Macrophage specific delivery of TNF-α siRNA complexed with β-1,3-glucan inhibits LPS-induced cytokine production in a murine acute hepatitis model

RNA interference therapy utilizes physiological gene silencing that is originally found as a defense function against foreign RNAs. To silence the target gene, short double stranded RNA has to be delivered to cytosol. However, lack of a suitable delivering carrier is the major obstacle to practical usage. In this study, we present a novel complex consisting of β-1,3-glucan and short interference RNA (siRNA) as a solution for the problem. We used a β-1,3-glucan schizophyllan (SPG) and a siRNA (dA-siTNFα) that is designed to suppress tumor necrosis factor alpha (TNF-α), where the sense strand of siRNA has (dA40) tail to induce complexation with SPG. The dA-siTNFα/SPG complex showed higher affinity to recombinant dectin-1 than SPG itself, where dectin-1 is a β-1,3-glucan receptor expressed on antigen presenting cells and can be a target for specific delivery. The complex suppressed lipopolysaccharide (LPS)-induced TNF-α secretion by peritoneal macrophages in vitro. When the complex was intravenously injected, the oligonucleotide accumulated in liver; especially distributed into Kupffer cells. The complex significantly decreased the serum TNF-α level for the mouse model of LPS-induced acute hepatitis. This new siRNA delivery system may overcome the problem for RNA interference therapy because of its non-toxicity and high target specificity.