Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer.

The gastrointestinal tract is a complex interface between the external environment and the immune system. Its ability to control uptake across the mucosa and to protect the body from damage of harmful substances from the lumen is defined as the intestinal barrier function (IBF). The IBF involves four elements: the intestinal microbiota, the mucus layer, the epithelium and the immune system. Its dysfunction is linked with human diseases including inflammatory, metabolic, infectious, autoimmune and neurologic disorders. Most of these diseases are complex and involve genetic, psychological and environmental factors. Over the past 10 years, many genetic polymorphisms predisposing to inflammatory bowel disease (IBD) have been identified. Yet, it is now clear that they are insufficient to explain the onset of these chronic diseases. Although it has been evidenced that some environmental factors such as cigarette smoking or carbohydrate intake are associated with IBD, other environmental factors also present potential health risks such as ingestion of food additives introduced in the human diet, including those composed of mineral particles, by altering the four elements of the intestinal barrier function. The aim of this review is to provide a critical opinion on the potential of TiO2 particles, especially when used as a food additive, to alter the four elements of the intestinal barrier function, and consequently to evaluate if this additive would likely play a role in the development and/or exacerbation of IBD.

FAK alternative splice mRNA variants expression pattern in colorectal cancer.

The Focal adhesion kinase (FAK) is a ubiquitous cytoplasmic tyrosine-kinase promoting tumor progression and metastasis processes by acting in cancer cells and their tumor microenvironment partners. FAK overexpression in primary colon tumors and their metastasis is associated to poor colorectal cancer (CRC) patients' outcome. Eight FAK mRNA alternative splice variants have been described and contribute to additional level of FAK activity regulation, some of them corresponding to overactivated FAK isoforms. To date, FAK mRNA alternative splice variants expression and implication in CRC processes remain unknown. Here, using different human CRC cells lines displaying differential invasive capacities in an in vivo murine model recapitulating the different steps of CRC development from primary tumors to liver and lung metastasis, we identified three out of the eight mRNA variants (namely FAK0 , FAK28 and FAK6 ) differentially expressed along the CRC process and the tumor sites. Our results highlight an association between FAK0 and FAK6 expressions and the metastatic potential of the most aggressive cell lines HT29 and HCT116, suggesting that FAK0 and FAK6 could represent aggressiveness markers in CRC. Our findings also suggest a more specific role for FAK28 in the interactions between the tumors cells and their microenvironment. In conclusion, targeting FAK0 , the common form of FAK, might not be a good strategy based on the numerous roles of this kinase in physiological processes. In contrast, FAK6 or FAK28 splice variants, or their corresponding protein isoforms, may putatively represent future therapeutic target candidates in the development of CRC primary tumors and metastasis.

Latest Advances in Targeting the Tumor Microenvironment for Tumor Suppression.

The tumor bulk is composed of a highly heterogeneous population of cancer cells, as well as a large variety of resident and infiltrating host cells, extracellular matrix proteins, and secreted proteins, collectively known as the tumor microenvironment (TME). The TME is essential for driving tumor development by promoting cancer cell survival, migration, metastasis, chemoresistance, and the ability to evade the immune system responses. Therapeutically targeting tumor-associated macrophages (TAMs), cancer-associated fibroblasts (CAFs), regulatory T-cells (T-regs), and mesenchymal stromal/stem cells (MSCs) is likely to have an impact in cancer treatment. In this review, we focus on describing the normal physiological functions of each of these cell types and their behavior in the cancer setting. Relying on the specific surface markers and secreted molecules in this context, we review the potential targeting of these cells inducing their depletion, reprogramming, or differentiation, or inhibiting their pro-tumor functions or recruitment. Different approaches were developed for this targeting, namely, immunotherapies, vaccines, small interfering RNA, or small molecules.

Anti-inflammatory and anticancer effects of flavonol glycosides from Diplotaxis harra through GSK3ß regulation in intestinal cells.

CONTEXT AND OBJECTIVE: Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) is traditionally used as an antidiabetic, anti-inflammatory or anticancer agent. In these pathologies, the glycogen synthase kinase 3 ß (GSK3ß) is overactivated and represents an interesting therapeutic target. Several flavonoids can inhibit GSK3ß and the purpose of this study was to search for the compounds in Diplotaxis harra which are able to modulate GSK3ß. MATERIALS AND METHODS: Methanol extracts from D. harra flowers were prepared and the bio-guided fractionation of their active compounds was performed using inflammatory [protease-activated receptor 2 (PAR2)-stimulated IEC6 cells] and cancer (human Caco-2 cell line) intestinal cells. 50-100 µg/mL of fractions or compounds purified by HPLC were incubated with cells whose inhibited form of GSK3ß (Pser9 GSK3ß) and survival were analyzed by Western blot at 1 h and colorimetric assay at 24 h, respectively. LC-UV-MS profiles and MS-MS spectra were used for the characterization of extracts and flavonoids-enriched fractions, and the identification of pure flavonoids was achieved by MS and NMR analysis. RESULTS: The methanol extract from D. harra flowers and its flavonoid-enriched fraction inhibit GSK3ß in PAR2-stimulated IEC6 cells. GSK3ß inhibition by the flavonoid-enriched D. harra fraction was dependent on PKC activation. The flavonoid-enriched D. harra fraction and its purified compound isorhamnetin-3,7-di-O-glucoside induced a 20% decrease of PAR2-stimulated IEC6 and Caco-2 cell survival. Importantly, normal cells (non-stimulated IEC6 cells) were spared by these treatments. CONCLUSION: This work indicates that flavonoids from D. harra display cytotoxic activity against inflammatory and cancer intestinal cells which could depend on GSK3ß inhibition.

PAR2-dependent activation of GSK3ß regulates the survival of colon stem/progenitor cells.

Protease-activated receptors PAR1 and PAR2 play an important role in the control of epithelial cell proliferation and migration. However, the survival of normal and tumor intestinal stem/progenitor cells promoted by proinflammatory mediators may be critical in oncogenesis. The glycogen synthase kinase-3ß (GSK3ß) pathway is overactivated in colon cancer cells and promotes their survival and drug resistance. We thus aimed to determine PAR1 and PAR2 effects on normal and tumor intestinal stem/progenitor cells and whether they involved GSK3ß. First, PAR1 and PAR2 were identified in colon stem/progenitor cells by immunofluorescence. In three-dimensional cultures of murine crypt units or single tumor Caco-2 cells, PAR2 activation decreased numbers and size of normal or cancerous spheroids, and PAR2-deficient spheroids showed increased proliferation, indicating that PAR2 represses proliferation. PAR2-stimulated normal cells were more resistant to stress (serum starvation or spheroid passaging), suggesting prosurvival effects of PAR2 Accordingly, active caspase-3 was strongly increased in PAR2-deficient normal spheroids. PAR2 but not PAR1 triggered GSK3ß activation through serine-9 dephosphorylation in normal and tumor cells. The PAR2-triggered GSK3ß activation implicates an arrestin/PP2A/GSK3ß complex that is dependent on the Rho kinase activity. Loss of PAR2 was associated with high levels of GSK3ß nonactive form, strengthening the role of PAR2 in GSK3ß activation. GSK3 pharmacological inhibition impaired the survival of PAR2-stimulated spheroids and serum-starved cells. Altogether our data identify PAR2/GSK3ß as a novel pathway that plays a critical role in the regulation of stem/progenitor cell survival and proliferation in normal colon crypts and colon cancer.

Activation of Src family tyrosine kinases by ferric ions.

The Src-family tyrosine kinases (SFKs) are oncogenic enzymes that contribute to the initiation and progression of many types of cancer. In normal cells, SFKs are kept in an inactive state mainly by phosphorylation of a consensus regulatory tyrosine near the C-terminus (Tyr(530) in the SFK c-Src). As recent data indicate that tyrosine modification enhances binding of metal ions, the hypothesis that SFKs might be regulated by metal ions was investigated. The c-Src C-terminal peptide bound two Fe(3+) ions with affinities at pH4.0 of 33 and 252µM, and phosphorylation increased the affinities at least 10-fold to 1.4 and 23µM, as measured by absorbance spectroscopy. The corresponding phosphorylated peptide from the SFK Lyn bound two Fe(3+) ions with much higher affinities (1.2pM and 160nM) than the Src C-terminal peptide. Furthermore, when Lyn or Hck kinases, which had been stabilised in the inactive state by phosphorylation of the C-terminal regulatory tyrosine, were incubated with Fe(3+) ions, a significant enhancement of kinase activity was observed. In contrast Lyn or Hck kinases in the unphosphorylated active state were significantly inhibited by Fe(3+) ions. These results suggest that Fe(3+) ions can regulate SFK activity by binding to the phosphorylated C-terminal regulatory tyrosine.

Identification of the F1-ATPase at the cell surface of colonic epithelial cells: role in mediating cell proliferation.

F1 domain of F(1)F(o)-ATPase was initially believed to be strictly expressed in the mitochondrial membrane. Interestingly, recent reports have shown that the F1 complex can serve as a cell surface receptor for apparently unrelated ligands. Here we show for the first time the presence of the F(1)-ATPase at the cell surface of normal or cancerous colonic epithelial cells. Using surface plasmon resonance technology and mass spectrometry, we identified a peptide hormone product of the gastrin gene (glycine-extended gastrin (G-gly)) as a new ligand for the F(1)-ATPase. By molecular modeling, we identified the motif in the peptide sequence (E(E/D)XY), that directly interacts with the F(1)-ATPase and the amino acids in the F(1)-ATPase that bind this motif. Replacement of the Glu-9 residue by an alanine in the E(E/D)XY motif resulted in a strong decrease of G-gly binding to the F(1)-ATPase and the loss of its biological activity. In addition we demonstrated that F(1)-ATPase mediates the growth effects of the peptide. Indeed, blocking F(1)-ATPase activity decreases G-gly-induced cell growth. The mechanism likely involves ADP production by the membrane F(1)-ATPase, which is induced by G-gly. These results suggest an important contribution of cell surface F(1)-ATPase in the pro-proliferative action of this gastrointestinal peptide.

Establishing 20S Proteasome Genetic, Translational and Post-Translational Status from Precious Biological and Patient Samples with Top-Down MS.

The mammalian 20S catalytic core of the proteasome is made of 14 different subunits (α1-7 and ß1-7) but exists as different subtypes depending on the cell type. In immune cells, for instance, constitutive catalytic proteasome subunits can be replaced by the so-called immuno-catalytic subunits, giving rise to the immunoproteasome. Proteasome activity is also altered by post-translational modifications (PTMs) and by genetic variants. Immunochemical methods are commonly used to investigate these PTMs whereby protein-tagging is necessary to monitor their effect on 20S assembly. Here, we present a new miniaturized workflow combining top-down and bottom-up mass spectrometry of immunopurified 20S proteasomes that analyze the proteasome assembly status as well as the full proteoform footprint, revealing PTMs, mutations, single nucleotide polymorphisms (SNPs) and induction of immune-subunits in different biological samples, including organoids, biopsies and B-lymphoblastoid cell lines derived from patients with proteasome-associated autoinflammatory syndromes (PRAAS). We emphasize the benefits of using top-down mass spectrometry in preserving the endogenous conformation of protein modifications, while enabling a rapid turnaround (1 h run) and ensuring high sensitivity (1-2 pmol) and demonstrate its capacity to semi-quantify constitutive and immune proteasome subunits.

Colon Fibroblasts and Inflammation: Sparring Partners in Colorectal Cancer Initiation?

Colorectal cancer (CRC) is the third most common cause of cancer-related death. Significant improvements in CRC treatment have been made for the last 20 years, on one hand thanks to a better detection, allowing surgical resection of the incriminated area, and on the other hand, thanks to a better knowledge of CRC's development allowing the improvement of drug strategies. Despite this crucial progress, CRC remains a public health issue. The current model for CRC initiation and progression is based on accumulation of sequential known genetic mutations in the colon epithelial cells' genome leading to a loss of control over proliferation and survival. However, increasing evidence reveals that CRC initiation is more complex. Indeed, chronic inflammatory contexts, such as inflammatory bowel diseases, have been shown to increase the risk for CRC development in mice and humans. In this manuscript, we review whether colon fibroblasts can go from the main regulators of the ISC homeostasis, regulating not only the renewal process but also the epithelial cells' differentiation occurring along the colon crypt, to the main player in the initiation of the colorectal cancer process due to chronic inflammation.

Morphological profiling of human T and NK lymphocytes by high-content cell imaging.

The immunological synapse is a complex structure that decodes stimulatory signals into adapted lymphocyte responses. It is a unique window to monitor lymphocyte activity because of development of systematic quantitative approaches. Here we demonstrate the applicability of high-content imaging to human T and natural killer (NK) cells and develop a pipeline for unbiased analysis of high-definition morphological profiles. Our approach reveals how distinct facets of actin cytoskeleton remodeling shape immunological synapse architecture and affect lytic granule positioning. Morphological profiling of CD8+ T cells from immunodeficient individuals allows discrimination of the roles of the ARP2/3 subunit ARPC1B and the ARP2/3 activator Wiskott-Aldrich syndrome protein (WASP) in immunological synapse assembly. Single-cell analysis further identifies uncoupling of lytic granules and F-actin radial distribution in ARPC1B-deficient lymphocytes. Our study provides a foundation for development of morphological profiling as a scalable approach to monitor primary lymphocyte responsiveness and to identify complex aspects of lymphocyte micro-architecture.

Cytolethal Distending Toxin Promotes Replicative Stress Leading to Genetic Instability Transmitted to Daughter Cells.

The cytolethal distending toxin (CDT) is produced by several Gram-negative pathogenic bacteria. In addition to inflammation, experimental evidences are in favor of a protumoral role of CDT-harboring bacteria such as Escherichia coli, Campylobacter jejuni, or Helicobacter hepaticus. CDT may contribute to cell transformation in vitro and carcinogenesis in mice models, through the genotoxic action of CdtB catalytic subunit. Here, we investigate the mechanism of action by which CDT leads to genetic instability in human cell lines and colorectal organoids from healthy patients' biopsies. We demonstrate that CDT holotoxin induces a replicative stress dependent on CdtB. The slowing down of DNA replication occurs mainly in late S phase, resulting in the expression of fragile sites and important chromosomic aberrations. These DNA abnormalities induced after CDT treatment are responsible for anaphase bridge formation in mitosis and interphase DNA bridge between daughter cells in G1 phase. Moreover, CDT-genotoxic potential preferentially affects human cycling cells compared to quiescent cells. Finally, the toxin induces nuclear distension associated to DNA damage in proliferating cells of human colorectal organoids, resulting in decreased growth. Our findings thus identify CDT as a bacterial virulence factor targeting proliferating cells, such as human colorectal progenitors or stem cells, inducing replicative stress and genetic instability transmitted to daughter cells that may therefore contribute to carcinogenesis. As some CDT-carrying bacterial strains were detected in patients with colorectal cancer, targeting these bacteria could be a promising therapeutic strategy.

Expression of gastrin precursors by CD133-positive colorectal cancer cells is crucial for tumour growth.

Precursors of the hormone gastrin, progastrin and glycine-extended gastrin (G-gly), have been detected in colorectal polyps and tumours, and in the blood of patients with colorectal cancer (CRC), while their expression is lower in healthy subjects. The surface glycoproteins CD133 and CD44 have been identified as possible markers for CRC stem cells. Our aims were to investigate whether progastrin and G-gly are expressed by CD133-positive cells in human CRC tissues and in the human CRC cell line DLD-1, and to determine whether this expression is biologically relevant. The great majority of the cells expressing CD133 also expressed gastrin precursors in both DLD-1 cells, which retain a stem cell-like subpopulation, and human CRC specimens. The CD133high/CD44high/progastrinhigh cells gave rise to larger tumours in SCID mice compared to CD133low/CD44low/progastrinlow cells. The CD133high/CD44high/progastrinhigh cells displayed enhanced activation of the signalling molecules JAK2, STAT3, ERK1/2 and Akt, known to regulate the induction of proliferation and/or survival by gastrin precursors. Moreover, downregulation of the gastrin gene in DLD-1 cells reduced the expression of cancer stem cell markers and abolished tumour development in SCID mice. We conclude that gastrin precursors may provide a target for therapies directed against the cells responsible for tumour development and recurrence.

A gastrin precursor, gastrin-gly, upregulates VEGF expression in colonic epithelial cells through an HIF-1-independent mechanism.

One of the major angiogenic factor released by tumor cells is VEGF. Its high expression is correlated with poor prognosis in colorectal tumors. In colon cancer, gastrin gene expression is also upregulated. In these tumors, gastrin precursors are mainly produced and act as growth factors. Recently, a study has also shown that the gastrin precursor, G-gly induced in vitro tubules formation by vascular endothelial cells suggesting a potential proangiogenic role. Here, we demonstrate that stimulation of human colorectal cancer cell lines with G-gly increases the expression of the proangiogenic factor VEGF at the mRNA and protein levels. In addition, blocking the progastrin autocrine loop leads to a downregulation of VEGF. Although HIF-1 is a major transcriptional activator for VEGF our results suggest an alternative mechanism for VEGF regulation in normoxic conditions, independent of HIF-1 that involves the PI3K/AKT pathway. Indeed we show that G-gly does not lead to HIF-1 accumulation in colon cancer cells. Moreover, we found that G-gly activates the PI3K/AKT pathway and inhibition of this pathway reverses the effects of G-gly observed on VEGF mRNA and protein levels. In correlation with these results, we observed in vivo, on colon tissue sections from transgenic mice overexpressing G-gly, an increase in VEGF expression in absence of HIF-1 accumulation. In conclusion, our study demonstrates that gastrin precursors, known to promote colon epithelial cells proliferation and survival can also contribute to the angiogenesis process by stimulating the expression of the proangiogenic factor VEGF via the PI3K pathway and independently of hypoxia conditions.

Stimulation of proliferation in the colorectal mucosa by gastrin precursors is blocked by desferrioxamine.

Precursors of the peptide hormone gastrin stimulate proliferation in the colorectal mucosa and promote the development of colorectal carcinoma. Gastrins bind two ferric ions selectively and with high affinity, and the biological activity of glycine-extended gastrin (Ggly) in vitro is dependent on the presence of ferric ions. The aim of the present study was to determine whether or not iron is required for biological activity of progastrin and Ggly in vivo. Rats that had undergone a colostomy were infused with Ggly, and proliferation was measured in the defunctioned rectal mucosa. Proliferation was also measured in the colonic mucosa of hGAS and MTI-Ggly mice, which, by definition, overexpress progastrin and Ggly, respectively. The requirement for iron was assessed by thrice-weekly injection of the chelating agent desferrioxamine (DFO). The proliferation index in the defunctioned rectal mucosa was significantly increased in the Ggly-infused rats, and the increase was significantly reduced after treatment with DFO. Treatment with DFO significantly reduced the crypt height and proliferation index in the colonic mucosa of hGAS and MTI-Ggly mice but had no effect on the same variables in wild-type mice. These observations are consistent with the hypothesis that the biological activity of progastrin and Ggly in vivo is dependent on the presence of ferric ions and further suggest that chelating agents may block the stimulatory effects of gastrin precursors in the development of colorectal carcinoma.

Extracellular Matrix Mechanical Properties and Regulation of the Intestinal Stem Cells: When Mechanics Control Fate.

Intestinal stem cells (ISC) are crucial players in colon epithelium physiology. The accurate control of their auto-renewal, proliferation and differentiation capacities provides a constant flow of regeneration, maintaining the epithelial intestinal barrier integrity. Under stress conditions, colon epithelium homeostasis in disrupted, evolving towards pathologies such as inflammatory bowel diseases or colorectal cancer. A specific environment, namely the ISC niche constituted by the surrounding mesenchymal stem cells, the factors they secrete and the extracellular matrix (ECM), tightly controls ISC homeostasis. Colon ECM exerts physical constraint on the enclosed stem cells through peculiar topography, stiffness and deformability. However, little is known on the molecular and cellular events involved in ECM regulation of the ISC phenotype and fate. To address this question, combining accurately reproduced colon ECM mechanical parameters to primary ISC cultures such as organoids is an appropriated approach. Here, we review colon ECM physical properties at physiological and pathological states and their bioengineered in vitro reproduction applications to ISC studies.

Characterization of Human Colon Organoids From Inflammatory Bowel Disease Patients.

Inflammatory Bowel Diseases (IBD) are chronic inflammatory disorders, where epithelial defects drive, at least in part, some of the pathology. We reconstituted human intestinal epithelial organ, by using three-dimension culture of human colon organoids. Our aim was to characterize morphological and functional phenotypes of control (non-IBD) organoids, compared to inflamed organoids from IBD patients. The results generated describe the epithelial defects associated with IBD in primary organoid cultures, and evaluate the use of this model for pharmacological testing of anti-inflammatory approaches. Human colonic tissues were obtained from either surgical resections or biopsies, all harvested in non-inflammatory zones. Crypts were isolated from controls (non-IBD) and IBD patients and were cultured up to 12-days. Morphological (size, budding formation, polarization, luminal content), cell composition (proliferation, differentiation, immaturity markers expression), and functional (chemokine and tight junction protein expression) parameters were measured by immunohistochemistry, RT-qPCR or western-blot. The effects of inflammatory cocktail or anti-inflammatory treatments were studied in controls and IBD organoid cultures respectively. Organoid cultures from controls or IBD patients had the same cell composition after 10 to 12-days of culture, but IBD organoid cultures showed an inflammatory phenotype with decreased size and budding capacity, increased cell death, luminal debris, and inverted polarization. Tight junction proteins were also significantly decreased in IBD organoid cultures. Inflammatory cytokine cocktail reproduced this inflammatory phenotype in non-IBD organoids. Clinically used treatments (5-ASA, glucocorticoids, anti-TNF) reduced some, but not all parameters. Inflammatory phenotype is associated with IBD epithelium, and can be studied in organoid cultures. This model constitutes a reliable human pre-clinical model to investigate new strategies targeting epithelial repair.

Evidence for a direct and functional interaction between the regulators of G protein signaling-2 and phosphorylated C terminus of cholecystokinin-2 receptor.

Signaling of G protein-coupled receptors (GPCRs) is regulated by different mechanisms. One of these involves regulators of G protein signaling (RGS), which are diverse and multifunctional proteins that bind to active Galpha subunits of G proteins and act as GTPase-activating proteins. Little is known about the molecular mechanisms that govern the selective use of RGS proteins in living cells. We first demonstrated that CCK2R-mediated inositol phosphate production, known to be G(q)-dependent, is more sensitive to RGS2 than to RGS4 and is insensitive to RGS8. Both basal and agonist-stimulated activities of the CCK2R are regulated by RGS2. By combining biochemical, functional, and in silico structural approaches, we demonstrate that a direct and functional interaction occurs between RGS2 and agonist-stimulated cholecystokinin receptor-2 (CCK2R) and identified the precise residues involved: phosphorylated Ser434 and Thr439 located in the C-terminal tail of CCK2R and Lys62, Lys63, and Gln67, located in the N-terminal domain of RGS2. These findings confirm previous reports that RGS proteins can interact with GPCRs to modulate their signaling and provide a molecular basis for RGS2 recognition by the CCK2R.

Epidermal growth factor receptor mutants from human lung cancers exhibit enhanced catalytic activity and increased sensitivity to gefitinib.

Somatic mutations within the epidermal growth factor receptor (EGFR) kinase domain are detected in 10% to 30% of human non-small cell lung cancers and are correlated with striking clinical responses in a subset of patients treated with EGFR kinase inhibitors, such as gefitinib and erlotinib. Cell-based studies suggest that these mutant EGFRs promote increased autophosphorylating activity on a subset of EGFR COOH-terminal tyrosines and the consequent engagement of a subset of downstream effectors. Because EGFR function is regulated at multiple levels in vivo, and it is therefore difficult to assess the direct consequences of these mutations on EGFR enzyme function, we measured EGFR catalytic activity in in vitro kinase assays using purified recombinant proteins corresponding to the cytoplasmic domain of wild-type and two frequently detected EGFR mutants (DelL747-P753insS and L858R). Both mutants exhibit substantially increased autophosphorylating activity relative to wild-type EGFR, and they exhibit distinct reaction kinetics. In addition, the mutant kinases are more sensitive to kinase inhibition by gefitinib, which seems to reflect their increased drug affinity. These findings suggest that the altered signaling properties and drug sensitivity of these EGFR mutants that have been observed in vivo largely result from differences in the catalytic properties of the kinase. In addition, we find that the T790M secondary "drug resistance mutation" of EGFR, which frequently arises in relapsed patients that initially responded to treatment, confers enhanced kinase activity to primary activating EGFR alleles and may, therefore, be oncogenic in some contexts.

Protease-Activated Receptors in the Intestine: Focus on Inflammation and Cancer.

Protease-activated receptors (PARs) belong to the G protein-coupled receptor (GPCR) family. Compared to other GPCRs, the specificity of the four PARs is the lack of physiologically soluble ligands able to induce their activation. Indeed, PARs are physiologically activated after proteolytic cleavage of their N-terminal domain by proteases. The resulting N-terminal end becomes a tethered activation ligand that interact with the extracellular loop 2 domain and thus induce PAR signal. PARs expression is ubiquitous and these receptors have been largely described in chronic inflammatory diseases and cancer. In this review, after describing their discovery, structure, mechanisms of activation, we then focus on the roles of PARs in the intestine and the two main diseases affecting the organ, namely inflammatory bowel diseases and cancer.