Lectin-like oxidized low-density lipoprotein receptor-1 promotes endothelial dysfunction in LDL receptor knockout background.

OBJECTIVE:Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major receptor for oxidized LDL in endothelial cells. LOX-1 is highly expressed in atherosclerotic plaques. The impact of LOX-1 on development of endothelial dysfunction in large vessels in absence or presence of atherosclerosis-prone conditions has not been studied to date. METHODS:Mice with endothelial cell-specific LOX-1 overexpression (bLOX-1tg) were analyzed. Wild-type (WT) mice served as controls. In addition, bLOX-1tg mice were crossed with LDL receptor knockout (Ldlr-/-) mice. All mice were fed a western-type diet (WD) or control diet (CD) for 20 weeks. Afterwards, endothelial function was analyzed ex vivo in thoracic aortas using a Mulvany myograph. RESULTS:WD induced hypertriglyceridemia (bLOX-1tg: 1.6-fold; WT: 1.4-fold) and hypercholesterolemia (P < 0.0001) in bLOX-1tg and WT mice without HDL-elevation in bLOX-1tg mice. Gonadal fat pad weight was 1.7 and 1.2-fold increased on CD and WD in bLOX-1tg mice compared to WT. LOX-1 overexpression impaired endothelial function by 15-16% (P < 0.05) on CD and WD. Crossing bLOX-1tg mice into Ldlr-/- background strongly elevated total (∼6-fold) and LDL-cholesterol (∼9-fold) compared to WT and bLOX-1tg mice on WD. Endothelial function in response to WD was impaired in bLOX-1tg/Ldlr-/- mice (Effmax: 56.7 ± 23.0%) compared to WT (Effmax: 88.2 ± 15.8%, P < 0.001), bLOX-1tg (Effmax: 76.7 ± 12.9%, P < 0.05) and Ldlr-/- mice (Effmax: 70.1 ± 13.1%, P < 0.05). No differences between WT, bLOX-1tg and Ldlr-/- mice were detectable when comparing all genotypes. CONCLUSION:Endothelial LOX-1 overexpression in an atherosclerosis-prone background impairs endothelial function, proving its importance in the development of atherosclerosis.

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