Enhanced intracellular uptake and inhibition of NF-κB activation by decoy oligonucleotide released from PLGA microspheres

Background Nuclear factor-kappa B (NF-kappa B) transcription factor regulates the expression of genes involved in immune response and inflammation. NF-kappa B activity can be efficiently inhibited by double-stranded oligodeoxynucleotides (ODNs). In the present study, we investigated the potential of poly(DL-lactic-co-glycolic acid) (PLGA) microspheres as delivery system for an ODN against NF-kappa B in RAW 264.7 macrophages stimulated with lipopolysaccharide (LPS). Methods Microspheres encapsulating ODN were prepared by the multiple emulsion/solvent evaporation technique and characterised in terms of size, morphology, encapsulation efficiency and in vitro release profile. In vitro uptake after 4 h and activity of ODN released from microspheres were evaluated in RAW 264.7 macrophages stimulated with LPS for 24, 48 and 72 h. Results We prepared microspheres with a high encapsulation efficiency showing a very slow and almost constant in vitro release of ODN for up to 1 month. ODN slowly released from microspheres translocated. better into LPS-stimulated cells as compared with naked ODN. Incubation of cells with ODN-encapsulating microspheres resulted in a decrease of tumor necrosis factor-alpha (TNF-alpha) and nitrite production, inducible nitric oxide synthase (iNOS) protein expression, as well as NF-kappa B/DNA-binding activity. Similar results were obtained with naked ODN only at about 80 times higher concentrations. Conclusions Our results suggest that PLGA microspheres could be a useful tool to improve pharmacokinetics of a ODN decoy to NF-kappa B and may represent a promising strategy to effectively inhibit the transcriptional activity of NF-kappa B in inflammatory process. Copyright (c) 2005 John Wiley & Sons, Ltd.