On the Mechanism of Eukaryotic Cell Penetration by alpha- and beta-Oligoarginines - Targeting Infected Erythrocytes

Fluorescein-labeled alpha- and beta-octaarginine amides were synthesized. The route, by which these oligoarginine (OA) derivatives enter cells (hepatocytes, fibroblasts, macrophages), was investigated by confocal fluorescence microscopy. Comparisons (by co-localization experiments) with compounds of known penetration modes revealed that the beta-octaarginine amide also uses multiple pathways to enter cells. There was no difference between the alpha- and the beta-OAs. Like other cell-penetrating peptides (CPPs), the beta-octaarginine eventually winds up in the nucleoli of the cell nuclei (cf Chem. Biodiversity, 2004, 1, 65). Surprisingly, there was no entry of alpha- or beta-OA into intact and healthy human erythrocytes (which do not possess a nucleus). Blood cells infected by Plasmodium fakiparum (malaria parasite) were, however, entered readily, and the OAs went all the way through a couple of membranes into the parasite. The potential of these results for delivering specific antimalarial drugs directly into the parasite is discussed.