Intestinal mucosal injury induced by tryptase-activated protease-activated receptor 2 requires β-arrestin-2 in vitro

Abstract

Tryptase exacerbates intestinal ischemia-reperfusion injury, however, the direct role of tryptase in intestinal mucosal injury and the underlying mechanism remains largely unknown. Protease-activated receptor 2 (PAR-2), commonly activated by tryptase, interacts with various adaptor proteins, including β-arrestin-2. The present study aimed to determine whether tryptase is capable of inducing intestinal mucosal cell injury via PAR-2 activation and to define the role of β-arrestin-2 in the process of injury. The IEC-6 rat intestinal epithelial cell line was challenged by tryptase stimulation. Cell viability, lactate dehydrogenase (LDH) activity and apoptosis were analyzed to determine the severity of cell injury. Injury was also evaluated following treatments with specific PAR-2 and extracellular signal-related kinases (ERK) inhibitors, and knockdown of β-arrestin-2. PAR-2, ERK and β-arrestin-2 protein expression levels were evaluated. Tryptase treatment (100 and 1,000 ng/ml) resulted in IEC-6 cell injury, as demonstrated by significant reductions in cell viability, accompanied by concomitant increases in LDH activity and levels of cleaved caspase-3 protein expression. Furthermore, tryptase treatment led to a marked increase in PAR-2 and phosphorylated-ERK expression, and exposure to specific PAR-2 and ERK inhibitors eliminated the changes induced by tryptase. Knockdown of β-arrestin-2 blocked tryptase-mediated cell injury, whereas tryptase exerted no influence on β-arrestin-2 expression in IEC-6 cells. These data indicate that tryptase may directly damage IEC-6 cells via PAR-2 and the downstream activation of ERK, and demonstrate that the signaling pathway requires β-arrestin-2.