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A533
October 13, 2012
1:00:00 PM - 4:00:00 PM
Room Hall C-Area J
Paradoxical Expression Profiles of Sema3A and CDK5 in Spinal Dorsal Horn and Dorsal Root Ganglion of Neuropathic Pain Model Rat
Kensuke Saeki, B.S., Yoshinori Kamiya, M.D.,Ph.D., Yusuke Nakahashi, M.D., Naoya Yamashita, Ph.D., Kengo Funakoshi, M.D.,Ph.D.
Yokohama City University School of Medicine, Yokohama, Japan
Introduction: Previously we showed that intrathecally administered recombinant Sema3A protein, one of the repulsive axonal guidance factors, could suppress mechanical and heat hypersensitivity in neuropathic pain model rat without obvious sprouting in dorsal spinal horn. However, change of expression level of Sema3A and its downstream cascade proteins in neuropathic rats remains to be elucidated. In this study, we analyzed the temporary changes of expression level of Sema3A protein and CDK5, key molecule of the downstream of Sema3A signaling, in chronic constriction injury (CCI) model rat.

Methods: Following institutional ethical committee approval, male SD rats (170-190g) divided 3 groups (CCI group, sham op group and naïve rats). CCI group received chronic constriction injury of left sciatic nerve and sham op group received left sciatic nerve isolation only. We checked mechanical hypersensitivity before operation and 2,5,7,9,12,14 days after the operation. Spinal dorsal horn (SDH) and bilateral L4-6 DRG was harvested at 3 days and 14 days after CCI or sham operation (n=8 each) and naïve rat (n=4), then processed for Western blotting analyses for Sema3A and CDK5. Quantification of the Western blotting was normalized by b-actin and inter-membrane control sample. Data were analyzed using 2-way ANOVA followed by Turkey-Kramer test, and P < 0.05 was considered significant.

Results: After CCI operation, mechanical hypersensitivity was observed at 2POD and plateaued at 7POD. Sham operation did not induced mechanical hypersensitivity. Interestingly, there was no difference in Sema3A and CDK5 expression level between injured side and uninjured side. Sema3A Expression was higher about 4.7 folds in SDH than in DRG in naïve rats and was significantly increased in the DRG almost identical level of that in naïve rats SDH in accordance with the time course after operation. On the other hand, changes of Sema3A in the SDH were smaller than that in the DRG. CDK5 expression pattern in naïve rats is almost the same as that of Sema3A (SDH: 3.3 folds compared to DRG). Interestingly, CDK5 expression in SDH was decreased in CCI group but not sham op group, even though that in DRG was completely identical to that of Sema3A. Protein expression changes of Sema3A and CDK5 were observed in both CCI group and sham op group, but the magnitude of the change was greater in CCI group (Figure 1).

Conclusions: Our data showed that Sema3A protein and CDK5, a downstream protein of Sema3A signaling, were increased both neuronal injury and skin damage (sham op) in DRG, and CDK5 in SDH was significantly decreased by neuronal injury. Previous reports suggested that exogenous applied Sema3A inhibit neuropathic pain development and inflammatory pain was involved in CDK5 activation. Our result suggested that CDK5 signaling in neuropathic pain would be different form that in inflammatory pain, and anti-nociceptive effect of intrathecal Sema3A protein administration would be indirect.
Figure 1

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