A Strategic Decision for Information Security

A utilização de recursos informáticos é a estratégia mais comum à maioria das organizações para gerirem os seus ativos e propriedade intelectual. Esta decisão estratégica implica a sua exposição ao exterior através de canais de comunicação (infraestrutura de dados). McDermott e Redish (1999), descrevem a terceira lei de Newton como o princípio da ação - reação, as organizações ao exporem a sua infraestrutura ao exterior despoletaram, como reação, estranhos quererem aceder à sua infraestrutura para diversos fins, seja como puro divertimento, detetarem fragilidades ou, mais relevante para este trabalho, roubarem ativos/propriedade intelectual e criarem uma disrupção no serviços. As organizações sentem necessidade de se protegerem contra estes estranhos/ataques ao implementarem estratégias de segurança, mas a realidade é que as linhas de defesa da rede são permeáveis e as arquiteturas de segurança não são suficientemente dinâmicas para travar as ameaças existentes. Uma estratégia de segurança informática baseada na tecnologia “Deception” poderá permitir de uma forma rápida detetar, analisar e defender as redes organizacionais contra-ataquesem tempo real. Esta tecnologia “Deception” poderá oferecer informações precisas sobre “malware” e atividades maliciosas não detetadas por outros tipos de defesa cibernética. Este trabalho pretende explorar esta estratégia recente baseada em “Deception”, que pretende ser diferenciadora face à panóplia de dispositivos/software de segurança informática existentes. Como resultados, pretende-se elaborar uma análise onde as organizações possam perceber a tecnologia “Deception” nas suas vertentes da eficácia, eficiência e o seu valor estratégico para que, eventualmente, a possam utilizar para suportar/adicionar valor a uma decisão de estratégia de segurança informática.The use of Information Technology (IT) resources are the common approach for most organizations so they assets and intellectual property are properly managed. This strategic decision implies its exposure to the outside world through the data infrastructure. McDermott and Redish (1999), described the third Newton’s law as the principle of action- reaction, when organizations expose their infrastructure to the outside world and, as a response, strangers want to access their infrastructure for various purposes, either as pure fun, detect weaknesses or, more relevant for this work, steal assets/intellectual property. Organizations feel the need to protect themselves against these strangers/attacks by implementing security strategies, but truly, the network's first defense lines are permeable, and the security architectures are not dynamic enough to face existing or future threats. A Deception-based technology could enable the organizations to quickly detect, analyze and defend organizational networks against real-time attacks. Deception technology may provide accurate information on malware and malicious activity not detected by other types of cyber defense. This work intends to explore a new technology, Deception, that claims a differentiation when compared with the range of existing information security suite. The types of cyber-threats and their materialization could be relevant to the information technology and risk analysis. Thus, the intent is to elaborate an analysis where organizations can understand the Deception technology, his effectiveness, and strategic value so they can, eventually, use it to support/add value to a decision regarding information security strategy

Exploring the use of high-dose simvastatin as therapy for oxidative stress in disease models of neuroinflammation

Background: There is growing evidence that HMG-CoA reductase inhibitors, otherwise known as the statin family, can exert pleiotropic effects in many areas. Of these, potential neuroprotective effects have gained significant attention. It is well established that microglia, the brain’s resident phagocytes, play a pivotal role in the pathogenesis of neuroinflammation and neurodegeneration. This process is thought to be, in part, due to the presence of chronically activated microglia. In this study, we investigated the potential neuroprotective properties of HMG-CoA reductase using an in vitro model of inflammatory cell activation and in vivo models of posterior uveitis and multiple sclerosis. The focus of this study was to investigate the effect of simvastatin on the microglial cell and its activation products. Emphasis was placed on the production of reactive species released by this cell type and the subsequent damage these cause to biological macromolecules. Methods: The microglial cell line BV2 were treated with simvastatin (1μM; 2 to 120 h), in vitro before being activated for 48 hours with a pro-inflammatory mix of LPS, TNFa and IFNg. Supernatants were taken and nitric oxide levels measured using the Griess assay. The animal model of posterior uveitis, experimental autoimmune uveoretinitis (EAU), was established in wild type C57BL/6 mice through subcutaneous injection of IRBP1-20. Mice were treated orally with simvastatin at 50, 75 or 100 mg/kg. Fundus images were taken before and after treatment administration for evaluation of clinical ocular pathology. Retinal flat mounts were prepared from simvastatin treated mice to assess cellular infiltrates. Experimental autoimmune encephalomyelitis (EAE), an in vivo model of MS, was induced by rMOG subcutaneous immunisation. The effect of simvastatin treatment was assessed clinically and by immunohistochemical analysis of tissue sections to determine cellular infiltrates and levels of oxidative damage to biological macromolecules, consistent with those assessed in EAU. Results: The levels of nitric oxide produced by microglial cells were significantly reduced when exposed to a pre-incubation of simvastatin for 3 48 hours, compared to cells receiving the pro-inflammatory mix alone. In EAU, fundoscopic analysis revealed that high-dose simvastatin halts clinical disease progression in IRBP1-20 induced posterior uveitis. Retinal flat mounts prepared from these cohorts showed a significant decrease in the expression of the innate immune cell surface receptor CD11b. Additionally, histological examination of eye sections displayed a significant reduction in lipid peroxidation as revealed by the marker 4-Hydroxynonenal (4HNE), nitrosylated proteins, as measured by 3-nitrotyrosine and oxidised DNA/RNA as determined by 8-OHdG. In line with this study, results from our EAE model demonstrated an important role for microglial cell number in disease, whilst also providing evidence of simvastatin decreasing oxidative damage to macromolecules in areas of extensive pathology. Discussion: These data provide evidence to support the notion that microglial cell activation may contribute to the pathogenesis of neuroinflammatory disease and that statins may attenuate damage through their ability to inhibit the production of reactive species. Further to this, we provide therapeutic, chemical and physical evidence that simvastatin can provide protection against 1) nitric oxide production in an inflammatory environment 2) clinical disease attenuation in EAU and EAE and 3) reduction in peroxynitrite levels in vivo. Collectively, these data provide evidence that statins may attenuate microglial cell activation by ways of inhibiting the production of reactive species. Thus, the evidence presented in this thesis points to the importance and potential use of simvastatin therapy as a neuroprotective therapeutic agent

Identification of biomarkers involved in the resolution phase of inflammation: a translational study of Specialized Pro-resolving Mediators role in Rheumatoid Arthritis

OBJECTIVES: Rheumatoid Arthritis (RA) is a chronic autoimmune disease in which uncontrolled inflammation lead by cells from innate and adaptive immune system leads to tissue damage and disability. To date, the wider pharmacological armamentarium significantly increased the chance of disease control and sustained clinical remission achievement in RA. However, little is known about the mechanisms involved in the resolution phase of inflammation in rheumatic diseases as well as the possible role of Specialized Pro-resolving Mediators (SPMs) as putative pathogenetic and/or therapeutic targets. The aim of this translation study was to dissect whether SPMs and their receptors ERV1, ALX/FPR2 and BLT1 might act as soluble or tissue biomarkers in RA useful for patient stratification across disease phases in clinical practice, improving the therapy management. Moreover, the secondary outcome was wider aiming to increase our knowledge about RA pathophysiology of remission status in. METHODS: 68 patients with RA (27 naïve-to-treatment, 23 DMARDs-not-responder and 18 in sustained clinical and ultrasound remission respectively) were enrolled in the study and underwent PB drawing and ultrasound-guided ST biopsy (n=48). 13 patients with undifferentiated peripheral inflammatory arthritis (UPIA) and 9 with osteoarthritis (OA) were enrolled as comparison groups. Demographic, clinical, immunological and ultrasonographic features were collected for each patient. Determination of serum cytokines and chemokines concentrations (IL-1beta, TNF-alpha, IL-6, IFN-gamma, IL-12p70, IL-10, IL-4, IL-2, Chemerin and GAS6) were performed by ELISA. Furthermore, SPMs and Arachidonic Acid (AA) derived pro-inflammatory molecules determinations in snap frozen synovial tissue biopsies from RA patients in different disease phases (active and remission respectively) were performed by LC-MS/MS. Expression of ERV1, ALX/FPR2 and BLT1 in CD45+CD3+ and CD45+CD19+ was assessed by FACS on PB and on synovial tissue-derived cell suspensions. Moreover, ERV1, ALX/FPR2 and BLT1 expression was assessed by FACS on NK cells (CD45+CD3-CD19-CD56+), neutrophils and monocytes (CD45+CD14+) from PB and macrophages (CD45+CD11b+CD64+) from ST only respectively. Synovitis degree was determined using a H&E based semiquantitative score. Some ST samples were used for quantification of ERV1, ALX/FPR2 and BLT1 genes expression by RT-PCR. RESULTS: Synovial tissue inflammation in terms of semiquantitive score and the cytokine milieu in peripheral blood directly mirror the disease Activity status in RA. RT-PCR on ST samples revealed that ST from RA in high disease activity was enriched of SPM receptors when compared to RA in sustained remission and OA (ERV1: 4.4 vs 1.1 (p= 0.012) and 1.2 (p= 0.005); ALX/FPR2: 4.9 vs 1.5 (p= 0.0006) and 0.8 (p= 0.003); BLT1: 5.9 vs 1.6 (p= 0.016) and 1.1 (p= 0.002) respectively). In particular, C-Reactive Protein (CRP) serum levels, directly correlated with BLT1 expression on PB-derived CD45+CD14+ cells (r=0.27; p=0.023) of RA regardless to the disease phase. Conversely, ST of RA in sustained remission was depleted of BLT1 in CD45+CD3+ cells compared to other conditions (OA p=0.017; UPIA p=0.002; naïve-to-treatment RA p=0.01). LC-MS/MS analysis revealed that synovial tissue of RA in sustained remission the ratio between SPM and AA-derived pro-inflammatory molecules is significantly increased when compared to synovial tissue of RA patients with high disease activity (101.3 vs 2153.00 (84.06-3333.00) respectively) CONCLUSIONS: SPM receptors expression in PB and ST compartments are reciprocally related to disease activity across disease phases in RA suggesting a putative active modulatory role in maintaining the remission phase

Performance and Memory Space Optimizations for Embedded Systems

Embedded systems have three common principles: real-time performance, low power consumption, and low price (limited hardware). Embedded computers use chip multiprocessors (CMPs) to meet these expectations. However, one of the major problems is lack of efficient software support for CMPs; in particular, automated code parallelizers are needed. The aim of this study is to explore various ways to increase performance, as well as reducing resource usage and energy consumption for embedded systems. We use code restructuring, loop scheduling, data transformation, code and data placement, and scratch-pad memory (SPM) management as our tools in different embedded system scenarios. The majority of our work is focused on loop scheduling. Main contributions of our work are: We propose a memory saving strategy that exploits the value locality in array data by storing arrays in a compressed form. Based on the compressed forms of the input arrays, our approach automatically determines the compressed forms of the output arrays and also automatically restructures the code. We propose and evaluate a compiler-directed code scheduling scheme, which considers both parallelism and data locality. It analyzes the code using a locality parallelism graph representation, and assigns the nodes of this graph to processors.We also introduce an Integer Linear Programming based formulation of the scheduling problem. We propose a compiler-based SPM conscious loop scheduling strategy for array/loop based embedded applications. The method is to distribute loop iterations across parallel processors in an SPM-conscious manner. The compiler identifies potential SPM hits and misses, and distributes loop iterations such that the processors have close execution times. We present an SPM management technique using Markov chain based data access. We propose a compiler directed integrated code and data placement scheme for 2-D mesh based CMP architectures. Using a Code-Data Affinity Graph (CDAG) to represent the relationship between loop iterations and array data, it assigns the sets of loop iterations to processing cores and sets of data blocks to on-chip memories. We present a memory bank aware dynamic loop scheduling scheme for array intensive applications.The goal is to minimize the number of memory banks needed for executing the group of loop iterations

서비스 균등 분배와 고성능을 위한 다중프로세서칩 상의 재구성형 통신 구조

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 최기영.The chip multiprocessor (CMP) era has long begun due to the diminishing return from instruction-level parallelism (ILP) harvesting techniques, the rising power and temperature from frequency scaling, etc. One powerful processor has been replaced by many less-powerful processors forming a CMP. One of the issues arose from this paradigm shift is the management of communication among the processors. Buses, which has been a common choice for the systems with one or several processors, failed to sustain the increased communication burden of CMPs. Many bus-based improvements including hierarchical buses and bus-matrices, were proposed but eventually, network-on-chip (NoC) has become the de facto standard for designing a CMP system, replacing the bus-based techniques. NoCs strengths over bus mainly come from its capability of conveying multiple transactions simultaneously from different components to the others. The concurrent communications between the cores are conducted by the distributed, yet shared network components, routers. Routers provide cores with services such as bandwidths. One of the design issues in implementing NoC is to distribute these services evenly across all the cores requesting for them. Arbiter is a component that regulates the accesses to shared resources such as channels and buffers. It has the policy under which requests get services in turn from the shared resources so that the requestors dont fall into deadlock or starvation. One of the common policies for an arbiter is the round-robin, where requests get their grant one by one so that fairness is assured among the requestors. When applied to routers in NoC, it fails to provide the fairness because each request goes through multiple routers, thus multiple round-robin arbiters on a transaction route. The cascaded effect of the round-robin arbitration is that the farther a source is from the destination, the less service it gets from the destination. The first part of this thesis addresses this issue, and proposes thus far the simplest yet the most effective way of providing the fairness to all the nodes on NoC. It applies weighted round-robin scheme where the weights are determined at run-time depending on which cores are allocated to applications or threads running on the CMP. RTL implementation and synthesis are done to show the simplicity of the proposed scheme. Simulation with synthetic traffic patterns and SPEC CPU2006 benchmark applications show that the proposed approach results in outstanding equality-of-service characteristics. The second part of this thesis deals with the impact of the reconfigurable communication architecture on the performance of a CMP system. One of the pitfalls of NoC is long access latency due to increased hop count between a source and its destination. For example, NoC with mesh topology has its hop count proportional to its size. Because of this, while being a common choice for CMP, mesh topology is said to be inscalable in terms of the number of cores. Some alternatives to mesh topology exist, one of them being high radix NoCs. They replace short and wide channels of mesh with long and narrow ones achieving fewer hop counts. Another option is to cluster cores so that the dimension of mesh network reduces. The clusters are formed by grouping cores via local communication fabric. The clusters are interconnected by a global communication fabric, often in the shape of mesh topology. Many types of local communication fabric are explored in previous researches, including another NoC with topologies of mesh, ring, etc. However, bus has become one of the most favorable choices for the local connection because of its simplicity. The simplicity leads local communications to be performed with high performance, low chip area, low power consumption, etc. One of the issues in forming core clusters in CMP is their grain size. Tying too many cores into a cluster results in the congestion on the bus, reducing the performance of the local communications. On the other hand, too few cores in a cluster misses the chances of improving system performance by efficient local communications through the bus. It is obvious that the optimal number of cores in a cluster depends on the applications that run on the CMP. Bus reconfiguration with bus segments and switches can be a solution for varying cluster size on a CMP. In addition to the variable cluster sizes, bus reconfiguration has another advantage of processor (not process) migration. Bus reconfiguration can reconnect cores and caches so that the distance between cores and data are reduced dynamically. In this way, data copies and network transactions can be dramatically reduced to improve the system performance. The second part of this thesis addresses this issue and proposes a reconfigurable bus-mesh architecture to accelerate pipelined applications. With the proposed architecture, the data transfer between the successive pipeline stages are done not by data copies but by processor migrations. Systematic management of bus segments and L1 data caches are required to achieve efficient use of the reconfigurability. The proposed architecture is compared with the baseline architecture, which maintains cache coherence with hardware. Multilayer perceptron (MLP), convolutional neural network (CNN), and JPEG decoder are implemented as example pipelined applications using multi-threaded programming model. The in-house full system simulator is implemented and used to measure the performance improvement of the proposed architecture. The experimental results show that 21.75 %, 14.40 %, and 12.74 % execution cycle reductions are achieved for MLP, CNN, and JPEG decoder, respectively.Part I Adaptively Weighted Round-Robin Arbitration for Equality of Service in a Many-Core Network-on-Chip [1] 1 Chapter 1 Introduction 3 Chapter 2 Previous Work 7 Chapter 3 Position-Based Weighted Round-Robin Arbitration 11 Chapter 4 Adaptively Weighted Round-Robin Arbitration 17 4.1 Hardware Implementation for weight update 18 4.2 Arbitration Weight Determination 22 Chapter 5 Experimental Results 25 5.1 Open-Loop Measurements 25 5.2 Closed-Loop Measurements 29 5.3 Hardware Implementation 33 Chapter 6 Conclusion 35 Part II Accelerating Pipelined Applications with Reconfigurable Bus-Mesh Communication Architecture in Chip Multiprocessors 37 Chapter 7 Introduction 39 Chapter 8 Backgrounds and Previous Work 43 8.1 Segmented Bus 43 8.2 CMPs with Reconfigurable Bus-Mesh Communication Architecture 44 8.3 Near-Threshold Computing 48 Chapter 9 Baseline Architecture 51 Chapter 10 Motivation 55 Chapter 11 Reconfigurable Bus-Mesh Architecture 61 11.1 Thread Programming Model 61 11.2 Cluster Size 64 11.3 Organizing Multiple L1Ds and SPM Banks in a Cluster 66 11.4 L1 Data Cache / SPM Partitioning 70 11.5 Reconfiguration Overheads 71 Chapter 12 Experimental Results 75 12.1 Pipelined Applications 75 12.2 Simulation Environment 78 12.3 Memory Operations Latency Breakdown 79 Chapter 13 Conclusion 85 Bibliography 87 국문초록 95Docto

Screening of candidate bioactive secondary plant metabolite Ion-features from Moringa oleifera accessions associated with high and low enteric methane inhibition from ruminants

DATA AVAILABILITY STATEMENT : Data will be stored in the University of Pretoria repository, and access to the data will be granted by making a reasonable request to the University of Pretoria or the corresponding author.This study evaluated the relationship of secondary bioactive plant metabolite ion-features (MIFs) of Moringa oleifera accessions with antimethanogenesis to identify potential MIFs that were responsible for high and low methane inhibition from ruminants. Plant extracts from 12 Moringa accessions were evaluated at a 50 mg/kg DM feed for gas production and methane inhibition. Subsequently, the accessions were classified into low and high enteric methane inhibition groups. Four of twelve accessions (two the lowest and two the highest methane inhibitors), were used to characterize them in terms of MIFs. A total of 24 samples (12 from lower and 12 from higher methane inhibitors) were selected according to their methane inhibition potential, which ranged from 18% to 29%. Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and untargeted metabolomics with univariate and multivariate statistical analysis with MetaboAnalyst were used in the study. Although 86 MIFs showed (p < 0.05) variation between higher and lower methane inhibition groups and lay within the detection ranges of the UPLC-MS column, only 14 were significant with the volcano plot. However, Bonferroni correction reduced the candidate MIFs to 10, and their R2-value with methane production ranged from 0.39 to 0.64. Eventually, MIFs 4.44_609.1462 and MIF 4.53_433.1112 were identified as bioactive MIFs associated with higher methane inhibition, whereas MIF 9.06_443.2317 and 15.00_487.2319 were associated with lower methane inhibition with no significant effect on in vitro organic matter digestibility of the feed. These MIFs could be used by plant breeders as potential markers to develop new M. oleifera varieties with high methane inhibition characteristics. However, further investigation on identifying the name, structure, and detailed biological activities of these bioactive metabolites needs to be carried out for future standardization, commercialization, and application as dietary methane mitigation additives.The National Research Foundation (NRF) of South Africa.https://www.mdpi.com/journal/metabolitesam2023Animal and Wildlife SciencesBiochemistryGeneticsMicrobiology and Plant Patholog

Eye as a window to the brain: investigating the clinical utility of retinal imaging derived biomarkers in the phenotyping of neurodegenerative disease.

Background Neurodegenerative diseases, like multiple sclerosis, dementia and motor neurone disease, represent one of the major public health threats of our time. There is a clear persistent need for novel, affordable, and patient‐acceptable biomarkers of these diseases, to assist with diagnosis, prognosis and impact of interventions. And these biomarkers need to be sensitive, specific and precise. The retina is an attractive site for exploring this potential, as it is easily accessible to non‐invasive imaging. Remarkable technology revolutions in retinal imaging are enabling us to see the retina in microscopic level detail, and measure neuronal and vascular integrity. Aims and objectives I therefore propose that retinal imaging could provide reliable and accurate markers of these neurological diseases. In this project, I aimed to explore the clinical utility of retinal imaging derived measures of retinal neuronal and vessel size and morphology, and determine their candidacy for being reliable biomarkers in these diseases. I also aimed to detail the methods of retinal imaging acquisition, and processing, and the principles underlying all these stages, in relation to understanding of retinal structure and function. This provides an essential foundation to the application of retinal imaging analysis, highlighting both the strengths and potential weaknesses of retinal biomarkers and how they are interpreted. Methods After performing detailed systematic reviews and meta‐analyses of the existing work on retinal biomarkers of neurodegenerative disease, I carried out a prospective, controlled, cross‐sectional study of retinal image analysis, in patients with MS, dementia, and ALS. This involved developing new software for vessel analysis, to add value and maximise the data available from patient imaging episodes. Results From the systematic reviews, I identified key unanswered questions relating to the detailed analysis and utility of neuroretinal markers, and diseases with no studies yet performed of retinal biomarkers, such as non‐AD dementias. I recruited and imaged 961 participants over a two‐year period, and found clear patterns of significance in the phenotyping of MS, dementia and ALS. Detailed analysis has provided new insights into how the retina may yield important disease information for the individual patient, and also generate new hypotheses with relation to the disease pathophysiology itself. Conclusions Overall, the results show that retinal imaging derived biomarkers have an important and specific role in the phenotyping of neurodegenerative diseases, and support the hypothesis that the eye is an important window to neurological brain disease

Neuroinflammation causes changes to the nodes of Ranvier in Multiple Sclerosis normal-appearing white matter.

Background: In addition to the focal demyelinating lesions in multiple sclerosis (MS), both imaging and neuropathological analyses have demonstrated the presence of a more diffuse pathology in both the white and grey matter, including changes to the structure of nodes of Ranvier in the normal-appearing white matter (NAWM). Objective: We have examined the expression of the paranodal axonal protein Caspr1, the voltage-gated channels Nav and Kv1.2 at nodes and juxtaparanodes respectively, and SMI32+ (dephosphorylated neurofilament) axons in NAWM areas from post-mortem progressive MS brains compared to controls. This axo-geometrical data on nodal changes was then integrated into a computational model of an axon developed with NEURON. To test our hypothesis, rats were injected into the cerebral subarachnoid space with lentiviral vectors for lymphotoxin-α and interferon-γ, and structural changes were examined 3 months later. Furthermore, a cerebellar tissue culture model was used to induce nodal pathology by the activation of microglia with TNF, interferon-γ, conditioned microglial medium and glutamate administration. Results: The paranodal domain in MS NAWM tissue was longer on average than in control and Kv1.2 channels appeared dislocated towards the paranode. These changes were associated with stressed axons and activation of microglia. When these changes were inserted into the computational model, a rapid decrease in velocity was observed as the paranodal peri-axonal space was increased, reaching conduction failure when the axons were less than 1mm of diameter. The same structural changes were observed in the corpus callosum of our rat model and were associated with microglia/astrocyte activation. TNF, interferon-γ, conditioned microglial medium and glutamate also generated paranodal elongation in the cerebellar cultures axons and was reversed/halted by an NMDA blocker. Conclusion: Microglia activated by pro-inflammatory cytokines may release high levels of glutamate, which triggers paranodal pathology in MS NAWM, contributing to axonal damage and subsequent conduction deficits.Open Acces

ALCAM : cell adhesion molecule or tight junction? The characterization of its role in the context of neuroinflammation

But : La perte de l’intégrité de la barrière hémo-encéphalique (BHE) est l’une des caractéristiques principales de la sclérose en plaques. Cette augmentation de la perméabilité est associée à une désorganisation des molécules de jonction serrée et à une augmentation de l’expression de molécules d’adhérence essentielles à l’extravasation des cellules immunitaires. Identifier de nouvelles molécules impliquées dans ce processus est donc crucial pour le développement de nouvelles thérapies contre la sclérose en plaques visant à promouvoir l’intégrité de la BHE et à diminuer la migration des leucocytes dans le système nerveux central (SNC) au cours du processus neuro-inflammatoire. Dans cette étude, le rôle spécifique de la molécule d’adhérence ALCAM, qui est exprimé à la surface des cellules endothéliales de la BHE (CE-BHE) et de certains sous-types de leucocytes, a été évalué. Méthodologie : À l’aide d’une analyse protéomique exhaustive, notre laboratoire a identifié ALCAM comme étant une molécule d’adhérence surexprimée par les CE-BHE mises en culture dans un milieu pro-inflammatoire. Dans le but d’étudier le rôle spécifique d’ALCAM durant la diapédèse leucocytaire, nous avons induit chez des souris de type sauvages et des souris ALCAM déficientes l’encéphalite auto-immune expérimentale (EAE), le modèle animal de la sclérose en plaques. Le rôle d’ALCAM a aussi été étudié à l’aide d’un système d’adhérence sous flux laminaire. Cet appareil, qui imite un capillaire cérébral, permet de suivre en temps réel le mouvement des leucocytes, soumis à une pression physiologique, dans un tube couvert à sa base par des CE-BHE. Résultats : En utilisant ce système d’adhérence, j’ai pu démontrer que des anticorps dirigés contre ALCAM réduisent de façon significative le roulement et l’adhérence de monocytes CD14+ humains à la surface de CE-BHE. Par ailleurs, ces anticorps préviennent de façon marquée la diminution de la vitesse moyenne des cellules au cours de l’expérience. Par le fait même, j’ai aussi observé une réduction significative de l’extravasation des monocytes traités avec de l’anti-ALCAM au travers de CE-BHE dans un modèle statique de migration. Subséquemment, j’ai démontré que ces monocytes migrent plus rapidement et en plus grand nombre au travers d’une barrière constituée de cellules endothéliales méningées à comparer à des CE-BHE. Bien que des observations similaires ont été effectuées en utilisant des lymphocytes T CD4+ humains ex vivo, j’ai été incapable de reproduire ces résultats à l’aide de cellules Th1 et Th17 réactivées in vitro. Par opposition à nos données in vitro, j’ai découvert que les souris déficientes en ALCAM développent une EAE active plus sévère que celle observée chez des souris de type sauvages. Cette EAE est par ailleurs associée à une infiltration périvasculaire de lymphocytes T pro-inflammatoires et de monocytes/macrophages de type M1 plus marqué chez les souris ALCAM déficientes. L’induction d’une EAE par transfert adoptif, dans laquelle des cellules immunitaires de type sauvage réactivées par du MOG sont injectées à des souris déficientes en ALCAM, suggère que la pathophysiologie observée durant l’EAE active serait liée à l’absence d’ALCAM au niveau de la BHE. Une caractérisation de la barrière des souris ALCAM déficientes non immunisées a par la suite révélé une réduction de l’expression de certaines molécules de jonction serrée. Une analyse plus poussée a par ailleurs démontré qu’ALCAM est lié indirectement à des molécules de jonction serrée des CE-BHE, ce qui expliquerait l’augmentation de la perméabilité de celle-ci chez les souris déficientes en ALCAM. Une analyse de la perméabilité intercellulaire de la BHE effectuée in vitro a d’autre part corrélé ces résultats. Conclusion : Collectivement, nos données prouvent qu’ALCAM joue un rôle prépondérant dans la diapédèse des monocytes, mais pas des lymphocytes Th1 et Th17 au travers de la BHE. Par ailleurs, nos résultats suggèrent qu’ALCAM remplit une fonction biologique cruciale favorisant le maintien de l’intégrité de la BHE en agissant comme molécule adaptatrice intermédiaire entre les molécules de jonction serrées et le cytosquelette. De cette façon, l’absence d’ALCAM au niveau des CE-BHE promeut indirectement le recrutement de leucocytes pro-inflammatoires dans le SNC des souris atteintes de l’EAE en augmentant la perméabilité des vaisseaux sanguins de la BHE.Aim: The loss of blood-brain barrier (BBB) integrity is a hallmark of multiple sclerosis. It is associated with a disorganization of junctional molecules and an upregulation of cell adhesion molecules essential for immune cell transmigration. Identifying novel key players involved in this process is thus crucial for the development of MS therapies aimed at promoting BBB integrity and decreasing leukocytes trafficking into the central nervous system (CNS) during neuroinflammation. In this study, the specific role of the adhesion molecule ALCAM, found on BBB endothelial cells (BBB-ECs) and subsets of leukocytes, was assessed. Methods: We first identified ALCAM as an important molecule upregulated during inflammation in a proteomic screen of in vitro cultured primary human BBB-ECs. In order to study the effects of ALCAM on leukocyte transmigration, both active and passive experimental autoimmune encephalomyelitis (EAE) was induced in ALCAM KO and WT animals. The specific role of ALCAM during leukocyte transmigration was also assessed using a modified adhesion assay under sheer-stress, in which leukocytes flow across a capillary-like channel lined with a monolayer of BBB-ECs under physiological pressure. Results: Using the modified adhesion assay, we demonstrated that anti-ALCAM blocking antibodies significantly reduce the rolling and the adhesion of human CD14+ monocytes interacting with primary human BBB-ECs, as well as prevent their overall decrease in velocity. Concurrently, we also observed a significant reduction in the migration of ex vivo CD14+ monocytes, across a monolayer of human BBB-ECs. These monocytes also migrated more rapidly and in higher number across meningeal endothelial cells, as compared to BBB-ECs. While similar observations were made using ex vivo CD4+ T lymphocytes, we failed to reproduce these results using in vitro activated Th1 and Th17 cells. In opposition to our in vitro data, ALCAM KO mice developed a more severe active EAE associated with a significant increase in perivascular infiltration of pro-inflammatory lymphocytes (Th1/Th17) and M1 monocytes/macrophages, as compared to WT controls. In addition, EAE transfer experiments, in which ALCAM KO mice received WT MOG-reactivated splenocytes, suggested that the pathophysiology observed in active EAE was linked to the absence of ALCAM on BBB-ECs. Phenotypic characterization of un-immunized ALCAM KO mice revealed a reduced expression of BBB junctional proteins. Further analysis showed that ALCAM is indirectly associated with tight junction molecules of the BBB-ECs, which explains the increased CNS parenchymal blood vessel in vivo permeability in ALCAM KO animals. Correlating with these data, primary culture of mouse brain BBB-ECs was shown to possess a lower TEER and an increased permeability coefficient. Conclusion: Collectively, our data provide evidence of the implication of ALCAM in monocyte transmigration, but not Th1 or Th17 lymphocyte diapedesis across CNS endothelium. Our results also point to a biologically crucial function of ALCAM in maintaining BBB integrity by acting as an adaptor molecule between tight junctions and the cytoskeleton. As such, the absence of ALCAM at the level of BBB-ECs indirectly promotes the recruitment of pro-inflammatory leukocytes in the CNS of EAE animals by increasing the BBB vessels permeability