Search Results (68)

Neuropathic pain represents a complex, prolonged pain state arising from lesions within the somatosensory nervous system. Despite significant advances in elucidating its pathophysiology, current therapeutic approaches remain largely symptomatic and frequently inadequate. MicroRNAs, a class of small non-coding RNAs that regulate gene expression post-transcriptionally, have recently emerged as critical modulators of neuronal excitability, neuroinflammation, and synaptic plasticity, which are crucial processes in the development and maintenance of neuropathic pain. This review summarizes the current evidence linking specific miRNAs to the onset and maintenance of neuropathic pain, with an emphasis on their roles in peripheral and central sensitization. The potential of miRNA-based biomarkers for diagnosis and prognostic evaluation is also highlighted. A thorough understanding of the complex miRNA regulatory networks underlying neuropathic pain could facilitate the development of novel, mechanism-based therapies and ultimately improve clinical outcomes. Full article

Background: Neuropathic pain remains a major unmet clinical challenge. Growing evidence identifies sigma receptors (σRs) as pivotal intracellular modulators of maladaptive stress signaling, positioning them as promising non-opioid targets for chronic pain management. Notably, despite the pleiotropic nature of σRs in regulating diverse cellular pathways—which might theoretically suggest a high risk of off-target effects—current selective antagonists have demonstrated remarkable safety and tolerability profiles. Sigma-1 and sigma-2 receptors (σ1R and σ2R) are molecularly and functionally distinct proteins that regulate neuronal excitability, proteostasis, and neuroimmune communication, all mechanisms that characterize neuronal excitability and cellular stress adaptation. σ1R acts as a ligand-operated molecular chaperone at the mitochondria-associated endoplasmic reticulum membrane. Extensive preclinical data demonstrate that σ1R antagonism attenuates peripheral and central sensitization, suppresses neuroinflammation, and restores opioid analgesic efficacy. These findings are supported by the advanced clinical candidate E-52862, which has shown efficacy and a favorable safety profile in neuropathic pain conditions. σ2R, identified as transmembrane protein 97 (σ2R/TMEM97), functions as a regulator of cholesterol trafficking, lysosomal integrity, and integrated stress response (ISR). σ2R modulation alleviates neuropathic pain by restoring proteostatic balance and reducing ISR-driven neuronal vulnerability rather than directly suppressing excitability. Emerging σ2R ligands such as FEM-1689, UKH-1114, and CM-398 provide compelling proof-of-concept for durable, disease-modifying analgesia. Methods: A structured literature search was conducted using PubMed, Scopus, and Web of Science to identify studies published within the last decade describing σ1R and σ2R/TMEM97 biology, ligand development, and their preclinical or clinical evaluation in neuropathic pain. Reference lists were manually screened to ensure comprehensive coverage. Conclusions: This review synthesizes pharmacology, ligand development, and translational evidence supporting σRs as next-generation targets for neuropathic pain therapy, highlighting convergent roles of σ1R and σ2R in pain chronification and outlining future directions for structure-guided therapeutic strategies. Full article

The 2025 approval of the selective NaV1.8 blocker suzetrigine for acute pain marked a pivotal advance in analgesic drug development. Yet the subsequent failure of Vertex’s next-generation NaV1.8 inhibitor VX993 to demonstrate clinical analgesia underscores enduring challenges in translating mechanistic promise into patient benefit. This review examines why promising targets and compounds, spanning NaV and TRP channels, often falter and outlines a path toward more reliable target selection and validation. I first summarize the pain pathway, from nociceptor transduction through spinal processing to cortical perception, emphasizing how inflammation and peripheral sensitization reshape excitability. Historically serendipitous, pain drug discovery now prioritizes molecular precision. Most approved chronic pain therapies act in the CNS and are limited by modest efficacy and adverse effects. Nociceptor-enriched targets (NaV1.7/1.8/1.9; TRP channels) remain attractive, yet redundancy among NaV subtypes and the necessity of blocking targets at the correct anatomical sites complicate translation. Human genetics and multi-omics provide a powerful, unbiased engine for target discovery. Rare high-impact variants offer strong causal hypotheses, while common polygenic contributions illuminate broader susceptibility. Large biobanks increasingly reveal a mismatch between legacy pain targets and genetically supported candidates across neuronal and non-neuronal cells. Human DRG transcriptomics highlight NaV channel redundancy. Human in vitro electrophysiology and PK/PD analyses show suzetrigine achieves ~90–95% NaV1.8 engagement, yet neurons can still fire unless additional channels are blocked. Species differences and drug distribution (including BBB/PNS penetration and P-gp efflux) critically influence efficacy; centrally accessible blockade (e.g., for NaV1.7 or TRPA1) may be necessary to achieve robust analgesia, challenging peripherally restricted strategies. Osteoarthritis illustrates how obesity-driven metabolic inflammation, synovial immune activation, subchondral bone remodeling, and specific nociceptor subtypes converge to drive mechanical pain. Multi-omic integration across diseased human tissues can pinpoint causal processes and cell types, enabling more selective and safer target choices. I propose a practical framework for target validation that integrates: (i) rigorous human genetic support; (ii) cell-type and site-of-action mapping; (iii) human-relevant electrophysiology and PK/PD with verified target engagement; (iv) species-appropriate models; (v) consideration of modality (small molecule, biologic, RNA, targeted protein degradation). Advancing genetically and anatomically aligned targets, tested at the right sites and exposures, offers the best path to genuinely effective, better-tolerated pain therapeutics. Full article

Protease-activated receptor 2 (PAR2) is a G protein-coupled receptor (GPCR) expressed in both the peripheral and central nervous systems. It plays a pivotal role in mediating neuroimmune interactions, particularly in the context of inflammation and pain. Upon activation by proteases, PAR2 modulates nociception through signaling cascades that influence key ion channels, including transient receptor potential (TRP) ion channels vanilloid 1 and 4 (TRPV1 and TRPV4), ankyrin 1 (TRPA1), acid-sensing ion channel 3 (ASIC3), P2X purinoceptor 3 (P2X3), Cav3.2 (T-type Ca²⁺ channel), and potassium Kv7 (M-current) channels, altering their expression and function. Through this crosstalk, PAR2 contributes to heightened neuronal excitability and pain hypersensitivity in various inflammatory conditions. In this narrative review, we highlight and discuss the mechanistic and functional interplay between PAR2 and nociceptive ion channels, which might be contributing to the pathogenesis of inflammatory pain. Targeting these specific molecular interactions between PAR2 and nociceptive ion channels may offer a promising therapeutic strategy for treating inflammatory pain. Full article

Headache disorders, including migraine, tension-type headache, trigeminal autonomic cephalalgias, post-traumatic headache and medication overuse headache, represent a major global health burden and remain difficult to treat despite therapeutic advances. The endocannabinoid system (ECS) has emerged as a key regulator of neural, vascular, and immune processes central to headache pathophysiology. Through coordinated actions of CB1 and CB2 receptors, the endogenous ligands anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and their metabolic enzymes, the ECS modulates trigeminovascular activity, descending pain control, cortical excitability, and neuroimmune sensitization. Preclinical studies demonstrate that ECS activation suppresses trigeminal firing, reduces calcitonin gene-related peptide (CGRP) release, attenuates neurogenic inflammation, stabilizes cortical susceptibility to spreading depression, and limits glial activation following traumatic brain injury. Conversely, ECS dysregulation contributes to central sensitization and impaired descending inhibition underlying medication overuse headache and other headache disorders. Pharmacological strategies targeting endocannabinoid degradation, such as inhibition of FAAH, MAGL, and COX-2, enhance endogenous cannabinoid tone and consistently reduce headache-like behaviors across diverse models. Importantly, sex differences shape ECS function, with females exhibiting distinct hormonal regulation, receptor expression, and glial activation that influence responsiveness to ECS-targeted interventions. Collectively, mechanistic and translational evidence highlights the ECS as a promising therapeutic target across primary and secondary headache disorders. Future clinical studies should incorporate sex-informed designs, integrate biomarkers of trigeminovascular and neuroimmune activity, and evaluate peripherally restricted ECS modulators and cannabinoid-based formulations as candidates for individualized headache therapy. Full article

Sympathetic nervous system (SNS) imbalance is a common pathological basis for cardiovascular diseases, non-alcoholic fatty liver disease, and diabetes. This review focuses on these diseases, analyzing two core mechanisms: excessive sympathetic excitation induced by endoplasmic reticulum stress (ERS) or autophagy dysfunction in key central nuclei (e.g., hypothalamus, rostral ventrolateral medulla); and ERS/autophagy abnormalities in peripheral target organs caused by chronic SNS overactivation. Existing studies confirm that chronic SNS overactivation promotes peripheral metabolic overload via sustained catecholamine release, inducing persistent ERS and disrupting the protective unfolded protein response (UPR)–autophagy network, ultimately leading to cell apoptosis, inflammation, and fibrosis. Notably, central ERS or autophagy dysfunction further perturbs autonomic homeostasis, exacerbating sympathetic overexcitation. This review systematically elaborates on SNS overactivation as a critical bridge mediating UPR–autophagy network dysregulation in central and peripheral tissues, and explores therapeutic prospects of targeting key nodes (e.g., chemical chaperones, specific UPR modulators, nanomedicine), providing a theoretical basis for basic research and clinical translation. Full article

Background: Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental condition influenced by both genetic and non-genetic factors, although the underlying pathomechanisms remain unclear. We systematically analyzed microRNA (miRNA) expression and associated functional pathways in ASD to evaluate their potential as prenatal/postnatal, diagnostic, and prognostic biomarkers. Methods: Peripheral blood mononuclear cells from 12 Sicilian patients with ASD (eight with normal cognitive function) and 15 healthy controls were analyzed using small RNA sequencing. Differential expression analysis was performed with DESeq2 (|fold change| ≥ 1.5; adjusted p ≤ 0.05). Functional enrichment and network analyses were conducted using Ingenuity Pathway Analysis, focusing on Diseases and Biofunctions. Results: 998 miRNAs were differentially expressed in ASD, 424 upregulated and 553 downregulated. Enriched pathways were primarily associated with psychological and neurological disorders. Network analysis highlighted three principal interaction clusters related to inflammation, cell survival and mechanotransduction, synaptic plasticity, and neuronal excitability. Four miRNAs (miR-296-3p, miR-27a, miR-146a-5p, and miR-29b-3p) emerged as key regulatory candidates. Conclusions: The marked divergence in miRNA expression between ASD and controls suggests distinct regulatory patterns, thus reinforcing the central involvement of inflammatory, autoimmune, and infectious mechanisms in ASD, mediated by miRNAs regulating S100 family genes, neuronal migration, and synaptic communication. However, rather than defining a predictive biomarker panel, this study identified candidate miRNAs and regulatory networks that may be relevant to ASD pathophysiology. As such, further validation in appropriately powered cohorts with predictive modeling frameworks are warranted before any biomarker or diagnostic implications can be inferred. Full article

Ergogenic aids have long attracted scientific interest for their potential to enhance neuromuscular performance, with caffeine being among the most extensively studied. While traditionally attributed to peripheral actions on skeletal muscle, accumulating evidence indicates that, at physiological doses, caffeine’s ergogenic effects are predominantly mediated by antagonism of central adenosine receptors. This antagonism leads to increased arousal, reduced inhibitory neuromodulation, enhanced corticospinal excitability, and altered motor unit recruitment and firing behavior. Importantly, the concentrations required to elicit direct effects on excitation–contraction coupling via ryanodine receptors exceed those compatible with human safety, rendering such mechanisms unlikely in vivo. This narrative review synthesizes contemporary neurophysiological evidence to propose that caffeine acts primarily by “tuning” motor system gain through central neurotransmitter modulation, rather than by directly augmenting muscle contractile properties. Additionally, we highlight unresolved questions regarding persistent inward currents, sex-dependent neuromodulatory influences—including the potential role of estrogen in regulating adenosine receptor expression—and the implications of repeated caffeine use during training for neural adaptation and motor control. Finally, we outline key methodological and conceptual directions for future research aimed at refining our understanding of caffeine’s neuromuscular effects in both acute and chronic contexts. Full article

Temporomandibular disorders (TMDs) are common musculoskeletal chronic orofacial pain conditions involving peripheral and central sensitization within trigeminal nociceptive pathways, manifesting as mechanical allodynia and functional impairment. Botulinum toxin type A (BoNT-A) has been explored as a treatment targeting both muscle hyperactivity and nociceptive modulation. Preclinical and clinical evidence demonstrate that BoNT-A reduces peripheral neurotransmitter release, neurogenic inflammation, and central neuronal excitability, leading to attenuation of mechanical allodynia in TMD models and patients. Clinical trials show modest and variable analgesic effects, with patients displaying sensory sensitization appearing to respond more favorably, though methodological heterogeneity limits definitive conclusions. Safety concerns related to muscle weakening, changes in bone density, and structural changes underscore the need for standardized protocols optimizing dosing and monitoring, in addition to prospective studies. These findings suggest that BoNT-A may serve as an adjunctive, mechanism-based therapy within multimodal TMD management. Future research should focus on standardized sensory phenotyping and trial design to clarify BoNT-A’s role in modulating central sensitization and improving patient outcomes. Full article

Given the limited efficacy of current interventions and the complexity of chronic pain, identifying perpetuating factors is crucial for uncovering new mechanistic pathways and treatment targets. The oral and gut microbiome has emerged as a potential modulator of pain through immune, metabolic, and neural mechanisms. Contemporary evidence indicates that chronic pain populations exhibit altered oral and gut microbiota, characterized by reduced short-chain fatty acid (SCFA)-producing taxa and an overrepresentation of pro-inflammatory species. These compositional changes affect metabolites such as SCFAs, bile acids, and microbial cell wall components, which interact with host receptors to promote peripheral and central sensitization. Microbiota-derived metabolites modulate peripheral sensitization by altering nociceptive neuron excitability and stimulating immune cells to release pro-inflammatory cytokines that increase blood–brain barrier permeability, activate microglia, and amplify neuroinflammation. Activated microglia further disrupt the balance between excitatory and inhibitory neurotransmission by enhancing glutamatergic activity and weakening GABAergic signaling, thereby contributing to the induction and maintenance of central sensitization. While observational studies establish associations between dysbiosis and chronic pain, animal models and early human fecal microbiota transplantation studies suggest a potential causal role of dysbiosis in pain, although human evidence remains preliminary and influenced by diet, lifestyle, and comorbidities. Overall, microbiota appears to regulate pain via peripheral and central mechanisms, and targeting it through specific interventions, such as dietary modulation to enhance SCFA production, alongside broader lifestyle measures like sleep, physical activity, stress management, and oral hygiene, may represent a new therapeutic strategy for the management of chronic pain. Full article

Experimental animal models of orofacial pain have been instrumental in elucidating biological pathways underlying the antinociceptive effect of botulinum neurotoxin type A (BoNT/A). Although several mechanisms have been proposed to explain how BoNT/A relieves pain, the precise modes of action, particularly in the oral and maxillofacial areas, remain elusive. The purpose of this review was to synthesize and assess the latest proposed mechanisms of action through which BoNT/A attenuates orofacial pain in established animal models. A comprehensive search was conducted using the terms “botulinum neurotoxin,” “mechanism,” and “orofacial pain” or “trigeminal neuralgia.” Only animal studies involving the establishment of an orofacial pain model were selected. Additional relevant studies were identified through manual screening of cited references. Over the past five years, several animal pain models have been established to decipher the mechanisms underlying the BoNT/A-mediated antinociception in orofacial pain. The proposed mechanisms include retrograde transport, neuronal excitability regulation, neuropeptide inhibition, inflammatory modulation, and opioid system stimulation in both the peripheral and central nervous systems. Despite the insubstantial number of investigations and findings, BoNT/A exhibits multidimensional modulation of nociceptive responses and, therefore, remains a promising therapeutic agent for managing orofacial pain conditions, with animal studies consistently providing insights into the mechanism of its antinociceptive action. Full article

Swallowing is mediated by the central nervous system, including cortical and subcortical structures, the cerebellum, and the brainstem. The brainstem contains the swallowing centre that is crucial for initiating and coordinating swallowing. Consequently, brainstem damage due to stroke often leads to severe and persistent dysphagia. The aim of the present narrative review is to provide an overview of dysphagia following brainstem stroke and its management. It summarizes the physiology and pathophysiology of dysphagia following brainstem stroke and the available therapeutic options, and evaluate their effectiveness for dysphagia following brainstem stroke, which would promote the development of therapeutic protocols. Neuromodulatory techniques, including pharyngeal electrical stimulation (PES), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS), modulate the excitability of corticobulbar circuits. These techniques promote neuroplasticity through peripheral or cortical electrical or electromagnetic inputs. Skill-based swallowing training emphasizes cortical involvement in enhancing swallowing skill, offering a targeted approach to behavioural rehabilitation. Finally, transient receptor potential (TRP) agonists increase sensory inputs to the swallowing system by stimulating the sensory receptors in the oropharynx, potentially activating the swallowing network. While these options have shown promise in dysphagia rehabilitation following stroke, most the available data comes from patients with mixed stroke lesions, with limited data focused specifically on brainstem lesions. Therefore, the evidence for their efficacy in patients with brainstem stroke remains underexplored. Therefore, treatment decisions should rely on the understanding of swallowing physiology, neuroplasticity, and clinical evidence from related stroke populations. Full article

Venomous invertebrates have provided a large diversity of toxins that selectively and potently modulate ion channels that are indispensable tools for elucidating the structure and underlying mechanisms of these channels. Voltage-gated sodium channels (VGSC) are responsible for the initiation and propagation of action potentials in excitable cells and represent an important target for a variety of diseases. The Na_v1.7 isoform, located in the peripheral nervous system, is central to pain signaling and is under intense investigation as a target for the treatment of pain. Closed-state inactivation (CSI) has been implicated in various disease states, such as arrhythmias and neuropathic pain. The investigation of venom toxins and VGSC CSI is poorly understood. However, many scorpion and spider toxins bind to site 3, characterized by a delay in steady-state inactivation, and interact with domain IV of the channel alpha subunit. In this study, two novel toxins were isolated from the venoms of Heteroctenus junceus and Poecilotheria regalis that demonstrated similar activity to site 3 modulators. Both toxins were shown to inhibit CSI while enhancing the rate at which CSI can occur. Taken together, this study demonstrates the need for additional investigation in CSI as well as the ability for toxins to modulate this phenomenon. Full article

Chronic pain is a complex and persistent condition involving sustained nociceptive input, maladaptive neuroplastic changes, and neuroimmune interactions. Central to its pathophysiology is the dysregulation of neuromodulatory signaling pathways, including neurotransmitters (e.g., dopamine, serotonin, norepinephrine), neuropeptides (e.g., substance P, CGRP), and neurotrophic factors (e.g., BDNF), which modulate both central and peripheral sensitization mechanisms. In disorders such as fibromyalgia, altered monoaminergic transmission has been implicated in the attenuation of descending inhibitory control, thereby enhancing pain perception and reducing responsiveness to conventional therapies. Concurrently, neuroinflammation, driven by glial cell activation and cytokine release, further exacerbates neuronal excitability and reinforces maladaptive signaling loops. Recent technological advances, including transcriptomic profiling, functional neuroimaging, and single-cell RNA sequencing, have provided new insights into patient-specific patterns of neuromodulatory dysfunction, highlighting potential biomarkers for disease stratification and therapeutic targeting. These developments support the hypothesis that dysregulated neuromodulatory circuits not only underlie diverse chronic pain phenotypes but may also serve as intervention points for precision medicine. This narrative review synthesizes current evidence on the roles of neuromodulatory systems in chronic pain, focusing on synaptic plasticity, nociceptor sensitization, and neuroimmune crosstalk. By integrating preclinical findings with clinical observations, we propose a mechanistic framework for understanding pain chronification and guiding future therapeutic strategies. Harnessing neuromodulatory targets, whether pharmacologically or via neuromodulation technologies, could offer more personalized and effective approaches to chronic pain management. Full article