Neuropathic Pain: Mechanisms, Sex Differences, and Potential Therapies for a Global Problem

Global, Regional, and National Epidemiology of Opioid Use Disorder Among Adolescents and Young Adults, 1990-2019

PURPOSE

Opioid use disorder (OUD) is a growing public health crisis. However, no study to date has systematically evaluated the burden of OUD among adolescents and young adults (AYAs). We aimed to report the global level and trends of OUD burden among AYAs.

METHODS

Data were obtained from the Global Burden of Disease study 2019, which was conducted from 1990 to 2019 in 204 countries. AYAs were defined as individuals aged 15-39 years, and the study period was 1990-2019. The burden of OUD was evaluated in terms of case numbers and age-standardized rates per 100,000 population.

RESULTS

In 2019, there were 2,396,734 incident cases, 14,502,031 prevalent cases, 43,447 deaths, and 8,651,931 disability-adjusted life years of OUD among AYAs globally. High-income North America had the greatest regional burden, with the United States having the highest burden nationally. From 1990 to 2019, age-standardized incidence rate (ASIR), age-standardized prevalence rate, age-standardized mortality rate, and age-standardized disability-adjusted life years rate (ASDR) showed upward trends, with average annual percentage change of 0.62, 0.81, 1.55, and 1.01, respectively. Despite the burden of OUD was higher in males than in females, the increment in ASIR was greater in females than in males after 2014. Nationally, OUD burden showed increasing trends in ASIR, age-standardized prevalence rate, and ASDR across 150+ countries, with the United States experiencing the greatest increase in age-standardized mortality rate and ASDR. Meanwhile, there was a positive correlation between sociodemographic index and OUD burden, with higher sociodemographic index associated with a higher burden of OUD in 2019.

DISCUSSION

OUD in AYAs is a major global public health issue, and the burden of OUD is increasing. This alarming trend underscores the urgent need for comprehensive prevention strategies, targeted interventions, and effective treatment options tailored to younger populations.

ACVR1 drives neuropathic pain by regulating NLRP3-Induced neuronal pyroptosis through the p38 and Smad1/5/8 pathways

BACKGROUND

Neuropathic pain is characterized by sustained pain hypersensitivity caused by nerve injury. The molecular mechanisms underlying this condition remain poorly understood. This study aims to elucidate the role of ACVR1 and its downstream pathways in mediating neuropathic pain through neuronal pyroptosis and neuroinflammation.

METHODS

A spared nerve injury (SNI) model was established both in male and female mouse to induce neuropathic pain. Behavioral tests, Western blot, PCR, and immunofluorescence were used to assess the expression of ACVR1, p-Smad1/5/8, p-p38, and pyroptosis-related proteins (NLRP3, Caspase-1, and GSDMD-N). ACVR1, p38, and Smad1/5/8 were pharmacologically inhibited to evaluate their roles in neuropathic pain and pyroptosis.

RESULTS

Behavioral analysis confirmed successful SNI model establishment, marked by reduced paw withdrawal thresholds (PWT). Protein and mRNA expression analysis revealed significant upregulation of ACVR1, p-Smad1/5/8, and p-p38 in the spinal cord, particularly in neurons. Furthermore, SNI enhanced pyroptosis-related protein expression, including NLRP3, Caspase-1, GSDMD-N, IL-1β and IL-18. Inhibition of ACVR1 alleviated mechanical allodynia, reduced neuronal pyroptosis, and decreased serum IL-1β and IL-18 levels. Similarly, p38 inhibition mitigated NLRP3-induced pyroptosis without altering ACVR1 expression. In contrast, Smad1/5/8 inhibition by DMH-1 effectively reduced pyroptosis and inflammation via NLRP3 but had no effect on p38 phosphorylation. Combined p38 and Smad1/5/8 pathway inhibition synergistically decreased pyroptosis-related protein expression, highlighting their interactive roles in ACVR1-mediated neuropathic pain.

CONCLUSION

These findings suggest that ACVR1 exacerbates neuropathic pain by activating neuronal pyroptosis and neuroinflammation via the p38 and Smad1/5/8 pathways. Targeting ACVR1 and its downstream signaling pathways may offer novel therapeutic strategies for neuropathic pain.

Analgesic Mechanism of Emodin in Neuropathic Pain Through Inhibiting P2X4 Purinoceptor Signaling

Neuropathic pain (NeP) is a most intractable health problem due to its unsatisfactory treatment effect. Emodin, a natural anthraquinone derivative extracted from Rheum palmatum and Polygonam cuspidatum, exhibits the analgesic effects in various NeP models. However, the underlying mechanisms remain elusive. This study employed whole transcriptome sequencing and metabolomics to elucidate emodin's analgesic mechanism in the spinal cord of chronic constriction injury (CCI) rats. Fifteen-day emodin treatment reversed hyperalgesia and deficit of sciatic nerve function induced by CCI and significantly decreased the concentrations of TNF-α, IL- 1β, IL- 6, IL- 18, and BDNF in the spinal cord of the CCI rats. Transcriptome sequencing revealed altered expression of 85 mRNAs in the spinal cord of emodin-treated and CCI rats, with 53 mRNAs upregulated and 32 mRNAs downregulated. Notably, seven genes (P2RX4, CXCL10, ALOX5, SCN4 A, AURKB, AQP9) overlapped with established NeP targets. Untargeted metabolomic analyses identified 67 significantly altered metabolites (46 upregulated, 32 downregulated) in the spinal cord upon emodin treatment. Integrative analysis highlighted shared pathways between differentially expressed genes and metabolites, including arachidonic acid metabolism, cAMP signaling pathway, and Fc epsilon RI signaling pathway. Western blot and immunofluorescent staining further proved the decreased expression of IBA1, P2X4R, p38 MAPK, p-p38 MAPK, NF-κB, p-NF-κB, and TNF-α, IL- 1β. In conclusion, this study demonstrated that emodin played the analgesic effect in the CCI rats, possibly through suppression of P2X4 purinoceptor signaling in spinal microglia, suggesting a potential therapeutic target for NeP.

RIN1 regulates ferroptosis and nociceptive perception via the Nrf2/HO-1 pathway in chronic constriction injury

Neuropathic pain (NP) has been a major focus of clinical research for decades. This study investigates the function of RAS- and RAB-interacting protein 1 (RIN1) in modulating NP and explore the involvement of the nuclear factor-2 erythroid factor-2 (Nrf2) and heme oxygenase 1 (HO-1) pathway in this context. A rat model of CCI was generated. The presence of mechanical and thermal hypersensitivity, as well as spontaneous pain behaviors, confirmed the successful modeling. Intrathecal injection of AAV9-shRNA targeting RIN1 attenuated nociception, reduced microglial activation in the L4-L6 spinal cord, and decreased the expression levels of c-Fos, GFAP, and IBA-1. Furthermore, the levels of NMDAR, PKC, Src, enzymes linked to neural hypersensitivity, was inhibited by RIN1 silencing. RIN1 was found to interact to Nrf2 protein, inhibiting its nuclear translocation and transcriptional activation. The RIN1 knockdown activated the Nrf2/HO-1 pathway, reducing oxidative stress and ROS levels in the spinal cord, while increasing the expression of Nrf2-target genes, including Nqo1, Gclc, and Gclm, which are key players in cellular antioxidant defense. Additionally, ferroptosis, characterized by mitochondrial damage and elevated Fe2+ levels, was reduced in RIN1 knockdown rats. Treatment with Nrf2 or HO-1 activators improved pain sensitivity and reduced inflammation, while inhibition of Nrf2 activity attenuated the protective effects of RIN1 silencing. In vitro, RIN1 silencing reduced activation LPS-treated of mouse BV2 microglial cells, leading to a decrease in the secretion of pro-inflammatory cytokines (IL-6, TNFα, and IL-1β), reduced microglial ferroptosis, and decreased the cytotoxicity of BV2 cells to co-cultured neurons. These effects were mediated by the Nrf2 pathway, as Nrf2 antagonism reversed the effects of RIN1 knockdown. These findings suggest that RIN1 plays a critical role in spinal cord hypersensitivity and pain perception by inhibiting the Nrf2/HO-1 pathway, influencing neuroinflammation and ferroptosis. Targeting RIN1 could provide a potential therapeutic strategy for managing NP and neuroinflammation.

Distribution and morphology of CGRP-IR axons in flat-mounts of whole male and female mouse atria

Due to a lack of anatomical studies utilizing female specimens, it is unclear how the nociceptive innervation of the mouse heart compares between sexes. To address this, flat-mount preparations of the left and right atria of male and female mice were immunohistochemically labeled for calcitonin gene-related peptide (CGRP, a common marker for nociceptive nerves), imaged, and digitally traced in high quality. The results show that 1) A network of CGRP-IR axons densely innervated the right and left atria. Large nerve bundle entry points and regional concentration of CGRP-IR axons were similar in both sexes. 2) The detailed distribution of CGRP-IR bundles and axons were digitized and mapped using Arivis (Zeiss) Vision4D software. The general distribution patterns in male and female mice were comparable to one another. 3) The density of CGRP-IR axons in the sinoatrial (SA) node region (Male: 0.0258 μm/μm2 ± 0.003; Female: 0.0347 μm/μm2 ± 0.006) and atrioventricular (AV) node region (Male: 0.0138 μm/μm2 ± 0.001; Female: 0.0228 μm/μm2 ± 0.005) were not found to be significantly different. 4) The distance between adjacent varicosities in the auricle (Male: 4.049 μm ± 0.3; Female: 4.241 μm ± 0.34), SA node region (Male: 2.812 μm ± 0.21; Female: 3.352 μm ± 0.29), and AV node region (Male: 2.999 μm ± 0.3; Female: 3.526 μm ± 0.26) were not significantly different between sexes. 5) Likewise, maximum varicosity diameters in the auricle (Male: 0.5356 μm ± 0.04; Female: 0.5274 μm ± 0.03), SA node region (Male: 0.4714 μm ± 0.02; Female: 0.5634 μm ± 0.04), and AV node region (Male: 0.5103 μm ± 0.02; Female: 0.5103 μm ± 0.03) between male and female specimens were similar. Our data shows the comparable nature of the CGRP-IR axons in mouse atria in both sexes. Moreover, this is the first time we employed flat-mount preparations of whole atria to analyze the distribution of CGRP-IR axons in male and female mice.

Hippocampal P2X4 receptor induces type 1 diabetes rats with neuropathic pain through microglial-derived neuroinflammation and neuronal damage

Diabetic neuropathic pain (DNP) is a serious complication of diabetes, characterized by spontaneous burning pain, hyperalgesia or allodynia, and is associated with severely reduced quality of life. The purinergic P2X4 receptor (P2X4R) plays an essential role in neuropathic pain. In this study, we investigated the roles of hippocampal P2X4R in type 1 diabetes (T1D) rats with DNP. The reduced body weight, elevated blood glucose, and reduced mechanical withdrawal threshold (MWT) were manifested in DNP rats. The increased hippocampal P2X4R enhanced the release of TNF-α, IL-1β, IL-6, which may be related to activated microglia, thereby inducing the development of DNP, and these changes were attenuated by P2X4R antagonist. Our findings suggest that in the state of T1D, hippocampal P2X4R was elevated and enhanced reactive microglia, thereby aggravating the release of pro-inflammatory cytokines and neuronal damage to aggravate hyperalgesia.

Trends in Mixed Pain Research Over Three Decades (1993-2024): A Bibliometric Analysis

BACKGROUND

The term "mixed pain" is frequently used in clinical practice to describe the coexistence of nociceptive, neuropathic, and nociplastic pain mechanisms. However, its inconsistent use and lack of a formal definition warrant further investigation. This bibliometric analysis aims to explore publication trends, research networks, and key themes in mixed pain literature.

METHODS

A bibliometric analysis was conducted using the Web of Science Core Collection. The search was performed in February 2024, with journal rankings obtained from Journal Citation Reports™ 2022 (Clarivate Analytics). Extracted data included publication trends, citation analysis, co-authorship networks, and keyword mapping.

RESULTS

A total of 229 publications were identified, demonstrating an increasing trend in both publication volume and citations. Most studies were published in high-ranking Q1 journals as research (77%) and review articles (19%). The USA (21%), Italy (15%), and Germany (12%) were the leading contributors, yet global collaboration was weak, with limited co-authorship connections except within the USA. The keyword analysis revealed five major research clusters, with "neuropathic pain," "management," and "quality of life" emerging as central themes.

CONCLUSIONS

Despite the progressive increase in mixed pain articles in highly ranked journals, this bibliometric analysis highlighted the absence of a well-structured collaborative network among authors and a lack of clear connections between keywords. Given the critical clinical implications of mixed pain, further high-quality studies on this topic and enhanced international collaborations are recommended.

Divergent sex-specific pannexin-1 mechanisms in microglia and T cells underlie neuropathic pain

Chronic pain is a leading cause of disability, affecting more women than men. Different immune cells contribute to this sexual divergence, but the mechanisms, especially in females, are not well defined. We show that pannexin-1 (Panx1) channels on microglia and T cells differentially cause mechanical allodynia, a debilitating symptom of neuropathic pain. In male rodents, Panx1 drives vascular endothelial growth factor-A (VEGF-A) release from microglia. Cell-specific knockdown of microglial Panx1 or pharmacological blockade of the VEGF receptor attenuated allodynia in nerve-injured males. In females, nerve injury increased spinal CD8+ T cells and leptin levels. Leptin release from female-derived CD8+ T cells was Panx1 dependent, and intrathecal leptin-neutralizing antibody injection sex-specifically reversed allodynia. Adoptive transfer of female-derived CD8+ T cells caused robust allodynia, which was prevented by a leptin-neutralizing antibody or leptin small interfering RNA (siRNA) knockdown. Panx1-targeted approaches may alleviate neuropathic pain in both sexes, while T cell- and leptin-directed treatments could have sex-dependent benefits for women.

Roles of non-coding RNAs and exosomal non-coding RNAs, particularly microRNAs, long non-coding RNAs, and circular RNAs, in pathogenic mechanisms behind chronic pain: A review

Chronic pain is a significant public health concern that diminishes patients' quality of life and imposes considerable socioeconomic costs. Effective pharmacological treatments for ongoing pain are limited. Recent studies have indicated that various models of chronic pain-such as neuropathic pain, inflammatory pain, and pain associated with cancer-have abnormal levels of long noncoding RNAs (lncRNAs). Research has explored how these abnormal lncRNAs influence the activation of inflammatory cytokines, microRNAs, and other related molecules, which are crucial to the development of chronic pain. These findings suggest that these lncRNAs are vital in chronic pain mechanisms within the spinal cord and dorsal root ganglion following nerve injury. Additionally, exosomes, which can traverse the blood-brain barrier, are considered carriers of noncoding RNAs (ncRNAs) from neurons to systemic circulation. This study aims to summarize the existing knowledge on ncRNAs and exosomal ncRNAs in the context of chronic pain, highlighting potential biomarkers for diagnosis, regulatory roles in disease progression, therapeutic strategies, and clinical implications.

Emerging role of macrophages in neuropathic pain

Neuropathic pain is a complex syndrome caused by injury to the neurons, which causes persistent hypersensitivity and considerable inconvenience to the patient's whole life. Over the past two decades, the interaction between immune cells and neurons has been proven to play a crucial role in the development of neuropathic pain. Increasing studies have indicated the important role of macrophages for neuroinflammation and have shed light on the underlying molecular and cellular mechanisms. In addition, novel therapeutic methods targeting macrophages are springing up, which provide more options in our clinical treatment. Herein, we reviewed the characteristics of peripheral macrophages and their function in neuropathic pain, with the aim of better understanding how these cells contribute to pathological processes and paving the way for therapeutic approaches.

Translational potential statement

This review provides a comprehensive overview of the mechanisms underlying the interplay between the macrophages and nervous system during the progression of nerve injury. Additionally, it compiles existing intervention strategies targeting macrophages for the treatment of neuropathic pain. This information offers valuable insights for researchers seeking to address the challenge of this intractable pain.

Epigenomic landscape of the human dorsal root ganglion: sex differences and transcriptional regulation of nociceptive genes

ABSTRACT

Cell states are influenced by the regulation of gene expression orchestrated by transcription factors capable of binding to accessible DNA regions. To uncover if sex differences exist in chromatin accessibility in the human dorsal root ganglion (hDRG), where nociceptive neurons innervating the body are found, we performed bulk and spatial assays for transposase-accessible chromatin technology followed by sequencing (ATAC-seq) from organ donors without a history of chronic pain. Using bulk ATAC-seq, we detected abundant sex differences in the hDRG. In women, differentially accessible regions (DARs) mapped mostly to the X chromosome, whereas in men, they mapped to autosomal genes. Hormone-responsive transcription factor binding motifs such as EGR1/3 were abundant within DARs in women, while JUN, FOS, and other activating protein 1 factor motifs were enriched in men, suggesting a higher activation state of cells compared with women. These observations were consistent with spatial ATAC-seq data. Furthermore, we validated that EGR1 expression is biased to female hDRG using RNAscope. In neurons, spatial ATAC-seq revealed higher chromatin accessibility in GABAergic, glutamatergic, and interferon-related genes in women and in Ca2+-signaling-related genes in men. Strikingly, XIST, responsible for inactivating 1 X chromosome by compacting it and maintaining at the periphery of the nucleus, was found to be highly dispersed in female neuronal nuclei. This is likely related to the higher chromatin accessibility in X in female hDRG neurons observed using both ATAC-seq approaches. We have documented baseline epigenomic sex differences in the hDRG which provide important descriptive information to test future hypotheses.

Role of Exercise on Neuropathic Pain in Preclinical Models: Perspectives for Neuroglia

The benefits of exercise on neuropathic pain (NP) have been demonstrated in numerous studies. In recent studies, inflammation, neurotrophins, neurotransmitters, and endogenous opioids are considered as the main mechanisms. However, the role of exercise in alleviating NP remains unclear. Neuroglia, widely distributed in both the central and peripheral nervous systems, perform functions such as support, repair, immune response, and maintenance of normal neuronal activity. A large number of studies have shown that neuroglia play an important role in the occurrence and development of NP, and exercise can alleviate NP by regulating neuroglia. This article reviewed the involvement of neuroglia in the development of NP and their role in the exercise treatment of NP, intending to provide a theoretical basis for the exercise treatment strategy of NP.

TNF-α Enhanced Activity of Sympathetic Neurons in Superior Cervical Ganglion to Promote Chronic Sleep Deprivation-Related Hyperalgesia

The mechanisms underlying the association between sleep deprivation (SD) and hyperalgesia remain incompletely understood. In this study, the Modified Horizontal Platform Method was employed to induce chronic SD. Neuropathic pain was induced using chronic constriction injury of the sciatic nerve. Pain-like behaviors were assessed through measurements of mechanical allodynia and thermal hyperalgesia, while gait analysis was used to evaluate motor function. Immunofluorescence and western blot analyses were conducted to examine the expression of TNF-α, Iba-1, TH, neurons and c-Fos. Apoptosis was assessed using TUNEL staining. To explore anatomical connections, anterograde and retrograde tracer viruses were injected into the superior cervical ganglion (SCG) and the spinal cord, respectively. Local injection of 6-OHDA was used to ablate sympathetic neurons in the SCG, and R-7050 was administrated to block the TNF-α receptor. We found that chronic SD induced hyperalgesia in both normal and neuropathic pain model, accompanied by significant infiltration of microglia in the dorsal horn. TH expression and apoptotic cells were increased in the SCG following chronic SD. Viral tracer results demonstrated the existence of anatomical connections between the SCG and the spinal cord. Ablation of sympathetic innervation improved pain-like behaviors and reduced microglia, without affecting movement. Furthermore, chronic SD led to increased expression of TNF-α in sympathetic neurons, which was associated with heightened SCG activity. Blocking the TNF-α receptor ameliorated pain-like behaviors, decreased microglia, reduced apoptosis, lowered SCG activity. In conclusion, TNF-α enhanced the activity of sympathetic neurons in the SCG, promoting hyperalgesia related to chronic SD.

Neuropathic Symptoms and Frequency of Chronic Pain in an International Online Sample of Individuals with Sub-Acute and Chronic Stroke

Background/Objectives: Chronic pain is common following a stroke and is associated with increased disability. Yet, little is known about the chronic pain experience in the stroke population. This study aimed to identify and explore the features and neuropathic symptoms of chronic pain in individuals with longstanding stroke. Methods: This observational study utilized an online survey that was developed for individuals who have had a stroke (>3 months). Data sought included participant demographics, medical history, and details of the stroke(s). Participants who reported experiencing chronic pain completed the Numerical Rating Scale for Pain, the Neuropathic Pain Symptom Inventory, and body maps to indicate region(s) of pain. Results: A total of 533 individuals with longstanding stroke participated. Chronic pain was reported as being experienced by 60% of participants and was more frequently experienced by individuals who reported being female (p = 0.002). Moderate or severe pain intensity was commonly reported (mean = 5.98, SD = 1.89). Individuals with chronic pain post-stroke reported a range of neuropathic symptoms rather than a common pain experience, with combinations of spontaneous, paroxysmal, and evoked pains in addition to pain associated with paraesthesia/dysaesthesia. Pain involving the upper limb was the most common region (shoulder 39%, hand and forearm 38%), followed by the lower limb (foot 30%, leg 29%). Having multiple strokes was associated with a higher frequency of chronic pain (p = 0.01), as was peripheral vascular disease (p < 0.001) and lipid disorders (p = 0.001). Conclusions: These findings highlight the varied nature of chronic pain experienced by individuals following a stroke, while also detailing stroke and medical history associated with chronic pain. It builds on existing knowledge of chronic pain post-stroke and provides new insight into the neuropathic symptoms experienced. This knowledge has the potential to assist in the development of tailored interventions based on addressing pain symptomatology and health literacy.

Sex differences in the antinociceptive effect of codeine and its peripheral but not central metabolism in adult mice

Codeine is a natural opiate extracted from opium poppy (Papaver somniferum) and used to alleviate mild to moderate pain. The analgesic effect of this molecule results from its metabolism into morphine which is an agonist of the mu opioid receptor. Morphine's major metabolite morphine-3-glucuronide induces both thermal and mechanical hypersensitivies while codeine-6-glucuronide has been proposed to be antinociceptive. However, sex differences in codeine antinociceptive effect and pharmacokinetics were barely studied. To this purpose, we injected male and female mice with codeine (2.5, 5, 10, 20 and 40 mg/kg) and thermal hypersensitivity was assessed 30 min after injection using the Tail Immersion Test. Moreover, both peripheral and central metabolism of codeine were evaluated respectively in the blood or pain-related brain structures in the central nervous system. The amounts of codeine and its metabolites were quantified using the isotopic dilution method by liquid chromatography coupled to a mass spectrometer. Our results show that codeine induces a greater antinociceptive effect in males than females mice independently of the estrous cycle. Moreover, major sex differences were found in the peripheral metabolism of this molecule, with higher amounts of pronociceptive morphine-3-glucuronide and less antinociceptive codeine-6-glucuronide in females than in males. Concerning the central metabolism of codeine, we did not find significant sex differences in pain-related brain structures. Collectively, these findings support a greater codeine antinociceptive effect in males than females in mice. These sex differences could be influenced by a higher peripheral metabolism of this molecule in female mice rather than central metabolism.

Qisheng wan decoction alleviates the inflammation of CCI rats via TRP channels

ETHNOPHARMACOLOGICAL RELEVANCE

Qisheng wan decoction (QWD), a traditional Chinese medicine, has promising potential anti-inflammatory effects against neuropathic pain (NP). However, its valid ingredients and specific anti-inflammatory mechanisms are still unclear.

AIM OF THE STUDY

This study aimed to identify the active ingredients of QWD responsible for its anti-inflammatory effect by combining liquid chromatography with network pharmacology, and to explore its anti-inflammatory mechanism by chronic constriction injury (CCI) model rats.

MATERIALS AND METHODS

The UHPLC-Q Exactive Orbitrap-MS technique was used to identify the active ingredients of QWD. The potential ingredients of QWD, which targeted to the pathways of treating NP, were performed by network pharmacology, molecular docking and molecular dynamics simulations. After CCI rats-induced NP model operation, QWD (5.6 g/kg/d, 11.2 g/kg/d, 22.4 g/kg/d) and Pregabalin (10 g/kg/d) as positive controls, were administered to the rats for 7 days. The behaviors of the different groups were tested at 0, 1, 3, 5, 7, 12 days, respectively. And the inflammatory factor including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) was detected by ELISA. Meantime, the inflammation of the sciatic nerve was evaluated by the hematoxylin-eosin staining. Ionized calcium-binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) were detected by immunohistochemistry. Moreover, the expressions of TRPA1, TRPV1, TRPV2, TRPV3, TRPV4, TRPM8, and P38 mitogen-activated protein kinase (MAPK) were tested by RT-PCR, Western blot, and immunohistochemistry.

RESULTS

After screening by the liquid chromatography and network pharmacology approach, seventy ingredients of QWD were identified, and seven core targets including oncogene tyrosine-protein kinase (SRC), mitogen-activated protein kinase 3 (MAPK3), signal transducer and activator of transcription 1 (STAT1), protein-serine-threonine kinase 1 (AKT1), mitogen-activated protein kinase 1 (MAPK1), TNF-α, and IL-6 were confirmed. Six active ingredients exhibited binding energies less than -5 kcal/mol, and the complexes were structurally stable within 50 ns. Pathway analysis indicated that transient receptor potential (TRP) channels were mainly responsible for anti-inflammatory mediator regulation. Compared with the CCI group, the behavioral tests showed that QWD-L, QWD-M, and QWD-H group alleviated mechanical, thermal and cold hyperalgesia (p < 0.05). HE staining results found out QWD-L, QWD-M, and QWD-H group decreased the inflammation of the sciatic nerve (p < 0.05). Similarly, compared with the CCI group, the serum level of TNF-α and IL-6 of QWD groups decreased conformably (p < 0.05). This reduction was downtrend with the inhibition of Iba-1, GFAP, and the TRP channel signaling pathway and p38 MAPK.

CONCLUSIONS

This study provides a primary investigation of the composition of QWD for its anti-inflammation effect and its molecular mechanism in CCI model rats. And this therapeutic efficacy of QWD was achieved by decreasing the inflammation. QWD also inhibited the level TNF-α and IL-6 and decreasing the activation of Iba-1 and GFAP in glia. And this anti-inflammation mechanism involved in inhibiting the TRPA1, TRPV1, TRPV2, TRPV4, and TRPM8 and p38 MAPK signaling pathways. These findings provide a scientific and theoretical basis for the prevention and treatment of NP with QWD.

Astaxanthin alleviates spinal nerve ligation-induced neuropathic pain by modulating propionic acid levels

BACKGROUND

The treatment for neuropathic pain (NP) remains challenging. Propionic acid (PA), derived from gut microbiota, is a promising therapeutic target for NP. However, the precise role of PA in NP is nebulous; further, whether Astaxanthin (AST), which exhibits analgesic properties, is involved in regulating PA in NP remains unknown.

OBJECTIVE

We explored the role of PA in NP development and whether AST relieves NP by modulating PA levels; further, we identified novel therapeutic strategies for NP.

METHODS

The L4 spinal nerve was ligated (SNL) to establish a mouse model of NP. The composition of the gut microbiota was analysed through 16S rRNA sequencing. PA in faeces, blood, and spinal cord were quantitatively measured using gas chromatography-tandem mass spectrometry (GC-MS). Network pharmacology was used to identify therapeutic targets of PA for NP. The interactions between PA and its targets were analysed using molecular docking, molecular dynamics simulations, quantitative real-time polymerase chain reaction, and western blot.

RESULTS

Analysis of faecal samples from SNL mice showed dysregulation in the gut microbiota and alterations in PA metabolism-related enzymes. GC-MS analysis revealed reduced PA levels in faeces, serum, and spinal cord tissue. Network pharmacology and molecular docking identified therapeutic targets shared between PA and NP, primarily related to inflammation regulation. Treatment with exogenous PA supplementation alleviated pain and inhibited inflammation in the intestine and spinal cord, including NLRP3 inflammasome and NF-κB activation.

CONCLUSION

AST treatment modulated the gut microbiota, elevated PA levels, reduced inflammation, and strengthened the intestinal barrier, exerting an analgesic effect. Enhancing the levels of PA is a potentially novel mechanism underlying the analgesic effects of AST.

Calcium signaling at the interface between astrocytes and brain inflammation

Astrocytes are the most prevalent glial cells of the brain and mediate vital roles in the development and function of the nervous system. Astrocytes, along with microglia, also play key roles in initiating inflammatory immune responses following brain injury, stress, or disease-related triggers. While these glial immune responses help contain and resolve cellular damage to the brain, dysregulation of astrocyte activity can in some cases amplify inflammation and worsen impact on neural tissue. As nonexcitable cells, astrocytes excitability is regulated primarily by Ca2+ signals that control key functions such as gene expression, release of inflammatory mediators, and cell metabolism. In this review, we examine the molecular and functional architecture of Ca2+ signaling networks in astrocytes and their impact on astrocyte effector functions involved in inflammation and immunity.

Spinal AT1R contributes to neuroinflammation and neuropathic pain via NOX2-dependent redox signaling in microglia

Microglia-mediated neuroinflammation demonstrates a crucial act in the progression of neuropathic pain. Oxidative damage induced by reactive oxygen species (ROS) derived from NADPH oxidase (NOX) in microglia drives proinflammatory microglia activation. Recent evidence points to the central renin angiotensin system (RAS) is involved in oxidative stress and neuroinflammation, with the angiotensin converting enzyme/angiotensin II/angiotensin receptor-1 (ACE/Ang II/AT1R) axis promoting inflammation through increased ROS production, counteracted by the ACE2/Ang (1-7)/Mas receptor (MasR) axis. While interventions targeting spinal AT1R have been shown to alleviate nociceptive hypersensitivity; yet the mechanisms remain elusive. Here, we discovered that spared nerve injury (SNI)-induced mechanical allodynia in rats were associated with M1-like microglia activation, oxidative stress and overactivity of ACE/Ang II/AT1R axis in the spinal cord. Increased AT1R and NOX2 expression were observed in activated dorsal horn microglia following SNI. Blockade of AT1R with losartan potassium (LOP) suppressed NOX2-mediated oxidative stress, and promoted a shift in microglia from the proinflammatory M1 phenotype to the anti-inflammatory M2 phenotype in LPS-treated BV-2 cells. Additionally, NOX2 overexpression triggered the activation of the high-mobility group box 1/nuclear factor-kappa B (HMGB1/NF-κB) signaling pathway. Intrathecal administration of LOP effectively inhibited SNI-induced NOX2 overactivation in microglia and suppressed the HMGB1/NF-kB pathway, reducing oxidative stress and shifting the microglia polarization from M1 to M2 in the spinal cord, thereby attenuating neuroinflammation and pain hypersensitivity. Collectively, these findings underscore the neuroimmune-modulating effects of spinal AT1R in neuropathic pain, highlighting the regulation of redox homeostasis in microglia via a NOX2 dependent mechanism.

Persistent changes in the dorsal root ganglion nociceptor translatome governs hyperalgesic priming in mice: roles of GPR88 and Meteorin

ABSTRACT

Hyperalgesic priming is a model system that has been widely used to understand plasticity in painful stimulus-detecting sensory neurons, called nociceptors. A key feature of this model system is that following priming, stimuli that do not normally cause hyperalgesia now readily provoke this state. We hypothesized that hyperalgesic priming occurs because of reorganization of translation of mRNA in nociceptors. To test this hypothesis, we used paclitaxel treatment as the priming stimulus and translating ribosome affinity purification to measure persistent changes in mRNA translation in Nav1.8+ nociceptors. Translating ribosome affinity purification sequencing revealed 161 genes with persistently altered mRNA translation in the primed state. Among these genes, we identified Gpr88 as upregulated and Metrn as downregulated. To provide functional evidence for these changes in hyperalgesic priming in a related priming model, we used the interleukin-6 priming model. A GPR88 agonist injection into the paw had no effect in naive mice but caused mechanical hypersensitivity and grimacing responses in female primed mice. Systemic Meteorin treatment in primed mice completely reversed established hyperalgesic priming mechanical hypersensitivity and grimacing responses to prostaglandin E2 in female mice. Our work demonstrates that altered nociceptor translatomes are causative in producing hyperalgesic priming in multiple models in female mice.

Macrophage depletion restores the DRG microenvironment and prevents axon degeneration in bortezomib-induced neuropathy

Peripheral neuropathy is a common and debilitating side effect of the chemotherapeutic bortezomib (BTZ). To explore the mechanisms underlying BTZ-induced neuropathy (BIPN), we developed a mouse model that replicates the route of administration and approximates the prolonged BTZ exposure experienced by patients. We find that male mice treated with BTZ experience more severe sensorimotor dysfunction and axon loss compared to females and observed similar results when analyzing human data. Using single cell RNA-sequencing, we reveal that BTZ significantly alters the dorsal root ganglia (DRG) microenvironment in mice, producing pronounced sex-specific changes in satellite glial cells (SGCs) in males and females and dysregulation of the extracellular matrix (ECM), particularly in males. These changes are accompanied by expansion of macrophages, which is more pronounced in males. We identify four macrophage subtypes in the DRG, including a pro-fibrotic population that is exclusively associated with BIPN. Depletion of macrophages via anti-CSF1R treatment in male mice prevents BTZ-induced SGC activation and aberrant collagen deposition in DRGs, potently preserves peripheral axons, and improves functional outcomes. These findings highlight SGCs, neuroinflammation and dysregulation of the ECM as drivers of sex-specific differences in BIPN and suggest that targeting neuroinflammation is a promising therapeutic strategy to treat this disease.

N-Demethylsinomenine Relieves Neuropathic Pain in Male Mice Mainly via Regulating α2-Subtype GABAA Receptors

AIMS

N-Demethylsinomenine (NDSM) demonstrates good analgesic efficacy in preclinical pain models. However, how NDSM exerts analgesic actions remains unknown.

METHODS

We examined the analgesic effects of NDSM using both pain-evoked and pain-suppressed behavioral assays in two persistent pain models. Then western blot assay and immunofluorescence staining were used to investigate the effects of NDSM on the expression of the GABAA receptor α2 subunit (GABRA2) and inflammatory factors in the spinal cord and brain tissues of male spared nerve injury (SNI) mice. Finally, the individual subtypes of GABAARs (α1, α2, α3, and α5) were respectively silenced by viral-mediated knockdown to explore the involvement of subtypes of GABAARs in the effects of NDSM on the pain-like behaviors in male SNI mice.

RESULTS

NDSM demonstrated significant analgesic effects against chronic pain both in pain-evoked and pain-suppressed behavioral assays. NDSM treatment significantly reversed the SNI induced down-regulation of GABRA2 and up-regulation of TNF-α and IL-1β. The analgesic effects of NDSM were completely blocked by silencing GABRA2 or partially blocked by silencing GABRA3.

CONCLUSION

This study provided the first evidence that the analgesic effects of NDSM are mediated primarily by GABRA2 and partially by GABRA3, and the inhibition of neuroinflammation also contributes to the analgesic effects of NDSM.

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.

Compound Probiotics Improve Neuropathic Pain Prognosis in a Murine Model of Chronic Constriction Injury

Purpose

Compound probiotics have been reported to ameliorate imbalances in the intestinal flora that may play a critical role in neuropathic pain. This study aimed to investigate the efficacy of compound probiotic treatment on neuropathic pain.

Methods

Thirty mice were randomly divided into three groups: 1) sham group, 2) mouse with chronic constrictive injury (CCI), and 3) probiotic gavage with CCI (CCI+Prob). The degree of pain and gait recovery was assessed by Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), and mouse footprints. The degree of atrophy of the gastrocnemius muscle was assessed by muscle weight, hematoxylin and eosin (H&E) staining. Gut microbiota were analyzed by 16S ribosomal RNA sequencing (16SrRNA).

Results

Four weeks after surgery, TWL and MWT assessment showed significant increases in the CCI+Prob group compared with the CCI group (P < 0.01). Gait analysis results as well as gastrocnemius muscle weight showed a significant improvement in the CCI+Prob group compared with the CCI group. Measurement of alpha diversity showed a significant increase in the CCI group compared with the sham group, but this increase was attenuated by probiotic intervention in the CCI+Prob group. Although the CCI group had significantly decreased levels of Akkermansia and significantly increased levels of Ruminococcaceae, probiotic treatment reversed these changes.

Conclusion

Compound probiotics treatment can improve the pain and muscle atrophy in mice with CCI-induced neuropathic pain. The improvement of symptoms is associated with changes in the composition of gut microbiota.

Painful Diabetic Neuropathy: Sex-Specific Mechanisms and Differences from Animal Models to Clinical Outcomes

Diabetes is a chronic and progressive disease associated with high blood glucose levels. Several co-morbidities arise from diabetes, the most common and severe one is diabetic neuropathy whose symptoms also include pain hypersensitivity. Currently, there are no effective therapies to counteract painful diabetic neuropathy or slow down the progression of the disease, and the underlying mechanisms are yet to be fully understood. Emerging data in recent decades have provided compelling evidence that the molecular and cellular mechanisms underlying chronic pain are different across the sexes. Interestingly, relevant differences have also been observed in the course and clinical presentation of painful diabetic neuropathy in humans. Here, we reviewed the current state of the art on sex differences in diabetic neuropathy, from animal models to clinical data. Comparing the output of both preclinical and clinical studies is necessary for properly orienting future choices in pain research, refining animal models, and interpreting clinical data. The identification of sex-specific mechanisms may help to develop more targeted therapies to counteract pain symptoms in diabetes.

The Role of Astrocyte-Neuron Lactate Shuttle in Neuropathic Orofacial Pain

BACKGROUND

Inhibition of astrocytic energy metabolism alleviates neuropathic pain.

OBJECTIVES

To explore whether astrocyte-neuron lactate shuttle (ANLS) played any role in neuropathic orofacial pain.

METHODS

Rats with partial transection of the right infraorbital nerve (p-IONX) or sham operation were intrathecally injected with acetazolamide (a carbonic anhydrase inhibitor), bithionol (a soluble adenylyl cyclase inhibitor), α-cyano-4-hydroxycinnamic acid [α-CHCA, a monocarboxylate transporter (MCT) inhibitor] or vehicle once a day from postoperative day 1-14. The facial mechanical thresholds were tested on preoperative day 1 and 2 and postoperative days 1, 3, 5, 7, 10 and 14, expression of glucose transporters (GLUTs) and MCTs in the trigeminal subnucleus caudalis (Vc) were examined on the postoperative day 3 and neuronal activities in the Vc were examined in the p-IONX rats on postoperative days 3-5.

RESULTS

Compared with the sham group, the mechanical thresholds in the p-IONX group were significantly reduced at postoperative days 1-7, and the number of astrocytes expressing GLUT1 and MCT1/4, and neurons expressing MCT2 was significantly increased on postoperative day 3. In the p-IONX groups, neurons in the Vc were sensitised, and acetazolamide, bithionol and α-CHCA reversed the central sensitisation, significantly increased the mechanical thresholds at postoperative days 1-7 and decreased the number of astrocytes expressing GLUT1 and MCT1/4, and neurons expressing MCT2 at postoperative day 3 compared with those in the vehicle-treated rats.

CONCLUSIONS

Inhibition of ANLS alleviates p-IONX-related neuronal, behavioural and immunohistochemical changes, which suggests that ANLS plays an important role in trigeminal neuropathic pain.

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.

Psilocybin as a novel treatment for chronic pain

Psychedelic drugs are under active consideration for clinical use and have generated significant interest for their potential as anti-nociceptive treatments for chronic pain, and for addressing conditions like depression, frequently co-morbid with pain. This review primarily explores the utility of preclinical animal models in investigating the potential of psilocybin as an anti-nociceptive agent. Initial studies involving psilocybin in animal models of neuropathic and inflammatory pain are summarised, alongside areas where further research is needed. The potential mechanisms of action, including targeting serotonergic pathways through the activation of 5-HT2A receptors at both spinal and central levels, as well as neuroplastic actions that improve functional connectivity in brain regions involved in chronic pain, are considered. Current clinical aspects and the translational potential of psilocybin from animal models to chronic pain patients are reviewed. Also discussed is psilocybin's profile as an ideal anti-nociceptive agent, with a wide range of effects against chronic pain and its associated inflammatory or emotional components.

Intrathecal lactate dehydrogenase A inhibitors FX11 and oxamate alleviate chronic constriction injury-induced nociceptive sensitization through neuroinflammation and angiogenesis

BACKGROUND

Neuropathic pain involves neuroinflammation and upregulation of glycolysis in the central nervous system. Unfortunately, few effective treatments are available for managing this type of pain. The overactivation of lactate dehydrogenase A (LDHA), an essential enzyme in glycolysis, can cause neuroinflammation and nociception. This study investigated the spinal role of LDHA in neuropathic pain.

METHOD

Using immunohistochemical analysis, nociceptive behavior, and western blotting, we evaluated the cellular mechanisms of intrathecal administration of LDHA inhibitors, including FX11 and oxamate, in chronic constriction injury (CCI)-induced neuropathic rats.

RESULT

FX11 and oxamate attenuated CCI-induced neuronal LDHA upregulation and nociceptive sensitization. Moreover, CCI-induced neuroinflammation, microglial polarization, and angiogenesis were attenuated by LDHA inhibitors. These inhibitors regulate the TANK binding kinase-1 (TBK1)/hypoxia-inducible factor 1 subunit alpha (HIF-1α) axis, crucial for controlling inflammation and new blood vessel growth. Additionally, CCI-induced nuclear LDHA translocation, as associated with oxidative stress resistance, was attenuated by LDHA inhibitors.

CONCLUSION

In conclusion, LDHA may be a potential therapeutic target for treating neuropathic pain by regulating neuroinflammation and angiogenesis.

The Social Determinants of Health in a Cohort of Romanian Patients with Diabetic and Nondiabetic Neuropathy

Background/Objectives: The importance of the social determinants of health (SODHs) in diabetic and nondiabetic neuropathy has recently gained more attention. This retrospective study examined the correlation of incident diabetic neuropathy and neuropathy of other etiologies with SODH in Romania. Methods: All cases with the primary or secondary discharge diagnosis codes of neuropathy reported across Romania in 2019 were analyzed. The crude incidence rate was calculated per 100,000 persons for the whole population resident in Romania on the 1 July 2019. As SODHs sex, gross domestic product (GDP) per capita, unemployment rate, and the number of physicians/1000 persons were evaluated. Results: In total, 207,026 hospitalizations with a discharge diagnosis of neuropathy were recorded. Of these, 80,480 had a discharge diagnosis of diabetic neuropathy, with an incidence rate of 414.97 cases/100,000 persons. The incidence rate of diabetic neuropathy by county was correlated with the corresponding GDP (p = 0.013) and unemployment rate (p = 0.001). By sex, the correlation with GDP remained significant only for women (p = 0.010), while the correlation with unemployment rate remained significant in both sexes. No correlation was observed with the number of physicians/1000 persons/county. The incidence rate of neuropathy of other etiology was 652.49 cases/100,000 persons. No correlation between the incidence rate of neuropathy of other etiology by county and the corresponding GDP, unemployment rate or number of physicians/1000 persons was observed neither in the total sample nor by sex. Conclusions: Lower socioeconomic status was correlated with a higher incidence rate of hospitalized diabetic neuropathy and not with neuropathies of other etiologies.

KDM4A facilitates neuropathic pain and microglial M1 polarization by regulating BDNF in a rat model of brachial plexus avulsion

BACKGROUND

Many patients with brachial plexus avulsion (BPA) suffer from neuropathic pain, but the mechanism remains elusive. Modifications of histones, the proteins responsible for organizing DNA, may play an important role in neuropathic pain. Lysine demethylase 4A (KDM4A), an essential component of histone demethylase, can modify the function of chromatin and thus regulate the vital gene expressions. However, the mechanism by which KDM4A regulates neuropathic pain following BPA remains unclear.

METHODS

The pain model was developed in adult rats that received BPA surgery. Western blot, ELISA, and reverse transcription-PCR were used to examine the protein and mRNA levels of targeted genes. Immunofluorescence studies were conducted to analyze their cellular distribution in the spinal cord. Pharmacological and genetic methods were used to modulate the expression of KDM4A. Co-immunoprecipitation and chromatin immunoprecipitation PCR were used to assess the binding potential between KDM4A and the promoter of brain-derived neurotrophic factor (BDNF).

RESULTS

KDM4A and BDNF levels were significantly upregulated in the ipsilateral spinal cord dorsal horn in the BPA group compared with the sham surgery group. Additionally, knockdown of KDM4A decreased BDNF expression and microgliosis and reduced neuropathic pain-like behaviors in BPA rats. Conversely, KDM4A overexpression increased BDNF expression and microgliosis and exacerbated neuropathic pain. BDNF inhibitors and activators also regulated the activation of spinal microglia and neuropathic pain. Importantly, we showed that KDM4A modulates BDNF expression by regulating the methylation of histone 3 lysine 9 and histone 3 lysine 36 in its promoter region.

CONCLUSION

Current findings suggest that the upregulation of KDM4A increases BDNF expression in the spinal cord in rats after BPA, contributing to microgliosis, neuroinflammation, and neuropathic pain.

Agomelatine-loaded nanostructured lipid carriers alleviate neuropathic pain in rats by Nrf2/HO-1 signalling pathway

Neuropathic pain arises from impairments or malfunctions within the nervous system, resulting in atypical transmission and interpretation of pain signals. In the present study, we examined the neuroprotective effects of agomelatine (AGM) and agomelatine-loaded nanostructured lipid carriers (AGM-NLCs) in neuropathic animal models induced by chronic constriction injury (CCI) of the sciatic nerve. Male Sprague Dawley rats were divided into seven experimental groups to compare the effects of AGM and AGM-NLCs, which were administered at 20 mg/kg for 14 consecutive days after CCI. Our finding demonstrated that CCI triggered the onset of analgesia in these animals, corroborated by mechanical allodynia and thermal hyperalgesia. Furthermore, CCI induced an elevation in inflammatory mediators such as interleukin (IL)-1β and inducible nitric oxide synthase (iNOS), and downregulated heme oxygenase-1 (HO-1) and nuclear factor E2-related factor (Nrf2). Treatment with AGM and AGM-NLCs reversed inflammatory cascades and elevated antioxidant enzyme levels, leading to a reduction in paw withdrawal latency and threshold in rats. To further investigate the effect of AGM and AGM-NLCs, all-trans retinoic acid (ATRA) was administered, which antagonizes Nrf2. ATRA substantially downregulated Nrf2 expression and exacerbated thermal hyperalgesia, whereas Nrf2 and HO-1 expressions were significantly upregulated after AGM-NLCs administration. Overall, the results demonstrated that AGM-NLCs offer promising antinociceptive and anti-inflammatory properties in alleviating neuropathic pain symptoms, which can be attributed to improved drug delivery and therapeutic outcomes compared with AGM alone.

Influencing factors and repair advancements in rodent models of peripheral nerve regeneration

Peripheral nerve injuries lead to severe functional impairments, with rodent models essential for studying regeneration. This review examines key factors affecting outcomes. Age-related declines, like reduced nerve fiber density and impaired axonal transport of vesicles, hinder recovery. Hormonal differences influence regeneration, with BDNF/trkB critical for testosterone and nerve growth factor for estrogen signaling pathways. Species and strain selection impact outcomes, with C57BL/6 mice and Sprague-Dawley rats exhibiting varying regenerative capacities. Injury models - crush for early regeneration, chronic constriction for neuropathic pain, stretch for traumatic elongation and transection for severe lacerations - provide insights into clinically relevant scenarios. Repair techniques, such as nerve grafts and conduits, show that autografts are the gold standard for gaps over 3 cm, with success influenced by graft type and diameter. Time course analysis highlights crucial early degeneration and regeneration phases within the first month, with functional recovery stabilizing by three to six months. Early intervention optimizes regeneration by reducing scar tissue formation, while later interventions focus on remyelination. Understanding these factors is vital for designing robust preclinical studies and translating research into effective clinical treatments for peripheral nerve injuries.

A Missing Puzzle in Preclinical Studies-Are CCR2, CCR5, and Their Ligands' Roles Similar in Obesity-Induced Hypersensitivity and Diabetic Neuropathy?-Evidence from Rodent Models and Clinical Studies

Research has shown that obesity is a low-grade inflammatory disease that is often associated with comorbidities, such as diabetes and chronic pain. Recent data have indicated that chemokines may play a role in these conditions due to their pronociceptive and chemotactic properties, which promote hypersensitivity and inflammation. Accumulating evidence suggests that CCR2, CCR5, and their ligands (CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11 CCL12, and/or CCL13) play a role in rodent models of pain and obesity, as well as in patients with diabetes and obesity. It was proven that the blockade of CCR2 and CCR5, including the simultaneous blockade of both receptors by dual antagonists, effectively reduces hypersensitivity to thermal and mechanical stimuli in chronic pain states, including diabetic neuropathy. The present review discusses these chemokine receptors and the role of their ligands in diabetes and obesity, as well as their involvement in diabetic neuropathy and obesity-induced hypersensitivity.

KLS-13019, a Novel Structural Analogue of Cannabidiol and GPR55 Receptor Antagonist, Prevents and Reverses Chemotherapy-Induced Peripheral Neuropathy in Rats

Neuropathic pain is a form of chronic pain that develops because of damage to the nervous system. Treatment of neuropathic pain is often incompletely effective, and most available therapeutics have only moderate efficacy and present side effects that limit their use. Opioids are commonly prescribed for the management of neuropathic pain despite equivocal results in clinical studies and significant abuse potential. Thus, neuropathic pain represents an area of critical unmet medical need, and novel classes of therapeutics with improved efficacy and safety profiles are urgently needed. The cannabidiol structural analog and novel antagonist of GPR55, KLS-13019, was screened in rat models of neuropathic pain. Tactile sensitivity associated with chemotherapy exposure was induced in rats with once-daily 1-mg/kg paclitaxel injections for 4 days or 5 mg/kg oxaliplatin every third day for 1 week. Rats were then administered KLS-13019 or comparator drugs on day 7 in an acute dosing paradigm or days 7-10 in a chronic dosing paradigm, and mechanical or cold allodynia was assessed. Allodynia was reversed in a dose-dependent manner in the rats treated with KLS-13019, with the highest dose reverting the response to prepaclitaxel injection baseline levels with both intraperitoneal and oral administration after acute dosing. In the chronic dosing paradigm, four consecutive doses of KLS-13019 completely reversed allodynia for the duration of the phenotype in control animals. Additionally, coadministration of KLS-13019 with paclitaxel prevented the allodynic phenotype from developing. Together, these data suggest that KLS-13019 represents a potential new drug for the treatment of neuropathic pain. SIGNIFICANCE STATEMENT: Chemotherapy-induced peripheral neuropathy (CIPN) is a common, debilitating side effect of cancer treatment with no known cure. The GPR55 antagonist KLS-13019 represents a novel class of drug for this condition that is a potent, durable inhibitor of allodynia associated with CIPN in rats in both prevention and reversal-dosing paradigms. This novel therapeutic approach addresses a critical area of unmet medical need.

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.

Recent developments and challenges in positron emission tomography imaging of gliosis in chronic neuropathic pain

ABSTRACT

Understanding the mechanisms that underpin the transition from acute to chronic pain is critical for the development of more effective and targeted treatments. There is growing interest in the contribution of glial cells to this process, with cross-sectional preclinical studies demonstrating specific changes in these cell types capturing targeted timepoints from the acute phase and the chronic phase. In vivo longitudinal assessment of the development and evolution of these changes in experimental animals and humans has presented a significant challenge. Recent technological advances in preclinical and clinical positron emission tomography, including the development of specific radiotracers for gliosis, offer great promise for the field. These advances now permit tracking of glial changes over time and provide the ability to relate these changes to pain-relevant symptomology, comorbid psychiatric conditions, and treatment outcomes at both a group and an individual level. In this article, we summarize evidence for gliosis in the transition from acute to chronic pain and provide an overview of the specific radiotracers available to measure this process, highlighting their potential, particularly when combined with ex vivo / in vitro techniques, to understand the pathophysiology of chronic neuropathic pain. These complementary investigations can be used to bridge the existing gap in the field concerning the contribution of gliosis to neuropathic pain and identify potential targets for interventions.

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.

The involvement and significance of M2 macrophages in neuropathic pain following spinal cord injury: a systematic review

Neuropathic pain (NeP) is a type of persistent pain initiated by diseases or injuries of the nervous system. Although the underlying pathophysiological mechanisms of NeP are poorly understood, the immune system plays a key role in this condition. M2 macrophages have a key role in tissue healing and the reduction of inflammation. This systematic study aims to provide an overview of the role and importance of M2 macrophages in NeP after spinal cord injury (SCI). A comprehensive systematic review was conducted utilizing Scopus, PubMed, Embase, and ISI Web of Science databases. Two independent reviewers conducted the article selection. All publications examine the impact of M2 macrophages on NeP following spinal cord injuries. A quality assessment was conducted on bias entities that had been predetermined. Eleven papers met the criteria. According to the findings, focusing on immune cell polarization presents viable therapeutic options for treating NeP and enhancing recovery after SCI. M2 macrophages are essential for reducing neuropathic pain and promoting recovery after spinal cord injury. The modulation of M2 macrophages by a number of therapeutic approaches, including ivermectin-functionalized MWCNTs, isorhamnetin, Neuregulin-1 administration, TMEM16F inhibition, lentivirus-mediated delivery of anti-inflammatory cytokines, epigallocatechin-3-gallate, and red-light therapy promotes neuroregeneration, decreases neuroinflammatory cytokines, and reduces NeP. The results of these preclinical investigations must, however, be interpreted with caution, according to the quality assessment and risk of bias analysis of the studies that were included. Targeting M2 macrophages may have therapeutic benefits as they are essential for the management of NeP and recovery following spinal cord damage.

Diabetic Neuropathic Pain and Circadian Rhythm: A Future Direction Worthy of Study

More than half of people with diabetes experience neuropathic pain. Previous research has shown that diabetes patients' neuropathic pain exhibits a circadian cycle, which is characterized by increased pain sensitivity at night. Additional clinical research has revealed that the standard opioid drugs are ineffective at relieving pain and do not change the circadian rhythm. This article describes diabetic neuropathic pain and circadian rhythms separately, with a comprehensive focus on circadian rhythms. It is hoped that this characteristic of diabetic neuropathic pain can be utilized in the future to obtain more effective treatments for it.

Sigma-1 Receptors Control Neuropathic Pain and Peripheral Neuroinflammation After Nerve Injury in Female Mice: A Transcriptomic Study

The mechanisms for neuropathic pain amelioration by sigma-1 receptor inhibition are not fully understood. We studied genome-wide transcriptomic changes (RNAseq) in the dorsal root ganglia (DRG) from wild-type and sigma-1 receptor knockout mice prior to and following Spared Nerve Injury (SNI). In wildtype mice, most of the transcriptomic changes following SNI are related to the immune function or neurotransmission. Immune function transcripts contain cytokines and markers for immune cells, including macrophages/monocytes and CD4 + T cells. Many of these immune transcripts were attenuated by sigma-1 knockout in response to SNI. Consistent with this we found, using flow cytometry, that sigma-1 knockout mice showed a reduction in macrophage/monocyte recruitment as well as an absence of CD4 + T cell recruitment in the DRG after nerve injury. Sigma-1 knockout mice showed a reduction of neuropathic (mechanical and cold) allodynia and spontaneous pain-like responses (licking of the injured paw) which accompany the decreased peripheral neuroinflammatory response after nerve injury. Treatment with maraviroc (a CCR5 antagonist which preferentially inhibits CD4 + T cells in the periphery) of neuropathic wild-type mice only partially replicated the sigma-1 knockout phenotype, as it did not alter cold allodynia but attenuated spontaneous pain-like responses and mechanical hypersensitivity. Therefore, modulation of peripheral CD4 + T cell activity might contribute to the amelioration of spontaneous pain and neuropathic tactile allodynia seen in the sigma-1 receptor knockout mice, but not to the effect on cold allodynia. We conclude that sigma-1 receptor inhibition decreases DRG neuroinflammation which might partially explain its anti-neuropathic effect.

Persistent changes in nociceptor translatomes govern hyperalgesic priming in mouse models

Hyperalgesic priming is a model system that has been widely used to understand plasticity in painful stimulus-detecting sensory neurons, called nociceptors. A key feature of this model system is that following priming, stimuli that do not normally cause hyperalgesia now readily provoke this state. We hypothesized that hyperalgesic priming occurs due to reorganization of translation of mRNA in nociceptors. To test this hypothesis, we used paclitaxel treatment as the priming stimulus and translating ribosome affinity purification (TRAP) to measure persistent changes in mRNA translation in Nav1.8+ nociceptors. TRAP sequencing revealed 161 genes with persistently altered mRNA translation in the primed state. We identified Gpr88 as upregulated and Metrn as downregulated. We confirmed a functional role for these genes, wherein a GPR88 agonist causes pain only in primed mice and established hyperalgesic priming is reversed by Meteorin. Our work demonstrates that altered nociceptor translatomes are causative in producing hyperalgesic priming.

Sex differences in mechanisms of pain hypersensitivity

The introduction of sex-as-a-biological-variable policies at funding agencies around the world has led to an explosion of very recent observations of sex differences in the biology underlying pain. This review considers evidence of sexually dimorphic mechanisms mediating pain hypersensitivity, derived from modern assays of persistent pain in rodent animal models. Three well-studied findings are described in detail: the male-specific role of spinal cord microglia, the female-specific role of calcitonin gene-related peptide (CGRP), and the female-specific role of prolactin and its receptor. Other findings of sex-specific molecular involvement in pain are subjected to pathway analyses and reveal at least one novel hypothesis: that females may preferentially use Th1 and males Th2 T cell activity to mediate chronic pain.

Sexually dimorphic effects of pexidartinib on nerve injury-induced neuropathic pain in mice

It is well-established that spinal microglia and peripheral macrophages play critical roles in the etiology of neuropathic pain; however, growing evidence suggests sex differences in pain hypersensitivity owing to microglia and macrophages. Therefore, it is crucial to understand sex- and androgen-dependent characteristics of pain-related myeloid cells in mice with nerve injury-induced neuropathic pain. To deplete microglia and macrophages, pexidartinib (PLX3397), an inhibitor of the colony-stimulating factor 1 receptor, was orally administered, and mice were subjected to partial sciatic nerve ligation (PSL). Following PSL induction, healthy male and female mice and male gonadectomized (GDX) mice exhibited similar levels of spinal microglial activation, peripheral macrophage accumulation, and mechanical allodynia. Treatment with PLX3397 significantly suppressed mechanical allodynia in normal males; this was not observed in female and GDX male mice. Sex- and androgen-dependent differences in the PLX3397-mediated preventive effects were observed on spinal microglia and dorsal root ganglia (DRG) macrophages, as well as in expression patterns of pain-related inflammatory mediators in these cells. Conversely, no sex- or androgen-dependent differences were detected in sciatic nerve macrophages, and inhibition of peripheral CC-chemokine receptor 5 prevented neuropathic pain in both sexes. Collectively, these findings demonstrate the presence of considerable sex- and androgen-dependent differences in the etiology of neuropathic pain in spinal microglia and DRG macrophages but not in sciatic nerve macrophages. Given that the mechanisms of neuropathic pain may differ among experimental models and clinical conditions, accumulating several lines of evidence is crucial to comprehensively clarifying the sex-dependent regulatory mechanisms of pain.

Epigenomic landscape of the human dorsal root ganglion: sex differences and transcriptional regulation of nociceptive genes

Gene expression is influenced by chromatin architecture via controlled access of regulatory factors to DNA. To better understand gene regulation in the human dorsal root ganglion (hDRG) we used bulk and spatial transposase-accessible chromatin technology followed by sequencing (ATAC-seq). Using bulk ATAC-seq, we detected that in females diverse differentially accessible chromatin regions (DARs) mapped to the X chromosome and in males to autosomal genes. EGR1/3 and SP1/4 transcription factor binding motifs were abundant within DARs in females, and JUN, FOS and other AP-1 factors in males. To dissect the open chromatin profile in hDRG neurons, we used spatial ATAC-seq. The neuron cluster showed higher chromatin accessibility in GABAergic, glutamatergic, and interferon-related genes in females, and in Ca2+- signaling-related genes in males. Sex differences in transcription factor binding sites in neuron-proximal barcodes were consistent with the trends observed in bulk ATAC-seq data. We validated that EGR1 expression is biased to female hDRG compared to male. Strikingly, XIST, the long-noncoding RNA responsible for X inactivation, hybridization signal was found to be highly dispersed in the female neuronal but not non-neuronal nuclei suggesting weak X inactivation in female hDRG neurons. Our findings point to baseline epigenomic sex differences in the hDRG that likely underlie divergent transcriptional responses that determine mechanistic sex differences in pain.

A New Application for Cenicriviroc, a Dual CCR2/CCR5 Antagonist, in the Treatment of Painful Diabetic Neuropathy in a Mouse Model

The ligands of chemokine receptors 2 and 5 (CCR2 and CCR5, respectively) are associated with the pathomechanism of neuropathic pain development, but their role in painful diabetic neuropathy remains unclear. Therefore, the aim of our study was to examine the function of these factors in the hypersensitivity accompanying diabetes. Additionally, we analyzed the analgesic effect of cenicriviroc (CVC), a dual CCR2/CCR5 antagonist, and its influence on the effectiveness of morphine. An increasing number of experimental studies have shown that targeting more than one molecular target is advantageous compared with the coadministration of individual pharmacophores in terms of their analgesic effect. The advantage of using bifunctional compounds is that they gain simultaneous access to two receptors at the same dose, positively affecting their pharmacokinetics and pharmacodynamics and consequently leading to improved analgesia. Experiments were performed on male and female Swiss albino mice with a streptozotocin (STZ, 200 mg/kg, i.p.) model of diabetic neuropathy. We found that the blood glucose level increased, and the mechanical and thermal hypersensitivity developed on the 7th day after STZ administration. In male mice, we observed increased mRNA levels of Ccl2, Ccl5, and Ccl7, while in female mice, we observed additional increases in Ccl8 and Ccl12 levels. We have demonstrated for the first time that a single administration of cenicriviroc relieves pain to a similar extent in male and female mice. Moreover, repeated coadministration of cenicriviroc with morphine delays the development of opioid tolerance, while the best and longest-lasting analgesic effect is achieved by repeated administration of cenicriviroc alone, which reduces pain hypersensitivity in STZ-exposed mice, and unlike morphine, no tolerance to the analgesic effects of CVC is observed until Day 15 of treatment. Based on these results, we suggest that targeting CCR2 and CCR5 with CVC is a potent therapeutic option for novel pain treatments in diabetic neuropathy patients.

Bioinformatics and systems biology approach to identify the pathogenetic link of neurological pain and major depressive disorder

Neurological pain (NP) is always accompanied by symptoms of depression, which seriously affects physical and mental health. In this study, we identified the common hub genes (Co-hub genes) and related immune cells of NP and major depressive disorder (MDD) to determine whether they have common pathological and molecular mechanisms. NP and MDD expression data was downloaded from the Gene Expression Omnibus (GEO) database. Common differentially expressed genes (Co-DEGs) for NP and MDD were extracted and the hub genes and hub nodes were mined. Co-DEGs, hub genes, and hub nodes were analyzed for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Finally, the hub nodes, and genes were analyzed to obtain Co-hub genes. We plotted Receiver operating characteristic (ROC) curves to evaluate the diagnostic impact of the Co-hub genes on MDD and NP. We also identified the immune-infiltrating cell component by ssGSEA and analyzed the relationship. For the GO and KEGG enrichment analyses, 93 Co-DEGs were associated with biological processes (BP), such as fibrinolysis, cell composition (CC), such as tertiary granules, and pathways, such as complement, and coagulation cascades. A differential gene expression analysis revealed significant differences between the Co-hub genes ANGPT2, MMP9, PLAU, and TIMP2. There was some accuracy in the diagnosis of NP based on the expression of ANGPT2 and MMP9. Analysis of differences in the immune cell components indicated an abundance of activated dendritic cells, effector memory CD8+ T cells, memory B cells, and regulatory T cells in both groups, which were statistically significant. In summary, we identified 6 Co-hub genes and 4 immune cell types related to NP and MDD. Further studies are needed to determine the role of these genes and immune cells as potential diagnostic markers or therapeutic targets in NP and MDD.

Sex-Gender Differences Are Completely Neglected in Treatments for Neuropathic Pain

As sex-gender differences have been described in the responses of patients to certain medications, we hypothesized that the responses to medications recommended for neuropathic pain may differ between men and women. We conducted a literature review to identify articles reporting potential sex-gender differences in the efficacy and safety of these medications. Only a limited number of studies investigated potential sex-gender differences. Our results show that women seem to achieve higher blood concentrations than men during treatment with amitriptyline, nortriptyline, duloxetine, venlafaxine, and pregabalin. Compared to men, higher rates of women develop side effects during treatment with gabapentin, lidocaine, and tramadol. Globally, the sex-gender differences would suggest initially administering smaller doses of these medications to women with neuropathic pain compared to those administered to men. However, most of these differences have been revealed by studies focused on the treatment of other diseases (e.g., depression). Studies focused on neuropathic pain have overlooked potential sex-gender differences in patient responses to medications. Despite the fact that up to 60% of patients with neuropathic pain fail to achieve an adequate response to medications, the potential role of sex-gender differences in the efficacy and safety of pharmacotherapy has not adequately been investigated. Targeted studies should be implemented to facilitate personalized treatments for neuropathic pain.

Pain hypersensitivity is dependent on autophagy protein Beclin 1 in males but not females

Chronic pain is associated with alterations in fundamental cellular processes. Here, we investigate whether Beclin 1, a protein essential for initiating the cellular process of autophagy, is involved in pain processing and is targetable for pain relief. We find that monoallelic deletion of Becn1 increases inflammation-induced mechanical hypersensitivity in male mice. However, in females, loss of Becn1 does not affect inflammation-induced mechanical hypersensitivity. In males, intrathecal delivery of a Beclin 1 activator, tat-beclin 1, reverses inflammation- and nerve injury-induced mechanical hypersensitivity and prevents mechanical hypersensitivity induced by brain-derived neurotrophic factor (BDNF), a mediator of inflammatory and neuropathic pain. Pain signaling pathways converge on the enhancement of N-methyl-D-aspartate receptors (NMDARs) in spinal dorsal horn neurons. The loss of Becn1 upregulates synaptic NMDAR-mediated currents in dorsal horn neurons from males but not females. We conclude that inhibition of Beclin 1 in the dorsal horn is critical in mediating inflammatory and neuropathic pain signaling pathways in males.

Neuroinflammation signatures in dorsal root ganglia following chronic constriction injury

Neuropathic pain (NP) is a common debilitating chronic pain condition with limited effective therapeutics. Further investigating mechanisms underlying NP is therefore of great importance for discovering more promising therapeutic targets. In the current study, we employed high-throughput RNA sequencing to explore transcriptome profiles of mRNAs and microRNAs in the dorsal root ganglia (DRG) following chronic constriction injury (CCI) and also integrated published datasets for comprehensive analysis. First, we established CCI rat model confirmed by behavioral testings, and excavated 467 differentially expressed mRNAs (DEGs) and 16 differentially expressed microRNAs (DEmiRNAs) in the ipsilateral lumbar 4-6 DRG of CCI rats 11 days after surgery. Functional enrichment analysis of 337 upregulated DEGs showed that most of the DEGs were enriched in inflammation- and immune-associated biological processes and signaling pathways. The protein-protein interaction networks were constructed and hub DEGs were screened. Besides hub DEGs, we also identified 113 overlapped DEGs by intersecting our dataset with dataset GSE100122. Subsequently, we predicted potential miRNA-mRNA regulatory pairs using DEmiRNAs and a given set of key DEGs (including hub and overlapped DEGs). By integrative analysis, we found commonly differentially expressed mRNAs and miRNAs following CCI of different time points and different nerve injury types. Highlighted mRNAs include Atf3, Vip, Gal, Npy, Adcyap1, Reg3b, Jun, Cd74, Gadd45a, Tgm1, Csrp3, Sprr1a, Serpina3n, Gap43, Serpinb2 and Vtcn1, while miRNAs include miR-21-5p, miR-34a-5p, miR-200a-3p, miR-130a-5p, miR-216b-5p, miR-217-5p, and miR-541-5p. Additionally, 15 DEGs, including macrophages-specific (Cx3cr1, Arg1, Cd68, Csf1r) and the ones related to macrophages' involvement in NP (Ccl2, Fcgr3a, Bdnf, Ctss, Tyrobp) were verified by qRT-PCR. By functional experiments in future studies, promising therapeutic targets for NP treatment may be identified among these mRNAs and miRNAs.