Proteinase-activated receptor 1 activation induces epithelial apoptosis and increases intestinal permeability

Abstract

Proteinase-activated receptor 1 (PAR1)-mediated inflammation remains poorly understood. Here we characterize previously unrecognized effects of PAR1-induced apoptosis signaling, which contributes to epithelial barrier dysfunction. Incubation of epithelial cells with PAR1 agonists induced apoptosis and increased epithelial permeability in a caspase-3-dependent manner. Similarly, studies in vivo demonstrated that intracolonic infusion with PAR1 agonists increased colonic permeability in mice, and that this effect was abolished by pretreatment with a caspase-3 inhibitor. PAR1 agonists induced tight junctional zonula-occludens 1 disruption and apoptotic nuclear condensation. Investigation into signaling pathways showed that these effects were dependent on caspase-3, tyrosine kinase, and myosin light chain kinase. Conversely, the Src kinase inhibitor PP1 augmented zonula-occludens 1 injury and nuclear condensation induced by PAR1 agonists. These results support a role for proteinases and PARs in intestinal disease and provide new directions for possible therapeutic applications of PAR1 antagonists.

SGLT-1-mediated glucose uptake protects human intestinal epithelial cells against Giardia duodenalis-induced apoptosis

“…Giardia duodenalis trophozoite proteases play an important role in the microbial-host epithelial interaction during infection ( [Farthing, 1993] and [Guimaraes et al, 2003]). Moreover, protease-activated receptors have been identified on intestinal epithelial cells and are involved in the regulation of cell apoptosis and inflammatory responses ( [Chin et al, 2003] and [Hansen et al, 2005]). Therefore, the potential role of proteases in G. duodenalis-induced enterocytic sugar uptake was examined by the addition of various protease inhibitors to the co-cultures.…”

Intestinal Epithelial Cell Apoptosis, Immunoregulatory Molecules, and Necrotizing Enterocolitisb

“…Some GPCRs have been shown to signal cell survival in enterocytes, such as cholinergic receptors [99] and the lysophosphatidic acid (LPA) receptor [41], and some have shown to induce apoptosis, such as proteinase-activated receptor [100] and PAFR [28]. Since PAF has been shown to have pathogenic significance in NEC, we investigated the mechanisms of PAF induced apoptosis in IEC-6 cells.…”

“…Furthermore, TLR4 activation leads to induction of inflammatory molecules such as TNFα [102] and nitric oxide (NO) [103]; both of these molecules have been shown to be involved in NEC pathogenesis [15,81,104] and have been shown to be pro-apoptotic for enterocytes [81,105]. It is notable that other GPCRs that are closely related to PAFR may impart either pro or anti-apoptotic signals on enterocytes as discussed above [41, 99,100] signaling in other cell types that can actively promote inflammation such as PMN [106] and lymphocytes [108]. These findings suggest that we are only beginning to skim the surface of the intricate mechanisms of GPCR-mediated cell death and survival and that other GPCRs may play significant roles in NEC.…”

Epithelial effects of proteinase-activated receptors in the gastrointestinal tract

“…The subsequent liberation of arachidonic acid stimulates chloride secretion via a mechanism dependent upon both cyclooxygenase (COX)-1 and COX-2 (Buresi et al 2002). In contrast, activation of apical PAR-1 in the same cell line activates a different signaling pathway, which is not Src-dependent, leading to apoptosis and increases in epithelial monolayer permeability (Chin et al 2003). Since these results were obtained from a cell line, caution must be exercised when extrapolating the data to an integrated system like the whole intestine, but these studies clearly illustrate the point that polarity of PAR expression can have profound effects in terms of the cellular response.…”