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J. Biol. Chem., Vol. 282, Issue 15, 11009-11020, April 13, 2007

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Polyamine-mediated Apoptosis of Alveolar Macrophages during Pneumocystis Pneumonia^*

Mark E. Lasbury¹, Salim Merali, Pamela J. Durant, Dennis Tschang, Chad A. Ray^¶, and Chao-Hung Lee

From the Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, the Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, and the ^¶Department of Pharmacokinetics and Drug Metabolism, Amgen, Thousand Oaks, California 91320

The number of alveolar macrophages is decreased during Pneumocystis pneumonia (Pcp), partly because of activation of apoptosis in these cells. This apoptosis occurs in both rat and mouse models of Pcp. Bronchoalveolar lavage (BAL) fluids from Pneumocystis-infected animals were found to contain high levels of polyamines, including spermidine, N¹-acetylspermine, and N¹-acetylspermidine. These BAL fluids and exogenous polyamines were able to induce apoptosis in alveolar macrophages. Apoptosis of alveolar macrophages during infection, after incubation with BAL fluids from Pneumocystis-infected animals, or after incubation with polyamines was marked by an increase in intracellular reactive oxygen species, activation of caspases-3 and -9, DNA fragmentation, and leakage of mitochondrial cytochrome c into the cytoplasm. When polyamines were depleted from the BAL fluids of infected animals, the ability of these BAL fluids to induce apoptosis was lost. Interestingly, the apoptosis inducing activity of the polyamine-depleted BAL fluids was restored when polyamines were added back. The results of this study suggested that Pneumocystis infection results in accumulation of high levels of polyamines in the lung. These polyamines activate apoptosis of alveolar macrophages, perhaps because of the ROS that are produced during polyamine metabolism.

Received for publication, December 21, 2006 , and in revised form, January 30, 2007.

^* This work was supported in part by National Institutes of Health Grants RO1 HL65170 and RO1 AI062259. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Pathology and Laboratory Medicine, Indiana University School of Medicine, 1120 South Dr., Fesler Hall, Rm. 406, Indianapolis, IN 46202-5113. Tel.: 317-274-4606; Fax: 317-278-0643; E-mail: melasbur{at}iupui.edu.

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