Regulation of VIP and other neuropeptides by c-Jun in sensory neurons: implications for the neuropeptide response to axotomy.

Peripheral axotomy of adult rat sensory neurons causes induction of the transcription factor c-Jun and increased expression of the neuropeptides vasoactive intestinal polypeptide (VIP), galanin and neuropeptide Y. To determine whether VIP induction is dependent on transcriptional regulation by c-Jun, we exploited the fact that c-Jun and VIP are also induced in cultured sensory neurons. We blocked c-Jun synthesis by microinjecting antisense oligonucleotides and found that VIP expression, determined by quantitative immunofluorescence, was specifically reduced. Blockade of c-June expression also resulted in reduced neuropeptide Y expression but left galanin, substance P and calcitonin gene-related peptide unaffected. Since in vitro electrophoretic mobility shift assays showed that a nominal cyclic AMP responsive element (CRE) associated with the rat VIP gene could bind c-Jun-containing transcription factor complexes, we next investigated whether VIP expression in sensory neurons might depend on transcription factor binding to the CRE. When a DNA plasmid containing multiple copies of the CRE was injected into newly cultured sensory neurons to sequester transcription factors binding the endogenous CRE, there was a selective reduction in VIP expression. VIP induction in sensory neurons therefore probably results from transcriptional activation by c-Jun acting in combination with other factor(s), possibly acting through the CRE. These results show that c-Jun can regulate transcription of other genes affected by axotomy and imply that it could be a key regulator of the neuronal axotomy response.