Preventing oxaliplatin‑induced neuropathic pain: Using berberine to inhibit the activation of NF‑κB and release of pro‑inflammatory cytokines in dorsal root ganglions in rats

Background and objectivesPulsed radiofrequency (PRF) is a minimal neurodestructive interventional pain therapy. However, its analgesic mechanism remains largely unclear. We aimed to investigate the peripheral and spinal mechanisms of PRF applied either adjacent to the ipsilateral L5 dorsal root ganglion (PRF-DRG) or PRF to the sciatic nerve (PRF-SN) in the neuropathic pain behavior induced by chronic constriction injury (CCI) in rats.MethodsOn day 0, CCI or sham surgeries were performed. Rats then received either PRF-DRG, PRF-SN, or sham PRF treatment on day 4. Pain behavioral tests were conducted before surgeries and on days 1, 3, 5, 7, 9, 11, 13, and 14. After the behavioral tests, the rats were sacrificed. The venous blood or sciatic nerve samples were collected for ELISAs and the dorsal horns of the L4–L6 spinal cord were collected for western blot examination.ResultsThe mechanical allodynia and the thermal hyperalgesia has been relieved by a single PRF-DRG or PRF-SN application. In addition, the analgesic effect of PRF-DRG was superior to PRF-SN on CCI-induced neuropathic pain. Either PRF-DRG or PRF-SN reversed the enhancement of interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α) levels in the blood of CCI rats. PRF-DRG or PRF-SN also downregulated spinal β-catenin expression.ConclusionsPRF treatment either to DRG or to sciatic nerve reduced neuropathic pain behavior, and reduced peripheral levels of pro-inflammatory cytokines and spinal β-catenin expression in CCI rats. PRF to DRG has a better analgesic effect than PRF to the nerve.

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TLR8 in the Trigeminal Ganglion Contributes to the Maintenance of Trigeminal Neuropathic Pain in Mice

Neuroscience Bulletin ◽

10.1007/s12264-020-00621-4 ◽

2020 ◽

Author(s):

Lin-Xia Zhao ◽

Ming Jiang ◽

Xue-Qiang Bai ◽

De-Li Cao ◽

Xiao-Bo Wu ◽

...

Keyword(s):

Neuropathic Pain ◽

Inflammatory Cytokines ◽

Trigeminal Ganglion ◽

Dorsal Root ◽

Mechanical Allodynia ◽

Infraorbital Nerve ◽

Trigeminal Neuropathic Pain ◽

Intracellular Ca ◽

Significant Health ◽

Pro Inflammatory Cytokines

AbstractTrigeminal neuropathic pain (TNP) is a significant health problem but the involved mechanism has not been completely elucidated. Toll-like receptors (TLRs) have recently been demonstrated to be expressed in the dorsal root ganglion and involved in chronic pain. Here, we show that TLR8 was persistently increased in the trigeminal ganglion (TG) neurons in model of TNP induced by partial infraorbital nerve ligation (pIONL). In addition, deletion or knockdown of Tlr8 in the TG attenuated pIONL-induced mechanical allodynia, reduced the activation of ERK and p38-MAPK, and decreased the expression of pro-inflammatory cytokines in the TG. Furthermore, intra-TG injection of the TLR8 agonist VTX-2337 induced pain hypersensitivity. VTX-2337 also increased the intracellular Ca2+ concentration, induced the activation of ERK and p38, and increased the expression of pro-inflammatory cytokines in the TG. These data indicate that TLR8 contributes to the maintenance of TNP through increasing MAPK-mediated neuroinflammation. Targeting TLR8 signaling may be effective for the treatment of TNP.

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