Neurogenic inflammation and the peripheral nervous system in host defense and immunopathology

Potential applications of mesenchymal stem cells in ocular surface immune-mediated disorders

We explore the interaction between corneal immunity and mesenchymal stem/stromal cells (MSCs) and their potential in treating corneal and ocular surface disorders. We outline the cornea's immune privilege mechanisms and the immunomodulatory substances involved. In this realm, MSCs are characterized by their immunomodulatory properties and regenerative potential, making them promising for therapeutic application. Therefore, we focus on the role of MSCs in immune-mediated corneal diseases such as dry eye disease, corneal transplantation rejection, limbal stem cell deficiency, and ocular graft-versus-host disease. Preclinical and clinical studies demonstrate MSCs' efficacy in promoting corneal healing and reducing inflammation in these conditions. Overall, we emphasize the potential of MSCs as innovative therapies in ophthalmology, offering promising solutions for managing various ocular surface pathologies.

Neurturin GF Enhances the Acute Cytokine Response of Inflamed Skin

Epidermal keratinocytes, immune cells, and sensory nerves all contribute to immune balance and skin homeostasis. Keratinocyte's release of GFs, neuromodulators, and immune activators is particularly important because each can evoke local (skin) and systemic (ie, immune and neural) responses that can initiate and exacerbate skin pathophysiology. From studies of skin and neural GFs, we hypothesized that neurturin (Nrtn), a member of the GDNF family that is expressed in the skin, has particular importance in this process. In this study, we examine how elevation of Nrtn in skin keratinocytes impacts early cytokine expression in response to complete Freund's adjuvant-mediated inflammation. Nrtn-overexpressing mice and wild-type mice injected with Nrtn exhibit an enhanced level of TNFα and IL-1β cytokines in the skin, a response previously shown to support healing. In vitro assays suggest that one source of the Nrtn-induced TNFα increase is keratinocytes, which are shown to express Nrtn and mRNAs encoding the Nrtn receptors GFRα2, Ret, ITGB1, and NCAM. These findings support the contribution of keratinocyte-derived Nrtn as an autocrine/paracrine factor that acts as a first-line defense molecule that regulates the initial cytokine response to inflammatory challenge.

Neuroimmunology of psoriasis: Possible roles for calcitonin gene-related peptide in its pathogenesis

The nervous system has a complex interplay with the immune system, especially at barrier sites such as the skin. This allows it to play a role in a variety of cutaneous inflammatory disorders such as psoriasis, exerting effects on various immune cells via effector molecules such as neuropeptides. In this review, we discuss the role of calcitonin gene-related peptide in modulating the immune system and inflammation, with a focus on psoriasis.

Substance P receptor signaling contributes to host maladaptive responses during enteric bacterial infection

Immune responses in the intestine are intricately balanced to prevent pathogen entry without inducing immunopathology. The nervous system is well established to interface with the immune system to fine-tune immunity in various organ systems including the gastrointestinal tract. Specialized sensory neurons can detect bacteria, bacterial products, and the resulting inflammation, to coordinate the immune response in the gastrointestinal tract. These sensory neurons release peptide neurotransmitters such as Substance P (SP), to induce both neuronal signaling and localized responses in nonneuronal cells. With this in mind, we assessed the immunoregulatory roles of SP receptor signaling during enteric bacterial infection with the noninvasive pathogen Citrobacter rodentium. Pharmacological antagonism of the SP receptor significantly reduced bacterial burden and prevented colonic crypt hyperplasia. Mice with SP receptor signaling blockade had significantly reduced inflammation and recruitment of T cells in the colon. Reduced colonic T cell recruitment is due to reduced expression of adhesion molecules on colonic endothelial cells in SP receptor antagonist-treated mice. Using SP receptor T cell conditional knockout mice, we further confirmed SP receptor signaling enhanced select aspects of T cell responses. Our data demonstrate that SP receptor signaling can significantly reduce inflammation and prevent host-maladaptive responses without impinging upon host protection.

Neuroinflammatory and Immunological Aspects of Fibromyalgia

Fibromyalgia is a common, high-impact condition of chronic widespread pain and sensory dysfunction associated with altered central and peripheral sensory processing. A growing body of evidence supports the role of neuroinflammation and immune changes in fibromyalgia, and a narrative review of this literature was undertaken. Published data suggest that the interactions between the neural pain networks and the immune system in fibromyalgia appear to be bidirectional and operate both centrally and peripherally. There is a growing focus on processes occurring in the dorsal root ganglia and the role of maladaptive microglial cell activation. Ongoing insight into neuroinflammatory mechanisms in fibromyalgia opens potential avenues for the development of mechanism-based therapies in what is, at present, a challenging-to-manage condition.

Implications of nociceptor receptors and immune modulation: emerging therapeutic targets for autoimmune diseases

Chronic painful autoimmune disorders such as multiple sclerosis (MS), inflammatory bowel disease (IBD), and rheumatoid arthritis (RA) induce significant discomfort. They are defined by persistent inflammation and immune-mediated tissue injury. The activation and sensitisation of nociceptors, mutated in various disorders, are fundamental components contributing to the pain experienced in these conditions. Recent discoveries indicate that immunological mediators and nociceptive receptors interact functionally within peripheral and central sensitisation pathways, amplifying chronic pain. This research examines the involvement of nociceptors in rheumatoid arthritis, multiple sclerosis, and inflammatory bowel disease. It explores how immune cells and pro-inflammatory cytokines induce, sensitise and regulate various nociceptive receptors (P2X, TRPA1 and TRPV1). Finally, we address possible future directions with respect to the treatment of long-lasting effects on immunity, and what new drug targets could be pursued as well, in order to counteract such either neuro-immune interactions in conditions involving the immunological system. By studying nociceptive mechanisms across autoimmune illnesses, we want to identify shared pathways and activation of nociceptors specific to individual diseases. This will shed insight on potential therapies for managing pain associated with autoimmune diseases.

Topical neurokinin-1 receptor antagonism ameliorates ocular pain and prevents corneal nerve degeneration in an animal model of dry eye disease

Introduction

Ocular pain is a common complaint to eye care providers, associated with a variety of ocular conditions, among which dry eye disease (DED) is affecting millions of people worldwide. Despite being highly prevalent, ocular pain is not managed adequately in the clinic.

Objectives

The aim of this study was to investigate the analgesic potential of neurokinin-1 receptor (NK1R) antagonism in DED.

Methods

Dry eye disease was induced in mice, and an NK1R antagonist L-733,060 was topically administered twice daily throughout the study for 14 days. Hyperalgesia and allodynia were assessed using the eye-wiping test and palpebral ratio measurements. Corneas were collected for measuring substance P (SP) levels by enzyme-linked immunosorbent assay (ELISA) and imaging nerves by immunostaining. Trigeminal ganglions (TG) were collected to determine SP levels by ELISA and transient receptor potential cation channel subfamily V member 1 (TRPV1), transient receptor potential cation channel subfamily M (melastatin) member 8, c-Fos, and activating transcription factor 3 (ATF3) mRNA levels by real-time polymerase chain reaction.

Results

Treating DED mice with L-733,060 resulted in a significant reduction in eye wipe behavior, a significant increase in palpebral ratio, and significant decreases in SP levels in both the cornea and TG compared with the vehicle-treated group. In addition, NK1R antagonist treatment significantly suppressed the upregulation of TRPV1, ATF3, and c-Fos and prevented corneal nerve loss.

Conclusion

Neurokinin-1 receptor antagonism effectively reduced ocular nociception, decreased neuronal activation, and preserved corneal nerves in mice with DED. These findings suggest that blockade of SP signaling pathway is a promising therapeutic strategy for managing DED pain.

Multiple lesion inductions intensify central sensitization driven by neuroinflammation in a mouse model of endometriosis

Introduction

Endometriosis is an inflammatory disease associated with chronic pelvic pain (CPP). Growing evidence indicates that endometriotic lesions are not the sole source of pain. Instead, central nervous system (CNS) dysfunction created by prolonged peripheral and central sensitization plays a role in developing endometriosis-associated CPP. This study investigated how CPP is established using a multiple lesion induction mouse model of endometriosis, as repeated retrograde menstruation is considered underlying endometriosis pathogenesis.

Methods

We generated endometriosis-like lesions by injecting endometrial tissue fragments into the peritoneal cavity in mice. The mice received a single (1x) or multiple inductions (6x) to simulate recurrent retrograde menstruation. Lesion development, hyperalgesia by behavioral testing, signs of peripheral sensitization, chronic inflammation, and neuroinflammation were examined with lesions, peritoneal fluids, dorsal root ganglia (DRG), spinal codes, and brain.

Results

Multiple lesion inductions increased lesion numbers and elevated abdominal and hind paw hypersensitivity compared to single induction mice. Elevated persistent glial cell activation across several brain regions and/or spinal cords was found in the multiple induction mice. Specifically, IBA1+ microglial soma size was increased in the hippocampus and thalamus. IBA1+ cells were abundant in the cortex, hippocampus, thalamus, and hypothalamus of the multiple induction mice. GFAP+ astrocytes were mainly elevated in the hippocampus. Elevated TRPV1, SP, and CGRP expressions in the DRG were persistent in the multiple induction mice. Furthermore, multiple inductions induced the severe disappearance of TIM4hi MHCIIlo residential macrophages and the influx of increased proinflammatory TIM4lo MHCIIhi macrophages in the peritoneal cavity. The single and multiple inductions elevated secreted TNFα, IL-1β, and IL-6 levels in the peritoneal cavity at 2 weeks. Elevated cytokine levels returned to the pre-induction levels in the single induction mice at 6 weeks; however, they remained elevated in the multiple induction mice.

Conclusions

Our results indicate that the repeatedly occurring lesion inductions (=mimic retrograde menstruation) can be a peripheral stimulus that induces nociceptive pain and creates composite chronic inflammatory stimuli to cause neuroinflammation and sensitize the CNS. The circuits of neuroplasticity and stimulation of peripheral organs via a feedback loop of neuroinflammation may mediate widespread endometriosis-associated CPP.

Lipid nanoparticle delivery of siRNA to dorsal root ganglion neurons to treat pain

Sensory neurons within the dorsal root ganglion (DRG) are the primary trigger of pain, relaying activity about noxious stimuli from the periphery to the central nervous system; however, targeting DRG neurons for pain management has remained a clinical challenge. Here, we demonstrate the use of lipid nanoparticles (LNPs) for effective intrathecal delivery of small interfering RNA (siRNA) to DRG neurons, achieving potent silencing of the transient receptor potential vanilloid 1 (TRPV1) ion channel that is predominantly expressed in nociceptor sensory neurons. This leads to a reversible interruption of heat-, capsaicin-, and inflammation-induced nociceptive conduction, as observed by behavioral outputs. Our work provides a proof-of-concept for intrathecal siRNA therapy as a novel and selective analgesic modality.

Neurogenic inflammation and itch in barrier tissues

Once regarded as distinct systems, the nervous system and the immune system are now recognized for their complex interactions within the barrier tissues. The neuroimmune circuitry comprises a dual-network system that detects external and internal disturbances, providing critical information to tailor a context-specific response to various threats to tissue integrity, such as wounding or exposure to noxious and harmful stimuli like pathogens, toxins, or allergens. Using the skin as an example of a barrier tissue with the polarized sensory neuronal responses of itch and pain, we explore the molecular pathways driving neuronal activation and the effects of this activation on the immune response. We then apply these findings to other barrier tissues, to find common pathways controlling neuroimmune responses in the barriers.

The Role of Central Sensitization in Autoimmune Connective Tissue Diseases: A Comparative Cross-Sectional Study

OBJECTIVE

To investigate the central sensitization (CS) in patients with autoimmune connective tissue diseases (ACTDs) and its relationship with disease activity, laboratory findings, medical treatments, organ involvements, and comorbidity.

METHODS

One hundred and eleven patients with ACTDs and 40 healthy individuals were included. All patients were divided into three groups in terms of their diseases: Sjögren's syndrome (SS), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). The CS was assessed using the central sensitization inventory (CSI-A and CSI-B scores). The disease activity, laboratory findings, medical treatments, organ involvements, and comorbidity of all patients were evaluated.

RESULTS

Overall, 41.4% patients with ACTDs had CS. SS group had the highest CS positivity (n = 21, 58.3%) compared to the RA (n = 14, 36.8%) and SLE (n = 11, 29.7%) groups. The SS group had a significantly higher CSI-A score (p < 0.016) than the RA and SLE group, which had similar scores. CSI-A (p = 0.008, r = -0.63) and CSI-B (p = 0.001, r = -0.76) scores were moderately to high correlated with vitamin D3 levels in SLE group. CSI-B score was moderately correlated with folic acid levels (p = 0.03, r = 0.50) and TSH (p = 0.005, r = 0.55) in SS group. The CSI-A score ≥ 40 subgroup had more female gender, frequency of COPD or asthma, more coexisting fibromyalgia, higher VAS score, more common exocrine gland involvement, and higher corticosteroid dose compared to the CSI score < 40 subgroup.

CONCLUSIONS

CS is commonly seen in patients with ACTDs, especially in SS. CS is associated with vitamin D3, folic acid, and TSH levels in ACTD subgroups and the patients with clinical CS have a specific profile.

Animal neuropathic pain aroused by conglutinating oxidative regenerative cellulose on dorsal root ganglion

Neuropathic pain arises as a consequence of injury or disease in the peripheral or central nervous system. Clinical cases have shown that spine postoperative chronic neuropathic pain remains a troublesome issue in medical treatment due to the presence of various degrees of peridural fibrosis and different inflammatory factors after spinal surgery. To address this issue, we developed a new neuropathic mice model that successfully simulates the real clinical situation by applying oxidative regenerative cellulose to L5 DRG (dorsal root ganglion). Behavior tests were done by von Fray and thermal stimuli. ELISA and real-time PCR were employed to detect the expression of genes involved in neuropathic pain. This model not only successfully induces chronic pain but also causes membrane thickening, non-neuronal cell recruitment, and a local increase of TNFα and interleukin-6. Additionally, this model did not cause neuron loss in the affected DRG, which mimics the characteristics of sticky tissue-induced neuropathic pain after clinic surgery. Based on this model, we administrated a TNF inhibitor to mice and successfully reduced mechanical allodynia after DRG surgery. In this study, the developed animal model may be a novel platform for delivering neuropathic pain treatments, such as target-based drug discovery or personalized diagnostic approaches.

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential environmental dangers. However, this function can be detrimental during allergic reactions, as vagal nociceptors contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we investigate the changes in the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identify a specific class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of allergic airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the neuropeptide Y (NPY) receptor Npy1r. A screening of cytokines and neurotrophins reveals that interleukin 1β (IL-1β), IL-13, and brain-derived neurotrophic factor (BDNF) drive part of this reprogramming. IL-13 triggers Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, NPY is released into the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells reveals that a cell-specific knockout of NPY1R in nociceptor neurons in asthmatic mice altered T cell infiltration. Opposite findings are observed in asthmatic mice in which nociceptor neurons are chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits the activity of nociceptor neurons.

Bimodal functions of calcitonin gene-related peptide in the brain

AIMS

Calcitonin gene-related peptide (CGRP) is a pluripotent neuropeptide crucial for maintaining vascular homeostasis, yet its full therapeutic potential remains incompletely exploited. Within the brain, CGRP demonstrates a distinct bimodal effect, contributing to neuroprotection in ischemic conditions while inducing neuronal sensitization and inflammation in non-ischemic settings. Despite extensive research on CGRP, the absence of a definitive determinant for this observed dichotomy has limited its potential for therapeutic applications in the brain. This review examines the effects of CGRP in both physiological and pathological conditions, aiming to identify a unifying factor that could enhance its therapeutic applicability.

MATERIALS AND METHODS

This comprehensive literature review analyzes the molecular pathways associated with CGRP and the specific cellular responses observed in these contexts. Additionally, the review investigates the psychological implications of CGRP in relation to cerebral perfusion levels, aiming to elucidate its underlying factors.

KEY FINDINGS

Reviewing the literature reveals that, elevated levels of CGRP in non-ischemic conditions exert detrimental effects on brain function, while they confer protective effects in the context of ischemia. These encompass anti-oxidative, anti-inflammatory, anti-apoptotic, and angiogenic properties, along with behavioral normalization. Current findings indicate promising therapeutic avenues for CGRP beyond the acute phases of cerebral injury, extending to neurodegenerative and psychological disorders associated with cerebral hypoperfusion, as well as chronic recovery following acute cerebral injuries.

SIGNIFICANCE

Improved understanding of CGRP's bimodal properties, alongside advancements in CGRP delivery methodologies and brain ischemia detection technologies, paves the way for realizing its untapped potential and broad therapeutic benefits in diverse pathological conditions.

Calmodulin binding is required for calcium mediated TRPA1 desensitization

Calcium (Ca2+) ions affect nearly all aspects of biology. Excessive Ca2+ entry is cytotoxic and Ca2+-mobilizing receptors have evolved diverse mechanisms for tight regulation that often include Calmodulin (CaM). TRPA1, an essential Ca2+-permeable ion channel involved in pain signaling and inflammation, exhibits complex Ca2+ regulation with initial channel potentiation followed by rapid desensitization. The molecular mechanisms of TRPA1 Ca2+ regulation and whether CaM plays a role remain elusive. We find that TRPA1 binds CaM best at basal Ca2+ concentration, that they co-localize in resting cells, and that CaM suppresses TRPA1 activity. Combining biochemical, biophysical, modeling, NMR spectroscopy, and functional approaches, we identify an evolutionarily conserved, high-affinity CaM binding element in the distal TRPA1 C-terminus (DCTCaMBE). Genetic or biochemical perturbation of Ca2+/CaM binding to the TRPA1 DCTCaMBE yields hyperactive channels that exhibit drastic slowing of desensitization with no effect on potentiation. Ca2+/CaM TRPA1 regulation does not require the N-lobe, raising the possibility that CaM is not the Ca2+ sensor, per se. Higher extracellular Ca2+ can partially rescue slowed desensitization suggesting Ca2+/CaM binding to the TRPA1 DCTCaMBE primes an intrinsic TRPA1 Ca2+ binding site that, upon binding Ca2+, triggers rapid desensitization. Collectively, our results identify a critical regulatory element in an unstructured TRPA1 region highlighting the importance of these domains, they reveal Ca2+/CaM is an essential TRPA1 auxiliary subunit required for rapid desensitization that establishes proper channel function with implications for all future TRPA1 work, and they uncover a mechanism for receptor regulation by Ca2+/CaM that expands the scope of CaM biology.

Pain persists in mice lacking both Substance P and CGRPα signaling

The neuropeptides Substance P and CGRPα have long been thought important for pain sensation. Both peptides and their receptors are expressed at high levels in pain-responsive neurons from the periphery to the brain making them attractive therapeutic targets. However, drugs targeting these pathways individually did not relieve pain in clinical trials. Since Substance P and CGRPα are extensively co-expressed we hypothesized that their simultaneous inhibition would be required for effective analgesia. We therefore generated Tac1 and Calca double knockout (DKO) mice and assessed their behavior using a wide range of pain-relevant assays. As expected, Substance P and CGRPα peptides were undetectable throughout the nervous system of DKO mice. To our surprise, these animals displayed largely intact responses to mechanical, thermal, chemical, and visceral pain stimuli, as well as itch. Moreover, chronic inflammatory pain and neurogenic inflammation were unaffected by loss of the two peptides. Finally, neuropathic pain evoked by nerve injury or chemotherapy treatment was also preserved in peptide-deficient mice. Thus, our results demonstrate that even in combination, Substance P and CGRPα are not required for the transmission of acute and chronic pain.

Adenosine triphosphate: a new player in complex regional pain syndrome type 1

The complex regional pain syndrome type 1 (CRPS-1) is one of the most discussed painful syndromes due to the variability and severity of its symptoms. CRPS-1 generally occurs after a trauma, a fracture or a sprain followed by an immobilization. Classical diagnostic criteria are not always clear; hence, the diagnosis is difficult. The definition of CRPS itself defines and considers the pain as key symptom neglecting the bone damage. Early CRPS involves the activation of the innate cutaneous immune system with altered sensory and sympathetic signaling, activation and proliferation of keratinocytes and mast cells in addition to the release of inflammatory mediators and pain. The role of the immune system and the response to the disease is becoming clearer as the microglia is activated as a result of injury and can induce a central sensitization while astrocytes can maintain the process. Adenosine triphosphate (ATP) exerts a fundamental role in the activation of innate cutaneous immune system, in the proliferation of keratinocytes and mast cells, in the release of several proinflammatory cytokines and in the microglia activation. It is essential to intervene on this pathology as soon as possible with drugs, as clodronate, able to reduce bone marrow edema and pain through the inhibition of the primary inflammatory process and the immune reaction, limiting the activation of macrophages and the release of cytokines activating nuclear growth factor (NGF). In this review the role of ATP, bisphosphonates and rehabilitation are discussed.

Chinese Herbal Medicine for Irritable Bowel Syndrome: A Perspective of Local Immune Actions

Irritable bowel syndrome (IBS) is the functional gastrointestinal disorder, characterized by abdominal pain and altered bowel habits. The interest in intestinal immune activation as a potential disease mechanism for IBS has increased exponentially in recent years. This study was designed to summarize the Chinese herbal medicine (CHM) that potentially exert protective effects against IBS through inhibition of intestinal immune activation. We detailed the current evidence that immune activation contributes to the pathology of IBS and discussed the potential mechanisms involved. Then, therapeutic effects and possible mechanisms related to immune response of herbal medicine prescriptions, extracts, and monomers were analyzed. The reasons leading to the aberrant and persistent immune activation noted in IBS are mainly associated with the increased number of mast cells, CD3[Formula: see text] T cells, and CD4[Formula: see text] T cells. The mechanisms mainly focused on the gut microbiota disorder induced alteration of the PGE2/COX2/SERT/5-HT, TLR4/MyD88/NF-κB, and BDNF/TrkB pathways. Most of the CHM alleviated IBS through interventions of intestinal immune activation via gut microbiota related to the TLR4/MyD88/NF-κB and SCF/c-kit pathways. We hope this review will provide some clues for the further development of novel candidate agents for IBS and other intestinal immune disorders.

Substance P regulates memory Th17 cell generation and maintenance in chronic dry eye disease

Substance P is a neuropeptide expressed by nerves and an array of cells that serves as a critical mediator of neuroinflammation. Our recent work has demonstrated that blocking the preferred receptor for substance P, neurokinin 1 receptor, effectively suppresses the induction of acute dry eye disease by preserving regulatory T-cell function, while inhibiting antigen-presenting cell maturation and subsequent generation of effector Th17 cells. Clinically, dry eye disease is a chronic disorder characterized by sustained ocular surface inflammation, which is mediated by long-lived memory Th17 cells demonstrated in our well-established chronic dry eye disease model. The present study aimed to further understand the function of substance P in the chronic phase of dry eye disease and its role in regulating the underlying pathogenic memory Th17. In vitro culture of effector T cells isolated from acute dry eye disease with substance P led to an enhanced conversion of effector Th17 to memory Th17, while culturing memory T cells isolated from chronic dry eye disease with substance P effectively preserved the memory Th17 cells. In contrast, the addition of a neurokinin 1 receptor antagonist in the cultures abolished the substance P-mediated effects. Furthermore, in vivo treatment with the neurokinin 1 receptor antagonist during the resolution phase of acute dry eye disease significantly suppressed memory Th17 generation, and treatment in the chronic phase of dry eye disease disrupted the maintenance of memory Th17. Taken together, our results demonstrate that increased expression of substance P promotes memory Th17 generation and maintenance in chronic dry eye disease, and thus blockade of substance P represents a novel promising memory Th17-targeting strategy in treating chronic ocular surface inflammation.

Neuronal substance P-driven MRGPRX2-dependent mast cell degranulation products differentially promote vascular permeability

Mas-related G protein-coupled receptor b2 (Mrgprb2) binding to its cationic endogenous and exogenous ligands induces mast cell degranulation and promotes inflammation in mice. However, the physiological roles of its human homologue MRGPRX2 remain unclear. Here we aimed to elucidate the mechanisms by which MRGPRX2 regulates vascular permeability, and generated MRGPRX2 knock-in (MRGPRX2-KI) and Mrgprb2 knockout (Mrgprb2-KO) mice. Substance P (SP) and ciprofloxacin strongly degranulated MRGPRX2-KI peritoneal mast cells (PMCs) better than WT PMCs, whereas Dermatophagoides pteronyssinus (Der p) extract and phenol-soluble modulin α3 (PSMα3) did not degranulate PMCs. SP-stimulated MRGPRX2-KI PMCs released large amounts of histamine and mast cell protease 4 (MCPT4) chymase. Der p extract, PSMα3, and MCPT4, but not histamine, induced SP release from dorsal root ganglion (DRG) cells. However, this effect of Der p extract/PSMα3 was suppressed by a transient receptor potential vanilloid 1 (TRPV1) antagonist. SP-, ciprofloxacin-, Der p extract-, PSMα3-, and MCPT4-induced vascular permeability was highest in MRGPRX2-KI mice, which depended on SP. In addition, SP-, ciprofloxacin- and PSMα3-induced MRGPRX2-dependent vascular hyperpermeability was suppressed by antihistamine and chymase inhibitor. TRPV1 antagonist also inhibited PSMα3-induced MRGPRX2-dependent vascular hyperpermeability. Both Mrgprb2-KO and MRGPRX2-KI did not influence the histamine-induced murine vascular hyperpermeability. Overall, our results suggest that neuronal SP induces MRGPRX2-dependent mast cell degranulation, releasing histamine and chymase, which promote vascular hyperpermeability directly or indirectly via DRG cell activation. Importantly, the worsening cycle (MRGPRX2 → mast cell degranulation → chymase → DRG activation → SP → MRGPRX2) seems to play an important role in human MRGPRX2-depdendent inflammation.

Nociceptor-to-macrophage communication through CGRP/RAMP1 signaling drives endometriosis-associated pain and lesion growth in mice

Endometriosis is a debilitating and painful gynecological inflammatory disease affecting up to 15% of women and transgender men. Current treatments are ineffective for a substantial proportion of patients, underscoring the need for additional therapies with long-term benefits. Nociceptors release neuropeptides, such as calcitonin gene-related peptide (CGRP), which are known to shape immunity through neuroimmune communication. Given the comorbidity between endometriosis and migraine and the integral role of immune cells and inflammation in endometriosis, we investigated the role of CGRP-mediated neuroimmune communication in endometriosis. Using samples from eight patients with endometriosis and a nonsurgical mouse model of the disease, we found that mouse and human endometriosis lesions contain both CGRP and its coreceptor, receptor activity modifying protein 1 (RAMP1). In mice, nociceptor ablation reduced pain, monocyte recruitment, and lesion size, suggesting that nociceptor activation and neuropeptide release contribute to endometriosis lesion growth and pain. Mechanistically, CGRP changed the phenotype of macrophages to a pro-endometriosis phenotype. CGRP-stimulated macrophages demonstrated impaired efferocytosis and supported increased endometrial cell growth in a RAMP1-dependent manner. Treatment of lesion-bearing mice with US Food and Drug Administration-approved drugs that block CGRP-RAMP1 signaling reduced mechanical hyperalgesia, spontaneous pain, and lesion size. Together, our data demonstrated the effectiveness and underlying cellular mechanisms of nonhormonal and nonopioid CGRP/RAMP1 blockade in a mouse model of endometriosis, suggesting that targeting this axis may lead to clinical benefit for patients with endometriosis.

Molecular mechanisms of neuropathic pain

Peripheral neuropathic pain, which occurs after a lesion or disease affecting the peripheral somatosensory nervous system, is a complex and challenging condition to treat. This chapter will cover molecular mechanisms underlying the pathophysiology of peripheral neuropathic pain, focusing on (1) sensitization of nociceptors, (2) neuro-immune crosstalk, and (3) axonal degeneration and regeneration. The chapter will also emphasize the importance of identifying novel therapeutic targets in non-neuronal cells. A comprehensive understanding of how changes at both neuronal and non-neuronal levels contribute to peripheral neuropathic pain may significantly improve pain management and treatment options, expanding to topical application that bypass the side effects associated with systemic administration.

Understanding dental pulp inflammation: from signaling to structure

The pulp is a unique tissue within each tooth that is susceptible to painful inflammation, known as pulpitis, triggered by microbial invasion from carious lesions or trauma that affect many individuals. The host response involves complex immunological processes for pathogen defense and dentin apposition at the site of infection. The interplay of signaling between the immune and non-immune cells via cytokines, chemokines, neuropeptides, proteases, and reactive nitrogen and oxygen species leads to tissue reactions and structural changes in the pulp that escalate beyond a certain threshold to irreversible tissue damage. If left untreated, the inflammation, which is initially localized, can progress to pulpal necrosis, requiring root canal treatment and adversely affecting the prognosis of the tooth. To preserve pulp vitality and dental health, a deeper understanding of the molecular and cellular mechanisms of pulpitis is imperative. In particular, elucidating the links between signaling pathways, clinical symptoms, and spatiotemporal spread is essential to develop novel therapeutic strategies and push the boundaries of vital pulp therapy.

Ageing-Related Macrophage Polarisation in the Trigeminal Ganglion Enhances Incisional Intraoral Pain

OBJECTIVE

Although macrophage polarisation in the trigeminal ganglion (TG) is crucial in orofacial pain hypersensitivity, the effect of ageing-related changes and their involvement in intra-oral nociception remains unclear. We assessed the effect of ageing-related macrophage polarisation in TG on intra-oral mechanical pain hypersensitivity following palatal mucosal incision using senescence-accelerated mice (SAM)-prone8 (SAMP8) and SAM-resistant 1 (SAMR1).

MATERIALS AND METHODS

Mechanical head-withdrawal reflex threshold (MHWRT) of the palatal mucosa was measured for 21 days after palatal mucosal incision. On days 3 and 14, the abundance of Iba-1-immunoreactive (IR) cells, CD11c-IR cells (pro-inflammatory macrophages (M1)), C-C motif chemokine ligand 2 (CCL2)-IR M1-macrophages, CD206-IR cells (anti-inflammatory macrophages (M2)) and transforming growth factor-β (TGF-β)-IR M2-macrophages in the TG was analysed. The effect of continuous intra-TG administration of CCL2-neutralising antibody or recombinant-CCL2 on MHWRT was examined.

RESULTS

Incision-induced decrease in MHWRT was enhanced in SAMP8 compared with that in SAMR1. On days 3 and 14, the number of CCL2-IR M1-macrophages in TG was increased in SAMP8 compared with that in SAMR1. CCL2-neutralising antibody suppressed, whereas recombinant-CCL2 increased pain hypersensitivity in SAMP8.

CONCLUSIONS

Mechanical pain hypersensitivity after oral mucosal injury is potentiated and sustained by age-related enhancement of CCL2 signalling via M1-macrophage hyperactivation in TG.

The influence of sex on neuroimmune communication, pain, and physiology

With the National Institutes of Health's mandate to consider sex as a biological variable (SABV), there has been a significant increase of studies utilizing both sexes. Historically, we have known that biological sex and hormones influence immunological processes and now studies focusing on interactions between the immune, endocrine, and nervous systems are revealing sex differences that influence pain behavior and various molecular and biochemical processes. Neuroendocrine-immune interactions represent a key integrative discipline that will reveal critical processes in each field as it pertains to novel mechanisms in sex differences and necessary therapeutics. Here we appraise preclinical and clinical literature to discuss these interactions and key pathways that drive cell- and sex-specific differences in immunity, pain, and physiology.

Corneal nerve loss in adolescents with obesity and acanthosis nigricans

BACKGROUND/AIM

Obesity and related metabolic abnormalities in adults are associated with peripheral neuropathy. Acanthosis nigricans (AN) is associated with insulin resistance, fatty liver, hyperlipidemia and glucose intolerance, all of which are risk factors for neuropathy. The aim of this study was to investigate if obese adolescents with AN have evidence of small nerve fiber damage.

MATERIAL AND METHODS

Adolescents with obesity with and without AN underwent body composition analysis, assessment of vibration perception threshold (VPT), monofilament sensitivity and corneal confocal microscopy (CCM) to quantify corneal nerve fiber density (CNFD), branch density (CNBD), length (CNFL) and inferior whorl length (IWL).

RESULTS

Forty-six participants with obesity with (n = 31) and without (n = 15) AN aged 15(14-17) years were compared to 20 healthy controls aged 13(12-14) years. There was no difference in VPT, monofilament sensitivity and CCM measures between adolescents with obesity and controls. However, adolescents with AN had a significantly higher weight (P = 0.022), fat% (P = 0.029) and fat-muscle ratio (P = 0.012) with a lower CNFD (P = 0.045) compared to those with obesity without AN.

CONCLUSION

Adolescents with obesity and acanthosis nigricans have a higher fat mass and small nerve fibre loss, indicative of a sub-clinical neuropathy.

T cell death-associated gene 8-mediated distinct signaling pathways modulate the early and late phases of neuropathic pain

Peripheral nerve injury alters the transduction of nociceptive signaling. The coordination of neurons, glia, and immune cells results in persistent pain and inflammation. T cell death-associated gene 8 (TDAG8), located at nociceptors and immune cells, is involved in inflammatory pain and arthritis-induced pain. Here, we employed TDAG8-deficient mice, pharmacological approaches, and calcium/sodium imaging to elucidate how TDAG8-mediated signaling modulates neuron activities in a mouse model of chronic constriction injury-induced neuropathic pain. We demonstrated that TDAG8 participated alone in mechanical allodynia induced by constriction injury. (1) TDAG8-Nav1.8 signaling in small-diameter isolectin B4-positive [IB4(+)] neurons initiates mechanical allodynia; it also modulated substance P release from IB4(-) neurons to facilitate the development of early mechanical allodynia. (2) TDAG8-mediated signaling increased medium-to large-diameter IB4(-) neuron activity to maintain late mechanical allodynia; it also modulated substance P release in soma to reduce satellite glial number and Nav1.7 expression, thus attenuating chronic mechanical allodynia.

CARTp/GPR160 mediates behavioral hypersensitivities in mice through NOD2

ABSTRACT

Neuropathic pain is a debilitating chronic condition that remains difficult to treat. More efficacious and safer therapeutics are needed. A potential target for therapeutic intervention recently identified by our group is the G-protein coupled receptor 160 (GPR160) and the cocaine- and amphetamine-regulated transcript peptide (CARTp) as a ligand for GPR160. Intrathecal administration of CARTp in rodents causes GPR160-dependent behavioral hypersensitivities. However, the molecular and biochemical mechanisms underpinning GPR160/CARTp-induced behavioral hypersensitivities in the spinal cord remain poorly understood. Therefore, we performed an unbiased RNA transcriptomics screen of dorsal horn spinal cord (DH-SC) tissues harvested at the time of peak CARTp-induced hypersensitivities and identified nucleotide-binding oligomerization domain-containing protein 2 (Nod2) as a gene that is significantly upregulated. Nucleotide-binding oligomerization domain-containing protein 2 is a cytosolic pattern-recognition receptor involved in activating the immune system in response to bacterial pathogens. While NOD2 is well studied under pathogenic conditions, the role of NOD2-mediated responses in nonpathogenic settings is still not well characterized. Genetic and pharmacological approaches reveal that CARTp-induced behavioral hypersensitivities are driven by NOD2, with co-immunoprecipitation studies indicating an interaction between GPR160 and NOD2. Cocaine- and amphetamine-regulated transcript peptide-induced behavioral hypersensitivities are independent of receptor-interacting protein kinase 2 (RIPK2), a common adaptor protein to NOD2. Immunofluorescence studies found NOD2 co-expressed with endothelial cells rather than glial cells, implicating potential roles for CARTp/NOD2 signaling in these cells. While these findings are based only on studies with male mice, our results identify a novel pathway by which CARTp causes behavioral hypersensitivities in the DH-SC through NOD2 and highlights the importance of NOD2-mediated responses in nonpathogenic settings.

Setting the tone: nociceptors as conductors of immune responses

Nociceptors have emerged as master regulators of immune responses in both homeostatic and pathologic settings; however, their seemingly contradictory effects on the functions of different immune cell subsets have been a source of confusion. Nevertheless, work by many groups in recent years has begun to identify patterns of the modalities and consequences of nociceptor-immune system communication. Here, we review recent findings of how nociceptors affect immunity and propose an integrated concept whereby nociceptors are neither inherently pro- nor anti-inflammatory. Rather, we propose that nociceptors have the role of a rheostat that, in a context-dependent manner, favors tissue homeostasis and fine-tunes immunity by preventing excessive histotoxic inflammation, promoting tissue repair, and potentiating anticipatory and adaptive immune responses.

Neuroimmune recognition of allergens

Interactions between the nervous system and the immune system play crucial roles in initiating and directing the type 2 immune response. Sensory neurons can initiate innate and adaptive type 2 immunity through their ability to detect allergens and promote dendritic cell and mast cell responses. Neurons also indirectly promote type 2 inflammation through suppression of type 1 immune responses. Type 2 cytokines promote neuronal function by directly activating or sensitizing neurons. This positive neuroimmune feedback loop may not only enhance allergic inflammation but also promote the system-wide responses of aversion, anaphylaxis, and allergen polysensitization that are characteristic of allergic immunity.

TRPV1: The key bridge in neuroimmune interactions

The nervous and immune systems are crucial in fighting infections and inflammation and in maintaining immune homeostasis. The immune and nervous systems are independent, yet tightly integrated and coordinated organizations. Numerous molecules and receptors play key roles in enabling communication between the two systems. Transient receptor potential vanilloid subfamily member 1 (TRPV1) is a non-selective cation channel, recently shown to be widely expressed in the neuroimmune axis and implicated in neuropathic pain, autoimmune disorders, and immune cell function. TRPV1 is a key bridge in neuroimmune interactions, allowing for smooth and convenient communication between the two systems. Here, we discuss the coordinated cross-talking between the immune and nervous systems and the functional role and the functioning manner of the TRPV1 involved. We suggest that TRPV1 provides new insights into the collaborative relationship between the nervous and immune systems, highlighting exciting opportunities for advanced therapeutic approaches to treating neurogenic inflammation and immune-mediated diseases.

Cytokines reprogram airway sensory neurons in asthma

Nociceptor neurons play a crucial role in maintaining the body's homeostasis by detecting and responding to potential dangers in the environment. However, this function can be detrimental during allergic reactions, since vagal nociceptors can contribute to immune cell infiltration, bronchial hypersensitivity, and mucus imbalance, in addition to causing pain and coughing. Despite this, the specific mechanisms by which nociceptors acquire pro-inflammatory characteristics during allergic reactions are not yet fully understood. In this study, we aimed to investigate the molecular profile of airway nociceptor neurons during allergic airway inflammation and identify the signals driving such reprogramming. Using retrograde tracing and lineage reporting, we identified a unique class of inflammatory vagal nociceptor neurons that exclusively innervate the airways. In the ovalbumin mouse model of airway inflammation, these neurons undergo significant reprogramming characterized by the upregulation of the NPY receptor Npy1r. A screening of cytokines and neurotrophins revealed that IL-1β, IL-13 and BDNF drive part of this reprogramming. IL-13 triggered Npy1r overexpression in nociceptors via the JAK/STAT6 pathway. In parallel, sympathetic neurons and macrophages release NPY in the bronchoalveolar fluid of asthmatic mice, which limits the excitability of nociceptor neurons. Single-cell RNA sequencing of lung immune cells has revealed that a cell-specific knockout of Npy1r in nociceptor neurons in asthmatic mice leads to an increase in airway inflammation mediated by T cells. Opposite findings were observed in asthmatic mice in which nociceptor neurons were chemically ablated. In summary, allergic airway inflammation reprograms airway nociceptor neurons to acquire a pro-inflammatory phenotype, while a compensatory mechanism involving NPY1R limits nociceptor neurons' activity.

Sensory sentinels: Neuroimmune detection and food allergy

Food allergy is classically characterized by an inappropriate type-2 immune response to allergenic food antigens. However, how allergens are detected and how that detection leads to the initiation of allergic immunity is poorly understood. In addition to the gastrointestinal tract, the barrier epithelium of the skin may also act as a site of food allergen sensitization. These barrier epithelia are densely innervated by sensory neurons, which respond to diverse physical environmental stimuli. Recent findings suggest that sensory neurons can directly detect a broad array of immunogens, including allergens, triggering sensory responses and the release of neuropeptides that influence immune cell function. Reciprocally, immune mediators modulate the activation or responsiveness of sensory neurons, forming neuroimmune feedback loops that may impact allergic immune responses. By utilizing cutaneous allergen exposure as a model, this review explores the pivotal role of sensory neurons in allergen detection and their dynamic bidirectional communication with the immune system, which ultimately orchestrates the type-2 immune response. Furthermore, it sheds light on how peripheral signals are integrated within the central nervous system to coordinate hallmark features of allergic reactions. Drawing from this emerging evidence, we propose that atopy arises from a dysregulated neuroimmune circuit.

Postictal Rash: A Rare Case Reporting to Neurology

Generalized epileptic seizures are usually followed by a postictal phase that is often characterized by drowsiness, lethargy, weakness, and confusion. In rare cases, it can present with cutaneous manifestations. Here, we present the case of a 45-year-old male who experienced a seizure and subsequently developed a pinpoint rash with non-blanchable petechiae on various parts of his body. The rash appeared during transport to the emergency department and was resolved after seven days once the seizures were controlled. Initial imaging and basic labs were unremarkable other than a slight increase in postictal markers. No other cause behind this new rash was identified. Our case emphasizes the importance of postictal skin manifestations to aid in diagnosing seizures and avoid unnecessary investigations. The possible pathophysiology behind these generalized non-blanchable petechiae has been attributed to hemodynamic changes and neurogenic inflammation triggered in response to the seizures. Further research into the underlying mechanism and prompt recognition of these symptoms can improve the management of epilepsy care.

NOCICEPTOR NEURONS CONTROL POLLUTION-MEDIATED NEUTROPHILIC ASTHMA

The immune and sensory nervous systems, having evolved together, use a shared language of receptors and transmitters to maintain homeostasis by responding to external and internal disruptions. Although beneficial in many cases, neurons can exacerbate inflammation during allergic reactions, such as asthma. Our research modeled asthma aggravated by pollution, exposing mice to ambient PM2.5 particles and ovalbumin. This exposure significantly increased bronchoalveolar lavage fluid neutrophils and γδ T cells compared to exposure to ovalbumin alone. We normalized airway inflammation and lung neutrophil levels by silencing nociceptor neurons at inflammation's peak using intranasal QX-314 or ablating TRPV1-expressing neurons. Additionally, we observed heightened sensitivity in chemical-sensing TRPA1 channels in neurons from pollution-exacerbated asthmatic mice. Elevated levels of artemin were detected in the bronchoalveolar lavage fluid from pollution-exposed mice, with artemin levels normalizing in mice with ablated nociceptor neurons. Upon exposure PM2.5 particles, alveolar macrophages expressing pollution-sensing aryl hydrocarbon receptors, were identified as the source of artemin. This molecule enhanced TRPA1 responsiveness and increased neutrophil influx, providing a novel mechanism by which lung-innervating neurons respond to air pollution and suggesting a potential therapeutic target for controlling neutrophilic airway inflammation in asthma, a clinically intractable condition.

Psychological Aspects of Cutaneous Pain in Psoriasis

Introduction: Psoriasis is a chronic inflammatory disease that negatively impacts patients' quality of life (QoL) and mental health. Itch and pain are prevalent symptoms of psoriasis and contribute to the psychosocial burden of this disease. This study aimed to evaluate the impact of skin pain on the prevalence and severity of symptoms of anxiety and depression and on the QoL in psoriasis patients. Methods: The studied population comprised 106 adults with psoriasis (34% female; mean age 42.1 ± 13.0 years). Disease severity was measured with the Psoriasis Area and Severity Index (PASI). The intensity of skin pain was assessed with the NRS and the Short Form McGill Pain Questionnaire (SF-MPQ). The Generalized Anxiety Disorder-7 (GAD-7) and Patient Health Questionnaire-9 (PHQ-9) questionnaires were used to estimate the severity of depression and anxiety, respectively, as was the Hospital Anxiety and Depression Scale (HADS). Quality of life (QoL) was studied using the Dermatology Life Quality Index (DLQI). Results: Regarding anxiety assessment, females reported significantly higher scores with the HADS-A (8.42 ± 4.85 points vs. 5.14 ± 3.9 points; p < 0.001) and the GAD-7 compared to men (7.50 ± 5.58 points vs. 5.24 ± 4.79 points; p = 0.036). Similarly, the severity of depression was significantly higher in women, as measured with the PHQ-9 (7.50 ± 5.58 points vs. 5.24 ± 4.79 points, p = 0.021). Psoriasis patients with skin pain scored significantly higher in HADS Total score (p = 0.043), HADS-A (p = 0.022), PHQ-9 (p = 0.035), and DLQI (p < 0.001) than the rest of the studied group. The intensity of skin pain measured with the SF-MPQ correlated significantly with HADS Total score (p = 0.021), HADS-A (p < 0.001), HADS-D (p = 0.038), and PHQ-9 (p < 0.001). Additionally, there was a significant correlation between the intensity of cutaneous pain assessed using the VAS and the PHQ-9 (p = 0.022). Conclusions: Skin pain significantly influences the well-being of patients with psoriasis as well as the symptoms of anxiety and depression. In particular, women with psoriasis are at increased risk of developing anxiety and depression. Our findings underline the necessity for a multidisciplinary approach to the management of this dermatosis.

Impact of streptozotocin-induced diabetes on experimental masseter pain in rats

This study aimed to assess the influence of streptozotocin (STZ)-induced diabetes on the nociceptive behavior evoked by the injection of hypertonic saline (HS) into the masseter muscle of rats. Forty male rats were equally divided into four groups: a) isotonic saline control, which received 0.9% isotonic saline (IS), (Ctrl-IS); b) hypertonic saline control, which received 5% HS (Ctrl-HS); c) STZ-induced diabetic, which received IS, (STZ-IS); d) STZ-induced diabetic, which received HS (STZ-HS). Experimental diabetes was induced by a single intraperitoneal injection of STZ at dose of 60 mg/kg dissolved in 0.1 M citrate buffer, and 100 μL of HS or IS were injected into the left masseter to measure the nociceptive behavior. Later on, muscle RNA was extracted to measure the relative expression of the following cytokines: cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-α), and interleukins (IL)-1β, -2, -6, and -10. One-way analysis of variance (ANOVA) was applied to the data (p < 0.050). We observed a main effect of group on the nociceptive response (ANOVA: F = 11.60, p < 0.001), where the Ctrl-HS group presented the highest response (p < 0.001). However, nociceptive response was similar among the Ctrl-IS, STZ-IS, and STZ-HS group (p > 0.050). In addition, the highest relative gene expression of TNF-α and IL-6 was found in the masseter of control rats following experimental muscle pain (p < 0.050). In conclusion, the loss of somatosensory function can be observed in deep orofacial tissues of STZ-induced diabetic rats.

A chemogenetic screen reveals that Trpv1-expressing neurons control regulatory T cells in the gut

Neuroimmune cross-talk participates in intestinal tissue homeostasis and host defense. However, the matrix of interactions between arrays of molecularly defined neuron subsets and of immunocyte lineages remains unclear. We used a chemogenetic approach to activate eight distinct neuronal subsets, assessing effects by deep immunophenotyping, microbiome profiling, and immunocyte transcriptomics in intestinal organs. Distinct immune perturbations followed neuronal activation: Nitrergic neurons regulated T helper 17 (TH17)-like cells, and cholinergic neurons regulated neutrophils. Nociceptor neurons, expressing Trpv1, elicited the broadest immunomodulation, inducing changes in innate lymphocytes, macrophages, and RORγ+ regulatory T (Treg) cells. Neuroanatomical, genetic, and pharmacological follow-up showed that Trpv1+ neurons in dorsal root ganglia decreased Treg cell numbers via the neuropeptide calcitonin gene-related peptide (CGRP). Given the role of these neurons in nociception, these data potentially link pain signaling with gut Treg cell function.

Beyond the urothelium: Interplay between autonomic nervous system and bladder inflammation in urinary tract infection, bladder pain syndrome with interstitial cystitis and neurogenic lower urinary tract dysfunction in spinal cord injury-ICI-RS 2023

INTRODUCTION

Inflammation and neuronal hypersensitivity are reactive protective mechanisms after urothelial injury. In lower urinary tract dysfunctions (LUTD), such as urinary tract infection (UTI), bladder pain syndrome with interstitial cystitis (BPS/IC) and neurogenic LUTD after spinal cord injury (SCI), chronic inflammation can develop. It is unclear how the protective reactionary inflammation escalates into chronic disease in some patients.

METHODS

During its 2023 meeting in Bristol, the International Consultation on Incontinence-Research Society (ICI-RS) reviewed the urothelial and inflammatory changes after UTI, BPS/IC and SCI. Potential factors contributing to the evolution into chronic disease were explored in a think-tank.

RESULTS

Five topics were discussed. (1) Visceral fat metabolism participates in the systemic pro-inflammatory effect of noradrenalin in BPS/IC and SCI. Sympathetic nervous system-adipocyte-bladder crosstalk needs further investigation. (2) Sympathetic hyperactivity also potentiates immune depression in SCI and needs to be investigated in BPS/IC. Gabapentin and tumor necrosis factor-α are promising research targets. (3) The exact peripheral neurons involved in the integrative protective unit formed by nervous and immune systems need to be further identified. (4) Neurotransmitter changes in SCI and BPS/IC: Neurotransmitter crosstalk needs to be considered in identifying new therapeutic targets. (5) The change from eubiosis to dysbiosis in SCI can contribute to UTI susceptibility and needs to be unraveled.

CONCLUSIONS

The think-tank discussed whether visceral fat metabolism, immune depression through sympathetic hyperactivity, peripheral nerves and neurotransmitter crosstalk, and the change in microbiome could provide explanations in the heterogenic development of chronic inflammation in LUTD. High-priority research questions were identified.

Meningeal Lymphatics in Central Nervous System Diseases

Since its recent discovery, the meningeal lymphatic system has reshaped our understanding of central nervous system (CNS) fluid exchange, waste clearance, immune cell trafficking, and immune privilege. Meningeal lymphatics have also been demonstrated to functionally modify the outcome of neurological disorders and their responses to treatment, including brain tumors, inflammatory diseases such as multiple sclerosis, CNS injuries, and neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. In this review, we discuss recent evidence of the contribution of meningeal lymphatics to neurological diseases, as well as the available experimental methods for manipulating meningeal lymphatics in these conditions. Finally, we also provide a discussion of the pressing questions and challenges in utilizing meningeal lymphatics as a prime target for CNS therapeutic intervention and possibly drug delivery for brain disorders.

5-aminolevulinic acid induced photodynamic reactions in diagnosis and therapy for female lower genital tract diseases

Since the patients suffering from female lower genital tract diseases are getting younger and younger and the human papilloma virus (HPV) infection is becoming more widespread, the novel non-invasive precise modalities of diagnosis and therapy are required to remain structures of the organ and tissue, and fertility as well, by which the less damage to normal tissue and fewer adverse effects are able to be achieved. In all nucleated mammalian cells, 5-Aminolevulinic acid (5-ALA) is an amino acid that occurs spontaneously, which further synthesizes in the heme biosynthetic pathway into protoporphyrin IX (PpIX) as a porphyrin precursor and photosensitizing agent. Exogenous 5-ALA avoids the rate-limiting step in the process, causing PpIX buildup in tumor tissues. This tumor-selective PpIX distribution after 5-ALA application has been used successfully for tumor photodynamic diagnosis (PDD) and photodynamic therapy (PDT). Several ALA-based drugs have been used for ALA-PDD and ALA-PDT in treating many (pre)cancerous diseases, including the female lower genital tract diseases, yet the ALA-induced fluorescent theranostics is needed to be explored further. In this paper, we are going to review the studies of the mechanisms and applications mainly on ALA-mediated photodynamic reactions and its effectiveness in treating female lower genital tract diseases.

Neurological symphony: post-acute COVID-19 syndrome, an innovative pathophysiological exploration from neuraltherapeutic medicine

The SARS-CoV-2 pandemic has affected 771 million people and caused 6.9 million confirmed deaths as of November 2023. Beyond the adversity, a crucial and less-explored chapter unfolds: adaptive sequelae. These have altered social, mental, and emotional conditions, leaving an imprint on biological systems. While some cases fully resolve the pathological process post-acute infection, others persist with symptoms, posing a challenge that underscores the need to comprehend pathophysiology from innovative perspectives. The article delves into “Long COVID” or Post-Acute COVID-19 Syndrome (PACS), where symptoms persist for ≥4 weeks irrespective of initial severity. Risk factors include a history of severe illness, in-hospital management, and intensive care. This article also explores theories, derived from various experimental models, that have demonstrated the involvement of the nervous system in coordination with the psychoneuroimmunoendocrine axes in the expression of inflammation. It is posited that PACS involves processes of peripheral and central sensitization (corticalization), facilitating dishomeostasis and the chronicity of the inflammatory process. In this context, various therapeutic strategies grounded in modulating the inflammatory reflex are reviewed, primarily through the infiltration of local anesthetics via linear and non-linear approaches. Neural therapeutic use is considered to stimulate the regulatory inflammatory circuits coordinated by the neuroimmune-endocrine system.

Transient Telangiectatic Purpura: A Rare Post-operative Phenomenon

Axillary lymph node dissection (ALND) is a surgical procedure for malignant disease with well known complications, that is less well known is its association with a painless dermatomal rash formally known as transient telangiectatic purpura. This is a case report describing a case of transient telangiectatic purpura, describing its natural history and inferring on its pathophysiology.

Mas-related G protein-coupled receptors in gastrointestinal dysfunction and inflammatory bowel disease: A review

Inflammatory bowel disease (IBD) is a chronic debilitating condition, hallmarked by persistent inflammation of the gastrointestinal tract. Despite recent advances in clinical treatments, the aetiology of IBD is unknown, and a large proportion of patients are refractory to pharmacotherapy. Understanding IBD immunopathogenesis is crucial to discern the cause of IBD and optimise treatments. Mas-related G protein-coupled receptors (Mrgprs) are a family of approximately 50 G protein-coupled receptors that were first identified over 20 years ago. Originally known for their expression in skin nociceptors and their role in transmitting the sensation of itch in the periphery, new reports have described the presence of Mrgprs in the gastrointestinal tract. In this review, we consider the impact of these findings and assess the evidence that suggests that Mrgprs may be involved in the disrupted homeostatic processes that contribute to gastrointestinal disorders and IBD. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Substance P receptor signaling contributes to host maladaptive responses during enteric bacterial infection

Immune responses in the intestine are intricately balanced to prevent pathogen entry without inducing immunopathology. The nervous system is well-established to interface with the immune system to fine-tune immunity in various organ systems including the gastrointestinal tract. Specialized sensory neurons can detect bacteria, bacterial products, and the resulting inflammation, to coordinate the immune response in the gastrointestinal tract. These sensory neurons release peptide neurotransmitters such as Substance P (SP), to induce both neuronal signaling and localized responses in non-neuronal cells. With this in mind, we assessed the immunoregulatory roles of SP receptor signaling during enteric bacterial infection with the non-invasive pathogen Citrobacter rodentium. Pharmacological antagonism of the SP receptor significantly reduced bacterial burden and prevented colonic crypt hyperplasia. Mice with SP receptor signaling blockade had significantly reduced inflammation and recruitment of T-cells in the colon. Reduced colonic T-cell recruitment is due to reduced expression of adhesion molecules on colonic endothelial cells in SP receptor antagonist-treated mice. Using SP receptor T-cell conditional knockout mice, we further confirmed SP receptor signaling enhanced select aspects of T-cell responses. Our data demonstrates that SP receptor signaling can significantly reduce inflammation and prevent host-maladaptive responses without impinging upon host protection.

Clinical Characteristics of Cutaneous Pain in Psoriasis

Background: Psoriasis is a common inflammatory disease that is often associated with itch and pain. This study aimed to evaluate the clinical characteristics of skin pain among patients with psoriasis. Materials: A total of 106 patients diagnosed with psoriasis were included in the study (34% female; mean age 42.1 ± 13.0 years). Disease severity was assessed using the Psoriasis Area and Severity Index (PASI). Itch severity was evaluated using the numeric rating scale (NRS) and 4-Item Itch Score (4IIS). The intensity of skin pain was measured through the NRS, short-form McGill pain questionnaire (SF-MPQ), visual analog scale (VAS), and Douleur Neuropathique-4 questionnaire (DN4). Results: In the past week, 84.9% of psoriasis patients reported itch, while 50% of them reported skin pain. The average NRS for itch was 4.52 ± 2.88 points, and the 4IIS yielded a mean score of 6.79 ± 4.37 points. In terms of the intensity of cutaneous pain, the mean NRS was 2.42 ± 2.96 points; the SF-MPQ score averaged 4.84 ± 7.51 points; and the VAS score was 1.92 ± 2.65 points. Furthermore, 17% of adult psoriasis patients reported neuropathic pain. In 84.9% of the participants, skin pain was concurrent with areas affected by itch, while 18.9% of patients exhibited cutaneous pain encompassing all itchy areas. The pain NRS demonstrated significant correlations with the SF-MPQ (r = 0.531, p < 0.001), VAS (r = 0.779, p < 0.001), itch NRS (r = 0.551, p < 0.001), and 4IIS (r = 0.569, p < 0.001). No association was found between the pain NRS and PASI or disease duration. Conclusions: Skin pain of mild intensity and itch of moderate intensity are prevalent symptoms in psoriasis patients. Strong correlations between skin pain and itch can be explained by the process of neurogenic inflammation.

Sensory ASIC3 channel exacerbates psoriatic inflammation via a neurogenic pathway in female mice

Psoriasis is an immune-mediated skin disease associated with neurogenic inflammation, but the underlying molecular mechanism remains unclear. We demonstrate here that acid-sensing ion channel 3 (ASIC3) exacerbates psoriatic inflammation through a sensory neurogenic pathway. Global or nociceptor-specific Asic3 knockout (KO) in female mice alleviates imiquimod-induced psoriatic acanthosis and type 17 inflammation to the same extent as nociceptor ablation. However, ASIC3 is dispensable for IL-23-induced psoriatic inflammation that bypasses the need for nociceptors. Mechanistically, ASIC3 activation induces the activity-dependent release of calcitonin gene-related peptide (CGRP) from sensory neurons to promote neurogenic inflammation. Botulinum neurotoxin A and CGRP antagonists prevent sensory neuron-mediated exacerbation of psoriatic inflammation to similar extents as Asic3 KO. In contrast, replenishing CGRP in the skin of Asic3 KO mice restores the inflammatory response. These findings establish sensory ASIC3 as a critical constituent in psoriatic inflammation, and a promising target for neurogenic inflammation management.

Endometriosis, Pain, and Related Psychological Disorders: Unveiling the Interplay among the Microbiome, Inflammation, and Oxidative Stress as a Common Thread

Endometriosis (EM), a chronic condition in endometrial tissue outside the uterus, affects around 10% of reproductive-age women, significantly affecting fertility. Its prevalence remains elusive due to the surgical confirmation needed for diagnosis. Manifesting with a range of symptoms, including dysmenorrhea, dyschezia, dysuria, dyspareunia, fatigue, and gastrointestinal discomfort, EM significantly impairs quality of life due to severe chronic pelvic pain (CPP). Psychological manifestations, notably depression and anxiety, frequently accompany the physical symptoms, with CPP serving as a key mediator. Pain stems from endometrial lesions, involving oxidative stress, neuroinflammation, angiogenesis, and sensitization processes. Microbial dysbiosis appears to be crucial in the inflammatory mechanisms underlying EM and associated CPP, as well as psychological symptoms. In this scenario, dietary interventions and nutritional supplements could help manage EM symptoms by targeting inflammation, oxidative stress, and the microbiome. Our manuscript starts by delving into the complex relationship between EM pain and psychological comorbidities. It subsequently addresses the emerging roles of the microbiome, inflammation, and oxidative stress as common links among these abovementioned conditions. Furthermore, the review explores how dietary and nutritional interventions may influence the composition and function of the microbiome, reduce inflammation and oxidative stress, alleviate pain, and potentially affect EM-associated psychological disorders.

Impact of Migraine and Vestibular Migraine on Audiometric Profiles and Quality of Life in Patients With Tinnitus

OBJECTIVE

To investigate the clinical manifestations and complete auditory function in primary tinnitus patients with and without migraine or vestibular migraine.

DESIGN

Retrospective case-control study.

SETTING

A tertiary referral center.

PARTICIPANTS

This study enrolled 298 patients from the Kaohsiung Veterans General Hospital. All patients were diagnosed with primary tinnitus by a neurotologist between April 2020 and August 2021. Patients were excluded if they had histories of chronic otitis media, idiopathic sudden sensorineural hearing loss, Ménière's disease, skull base neoplasm, or temporal bone trauma.

INTERVENTIONS

Twenty-five-item Tinnitus Handicap Inventory (THI), speech audiometry including speech recognition threshold, most comfortable level, uncomfortable loudness levels, dynamic range, and pure-tone audiometry.

MAIN OUTCOMES MEASURES

Objective hearing loss is defined as a mean threshold greater than 25 dB. Extremely elevated THI is defined as a score greater than 1 standard deviation above the mean THI.

RESULTS

Among the 298 patients with tinnitus, 149 were women and 149 were men, with a mean age of 57.06 (range, 19.22-94.58) years.A total of 125 patients completed the THI questionnaire during their initial visit. The median THI score was 32 (95% confidence interval: 13.98-56.00), and the mean score was 34.99 with a standard deviation of 21.01. The sole contributing factor significantly associated with higher total THI score was the diagnosis of migraine or vestibular migraine (p < 0.001, odds ratio = 19.41).Tinnitus patients with migraine or vestibular migraine exhibited significantly lower mean pure-tone auditory thresholds (right 22.2 versus 29.5, p = 0.002; left 22.5 versus 30.4, p < 0.001), speech recognition threshold (right 20.0 versus 25.2, p = 0.016; left 20.2 versus 25.5, p = 0.019), and most comfortable levels values (right 46.1 versus 51.4, p = 0.007; left 46.9 versus 51.4, p = 0.021) compared with the tinnitus patients without migraine.

CONCLUSIONS

In this population-based study, patients with primary tinnitus experienced significantly higher THI scores and exhibited concurrent symptoms, including dizziness/vertigo, cervicalgia, and migraine or vestibular migraine. Among these parameters, the diagnosis of migraine or vestibular migraine was the sole contributor to significant higher THI score.

Behavioral characterization of G-protein-coupled receptor 160 knockout mice

ABSTRACT

Neuropathic pain is a devastating condition where current therapeutics offer little to no pain relief. Novel nonnarcotic therapeutic targets are needed to address this growing medical problem. Our work identified the G-protein-coupled receptor 160 (GPR160) as a potential target for therapeutic intervention. However, the lack of small-molecule ligands for GPR160 hampers our understanding of its role in health and disease. To address this void, we generated a global Gpr160 knockout (KO) mouse using CRISPR-Cas9 genome editing technology to validate the contributions of GPR160 in nociceptive behaviors in mice. Gpr160 KO mice are healthy and fertile, with no observable physical abnormalities. Gpr160 KO mice fail to develop behavioral hypersensitivities in a model of neuropathic pain caused by constriction of the sciatic nerve. On the other hand, responses of Gpr160 KO mice in the hot-plate and tail-flick assays are not affected. We recently deorphanized GPR160 and identified cocaine- and amphetamine-regulated transcript peptide (CARTp) as a potential ligand. Using Gpr160 KO mice, we now report that the development of behavioral hypersensitivities after intrathecal or intraplantar injections of CARTp are dependent on GPR160. Cocaine- and amphetamine-regulated transcript peptide plays a role in various affective behaviors, such as anxiety, depression, and cognition. There are no differences in learning, memory, and anxiety between Gpr160 KO mice and their age-matched and sex-matched control floxed mice. Results from these studies support the pronociceptive roles of CARTp/GPR160 and GPR160 as a potential therapeutic target for treatment of neuropathic pain.