Protease‐activated receptor signaling in intestinal permeability regulation

Protease-activated receptors (PARs) are a unique class of G-protein-coupled transmembrane receptors, which revolutionized the perception of proteases from degradative enzymes to context-specific signaling factors. Although PARs are traditionally known to affect several vascular responses, recent investigations have started to pinpoint the functional role of PAR signaling in the gastrointestinal (GI) tract. This organ is exposed to the highest number of proteases, either from the gut lumen or from the mucosa. Luminal proteases include the host's digestive enzymes and the proteases released by the commensal microbiota, while mucosal proteases entail extravascular clotting factors and the enzymes released from resident and infiltrating immune cells. Active proteases and, in case of a disrupted gut barrier, even entire microorganisms are capable to translocate the intestinal epithelium, particularly under inflammatory conditions. Especially PAR-1 and PAR-2, expressed throughout the GI tract, impact gut permeability regulation, a major factor affecting intestinal physiology and metabolic inflammation. In addition, PARs are critically involved in the onset of inflammatory bowel diseases, irritable bowel syndrome, and tumor progression. Due to the number of proteases involved and the multiple cell types affected, selective regulation of intestinal PARs represents an interesting therapeutic strategy. The analysis of tissue/cell-specific knockout animal models will be of crucial importance to unravel the intrinsic complexity of this signaling network. Here, we provide an overview on the implication of PARs in intestinal permeability regulation under physiologic and disease conditions.info:eu-repo/semantics/publishedVersio

Toll-like Receptors are Key Participants in Innate Immune Responses

During an infection, one of the principal challenges for the host is to detect the pathogen and activate a rapid defensive response. The Toll-like family of receptors (TLRs), among other pattern recognition receptors (PRR), performs this detection process in vertebrate and invertebrate organisms. These type I transmembrane receptors identify microbial conserved structures or pathogen-associated molecular patterns (PAMPs). Recognition of microbial components by TLRs initiates signaling transduction pathways that induce gene expression. These gene products regulate innate immune responses and further develop an antigen-specific acquired immunity. TLR signaling pathways are regulated by intracellular adaptor molecules, such as MyD88, TIRAP/Mal, between others that provide specificity of individual TLR- mediated signaling pathways. TLR-mediated activation of innate immunity is involved not only in host defense against pathogens but also in immune disorders. The involvement of TLR-mediated pathways in auto-immune and inflammatory diseases is described in this review articl

Intra- and intercompartmental movement of gammadelta T cells: intestinal intraepithelial and peripheral gammadelta T cells represent exclusive nonoverlapping populations with distinct migration characteristics.

International audienceUnlike the ∼1% of γδ TCR-positive T cells being regularly present in blood and secondary lymphoid organs (peripheral γδ T cells), ∼50-60% of small intestinal intraepithelial lymphocytes (iIELs) in the mouse express the γδ TCR (γδ iIELs). In this study, we investigated the overlap and exchange of γδ iIELs and γδ T cells found in peripheral secondary lymphoid organs. Using two-photon laser-scanning microscopy, we found γδ T cells within peripheral lymph nodes to be highly motile, whereas γδ iIELs were characterized by a locally confined scanning behavior. Our results implied a strict separation of peripheral γδ T cells and γδ iIELs. Nevertheless, γδ iIELs could be efficiently regenerated from bone marrow-derived precursors in irradiated or T cell-deficient adult mice. However, outside the intestinal epithelium, survival of γδ iIELs was very poor. In CCR9-deficient mice, homing of γδ iIELs was impaired, but did not lead to an accumulation of γδ iIEL-like cells in the periphery. Conversely, in situations in which specific γδ iIEL niches were empty, adoptive transfer of isolated γδ iIELs led to a sustained engraftment of transferred γδ iIELs in the intestinal epithelium for at least 100 d. Furthermore, we demonstrated by heterotopic intestinal transplantation experiments that an exchange of γδ iIELs only rarely happens in the steady state of adult mice. We therefore conclude that peripheral versus intestinal intraepithelial γδ T cells are exclusive, nonoverlapping populations that virtually do not exchange with each other

Mice deficient in the anti-haemophilic coagulation factor VIII show increased von Willebrand factor plasma levels - Table 1

<p>Mice deficient in the anti-haemophilic coagulation factor VIII show increased von Willebrand factor plasma levels</p> - Table

Increased VWF staining of the hepatic endothelium of <i>F8</i>^<i>-/y</i> mice.

<p>(<b>A</b>) Representative hepatic tissue sections of <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice stained with anti-human VWF antibody (100x and 400x magnification). (<b>B</b>) Visual scoring of the VWF stained hepatic tissue sections of <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 7,6). (<b>C</b>) Hepatic VWF transcript levels in <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 4,7). All data were expressed as means ± SEM. Statistical comparisons were performed using the Student’s <i>t</i>-test, ** p<0.01.</p

Increased VWF levels in the plasma of <i>F8</i>^<i>-/y</i> mice.

<p>(<b>A</b>) VWF antigen levels in plasma of <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 9). (<b>B</b>) VWF multimer analysis of plasma samples from <i>F8</i>^<i>+/y</i> vs <i>F8</i>^<i>-/y</i> mice (n = 5). (<b>C</b>) ADAMTS13 levels in plasma of <i>F8</i>^<i>+/y</i> vs <i>F8</i>^<i>-/y</i> mice (n = 7). (<b>D</b>) VWF antigen levels in plasma of <i>F8</i>^<i>-/y</i> mice, 2h after tail vein injection of recombinant FVIII (Kogenate) at a dose of 1.5 U per 30g body weight or with 0.9% NaCl solution as a vehicle control (n = 11,10,12). All data were expressed as means ± SEM. Statistical comparisons were performed using the Student’s <i>t</i>-test or one-way ANOVA, * p< 0.05, ** p<0.01.</p

Bleeding phenotype of the <i>F8</i>^<i>-/y</i> mice.

<p>(<b>A</b>) Patella diameter before and 24h after joint bleeding induction to the right knee (n = 7,6) of C57BL/6J and <i>F8</i>^<i>-/y</i> with the left knee (n = 6,6) set as a control. (<b>B</b>) Representative rotational thromboelastometry (ROTEM) graphs of a C57BL/6J and a <i>F8</i>^<i>-/y</i>, illustrating clotting time (green), clot formation time (pink) and clot firmness (blue). (<b>C</b>) Clotting times and (<b>D</b>) clot formation times of C57BL/6J, <i>F8</i>^<i>-/y</i>, and <i>F8</i>^<i>-/y</i> blood samples reconstituted with 2.5 U/ml of human recombinant FVIII (n = 3). All data were expressed as means ± SEM. Statistical comparisons were performed using one-way ANOVA or two-way ANOVA * p< 0.05, ** p<0.01, ***p<0.001.</p

Low-grade inflammatory phenotype in the liver of <i>F8</i>^<i>-/y</i> mice.

<p>(<b>A</b>) FVIII (n = 5,4), (<b>B</b>) TNFα (n = 6,7), (<b>C</b>) CD45 (n = 7), and (<b>D</b>) TLR4 (n = 6,4) hepatic transcript levels of <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice. (<b>E</b>) Representative hepatic tissue sections of <i>F8</i>^<i>+/y</i> vs <i>F8</i>^<i>-/y</i> stained with anti-mouse F4/80 antibody (200x magnification). (<b>F</b>) Visual scoring of the F4/80 stained hepatic tissue sections (n = 5). (<b>G</b>) Hepatic transcript levels of the macrophage marker F4/80 in <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 4,7). (<b>H</b>) Hepatic SAA3 transcript levels in <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 5,5). (<b>I</b>) Serum glutamate-pyruvate-transaminase levels in <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 5,5). (<b>J</b>) Serum glutamat-oxalacetat-transaminase levels in <i>F8</i>^<i>+/y</i> (WT) vs <i>F8</i>^<i>-/y</i> mice (n = 6,5). All data were expressed as means ± SEM. Statistical comparisons were performed using the Student’s <i>t</i>-test, * p< 0.05, ***p<0.001, ****p<0.0001.</p