Les récepteurs aux éléments microbiens dans l'intestin : analyse de leur expression dans les différents segments et organes lymphoïdes et le long de l'axe crypto-villositaire

Session 3 : Dialogue agresseurs-hôtes, adaptation réciproquesCommunication oraleabsen

Des prébiotiques capables d’induire des mécanismes de tolérance sans réduire les symptômes d’allergie chez la souris

National audienc

Pattern recognition receptors are differentially expressed in the pig small intestine

International audiencePattern Recognition Receptors (PRR) include Toll-like receptors and NOD-like receptors. These molecules are involved in the innate immune response to infection, triggering inflammatory responses. The aim of this study was to determine if PRR and inflammatory cytokines are differentially expressed along the intestinal segments and relative lymphoid organs of healthy pigs. Duodenum, jejunum, ileum, jejunal Peyer patches, ileal Peyer patches and mesenteric lymph nodes were collected from 32 healthy pigs to study the expression of genes encoding for PRR (Tolllike receptors 1 to 10, NOD1 and NOD2) and inflammatory cytokines by quantitative PCR. Toll-like receptors 1, 2, 4, 5, 6, 8, 9, 10 were less expressed in the duodenum than in the other intestinal segments. Toll-like receptors 1, 2, 4, 7, 8, 9, 10, NOD1, 2 were more expressed in the mesenteric lymph nodes than in the intestinal segments. Toll-like receptors 1, 7, 8, 9, 10 showed a more pronounced expression in Peyer patches than in relative intestinal segment. A heatmap analysis of our data highlights two distinct clusters of organs. Intestinal segments belong to the first cluster. They displayed high expression levels of TLR 5, 6 and IL-1 beta. Among these segments, duodenum was characterized by a weak expression of PRRs and cytokines, which may be related to its local lumen environment, poor in microorganisms. Lymphoid organs belong to the second cluster. They showed weak expression levels of TLR3, 5 and IL-1 beta and a high expression of TLR 1, 2, 7, 9, 10, IL-6 and TNF-alpha. Among these organs, mesenteric lymph nodes presented a high expression of most PRR and inflammatory cytokines, which may be related to their antigen uptake function. Our findings demonstrate thus that PRR and cytokines are differentially expressed along the intestine, highlighting segment-specific mechanisms. Acknowledgment: The present study was supported by the ANR “Sus Flora” research grant (coordinator: Claire Rogel-Gaillard)

Previous food allergy aggravates allergic markers and intestinal damages in a mouse model of asthma

International audienceIncreasing clinical data suggest a link between food allergy and the later development of respiratory allergy. This progression may be triggered by exposures to different allergens but the mechanism implicated remains unknown. This study aimed to identify the impact of a first exposure to food allergen on the development of a new form of allergy caused by exposure to a novel allergen using a mouse model

Pattern recognition receptors in the gut: analysis of their expression along the intestinal tract and the crypt/villus axis

Pattern recognition receptors (PRRs) play a critical role in the detection of microorganisms and the induction of inflammatory and immune responses. Using PCR and Western-blot analysis, this study investigated the differential expression in the intestine of 14 PRRs and nine associated cytokines. Thirty-two pigs were used to determine the expression of these markers (1) along the proximal/distal axis of the small intestine (duodenum, jejunum, and ileum) and (2) between the intestinal segments and their respective lymphoid organs (Peyer's patches [PP] and mesenteric lymph nodes [MLN]). Six additional animals were used to quantify the expression of these genes along the crypt/villus axis of jejunum, using microdissected samples. Most genes showed increased expression (1) in the distal than in the proximal parts of the small intestine (TLR3, 5, RIG-I, IL-1β, IL-8, and IFN-γ); (2) in lymphoid organs (TLR1, 2, 6, 9, 10, IL-10, TNF-α), especially the MLN (TLR4, 7, 8, NOD1, NOD2, NALP3, IFN-α, IL-6, IL-12, and TGF-β), than in intestinal segments. The analysis along the crypt/villus identified: (1) genes with higher expression in lamina propria (TLR1, 2, 4, 9, NOD1, NOD2, IL-1β, IL-10, TGF-β, TNF-α) and (2) genes with higher expression in the villus (TLR3, 5, 6, RIG-I, IL-6). These results highlight the differential expression of PRRs and cytokines along the proximal/distal and the crypt/villus axis of the intestine, contributing to a fine analysis of the complex functional architecture of the small intestine and should be related to the gut microbiota

Identification of signaling pathways targeted by the food contaminant FB1: Transcriptome and kinome analysis of samples from pig liver and intestine

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium species. In mammals, this toxin causes widespread organ-specific damage; it promotes hepatotoxicity, is immunotoxic, alters intestinal functions… Despite its inhibitory effect on de novo ceramide synthesis, its molecular mechanism of action and toxicity are not totally elucidated. To explore the mechanism of FB1 toxicity, we analyzed the transcriptome and kinome of two organs targeted by FB1: the liver and the jejunum. Pigs were fed for 4 weeks on a control diet or a FB1-contaminated diet (10 mg/kg). As expected, FB1-exposed pigs gained less weight and displayed a higher sphinganine/sphingosine ratio. Comparison of the transcriptomes and the kinomes of treated versus control pigs showed striking differences. Among the disrupted pathways in liver and jejunum, we highlight Protein Kinase B (AKT) / Phosphatase and tensin homolog (PTEN) at the intersection of the FB1-modulated pathways. Most of the effects of FB1 are mediated by the regulation of ceramide level, which influences protein phosphatase 2 (PP2A) and the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway. This pathway might be a new target to counteract toxic effect of Fumonin B1 which are on of the most spread nutritional's contaminant in the world. This article is protected by copyright. All rights reserved

Tissular Genomic Responses to Oral FB1 Exposure in Pigs

Fumonisin B1 (FB1) is a widespread mycotoxin produced by fungal Fusarium species—mainly in maize, one of the plants most commonly used for food and feed. Pigs and horses are the animal species most susceptible to this mycotoxin. FB1 exposure can cause highly diverse clinical symptoms, including hepatotoxicity, immunotoxicity, and intestinal barrier function disturbance. Inhibition of ceramide synthetase is a well-understood ubiquitous molecular mechanism of FB1 toxicity, but other more tissue-specific effects remain to be elucidated. To investigate the effects of FB1 in different exposed tissues, we cross-analyzed the transcriptomes of fours organs: liver, jejunum, jejunal Peyer’s patches, and spleen. During a four-week study period, pigs were fed a control diet or a FB1-contaminated diet (10 mg/kg feed). In response to oral FB1 exposure, we observed common biological processes in the four organs, including predominant and recurrent processes (extracellular matrix organization, integrin activation, granulocyte chemotaxis, neutrophil migration, and lipid and sterol homeostasis), as well as more tissue-specific processes that appeared to be related to lipid outcomes (cell cycle regulation in jejunum, and gluconeogenesis in liver)

The protective role of liver X receptor (LXR) during fumonisin B1-induced hepatotoxicity

International audienceFumonisin B1 (FB1), a congener of fumonisins produced by Fusarium species, is the most abundant and most toxicologically active fumonisin. FB1 causes severe mycotoxicosis in animals, including nephrotoxicity, hepatotoxicity, and disruption of the intestinal barrier. However, mechanisms associated with FB1 toxicity are still unclear. Preliminary studies have highlighted the role of liver X receptors (LXRs) during FB1 exposure. LXRs belong to the nuclear receptor family and control the expression of genes involved in cholesterol and lipid homeostasis. In this context, the toxicity of FB1 was compared in female wild-type (LXR+/+) and LXR, double knockout (LXR-/-) mice in the absence or presence of FB1 (10mg/kg body weight/day) for 28days. Exposure to FB1 supplemented in the mice's drinking water resulted in more pronounced hepatotoxicity in LXR-/- mice compared to LXR+/+ mice, as indicated by hepatic transaminase levels (ALT, AST) and hepatic inflammatory and fibrotic lesions. Next, the effect of FB1 exposure on the liver transcriptome was investigated. FB1 exposure led to a specific transcriptional response in LXR-/- mice that included altered cholesterol and bile acid homeostasis. ELISA showed that these effects were associated with an elevated FB1 concentration in the plasma of LXR-/- mice, suggesting that LXRs participate in intestinal absorption and/or clearance of the toxin. In summary, this study demonstrates an important role of LXRs in protecting the liver against FB1-induced toxicity, suggesting an alternative mechanism not related to the inhibition of sphingolipid synthesis for mycotoxin toxicity

EUREC⁴A observations from the SAFIRE ATR42 aircraft

International audienceAs part of the EUREC 4 A (Elucidating the role of cloud-circulation coupling in climate) field campaign, which took place in January and February 2020 over the western tropical Atlantic near Barbados, the French SAFIRE ATR42 research aircraft conducted 19 flights in the lower troposphere. Each flight followed a common flight pattern that sampled the atmosphere around the cloud-base level, at different heights of the subcloud layer, near the sea surface and in the lower free troposphere. The aircraft's payload included a backscatter lidar and a Doppler cloud radar that were both horizontally oriented, a Doppler 5 cloud radar looking upward, microphysical probes, a cavity ring-down spectrometer for water isotopes, a multiwavelength radiometer, a visible camera and multiple meteorological sensors, including fast rate sensors for turbulence measurements. With this instrumentation, the ATR characterized the macrophysical and microphysical properties of trade-wind clouds together with their thermodynamical, turbulent and radiative environment. This paper presents the airborne operations, the flight segmentation, the instrumentation, the data processing and the EUREC 4 A datasets produced from the ATR measurements. It 10 shows that the ATR measurements of humidity, wind and cloud-base cloud fraction measured with different techniques and samplings are internally consistent, that meteorological measurements are consistent with estimates from dropsondes launched from an overflying aircraft (HALO), and that water isotopic measurements are well correlated with data from the Barbados Cloud Observatory. This consistency demonstrates the robustness of the ATR measurements of humidity, wind, cloud-base