Monitoring the Protective Effects of Minocycline Treatment with Radiolabeled Annexin V in an Experimental Model of Focal Cerebral Ischemia

Minocycline is an antibiotic now recognized to have anti-apoptotic and antiinflammatory properties. Because of these properties, minocycline may be of benefit in reducing neuronal apoptosis from ischemia and subsequent postischemic inflam-mation if administered soon after a stroke. We now explore the feasibility of using 99mTc-annexin V, an in vivo marker of apopto-sis, with SPECT to monitor the antiapoptotic effects of minocy-cline therapy. Methods: CB6/F1 adult male mice underwent unilateral distal middle cerebral artery occlusion (dMCA) occlu-sion andwere imaged and sacrificed at 1, 3, 7, or 30 d after injury. Animals were givenminocycline (or vehicle) 30min and 12 h after dMCA occlusion and then given 22.5 mg/kg twice daily for up to 7 d. Before imaging, behavioral tests were performed to evaluate the neurologic function. After imaging, brains were collected for histology and assessed for the degree of apoptosis and micro-glial activation.Results: 99mTc-Annexin V uptake in injured hemi-spheres was significantly decreased 2- to 3-fold by minocycline at all time points. Minocyline reduced infarct size as seen histo-logically and improved behavioral indices as late as 30 d. Infarct volume as seen histologically correlated with radiolabeled annexin V uptake seen by SPECT. In situ fluorescent microscopy demonstrated that annexin V bound primarily to neurons at 1 and 3 d, with a shift toward microglia by 7 and 30 d. Conclusion: We found that minocycline significantly reduces neuronal apoptosis and infarct size and improves neurologic outcome in mice after acute focal cortical ischemia. Key Words: apoptosis; neuroprotective agents; in vivo imaging; strok