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Isolation of Atrial Myocytes from Adult Mice
Published on: July 25, 2019
Gene expression and secretion of atrial natriuretic peptide by murine macrophages
1Institute of Pharmacology, Toxicology and Pharmacy, University of Munich, Germany.
Abstract:
An increased expression of atrial natriuretic peptide (ANP) has been reported in activated macrophages of the acutely involuted rat thymus. We communicate here that ANP may reflect a common constituent of macrophages, as mRNA coding for ANP is present in peritoneal- as well as in bone marrow-derived macrophages (PM, BMM). Furthermore, both types of macrophages synthesize and release ANP which was found to mainly represent the biologically active fragment ANP99-126. ANP expression in macrophages is regulated by compounds affecting the activity of these immune cells. For example, incubation of PM or BMM in vitro with LPS and zymosan, respectively, increased ANP-mRNA up to sixfold as determined by competitive PCR quantification. Exposure of macrophages to dexamethasone (Dex, 10(-7) M) elicits moderate effects (1.4-fold), while PMA (10(-7) M) failed to affect its abundance. These findings are complemented by data regarding ANP synthesis and secretion. Incubation of macrophages with LPS, Dex or a combination of both results in an up to 3.5-fold increase of intracellular ANP99-126 (basal 10 fmol/mg protein), and an up to 6.6-fold increase of its secretion (basal 40 fmol/mg protein, 24 h). Since macrophages synthesize and release ANP, the peptide may be involved in the complex mechanisms of host defense, a major function of these immune cells.
Insights
Atrial natriuretic peptide (ANP) is produced by macrophages, key immune cells. Macrophage activation by substances like LPS increases ANP production, suggesting a role for ANP in host defense mechanisms.
Area of Science:
- Immunology
- Endocrinology
- Molecular Biology
Background:
- Atrial natriuretic peptide (ANP) expression is noted in activated macrophages within the involuted rat thymus.
- Macrophages are crucial immune cells involved in host defense.
Purpose of the Study:
- To investigate the presence and synthesis of ANP in different macrophage populations.
- To determine the regulation of ANP expression and release by immune-stimulating agents.
Main Methods:
- Competitive PCR was used to quantify ANP mRNA levels in peritoneal (PM) and bone marrow-derived macrophages (BMM).
- Macrophage cultures were treated with lipopolysaccharide (LPS), zymosan, dexamethasone (Dex), and phorbol 12-myristate 13-acetate (PMA).
- Intracellular and secreted levels of the active ANP fragment (ANP99-126) were measured.
Main Results:
- ANP mRNA was detected in both PM and BMM, indicating ANP is a common macrophage constituent.
- LPS and zymosan significantly increased ANP mRNA levels (up to sixfold).
- Dexamethasone showed moderate effects, while PMA had no significant impact on ANP mRNA abundance. Both LPS and Dex increased intracellular and secreted ANP99-126.
Conclusions:
- Macrophages synthesize and release biologically active ANP (ANP99-126).
- ANP expression in macrophages is modulated by immune cell activators.
- ANP may play a role in the intricate mechanisms of host defense executed by macrophages.
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