Isotalatizidine, a C19-diterpenoid alkaloid, attenuates chronic neuropathic pain through stimulating ERK/CREB signaling pathway-mediated microglial dynorphin A expression

Shuai Shao,Chengjuan Chen,Qinglan Guo,Yu Zhou,Jiangong Shi,Gaona Shi,Tiantai Zhang,Junmin Fu,Huan Xia,Wenjie Wang,Min Hu

doi:10.1186/s12974-019-1696-9

Abstract

BackgroundIsotalatizidine is a representative C19-diterpenoid alkaloid extracted from the lateral roots of Aconitum carmichaelii, which has been widely used to treat various diseases on account of its analgesic, anti-inflammatory, anti-rheumatic, and immunosuppressive properties. The aim of this study was to evaluate the analgesic effect of isotalatizidine and its underlying mechanisms against neuropathic pain.MethodsA chronic constrictive injury (CCI)-induced model of neuropathic pain was established in mice, and the limb withdrawal was evaluated by the Von Frey filament test following isotalatizidine or placebo administration. The signaling pathways in primary or immortalized microglia cells treated with isotalatizidine were analyzed by Western blotting and immunofluorescence.ResultsIntrathecal injection of isotalatizidine attenuated the CCI-induced mechanical allodynia in a dose-dependent manner. At the molecular level, isotalatizidine selectively increased the phosphorylation of p38 and ERK1/2, in addition to activating the transcription factor CREB and increasing dynorphin A production in cultured primary microglia. However, the downstream effects of isotalatizidine were abrogated by the selective ERK1/2 inhibitor U0126-EtOH or CREB inhibitor of KG-501, but not by the p38 inhibitor SB203580. The results also were confirmed in in vivo experiments.ConclusionTaken together, isotalatizidine specifically activates the ERK1/2 pathway and subsequently CREB, which triggers dynorphin A release in the microglia, eventually leading to its anti-nociceptive action.

Highlights

Isotalatizidine is a representative C19-diterpenoid alkaloid extracted from the lateral roots of Aconitum carmichaelii, which has been widely used to treat various diseases on account of its analgesic, anti-inflammatory, anti-rheumatic, and immunosuppressive properties
Isotalatizidine treatment alleviated constrictive injury (CCI)-induced neuropathic pain We determined its effects on mechanical allodynia in a CCI-induced neuropathic pain model by evaluating limb withdrawal
Pre-treatment of the microglial cells with the p38 inhibitor SB203580 (50 μM) and ERK1/ 2 inhibitor U0126-EtOH (50 μM) significantly abrogated the effects of isotalatizidine (Fig. 3f–i). These results strongly suggested that the analgesic effect of isotalatizidine is likely related to the activation of p38 and the ERK1/2 Mitogen-activated protein kinase (MAPK) signaling pathways in the microglia

Summary

Introduction

Isotalatizidine is a representative C19-diterpenoid alkaloid extracted from the lateral roots of Aconitum carmichaelii, which has been widely used to treat various diseases on account of its analgesic, anti-inflammatory, anti-rheumatic, and immunosuppressive properties. Neuropathic pain is caused by an injury or disease in the somatosensory nervous system, including the central nerves, spinal cord, posterior root of the spinal cord, and peripheral nerves. It is highly prevalent and has an immense impact on the quality of life of patients [1]. The mitogen-activated protein kinase (MAPKs) family of proteins, including extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK), plays a crucial role in the signaling pathways mediating microglial activation and nociceptive responses, which eventually lead to neuropathic pain [20, 21]. Dynorphin A is elevated during neuropathic pain, it is not clear whether it is pro- or anti-nociceptive

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