Mechanisms of Poly(amido amine) Dendrimer Transepithelial Transport and Tight Junction Modulation in Caco-2 Cells

摘要

The purpose of this study was to investigate the mechanisms of cellular uptake, intracellular trafficking, transepithelial transport and tight junction modulation of G3.S poly (amido amine) dendrimers in Caco-2 cells. G3.S den-drimers have shown promise as oral drug delivery carriers due to their ability to translocate across epithelial cell monolayers by both transcellular and paracellular mechanisms. Chemical inhibitors blocking clathrin-, caveolin- and dynamin-dependent endocytosis pathways were used to investigate the mechanisms of dendrimer cellular uptake and transport across Caco-2 cells. Cellular uptake was found to be dynamin dependent, and was reduced by both clathrin and caveolin endocytosis inhibitors, suggesting that dendrimers take advantage of several receptor-mediated endocytosis pathways for cellular entry. In contrast, dendrimer transepithelial transport was found to be governed by dynamin- and clathrin-dependent pathways only. Intracellular trafficking studies showed that dendrimers are found in early endosomes and trafficked to lysosomes within 15 minutes, but that the pathway becomes saturated, leading to increased presence in the endosomes at later time points. The dendrimers were unable to open tight junctions in cell monolayers treated with dynasore, a selective inhibitor of dynamin, a small GTPase required for vesicle scission in endocytosis. This suggests that dendrimer inter-nalization is required prior to its subsequent modulation of tight junctional integrity and that dendrimers act on intracellular cytoskeletal proteins to open tight junctions.