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(Circulation Research. 2007;101:792.)
© 2007 American Heart Association, Inc.

Molecular Medicine

Oxidized Phospholipids Induce Phenotypic Switching of Vascular Smooth Muscle Cells In Vivo and In Vitro

Nataliya A. Pidkovka, Olga A. Cherepanova, Tadashi Yoshida, Matthew R. Alexander, Rebecca A. Deaton, James A. Thomas, Norbert Leitinger, Gary K. Owens

From the Department of Molecular Physiology and Biophysics, Cardiovascular Research Center, University of Virginia, Charlottesville.

Correspondence to Dr Gary K. Owens, University of Virginia, Cardiovascular Research Center, 415 Lane Road, MR5 RM 1328, Charlottesville, VA 22908. E-mail gko{at}virginia.edu

Atherosclerosis is a vascular disease characterized by lipid deposition and inflammation within the arterial wall. Oxidized phospholipids (oxPLs), such as 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (oxPAPC) and its constituents 1-palmytoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) are concentrated within atherosclerotic lesions and are known to be potent proinflammatory mediators. Phenotypic switching of smooth muscle cells (SMCs) plays a critical role in the development, progression, and end-stage clinical consequences of atherosclerosis, yet little is known regarding the effects of specific oxPLs on SMC phenotype. The present studies were focused on determining whether oxPLs regulate expression of SMC differentiation marker genes and the molecular mechanisms involved. Results showed that POVPC and PGPC induced profound suppression of smooth muscle (SM) -actin and SM myosin heavy chain expression while simultaneously increasing expression of MCP-1, MCP-3, and cytolysin. OxPLs also induced nuclear translocation of Krüppel-like transcription factor 4 (KLF4), a known repressor of SMC marker genes. siRNA targeting of KLF4 nearly blocked POVPC-induced suppression of SMC marker genes, and myocardin. POVPC-induced repression of SMC marker genes was also significantly attenuated in KLF4 knockout SMCs. Taken together, these results suggest a novel role for oxPLs in phenotypic modulation of SMCs and indicate that these effects are dependent on the transcription factor, KLF4. These results may have important novel implications for the mechanisms by which oxPLs contribute to the pathogenesis of atherosclerosis.

Key Words: atherosclerosis • smooth muscle cell phenotypic switching • oxidized phospholipids

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