Oxidized Alkyl Phospholipids Are Specific, High Affinity Peroxisome Proliferator-activated Receptor γ Ligands and Agonists

• Published in: The Journal of biological chemistry 2001-05, Vol.276 (19), p.16015-16023
• Main Authors: Davies, Sean S., Pontsler, Aaron V., Marathe, Gopal K., Harrison, Kathleen A., Murphy, Robert C., Hinshaw, Jerald C., Prestwich, Glenn D., Hilaire, Andy St, Prescott, Stephen M., Zimmerman, Guy A., McIntyre, Thomas M.
• Format: Article
• Language: English
• Subjects: Animals; Binding Sites; Binding, Competitive; CD36 Antigens - physiology; Cell Line; DNA-Binding Proteins - metabolism; Genes, Reporter; Humans; In Vitro Techniques; Kinetics; Ligands; Lipoproteins, LDL - metabolism; Monocytes - metabolism; Oxidation-Reduction; Phosphatidylcholines - chemistry; Phosphatidylcholines - metabolism; Receptors, Cytoplasmic and Nuclear - agonists; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Cytoplasmic and Nuclear - metabolism; Recombinant Fusion Proteins - metabolism; Rosiglitazone; Thiazoles - pharmacokinetics; Thiazolidinediones; Transcription Factors - agonists; Transcription Factors - genetics; Transcription Factors - metabolism; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M100878200

Synthetic high affinity peroxisome proliferator-activated receptor (PPAR) agonists are known, but biologic ligands are of low affinity. Oxidized low density lipoprotein (oxLDL) is inflammatory and signals through PPARs. We showed, by phospholipase A1 digestion, that PPARγ agonists in oxLDL arise from the small pool of alkyl phosphatidylcholines in LDL. We identified an abundant oxidatively fragmented alkyl phospholipid in oxLDL, hexadecyl azelaoyl phosphatidylcholine (azPC), as a high affinity ligand and agonist for PPARγ. [3H]azPC bound recombinant PPARγ with an affinity (Kd(app) ≈40 nm) that was equivalent to rosiglitazone (BRL49653), and competition with rosiglitazone showed that binding occurred in the ligand-binding pocket. azPC induced PPRE reporter gene expression, as did rosiglitazone, with a half-maximal effect at 100 nm. Overexpression of PPARα or PPARγ revealed that azPC was a specific PPARγ agonist. The scavenger receptor CD36 is encoded by a PPRE-responsive gene, and azPC enhanced expression of CD36 in primary human monocytes. We found that anti-CD36 inhibited azPC uptake, and it inhibited PPRE reporter induction. Results with a small molecule phospholipid flippase mimetic suggest azPC acts intracellularly and that cellular azPC accumulation was efficient. Thus, certain alkyl phospholipid oxidation products in oxLDL are specific, high affinity extracellular ligands and agonists for PPARγ that induce PPAR-responsive genes.