Pioglitazone Suppresses Inflammation In Vivo in Murine Carotid Atherosclerosis Novel Detection by Dual-Target Fluorescence Molecular Imaging

Objective-To investigate the effects of pioglitazone (PIO), a peroxisome proliferator-activated receptor gamma agonist, on plaque matrix metalloproteinase (MMP) and macrophage (Mac) responses in vivo in a molecular imaging study. Methods and Results-In vitro, PIO suppressed MMP-9 protein expression in murine peritoneal Macs (P < 0.05). To assess PIO's effects on plaque inflammation, nondiabetic apolipoprotein E-/- mice receiving a high-cholesterol diet (HCD) were administered an MMP-activatable fluorescence imaging agent and a spectrally distinct Mac-avid fluorescent nanoparticle. After 24 hours, mice underwent survival dual-target intravital fluorescence microscopy of carotid arterial plaques. These mice were then randomized to HCD or HCD plus 0.012% PIO for 8 weeks, followed by a second intravital fluorescence microscopy study of the same carotid plaque. In the HCD group, in vivo MMP and Mac target-to-background ratios increased similarly (P < 0.01 versus baseline). In contrast, PIO reduced MMP and Mac target-to-background ratios (P < 0.01) versus HCD. Changes in MMP and Mac signals correlated strongly (r >= 0.75). Microscopy demonstrated MMP and Mac reductions in PIO-treated mice and a PIO-modulated increase in plaque collagen. Conclusion-Serial optical molecular imaging demonstrates that plaque MMP and Mac activity in vivo intensify with hypercholesterolemia and are reduced by PIO therapy. (Arterioscler Thromb Vasc Biol. 2010;30:1933-1939.)