Down-regulation of GAP-43 by inhibition of caspases-3 in a rat model of neuropathic pain

Int J Clin Exp Pathol. 2012;5(9):948-55. Epub 2012 Oct 20.

Abstract

Background: Neuropathic pain remains a prevalent and persistent clinical problem due to incomplete understanding of its pathogenesis.

Objective: The present study aimed to investigate the role of caspase-3 in the neuropathic pain in rats with chronic constriction injury (CCI).

Methods: SD rats were randomly assigned four groups (n=18 per group): sham group, normal saline group (NS group), Z-DEVD-FMK group (DEVD group) and RNA interference group (siRNA group). Z-DEVD-FMK (1 U/30 μl), siRNA targeting caspase-3 (10 μg/30 μl) and NS of equal volume were intrathecally administered once daily for 5 days starting 1 day before surgery in the DEVD, siRNA and NS group, respectively. Thermal hyperalgesia was assessed at one day before and 1, 2, 4, 5, 6, 7 and 10 days after surgery. The mRNA and protein expressions of caspase-3 were measured by real time PCR and immunofluorescence assay. Apoptosis was detected by TUNEL staining. GAP-43 expression was measured by immunofluorescence and western blot assays.

Results: The right paw withdrawal latency (PWL) was decreased after CCI (P<0.05). TUNEL-positive neurons and the mRNA and protein expressions of caspase-3 in the spinal cord were increased significantly. After Z-DEVD-FMK or siRNA treatment, TUNEL-positive neurons were decreased, PWLs increased (P<0.05) and the mRNA and protein expressions of caspase-3 decreased. The expression of GAP-43, a sprouting related protein, was decreased in the DEVD and siRNA group as compared to NS group (P<0.05). Up-regulation of GAP-43 following CCI was decreased following caspase-3 inhibition. Following sciatic nerve ligation, the gene expression, translation and transcription are significantly changed in the neurons which finally results in neuron apoptosis. The neuron apoptosis induce the up-regulation of GAP-43 expression leading to hyperalgesia.

Conclusion: Caspase-3 mediated neuron apoptosis is probably responsible for the neuropathic pain in CCI rats. Inhibition of caspase-3 may serve as a treatment of neuropathic pain.

Keywords: Apoptosis; GAP-43; RNA interference; caspase-3; neuropathic pain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Caspase 3 / genetics
  • Caspase 3 / metabolism*
  • Caspase Inhibitors / administration & dosage
  • Caspase Inhibitors / pharmacology*
  • Disease Models, Animal
  • Down-Regulation
  • Fluorescent Antibody Technique
  • GAP-43 Protein / metabolism*
  • Hyperalgesia / enzymology
  • Hyperalgesia / genetics
  • Hyperalgesia / physiopathology
  • Hyperalgesia / prevention & control
  • In Situ Nick-End Labeling
  • Injections, Spinal
  • Male
  • Neuralgia / enzymology
  • Neuralgia / genetics
  • Neuralgia / pathology
  • Neuralgia / physiopathology
  • Neuralgia / prevention & control*
  • Oligopeptides / administration & dosage
  • Oligopeptides / pharmacology*
  • Pain Measurement
  • Pain Threshold / drug effects
  • RNA Interference*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / administration & dosage
  • RNA, Small Interfering / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Reaction Time / drug effects
  • Real-Time Polymerase Chain Reaction
  • Spinal Nerves / drug effects*
  • Spinal Nerves / enzymology
  • Spinal Nerves / pathology
  • Spinal Nerves / physiopathology
  • Time Factors

Substances

  • Caspase Inhibitors
  • GAP-43 Protein
  • Oligopeptides
  • RNA, Messenger
  • RNA, Small Interfering
  • benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone
  • Casp3 protein, rat
  • Caspase 3