Nur77 Mediates Anaphylaxis by Regulating miR-21a.

Area of Science:

• Immunology
• Molecular Biology
• Endocrinology

Background:

• Nur77 (NR4A1) is an orphan nuclear receptor involved in various cellular processes.
• Its role in allergic inflammation, particularly anaphylaxis, remains unexplored.
• Understanding mediators of allergic reactions is crucial for therapeutic development.

Purpose of the Study:

• To investigate the role of Nur77 in allergic inflammation, focusing on anaphylaxis.
• To identify molecular mechanisms and potential therapeutic targets for allergic diseases.

Main Methods:

• RNA sequencing on bone marrow-derived mast cells (BMMCs).
• Stimulation of rat basophilic leukemia cells (RBL2H3) with antigen (DNP-HSA).
• Analysis of Nur77 expression, β-hexosaminidase activity, and allergic markers (HDAC3, COX2, MCP1).
• Assessment of passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA) models.
• TargetScan analysis and miR-21a mimic experiments.
• Chromatin immunoprecipitation (ChIP) assays for c-JUN binding.

Main Results:

• Antigen stimulation upregulated Nur77 expression in a time- and dose-dependent manner.
• Nur77 downregulation inhibited anaphylaxis hallmarks and β-hexosaminidase release.
• Nur77 was essential for both PCA and PSA.
• A Nur77-miR-21a regulatory loop was identified, with miR-21a acting as a negative regulator.
• c-JUN was found to bind the Nur77 promoter, with its expression increasing upon antigen stimulation.

Conclusions:

• Nur77 plays a critical regulatory role in anaphylaxis.
• The Nur77-miR-21a feedback loop is implicated in allergic inflammation.
• Nur77 and miR-21 represent potential therapeutic targets for anti-allergy drug development.