Pancreatitis-associated protein: from a lectin to an anti-inflammatory cytokine.

Pancreatitis-associated protein (PAP) was discovered in the pancreatic juice of rats with acute pancreatitis. PAP is a 16 kDa secretory protein structurally related to the C-type lectins although classical lectin-related function has not been reported yet. Then, it was demonstrated that PAP expression may be activated in some tissues in a constitutive or injury- and inflammation-induced manner. More recently, it has been found that PAP acts as an anti-inflammatory factor in vitro and in vivo. PAP expression can be induced by several pro- and anti-inflammatory cytokines and by itself through a JAK/STAT3-dependent pathway. PAP is able to activate the expression of the anti-inflammatory factor SOCS3 through the JAK/STAT3-dependent pathway. The JAK/STAT3/SOCS3 pathway seems to be a common point between PAP and several cytokines. Therefore, it is reasonable to propose that PAP is a new anti-inflammatory cytokine.