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(Circulation. 1999;99:2876-2882.)
© 1999 American Heart Association, Inc.

Clinical Investigation and Reports

Glycosylphosphatidylinositol-Specific Phospholipase D Is Expressed by Macrophages in Human Atherosclerosis and Colocalizes With Oxidation Epitopes

Kevin D. O'Brien, MD; Christine Pineda; Winnie S. Chiu, BS; Rosario Bowen, BS; Mark A. Deeg, MD, PhD

From the Division of Cardiology, Department of Medicine, University of Washington, Seattle (K.D.O., C.P., W.S.C.), and the Division of Endocrinology and Metabolism, Department of Medicine, Indiana University, and the Roudebush Veterans' Affairs Medical Center, Indianapolis, Ind (R.B., M.A.D.).

Correspondence to Kevin D. O'Brien, MD, Division of Cardiology, Box 356422, University of Washington, Seattle, WA 98195-6422. E-mail cardiac{at}u.washington.edu

Background—Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) may play an important role in inflammation, because it can hydrolyze the GPI anchors of several inflammatory membrane proteins (eg, CD106, CD55, and CD59) and its hydrolytic products upregulate macrophage cytokine expression (eg, interleukin-1 and tumor necrosis factor-). Because of its potential regulatory role in inflammatory reactions, we hypothesized that GPI-PLD might be expressed in atherosclerosis.

Methods and Results—Immunohistochemistry using human GPI-PLD–specific rabbit polyclonal antiserum was performed on a total of 83 nonatherosclerotic and atherosclerotic human coronary arteries from 23 patients. Macrophages, smooth muscle cells, apoA-I, and oxidation epitopes also were identified immunohistochemically. Cell-associated GPI-PLD was detected in 95% of atherosclerotic segments, primarily on a subset of macrophages. Extracellular GPI-PLD was present in only 30% of atherosclerotic segments and localized to regions with extracellular apoA-I. In contrast, GPI-PLD was not detected in nonatherosclerotic segments. Expression of GPI-PLD mRNA by human macrophages was confirmed in vitro by reverse transcription/polymerase chain reaction. Further studies demonstrated that GPI-PLD–positive plaque macrophages contained oxidation epitopes, suggesting a link between oxidant stress and GPI-PLD expression. This possibility was supported by studies in which exposure of a macrophage cell line to H₂O₂ led to a 50±3% increase in steady-state GPI-PLD mRNA levels.

Conclusions—Collectively, these results suggest that oxidative processes may regulate GPI-PLD expression and suggest a role for GPI-PLD in inflammation and in the pathogenesis of atherosclerosis.

Key Words: enzymes • proteins • cells • atherosclerosis

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