Endocytosis and intracellular trafficking of fatty acid esters of phenylaminopropanediol, the putative etiologic agents of the toxic oil syndrome (TOS)

The toxic oil syndrome (TOS) caused by ingestion of rapeseed oil adulterated with aniline is characterized by symptoms of an allergic and/or autoimmune illness associated with vessel wall lesions similar to those of atherosclerosis. Fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP) have been incriminated as the etiologic agents of TOS. However, the pathogenesis of TOS is yet unknown. Here, we addressed whether PAP fatty acid esters are incorporated into lipoproteins, which after transport to vascular endothelial cells are taken up to initiate TOS vasculopathy. After loading 14C-dioleyl-ester of PAP into LDL labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindolcarbocyanine (DiI) we assessed receptor mediated endocytosis and intracellular localization of these lipopoproteins in vascular endothelial cells. Our data suggest that these lipoprotein-derivatives are internalized into endothelial cells by LDL receptor mediated endocytosis. Confocal microscopy revealed that DiI-LDL loaded with dioleyl-ester of PAP and incubated for 60 min with endothelial cells colocalizes with the lysosomotropic compound LysoTracker Green, indicating that internalized PAP-loaded LDL are targetted to the endolysosomal compartment for further processing. Subcellular fractionation of endothelial-like ECV-304 cells after incubation with LDL loaded with the 14C-dioleyl-ester of PAP for 6 h showed that the radioactive label accumulated in fractions containing endosomes, the Golgi apparatus and the endoplasmic reticulum.