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

Background Nuclear factor‐κB (NF‐κB) transcription factor regulates the expression of genes involved in immune response and inflammation. NF‐κB 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‐κB 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‐α) and nitrite production, inducible nitric oxide synthase (iNOS) protein expression, as well as NF‐κB/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‐κB and may represent a promising strategy to effectively inhibit the transcriptional activity of NF‐κB in inflammatory process. Copyright © 2005 John Wiley & Sons, Ltd.