The J Domain of Sacsin Disrupts Intermediate Filament Assembly.

Autosomal Recessive Spastic Ataxia of the Charlevoix Saguenay (ARSACS) is caused by mutation in the SACS gene resulting in loss of function of the protein sacsin. A key feature is the formation of abnormal bundles of neurofilaments (NF) in neurons and vimentin intermediate filaments (IF) in cultured fibroblasts, suggesting a role of sacsin in IF homeostasis. Sacsin contains a J domain (SacsJ) homologous to Hsp40, that can interact with Hsp70 chaperones. The SacsJ domain resolved NF bundles in cultured Sacs-/- neurons. Having studied the mechanism using NF assembled in vitro from purified NF proteins, we report that the SacsJ domain interacts with NF proteins to disassemble NFL filaments, and to inhibit their initial assembly. A cell-penetrating peptide derived from this domain, SacsJ-myc-TAT was efficient in disassembling NF bundles in cultured Sacs-/- motor neurons, restoring the NF network; however, there was some loss of vimentin IF and NF in cultured Sacs+/+ fibroblasts and motor neurons, respectively. These results suggest that sacsin through its SacsJ domain is a key regulator of NF and vimentin IF networks in cells.

Évaluation d'HyQviaMC (immunoglobulines humaines normales à 10 % et hyaluronidase): Déficit immunitaire primaire et secondaire / HyQvia™ Assessment (10% Human Normal Immunoglobulins and Hyaluronidase): Primary and Secondary Immunodeficiency

MANDAT: À la demande du fabricant Takeda Canada Inc., l'Institut national d'excellence en santé et en services sociaux (INESSS) a procédé à l'évaluation du produit HyQviaMC, une combinaison d'immunoglobulines normales humaines à 10 % et d'hyaluronidase, qui s'administre par voie sous-cutanée (s.c.). Ce produit est indiqué pour le traitement substitutif du déficit immunitaire humoral primaire (DIP) et du déficit immunitaire humoral secondaire (DIS) chez les adultes. Il s'agit de la première évaluation de cette préparation d'immunoglobulines. DÉMARCHE D'ÉVALUATION: Une revue des données issues de la littérature et de celles fournies par le fabricant a été réalisée afin d'évaluer l'efficacité, l'innocuité et l'efficience d'HyQviaMC. Des données contextuelles et expérientielles issues de la consultation d'experts sont également présentées. BESOIN DE SANTÉ: Idéalement, les traitements du DIP et du DIS devraient offrir une protection contre les infections comparable à la normale. Sont également souhaitables des traitements qui préviennent davantage les risques d'infection par rapport aux thérapies prophylactiques actuelles et qui favorisent l'atténuation des contraintes liées aux perfusions répétées d'immunoglobulines intraveineuses (i.v.) ou s.c. L'approvisionnement et la disponibilité des immunoglobulines de remplacement sont précaires. De plus, la demande ne cessant d'augmenter au Québec, il apparaît important de sécuriser plusieurs sources d'immunoglobulines. Actuellement, 8 produits sont inscrits sur la Liste des produits du système du sang du Québec, dont 3 s'administrent par voie s.c. RÉSULTATS: Efficacité: Les études pivot, de prolongation et en contexte réel de soins montrent que le taux annuel d'infections bactériennes aiguës sévères était inférieur à la valeur seuil de 1 chez les patients atteints de DIP ou de DIS traités avec HyQviaMC. Le taux annuel d'infection global variait de 0,88 à 2,99 selon les études. Ces résultats sont comparables à ceux des autres préparations d'immunoglobulines actuellement disponibles au Québec. La qualité des études considérées varie de faible à modérée. La force de la preuve est faible. Innocuité: Des événements indésirables faibles à sévères ont été observés au cours des études pivot et de prolongation, dont des cas de thrombose jugés non liés au traitement. L'absence de conséquences cliniques liées aux anticorps anti-hyaluronidase ainsi que l'usage historique d'HyQviaMC en Europe et aux États-Unis semblent indiquer qu'il ne serait pas nécessaire de surveiller le taux d'anticorps contre l'hyaluronidase chez les patients traités avec HyQviaMC. La qualité méthodologique des études considérées varie de faible à modérée. La force de la preuve est très faible. Qualité de vie: La voie d'administration des immunoglobulines i.v. et s.c. ne semblait pas avoir un effet important sur la qualité de vie liée à la santé. La qualité méthodologique de l'étude considérée est modérée. La force de la preuve est modérée. Perspective des experts: Malgré la faible qualité des études, les experts consultés jugent l'efficacité d'HyQviaMC à prévenir les infections et son profil d'innocuité comparables à ceux des immunoglobulines présentement disponibles. Selon les experts, l'effet d'HyQviaMC sur la qualité de vie des patients est comparable à celui des autres préparations d'immunoglobulines. Perspective des patients: Le traitement de remplacement des immunoglobulines par perfusion i.v. (IgIV) ou par injection s.c. (IgSC) est vécu comme un fardeau par de nombreux patients. Certains patients aimeraient bénéficier d'une thérapie comme HyQviaMC, qui peut être administrée à domicile tout en offrant la même fréquence d'administration que les IgIV. Aspect organisationnel: L'administration d'HyQviaMC requiert que les patients soient adéquatement formés. Les experts soulignent que l'utilisation d'HyQviaMC requiert un niveau d'habileté plus élevé que celui exigé pour l'administration d'une IgSC conventionnelle. Un programme de soutien aux patients est offert par le fabricant. Néanmoins, selon les experts, il serait utile d'élaborer un protocole pour les soins à domicile des centres locaux de services communautaires (CLSC). ANALYSES ÉCONOMIQUES: Analyse d'efficience: Au prix soumis par le fabricant, le traitement par HyQviaMC est une option thérapeutique moins efficiente que les autres immunoglobulines actuellement distribuées au Québec. Analyse d'impact budgétaire: L'ajout d'HyQviaMC à la Liste des produits du système du sang du Québec pourrait entraîner une augmentation des dépenses estimée à 11 M$ pour les trois prochaines années.

Differential attenuation of ß2 integrin-dependent and -independent neutrophil migration by Ly6G ligation.

Antibody ligation of the murine neutrophil surface protein Ly6G disrupts neutrophil migration in some contexts but not others. We tested whether this variability reflected divergent dependence of neutrophil migration on ß2 integrins, adhesion molecules that interact with Ly6G at the neutrophil surface. In integrin-dependent murine arthritis, Ly6G ligation attenuated joint inflammation, even though mice lacking Ly6G altogether developed arthritis normally. By contrast, Ly6G ligation had no impact on integrin-independent neutrophil migration into inflamed lung. In peritoneum, the role of ß2 integrins varied with stimulus, proving dispensable for neutrophil entry in Escherichia coli peritonitis but contributory in interleukin 1 (IL-1)-mediated sterile peritonitis. Correspondingly, Ly6G ligation attenuated only IL-1 peritonitis, disrupting the molecular association between integrins and Ly6G and inducing cell-intrinsic blockade restricted to integrin-dependent migration. Consistent with this observation, Ly6G ligation impaired integrin-mediated postadhesion strengthening for neutrophils arresting on activated cremaster endothelium in vivo. Together, these findings identify selective inhibition of integrin-mediated neutrophil emigration through Ly6G ligation, highlighting the marked site and stimulus specificity of ß2 integrin dependence in neutrophil migration.

IL-1ß enables CNS access to CCR2hi monocytes and the generation of pathogenic cells through GM-CSF released by CNS endothelial cells.

Molecular interventions that limit pathogenic CNS inflammation are used to treat autoimmune conditions such as multiple sclerosis (MS). Remarkably, IL-1ß-knockout mice are highly resistant to experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we show that interfering with the IL-1ß/IL-1R1 axis severely impairs the transmigration of myeloid cells across central nervous system (CNS) endothelial cells (ECs). Notably, we report that IL-1ß expression by inflammatory CCR2hi monocytes favors their entry into the spinal cord before EAE onset. Following activation with IL-1ß, CNS ECs release GM-CSF, which in turn converts monocytes into antigen-presenting cells (APCs). Accordingly, spinal cord-infiltrated monocyte-derived APCs are associated with dividing CD4+ T cells. Factors released from the interaction between IL-1ß-competent myeloid cells and CD4+ T cells are highly toxic to neurons. Together, our results suggest that IL-1ß signaling is an entry point for targeting both the initiation and exacerbation of neuroinflammation.

Ly6Chigh monocytes facilitate transport of Murid herpesvirus 68 into inflamed joints of arthritic mice.

Viruses, particularly the Epstein-Barr virus (EBV) has long been suspected to exacerbate acute arthritic symptoms. However, the cell populations that contribute to import viruses into the inflamed tissues remain to be identified. In the present study, we have investigated the role of monocytes in the transport of Murid herpesvirus 68 (MHV-68), a mouse virus closely related to EBV, using the serum transfer-induced arthritis (STIA) model. We found compelling evidence that MHV-68 infection markedly increased disease severity in NR4A1-/- mice, which are deficient for Ly6Clow monocytes. In contrast, the MHV-68-induced enhancement of joint inflammation was lessened in CCR2-/- mice, suggesting the involvement of inflammatory Ly6Chigh monocytes in viral transport. We also observed that following selective depletion of monocyte subsets by administration of clodronate, MHV-68 transport into the synovium occurs only in the presence of Ly6Chigh monocytes. Tracking of adoptively transferred Ly6Chigh GFP infected monocytes into arthritic CCR2-/- mice by two-photon intravital microscopy showed that this monocyte subset has the capacity to deliver viruses to inflamed AR joints, as confirmed by the detection of viral DNA in inflamed tissues of recipient mice. We thus conclude that Ly6Chigh monocytes import MHV-68 when they are mobilized to the inflamed arthritic joint.

Involvement of the IL-1 system in experimental autoimmune encephalomyelitis and multiple sclerosis: Breaking the vicious cycle between IL-1ß and GM-CSF.

Multiple sclerosis (MS) is an autoimmune disease that affects hundreds of thousands of people worldwide. Given the autoimmune nature of the disease, a large part of the research has focused on autoreactive T and B cells. However, research on the involvement of myeloid cells in the pathophysiology of MS has received a strong and renewed attention over the recent years. Despite the multitude of inflammatory mediators involved in innate immunity, only a select group of cytokines are absolutely critical to the development of CNS autoimmunity, among which is interleukin (IL)-1. While the importance of the IL-1 system in experimental autoimmune encephalomyelitis (EAE) and MS has been recognized for about 20years, it is only recently that we have begun to understand that IL-1 plays multifaceted roles in disease initiation, development, amplification and chronicity. Here, we review the recent findings showing an implication of the IL-1 system in EAE and MS, and introduce a model that highlights how IL-1ß and granulocyte-macrophage colony-stimulating factor (GM-CSF) are interacting together to create a vicious feedback cycle of CNS inflammation that ultimately leads to myelin and neuronal damage.

Myeloid cell transmigration across the CNS vasculature triggers IL-1ß-driven neuroinflammation during autoimmune encephalomyelitis in mice.

Growing evidence supports a role for IL-1 in multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), but how it impacts neuroinflammation is poorly understood. We show that susceptibility to EAE requires activation of IL-1R1 on radiation-resistant cells via IL-1ß secreted by bone marrow-derived cells. Neutrophils and monocyte-derived macrophages (MDMs) are the main source of IL-1ß and produce this cytokine as a result of their transmigration across the inflamed blood-spinal cord barrier. IL-1R1 expression in the spinal cord is found in endothelial cells (ECs) of the pial venous plexus. Accordingly, leukocyte infiltration at EAE onset is restricted to IL-1R1(+) subpial and subarachnoid vessels. In response to IL-1ß, primary cultures of central nervous system ECs produce GM-CSF, G-CSF, IL-6, Cxcl1, and Cxcl2. Initiation of EAE or subdural injection of IL-1ß induces a similar cytokine/chemokine signature in spinal cord vessels. Furthermore, the transfer of Gr1(+) cells on the spinal cord is sufficient to induce illness in EAE-resistant IL-1ß knockout (KO) mice. Notably, transfer of Gr1(+) cells isolated from C57BL/6 mice induce massive recruitment of recipient myeloid cells compared with cells from IL-1ß KO donors, and this recruitment translates into more severe paralysis. These findings suggest that an IL-1ß-dependent paracrine loop between infiltrated neutrophils/MDMs and ECs drives neuroinflammation.

Platelets release mitochondria serving as substrate for bactericidal group IIA-secreted phospholipase A2 to promote inflammation.

Mitochondrial DNA (mtDNA) is a highly potent inflammatory trigger and is reportedly found outside the cells in blood in various pathologies. Platelets are abundant in blood where they promote hemostasis. Although lacking a nucleus, platelets contain functional mitochondria. On activation, platelets produce extracellular vesicles known as microparticles. We hypothesized that activated platelets could also release their mitochondria. We show that activated platelets release respiratory-competent mitochondria, both within membrane-encapsulated microparticles and as free organelles. Extracellular mitochondria are found in platelet concentrates used for transfusion and are present at higher levels in those that induced acute reactions (febrile nonhemolytic reactions, skin manifestations, and cardiovascular events) in transfused patients. We establish that the mitochondrion is an endogenous substrate of secreted phospholipase A2 IIA (sPLA2-IIA), a phospholipase otherwise specific for bacteria, likely reflecting the ancestral proteobacteria origin of mitochondria. The hydrolysis of the mitochondrial membrane by sPLA2-IIA yields inflammatory mediators (ie, lysophospholipids, fatty acids, and mtDNA) that promote leukocyte activation. Two-photon microscopy in live transfused animals revealed that extracellular mitochondria interact with neutrophils in vivo, triggering neutrophil adhesion to the endothelial wall. Our findings identify extracellular mitochondria, produced by platelets, at the midpoint of a potent mechanism leading to inflammatory responses.

Neutrophils mediate blood-spinal cord barrier disruption in demyelinating neuroinflammatory diseases.

Disruption of the blood-brain and blood-spinal cord barriers (BBB and BSCB, respectively) and immune cell infiltration are early pathophysiological hallmarks of multiple sclerosis (MS), its animal model experimental autoimmune encephalomyelitis (EAE), and neuromyelitis optica (NMO). However, their contribution to disease initiation and development remains unclear. In this study, we induced EAE in lys-eGFP-ki mice and performed single, nonterminal intravital imaging to investigate BSCB permeability simultaneously with the kinetics of GFP(+) myeloid cell infiltration. We observed a loss in BSCB integrity within a day of disease onset, which paralleled the infiltration of GFP(+) cells into the CNS and lasted for ∼4 d. Neutrophils accounted for a significant proportion of the circulating and CNS-infiltrating myeloid cells during the preclinical phase of EAE, and their depletion delayed the onset and reduced the severity of EAE while maintaining BSCB integrity. We also show that neutrophils collected from the blood or bone marrow of EAE mice transmigrate more efficiently than do neutrophils of naive animals in a BBB cell culture model. Moreover, using intravital videomicroscopy, we demonstrate that the IL-1R type 1 governs the firm adhesion of neutrophils to the inflamed spinal cord vasculature. Finally, immunostaining of postmortem CNS material obtained from an acutely ill multiple sclerosis patient and two neuromyelitis optica patients revealed instances of infiltrated neutrophils associated with regions of BBB or BSCB leakage. Taken together, our data provide evidence that neutrophils are involved in the initial events that take place during EAE and that they are intimately linked with the status of the BBB/BSCB.

Automated filtering of intrinsic movement artifacts during two-photon intravital microscopy.

In vivo imaging using two-photon microscopy is an essential tool to explore the dynamic of physiological events deep within biological tissues for short or extended periods of time. The new capabilities offered by this technology (e.g. high tissue penetrance, low toxicity) have opened a whole new era of investigations in modern biomedical research. However, the potential of using this promising technique in tissues of living animals is greatly limited by the intrinsic irregular movements that are caused by cardiac and respiratory cycles and muscular and vascular tone. Here, we show real-time imaging of the brain, spinal cord, sciatic nerve and myenteric plexus of living mice using a new automated program, named Intravital_Microscopy_Toolbox, that removes frames corrupted with motion artifacts from time-lapse videos. Our approach involves generating a dissimilarity score against precalculated reference frames in a specific reference channel, thus allowing the gating of distorted, out-of-focus or translated frames. Since the algorithm detects the uneven peaks of image distortion caused by irregular animal movements, the macro allows a fast and efficient filtering of the image sequence. In addition, extra features have been implemented in the macro, such as XY registration, channel subtraction, extended field of view with maximum intensity projection, noise reduction with average intensity projections, and automated timestamp and scale bar overlay. Thus, the Intravital_Microscopy_Toolbox macro for ImageJ provides convenient tools for biologists who are performing in vivo two-photon imaging in tissues prone to motion artifacts.

Platelets can enhance vascular permeability.

Platelets survey blood vessels, searching for endothelial damage and preventing loss of vascular integrity. However, there are circumstances where vascular permeability increases, suggesting that platelets sometimes fail to fulfill their expected function. Human inflammatory arthritis is associated with tissue edema attributed to enhanced permeability of the synovial microvasculature. Murine studies have suggested that such vascular leak facilitates entry of autoantibodies and may thereby promote joint inflammation. Whereas platelets typically help to promote microvascular integrity, we examined the role of platelets in synovial vascular permeability in murine experimental arthritis. Using an in vivo model of autoimmune arthritis, we confirmed the presence of endothelial gaps in inflamed synovium. Surprisingly, permeability in the inflamed joints was abrogated if the platelets were absent. This effect was mediated by platelet serotonin accumulated via the serotonin transporter and could be antagonized using serotonin-specific reuptake inhibitor antidepressants. As opposed to the conventional role of platelets to microvascular leakage, this demonstration that platelets are capable of amplifying and maintaining permeability adds to the rapidly growing list of unexpected functions for platelets.