Neuropathic Pain Responses Research Articles

The role of walking exercise on axonal regrowth and neuropathic pain markers in dorsal root ganglion after sciatic nerve injury.

The aim of this study was to determine whether walking exercise can regulate the expression level of neuropathic pain- and inflammatory response markers in the ipsilateral lumbar 4 to 6 dorsal root ganglion neurons after sciatic nerve injury (SNI). The experimental rats were randomly divided into seven groups: the normal control group, sedentary groups for 3, 7, and, 14 days postinjury (dpi), and walking exercise groups for 3, 7, and 14 dpi. Western blot techniques were used to evaluate specific neuropathic pain- and cytokine markers and mechanical allodynia was confirmed by paw withdrawal test. Mechanical allodynia was significantly improved in the walking exercise group compared to the sedentary group at all 7, 10, and 14 dpi. Furthermore, growth associated protein 43 and brain-derived neurotrophic factor levels were significantly increased in the walking exercise groups compared to the sedentary group at all 3, 7, and 14 dpi. Conversely, nuclear factor kappa-light-chain-enhancer of activated B cells, interleukin-6, tumor necrosis factor α, calcitonin gene-related peptide, and c-Fos expression levels were significantly decreased in the walking exercise groups compared to the sedentary group at all 3, 7, and 14 dpi. These findings suggest meaningful information that aggressive rehabilitation walking exercise applied early after SNI might be improve mechanical allodynia, neuropathic pain and inflammatory response markers following SNI.

An analysis of neuropathic pain, vasomotor manifestations, and sympathetic skin reactions in post-COVID-19 patients relative to healthy individuals.

This study aims to assess the incidence of neuropathic pain, vasomotor symptoms, and sympathetic skin responses (SSR) in patients who have recovered from COVID-19 infection and contrast these findings with healthy controls. The study encompassed 56 post-COVID-19 patients and 40 healthy controls (group 1: post-COVID-19 patients, and group 2: healthy controls). The presence of autonomic dysfunction symptoms (ADS) and orthostatic hypotension following COVID-19 infection was documented in group 1. Concurrently, fatigue and forgetfulness levels were appraised using the numerical rating scale, and the leeds assessment of neuropathic symptoms and signs pain scale was deployed to probe for the incidence of neuropathic pain among participants. SSR of all participants was conducted bilaterally from median and tibial nerves using an electroneuromyographic device. Among post-COVID-19 patients, neuropathic pain was observed in 17.9% of cases. There were no notable variations in the initiation and magnitude of bilateral median and tibial nerve SSR across the 2 groups. Significant discrepancies were observed in ADS scores between groups 1 and 2 (P = .001). Furthermore, a positive correlation was established between the latencies of the left median nerve SSR and ADS scores (R = 0.339, P = .014). The SSR patterns were congruous between healthy individuals and post-COVID-19 patients. However, a higher prevalence of autonomic dysfunction symptoms and correlations among SSR, autonomic dysfunction scores, fatigue, and forgetfulness levels were identified among post-COVID-19 patients.

Sex-specific adipose tissue’s dynamic role in metabolic and inflammatory response following peripheral nerve injury

Epidemiological data and research highlight increased neuropathy and chronic pain prevalence among females, spanning metabolic and normometabolic contexts, including murine models. Prior findings demonstrated diverse immune and neuroimmune responses between genders in neuropathic pain (NeP), alongside distinct protein expression in sciatic nerves. This study unveils adipose tissue's (AT) role in sex-specific NeP responses after peripheral nerve injury. Metabolic assessments, metabolomics, energy expenditure evaluations, AT proteomic analyses, and adipokine mobilization depict distinct AT reactions to nerve damage. Females exhibit altered lipolysis, fatty acid oxidation, heightened energy expenditure, and augmented steroids secretion affecting glucose and insulin metabolism. Conversely, male neuropathy prompts glycolysis, reduced energy expenditure, and lowered unsaturated fatty acid levels. Males' AT promotes regenerative molecules, oxidative stress defense, and stimulates peroxisome proliferator-activated receptors (PPAR-γ) and adiponectin. This study underscores AT's pivotal role in regulating gender-specific inflammatory and metabolic responses to nerve injuries, shedding light on female NeP susceptibility determinants.

TRPA1 activation and Hsp90 inhibition synergistically downregulate macrophage activation and inflammatory responses in vitro

BackgroundTransient receptor potential ankyrin 1 (TRPA1) channels are known to be actively involved in various pathophysiological conditions, including neuronal inflammation, neuropathic pain, and various immunological responses. Heat shock protein 90 (Hsp90), a cytoplasmic molecular chaperone, is well-reported for various cellular and physiological processes. Hsp90 inhibition by various molecules has garnered importance for its therapeutic significance in the downregulation of inflammation and are proposed as anti-cancer drugs. However, the possible role of TRPA1 in the Hsp90-associated modulation of immune responses remains scanty.ResultsHere, we have investigated the role of TRPA1 in regulating the anti-inflammatory effect of Hsp90 inhibition via 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) in lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) stimulation in RAW 264.7, a mouse macrophage cell lines and PMA differentiated THP-1, a human monocytic cell line similar to macrophages. Activation of TRPA1 with Allyl isothiocyanate (AITC) is observed to execute an anti-inflammatory role via augmenting Hsp90 inhibition-mediated anti-inflammatory responses towards LPS or PMA stimulation in macrophages, whereas inhibition of TRPA1 by 1,2,3,6-Tetrahydro-1,3-dimethyl-N-[4-(1-methylethyl)phenyl]-2,6-dioxo-7 H-purine-7-acetamide,2-(1,3-Dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7 H-purin-7-yl)-N-(4-isopropylphenyl)acetamide (HC-030031) downregulates these developments. LPS or PMA-induced macrophage activation was found to be regulated by TRPA1. The same was confirmed by studying the levels of activation markers (major histocompatibility complex II (MHCII), cluster of differentiation (CD) 80 (CD80), and CD86, pro-inflammatory cytokines (tumor necrosis factor (TNF) and interleukin 6 (IL-6)), NO (nitric oxide) production, differential expression of mitogen-activated protein kinase (MAPK) signaling pathways (p-p38 MAPK, phospho-extracellular signal-regulated kinase 1/2 (p-ERK 1/2), and phosphor-stress-activated protein kinase/c-Jun N-terminal kinase (p-SAPK/JNK)), and induction of apoptosis. Additionally, TRPA1 has been found to be an important contributor to intracellular calcium levels toward Hsp90 inhibition in LPS or PMA-stimulated macrophages.ConclusionThis study indicates a significant role of TRPA1 in Hsp90 inhibition-mediated anti-inflammatory developments in LPS or PMA-stimulated macrophages. Activation of TRPA1 and inhibition of Hsp90 has synergistic roles towards regulating inflammatory responses associated with macrophages. The role of TRPA1 in Hsp90 inhibition-mediated modulation of macrophage responses may provide insights towards designing future novel therapeutic approaches to regulate various inflammatory responses.

Clinical Spectrum and Prognosis in Patients With Acute Nutritional Axonal Neuropathy.

To describe the clinical, micronutrient, and electrophysiologic spectra and prognosis in patients with acute nutritional axonal neuropathy (ANAN). Patients with ANAN were identified between 1999 and 2020 by a retrospective review of our EMG database and electronic health records and categorized on clinical and electrodiagnostic grounds, as pure sensory, sensorimotor, or pure motor; and by risk factor (alcohol use disorder, bariatric surgery, or anorexia). Laboratory abnormalities were recorded including thiamine, vitamin B6, B12, and E, folate, and copper. Ambulatory and neuropathic pain status at last follow-up were recorded. Of 40 patients with ANAN, 21 had alcohol use disorder, 10 were anorexic, and 9 had recently undergone bariatric surgery. Their neuropathy was pure sensory in 14 (7 with low thiamine), sensorimotor in 23 (8 with low thiamine), and pure motor in 3 (1 with low thiamine). Vitamin B1 was most commonly low (85%), followed by vitamin B6 (77%) and folate (50%). The risk factor and neuropathy type were not associated with a particular micronutrient deficiency. Of the 37 patients who were seen in follow-up, only 13 (35%) were walking independently, and only 8 (22%) were pain free at the last follow-up visit at a mean of 22 months (range 2-88 months) from onset. The spectrum of ANAN is wide, ranging from: (1) a pure sensory neuropathy with areflexia, limb and gait ataxia, neuropathic pain, and unevocable sensory responses to (2) a motor axonal neuropathy with low-amplitude motor responses without conduction slowing, block, or dispersion, and (3) a mixed sensorimotor axonal polyneuropathy. Specific micronutrient deficiencies or risk factors do not predict neuropathy subtype. The subgroup of patients with ANAN with documented thiamine deficiency also range from pure sensory to pure motor, and only a minority have Wernicke encephalopathy. We do not know whether coexistent micronutrient deficiencies may help explain the wide clinical spectrum of thiamine-deficient ANAN. The prognosis of ANAN is guarded due to residual neuropathic pain and slow recovery of independent ambulation. Therefore, early recognition of patients at risk is important.

Pharmacological activation of mediodorsal thalamic GABA-A receptors modulates morphine/cetirizine-induced changes in the prefrontal cortical GFAP expression in a rat model of neuropathic pain

The present study investigated the involvement of mediodorsal thalamic (MD) GABA-A receptors in cetirizine/morphine-induced anti-allodynia using a rat model of neuropathic pain. To assess the importance of the prefrontal cortex (PFC) for chronic pain processing, its expression level changes of glial fibrillary acidic protein (GFAP) were measured following drug treatments. Each animal was subjected to chronic constriction of the sciatic nerve surgery simultaneously with the MD cannulation under stereotaxic surgery. The results showed that the administration of morphine (3–5 mg/kg) or cetirizine (1–3 mg/kg) produced significant analgesia in neuropathic rats. Systemic administration of cetirizine (2.5 and 3 mg/kg) potentiated the analgesic response to a low and intolerance dose of morphine (3 mg/kg). Intra-MD microinjection of muscimol, a selective GABA-A receptor agonist (0.005–0.01 μg/rat), increased the cetirizine/morphine-induced anti-allodynia, while muscimol by itself did not affect neuropathic pain. The neuropathic pain was associated with the increased PFC expression level of GFAP, suggesting the impact of chronic pain on PFC glial management. Interestingly, the anti-allodynia was associated with a decrease in the PFC expression level of GFAP under the drugs' co-administration. Thus, cetirizine has a significant potentiating effect on morphine response in neuropathic pain via interacting with the MD GABA-A receptors. It seems that neuropathic pain affects the prefrontal cortex GFAP signaling pathway. In clinical studies, these findings can be considered to create a combination therapy with low doses of GABA-A receptor agonist plus cetirizine and morphine to manage neuropathic pain.

Positive interaction between GPER and β-alanine in the dorsal root ganglion uncovers potential mechanisms: mediating continuous neuronal sensitization and neuroinflammation responses in neuropathic pain

BackgroundThe pathogenesis of neuropathic pain and the reasons for the prolonged unhealing remain unknown. Increasing evidence suggests that sex oestrogen differences play a role in pain sensitivity, but few studies have focused on the oestrogen receptor which may be an important molecular component contributing to peripheral pain transduction. We aimed to investigate the impact of oestrogen receptors on the nociceptive neuronal response in the dorsal root ganglion (DRG) and spinal dorsal horn using a spared nerve injury (SNI) rat model of chronic pain.MethodsWe intrathecally (i.t.) administered a class of oestrogen receptor antagonists and agonists intrathecal (i.t.) administrated to male rats with SNI or normal rats to identify the main receptor. Moreover, we assessed genes identified through genomic metabolic analysis to determine the key metabolism point and elucidate potential mechanisms mediating continuous neuronal sensitization and neuroinflammatory responses in neuropathic pain. The excitability of DRG neurons was detected using the patch-clamp technique. Primary culture was used to extract microglia and DRG neurons, and siRNA transfection was used to silence receptor protein expression. Immunofluorescence, Western blotting, RT-PCR and behavioural testing were used to assess the expression, cellular distribution, and actions of the main receptor and its related signalling molecules.ResultsIncreasing the expression and function of G protein-coupled oestrogen receptor (GPER), but not oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ), in the DRG neuron and microglia, but not the dorsal spinal cord, contributed to SNI-induced neuronal sensitization. Inhibiting GPER expression in the DRG alleviated SNI-induced pain behaviours and neuroinflammation by simultaneously downregulating iNOS, IL-1β and IL-6 expression and restoring GABAα2 expression. Additionally, the positive interaction between GPER and β-alanine and subsequent β-alanine accumulation enhances pain sensation and promotes chronic pain development.ConclusionGPER activation in the DRG induces a positive association between β-alanine with iNOS, IL-1β and IL-6 expression and represses GABAα2 involved in post-SNI neuropathic pain development. Blocking GPER and eliminating β-alanine in the DRG neurons and microglia may prevent neuropathic pain development.

Berberine Alleviate Cisplatin-Induced Peripheral Neuropathy by Modulating Inflammation Signal via TRPV1.

Chemotherapy induced peripheral neuropathy (CIPN) is a severe neurodegenerative disorder caused by chemotherapy drugs. Berberine is a natural monomer compound of Coptis chinensis, which has anti-tumor effect and can improve neuropathy through anti-inflammatory mechanisms. Transient receptor potential vanilloid (TRPV1) can sense noxious thermal and chemical stimuli, which is an important target for the study of pathological pain. In both vivo and in vitro CIPN models, we found that berberine alleviated peripheral neuropathy associated with dorsal root ganglia inflammation induced by cisplatin. We confirmed that berberine mediated the neuroinflammatory reaction induced by cisplatin by inhibiting the overexpression of TRPV1 and NF-κB and activating the JNK/p38 MAPK pathways in early injury, which inhibited the expression of p-JNK and mediated the expression of p38 MAPK/ERK in late injury in vivo. Moreover, genetic deletion of TRPV1 significantly reduced the protective effects of berberine on mechanical and heat hyperalgesia in mice. In TRPV1 knockout mice, the expression of NF-κB increased in late stage, and berberine inhibited the overexpression of NF-κB and p-ERK in late injury. Our results support berberine can reverse neuropathic inflammatory pain response induced by cisplatin, TRPV1 may be involved in this process.

Exosomes carried miR-181c-5p alleviates neuropathic pain in CCI rat models.

Mesenchymal stem cells (MSCs) derived exosomes (Exos) are one of the most promising candidate for the treatment of this condition. However, the underlying molecular mechanism remains uncertain. Here we investigated the therapeutic effect of exosomal miR-181c-5p (ExomiR-181c-5p) on a rat model of neuropathic pain induced by sciatic nerve chronic constriction injury (CCI). In this study NP model was established using the CCI method. NP levels were assessed using PWT and PWL. Microarray analysis and RT-PCR were used to determine the relative expression of miR-181c-5p. MSC-derived exosomes were extracted using the total exosome isolation reagent characterized by WB and NTA. MiR-181c-5p was loading into Exos using electroporation. The inflammation response in microglia cells and CCI rats were assessed by ELISA assay respectively. Our study demonstrates that miR-181c-5p expression was obviously decreased in a time-dependent manner in CCI rats. MiR-181c-5p was effectively electroporated and highly detected in MSC-derived Exos. ExomiR-181c-5p internalized by microglia cells and inhibit the secretion of inflammation factors. ExomiR-181c-5p intrathecal administration alleviated neuropathic pain and neuroinflammation response in CCI rats. Taken together, ExomiR-181c-5p alleviated CCI-induced NP by inhibiting neuropathic inflammation. ExomiR-181c-5p may be a valid alternative for the treatment of neuropathic pain and has vast potential for future development.

Neuropathic Pain and Spasticity Response to Traditional Acupuncture after Spinal Cord Injury

Introduction: One of the most relevant disabilities is caused by spinal cord injury (SCI). Typical causes of spinal cord damage are trauma, disease, or congenital disorders. Tetraplegia is a paralysis results in the partial or total loss of use of all limbs and torso; paraplegia is similar but does not affect the arms. Pain and spasticity are common sequelae of SCI [1]. Both pain and spasticity can have a late onset and develop slowly over time after SCI, and once developed, they often become chronic. In this paper we have provided to assess the effectiveness of acupuncture for treating SCI sequelae and summarize the potential mechanisms of acupuncture therapy. Method: We considered 30 patients with diagnosis of tetra or paraplegia after SCI complicated by neuropathic pain and spasticity. Neurologist trained in medical acupuncture conducted the therapeutic treatments. A specific set of acupuncture points was used in all sessions. Participants were treated for 8 sessions of acupuncture over 4 week’s period. Pain and spasticity were evaluated with Numeric Raiting Scale (VAS) (2) and the Modified Ashworth Scale [3] at the beginning of the first, the fourth an eighth treatment session. Results: 28 patients (93%) showed improvement in pain intensity and spasticity after two weeks of acupuncture treatment. The therapeutic effect continued until the eighth week of treatment. However, 15 patients (53,5%) reported an increase in spasticity and pain 2 months after acupuncture sessions. Conclusions: Acupuncture sessions using defined acupoint set reduced pain intentensity and spasticity in patients with SCI.

Multi-Omics Approach to Elucidate Cerebrospinal Fluid Changes in Dogs with Intervertebral Disc Herniation.

Herniation of the intervertebral disc (IVDH) is the most common cause of neurological and intervertebral disc degeneration-related diseases. Since the disc starts to degenerate before it can be observed by currently available diagnostic methods, there is an urgent need for novel diagnostic approaches. To identify molecular networks and pathways which may play important roles in intervertebral disc herniation, as well as to reveal the potential features which could be useful for monitoring disease progression and prognosis, multi-omics profiling, including high-resolution liquid chromatography-mass spectrometry (LC-MS)-based metabolomics and tandem mass tag (TMT)-based proteomics was performed. Cerebrospinal fluid of nine dogs with IVDH and six healthy controls were used for the analyses, and an additional five IVDH samples were used for proteomic data validation. Furthermore, multi-omics data were integrated to decipher a complex interaction between individual omics layers, leading to an improved prediction model. Together with metabolic pathways related to amino acids and lipid metabolism and coagulation cascades, our integromics prediction model identified the key features in IVDH, namely the proteins follistatin Like 1 (FSTL1), secretogranin V (SCG5), nucleobindin 1 (NUCB1), calcitonin re-ceptor-stimulating peptide 2 precursor (CRSP2) and the metabolites N-acetyl-D-glucosamine and adenine, involved in neuropathic pain, myelination, and neurotransmission and inflammatory response, respectively. Their clinical application is to be further investigated. The utilization of a novel integrative interdisciplinary approach may provide new opportunities to apply innovative diagnostic and monitoring methods as well as improve treatment strategies and personalized care for patients with degenerative spinal disorders.

MP35-13 NEUROINFLAMMATORY GENE EXPRESSION IN CHRONIC PROSTATITIS/CHRONIC PELVIC PAIN SYNDROME (CP/CPPS): INSIGHTS INTO ETIOLOGY AND PHENOTYPE BIOLOGY

You have accessJournal of UrologyInfections/Inflammation/Cystic Disease of the Genitourinary Tract: Prostate & Genitalia (MP35)1 Sep 2021MP35-13 NEUROINFLAMMATORY GENE EXPRESSION IN CHRONIC PROSTATITIS/CHRONIC PELVIC PAIN SYNDROME (CP/CPPS): INSIGHTS INTO ETIOLOGY AND PHENOTYPE BIOLOGY Johnathan Doolittle, Karen Keslar, Paige Gotwald, Sarah Vij, and Daniel Shoskes Johnathan DoolittleJohnathan Doolittle More articles by this author , Karen KeslarKaren Keslar More articles by this author , Paige GotwaldPaige Gotwald More articles by this author , Sarah VijSarah Vij More articles by this author , and Daniel ShoskesDaniel Shoskes More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002044.13AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: CP/CPPS has diverse clinical phenotypes and its etiology is multifactorial with inflammatory, immune and neuromuscular pathways implicated. Studies to date of gene expression in humans have been limited to small numbers of target genes. NanoString uses barcoded probes to simultaneously measure hundreds of genes. We wished to study gene expression in blood and urine of CP/CPPS patients compared to controls for a broad variety of neuroinflammatory genes and characterize the results by patient phenotype. METHODS: Blood and urine were collected from 10 men with CP/CPPS and 7 asymptomatic controls. RNA was isolated from urine pellets using Qiagen RNeasy kits. Whole blood was collected and RNA isolated using the Tempus Spin RNA isolation kit. 100 ng of RNA was used for gene expression analysis with the 770-gene NanoString Human Neuroinflammation gene panel. Data was imported into Rosalind (OnRamp Bioinformatics) for normalization, calculation of fold-changes and p values, and identification of enriched pathways. Gene expression was considered significantly different if there was a greater than 1.5x change compared to controls and corrected p was <0.05. RESULTS: Mean patient age was 42.2 years, median symptom duration was 15.5 months, median UPOINT domains was 3 and mean total NIH-CPSI score was 28.8. In blood, there were 5 genes with significantly different expression to controls, the largest differences found in FOS1 (neuropathic pain control), PROS1 (blood clotting and found in prostate cancer cells) and DDX58 (antiviral innate immunity). Gene set analysis showed differences in inflammation, angiogenesis and cytokine signaling. In urine there were 48 genes with significantly different expression including SLAMF8 (CD2 mediated lymphocyte activation) and LAIR1 (inhibits B and T cell function). Gene set analysis showed differences in Wnt (adaptive immune response in neuropathic pain), microglial function and inflammatory signaling. Subgroup analysis by UPOINT domain showed unique gene expression in the Psychosocial, Organ Specific and Neurologic/Systemic domains in both blood and urine for neurogenic pain and cytokine signaling associated genes. CONCLUSIONS: Men with CP/CPPS have a diverse set of neuroinflammatory genes with differential expression compared to controls including some never before implicated in the etiology of this condition. Furthermore, clinical phenotypes have distinct patterns of gene expression. These findings could lead to novel biomarker development, novel treatment options and further validates the biologic basic of clinical phenotyping. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e632-e632 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Johnathan Doolittle More articles by this author Karen Keslar More articles by this author Paige Gotwald More articles by this author Sarah Vij More articles by this author Daniel Shoskes More articles by this author Expand All Advertisement Loading ...

The Neuropeptide Cortistatin Alleviates Neuropathic Pain in Experimental Models of Peripheral Nerve Injury.

Neuropathic pain is one of the most severe forms of chronic pain caused by the direct injury of the somatosensory system. The current drugs for treating neuropathies have limited efficacies or show important side effects, and the development of analgesics with novel modes of action is critical. The identification of endogenous anti-nociceptive factors has emerged as an attractive strategy for designing new pharmacological approaches to treat neuropathic pain. Cortistatin is a neuropeptide with potent anti-inflammatory activity, recently identified as a natural analgesic peptide in several models of pain evoked by inflammatory conditions. Here, we investigated the potential analgesic effect of cortistatin in neuropathic pain using a variety of experimental models of peripheral nerve injury caused by chronic constriction or partial transection of the sciatic nerve or by diabetic neuropathy. We found that the peripheral and central injection of cortistatin ameliorated hyperalgesia and allodynia, two of the dominant clinical manifestations of chronic neuropathic pain. Cortistatin-induced analgesia was multitargeted, as it regulated the nerve damage-induced hypersensitization of primary nociceptors, inhibited neuroinflammatory responses, and enhanced the production of neurotrophic factors both at the peripheral and central levels. We also demonstrated the neuroregenerative/protective capacity of cortistatin in a model of severe peripheral nerve transection. Interestingly, the nociceptive system responded to nerve injury by secreting cortistatin, and a deficiency in cortistatin exacerbated the neuropathic pain responses and peripheral nerve dysfunction. Therefore, cortistatin-based therapies emerge as attractive alternatives for treating chronic neuropathic pain of different etiologies.

Investigating post-transcriptional mechanisms of neuropathic pain

Neuropathic pain is a chronic condition which can arise following damage to the somatosensory system and often involves both hyperalgesia and allodynia. The molecular mechanisms of neuropathic pain remain incompletely understood but require enduring alterations in specific gene program expression and protein synthesis affecting neuronal signaling and excitability. We investigate the roles of non-coding RNA regulatory pathways in impacting hyperalgesia and determining the mRNA complement recruited during the protein synthesis response in neuropathic pain. Nerve injury alters the expression of many miRNAs, including the highly conserved let-7 family miRNAs, which repress pro-growth mRNAs and are implicated in axon growth, neuronal plasticity, and brain circuit development. The Lin28 RNA binding protein can prevent maturation of let-7 precursor RNAs; consequently, increased Lin28 signaling promotes pro-growth gene expression. The regulation and potential roles role of Lin28/let-7 pathway in neuropathic pain remain largely unexplored. Using spared nerve injury (SNI) mouse models of neuropathic pain, we find in preliminary data that Lin28a loss of function in sensory neuron populations can result in a deficit in mechanical hypersensitivity post-surgery. In SNI and sciatic nerve transection (SNT) mouse models, we evaluate molecular mechanisms underlying pain using single molecule detection and genetic manipulation. A sensitive RNA imaging assays, RNAScope in situ hybridization (ISH), is used to amplify single RNA target signals in fixed tissues to allow mapping of the spatiotemporal patterns and cell type specificity of changes in non-coding RNA regulatory pathways. Digital PCR is used to provide sensitive and quantitative validation. We find lin28 mRNA level are elevated in injured dorsal root ganglion cells, injured sciatic nerves and their surrounding Schwann cells at 3 days post SNI and SNT surgery accordingly. Neuropathic pain is a chronic condition which can arise following damage to the somatosensory system and often involves both hyperalgesia and allodynia. The molecular mechanisms of neuropathic pain remain incompletely understood but require enduring alterations in specific gene program expression and protein synthesis affecting neuronal signaling and excitability. We investigate the roles of non-coding RNA regulatory pathways in impacting hyperalgesia and determining the mRNA complement recruited during the protein synthesis response in neuropathic pain. Nerve injury alters the expression of many miRNAs, including the highly conserved let-7 family miRNAs, which repress pro-growth mRNAs and are implicated in axon growth, neuronal plasticity, and brain circuit development. The Lin28 RNA binding protein can prevent maturation of let-7 precursor RNAs; consequently, increased Lin28 signaling promotes pro-growth gene expression. The regulation and potential roles role of Lin28/let-7 pathway in neuropathic pain remain largely unexplored. Using spared nerve injury (SNI) mouse models of neuropathic pain, we find in preliminary data that Lin28a loss of function in sensory neuron populations can result in a deficit in mechanical hypersensitivity post-surgery. In SNI and sciatic nerve transection (SNT) mouse models, we evaluate molecular mechanisms underlying pain using single molecule detection and genetic manipulation. A sensitive RNA imaging assays, RNAScope in situ hybridization (ISH), is used to amplify single RNA target signals in fixed tissues to allow mapping of the spatiotemporal patterns and cell type specificity of changes in non-coding RNA regulatory pathways. Digital PCR is used to provide sensitive and quantitative validation. We find lin28 mRNA level are elevated in injured dorsal root ganglion cells, injured sciatic nerves and their surrounding Schwann cells at 3 days post SNI and SNT surgery accordingly.

Does transcutaneous electrical nerve stimulation affect pain, neuropathic pain, and sympathetic skin responses in the treatment of chronic low back pain? A randomized, placebo-controlled study.

BackgroundThe purpose of this study was to assess the effectiveness of transcutaneous electrical nerve stimulation (TENS) in chronic low back pain and neuropathic pain.MethodsSeventy-four patients aged 18-65 with chronic low back pain were included in the study. Baseline measurements were performed, and patients were randomized into three groups. The first group received burst TENS (bTENS), the second group conventional TENS (cTENS), and the third group placebo TENS (pTENS), all over 15 sessions. Patients’ visual analogue scale (VAS) scores were evaluated before treatment (preT), immediately after treatment (postT), and in the third month after treatment (postT3). Douleur Neuropathique 4 Questions (DN4), the Modified Oswestry Low Back Pain Disability Questionnaire (MOS), the Beck Depression Inventory (BDI), and sympathetic skin response (SSR) values were also evaluated preT and postT3.ResultsA statistically significant improvement was observed in mean VAS scores postT compared to preT in all three groups. Intergroup comparison revealed a significant difference between preT and postT values, that difference being assessed in favor of bTENS at multiple comparison analysis. Although significant improvement was determined in neuropathic pain DN4 scores measured at postT3 compared to preT in all groups, there was no significant difference between the groups. No statistically significant difference was also observed between the groups in terms of MOS, BDI, or SSR values at postT3 (P > 0.05).ConclusionsbTENS therapy in patients with low back pain is an effective and safe method that can be employed in short-term pain control.

Inflammatory cytokines in midbrain periaqueductal gray contribute to diabetic induced pain hypersensitivity through phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway.

BackgroundDiabetes-related neuropathic pain frequently occurs, and the underpinning mechanism remains elusive. The periaqueductal gray (PAG) exhibits descending inhibitory effects on central pain transmission. The current work aimed to examine whether inflammatory cytokines regulate mechanical allodynia and thermal hyperalgesia induced by diabetes through the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway in the PAG.MethodsStreptozotocin (STZ) was administered intraperitoneally to mimic allodynia and hyperalgesia evoked by diabetes in rats. Behavioral assays were carried out for determining mechanical pain and thermal hypersensitivity. Immunoblot and ELISA were performed to examine PAG protein amounts of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), as well as their corresponding receptors in STZ rats, and the expression of PI3K/protein kinase B (Akt)/mTOR signaling effectors.ResultsIncreased PAG p-PI3K/p-Akt/p-mTOR protein amounts were observed in STZ-induced animals, a PI3K-mTOR pathway inhibition in the PAG attenuated neuropathic pain responses. Moreover, the PAG concentrations of IL-1β, IL-6, and TNF-α and their receptors (namely, IL-1R, IL-6R, and tumor necrosis factor receptor [TNFR] subtype TNFR1, respectively) were increased in the STZ rats. Additionally, inhibiting IL-1R, IL-6R, and TNFR1 ameliorated mechanical allodynia and thermal hyperalgesia in STZ rats, alongside the downregulation of PI3K-mTOR signaling.ConclusionsOverall, the current study suggests that upregulated proinflammatory cytokines and their receptors in the PAG activate PI3K-mTOR signaling, thereby producing a de-inhibition effect on descending pathways in modulating pain transmission, and eventually contributing to neuropathic pain.

Impact of Hepatoma-Derived Growth Factor Blockade on Resiniferatoxin-Induced Neuropathy.

Resiniferatoxin is an ultrapotent capsaicin analog that mediates nociceptive processing; treatment with resiniferatoxin can cause an inflammatory response and, ultimately, neuropathic pain. Hepatoma-derived growth factor, a growth factor related to normal development, is associated with neurotransmitters surrounding neurons and glial cells. Therefore, the study aims to investigate how blocking hepatoma-derived growth factor affects the inflammatory response in neuropathic pain. Serum hepatoma-derived growth factor protein expression was measured via ELISA. Resiniferatoxin was administrated intraperitoneally to induce neuropathic pain in 36 male Sprague-Dawley rats which were divided into three groups (resiniferatoxin+recombinant hepatoma-derived growth factor antibody group, resiniferatoxin group, and control group) (n = 12/group). The mechanical threshold response was tested with calibration forceps. Cell apoptosis was measured by TUNEL assay. Immunofluorescence staining was performed to detect apoptosis of neuron cells and proliferation of astrocytes in the spinal cord dorsal horn. RT-PCR technique and western blot were used to measure detect inflammatory factors and protein expressions. Serum hepatoma-derived growth factor protein expression was higher in the patients with sciatica compared to controls. In resiniferatoxin-group rats, protein expression of hepatoma-derived growth factor was higher than controls. Blocking hepatoma-derived growth factor improved the mechanical threshold response in rats. In dorsal root ganglion, blocking hepatoma-derived growth factor inhibited inflammatory cytokines. In the spinal cord dorsal horn, blocking hepatoma-derived growth factor inhibited proliferation of astrocyte, apoptosis of neuron cells, and attenuated expressions of pain-associated proteins. The experiment showed that blocking hepatoma-derived growth factor can prevent neuropathic pain and may be a useful alternative to conventional analgesics.

A novel gabapentin analogue assuages neuropathic pain response in chronic sciatic nerve constriction model in rats

Gabapentin (GBP) is an established drug that has been used in the management of symptoms of neuropathy but it is associated with unwanted side effects such as sedation and motor incoordination. The goal of the study was to find out a drug with greater efficacy and safety for the treatment of neuropathic pain. Our previously synthesized GABA analogue (Gabapentsal, GPS) was tested (25-100 mg/kg, i.p) in chronic constriction injury (CCI) induced nociceptive model of static allodynia, dynamic allodynia, thermal hyperalgesia, mechanical hyperalgesia and cold allodynia in rats (Sprague Dawley). Open field and rotarod tests were performed to assess the impact of GPS on the motor performance of the animals. GBP (100 mg/kg, i.p) was used as a standard for comparison. GPS dose dependently reduced static (P <0.001) and dynamic allodynia (P <0.001), thermal hyperalgesia (P <0.001), mechanical hyperalgesia (P < 0.001) and cold allodynia (P < 0.001). In comparison to GBP, GPS failed to alter any significantly the motor performance of rats in both the open field and rotarod assays. These results suggest that GPS is effective in alleviating nociception in CCI neuropathic pain model but free from the side effect of motor discoordination seen in the treatment with GBP. In conclusion, GPS may prove to be a prospectively more effective and safer option in the management of neuropathic syndromes.

Dexmedetomidine relieved neuropathic pain and inflammation response induced by CCI through HMGB1/TLR4/NF-κB signal pathway.

Neuropathic pain is one of the most intractable diseases. The lack of effective therapy measures remains a critical problem due to the poor understanding of the cause of neuropathic pain. The aim of this study was to investigate the effect of dexmedetomidine (Dex) in trigeminal neuropathic pain and the underlying molecular mechanism in order to identify possible therapeutic targets. We used a chronic constriction injury (CCI) model of mice to investigate whether Dex prevents neuropathic pain and the inflammation response. The α 2-adrenoceptors (α2AR) inhibitor BRL44408 and adenovirus for knocking down High mobility group box 1 (HMGB1) was administrated to confirm whether Dex exert its effect through targeting α2AR and HMGB1. The results indicated that Dex significantly inhibited CCI induced neuropathic pain through targeting α2AR and HMGB1. Dex inhibited the inflammatory response through decreasing the release and the mRNA expression of IL-1β, IL-6, and TNF-ɑ while increasing that of IL-10. Moreover, Dex participates in the regulation of HMGB1, Toll-like receptor 4 (TLR4), NFκb (p-65) expression and the phosphorylation of IκB-ɑ. In conclusion, Dex could relieve neuropathic pain through α2AR and HMGB1 and attenuate inflammation response.

DOK3 is involved in microglial cell activation in neuropathic pain by interacting with GPR84.

Adaptor molecule downstream of kinase-3 (DOK3) is a vital regulator of innate immune responses in macrophages and B cells, and G-protein-coupled receptor 84 (GPR84) is significant in mediating the biosynthesis and maintenance of inflammatory mediators that are induced by neuropathic pain in microglia. In the present study, we determined the role of DOK3 in activating microglia-induced neuropathic pain and investigated the underlying mechanisms associated with GPR84. We found that knockdown of DOK3 in microglial cells dramatically reduced the levels of inflammatory factors, and we uncovered a physical association between DOK3 and GPR84 in the induction of inflammatory responses. We also observed that neuropathic pain and inflammatory responses induced by chronic constriction injury (CCI) of the sciatic nerve or intrathecal injection of a GPR84 agonist were compromised in DOK3-/- mice in vivo. Finally, enforced expression of DOK3 provoked inflammatory responses, and administration of pregabalin relieved neuropathic pain via inhibition of DOK3 expression. In conclusion, DOK3 induced neuropathic pain in mice by interacting with GPR84 in microglia. We hypothesize that targeting the adaptor protein DOK3 may open new avenues for pharmaceutical approaches to the alleviation of neuropathic pain in the spinal cord.