Articles: neuropathic-pain.
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Brain Behav. Immun. · Oct 2015
MicroRNA-146a-5p attenuates neuropathic pain via suppressing TRAF6 signaling in the spinal cord.
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. ⋯ 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.
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Aberrant increases in NMDA receptor (NMDAR) signaling contributes to central nervous system sensitization and chronic pain by activating neuronal nitric oxide synthase (nNOS) and generating nitric oxide (NO). Because the scaffolding protein postsynaptic density 95kDA (PSD95) tethers nNOS to NMDARs, the PSD95-nNOS complex represents a therapeutic target. Small molecule inhibitors IC87201 (EC5O: 23.94 μM) and ZL006 (EC50: 12.88 μM) directly inhibited binding of purified PSD95 and nNOS proteins in AlphaScreen without altering binding of PSD95 to ErbB4. ⋯ Our studies establish the utility of using AlphaScreen and purified protein pairs to establish and quantify disruption of protein-protein interactions. Our results demonstrate previously unrecognized antinociceptive efficacy of ZL006 and establish, using two small molecules, a broad application for PSD95-nNOS inhibitors in treating neuropathic and inflammatory pain. Collectively, our results demonstrate that disrupting PSD95-nNOS protein-protein interactions is effective in attenuating pathological pain without producing unwanted side effects (i.e. motor ataxia) associated with NMDAR antagonists.
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Intrathecal delivery of glial cell line-derived neurotrophic factor (GDNF) reverses mechanical allodynia after 5th lumbar (L5) spinal nerve ligation (SNL). However, the molecular mechanism behind this process is not fully understood. Following sciatic nerve injury, primary afferent neurons in the injured dorsal root ganglion (DRG) begin to express neuropeptide Y (NPY) that is absent in normal DRG. ⋯ NPY could facilitate touch-sense processing by Y1 receptor in the gracile nucleus after peripheral nerve injury. GDNF may exert anti-allodynic effects through mitigation of this NPY up-regulation. The effectiveness of delayed treatment further indicates the therapeutic potential of GDNF on neuropathic pain.
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Neuropathic pain is a debilitating condition for which the development of effective treatments has been limited by an incomplete understanding of its molecular basis. The cationic current Ih mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels plays an important role in pain by facilitating ectopic firing and hyperexcitability in DRG neurons, however little is known regarding the role of Ih in supraspinal pain pathways. The medial prefrontal cortex (mPFC), which is reported to be involved in the affective aspects of pain, exhibits high HCN channel expression. ⋯ It is therefore imperative that we advance our understanding of the involvement of supraspinal pain pathways. Our electrophysiological and behavioral results support an important role for hyperpolarization-activated cyclic nucleotide-gated channels and the cAMP/protein kinase A signaling axis in promoting hyperexcitability and persistent firing in pyramidal neurons of the mPFC in neuropathic animals. These findings offer novel insights, with potential therapeutic implications, into pathophysiological mechanisms underlying the abnormal contribution of layer II/III prefrontal pyramidal neurons to chronic pain states.
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The Veterinary record · Sep 2015
Randomized Controlled Trial Comparative StudyComparison of gabapentin versus topiramate on clinically affected dogs with Chiari-like malformation and syringomyelia.
To date there is no evidence-based data for efficacious treatment of neuropathic pain in dogs with Chiari-like malformation (CM) and syringomyelia (SM). The objective of this prospective cross-over study was to compare the effect of gabapentin versus topiramate, as an add-on treatment to carprofen, on quality of life (QoL) of dogs experiencing signs of neuropathic pain due to CM/SM. A visual analogue scale (VAS) was used to assess the QoL: (1) on day 0; (2) after 1 week of carprofen only; (3) after 2 weeks on carprofen and gabapentin; and (4) after 2 weeks on carprofen and topiramate. ⋯ However, an improvement in QoL was observed when gabapentin was compared with baseline (P=0.009), but not for topiramate. In conclusion, the addition of gabapentin was more effective in improving QoL than carprofen alone, but the study failed to identify that gabapentin was more efficacious than topiramate. Perhaps the more favourable side effect profile of the former makes it more suitable for the treatment of neuropathic pain associated with CM/SM but further placebo-controlled trials are required to assess the efficacy of these drugs.