Diabetic neuropathic pain: Physiopathology and treatment

Aspirin-triggered lipoxin A4 reduces neuropathic pain and anxiety-like behaviours in male diabetic rats: antinociceptive enhancement by cannabinoid receptor agonists

Neuropathy is the most common complication of diabetes, leading to painful symptoms like hyperalgesia. Current treatments for diabetic painful neuropathy often prove inadequate, necessitating the exploration of new pharmacological approaches. Therefore, this study aimed to investigate the potential antinociceptive effect of aspirin-triggered lipoxin A4 (ATL), a specialized pro-resolving lipid mediator, when administered alone or in combination with cannabinoid agonists, to alleviate diabetic neuropathic pain. Mechanical hyperalgesia in the hindpaws of streptozotocin (STZ)-induced diabetic (DBT) rats was assessed using the electronic Von Frey test (VFT), before diabetes induction and for up to 32 days after STZ administration and intraperitoneal ATL (0.3, 1, 3, 10, or 30 ng/rat) treatment, alone or in combination with intrathecal CB1 or CB2 receptor agonists (ACEA or JWH-133, respectively; 10 or 30 μg/rat). The effect of ATL treatment on locomotor activity and anxious or depressive-like behaviors was also evaluated. In comparison to control normoglycemic rats, control DBT rats developed: 1) mechanical hyperalgesia; 2) increase in anxious and depressive-like behaviors. ATL treatment attenuated mechanical hyperalgesia in DBT rats both acutely (at 30 ng) and cumulatively (at doses of 1, 3, 10, or 30 ng), without compromising locomotor activity. The antinociceptive effect of ATL (at 1 or 3 ng) was augmented when combined with ACEA or JWH-133 treatments (only at a dose of 30 μg/rat). While ATL treatment alone reduced anxious-like behavior in DBT rats, it did not affect depressive-like behavior. These findings underscore the therapeutic potential of ATL, in diabetic complications, suggesting a possible interaction with the endocannabinoid system.

Modulation of pain sensitivity by Ascl1-and Lhx6-dependent GABAergic neuronal function in streptozotocin diabetic mice

Painful diabetic neuropathy commonly affects the peripheral nervous system in individuals with diabetes. However, the pathological processes and mechanisms underlying diabetic neuropathic pain remain unclear. We aimed to identify the overall profiles and screen for genes potentially involved in pain mechanisms using transcriptome analysis of the dorsal root ganglion of diabetic mice treated with streptozotocin (STZ). Using RNA sequencing, we identified differentially expressed genes between streptozotocin-treated diabetic mice and controls, focusing on altered GABAergic neuron-related genes and inflammatory pathways. Behavioral and molecular analyses revealed a marked reduction in GABAergic neuronal markers (GAD65, GAD67, VGAT) and increased pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in the diabetic group compared with controls. Intrathecal administration of lentiviral vectors expressing transcription factors Ascl1 and Lhx6 reversed pain hypersensitivity and restored normal expression of GABAergic genes and inflammatory mediators. Protein-protein interaction network analysis revealed five key proteins influenced by Ascl1 and Lhx6 treatment, including those in the JunD/FosB/C-fos signaling pathway. These findings suggest that Ascl1 and Lhx6 mitigate diabetic neuropathic pain by modulating GABAergic neuronal function, pro-inflammatory responses, and pain-related channels (TRPV1, Nav1.7). These results provide a basis for developing transcription factor-based therapies targeting GABAergic neurons for diabetic neuropathic pain relief.

siRNA targeting PARP-1 alleviates diabetic peripheral neuropathy in a streptozotocin-induced rat model

Diabetic peripheral neuropathy (DPN) is a debilitating complication of diabetes mellitus, affecting nearly 50% of diabetic patients and leading to chronic pain, numbness and progressive sensory and motor function loss. This study investigates the potential of siRNA-mediated silencing of poly(ADP-ribose) polymerase 1 (PARP1) to alleviate DPN in a rat model. PARP1 overactivation, driven by hyperglycaemia-induced oxidative stress, exacerbates neuronal damage in DPN. Using chitosan nanoparticles (ChNPs) to deliver PARP1-targeting siRNA intrathecally in diabetic rats induced with streptozotocin (STZ) 55 mg/kg intraperitoneally, we conducted behavioural and physiological assessments, including Sciatic Functional Index (SFI), motor nerve conduction velocity (MNCV), grip strength and pain sensitivity tests, alongside qRT-PCR analyses, to evaluate therapeutic outcomes. Our findings indicate statistically significant improvements, with siRNA ChNPs-mediated PARP1 silencing alleviating neuropathic symptoms in DPN rats (p < .001 for SFI and MNCV improvements). Biochemical analyses revealed reductions in oxidative stress markers, such as MDA, and increased antioxidant levels, including GSH, CAT and SOD (p < .001). Pro-inflammatory cytokines and apoptotic markers, including NF-κB, IL6, IL1β, TNFa, TGF-β, CAS3, CAS9, BAK and BAX, also showed significant reductions (p < .01), confirming the neuroprotective effects of PARP1 inhibition. These results highlight the potential of siRNA-based therapies targeting PARP1 as a promising therapeutic approach for DPN, paving the way for future research with clinical applications.

The irreversible, towards fatalic neuropathy: from the genesis of diabetes

Diabetic neuropathy is the most prevalent diabetes-associated complication that negatively impacts the quality of life of the patients. The extensive complications of diabetic peoples in the world are the leading cause of neuropathic pain, and over-activation of different biochemical signalling process induces the pathogenic progression and are also corresponding the epidemic painful symptom of diabetic neuropathy. The main prevalent abnormality is neuropathy, which further causing distal symmetric polyneuropathy and focal neuropathy. The exact pathological complication of diabetes associated neuropathic algesia is still unclear, but the alteration in micro-angiopathy associated nerve fibre loss, hyper polyol formation, MAPK signalling, WNT signalling, tau-derived insulin signalling processes are well known. Furthermore, the post-translational modification of different ion channels, oxidative and nitrosative stress, brain plasticity and microvascular changes can contributes the development of neuropathic pain. However, in the current review we discussed about these pathogenic development of neuropathic pain from the genesis of diabetes, and how diabetes affects the physiological and psychological health, and quality of life of the patients. Furthermore, the treatment of diabetic neuropathy with conventional monotherapy and emerging therapy are discussed. In addition, the treatment with phytochemical constituents their mechanisms and clinical evidences are also reported. The future investigation is required on pathological alteration occurs in neuropathic individuals, and on molecular mechanisms as well as the adverse effect of phytochemicals to determine all aspects of neuropathic algesia including effective treatments, which will prevents the sympathetic pain in patients.

Predictive Value of Preoperative Pain Sketches in Lower Extremity Amputees Undergoing Secondary Targeted Muscle Reinnervation for Treatment of Neuropathic Pain

BACKGROUND

Targeted muscle reinnervation (TMR) is an effective surgical treatment for neuropathic pain in amputees. Qualitative descriptions of pain, depicted by pain sketches, could enhance the understanding of symptomatic improvement after surgery. Our aim is to assess whether preoperative pain sketches, drawn by lower extremity (LE) amputees, can predict surgical outcomes after secondary TMR surgery.

STUDY DESIGN

Eligible patients were LE amputees who underwent secondary TMR surgery between 2017 and 2023. Pain sketches and pain scores were prospectively collected both before and after surgery. The pain trajectory, as categorized by preoperative pain sketches, was analyzed and assessed for improvement, defined as reaching the minimal clinically important difference. The transition into different pain sketches and the occurrence of phantom drawings were evaluated for their association with improvement.

RESULTS

Fifty-eight patients were included, of which 18 (31.1%) depicted diffuse pain, 26 (44.8%) depicted focal pain (FP), and 18 (24.1%) depicted radiating pain (RP) in their preoperative sketch. FP sketches were associated with the lowest pre- and postoperative pain scores and most frequently developed into sketches indicating "no pain." RP sketches were associated with the least pain improvement, the lowest likelihood of achieving the minimal clinically important difference, and were more prevalent in patients with diabetes or depression. RP sketches were associated with phantom drawings; no other sketch types developed into RP sketches at the final follow-up.

CONCLUSIONS

In LE amputees who underwent secondary TMR, preoperative pain sketches could serve as a helpful tool in predicting pain outcomes. RP sketches seemed to be associated with worse outcomes and FP sketches with the most improvement.

Neuroma morphology: A macroscopic classification system

INTRODUCTION/AIMS

Neuromas come in different shapes and sizes; yet the correlation between neuroma morphology and symptomatology is unknown. Therefore, we aim to investigate macroscopic traits of excised human neuromas and assess the validity of a morphological classification system and its potential clinical implications.

METHODS

End-neuroma specimens were collected from prospectively enrolled patients undergoing symptomatic neuroma surgery. Protocolized images of the specimens were obtained intraoperatively. Pain data (Numeric rating scale, 0-10) were prospectively collected during preoperative interview, patient demographic and comorbidity factors were collected from chart review. A morphological classification is proposed, and the inter-rater reliability (IRR) was assessed. Distribution of neuroma morphology with patient factors, was described.

RESULTS

Forty-five terminal neuroma specimens from 27 patients were included. Residual limb patients comprised 93% of the population, of which 2 were upper (8.0%) and 23 (92.0%) were lower extremity residual limb patients. The proposed morphological classification, consisting of three groups (bulbous, fusiform, atypical), demonstrated a strong IRR (Cohen's kappa = 0.8). Atypical neuromas demonstrated higher preoperative pain, compared with bulbous and fusiform. Atypical morphology was more prevalent in patients with diabetes and peripheral vascular disease.

DISCUSSION

A validated morphological classification of neuroma is introduced. These findings may assist surgeons and researchers with better understanding of symptomatic neuroma development and their clinical implications. The potential relationship of neuroma morphology with the vascular and metabolic microenvironment requires further investigation.

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.

Diabetic myonecrosis: A rare complication of long-standing diabetes mellitus

BACKGROUND

Diabetes mellitus is a rapidly growing health illness worldwide and its incidence is expected to continue rising. Various complications have been cited including retinopathy, nephropathy, peripheral artery disease and ulceration among others. However, rarer complications such as diabetic myonecrosis are limited in literature. This case report demonstrates the presentation of this complication to allow for earlier detection and treatment by providers.

CASE REPORT

This case highlights a 49-year-old man with an extensive past medical history inclusive of diabetes mellitus type 2, who presented with acute onset left thigh pain and swelling. On presentation, the patient has an HbA1c of 8 % and hyperpigmented spots were noted bilaterally on the lower extremities. Initial management was centered around infectious etiologies and management which failed to improve his symptoms. Further work-up included a negative lower extremity duplex ultrasound and a CT scan showing a hypodense lesion in the left lower extremity. Following unsuccessful drainage of the lesion to assess for a possible abscess, MRI of the lower extremities showed bilateral myositis and myonecrosis centered in the left vastus medialis.

CONCLUSION

This case report highlights a rare complication of diabetes mellitus known as diabetic myonecrosis (DMN). The gold-standard diagnostic tool is a muscle biopsy, however, sensitive imaging like MRI and clinical context are sufficient for a diagnosis. Supportive care centered around pain management remains the standard of care. While this remains as a diagnosis of exclusion, early identification may decrease the number of unnecessary treatments and should remain as a differential in patients with this presentation.

Implementation of Pharmacist Driven Gabapentinoid Titration for Diabetic Peripheral Neuropathy in a Primary Care Setting

Previous studies suggest that patients with diabetic peripheral neuropathy (DPN) frequently do not receive the minimum effective doses of a gabapentinoid according to guidance from national organizations. There is opportunity to assess the implementation of pharmacist intervention for patients not meeting minimum effective gabapentinoid dosing for DPN. This prospective, single site quality improvement project was conducted at a primary care clinic and included patients with DPN prescribed a gabapentinoid by their primary care provider (PCP) at a dose lower than minimum effective dosing. Pharmacists assessed patient-reported pain ratings, adverse effects, and renal function for appropriate dosing and titrated to minimum effective dosing based on clinical judgment. All patients that were followed through week 13 had a clinically significant improvement in pain. No patients met a 50% reduction in patient-reported pain rating scales on guidance-directed minimum effective dosing. No patients were able to meet the minimum effective dose. The majority of patients declined pharmacist services due to neuropathy being controlled on the current gabapentinoid dose. This study supports the ability for pharmacists to assess patient specific factors for adequate dosing, titration, and deprescribing recommendations for analgesic medications in diabetic peripheral neuropathy.

Reduced Graphene Oxide-Substituted Nanohydroxyapatite: Rejuvenating Bone-Nerve Crosstalk with Electrical Cues in a Fragility Fracture Rat Model under Hyperglycemia

Diabetes has currently acquired the status of epidemic worldwide, and among its various pathological consequences like retinopathy and nephropathy, bone fragility fractures from diabetic osteopathy occurs in later stages and is equally destructive. Chronic hyperglycemia culminates into deteriorating microvasculature and quality of bone, making it prone to fractures. Among these, hip fractures are most common, especially in older diabetic patients apart from underlying neuropathy. Our study is an attempt to ameliorate hip fragility fracture and nerve trauma with electrical stimulation as an interface in a chronic diabetic rat model. We have fabricated reduced graphene oxide-substituted hydroxyapatite as an electroactive bone substitute and incorporated it into chitosan gelatin cryogels. The in situ reduction of graphene oxide during sintering of hydroxyapatite imparts higher potential to the fabricated composite in dealing with problem at question. The cryogels depicted optimum in vitro biocompatibility and enhanced mineralization after ectopic subcutaneous implantation in rats. The therapeutic potency of composite cryogels was evaluated in a hip fracture model with compression to the sciatic nerve in diabetic rats, mimicking the severe clinical trauma. The presence of cryogels in the femoral neck canal coupled with electrical stimulation and biochemical factors significantly improved bone regeneration in diabetic rats as depicted with microcomputed tomography analysis and histology images. The application of electrical stimulation also ameliorated the nerve trauma observed with 70% improvement in electrophysiological parameters such as the compound muscle action potential with combinatorial therapy. We therefore report the successful implication of a multitarget therapy in a chronic diabetic rat model unraveling the bone-nerve crosstalk with electroactive smart cryogels.

Mitochondrial dysfunction in diabetic neuropathy: Impaired mitophagy triggers NLRP3 inflammasome

Diabetic neuropathy is one of the challenging complications of diabetes and is characterized by peripheral nerve damage due to hyperglycemia in diabetes. Mitochondrial dysfunction has been reported as one of the key pathophysiological factor contributing to nerve damage in diabetic neuropathy, clinically manifesting as neurodegenerative changes like functional and sensorimotor deficits. Accumulating evidence suggests a clear correlation between mitochondrial dysfunction and NLRP3 inflammasome activation. Unraveling deeper molecular aspects of mitochondrial dysfunction may provide safer and effective therapeutic alternatives. This review links mitochondrial dysfunction and appraises its role in the pathophysiology of diabetic neuropathy. We have also tried to delineate the role of mitophagy in NLRP3 inflammasome activation in experimental diabetic neuropathy.

Targeting PI3K/AKT and MEK/ERK pathways for synergic effects on improving features of peripheral diabetic neuropathy

Diabetic neuropathy is one of the most serious and common complications of diabetes with a wide spectrum, affecting 30-50% of diabetic patients. However, the current treatments of this disorder, mainly based on controlling blood glucose level, show an inadequate clinical outcome. Better approaches are needed. In this fashion, it is noted that promoting nerve regeneration and preventing nerve degeneration should be focused on equally and appropriately. In this mini review, how more effective approaches are in targeting PI3K/AKT and MEK/ERK pathways in the treatment of peripheral diabetic neuropathy is discussed. Future treatment of peripheral diabetic neuropathy should consider these approaches.

Unveiling the Role of Schwann Cell Plasticity in the Pathogenesis of Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a prevalent complication of diabetes that affects a significant proportion of diabetic patients worldwide. Although the pathogenesis of DPN involves axonal atrophy and demyelination, the exact mechanisms remain elusive. Current research has predominantly focused on neuronal damage, overlooking the potential contributions of Schwann cells, which are the predominant glial cells in the peripheral nervous system. Schwann cells play a critical role in neurodevelopment, neurophysiology, and nerve regeneration. This review highlights the emerging understanding of the involvement of Schwann cells in DPN pathogenesis. This review explores the potential role of Schwann cell plasticity as an underlying cellular and molecular mechanism in the development of DPN. Understanding the interplay between Schwann cell plasticity and diabetes could reveal novel strategies for the treatment and management of DPN.

Antiapoptotic and antinociceptive effects of Achillea millefolium L. aqueous extract in rats with experimental painful diabetic neuropathy

Background and purpose

Neuropathy is one of the common complications of diabetes mellitus. This study aimed to determine the analgesic and antiapoptotic effects of the aqueous extract of Achillea millefolium L. (Ach) in rats with experimental painful diabetic neuropathy by behavioral and molecular procedures.

Experimental approach

Thirty male Wistar rats were divided into 5 groups including control, diabetes + saline, and diabetes + Ach extract (doses of 150, 300, and 600 mg/kg/day for 3 weeks, orally). A tail-flick test was performed to assess the pain threshold in different groups. Western blotting test was used to evaluate the apoptotic (Bax, Bcl2, cleaved caspase-3, and cytochrome-c) and inflammatory (TNF-α and NF-kB) protein factors in the lumbar portion of the spinal cord tissue. Also, commercial assay kits were used to evaluate oxidative stress factors (MDA, GPx, and SOD enzyme activity) in the lumbar portion of the spinal cord tissue.

Findings/Results

Results showed that administering Ach extract at the doses of 300 and 600 mg/kg/day significantly increased the nociception threshold in treated diabetic animals compared to untreated diabetic animals. Moreover, the treatment of diabetic animals with Ach extract (300 and 600 mg/kg/day) significantly reduced the oxidative stress, inflammation, and apoptosis biochemical indicators in the lumbar spinal cord tissue compared to the untreated diabetic group.

Conclusion and implications

The findings showed that Ach extract has neuroprotective and anti-nociceptive effects in rats with diabetic neuropathy. The effects can be due to the inhibition of oxidative stress, inflammation, and apoptosis in the spinal cord tissue.

Management and Diagnosis of Empagliflozin-Induced Burning Mouth Syndrome: A Case Report

Burning mouth syndrome (BMS) poses a significant clinical challenge. Patients often present with symptoms that can severely affect their quality of life, leading to anxiety, depression, and social withdrawal. The etiology of BMS remains poorly understood, which complicates its diagnosis and treatment. This case report describes an 80-year-old woman who presented with BMS following the administration of empagliflozin, a sodium-glucose cotransporter-2 (SGLT2) inhibitor used for glycemic control, along with its benefits in the progression and prognosis of cardiac insufficiency and chronic renal disease. Despite multiple treatments, her symptoms persisted until empagliflozin withdrawal, resulting in significant improvement at the six-month follow-up. This report suggests a potential association between empagliflozin and BMS, underscoring the need for clinicians to be vigilant regarding drug-related etiologies in the diagnosis and management of oral symptoms.

Glycemic variability's impact on painful diabetic peripheral neuropathy in type 2 diabetes patients

Hyperglycemia in type 2 diabetes leads to diabetic peripheral neuropathy (DPN) and neuropathic pain, yet the association between glycemic variability and painful DPN remains insufficiently evidenced. To address this, we conducted a prospective longitudinal cohort study involving adult type 2 diabetes patients at a medical center. DPN was identified using the Michigan Neuropathy Screening Instrument (MNSI), and neuropathic pain was assessed with the Taiwan version of the Douleur Neuropathique 4 (DN4-T) questionnaire. At baseline in 2013, all participants were free of DPN and were re-evaluated in 2019 for the development of painful DPN. We measured visit-to-visit glycemic fluctuations using the coefficient of variation (CV) of fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c). Patients were stratified into tertiles according to their FPG-CV and HbA1c-CV. Among the 622 participants, 267 developed DPN during the six-year follow-up. Following matching of age and sex, 210 patients without DPN and 210 with DPN (including 26 with neuropathic pain) were identified. Our findings revealed a significant association between high FPG-CV and painful DPN, with the highest tertile showing an adjusted odds ratio of 2.82 (95% confidence interval 1.04-7.64) compared to the lowest tertile. On the contrary, HbA1c-CV did not show a significant association with the risk of painful DPN. Our study indicates that higher FPG-CV is associated with an increased risk of painful DPN, supporting the role of glycemic variability in the development of painful DPN.

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.

A comprehensive review of traditional Chinese medicine in treating neuropathic pain

Neuropathic pain (NP) is a common, intractable chronic pain caused by nerve dysfunction and primary lesion of the nervous system. The etiology and pathogenesis of NP have not yet been clarified, so there is a lack of precise and effective clinical treatments. In recent years, traditional Chinese medicine (TCM) has shown increasing advantages in alleviating NP. Our review aimed to define the therapeutic effect of TCM (including TCM prescriptions, TCM extracts and natural products from TCM) on NP and reveal the underlying mechanisms. Literature from 2018 to 2024 was collected from databases including Web of Science, PubMed, ScienceDirect, Google academic and CNKI databases. Herbal medicine, Traditional Chinese medicines (TCM), neuropathic pain, neuralgia and peripheral neuropathy were used as the search terms. The anti-NP activity of TCM is clarified to propose strategies for discovering active compounds against NP, and provide reference to screen anti-NP drugs from TCM. We concluded that TCM has the characteristics of multi-level, multi-component, multi-target and multi-pathway, which can alleviate NP through various pathways such as anti-inflammation, anti-oxidant, anti-apoptotic pathway, regulating autophagy, regulating intestinal flora, and influencing ion channels. Based on the experimental study and anti-NP mechanism of TCM, this paper can offer analytical evidence to support the effectiveness in treating NP. These references will be helpful to the research and development of innovative TCM with multiple levels and multiple targets. TCM can be an effective treatment for NP and can serve as a treasure house for new drug development.

Exploring the role of miRNA in diabetic neuropathy: from diagnostics to therapeutics

Diabetic neuropathy (DN) is one of the major microvascular complications of diabetes mellitus affecting 50% of the diabetic population marred by various unmet clinical needs. There is a need to explore newer pathological mechanisms for designing futuristic regimens for the management of DN. There is a need for post-transcriptional regulation of gene expression by non-coding RNAs (ncRNAs) to finetune different cellular mechanisms with significant biological relevance. MicroRNAs (miRNAs) are a class of small ncRNAs (~ 20 to 24 nucleotide length) that are known to regulate the activity of ~ 50% protein-coding genes through repression of their target mRNAs. Differential expression of these miRNAs is associated with the pathophysiology of diabetic neuropathy via regulating various pathways such as neuronal hyperexcitability, inflammation, axonal growth, regeneration, and oxidative stress. Of note, the circulating and extracellular vesicular miRNAs serve as potential biomarkers underscoring their diagnostic potential. Recent pieces of evidence highlight the potential of miRNAs in modulating the initiation and progression of DN and the possibility of developing miRNAs as treatment options for DN. In this review, we have elaborated on the role of different miRNAs as potential biomarkers and emphasized their druggable aspects for promising future therapies for the clinical management of DN.

Recent advances in small molecule Nav 1.7 inhibitors for cancer pain management

The dorsal root ganglion (DRG) is the primary neuron responsible for transmitting peripheral pain signals to the central nervous system and plays a crucial role in pain transduction. Modulation of DRG excitability is considered a viable approach for pain management. Neuronal excitability is intricately linked to the ion channels on the neurons. The small and medium-sized DRG neurons are chiefly engaged in pain conduction and have high levels of TTX-S sodium channels, with Nav1.7 accounting for approximately 80% of the current. Voltage-gated sodium channel (VGSC or Nav) blockers are vital targets for the management of central nervous system diseases, particularly chronic pain. VGSCs play a key role in controlling cellular excitability. Clinical research has shown that Nav1.7 plays a crucial role in pain sensation, and there is strong genetic evidence linking Nav1.7 and its encoding gene SCN9A gene to painful disorders in humans. Many studies have shown that Nav1.7 plays an important role in pain management. The role of Nav1.7 in pain signaling pathways makes it an attractive target for the potential development of new pain drugs. Meanwhile, understanding the architecture of Nav1.7 may help to develop the next generation of painkillers. This review provides updates on the recently reported molecular inhibitors targeting the Nav1.7 pathway, summarizes their structure-activity relationships (SARs), and discusses their therapeutic effects on painful diseases. Pharmaceutical chemists are working to improve the therapeutic index of Nav1.7 inhibitors, achieve better analgesic effects, and reduce side effects. We hope that this review will contribute to the development of novel Nav1.7 inhibitors as potential drugs.

Perspectives on Stem Cell Therapy in Diabetic Neuropathic Pain

Diabetes mellitus-related morbidity and mortality are primarily caused by long-term complications such as retinopathy, nephropathy, cardiomyopathy, and neuropathy. Diabetic neuropathy (DN) involves the progressive degeneration of axons and nerve fibers due to chronic exposure to hyperglycemia. This metabolic disturbance leads to excessive activation of the glycolytic pathway, inducing oxidative stress and mitochondrial dysfunction, ultimately resulting in nerve damage. There is no specific treatment for painful DN, and new approaches should aim not only to relieve pain but also to prevent oxidative stress and reduce inflammation. Given that existing therapies for painful DN are not effective for diabetic patients, mesenchymal stromal cells (MSCs)-based therapy shows promise for providing immunomodulatory and paracrine regulatory functions. MSCs from various sources can improve neuronal dysfunction associated with DN. Transplantation of MSCs has led to a reduction in hyperalgesia and allodynia, along with the recovery of nerve function in diabetic rats. While the pathogenesis of diabetic neuropathic pain is complex, clinical trials have demonstrated the importance of MSCs in modulating the immune response in diabetic patients. MSCs reduce the levels of inflammatory factors and increase anti-inflammatory cytokines, thereby interfering with the progression of DM. Further investigation is necessary to ensure the safety and efficacy of MSCs in preventing or treating neuropathic pain in diabetic patients.

Electroacupuncture alleviates diabetes-induced mechanical allodynia and downregulates bradykinin B1 receptor expression in spinal cord dorsal horn

OBJECTIVE

Diabetic neuropathic pain (DNP) is one of the most prevalent symptoms of diabetes. The alteration of proteins in the spinal cord dorsal horn (SCDH) plays a significant role in the genesis and the development of DNP. Our previous study has shown electroacupuncture could effectively relieve DNP. However, the potential mechanism inducing DNP's genesis and development remains unclear and needs further research.

METHODS

This study established DNP model rats by intraperitoneally injecting a single high-dose streptozotocin; 2 Hz electroacupuncture was used to stimulate Zusanli (ST36) and Kunlun (BL60) of DNP rats daily from day 15 to day 21 after streptozotocin injection. Behavioral assay, quantitative PCR, immunofluorescence staining, and western blotting were used to study the analgesic mechanism of electroacupuncture.

RESULTS

The bradykinin B1 receptor (B1R) mRNA, nuclear factor-κB p65 (p65), substance P, and calcitonin gene-related peptide (CGRP) protein expression were significantly enhanced in SCDH of DNP rats. The paw withdrawal threshold was increased while body weight and fasting blood glucose did not change in DNP rats after the electroacupuncture treatment. The expression of B1R, p65, substance P, and CGRP in SCDH of DNP rats was also inhibited after the electroacupuncture treatment.

CONCLUSION

This work suggests that the potential mechanisms inducing the allodynia of DNP rats were possibly related to the increased expression of B1R, p65, substance P, and CGRP in SCDH. Downregulating B1R, p65, substance P, and CGRP expression levels in SCDH may achieve the analgesic effect of 2 Hz electroacupuncture treatment.