Anaphylaxis: a review of causes and mechanisms

Dietary Polyphenols, Plant Metabolites, and Allergic Disorders: A Comprehensive Review

Given the ongoing rise in the occurrence of allergic disorders, alterations in dietary patterns have been proposed as a possible factor contributing to the emergence and progression of these conditions. Currently, there is a significant focus on the development of dietary therapies that utilize natural compounds possessing anti-allergy properties. Dietary polyphenols and plant metabolites have been intensively researched due to their well-documented anti-inflammatory, antioxidant, and immunomodulatory characteristics, making them one of the most prominent natural bioactive chemicals. This study seeks to discuss the in-depth mechanisms by which these molecules may exert anti-allergic effects, namely through their capacity to diminish the allergenicity of proteins, modulate immune responses, and modify the composition of the gut microbiota. However, further investigation is required to fully understand these effects. This paper examines the existing evidence from experimental and clinical studies that supports the idea that different polyphenols, such as catechins, resveratrol, curcumin, quercetin, and others, can reduce allergic inflammation, relieve symptoms of food allergy, asthma, atopic dermatitis, and allergic rhinitis, and prevent the progression of the allergic immune response. In summary, dietary polyphenols and plant metabolites possess significant anti-allergic properties and can be utilized for developing both preventative and therapeutic strategies for targeting allergic conditions. The paper also discusses the constraints in investigating and broad usage of polyphenols, as well as potential avenues for future research.

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.

Positive Predictive Values of Anaphylaxis Diagnosis in Claims Data: A Multi-Institutional Study in Taiwan

Real-world data sources can facilitate essential understanding of the epidemiological features of anaphylaxis. However, the accuracy of case-identifying definitions based on diagnosis codes for anaphylaxis in healthcare databases remains understudied. We conducted a cross-sectional study analyzing claims data from the largest multi-institutional healthcare system in Taiwan during 2017-2021. We included patients with incident anaphylaxis identified by either ICD-10-CM codes for anaphylaxis (Group 1) or ICD-10-CM codes for severe allergic or drug adverse events and additional modifier codes for acute allergy events (Group 2). We randomly selected 20% of the cases to determine the positive predictive value (PPV) of anaphylaxis case-identifying definitions in Groups 1 and 2 after review of electronic medical records by two physicians. From the original cohort (n = 2,176), we randomly selected 433 patients with either a diagnosis of anaphylaxis (Group 1), or a diagnosis of severe allergic and drug adverse events with additional modifier codes for acute allergy events (Group 2). In Group 1, we judged 135 / 170 patients as true anaphylaxis cases, giving a PPV of 79.4% (95% CI: 73.3-85.5). In Group 2, we judged 47 / 263 patients as true anaphylaxis cases, giving a PPV of 17.9% (95% CI: 13.3-22.5). In conclusion, acceptable PPVs were observed when anaphylaxis cases were identified by ICD-10-CM codes for anaphylaxis, but not by ICD-10-CM codes for severe allergic or drug adverse event with additional modifier codes for acute allergy events. Our multi-institutional findings could serve as a fundamental reference for further studies of anaphylaxis based on real-world healthcare databases.

P19-derived neuronal cells express H1, H2, and H3 histamine receptors: a biopharmaceutical approach to evaluate antihistamine agents

Histamine is a biogenic amine implicated in various biological and pathological processes. Convenient cellular models are needed to screen and develop new antihistamine agents. This report aimed to characterize the response of neurons differentiated from mouse P19 embryonal carcinoma cells to histamine treatment, and to investigate the modulation of this response by antihistamine drugs, vegetal diamine oxidase, and catalase. The exposure of P19 neurons to histamine reduced cell viability to 65% maximally. This effect involves specific histamine receptors, since it was prevented by treatment with desloratadine and cimetidine, respectively, H₁ and H₂ antagonists, but not by the H₃ antagonist ciproxifan. RT-PCR analysis showed that P19 neurons express H₁ and H₂ receptors, and the H₃ receptor, although it seemed not involved in the histamine effect on these cells. The H₄ receptor was not expressed. H₁ and H₂ antagonists as well as vegetal diamine oxidase diminished the intracellular Ca²⁺ mobilization triggered by histamine. The treatment with vegetal diamine oxidase or catalase protected against mortality and a significant reduction of H₂O₂ level, generated from the cells under the histamine action, was found upon treatments with desloratadine, cimetidine, vegetal diamine oxidase, or catalase. Overall, the results indicate the expression of functional histamine receptors and open the possibility of using P19 neurons as model system to study the roles of histamine and related drugs in neuronal pathogenesis. This model is less expensive to operate and can be easily implemented by current laboratories of analysis and by Contract Research Organizations.

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

IgE-mediated anaphylaxis is an acute life-threatening systemic reaction to allergens, including certain foods and venoms. Anaphylaxis is triggered when blood-borne allergens activate IgE-bound perivascular mast cells (MCs) throughout the body, causing an extensive systemic release of MC mediators. Through precipitating vasodilatation and vascular leakage, these mediators are believed to trigger a sharp drop in blood pressure in humans and in core body temperature in animals. We report that the IgE/MC-mediated drop in body temperature in mice associated with anaphylaxis also requires the body's thermoregulatory neural circuit. This circuit is activated when granule-borne chymase from MCs is deposited on proximal TRPV1⁺ sensory neurons and stimulates them via protease-activated receptor-1. This triggers the activation of the body's thermoregulatory neural network, which rapidly attenuates brown adipose tissue thermogenesis to cause hypothermia. Mice deficient in either chymase or TRPV1 exhibited limited IgE-mediated anaphylaxis, and, in wild-type mice, anaphylaxis could be recapitulated simply by systemically activating TRPV1⁺ sensory neurons. Thus, in addition to their well-known effects on the vasculature, MC products, especially chymase, promote IgE-mediated anaphylaxis by activating the thermoregulatory neural circuit.

Tumor-associated neutrophils and macrophages exacerbate antidrug IgG-mediated anaphylactic reaction against an immune checkpoint inhibitor

BACKGROUND

With the increased use of immune checkpoint inhibitors (ICIs), side effects and toxicity are a great concern. Anaphylaxis has been identified as a potential adverse event induced by ICIs. Anaphylaxis is a life-threatening medical emergency. However, the mechanisms and factors that can potentially influence the incidence and severity of anaphylaxis in patients with cancer remain unclear.

METHODS

Healthy, murine colon 26, CT26, breast 4T1, EMT6, and renal RENCA tumor-bearing mice were treated with an anti-PD-L1 antibody (clone 10F.9G2). Symptoms of anaphylaxis were evaluated along with body temperature and mortality. The amounts of antidrug antibody and platelet-activating factor (PAF) in the blood were quantified via ELISA and liquid chromatography-mass spectrometry (LC-MS/MS). Immune cells were analyzed and isolated using a flow cytometer and magnetic-activated cell sorting, respectively.

RESULTS

Repeated administration of the anti-PD-L1 antibody 10F.9G2 to tumor-bearing mice caused fatal anaphylaxis, depending on the type of tumor model. After administration, antidrug immunoglobulin G (IgG), but not IgE antibodies, were produced, and PAF was released as a chemical mediator during anaphylaxis, indicating that anaphylaxis was caused by an IgG-dependent pathway. Anaphylaxis induced by 10F.9G2 was treated with a PAF receptor antagonist. We identified that neutrophils and macrophages were PAF-producing effector cells during anaphylaxis, and the tumor-bearing models with increased numbers of neutrophils and macrophages showed lethal anaphylaxis after treatment with 10F.9G2. Depletion of both neutrophils and macrophages using clodronate liposomes prevented anaphylaxis in tumor-bearing mice.

CONCLUSIONS

Thus, increased numbers of neutrophils and macrophages associated with cancer progression may be risk factors for anaphylaxis. These findings may provide useful insights into the mechanism of anaphylaxis following the administration of immune checkpoint inhibitors in human subjects.

A case series of perioperative anaphylaxis to cefazolin during kidney transplant and review of literature

BACKGROUND

Intraoperative anaphylaxis is a life threatening and multiorgan system hypersensitivity reaction that frequently leads to cessation of operations. Despite the incidence of Cefazolin allergy being on the rise, the cases of anaphylaxis to Cefazolin during surgeries and its management are seldom reported.

CASE PRESENTATION

We present two patients with no known beta-lactam allergy and end stage kidney disease who received perioperative intravenous Cefazolin for planned deceased kidney transplant surgery at our academic medical center. Both patients developed anaphylaxes approximately three minutes following the administration of the antibiotic and experienced severe, refractory hypotension that required the use of vasopressors. The severity of the anaphylactic reactions resulted in the cessation of the transplant operation and multiple days of intensive care unit admission.

CONCLUSION

Peri-or intraoperative anaphylaxis to Cefazolin is on the rise and its consequences in transplant candidates are even more dire given the pre-existing end organ failure, financial burden for health care system, potential loss of donor organs, and emotional burden for recipients and their families. These are the first two cases of reported Cefazolin-induced anaphylaxis that actually resulted in aborting the kidney transplant operation. In addition, cases of previously reported Type 1 hypersensitivity to Cefazolin as prophylaxis for operations were reviewed and the allergy workups were discussed.

The First Case of Erythritol-Induced Anaphylaxis in Korea

Erythritol is a natural sugar alcohol found in some fruits and fermented foods, which is used as a dietary sweetener because it has few calories. Here, we describe a 36-year-old woman who experienced anaphylaxis upon ingestion of an erythritol-containing drink. She presented to the emergency department with dyspnea and angioedema after drinking a peach-containing diet beverage. Her blood pressure dropped to 70/40 mmHg and the symptoms improved after administration of an antihistamine, glucocorticoid, and epinephrine. After 10 days, she drank another peach-containing diet beverage and experienced urticaria. No serum-specific immunoglobulin E findings were observed, including against peach components. A skin prick test (SPT) was performed using a peach, the two ingested diet beverages, and another peach-containing beverage. The SPT results for the peach and the peach-containing product were negative, but the wheal sizes for the two diet beverages were > 3 mm. The diet beverages contained erythritol as a food additive. The SPT result was positive for erythritol. The patient was diagnosed with anaphylaxis to erythritol and was instructed to avoid foods containing erythritol. She was prescribed a self-injectable epinephrine pen. To our knowledge, this is the first case of erythritol-induced anaphylaxis in Korea. Physicians should be aware of the possibility of allergic reactions to food additives, and additives should be evaluated to prevent the recurrence of symptoms.

Management of Anaphylaxis

The key to managing anaphylaxis is early epinephrine administration. This can improve outcomes and prevent progression to severe and fatal anaphylaxis. Delayed or lack of administration of epinephrine is associated with fatal reactions. Positioning in a recumbent supine position, airway management, and intravenous fluids are essential in its management. Antihistamines and glucocorticosteroids should not be prescribed in place of epinephrine. β-adrenergic agonists by inhalation are indicated for bronchospasm associated with anaphylaxis despite optimal epinephrine treatment. Long-term management of anaphylaxis includes the identification and avoidance of triggers; identification of cofactors, such as mast cell disorders; patient, parent, and caregiver education, and interventions to reduce allergen sensitivity, such as the use of venom immunotherapy for Hymenoptera hypersensitivity. Long-term management is covered in other articles. Consultation with an allergist/immunologist is recommended when necessary.

Allergic Diseases: A Comprehensive Review on Risk Factors, Immunological Mechanisms, Link with COVID-19, Potential Treatments, and Role of Allergen Bioinformatics

The prevalence of allergic diseases is regarded as one of the key challenges in health worldwide. Although the precise mechanisms underlying this rapid increase in prevalence are unknown, emerging evidence suggests that genetic and environmental factors play a significant role. The immune system, microbiota, viruses, and bacteria have all been linked to the onset of allergy disorders in recent years. Avoiding allergen exposure is the best treatment option; however, steroids, antihistamines, and other symptom-relieving drugs are also used. Allergen bioinformatics encompasses both computational tools/methods and allergen-related data resources for managing, archiving, and analyzing allergological data. This study highlights allergy-promoting mechanisms, algorithms, and concepts in allergen bioinformatics, as well as major areas for future research in the field of allergology.

Structure-guided design of ultrapotent disruptive IgE inhibitors to rapidly terminate acute allergic reactions

BACKGROUND

Anaphylaxis represents one of the most severe and fatal forms of allergic reactions. Like most other allergies, it is caused by activation of basophils and mast cells by allergen-mediated cross-linking of IgE bound to its high-affinity receptor, FcεRI, on the cell surface. The systemic release of soluble mediators induces an inflammatory cascade, rapidly causing symptoms with peak severity in minutes to hours after allergen exposure. Primary treatment for anaphylaxis consists of immediate intramuscular administration of adrenaline.

OBJECTIVE

While adrenaline alleviates life-threatening symptoms of an anaphylactic reaction, there are currently no disease-modifying interventions available. We sought to develop potent and fast-acting IgE inhibitors with the potential to rapidly terminate acute allergic reactions.

METHODS

Using affinity maturation by yeast display and structure-guided molecular engineering, we generated 3 optimized disruptive IgE inhibitors based on designed ankyrin repeat proteins and assessed their ability to actively remove IgE from allergic effector cells in vitro as well as in vivo in mice.

RESULTS

The engineered IgE inhibitors rapidly dissociate preformed IgE:FcεRI complexes, terminate IgE-mediated signaling in preactivated human blood basophils in vitro, and shut down preinitiated allergic reactions and anaphylaxis in mice in vivo.

CONCLUSIONS

Fast-acting disruptive IgE inhibitors demonstrate the feasibility of developing kinetically optimized inhibitors for the treatment of anaphylaxis and the rapid desensitization of allergic individuals.

Characterization of anaphylaxis reveals different metabolic changes depending on severity and triggers

BACKGROUND

Despite the increasing incidence of anaphylaxis, its underlying molecular mechanisms and biomarkers for appropriate diagnosis remain undetermined. The rapid onset and potentially fatal outcome in the absence of managed treatment prevent its study. Up today, there are still no known biomarkers that allow an unequivocal diagnosis. Therefore, the aim of this study was to explore metabolic changes in patients suffering anaphylactic reactions depending on the trigger (food and/or drug) and severity (moderate and severe) in a real-life set-up.

METHODS

Eighteen episodes of anaphylaxis, one per patient, were analysed. Sera were collected during the acute phase (T1), the recovery phase (T2) and around 2-3 months after the anaphylactic reaction (T0: basal state). Reactions were classified following an exhaustive allergological evaluation for severity and trigger. Sera samples were analysed using untargeted metabolomics combining liquid chromatography coupled to mass spectrometry (LC-MS) and proton nuclear magnetic resonance spectroscopy (¹ H-NMR).

RESULTS

'Food T1 vs T2' and 'moderate T1 vs T2' anaphylaxis comparisons showed clear metabolic patterns during the onset of an anaphylactic reaction, which differed from those induced by drugs, food + drug or severe anaphylaxis. Moreover, the model of food anaphylaxis was able to distinguish the well-characterized IgE (antibiotics) from non-IgE-mediated anaphylaxis (nonsteroidal anti-inflammatory drugs), suggesting a differential metabolic pathway associated with the mechanism of action. Metabolic differences between 'moderate vs severe' at the acute phase T1 and at basal state T0 were studied. Among the altered metabolites, glucose, lipids, cortisol, betaine and oleamide were observed altered.

CONCLUSIONS

The results of this exploratory study provide the first evidence that different anaphylactic triggers or severity induce differential metabolic changes along time or at specific time-point, respectively. Besides, the basal status T0 might identify high-risk patients, thus opening new ways to understand, diagnose and treat anaphylaxis.

Investigation of the association between gall bladder wall thickness and hypoalbuminaemia in dogs

OBJECTIVES

To assess the correlation between gallbladder wall thickness and serum/plasma albumin concentrations in dogs.

MATERIALS AND METHODS

Retrospective searches of digital medical record databases were conducted to identify dogs that had either severely low serum/plasma albumin concentration (<1.5 g/dL) or ultrasonographic evidence of gallbladder wall thickening (>2 mm). Analysis of covariance models were used to analyze gallbladder wall thickness with sample type (serum vs plasma), age, etiology, albumin, and albumin ' etiology as the covariates.

RESULTS

A total of 216 dogs met inclusion criteria. One-hundred and forty-six dogs had a thickened gallbladder wall (Group 1). Median serum/plasma albumin concentration for dogs in this group was 2.2 g/dL (1 to 5 g/dL), and 84 dogs (57.5%) had hypoalbuminemia (<2.5 g/dL). The search for dogs with severe hypoalbuminemia (< 1.5 g/dL) identified 70 dogs (Group 2). In this group, median gallbladder wall thickness was 1.3 mm (0.2 to 6.1 mm) and 17 dogs (24.3%) had a thickened gallbladder wall. Serum/plasma albumin concentration and gallbladder wall thickness were not significantly correlated for Group 1 (r = 0.0044, p = 0.9580) or Group 2 (r = -0.1137, p = 0.3487). A moderate negative correlation (-0.64) was identified between gallbladder wall thickness and albumin concentration in dogs with immune-mediated diseases (p = 0.03).

CLINICAL SIGNIFICANCE

Gallbladder wall thickness and serum/plasma albumin concentration are independent variables in dogs.

Evaluation of Antibiotic Allergies in Surgical Patients

Antibiotic administration in the perioperative period is the foundation of preventing surgical site infections. β-Lactam antibiotics, notably the first-generation cephalosporin cefazolin, are the drugs of choice for this indication. However, reported antibiotic allergies often result in the use of suboptimal alternative agents that can lead to an increased risk of infection and adverse effects. A comprehensive allergy history and risk stratification should be completed preoperatively to determine whether or not a patient can be rechallenged with a β-lactam antibiotic and what testing may be necessary prior to administration. Nursing staff can play a critical role in understanding the implications and management of reported antibiotic allergies in surgical patients in order to optimize patient care.

Medicolegal Implications of Biphasic Anaphylaxis

ABSTRACT

Biphasic anaphylaxis is an uncommon IgE-mediated condition whose pathophysiological mechanisms, risk factors, and predictive signs are not properly understood. Fortunately, the lethality of biphasic anaphylaxis, although probably underestimated, is low. Preventive clinical measures for biphasic anaphylaxis are neither standardized nor commonly applied. Furthermore, there are no laboratory protocols or anaphylactic markers to help identify the onset of biphasic anaphylaxis in clinical settings. The aim of this review is to highlight the medicolegal difficulties facing coroners and forensic pathologists in terms of the diagnosis and assessment of harm for victims and survivors of biphasic anaphylaxis.

Effects of Glucocorticoids on Hospitalized Children With Anaphylaxis

BACKGROUND

The benefits of glucocorticoid treatment and recent trends of adjunctive treatments during episodes of anaphylaxis remain unclear.

OBJECTIVES

The aims of this study were to investigate the recent practice patterns and compare the effects of glucocorticoid for children hospitalized with anaphylaxis.

METHODS

Using the Japanese Diagnosis Procedure Combination inpatient database, we compared the length of hospital stay, risk of 10-day readmission, and total hospitalization cost between the steroid and nonsteroid groups. We also evaluated recent trends of adjunctive treatments for anaphylaxis.

RESULTS

From 2010 to 2014, the proportions of H1-receptor antagonist use increased from 65.1% to 71.8% (Ptrend = 0.02). The proportions of H2-receptor antagonist use showed an upward trend, ranging from 12.8% to 16.7% (Ptrend = 0.01). No significant change in glucocorticoid use was observed (from 86.7% to 82.6%; Ptrend = 0.08). Stabilized inverse probability-weighting analyses showed that the total length of hospital stay was 0.39 days longer in the steroid group than in the nonsteroid group (95% confidence interval, 0.29-0.49 days). Total hospitalization cost was greater in the steroid group than in the nonsteroid group (difference, ¥3896; 95% confidence interval, ¥2464-¥5562). No significant difference in risk of 10-day readmission was observed between the groups. Instrumental variable analyses showed similar results to stabilized inverse probability-weighting analyses.

CONCLUSIONS

We observed increasing trends of H1- and H2-receptor antagonist use. Length of hospital stay and total hospitalization cost were greater in the steroid group than in the nonsteroid group, whereas readmission risks were similar between the 2 groups.

Cellular Signal Transductions and Their Inhibitors Derived from Deep-Sea Organisms

Not only physiological phenomena but also pathological phenomena can now be explained by the change of signal transduction in the cells of specific tissues. Commonly used cellular signal transductions are limited. They consist of the protein-tyrosine kinase dependent or independent Ras-ERK pathway, and the PI3K-Akt, JAK-STAT, SMAD, and NF-κB-activation pathways. In addition, biodegradation systems, such as the ubiquitin-proteasome pathway and autophagy, are also important for physiological and pathological conditions. If we can control signaling for each by a low-molecular-weight agent, it would be possible to treat diseases in new ways. At present, such cell signaling inhibitors are mainly looked for in plants, soil microorganisms, and the chemical library. The screening of bioactive metabolites from deep-sea organisms should be valuable because of the high incidence of finding novel compounds. Although it is still an emerging field, there are many successful examples, with new cell signaling inhibitors. In this review, we would like to explain the current view of the cell signaling systems important in diseases, and show the inhibitors found from deep-sea organisms, with their structures and biological activities. These inhibitors are possible candidates for anti-inflammatory agents, modulators of metabolic syndromes, antimicrobial agents, and anticancer agents.

Anaphylactic Death: A New Forensic Workflow for Diagnosis

Anaphylaxis is a life-threatening or fatal clinical emergency characterized by rapid onset, and death may be sudden. The margin of certainty about the diagnosis of anaphylactic death is not well established. The application of immunohistochemical techniques combined with the evaluation of blood tryptase concentrations opened up a new field of investigation into anaphylactic death. The present study investigated eleven autopsy cases of anaphylactic death, carried out between 2005 and 2017, by the Departments of Forensic Pathology of the Universities of Foggia and Catania (Italy). An analysis of the medical records was carried out in all autopsies. Seven autopsies were carried out on males and four on females. Of the eleven cases, one showed a history of asthma, one of food ingestion, two of oral administration of medications, six did not refer any allergy history, and one subject was unknown. All cases (100%) showed pulmonary congestion and edema; 7/11 (64%) of the cases had pharyngeal/laryngeal edema and mucus plugging in the airway; only one case (9%) had a skin reaction that was found during external examination. Serum tryptase concentration was measured in ten cases, and the mean value was 133.5 µg/L ± 177.9. The immunohistochemical examination using an anti-tryptase antibody on samples from the lungs, pharynx/larynx, and skin site of medication injection showed that all cases (100%) were strongly immunopositive for anti-tryptase antibody staining on lung samples; three cases (30%) were strongly immunopositive for anti-tryptase antibody staining on pharyngeal/laryngeal samples; and eight cases (80%) were strongly immunopositive for anti-tryptase antibody staining on skin samples. We conclude that a typical clinical history, blood tryptase level >40 µg/L, and strongly positive anti-tryptase antibody staining in the immunohistochemical investigation may represent reliable parameters in the determination of anaphylactic death with the accuracy needed for forensic purposes.

The anti-allergic potential of tea: a review of its components, mechanisms and risks

Allergy is an immune-mediated disease with increasing prevalence worldwide. Regular treatment with glucocorticoids and antihistamine drugs for allergy patients is palliative rather than permanent. Daily use of dietary anti-allergic natural products is a superior way to prevent allergy and alleviate the threat. Tea, as a health-promoting beverage, has multiple compounds with immunomodulatory ability. Persuasive evidence has shown the anti-allergic ability of tea against asthma, food allergy, atopic dermatitis and anaphylaxis. Recent advances in potential anti-allergic ability of tea and anti-allergic compounds in tea have been reviewed in this paper. Tea exerts its anti-allergic effect mainly by reducing IgE and histamine levels, decreasing FcεRI expression, regulating the balance of Th1/Th2/Th17/Treg cells and inhibiting related transcription factors. Further research perspectives are also discussed.

Effects of NO/cGMP inhibitors in a rat model of anaphylactoid shock

Anaphylactic shock can be defined as an acute syndrome, and it is the most severe clinical manifestation of allergic diseases. Anaphylactoid reactions are similar to anaphylactic events but differ in the pathophysiological mechanism. Nitric oxide (NO) inhibitors during anaphylaxis suggest that NO might decrease the signs and symptoms of anaphylaxis but exacerbate associated vasodilation. Therefore, blocking the effects of NO on vascular smooth muscle by inhibiting the guanylate cyclase (GC) would be a reasonable strategy. This study aimed to investigate the effects of NO/cGMP pathway inhibitors methylene blue (MB), N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and indigo carmine (IC) in shock induced by compound 48/80 (C48/80) in rats. The effect was assessed by invasive blood pressure measurement. Shock was initiated by C48/80 intravenous bolus injection 5 min before (prophylactic) or after (treatment) the administration of the inhibitors MB (3 mg/kg), L-NAME (1 mg/kg), and IC (3 mg/kg). Of the groups that received drugs as prophylaxis for shock, only the IC group did not present the final systolic blood pressure (SBP) better than the C48/80 group. Regarding shock treatment with the drugs tested, all groups had the final SBP similar to the C48/80group. Altogether, our results suggested that inhibition of GC and NO synthase in NO production pathway was not sufficient to revert hypotension or significantly improve survival.

Cellular Stress and General Pathological Processes

From the viewpoint of the general pathology, most of the human diseases are associated with a limited number of pathogenic processes such as inflammation, tumor growth, thrombosis, necrosis, fibrosis, atrophy, pathological hypertrophy, dysplasia and metaplasia. The phenomenon of chronic low-grade inflammation could be attributed to non-classical forms of inflammation, which include many neurodegenerative processes, pathological variants of insulin resistance, atherosclerosis, and other manifestations of the endothelial dysfunction. Individual and universal manifestations of cellular stress could be considered as a basic element of all these pathologies, which has both physiological and pathophysiological significance. The review examines the causes, main phenomena, developmental directions and outcomes of cellular stress using a phylogenetically conservative set of genes and their activation pathways, as well as tissue stress and its role in inflammatory and para-inflammatory processes. The main ways towards the realization of cellular stress and its functional blocks were outlined. The main stages of tissue stress and the classification of its typical manifestations, as well as its participation in the development of the classical and non-classical variants of the inflammatory process, were also described. The mechanisms of cellular and tissue stress are structured into the complex systems, which include networks that enable the exchange of information with multidirectional signaling pathways which together make these systems internally contradictory, and the result of their effects is often unpredictable. However, the possible solutions require new theoretical and methodological approaches, one of which includes the transition to integral criteria, which plausibly reflect the holistic image of these processes.

The protective effect of Ellagic acid (EA) in osteoarthritis: An in vitro and in vivo study

Osteoarthritis (OA), a progressive joint disorder, is principally characterized by the degeneration and destruction of the articular cartilage. Ellagic acid (EA), a natural polyphenol found in berries and nuts has shown potent anti-inflammatory effects, however, its effects and underlying mechanisms on OA have seldom been systematically illuminated. In this study, we reported the anti-inflammatory effects of Ellagic acid (EA) in the progression of OA in both in vitro and in vivo experiments. in vitro study, IL-1β-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), Nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), prostaglandin E2 (PGE2), and interleukin-6 (IL-6) were inhibited by Ellagic acid (EA). Moreover, Ellagic acid (EA) down-regulated the IL-1β-stimulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) while up-regulated the collagen of type II and aggrecan. Mechanistically, we revealed that Ellagic acid (EA) suppressed nuclear factor kappa B (NF-κB) signaling in IL-1β -induced chondrocytes. And Ellagic acid (EA)-induced protectiveness in OA development was also shown by the DMM model. Taken together, our data indicate that Ellagic acid (EA) may serve as a potential drug for OA treatment.

High prevalence of allergy in patients undergoing in vitro fertilization and embryo transfer

PURPOSE

To determine the prevalence of allergy in couples undergoing in vitro fertilization (IVF) and the relationship between having allergy and IVF treatment outcomes.

DESIGN

A retrospective cohort study of female infertility patients aged 20-49 years and their male partners undergoing IVF cycles from August 2010 to December 2016 in an academic fertility program.

RESULTS

Prevalence data was collected for 493 couples (935 cycles). Over half of the female patients (54%) had at least one reported allergy versus the cited US prevalence of 10-30%. Antibiotic (54.7%) and non-antibiotic medication (39.2%) were the most common female allergy subtypes. Fewer male patients reported allergy (21.7%). Data on β-hCG outcomes were calculated for 841 cycles from 458 couples with no significant relationship found except for number of cycles including ICSI and number of embryos transferred per cycle (1.81 for those without allergy vs 2.07 for those with allergy, p = 0.07). Female patients with allergy were marginally statistically more likely to have a negative β-hCG (p = 0.07) and less likely to have a successful cycle (p = 0.06). When allergy subgroups were evaluated, there were no significant differences between groups except for a higher number of embryos transferred in women with environmental/other allergies (p = 0.02).

CONCLUSION

The prevalence of allergy among patients seeking infertility treatment is high compared with the general population. However, allergy was not found to be associated with IVF cycle outcomes. These findings are likely primarily limited by difficulty in defining specific allergy types within a retrospective study.

A Prospective Observation of Psychological Distress in Patients With Anaphylaxis

Purpose

Anaphylaxis is an immediate allergic reaction characterized by potentially life-threatening, severe, systemic manifestations. While studies have evaluated links between serious illness and posttraumatic stress disorder (PTSD), few have investigated PTSD after anaphylaxis in adults. We sought to investigate the psychosocial burden of recent anaphylaxis in Korean adults.

Methods

A total of 203 (mean age of 44 years, 120 females) patients with anaphylaxis were recruited from 15 university hospitals in Korea. Questionnaires, including the Impact of Event Scale-Revised-Korean version (IES-R-K), the Korean version of the Beck Anxiety Inventory (K-BAI), and the Korean version of the Beck Depression Inventory (K-BDI), were administered. Demographic characteristics, causes and clinical features of anaphylaxis, and serum inflammatory markers, including tryptase, platelet-activating factor, interleukin-6, tumor necrosis factor-α, and C-reactive protein, were evaluated.

Results

PTSD (IES-R-K ≥ 25) was noted in 84 (41.4%) patients with anaphylaxis. Of them, 56.0% had severe PTSD (IES-R-K ≥ 40). Additionally, 23.2% and 28.1% of the patients had anxiety (K-BAI ≥ 22) and depression (K-BDI ≥ 17), respectively. IES-R-K was significantly correlated with both K-BAI (r = 0.609, P < 0.0001) and K-BDI (r = 0.550, P < 0.0001). Among the inflammatory mediators, tryptase levels were lower in patients exhibiting PTSD; meanwhile, platelet-activating factor levels were lower in patients exhibiting anxiety and depression while recovering from anaphylaxis. In multivariate analysis, K-BAI and K-BDI were identified as major predictive variables of PTSD in patients with anaphylaxis.

Conclusions

In patients with anaphylaxis, we found a remarkably high prevalence of PTSD and associated psychological distresses, including anxiety and depression. Physicians ought to be aware of the potential for psychological distress in anaphylactic patients and to consider psychological evaluation.

Toward the Existence of a Sympathetic Neuroplasticity Adaptive Mechanism Influencing the Immune Response. A Hypothetical View-Part II

In the preceding work, a hypothesis on the existence of a specific neural plasticity program from sympathetic fibers innervating secondary lymphoid organs was introduced. This proposed adaptive mechanism would involve segmental retraction and degeneration of noradrenergic terminals during the immune system (IS) activation followed by regeneration once the IS returns to the steady-state. Starting from such view, this second part presents clinical and experimental evidence allowing to envision that this sympathetic neural plasticity mechanism is also operative on inflamed non-lymphoid peripheral tissues. Importantly, the sympathetic nervous system regulates most of the physiological bodily functions, ranging from cardiovascular, respiratory and gastro-intestinal functions to endocrine and metabolic ones, among others. Thus, it seems sensible to think that compensatory programs should be put into place during inflammation in non-lymphoid tissues as well, to avoid the possible detrimental consequences of a sympathetic blockade. Nevertheless, in many pathological scenarios like severe sepsis, chronic inflammatory diseases, or maladaptive immune responses, such compensatory programs against noradrenergic transmission impairment would fail to develop. This would lead to a manifest sympathetic dysfunction in the above-mentioned settings, partly accounting for their underlying pathophysiological basis; which is also discussed. The physiological/teleological significance for the whole neural plasticity process is postulated, as well.

The Role of KIT Mutations in Anaphylaxis

PURPOSE OF REVIEW

Gain of function KIT mutations are detected in clonal mast cell diseases, namely mastocytosis and monoclonal mast cell activation syndrome. Timely diagnosis and treatment of these disorders are crucial because of their association with severe and life-threatening anaphylaxis. KIT mutations also have implications for targeted therapies of mast cell disorders. This review article strives to serve as an overview of the role of clonal mast cell disorders in anaphylaxis while elucidating current and future therapies.

RECENT FINDINGS

Clonal mast cell disease has been increasingly diagnosed in patients with severe hymenoptera allergy and those with recurrent unexplained anaphylaxis. The current state of knowledge of the epidemiology, pathophysiology, diagnosis, and treatment of mastocytosis with a particular focus on anaphylaxis and its triggers which are described in this context. Novel and forthcoming treatments are discussed including the relevance of KIT mutation status. This review provides an overview of the role of KIT mutations in mastocytosis and anaphylaxis, and highlights emerging therapies for mastocytosis, targeting these mutations.

Non-digestible oligosaccharides scFOS/lcFOS facilitate safe subcutaneous immunotherapy for peanut allergy

BACKGROUND

Improving the safety of subcutaneous immunotherapy (SCIT) for food allergy is necessary to reduce side effects and achieve long-term tolerance. We determined the effect of dietary supplementation with 1% non-digestible short- and long-chain fructo-oligosaccharides (scFOS/lcFOS) on safety and efficacy of SCIT using a peanut allergy mouse model.

METHODS

After sensitization, mice received a scFOS/lcFOS or control diet for the rest of the study. To study safety of SCIT, mice were dosed with a single subcutaneous injection of peanut extract (PE) or PBS. To study efficacy, mice were dosed subcutaneously (SCIT, 3 times/week) with PE or PBS for 3 weeks. Hereafter, acute allergic skin responses, anaphylactic shock symptoms and body temperature were assessed. To study the mechanism in vitro, the human IgE receptor (FcεRI)-transfected rat mast cell (RBL) line was sensitized with an oligoclonal pool of chimeric human (chu)IgE antibodies against bovine β-lactoglobulin (BLG) and incubated with the oligosaccharides before exposure to BLG to assess direct the effect on degranulation.

RESULTS

scFOS/lcFOS reduced anaphylaxis caused by a single PE SCIT dose. scFOS/lcFOS alone also reduced the acute allergic skin response. Moreover, scFOS/lcFOS supplementation resulted in lower MMCP-1 levels in serum after PE SCIT dose compared to control diet, while antibody levels were not affected by the diet. In vitro incubation with scFOS/lcFOS at 0.5% suppressed the degranulation of IgE-sensitized RBL cells. However, dietary supplementation with scFOS/lcFOS did not improve the efficacy of SCIT.

CONCLUSIONS

We show that scFOS/lcFOS diet improves the safety of SCIT, as evidenced by lower anaphylactic responses without compromising the efficacy in a mouse model for peanut allergy. This effect is likely to result from the suppression of mast cell effector function.

Peiminine inhibits the IL-1β induced inflammatory response in mouse articular chondrocytes and ameliorates murine osteoarthritis

Osteoarthritis (OA) is a common arthrosis characterized by degeneration and inflammation of articular cartilage. In recent decades, peiminine (Pm) has been identified as one of the active ingredients of Fritillaria plants. According to reports, Pm has a potent anti-inflammatory effect in various diseases. However, the effectiveness of Pm as an anti-inflammatory in OA has not previously been reported. This research aims to evaluate the anti-inflammatory effect of Pm on interleukin (IL)-1β-induced mice chondrocytes and its chondroprotective effect in a mouse OA model with surgical destabilization of the medial meniscus. IL-1β-induced expression of nitric oxide (NO), prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), inducible nitric oxide synthase (iNOS) and interleukin-6 (IL-6) were all inhibited significantly by Pm pretreatment in vitro. In addition, Pm also inhibited the expression of thrombospondin motifs 5 (ADAMTS-5) and matrix metalloproteinase-13 (MMP-13), which are responsible for the degradation of the extracellular matrix (ECM). Additionally, the degradation of aggrecan and collagen II was reversed by Pm. Furthermore, Pm inhibited Akt phosphorylation and the nuclear transfer of nuclear factor-κB (NF-κB) and activated Nrf2/HO-1 signaling pathways both in vitro and in vivo. These findings suggested that Pm alleviated inflammatory effects in the IL-1β-induced chondrocytes. Therefore, Pm might be a potential therapeutic agent for OA.

Cellular and Immunohistochemical Changes in Anaphylactic Shock Induced in the Ovalbumin-Sensitized Wistar Rat Model

Anaphylactic shock (AS) is a life-threatening, multisystem disorder arising from sudden release of mast cell- and basophil-derived mediators into the circulation. In this study, we have used a Wistar rat model to investigate AS-associated histopathologic changes in various organs. Rats were sensitized with ovalbumin (1 mg s.c), and AS was induced by intravenous injection of ovalbumin (1 mg). Experimental groups included nonallergic rats (n = 6) and allergic rats (n = 6). Heart rate and blood pressure were monitored during one hour. Organs were harvested at the end of the experiment and prepared for histologic and immunohistochemical studies. Lung, small bowel mucosa and spleen were found to undergo heavy infiltration by mast cells and eosinophils, with less prominent mast cell infiltration of cardiac tissue. The mast cells in lung, small bowel and spleen exhibited increased expression of tryptase, c-kit and induced nitric oxide synthase (iNOS). Increased expression of endothelial nitric oxide synthase (eNOS) by vascular endothelial cells was noted principally in lung, heart and small bowel wall. The Wistar rat model of AS exhibited accumulation of mast cells and eosinophils in the lung, small bowel, and spleen to a greater extent than in the heart. We conclude that lung and gut are principal inflammatory targets in AS, and likely contribute to the severe hypotension of AS. Targeting nitric oxide (NO) production may help reduce AS mortality.

Human mast cells and basophils-How are they similar how are they different?

Mast cells and basophils are key contributors to allergies and other inflammatory diseases since they are the most prominent source of histamine as well as numerous additional inflammatory mediators which drive inflammatory responses. However, a closer understanding of their precise roles in allergies and other pathological conditions has been marred by the considerable heterogeneity that these cells display, not only between mast cells and basophils themselves but also across different tissue locations and species. While both cell types share the ability to rapidly degranulate and release histamine following high-affinity IgE receptor cross-linking, they differ markedly in their ability to either react to other stimuli, generate inflammatory eicosanoids or release immunomodulating cytokines and chemokines. Furthermore, these cells display considerable pharmacological heterogeneity which has stifled attempts to develop more effective anti-allergic therapies. Mast cell- and basophil-specific transcriptional profiling, at rest and after activation by innate and adaptive stimuli, may help to unravel the degree to which these cells differ and facilitate a clearer understanding of their biological functions and how these could be targeted by new therapies.

Dihydroxyacetone as a definitive treatment for aluminium phosphide poisoning in rats

Aluminium phosphide (AlP), a very toxic pesticide also known as the rice tablet, releases phosphine gas upon contact with water, moisture, or gastric acid. Its mortality rate in humans is 70-100 % due to cardiogenic shock and refractory hypotension. Dihydroxyacetone (DHA) is a simple ketonic carbohydrate, mainly used for sunless skin tanning. It also plays a beneficial role in the treatment of hypotension and cardiogenic shock by restoring blood volume and cellular respiration. The aim of this study was to investigate the its effect on the haemodynamics and electrocardiogram (ECG) in male rats poisoned with AlP. The animals were divided into the following groups: control (received 1 mL corn oil, orally), AlP (received 15 mg kg-1 AlP solved in corn oil, orally), AlP plus DHA (treated with 50 mg kg-1 of DHA 30 min after receiving AlP), and AlP plus N-acetyl cysteine (NAC) (treated with 200 mg kg-1 of NAC 30 min after receiving AlP). The animals were then anaesthetised and ECG, blood pressure, and heart rate were recorded for 120 min. Treatment with AlP alone and in combination with NAC was associated with progressive hypotension, tachycardia, and ECG disturbances in rats, resulting in 100 % mortality 3 h after poisoning. However, DHA achieved 100 % survival in the poisoned rats and prevented AlP-induced ECG and haemodynamic abnormalities. The main mechanism of DHA in the treatment of AlP poisoning is unclear, but the findings suggest the promising therapeutic potential of DHA against AlP poisoning.

Response of Cellular Innate Immunity to Cnidarian Pore-Forming Toxins

A group of stable, water-soluble and membrane-bound proteins constitute the pore forming toxins (PFTs) in cnidarians. They interact with membranes to physically alter the membrane structure and permeability, resulting in the formation of pores. These lesions on the plasma membrane causes an imbalance of cellular ionic gradients, resulting in swelling of the cell and eventually its rupture. Of all cnidarian PFTs, actinoporins are by far the best studied subgroup with established knowledge of their molecular structure and their mode of pore-forming action. However, the current view of necrotic action by actinoporins may not be the only mechanism that induces cell death since there is increasing evidence showing that pore-forming toxins can induce either necrosis or apoptosis in a cell-type, receptor and dose-dependent manner. In this review, we focus on the response of the cellular immune system to the cnidarian pore-forming toxins and the signaling pathways that might be involved in these cellular responses. Since PFTs represent potential candidates for targeted toxin therapy for the treatment of numerous cancers, we also address the challenge to overcoming the immunogenicity of these toxins when used as therapeutics.

Vitis amurensis Rupr: A review of chemistry and pharmacology

PURPOSE

Vitis amurensis Rupr. from the family Vitaceae, is a grape species native to the Asian continent. It is a highly attractive plant, used widely worldwide. It has been used for several hundred years as a traditional Chinese herb. The review focuses on the botanical description, traditional uses, phytochemistry, and the biological activities of Vitis amurensis Rupr. to evaluate its therapeutic potential uses.

METHODS

This review summarizes the published data concerning the botanical aspects, traditional usage, phytochemistry, and pharmacology of Vitis amurensis Rupr., to evaluate its therapeutic potential as an important source of natural compounds with effect activities that benefit human health.

RESULTS

Vitis amurensis Rupr. has been used for several hundred years as a traditional Chinese herb to treat stranguria, rheumatoid arthritis-associated edema, chronic hepatitis, nephritis, chronic arthritis and traumatic hemorrhage. It is a particularly rich source of the oligostilbenes, flavonoids, and anthocyanins, phytochemicals that are associated with antioxidant, anti-inflammatory, antibacterial and cardioprotective activities. Due to the presence of a multitude of bioactives, a wide array of pharmacological activities have been ascribed to different parts of this herb and individual compounds, which include antioxidant, antimicrobial, anti-inflammatory, anticancer, anti-aging, anti-melanogenic, anti-allergic and anti-viral.

CONCLUSION

From a health perspective, Vitis amurensis Rupr. presents excellent options for treating various diseases due to its bioactive compounds (drug candidates) that exhibit important activities or for developing new products.

Renal response to anaphylaxis in anesthetized rats and isolated perfused rat kidneys: roles of nitric oxide

We determined the renal responses to anaphylaxis and the effects of a nitric oxide synthesis inhibitor, L-NAME, in anesthetized rats and isolated perfused rat kidneys. After the ovalbumin antigen injection, the sensitized rats showed transient and substantial decreases in mean blood pressure and renal blood flow and an increase in renal vascular resistance. Creatinine clearance, a measure of renal function, decreased to 53% baseline at 2 h after antigen. L-NAME pretreatment significantly enhanced the antigen-induced renal vasoconstriction and renal dysfunction. Moreover, plasma creatinine levels significantly increased only in the L-NAME pretreated rats. Separately, in isolated perfused kidneys, we observed the antigen-induced renal vasoconstriction and its augmentation by L-NAME. In conclusion, the renal vascular response to the antigen is vasoconstriction, which is enhanced by L-NAME in both isolated perfused rat kidneys and anesthetized rats; it is accompanied by renal dysfunction, which is also augmented by L-NAME.

Patients with urticaria are at a higher risk of anaphylaxis: A nationwide population-based retrospective cohort study in Taiwan

The clinical features of urticaria and anaphylaxis are similar, and they share common causal immune-mediated pathways. We aimed to investigate the risk of anaphylaxis among patients with urticaria. A 12-year population-based retrospective cohort study was conducted. Investigated subjects were identified from the Taiwan National Health Insurance Research Database by the International Classification of Disease, Ninth Revision, Clinical Modification. We included 126 031 subjects with newly diagnosed urticaria and 252 062 matched controls between 2000 and 2013. Risk of anaphylaxis among patients with urticaria was calculated by calculating adjusted hazards ratios (HR) after matching for confounding comorbidities. Urticaria was more common in women than it was in men (58% vs 42%), with a peak onset age of 20-40 years. The number of comorbidities including asthma, allergic rhinitis, herpes zoster, hepatitis B and C, rheumatoid arthritis and gout were higher in patients with urticaria than that in age- and sex-matched controls. The crude HR for anaphylaxis among urticaria subjects was 2.883 (95% confidence interval [CI], 2.787-2.982; P < 0.001). After adjustment for potential confounders which have been proposed to increase the risk of anaphylaxis, patients with urticaria were found to be at a significantly high risk of anaphylaxis with an adjusted HR of 2.529 (95% CI, 2.442-2.619; P < 0.001). We conclude that the incidence rate of anaphylaxis is significantly high in patients with urticaria in Taiwan.

Milonine, an Alkaloid of Cissampelos sympodialis Eichl. (Menispermaceae) Inhibits Histamine Release of Activated Mast Cells

Milonine is an alkaloid of Cissampelos sympodialis Eichl. (Menispermaceae), a plant used in the northeast of Brazil to treat allergies such as asthma, rhinitis, and other conditions. Previously, several alkaloids were isolated from its roots and leaves with pharmacological properties in asthma and acute inflammation models. Therefore, the aim of this study was to evaluate the milonine effect on mast cells degranulation in vivo and in vitro. Swiss mice (n = 8) were used in models of paw edema induced by carrageenan, compound 48/80, or histamine. One hour before challenge, the animals were treated with milonine (at different doses) or standard drugs and, at different time points, the edema formation was measured. In addition, other different methods, such as anaphylactic shock reaction and scratching behavior models both induced by compound 48/80, a mast cell degranulator, were used to assess milonine effect histamine release in vivo. Moreover, milonine effect on mast cell degranulation in vitro was also carried out. Firstly, it was observed that milonine significantly decreased the carrageenan edema formation only at the beginning of the reaction (i.e., up to 2 h after challenge). Furthermore, this alkaloid decreased the edema induced by compound 48/80, maintained the paw tissue integrity, without modulating histamine-induced paw edema. In anaphylactic shock reaction, milonine increased the time of animal survival when compared with compound 48/80 group. Milonine also significantly decreased the scratching behavior induced by compound 48/80 with decreasing of mast cell degranulation in vitro. Therefore, these data indicated that milonine presents anti-allergic properties by decreasing mast cell degranulation rather than acting on histamine effect.

Can H2 -receptor upregulation and raised histamine explain an anaphylactoid reaction on cessation of ranitidine in a 19-year-old female? A case report

The anaphylactoid reaction described follows cessation of ranitidine in a 19-year-old female with the disease cluster: mast cell activation syndrome, hypermobile Ehlers-Danlos syndrome and postural tachycardia syndrome. Anaphylaxis can give wide-ranging symptoms from rhinorrhoea and urticaria to tachycardia and system-wide, life-threatening, anaphylactic shock. Individuals with a disorder of mast cell activation can experience many such symptoms. H2 receptor antagonists, such as ranitidine, are commonly prescribed in this population. A mechanism for the reaction is proposed in the context of ranitidine, as an inverse agonist, causing upregulation of H2 histamine receptors and raised histamine levels due to enzyme induction. This effect, following extended and/or high antihistamine dosing, may have implications for other individuals with a disorder of mast cell activation, such as mastocytosis or mast cell activation syndrome. There are potential policy and patient guidance implications for primary and secondary care with respect to cessation of H2 antagonists.

Molecular Regulation of Histamine Synthesis

Histamine is a critical mediator of IgE/mast cell-mediated anaphylaxis, a neurotransmitter and a regulator of gastric acid secretion. Histamine is a monoamine synthesized from the amino acid histidine through a reaction catalyzed by the enzyme histidine decarboxylase (HDC), which removes carboxyl group from histidine. Despite the importance of histamine, transcriptional regulation of HDC gene expression in mammals is still poorly understood. In this review, we focus on discussing advances in the understanding of molecular regulation of mammalian histamine synthesis.