Which of the following contributes to unstable plaques?

Unstable plaques, which are a key feature of atherosclerosis, are characterized by their propensity to rupture and lead to thromboembolic events. Macrophage activity plays a critical role in this process. Macrophages are immune cells that infiltrate the vessel wall and transform into foam cells after ingesting oxidized low-density lipoprotein (LDL). Their activity contributes to plaque instability in several ways:

1. Inflammation: Macrophages secrete various cytokines and inflammatory mediators that promote an inflammatory response. This inflammation can weaken the fibrous cap of the plaque, rendering it more prone to rupture.

2. Tissue remodeling: Macrophages produce matrix metalloproteinases (MMPs) that degrade extracellular matrix components. This degradation can further compromise the structural integrity of the plaque.

3. Apoptosis: They can also induce apoptosis in vascular smooth muscle cells (VSMCs) within the plaque, which diminishes the protective fibrous cap, leading to increased instability.

Overall, the activity of macrophages is instrumental in the development and progression of unstable plaques, making them a significant contributor to cardiovascular risk. The involvement of macrophages in promoting inflammation and disrupting the structural integrity of