Cui Wei, Li Yize, Wang Zhen, Song Chengcheng, Yu Yonghao, Wang Guolin, Li Jing, Wang Chunyan, Zhang Linlin
Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin Research Institute of Anesthesiology, Tianjin, China.
Pain. 2021 Jan;162(1):124-134. doi: 10.1097/j.pain.0000000000002021.
Chronic postoperative pain hinders functional recovery after bone fracture and orthopedic surgery. Recently reported evidence indicates that caspase-6 is important in excitatory synaptic plasticity and pathological pain. Meanwhile, netrin-1 controls postsynaptic recruitment of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and synaptogenesis. The present work aimed to examine whether caspase-6 and netrin-1 contribute to fracture-induced postoperative allodynia. A mouse model of tibial fracture by intramedullary pinning was generated for inducing postoperative pain. Then, paw withdrawal threshold, spinal caspase-6 activity, netrin-1 secretion, AMPAR trafficking, and spine morphology were examined. Caspase-6 inhibition and netrin-1 knockdown by shRNA were performed to elucidate the pathogenetic mechanism of allodynia and its prevention. Whole-cell patch-clamp recording was performed to assess caspase-6's function in spinal AMPAR-induced current. Tibial fractures after orthopedic operation initiated persistent postsurgical mechanical and cold allodynia, accompanied by increased spinal active caspase-6, netrin-1 release, GluA1-containing AMPAR trafficking, spine density, and AMPAR-induced current in dorsal horn neurons. Caspase-6 inhibition reduced fracture-associated allodynia, netrin-1 secretion, and GluA1 trafficking. Netrin-1 deficiency impaired fracture-caused allodynia, postsynaptic GluA1 recruitment, and spine plasticity. The specific GluA2-lacking AMPAR antagonist NASPM also dose dependently prevented postoperative pain. The reduction of fracture-mediated postoperative excitatory synaptic AMPAR current in the dorsal horn by caspase-6 inhibition was compromised by recombinant netrin-1. Exogenous caspase-6 induced pain hypersensitivity, reversing by netrin-1 knockdown or coapplication of NASPM. Thus, spinal caspase-6 modulation of GluA1-containing AMPAR activation and spine morphology through netrin-1 secretion is important in the development of fracture-related postsurgical pain in the mouse.
慢性术后疼痛会阻碍骨折和骨科手术后的功能恢复。最近报道的证据表明，半胱天冬酶-6在兴奋性突触可塑性和病理性疼痛中起重要作用。同时，网蛋白-1控制α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体（AMPAR）的突触后募集和突触形成。本研究旨在探讨半胱天冬酶-6和网蛋白-1是否与骨折诱导的术后痛觉过敏有关。通过髓内穿针建立小鼠胫骨骨折模型以诱导术后疼痛。然后，检测爪部退缩阈值、脊髓半胱天冬酶-6活性、网蛋白-1分泌、AMPAR转运和脊柱形态。通过shRNA抑制半胱天冬酶-6和敲低网蛋白-1，以阐明痛觉过敏的发病机制及其预防方法。采用全细胞膜片钳记录来评估半胱天冬酶-6在脊髓AMPAR诱导电流中的功能。骨科手术后的胫骨骨折引发了持续的术后机械性和冷痛觉过敏，同时伴有脊髓活性半胱天冬酶-6增加、网蛋白-1释放、含GluA1的AMPAR转运、脊柱密度增加以及背角神经元中AMPAR诱导电流增加。抑制半胱天冬酶-6可减轻与骨折相关的痛觉过敏、网蛋白-1分泌和GluA1转运。网蛋白-1缺乏会损害骨折引起的痛觉过敏、突触后GluA1募集和脊柱可塑性。特异性缺乏GluA2的AMPAR拮抗剂NASPM也能剂量依赖性地预防术后疼痛。重组网蛋白-1可抵消抑制半胱天冬酶-6对背角骨折介导的术后兴奋性突触AMPAR电流的降低作用。外源性半胱天冬酶-6可诱导疼痛超敏反应，而敲低网蛋白-1或联合应用NASPM可逆转这种反应。因此，脊髓半胱天冬酶-6通过网蛋白-1分泌调节含GluA1的AMPAR激活和脊柱形态，在小鼠骨折相关术后疼痛的发生发展中起重要作用。
