Down-regulation of TNF-α via macrophage-targeted RNAi system for the treatment of acute inflammatory sepsis

Sepsis is a systemic inflammatory response syndrome caused by bacterial infection. The sepsis therapy has involved prescription of adequate antibiotics, requiring several days to determine the proper type without reducing the inflammatory response. Thus, it is necessary to rapidly decrease fundamental inflammation, which can induce serious organ damage. In the inflammatory mechanism, tumor necrosis factor-alpha (TNF-α) produced by macrophages has an important role in infiltration of macrophages into infected sites and as a trigger for secretion of pro-inflammatory cytokines. However, commercialized TNF-α antibody medicines have limits such as fibrosis, cytokine storms, and high production costs. There is a growing need for anti-inflammatory sepsis treatment free from side effects. For this reason, TNF-α converting enzyme (TACE) could be an innovative target to break the positive feedback loop of inflammatory mediators (TNF-α) since it converts the inactive TNF-α membrane bound form to the activated soluble form in macrophages. A non-viral gene delivery system was developed in this study to deliver siRNA into inflammation-mediated macrophages without toxicity. The peptide-based gene carrier created by conjugating positively-charged nine arginine (9R) and the TKPR (Thr-Lys-Pro-Arg) sequence from the Fc region of Immunoglobulin G (IgG) specifically binds to the neuropilin-1 (NRP-1) receptor on the macrophage surface. Our results demonstrated that siTACE/TKPR-9R complexes were internalized in macrophages and successfully down-regulated TACE mRNA level. Finally, RNA interference with cell-targeted peptide carriers indicates a fundamental therapy for acute inflammatory sepsis free of off-target effects.