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  4. P75 and phosphorylated c-Jun are differentially regulated in spinal motoneurons following axotomy in rats

P75 and phosphorylated c-Jun are differentially regulated in spinal motoneurons following axotomy in rats

Neural Regeneration Research, 2012 · DOI: 10.3969/j.issn.1673-5374.2012.26.001 · Published: September 1, 2012

Spinal Cord InjuryRegenerative MedicineNeurology

Simple Explanation

This study investigates the roles of p75 and phosphorylated c-Jun (p-c-Jun) in spinal motoneurons after axonal injury (axotomy) in rats of different ages: postnatal days 1, 7, 14, and adults. The researchers compared the presence of these proteins to understand their involvement in motoneuron response to injury. The study found that p-c-Jun was highly present in injured motoneurons of very young rats (PN1 and PN7), but this presence decreased sharply in PN14 rats. Interestingly, the reduced p-c-Jun expression coincided with the re-expression of p75 in the injured cells. In adult rats, the researchers observed intensive p75 but no p-c-Jun in the injured motoneurons. This suggests that p75 and p-c-Jun might have different roles or are regulated differently in immature versus mature spinal motoneurons when responding to axonal injury.

Study Duration
July 2010 to December 2011
Participants
Sprague-Dawley postnatal day (PN) 1, 7, 14 and adult rats
Evidence Level
Not specified

Key Findings

  • 1
    Intensive phosphorylated c-Jun (p-c-Jun) was induced in axotomized motoneurons in postnatal day (PN)1 and PN7 but not in adults.
  • 2
    Intensive p75 was induced in axotomized motoneurons in adult but not in PN1 and PN7.
  • 3
    The non-co-occurrence of p75 and p-c-Jun in injured motoneurons suggest that p75 may not activate JNK pathway.

Research Summary

The study examined the differential regulation of p75 and phosphorylated c-Jun (p-c-Jun) in spinal motoneurons of rats at different developmental stages (PN1, PN7, PN14, and adult) following axotomy. Results showed that p-c-Jun was highly induced in axotomized motoneurons in PN1 and PN7 rats, but its expression sharply reduced in PN14 rats, coinciding with the re-expression of p75. In adult rats, intensive p75 but no p-c-Jun was detected in axotomized motoneurons. The non-co-occurrence of p75 and p-c-Jun suggests that p75 may not activate the JNK pathway in injured motoneurons, indicating that p75 may not be involved in cell death in axotomized motoneurons.

Practical Implications

Understanding Motoneuron Response

The study provides insights into the age-dependent responses of spinal motoneurons to axonal injury, highlighting the differential roles of p75 and p-c-Jun.

Re-evaluating p75's Role

The findings suggest that p75 may not be involved in motoneuron death following axonal injury, contrary to some previous studies, which could lead to a re-evaluation of therapeutic strategies targeting p75.

Developmental Stage Considerations

The results emphasize the importance of considering the developmental stage when studying neuronal responses to injury and designing interventions.

Study Limitations

  • 1
    The study was conducted only on rats, and results may not be directly applicable to humans.
  • 2
    The study focused on specific time points after axotomy, and the long-term effects of p75 and p-c-Jun expression were not investigated.
  • 3
    The specific mechanisms regulating the switch between p-c-Jun and p75 expression were not fully elucidated.

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