Guogang Tian1, Xin Luo2, Chaoliang Tang2, Xiang Cheng3, Sookja Kim Chung4, Zhengyuan Xia5, Chi Wai Cheung6, Qulian Guo7. 1. Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha, China; Department of Anesthesiology and Pain Medicine, Affiliated Haikou Hospital of Xiangya Medical School, Central South University, Haikou, China. 2. Department of Anaesthesiology, The University of Hong Kong, HKSAR, China; Laboratory and Clinical Research Institute for Pain, The University of Hong Kong, HKSAR, China. 3. Department of Anesthesiology and Pain Medicine, Affiliated Haikou Hospital of Xiangya Medical School, Central South University, Haikou, China. 4. Department of Anatomy, The University of Hong Kong, HKSAR, China; Research Center of Heart, Brain, Hormone and Healthy Aging, The University of Hong Kong, HKSAR, China; Laboratory and Clinical Research Institute for Pain, The University of Hong Kong, HKSAR, China. 5. Department of Anaesthesiology, The University of Hong Kong, HKSAR, China. 6. Department of Anaesthesiology, The University of Hong Kong, HKSAR, China; Research Center of Heart, Brain, Hormone and Healthy Aging, The University of Hong Kong, HKSAR, China; Laboratory and Clinical Research Institute for Pain, The University of Hong Kong, HKSAR, China. Electronic address: cheucw@hku.hk. 7. Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha, China. Electronic address: qulianguo2011@163.com.
Abstract
BACKGROUND: The activation of spinal glial cells (astrocyte and microglia) is reported in patient with complex regional pain syndrome (CRPS). However, the roles of spinal glial activities in the pathophysiology of CRPS are unclear. Here, we explored the roles of spinal astrocyte and microglia and the molecular mechanisms underlying CRPS using a mouse model of chronic post-ischemia pain (CPIP). RESULTS: CPIP injury increased the level of glial fibrillary acidic protein (GFAP, reactive astrocyte biomarker), but had no significant impact on ionized calcium binding adaptor molecule 1 (IBA1, reactive microglia biomarker), in the ipsilateral dorsal horn on post-injury day (PID) 3 when the pain threshold started to reduce significantly. Astrocytic inhibition with fluorocitrate but not microglial inhibition with minocycline attenuated the development of allodynia in CPIP-injured mice, which was concomitant with increased spinal levels of phosphorylated c-jun N-terminal kinase 1/2 (pJNK1/2) on PID 3. Furthermore, the intrathecal administration of SP600125 (JNK inhibitor) prevented the development of allodynia in CPIP-injured mice. Double immunofluorescence staining showed that pJNK1/2 was mainly co-localized with GFAP. Subsequently, increased levels of pJNK1/2 were reversed by intrathecal fluorocitrate. Furthermore, the level of spinal matrix metalloproteinase-2 (MMP2) was increased and mainly expressed in NeuN (neuron biomarker) on PID 3 in the CPIP-injured mice, while intrathecal APR 100 (MMP2 inhibitor) delayed the development of allodynia and decreased spinal levels of GFAP and pJNK1/2 on PID 3. CONCLUSION: This study shows that activation of astrocyte MMP2/JNK1/2 signaling pathway contributes to the pathogenesis of pain hypersensitivity in the CPIP model.
BACKGROUND: The activation of spinal glial cells (astrocyte and microglia) is reported in patient with complex regional pain syndrome (CRPS). However, the roles of spinal glial activities in the pathophysiology of CRPS are unclear. Here, we explored the roles of spinal astrocyte and microglia and the molecular mechanisms underlying CRPS using a mouse model of chronic post-ischemia pain (CPIP). RESULTS: CPIP injury increased the level of glial fibrillary acidic protein (GFAP, reactive astrocyte biomarker), but had no significant impact on ionizedcalcium binding adaptor molecule 1 (IBA1, reactive microglia biomarker), in the ipsilateral dorsal horn on post-injury day (PID) 3 when the pain threshold started to reduce significantly. Astrocytic inhibition with fluorocitrate but not microglial inhibition with minocycline attenuated the development of allodynia in CPIP-injured mice, which was concomitant with increased spinal levels of phosphorylated c-jun N-terminal kinase 1/2 (pJNK1/2) on PID 3. Furthermore, the intrathecal administration of SP600125 (JNK inhibitor) prevented the development of allodynia in CPIP-injured mice. Double immunofluorescence staining showed that pJNK1/2 was mainly co-localized with GFAP. Subsequently, increased levels of pJNK1/2 were reversed by intrathecal fluorocitrate. Furthermore, the level of spinal matrix metalloproteinase-2 (MMP2) was increased and mainly expressed in NeuN (neuron biomarker) on PID 3 in the CPIP-injured mice, while intrathecal APR 100 (MMP2 inhibitor) delayed the development of allodynia and decreased spinal levels of GFAP and pJNK1/2 on PID 3. CONCLUSION: This study shows that activation of astrocyte MMP2/JNK1/2 signaling pathway contributes to the pathogenesis of painhypersensitivity in the CPIP model.