Early Detection of Apoptotic Dopaminergic Neurons Using ~(99m)Tc-Annexin V

Objective To investigate the binding characteristics of radiolabeled Annexin V to apoptotic dopaminergic neurons,as to seek the feasibility of 99mTc-Annexin V imaging for in vivo early detection apoptosis in Parkinson disease.Methods PC12 and SH-SY5Y cell lines were induced apoptosis by 1-methyl-4-phenylpyridinium(MPP+)in different concentrations,then analyzed by flow cytometry with fluorescein isothiocyanate-conjugated Annexin V(FITC-Annexin V)and propidium iodide(PI)staining.Meanwhile,Annexin V was radiolabeled with 99mTc.The saturable binding and cell uptake test were carried out.The correlation of apoptotic rate detected by flow cytometry and cell uptake was analyzed.Results MPP+ at different concentrations can induce cell apoptosis in a dose-dependent manner.99mTc-Annexin V can bind to apoptotic cells with a high affinity of 7.16±1.78 nmol/L,and the binding sites were 179±33 fmol/106cells(PC12)and 220±26 fmol/106cells(SH-SY5Y).The membrane-bound radiolabeled Annexin V activity linearly correlated to total fluorescence as observed by FITC-Annexin V flow cytometry(r=0.924 for PC12 and r=0.937 for SH-SY5Y,P0.01).Conclusions 99mTc-Annexin V has a high affinity to apoptotic dopaminergic neurons,and the radioactivity correlated well with cell apoptosis rate,thus we can detect neuron apoptosis using 99mTc-Annexin V in vivo.