A mast cell-thermoregulatory neuron circuit axis regulates hypothermia in anaphylaxis

Update on mast cell biology

Mast cells (MCs) are heterogeneous tissue-resident effector cells that are thought to play central roles in allergic inflammatory disease, yet the degree of heterogeneity and nature of these roles has remained elusive. In recent years, advances in tissue culture systems, preclinical mouse models, and the continued spread of single-cell RNA sequencing have greatly advanced our understanding of MC phenotypes in health and disease. These approaches have identified novel interactions of MC subsets with immune cells, neurons, and tissue structural cells, changing our understanding of how MCs both drive and help resolve tissue inflammation, reshape tissue microenvironments, and influence host behavior. This review addresses key studies from 2022 to 2024 that have advanced our understanding of MC biology in mice and humans.

FosB/ΔFosB activation in mast cells regulates gene expression to modulate allergic inflammation in male mice

Mast cells are innate immune cells that regulate physiological processes by releasing pre-stored and newly synthesized mediators in response to allergens, infection, and other stimuli. Dysregulated mast cell activity can lead to multisystemic pathologies, but the underlying regulatory mechanisms remain poorly understood. We found that FOSB and ΔFOSB, transcription factors encoded by the FosB gene, are robustly expressed in mast cells following IgE-antigen stimulation, suggesting a role in modulating stimulus-induced mast cell functions. Using phenotypic, gene binding, and gene expression analyses in wild-type and mast cell-specific FosB knockout male mice, we demonstrate that FOSB/ΔFOSB modulates mast cell functions by limiting reactivity to allergen-like stimuli both in vitro and in vivo . These effects seem to be mediated, at least in part, by FOSB/ΔFOSB-driven enhanced expression of DUSP4, a dual-specificity phosphatase that attenuates MAPK signaling. These findings highlight FOSB/ΔFOSB as critical regulators of mast cell activity and potential targets for therapeutic intervention.

Mast cell activators as adjuvants for intranasal mucosal vaccines

Mast cells have roles in immune regulation, allergy, and host response to pathogens. Compounds that activate mast cells (MCAs) can serve as vaccine adjuvants, potentially outperforming current FDA-approved options, especially for mucosal vaccines. While most vaccines are administered intramuscularly, intranasal and needle-free formulations offer benefits like improved compliance and accessibility. However, the lack of effective adjuvants limits mucosal vaccine development. This review explores MCAs as promising alternatives to traditional adjuvants, aiming to enhance mucosal vaccine efficacy. We summarize the nascent work of formulating MCAs like compound 48/80 into nanoparticles, with excipients such as chitosan and chitosan/alginate. Other MCAs like the peptide mastoparan 7 complexed with CpG have formed nanoparticle complexes that illustrate protective mucosal immunity in a model of influenza. The small molecule MCA ST101036, when encapsulated in acetalated dextran particles, has demonstrated enhanced immune responses and protection in a West Nile Virus model of infection. This review highlights the potential of MCAs as potent vaccine adjuvants, particularly for mucosal vaccines, and summarizes, recent advancements in formulating these activators into nanoparticles to enhance immune responses and protection.

Advances in Mechanisms of Anaphylaxis in Wheat Allergy: Utility of Rodent Models

Wheat is a staple and nutritious food that is consumed globally. However, it is identified as a major allergenic food because of its capacity to trigger life-threatening systemic anaphylaxis. The specific mechanisms that underlie this systemic anaphylaxis in wheat allergy are incompletely understood. As a result, several rodent models have been developed to study anaphylaxis in wheat allergies. In this paper, we have conducted a comprehensive review of wheat-induced anaphylaxis using Google Scholar and PubMed databases with relevant keywords. The following objectives were addressed: (1) to determine the complexity of wheat-induced anaphylaxis; (2) to summarize the role of genetic susceptibility in wheat anaphylaxis; (3) to identify the environmental factors involved in the development of wheat anaphylaxis; (4) to map the current status of mechanisms involved in wheat anaphylaxis; (5) to identify the approaches, strengths, and limitations of rodent models of wheat anaphylaxis; and (6) to identify challenges and opportunities in this area of science. Our findings provide a comprehensive updated critical resource for the future research agenda in wheat allergy-associated anaphylaxis, particularly using rodent models as attractive pre-clinical tools.

Acetylsalicylic acid aggravates anaphylaxis in a PGE2-dependent manner

Acetylsalicylic acid (ASA) can exert proanaphylactic effects, but the extent of this phenomenon and its underlying mechanisms are undefined. Yet, low homeostatic prostaglandin E2 (PGE2) levels have been associated with anaphylaxis. In this study, we investigated whether the proanaphylactic effect of ASA is PGE2 dependent. We assessed the effect of ASA in experimental anaphylaxis models, analyzed a large dataset of patients with anaphylaxis, and performed titrated allergen challenges in ASA-treated allergic individuals. Registry data indicated an increased risk for severe anaphylaxis in patients with ASA comedication. ASA pretreatment aggravated allergen-dependent anaphylaxis in mice, whereas histamine-induced anaphylaxis remained unaffected. Exacerbation was due to reduced PGE2, as its stabilization or the use of prostanoid E receptor (EP) agonists reversed the proanaphylactic effects of ASA. EP2-, EP3-, and EP4 receptor-deficient mice revealed that each receptor individually contributed to ASA susceptibility. In patients with allergy, prior ASA intake increased skin responsiveness to allergen but not to histamine. Conversely, the responses of basophils to ex vivo FcεRI aggregation remained unaltered, indicating that ASA operated by enhancing the stimulability of mast cells in a PGE2-dependent manner. Collectively, our data reveal a central role of the PGE2 network in ASA-aggravated anaphylaxis. EP receptors could be potential targets to prevent or alter the outcome of anaphylaxis.

Beyond classical immunity: Mast cells as signal converters between tissues and neurons

Mast cells are regarded as effectors in immune defense against parasites and venoms and play an essential role in the pathology of allergic diseases. More recently, mast cells have been shown to receive stimuli derived from type 2 immunity, tissue damage, stress, and inflammation. Mast cells then rapidly convert these diverse signals into appropriate, organ-specific protective reflexes that can limit inflammation or reduce tissue damage. In this review, we consider functions of mast cells in sensations-such as pain, itch, and nausea-arising from tissue insults and inflammation and the ensuing protective responses. In light of emerging data highlighting the involvement of mast cells in neuroimmune communication, we also propose that mast cells are "signal converters" linking immunological and tissue states with nervous system responses.

Targeting Dlat-Trpv3 pathway by hyperforin elicits non-canonical promotion of adipose thermogenesis as an effective anti-obesity strategy

INTRODUCTION

Promoting adipose thermogenesis is considered as a promising therapeutic intervention in obesity. However, endeavors to develop anti-obesity medications by targeting the canonical thermogenesis regulatory pathway, particularly β3-adrenergic receptor (β3-AR)-dependent mechanism, have failed due to the off-target effects of β3-AR agonists, exacerbating the risk of cardiovascular disease. Hyperforin (HPF), a natural compound extracted from the traditional herbal St. John's Wort, binds to Dihydrolipoamide s-acetyltransferase (Dlat) and exerts effective anti-obesity properties through promoting adipose thermogenesis.

OBJECTIVES

The objective of this study was to investigate the oral efficacy and pharmacokinetics profile of HPF, and explore the detailed mechanism by which Dlat modulates HPF-mediated adipose thermogenesis.

METHODS

To assess the anti-obesity efficacy of orally administered HPF in vivo, Dlat heterozygous knockout (Dlat+/-) mice and wild-type (WT) mice, both fed a high-fat diet (HFD), underwent a validation process that involved the use of metabolic cages, NMR analysis, and infrared imaging. Sprague Dawley rats were employed to determine the pharmacokinetic parameters of HPF. Seahorse assays, JC-1 staining, qPCR, and immunoblotting were performed to evaluate cellular thermogenic efficacy of HPF and Dlat in vitro.

RESULTS

Our study uncovered a non-canonical thermogenesis pathway involving Dlat, transient receptor potential vanilloid 3 (Trpv3, a calcium channel) and AMPK. Dlat interacted with Trpv3 to activate it, resulting in an increase in intracellular calcium (Ca2+) and the activation of Camkkβ. Camkkβ then stimulated AMPK, leading to elevated Ucp1 expression and initiating adipose thermogenesis. HPF promoted thermogenesis in adipose tissues through enhancing the Dlat-Trpv3 interaction independently of β3-AR, causing minimal cardiac side effects. Notably, HPF's thermogenic effects were reduced in Dlat+/- mice. Moreover, HPF exerted favorable oral bioavailability, a relatively long half-life, and extensive distribution within adipose tissues.

CONCLUSION

In summary, our study demonstrates that HPF targets a novel mechanism for promoting adipose thermogenesis and exhibits potent and safe anti-obesity efficacy.

From bite to brain: Neuro-immune interactions in food allergy

Immunoglobulin E (IgE)-mediated food allergies are reported to affect around 3.5% of children and 2.4% of adults, with symptoms varying in range and severity. While being the gold standard for diagnosis, oral food challenges are burdensome, and diagnostic tools based on specific IgE can be flawed. Furthering our understanding of the mechanisms behind food allergy onset, severity and persistence could help reveal immune profiles associated with the disease, to ultimately aid in diagnosis. Alterations to cytokine levels and immune cell ratios have been identified, though further research is needed to fully capture the heterogenous nature of food allergy. Moreover, the existence of such immune alterations also raises the question of potential wider systemic effects. For example, recent research has emphasised the existence and impact of neuro-immune interactions and implicated behavioural and neurological changes associated with food allergy. This review will provide an overview of such food allergy-driven neuro-immune interactions, with the aim of emphasising the importance of furthering our understanding of the immune mechanisms underlying IgE-mediated food allergy.

Sensory neuroimmune interactions at the barrier

Epithelial barriers such as the skin, lung, and gut, in addition to having unique physiologic functions, are designed to preserve tissue homeostasis upon challenge with a variety of allergens, irritants, or pathogens. Both the innate and adaptive immune systems play a critical role in responding to epithelial cues triggered by environmental stimuli. However, the mechanisms by which organs sense and coordinate complex epithelial, stromal, and immune responses have remained a mystery. Our increasing understanding of the anatomic and functional characteristics of the sensory nervous system is greatly advancing a new field of peripheral neuroimmunology and subsequently changing our understanding of mucosal immunology. Herein, we detail how sensory biology is informing mucosal neuroimmunology, even beyond neuroimmune interactions seen within the central and autonomic nervous systems.

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.

Mast cell extracellular trap formation underlies vascular and neural injury and hyperalgesia in sickle cell disease

Sickle cell disease (SCD) is the most common inherited monogenetic disorder. Chronic and acute pain are hallmark features of SCD involving neural and vascular injury and inflammation. Mast cells reside in the vicinity of nerve fibers and vasculature, but how they influence these structures remains unknown. We therefore examined the mechanism of mast cell activation in a sickle microenvironment replete with cell-free heme and inflammation. Mast cells exposed to this environment showed an explosion of nuclear contents with the release of citrullinated histones, suggestive of mast cell extracellular trap (MCET) release. MCETs interacted directly with the vasculature and nerve fibers, a cause of vascular and neural injury in sickle cell mice. MCET formation was dependent upon peptidylarginine deiminase 4 (PAD4). Inhibition of PAD4 ameliorated vasoocclusion, chronic and acute hyperalgesia, and inflammation in sickle mice. PAD4 activation may also underlie neutrophil trap formation in SCD, thus providing a novel target to treat the sequelae of vascular and neural injury in SCD.

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.

Maternal High-Fat Diet Exacerbates Epicutaneous Sensitization and Oral Challenge-Induced Food Allergy to Ovalbumin in Offspring Mice

Dietary factors have been associated with an increased prevalence of food allergy (FA). However, little is known about how an unhealthy diet in early life affects FA reactions in offspring. The objective of this study is to provide a scientific foundation for developing and promoting healthy dietary patterns in early life. In this study, we found that maternal high-fat diet (HFD) during pregnancy and lactation exacerbates FA (HFD-FA) in offspring mice, leading to increased serum levels of mast cell protease 1. First, we studied the systemic immunity of the HFD-FA mice and observed elevated levels of proinflammatory cytokines (IL-4, IL-6, and IL-1β) and a reduced frequency of Treg cells in splenocytes. Additionally, the HFD-FA mice showed increased gut permeability, accumulation of intestinal mast cells, and a decrease in the Treg cell frequency in the mesenteric lymph nodes. Furthermore, our findings also indicated a reduction in gut microbial diversity and abundance in HFD-FA mice. Importantly, lipid metabolism profiling revealed unique lipid profiles in the HFD-FA mice, with significant upregulation of triglycerides and downregulation of sphingolipids. Taken together, our results suggest that maternal HFD alters intestinal homeostasis and increases FA susceptibility in offspring mice.

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.

Melatonergic Signaling Sustains Food Allergy Through FcεRI Recycling

The prevalence of food allergies is increasing dramatically and causing serious public health concerns. Notably, melatonin metabolism imbalance in patients with food allergies; however, the role of melatonin in food allergies remains unclear. Here, we demonstrated that melatonin suppresses food allergy responses and reprograms the gut microbiota of food-allergic mice, while melatonin aggravates food allergy during gut microbiota depletion. Mechanistically, melatonin boosts the degranulation of mast cells by up-regulating the expression of membrane high-affinity immunoglobulin E (IgE) receptor (FcεRI). Melatonin increases the mRNA expression of Rabenosyn-5 (a component of factors for endosome recycling and Rab interactions) through melatonin receptor 2 (MT2)-extracellular signal-regulated kinase (ERK) signaling, thereby driving the recycling of FcεRI and elevating the abundance of membrane FcεRI. Likewise, the inhibition of MT2 attenuates melatonin-induced food allergy in mice with gut microbiota depletion. Collectively, our finding provides insights into the pathogenesis of food allergies and provides a potential therapeutic target for the prevention and treatment of food allergies.

T cell independent antibody responses with class switch and memory using peptides anchored on liposomes

Vaccines generally require T lymphocytes for B-cell activation and immunoglobulin class switching in response to peptide or protein antigens. In the absence of T cells, limited IgG class switch takes place, germinal centers are short-lived, and the B cells lack memory. Here, immunization of mice with liposomes containing 15mer peptides and monophosphoryl lipid A (MPLA) as adjuvant, induced T-cell independent (TI) IgG class switch within three days, as well as germinal center formation. The antibody responses were long-lived, strictly dependent on Toll-like receptor 4 (TLR4) signaling, partly dependent on Bruton's tyrosine kinase (BTK) signal transmission, and independent of signaling through T-cell receptors, MHC class II and inflammasome. The antibody response showed characteristics of both TI type 1 and TI type 2. All IgG subclasses could be boosted months after primary immunization, and the biological function of the secreted antibodies was demonstrated in murine models of allergic anaphylaxis and of bacterial infection. Moreover, antibody responses after immunization with peptide- and MPLA-loaded liposomes could be triggered in neonatal mice and in mice receiving immune-suppressants. This study demonstrates T-cell independent endogenous B-cell memory and recall responses in vivo using a peptide antigen. The stimulation of these antibody responses required a correct and dense assembly and administration of peptide and adjuvant on the surface of liposomes. In the future, TI vaccines may prove beneficial in pathological conditions in which T-cell immunity is compromised through disease or medicines or when rapid, antibody-mediated immune protection is needed.

TRPV1 analgesics disturb core body temperature via a biased allosteric mechanism involving conformations distinct from that for nociception

Efforts on developing transient receptor potential vanilloid 1 (TRPV1) drugs for pain management have been hampered by deleterious hypo- or hyperthermia caused by TRPV1 agonists/antagonists. Here, we compared the effects of four antagonists on TRPV1 polymodal gating and core body temperature (CBT) in Trpv1+/+, Trpv1-/-, and Trpv1T634A/T634A. Neither the effect on proton gating nor drug administration route, hair coverage, CBT rhythmic fluctuations, or inflammation had any influence on the differential actions of TRPV1 drugs on CBT. We identified the S4-S5 linker region exposed to the vanilloid pocket of TRPV1 to be critical for hyperthermia associated with certain TRPV1 antagonists. PSFL2874, a TRPV1 antagonist we discovered, is effective against inflammatory pain but devoid of binding to the S4-S5 linker and inducing CBT changes. These findings implicate that biased allosteric mechanisms exist for TRPV1 coupling to nociception and CBT regulation, opening avenues for the development of non-opioid analgesics without affecting CBT.

Controlled adsorption of multiple bioactive proteins enables targeted mast cell nanotherapy

Protein adsorption onto nanomaterials often results in denaturation and loss of bioactivity. Controlling the adsorption process to maintain the protein structure and function has potential for a range of applications. Here we report that self-assembled poly(propylene sulfone) (PPSU) nanoparticles support the controlled formation of multicomponent enzyme and antibody coatings and maintain their bioactivity. Simulations indicate that hydrophobic patches on protein surfaces induce a site-specific dipole relaxation of PPSU assemblies to non-covalently anchor the proteins without disrupting the protein hydrogen bonding or structure. As a proof of concept, a nanotherapy employing multiple mast-cell-targeted antibodies for preventing anaphylaxis is demonstrated in a humanized mouse model. PPSU nanoparticles displaying an optimized ratio of co-adsorbed anti-Siglec-6 and anti-FcεRIα antibodies effectively inhibit mast cell activation and degranulation, preventing anaphylaxis. Protein immobilization on PPSU surfaces provides a simple and rapid platform for the development of targeted protein nanomedicines.

Evaluation of Urtica dioica Phytochemicals against Therapeutic Targets of Allergic Rhinitis Using Computational Studies

Allergic rhinitis (AR) is a prevalent inflammatory condition affecting millions globally, with current treatments often associated with significant side effects. To seek safer and more effective alternatives, natural sources like Urtica dioica (UD) are being explored. However, UD's mechanism of action remains unknown. Therefore, to elucidate it, we conducted an in silico evaluation of UD phytochemicals' effects on known therapeutic targets of allergic rhinitis: histamine receptor 1 (HR1), neurokinin 1 receptor (NK1R), cysteinyl leukotriene receptor 1 (CLR1), chemoattractant receptor-homologous molecule expressed on type 2 helper T cells (CRTH2), and bradykinin receptor type 2 (BK2R). The docking analysis identified amentoflavone, alpha-tocotrienol, neoxanthin, and isorhamnetin 3-O-rutinoside as possessing a high affinity for all the receptors. Subsequently, molecular dynamics (MD) simulations were used to analyze the key interactions; the free energy of binding was calculated through Generalized Born and Surface Area Solvation (MMGBSA), and the conformational changes were evaluated. Alpha-tocotrienol exhibited a high affinity while also inducing positive conformational changes across all targets. Amentoflavone primarily affected CRTH2, neoxanthin targeted NK1R, CRTH2, and BK2R, and isorhamnetin-3-O-rutinoside acted on NK1R. These findings suggest UD's potential to treat AR symptoms by inhibiting these targets. Notably, alpha-tocotrienol emerges as a promising multi-target inhibitor. Further in vivo and in vitro studies are needed for validation.

Biofilm exopolysaccharides alter sensory-neuron-mediated sickness during lung infection

Infections of the lung cause observable sickness thought to be secondary to inflammation. Signs of sickness are crucial to alert others via behavioral-immune responses to limit contact with contagious individuals. Gram-negative bacteria produce exopolysaccharide (EPS) that provides microbial protection; however, the impact of EPS on sickness remains uncertain. Using genome-engineered Pseudomonas aeruginosa (P. aeruginosa) strains, we compared EPS-producers versus non-producers and a virulent Escherichia coli (E. coli) lung infection model in male and female mice. EPS-negative P. aeruginosa and virulent E. coli infection caused severe sickness, behavioral alterations, inflammation, and hypothermia mediated by TLR4 detection of the exposed lipopolysaccharide (LPS) in lung TRPV1+ sensory neurons. However, inflammation did not account for sickness. Stimulation of lung nociceptors induced acute stress responses in the paraventricular hypothalamic nuclei by activating corticotropin-releasing hormone neurons responsible for sickness behavior and hypothermia. Thus, EPS-producing biofilm pathogens evade initiating a lung-brain sensory neuronal response that results in sickness.

Case Report: A Rare Case of Iodixanol-Induced Anaphylactic Shock in Cerebral Angiography

Background

Adverse reactions induced by isoosmolar contrast medium (iodixanol) are mostly mild, with rashes and headaches being the most common. Although anaphylactic shock has been reported, no related incidents have been documented on cerebral angiography.

Objective

This article reports a serious case of anaphylactic shock possibly induced by iodixanol and provides an overview of the case report.

Case Summary

A 65-year-old female with persistent headaches for nearly six months and CTA examination revealed multiple intracranial aneurysms. After two treatments, she returned to the hospital for aneurysm of reexamination a month ago. Following a preoperative assessment, cerebral angiography was performed. Three minutes after the procedure, the patient experienced dizziness, increased heart rate, followed by hypotension (BP 90/43 mm Hg), a sudden drop-in heart rate (HR 68 bpm), and a drop in SpO2 to 92%. Intravenous dexamethasone for anti-allergic were administered immediately, along with therapy through oxygen-inhalation. However, the patient then developed limb convulsions, unresponsiveness, and was urgently given diazepam for sedation and sputum aspiration to maintain airway patency. Blood pressure decrease to 53/29 mm Hg, and SpO2 readings were unavailable. Intravenous dopamine to elevates blood pressure, and assists breathing by intubating in the endotracheal. After 3 minutes, as the blood pressure remained undetectable, intermittent intravenous epinephrine 1mg was administered to raise the blood pressure, gradually restoring it to 126/90 mm Hg, and SpO2 increased to 95%. The patient was diagnosed with iodixanol-induced anaphylactic shock and urgently transferred to the NICU for monitoring and treatment. The patient died despite immediate treatment.

Conclusion

A 65-year-old female developed serious anaphylactic shock during cerebral angiography after receiving iodixanol. Although iodixanol is considered one of the safest iodinated contrast mediums (ICM), clinicians should be aware of its the potential for serious hypersensitivity reactions that can lead to fatal and life-threatening events.

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

Mast cell-sensory neuron crosstalk in allergic diseases

Mast cells (MCs) are tissue-resident immune cells, well-positioned at the host-environment interface for detecting external antigens and playing a critical role in mobilizing innate and adaptive immune responses. Sensory neurons are afferent neurons innervating most areas of the body but especially in the periphery, where they sense external and internal signals and relay information to the brain. The significance of MC-sensory neuron communication is now increasingly becoming recognized, especially because both cell types are in close physical proximity at the host-environment interface and around major organs of the body and produce specific mediators that can activate each other. In this review, we explore the roles of MC-sensory neuron crosstalk in allergic diseases, shedding light on how activated MCs trigger sensory neurons to initiate signaling in pruritus, shock, and potentially abdominal pain in allergy, and how activated sensory neurons regulate MCs in homeostasis and atopic dermatitis associated with contact hypersensitivity and type 2 inflammation. Throughout the review, we also discuss how these 2 sentinel cell types signal each other, potentially resulting in a positive feedback loop that can sustain inflammation. Unraveling the mysteries of MC-sensory neuron crosstalk is likely to unveil their critical roles in various disease conditions and enable the development of new therapeutic approaches to combat these maladies.

The effect of myeloablative radiation on urinary bladder mast cells

Radiation-induced cystitis is an inflammatory condition affecting the urinary bladder, which can develop as a side effect of abdominopelvic radiotherapy, specifically external-beam radiation therapy or myeloablative radiotherapy. A possible involvement of mast cells in the pathophysiology of radiation-induced cystitis has been indicated in cases of external-beam radiation therapy; however, there is no evidence that these findings apply to the myeloablative aetiology. As such, this study investigated potential changes to urinary bladder mast cell prevalence when exposed to myeloablative radiation. Lethally irradiated C57BL/6J mice that received donor rescue bone marrow cells exhibited an increased mast cell frequency amongst host leukocytes 1 week following irradiation. By 4 weeks, no significant difference in either frequency or cell density was observed. However mast cell diameter was smaller, and a significant increase in mast cell number in the adventitia was observed. This study highlights that mast cells constitute a significant portion of the remaining host leukocyte population following radiation exposure, with changes to mast cell distribution and decreased cell diameter four weeks following radiation-induced injury.

S. aureus drives itch and scratch-induced skin damage through a V8 protease-PAR1 axis

Itch is an unpleasant sensation that evokes a desire to scratch. The skin barrier is constantly exposed to microbes and their products. However, the role of microbes in itch generation is unknown. Here, we show that Staphylococcus aureus, a bacterial pathogen associated with itchy skin diseases, directly activates pruriceptor sensory neurons to drive itch. Epicutaneous S. aureus exposure causes robust itch and scratch-induced damage. By testing multiple isogenic bacterial mutants for virulence factors, we identify the S. aureus serine protease V8 as a critical mediator in evoking spontaneous itch and alloknesis. V8 cleaves proteinase-activated receptor 1 (PAR1) on mouse and human sensory neurons. Targeting PAR1 through genetic deficiency, small interfering RNA (siRNA) knockdown, or pharmacological blockade decreases itch and skin damage caused by V8 and S. aureus exposure. Thus, we identify a mechanism of action for a pruritogenic bacterial factor and demonstrate the potential of inhibiting V8-PAR1 signaling to treat itch.

The role of cellular and molecular neuroimmune crosstalk in gut immunity

The gastrointestinal tract is densely innervated by the peripheral nervous system and populated by the immune system. These two systems critically coordinate the sensations of and adaptations to dietary, microbial, and damaging stimuli from the external and internal microenvironment during tissue homeostasis and inflammation. The brain receives and integrates ascending sensory signals from the gut and transduces descending signals back to the gut via autonomic neurons. Neurons regulate intestinal immune responses through the action of local axon reflexes or through neuronal circuits via the gut-brain axis. This neuroimmune crosstalk is critical for gut homeostatic maintenance and disease resolution. In this review, we discuss the roles of distinct types of gut-innervating neurons in the modulation of intestinal mucosal immunity. We will focus on the molecular mechanisms governing how different immune cells respond to neural signals in host defense and inflammation. We also discuss the therapeutic potential of strategies targeting neuroimmune crosstalk for intestinal diseases.

Landscape of mast cell populations across organs in mice and humans

Mast cells (MCs) are tissue-resident immune cells that exhibit homeostatic and neuron-associated functions. Here, we combined whole-tissue imaging and single-cell RNA sequencing datasets to generate a pan-organ analysis of MCs in mice and humans at steady state. In mice, we identify two mutually exclusive MC populations, MrgprB2+ connective tissue-type MCs and MrgprB2neg mucosal-type MCs, with specific transcriptomic core signatures. While MrgprB2+ MCs develop in utero independently of the bone marrow, MrgprB2neg MCs develop after birth and are renewed by bone marrow progenitors. In humans, we unbiasedly identify seven MC subsets (MC1-7) distributed across 12 organs with different transcriptomic core signatures. MC1 are preferentially enriched in the bladder, MC2 in the lungs, and MC4, MC6, and MC7 in the skin. Conversely, MC3 and MC5 are shared by most organs but not skin. This comprehensive analysis offers valuable insights into the natural diversity of MC subtypes in both mice and humans.

Macrophages and microglia in inflammation and neuroinflammation underlying different pain states

Pain is a main symptom in inflammation, and inflammation induces pain via inflammatory mediators acting on nociceptive neurons. Macrophages and microglia are distinct cell types, representing immune cells and glial cells, respectively, but they share similar roles in pain regulation. Macrophages are key regulators of inflammation and pain. Macrophage polarization plays different roles in inducing and resolving pain. Notably, macrophage polarization and phagocytosis can be induced by specialized pro-resolution mediators (SPMs). SPMs also potently inhibit inflammatory and neuropathic pain via immunomodulation and neuromodulation. In this review, we discuss macrophage signaling involved in pain induction and resolution, as well as in maintaining physiological pain. Microglia are macrophage-like cells in the central nervous system (CNS) and drive neuroinflammation and pathological pain in various inflammatory and neurological disorders. Microglia-produced inflammatory cytokines can potently regulate excitatory and inhibitory synaptic transmission as neuromodulators. We also highlight sex differences in macrophage and microglial signaling in inflammatory and neuropathic pain. Thus, targeting macrophage and microglial signaling in distinct locations via pharmacological approaches, including immunotherapies, and non-pharmacological approaches will help to control chronic inflammation and chronic pain.