Characterization of dexamethasone conjugated polyethylenimine as a gene carrier with anti-inflammatory effect in LPS-induced acute lung injury

Abstract

Acute lung injury (ALI) is characterized by disruption of the lung alveolar-capillary membrane barrier with severe acute inflammatory response. Dexamethasone is a potent glucocorticoid and has anti-inflammatory effect. In this study, dexamethasone conjugated low molecular polyethylenimine (2 kDa), PEI-Dexa, was synthesized as a water-soluble glucocorticoid and gene carrier for gene therapy of ALI. To confirm the anti-inflammatory effect of PEI-Dexa, PEI-Dexa/pβ-Luc complexes were transfected into LPS stimulated RAW264.7 cells. After 24 hrs, the levels of TNF-α, IL-1β, and IL-6 were measured by ELISA. The results showed that PEI-Dexa reduced inflammatory cytokines, compared to the control cells. However, PEI2K/pβ and PEI25K/pβ did not show this effect. Then, PEI-Dexa was characterized as a gene carrier. MTT assays showed PEI-Dexa had lower toxicity to L2 lung epithelial cells than PEI25K. In addition, PEI-Dexa had high transfection efficiency comparable to PEI25K. For in vivo study, PEI-Dexa/pβ-Luc, PEI 2K/pβ-Luc and PEI25K/pβ-Luc complexes were administrated into the mice lung by intratracheal injection. Luciferase assay showed that PEI-Dexa had higher delivery efficiency to the mouse lung than PEI 2K or PEI 25K. Anti-inflammatory effect of PEI-Dexa was evaluated in LPS induced ALI mouse model. PEI-Dexa/pβ-Luc complexes were administered in the lungs. After 24hrs, TNF-α and IL-6 levels were determined in BALF and lung tissues. Finally, H&E staining showed that PEI-Dexa reduced the inflammation in the lungs. The results suggest that PEI-Dexa is an efficient carrier for acute lung injury gene therapy.