Delivery of small interfering RNA into airway epithelial cells. Downregulation of the pro-inflammatory cytokine high mobility group BOX 1

polyplexes with cells. In conclusion, we have found optimal conditions for downregulation of HMGB1 by siRNA delivery mediated by polyaminoacidic polymers in airway epithelial cells in the absence of cytotoxicity. Functional and in-vivo studies are warranted. In the second part of this thesis, having demonstrated that the PHEA- and CSNAC- based nanoparticles are able to downregulate HMGB1 in airway epithelial cells, we sought to determine whether inflammatory conditions could regulate HMGB1 expression. H441 cells incubated with lipopolysaccharide (LPS) from Pseudomonas aeruginosa presented higher levels of HMGB1 as compared to untreated controls both as mRNA and protein as assessed by real time PCR and western blotting, respectively. This increase was observed both at 3 and 48 hours post treatment. LPS was also able to induce an increase in the metabolic state of cells (shown up by the MTT assay) at the same time points, but not in the proliferation (cell counts), while cell cycle analysis (by cytofluorimetry) showed a decrease of Go/G1 phase and an increase in G2/M at 6 and 24 h post-treatment. These data suggest that HMGB1 is involved in the activation of metabolic state of cells upon induction of an inflammatory condition, and it should further studied by siRNA downregulation.