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Atrial natriuretic peptide inhibits nitric oxide synthesis in mouse macrophages
1Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Germany.
Abstract:
The atrial natriuretic peptide (ANP) affects cardiovascular physiology, and, as has been suggested more recently, exerts immunomodulatory activities. In this context, we examined the effect of ANP on nitric oxide (NO) synthesis in murine bone marrow derived macrophages as well as in peritoneal macrophages. Cultured macrophages were stimulated with lipopolysaccharides (LPS 0.1-10 micrograms/ml) and NO synthesis was monitored by measuring increased concentrations of NO2 in the medium. In initial experiments employment of NG-monomethyl-L-arginine (L-NMMA) and dexamethasone, two specific inhibitors of nitric oxide synthase (NOS), confirmed the presence of inducible NOS activity in the cells. Exposure of cells to rat ANP99-126 in the range of 10(-8) to 10(-6) M significantly decreased LPS induced NO synthesis over 24 hours of incubation. Thus, ANP may alter macrophage function by affecting their nitric oxide synthesizing pathway.
Insights
Atrial natriuretic peptide (ANP) reduces nitric oxide (NO) production in macrophages. This finding suggests ANP influences immune responses by modulating macrophage NO synthesis pathways.
Area of Science:
- Immunology
- Cardiovascular Physiology
- Molecular Biology
Background:
- Atrial natriuretic peptide (ANP) is known for its cardiovascular effects.
- Emerging evidence suggests ANP also possesses immunomodulatory activities.
- Macrophages play a crucial role in immune responses, partly through nitric oxide (NO) production.
Purpose of the Study:
- To investigate the effect of ANP on nitric oxide (NO) synthesis in macrophages.
- To determine if ANP modulates the activity of inducible nitric oxide synthase (iNOS) in macrophages.
Main Methods:
- Murine bone marrow-derived and peritoneal macrophages were cultured.
- Macrophages were stimulated with lipopolysaccharides (LPS).
- Nitric oxide (NO) synthesis was measured by quantifying nitrite (NO2) concentrations.
- Inhibitors of nitric oxide synthase (NOS), L-NMMA and dexamethasone, were used to confirm iNOS activity.
Main Results:
- Lipopolysaccharide (LPS) stimulation significantly increased NO synthesis in macrophages.
- Exposure to rat ANP99-126 (10^-8 to 10^-6 M) significantly decreased LPS-induced NO synthesis.
- The inhibitory effect of ANP on NO synthesis was observed over a 24-hour incubation period.
Conclusions:
- Atrial natriuretic peptide (ANP) inhibits nitric oxide (NO) production in macrophages.
- ANP may modulate macrophage function by influencing the nitric oxide synthesizing pathway.
- These findings highlight a potential role for ANP in regulating immune cell activity.