Resiquimod Induces C-C Motif Chemokine Ligand 2 Via Nuclear Factor-Kappa B in SH-SY5Y Human Neuroblastoma Cells

Toll-like receptor (TLR) 7 plays an important role in recognizing virus-derived nucleic acids. TLR7 signaling in astrocytes and microglia is critical for activating immune responses against neurotrophic viruses. Neurons express TLR7, similar to glial cells; however, the role of neuronal TLR7 has not yet been fully elucidated. This study sought to determine whether resiquimod, the TLR7/8 agonist, induces the expression of inflammatory chemokines in SH-SY5Y human neuroblastoma cells. Immunofluorescence microscopy revealed that TLR7 was constitutively expressed in SH-SY5Y cells. Stimulation with resiquimod induced C-C motif chemokine ligand 2 (CCL2) expression, accompanied by the activation of nuclear factor-kappa B (NF-κB) in SH-SY5Y cells. Resiquimod increased mRNA levels of C-X-C motif chemokine ligand 8 (CXCL8) and CXCL10, while the increase was slight at the protein level. Knockdown of NF-κB p65 eliminated resiquimod-induced CCL2 production. This study provides novel evidence that resiquimod has promising therapeutic potential against central nervous system viral infections through its immunostimulatory effects on neurons.