A novel method for imaging apoptosis using a caspase-1 near-infrared fluorescent probe.
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.
Messerli
Shanta M
SM
Departments of Neurology and Radiology, Massachusetts General Hospital and Neuroscience Program, Harvard Medical School, Boston, MA 02115, USA.
Prabhakar
Shilpa
S
Tang
Yi
Y
Shah
Khalid
K
Cortes
Maria L
ML
Murthy
Vidya
V
Weissleder
Ralph
R
Breakefield
Xandra O
XO
Tung
Ching-Hsuan
CH
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
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D020170:Caspase 1; D019311:Staurosporine; D015774:Ganciclovir