Abstract 1079: Modulation of Atherosclerotic Plaque Characteristics by Minocycline: An Evaluation by Molecular Imaging of Matrix Metalloprotainase (MMP) Expression
MMP activation in atherosclerotic lesions plays an important role in plaque progression and vulnerability, and is a potential target for plaque stabilization. We evaluated the effectiveness of minocycline (MC) in modulation of plaque characteristics using molecular imaging of MMP expression, compared with fluvastatin (FS). 38 NZW rabbits with experimental atherosclerotic lesions were subjected to in vivo micro SPECT/CT imaging for the assessment of MMP activity using 99mTc-labeled broad spectrum MMP inhibitor (MPI). Atherosclerotic lesions were produced by balloon deendotheliazation of abdominal aorta, and high cholesterol diet for 4 months. Of these, 7 received low dose MC (1.5mg/kg), 7 high dose MC (3mg/kg, N=7), 6 FS (1mg/kg), and 6 combination of low dose MC and FS (MC+FS) in the fourth month, 12 received no intervention (Rx-control). 8 unmanipulated normal chow-fed rabbits were used as disease controls (Dz-control). After in vivo imaging, aortas were explanted for %ID/g MPI uptake, histological characterization, and MMP activity assays. Parallel in vitro studies were performed for the effect of MC and FS on NF-κB, VCAM-1 and MMP-9 expression from cultured TNF-α-stimulated smooth muscle cells and macrophages. Target accumulation of MPI was best visualized in atherosclerotic aorta in Rx-control atherosclerotic rabbits. % ID/g MPI in Rx-control (.10±.04%) was significantly higher than Dz-control (.016±.004%), MC-low (.081±.02%) and high (.045±.01%) dose, FS (.056±.011%), and MC+FS (.049±.005%) rabbits, and showed a significant correlation with histologically and biochemically-verified MMP-2, -9 activity. MC-treated plaques showed marked reduction in inflammation and increase in smooth muscle content. In vitro cell culture confirmed that NF-κB and VCAM-1 expression in activated VSMC were reduced by MC, and that MMP-9 expression in activated macrophage was also inhibited by MC. The present study demonstrates that MC is equally effective as FS in modulation of plaque characteristics, and that molecular imaging can characterize various biologic processes in vivo and allows for the study of the efficacy of targeted interventions.