title: MicroRNA-146a-5p attenuates neuropathic pain via suppressing TRAF6 signaling in the spinal cord.
abstract: Glia-mediated neuroinflammation plays an important role in the pathogenesis of neuropathic pain. Our recent study demonstrated that TNF receptor associated factor-6 (TRAF6) is expressed in spinal astrocytes and contributes to the maintenance of spinal nerve ligation (SNL)-induced neuropathic pain. MicroRNA (miR)-146a is a key regulator of the innate immune response and was shown to target TRAF6 and reduce inflammation. In this study, we found that in cultured astrocytes, TNF-α, IL-1β, or lipopolysaccharide (LPS) induced rapid TRAF6 upregulation and delayed miR-146a-5p upregulation. In addition, miR-146a-5p mimic blocked LPS-induced TRAF6 upregulation, as well as LPS-induced c-Jun N-terminal kinase (JNK) activation and chemokine CCL2 expression in astrocytes. Notably, LPS incubation with astrocytes enhanced the DNA binding activity of AP-1 to the promoters of mir-146a and ccl2. TRAF6 siRNA or JNK inhibitor SP600125 significantly reduced LPS-induced miR-146a-5p increase in astrocytes. In vivo, intrathecal injection of TNF-α or LPS increased spinal TRAF6 expression. Pretreatment with miR-146a-5p mimic alleviated TNF-α- or LPS-induced mechanical allodynia and reduced TRAF6 expression. Finally, SNL induced miR-146a-5p upregulation in the spinal cord at 10 and 21days. Intrathecal injection of miR-146a-5p mimic attenuated SNL-induced mechanical allodynia and decreased spinal TRAF6 expression. Taken together, the results suggest that (1) miR-146a-5p attenuates neuropathic pain partly through inhibition of TRAF6 and its downstream JNK/CCL2 signaling, (2) miR-146a-5p is increased by the activation of TRAF6/JNK pathway. Hence, miR-146a-5p may be a novel treatment for chronic neuropathic pain.
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Inflammation and Molecular Drug Target, Nantong University, Jiangsu 226019, China; Department of Nutrition, School of Public Health, Nantong University, Jiangsu 226019, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Inflammation and Molecular Drug Target, Nantong University, Jiangsu 226019, China.
authors.forename: De-Li
authors.initials: DL
authors.lastname: Cao
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Inflammation and Molecular Drug Target, Nantong University, Jiangsu 226019, China.
authors.forename: Bao-Chun
authors.initials: BC
authors.lastname: Jiang
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Inflammation and Molecular Drug Target, Nantong University, Jiangsu 226019, China.
authors.forename: Tian
authors.initials: T
authors.lastname: Yang
authors.affiliation: Pain Research Laboratory, Institute of Nautical Medicine, Jiangsu Key Laboratory of Inflammation and Molecular Drug Target, Nantong University, Jiangsu 226019, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China. Electronic address: gaoyongjing@hotmail.com.
authors.forename: Yong-Jing
authors.initials: YJ
authors.lastname: Gao
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism; D008070:Lipopolysaccharides; D020935:MAP Kinase Signaling System; D008297:Male; D008813:Mice, Inbred ICR; D035683:MicroRNAs / Q000378:metabolism*; D009437:Neuralgia / Q000378:metabolism*; D015398:Signal Transduction; D013116:Spinal Cord / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D008070:Lipopolysaccharides; D035683:MicroRNAs; C534190:Mirn146 microRNA, mouse; D048029:TNF Receptor-Associated Factor 6; D014409:Tumor Necrosis Factor-alpha
keywords: Astrocyte; CCL2; JNK; MiR-146a-5p; Neuropathic pain; TRAF6