title: Bis(zinc-dipicolylamine), Zn-DPA, a new marker for apoptosis.
abstract: OBJECTIVE
  To characterize the labeling of apoptotic cells with a molecular probe of bis(zinc(II)-dipicolylamine) (Zn-DPA) conjugated with a fluorescent reporter in a rat model of retinal ganglion cell (RGC) degeneration induced by N-methyl-D-aspartate (NMDA).
  
  
  METHODS
  Adult Wistar rats were given unilateral intravitreal injections of 3 μL 40 mM neutralized NMDA and euthanized at 1, 2, 4, 24, and 48 hours. One hour before euthanasia, 3 μL Zn-DPA conjugated with fluorescein (Zn-DPA 480) was intravitreally injected. Prelabeling of RGC with retrograde fluorogold (FG), TUNEL, and immunohistochemistry with III β-tubulin and vimentin were performed.
  
  
  RESULTS
  Fluorescence labeling of Zn-DPA 480 was observed in the retinas from 1 hour up to 24 hours after NMDA injection, whereas the labeling was reduced at 48 hours postinjection. At both 4 and 24 hours postinjection, most Zn-DPA 480-positive cells in the RGC layer were labeled by FG and III β-tubulin. The number of TUNEL-positive cells increased from 4 to 24 hours. At 24 hours, 95.7% of Zn-DPA 480-positive cells were TUNEL positive, whereas 95.1% of TUNEL-positive cells were Zn-DPA 480 positive. The numbers of Zn-DPA 480-positive cells at 1 and 2 hours after NMDA injection were significantly higher than TUNEL.
  
  
  CONCLUSIONS
  Our findings demonstrate that intravitreal injection of fluorescent Zn-DPA 480 labels retinal neurons undergoing apoptosis and that recognition of exposed phosphatidylserine appears earlier than detection of DNA fragmentation, indicating the potential of Zn-DPA as an imaging probe for tracking degenerating retinal neurons.
authors.affiliation: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States.
authors.forename: Jacky M K
authors.initials: JM
authors.lastname: Kwong
authors.affiliation: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States.
authors.forename: Celia
authors.initials: C
authors.lastname: Hoang
authors.affiliation: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States.
authors.forename: Reshil T
authors.initials: RT
authors.lastname: Dukes
authors.affiliation: Cizik Eye Clinic, Hermann University Eye Associates, Houston, Texas, United States.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Yee
authors.affiliation: Molecular Targeting Technologies, Inc., West Chester, Pennsylvania, United States.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Gray
authors.affiliation: Molecular Targeting Technologies, Inc., West Chester, Pennsylvania, United States.
authors.forename: Koon Y
authors.initials: KY
authors.lastname: Pak
authors.affiliation: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Caprioli
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002452:Cell Count; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology; D008297:Male; D004369:Pentetic Acid / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*
chemical_list: D004369:Pentetic Acid
keywords: apoptosis; fluorescent probes; ganglion cells; glaucoma; retina