Molecular Imaging of Apoptosis in Ischemia Reperfusion Injury With Radiolabeled Duramycin Targeting Phosphatidylethanolamine: Effective Target Uptake and Reduced Nontarget Organ Radiation Burden.

OBJECTIVES: The purpose of this study was to evaluate the feasibility of imaging apoptosis in experimental ischemia-reperfusion model by technetium-99m (99mTc)-labeled Duramycin, and compare it to an established tracer, 99mTc-labeled Annexin-V, which has a relative disadvantage of high radiation burden to nontarget organs. BACKGROUND: During apoptosis, the cell membrane phospholipids-phosphatidylserine (PS) and phosphatidylethanolamine (PE) are exposed and can be targeted by Annexin-V and Duramycin, respectively, for in vivo imaging. Identification of a reversible cell death process should permit therapeutic intervention to help reduce myocyte loss and left ventricle dysfunction. METHODS: In a 40-min left coronary artery ischemia-reperfusion model in 17 rabbits, 7 mCi of 99mTc-labeled Duramycin (n = 10), 99mTc-linear Duramycin (a negative tracer control; n = 3), or 99mTc-Annexin-V (a positive tracer-control; n = 4) were intravenously administered 30 min after reperfusion. Of the 10 Duramycin group animals, 4 animals were treated with an antiapoptotic agent, minocycline at the time of reperfusion. In vivo and ex vivo micro-single-photon emission computed tomography (µSPECT) and micro-computed tomography (µCT) imaging was performed 3 h after reperfusion, followed by quantitative assessment of tracer uptake and pathological characterization. Fluorescent Duramycin and Annexin-V were injected in 4 rats to visualize colocalization in infarct areas in a 40-min left coronary artery occlusion and 30-min reperfusion model. RESULTS: Intense uptake of Duramycin and Annexin-V was observed in the apical (infarcted) areas. The percent injected dose per gram uptake of Duramycin in apical region (0.751 ± 0.262%) was significantly higher than remote area in same animals (0.045 ± 0.029%; p < 0.01). Duramycin uptake was insignificantly lower than Annexin-V uptake (1.23 ± 0.304%; p > 0.01) but demonstrated substantially lower radiation burden to kidneys (0.358 ± 0.210% vs. 1.58 ± 0.316%, respectively; p < 0.001). Fluorescence studies with Duramycin and Annexin V showed colocalization in infarct areas. Minocycline treatment substantially resolved Duramycin uptake (0.354% ± 0.0624%; p < 0.01). CONCLUSIONS: Duramycin is similarly effective in imaging apoptotic cell death as Annexin-V with lower nontarget organ radiation. Clinical feasibility of apoptosis imaging with a PE-seeking tracer should be tested.

Cardioprotective effects of erythropoietin in rats subjected to ischemia-reperfusion injury: assessment of infarct size with 99mTc-annexin V.

UNLABELLED: Administration of erythropoietin (EPO) during or immediately after myocardial ischemia can reduce subsequent myocardial apoptosis, a key phenomenon in myocardial ischemia-reperfusion injury. In this study, we assessed the effect of EPO on (99m)Tc-annexin V myocardial uptake and whether the accumulation of (99m)Tc-annexin V can predict cardiac remodeling and functional deterioration. METHODS: Eighteen rats with left coronary artery (LCA) occlusion were randomized to receive either an intravenous injection of EPO (EPO group) or saline (nontherapy [nT] group) immediately after release of the occlusion. After 20 min of LCA occlusion and 30 min of reperfusion, the rats were injected with (99m)Tc-annexin V. One hour after (99m)Tc-annexin V injection, the LCA was reoccluded and (201)Tl was injected intravenously, and the rats were sacrificed 1 min later. The heart was removed and sectioned, and dual-tracer autoradiography was performed to evaluate the distribution of the area at risk (defined on the thallium autoradiograph) and the area of apoptosis (defined on the annexin autoradiograph). Adjacent histologic specimens had deoxyuridine triphosphate nick-end labeling (TUNEL) staining to confirm the presence of apoptosis and were compared with autoradiography. Another 16 rats were randomized to EPO and nT groups and underwent echocardiography immediately after release of the LCA occlusion and at 2 and 4 wk after surgery. RESULTS: The areas of (99m)Tc-annexin V accumulation in the EPO group were smaller than those in the nT group, though the (201)Tl defect areas of these 2 groups were comparable (area ratio, 0.318 +/- 0.038 vs. 0.843 +/- 0.051, P < 0.001, for annexin and 24.8 +/- 2.1 vs. 25.9 +/- 2.6 mm(2), P = NS, for thallium). (99m)Tc-annexin V accumulation correlated with the density of TUNEL-positive cells (r = 0.886, P < 0.001). In the nT group, left ventricular end-diastolic dimension (Dd) increased from baseline at 2 wk by 34.7% +/- 3.8% and remained stable at 34.9% +/- 5.0% at 4 wk after coronary occlusion. In the EPO group, Dd increased by 8.5% +/- 2.1% (P < 0.01 vs. nT at 2 wk) and 13.2% +/- 2.8% (P < 0.01 vs. nT at 4 wk). In the nT group, the left ventricular percentage of fractional shortening decreased by 42.2% +/- 3.4% and 52.9% +/- 3.4% at 2 and 4 wk, respectively, whereas in the EPO group it decreased 9.0% +/- 1.9% at 2 wk (P < 0.01 vs. nT at 2 wk) and 11.1% +/- 6.7% at 4 wk (P < 0.01 vs. nT at 4 wk). CONCLUSION: This study demonstrated that a single treatment with EPO immediately after release of coronary ligation suppressed cardiac remodeling and functional deterioration. (99m)Tc-annexin V autoradiographs and TUNEL staining confirm that this change is due to a decrease in the extent of myocardial apoptosis in the ischemic/reperfused region.

Coronary artery disease after radiation therapy for Hodgkin's lymphoma: coronary CT angiography findings and calcium scores in nine asymptomatic patients.

OBJECTIVE: Long-term survivors of Hodgkin's lymphoma treated with radiation therapy have an increased incidence of coronary artery disease. The purpose of this study is to describe the coronary CT angiography findings and calcium scores of asymptomatic patients who had mediastinal irradiation for Hodgkin's lymphoma and to evaluate the impact of coronary CT angiography on patient management. MATERIALS AND METHODS: We evaluated nine consecutive patients, age range 35-60 years, who had been treated for Hodgkin's lymphoma by radiation therapy between the ages of 11 and 27 years. The total mediastinal dose ranged from 34 to 45 Gy. All patients were evaluated with 64-MDCT with calcium scoring followed by CT angiography of the coronary arteries. Imaging findings and clinical follow-up were analyzed. RESULTS: Eight of nine patients had coronary artery disease. CT showed long segments of diffuse disease; areas of stenosis from soft plaque; and calcification in the proximal right coronary, left anterior descending, and left circumflex arteries. Calcium scores were significantly higher than in other patients of this age group. Additional tests, including selective coronary angiography, were necessary in patients with diffuse disease with calcifications. CT evaluation led to bypass surgery and angioplasty in two patients. CONCLUSION: Coronary CT angiography and calcium scores are useful tools for evaluation of irradiation-related coronary artery disease. Complementary tests might be necessary in selected patients. Prospective larger studies are needed to better define the role of coronary CT angiography and calcium scores and to establish an algorithm for evaluation and treatment of these patients.