Different endocytotic uptake mechanisms for nanoparticles in epithelial cells and macrophages.
Precise knowledge regarding cellular uptake of nanoparticles is of great importance for future biomedical applications. Four different endocytotic uptake mechanisms, that is, phagocytosis, macropinocytosis, clathrin- and caveolin-mediated endocytosis, were investigated using a mouse macrophage (J774A.1) and a human alveolar epithelial type II cell line (A549). In order to deduce the involved pathway in nanoparticle uptake, selected inhibitors specific for one of the endocytotic pathways were optimized regarding concentration and incubation time in combination with fluorescently tagged marker proteins. Qualitative immunolocalization showed that J774A.1 cells highly expressed the lipid raft-related protein flotillin-1 and clathrin heavy chain, however, no caveolin-1. A549 cells expressed clathrin heavy chain and caveolin-1, but no flotillin-1 uptake-related proteins. Our data revealed an impeded uptake of 40 nm polystyrene nanoparticles by J774A.1 macrophages when actin polymerization and clathrin-coated pit formation was blocked. From this result, it is suggested that macropinocytosis and phagocytosis, as well as clathrin-mediated endocytosis, play a crucial role. The uptake of 40 nm nanoparticles in alveolar epithelial A549 cells was inhibited after depletion of cholesterol in the plasma membrane (preventing caveolin-mediated endocytosis) and inhibition of clathrin-coated vesicles (preventing clathrin-mediated endocytosis). Our data showed that a combination of several distinguishable endocytotic uptake mechanisms are involved in the uptake of 40 nm polystyrene nanoparticles in both the macrophage and epithelial cell line.
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland, Phone +41 26 300 95 02.
Dagmar A
DA
Kuhn
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland, Phone +41 26 300 95 02.
Dimitri
D
Vanhecke
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland, Phone +41 26 300 95 02.
Benjamin
B
Michen
Respiratory Medicine, University Hospital of Bern, Murtenstrasse 50, 3008 Bern, Switzerland.
Fabian
F
Blank
Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3000 Bern 9, Switzerland.
Peter
P
Gehr
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland, Phone +41 26 300 95 02.
Alke
A
Petri-Fink
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland, Phone +41 26 300 95 02 ; Respiratory Medicine, University Hospital of Bern, Murtenstrasse 50, 3008 Bern, Switzerland.
Barbara
B
Rothen-Rutishauser
cell lines; endocytosis; inhibition; nanoparticles; uptake proteins