities remained poorly understood. Thus, we employed pulsed stable isotope labeling of amino acids in cell culture to elucidate the macrophage proteome and assess any alterations in cellular functions that would affect cell-drug carriage and release kinetics. NanoART-MP interactions resulted in the induction of a broad range of activation-related proteins that can enhance phagocytosis, secretory functions, and cell migration. Notably, we now demonstrate that particle-cell interactions serve to enhance drug loading while facilitating drug tissue depots and transportation.
Background
Manganese (Mn2+)-enhanced MRI (MEMRI) is a valuable imaging tool to study brain structure and function in normal and diseased small animals. The brain retention of Mn2+ is relatively long with a half-life (t1/2) of 51 to 74 days causing a slow decline of MRI signal enhancement following Mn2+ administration. Such slow decline limits using repeated MEMRI to follow the central nervous system longitudinally in weeks or months. This is because residual Mn2+ from preceding administrations can confound the interpretation of imaging results. We investigated whether the Mn2+ enhancement decline could be accelerated thus enabling repeated MEMRI, and as a consequence broadens the utility of MEMRI tests.
New Methods
We investigated whether N-acetyl-para-aminosalicylic acid (AcPAS), a chelator of Mn2+, could affect the decline of Mn2+ induced MRI enhancement in brain.
Results and Conclusion
Two-week treatment with AcPAS (200 mg/kg/dose × 3 daily) accelerated the decline of Mn2+ induced enhancement in MRI. In the whole brain on average the enhancement declined from 100% to 17% in AcPAS treated mice, while in PBS controls the decline is from 100% to 27%. We posit that AcPAS could enhance MEMRI utility for evaluating brain biology in small animals.
Comparison with Existing Methods
To the best of our knowledge, no method exists to accelerate the decline of the Mn2+ induced MRI enhancement for repeated MEMRI tests.
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