High-dose recombinant apolipoprotein A-I-Milano mobilizes tissue cholesterol and rapidly reduces plaque lipid and macrophage content in apolipoprotein E-deficient mice - Potential implications for acute plaque stabilization

Background-Repeated doses of recombinant apolipoprotein A-I-Milano phosphol ipid complex (apoA-I-m) reduce atherosclerosis and favorably change plaque composition in rabbits and mice. In this study, we tested whether a single high dose of recombinant apoA-I-m could rapidly mobilize tissue cholesterol and reduce plaque lipid and macrophage content in apoE-deficient mice. Methods and Results-High cholesterol-fed, 26-week-old apoE-deficient mice r eceived a single intravenous injection of saline (n=16), 1080 mg/kg dipalmi toylphosphatidylcholine (DPPC; n=14), or 400 mg/kg of recombinant apoA-I-m complexed with DPPC (1:2.7 weight ratio; n=18), Blood was sampled before an d 1 and 48 hours after injection, and aortic root plaques were evaluated fo r lipid content and macrophage content after oil-red O and immunostaining, respectively. One hour after injection, the plasma cholesterol efflux-promo ting capacity was nearly 2-fold higher in recombinant apoA-I-m-treated mice compared with saline and DPPC-treated mice (P<0.01). Compared with baselin e values, serum free cholesterol, an index of tissue cholesterol mobilizati on, increased 1.6-fold by 1 hour after recombinant apoA-I-m injection, and it remained significantly elevated at 48 hours (P<0.01). Mice receiving rec ombinant apoA-I-m had 40% to 50% lower lipid content (P<0.01) and 29% to 36 % lower macrophage content (P<0.05) in their plaques compared with the sali ne- and DPPC-treated mice, respectively. Conclusions-A single high dose of recombinant apoA-I-m rapidly mobilizes ti ssue cholesterol acid reduces plaque lipid and macrophage content in apoE-d eficient mice. These findings suggest that this strategy could rapidly chan ge plaque composition toward a more stable phenotype.