Protease-Activated Receptor 2, Dipeptidyl Peptidase I, and Proteases Mediate Clostridium difficile Toxin A Enteritis

Harvard University, Cambridge, Massachusetts, United States
Gastroenterology (Impact Factor: 16.72). 06/2007; 132(7):2422-37. DOI: 10.1053/j.gastro.2007.03.101
Source: PubMed


We studied the role of protease-activated receptor 2 (PAR(2)) and its activating enzymes, trypsins and tryptase, in Clostridium difficile toxin A (TxA)-induced enteritis.
We injected TxA into ileal loops in PAR(2) or dipeptidyl peptidase I (DPPI) knockout mice or in wild-type mice pretreated with tryptase inhibitors (FUT-175 or MPI-0442352) or soybean trypsin inhibitor. We examined the effect of TxA on expression and activity of PAR(2) and trypsin IV messenger RNA in the ileum and cultured colonocytes. We injected activating peptide (AP), trypsins, tryptase, and p23 in wild-type mice, some pretreated with the neurokinin 1 receptor antagonist SR140333.
TxA increased fluid secretion, myeloperoxidase activity in fluid and tissue, and histologic damage. PAR(2) deletion decreased TxA-induced ileitis, reduced luminal fluid secretion by 20%, decreased tissue and fluid myeloperoxidase by 50%, and diminished epithelial damage, edema, and neutrophil infiltration. DPPI deletion reduced secretion by 20% and fluid myeloperoxidase by 55%. In wild-type mice, FUT-175 or MPI-0442352 inhibited secretion by 24%-28% and tissue and fluid myeloperoxidase by 31%-71%. Soybean trypsin inhibitor reduced secretion to background levels and tissue myeloperoxidase by up to 50%. TxA increased expression of PAR(2) and trypsin IV in enterocytes and colonocytes and caused a 2-fold increase in Ca(2+) responses to PAR(2) AP. AP, tryptase, and trypsin isozymes (trypsin I/II, trypsin IV, p23) caused ileitis. SR140333 prevented AP-induced ileitis.
PAR(2) and its activators are proinflammatory in TxA-induced enteritis. TxA stimulates existing PAR(2) and up-regulates PAR(2) and activating proteases, and PAR(2) causes inflammation by neurogenic mechanisms.

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Available from: Graeme Cottrell, May 08, 2014
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    • "This is supported by our observations of colocalization of PAR2 and tryptase expression in and around goblet cells, the induced mucin depletion within these cells, and the blockade of inflammation , mucin depletion, and mastocytosis by the PAR2 antagonist GB88. Various serine proteases and their precursors [e.g., trypsinogens (Hansen et al., 2005; Cottrell et al., 2007) and tryptases (He and Xie, 2004; He et al., 2004)] released by cells resident in the colon may have antibacterial roles (Huang et al., 2001; Thakurdas et al., 2007). These endogenous antibiotics could contribute to the primary barrier protection of the gut. "
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    • "One explanation for these findings is that C. difficile toxins cause direct injury to the intestinal epithelium, which is associated with a robust host inflammatory response with neutrophil activation and recruitment leading in turn to greatly amplified intestinal injury. In fact, a wide range of anti-inflammatory agents can reduce intestinal injury in animal models of CDI (Anton et al., 2004; Chen et al., 2006; Cottrell et al., 2007; Kim et al., 2005, 2007; Kokkotou et al., 2009; Pothoulakis et al., 1993; Warny et al., 2000). The use of combinations of antibiotic and anti-inflammatory agents to treat severe CDI in humans warrants greater attention and investigation, especially given the rising incidence of severe and fatal disease (McDonald et al., 2006; Redelings et al., 2007). "
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