Targeting Early Atherosclerosis: A Focus on Oxidative Stress and Inflammation

Abstract

Atherosclerosis is a chronic vascular inflammatory disease associated to oxidative stress and endothelial dysfunction. Oxidation of low-density lipoprotein (LDL) cholesterol is one of the key factors for the development of atherosclerosis. Nonoxidized LDL have a low affinity for macrophages, so they are not themselves a risk factor. However, lowering LDL levels is a common clinical practice to reduce oxidation and the risk of major events in patients with cardiovascular diseases (CVD). Atherosclerosis starts with dysfunctional changes in the endothelium induced by disturbed shear stress which can lead to endothelial and platelet activation, adhesion of monocytes on the activated endothelium, and differentiation into proinflammatory macrophages, which increase the uptake of oxidized LDL (oxLDL) and turn into foam cells, exacerbating the inflammatory signalling. The atherosclerotic process is accelerated by a myriad of factors, such as the release of inflammatory chemokines and cytokines, the generation of reactive oxygen species (ROS), growth factors, and the proliferation of vascular smooth muscle cells. Inflammation and immunity are key factors for the development and complications of atherosclerosis, and therefore, the whole atherosclerotic process is a target for diagnosis and treatment. In this review, we focus on early stages of the disease and we address both biomarkers and therapeutic approaches currently available and under research.

Figure 1

The structure of the vascular wall. PVAT: perivascular adipose tissue; VSMC: vascular smooth muscle cells; EC: endothelial cells; EEL: external elastic lamina; IEL: internal elastic lamina; BM: basement membrane.

Figure 2

Atheroma plaque formation steps from endothelial dysfunction to rupture into the vascular lumen.

Figure 3

Effects of oxLDL and oxidative stress on endothelium. LOX-1 activation by oxLDL induces endothelial oxidative stress by increasing NADPH oxidase (Nox) activity and uncoupling eNOS. Oxidative stress activates NF-κB through p38 mitogen-activated protein kinase (p38MAPK) and phosphatidylinositol 3-kinase (PI3K) transduction pathways initiating intranuclear apoptotic signal transduction. The formation of peroxynitrite (ONOO⁻) reduces nitric oxide (NO) and prostacyclin (PGI2) bioavailability leading to endothelial dysfunction. In addition, oxidative stress reduces PPARγ activity and adiponectin levels. Both of them stimulate AMP-activated protein kinase (AMPK) which in turn upregulates eNOS activity through Akt phosphorylation (Akt-P). Moreover, AMPK is a negative regulator of Nox.

Figure 4

Prothrombotic, proatherogenic, and inflammatory effects of platelet activation. The platelet-endothelium interaction triggers platelet activation, considered as a critical point in all phases of atherosclerosis. ECM: extracellular matrix; MMP-2: matrix metalloproteinases 2; MMP-9: matrix metalloproteinases 9; PF4: platelet factor 4; SDF-1: stromal cell-derived factor-1.