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PPAR Research
Volume 2007, Article ID 52546, 8 pages
http://dx.doi.org/10.1155/2007/52546
Research Article

Stimulatory Effects of Peroxisome Proliferator-Activated Receptor-γ on Fcγ Receptor-Mediated Phagocytosis by Alveolar Macrophages

1Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109, USA
2Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109, USA

Received 16 March 2007; Accepted 31 July 2007

Academic Editor: Jesse Roman

Copyright © 2007 David M. Aronoff et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Alveolar macrophages abundantly express PPAR-γ, with both natural and synthetic agonists maintaining the cell in a quiescent state hyporesponsive to antigen stimulation. Conversely, agonists upregulate expression and function of the cell-surface receptor CD36, which mediates phagocytosis of lipids, apoptotic neutrophils, and other unopsonized materials. These effects led us to investigate the actions of PPAR-γ agonists on the Fcγ receptor, which mediates phagocytosis of particles opsonized by binding of immunoglobulin G antibodies. We found that troglitazone, rosiglitazone, and 15-deoxy-Δ12,14-prostaglandin J2 increase the ability of alveolar, but not peritoneal, macrophages to carry out phagocytosis mediated by the Fcγ receptor. Receptor expression was not altered but activation of the downstream signaling proteins Syk, ERK-1, and ERK-2 was observed. Although it was previously known that PPAR-γ ligands stimulate phagocytosis of unopsonized materials, this is the first demonstration that they stimulate phagocytosis of opsonized materials as well.