J. Biomater. Sci. Polymer Edn, Vol. 19, No. 10, pp. 1333–1346 (2008)  Koninklijke Brill NV, Leiden, 2008. Also available online - www.brill.nl/jbs Mechanistic analysis of macrophage response to IRAK-1 gene knockdown by a smart polymer-antisense oligonucleotide therapeutic RACHEL E. JOHNS 1 , MOHAMED E. H. EL-SAYED 1 , VOLGA BULMUS 1 , JOSEPH CUSCHIERI 2 , RONALD MAIER 2 , ALLAN S. HOFFMAN 1 and PATRICK S. STAYTON 1,∗ 1 University of Washington, Department of Bioengineering, Box 355061, Seattle, WA 98195, USA 2 University of Washington, Department of Surgery, Seattle, WA 98195, USA Received 16 May 2007; accepted 14 February 2008 Abstract—An excessive inflammatory response is a clinical problem following major infections and severe injury that may lead to Sepsis Syndrome and Multiple Organ Failure (MOF), including the Acute Respiratory Distress Syndrome (ARDS). Management of excessive inflammation may be possible through control of key inflammatory pathways such as those mediated by the important interleukin-1 receptor associated kinase-1 (IRAK-1). In the current study, we report the impact on gene expression induced by lipopolysaccharide (LPS) stimulation of THP-1 cells treated with an antisense oligonucleotide (ASODN) against the IRAK-1 gene using cDNA microarrays and quantitative RT-PCR. The therapeutic ASODN was delivered using a pH-sensitive, membrane- interactive polymer that destabilizes the endosomal membrane to enhance access cytoplasmic delivery in targeted cells. Following LPS stimulation, the anti-inflammatory activity of ASODN against the IRAK-1 gene expression is evidenced by the lower expression of inflammatory chemokines, cytokines and acute-phase proteins compared to control cells. These results provide a larger mechanistic picture of IRAK-1 knockdown by this polymer therapeutic in macrophage-like cells. Key words: Expression profiling; smart polymers; intracellular drug delivery; macrophage. INTRODUCTION Excessive activation of the inflammatory cascade following severe infection or injury can lead to the development of sepsis syndrome and/or Multiple Organ Failure (MOF), including Acute Respiratory Distress Syndrome (ARDS) [1, 2]. Major inflammatory cytokines, such as interleukin-1β (IL-1β), tumor necrosis ∗ To whom correspondence should be addressed. Tel.: (1-206) 685-8148; Fax: (1-206) 685-8526; e-mail: stayton@u.washington.edu