Protease-Activated Receptors: New Concepts in Regulation of G Protein-Coupled Receptor Signaling and Trafficking

Abstract

It is therapeutically desirable to effectively deliver ceramide, an antimitogenic and proapoptotic lipid second messenger, to transformed cell types. However, the targeted delivery of cell-permeable ceramide analogs, including C₆-ceramide, to cells may be impeded by the hydrophobicity of these bioactive lipids, resulting in reduced efficacy. The objective of this study is to develop and optimize liposomal vehicles to augment ceramide delivery to a breast adenocarcinoma cell line. We designed conventional, cationic, and pegylated drug release vesicles to efficaciously deliver ceramide to MDA-MB-231 breast adenocarcinoma cells. In vitro pharmacokinetic analysis demonstrated that liposomal ceramide delivery resulted in significantly greater accumulation of ceramide in MDA-MB-231 cells. Ceramide-formulated liposomes significantly inhibited MDA-MB-231 cell proliferation as compared with nonliposomal administration of ceramide. Ceramide-induced apoptosis correlated with the pharmacokinetic profile and the diminished proliferation in this highly aggressive, metastatic cell line. Liposomal ceramide formulations inhibited phosphorylated Akt levels and stimulated caspase-3/7 activity more effectively than nonliposomal ceramide, events consistent with apoptosis. Together, these results indicate that bioactive ceramide analogs can be incorporated into conventional, cationic, or pegylated liposomal vehicles for improved drug delivery and release.