title: Single-cell imaging of retinal ganglion cell apoptosis with a cell-penetrating, activatable peptide probe in an in vivo glaucoma model.
abstract: Molecular imaging probes have potential for in vivo identification of apoptosis and other intracellular processes. TcapQ, a cell-penetrating, near-infrared fluorescent peptide probe designed to be optically silent through intramolecular fluorescence quenching and activated by effector caspases, has been previously described and validated in vitro. Herein, using NMDA-induced apoptosis of retinal ganglion cells (RGCs), representing an in vivo rat model of glaucoma, we assessed the ability of TcapQ to image single-cell apoptosis through effector caspase activity. Following intravitreal injection, intracellular TcapQ activation occurred specifically in RGCs, identified individual apoptotic cells, showed a clear dose-response relationship with NMDA, and colocalized with TUNEL labeling in the retina. There was a significant diminution of probe activation following pretreatment with a specific inhibitor of caspase-3. Stereospecificity was also exhibited by the lack of intracellular fluorescence upon administration of the noncleavable isomer, dTcapQ. TcapQ has potential utility in detecting and monitoring single-cell apoptosis in glaucoma in vivo.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Barnett
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.forename: Dustin
authors.initials: D
authors.lastname: Maxwell
authors.forename: Qing
authors.initials: Q
authors.lastname: Chang
authors.forename: David
authors.initials: D
authors.lastname: Piwnica-Worms
mesh_terms: D000818:Animals; D017209:Apoptosis; D003584:Cytological Techniques / Q000379:methods*; D005901:Glaucoma / Q000473:pathology*; D020287:In Situ Nick-End Labeling; D008297:Male; D016202:N-Methylaspartate; D010455:Peptides / Q000378:metabolism; D051381:Rats; D012165:Retinal Ganglion Cells / Q000166:cytology*
chemical_list: D010455:Peptides; C519706:TcapQ647 peptide; D016202:N-Methylaspartate