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

[摘要] 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). 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.

[学科分类] 生理学与病理学

[关键词] Apoptosis;caspase-3;neuropathic pain;GAP-43;RNA interference