Molecular and Cellular Mediators of the Gut-Liver Axis in the Progression of Liver Diseases

The gut-liver axis covers the bidirectional communication between the gut and the liver, and thus includes signals from liver-to-gut (e.g., bile acids, immunoglobulins) and from gut-to-liver (e.g., nutrients, microbiota-derived products, and recirculating bile acids). In a healthy individual, liver homeostasis is tightly controlled by the mostly tolerogenic liver resident macrophages, the Kupffer cells, capturing the gut-derived antigens from the blood circulation. However, disturbances of the gut-liver axis have been associated to the progression of varying chronic liver diseases, such as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, and primary sclerosing cholangitis. Notably, changes of the gut microbiome, or intestinal dysbiosis, combined with increased intestinal permeability, leads to the translocation of gut-derived bacteria or their metabolites into the portal vein. In the context of concomitant or subsequent liver inflammation, the liver is then infiltrated by responsive immune cells (e.g., monocytes, neutrophils, lymphoid, or dendritic cells), and microbiota-derived products may provoke or exacerbate innate immune responses, hence perpetuating liver inflammation and fibrosis, and potentiating the risks of developing cirrhosis. Similarly, food derived antigens, bile acids, danger-, and pathogen-associated molecular patterns are able to reshape the liver immune microenvironment. Immune cell intracellular signaling components, such as inflammasome activation, toll-like receptor or nucleotide-binding oligomerization domain-like receptors signaling, are potent targets of interest for the modulation of the immune response. This review describes the current understanding of the cellular landscape and molecular pathways involved in the gut-liver axis and implicated in chronic liver disease progression. We also provide an overview of innovative therapeutic approaches and current clinical trials aiming at targeting the gut-liver axis for the treatment of patients with chronic liver and/or intestinal diseases

Deciphering the Immune Microenvironment on A Single Archival Formalin-Fixed Paraffin-Embedded Tissue Section by An Immediately Implementable Multiplex Fluorescence Immunostaining Protocol

Technological breakthroughs have fundamentally changed our understanding on the complexity of the tumor microenvironment at the single-cell level. Characterizing the immune cell composition in relation to spatial distribution and histological changes may provide important diagnostic and therapeutic information. Immunostaining on formalin-fixed paraffin-embedded (FFPE) tissue samples represents a widespread and simple procedure, allowing the visualization of cellular distribution and processes, on preserved tissue structure. Recent advances in microscopy and molecular biology have made multiplexing accessible, yet technically challenging. We herein describe a novel, simple and cost-effective method for a reproducible and highly flexible multiplex immunostaining on archived FFPE tissue samples, which we optimized for solid organs (e.g., liver, intestine, lung, kidney) from mice and humans. Our protocol requires limited specific equipment and reagents, making multiplexing (>12 antibodies) immediately implementable to any histology laboratory routinely performing immunostaining. Using this method on single sections and combining it with automated whole-slide image analysis, we characterize the hepatic immune microenvironment in preclinical mouse models of liver fibrosis, steatohepatitis and hepatocellular carcinoma (HCC) and on human-patient samples with chronic liver diseases. The data provide useful insights into tissue organization and immune-parenchymal cell-to-cell interactions. It also highlights the profound macrophage heterogeneity in liver across premalignant conditions and HCC

Three long period transiting giant planets from TESS

We report the discovery and orbital characterization of three new transiting warm giant planets. These systems were initially identified as presenting single transit events in the light curves generated from the full frame images of the Transiting Exoplanet Survey Satellite (TESS). Follow-up radial velocity measurements and additional light curves were used to determine the orbital periods and confirm the planetary nature of the candidates. The planets orbit slightly metal-rich late F- and early G-type stars. We find that TOI 4406b has a mass of $M_P$= 0.30 $\pm$ 0.04 $M_J$ , a radius of $R_P$= 1.00 $\pm$ 0.02 $R_J$ , and a low eccentricity orbit (e=0.15 $\pm$ 0.05) with a period of P= 30.08364 $\pm$ 0.00005 d . TOI 2338b has a mass of $M_P$= 5.98 $\pm$ 0.20 $M_J$ , a radius of $R_P$= 1.00 $\pm$ 0.01 $R_J$ , and a highly eccentric orbit (e= 0.676 $\pm$ 0.002 ) with a period of P= 22.65398 $\pm$ 0.00002 d . Finally, TOI 2589b has a mass of $M_P$= 3.50 $\pm$ 0.10 $M_J$ , a radius of $R_P$= 1.08 $\pm$ 0.03 $R_J$ , and an eccentric orbit (e = 0.522 $\pm$ 0.006 ) with a period of P= 61.6277 $\pm$ 0.0002 d . TOI 4406b and TOI 2338b are enriched in metals compared to their host stars, while the structure of TOI 2589b is consistent with having similar metal enrichment to its host star.Comment: 24 pages, 16 figures, accepted in A

A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS

Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1.We report the discovery and characterization of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in the Transiting Exoplanet Survey Satellite (TESS) photometry. To characterize the system, we performed and retrieved the CHaracterising ExOPlanets Satellite (CHEOPS), TESS, and ground-based photometry, the High Accuracy Radial velocity Planet Searcher (HARPS) high-resolution spectroscopy, and Gemini speckle imaging. We characterize the host star and determine Teff,⋆=4734±67K⁠, R⋆=0.726±0.007R⊙⁠, and M⋆=0.748±0.032M⊙⁠. We present a novel detrending method based on point spread function shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of Pb = 6.44387 ± 0.00003 d, a radius of Rb = 2.59 ± 0.04 R⊕, and a mass of Mb=13.5+1.7−1.8 M⊕, whilst TOI-1064 c has an orbital period of Pc=12.22657+0.00005−0.00004 d, a radius of Rc = 2.65 ± 0.04 R⊕, and a 3σ upper mass limit of 8.5 M⊕. From the high-precision photometry we obtain radius uncertainties of ∼1.6 per cent, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterized sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further radial velocities are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of mass–radius space, and it allow us to identify a trend in bulk density–stellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets.Publisher PDFPeer reviewe

TOI-836 : a super-Earth and mini-Neptune transiting a nearby K-dwarf

Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1.We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82 day orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.Publisher PDFPeer reviewe

TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf

We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright ($T = 8.5$ mag), high proper motion ($\sim\,200$ mas yr$^{-1}$), low metallicity ([Fe/H]$\approx\,-0.28$) K-dwarf with a mass of $0.68\pm0.05$ M$_{\odot}$ and a radius of $0.67\pm0.01$ R$_{\odot}$. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a $1.70\pm0.07$ R$_{\oplus}$ super-Earth in a 3.82 day orbit, placing it directly within the so-called 'radius valley'. The outer planet, TOI-836 c, is a $2.59\pm0.09$ R$_{\oplus}$ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of $4.5\pm0.9$ M$_{\oplus}$ , while TOI-836 c has a mass of $9.6\pm2.6$ M$_{\oplus}$. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet

TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf

peer reviewe

Influence of IL-17 response in liver pathophysiology

La persistance et la récurrence de la réponse inflammatoire dans le foie est la principale cause de développement des lésions hépatiques et de ses complications. Cette réponse immune est caractérisée par le recrutement de cellules inflammatoires, notamment de monocytes/macrophages et de lymphocytes. Elle est aussi impliquée d'une part dans le développement de la fibrose en activant les cellules fibrogéniques du foie, et d'autre part dans les mécanismes de régénération. Récemment, la présence d'une sous-population de lymphocytes T appelés Th17 a été identifiée dans de nombreuses pathologies hépatiques incluant la fibrose. Leur présence a également été observée lors de la régénération hépatique à partir de cellules progénitrices. Ces lymphocytes Th17 sont caractérisés principalement par la production de deux cytokines l'IL-17 et l'IL-22. Alors que le rôle de l'IL-22 a été récemment caractérisé dans la fibrose et la régénération hépatique, le rôle de l'IL-17 nécessitait d'être défini.Les objectifs de ma thèse ont donc été d'étudier le rôle et la régulation de l'IL-17 dans 1) les mécanismes de développement de la fibrose, et 2) son impact sur la régénération hépatique à partir de cellules progénitrices.1) L'équipe a démontré l'implication du système endocannabinoïde dans les maladies chroniques du foie. Ce système est composé de deux types de récepteurs, CB1 et CB2, couplés aux protéines G, et de ligands lipidiques endogènes. Alors que CB1 est majoritairement exprimé dans le cerveau et faiblement dans les tissus périphériques, CB2 est très fortement exprimé par les cellules immunitaires et présente en général des propriétés anti-inflammatoires. Notre hypothèse a donc été que l'activation du récepteur CB2, exprimé par les lymphocytes T régulerait négativement la réponse de type Th17 et le développement de la fibrose hépatique. Dans un modèle murin de fibrose induite par la ligature de la voie biliaire principale, nous avons montré que des souris CB2-/- développent une fibrose plus importante associée à une réponse inflammatoire de type Th17 augmentée par rapport à des souris sauvages. De plus, l'inhibition de la production de l'IL-17 chez ces souris CB2-/- à l'aide d'un inhibiteur de la différenciation Th17 (la digoxine), permet de réduire le développement de la fibrose. In vitro, l'activation du récepteur CB2 sur les lymphocytes Th17 par un agoniste sélectif, le JWH-133, diminue leur capacité à produire l'IL-17. Par ailleurs, nous avons montré par immunocyto-fluorescence, que l'activation de CB2 inhibe la production de l'IL-17 par une voie STAT5-dépendante. Ainsi, l'immuno-modulation de la réponse inflammatoire associée à la fibrose représente une stratégie anti-fibrosante prometteuse.2) L'infiltration de ces cellules Th17 a également été observée dans de nombreuses hépatopathies associées à une accumulation de cellules progénitrices intra-hépatiques (CPIH), appelées cellules ovales chez les rongeurs. La deuxième partie de ma thèse a donc consisté en l'étude du rôle de l'IL-17 dans la régénération du foie à partir de CPIH. Dans un modèle murin de régénération hépatique à partir de CPIH induit par un régime déficient en choline, et supplémenté en éthionine (CDE), nous avons montré que des souris invalidées pour l'IL-17 (IL-17-/-) présentent une diminution du nombre de CPIH CK19+, par rapport aux souris sauvages. L'invalidation de l'IL-17-/- a également été associée à une réduction du recrutement macrophagique et de la réponse pro-inflammatoire incluant l'IL-6, l'IL-1b et l'IL-27. Parmi ces cytokines, nous avons identifié l'IL-27 comme étant un facteur clé dans la différenciation des CPIH. In vitro, nous avons également montré que la production de l'IL-27 est induite par la stimulation des macrophages par l'IL-17. Ainsi, nos résultats révèlent que l'action combinée de l'IL-17 et de l'IL-27 orchestre la régénération du foie à partir de CPIH en favorisant leur prolifération et leur différenciation en hépatocytes, respectivement.Persistence and recurrence of inflammatory response in the liver is the major cause of liver damage and its complications. This immune response is characterized by inflammatory cell recruitment, in particular monocytes / macrophages and lymphocytes. It has also been implicated in fibrosis development by activating liver fibrogenic cells, and also in regeneration mechanisms. Recently, a sub population of T lymphocytes called Th17 has been identified in numerous liver pathologies including fibrosis. These cells have also been observed in regenerating livers from progenitor cells. Th17 lymphocytes are mainly characterized by the production of two cytokines, namely IL-17 and IL-22. While the role of IL-22 has been recently described in liver fibrosis and regeneration, the role of IL-17 remained to be studied.The aims of my thesis were to study the role and the regulation of IL-17 in 1) fibrosis development, and 2) its impact on liver regeneration from progenitor cells.1) Our team has demonstrated the implication of the endocannabinoid system in chronic liver disease. This system is composed of two G-protein coupled receptors, CB1 and CB2, and their endogenous lipidic ligands. While CB1 is mainly expressed in the brain and slightly in peripheral tissues, CB2 is strongly expressed by immune cells and generally displays anti-inflammatory properties. Our hypothesis was that CB2 receptor activation, expressed by T lymphocytes, would negatively regulate Th17 response and liver fibrosis development. In a murine fibrosis model induced by bile duct ligation and section, we have showed that CB2-/- mice have an enhanced fibrosis associated with an increased Th17 inflammatory response as compared to wild-type animals. Additionally, IL-17 production inhibition in these CB2-/- mice with an inhibitor of Th17 differentiation (digoxin), reduced fibrosis development. In vitro, CB2 receptor activation on Th17 lymphocytes by a selective agonist, JWH-133, diminished their ability to produce IL-17. Moreover, we demonstrated by immunocyto-fluorescence, that CB2 activation inhibits IL-17 production in a STAT5-dependent manner. Thus, the modulation of the inflammatory response associated with fibrosis is a promising strategy against fibrosis.2) Th17 cell infiltration has also been observed in liver disease associated with liver progenitor cell (LPC) accumulation, called oval cells in rodents. The second part of my thesis was aimed to study IL-17 role in liver regeneration from LPC. In a murine model of liver regeneration from LPC induced by a choline deficient and éthionine supplemented diet (CDE), we have demonstrated that IL-17 deficient mice (IL-17-/-) have a reduced number of CK19+ LPC as compared to wild-type animals. IL-17 deficiency was also associated with a decrease in macrophage recruitment and reduced pro-inflammatory response including IL-6, IL-1b and IL-27. Among these cytokines, we identified IL-27 as a key factor in LPC differentiation. In vitro, we also showed that IL-27 production is induced after IL-17-induced macrophage activation. Thereby our results revealed that the combined action of IL-17 and IL-27 leads to LPC driven liver regeneration by enhancing their proliferation and their differentiation towards hepatocytes, respectively