Les amyloses, un modèle de maladie du repliement des protéines

Longtemps considérée comme une maladie unique, l'amylose est aujourd'hui reconnue comme la marque histologique d'un ensemble de maladies, les amyloses. L'amylose est la voie finale commune, chez l'homme et dans de nombreuses espèces animales, de l'agrégation pathologique de plus de vingt protéines appartenant à des familles dénuées de relation fonctionnelle ou structurale. Les mécanismes de formation de ces agrégats commencent à être mieux connus. L'étape centrale, que l'on peut artificiellement reproduire in vitro, est un changement de conformation d'une protéine native en une protéine apte à l'auto-agrégation, sous une forme essentiellement formée de feuillets β. Le traitement actuel des amyloses, qui consiste à réduire la disponibilité en protéine amyloïde, n'est pas pleinement satisfaisant. La reconnaissance progressive des différentes étapes de ce phénomène pathologique a conduit à la conception de cibles thérapeutiques nouvelles : stabilisation de la protéine native, désagrégation des structures déjà β-plissées ou, encore, inhibition des liaisons avec certains composants du tissu conjonctif. Différentes approches, pharmacologiques et immunologiques, sont à l'étude sur des systèmes cellulaires et des modèles animaux, et certaines molécules sont parvenues au stade de l'essai clinique chez l'homme.Amyloidosis bears many characteristics of orphan diseases. Its diagnosis is difficult and often delayed. The main reasons thereof are its quite various clinical presentation: amyloidosis behaves as a new great masquerader, and the need to get a tissue sample to submit to specific dyes. Although we have been able for a long time to recognize amyloid, its intimate nature has remained quite completely enigmatic until recently. In fact, major advances in this way have appeared only in the last decade and it is now possible to consider the mechanisms of amyloidosis as a multistep phenomenon. Amyloidosis is no more thought only as a « storage disease » of the extracellular space. This archaic viewpoint has shifted to the emerging paradigm of misfolded protein disorders. Amyloid proteins thus appear as a subgroup of misfolded proteins, where misfolding leads to subsequent aggregation. This aggregation may be a generic property of polypeptide chains possibly linked to their common peptide backbone that does not depend on specific amino acid sequences. And, in fact, many proteins can in vitro form amyloid-like aggregates, while in vivo, only 20 amyloid proteins have been so far identified. Although misfolding and aggregation are quite well studied in vitro, the last step of amyloid deposition, i.e. anchorage to the extracellular matrix, can not be so easily approached. Proteoglycans and serum amyloid P component have nevertheless been identified as key elements involved in extracellular deposition of amyloid proteins. These advances have opened new avenues in the therapeutic of amyloid disorders. Current treatment consists of support or replacement of impaired organ function and measures to reduce the production of amyloidogenic precursor proteins. Potential novel therapeutic strategies include stabilisation of the native fold of precursor proteins with targeted small molecules, reversion of misfolded proteins to their native state with « beta-sheet breakers », inhibition of amyloid fibril propagation and enhancement of amyloid clearance either through immunotherapy or by reducing the stability of deposits through depletion of serum amyloid P component, and breaking the anchorage to the extracellular matrix with glycosaminoglycan analogs

Association of Vasculitis and Familial Mediterranean Fever

Certain types of vasculitis occur more frequently and present differently in patients with familial Mediterranean fever (FMF). We assessed the characteristics of patients with FMF and systemic vasculitis through a systematic review of the literature. Medline was searched by two independent investigators until December 2017. We screened 310 articles and selected 58 of them (IgA vasculitis n = 12, polyarteritis nodosa (PAN) n = 25, Behçet's disease (BD) n = 7, other vasculitis n = 14). Clinical case reports were available for 167 patients (IgA vasculitis n = 46, PAN n = 61, BD n = 46, other vasculitis n = 14), and unavailable for 45 patients (IgA vasculitis n = 38, PAN n = 7). IgA vasculitis was the most common vasculitis in FMF patients with a prevalence of 2.7–7%, followed by PAN with a prevalence of 0.9–1.4%. Characteristics of FMF did not differ between patients with and without vasculitis. Patients with FMF and IgA vasculitis displayed more intussusception (8.7%) and possibly less IgA deposits on histological analysis than patients with IgA vasculitis alone. Patients with FMF and PAN had a younger age at vasculitis onset (mean age = 17.9 years), as well as more perirenal hematomas (49%) and CNS involvement (31%) than patients with PAN alone. Glomerular involvement was noted in 33% of patients diagnosed with PAN, suggesting an alternative diagnosis. Sequencing of the MEFV gene confirmed the presence of two pathogenic variants in 73% of FMF patients with IgA vasculitis or PAN. The majority of patients with BD were from one case series, and presented more skin, gastrointestinal, and CNS involvement than patients with isolated BD. In conclusion, FMF, particularly when supported by two pathogenic MEFV mutations, could predispose to IgA vasculitis, or a PAN-like vasculitis with more perirenal bleeding and CNS involvement

Inflammasome biology, molecular pathology and therapeutic implications

Inflammasomes are intracellular multiprotein signaling complexes, mainly present in myeloid cells. They commonly assemble around a cytoplasmic receptor of the nucleotide-binding leucine-rich repeat containing receptor (NLR) family, although other cytoplasmic receptors like pyrin have been shown to forminflammasomes. The nucleation of the multiprotein scaffolding platform occurs upon detection of a microbial, a danger or a homeostasis pattern by the receptor that will, most commonly, associate with the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) through homotypic domain interactions resulting in recruitment of procaspase-1. This will lead to the autoproteolytic activation of caspase-1, which regulates the secretion of proinflammatory IL1β and IL18 cytokines and pyroptosis, a caspase-1-mediated form of cell death. Pyroptosis occurs through cleavage of Gasdermin D, a membrane pore forming protein. Recently, non-canonical inflammasomes have been described, which directly sense intracellular pathogens through caspase-4 and -5 in humans, leading to pyroptosis. Inflammasomes are important in host defense; however, a deregulated activity is associated with a number of inflammatory, immune and metabolic disorders. Furthermore, mutations in inflammasome receptor coding genes are causal for an increasing number of rare autoinflammatory diseases. Biotherapies targeting the products of inflammasome activation aswell as molecules that directly or indirectly inhibit inflammasome nucleation and activation are promising therapeutic areas. This review discusses recent advances in inflammasome biology, the molecular pathology of several inflammasomes, and current therapeutic approaches in autoinflammatory diseases and in selected common multifactorial inflammasome-mediated disorders

Recommendations for the management of autoinflammatory diseases.

Autoinflammatory diseases are characterised by fever and systemic inflammation, with potentially serious complications. Owing to the rarity of these diseases, evidence-based guidelines are lacking. In 2012, the European project Single Hub and Access point for paediatric Rheumatology in Europe (SHARE) was launched to optimise and disseminate regimens for the management of children and young adults with rheumatic diseases, facilitating the clinical practice of paediatricians and (paediatric) rheumatologists. One of the aims of SHARE was to provide evidence-based recommendations for the management of the autoinflammatory diseases cryopyrin-associated periodic syndromes (CAPS), tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) and mevalonate kinase deficiency (MKD). These recommendations were developed using the European League Against Rheumatism standard operating procedure. An expert committee of paediatric and adult rheumatologists was convened. Recommendations derived from the systematic literature review were evaluated by an online survey and subsequently discussed at a consensus meeting using Nominal Group Technique. Recommendations were accepted if more than 80% agreement was reached. In total, four overarching principles, 20 recommendations on therapy and 14 recommendations on monitoring were accepted with ≥ 80% agreement among the experts. Topics included (but were not limited to) validated disease activity scores, therapy and items to assess in monitoring of a patient. By developing these recommendations, we aim to optimise the management of patients with CAPS, TRAPS and MKD

Involvement of the Modifier Gene of a Human Mendelian Disorder in a Negative Selection Process

BACKGROUND:Identification of modifier genes and characterization of their effects represent major challenges in human genetics. SAA1 is one of the few modifiers identified in humans: this gene influences the risk of renal amyloidosis (RA) in patients with familial Mediterranean fever (FMF), a Mendelian autoinflammatory disorder associated with mutations in MEFV. Indeed, the SAA1 alpha homozygous genotype and the p.Met694Val homozygous genotype at the MEFV locus are two main risk factors for RA. METHODOLOGY/PRINCIPAL FINDINGS:HERE, WE INVESTIGATED ARMENIAN FMF PATIENTS AND CONTROLS FROM TWO NEIGHBORING COUNTRIES: Armenia, where RA is frequent (24%), and Karabakh, where RA is rare (2.5%). Sequencing of MEFV revealed similar frequencies of p.Met694Val homozygotes in the two groups of patients. However, a major deficit of SAA1 alpha homozygotes was found among Karabakhian patients (4%) as compared to Armenian patients (24%) (p = 5.10(-5)). Most importantly, we observed deviations from Hardy-Weinberg equilibrium (HWE) in the two groups of patients, and unexpectedly, in opposite directions, whereas, in the two control populations, genotype distributions at this locus were similar and complied with (HWE). CONCLUSIONS/SIGNIFICANCE:The excess of SAA1alpha homozygotes among Armenian patients could be explained by the recruitment of patients with severe phenotypes. In contrast, a population-based study revealed that the deficit of alpha/alpha among Karabakhian patients would result from a negative selection against carriers of this genotype. This study, which provides new insights into the role of SAA1 in the pathophysiology of FMF, represents the first example of deviations from HWE and selection involving the modifier gene of a Mendelian disorder

Méningite récurrente AE. Coli d' origine sinusienne guérie par le traitement chirurgical

PARIS-BIUM (751062103) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

MALADIE DE HORTON ET ACCIDENT ARTERIEL ISCHEMIQUE CEREBRAL (A PROPOS D'UNE OBSERVATION)

PARIS5-BU Méd.Cochin (751142101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF