ACAT inhibition reduces the progression of preexisting, advanced atherosclerotic mouse lesions without plaque or systemic toxicity.

Objective: Acyl-CoA:cholesterol acyltransferase (ACAT) converts cholesterol to cholesteryl esters in plaque foam cells. Complete deficiency of macrophage ACAT has been shown to increase atherosclerosis in hypercholesterolemic mice because of cytotoxicity from free cholesterol accumulation, whereas we previously showed that partial ACAT inhibition by Fujirebio compound F1394 decreased early atherosclerosis development. In this report, we tested F1394 effects on preestablished, advanced lesions of apolipoprotein-E-deficient mice.

Methods And Results: Apolipoprotein-E-deficient mice on Western diet for 14 weeks developed advanced plaques, and were either euthanized (Baseline), or continued on Western diet with or without F1394 and euthanized after 14 more weeks. F1394 was not associated with systemic toxicity. Compared with the baseline group, lesion size progressed in both groups; however, F1394 significantly retarded plaque progression and reduced plaque macrophage, free and esterified cholesterol, and tissue factor contents compared with the untreated group. Apoptosis of plaque cells was not increased, consistent with the decrease in lesional free cholesterol. There was no increase in plaque necrosis and unimpaired efferocytosis (phagocytic clearance of apoptotic cells). The effects of F1394 were independent of changes in plasma cholesterol levels.

Conclusions: Partial ACAT inhibition by F1394 lowered plaque cholesterol content and had other antiatherogenic effects in advanced lesions in apolipoprotein-E-deficient mice without overt systemic or plaque toxicity, suggesting the continued potential of ACAT inhibition for the clinical treatment of atherosclerosis, in spite of recent trial data.