Neuropathic pain: diagnosis, pathophysiological mechanisms, and treatment. Lancet Neurol. 2010;9:807-819. [PMID: 20650402 DOI: 10.1016/s1474-4422(10)70143-5]

Effects of multiple transcranial magnetic stimulation sessions on pain relief in patients with chronic neuropathic pain: A French cohort study in real-world clinical practice

BACKGROUND

Current clinical trials indicate that repetitive transcranial magnetic stimulation (rTMS) is effective in reducing drug-resistant neuropathic pain (NP). However, there is a lack of studies evaluating the long-term feasibility and clinical efficacy of rTMS in large patient cohorts in real-world conditions.

METHODS

In this retrospective cohort study, we analysed 12 years of clinical data to assess the long-term analgesic effects of 20 Hz rTMS over the primary motor cortex in patients with NP. Subgroup analyses were conducted to identify predictive factors and assess the potential role of epidural motor cortex stimulation (eMCS) as a sustained solution.

RESULTS

In total, 193 patients completed test period of 4 rTMS sessions and 42% of them reported a pain relief (PR) greater than 30%, with concurrent improvement in their most disabling symptom. Iterative rTMS sessions maintained analgesic effects over 10 years in certain patients identified as responders (≥10% PR) without adverse effects. Success probability was higher in patients with central NP compared to peripheral NP (OR = 2.03[1.04;4.00]), and among those with central post-stroke pain, this probability was higher in ischemic versus hemorrhagic strokes (OR = 3.36[1.17;10.05]). PR obtained with iterative rTMS sessions was an excellent predictor of eMCS efficacy.

CONCLUSIONS

While rTMS shows promise as a therapeutic option for some patients with drug-resistant NP, it does not benefit all patients. Efficacy varies by NP aetiology, aiding patient selection. For responders, eMCS may offer a permanent solution. These findings support a tailored approach to rTMS in NP management, while recognizing both its potential and limitations across diverse patient profiles.

SIGNIFICANCE STATEMENT

Multiple rTMS sessions demonstrate long-term efficacy and safety in treating drug-resistant neuropathic pain. Extending session numbers for the test period can enhance responder identification, especially in patients with initial low pain relief. This identification refines patient selection for neurosurgery, reducing non-responders. Central neuropathic pain shows higher success rates than peripheral. For post-stroke central pain, patients with ischemic stroke are more likely to respond than those with hemorrhagic stroke. These results support integrating rTMS into clinical practice for managing neuropathic pain.

Design of an equilibrative nucleoside transporter subtype 1 inhibitor for pain relief

The current opioid crisis urgently calls for developing non-addictive pain medications. Progress has been slow, highlighting the need to uncover targets with unique mechanisms of action. Extracellular adenosine alleviates pain by activating the adenosine A1 receptor (A1R). However, efforts to develop A1R agonists have faced obstacles. The equilibrative nucleoside transporter subtype 1 (ENT1) plays a crucial role in regulating adenosine levels across cell membranes. We postulate that ENT1 inhibition may enhance extracellular adenosine levels, potentiating endogenous adenosine action at A1R and leading to analgesic effects. Here, we modify the ENT1 inhibitor dilazep based on its complex X-ray structure and show that this modified inhibitor reduces neuropathic and inflammatory pain in animal models while dilazep does not. Notably, our ENT1 inhibitor surpasses gabapentin in analgesic efficacy in a neuropathic pain model. Additionally, our inhibitor exhibits less cardiac side effect than dilazep via systemic administration and shows no side effects via local/intrathecal administration. ENT1 is colocalized with A1R in mouse and human dorsal root ganglia, and the analgesic effect of our inhibitor is linked to A1R. Our studies reveal ENT1 as a therapeutic target for analgesia, highlighting the promise of rationally designed ENT1 inhibitors for non-opioid pain medications.

Comprehensive nursing care improves symptoms and quality of life in elderly patients with postherpetic neuralgia

This study evaluates the clinical impact of comprehensive nursing care on senior patients suffering from postherpetic neuralgia (PHN), a chronic neuropathic pain condition resulting from the reactivation of the varicella-zoster virus. A total of 102 elderly patients diagnosed with PHN and treated at our hospital were divided into two groups: the control group, which received conventional nursing care, and the intervention group, which received comprehensive nursing care. Comparative analyses were conducted on pain levels, sleep quality, symptoms of depression and anxiety before and after the intervention. After a two-month period of nursing care, both groups exhibited a significant reduction in pain levels (p < 0.05), with the intervention group demonstrating a more substantial decrease (p < 0.001). Sleep quality improved in both groups (p < 0.05), with the intervention group showing a significantly greater improvement (p < 0.05). Additionally, the intervention group experienced a notable reduction in anxiety and depression ratings compared to the control group. Comprehensive nursing care interventions may effectively alleviate clinical symptoms, and diminish levels of depression and anxiety, while improving sleep quality in elderly patients with PHN. These findings underscore the potential benefits of employing a comprehensive approach to managing PHN in the elderly population.

Isoliquiritigenin alleviates neuropathic pain by reducing microglia inflammation through inhibition of the ERK signaling pathway and decreasing CEBPB transcription expression

BACKGROUND

Natural compounds are invaluable for their therapeutic effects in treating various diseases. Isoliquiritigenin (ISL) stands out due to its potent anti-inflammatory and antioxidative properties, offering significant therapeutic effects in many diseases. However, there is currently no existing literature on the role of ISL in neuropathic pain treatment.

METHODS

We used lipopolysaccharide to stimulate BV-2 microglia in order to evaluate the inhibitory effects of ISL on neuroinflammation. Proteomics data and protein-protein interaction network analysis were used to identify differential proteins expressed in BV-2 microglia treated with ISL. This allowed for the identification of targets impacted by ISL action. Additionally, we assessed the analgesic efficacy of ISL in a mouse model of chronic constriction injury of the sciatic nerve (CCI) and investigated its inhibitory influence on pro-inflammatory cytokine production and spinal microglia activation.

RESULTS

Our results indicate that ISL efficiently inhibits BV-2 microglia activation and pro-inflammatory cytokine expression. Furthermore, CEBPB has been recognized as a possible target for ISL activity. Crucially, microglia activation was successfully reduced by CEBPB knockdown. Functional recovery tests carried out later on validated that ISL works by specifically inhibiting the ERK/CEBPB signaling pathway. In vivo studies showed that giving mice ISL reduces the mechanical and thermal pain caused on by chronic contraction injuries.

CONCLUSION

The analgesic effect of ISL on neuropathic pain primarily stems from its ability to inhibit the activation of spinal microglia and neuroinflammation. This mechanism may be attributed to the capacity of ISL to suppress microglial activation, reduce the expression of pro-inflammatory cytokines by inhibiting the ERK signaling pathway, and decrease transcriptional expression of CEBPB.

Methyltransferase METTL3 regulates neuropathic pain through m6A methylation modification of SOCS1

The mechanisms of neuropathic pain (NP) are considered multifactorial. Alterations in the suppressor of cytokine signaling 1 (SOCS1) play a critical role in neural damage and inflammation. Epigenetic RNA modifications, specifically N6-methyladenosine (m6A) methylation, have increasingly been observed to impact the nervous system. Nevertheless, there is a scarcity of studies investigating the connection between m6A methylation and SOCS1 in the molecular mechanisms of NP. This study investigates the roles and potential mechanisms of the m6A methyltransferase like 3 (METTL3) and SOCS1 in female rats with spinal nerve ligation (SNL)-induced NP. It was found that in NP, both METTL3 and overall m6A levels were downregulated, leading to the activation of pro-inflammatory cytokines, such as interleukin-1β, interleukin 6, and tumor necrosis factor-α. Notably, The SOCS1 mRNA is significantly enriched with m6A methylation modifications, with the most prevalent m6A methyltransferase METTL3 stabilizing the downregulation of SOCS1 by targeting m6A methylation modifications at positions 151, 164, and 966.Exogenous supplementation of METTL3 improved NP-related neuroinflammation and behavioral dysfunctions, but these effects could be reversed by the absence of SOCS1. Additionally, the depletion of endogenous SOCS1 promoted NP progression by inducing the toll-like receptor 4 (TLR4) signaling pathway. The dysregulation of METTL3 and the resulting m6A modification of SOCS1 form a crucial epigenetic regulatory loop that promotes the progression of NP. Targeting the METTL3/SOCS1 axis might offer new insights into potential therapeutic strategies for NP.

Overexpression of miR-133a-3p reduces microglia activation by binding to GCH1, alleviating neuroinflammation and neuropathic pain

Neuropathic pain is a chronic pain condition that is primarily caused by underlying neurological damage and dysfunction. Recent studies have identified microRNAs (miRNAs) as a key factor in the treatment of neuropathic pain. To explore the effects of miR-133a-3p on neuroinflammation and neuropathic pain via GTP cyclohydrolase (GCH1), and its underlying mechanisms. In vitro models were constructed using BV-2 cells that had been treated with lipopolysaccharide, followed by treatment with either miR-133a-3p mimic or GCH1 viral knockdown/overexpression. The expression of miR-133a-3p and GCH1 in BV-2 cells was quantified by RT-qPCR. The degree of neuroinflammation was quantified using an enzyme-linked immunosorbent assay (ELISA). The targeting relationship between miR-133a-3p and GCH1 was confirmed by western blot and dual luciferase reporter assay. A chronic constriction injury model was employed to induce neuropathic pain in rats, and the mechanical withdrawal threshold (MWT) was quantified. Immunofluorescence was used to demonstrate alterations in microglial cells. The expression of miR-133a-3p was found to be decreased in lipopolysaccharide-induced BV-2 cells. The overexpression of miR-133a-3p was observed to inhibit the expression of IL-1β, IL-6, TNF-α and iNOS, which was attributed to a reduction in GCH1.Nevertheless, OE-GCH1 could partially reverse the downregulation by miR-133a-3p of the expression of inflammatory factors. In animal experiments, intrathecal injection of AVV-miR-133a-3p was observed to alleviate mechanical nociceptive abnormalities induced by activated microglia. Furthermore, miR-133a-3p ameliorated neuroinflammation in the spinal cord of chronic constriction injury rats. In summary, miR-133a-3p improves neuroinflammation and neuropathic pain by binding to GCH1. The binding of miR-133a-3p to GCH1 has been demonstrated to improve neuroinflammation and neuropathic pain.This insight will facilitate the development of new methods to effectively treat neuropathic pain.

MiR-200a-3p Attenuates Neuropathic Pain by Suppressing the Bromodomain-Containing Protein 3-Nuclear Factor-κB Pathway

MicroRNAs (miRNAs) have key roles in the pathological processes of neuropathic pain. Here, our aim was to elucidate the function of miR-200a-3p as well as its related regulatory mechanism in neuropathic pain. An animal model of neuropathic pain was established by chronic constriction injury (CCI) induction. The knockdown experiments are performed by injecting a lentiviral construct intrathecally. MiR-200a-3p and bromodomain-containing protein 3 (BRD3) expression in rat spinal cord was determined using RT-qPCR. The mechanical, thermal, and cold responses in animals were assessed at the indicated time after surgery. The levels of inflammatory cytokines in rat spinal cord were measured by ELISA. The changes in NF-κB signaling-related molecules in rat spinal cord were determined using western blot and immunofluorescence. MiR-200a-3p was underexpressed in CCI rats in a time-dependent manner. Overexpression of miR-200a-3p decreased mechanical hyperalgesia and thermal sensitivity to attenuate neuropathic pain in rats. BRD3 was targeted by miR-200a-3p. Additionally, downregulation of BRD3 inhibited neuropathic pain progression. Moreover, overexpression of BRD3 rescued the effect of miR-200a-3p on NF-κB signaling and neuropathic pain in CCI rats. MiR-200a-3p attenuates neuropathic pain via downregulating BRD3 to block NF-κB signaling.

What is associated with painful polyneuropathy? A cross-sectional analysis of symptoms and signs in patients with painful and painless polyneuropathy

ABSTRACT

It is still unclear how and why some patients develop painful and others painless polyneuropathy. The aim of this study was to identify multiple factors associated with painful polyneuropathies (NeuP). A total of 1181 patients of the multicenter DOLORISK database with painful (probable or definite NeuP) or painless (unlikely NeuP) probable or confirmed neuropathy were investigated clinically, with questionnaires and quantitative sensory testing. Multivariate logistic regression including all variables (demographics, medical history, psychological symptoms, personality items, pain-related worrying, life-style factors, as well as results from clinical examination and quantitative sensory testing) and machine learning was used for the identification of predictors and final risk prediction of painful neuropathy. Multivariate logistic regression demonstrated that severity and idiopathic etiology of neuropathy, presence of chronic pain in family, Patient-Reported Outcomes Measurement Information System Fatigue and Depression T-Score, as well as Pain Catastrophizing Scale total score are the most important features associated with the presence of pain in neuropathy. Machine learning (random forest) identified the same variables. Multivariate logistic regression archived an accuracy above 78%, random forest of 76%; thus, almost 4 out of 5 subjects can be classified correctly. This multicenter analysis shows that pain-related worrying, emotional well-being, and clinical phenotype are factors associated with painful (vs painless) neuropathy. Results may help in the future to identify patients at risk of developing painful neuropathy and identify consequences of pain in longitudinal studies.

Is chronic pain caused by central sensitization? A review and critical point of view

Chronic pain causes disability and loss of health worldwide. Yet, a mechanistic explanation for it is still missing. Frequently, neural phenomena, and among them, Central Sensitization (CS), is presented as causing chronic pain. This narrative review explores the evidence substantiating the relationship between CS and chronic pain: four expert researchers were divided in two independent teams that reviewed the available evidence. Three criteria were established for a study to demonstrate a causal relationship: (1) confirm presence of CS, (2) study chronic pain, and (3) test sufficiency or necessity of CS over chronic pain symptoms. No study met those criteria, failing to demonstrate that CS can cause chronic pain. Also, no evidence reporting the occurrence of CS in humans was found. Worryingly, pain assessments are often confounded with CS measures in the literature, omitting that the latter is a neurophysiological and not a perceptual phenomenon. Future research should avoid this misconception to directly interrogate what is the causal contribution of CS to chronic pain to better comprehend this problematic condition.

Diagnosis and Management of Neuropathic Breast Pain

Chronic postoperative pain after breast surgery is a significant concern, with studies indicating varying rates depending on the type of surgical procedure. The risk of developing neuropathic pain is notably increased with axillary lymph node dissection due to potential nerve injuries. Additionally, the method of breast reconstruction may influence postsurgical pain rates, with conflicting findings on the impact of reconstruction type. Recent advancements in techniques such as targeted muscle reinnervation, among others, show promise in addressing postoperative pain in these patients. As the prevalence of these procedures rises, future research is likely to focus on assessing and managing pain in this patient population. The development of patient-reported outcome measures specific to breast surgery pain can aid in clinical assessment and treatment planning. This review emphasizes the importance of gaining a deeper understanding of risk factors, nerve anatomy, and treatment options to enhance outcomes and quality of life for individuals undergoing breast surgery.

Neuropathic pain in spondyloarthritis: Decoding its prevalence, risk factors, and impact on disease activity

OBJECTIVES

This study aimed to evaluate the prevalence and characteristics of neuropathic pain in patients with various subtypes of spondyloarthritis (SpA), including axial SpA (axSpA), psoriatic arthritis (PsA), and undifferentiated peripheral SpA (p-SpA). Additionally, the study sought to identify potential risk factors associated with the presence or severity of neuropathic pain and to investigate its impact on clinical disease activity assessment.

METHODS

We conducted a cross-sectional study at two tertiary rheumatology centers, enrolling patients diagnosed with SpA. Data on demographic and clinical characteristics, comorbidities, and current therapies were collected. Neuropathic pain was assessed using the PainDETECT Questionnaire (PD-Q) and the Neuropathic Pain Symptom Inventory (NPSI). Statistical analyses included descriptive statistics, t-tests, and Pearson's correlations to evaluate the relationships between neuropathic pain scores and clinical disease activity indices.

RESULTS

The study included 177 patients. Of these, 22.2% had a PD-Q score ≥19, showing a high likelihood of neuropathic pain, while 64.9% scored ≤12, suggesting the absence of significant neuropathic components. The mean PD-Q score was 11.5 ± 10.1. Subgroup analyses showed that females had significantly higher scores for paroxysmal and evoked pain (p < 0.05), and obese patients had significantly higher scores across all NPSI subscores (p < 0.05). Moderate positive correlations were found between neuropathic pain scores and clinical disease activity indices, such as DAPSA (r = 0.46, p < 0.0001) and ASDAS-CRP (r = 0.42, p < 0.01).

CONCLUSIONS

Neuropathic pain is prevalent among patients with SpA and is significantly associated with disease activity assessments and management. This study highlights the importance of integrating neuropathic pain evaluation into the clinical assessment of SpA to tailor treatment approaches effectively and improve patient outcomes.

Procaine Regulates the STAT3/CCL5 Axis and Inhibits Microglia M1 Polarization to Alleviate Complete Freund's Adjuvant Rats Pain Behavior

Neuropathic pain (NP) caused by sciatic nerve injury can significantly impact the quality of life of patients. The M1 phenotype of microglia has been reported to promote the progression of NP. Procaine is a lipid-soluble local anesthetic drug that exerts narcotic analgesic effects. Nevertheless, the detailed effect of procaine in NP is not clear. In order to explore the role of procaine in the polarization of NP microglia, HAPI cells were exposed to LPS to polarize into M1 type. In addition, the number of the M1 phenotype of HAPI cells was assessed using flow cytometry. The binding site between CCL5 and STAT3 was explored using the dual luciferase assay. Furthermore, in vivo experiments were applied for testing the impact of procaine on NP. LPS significantly inhibited HAPI cell viability, which was reversed by procaine. Consistently, procaine alleviated LPS-induced upregulation of inflammatory factors. Additionally, it significantly inhibited HAPI cell M1 polarization induced by LPS. Meanwhile, overexpression of STAT3 was able to promote HAPI cells M1 polarization through binding with the CCL5 promoter region and activating the PI3K/Akt signaling. Procaine could alleviate the painful behavior of complete Freund's adjuvant (CFA) rats by modulating the STAT3/CCL5 axis and inhibiting microglia M1 polarization. In conclusion, procaine alleviated the painful behavior of CFA rats via regulating the STAT3/CCL5 axis and inhibiting microglia M1 polarization. Hence, the research might provide a novel agent for NP treatment.

Activation of MSK-1 exacerbates neuropathic pain through histone H3 phosphorylation in the rats' dorsal root ganglia and spinal dorsal horn

The exact mechanism underlies the development of neuropathic pain is not yet completely understood. Mitogen and stress-activated kinase 1 (MSK-1) is an important downstream kinase of the mitogen-activated protein kinase (MAPK). It has been extensively studied in the central nervous system, but whether MSK-1 is associated with the neuropathic pain remains elusive. In this experiment, Lumbar 5 spinal nerve ligation (SNL) was used to establish a neuropathic pain condition in the rats. Western blotting, qRT-PCR, immunohistochemistry, intrathecal catheterization and drugs delivery were evaluated to study the physiological responses of the animals. The results showed that SNL resulted in elevated phosphorylated MSK-1 (p-MSK-1) expression in the ipsilateral dorsal root ganglion (DRG) and the spinal dorsal horn in rats, while total MSK-1 (t-MSK-1) did not change significantly. Intrathecal injection of the MSK-1 inhibitor SB747651A partially reversed established neuropathic pain. Additionally, intrathecal administration of MSK-1 siRNA either preoperatively or 7 days postoperatively relieves the development and maintenance of pain, respectively. Meanwhile, the expression levels of p-H3S10, a downstream target of MSK-1, also displayed a significant increase after SNL. And these changes could be reversed by using MSK-1 siRNA. Collectively, the increase of MSK-1 induced by SNL participates in the development and maintenance of neuropathic pain by regulating the expression of p-H3S10 in DRG and spinal dorsal horn. Concentrating on MSK-1 may result in a novel approach to the treatment of neuropathic pain.

Spinal Nerve Axotomy: Effects on Ih In Vivo and HCNs in DRG Neurons

In vitro experiments performed on dissociated dorsal root ganglion (DRG) neurons suggest the involvement of the hyperpolarization-activated cation current (Ih) in enhancing neuronal excitability, potentially contributing to neuropathic pain. However, the more confirmative in vivo information about how nerve injury interacts with Ih is lacking. In this study, Ih was recorded in vivo using the dynamic single-electrode voltage clamp (dSEVC) technique on L5 DRG neurons of normal rats and those seven days after spinal nerve axotomy (SNA). Compared to normal rats, SNA unexpectedly inhibited the activity of Ih channels on A-fiber DRG neurons: (a) the Ih current magnitude, density, and conductance were consistently diminished; and (b) the Ih activation velocity was slowed and the voltage for Ih activation was hyperpolarized. The half-activation voltage (V0.5) exhibited a negative shift, and the time constant for Ih activation was prolonged across all test potentials, indicating the reduced availability of Ih after SNA. To further investigate the mechanisms of SNA on Ih, the underlying HCN channels and the correlated mRNA were quantified and compared. The mRNA expression level of HCN1-4 was uniformly enhanced after SNA, which might have contributed to the increased cytoplasmic HCN1 intensity observed in both medium- and large-sized DRG neurons. This finding contradicted the functional reduction of Ih after SNA. Surprisingly, the HCN labeling pattern was altered after SNA: the labeling area of HCN1 and HCN2 at the membranous ring region of the axotomized large neurons became significantly thinner or absent. We concluded that the diminished ring immunoreactivity for HCN1 and HCN2 correlated with a reduced availability of Ih channels, elucidating the observed decrease in Ih in axotomized A-fiber neurons.

Understanding neuropathic pain: the role of neurophysiological tests in unveiling underlying mechanisms

Neuropathic pain, arising from lesions of the somatosensory nervous system, presents with diverse symptoms including ongoing pain, paroxysmal pain, and provoked pain, usually accompanied by sensory deficits. Understanding the pathophysiological mechanisms behind these symptoms is crucial for targeted treatment strategies. Neurophysiological techniques such as nerve conduction studies, reflexes, and evoked potentials help elucidate these mechanisms by assessing large myelinated non-nociceptive fibres and small nociceptive fibres. This argumentative review highlights the importance of tailored neurophysiological assessments for improving our understanding of the pathophysiological mechanisms behind neuropathic pain symptoms.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Clinical pharmacology of neuropathic pain

This chapter aims to review the current pharmacological options for neuropathic pain treatment, their mechanisms of action, and future directions for clinical practice. Achieving pain relief in neuropathic pain conditions remains a challenge in clinical practice. The field of pharmacotherapy for neuropathic pain has encountered significant difficulties in translating substantial advances in our understanding of the underlying pathophysiological mechanisms into clinically effective therapies. This chapter presents the drugs recommended for the pharmacotherapy of neuropathic pain, based on the widely accepted treatment guidelines formulated by the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain. In addition to discussing how the evidence base is created as part of international consortia, the drugs are also examined in terms of their putative molecular mechanisms as well as pharmacological pleiotropy, i.e., their potential unspecific and multi-target effects resulting in modulation of neuronal hyperexcitability. The chapter closes with a discussion of potential future developments in the field.

Electroacupuncture alleviates neuropathic pain in a rat model of CCD via suppressing P2X3 expression in dorsal root ganglia

BACKGROUND

Sciatica and low back pain are prevalent clinical types of neuropathic pain that significantly impair patients' quality of life. Conventional therapies often lack effectiveness, making these conditions challenging to treat. Electroacupuncture (EA) is an effective physiotherapy for pain relief. Prior research has demonstrated a relationship between the frequency of neuropathic pain and the analgesic impact of EA stimulation. This work aimed to assess the analgesic effects of EA in a rat model of chronic compression of the dorsal root ganglion (CCD) and to understand the underlying processes.

METHODS

We established a rat CCD model to simulate sciatica and low back pain. EA was applied to rats with CCD at various frequencies (2 Hz, 100 Hz, and 2/100 Hz). The paw withdrawal threshold (PWT) was measured to assess analgesic effects. Additionally, protein levels of the purinergic receptor P2X3 (P2X3) and the expression of nociceptive neuronal markers were analyzed using immunohistochemistry and western blot (WB) techniques. The study also measured levels of proinflammatory cytokines TNF-α and IL-1β in the dorsal root ganglion (DRG). The involvement of P2X3 receptors was further investigated using the P2X3 agonist, α,β-methylene ATP (α,β-meATP).

RESULTS

CCD rats developed pronounced mechanical allodynia. EA stimulation at all tested frequencies produced analgesic effects, with 2/100 Hz showing superior efficacy compared to 2 Hz and 100 Hz. The expression of P2X3 was increased in ipsilateral DRG of CCD model rats. P2X3 were co-labeled with isolectin B4 (IB4) and transient receptor potential vanilloid (TRPV1), indicating their role in nociception. 2/100 Hz EA treatment significantly reduced mechanical allodynia and inhibited the overexpression of P2X3, TRPV1, substance P (SP), and calcitonin gene-related peptide (CGRP) in the ipsilateral DRG of CCD model rats. Additionally, EA reduced the levels of proinflammatory cytokines TNF-α and IL-1β in the ipsilateral DRG, indicating an anti-inflammatory effect. The P2X3 agonist α,β-me ATP attenuated the analgesic effect of 2/100 Hz EA in CCD rats. The WB and immunofluorescence results consistently demonstrated P2X3 inhibition contributed to the analgesic effects of 2/100 Hz EA on CCD-induced neuropathic pain.

CONCLUSIONS

Our findings suggest that 2/100 Hz EA alleviates neuropathic pain in rats by inhibiting the upregulation of P2X3 receptors in the ipsilateral DRG. This study backs up EA as a viable treatment option for sciatica and low back pain in clinical settings.

A Systematic Review of Dietary Lifestyle Interventions for Neuropathic Pain

Background/Objectives: Chronic severe neuropathic pain (NP) affects one in 10 individuals over the age of 30 in North America. Standard pharmacological interventions are associated with significant side effects and have limited effectiveness. Diets seeking to improve physiological health, support gut barrier integrity, and decrease systemic inflammation have recently emerged as powerful tools conferring neuroprotective and anti-inflammatory effects, potentially reducing the overall morbidity and mortality of multiple neurological and metabolic diseases. This systematic review aimed to synthesize the literature around NP outcomes following dietary interventions compared to routine standard of care. Methods: Following PRISMA guidelines, an initial search yielded 15,387 records after deduplication. Six interventional trials specifically assessing dietary interventions for neuropathic pain were included and analyzed. The dietary lifestyle interventions included low-fat plant-based, plant-based fasting-mimicking, low-calorie, potassium-reduced, gluten-free, and intermittent high-protein/Mediterranean diets. Results: The included studies described some statistically significant improvements in pain severity on objective quantitative sensory testing, electrophysiology, imaging, and subjective questionnaires. The overall risk of bias was moderate, with only one trial demonstrating a low risk of bias across all assessed domains. No serious adverse events were identified, and dietary interventions were generally well tolerated. Conclusions: The data collected and synthesized in this systematic review indicate that dietary lifestyle interventions may offer a low-risk, low-cost, low-tech option for chronic neuropathic pain management, potentially improving quality of life and reducing overall morbidity. However, given substantial variability across studies and a moderate risk of bias, further research is warranted to substantiate these findings.

Establishment of a Magnetically Controlled Scalable Nerve Injury Model

Animal models of peripheral nerve injury (PNI) serve as the fundamental basis for the investigations of nerve injury, regeneration, and neuropathic pain. The injury properties of such models, including the intensity and duration, significantly influence the subsequent pathological changes, pain development, and therapeutic efficacy. However, precise control over the intensity and duration of nerve injury remains challenging within existing animal models, thereby impeding accurate and comparative assessments of relevant cases. Here, a new model that provides quantitative and off-body controllable injury properties via a magnetically controlled clamp, is presented. The clamp can be implanted onto the rat sciatic nerve and exert varying degrees of compression under the control of an external magnetic field. It is demonstrated that this model can accurately simulate various degrees of pathology of human patients by adjusting the magnetic control and reveal specific pathological changes resulting from intensity heterogeneity that are challenging to detect previously. The controllability and quantifiability of this model may significantly reduce the uncertainty of central response and inter-experimenter variability, facilitating precise investigations into nerve injury, regeneration, and pain mechanisms.

The role of non-coding RNAs in neuropathic pain

Neuropathic pain (NPP) is a refractory pain syndrome, caused by damage or disease of the somatosensory nervous system and characterized by spontaneous pain, hyperalgesia, abnormal pain and sensory abnormality. Non-coding RNAs (ncRNAs), including microRNA (miRNA), long non-coding RNA (lncRNA), circular RNA (circRNA) and Piwi interacting RNA (piRNA), play a notable role in initiation and maintenance of NPP. In this review, we summarize the role of ncRNAs in NPP and their underlaying mechanism. Generally, ncRNAs are interacted with mRNA, protein or DNA to regulate the molecules and signals assciated with neuroinflammation, ion channels, neurotrophic factors and others, and then involved in the occurrence and development of NPP. Therefore, this review not only contributes to deepen our understanding of the pathophysiological mechanism of NPP, but also provides theoretical basis for the development of new therapy strategies for this disorder.

Smart Response Biomaterials for Pain Management

The intricate nature of pain classification and mechanism constantly affects the recovery of diseases and the well-being of patients. Key medical challenges persist in devising effective pain management strategies. Therefore, a comprehensive review of relevant methods and research advancements in pain management is conducted. This overview covers the main categorization of pain and its developmental mechanism, followed by a review of pertinent research and techniques for managing pain. These techniques include commonly prescribed medications, invasive procedures, and noninvasive physical therapy methods used in rehabilitation medicine. Additionally, for the first time, a systematic summary of the utilization of responsive biomaterials in pain management is provided, encompassing their response to physical stimuli such as ultrasound, magnetic fields, electric fields, light, and temperature, as well as changes in the physiological environment like reactive oxygen species (ROS) and pH. Even though the application of responsive biomaterials in pain management remains limited and at a fundamental level, recent years have seen the examination and debate of relevant research findings. These profound discussions aim to provide trends and directions for future research in pain management.

Prevalence of weakness and factors mediating discrepancy between reported and observed leg weakness in people with sciatica

PURPOSE

To establish the prevalence and agreement between reported and observed leg weakness in people with sciatica. To establish which factors mediate any identified difference between reported and observed leg weakness in people with sciatica.

METHODS

68 people with a clinical diagnosis of sciatica, records from spinal service, secondary care NHS Hospital, England, UK reviewed. Primary outcome measures were the sciatica bothersome index for reported leg weakness and the Medical Research Council scale for observed weakness. Agreement was established with Cohen's Kappa and intraclass correlation coefficient. Potential factors that may mediate a difference between reported and observed weakness included leg pain, sciatica bothersome index sensory subscale, age, hospital anxiety and depression subscale for anxiety.

RESULTS

85% of patients reported weakness but only 34% had observed weakness. Cohen's Kappa (0.066, 95% CI - 0.53, 0.186; p = 0.317)] and ICC 0.213 (95% CI - 0.26, 0.428, p = 0.040) both showed poor agreement between reported and observed weakness. The difference between reported and observed measures of weakness was mediated by the severity of leg pain (b = 0.281, p = 0.024) and age (b = 0.253, p = 0.042).

CONCLUSION

There is a high prevalence of reported leg weakness in people with sciatica, which is not reflected in observed clinical measures of weakness. Differences between reported and observed weakness may be driven by the severity of leg pain and age. Further work needs to establish whether other objective measures can detect patient reported weakness.

Paeoniflorin regulates microglia-astrocyte crosstalk, inhibits inflammatory response, and alleviates neuropathic pain through HSP90AA1/HMGB1 signaling pathway

Given the unclear, complex pathogenesis of neuropathic pain and the potential of paeoniflorin in relieving neuropathic pain, this study aimed to further clarify the therapeutic effect of paeoniflorin on neuropathic pain and to preliminarily explore the possible protective mechanisms of paeoniflorin. Chronic constrictive injury-induced Sprague Dawley rats and lipopolysaccharide-induced BV-2 cells were used for in vivo and in vitro experiments, respectively. The exosome uptake assay of mouse astrocytes (PKH-67 fluorescent labeling) and the mechanical nociceptive assay (the von Frey fibrous filaments) were performed. The effects of paeoniflorin and its downstream mechanisms on microglial and astrocyte activation, inflammation-associated proteins and exosome marker were determined. Paeoniflorin alleviated mechanical abnormal pain, decreased levels of ionized calcium binding adapter molecule-1 (Iba-1), glial fibrillary acidic protein, Heat Shock Protein 90 Alpha Family Class A Member 1 (HSP90AA1, inflammatory factor) and High Mobility Group Box 1 (HMGB1, inflammation-related protein), and inhibited neuronal apoptosis in chronic constrictive injury rats or lipopolysaccharide-induced BV-2 cells. However, these effects were offset by HSP90AA1 overexpression in lipopolysaccharide-induced BV-2 cells. Exosomes of BV-2 cells could be absorbed by mouse astrocytes. In addition, HSP90AA1 overexpression reversed the effects of paeoniflorin on HMGB1 expression and inflammatory factors and proteins in mouse astrocytes co-cultured with exosome. Collectively, paeoniflorin alleviates neuropathic pain and inhibits inflammatory responses in chronic constrictive injury by modulating microglia-astrocyte crosstalk through HSP90AA1/HMGB1 pathways, which further evidences the potential of paeoniflorin in the treatment of neuropathic pain.

Activation of TGR5 in the injured nerve site according to a prevention protocol mitigates partial sciatic nerve ligation-induced neuropathic pain by alleviating neuroinflammation

ABSTRACT

Neuropathic pain is a pervasive medical challenge currently lacking effective treatment options. Molecular changes at the site of peripheral nerve injury contribute to both peripheral and central sensitization, critical components of neuropathic pain. This study explores the role of the G-protein-coupled bile acid receptor (GPBAR1 or TGR5) in the peripheral mechanisms underlying neuropathic pain induced by partial sciatic nerve ligation in male mice. TGR5 was upregulated in the injured nerve site and predominantly colocalized with macrophages. Perisciatic nerve administration of the TGR5 agonist, INT-777 according to a prevention protocol (50 μg/μL daily from postoperative day [POD] 0 to POD6) provided sustained relief from mechanical allodynia and spontaneous pain, whereas the TGR5 antagonist, SBI-115 worsened neuropathic pain. Transcriptome sequencing linked the pain relief induced by TGR5 activation to reduced neuroinflammation, which was further evidenced by a decrease in myeloid cells and pro-inflammatory mediators (eg, CCL3, CXCL9, interleukin [IL]-6, and tumor necrosis factor [TNF] α) and an increase in CD86-CD206+ anti-inflammatory macrophages at POD7. Besides, myeloid-cell-specific TGR5 knockdown in the injured nerve site exacerbated both neuropathic pain and neuroinflammation, which was substantiated by bulk RNA-sequencing and upregulated expression levels of inflammatory mediators (including CCL3, CCL2, IL-6, TNF α, and IL-1β) and the increased number of monocytes/macrophages at POD7. Furthermore, the activation of microglia in the spinal cord on POD7 and POD14 was altered when TGR5 in the sciatic nerve was manipulated. Collectively, TGR5 activation in the injured nerve site mitigates neuropathic pain by reducing neuroinflammation, while TGR5 knockdown in myeloid cells worsens pain by enhancing neuroinflammation.

miR-30c-5p Gain and Loss of Function Modulate Sciatic Nerve Injury-Induced Nucleolar Stress Response in Dorsal Root Ganglia Neurons

Neuropathic pain is a prevalent and debilitating chronic syndrome that is often resistant to treatment. It frequently arises as a consequence of damage to first-order nociceptive neurons in the lumbar dorsal root ganglia (DRG), with chromatolysis being the primary neuropathological response following sciatic nerve injury (SNI). Nevertheless, the function of miRNAs in modulating this chromatolytic response in the context of neuropathic pain remains unexplored. Our previous research demonstrated that the intracisternal administration of a miR-30c mimic accelerates the development of neuropathic pain, whereas the inhibition of miR-30c prevents pain onset and reverses established allodynia. In the present study, we sought to elucidate the role of miR-30c-5p in the pathogenesis of neuropathic pain, with a particular focus on its impact on DRG neurons following SNI. The organisation and ultrastructural changes in DRG neurons, particularly in the protein synthesis machinery, nucleolus, and Cajal bodies (CBs), were analysed. The results demonstrated that the administration of a miR-30c-5p mimic exacerbates chromatolytic damage and nucleolar stress and induces CB depletion in DRG neurons following SNI, whereas the administration of a miR-30c-5p inhibitor alleviates these effects. We proposed that three essential cellular responses-nucleolar stress, CB depletion, and chromatolysis-are the pathological mechanisms in stressed DRG neurons underlying neuropathic pain. Moreover, miR-30c-5p inhibition has a neuroprotective effect by reducing the stress response in DRG neurons, which supports its potential as a therapeutic target for neuropathic pain management. This study emphasises the importance of miR-30c-5p in neuropathic pain pathogenesis and supports further exploration of miRNA-based treatments.

High-Fat Diet-Induced Blood-Brain Barrier Dysfunction: Impact on Allodynia and Motor Coordination in Rats

The associations among increased pain sensitivity, obesity, and systemic inflammation have not been described as related to BBB dysfunctions. To analyze the metabolic, behavioral, and inflammatory effects of a high-fat diet (HFD) and ultrastructural modifications in brain regions, we used an in vivo experimental model. Adult male Wistar rats were randomly assigned to one of two conditions, an ad libitum control group or an HFD (60%)-fed group, for eight weeks. At the end of the protocol, glucose and insulin tolerance tests were performed. Additionally, we analyzed the response to a normally innocuous mechanical stimulus and changes in motor coordination. At the end of the protocol, HFD-fed rats presented increased HOMA-IR and metabolic syndrome (MetS) prevalence. HFD-fed rats also developed an increased nociceptive response to mechanical stimuli and neurological injury, resulting in impaired motor function. Hypothalamus and cerebellum neurons from HFD-fed rats presented with nuclear swelling, an absence of nucleoli, and karyolysis. These results reveal that HFD consumption affects vital brain structures such as the cerebellum, hippocampus, and hypothalamus. This, in turn, could be producing neuronal damage, impairing cellular communication, and consequently altering motricity and pain sensitivity. Although direct evidence of a causal link between BBB dysfunction and sensory-motor changes was not observed, understanding the association uncovered in this study could lead to targeted therapeutic strategies.

Nicorandil antiallodynic activity in a model of neuropathic pain is associated with the activation of ATP-dependent potassium channels and opioidergic pathways, and reduced production of cytokines and neutrophils recruitment in paw, sciatic nerve, and dorsal root ganglia

BACKGROUND

Recently, we demonstrated that nicorandil inhibits mechanical allodynia induced by paclitaxel. In the present study, we evaluated the effect induced by nicorandil in a model of neuropathic pain induced by chronic constriction injury (CCI) in mice. We also investigated putative mechanisms underlying such an effect.

METHODS

CCI was induced by three ligatures of the left sciatic nerve. Mechanical allodynia was evaluated by measuring the paw withdrawal threshold with an electronic von Frey apparatus. Concentrations of cytokines and myeloperoxidase activity were determined in the paw tissue, sciatic nerve, and dorsal root ganglia (DRG).

RESULTS

Oral administration of two doses of nicorandil (150 mg/kg po), but not equimolar doses of nicotinamide or nicotinic acid, attenuated mechanical allodynia induced by CCI. Nicorandil activity was reduced by previous administration of glibenclamide (40 mg/kg) or naltrexone (5 mg/kg or 10 mg/kg). Two doses of nicorandil (150 mg/kg, po) reduced tumor necrosis factor-α, interleukin-1β and interleukin-6, but not CXCL-1, concentrations in the paw tissue of CCI mice. Two doses of nicorandil (150 mg/kg, po) reduced concentrations of all these mediators in the sciatic nerve and DRG. Two doses of nicorandil (150 mg/kg, po) also reduced the myeloperoxidase activity in the paw tissue, sciatic nerve, and DRG.

CONCLUSIONS

Nicorandil exhibits antiallodynic activity in a model of neuropathic pain induced by CCI. Inhibition of cytokines production and reduction of neutrophils recruitment in paw tissue, sciatic nerve, and DRG as well as activation of ATP-dependent potassium channels and opioidergic pathways, underlie nicorandil antiallodynic activity.

The efficacy of botulinum toxin in neuropathic pain: a systematic review

Introduction

Neuropathic pain (NP) is characterised as a lesion or disease directly affecting the somatosensory system. This study aims to analyse the efficacy of botulinum toxin type A (BT-A) in the treatment of neuropathic pain.

Methods

This systematic literature review, guided by PRISMA, applied the PICO strategy with the following criteria: (P = patients with neuropathic pain, I = botulinum toxin, C = placebo or active drug, and O = pain relief).

Results

Fourteen articles, all randomised controlled trials with a placebo control, were included in the review. A total of 645 patients were randomised, with 353 patients receiving treatment with botulinum toxin type A in doses ranging from 25U to 400U. The evaluated studies addressed trigeminal neuralgia, diabetic polyneuropathy, post-herpetic neuralgia, spinal cord injury, phantom limb pain, and peripheral neuropathic pain after trauma or surgery.

Conclusion

BT-A has emerged as a promising treatment for various origins of neuropathic pain. Therefore, future studies should adopt stricter criteria regarding dosage and routes of administration to ensure effective and consistent BT-A application.

Sigma-1 receptor targeting inhibits connexin 43 based intercellular communication in chronic neuropathic pain

BACKGROUND AND OBJECTIVE

Neuropathic pain is a chronic condition characterized by aberrant signaling within the somatosensory system, affecting millions of people worldwide with limited treatment options. Herein, we aim at investigating the potential of a sigma-1 receptor (σ1R) antagonist in managing neuropathic pain.

METHODS

A Chronic Constriction Injury (CCI) model was used to induce neuropathic pain. The potential of (+)-MR200 was evaluated following daily subcutaneous injections of the compound. Its mechanism of action was confirmed by administration of a well-known σ1R agonist, PRE084.

RESULTS

(+)-MR200 demonstrated efficacy in protecting neurons from damage and alleviating pain hypersensitivity in CCI model. Our results suggest that (+)-MR200 reduced the activation of astrocytes and microglia, cells known to contribute to the neuroinflammatory process, suggesting that (+)-MR200 may not only address pain symptoms but also tackle the underlying cellular mechanism involved. Furthermore, (+)-MR200 treatment normalized levels of the gap junction (GJ)-forming protein connexin 43 (Cx43), suggesting a reduction in harmful intercellular communication that could fuel the chronicity of pain.

CONCLUSIONS

This approach could offer a neuroprotective strategy for managing neuropathic pain, addressing both pain symptoms and cellular processes driving the condition. Understanding the dynamics of σ1R expression and function in neuropathic pain is crucial for clinical intervention.

Urinary kallikrein reverses neuropathic pain by inhibiting ectopic neural discharges, neural inflammation and oxidative stress

Background

Neuropathic pain is a refractory disease and badly impacts the lives of patients. Urinary kallikrein (UK) acted as a glycoprotein has been discovered to play a pivotal role in neuroprotection. However, the regulatory impacts and correlative pathways of UK in the progression of neuropathic pain remain dimness.

Methods

The chronic constriction injury (CCI) rat model was firstly established to mimic neuropathic pain. The withdrawal threshold was measured through the Von Frey test. The levels of TNF-α, IL-1β and IL-6 were determined through ELISA. The levels of ROS, GSH, SOD and GSH-Px were examined through the commercial kits. The ectopic discharges were assessed. The protein expressions were inspected through western blot.

Results

It was demonstrated that withdrawal threshold was reduced in CCI rat model, but this change was reversed after UK treatment, indicating that UK relieved mechanical allodynia. Moreover, UK alleviated the inflammatory response through reducing TNF-α, IL-1β and IL-6 levels. It was uncovered that oxidative stress was strengthened in CCI rat model, but this impact was restrained after UK treatment. Additionally, UK suppressed ectopic discharge. At last, it was proved that UK triggered the Nrf2/ARE signaling pathway in CCI rat model.

Conclusion

This study manifested that UK reversed neuropathic pain by inhibiting ectopic neural pathways, neural pathways and oxidation via the Nrf2/ARE pathway. This study may offer useful proofs the regulatory functions of UK in the cure of neuropathic pain.

Role of l -arginine/nitric oxide/cyclic GMP/K ATP channel signaling pathway and opioid receptors in the antinociceptive effect of rutin in mice

The l -arginine ( l -Arg)/nitric oxide/cyclic GMP/potassium channel (K ATP ) pathway and opioid receptors are known to play critical roles in pain perception and the antinociceptive effects of various compounds. While there is evidence suggesting that the analgesic effects of rutin may involve nitric oxide modulation, the direct link between rutin and the l -Arg/nitric oxide/cyclic GMP/K ATP pathway in the context of pain modulation requires further investigation. The antinociceptive effect of rutin was studied in male NMRI mice using the formalin test. To investigate the role of the l -Arg/nitric oxide/cyclic GMP/K ATP pathway and opioid receptors, the mice were pretreated intraperitoneally with different substances. These substances included l -Arg (a precursor of nitric oxide), S-nitroso- N -acetylpenicillamine (SNAP, a nitric oxide donor), N(gamma)-nitro- l -arginine methyl ester (L-NAME, an inhibitor of nitric oxide synthase), sildenafil (an inhibitor of phosphodiesterase enzyme), glibenclamide (a K ATP channel blocker), and naloxone (an opioid receptor antagonist). All pretreatments were administered 20 min before the administration of the most effective dose of rutin. Based on our investigation, it was found that rutin exhibited a dose-dependent antinociceptive effect. The administration of SNAP enhanced the analgesic effects of rutin during both the initial and secondary phases. Moreover, L-NAME, naloxone, and glibenclamide reduced the analgesic effects of rutin in both the primary and secondary phases. In conclusion, rutin holds significant value as a flavonoid with analgesic properties, and its analgesic effect is directly mediated through the nitric oxide/cyclic GMP/K ATP channel pathway.

Predictors for severe persisting pain in rheumatoid arthritis are associated with pain origin and appraisal of pain

OBJECTIVES

To determine the proportion of patients with rheumatoid arthritis (RA) with severe persisting pain and to identify predictive factors despite treatment-controlled disease activity.

METHODS

This prospective multicentre study included outpatients with RA scheduled for escalation of anti-inflammatory treatment due to active disease and severe pain (Disease Activity Score 28 (DAS28)>3.2 and Visual Analogue Scale (VAS)>50). At week 24, patients were stratified into reference group (DAS28 improvement>1.2 or DAS28≤3.2 and VAS pain score<50), non-responders (DAS28 improvement≤1.2 and DAS28>3.2, regardless of VAS pain score) and persisting pain group (DAS28 improvement>1.2 or DAS28≤3.2 and VAS pain score≥50). The former two subgroups ended the study at week 24. The latter continued until week 48. Demographic data, DAS28-C reactive protein, VAS for pain, painDETECT Questionnaire (PD-Q) to identify neuropathic pain (NeP) and the Pain Catastrophising Scale were assessed and tested for relation to persisting pain.

RESULTS

Of 567 patients, 337 (59.4%) were classified as reference group, 102 (18.0%) as non-responders and 128 (22.6%) as patients with persisting pain. 21 (8.8%) responders, 28 (35.0%) non-responders and 27 (26.5%) persisting pain patients tested positive for NeP at week 24. Pain catastrophising (p=0.002) and number of tender joints (p=0.004) were positively associated with persisting pain at week 24. Baseline PD-Q was not related to subsequent persisting pain.

CONCLUSIONS

Persisting and non-nociceptive pain occur frequently in RA. Besides the potential involvement of NeP, pain catastrophising and a higher number of tender joints coincide with persisting pain.

Transcranial direct current stimulation in the management of pain in oncology patients. A systematic review and meta-analysis with meta-regression of randomized controlled trials

PURPOSE

To evaluate the efficacy of transcranial direct current stimulation (tDCS) in pain management in subjects with oncologic process.

MATERIAL AND METHODS

Several databases were searched in December 2023. Randomized Controlled Trials that evaluated the application of tDCS on pain in adults with oncologic process were selected. Random-effects meta-analysis with 95%CI were used to quantify the change scores in pain between tDCS and control groups.

RESULTS

Six trials with 482 participants were included. There were significant differences in favor of tDCS in pain intensity in surgical oncology patients compared to sham stimulation (p < 0.001). Non-surgical patients showed no significant effect. Meta-regression analysis in this group of patients showed that the timing of the evaluation moderated the effect of tDCS on pain (p= .042), with longer time after tDCS being associated with greater pain reduction.

CONCLUSIONS

The application of a-tDCS for at least 20 min, with a current density higher than 0.057 mA/cm2, applied over M1, left DLPFC, or the insula area, between 2-5 sessions appears to be an effective and safe treatment of pain in surgical oncology patients compared to sham. The tDCS appears to be more effective for high-intensity pain, and in the long term.

High-frequency terahertz stimulation alleviates neuropathic pain by inhibiting the pyramidal neuron activity in the anterior cingulate cortex of mice

Neuropathic pain (NP) is caused by a lesion or disease of the somatosensory system and is characterized by abnormal hypersensitivity to stimuli and nociceptive responses to non-noxious stimuli, affecting approximately 7-10% of the general population. However, current first-line drugs like non-steroidal anti-inflammatory agents and opioids have limitations, including dose-limiting side effects, dependence, and tolerability issues. Therefore, developing new interventions for the management of NP is urgent. In this study, we discovered that the high-frequency terahertz stimulation (HFTS) at approximately 36 THz effectively alleviates NP symptoms in mice with spared nerve injury. Computational simulation suggests that the frequency resonates with the carbonyl group in the filter region of Kv1.2 channels, facilitating the translocation of potassium ions. In vivo and in vitro results demonstrate that HFTS reduces the excitability of pyramidal neurons in the anterior cingulate cortex likely through enhancing the voltage-gated K+ and also the leak K+ conductance. This research presents a novel optical intervention strategy with terahertz waves for the treatment of NP and holds promising applications in other nervous system diseases.

Assessing Gender Differences in Neuropathic Pain Management: Findings from a Real-Life Clinical Cross-Sectional Observational Study

Introduction: Neuropathic pain is defined as pain induced by a lesion or disease of the somatosensory nervous system. Pharmacological and non-pharmacological treatments are frequently employed. In the current clinical investigation, we assessed the effects of sex on the safety and effectiveness of medications used to treat neuropathic pain. Methods: We conducted a prospective analysis between 1 February 2021 and 20 April 2024, involving patients with neuropathic pain referred to the Ambulatory of Pain Medicine of "Renato Dulbecco" University Hospital in Catanzaro (Calabria, Italy). Patients over 18 years old with signs of neuropathic pain (Douleur Neuropathique en 4 questionnaire ≥ 4) were included. Exclusion criteria comprised patients with Alzheimer's disease; patients with nociplastic or nociceptive pain; and patients with neoplasms. Patients with fewer than two accesses to ambulatory care were excluded, as were those who did not sign the informed consent. Clinical data were collected from each enrolled patient and subsequently analyzed, considering clinical outcomes. Sex and gender differences in efficacy were estimated using multivariate linear modeling and propensity-score matching. Results: During the study, 531 patients were screened, and 174 were enrolled (33.5%, mean age 61.5 ± 13.1; 64 males and 110 females, mean age 60.6 ± 13.4 and 61.96 ± 13.0) in accordance with the inclusion and exclusion criteria. Only minor differences in treatment prescription were observed based on age, body mass index, and comorbidities. Smoking, sex, educational level, and body mass index did not induce a significant change in pain perception. Males required slightly higher, though not significantly, doses of drugs for pain control than females. The treatment was not significantly more effective for females than for males. Females did not exhibit a significantly lower number of adverse drug reactions compared to males. Conclusions: The current study found that there are no appreciable differences between the sexes when it comes to the treatment of neuropathic pain.

Risk Factors for Postoperative Donor Site Complications in Radial Forearm Free Flaps

Background and Objectives: The radial forearm free flap (RFFF) is the most commonly used flap for head and neck reconstruction. However, complications at the donor site are its major drawbacks. We aimed to identify the patient comorbidities and factors that predict donor site complications after RFFF. Materials and Methods: A retrospective chart review of consecutive patients who underwent RFFF reconstruction for head and neck cancer between 2015 and 2022 was performed. Demographic variables, clinical processes, and postoperative complications were assessed. All variables were analyzed using univariate and multivariate analyses. Results: Sixty-seven patients underwent RFFF reconstruction, and all received a split-thickness skin graft at the donor site. Twenty-five patients experienced delayed skin graft healing, whereas nine experienced sensory changes at the donor site. Hypertension and age had statistically significant negative effects on wound healing. The incidence of hand swelling was related to graft size, and the occurrence of paresthesia was significantly higher in diabetic patients and significantly lower in those with acellular dermal matrix (ADM). Conclusions: Patients with hypertension had a higher risk of prolonged wound healing after RFFF than their normotensive patients. Clinicians should pay particular attention to wound healing strategies in patients with hypertension. Additionally, better neuropathy care is recommended to achieve sensory recovery after RFFF in patients with diabetes. Using a skin graft with ADM could be a method to alleviate neurological symptoms.

The dual role of TRPV1 in peripheral neuropathic pain: pain switches caused by its sensitization or desensitization

The transient receptor potential vanilloid 1 (TRPV1) channel plays a dual role in peripheral neuropathic pain (NeuP) by acting as a "pain switch" through its sensitization and desensitization. Hyperalgesia, commonly resulting from tissue injury or inflammation, involves the sensitization of TRPV1 channels, which modulates sensory transmission from primary afferent nociceptors to spinal dorsal horn neurons. In chemotherapy-induced peripheral neuropathy (CIPN), TRPV1 is implicated in neuropathic pain mechanisms due to its interaction with ion channels, neurotransmitter signaling, and oxidative stress. Sensitization of TRPV1 in dorsal root ganglion neurons contributes to CIPN development, and inhibition of TRPV1 channels can reduce chemotherapy-induced mechanical hypersensitivity. In diabetic peripheral neuropathy (DPN), TRPV1 is involved in pain modulation through pathways including reactive oxygen species and cytokine production. TRPV1's interaction with TRPA1 channels further influences chronic pain onset and progression. Therapeutically, capsaicin, a TRPV1 agonist, can induce analgesia through receptor desensitization, while TRPV1 antagonists and siRNA targeting TRPV1 show promise in preclinical studies. Cannabinoid modulation of TRPV1 provides another potential pathway for alleviating neuropathic pain. This review summarizes recent preclinical research on TRPV1 in association with peripheral NeuP.

Current Treatment Methods for Charcot-Marie-Tooth Diseases

Charcot-Marie-Tooth (CMT) disease, the most common inherited neuromuscular disorder, exhibits a wide phenotypic range, genetic heterogeneity, and a variable disease course. The diverse molecular genetic mechanisms of CMT were discovered over the past three decades with the development of molecular biology and gene sequencing technologies. These methods have brought new options for CMT reclassification and led to an exciting era of treatment target discovery for this incurable disease. Currently, there are no approved disease management methods that can fully cure patients with CMT, and rehabilitation, orthotics, and surgery are the only available treatments to ameliorate symptoms. Considerable research attention has been given to disease-modifying therapies, including gene silencing, gene addition, and gene editing, but most treatments that reach clinical trials are drug treatments, while currently, only gene therapies for CMT2S have reached the clinical trial stage. In this review, we highlight the pathogenic mechanisms and therapeutic investigations of different subtypes of CMT, and promising therapeutic approaches are also discussed.

Amitriptyline nanoparticle repositioning prolongs the anti-allodynic effect of enhanced microglia targeting

Aim: Amitriptyline (AMI) has been used to treat neuropathic pain. However, the clinical outcomes remain unsatisfactory, presumably due to a limited understanding of the underlying molecular mechanisms. Here, we investigated a drug repositioning strategy using a low-dose of AMI encapsulated in poly (D, L lactic-co-glycolic acid) (PLGA) nanoparticles (AMI NPs) for neuropathic pain, since PLGA nanoparticles are known to enhance delivery to microglia.Methods: We evaluated the anti-allodynic effects of AMI and AMI NPs on neuropathic pain by assessing behaviors and inflammatory responses in a rat model of spinal nerve ligation (SNL). While the anti-allodynic effect of AMI (30 μg) drug injection on SNL-induced neuropathic pain persisted for 12 h, AMI NPs significantly alleviated mechanical allodynia for 3 days.Results: Histological and cytokine analyses showed AMI NPs facilitated the reduction of microglial activation and pro-inflammatory mediators in the spinal dorsal horn. This study suggests that AMI NPs can provide a sustained anti-allodynic effect by enhancing the targeting of microglia and regulating the release of pro-inflammatory cytokines from activated microglia.Conclusion: Our findings suggest that the use of microglial-targeted NPs continuously releasing AMI (2 μg) as a drug repositioning strategy offers long-term anti-allodynic effects.

Quantitative sensory testing and chronic pain syndromes: a cross-sectional study from TwinsUK

OBJECTIVE

The chronic pain syndromes (CPS) include syndromes such as chronic widespread pain (CWP), dry eye disease (DED) and irritable bowel syndrome (IBS). Highly prevalent and lacking pathognomonic biomarkers, the CPS are known to cluster in individuals in part due to their genetic overlap, but patient diagnosis can be difficult. The success of quantitative sensory testing (QST) and inflammatory biomarkers as phenotyping tools in conditions such as painful neuropathies warrant their investigation in CPS. We aimed to examine whether individual QST modalities and candidate inflammatory markers were associated with CWP, DED or IBS in a large, highly phenotyped population sample.

DESIGN

Cross-sectional study.

SETTING

Community-dwelling cohort.

PARTICIPANTS

Twins from the TwinsUK cohort PRIMARY AND SECONDARY OUTCOME MEASURES: We compared 10 QST modalities, measured in participants with and without a CWP diagnosis between 2007 and 2012. We investigated whether inflammatory markers measured by Olink were associated with CWP, including interleukin-6 (IL-6), IL-8, IL-10, monocyte chemoattractant protein-1 and tumour necrosis factor. All analyses were repeated in DED and IBS with correction for multiple testing.

RESULTS

In N=3022 twins (95.8% women), no association was identified between individual QST modalities and CPS diagnoses (CWP, DED and IBS). Analyses of candidate inflammatory marker levels and CPS diagnoses in n=1368 twins also failed to meet statistical significance.

CONCLUSION

Our findings in a large population cohort suggest a lack of true association between singular QST modalities or candidate inflammatory markers and CPS.

Exploring the high-quality ingredients and mechanisms of Da Chuanxiong Formula in the treatment of neuropathic pain based on network pharmacology, molecular docking, and molecular dynamics simulation

Da Chuanxiong Formula (DCXF) is a traditional herbal prescription used for pain management. It consists of Chuanxiong Rhizoma (CR) and Gastrodiae Rhizoma (GR). Despite its long history of use, the underlying therapeutic mechanism of DCXF remains insufficiently understood. Therefore, in this study, key target genes were obtained through network pharmacology research methods and molecular docking techniques, including transient receptor potential vanilloid 1 (TRPV1), adenosine A2a receptor (ADORA2A), nuclear receptor subfamily 3 group C member 1 (NR3C1), and protein kinase C beta (PRKCB). Molecular dynamics simulations demonstrated the favorable binding between all four key genes and their corresponding compounds. Notably, chronic constriction injury (CCI) treatment resulted in a significant decrease in mechanical threshold and thermal latency period for rat foot contraction, which was ameliorated upon administration of DCXF. Furthermore, real-time quantitative reverse transcription PCR (RT-qPCR) and western blot (WB) analyses indicated an upregulation of TRPV1, ADORA2A, NR3C1, and PRKCB expression in the rat dorsal root ganglion following CCI, which was attenuated by treatment with DCXF. The expressions of inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6), in the rat dorsal root ganglion were assessed using ELISA, confirming consistent trends with the aforementioned findings. The results of this study offer a promising theoretical foundation for the utilization of DCXF in the treatment of neuropathic pain (NP).

Long non-coding RNA Snhg16 Lessens Ozone Curative Effect on Chronic Constriction Injury mice via microRNA-719/SCN1A axis

We investigated the function and molecular mechanism of long non-coding RNA (lncRNA) small nucleolar RNA host gene 16 (Snhg16) in modifying ozone treatment for neuropathic pain (NP) in a mouse model of chronic constriction injury (CCI). Pain-related behavioral responses were evaluated using paw withdrawal threshold (PWT), paw lifting number (PLN), and paw withdrawal latency (PWL) tests. Interleukin (IL)-1β, IL-10, IL-6, and tumor necrosis factor-alpha (TNF-α) were measured by ELISA and qRT-PCR to evaluate neuroinflammation. qRT-PCR was performed to detect expressions of Snhg16, microRNA (miR)-719, sodium voltage-gated channel alpha subunit 1 (SCN1A), and inflammatory factors. Bioinformatics, dual-luciferase reporter assay, and RNA pull-down verified the underlying molecular mechanisms. Snhg16 expression increased in CCI mice. Snhg16 overexpression retarded the curative effect of ozone and induced NP. miR-719 was sponged by Snhg16. SCN1A was a target of miR-719. Inhibition of miR-719 markedly reversed the effects of Snhg16 on pain-related behavioral responses and neuroinflammation. Upregulation of SCN1A partly abrogated the effects of elevated miR-719 levels on the occurrence of NP. The findings demonstrate that lncRNA Snhg16 promotes NP progression in CCI mice by binding to miR-719 to increase SCN1A expression. The Snhg16/miR-719/SCN1A axis may influence the curative effects of ozone therapy in treating NP.

Mirogabalin as a Therapeutic Option for Neuropathic Pain Emerging Post-endodontic Treatment: A Two-Case Report

INTRODUCTION

Occlusal and percussion pain may manifest occasionally following endodontic treatment, influencing retreatment decisions. Two cases of periapical neuropathic pain, classified as post-traumatic trigeminal neuropathic pain according to the International Classification of Orofacial Pain, are presented. Although mirogabalin is effective in managing neuropathic pain, there is a lack of clinical reports on its use for occasional post-traumatic trigeminal neuropathic pain after endodontic treatment. These cases highlight clinical symptoms and successful treatment with mirogabalin for post-traumatic trigeminal neuropathic pain after endodontic treatment, providing clinicians a "take-away" lesson for improving patient condition.

METHODS

The patients, referred by their primary dentist due to postendodontic abnormal pain, found no relief with antibiotics or nonsteroidal anti-inflammatory drugs. Although no findings including swelling or periapical radiolucency were observed around the tooth, they experienced occlusal and percussion pain. Local anesthetic testing showed that the pain originated from the peripheral area around the tooth rather than from central sensitization. Dental radiography and cone-beam computed tomography revealed no abnormal findings. Root canal retreatment was performed by a specialist in endodontic treatment. Although endodontic retreatment drastically decreased visual analog scale pain score, pain persisted. Based on the International Classification of Orofacial Pain criteria, diseases other than post-traumatic trigeminal neuropathic pain were excluded. Mirogabalin (10 mg/d) was prescribed once daily before bedtime.

RESULTS

Visual analog scale scores gradually and drastically decreased 2 weeks after mirogabalin therapy. Several months later, no recurrence of postendodontic pain was observed after tapering off and discontinuing mirogabalin.

CONCLUSIONS

These findings suggest the possibility of a new treatment method for post-traumatic trigeminal neuropathic pain after endodontic treatment.

Efficacy of Desvenlafaxine in Reducing Migraine Frequency and Severity: A Retrospective Study

Background: Migraine is characterized by sudden acute episodes of pain, with a global prevalence of 18% among all age groups. It is the second leading cause of years lived with disability worldwide. Prophylactic treatment is important in managing migraine; however, its efficacy and safety are debated. This study aimed to evaluate the efficacy of desvenlafaxine in female patients with migraine. Methods: We conducted a retrospective observational case study involving 10 women diagnosed with migraine who were treated with desvenlafaxine. We measured the number of migraine days per month, average headache duration in minutes, headache severity using a visual analog scale, use of acute medications, and frequency of acute medication use per week. Results: Desvenlafaxine significantly reduced the number of migraine days from 14.70 ± 3.68 at baseline to 2.50 ± 2.50 at follow-up (p < 0.05). The average headache duration dropped from 131.25 ± 32.81 min to 52.50 ± 44.64 min. Headache severity scores improved from 6.80 ± 1.49 at baseline to 0.80 ± 0.92 at follow up, the frequency of acute medication use per week reduced from 3.30 ± 1.49 at baseline to 0.80 ± 0.92, and the frequency of acute medication use decreased from 3.30 ± 1.49 times per week to 0.80 ± 0.92. Conclusions: Desvenlafaxine shows potential as an effective prophylactic therapy for migraine. Larger-scale studies are necessary to further explore its benefits.

Right-to-left shunt-associated brain functional changes in migraine: evidences from a resting-state FMRI study

Background

Migraine, a neurological condition perpetually under investigation, remains shrouded in mystery regarding its underlying causes. While a potential link to Right-to-Left Shunt (RLS) has been postulated, the exact nature of this association remains elusive, necessitating further exploration.

Methods

The amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo) and functional connectivity (FC) were employed to investigate functional segregation and functional integration across distinct brain regions. Graph theory-based network analysis was utilized to assess functional networks in migraine patients with RLS. Pearson correlation analysis further explored the relationship between RLS severity and various functional metrics.

Results

Compared with migraine patients without RLS, patients with RLS exhibited a significant increase in the ALFF within left middle occipital and superior occipital gyrus; In migraine patients with RLS, significantly reduced brain functional connectivity was found, including the connectivity between default mode network and visual network, ventral attention network, as well as the intra-functional connectivity of somatomotor network and its connection with the limbic network, and also the connectivity between the left rolandic operculum and the right middle cingulate gyrus. Notably, a significantly enhanced functional connectivity between the frontoparietal network and the ventral attention network was found in migraine with RLS; Patients with RLS displayed higher values of the normalized clustering coefficient and greater betweenness centrality in specific regions, including the left precuneus, right insula, and right inferior temporal gyrus. Additionally, these patients displayed a diminished nodal degree in the occipital lobe and reduced nodal efficiency within the fusiform gyrus; Further, the study found positive correlations between ALFF in the temporal lobes, thalamus, left middle occipital, and superior occipital gyrus and RLS severity. Conversely, negative correlations emerged between ALFF in the right inferior frontal gyrus, middle frontal gyrus, and insula and RLS grading. Finally, the study identified a positive correlation between angular gyrus betweenness centrality and RLS severity.

Conclusion

RLS-associated brain functional alterations in migraine consisted of local brain regions, connectivity, and networks involved in pain conduction and regulation did exist in migraine with RLS.

Efficacy of Botulinum Type A Injection for the Treatment of Postherpetic Neuralgia and Pruritus Persisting for More Than Four Years-A Case Report

Background: Postherpetic neuralgia (PHN) and postherpetic pruritus (PHP) are common complications of shingles that affect patients' quality of life. PHN and PHP can be managed using various medications and interventional procedures; however, complications persisting for at least six months may hamper recovery. Subcutaneous injections of botulinum toxin type A (BTX-A) can control persistent PHN and PHP. Case presentation: A 71-year-old man presented at our hospital with itching and pain. He had been diagnosed with shingles in the ophthalmic branch of the trigeminal nerve one year previously. As the pain and itching persisted despite medication, a supraorbital nerve block, Gasserian ganglion block, epidural nerve block, and radiofrequency thermocoagulation were performed. A subcutaneous injection of BTX-A was administered into the ophthalmic area of the trigeminal nerve three years after the initial presentation. A decrease of >80% in pain and itching was reported after the injection; however, the left eyelid drooped and the eyeball shifted downward and outward immediately after the injection. No deterioration in vision or pupil dilation was observed, and almost complete resolution of these symptoms occurred spontaneously three months after the injection. Pain and itching continued to improve without further side-effects until six months after the injection. Conclusions: The subcutaneous injection of BTX-A may be an alternative treatment option for chronic and refractory neurological diseases such as PHN and PHP, which persist for four years and are resistant to conventional treatments. Nevertheless, care must be taken to minimize the risk of ptosis.

NIR-Remote Selectively Triggered Buprenorphine Hydrochloride Release from Microneedle Patches for the Treatment of Neuropathic Pain

Neuropathic pain is a prevalent form of intermittent chronic pain, affecting approximately 7-10% of the global population. However, the current clinical administration methods, such as injection and oral administration, are mostly one-time administration, which cannot achieve accurate control of pain degree and drug dose. Herein, we developed near-infrared (NIR) light-responsive microneedle patches (MNPs) to spatiotemporally control the drug dose released to treat neuropathic pain according to the onset state. The mechanism of action utilizes upconversion nanoparticles to convert NIR light into visible and ultraviolet light. This conversion triggers the rapid rotation of the azobenzene molecular motor in the mesoporous material, enabling the on-demand controlled release of a drug dose. Additionally, MNs are used to overcome the barrier of the stratum corneum in a minimally invasive and painless manner, effectively promoting the transdermal penetration of drug molecules. The effectiveness of these patches has been demonstrated through significant results. Upon exposure to NIR light for five consecutive cycles, with each cycle lasting 30 s, the patches achieved a precise release of 318 μg of medication. In a mouse model, maximum pain relief was observed within 1 h of one cycle of NIR light exposure, with the effects lasting up to 6 h. The same level of precise treatment efficacy was maintained for subsequent pain episodes with similar light exposure. The NIR-controlled drugs precision-released MNPs provide a novel paradigm for the treatment of intermittent neuropathic pain.

Examination of the effects of vitexin and vitexin-loaded solid lipid nanoparticles on neuropathic pain and possible mechanisms of action

This research aims to investigate the possible antiallodynic and antihyperalgesic effects of pure vitexin and vitexin-loaded solid lipid nanoparticles (SLN) on neuropathic pain and the pathways mediating these effects. Chronic constriction nerve injury was induced in female rats, and the effects of vitexin at the doses of 5, 10, 20, 40 mg/kg were evaluated. Ketanserin, ondansetron, WAY-100635, yohimbine and bicuculin, which are antagonists of receptors on pain pathways. were used to examine the mechanisms of the effects of vitexin. Pure vitexin exhibited antiallodynic activity at all administered doses, whereas antihyperalgesic activity was not observed at 5 mg/kg vitexin dose. SLN formulation was prepared with 5 mg/kg vitexin, the lowest dose. Vitexin-loaded formulation significantly increased antiallodynic and antihyperalgesic effects. Ondansetron, WAY-100635, yohimbine, and bicuculine antagonized the antiallodynic and antihyperalgesic effects of vitexin. So, it was concluded that serotonin (5-hydroxtryptamine, 5-HT) receptor subtypes 5-HT3 and 5-HT1A, alpha-2 adrenergic, and γ-Aminobutyric acid type A (GABA-A) receptors are involved in the antiallodynic and antihyperalgesic activity of vitexin. In conclusion, vitexin and vitexin-loaded formulation have the potential for clinical use in neuropathic pain management, and different pain pathways contributed to this effect. And also, it is thought that vitexin-loaded SLN formulation is more effective than pure vitexin, which will provide an advantage in treatment.

Rethinking neck-related arm pain: hypothetical clinical scenarios to differentiate the underlying IASP-defined pain mechanisms

Neck-related arm pain is frequently encountered in clinical settings, yet its underlying pain mechanisms remain elusive. While such pain radiating from the neck to the arm is often attributed to injuries or diseases of the nervous system (neuropathic pain), it can also arise from nociceptive (referred) or nociplastic sources. Regrettably, patients exhibiting this specific pain distribution are frequently diagnosed with varying terms, including 'cervicobrachialgia', 'cervicobrachial neuralgia', 'cervicobrachial pain syndrome', and 'cervical radiculopathy'. The ambiguity surrounding these diagnostic labels complicates the clinical reasoning process. It is imperative for clinicians to discern and comprehend the dominant pain mechanism. Three distinct hypothetical clinical scenarios depict patients with almost identical pain distribution but divergent dominant pain mechanisms. Within these scenarios, both subjective and objective examinations are employed to elucidate the dominant pain mechanism associated with neck-related arm pain: nociceptive, neuropathic, and nociplastic. Furthermore, clinicians must remain aware that the dominant pain mechanism can evolve over time.