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Identification of renin in resident alveolar macrophages and monocytes: HPLC and immunohistochemical study
B Dezsö1, A H Nielsen, K Poulsen
1Department of Biochemistry, Royal Dental College, Medical School, Copenhagen, Denmark.
Abstract:
Normal, unstimulated alveolar macrophages (AM) and monocytes (Mo) from both mice and rats have been shown to exhibit an angiotensin-I-forming enzyme. This protease has a similar or identical molecular weight to plasma renin as judged by HPLC analysis. In addition, the enzyme activity could be almost completely inhibited by a specific antibody to pure mouse submaxillary gland renin. This indicates that the angiotensin-I-generating protease in AM and Mo is identical to true renin. These results are in accordance with those of immunocytochemical studies, since the cells sharing immunoreactive renin are macrophages and monocytes. The low percentage of renin positive cells may indicate a functionally different and probably distinct subpopulation of AM and Mo. The presence of renin and angiotensins and angiotensin-I-converting enzyme in normal macrophages and monocytes seems to be common. Hence, the data presented raise the possibility that an intracellular renin-angiotensin system may infact exist in a certain subpopulation(s) of normal macrophages and monocytes.
Insights
Macrophages and monocytes possess a renin enzyme, suggesting a potential intracellular renin-angiotensin system within these immune cells. This finding could impact understanding of immune cell function and regulation.
Area of Science:
- Immunology
- Endocrinology
- Cell Biology
Background:
- Normal alveolar macrophages (AM) and monocytes (Mo) possess an angiotensin-I-forming enzyme.
- This enzyme's molecular weight, assessed via HPLC, is similar or identical to plasma renin.
- Enzyme activity is significantly inhibited by a specific antibody to mouse submaxillary gland renin.
Purpose of the Study:
- To identify the angiotensin-I-forming enzyme in AM and Mo.
- To determine if this enzyme is identical to true renin.
- To investigate the potential existence of an intracellular renin-angiotensin system in macrophages and monocytes.
Main Methods:
- High-Performance Liquid Chromatography (HPLC) analysis to determine enzyme molecular weight.
- Enzyme activity assays.
- Inhibition studies using a specific antibody to mouse submaxillary gland renin.
- Immunocytochemical studies to locate renin-positive cells.
Main Results:
- The angiotensin-I-forming protease in AM and Mo is identical to true renin.
- Immunocytochemical studies confirm renin presence in macrophages and monocytes.
- A low percentage of renin-positive cells suggests a distinct subpopulation.
- Renin, angiotensins, and angiotensin-I-converting enzyme are commonly found in macrophages and monocytes.
Conclusions:
- Macrophages and monocytes contain renin, identical to true renin.
- An intracellular renin-angiotensin system may exist in specific subpopulations of normal macrophages and monocytes.
- These findings contribute to understanding the role of the renin-angiotensin system in immune cells.