Novel charged sodium and calcium channel inhibitor active against neurogenic inflammation

Peripheral Ca V 2.2 channels in skin regulate prolonged heat hypersensitivity during neuroinflammation

Neuroinflammation can lead to chronic maladaptive pain affecting millions of people worldwide. Neurotransmitters, cytokines, and ion channels are implicated in neuro-immune cell signaling but their roles in specific behavioral responses are not fully elucidated. Voltage-gated Ca V 2.2 channel activity in skin controls rapid and transient heat hypersensitivity induced by intradermal capsaicin via IL-1α cytokine signaling. Ca V 2.2 channels are not, however, involved in mechanical hypersensitivity that developed in the same animal model. Here, we show that Ca V 2.2 channels are also critical for heat hypersensitivity induced by the intradermal ( id ) Complete Freund's Adjuvant (CFA) model of chronic neuroinflammation that involves ongoing cytokine signaling for days. Ongoing CFA-induced cytokine signaling cascades in skin lead to pronounced edema, and hypersensitivity to sensory stimuli. Peripheral Ca V 2.2 channel activity in skin is required for the full development and week-long time course of heat hypersensitivity induced by id CFA. Ca V 2.2 channels, by contrast, are not involved in paw edema and mechanical hypersensitivity. CFA induced increases in cytokines in hind paws including IL-6 which was dependent on Ca V 2.2 channel activity. Using IL-6 specific neutralizing antibodies, we show that IL-6 contributes to heat hypersensitivity and, neutralizing both IL-1α and IL-6 was even more effective at reducing the magnitude and duration of CFA-induced heat hypersensitivity. Our findings demonstrate a functional link between Ca V 2.2 channel activity and the release of IL-6 in skin and show that Ca V 2.2 channels have a privileged role in the induction and maintenance of heat hypersensitivity during chronic forms of neuroinflammation in skin.

Significance Statement

Neuroinflammation can lead to chronic maladaptive pain. Neurotransmitters, ion channels, cytokines, and cytokine receptors are implicated in neuron-immune signaling, but their importance in mediating specific behavioral responses are not fully elucidated. We show that the activity of peripheral Ca V 2.2 calcium ion channels in skin play a unique role in the induction and maintenance of heat hypersensitivity in the CFA model of prolonged neuroinflammation, without accompanying effects on edema and mechanical hypersensitivity. Blocking peripheral Ca V 2.2 channel activity reduces local cytokine levels in hind paws injected with CFA including IL-6 and neutralizing IL-6 reduces CFA- induced heat hypersensitivity. Our studies define key signaling molecules that act locally in skin to trigger and maintain heat hypersensitivity during chronic neuroinflammation.

Peptide and Peptidomimetic Inhibitors Targeting the Interaction of Collapsin Response Mediator Protein 2 with the N-Type Calcium Channel for Pain Relief

Ion channels serve pleiotropic functions. Often found in complexes, their activities and functions are sculpted by auxiliary proteins. We discovered that collapsin response mediator protein 2 (CRMP2) is a binding partner and regulator of the N-type voltage-gated calcium channel (CaV2.2), a genetically validated contributor to chronic pain. Herein, we trace the discovery of a new peptidomimetic modulator of this interaction, starting from the identification and development of CBD3, a CRMP2-derived CaV binding domain peptide. CBD3 uncouples CRMP2-CaV2.2 binding to decrease CaV2.2 surface localization and calcium currents. These changes occur at presynaptic sites of nociceptive neurons and indeed, CBD3 ameliorates chronic pain in preclinical models. In pursuit of a CBD3 peptidomimetic, we exploited a unique approach to identify a dipeptide with low conformational flexibility and high solvent accessibility that anchors binding to CaV2.2. From a pharmacophore screen, we obtained CBD3063, a small-molecule that recapitulated CBD3's activity, reversing nociceptive behaviors in rodents of both sexes without sensory, affective, or cognitive effects. By disrupting the CRMP2-CaV2.2 interaction, CBD3063 exerts these effects indirectly through modulating CaV2.2 trafficking, supporting CRMP2 as an auxiliary subunit of CaV2.2. The parent peptide CBD3 was also found by us and others to have neuroprotective properties at postsynaptic sites, through N-methyl-d-aspartate receptor and plasmalemmal Na+/Ca2+ exchanger 3, potentially acting as an auxiliary subunit for these pathways as well. Our new compound is poised to address several open questions regarding CRMP2's role in regulating the CaV2.2 pathways to treat pain with the potential added benefit of neuroprotection.

Emerging Medications and Strategies in Acute Pain Management: Evolving Role of Novel Sodium and Calcium Channel Blockers, Peptide-Based Pharmacologic Drugs, and Non-Medicinal Methods

PURPOSE OF REVIEW

The present investigation evaluated integration of novel medication technology to enhance treatment options, while improving patient outcomes in acute pain management. In this regard, we focused on determining the role of development and utilization of cutting-edge pharmaceutical advancements, such as targeted drug delivery systems, as well as non-pharmacologic interventions in addressing acute pain states. Further research in this area is warranted related to the need for increased patient comfort and reduced adverse effects.

RECENT FINDINGS

Recent innovations and techniques are discussed including pharmacologic drugs targeting sodium and calcium channels, peptide-based pharmacologic drugs, and non-medicinal methods of alleviating pain such as soothing music or virtual reality. The present investigation included review of current literature on the application of these innovative technologies, analyzing mechanisms of action, pharmacokinetics, and clinical effectiveness. Our study also investigated the potential benefits in terms of pain relief, reduced side effects, and improved patient adherence. The research critically examines the challenges and considerations associated with implementing these technologies in acute pain management, considering factors like cost, accessibility, and regulatory aspects. Additionally, case studies and clinical trials are highlighted which demonstrate practical implications of these novel medication technologies in real-world scenarios. The findings aim to provide healthcare professionals with a comprehensive understanding of the evolving landscape in acute pain management while guiding future research and clinical practices toward optimizing their use in enhancing patient care.

Analgesic potential of voltage gated sodium channel modulators for the management of pain

Neuronal electrochemical signals involve the flux of sodium ions through voltage-gated sodium channels (NaV) located in the neurolemma. Of the nine sodium channel subtypes, NaV-1.7, 1.8, and 1.9 are predominantly located on nociceptors, making them prime targets to control pain. This review highlights some of the latest discoveries targeting NaV channel activity, including: (1) charged local anaesthetic derivatives; (2) NaV channel toxins and associated small peptide blockers; (3) regulation of NaV channel accessory proteins; and (4) genetic manipulation of NaV channel function. While the translation of preclinical findings to a viable treatment in humans has remained a challenge, a greater understanding of NaV channel physiology could lead to the development of a new stream of therapies aimed at alleviating chronic pain.

High-plex immunofluorescence imaging and traditional histology of the same tissue section for discovering image-based biomarkers

Precision medicine is critically dependent on better methods for diagnosing and staging disease and predicting drug response. Histopathology using hematoxylin and eosin (H&E)-stained tissue (not genomics) remains the primary diagnostic method in cancer. Recently developed highly multiplexed tissue imaging methods promise to enhance research studies and clinical practice with precise, spatially resolved single-cell data. Here, we describe the 'Orion' platform for collecting H&E and high-plex immunofluorescence images from the same cells in a whole-slide format suitable for diagnosis. Using a retrospective cohort of 74 colorectal cancer resections, we show that immunofluorescence and H&E images provide human experts and machine learning algorithms with complementary information that can be used to generate interpretable, multiplexed image-based models predictive of progression-free survival. Combining models of immune infiltration and tumor-intrinsic features achieves a 10- to 20-fold discrimination between rapid and slow (or no) progression, demonstrating the ability of multimodal tissue imaging to generate high-performance biomarkers.

Role of macrophage autophagy in postoperative pain and inflammation in mice

BACKGROUND

Postoperative pain and inflammation are significant complications following surgery. Strategies that aim to prevent excessive inflammation without hampering natural wound-healing are required for the management of postoperative pain and inflammation. However, the knowledge of the mechanisms and target pathways involved in these processes is lacking. Recent studies have revealed that autophagy in macrophages sequesters pro-inflammatory mediators, and it is therefore being recognized as a crucial process involved in regulating inflammation. In this study, we tested the hypothesis that autophagy in macrophages plays protective roles against postoperative pain and inflammation and investigated the underlying mechanisms.

METHODS

Postoperative pain was induced by plantar incision under isoflurane anesthesia in mice lacking macrophage autophagy (Atg5flox/flox LysMCre +) and their control littermates (Atg5flox/flox). Mechanical and thermal pain sensitivity, changes in weight distribution, spontaneous locomotor activity, tissue inflammation, and body weight were assessed at baseline and 1, 3, and 7 days after surgery. Monocyte/macrophage infiltration at the surgical site and inflammatory mediator expression levels were evaluated.

RESULTS

Atg5flox/flox LysMCre + mice compared with the control mice exhibited lower mechanical and thermal pain thresholds and surgical/non-surgical hindlimb weight-bearing ratios. The augmented neurobehavioral symptoms observed in the Atg5flox/flox LysMCre + mice were associated with more severe paw inflammation, higher pro-inflammatory mediator mRNA expression, and more monocytes/macrophages at the surgical site.

CONCLUSION

The lack of macrophage autophagy augmented postoperative pain and inflammation, which were accompanied by enhanced pro-inflammatory cytokine secretion and surgical-site monocyte/macrophage infiltration. Macrophage autophagy plays a protective role in postoperative pain and inflammation and can be a novel therapeutic target.

Mechanisms of Transmission and Processing of Pain: A Narrative Review

Knowledge about the mechanisms of transmission and the processing of nociceptive information, both in healthy and pathological states, has greatly expanded in recent years. This rapid progress is due to a multidisciplinary approach involving the simultaneous use of different branches of study, such as systems neurobiology, behavioral analysis, genetics, and cell and molecular techniques. This narrative review aims to clarify the mechanisms of transmission and the processing of pain while also taking into account the characteristics and properties of nociceptors and how the immune system influences pain perception. Moreover, several important aspects of this crucial theme of human life will be discussed. Nociceptor neurons and the immune system play a key role in pain and inflammation. The interactions between the immune system and nociceptors occur within peripheral sites of injury and the central nervous system. The modulation of nociceptor activity or chemical mediators may provide promising novel approaches to the treatment of pain and chronic inflammatory disease. The sensory nervous system is fundamental in the modulation of the host's protective response, and understanding its interactions is pivotal in the process of revealing new strategies for the treatment of pain.

The natural product argentatin C attenuates postoperative pain via inhibition of voltage-gated sodium and T-type voltage-gated calcium channels

BACKGROUND AND PURPOSE

Postoperative pain occurs in as many as 70% of surgeries performed worldwide. Postoperative pain management still relies on opioids despite their negative consequences, resulting in a public health crisis. Therefore, it is important to develop alternative therapies to treat chronic pain. Natural products derived from medicinal plants are potential sources of novel biologically active compounds for development of safe analgesics. In this study, we screened a library of natural products to identify small molecules that target the activity of voltage-gated sodium and calcium channels that have important roles in nociceptive sensory processing.

EXPERIMENTAL APPROACH

Fractions derived from the Native American medicinal plant, Parthenium incanum, were assessed using depolarization-evoked calcium influx in rat dorsal root ganglion (DRG) neurons. Further separation of these fractions yielded a cycloartane-type triterpene identified as argentatin C, which was additionally evaluated using whole-cell voltage and current-clamp electrophysiology, and behavioural analysis in a mouse model of postsurgical pain.

KEY RESULTS

Argentatin C blocked the activity of both voltage-gated sodium and low-voltage-activated (LVA) calcium channels in calcium imaging assays. Docking analysis predicted that argentatin C may bind to Na_V 1.7-1.9 and Ca_V 3.1-3.3 channels. Furthermore, argentatin C decreased Na⁺ and T-type Ca²⁺ currents as well as excitability in rat and macaque DRG neurons, and reversed mechanical allodynia in a mouse model of postsurgical pain.

CONCLUSION AND IMPLICATIONS

These results suggest that the dual effect of argentatin C on voltage-gated sodium and calcium channels supports its potential as a novel treatment for painful conditions.

Calcium-Permeable Channels Cooperation for Rheumatoid Arthritis: Therapeutic Opportunities

Rheumatoid arthritis is a common autoimmune disease that results from the deposition of antibodies–autoantigens in the joints, leading to long-lasting inflammation. The main features of RA include cartilage damage, synovial invasion and flare-ups of intra-articular inflammation, and these pathological processes significantly reduce patients’ quality of life. To date, there is still no drug target that can act in rheumatoid arthritis. Therefore, the search for novel drug targets has become urgent. Due to their unique physicochemical properties, calcium ions play an important role in all cellular activities and the body has evolved a rigorous calcium signaling system. Calcium-permeable channels, as the main operators of calcium signaling, are widely distributed in cell membranes, endoplasmic reticulum membranes and mitochondrial membranes, and mediate the efflux and entry of Ca2+. Over the last century, more and more calcium-permeable channels have been identified in human cells, and the role of this large family of calcium-permeable channels in rheumatoid arthritis has gradually become clear. In this review, we briefly introduce the major calcium-permeable channels involved in the pathogenesis of RA (e.g., acid-sensitive ion channel (ASIC), transient receptor potential (TRP) channel and P2X receptor) and explain the specific roles and mechanisms of these calcium-permeable channels in the pathogenesis of RA, providing more comprehensive ideas and targets for the treatment of RA.

Further Understanding of Neuro-Immune Interactions in Allergy: Implications in Pathophysiology and Role in Disease Progression

The complicated interaction between the central and the autonomic (sympathetic, parasympathetic, and enteric) nervous systems on the one hand and the immune system and its components, on the other hand, seems to substantially contribute to allergy pathophysiology, uncovering an under-recognized association that could have diagnostic and therapeutic potentials. Neurons connect directly with and regulate the function of many immune cells, including mast cells, the cells that have a leading role in allergic disorders. Proinflammatory mediators such as cytokines, neurotrophins, chemokines, and neuropeptides are released by immune cells, which stimulate sensory neurons. The release of neurotransmitters and neuropeptides caused by the activation of these neurons directly impacts the functional activity of immune cells and vice versa, playing a decisive role in this communication. Successful application of Pavlovian conditioning in allergic disorders supports the existence of a psychoneuroimmunological interplay in classical allergic hypersensitivity reactions. Activation of neuronal homeostatic reflexes, like sneezing in allergic rhinitis, coughing in allergic asthma, and vomiting in food allergy, offers additional evidence of a neuroimmunological interaction that aims to maintain homeostasis. Dysregulation of this interaction may cause overstimulation of the immune system that will produce profound symptoms and exaggerated hemodynamic responses that will lead to severe allergic pathophysiological events, including anaphylaxis. In this article, we have systematically reviewed and discussed the evidence regarding the role of the neuro-immune interactions in common allergic clinical modalities like allergic rhinitis, chronic rhinosinusitis, allergic asthma, food allergy, atopic dermatitis, and urticaria. It is essential to understand unknown – to most of the immunology and allergy experts – neurological networks that not only physiologically cooperate with the immune system to regulate homeostasis but also pathogenetically interact with more or less known immunological pathways, contribute to what is known as neuroimmunological inflammation, and shift homeostasis to instability and disease clinical expression. This understanding will provide recognition of new allergic phenotypes/endotypes and directions to focus on specialized treatments, as the era of personalized patient-centered medicine, is hastening apace.

Uncovering a new route to pain therapy

High-voltage-activated calcium channels (HVACCs) are promising targets for developing analgesics given their roles in controlling synaptic transmission, neuronal excitability and neuropeptide release in primary nociceptive neurons. Despite previous efforts in developing HVACCs inhibitors of various drug modalities, it remains undetermined whether targeting HVACCs directly by a gene therapy approach could lead to pain alleviation in vivo. To test this, Sun and colleagues adopted a post-translational ubiquitination-based knockdown method targeting HVACCs in primary sensory neurons. They showed ablation of HVACC currents in a subset of primary sensory neurons, dampened hyperexcitability of sensory neurons after nerve injury and reduced pain behavior with no apparent adverse effects [1]. The results open the possibility of targeting ion channels with ubiquitination-based knockdown as a promising gene therapy candidate for pain treatment in future clinical studies.

Nanophotonics Enable Targeted Photothermal Silencing of Nociceptor Neurons

The sensory nervous and immune systems work in concert to preserve homeostasis. While this endogenous interplay protects from danger, it may drive chronic pathologies. Currently, genetic engineering of neurons remains the primary approach to interfere selectively with this potentially deleterious interplay. However, such manipulations are not feasible in a clinical setting. Here, this work reports a nanotechnology-enabled concept to silence subsets of unmodified nociceptor neurons that exploits their ability to respond to heat via the transient receptor potential vanilloid type 1 (TRPV1) channel. This strategy uses laser stimulation of antibody-coated gold nanoparticles to heat-activate TRPV1, turning this channel into a cell-specific drug-entry port. This delivery method allows transport of a charged cationic derivative of an N-type calcium channel blocker (CNCB-2) into targeted sensory fibers. CNCB-2 delivery blocks neuronal calcium currents and neuropeptides release, resulting in targeted silencing of nociceptors. Finally, this work demonstrates the ability of the approach to probe neuro-immune crosstalk by targeting cytokine-responsive nociceptors and by successfully preventing nociceptor-induced CD8⁺ T-cells polarization. Overall, this work constitutes the first demonstration of targeted silencing of nociceptor neuron subsets without requiring genetic modification, establishing a strategy for interfering with deleterious neuro-immune interplays.

Amiodarone Provides Long-Lasting Local Anesthesia and Analgesia in Open-State Mouse Nociceptors

Local anesthetics with long-lasting effects and selectivity for nociceptors have been sought over the past decades. In this study, we investigated whether amiodarone, a multiple channel blocker, provides long-lasting local anesthesia and whether adding a TRPV1 channel activator selectively prolongs sensory anesthetic effects without prolonging motor blockade. Additionally, we examined whether amiodarone provides long-lasting analgesic effects against inflammatory pain without TRPV1 channel activator co-administration. In the sciatic nerve block model, 32 adult C57BL/6J mice received either bupivacaine, amiodarone with or without capsaicin (a TRPV1 agonist), or vehicle via peri-sciatic nerve injection. Sensory and motor blockade were assessed either by pinprick and toe spread tests, respectively. In another set of 16 mice, inflammatory pain was induced in the hind paw by zymosan injection, followed by administration of either amiodarone or vehicle. Mechanical and thermal sensitivity and paw thickness were assessed using the von Frey and Hargreaves tests, respectively. The possible cardiovascular and neurological side effects of local amiodarone injection were assessed in another set of 12 mice. In the sciatic nerve block model, amiodarone produced robust anesthesia, and the co-administration of TRPV1 agonist capsaicin prolonged the duration of sensory blockade, but not that of motor blockade [complete sensory block duration: 195.0 ± 9.8 min vs. 28.8 ± 1.3 min, F (2, 21) = 317.6, p < 0.01, complete motor block duration: 27.5 ± 1.6 min vs. 21.3 ± 2.3 min, F (2, 22) = 11.1, p = 0.0695]. In the zymosan-induced inflammatory pain model, low-dose amiodarone was effective in reversing the mechanical and thermal hypersensitivity not requiring capsaicin co-administration [50% withdrawal threshold at 8 h (g): 0.85 ± 0.09 vs. 0.25 ± 0.08, p < 0.01, withdrawal latency at 4 h (s) 8.5 ± 0.5 vs. 5.7 ± 1.4, p < 0.05]. Low-dose amiodarone did not affect zymosan-induced paw inflammation. Local amiodarone did not cause cardiovascular or central nervous system side effects. Amiodarone may have the potential to be a long-acting and nociceptor-selective local anesthetic and analgesic method acting over open-state large-pore channels.

Peripheral Voltage-Gated Cation Channels in Neuropathic Pain and Their Potential as Therapeutic Targets

The persistence of increased excitability and spontaneous activity in injured peripheral neurons is imperative for the development and persistence of many forms of neuropathic pain. This aberrant activity involves increased activity and/or expression of voltage-gated Na⁺ and Ca²⁺ channels and hyperpolarization activated cyclic nucleotide gated (HCN) channels as well as decreased function of K⁺ channels. Because they display limited central side effects, peripherally restricted Na⁺ and Ca²⁺ channel blockers and K⁺ channel activators offer potential therapeutic approaches to pain management. This review outlines the current status and future therapeutic promise of peripherally acting channel modulators. Selective blockers of Na_v1.3, Na_v1.7, Na_v1.8, Ca_v3.2, and HCN2 and activators of K_v7.2 abrogate signs of neuropathic pain in animal models. Unfortunately, their performance in the clinic has been disappointing; some substances fail to meet therapeutic end points whereas others produce dose-limiting side effects. Despite this, peripheral voltage-gated cation channels retain their promise as therapeutic targets. The way forward may include (i) further structural refinement of K⁺ channel activators such as retigabine and ASP0819 to improve selectivity and limit toxicity; use or modification of Na⁺ channel blockers such as vixotrigine, PF-05089771, A803467, PF-01247324, VX-150 or arachnid toxins such as Tap1a; the use of Ca²⁺ channel blockers such as TTA-P2, TTA-A2, Z 944, ACT709478, and CNCB-2; (ii) improving methods for assessing “pain” as opposed to nociception in rodent models; (iii) recognizing sex differences in pain etiology; (iv) tailoring of therapeutic approaches to meet the symptoms and etiology of pain in individual patients via quantitative sensory testing and other personalized medicine approaches; (v) targeting genetic and biochemical mechanisms controlling channel expression using anti-NGF antibodies such as tanezumab or re-purposed drugs such as vorinostat, a histone methyltransferase inhibitor used in the management of T-cell lymphoma, or cercosporamide a MNK 1/2 inhibitor used in treatment of rheumatoid arthritis; (vi) combination therapy using drugs that are selective for different channel types or regulatory processes; (vii) directing preclinical validation work toward the use of human or human-derived tissue samples; and (viii) application of molecular biological approaches such as clustered regularly interspaced short palindromic repeats (CRISPR) technology.

Towards Structure-Guided Development of Pain Therapeutics Targeting Voltage-Gated Sodium Channels

Voltage-gated sodium (Na_V) channels are critical molecular determinants of action potential generation and propagation in excitable cells. Normal Na_V channel function disruption can affect physiological neuronal signaling and lead to increased sensitivity to pain, congenital indifference to pain, uncoordinated movement, seizures, or paralysis. Human genetic studies have identified human Na_V1.7 (hNa_V1.7), hNa_V1.8, and hNa_V1.9 channel subtypes as crucial players in pain signaling. The premise that subtype selective Na_V inhibitors can reduce pain has been reinforced through intensive target validation and therapeutic development efforts. However, an ideal therapeutic has yet to emerge. This review is focused on recent progress, current challenges, and future opportunities to develop Na_V channel targeting small molecules and peptides as non-addictive therapeutics to treat pain.

Analysis of Airway Vagal Neurons

Internal organs, including the airway, are innervated by neurons of the autonomic and sensory nervous systems. The airway-innervating sensory neurons primarily originate from the vagus nerve, whose cell bodies are found, in rodents, in the jugular and nodose ganglia complex (JNC). About half of these sensory neurons expressed the heat-sensing ion channel TRPV1 and evolved to limit tissue damage by detecting chemical, mechanical, or thermal threats and to initiate protective airway reflexes such as coughing and bronchoconstriction. They also help monitor the host homeostasis by sensing nutrients, pressure, and O₂ levels and help mount airway defenses by controlling immune and goblet cell activity. To better appreciate the scope of the physiological role and pathological contributions of these neurons, we will review gain and loss-of-function approaches geared at controlling the activity of these neurons. We will also present a method to study transcriptomic changes in airway-innervating neurons and a co-culture approach designed to understand how nociceptors modulate immune responses.

Bioprinting of Adult Dorsal Root Ganglion (DRG) Neurons Using Laser-Induced Side Transfer (LIST)

Cell bioprinting technologies aim to fabricate tissuelike constructs by delivering biomaterials layer-by-layer. Bioprinted constructs can reduce the use of animals in drug development and hold promise for addressing the shortage of organs for transplants. Here, we sought to validate the feasibility of bioprinting primary adult sensory neurons using a newly developed laser-assisted cell bioprinting technology, known as Laser-Induced Side Transfer (LIST). We used dorsal root ganglion neurons (DRG; cell bodies of somatosensory neurons) to prepare our bioink. DRG-laden- droplets were printed on fibrin-coated coverslips and their viability, calcium kinetics, neuropeptides release, and neurite outgrowth were measured. The transcriptome of the neurons was sequenced. We found that LIST-printed neurons maintain high viability (Printed: 86%, Control: 87% on average) and their capacity to release neuropeptides (Printed CGRP: 130 pg/mL, Control CGRP: 146 pg/mL). In addition, LIST-printed neurons do not show differences in the expressed genes compared to control neurons. However, in printed neurons, we found compromised neurite outgrowth and lower sensitivity to the ligand of the TRPV1 channel, capsaicin. In conclusion, LIST-printed neurons maintain high viability and marginal functionality losses. Overall, this work paves the way for bioprinting functional 2D neuron assays.

Inhibition of inflammatory pain and cough by a novel charged sodium channel blocker

BACKGROUND AND PURPOSE

Many pain-triggering nociceptor neurons express TRPV1 or TRPA1, cation-selective channels with large pores that enable permeation of QX-314, a cationic analogue of lidocaine. Co-application of QX-314 with TRPV1 or TRPA1 activators can silence nociceptors. In this study, we describe BW-031, a novel more potent cationic sodium channel inhibitor, and test whether its application alone can inhibit pain associated with tissue inflammation and whether this strategy can also inhibit cough.

EXPERIMENTAL APPROACH

We tested the ability of BW-031 to inhibit pain in three models of tissue inflammation:- inflammation in rat paws produced by complete Freund's adjuvant or by surgical incision and a mouse ultraviolet (UV) burn model. We tested the ability of BW-031 to inhibit cough induced by inhalation of dilute citric acid in guinea pigs.

KEY RESULTS

BW-031 inhibited Na_v 1.7 and Na_v 1.1 channels with approximately sixfold greater potency than QX-314 when introduced inside cells. BW-031 inhibited inflammatory pain in all three models tested, producing more effective and longer-lasting inhibition of pain than QX-314 in the mouse UV burn model. BW-031 was effective in reducing cough counts by 78%-90% when applied intratracheally under isoflurane anaesthesia or by aerosol inhalation in guinea pigs with airway inflammation produced by ovalbumin sensitization.

CONCLUSION AND IMPLICATIONS

BW-031 is a novel cationic sodium channel inhibitor that can be applied locally as a single agent to inhibit inflammatory pain. BW-031 can also effectively inhibit cough in a guinea pig model of citric acid-induced cough, suggesting a new clinical approach to treating cough.

Bidirectional sensory neuron-immune interactions: a new vision in the understanding of allergic inflammation

Peripheral neurons (including sensory neurons) are ubiquitously distributed in all tissues, particularly at the interface with the environment. The primary function of sensory neurons is the transmission of sensations of temperature, pain and itch to elicit appropriate behavioral responses. More recently, sensory neurons have emerged as potent regulators of type 2 immune responses and allergic inflammation. There is increasing evidence showing that neurons can express receptors previously thought to be restricted to the immune compartment. In addition, certain subtypes of immune cells (e.g. mast cells, ILC2s or macrophages) also express specific neuroreceptors that provide them with the capacity to integrate neuron-derived signals and modulate their activation status during the development of allergic inflammation.

Recent Advances in the Treatment of Opioid Use Disorder

PURPOSE OF REVIEW

Opioid use disorder (OUD) remains a national epidemic with an immense consequence to the United States' healthcare system. Current therapeutic options are limited by adverse effects and limited efficacy.

RECENT FINDINGS

Recent advances in therapeutic options for OUD have shown promise in the fight against this ongoing health crisis. Modifications to approved medication-assisted treatment (MAT) include office-based methadone maintenance, implantable and monthly injectable buprenorphine, and an extended-release injectable naltrexone. Therapies under investigation include various strategies such as heroin vaccines, gene-targeted therapy, and biased agonism at the G protein-coupled receptor (GPCR), but several pharmacologic, clinical, and practical barriers limit these treatments' market viability. This manuscript provides a comprehensive review of the current literature regarding recent innovations in OUD treatment.

Spider Venom Peptide Pn3a Inhibition of Primary Afferent High Voltage-Activated Calcium Channels

Despite potently inhibiting the nociceptive voltage-gated sodium (Na_v) channel, Na_v1.7, µ-theraphotoxin Pn3a is antinociceptive only upon co-administration with sub-therapeutic opioid agonists, or by itself at doses >3,000-fold greater than its Na_v1.7 IC₅₀ by a yet undefined mechanism. Na_v channels are structurally related to voltage-gated calcium (Ca_v) channels, Ca_v1 and Ca_v2. These channels mediate the high voltage-activated (HVA) calcium currents (I_Ca) that orchestrate synaptic transmission in nociceptive dorsal root ganglion (DRG) neurons and are fine-tuned by opioid receptor (OR) activity. Using whole-cell patch clamp recording, we found that Pn3a (10 µM) inhibits ∼55% of rat DRG neuron HVA-I_Ca and 60–80% of Ca_v1.2, Ca_v1.3, Ca_v2.1, and Ca_v2.2 mediated currents in HEK293 cells, with no inhibition of Ca_v2.3. As a major DRG I_Ca component, Ca_v2.2 inhibition by Pn3a (IC₅₀ = 3.71 ± 0.21 µM) arises from an 18 mV hyperpolarizing shift in the voltage dependence of inactivation. We observed that co-application of Pn3a and µ-OR agonist DAMGO results in enhanced HVA-I_Ca inhibition in DRG neurons whereas co-application of Pn3a with the OR antagonist naloxone does not, underscoring HVA channels as shared targets of Pn3a and opioids. We provide evidence that Pn3a inhibits native and recombinant HVA Ca_vs at previously reportedly antinociceptive concentrations in animal pain models. We show additive modulation of DRG HVA-I_Ca by sequential application of low Pn3a doses and sub-therapeutic opioids ligands. We propose Pn3a's antinociceptive effects result, at least in part, from direct inhibition of HVA-I_Ca at high Pn3a doses, or through additive inhibition by low Pn3a and mild OR activation.

FcεR1-expressing nociceptors trigger allergic airway inflammation

BACKGROUND

Lung nociceptor neurons amplify immune cell activity and mucus metaplasia in response to an inhaled allergen challenge in sensitized mice.

OBJECTIVE

We sought to identify the cellular mechanisms by which these sensory neurons are activated subsequent to allergen exposure.

METHODS

We used calcium microscopy and electrophysiologic recording to assess whether vagal neurons directly respond to the model allergen ovalbumin (OVA). Next, we generated the first nociceptor-specific FcεR1γ knockdown (TRPV1^Cre::FcεR1γ^fl/fl) mice to assess whether this targeted invalidation would affect the severity of allergic inflammation in response to allergen challenges.

RESULTS

Lung-innervating jugular nodose complex ganglion neurons express the high-affinity IgE receptor FcεR1, the levels of which increase in OVA-sensitized mice. FcεR1γ-expressing vagal nociceptor neurons respond directly to OVA complexed with IgE with depolarization, action potential firing, calcium influx, and neuropeptide release. Activation of vagal neurons by IgE-allergen immune complexes, through the release of substance P from their peripheral terminals, directly amplifies T_H2 cell influx and polarization in the airways. Allergic airway inflammation is decreased in TRPV1^Cre::FcεR1γ^fl/fl mice and in FcεR1α^-/- mice into which bone marrow has been transplanted. Finally, increased in vivo circulating levels of IgE following allergen sensitization enhances the responsiveness of FcεR1 to immune complexes in both mouse jugular nodose complex ganglion neurons and human induced pluripotent stem cell-derived nociceptors.

CONCLUSIONS

Allergen sensitization triggers a feedforward inflammatory loop between IgE-producing plasma cells, FcεR1-expressing vagal sensory neurons, and T_H2 cells, which helps to both initiate and amplify allergic airway inflammation. These data highlight a novel target for reducing allergy, namely, FcεR1γ expressed by nociceptors.

Future in regional anesthesia and pain medicine: the pharmacological view

Local anesthetics are still incompletely understood, and none of the currently available drugs are optimal. The primary target of local anesthetics is the voltage-gated sodium channel (VGSC), where they lead to a temporary interruption of nerve conduction. Unfortunately, local anesthetics are neither specific at blocking a specific VGSC isoform, nor a specific cell type. We realize now that the old classification of A and C fibers according to myelin thickness is outdated, that next to differing myelin configuration, cells differ also by their molecular biology, and that there are close to 20 different neuronal subgroups when function is concerned. The ideal local anesthetic would only block sensory impulses, or even only painful impulses. In the search for that drug, several research avenues have been followed. First, efforts have been undertaken to extend duration of local anesthetics, by additives or extended-release formulation. Second, blockade of specific pain fibers has been attempted by targeting permanently charged anesthetics specifically into nociceptors. Third, blockade of specific isoforms using antibodies, and adaptation of naturally occurring neurotoxins has shown promise. Lastly, combination of local anesthetics with other analgesics may improve their duration of action.

Neuro-Immunity Controls Obesity-Induced Pain

The prevalence of obesity skyrocketed over the past decades to become a significant public health problem. Obesity is recognized as a low-grade inflammatory disease and is linked with several comorbidities such as diabetes, circulatory disease, common neurodegenerative diseases, as well as chronic pain. Adipocytes are a major neuroendocrine organ that continually, and systemically, releases pro-inflammatory factors. While the exact mechanisms driving obesity-induced pain remain poorly defined, nociceptor hypersensitivity may result from the systemic state of inflammation characteristic of obesity as well as weight surplus-induced mechanical stress. Obesity and pain also share various genetic mutations, lifestyle risk factors, and metabolic pathways. For instance, fat pads are often found hyper-innervated and rich in immune cell types of multiple origins. These immunocytes release cytokines, amplifying nociceptor function, which, in turn, via locally released neuropeptides, sustain immunocytes' function. Here, we posit that along with mechanical stress stemming from extra weight, the local neuro-immune interplay occurring within the fat pads maintains the state of chronic low-grade inflammation and heightens sensory hypersensitivity. Overall, stopping such harmful neuro-immune crosstalk may constitute a novel pathway to prevent obesity-associated comorbidities, including neuronal hypersensitivity.

1-O-Acetylgeopyxin A, a derivative of a fungal metabolite, blocks tetrodotoxin-sensitive voltage-gated sodium, calcium channels and neuronal excitability which correlates with inhibition of neuropathic pain

Chronic pain can be the result of an underlying disease or condition, medical treatment, inflammation, or injury. The number of persons experiencing this type of pain is substantial, affecting upwards of 50 million adults in the United States. Pharmacotherapy of most of the severe chronic pain patients includes drugs such as gabapentinoids, re-uptake blockers and opioids. Unfortunately, gabapentinoids are not effective in up to two-thirds of this population and although opioids can be initially effective, their long-term use is associated with multiple side effects. Therefore, there is a great need to develop novel non-opioid alternative therapies to relieve chronic pain. For this purpose, we screened a small library of natural products and their derivatives in the search for pharmacological inhibitors of voltage-gated calcium and sodium channels, which are outstanding molecular targets due to their important roles in nociceptive pathways. We discovered that the acetylated derivative of the ent-kaurane diterpenoid, geopyxin A, 1-O-acetylgeopyxin A, blocks voltage-gated calcium and tetrodotoxin-sensitive voltage-gated sodium channels but not tetrodotoxin-resistant sodium channels in dorsal root ganglion (DRG) neurons. Consistent with inhibition of voltage-gated sodium and calcium channels, 1-O-acetylgeopyxin A reduced reduce action potential firing frequency and increased firing threshold (rheobase) in DRG neurons. Finally, we identified the potential of 1-O-acetylgeopyxin A to reverse mechanical allodynia in a preclinical rat model of HIV-induced sensory neuropathy. Dual targeting of both sodium and calcium channels may permit block of nociceptor excitability and of release of pro-nociceptive transmitters. Future studies will harness the core structure of geopyxins for the generation of antinociceptive drugs.