Acute pancreatitis is characterized by premature intracellular
protease activation and infiltration of inflammatory cells, mainly neutrophil granulocytes and macrophages, into the organ. The lysosomal
proteases cathepsin B, D, and L have been identified as regulators of early
zymogen activation and thus modulators of the severity of
pancreatitis.
Cathepsin C (CTSC, syn. dipeptidly-
peptidase I) is a widely expressed, exo-cystein-
protease involved in the proteolytic processing of various other lysosomal
enzymes. We have studied its role in
pancreatitis. We used CTSC-deleted mice and their WT littermates in two experimental models of
pancreatitis. The mild model involved eight hourly
caerulein injections and the severe model partial duct
ligation. Isolated pancreatic acini and spleen-derived leukocytes were used for ex vivo experiments. CTSC is expressed in the pancreas and in inflammatory cells. CTSC deletion reduced the severity of
pancreatitis (more prominently in the milder model) without directly affecting intra-acinar cell
trypsin activation in vitro The absence of CTSC reduced infiltration of neutrophil granulocytes impaired their capacity for cleaving
E-cadherin in adherens junctions between acinar cells and reduced the activity of neutrophil
serine proteases polymorphonuclear (neutrophil)
elastase,
cathepsin G, and
proteinase 3, but not neutrophil motility. Macrophage invasion was not dependent on the presence of CTSC. CTSC is a regulator and activator of various lysosomal
enzymes such as
cathepsin B, D, and L. Its loss mitigates the severity of
pancreatitis not by reducing intra-acinar cell
zymogen activation but by reducing infiltration of neutrophil granulocytes into the pancreas. In this context one of its key roles is that of an activator of
neutrophil elastase.