title: A novel method for imaging apoptosis using a caspase-1 near-infrared fluorescent probe.
abstract: Here we describe a novel method for imaging apoptosis in cells using a near-infrared fluorescent (NIRF) probe selective for caspase-1 (interleukin 1beta-converting enzyme, ICE). This biocompatible, optically quenched ICE-NIRF probe incorporates a peptide substrate, which can be selectively cleaved by caspase-1, resulting in the release of fluorescence signal. The specificity of this probe for caspase-1 is supported by various lines of evidence: 1) activation by purified caspase-1, but not another caspase in vitro; 2) activation of the probe by infection of cells with a herpes simplex virus amplicon vector (HGC-ICE-lacZ) expressing a catalytically active caspase-1-lacZ fusion protein; 3) inhibition of HGC-ICE-lacZ vector-induced activation of the probe by coincubation with the caspase-1 inhibitor YVAD-cmk, but not with a caspase-3 inhibitor; and 4) activation of the probe following standard methods of inducing apoptosis with staurosporine, ganciclovir, or ionizing radiation in culture. These results indicate that this novel ICE-NIRF probe can be used in monitoring endogenous and vector-expressed caspase-1 activity in cells. Furthermore, tumor implant experiments indicate that this ICE-NIRF probe can be used to detect caspase-1 activity in living animals. This novel ICE-NIRF probe should prove useful in monitoring endogenous and vector-expressed caspase-1 activity, and potentially apoptosis in cell culture and in vivo.
authors.affiliation: Departments of Neurology and Radiology, Massachusetts General Hospital and Neuroscience Program, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Shanta M
authors.initials: SM
authors.lastname: Messerli
authors.forename: Shilpa
authors.initials: S
authors.lastname: Prabhakar
authors.forename: Yi
authors.initials: Y
authors.lastname: Tang
authors.forename: Khalid
authors.initials: K
authors.lastname: Shah
authors.forename: Maria L
authors.initials: ML
authors.lastname: Cortes
authors.forename: Vidya
authors.initials: V
authors.lastname: Murthy
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
authors.forename: Xandra O
authors.initials: XO
authors.lastname: Breakefield
authors.forename: Ching-Hsuan
authors.initials: CH
authors.lastname: Tung
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D020170:Caspase 1 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D015774:Ganciclovir / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D011839:Radiation, Ionizing; D051381:Rats; D018139:Simplexvirus / Q000235:genetics; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D020170:Caspase 1; D019311:Staurosporine; D015774:Ganciclovir