Phospholipolyzed LDL induces an inflammatory response in endothelial cells through endoplasmic reticulum stress signaling.
Secreted phospholipases A2 (sPLA2s) are present in atherosclerotic plaques and are now considered novel attractive therapeutic targets and potential biomarkers as they contribute to the development of atherosclerosis through lipoprotein-dependent and independent mechanisms. We have previously shown that hGX-sPLA2-phospholipolyzed LDL (LDL-X) induces proinflammatory responses in human umbilical endothelial cells (HUVECs); here we explore the molecular mechanisms involved. Global transcriptional gene expression profiling of the response of endothelial cells exposed to either LDL or LDL-X revealed that LDL-X activates multiple distinct cellular pathways including the unfolded protein response (UPR). Mechanistic insight showed that LDL-X activates UPR through calcium depletion of intracellular stores, which in turn disturbs cytoskeleton organization. Treatment of HUVECs and aortic endothelial cells (HAECs) with LDL-X led to activation of all 3 proximal initiators of UPR: eIF-2alpha, IRE1alpha, and ATF6. In parallel, we observed a sustained phosphorylation of the p38 pathway resulting in the phosphorylation of AP-1 downstream targets. This was accompanied by significant production of the proinflammatory cytokines IL-6 and IL-8. Our study demonstrates that phospholipolyzed LDL uses a range of molecular pathways including UPR to initiate endothelial cell perturbation and thus provides an LDL oxidation-independent mechanism for the initiation of vascular inflammation in atherosclerosis.
Gora
Sarah
S
INSERM UMRS 937, Université Pierre et Marie Curie, UPMC-Paris 6, Paris, France.
Maouche
Seraya
S
Atout
Rajai
R
Wanherdrick
Kristell
K
Lambeau
Gérard
G
Cambien
François
F
Ninio
Ewa
E
Karabina
Sonia-Athina
SA
D051702:Activating Transcription Factor 6 / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism / Q000494:pharmacology*; D020411:Oligonucleotide Array Sequence Analysis; D054497:Phospholipases A2, Secretory; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014471:Umbilical Veins / Q000166:cytology; D056811:Unfolded Protein Response
C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D015852:Eukaryotic Initiation Factor-2; D015850:Interleukin-6; D016209:Interleukin-8; D008077:Lipoproteins, LDL; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; D054497:Phospholipases A2, Secretory