Journal of Pain Research (Sep 2022)
Activation of Neuroinflammation via mTOR Pathway is Disparately Regulated by Differential Target Multiplexed and Traditional Low-Rate Spinal Cord Stimulation in a Neuropathic Pain Model
Abstract
Dana M Tilley,1 Ricardo Vallejo,1,2 Francesco Vetri,3 David C Platt,1,2 David L Cedeno1,2 1Research and Development, SGX Medical, Bloomington, IL, USA; 2Neuroscience, Illinois Wesleyan University, Bloomington, IL, USA; 3Research Department, National Spine and Pain Centers, Bloomington, IL, USACorrespondence: David L Cedeno, SGX Medical, 2406 E. Empire St, Bloomington, IL, 61704, USA, Tel +1 309 826 6974, Email [email protected]: Spinal cord stimulation (SCS) has been used for decades to treat neuropathic pain conditions with limited understanding of its mechanisms of action. The mTOR pathway is a well-known co-factor in chronic pain and has not been previously linked to SCS therapy. Proteomic and phosphorylation analyses allow capturing a broad view of tissue response to an injury model and subsequent therapies such as SCS. Here, we evaluated the effect of differential target multiplexed SCS programming (DTMP) and traditional low-rate spinal cord stimulation (LR-SCS) on the mTOR pathway using proteomic and phosphoproteomic analyses.Methods: The spared nerve injury (SNI) model of neuropathic pain in animals was established followed by continuous treatment with either DTMP or LR-SCS for 48 hours. Control groups included sham-stimulated (No-SCS) and uninjured animals (No-SNI). Proteins were extracted from spinal cord tissue removed post-stimulation and subjected to liquid chromatography/tandem mass spectrometry to assess changes in protein expression and states of phosphorylation. Bioinformatics tools and literature were used to identify mTOR-related proteins in the various groups.Results: Over 7000 proteins were identified and filtered to find 1451 and 705 proteins significantly affected by DTMP and LR-SCS (p < 0.05), respectively, relative to No-SCS. Literature and bioinformatic tools yielded 192 mTOR-related proteins that were cross-referenced to the list of DTMP and LR-SCS affected proteins. Of these proteins, 49 were found in the proteomic dataset. Eight of these proteins showed a significant response to the pain model, 25 were significantly modulated by DTMP, and 8 by LR-SCS. Phosphoproteomic analyses yielded 119 mTOR-related phosphoproteins affected by the injury model with a 66% reversal following DTMP versus a 58% reversal by LR-SCS.Conclusion: Proteomic and phosphoproteomic analyses support the hypothesis that DTMP, and to a lesser extent LR-SCS, reverse injury induced changes of the mTOR pathway while treating neuropathic pain.Keywords: proteomic analysis, phosphoproteomic analysis, nerve injury, central sensitization, inflammation
