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The Discovery of a Novel Macrophage Binding Site

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Summary

1. During the course of studies directed to determine the transport of Angiotensin II AT2 receptors in the rat brain, we found that stab wounds to the brain revealed a binding site recognized by the AT2 receptor ligand CGP42112 but not by Angiotensin II.

2. We localized this novel site to macrophages/microglia associated with physical or chemical injuries of the brain.

3. The non-Angiotensin II site was also highly localized to inflammatory lesions of peripheral arteries.

4. In rodent tissues, high binding expression was limited to the spleen and to circulating monocytes. A high-affinity binding site was also characterized in human monocytes.

5. Lack of affinity for many ligands binding to known macrophage receptors indicated the possibility that the non-Angiotensin II CGP42112 binding corresponds to a novel site.

6. CGP42112 enhanced cell attachment to fibronectin and collagen and metalloproteinase-9 secretion from human monocytes incubated in serum-free medium but did not promote cytokine secretion.

7. When added in the presence of lipopolysaccharide, CGP42112 reduced the lipopolysaccharide-stimulated secretion of the pro-inflammatory cytokines TNF-α, IL-1, IL-1 ß, and IL-6, and increased protein kinase A.

8. Molecular modeling revealed that a CGP42112 derivative was selective for the novel macrophage site and did not recognize the Angiotensin II AT2 receptor.

9. These results demonstrate that CGP42112, previously considered as a selective Angiotensin II AT2 ligand, recognizes an additional non-Angiotensin II site different from AT2 receptors.

10. Our observations indicate that CGP42112 or related molecules could be considered of interest as potential anti-inflammatory compounds.

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Acknowledgment

This study is supported by the Division of Intramural Research Programs, National Institute of Mental Health, NIH, DHHS.

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Authors and Affiliations

  1. Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, USA

    Juan M. Saavedra & Jaroslav Pavel

  2. Section on Pharmacology, DIRP, NIMH, NIH, DHHS, 10 Center Drive, Bldg. 10, Room 2D-57, Bethesda, MD, 20892, USA

    Juan M. Saavedra

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  1. Juan M. Saavedra
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Correspondence to Juan M. Saavedra.

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Saavedra, J.M., Pavel, J. The Discovery of a Novel Macrophage Binding Site. Cell Mol Neurobiol 26, 507–524 (2006). https://doi.org/10.1007/s10571-006-9044-x

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  • DOI: https://doi.org/10.1007/s10571-006-9044-x

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