Engineering exosomes for pulmonary delivery of peptides and drugs to inflammatory lung cells by inhalation

Exosomes have been investigated as delivery vesicles for various drugs. However, exosome-mediated peptide delivery into the lungs has not been studied. In this study, exosomes were engineered for the pulmonary delivery of RAGE-binding peptide (RBP), an anti-inflammatory peptide. To load the peptide into exosomes, RBP was linked to an exosome membrane integral protein, Lamp2b, to produce RBP-linked exosomes (RBP-exo). The anti-inflammatory effects of RBP-exo were confirmed by cytokine assays in lipopolysaccharide (LPS)-activated macrophage cells. To increase anti-inflammatory effects, curcumin was loaded into RBP-exo. Curcumin loaded RBP-exo (RBP-exo/Cur) had higher intracellular curcumin delivery efficiency than curcumin alone or curcumin loaded into unmodified exosomes (unmod-exo/Cur). This suggests that RBP on the surface of RBP-exo may interact with RAGE and increase the intracellular delivery efficiency of curcumin. In addition, RBP-exo/Cur had higher anti-inflammatory effects than curcumin alone, a mixture of RBP and curcumin, and unmod-exo/Cur in vitro. For in vivo evaluation, RBP-exo/Cur was administrated by intratracheal instillation into the lungs of an acute lung injury (ALI) model. The results showed that RBP-exo/Cur reduced pro-inflammatory cytokines more efficiently than curcumin alone, RBP-exo, and unmod-exo/Cur. Hematoxylin and eosin staining confirmed that the inflammation reaction was inhibited in the RBP-exo and RBP-exo/Cur groups. Immunostaining assays showed that RBP-exo was co-localized mostly with type I epithelial cells. In conclusion, RBP was successfully delivered with exosomes into the lungs by inhalation. A combination of RBP and curcumin using exosomes as carriers may be useful as ALI therapy.