Macrophage-targeted anti-inflammatory siRNA delivery system for the treatment of sepsis

Abstract

Treatment for sepsis is done by administering adequate antibiotics to patients to remove bacteria, which requires few days to determine the causative species. Accordingly, it is important to reduce expeditiously inflammation that can make serious tissue failure until antibiotics get rid of bacteria. Tumor necrosis factor-alpha (TNF-α) is a major pro-inflammatory cytokine secreted from macrophages infiltrated into infected tissue, and stimulates other cytokines which induce serious tissue damage by inflammation. However, TNF-α inhibitors such as infliximab and adalimumab have side effects like fibrosis or off-target effects. Moreover, TNF-α converting enzyme (TACE) bound on cell membrane of macrophages make soluble TNF-α by cleavage of membrane-bounded TNF-α. Therefore, Delivering siRNA against TACE into macrophages specifically could breakdown positive feedback loop by TNF-α. In this study, nine arginine (9R) peptides with positive charge were conjugated with TKPR (Thr-Lys-Pro-Arg) sequence specifically binding to neuropilin-1(NRP-1) receptor on macrophage surface to penetrate the negative charged siRNA into the cytosol. I demonstrated that siRNA/TKPR-9R complexes targeted macrophages at in vitro and in vivo level and degraded successfully TACE mRNA. It resulted in downregulation of TNF- α and other pro-inflammatory cytokines. In septic mouse model, intravenously injected siRNA/TKPR-9R complexes increased survival rates 67% with antibiotics. This result correlated with inhibition of pro-inflammatory TNF-α, interleukin-6 (IL-6), interleukin -1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) by knockdown of TACE in inflamed macrophages. Consequently, RNA interference with macrophage targeted peptide indicated the fundamental therapy without any off-target effects for acute systemic inflammatory disease.