Objective. The use of glucocorticoids (GCs) in rheumatoid arthritis is limited by side effects related to unfavorable pharmacokinetics and biodistribution. Liposomal GC formulations have been studied since the 1970s in an attempt to overcome this obstacle, but none has entered clinical use. We undertook this study to determine whether a novel approach could overcome the limitations that have thus far prevented the clinical use of these formulations: low drug:lipid ratio, low encapsulation efficiency, and lack of controlled release.Methods. We used ϳ80-nm sterically stabilized (pegylated) nanoliposomes (NSSLs), which were remoteloaded with an amphipathic weak acid GC (such as methyl prednisolone hemisuccinate) utilizing an intraliposome (aqueous compartment)-high/extraliposome (bulk medium)-low transmembrane calcium acetate gradient. This unique method actually "traps" the GC in the liposomal aqueous phase as a calcium-GC precipitate.Results. Our liposome formulation exhibited high encapsulation efficiency (94%) and a high drug:lipid mole ratio (0.41) and demonstrated controlled release of the encapsulated GC during systemic circulation and in inflamed paws in rats with adjuvant-induced arthritis. In addition, both in arthritic rats and in a Beagle dog, we showed the pharmacokinetic advantage of using liposomes as GC carriers. Finally, we demonstrated the superior therapeutic efficacy of our liposome formulation over that of free GCs in arthritic rats, both in early and in peak disease stages.Conclusion. Amphipathic weak acid GCs remoteloaded into ϳ80-nm NSSLs overcome past limitations of liposomal GC formulations. The unique loading method, which also leads to controlled release, improves the therapeutic effect both systemically and locally. Such a development has great potential for improving GC therapy.
The piperidine nitroxide tempamine (TMN) is a cell-permeable, stable radical having antioxidant, anticancer, and proapoptotic and/or pronecrotic activities, as was demonstrated by us in cell cultures. We also demonstrated synergism between TMN and doxorubicin in doxorubicin-sensitive and doxorubicin-resistant cell lines. Treatment of the C26 mouse colon carcinoma model in vivo also demonstrated synergism between TMN and doxorubicin in sterically stabilized liposomes (SSLs) containing TMN (SSL-TMN) and those containing doxorubicin. The above effects of TMN and SSL-TMN motivated us to develop and optimize the SSL-TMN formulation so that it will be able to reach the disease site with a sufficiently high TMN level and a release rate needed to achieve a therapeutic effect. Because TMN is an amphipathic weak base, it was remote loaded by an intraliposome high/extraliposome low transmembrane ammonium sulfate gradient. The kinetics and level of TMN loading were monitored by cyclic voltammetry (CV) and electron paramagnetic resonance (EPR); the latter also indicates TMN precipitation in the intraliposomal aqueous phase. The regeneration of the original CV and EPR signals by the ionophore nigericin indicates that TMN remained fully intact during loading and release. The cardinal role of the transmembrane ammonium ion gradient in the loading process was proven by the use of the selective ionophores nonactin (for NH4+) and nigericin (for H+). The anion of the ammonium salts affects loading stability and the rate of TMN release, both mediated through the TMN state of aggregation in the intraliposomal aqueous phase. The greater the TMN salt precipitation, the slower the TMN release rate. This was supported by measurement of osmolality, which is inversely related to TMN salt precipitate. Precipitation is in the order SO4(-2)>Cl-1>glucuronate-1. Liposome lipid composition, magnitude of the transmembrane ammonium ion gradient, and type of anion of the ammonium salt determine the amount of TMN loaded and its release rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.