The unfolded protein response is an important regulator of inflammatory genes in endothelial cells.
OBJECTIVE
Oxidized 1-palmitoyl-2-arachidonyl-sn-3-glycero-phosphorylcholine (oxPAPC) accumulates in atherosclerotic lesions and in vitro studies suggest that it mediates chronic inflammatory response in endothelial cells (ECs). The goal of our studies was to identify pathways mediating the induction of inflammatory genes by oxPAPC.


RESULTS
Using expression arrays, quantitative polymerase chain reaction (PCR), and immunoblotting we demonstrate that oxPAPC leads to endoplasmic reticulum stress and activation of the unfolded protein response (UPR) in human aortic ECs. Immunohistochemistry analysis of human atherosclerotic lesions indicated that UPR is induced in areas containing oxidized phospholipids. Using the UPR inducing agent tunicamycin and selective siRNA targeting of the ATF4 and XBP1 branches of the UPR, we demonstrate that these transcription factors are essential mediators of IL8, IL6, and MCP1 expression in human aortic ECs required for maximal inflammatory gene expression in the basal state and after oxPAPC treatment. We also identify a novel oxPAPC-induced chemokine, the CXC motif ligand 3 (CXCL3), and show that its expression requires XBP1.


CONCLUSIONS
These data suggest that the UPR pathway is a general mediator of vascular inflammation and EC dysfunction in atherosclerosis, and, likely, other inflammatory disorders.
Gargalovic
Peter S
PS
UCLA Department of Medicine, Los Angeles, CA 90095-1679, USA.
Gharavi
Nima M
NM
Clark
Michael J
MJ
Pagnon
Joanne
J
Yang
Wen-Pin
WP
He
Aiqing
A
Truong
Amy
A
Baruch-Oren
Tamar
T
Berliner
Judith A
JA
Kirchgessner
Todd G
TG
Lusis
Aldons J
AJ
D051701:Activating Transcription Factor 4 / Q000378:metabolism; D001011:Aorta / Q000166:cytology; D050197:Atherosclerosis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D002478:Cells, Cultured; D002874:Chromosome Mapping; D004268:DNA-Binding Proteins / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D005786:Gene Expression Regulation; D006801:Humans; D007158:Immunologic Techniques; D007249:Inflammation / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism; D017510:Protein Folding; D000071701:Regulatory Factor X Transcription Factors; D014018:Tissue Distribution; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010713:Phosphatidylcholines; D010743:Phospholipids; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C472349:oxidized-L-alpha-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine; D051701:Activating Transcription Factor 4