MRGPRX2, drug pseudoallergies, inflammatory diseases, mechanisms and distinguishing MRGPRX2- and IgE/FcεRI-mediated events

Sugammadex hypersensitivity: a multicentre retrospective analysis of a large Australian cohort

BACKGROUND

Sugammadex hypersensitivity is an emerging safety concern. We aimed to describe the clinical and diagnostic features of perioperative hypersensitivity to sugammadex, and secondarily to provide an estimate of perioperative sugammadex hypersensitivity incidence in Australia.

METHODS

We retrospectively analysed cases of hypersensitivity to sugammadex diagnosed by positive intradermal or skin prick testing at six perioperative allergy clinics in Australia. We included all grades of hypersensitivity and compared life-threatening with non-life-threatening presentations. Incidence of hypersensitivity events was estimated relative to the estimated number of sugammadex administrations across two health services between January 1, 2010 and June 30, 2023.

RESULTS

Thirty cases were included (15 life-threatening and 15 non-life-threatening). The most common clinical signs were hypotension (n=25, 83.3%) and flushing/erythema (n=21, 70%). The median time to recognition of hypersensitivity was 5 (interquartile range 2-7.5) min. Five cases were recognised 10-30 min after administration. Serum tryptase was measured in 28 (93.3%) patients. Tryptase was positive in 15 (100%) life-threatening cases and nine (69.2%) non-life-threatening cases. The estimated incidence of sugammadex hypersensitivity was 0.004% (95% confidence interval 0.002-0.008%).

CONCLUSIONS

Sugammadex hypersensitivity presents similarly to other causes of perioperative hypersensitivity, however recognition can be delayed. The combination of positive serum tryptase and positive skin tests suggests an IgE-mediated mechanism of hypersensitivity. The estimated incidence of sugammadex hypersensitivity in Australia is lower than earlier reports.

A Skin Testing Strategy for Non-IgE-Mediated Reactions Associated With Vancomycin

BACKGROUND

Vancomycin infusion reaction (VIR), reportedly mediated through Mas-Related G Protein-Coupled Receptor-X2, is the primary vancomycin-induced immediate drug reaction. Clinically, distinguishing the underlying drug-induced immediate drug reaction mechanisms is crucial for future treatment strategies, including drug restriction, re-administration, and pretreatment considerations. However, the lack of validated diagnostic tests makes this challenging, often leading to unnecessary drug restriction.

OBJECTIVE

To determine whether intradermal tests (IDTs) and, separately, the basophil activation test (BAT) differentiate VIR from vancomycin-tolerant subjects.

METHODS

This was a cross-sectional study of vancomycin-exposed adults with and without a history of VIR. Data on demographics, allergy-related comorbidities, history of vancomycin exposures, and VIR characteristics were collected. IDT with vancomycin was performed. IDT dose-response EC50, IDT-related local symptoms, and BAT results were compared between groups.

RESULTS

A total of 11 VIR and 10 vancomycin-tolerant subjects were enrolled. The most reported VIR symptoms were pruritus (82%), flushing (82%), hives (46%), angioedema (27%), and dyspnea (19%). The IDT dose-response mean EC50 was 328 μg/mL (95% CI, 296-367) in the VIR versus 1166 μg/mL (95% CI, 1029-1379) in the tolerant group (P < .0001). All VIR subjects reported IDT-related local pruritus compared with 60% of tolerant subjects (P = .0185). The %CD63+ basophils were consistently less than 2%, without significant differences between groups (P < .54).

CONCLUSIONS

Variations in skin test methodologies could help identify other immediate drug reaction mechanisms beyond IgE. This skin test protocol holds the potential for identifying VIR, particularly in cases where patients have received multiple drugs while BAT is insufficient. Future studies will validate and delineate its predictive value, assessing the risk of VIR.

Based on UHPLC-Q-TOF-MS and bioinformatics strategies, the potential allergens and mechanisms of allergic reactions caused by Danshen injection were explored

The aim is to investigate the potential allergens and mechanisms underlying allergic-like reactions induced by Danshen injection (DSI). Utilizing ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS), metabolomics, and bioinformatics, we identified the key allergens, targets, and metabolic pathways involved in DSI-induced allergic-like reactions, validating binding efficiency through molecular docking and molecular dynamics. A total of 45 compounds were identified within DSI, with 24 compounds exhibiting strong binding activity to the MrgprX2 activation site. DSI was found to cause changes in 89 endogenous metabolites, including arachidonic acid, prostaglandins, and leukotrienes, primarily affecting pathways such as phenylalanine metabolism and arachidonic acid metabolism. The key allergens identified were Cryptotanshinone, Miltipolone, Neocryptotanshinone, Salvianolic acid B, and Isosalvianolic acid C, which primarily trigger allergic-like reactions by regulating upstream signaling targets such as ALOX5, PTGS1, PPARD, and LTB4R. Validation confirmed the high binding affinity and stability between key allergens and targets. These findings indicate that the allergic components in DSI primarily induce allergic-like reactions by modulating the aforementioned signaling targets, activating the AA metabolic pathway, promoting mast cell degranulation, and releasing downstream endogenous inflammatory mediators, subsequently eliciting allergic-like reactions.

Mouse Models of Itch

Murine models are vital preclinical and biological tools for studying itch. In this paper, we explore how these models have enhanced our understanding of the mechanisms underlying itch through both acute and chronic itch models. We provide detailed protocols and recommend experimental setups for specific models to guide researchers in conducting itch research. We distinguish between what constitutes a bona fide pruritogen versus a stimulus that causes pruritogen release, an acute itch model versus a chronic itch model, and how murine models can capture aspects of pruritus in human disease. Finally, we highlight how mouse models of itch have transformed our understanding and development of therapeutics for chronic pruritus in patients.

Mast cell stabilizers: from pathogenic roles to targeting therapies

Mast cells (MCs) are bone-marrow-derived haematopoietic cells that are widely distributed in human tissues. When activated, they will release tryptase, histamine and other mediators that play major roles in a diverse array of diseases/disorders, including allergies, inflammation, cardiovascular diseases, autoimmune diseases, cancers and even death. The multiple pathological effects of MCs have made their stabilizers a research hotspot for the treatment of related diseases. To date, the clinically available MC stabilizers are limited. Considering the rapidly increasing incidence rate and widespread prevalence of MC-related diseases, a comprehensive reference is needed for the clinicians or researchers to identify and choose efficacious MC stabilizers. This review analyzes the mechanism of MC activation, and summarizes the progress made so far in the development of MC stabilizers. MC stabilizers are classified by the action mechanism here, including acting on cell surface receptors, disturbing signal transduction pathways and interfering exocytosis systems. Particular emphasis is placed on the clinical applications and the future development direction of MC stabilizers.

Targeting dendritic cell activation: the therapeutic impact of paeoniflorin in cortosteroid-dependent dermatitis management

This study investigates the mechanism through which paeoniflorin inhibits TSLP expression to regulate dendritic cell activation in corticosteroid-dependent dermatitis treatment. Utilizing databases like TCMSP, we identified paeoniflorin's components, targets, and constructed networks. Molecular docking and gene enrichment analysis helped pinpoint key targets and pathways affected by paeoniflorin. In vitro and in vivo models were used to study CD80, CD86, cytokines, T-cell activation, skin lesions, histopathological changes, TSLP, CD80, and CD86 expression. Our study revealed paeoniflorin's active constituent targeting IL-6 in corticosteroid-dependent dermatitis. In vitro experiments demonstrated reduced TSLP expression, CD80, CD86, and cytokine secretion post-paeoniflorin treatment. In vivo, paeoniflorin significantly decreased skin lesion severity, cytokine levels, TSLP, CD80, and CD86 expression. The study highlights paeoniflorin's efficacy in inhibiting TSLP expression and suppressing dendritic cell activation in corticosteroid-dependent dermatitis, suggesting its potential as a therapeutic intervention. Additionally, it offers insights into the complex molecular mechanisms underlying paeoniflorin's anti-inflammatory properties in treating corticosteroid-dependent dermatitis.

Non-IgE-Mediated Immediate Drug-Induced Hypersensitivity Reactions

Immediate drug-induced hypersensitivity reactions (IDHSRs) have conventionally been attributed to an immunoglobulin E (IgE)-mediated mechanism. Nevertheless, it has now been acknowledged that IDHSRs can also occur independently of IgE involvement. Non-IgE-mediated IDHSRs encompass the activation of effector cells, both mast cell-dependent and -independent and the initiation of inflammatory pathways through immunogenic and nonimmunogenic mechanisms. The IDHSRs involve inflammatory mediators beyond histamine, including the platelet-activating factor, which activates multiple cell types, including smooth muscle, endothelium, and MC, and evidence supports its importance in IgE-mediated reactions in humans. Clinically, distinguishing IgE from non-IgE mechanisms is crucial for future treatment strategies, including drug(s) restriction, readministration approaches, and pretreatment considerations. However, this presents significant challenges because certain drugs can trigger both mechanisms, and their presentations can appear similarly, ranging from mild to life-threatening symptoms. Thus, history alone is often inadequate for differentiation, and skin tests lack a standardized approach. Moreover, drug-specific IgE immunoassays have favorable specificity but low sensitivity, and the usefulness of the basophil activation test remains debatable. Lastly, no biomarker reliably differentiates between both mechanisms. Whereas non-IgE-mediated mechanisms likely predominate in IDHSRs, reclassifying most drug-related IDHSRs as non-IgE-mediated, with suggested prevention through dose administration adjustments, is premature and risky. Therefore, continued research and validated diagnostic tests are crucial to improving our capacity to distinguish between these mechanisms, ultimately enhancing patient care.