Immunological Mechanisms of Drug Hypersensitivity

The role of corticosterone in nevirapine-induced idiosyncratic drug-induced liver injury

Nevirapine, an antiretroviral used in the treatment of HIV, is associated with idiosyncratic drug-induced liver injury (IDILI), a potentially life-threatening adverse drug reaction. Its usage has decreased due to this concern, but it is still widely used in lower-resource settings. In general, the mechanisms underlying idiosyncratic drug reactions (IDRs) are poorly understood, but evidence indicates that most are immune-mediated. There is very limited understanding of the early immune response following administration of drugs associated with IDRs, which likely occurs due to reactive metabolite formation. In this work, we aimed to characterize the links between covalent binding of nevirapine, the development of an early immune response, and the subsequent liver injury using a mouse model. We describe initial attempts to characterize an early immune response to nevirapine followed by the discovery that nevirapine induced the release of corticosterone. Corticosterone release was partially associated with the degree of drug covalent binding in the liver but was also likely mediated by additional mechanisms at higher drug doses. Transcriptomic analysis confirmed metabolic activation, glucocorticoid signaling, and decreased immune activation; GDF-15 also warrants further investigation as part of the immune response to nevirapine. Finally, glucocorticoid blockade preceding the first dose of nevirapine attenuated nevirapine-induced liver injury at 3 weeks, suggesting that acute glucocorticoid signaling is harmful in the context of nevirapine-induced liver injury. This work demonstrates that nevirapine induces acute corticosterone release, which contributes to delayed-onset liver injury. It also has implications for screening drug candidates for IDILI risk and preventing nevirapine-induced IDILI.

Characterization of amoxicillin and clavulanic acid specific T-cell clones from patients with immediate drug hypersensitivity

BACKGROUND

Betalactam (BL) antibiotics are the most common cause of drug hypersensitivity. Amoxicillin (AX), which is often prescribed alongside clavulanic acid (Clav), is the most common elicitor. The aim of this study was to determine whether AX and Clav-responsive T-cells are detectable in patients with immediate hypersensitivity to AX-Clav, to assess whether these T-cells display the same specificity as that detected in skin and provocation testing, and to explore T-cell activation pathways.

METHODS

Drug-specific T-cell clones were generated from immediate hypersensitive patients´ blood by serial dilution and repetitive mitogen stimulation. Antigen specificity was assessed by measurement of proliferation and cytokine release. CD4+ /CD8+ phenotype and chemokine receptor expression were analyzed by flow cytometry.

RESULTS

110 AX-specific and 96 Clav-specific T-cell clones were generated from seven patients with positive skin test to either AX or Clav. Proliferation of AX- and Clav-specific clones was dose-dependent, and no cross-reactivity was observed. AX- and Clav-specific clones required antigen-presenting cells to proliferate, and drugs were presented to CD4+ and CD8+ T-cells by MHC class-II and I, respectively. A higher secretion of IL-13 and IL-5 was detected in presence of the culprit drug compared with the alternative drug. Clones expressed CD69, CCR4, CXCR3, and CCR10.

CONCLUSIONS

Our study details the antigen specificity and phenotype of T-cell clones generated from patients with AX-Clav-induced immediate hypersensitivity diagnosed by positive skin test. AX- and Clav-specific clones were generated from patients irrespective of whether AX or Clav was the culprit, although differences in cytokine secretion were observed.

Dextromethorphan - A widely-used cough suppressant - Induces local anaphylaxis via MRGPRX2 on mast cells

Dextromethorphan (DM) is a cough suppressant available in many prescribed and over-the-counter medications. Adverse reactions induced by DM have been regularly reported, including allergic skin reactions in some cases. However, the underlying mechanisms of local anaphylaxis induced by DM have not been elucidated. In this study, we found that DM could activate mast cells to increase calcium mobilization and release β-hexosaminidase, histamine, tumor necrosis factor-α, MCP-1, and IL-8 in a dose-dependent manner. The allergic reactions were confirmed by hind paw swelling and extravasation assay in vivo. Furthermore, DM was revealed to induce local anaphylaxis via MRGPRX2 by the mast cell-deficient kit^W-sh/W-sh mice and MRGPRX2 knockdown mast cells. And the MRGPRX2-HEK293/CMC analysis and frontal analysis also showed that DM has a considerable affinity with MRGPRX2. Together, our findings suggest that close monitoring should be drawn on patients with DM for its potential anaphylaxis via MRGPRX2.

Sodium aescinate and its bioactive components induce degranulation via oxidative stress in RBL-2H3 mast cells

Sodium aescinate (SA) is a vital salt of sodium escin from Aesculus wilsonii Rehd seeds. SA injection (SAI) has received great success in treating cerebral edema, venous reflux disease and other inflammatory conditions. Recently, high incidences of immediate hypersensitivity reactions were reported after SA infusion, which raised questions on safety and risk associated with its clinical application. This study was designed to check whether SAI and its four components induce degranulation using RBL-2H3 mast cells. For this purpose, we evaluated different treatment levels of SAI (20, 40, 60, 80 and 100 μg ml^-1) and its four characteristic components, SA-A, SA-B, SA-C and SA-D, at 60 μg ml^-1 in different tests including cell viability test, β-hexosaminidase and histamine assays, oxidative stress indices, apoptosis analysis and intracellular calcium ions in RBL-2H3 cells. Our results demonstrated that SAI at 80 μg ml^-1 and 100 μg ml^-1, and its two components (SA-B and SA-D) at 60 μg ml^-1 were responsible for disturbing cell morphology and cell viability, elevated levels of β-hexosaminidase, histamine, modulation of oxidative stress indices, induced apoptosis and increase in intracellular calcium ions in RBL-2H3 cells, when compared with the control. Our results demonstrated for the first time that SAI was more likely to induce immediate hypersensitivity reactions attributable to degranulation via oxidative stress caused by SA-B and SA-D components. These results would not only be useful for the safety of end user but also for the industry to improve the quality of SA infusion.

Anti-pseudo-allergic capacity of alkaloids screened from Uncaria rhynchophylla

Two alkaloids were screened from Uncaria rhynchophylla (UR) by MRGPRX2-HEK293/CMC model and showed anti-pseudo-allergic effects in vivo and in vitro, which may provide evidence for anti-pseudo-allergic effects and bioactivity development of UR.

Phenothiazine antipsychotics exhibit dual properties in pseudo-allergic reactions: Activating MRGPRX2 and inhibiting the H1 receptor

Phenothiazines are a class of antipsychotics that share the same tricyclic structure and are widely used in clinical settings. Adverse reactions from these drugs, however, have been regularly reported, with allergic skin reactions noted in some cases. Nevertheless, the mechanisms underlying anaphylaxis by these drugs have not been described. In the present study, we found that phenothiazine antipsychotics increased calcium mobilization and activated mast cells to release β-hexosaminidase, histamine, and tumor necrosis factor-α via Mas-related G-protein-coupled receptor member X2 (MRGPRX2) in vitro. In addition, they induced histamine release in serum via Mrgprb2 in C57BL/6 mice without Evans blue extravasation or paw swell. Further experiments indicated these drugs had good interaction with the histamine H₁ receptor (H1R) and show an anti-calcium mobilization effect on H₁R-HEK293 cells, which confirmed a potential antagonist effect of these drugs on the H₁R. The molecular docking and activity experiments indicated that the N-methyl substitution on the side chain of these drugs played a significant role in activating MRGPRX2, while the phenothiazine tricyclic ring was associated with the inhibiting effect on the H₁R. Therefore, due to their dual properties of increasing histamine levels without obvious allergic symptoms, clinicians should be highly vigilant for damage from histamine accumulation and long-term inflammatory reactions during the clinical use of phenothiazine antipsychotics.

Relationship between MRGPRX2 and pethidine hydrochloride- or fentanyl citrate-induced LAD2 cell degranulation

OBJECTIVES

Pethidine hydrochloride (PH) and fentanyl citrate (FC) are opioid receptor agonists commonly used to treat pain clinically. PH and FC have been reported to have a high potential for pseudoallergic effects, but the underlying mechanism has not been well studied. MRGPRX2 is a novel atypical opioid receptor that is mainly expressed in human mast cells and considered to mediate drug-induced pseudoallergic reactions. This study aimed to investigate the allergy effect of these two opioid receptor agonists and the possible association of MRGPRX2 with this response.

METHODS

HEK293-MRGPRX2/CMC assay, molecular docking assay, calcium mobilization assay, the test of β-hexosaminidase, histamine and cytokine release assay were performed in this article.

KEY FINDINGS

PH but not FC induced LAD2 cell activation and degranulation dose-dependently. Histamine, tumour necrosis factor (TNF)-α, interleukin (IL)-8, monocyte chemotactic protein 1 (MCP-1) and macrophage inflammatory protein (MIP-1β) levels were upregulated by PH, but not FC. The PH-induced activation of mast cell was MRGPRX2-dependent.

CONCLUSIONS

PH but not FC activated mast cells, leading to degranulation mediated via MRGPRX2 receptors, which could be greatly significant in future clinical applications of opioid receptor drugs.