Phospholipase C beta 3 deficiency leads to macrophage hypersensitivity to apoptotic induction and reduction of atherosclerosis in mice

Atherosclerosis is an inflammatory disease that is associated with monocyte recruitment and subsequent differentiation into lipid-laden macrophages at sites of arterial lesions, leading to the development of atherosclerotic plaques. PLC is a key member of signaling pathways initiated by G protein-coupled ligands in macrophages. However, the role of this enzyme in the regulation of macrophage function is not known. Here, we studied macrophages from mice lacking PLC beta 2, PLC beta 3, or both PLC isoforms and found that PLC beta 3 is the major functional PLC beta isoform in murine macrophages. Although PLC beta 3 deficiency did not affect macrophage migration, adhesion, or phagocytosis, it resulted in macrophage hypersensitivity to multiple inducers of apoptosis. PLC beta 3 appeared to regulate this sensitivity via PKC-dependent upregulation of Bcl-XL. The significance of PLC beta signaling in vivo was examined using the apoE-deficient mouse model of atherosclerosis. Mice lacking both PLC beta 3 and apoE exhibited fewer total macrophages and increased macrophage apoptosis in atherosclerotic lesions, as well as reduced atherosclerotic lesion size when compared with mice lacking only apoE. These results demonstrate what we believe to be a novel role for PLC activity in promoting macrophage survival in atherosclerotic plaques and identify PLC beta 3 as a potential target for treatment of atherosclerosis.