Direct activation of Toll-like receptor 2 signaling stimulated by contact with the interfacial structures of chitin nanofibers
Risa Hatase, Qi Li, Mayumi Hatakeyama, Takuya Kitaoka
Abstract
The innate immune system , which eliminates pathogens and abnormal cells, is involved in the pathogenesis of various diseases and infections, where Toll-like receptors (TLRs) play a critical regulatory role. In this study, we investigated the potential of chitin nanofiber (CtNF) to induce an immune response, which is expected to act as an agonist of TLR2 . Crab-derived CtNF, surface-deacetylated CtNF, and surface-carboxylated cellulose NF were employed as TLR2-mediated immune stimulator, signal regulator, and cell adhesion promoter, respectively, to fabricate cell culture scaffolds for HEK293 cells with TLR2 and human monocyte THP-1 cells with or without TLR2 . Surface deacetylation of CtNF drastically diminished the immunological response of HEK293 cells, suggesting that the N -acetyl groups on the solid CtNF surface were pivotal for TLR2-mediated stimulation. A comparison of wild-type and TLR2-KO THP-1 cells on cell culture substrates with N -acetyl groups ranging from 0 to 1.39 mmol g −1 revealed that immune signaling for nuclear factor-κB and interferon regulatory factor pathways was strongly dependent on the surface N -acetyl group content. The immunostimulatory level at the interface of solid CtNF and immune cells could be regulated by simply mixing CtNF and surface-deacetylated CtNF, which is a significant advantage for its potential use as a novel immunostimulant .