PPARgamma ligands inhibit TNF-alpha-induced LOX-1 expression in cultured endothelial cells

Endothelial dysfunction or activation, elicited by oxidized low-density lipoprotein (OxLDL), has been implicated in the initiation and progression of atherosclerosis. We elucidated whether tumor necrosis factor-alpha (TNF-alpha)-induced endothelial OxLDL receptor, lectin-like OxLDL receptor-1 (LOX-1), mRNA expression is modified by peroxisome proliferator-activated receptor (PPAR) activators in cultured bovine aortic endothelial cells (BAEC). We confirmed that both PPARalpha and PPARgamma were expressed in BAEC by reverse transcription-polymerase chain reaction analysis. Natural PPARgamma ligand 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and the thiazolidinediones, pioglitazone and troglitazone, decreased TNF-alpha-induced LOX-1 mRNA expression in BAEC. LOX-1 expression induced by phorbol 12-myristrate 13-acetate was also inhibited by 15d-PGJ(2). In contrast, PPARalpha ligands, Wy14643 and fenofibric acid, did not alter TNF-alpha-induced LOX-1 expression. TNF-alpha-induced immunohistochemical staining of LOX-1 was suppressed by 15d-PGJ(2) but not Wy14643. Taken together, PPARgamma activators inhibit TNF-alpha-induced LOX-1 expression in cultured BAEC, which may beneficially influence inflammatory responses in atherosclerosis.