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Regulation of interleukin-1 synthesis by histamine produced by mouse peritoneal macrophages per se
Abstract:
The response of mouse peritoneal macrophages to Escherichia coli lipopolysaccharide (LPS) resulted in induction of histidine decarboxylase (HDC) and, consequently, of histamine production. Concanavalin A had no effect on the reactions. Alpha-fluoromethylhistidine, a suicide inhibitor of HDC, attenuated, in a dose-dependent manner, both spontaneous and LPS-stimulated IL-1 synthesis by macrophages. IL-1 production was significantly blocked by either an H1 anti-histamine, diphenhydramine, or H2 anti-histamine ranitidine, in the absence of any exogenous histamine. Addition of exogenous histamine accentuated the IL-1 production by macrophages as a function of its dose. These results suggest that IL-1 production by mouse peritoneal macrophages is regulated by histamine synthesized in the system per se and that the effect of histamine is dependent on both H1 and H2 histamine receptors located on the surface of the cells.
Insights
Mouse macrophages produce histamine, which regulates their own production of Interleukin-1 (IL-1). This histamine-mediated IL-1 synthesis involves both H1 and H2 histamine receptors.
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- Macrophages are key immune cells involved in inflammatory responses.
- Interleukin-1 (IL-1) is a critical cytokine in regulating immune and inflammatory processes.
- Histamine is a biogenic amine known for its role in allergic reactions and neurotransmission.
Purpose of the Study:
- To investigate the role of endogenously produced histamine in regulating IL-1 synthesis by mouse peritoneal macrophages.
- To determine the involvement of histidine decarboxylase (HDC) and histamine receptors in macrophage-derived IL-1 production.
Main Methods:
- Stimulation of mouse peritoneal macrophages with Escherichia coli lipopolysaccharide (LPS).
- Assessment of histidine decarboxylase (HDC) activity and histamine production.
- Inhibition of HDC with alpha-fluoromethylhistidine and blockade of histamine receptors with diphenhydramine (H1 antagonist) and ranitidine (H2 antagonist).
- Quantification of IL-1 synthesis under various experimental conditions.
Main Results:
- LPS stimulation induced HDC and histamine production in macrophages.
- HDC inhibition dose-dependently reduced spontaneous and LPS-stimulated IL-1 synthesis.
- Both H1 and H2 histamine receptor antagonists blocked IL-1 production, even without added histamine.
- Exogenous histamine addition dose-dependently enhanced IL-1 production.
Conclusions:
- Histamine synthesized intrinsically by macrophages plays a regulatory role in IL-1 production.
- The effects of endogenous histamine on IL-1 synthesis are mediated through both H1 and H2 histamine receptors on the macrophage surface.
- This suggests an autocrine/paracrine mechanism where macrophage-derived histamine modulates their own inflammatory cytokine output.