Trypsin IV or Mesotrypsin and p23 Cleave Protease-activated Receptors 1 and 2 to Induce Inflammation and Hyperalgesia

Although principally produced by the pancreas to degrade dietary proteins in the intestine, trypsins are also expressed in the nervous system and in epithelial tissues, where they have diverse actions that could be mediated by protease-activated receptors (PARs). We examined the biological actions of human trypsin IV (or mesotrypsin) and rat p23, inhibitor-resistant forms of trypsin. The zymogens trypsinogen IV and pro-p23 were expressed in Escherichia coli and purified to apparent homogeneity. Enteropeptidase cleaved both zymogens, liberating active trypsin IV and p23, which were resistant to soybean trypsin inhibitor and aprotinin. Trypsin IV cleaved N-terminal fragments of PAR1, PAR2, and PAR4 at sites that would expose the tethered ligand (PAR1 = PAR4 > PAR2). Trypsin IV increased [Ca2+]i in transfected cells expressing human PAR1 and PAR2 with similar potencies (PAR1, 0.5 μm; PAR2, 0.6 μm). p23 also cleaved fragments of PAR1 and PAR2 and signaled to cells expressing these receptors. Trypsin IV and p23 increased [Ca2+]i in rat dorsal root ganglion neurons that responded to capsaicin and which thus mediate neurogenic inflammation and nociception. Intraplantar injection of trypsin IV and p23 in mice induced edema and granulocyte infiltration, which were not observed in PAR –/–1(trypsin IV) and PAR –/–2 (trypsin IV and p23) mice. Trypsin IV and p23 caused thermal hyperalgesia and mechanical allodynia and hyperalgesia in mice, and these effects were absent in PAR –/–2 mice but maintained in PAR –/–1 mice. Thus, trypsin IV and p23 are inhibitor-resistant trypsins that can cleave and activate PARs, causing PAR1- and PAR2-dependent inflammation and PAR2-dependent hyperalgesia.