The analgesic effect on neuropathic pain of retrogradely transported botulinum neurotoxin A involves Schwann cells and astrocytes

PLoS One. 2012;7(10):e47977. doi: 10.1371/journal.pone.0047977. Epub 2012 Oct 24.


In recent years a growing debate is about whether botulinum neurotoxins are retrogradely transported from the site of injection. Immunodetection of cleaved SNAP-25 (cl-SNAP-25), the protein of the SNARE complex targeted by botulinum neurotoxin serotype A (BoNT/A), could represent an excellent approach to investigate the mechanism of action on the nociceptive pathways at peripheral and/or central level. After peripheral administration of BoNT/A, we analyzed the expression of cl-SNAP-25, from the hindpaw's nerve endings to the spinal cord, together with the behavioral effects on neuropathic pain. We used the chronic constriction injury of the sciatic nerve in CD1 mice as animal model of neuropathic pain. We evaluated immunostaining of cl-SNAP-25 in the peripheral nerve endings, along the sciatic nerve, in dorsal root ganglia and in spinal dorsal horns after intraplantar injection of saline or BoNT/A, alone or colocalized with either glial fibrillar acidic protein, GFAP, or complement receptor 3/cluster of differentiation 11b, CD11b, or neuronal nuclei, NeuN, depending on the area investigated. Immunofluorescence analysis shows the presence of the cl-SNAP-25 in all tissues examined, from the peripheral endings to the spinal cord, suggesting a retrograde transport of BoNT/A. Moreover, we performed in vitro experiments to ascertain if BoNT/A was able to interact with the proliferative state of Schwann cells (SC). We found that BoNT/A modulates the proliferation of SC and inhibits the acetylcholine release from SC, evidencing a new biological effect of the toxin and further supporting the retrograde transport of the toxin along the nerve and its ability to influence regenerative processes. The present results strongly sustain a combinatorial action at peripheral and central neural levels and encourage the use of BoNT/A for the pathological pain conditions difficult to treat in clinical practice and dramatically impairing patients' quality of life.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / metabolism
  • Analgesics / metabolism
  • Analgesics / pharmacology*
  • Animals
  • Astrocytes / metabolism*
  • Biological Transport
  • Botulinum Toxins, Type A / metabolism
  • Botulinum Toxins, Type A / pharmacology*
  • CD11b Antigen / metabolism
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • DNA-Binding Proteins
  • Ganglia, Spinal / metabolism
  • Glial Fibrillary Acidic Protein / metabolism
  • Hindlimb / drug effects
  • Hindlimb / metabolism
  • Hindlimb / physiopathology
  • Immunohistochemistry
  • Male
  • Mice
  • Microscopy, Confocal
  • Nerve Tissue Proteins / metabolism
  • Neuralgia / metabolism
  • Neuralgia / prevention & control*
  • Neuromuscular Agents / metabolism
  • Neuromuscular Agents / pharmacology
  • Nuclear Proteins / metabolism
  • Peripheral Nerves / metabolism
  • Schwann Cells / drug effects
  • Schwann Cells / metabolism*
  • Sciatic Nerve / injuries
  • Sciatic Nerve / metabolism
  • Spinal Cord / drug effects
  • Spinal Cord / metabolism
  • Synaptosomal-Associated Protein 25 / metabolism


  • Analgesics
  • CD11b Antigen
  • DNA-Binding Proteins
  • Glial Fibrillary Acidic Protein
  • Nerve Tissue Proteins
  • NeuN protein, mouse
  • Neuromuscular Agents
  • Nuclear Proteins
  • Snap25 protein, mouse
  • Synaptosomal-Associated Protein 25
  • Botulinum Toxins, Type A
  • Acetylcholine

Grants and funding

This publication was made possible thanks to the cooperation with the Regione Lazio, as part of the “Distretto Tecnologico delle Bioscienze”. SM was supported by a research fellowship from FILAS Regione Lazio Funds for “Sviluppo della Ricerca sul Cervello”. This work was supported by Progetti di Ricerca di Interesse Nazionale 2008. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.