Variable Effects Of LDL Subclasses Of Cholesterol On Endothelial Nitric Oxide/Peroxynitrite Balance – The Risks And Clinical Implications For Cardiovascular Disease

Abstract

Background

Elevated levels of low density lipoprotein (LDL), “bad cholesterol”, is not an accurate indicator of coronary disease. About 75% of patients with heart attacks have cholesterol levels that do not indicate a high risk for a cardiovascular event. LDL is comprised of three subclasses, with particles of different size and density. We used nanomedical systems to elucidate the noxious effects of LDL subclasses on endothelium.

Experimental

Nanosensors were employed to measure the concentrations of nitric oxide (NO) and peroxynitrite (ONOO⁻) stimulated by LDL subclasses in HUVECs. N-LDL and ox-LDL (subclass A: 1.016–1.019 g/mL, subclass I: 1.024–1.029 g/mL, and subclass B: 1.034–1.053 g/mL) stimulated NO and ONOO⁻ release. The concentrations ratio of (NO)/(ONOO⁻) was used to evaluate the noxious effects of the subclasses on endothelium.

Results

In HUVECs, the (NO)/(ONOO⁻) ratio for normal endothelium is about 5, but shifts to 2.7±0.4, 0.5±0.1, and 0.9±0.1 for subclasses A, B, and I, respectively. Ratios below 1.0 indicate an imbalance between NO and ONOO⁻, affecting endothelial function. LDL of 50% B and 50% I produced the most severe imbalance (0.45±0.04), whereas LDL of 60% A, 20% B, and 20% I had the most favorable balance of 5.66±0.69. Subclass B significantly elevated the adhesion of molecules and monocytes. The noxious effect was significantly higher for ox-LDL than n-LDL.

Conclusion

Subclass B of “bad cholesterol” is the most damaging to endothelial function and can contribute to the development of atherosclerosis. Contrary to the current national guidelines, this study suggests that it’s not the total LDL, rather it is the concentration of subclass B in relation to subclasses A and/or I, that should be used for diagnosis of atherosclerosis and the risk of heart attack. By utilizing specific pharmacological therapy to address the concentration of subclass B, there is a potential to significantly reduce the risk of heart attack and atherosclerosis.

Keywords:

• low density lipoprotein
• nitric oxide
• endothelium
• peroxynitrite
• cell adhesion

Acknowledgment

We would like to thank Dr. J. Jose Corbalan and Hazem Dawoud for technical assistance, as well as Collin Arocho for his assistance in the preparation of this manuscript.

Disclosure

Dr Tadeusz Malinski reports a pending patent 60609-US-PSP/OU-19018. The authors report no other conflicts of interest in this work.