Co-induction of nitric oxide synthase, bcl-2 and growth-associated protein-43 in spinal motoneurons during axon regeneration in the lizard tail.
In lizards, tail loss transects spinal nerves and the cut axons elongate in the regrowing tail, providing a natural paradigm of robust regenerative response of injured spinal motoneurons. We previously ascertained that these events involve nitric oxide synthase induction in the axotomized motoneurons, suggesting a correlation of this enzyme with regeneration-associated gene expression. Here we investigated, in lizards, whether the cell death repressor Bcl-2 protein and growth-associated protein-43 (GAP-43) were also induced in motoneurons that innervate the regenerated tail in the first month post-caudotomy. Single and multiple immunocytochemical techniques, and quantitative image analysis, were performed. Nitric oxide synthase, GAP-43 or Bcl-2 immunoreactivity was very low or absent in spinal motoneurons of control lizards with intact tail. Nitric oxide synthase and GAP-43 were induced during the first month post-caudotomy in more than 75% of motoneurons which innnervate the regenerate. Bcl-2 was induced in approximately 95% of these motoneurons at five and 15days, and in about 35% at one month. The intensity of Bcl-2 and GAP-43 immunostaining peaked at five days, and nitric oxide synthase at 15days; immunoreactivity to these proteins was still significantly high at one month. Immunofluorescence revealed co-localization of nitric oxide synthase, GAP-43 and Bcl-2 in the vast majority of motoneurons at five and 15days post-caudotomy. These findings demonstrate that co-induction of nitric oxide synthase, Bcl-2 and GAP-43 may be part of the molecular repertoire of injured motoneurons committed to survival and axon regeneration, and strongly favor a role of nitric oxide synthase in motoneuron plasticity.
Cristino
L
L
Department of Evolutionary and Comparative Biology, University of Naples "Federico II", Naples, Italy.
Pica
A
A
Della Corte
F
F
Bentivoglio
M
M
D000818:Animals; D019771:Axotomy / Q000009:adverse effects; D002470:Cell Survival / Q000502:physiology; D019922:GAP-43 Protein / Q000378:metabolism*; D008116:Lizards / Q000033:anatomy & histology / Q000378:metabolism*; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism*; D009416:Nerve Regeneration / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D020127:Recovery of Function / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D013127:Spinal Nerves / Q000166:cytology / Q000293:injuries* / Q000378:metabolism; D013623:Tail / Q000293:injuries* / Q000294:innervation; D013997:Time Factors
D019922:GAP-43 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D019001:Nitric Oxide Synthase