LOX-1, an oxidized LDL endothelial receptor, induces CD40/CD40L signaling in human coronary artery endothelial cells.
BACKGROUND
Despite increasing appreciation that atherogenesis involves participation of inflammatory cells, information on mediators of communication between different constituents of atherosclerotic plaque remain incomplete. We examined the role of LOX-1, a receptor for oxidized (ox) LDL, in the expression of CD40/CD40L in cultured human coronary artery endothelial cells (HCAECs).


RESULTS
We observed that ox-LDL increased the expression of CD40 and CD40L in a concentration (10 to 80 microg/mL)- and time (1 to 24 hours)- dependent manner. These effects of ox-LDL were mediated by activation of LOX-1, because pretreatment of HCAECs with a blocking antibody to LOX-1 (JTX92) prevented the expression of CD40 and CD40L in response to ox-LDL (P<0.01). In parallel experiments, HCAECs were incubated with the protein kinase C (PKC) inhibitor bisindolylmaleimide I, and the cells were then exposed to ox-LDL. Both LOX-1 antibody and the PKC inhibitor inhibited PKC activation in response to ox-LDL (P<0.01). The PKC inhibitor also blocked the effects of ox-LDL on the expression of CD40 and CD40L (P<0.01). In additional experiments, we found that it is the PKCalpha, but not PKCbeta and PKCgamma, isoform that mediated ox-LDL-induced CD40 and CD40L upregulation. Further experiments showed that upregulation of CD40 mediated induction of proinflammatory genes, because CD40 antibody markedly reduced ox-LDL-induced TNF-alpha generation and P-selectin expression, whereas nonspecific mouse IgG had no effect.


CONCLUSIONS
These findings indicate that ox-LDL through its receptor LOX-1 triggers the CD40/CD40L signaling pathway that activates the inflammatory reaction in HCAECs. These observations provide novel insight into ox-LDL-mediated inflammation in atherosclerosis.
Li
Dayuan
D
Department of Medicine, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA.
Liu
Ling
L
Chen
Hongjiang
H
Sawamura
Tatsuya
T
Mehta
Jawahar L
JL
D001161:Arteriosclerosis / Q000209:etiology; D019013:CD40 Antigens / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D023201:CD40 Ligand / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured / Q000187:drug effects / Q000502:physiology; D003331:Coronary Vessels / Q000166:cytology* / Q000502:physiology; D042783:Endothelial Cells / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D051571:Protein Kinase C-alpha; D021122:Protein Subunits; D011973:Receptors, LDL / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D014657:Vasculitis / Q000139:chemically induced / Q000378:metabolism
D019013:CD40 Antigens; D004791:Enzyme Inhibitors; D008077:Lipoproteins, LDL; D021122:Protein Subunits; D011973:Receptors, LDL; D014409:Tumor Necrosis Factor-alpha; C099252:oxidized low density lipoprotein; D023201:CD40 Ligand; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha