Cathepsins regulate premature
trypsinogen activation within acinar cells, a key initial step in
pancreatitis. The identity, origin, and causative roles of activated
cathepsins in pancreatic
inflammation and
pain are not defined. By using a near infrared-labeled activity-based probe (GB123) that covalently modifies active
cathepsins, we localized and identified activated
cathepsins in mice with
cerulein-induced
pancreatitis and in pancreatic juice from patients with
chronic pancreatitis. We used inhibitors of activated
cathepsins to define their causative role in pancreatic
inflammation and
pain. After GB123 administration to mice with
pancreatitis, reflectance and confocal imaging showed significant accumulation of the probe in inflamed pancreas compared with controls, particularly in acinar cells and macrophages, and in spinal cord microglia and neurons. Biochemical analysis of
pancreatic extracts identified them as
cathepsins B, L, and S (Cat-B, Cat-L, and Cat-S, respectively). These active
cathepsins were also identified in pancreatic juice from patients with
chronic pancreatitis undergoing an endoscopic procedure for the treatment of
pain, indicating
cathepsin secretion. The
cathepsin inhibitor
K11777 suppressed
cerulein-induced activation of Cat-B, Cat-L, and Cat-S in the pancreas and ameliorated pancreatic
inflammation, nocifensive behavior, and activation of spinal nociceptive neurons. Thus
pancreatitis is associated with an increase in the active forms of the
proteases Cat-B, Cat-L, and Cat-S in pancreatic acinar cells and macrophages, and in spinal neurons and microglial cells. Inhibition of
cathepsin activation ameliorated pancreatic
inflammation and
pain. Activity-based probes permit identification of
proteases that are predictive
biomarkers of
disease progression and response to
therapy and may be useful noninvasive tools for the detection of pancreatic
inflammation.