Novel mediator in anaphylaxis: decreased levels of miR-375-3p in serum and within extracellular vesicles of patients

Utility of biomarkers in the postmortem diagnosis of fatal Anaphylaxis: A scoping review

BACKGROUND

Diagnosing anaphylactic deaths is a challenging task for forensic pathologists. Although serum tryptase is considered to be a reliable biomarker, there are limitations to it. Thus, there is an urgent need to explore various other potential biomarkers which could be of diagnostic value, along with Tryptase, to diagnose anaphylactic shock at autopsy.

AIM

We want to systematically review the accuracy of newer postmortem biomarkers for anaphylaxis, such as chymase or eosinophilic cationic protein. Before embarking on this project, we intend to assess the feasibility of conducting systematic reviews on this topic. and identify any deficiencies in the existing literature to guide research priorities.

METHODOLOGY

We followed PRISMA guidelines and conducted the search in four databases, namely Medline, Scopus, EBSCO-CINAHL, and TRIP. Rayyan AI software was used to screen the articles.

RESULTS

A total of 6112 articles were retrieved from the search, and 5079 articles were screened after removing duplicates. Only 25 articles were finally available as per our inclusion criteria. Studies pertaining to post-mortem tryptase levels were found in large numbers, with two recently done systematic reviews on this topic. The number of studies available on other newer biomarkers was too few. More clinical studies are needed before a meta-analysis can be done. Hence, we could perform only a narrative review on the topic.

DISCUSSION

There is a scarcity of literature with definite cutoff levels for markers other than Tryptase. Based on the available studies, it is not possible to do diagnostic accuracy reviews at the moment. Hence, we narrate the usefulness of biomarkers like Immunoglobulin E, Chymase, Carboxypeptidase A3, Diamine Oxidase, Histamine and Eosinophilic Cationic Protein.

CONCLUSION

Based on the available evidence, serum tryptase is recognized as the primary biomarker for the postmortem diagnosis of anaphylactic death, with elevated levels strongly indicating anaphylaxis. Additionally, serum IgE, particularly allergen-specific IgE, is a valuable complementary biomarker. Further research is needed to understand the performance of other biomarkers.

Nur77 Mediates Anaphylaxis by Regulating miR-21a

Nur77 belongs to the NR4A subfamily of orphan nuclear hormone receptors. It has been shown to play important roles in metabolism, cancer progression, cellular differentiation, and the regulation of immune process. However, there has yet to be research reporting on the role of Nur77 in allergic inflammations such as anaphylaxis. This study aimed to identify molecules that could mediate allergic inflammations. To this end, we performed RNA sequencing analysis employing bone marrow-derived mast cells (BMMCs). Antigen (DNP-HSA) stimulation increased the expression levels of transcription factors such as Nr4a3 (NOR1), Nr4a1 (Nur77), and Nr4a2 (Nurr1). We focused our study on Nur77. Antigen stimulation increased the expression of Nur77 in a time- and dose-dependent manner in rat basophilic leukemia cells (RBL2H3). The downregulation of Nur77 prevented both antigen-induced increase in β-hexosaminidase activity as well as hallmarks of allergic reactions such as HDAC3, COX2, and MCP1 in RBL2H3 cells. Nur77 was necessary for both passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA). TargetScan analysis predicted that miR-21a would be a negative regulator of Nur77. miR-21a mimic negatively regulated PCA and PSA by inhibiting the hallmarks of allergic reactions. ChIP assays showed that c-JUN could bind to the promoter sequences of Nur77. Antigen stimulation increased the expression of c-JUN in RBL2H3 cells. Altogether, our findings demonstrate the regulatory role played by Nur77-miR-21a loop in allergic inflammations such as anaphylaxis, making this the first report to present the role played by Nur77 in an allergic inflammation. Our results suggest that Nur77 and miR-21 might serve as targets for developing anti-allergy drugs.

Circulating serum profile of small non-coding RNAs in patients with anaphylaxis beyond microRNAs

Introduction

Anaphylaxis is the most severe manifestation of allergic disorders. Currently, an increasing number of cells, pathways and molecules involved in the etiopathogenesis of anaphylaxis are being discovered. However, there are no conclusive biomarkers to confirm its diagnosis. Small non-coding RNAs (sncRNAs) are 18-200 nucleotide molecules that can be divided into: microRNAs (miRNAs), Piwi-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), small nuclear RNAs (snRNAs), transference RNA derived fragments (tRFs) and YRNA derived fragments (YRFs). These molecules participate in cell-cell communication modulating various physiological processes and have been postulated as non-invasive biomarkers of several pathologies. Therefore, in this study we characterized the serum circulating profile of other sncRNA beyond miRNAs in two populations of 5 adults and 5 children with drug- and food-mediated anaphylaxis, respectively.

Methods

Samples were obtained from each patient under two different conditions: during anaphylaxis and 14 days after the reaction (control). The sncRNA analysis was carried out by Next Generation Sequencing (NGS).

Results

A total of 671 sncRNAs (3 piRNAs, 74 snoRNAs, 54 snRNAs, 348 tRFs and 192 YRFs) were identified in adults with drug-induced anaphylaxis, while 612 sncRNAs (2 piRNAs, 73 snoRNAs, 52 snRNAs, 321 tRFs and 164 YRFs) were characterized in children with food-mediated anaphylaxis. However, only 33 (1 piRNA, 4 snoRNAs, 1 snRNAs, 7 tRFs and 20 YRFs) and 80 (4 snoRNAs, 6 snRNAs, 54 tRFs and 16 YRFs) of them were statistically different between both conditions, respectively. Among them, only three (Y_RNA.394, Y_RNA.781 and SCARNA2) were common to both adults and children analysis.

Discussion

This study provides a differential profile of circulating serum sncRNAs beyond miRNAs in patients with anaphylaxis, postulating them as candidate biomarkers for this pathological event and as novel mediators of the reaction.