Targeting GGTase-I Activates RHOA, Increases Macrophage Reverse Cholesterol Transport, and Reduces Atherosclerosis in Mice
Background—Statins have anti-inflammatory and antiatherogenic effects that have been attributed to inhibition of RHO protein geranylgeranylation in inflammatory cells. The activity of protein geranylgeranyltransferase type I (GGTase-I) is widely believed to promote membrane association and activation of RHO family proteins. However, we recently showed that knockout of GGTase-I in macrophages activates RHO proteins and proinflammatory signaling pathways, leading to increased cytokine production and rheumatoid arthritis. In this study, we asked whether the increased inflammatory signaling of GGTase-I-deficient macrophages would influence the development of atherosclerosis in LDL receptor-deficient mice.
Methods and Results—Aortic lesions in mice lacking GGTase-I in macrophages (Pggt1bΔ/Δ) contained significantly more T lymphocytes than the lesions in controls. Surprisingly, however, mean atherosclerotic lesion area in Pggt1bΔ/Δ mice was reduced by ~60%. GGTase-I deficiency reduced the accumulation of cholesterol esters and phospholipids in macrophages incubated with minimally modified and acetylated LDL. Analyses of GGTase-I-deficient macrophages revealed upregulation of the COX2-PPARγ pathway and increased SR-B1- and CD36-mediated basal and HDL-stimulated cholesterol efflux. Lentivirus-mediated knockdown of RHOA, but not RAC1 or CDC42, normalized cholesterol efflux. The increased cholesterol efflux in cultured cells was accompanied by high levels of macrophage reverse cholesterol transport and slightly reduced plasma lipid levels in vivo.
Conclusions—Targeting GGTase-I activates RHOA and leads to increased macrophage reverse cholesterol transport and reduced atherosclerosis development despite a significant increase in inflammation.
- Received December 11, 2012.
- Accepted January 4, 2013.
- Copyright © 2013, Circulation