TABLE 2.

Differences between M1 and M2 macrophages in atherosclerosis.

	M1	M2
Polarization stimuli	Cholesterol crystals; LPS; Pro-inflammatory cytokines; OxLDLs	TGF-β; IL-10; IL-4; IL-13
Activation pathway	TLR-4 or NF-κB pathway	LXR-α (liver X receptor-α)
Secretion of cytokines	TNF-α; IL-1β; IL-6; IL-12; IL-23	IL-10; TGF-β
Predominant metabolism	Aerobic glycolysis; Fatty acid synthesis; Production of mitochondrial ROS	Oxidative phosphorylation; Fatty acid oxidation (β-oxidation)
Localization	Plaque shoulder and lipid core	Adventitia and areas of neovascularization
Association with plaque stability	Abundant in symptomatic and unstable plaques	Abundant in stable zones of the plaque and asymptomatic lesions
Roles	Occurrence of postapoptotic necrosis after dead cell accumulation; Formation of a necrotic core; Contribution to plaque instability and rupture	Phagocytosis of apoptotic cells and debris; Increase of lipid degradation and prevention of foam cell formation; Resolution of inflammation