Inhibition of c-Jun phosphorylation reduces axonal outgrowth of adult rat nodose ganglia and dorsal root ganglia sensory neurons.

The role of c-Jun activation for survival and regeneration of sensory neurons is unclear. Here we report that c-Jun N-terminal kinase (JNK)-mediated c-Jun activation is important for axonal outgrowth of sensory neurons in rat nodose and dorsal root ganglia (DRG). Peripheral severance of the vagus or the sciatic nerve resulted in a massive and rapid, but transient increase of the activated JNK (p-JNK) in neuronal nuclei, followed by c-Jun phosphorylation and activating transcription factor-3 (ATF3) induction. JNK inhibition by the selective JNK inhibitors SP600125 and (D)-JNKI1 did not affect neuronal survival in explanted or dissociated ganglia, but dramatically reduced axonal outgrowth, c-Jun activation, and ATF3 induction. Using retrograde labeling, we demonstrated that activated c-Jun (p-c-Jun) and ATF3 were associated with regenerative neurons. Taken together, our results suggest that JNK-mediated c-Jun activation is one of the first cell body reactions in response to nerve injury and that this activation and subsequent ATF3 induction are associated with axonal outgrowth.