Uptake of Branched Polypeptides with Poly[L-Lys] Backbone by Bone-Marrow Culture-Derived Murine Macrophages:The Role of the Class A Scavenger Receptor

摘要

Selective delivery of antiparasitic or antibacterial drugs into infected macrophages could be a promising approach for improved therapies.Methotrexate conjugate with branched chain polypeptides exhibited pronounced anti-Leishmania activity in vitro and in vivo as reported here earlier.To identify structural requirements for efficient uptake of branched polypeptides,we have studied murine bone marrow culture-derived macrophages (BMM phi) from 129/ICR mice.We report on the translocation characteristics of structurally closely related compounds labeled with 5(6)-carboxyfluorescein.We found that this process is dependent on experimental conditions (e.g.polypeptide concentration,incubation time,and temperature).Using specific inhibitors as well as macrophages from wild-type and class-A scavenger receptor knockout (SR-A -/-) mice,we demonstrated that SR-A was involved in the endocytosis of some polypeptides depending on their charge.Uptake could be blocked by unlabeled polypeptide,by SR-A inhibitors,and by specific anti-SR-A monoclonal antibody.The polyanionic polypeptide poly[Lys(Succ-Glu_(1.0)-DL-Ala_(3.8))] (SuccEAK) with high charge density translocated more efficiently than poly[Lys(Ac-Glu_(1.0)-DL-Ala_(3.8))] (AcEAK),which had a lower anionic charge density.On the basis of experimental data presented,SuccEAK can be considered as a potential candidate for the design of a macromolecular carrier for specific drug delivery of bioactive entities into macrophages via SR-A.