Histamine receptor 2 modifies dendritic cell responses to microbial ligands

Area of Science:

• Immunology
• Microbiology
• Metabolomics

Background:

• Host and microbiota metabolites, like histamine, critically influence immune tolerance and protection against microbes.
• Understanding the role of histamine in modulating immune cell signaling is crucial for developing targeted immunotherapies.

Purpose of the Study:

• To elucidate the molecular mechanisms by which histamine affects pattern recognition receptor signaling.
• To investigate the impact of histamine on dendritic cell function and cytokine production.

Main Methods:

• Examined human monocyte-derived dendritic cells (MDDCs), myeloid dendritic cells, and plasmacytoid dendritic cells.
• Measured cytokine secretion, gene expression, and transcription factor activation following stimulation with microbial ligands and histamine.
• Utilized histamine receptor 2 (H₂R)-deficient mice to investigate receptor-specific signaling pathways.

Main Results:

• Histamine suppressed MDDC pro-inflammatory cytokine and chemokine secretion, NF-κB/AP-1 activation, and MAPK phosphorylation, while enhancing IL-10 secretion.
• Histamine inhibited TNF-α secretion in myeloid dendritic cells and IFN-α gene expression in plasmacytoid dendritic cells.
• H₂R signaling via cyclic AMP was essential for histamine's effects on MDDC responses to LPS; Lactobacillus rhamnosus-secreted histamine also demonstrated H₂R-dependent immune modulation.

Conclusions:

• Host- and microbiota-derived histamine significantly alter innate immune responses to microbes.
• The histamine receptor 2 (H₂R) is a key mediator of histamine's immunomodulatory effects.