SIMILAR, YET DISTINCT, PATHOGENIC PATHWAYS OF PLASMACYTOID DENDRITIC CELL-DERIVED TYPE-IINTERFERON-DRIVEN CUTANEOUS INFLAMMATION IN ROSACEA AND PARADOXICAL PSORIASIS

Cutaneous immunity coordinates necessary protection of the host against exogenous insults, yet its deregulation can have profound pathogenic consequences which can lead to development of disease. Type-I interferons are a class of pro-inflammatory cytokines with fundamental roles in innate and adaptive immune responses. In the skin, they not only mount responses against pathogens and tumours, but also sustain re-epithelialisation following injury, and provide tonic signals for maintaining homeostatic balance. Importantly, they are also involved in the pathogenesis of a number of organ- specific and systemic auto-immune diseases such as systemic lupus, type-I diabetes, and thyroid disease, and in the skin they are important drivers of psoriasis and discoid lupus. Exactly how perturbations of type-I interferons lead to cutaneous disease is still a hotly debated subject of research. Production of type-I interferons, in particular IFNβ, is achieved by all nucleated cells, yet small relative numbers of professional producers exist in the circulation and lymphoid organs, which produce many fold higher amounts of these inflammatory cytokines. Plasmacytoid dendritic cells (pDCs), though generally dispensable for many immune responses, are implicated in several type-I interferon-driven auto-immune diseases. Psoriasis, a TH1/TH17 disease with an important role for Tumour Necrosis Factor (TNF), is just such a disease. Intriguingly, treatment of psoriasis (or other diseases) with a class of biologics called anti- TNFs is effective in most patients, but can also result in the development of novel psoriasiform lesions in about 2-5% of all treated individuals. This side-effect of anti-TNFs, called paradoxical psoriasis, has many similarities to classical psoriasis yet we know little of its pathogenesis. We find that paradoxical psoriasis lesions are characterised by uniform overexpression of type-I interferons with concurrent pDC accumulation. Intriguingly, TNF directly regulates production of type-I interferons through maturation of pDCs in vitro, and in pDCs recruited to the site of inflammation in a novel mouse model recapitulating paradoxical psoriasis. The resulting inflammation is type-I interferon-driven yet, unlike classical psoriasis, independent of T-cells and adaptive immunity. Rosacea is a common cutaneous disorder affecting the facial convexities, characterised by recurrent flares of disease, with apparent localised microbial infestation and aberrant expression of cathelicidin antimicrobial peptides. We find that specifically during acute flare-ups, type-I interferons are uniformly and selectively overexpressed. In addition, stabilised lesions display TH1/TH17 signatures and upregulated interferon-response gene expression suggesting previous interferon-bursts. Using a pre-clinical mouse model of rosacea, we find that type-I interferons are produced by pDCs and that they are responsible for the TH17-related cytokine expression. Interestingly, killing of rosacea-associated bacteria by cathelicidin antimicrobial peptides is sufficient to drive this pathogenic signature. Taken together, our observations indicate that pDCs drive a type-I interferon-dependent innate skin inflammation in distinct cutaneous manifestations. These can be triggered by cytokine imbalances, such as for paradoxical psoriasis, or bacterial infestation and overexpression of antimicrobial peptides, such as for rosacea, and prime downstream pathogenic innate immune responses. These findings re-centre attention towards a pathogenic role for pDC-derived type-I interferon, and provide a rationale for targeting this particular axis whilst leaving intact interferon production by other cells and protective immune responses. -- L’immunité cutanée est responsable de coordonner la protection de l’hôte contre des dommages exogènes, néanmoins sa dérégulation peut avoir des conséquences pathogéniques qui peuvent engendrer le développent de maladies. Les interférons de type 1 sont une classe de cytokines pro -inflammatoires avec plusieurs rôles dans l’immunité. Dans la peau, non seulement ils génèrent des réponses immunitair es contre pathogènes envahissants et tumeurs, mais ils garantissent la réépithélialisation suite aux lésions, et fournissent des signaux toniques pour maintenir la balance homéostatique. Surtout, ils jouent un rôle dans la pathogénèse de maladies auto-immunes ciblées à des organes et systémiques telles que le lupus systémique, le diabète de type 1, et la maladie thyroïdienne. Dans la peau, ce sont des facteurs importants dans le développement du psoriasis et du lupus discoïde. Le mécanisme par lequel ces perturbations des interférons de type 1 mènent à des maladies cutanées reste un sujet d’intense recherche. Toutes les cellules nucléés sont capables de produire des interférons de type 1, en particulier l’IFN β, néanmoins une petite population professionnelle de cellules productrices existe dans la circulation et les organes lymphatiques, et peux produire une quantité plus importante de ces cytokines inflammatoires. Les cellules dendritiques plasmacytoïdes (pDCs), tandis qu’elles soient en général dispensables dans la génération de plusieurs réponses immunitaires, sont impliquées dans de nombreuses maladies auto-immunes menées par les interférons de type 1. Le psoriasis, une maladie TH1/TH17 avec un rôle important de la cytokine pro- inflammatoire Tumour Necrosis Factor (TNF), est justement une maladie de ce type. De façon intrigante, le traitement du psoriasis (et d’autres maladies) avec une classe de biologiques appelés les anti-TNFs résulte dans un traitement efficace dans la majorité des patients, mais aussi dans le développement de nouvelles lésions psoriasiformes dans 2-5% d’individus traités. Cet effet secondaire des anti-TNFs, appelé psoriasis paradoxal, a plusieurs similarités avec le psoriasis classique mais peu est connu sur sa pathogénèse. Nous trouvons que les lésions de psoriasis paradoxal sont caractérisées par la surexpression uniforme des interférons de type 1 avec concomitante accumulation de pDCs. Nous décrivons que le TNF régule la production d’interférons via la maturation des pDCs tout aussi bien in vitro que des pDCs recrutées au site d’inflammation psoriasiforme dans un modèle murin. L’inflammation qui en découle est dirigée par les interférons de type 1 mais, en contraste avec le psoriasis classique, est indépendant des lymphocytes T et du système immunitaire adaptatif. La rosacée est une maladie commune des convexités du visage, et caractérisée par des poussées récurrentes de la maladie. Nous découvrons que spécifiquement pendant des poussées aigües de la maladie, les interférons de type 1 sont surexprimés de façon sélective et uniforme. Les lésions stabilisées, tout comme les lésions de poussée aigüe, sont caractérisées par des signatures TH1/TH17 ainsi que de surexpression de gènes de réponse à l’interféron, suggérant des précédentes flambées d’interféron. En utilisant un modèle préclinique murin de rosacée, nous décrivons que les interférons de type 1 sont produits par les pDCs et qu’elles sont responsables pour l’expression associée aux cytoquines TH17. De façon intrigante, le tuage de bactéries associées à la rosacée par les peptides antimicrobiens cathelicidin est suffisant pour engendrer cette signature. Mis ensembles, nos observations indiquent que les pDCs mènent une inflammation dépendant des interférons de type 1 dans distinctes manifestations dans la peau. Celles-ci peuvent être déclenchées par des déséquilibres cytokiniques, comme pour le psoriasis paradoxal, ou l’infestation microbienne et la surexpression de peptides antimicrobiens, comme pour la rosacée, et initier des réponses immunitaires innées pathogéniques. Ces observations recentrent l’attention vers un rôle pathogénique de l’interféron de type 1 produit par la pDC, et justifient le ciblage de cet axe en particulier qui laisserait ainsi intacte la production d’interférons provenant d’autres cellules, et l’induction de réponses immunitaires protectrices

Optical imaging of the small intestine immune compartment across scales.

The limitations of 2D microscopy constrain our ability to observe and understand tissue-wide networks that are, by nature, 3-dimensional. Optical projection tomography (OPT) enables the acquisition of large volumes (ranging from micrometres to centimetres) in various tissues. We present a multi-modal workflow for the characterization of both structural and quantitative parameters of the mouse small intestine. As proof of principle, we evidence its applicability for imaging the mouse intestinal immune compartment and surrounding mucosal structures. We quantify the volumetric size and spatial distribution of Isolated Lymphoid Follicles (ILFs) and quantify the density of villi throughout centimetre-long segments of intestine. Furthermore, we exhibit the age and microbiota dependence for ILF development, and leverage a technique that we call reverse-OPT for identifying and homing in on regions of interest. Several quantification capabilities are displayed, including villous density in the autofluorescent channel and the size and spatial distribution of the signal of interest at millimetre-scale volumes. The concatenation of 3D imaging with reverse-OPT and high-resolution 2D imaging allows accurate localisation of ROIs and adds value to interpretations made in 3D. Importantly, OPT may be used to identify sparsely-distributed regions of interest in large volumes whilst retaining compatibility with high-resolution microscopy modalities, including confocal microscopy. We believe this pipeline to be approachable for a wide-range of specialties, and to provide a new method for characterisation of the mouse intestinal immune compartment

Map4k3 and the Posttranscriptional Control of Gene Expression: A closer look at the MAP kinase control over the tumour promoting mTOR pathway

A tight balance between growth and apoptosis is essential to a functional non-malignant cell. Cell growth is determined by one of its major regulators, mTOR, and is dependent on a number of nutrient- and energy-sensing input signals. These converge onto mTOR which controls protein synthesis and cell growth. Deregulation of this pathway is known to contribute to tumourigenesis and it is being investigated as a therapeutic target. Apoptosis, on the other hand, is an orderly choreography that comes together in causing the serene demise of a cell. Bcl-2 family members establish a tightly controlled balance over pro- and anti-apoptotic signals. Evasion from apoptosis is thought to be one of the hallmarks of cancer. MAP4K3 is a high order signal transducer that was recently found to both positively regulate mTOR through nutrient signalling and induce apoptosis through the intrinsic and extrinsic pathways. Recently, MAP4K3 was shown to activate mTORC1 targets in an amino aciddependent way and to cause cell growth. In another study, it was found to cause apoptosis through the JNK pathway and by upregulating pro-apoptotic Bcl-2 members through the mTORC1 pathway. These findings make it interesting to investigate its targeted translation changes. In addition to its role in apoptosis, MAP4K3 was found to be involved in a number of other pathways and diseases. In the present study, I focus on the contribution of MAP4K3 to the translation initiation-inducing mTORC1 pathway and investigate the translational changes it causes. MAP4K3 induces cell growth and increases protein synthesis rates. It also causes an increase in the number of highly translated mRNAs in polysome profiling experiments. Put together, these observations led me to identify the genes modulated byMAP4K3 with the aim of establishing new leads in the paths paved by this high order signal transducer. I pinpoint the most interesting and most likely MAP4K3-modulated genes at the translational level, and propose new paths worth validating and pursuing

Dataset - High resolution Optical Projection Tomography platform for multispectral imaging of the mouse gut

AbstractSetup design, microbeads projections and FBP reconstruction code relying to the 'High resolution Optical Projection Tomography platform for multispectral imaging of the mouse gut' paper

High resolution optical projection tomography platform for multispectral imaging of the mouse gut

Optical projection tomography (OPT) is a powerful tool for three-dimensional imaging of mesoscopic biological samples with great use for biomedical phenotyping studies. We present a fluorescent OPT platform that enables direct visualization of biological specimens and processes at a centimeter scale with high spatial resolution, as well as fast data throughput and reconstruction. We demonstrate nearly isotropic sub-28 μm resolution over more than 60 mm3 after reconstruction of a single acquisition. Our setup is optimized for imaging the mouse gut at multiple wavelengths. Thanks to a new sample preparation protocol specifically developed for gut specimens, we can observe the spatial arrangement of the intestinal villi and the vasculature network of a 3-cm long healthy mouse gut. Besides the blood vessel network surrounding the gastrointestinal tract, we observe traces of vasculature at the villi ends close to the lumen. The combination of rapid acquisition and a large field of view with high spatial resolution in 3D mesoscopic imaging holds an invaluable potential for gastrointestinal pathology research

Type I IFNs link skin-associated dysbiotic commensal bacteria to pathogenic inflammation and angiogenesis in rosacea

Rosacea is a common chronic inflammatory skin disease with a fluctuating course of excessive inflammation and apparent neovascularization. Microbial dysbiosis with a high density of Bacillus oleronius and increased activity of kallikrein 5, which cleaves cathelicidin antimicrobial peptide, are key pathogenic triggers in rosacea. However, how these events are linked to the disease remains unknown. Here, we show that type I IFNs produced by plasmacytoid DCs represent the pivotal link between dysbiosis, the aberrant immune response, and neovascularization. Compared with other commensal bacteria, B. oleronius is highly susceptible and preferentially killed by cathelicidin antimicrobial peptides, leading to enhanced generation of complexes with bacterial DNA. These bacterial DNA complexes but not DNA complexes derived from host cells are required for cathelicidin-induced activation of plasmacytoid DCs and type I IFN production. Moreover, kallikrein 5 cleaves cathelicidin into peptides with heightened DNA binding and type I IFN-inducing capacities. In turn, excessive type I IFN expression drives neoangiogenesis via IL-22 induction and upregulation of the IL-22 receptor on endothelial cells. These findings unravel a potentially novel pathomechanism that directly links hallmarks of rosacea to the killing of dysbiotic commensal bacteria with induction of a pathogenic type I IFN-driven and IL-22-mediated angiogenesis.LBE

Expert recommendation from the Swiss Amyloidosis Network (SAN) for systemic AL-amyloidosis

Systemic amyloidosis is a heterogeneous group of diseases associated with protein misfolding into insoluble beta-sheet rich structures that deposit extracellularly in different organs, eventually compromising their function. There are more than 30 different proteins, known to be amyloidogenic with “light chain” (AL)-amyloidosis being the most common type, followed by transthyretin (ATTR)-, and amyloid protein A (AA)-amyloidosis. Systemic amyloidosis is a rare disease with an incidence of around 10 patients in 1 million inhabitants. Recently several new therapeutic options have been developed for subgroups of amyloidosis patients, and the introduction of novel therapies for plasma cell myeloma has led to an increase in the therapeutic armamentarium for plasma cell disorders, including AL amyloidosis. Among them, proteasome inhibitors, immunomodulatory agents (-imids), and monoclonal antibodies have been successfully introduced into clinical practice. Still, high-quality data from randomised controlled trials regarding the benefit of these cost-intensive drugs in AL amyloidosis are widely lacking, and due to the rarity of the disease many physicians will not gain routine experience in the management of these frail patients. The diagnosis of AL amyloidosis relies on a close collaboration between clinicians, pathologists, imaging experts, and sometimes geneticists. Diagnosis and treatment options in this complex disorder should be discussed in dedicated multidisciplinary boards. In January 2020, the first meeting of the Swiss Amyloidosis Network took place in Zurich, Switzerland. One aim of this meeting was to establish a consensus guideline regarding the diagnostic work-up and the treatment recommendations for systemic amyloidosis tailored to the Swiss health care system. Forty-five participants from different fields in medicine discussed many aspects of amyloidosis. These are the Swiss Amyloidosis Network recommendations which focus on diagnostic work-up and treatment of AL-amyloidosis