Question:

Oxidized LDL has been identified as a principal mediator in the pathogenesis of atherogenesis. Cellular uptake of oxidized LDL is mediated through the oxidized LDL receptor-1, LOX-1. We investigated whether circulating factors link LOX-1 expression in endothelial cells and impaired endothelium-dependent vasoreactivity (EDVR) as a functional indicator of atherogenesis.

Methods:

EDVR was measured as flow-mediated dilation (FMD) of the brachial artery in 27 patients with coronary artery disease (based on diagnostic cardiac catheterization; stenosis of 50% or more in a major coronary artery or branch) and/or risk factors (diabetes: hyperlipidaemia; hypertension: systolic blood pressure of =130 mmHg or a diastolic blood pressure of =90 mmHg, or self-reported use of antihypertensive drugs) were included. Exclusion criteria were myocardial infarction and impaired left ventricular function (=60%). Human umbilical vein endothelial cells (HUVEC) were incubated with bradykinin or prostacyclin in the presence of tumour necrosis factor (TNF)-α or with serum of each patient for four hours. LOX-1 and eNOS mRNA and protein expressions were quantified by TaqMan and Western Blotting, corrected for GAPDH expression and analysed relative to the expression in medium-treated cells.

Results:

Prostacyclin and bradykinin did not modulate LOX-1 basal expression but were able to prevent significantly the up-regulation of LOX-1 expression by TNF-α in HUVEC in vitro. Impaired EDVR was associated with reduced eNOS protein expression in HUVEC (r=0.788, P<0.001), diabetes (P=0.024), and smoking status (yes/no, P=0.047). No association was established with LOX-1 mRNA (r=0.292, P=0.138) or with LOX-1 protein expression in HUVEC (r=0.201, P=0.312).

Conclusions:

Using a combination of in vitro experiments with in vivo measurements, we found no evidence that endothelial LOX-1 expression and EDVR mediated through circulating factors were associated.