Objective— Atherosclerosis is considered to be a chronic inflammatory disease and many cytokines participate in the development of atherosclerosis. We focused on the role of interleukin-1β (IL-1β), one of the proinflammatory cytokines secreted by monocytes/macrophages, in the progression of atherosclerosis.

Methods and Results— We generated mice lacking both apoE and IL-1β. The sizes of atherosclerotic lesions at the aortic sinus in apoE−/−/IL-1β−/−mice at 12 and 24 weeks of age showed a significant decrease of approximately 30% compared with apoE−/−/IL-1β^+/+ mice, and the percentage of the atherosclerotic area to total area of apoE−/−/IL-1β−/− at 24 weeks of age also showed a significant decrease of about 30% compared with apoE−/−/IL-1β^+/+. The mRNA levels of vascular cell adhesion molecule (VCAM)-1 and monocyte chemotactic protein-1 in the apoE−/−/IL-1β−/− aorta were significantly reduced compared with the apoE−/−/IL-1β^+/+. Furthermore, VCAM-1 was also reduced at the protein level in apoE−/−/IL-1β−/− aorta compared with apoE−/−/IL-1β^+/+.

Conclusions— The lack of IL-1β decreases the severity of atherosclerosis in apoE deficient mice, possibly through increased expressions of VCAM-1 and monocyte chemotactic protein-1 in the aorta.