title: Calpain-2 contributes to neuropathic pain following motor nerve injury via up-regulating interleukin-6 in DRG neurons.
abstract: Motor nerve injury by L5 ventral root transection (L5-VRT) initiates interleukin-6 (IL-6) up-regulation in primary afferent system contributing to neuropathic pain. However, the early upstream regulatory mechanisms of IL-6 after L5-VRT are still unknown. Here, we monitored both the activity of calpain, a calcium-dependent protease suggested as one of the earliest mediators for cytokine regulation, and the expression of IL-6 in bilateral L4-L6 dorsal root ganglias (DRGs) soon after L5-VRT. We found that the protein level of calpain-2 in DRGs, but not calpain-1 was increased transiently in the first 10 min(-1)h ipsilaterally and 20 min(-1)h contralaterally after L5-VRT, long before mechanical allodynia was initiated (5-15 h ipsilaterally and 15 h(-1)d contralaterally). The early activation of calpain evaluated by the generation of spectrin breakdown products (SBDP) correlated well with IL-6 up-regulation in bilateral DRGs. Double immunofluorescence staining revealed that almost all the calpain-2 positive neurons expressed IL-6, indicating an association between calpain-2 and IL-6. Inhibition of calpain by pre-treatment with MDL28170 (25mg/kg, i.p.) attenuated the rat mechanical allodynia and prevented the early up-regulation of IL-6 following L5-VRT. Addition of exogenous calpain-2 onto the surface of left L5 DRG triggered a temporal allodynia and increased IL-6 in bilateral DRGs simultaneously. Taken together, the early increase of calpain-2 in L5-VRT rats might be responsible for the induction of allodynia via up-regulating IL-6 in DRG neurons.
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China. Electronic address: zangying@mail.sysu.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zang
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Shao-Xia
authors.initials: SX
authors.lastname: Chen
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China; Department of Pathology, The Red Cross Hospital of Yulin, 1 Jinwang Rd., Yulin 537000, China.
authors.forename: Guang-Jie
authors.initials: GJ
authors.lastname: Liao
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: He-Quan
authors.initials: HQ
authors.lastname: Zhu
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Xu-Hong
authors.initials: XH
authors.lastname: Wei
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China; Department of Pathophysiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Na
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Rui-Ping
authors.initials: RP
authors.lastname: Pang
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Xin
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Zhou
authors.affiliation: Pain Research Center and Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou 510080, China.
authors.forename: Xian-Guo
authors.initials: XG
authors.lastname: Liu
mesh_terms: D000818:Animals; D002154:Calpain / Q000378:metabolism* / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000201:enzymology*; D006930:Hyperalgesia / Q000201:enzymology / Q000209:etiology; D015850:Interleukin-6 / Q000378:metabolism*; D008297:Male; D009437:Neuralgia / Q000201:enzymology* / Q000209:etiology; D009474:Neurons / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013049:Spectrin / Q000378:metabolism; D013126:Spinal Nerve Roots / Q000293:injuries; D015854:Up-Regulation
chemical_list: D015850:Interleukin-6; D013049:Spectrin; D002154:Calpain
keywords: Calpain; Dorsal root ganglia; Interleukin-6; L5 ventral root transection; Neuropathic pain