Bone marrow-specific caspase-1/11 deficiency inhibits atherosclerosis development in Ldlr-/- mice

Recent investigations have suggested that inflammasome activation plays an important role during atherosclerosis. Upon activation, the inflammasome induces processing and release of pro-inflammatory cytokines interleukin 1 beta (IL-1 beta) and interleukin 18 (IL-18) via activation of caspase-1/11. Previously, it was shown that complete caspase-1 deficiency is protective against atherosclerosis development. However, while macrophages are the main inflammatory cells involved in atherosclerosis, the exact role of macrophage-specific caspase-1/11 activation during development of cardiovascular disease has never been investigated. We hypothesized that hematopoietic caspase-1/11 deficiency leads to reduced atherosclerosis development. To investigate the specific contribution of hematopoietic caspase-1/11 activation to atherosclerosis development, Ldlr(-/-) mice received a transplant (tp) of wild-type (WT) or caspase-1/11(-/-) bone marrow, to create WT-tp mice and caspase-1/11(-/-)-tp mice, and fed a high-fat, high-cholesterol diet for 12 weeks. Our results showed an increase in anti-inflammatory blood leukocytes in caspase-1/11(-/-)-tp mice compared with WT-tp mice, as indicated by a decreased level of Ly6C(high) monocytes and an increased level of Ly6C(low) monocytes. In line with our hypothesis, hematopoietic deletion of caspase-1/11 resulted in a strong reduction in atherosclerotic plaque size. Furthermore, necrotic core content was dramatically decreased in caspase-1/11(-/-)-tp mice. Our data indicate that hematopoietic caspase-1/11 activation is involved in vascular inflammation and atherosclerosis, and plays an important role in cardiovascular disease progression.