title: In vivo imaging with fluorescent smart probes to assess treatment strategies for acute pancreatitis.
abstract: OBJECTIVE
  Endoprotease activation is a key step in acute pancreatitis and early inhibition of these enzymes may protect from organ damage. In vivo models commonly used to evaluate protease inhibitors require animal sacrifice and therefore limit the assessment of dynamic processes. Here, we established a non-invasive fluorescence imaging-based biomarker assay to assess real-time protease inhibition and disease progression in a preclinical model of experimental pancreatitis.
  
  
  METHODS
  Edema development and trypsin activation were imaged in a rat caerulein-injection pancreatitis model. A fluorescent "smart" probe, selectively activated by trypsin, was synthesized by labeling with Cy5.5 of a pegylated poly-L-lysine copolymer. Following injection of the probe, trypsin activation was monitored in the presence or absence of inhibitors by in vivo and ex vivo imaging.
  
  
  RESULTS
  We established the trypsin-selectivity of the fluorescent probe in vitro using a panel of endopeptidases and specific inhibitor. In vivo, the probe accumulated in the liver and a region attributed to the pancreas by necropsy. A dose dependent decrease of total pancreatic fluorescence signal occurred upon administration of known trypsin inhibitors. The fluorescence-based method was a better predictor of trypsin inhibition than pancreatic to body weight ratio.
  
  
  CONCLUSIONS
  We established a fluorescence imaging assay to access trypsin inhibition in real-time in vivo. This method is more sensitive and dynamic than classic tissue sample readouts and could be applied to preclinically optimize trypsin inhibitors towards intrapancreatic target inhibition.
authors: Novartis Institute of BioMedical Research, Cambridge, Massachusetts, USA.
authors: Abhiruchi
authors: A
authors: Agarwal
authors: Andreas
authors: A
authors: Boettcher
authors: Rainer
authors: R
authors: Kneuer
authors: Farid
authors: F
authors: Sari-Sarraf
authors: Adriana
authors: A
authors: Donovan
authors: Julian
authors: J
authors: Woelcke
authors: Oliver
authors: O
authors: Simic
authors: Trixi
authors: T
authors: Brandl
authors: Thomas
authors: T
authors: Krucker
mesh_terms: D000208:Acute Disease; D000818:Animals; D002232:Carbocyanines; D004195:Disease Models, Animal; D010450:Endopeptidases / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D005456:Fluorescent Dyes; D061848:Optical Imaging; D010195:Pancreatitis / Q000175:diagnosis* / Q000188:drug therapy / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D014357:Trypsin / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D005456:Fluorescent Dyes; D011480:Protease Inhibitors; D014361:Trypsin Inhibitors; D010450:Endopeptidases; D014357:Trypsin