The clinical impact of serum sLOX-1 level in coronary artery disease patients as inferred from its implication in the in vitro protective effects of metoprolol against hypoxic injury of HUVECs

Background

Ischemic coronary artery disease (CAD) is a major public health problem across the world. Early detection and appropriate management significantly reduced CAD-induced morbidities and death. Endothelial cells are pathogenically implicated.

Purpose

Our study was designed to investigate the role of the soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1) in the in vitro protective effect of Metoprolol against hypoxia-induced injury of Human umbilical vein endothelial cells (HUVECs). Secondly, the clinical significance of variations in serum levels of sLOX-1 in patients with CAD was assessed.

Methods

In vitro, hypoxic injury model of HUVECs was established in an atmosphere of 1% O2, 95% N2, and 5% CO2 for 24 hours. The protective effect and mechanism of action of the cardio-selective beta-blocker Metoprolol at 10–6 μM concentration was investigated.

Consented stable atherosclerotic CAD (n=150) and unstable angina pectoris patients (n=75) along with 150 healthy volunteer subjects were voluntarily enrolled in this ethically approved study. Invasive coronary angiogram with ≥50% stenosis at least in one major coronary artery was used for diagnosis. ESC/ACC/AHC/practical protocols were used for categorizing patients into stable or unstable CAD. Serum sLOX-1 level was measured using specific ELISA kit. The diagnostic significance of serum sLOX-1 levels was assessed by analyzing its area under the curve (AUC).

Results

In vitro hypoxic conditions induced high rate of cellular apoptosis, high levels of LOX-1 expression, reactive oxygen species (ROS) generation and LDH release from HUVECs after 24 hours incubation, compared to normoxic control cells. Metoprolol significantly decreased LOX-1 levels, and prevented the release of LDH and generation of ROS. This culminated into marked improvement in cellular viability of hypoxia-exposed HUVECs (p<0.001).

Compared to healthy subjects, serum levels of sLOX-1s were significantly elevated in atherosclerotic stable and unstable CAD patients (p<0.001). Serum sLOX-1 levels were increased by 4.21 folds in stable CAD patients and by 6.373 folds in atherosclerotic unstable angina patients vs. healthy participants. Moreover, the levels in the two patients' groups were significantly different (p<0.001). In stable angina CAD patients, sLOX-1 AUC = 0.929; and in unstable CAD patients, AUC = 0.944, indicating that serum sLOX-1 levels clearly differentiated patients from healthy participants with high specificity and sensitivity.

Conclusions

Extrapolated from HUVECs hypoxia-induced injury model and the protective effect of Metoprolol, elevation of the circulating levels of sLOX-1 correlated with increased risks for atherosclerotic CAD and is a highly sensitive and specific biomarker for early detection of the disease.

Funding Acknowledgement

Type of funding source: None