Background: The receptor for advanced glycation end-products (RAGE) is implicated in neuronal differentiation during embryogenesis and in regulation of peripheral nerve regeneration. However, the role of RAGE ligands and the signaling pathways utilized by activated RAGE in mediating axon regeneration in adult neurons remain unknown. We tested the hypothesis that RAGE signaling modulated neurotrophin-induced neurite outgrowth in cultured adult sensory neurons.
Results: Dorsal root ganglia (DRG) neurons from adult rats in vitro were exposed to specific RAGE ligands, signal transduction inhibitors and function blocking anti-RAGE IgG to assess their impact on neurite outgrowth. RAGE ligands including human glycated albumin (HGA), S100 calcium binding protein (S100B) and high mobility group 1 protein (HMGB1; alternatively termed amphoterin) in the presence of neurotrophins elevated neurite outgrowth 2-fold (p<0.05). shRNA to RAGE or anti-RAGE IgG blockade of RAGE inhibited neurite outgrowth by 40-90% (p<0.05). Western blotting and gene reporter analysis showed RAGE ligands activated NF-κB, JAK-STAT and ERK pathways. RAGE ligand induction of neurite outgrowth was blocked by inhibition of NF-κB, JAK-STAT or ERK pathways revealing the necessity for combined activation for optimal growth. RAGE ligands rapidly elevated NF-κB p65 expression in the cytoplasm while triggering translocation of NF-κB p50 to the nucleus. shRNA blockade of p50 demonstrated that translocation of p50 to the nucleus was implicated in driving axonal outgrowth.
Conclusions: RAGE signaling is a complex mediator of neurotrophin-dependent neurite outgrowth, operating through divergent but partly inter-dependent pathways.
Keywords: Axon regeneration; Human glycated albumin; JAK/STAT; Lentiviral shRNA; NF-kappaB; Neurotrophic factor; Signal transduction.