The effect of unilateral transection of the sciatic nerve on expression of immunoreactive galanin (GAL), galanin-message-associated peptide (GMAP) and neuropeptide tyrosine (NPY) in dorsal root ganglia (DRGs) was studied in wild-type mice and in leukemia inhibitory factor (LIF)-deficient mice. In normal and contralateral DRGs small numbers of weakly fluorescent GAL- and GMAP-positive neuronal cell bodies and numerous positive fibers were observed. No NPY-positive cell bodies but a few fibers surrounding blood vessels were seen. In LIF deficient mice hardly any GAL- or GMAP-positive neurons or fibers were seen, nor was NPY-like immunoreactivity present in cell bodies. After axotomy there was a dramatic upregulation of all three peptides in wild-type DRG neurons, whereby 50-60% of the neuron profiles, encompassing both small and large profiles, were GAL- and GMAP-immunoreactive (IR). About one third of all neuron profiles, mainly large ones, were NPY-positive. In LIF-deficient mice this upregulation was much less pronounced. Thus GAL- and GMAP-IR neuron profiles were reduced by 65-70% compared with the wild-type mice. The number of NPY-positive neuron profiles was reduced to half but this difference was not significant. There was also an ipsilateral decrease in fluorescence intensity for all three peptide immunoreactivities in the LIF-deficient mice as compared with wild-type mice after axotomy. There was no apparent difference in size between, respectively, GAL- and GMAP-positive profiles when comparing LIF-deficient and wild-type mice before or after axotomy. There were, however, no small NPY-IR profiles in the LIF-deficient group. The present results suggests that LIF is important for the dramatic upregulation of GAL and GMAP seen after axotomy. It may also be important for the normal expression of galanin in mouse DRGs, since wild-type mice seemed to have somewhat more positive cell bodies and more fluorescent fibers. LIF seems to be less important for the control of NPY synthesis, but may be involved in NPY regulation in small-sized neurons.

Glucocorticoids are known regulators of the cell cycle, normally exerting an anti-proliferative effect. We have previously shown that glucocorticoids stimulate expression of p57 Kip2 , a member of the Cip/Kip family of cyclin-dependent kinase inhibitors which, in some cell types, may account for the anti-proliferative responses seen after glucocorticoid treatment. The induction of p57Kip2 involves primary transcriptional effects where no de novo protein synthesis is necessary, suggesting a direct interaction of the glucocorticoid receptor with the p57 Kip2 gene. In this study we have identified a functional glucocorticoid response element (GRE), located 5 kilo bases (kb) upstream of the transcription start site in the human p57Kip2 promoter. This GRE was functional also when isolated, suggesting a direct transcriptional effect of the glucocorticoid receptor. Furthermore, mutation of this GRE abolished glucocorticoid induction of the reporter gene, whereas mutation of a nearby Sp1 site did not. Using electrophoretic mobility shift assays, we have shown that the -5 kb p57Kip2 promoter GRE was able to compete with a well-known GRE for glucocorticoid receptor binding. Sequence comparisons with the mouse genome showed that this GRE is highly conserved, further strengthening the biological importance of this site. All these data emphasize the involvement of this GRE in the glucocorticoid-mediated induction of p57 Kip2 expression.

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Nerve growth factor (NGF) is known to negatively regulate the transcription of the rat galanin gene both in vivo and in vitro in dorsal root ganglion neurons, yet it is unclear how this regulation actually occurs. We propose here several possible pathways whereby NGF could interact to exert negative control on galanin regulation. These include: (1) repression of AP1-mediated transcription, (2) repression of nuclear binding protein-mediated transcription, and (3) repression of cytokine-mediated transcription. Although not enough data are available for speculation on which, if any, of these pathways is most relevant for NGF repression of galanin transcription, the mechanisms we describe can provide putative models for regulatory pathways. From here we can carry out further experiments that may help to elucidate the possible mechanisms of NGF repression in vivo.