Search Results (361)

Neuropathic pain is a chronic condition resulting from injury or dysfunction of the nervous system, characterized by hyperalgesia, allodynia, and persistent alterations in sensory perception. Neuroligins, a family of postsynaptic adhesion proteins essential for synapse formation and maturation, have emerged as critical regulators of neuronal plasticity and nociceptive circuit excitability. Recent evidence suggests that dysregulation of neuroligin expression and function can modulate synaptic transmission in pain pathways, contributing to the onset and maintenance of neuropathic pain. This review highlights some findings on the role of neuroligins in neuropathic pain pathophysiology, underscoring molecular mechanisms, interactions with glutamatergic and GABAergic receptors, and their potential as innovative therapeutic targets for chronic pain management. Full article

Background/Objectives: Diabetic peripheral neuropathy (DPN) is a common and debilitating complication of diabetes mellitus characterized by progressive nerve degeneration and chronic neuropathic pain. Current therapies, including pregabalin, primarily provide symptomatic pain relief and have limited effects on preventing structural nerve damage. Therefore, the development of disease-modifying therapies remains an important unmet clinical need. This study investigated the neuroprotective effects of choline alfoscerate (CA) and its ability to attenuate mechanical hypersensitivity in a streptozotocin (STZ)-induced rat model of DPN. Methods: Diabetes was induced in rats using STZ, and administration protocols were optimized to establish sustained hyperglycemia while minimizing mortality. CA treatment was initiated immediately after STZ administration and continued throughout the study period. Mechanical sensitivity was assessed using the von Frey test. Histopathological examination of sciatic nerves was performed to evaluate structural alterations, and serum biochemical and lipid parameters were analyzed to assess systemic metabolic changes. Results: STZ-treated diabetic rats developed persistent hyperglycemia, mechanical allodynia, elevated serum triglyceride levels, and marked structural deterioration of sciatic nerve fascicles. CA treatment significantly increased paw withdrawal thresholds despite sustained hyperglycemia, indicating attenuation of mechanical hypersensitivity independent of glycemic control. Histopathological evaluation demonstrated reduced nerve fiber degeneration, attenuation of edema-like changes, and preservation of sciatic nerve architecture in CA-treated animals. In addition, CA significantly reduced serum triglyceride levels compared with diabetic controls. Conclusions: CA attenuated mechanical hypersensitivity and exerted neuroprotective effects in STZ-induced diabetic rats. These benefits occurred independently of glucose lowering and were accompanied by improvements in nerve morphology and lipid metabolism. The findings suggest that CA may represent a promising therapeutic candidate for preserving peripheral nerve integrity and attenuating neuropathic progression in diabetic peripheral neuropathy. Full article

Petiveria alliacea L. (commonly known as “anamu,” “guiné,” “hierba de zorro,” and “tipi”) has been widely used in Mesoamerican traditional medicine to treat pain and inflammation. However, scientific evidence supporting its efficacy in diabetic neuropathy remains limited. This study evaluated the antinociceptive potential of a methanolic leaf extract of P. alliacea in a murine model of alloxan-induced diabetic neuropathy and investigated its possible mechanisms of action. Diabetic CD-1 mice were evaluated for mechanical allodynia and hyperalgesia using the Von Frey test and for tonic pain using the formalin test. Pharmacological antagonists were administered to assess the involvement of opioid, nitric oxide, serotonergic, and GABAergic pathways. Phytochemical profiling was performed by LC-ESI-MS/MS, and potential pharmacological and pharmacokinetic properties of the identified metabolites were predicted using in silico tools (PASS online, SwissTargetPrediction, SwissADME, and pkCSM). The methanolic extract significantly reduced mechanical allodynia and hyperalgesia in diabetic mice and attenuated nociceptive responses in both phases of the formalin test, showing an effect comparable to gabapentin. Antinociceptive activity was not altered by naloxone or L-NAME but was significantly attenuated by methiothepin and bicuculline, suggesting that serotonergic and GABAergic pathways contribute, at least in part, to the observed antinociceptive effects. LC-ESI-MS/MS analysis identified 38 metabolites, including flavonoids, alkaloids, and terpenes, with in silico predictions supporting their potential analgesic and anti-inflammatory activities. The methanolic leaf extract of P. alliacea exhibits significant antinociceptive activity in diabetic neuropathy, partially likely to involve serotonergic and GABAergic mechanisms, supporting its ethnomedicinal use and its potential as a source of novel analgesic agents. Full article

Background/Objectives: Paclitaxel is a chemotherapy drug used to treat various tumours, but its use is often limited by an acute and chronic pain syndrome that is poorly managed. Naringin and its aglycone, naringenin, exhibit antioxidant, antitumour, anti-inflammatory, and antinociceptive effects, making them potential alternative treatments. However, their low water solubility limits their oral bioavailability in humans. Micronisation in a supercritical medium reduces particle size and enhances the dissolution of compounds, offering a possible solution. In this study, we investigated whether micronising naringin and naringenin via supercritical technology could improve their dissolution and oral efficacy against paclitaxel-induced pain syndrome. Methods: Micronisation was performed using supercritical CO₂. Molecular docking was used to analyse the binding of naringin and naringenin to TRPV1, a key target for pain relief. Swiss mice were used in capsaicin (TRPV1 agonist)-induced nociception and paclitaxel-caused acute and chronic pain models. We assessed mechanical, cold, and heat sensitivity, potential adverse effects, and TRPV1 mRNA expression. Results: Micronisation improved the apparent dissolution profile of molecules. Docking results showed that naringin and naringenin bind to TRPV1. Both micronised compounds reduced capsaicin-induced nociception without affecting locomotion or body temperature. Micronised naringin and naringenin alleviated mechanical and cold allodynia, as well as thermal hyperalgesia in both acute and chronic paclitaxel-induced pain, outperforming their conventional forms. They also downregulated TRPV1 mRNA expression in the mice’s sciatic nerve. Conclusions: Taken together, these results show that supercritical micronisation improved the apparent dissolution and oral antinociceptive efficacy of naringin and naringenin, emphasising their potential as promising alternatives for managing paclitaxel-induced pain, with TRPV1 being a probable contributor to the observed antinociceptive effects. Full article

Neuropathic pain is a debilitating condition lacking objective and quantitative assessment tools, as current evaluations rely largely on subjective reports. Hyperspectral imaging (HSI) is a non-invasive technology that quantifies spatial and spectral tissue characteristics and has been applied in rheumatologic and metabolic disorders. This study investigated whether HSI-detected paw skin alterations correlate with graded nerve injury severity in a chronic constriction injury (CCI) model. Sprague–Dawley rats were assigned to sham or CCI groups with one to four sciatic nerve ligatures. Behavioral assessments (CatWalk XT gait analysis, thermal hyperalgesia, and mechanical allodynia) and paw HSI measurements were performed longitudinally. Histological and molecular analyses were conducted from paw skin to dorsal spinal cord tissues. At 1100 nm, HSI demonstrated progressive and significant spectral deviations proportional to injury severity across all CCI groups, whereas 1300 nm changes were only detected in severe injuries. Histology revealed increased fibrosis, NGF, TNF-α, synaptophysin, and microglial activation with greater injury severity, alongside reduced PGP9.5, neurofilament, AChR, Desmin, GAP-43, Pax3, and BDNF expression. These molecular findings were supported by electrophysiological and behavioral impairments, which correlated with injury grade by HSI. In conclusion, HSI at 1100 nm provides a sensitive and objective indicator of neuropathic pain severity and holds promise as a quantitative translational tool. Full article

Background: Boswellia serrata has traditionally been used in Ayurvedic medicine for its anti-inflammatory and antioxidant properties. Although several studies support clinical analgesic efficacy, the underlying mechanisms have not been investigated in human experimental pain models. This randomized, double-blind, placebo-controlled, crossover pilot trial aimed to examine the mode of action of Boswellia serrata to differentiate between its peripheral and central effects. This exploratory pilot study was designed to generate preliminary effect size estimates and assess functional pain-processing outcomes, rather than to provide definitive evidence of clinical efficacy. Methods: Twelve healthy volunteers were recruited and received either 300 mg of Boswellia serrata extract or a visually identical placebo twice daily for 28 days, separated by a 4-week washout period. Pain and sensitization were induced using a topical capsaicin model. Outcomes included spontaneous pain intensity, mechanical allodynia, pinprick hyperalgesia, thermal thresholds, and conditioned pain modulation, alongside psychological assessments of mood, anxiety, sleep, and structured adverse-event monitoring. Results: Results showed no significant difference in the primary endpoint of spontaneous pain intensity between Boswellia and placebo (VAS 43 ± 21 vs. 47 ± 17; d = 0.18; p = 0.539). Conclusions: While Boswellia serrata did not significantly reduce acute peak pain in this model, the observed trends suggest a potential multi-level modulatory influence on nociceptive processing and endogenous pain inhibition. These findings warrant larger clinical trials to further elucidate its therapeutic potential, particularly in populations with impaired pain modulation. Full article

Background/Objectives: Trigeminal neuralgia (TN) is a debilitating neurological condition characterized by recurrent, severe pain linked to peripheral and central sensitization within trigeminal pathways. Current pharmacologic treatments are limited by inadequate efficacy or dose-limiting side effects, and botulinum neurotoxin type A (BoNT/A) has emerged as a viable option. However, its potential use in the management of TN is hampered by methodological limitations in existing studies and a lack of pivotal clinical trials. This study investigated the efficacy, optimal treatment site, preventive utility, and duration of effect of incobotulinumtoxinA (Inco/A), a BoNT/A, in a model of TN. Methods: An infraorbital nerve chronic constriction injury model was used to induce mechanical allodynia in male Sprague–Dawley rats, reproducing the trigeminal sensitization seen in TN. The effects of subcutaneous Inco/A (1, 2, and 4 U) were measured using the mechanical sensitivity (von Frey) test to evaluate the dose response, effect of injection location, potential preventive nature of treatment, and duration of benefit. Results: Inco/A produced a robust, dose-dependent reduction in mechanical allodynia, predominantly via a local mechanism of action. Both preventive and therapeutic administration of Inco/A was efficacious, with significant reduction in allodynia even when administered up to 28 days before nerve injury. The anti-allodynic effect persisted up to 56 days post-injection. Conclusions: Inco/A is highly effective in alleviating mechanical allodynia in a validated rat model of TN. The findings highlight Inco/A as a promising candidate for clinical translation in TN and related neuropathic pain syndromes and support systematic investigation in well-controlled human trials. Full article

Background: The plant Griffonia simplicifolia is marketed as a dietary supplement; it is said to have antidepressant and sleep-promoting properties. Its main ingredient, 5-hydroxytryptophan (5-HTP), is the immediate precursor of serotonin and crosses the blood–brain barrier, thereby enhancing central serotonergic neurotransmission. Reduced serotonergic activity has been associated with affective disorders, sleep disturbances, and impaired central pain modulation. Despite this neurobiological rationale, evidence for analgesic efficacy remains limited. This study investigated the effects of Griffonia simplicifolia on peripheral and central sensitization and descending pain inhibition. Methods: In a randomized, double-blind, placebo-controlled crossover trial, 18 healthy volunteers underwent quantitative sensory testing (QST). Participants received 100 mg Griffonia simplicifolia orally once daily for 28 days or matching placebo. Sensory parameters were reassessed, followed by repetitive phasic heat application (RPHA) to induce short-term peripheral and central sensitization. After a 4-week washout period, participants crossed over to the alternate intervention. Results: A total of 17 participants completed the study. Griffonia simplicifolia showed no significant effect on acute pain perception after RPHA (β = −4.17; 95% CI −14.44 to 6.10; p = 0.401). The only significant difference was an increased distance of mechanical allodynia in the verum group (β = 0.82; 95% CI 0.05–1.59; p = 0.038). No differences were observed in thermal detection or pain thresholds, pressure pain thresholds, conditioned pain modulation, wind-up ratio, mechanical pain sensitivity, or flare area. Mild, transient adverse events occurred in two participants (11%) during Griffonia simplicifolia intake. Conclusions: Griffonia simplicifolia demonstrated limited effects on experimentally induced pain mechanisms compared with placebo and was well tolerated. Increased distance of allodynia may reflect serotonergic facilitation of pronociceptive pathways, suggesting an enhanced central and peripheral sensitization. Larger controlled trials are required to clarify its impact on pain perception. Full article

Background/Objectives: While the functions of angiotensin-converting enzyme (ACE) 1 and 2 are well established in peripheral tissues, the role of the spinal ACE1 and ACE2 pathways in the development of neuropathic pain remains unclear. This study examined the role of the spinal ACE1 and ACE2 pathways in trigeminal neuropathic pain produced by inferior alveolar nerve (IAN) injury. Methods: The experiments were conducted using male Sprague-Dawley rats (6–8 weeks old, weighing 220–250 g). The left mandibular second molar was extracted, and a dental mini-implant was placed to induce IAN injury. IAN injury produced robust and long-lasting mechanical allodynia and markedly increased angiotensinogen (AGT) expression within the ipsilateral trigeminal subnucleus caudalis (iTSC). Results: Neuropathic mechanical allodynia was inhibited by intracisternally administered losartan (an angiotensin II type-1 receptor antagonist), but not by an angiotensin II type-2 receptor antagonist. Intracisternal treatment with captopril (an ACE1 inhibitor) and diminazene aceturate (an ACE2 activator) produced significant anti-allodynic effects. Intracisternally injected angiotensin-(1-7) reduced neuropathic mechanical allodynia, and this anti-allodynic effect was blocked by pretreatment with A779, a Mas receptor inhibitor. In naïve rats, the intracisternal administration of DX600 (an ACE2 inhibitor) resulted in mechanical allodynia, which was inhibited by intracisternal pretreatment with losartan. IAN injury led to upregulated ACE1 expression and downregulated ACE2 expression in the iTSC. Conclusions: Our findings indicate that IAN injury induces a polarized shift in the ACEs within the iTSC, characterized by increased ACE1 and decreased ACE2 expression. Their modulation may therefore offer a promising strategy for developing effective treatments for chronic pain. Full article

Migraines are a common neurological disorder that significantly reduces quality of life. The sensitization of trigeminal afferents is a key factor in the development of the pain syndrome associated with migraine. Carbon monoxide (CO) is produced endogenously by heme oxygenase (HO), widely expressed in structures involved in pain processing. In our study, the role of CO in an acute and chronic nitroglycerin (NTG)-induced rat migraine model was investigated using behavioral, electrophysiological, biochemical and histological methods. The repeated administration of a CO donor (CORM-2) or an HO-1 inducer (CoPP) decreased mechanical hypersensitivity and photophobia of rats in the NTG-induced migraine model. Additionally, CORM-2 and CoPP prevented an increase in trigeminal afferent excitability, which was evaluated by the frequency of action potentials in response to KCl application. Preliminary CORM-2 or CoPP injections promoted mast cell stability in the meninges and prevented NTG-induced CGRP elevation in blood plasma. Our results suggest that exogenously or endogenously produced CO has a protective potential in preventing inflammation and the sensitization of peripheral trigeminal afferents, the activity of which underlies the occurrence of pain in migraine. This could contribute to the development of new approaches for migraine prevention. Full article

As stem cell therapy in regenerative medicine becomes more socially accepted, human perinatal tissue is attracting attention as a source because it can be harvested non-invasively. Human placental extracts (HPEs), which are prepared using acid hydrolysis and autoclaving, have been approved for treating menopausal disorders and liver dysfunction. This study investigated a new HPE formulation prepared under milder conditions by omitting acid hydrolysis and autoclaving to improve its effectiveness. The new HPE contains relatively high-molecular-weight proteins, including high levels of thioredoxin-1, as well as primarily extracellular matrix proteins such as thrombospondin-1. These proteins appear to be intact or partially fragmented, but they can still potentially maintain their domain structure. The HPE showed both antioxidant and neurite outgrowth activities in a neuronal cell line SH-SY5Y. In a mouse model of hair graying caused by X-ray irradiation, multiple administration of the HPE significantly reduced it. Additionally, the HPE, but not heat-inactivated HPE, alleviated the mechanical allodynia in a mouse model with chemotherapy-induced peripheral neuropathy. Due to the fact that HPE can be produced non-invasively in large quantities in a short time without the need for culturing, the new HPE may have the potential to be an effective and feasible therapy via multiple mechanisms. Full article

Bortezomib (BTZ), the first-generation proteasome inhibitor, has been approved for the treatment of relapsed, refractory, and newly diagnosed multiple myeloma. Despite its remarkable antitumor efficacy, BTZ treatment is severely limited by a high incidence of systemic adverse reactions, primarily due to its non-selective cytotoxicity toward rapidly dividing normal cells and its potent neurotoxic effects on peripheral neurons. Bortezomib-induced peripheral neurotoxicity (BIPN) manifests as neuropathic pain and sensory abnormalities, affecting up to 31% to 64% of patients and limiting BTZ’s clinical use. Currently, the underlying mechanisms of BIPN are poorly understood. To evaluate the effects of BTZ on the functions of peripheral nerves in mice, we administered an intraperitoneal injection treatment for four weeks. Results indicated that BIPN caused mechanical allodynia, gait abnormalities, and pathological changes in myelin and axons in mice. This study confirms that BTZ upregulates the expression of the activating transcription factor 3 (ATF3), which in turn mediates the increased expression of the copper transporter SLC31A1, causing dysregulation of intracellular copper ion homeostasis and subsequent copper accumulation, and ultimately inducing the development of peripheral neurotoxicity. Elevated intracellular copper concentration exerts a dual effect: it directly promotes the oligomerization of Dihydrolipoamide S-acetyltransferase (DLAT) and concurrently damages the iron–sulfur cluster protein ferredoxin 1 (FDX1), collectively triggering the onset of cuproptosis. Green tea has garnered attention for its rich content of catechins, with (−)-Epigallocatechin Gallate (EGCG) being the most abundant catechin present. This study uncovers the molecular mechanism by which EGCG inhibits BTZ-induced cuproptosis through targeted regulation of copper homeostasis. Analyses demonstrate that EGCG significantly downregulates the expression of the copper transporter SLC31A1, thereby effectively suppressing transmembrane influx of extracellular copper ions. This intervention markedly reduces intracellular copper overload, eliciting a dual regulatory effect: on one hand, the decreased copper concentration directly inhibits the oligomerization of DLAT; on the other hand, it effectively protects the iron–sulfur cluster protein FDX1 from damage. This study aims to systematically elucidate the molecular mechanisms underlying BIPN and to evaluate the therapeutic potential of EGCG in alleviating BIPN, offering a novel therapeutic strategy for the prevention and treatment of BIPN. Full article

Botulinum neurotoxin injections are used off-label to treat chronic pain, but their efficacy is limited and paralytic effects restrict clinical utility in these applications. Here, we investigated whether combining the light chain and translocation domains of botulinum neurotoxin A (BoNT/A) with the GM1-binding B subunit of cholera toxin would be beneficial in silencing pain-associated sensory neurons. Chimeric ChoBot was assembled via a coiled-coil linking technology and was shown to retain the enzymatic activity of BoNT/A in vitro and in vivo. In cultured dorsal root ganglion neurons, ChoBot cleaved SNAP25 in a calcitonin gene-related peptide (CGRP)-rich subpopulation of sensory neurons, resulting in marked inhibition of CGRP release. ChoBot had a lesser effect on the compound muscle action potentials of the rat gastrocnemius muscle than BoNT/A following subcutaneous injections. In rat models of pain, including chemotherapy-induced peripheral neuropathy, intraplantar administration of ChoBot significantly attenuated mechanical allodynia. Immunohistochemical analysis confirmed SNAP25 cleavage in NF200- and CGRP-expressing sensory fibres in the epidermis following a single injection. ChoBot also mediated SNAP25 cleavage in human neuroblastoma cells in culture. Together, these findings indicate that ChoBot enables a silencing of pain-associated sensory pathways, providing a new strategy for the development of new long-lasting analgesics for chronic pain. Full article

DRG adhesion is a key pathological feature of failed back surgery syndrome and a major cause of neuropathic pain. DRG, or epidural adhesion, commonly results from spinal surgery, leakage of disk material into the epidural space, or inflammation. To better mimic this clinical condition, we developed a novel and reliable animal model of DRG adhesion-induced neuropathic pain. Using this model, we investigated the therapeutic potential and underlying mechanisms of CLARIX FLO, a sterile, particulate human amniotic membrane and umbilical cord tissue product. Our results demonstrate that CLARIX FLO exerts significant analgesic and anti-inflammatory effects in the DRG adhesion model. The application of CLARIX FLO to the injured DRG markedly attenuated mechanical allodynia. CLARIX FLO treatment also reduced outer sheath thickening, suppressed the inflammatory microenvironment, and decreased hypersensitivity of isolectin B4-positive neurons. Mechanistically, CD44 was identified as a potential downstream mediator of CLARIX FLO. Furthermore, a high dose of HC-HA/PTX3, the key bioactive component of CLARIX FLO, effectively reversed mechanical allodynia and inflammation. Notably, CLARIX FLO inhibited the overexpression of TNF-α and TRPV1 adhering to the DRG. In this study, we demonstrated that CLARIX FLO effectively alleviates DRG adhesion-induced neuropathic pain through a CD44–TRPV1-dependent mechanism. Full article

Fibromyalgia is a chronic nociplastic pain condition frequently accompanied by affective disturbances, particularly depression, for which effective treatments remain limited. Increasing evidence implicates central oxidative stress, maladaptive synaptic plasticity, and neuroinflammatory alterations in its pathophysiology. This study investigated the therapeutic effects of molecular hydrogen (H₂) in a reserpine-induced murine model of fibromyalgia, with emphasis on sex-dependent and region-specific mechanisms. Male and female C57BL/6 mice received repeated reserpine injections to induce fibromyalgia-like symptoms. Mechanical allodynia, thermal hyperalgesia, cold allodynia, and depressive-like behaviors were assessed, followed by molecular analyses in the spinal cord and amygdala. Reserpine induced persistent nociceptive hypersensitivity and depressive-like behaviors in both sexes, with earlier cold allodynia in females. Hydrogen-rich water (HRW) progressively reversed mechanical and thermal hypersensitivity and rapidly abolished cold allodynia, showing greater efficacy in females. HRW also normalized depressive-like behaviors in both sexes. At the molecular level, HRW reduced spinal oxidative stress and ERK-dependent plasticity without altering spinal NLRP3 expression, whereas it fully reversed NLRP3 upregulation and HO-1 downregulation in the amygdala. HRW additionally engaged sex-dependent antioxidant pathways in the spinal cord. These findings indicate that H₂ alleviates sensory and affective alterations through region- and sex-dependent central mechanisms, supporting HRW as a promising therapeutic strategy for nociplastic pain and its affective comorbidities. Full article