Abstract 1336: Chronic Ezetimibe Treatment Reduces Lesion Formation, ED-B Fibronectin Expression and Near Infrared Targeted Imaging in ApoE-Deficient Mice
Ezetimibe (EZE), an inhibitor of cholesterol absorption, reduces atherosclerosis in Apo E deficient mice (ApoE(−/−)mice). It has been recently demonstrated that the angiogenic matrix protein ED-B fibronectin (ED-B) is upregulated in atherosclerotic lesions and can be imaged using antibody conjugates. In the present study we used a newly developed anti-ED-B scFv conjugated with a near infrared(NIR) fluorochrom for imaging of lesion formation in ApoE(−/−)mice treated with EZE in order to investigate the effect of EZE on the expression of ED-B and its use as a target for molecular imaging. 36 6-week old ApoE(−/−) mice were fed with high fat diet (21%fat) containing EZE(5μg/kg/d) or chow for 2 or 4 month (n=9 /per group). ED-B imaging of the aortic lesions was performed 24 hours after intravenous injection of ED-B-conjugate (0.05μmol/kg). Mice were sacrificed and aortas were analysed using a laser equipped NIR imaging system. Plaque lesion formation was analyzed by histology, immuno-histochemistry (Mac3, CD31; actin, CD90), morphometry of the supraaortic arteries and by sudan stain of the thoracic aorta followed by densitometry.
Results: EZE treatment significantly reduced serum cholesterol levels (from 646 to 99 mg/dl, 4mo). The lesion formation, sudan stained areas in aortas were significantly reduced (2 month: 3.3% to 0.3%; 4 month 17.2% to 5.2%, both p>0.001) as well as ED-B positive areas (2 month: 2.1% to 0.1% p=0,022; 4 month 19.3% to 3% p=0,004. ED-B imaging significantly correlated with the sudan stainings (r= 0.803, P<0.001) at 2 and at 4 month, control animals (C57Bl6) were completely negative for ED-B. After 2 months EZE treatment immunohistochemistry showed significant reduction in macrophages, ED-B immunoreactivity (both, p<0.05) and foam cell formation in aortic lesions. There was a significant correlation between ED-B and macrophage content in the lesion
Conclusion: Ezetimibe significantly reduced atherosclerotic lesion formation and inflammation. Furthermore histological data revealed a reduced expression of ED-B and macrophages in the lesions. The results correlated with the data obtained with ED-B NIR imaging suggesting that this imaging tool can be used for monitoring atherosclerotic lesion formation in this experimental model.