Calpain Inhibitor Calpeptin Improves Pancreatic Fibrosis in Mice with Chronic Pancreatitis by Inhibiting the Activation of Pancreatic Stellate Cells

Background:: Pancreatic fibrosis is a hallmark feature of chronic pancreatitis (CP), resulting in persistent damage to the pancreas. The sustained activation of pancreatic stellate cells (PSCs) plays a pivotal role in the progression of pancreatic fibrosis and is a major source of extracellular matrix (ECM) deposition during pancreatic injury. Methods:: Calpain is a calcium-independent lysosomal neutral cysteine endopeptidase and was found to be correlated to various fibrotic diseases. Studies have revealed that calpeptin, a calpain inhibitor, can improve the fibrosis process of multiple organs. This study investigated the effect of the calpain inhibitor, calpeptin, on fibrosis in experimental CP and activation of cultured PSCs in mice. CP was induced in mice by repeated injections of cerulein for four weeks in vivo, and the activation process of mouse PSCs was isolated and cultured in vitro. Then, the inhibitory effect of calpeptin on pancreatic fibrosis was confirmed based on the histological damage of CP, the expression of α-smooth muscle actin (α-SMA) and collagen-Iα1(Col1α1), and the decrease in mRNA levels of calpain-1 and calpain-2. Results:: In addition, it was revealed that calpeptin can inhibit the activation process of PSCs and induce significant PSCs apoptosis by downregulating the expression of calpain-1, calpain-2 and TGF-β1, and the expression and phosphorylation of smad3 in vitro. Conclusion:: These results suggest that the calpain inhibitor, calpeptin, plays a key role in the regulation of PSC activation by inhibiting the TGF-β1/smad3 signaling pathway, which supports the potential of calpeptin as an inhibitor of pancreatic fibrosis in mice by interfering with calpain.