Interleukin 18 stimulates release of soluble lectin-like oxidized LDL receptor-1 (sLOX-1).
Lectin-like oxidized LDL receptor-1 (LOX-1) appears to play crucial roles in atherosclerotic plaque rupture. We previously reported that circulating soluble LOX-1 (sLOX-1) levels are elevated in acute coronary syndrome (ACS) and that sLOX-1 can be a specific and sensitive biomarker for ACS. A proinflammatory cytokine interleukin 18 (IL-18) and its receptor are prominently expressed in atherosclerotic plaques. In addition, circulating IL-18 levels were reported to be high in ACS. In this study, we have examined if IL-18 can stimulate shedding of LOX-1 and subsequent release of sLOX-1. After transfection with LOX-1 cDNA, HEK-293T cells were incubated with or without IL-18. Cell-conditioned media and total cell lysates were subjected to immunoblot analyses with an anti-LOX-1 monoclonal antibody. In addition, ADAM10 cDNA, ADAM10 siRNA or control vector were also co-transfected into HEK-293T cells, and the cell-conditioned media and total cell lysates were subjected to LOX-1 immunoblotting after treatment with or without IL-18. The cell-conditioned medium/total cell lysate ratios in the amounts of LOX-1 or sLOX-1 were determined as sLOX-1 cleavage ratios. IL-18 (10-100ng/mL) stimulation increased the sLOX-1 cleavage by 3-4-fold in a concentration- and time-dependent manner. ADAM10 overexpression alone similarly enhanced the sLOX-1 cleavage. ADAM10 inhibition by ADAM10 siRNA transfection significantly suppressed IL-18-induced sLOX-1 cleavage. IL-18 similarly enhanced sLOX-1 cleavage in TNF-alpha-activated cultured endothelial cells, as well as LOX-1 transgenic mice in vivo. IL-18 appears one of the stimuli that enhance sLOX-1 release in ACS and ADAM10 may be involved in this process.
Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
Hirokazu
H
Mitsuoka
Noriaki
N
Kume
Kazutaka
K
Hayashida
Atsuko
A
Inui-Hayashiada
Yo
Y
Aramaki
Masako
M
Toyohara
Toshikazu
T
Jinnai
Eiichiro
E
Nishi
Toru
T
Kita
D051722:ADAM Proteins / Q000378:metabolism; D000072197:ADAM10 Protein; D054058:Acute Coronary Syndrome / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000818:Animals; D015415:Biomarkers; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007249:Inflammation; D020382:Interleukin-18 / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D051127:Scavenger Receptors, Class E / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
D015415:Biomarkers; D016207:Cytokines; D020382:Interleukin-18; D008565:Membrane Proteins; C495137:OLR1 protein, human; C495138:Olr1 protein, mouse; D051127:Scavenger Receptors, Class E; D053829:Amyloid Precursor Protein Secretases; D051722:ADAM Proteins; D000072197:ADAM10 Protein; C491236:ADAM10 protein, human; C491234:Adam10 protein, mouse