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Int J Clin Exp Pathol 2012;5(9):948-955

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

Feixiang Wu, Xuerong Miao, Jiaying Chen, Yuming Sun, Zhiqiang Liu, Yong Tao, Weifeng Yu

Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical University, No. 225 Changhai Road, Shanghai
200433, China; Department of Anesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, No. 536
Changle Road, Shanghai 200126, China

Received August 15, 2012; Accepted September 27, 2012; Epub October 20, 2012; Published October 30, 2012

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/30μl) 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). TUNELpositive 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. (IJCEP1208013).

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

Address all correspondence to:
Dr. Weifeng Yu
Department of Anesthesiology
Eastern Hepatobiliary Hospital
Changhai Road 225, Yangpu District
Shanghai 200433, China.
Tel/Fax: +86 2125070783
E-mail: ywf808@smmu.edu.cn