oxLDL induces inflammatory responses in vascular smooth muscle cells via urokinase receptor association with CD36 and TLR4.
The pathogenesis of atherosclerosis involves an imbalanced lipid metabolism and a deregulated immune response culminating in chronic inflammation of the arterial wall. Recent studies show that endogenous ligands, such as modified plasma lipoproteins, can trigger pattern recognition receptors (PRR) of innate immunity for cellular and humoral reactions. The underlying molecular pathways remain less explored. In this study, we investigated the mechanisms of inflammatory effects of oxidized low-density lipoproteins (oxLDL) on human primary coronary artery smooth muscle cells (VSMC). We show that already low concentration of oxLDL initiated atherogenic signals triggering VSMC transition to proinflammatory phenotype. oxLDL impaired the expression of contractile proteins and myocardin in VSMC and initiated changes in cell functional responses, including expression of proinflammatory molecules. The effects of oxLDL were abolished by downregulation of the multifunctional urokinase receptor (uPAR). In response to oxLDL uPAR associated with CD36 and TLR4, the two main PRR for both pathogen and endogenous ligands. We demonstrate that uPAR association with CD36 and TLR4 mediated oxLDL-induced and NF-κB-dependent G-CSF and GM-CSF expression and changes in VSMC contractile proteins. uPAR-mediated release of G-CSF and GM-CSF by VSMC affected macrophage behavior and production of MCP-1. We provide evidence for functional relevance of our in vitro findings to in vivo human atherosclerotic tissues. Our data imply uPAR as a part of a PRR cluster interfering structurally and functionally with CD36 and TLR4 and responding to endogenous atherogenic ligands. They further point to specific function of each component of this cluster in mediating the ultimate signaling pattern.
Nephrology Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Electronic address: Kiian.ioulia@mh-hannover.de.
Yulia
Y
Kiyan
Nephrology Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Electronic address: Tkatchouk.Sergei@mh-hannover.de.
Sergey
S
Tkachuk
Cardiology Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Electronic address: Hilfiker.Denise@mh-hannover.de.
Denise
D
Hilfiker-Kleiner
Nephrology Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Electronic address: Nephrologie@mh-hannover.de.
Hermann
H
Haller
The Lipid Research Laboratory, Technion Faculty of Medicine, and Rambam Medical Center, Haifa, Israel. Electronic address: fuhrman@tx.technion.ac.il.
Bianca
B
Fuhrman
Nephrology Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany. Electronic address: dumler.inna@mh-hannover.de.
Inna
I
Dumler
D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D002633:Chemotaxis; D003285:Contractile Proteins / Q000235:genetics / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism / Q000473:pathology; D016179:Granulocyte Colony-Stimulating Factor / Q000096:biosynthesis / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000378:metabolism; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D000099251:Myocardin
D018955:CD36 Antigens; D018932:Chemokine CCL2; D003285:Contractile Proteins; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D008077:Lipoproteins, LDL; D016328:NF-kappa B; D009687:Nuclear Proteins; D055293:Receptors, Urokinase Plasminogen Activator; D051197:Toll-Like Receptor 4; D015534:Trans-Activators; D000099251:Myocardin; C111835:CCL2 protein, human; C495345:TLR4 protein, human; C099252:oxidized low density lipoprotein
Inflammation; LDL; LPS; SMA; Urokinase receptor; VSMC; Vascular smooth muscle cells; lipopolysaccharide; low density lipoprotein; oxLDL; oxidated LDL; smooth muscle α actin; uPA; uPA receptor; uPAR; urokinase-type plasminogen activator; vascular smooth muscle cells