A mast-cell-specific receptor mediates Iopamidol induced immediate IgE-independent anaphylactoid reactions

Transient pulmonary and gastric bleeding after iopamidol administration in a patient with marginal zone lymphoma: a case report

BACKGROUND

Iopamidol is a non-ionic, water-soluble iodine contrast agent that is considered safe for intravenous or intra-arterial administration and is widely used both in the general population and in patients undergoing oncological treatment. While adverse reactions to iopamidol have been documented, to date, no pulmonary and gastric hemorrhages induced by iopamidol have been reported in oncology patients. We report the first case of this complication.

CASE PRESENTATION

We report the case of a 60-year-old woman with marginal zone lymphoma who was receiving antineoplastic therapy. As part of the investigation for the condition, she underwent chest enhancement CT with iopamidol. Shortly thereafter(within five minutes), she experienced hemoptysis and hematemesis. She was intubated and admitted to the intensive care unit. Pre- and post-contrast images demonstrated the course of the hemorrhage. Flexible bronchoscopy and gastroscopy on the following day showed no active bleeding, and the patient recovered completely after antiallergy treatment. We speculate that contrast-induced hypersensitivity was the most likely cause of the transient pulmonary and gastric bleeding.

CONCLUSION

Although rare, the complications of iopamidol, which may cause allergic reactions in the lungs and stomach, should be considered.

Acute Adverse Events After Iodinated Contrast Agent Administration of 359,977 Injections: A Single-Center Retrospective Study

OBJECTIVE

To assess the effects of patient variables, examination variables, and seasonality on allergic-like and physiologic reactions to iodinated contrast material (ICM).

PATIENTS AND METHODS

All ICM-enhanced computed tomography (CT) examinations performed from June 1, 2009, to May 9, 2017, at our institution were included. Reactions were identified and categorized as allergic-like or physiologic and mild, moderate, or severe. The effect of patient and examination variables on reactions was evaluated by logistic regression models.

RESULTS

A total of 359,977 CT examinations performed on 176,886 unique patients were included. A total of 1150 allergic-like reactions (0.32%; 19 severe [0.005%]) and 679 physiologic reactions (0.19%; 3 severe [0.0008%]) occurred. On multivariable analysis, iopromide had higher rates of reactions compared with iohexol (allergic-like reactions: odds ratio [OR], 3.07 [95% CI, 2.37 to 3.98], P<.0001; physiologic reactions: OR, 2.60 [1.92 to 3.52], P<.0001). Non-White patients had higher rates of reactions compared with White patients (allergic-like reactions: OR, 1.77 [1.36-2.30], P<.0001; physiologic reactions: OR, 1.76 [1.27-2.42], P=.0006). Patient age, sex, prior ICM reaction, ICM dose, CT location, and CT type were also significantly associated with reactions. No significant seasonality trend was observed (P=.07 and .80).

CONCLUSION

Non-White patients and patients administered iopromide had higher rates of acute reactions compared with White patients and patients administered iohexol. Younger patients (<50 years vs 51 to 60 years), female sex, history of ICM allergy or other allergies, ICM dose, and contrast-enhanced CT location and type also correlated with higher acute reaction rates.

Nephrotoxicity of iopamidol is associated with mitochondrial impairment in human cell and teleost models

Iopamidol is a nonionic, low-osmolar iodinated contrast agent used for angiography. Its clinical use is associated with renal dysfunction. Patients suffering from preexisting kidney disease have an increased risk of renal failure upon iopamidol administration. Studies in animals confirmed renal toxicity, but the involved mechanisms remain unclear. Therefore, the aim of the present study was to use human embryonic kidney cells (HEK293T) as a general cell model of mitochondrial damage, as well as, zebrafish larvae, and isolated proximal tubules of killifish to investigate factors promoting renal tubular toxicity of iopamidol with a focus on mitochondrial damage. Results from in vitro HEK293T cell-based assays indicate that iopamidol affects mitochondrial function Treatment with iopamidol induces ATP depletion, reduces the mitochondrial membrane potential, and elevates mitochondrial superoxide and reactive oxygen species accumulation. Similar results were obtained with gentamicin sulfate and cadmium chloride, two well-known model compounds associated with renal tubular toxicity. Confocal microscopy confirms changes in mitochondrial morphology, such as mitochondrial fission. Importantly, these results were confirmed in proximal renal tubular epithelial cells using ex vivo and in vivo teleost models. In conclusion, this study provides evidence for iopamidol-induced mitochondrial damage in proximal renal epithelial cells. Teleost models allow studying proximal tubular toxicity with translational relevance for humans.

Neuroimmunology and Allergic Disease

The prevalence of allergic diseases is rising globally, inducing heavy quality of life and economic burdens. Allergic reactions are mediated by the complex bi-directional cross-talk between immune and nervous systems that we are only beginning to understand. Here, we discuss our current understanding of the molecular mechanisms of how this cross-talk occurs in the skin, gut, and lungs. An improved understanding of the communication between the immune and nervous system may lead to the development of novel therapies for allergic diseases.

PLC-IP3-ORAI pathway participates in the activation of the MRGPRB2 receptor in mouse peritoneal mast cells

A novel mast cell-specific G-protein-coupled receptor (GPCR), known as Mas-related G protein-coupled receptor-B2 (MRGPRB2), plays important roles in immune response. However, the opening of ion channels mediated by MRGPRB2 activation remains unclear. In this study, we found that [Ca²⁺]i elevation and voltage-dependent current generated by MRGPRB2 activation were correlated with extracellular calcium concentration. The increases in [Ca²⁺]i and voltage-dependent current caused by MRGPRB2 activation were blocked by U73122 (PLC blocker) or 2-APB (IP3 blocker) or synta66 (ORAI blocker). The voltage-dependent current induced by MRGPRB2 was inhibited by calcium-activated chlorine channel (CACCS) blockers, DIDS, or NPPB. Our results indicated the involvement of the PLC-IP3-ORAI signaling pathway and CACCS in MRGPRB2-mediated mast cell activation.

Mas-Related G Protein–Coupled Receptor-X2 and Its Role in Non-immunoglobulin E–Mediated Drug Hypersensitivity

A diverse group of Food and Drug Administration-approved cationic drugs including antibiotics, neuromuscular blocking drugs, opioids, antidepressants, and radiocontrast media activate mast cells and cause hypersensitivity reactions by both an immunoglobulin E IgE-dependent and independent manner. The recent discovery that these drugs activate mast cells via the G protein-coupled receptor known as Mas-related GPCR-X2 (MRGPRX2) has represented a paradigm shift of how drug hypersensitivity reactions are viewed. This article provides an overview of the current status of the role of MRGPRX2 on non-IgE-mediated drug hypersensitivity. Potential risk factors and evaluation for suspected MRGPRX2-mediated drug reactions are also discussed.

Iodixanol activation of mast cells: Implications in the pathogenesis of iodixanol-induced delayed cutaneous adverse reactions

Iodinated contrast media (ICM) is widely used in radiological examination and interventional therapy. In the commonly used ICM, iodixanol is considered to be the safer one. However, compared with other ICMs, it has a higher incidence of delayed cutaneous adverse reactions. The underlying mechanisms are unclear. In this study, mice with positive allergic reactions were selected based on the mouse clinical allergy symptom score and skin and blood samples taken 1, 6, 24, 48, and 72 h after ICMs (6 g iodine/kg) injection for histological and blood analyses. ICMs-induced pseudo-allergic reactions were investigated through in vivo intravital vascular imaging and passive cutaneous anaphylaxis (PCA) not mediated by IgE and through, calcium imaging degranulation of mast cells (MCs), and western blot assays in vitro. Results shows iodixanol-induced systemic anaphylaxis caused severe extravasation of plasma proteins and degranulation of skin MCs, and increased levels of plasma histamine, cytokines and inflammatory chemokines. Mechanistically, iodixanol increases degranulation of MCs and promotes the synthesis of inflammatory factors by activating PLC-γ and PI3K-related pathways. Trigonelline inhibit iodixanol-induced MC-related pseudo-allergic reactions in vitro and in vivo. These results suggest that mice in the iodixanol group had a higher incidence of delayed cutaneous reactions, characterized by cytokine release over time and delayed cutaneous MC degranulation. Iodixanol's delayed cutaneous adverse reactions may be due to a delayed phase of MC-related pseudo-allergic reactions. Trigonelline revealed anti-allergic activity in iodixanol-induced MC-related pseudo-allergic reactions.

Effects of G-Rh2 on mast cell-mediated anaphylaxis via AKT-Nrf2/NF-κB and MAPK-Nrf2/NF-κB pathways

Background

The effect of ginsenoside Rh2 (G-Rh2) on mast cell-mediated anaphylaxis remains unclear. Herein, we investigated the effects of G-Rh2 on OVA-induced asthmatic mice and on mast cell-mediated anaphylaxis.

Methods

Asthma model was established for evaluating airway changes and ear allergy. RPMCs and RBL-2H3 were used for in vitro experiments. Calcium uptake, histamine release and degranulation were detected. ELISA and Western blot measured cytokine and protein levels, respectively.

Results

G-Rh2 inhibited OVA-induced airway remodeling, the production of TNF-α, IL-4, IL-8, IL-1β and the degranulation of mast cells of asthmatic mice. G-Rh2 inhibited the activation of Syk and Lyn in lung tissue of OVA-induced asthmatic mice. G-Rh2 inhibited serum IgE production in OVA induced asthmatic mice. Furthermore, G-Rh2 reduced the ear allergy in IgE-sensitized mice. G-Rh2 decreased the ear thickness. In vitro experiments G-Rh2 significantly reduced calcium uptake and inhibited histamine release and degranulation in RPMCs. In addition, G-Rh2 reduced the production of IL-1β, TNF-α, IL-8, and IL-4 in IgE-sensitized RBL-2H3 cells. Interestingly, G-Rh2 was involved in the FcεRI pathway activation of mast cells and the transduction of the Lyn/Syk signaling pathway. G-Rh2 inhibited PI3K activity in a dose-dependent manner. By blocking the antigen-induced phosphorylation of Lyn, Syk, LAT, PLCγ2, PI3K ERK1/2 and Raf-1 expression, G-Rh2 inhibited the NF-κB, AKT-Nrf2, and p38MAPK-Nrf2 pathways. However, G-Rh2 up-regulated Keap-1 expression. Meanwhile, G-Rh2 reduced the levels of p-AKT, p38MAPK and Nrf2 in RBL-2H3 sensitized IgE cells and inhibited NF-κB signaling pathway activation by activating the AKT-Nrf2 and p38MAPK-Nrf2 pathways.

Conclusion

G-Rh2 inhibits mast cell-induced allergic inflammation, which might be mediated by the AKT-Nrf2/NF-κB and p38MAPK-Nrf2/NF-κB signaling pathways.

Diagnosing and Managing Patients with Reactions to Radiocontrast Media

Purpose of the review

Iodinated radio contrast media (RCM) belong to the most common elicitors of drug hypersensitivity reactions (HR). Urticaria or anaphylaxis may occur ≤ 1(−6) hour(s) (immediate HR) and exanthems (non-immediate HR) develop > 6 h after application of RCM. Evidence for an immunologic mechanism of RCM HR against the different RCM benzene ring molecules and the benefit of allergological testing in patients with previous hypersensitivity reactions is progressively increasing.

Recent findings

Positive skin tests can confirm allergy in patients with previous reactions to RCM and help to select alternative better tolerated RCMs. Severe hypersensitivity reactions are mainly caused by an allergic mechanism, whereas the majority of non-severe reactions appear to be non-allergic. Skin testing is highly recommended to help identify allergic hypersensitivity reactions and to select alternatives. Using structurally different RCM is more effective than premedication for the prevention of future reactions. Drug provocation tests to RCM have been increasingly used, but are not yet standardized among different centers.

Summary

In patients with previous severe hypersensitivity reactions to RCM, skin testing is recommended. For future RCM-enhanced examinations in patients with previous reactions, structurally different, skin test-negative preparations should be applied. Drug provocation tests do confirm or exclude RCM hypersensitivity or may demonstrate tolerability of alternative RCMs.

Ligands and Signaling of Mas-Related G Protein-Coupled Receptor-X2 in Mast Cell Activation

Mas-related G protein-coupled receptor-X2 (MRGPRX2) is known as a novel receptor to activate mast cells (MCs). MRGPRX2 plays a dual role in promoting MC-dependent host defense and immunomodulation and contributing to the pathogenesis of pseudo-allergic drug reactions, pain, itching, and inflammatory diseases. In this article, we discuss the possible signaling pathways of MCs activation mediated by MRGPRX2 and summarize and classify agonists and inhibitors of MRGPRX2 in MCs activation. MRGPRX2 is a low-affinity and low-selectivity receptor, which allows it to interact with a diverse group of ligands. Diverse MRGPRX2 ligands utilize conserved residues in its transmembrane (TM) domains and carboxyl-terminus Ser/Thr residues to undergo ligand binding and G protein coupling. The coupling likely initiates phosphorylation cascades, induces Ca²⁺ mobilization, and causes degranulation and generation of cytokines and chemokines via MAPK and NF-κB pathways, resulting in MCs activation. Agonists of MRGPRX2 on MCs are divided into peptides (including antimicrobial peptides, neuropeptides, MC degranulating peptides, peptide hormones) and nonpeptides (including FDA-approved drugs). Inhibitors of MRGPRX2 include non-selective GPCR inhibitors, herbal extracts, small-molecule MRGPRX2 antagonists, and DNA aptamer drugs. Screening and classifying MRGPRX2 ligands and summarizing their signaling pathways would improve our understanding of MRGPRX2-mediated physiological and pathological effects on MCs.

Unlocking the Non-IgE-Mediated Pseudo-Allergic Reaction Puzzle with Mas-Related G-Protein Coupled Receptor Member X2 (MRGPRX2)

Mas-related G-protein coupled receptor member X2 (MRGPRX2) is a class A GPCR expressed on mast cells. Mast cells are granulated tissue-resident cells known for host cell response, allergic response, and vascular homeostasis. Immunoglobulin E receptor (FcεRI)-mediated mast cell activation is a well-studied and recognized mechanism of allergy and hypersensitivity reactions. However, non-IgE-mediated mast cell activation is less explored and is not well recognized. After decades of uncertainty, MRGPRX2 was discovered as the receptor responsible for non-IgE-mediated mast cells activation. The puzzle of non-IgE-mediated pseudo-allergic reaction is unlocked by MRGPRX2, evidenced by a plethora of reported endogenous and exogenous MRGPRX2 agonists. MRGPRX2 is exclusively expressed on mast cells and exhibits varying affinity for many molecules such as antimicrobial host defense peptides, neuropeptides, and even US Food and Drug Administration-approved drugs. The discovery of MRGPRX2 has changed our understanding of mast cell biology and filled the missing link of the underlying mechanism of drug-induced MC degranulation and pseudo-allergic reactions. These non-canonical characteristics render MRGPRX2 an intriguing player in allergic diseases. In the present article, we reviewed the emerging role of MRGPRX2 as a non-IgE-mediated mechanism of mast cell activation in pseudo-allergic reactions. We have presented an overview of mast cells, their receptors, structural insight into MRGPRX2, MRGPRX2 agonists and antagonists, the crucial role of MRGPRX2 in pseudo-allergic reactions, current challenges, and the future research direction.

The Multifaceted Mas-Related G Protein-Coupled Receptor Member X2 in Allergic Diseases and Beyond

Recent research on mast cell biology has turned its focus on MRGPRX2, a new member of the Mas-related G protein-coupled subfamily of receptors (Mrgprs), originally described in nociceptive neurons of the dorsal root ganglia. MRGPRX2, a member of this group, is present not only in neurons but also in mast cells (MCs), specifically, and potentially in other cells of the immune system, such as basophils and eosinophils. As emerging new functions for this receptor are studied, a variety of both natural and pharmacologic ligands are being uncovered, linked to the ability to induce receptor-mediated MC activation and degranulation. The diversity of these ligands, characterized in their human, mice, or rat homologues, seems to match that of the receptor's interactions. Natural ligands include host defense peptides, basic molecules, and key neuropeptides such as substance P and vasointestinal peptide (known for their role in the transmission of pain and itch) as well as eosinophil granule-derived proteins. Exogenous ligands include MC secretagogues such as compound 48/80 and mastoparan, a component of bee wasp venom, and several peptidergic drugs, among which are members of the quinolone family, neuromuscular blocking agents, morphine, and vancomycin. These discoveries shed light on its capacity as a multifaceted participant in naturally occurring responses within immunity and neural stimulus perception, as in responses at the center of immune pathology. In host defense, the mice Mrgprb2 has been proven to aid mast cells in the detection of peptidic molecules from bacteria and in the release of peptides with antimicrobial activities and other immune mediators. There are several potential actions described for it in tissue homeostasis and repair. In the realm of pathologic response, there is evidence to suggest that this receptor is also involved in chronic inflammation. Furthermore, MRGPRX2 has been linked to the pathophysiology of non-IgE-mediated immediate hypersensitivity drug reactions. Different studies have shown its possible role in other allergic diseases as well, such as asthma, atopic dermatitis, contact dermatitis, and chronic spontaneous urticaria. In this review, we sought to cover its function in physiologic processes and responses, as well as in allergic and nonallergic immune disease.

In vitro prediction of in vivo pseudo-allergenic response via MRGPRX2

In development of peptide therapeutics, rodents are commonly-used preclinical models when screening compounds for efficacy endpoints in the early stages of discovery projects. During the screening process, some peptides administered subcutaneously to rodents caused injection site reactions manifesting as localized swelling. Screening by postmortem evaluations of injection site swelling as a marker for local subcutaneous histamine release, were conducted in rats to select drug candidates without this adverse effect. Histological analysis of skin samples revealed that the injection site reactions were concurrent with mast cell degranulation, resulting in histamine release. Mast cell activation can be mediated by MRGPRX2, a GPCR that induces a pseudo-allergenic immune response. The present study demonstrates that a commercially-available cell-based MRGPRX2 assay reliably identifies compounds that induce histamine release or localized edema in ex vivo human and rodent skin samples. In vitro screening was subsequently implemented using the MRGPRX2 assay as a substitute for postmortem injection site evaluation, thus achieving a significant reduction in animal use. Thus, in cases where injection site reactions are encountered during in vivo screening, to enable faster screening during the early drug discovery process, an MRGPRX2 in vitro assay can be used as an efficient, more ethical tool with human translational value for the development of safer pharmacotherapies for patients.