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SFKs/p38 Pathway is Involved in Radicular Pain by Promoting Spinal Expression of Pro-Inflammatory Cytokines in a Rat Model of Lumbar Disc Herniation

Zhong, Yi PhD∗,†; Huang, Yangliang MD; Hu, Yuming MM∗,†; Xu, Mingxian MB∗,†; Zhu, Lirong MB∗,†; Deng, Zhen MM∗,†

doi: 10.1097/BRS.0000000000003076
BASIC SCIENCE
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Study Design. A controlled, randomized, animal study.

Objective. The aim of this study was to investigate the role of src-family kinases/p38 pathway in a rat model of lumbar disc herniation (LDH).

Summary of Background Data. LDH always generates radicular pain, and the mechanism remains unclear. We have reported that spinal src-family kinases (SFKs) may be involved in the process, but the downstream mechanism needs further investigation.

Methods. LDH was induced by implantation of autologous nucleus pulposus (NP), harvest from the tail, in lumbar 4/5 spinal nerve roots of rat. Von Frey filaments and radiant heat tests were performed to determine mechanical and thermal pain threshold respectively. Basso, Beattie, and Bresnahan (BBB) scale was assessed to test the locomotor function. The protein level of p-SFKs, t-SFKs, p-p38, t-p38 in spinal cord was examined by western blotting analysis. Cellular location of p-p38 was determined by immunochemistry staining. Spinal tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6 levels were detected by enzyme-linked immunosorbent assay (ELISA).

Results. Rats with NP implantation showed persistent ipsilateral mechanical allodynia and thermal hyperalgesia, which manifested as obvious decrease of paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). BBB scale indicated the locomotor function of hindpaws in rats with NP implantation kept intact. Western blotting and immunohistochemistry staining revealed that phosphorylated SFKs (p-SFKs) and phosphorylated p38 MAPK (p-p38) were sequentially upregulated in ipsilateral spinal dorsal horn, but not in contralateral side of rats with NP. Intrathecal delivery of SFKs inhibitor reduced spinal p-p38 expression. Both SFKs and p38 inhibitors alleviated pain behaviors in a dose-responsive manner without disturbing locomotor function and reduced spinal expression of TNF-α, IL-1β, and IL-6 in rats with NP.

Conclusion. Spinal SFKs contribute to radicular pain by activation of p38 MAPK and increasing pro-inflammatory cytokines expression in rats with NP implantation. Targeting SFKs/p38 pathway may be helpful for alleviating radicular pain.

Level of Evidence: N/A

Lumbar disc herniation always generates radicular pain and mechanism is not clear. In this study, we found that spinal src-family kinases contributed to radicular pain by activating of p38 mitogen-activated protein kinase and increasing pro-inflammatory cytokines expression in rats with nucleus pulposus implantation. Targeting src-family kinases/p38 pathway may be helpful for alleviating radicular pain.

Key Laboratory of Neuroscience, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China

Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University; Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou, China

Department of Spine Surgery, First Affiliated Hospital of Sun Yet-Sen University, Guangzhou, China.

Address correspondence and reprint requests to Yi Zhong, PhD, Key Laboratory of Neuroscience, School of Basic Medical Science, Guangzhou Medical University, Xinzao, Pangyu District, Guangzhou 511436, China; E-mail: victoria0720@126.com

Received 31 October, 2018

Revised 27 February, 2019

Accepted 28 March, 2019

Yi Zhong and Yangliang Huang contributed equally to this work.

The manuscript submitted does not contain information about medical device(s)/ drug(s).

The National Natural Science Foundation of China (No. 81600968), Medical Scientific Research Foundation of Guangdong Province of China (No. A2017101, No. A2017319) grant funds were received in support of this work.

No relevant financial activities outside the submitted work.

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