Intravenous Lipid Emulsion Induces Endocytosis in Human Coronary Artery Endothelial Cells by a CD36/Caveolin‐1 Pathway

Abstract

IntroductionIntravenous lipid emulsion like Intralipid™ (ILP) are fatty emulsions commonly used in parenteral nutrition. Previous research has shown that they protect against myocardial ischemia/reperfusion injury (IR) in animal models through a mechanism involving activation of Akt/extracellular signal‐regulated kinase‐1/glycogen synthase kinase‐3β pathway ultimately leading to delayed mitochondrial permeability transition pore (mPTP) opening and the induction of a protective effect by ILP. They are also studied in connection with local anesthetic toxicity and mechanisms of scavenging anesthetics from the blood stream.HypothesisThe direct effect of ILP on endothelial cells has not been studied. Hence, the mechanisms by which ILP crosses the endothelium are not well understood especially the effects of ILP on human coronary artery endothelial cells (HCAEC). We hypothesize that uptake of ILP occurs through endocytosis in HCAECs by the formation of a CD36/caveolin‐1 cell membrane complex.MethodsILP in a 1% dilution was administered to HCAECs for 2 hours or control was left untreated. Western blots were conducted with anti‐CD36, caveolin‐1, dynamin‐2, src kinase‐1, eNOS, and phospho‐eNOS antibodies and equal loading of protein confirmed with beta‐actin. Additional cells were exposed to ILP, and then immunohistochemistry was performed, to visualize uptake of ILP into cells. This was accomplished by co‐labeling of lysosomal associated protein 3 CD63 and styryl peptide and lysosomal marker FM5‐95.ResultsThe association of CD36 with caveolin‐1 is increased after stimulation with ILP. The tyrosine kinase Src kinase‐1 acts to phosphorylate dynamin‐2, a GTPase responsible for separating the vesicle from the plasma membrane. ILP stimulation induced phosphorylation of Src kinase 1 and increase in expression of dynamin2. ILP induced increased phosphorylation and Hsp90 association of eNOS, leading to increased synthesis of nitric oxide. Furthermore, the association and expression of lysosomal markers CD63 and FM5‐95 are increased after ILP treatment compared to no treatment.Summary and ConclusionOur data suggest that administration of ILP to endothelial cells induces an endosomal pathway by formation of CD36/caveolin association which leads to enhanced endosome formation seen by increased lysosomal markers. Furthermore, we can report that stimulation of endothelial cells with ILP results in an increase of eNOS activity and increased NO synthesis which might be important for the cardioprotective abilities.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.