Characterization of cationic glucocorticoids as gene delivery, antimicrobial, and anti-inflammatory agents.

Cationic lipids facilitate gene delivery and some cationic sterol-based compounds have antimicrobial activity due to their amphiphilic character. These dual functions are relevant in local infection during intrapulmonary gene transfer for cystic fibrosis. The transfection activities of two cationic lipids, dexamethasone spermine (DS) and disubstituted spermine (D2S), displayed up to a 7-fold improvement in transgene expression for mixtures of DS/D2S. D2S demonstrated strong bactericidal activity against E. coli MG 1655, B. subtilis, and P. aeruginosa PAO1 with complete killing demonstrated at 5 muM and a two order of magnitude higher tolerance before eukaryotic membrane disruption. D2S exhibited LPS scavenging activity, resulting in significant inhibition of LPS-mediated activation of human neutrophils with 85% lower IL-8 released at 12 hrs, as well as in vivo antibacterial activity against a mucoid strain of P. aeruginosa (Xen5). We have demonstrated that DS and D2S can interact with viral vectors altering the surface properties of the particles by decreasing the net surface charge density. In vitro transduction showed a 6-fold and 7-fold increase in transgene expression with AAV2/6.2 and AAV2/9, respectively, when these viral vectors were pre-formulated with cationic lipids. Transduction of human airway epithelium with AAV2/6.2-lipid formulations showed greater than 2-fold increase in GFP positive cells and increases in total fluorescence compared to control. Intranasal administration of 1011 genome copies (GC) of AAV with lipid formulations resulted in an average 4-fold increase in transgene expression for both AAV2/6.2 and AAV2/9. Histological examination of lung cross-sections displayed increased transduction of conducting airway for formulations of AAV2/9 with DS compared to AAV2/9 alone. An inflammatory model of arthritis and bone remodeling was used to assess the pharmacological activity since prolonged glucocorticoid treatment can reduce inflammation but also lead to a profound impact on skeletal remodeling. Our results show that both DS and D2S reduce receptor activator of nuclear factor kappa B ligand (RANKL), increase osteoprotegerin (OPG), and reduce inflammatory cytokine transcripts (IL-6) in vitro. Local and systemic in vivo pharmacological activities for both compounds in a collagen-induced arthritis model indicate D2S has comparable systemic anti-inflammatory activity to dexamethasone and possible dissociated glucocorticoid character in the bone microenvironment.