Browsing by Author "Eksteen, Bertus"

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    Dynamic Alterations of the Mesenteric Lymphatic System in Murine Ileitis: Impications for Crohn’s Disease Pathogenesis
    (2017) Rehal, Sonia; von der Weid, Pierre-Yves; MacNaughton, Wallace; Eksteen, Bertus; McCafferty, Donna-Marie
    Inflammatory bowel disease (IBD) remains a challenging disease to treat due to its complex pathophysiology. It encompasses Crohn’s Disease and ulcerative colitis, both characterized by chronic inflammation. Exaggerated inflammatory responses in IBD are thought to be partly mediated by over-reactive immune cells. In particular, dendritic cells (DCs) have been shown to be over-recruited and hyper-responsive in clinical and experimental IBD tissue. DCs require trafficking through mucosal and mesenteric lymphatic vessels to drain into mesenteric lymph nodes (MLNs). Remodeling of these vessels during inflammation could have dire effects on DC effector function and immune responses in the inflamed intestine. Lymphatic vessel plasticity is also an important concept during acute intestinal injury for proper resolution of inflammation. Human and animal studies demonstrate pathological remodeling of mucosal lymphatic changes during IBD, including lymphangiogenesis and lymphatic vessel dilation. However, no studies have addressed the role of mesenteric lymphatic remodeling in replicable models of acute or chronic ileitis. These objectives were investigated using both the acute, dextran sodium sulphate (DSS) mouse model of ileitis and the chronic, transgenic TNFΔARE mouse model of ileitis. Plasticity of this remodeling was further assessed in recovery DSS mice. Our research findings demonstrate that chronic CD-like ileitis in TNFΔARE mouse model displays many lymphatic abnormalities. These include intestinal lymphangiectasia and MLN lymphadenopathy, reminiscent of human CD. TNFΔARE vessels have increased lipid transport, lymphangiogenesis and critically the development of mesenteric tertiary lymphoid organs (TLOs), actively involved in immune modulation; all of which we believe cause altered DC trafficking in these mice. Many of these changes were replicated in the acute DSS ileitis mouse model, albeit at a lesser extent. However, decreased lymph flow was observed during acute injury. Despite having recovered from DSS-induced intestinal inflammation, mice continued to display marked mesenteric lymphatic dysfunctions, such as lymphadenopathy and lymphangiogenesis. Lamina propria (LP), lymphatic vessels and mesenteric lymph nodes (MLNs) also continued to exhibit enhanced DC populations. This study contributes intriguing findings on remodeling of the lymphatic system within the context of small intestinal inflammation, commonly found in CD patients. Modulating lymphatic function during inflammation might offer new therapeutic avenues for IBD.
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    Gut microbiota manipulation with prebiotics in patients with non-alcoholic fatty liver disease: a randomized controlled trial protocol
    (BMC Gastroenterology, 2015-12-03) Lambert, Jennifer E.; Parnell, Jill A.; Eksteen, Bertus; Raman, Maitreyi; Bomhof, Marc R.; Rioux, Kevin P.; Madsen, Karen L.; Reimer, Raylene A.
    Background Evidence for the role of the gut microbiome in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) is emerging. Strategies to manipulate the gut microbiota towards a healthier community structure are actively being investigated. Based on their ability to favorably modulate the gut microbiota, prebiotics may provide an inexpensive yet effective dietary treatment for NAFLD. Additionally, prebiotics have established benefits for glucose control and potentially weight control, both advantageous in managing fatty liver disease. Our objective is to evaluate the effects of prebiotic supplementation, adjunct to those achieved with diet-induced weight loss, on heptic injury and liver fat, the gut microbiota, inflammation, glucose tolerance, and satiety in patients with NAFLD. Methods/design In a double blind, placebo controlled, parallel group study, adults (BMI ≥25) with confirmed NAFLD will be randomized to either a 16 g/d prebiotic supplemented group or isocaloric placebo group for 24 weeks (n = 30/group). All participants will receive individualized dietary counseling sessions with a registered dietitian to achieve 10 % weight loss. Primary outcome measures include change in hepatic injury (fibrosis and inflammation) and liver fat. Secondary outcomes include change in body composition, appetite and dietary adherence, glycemic and insulinemic responses and inflammatory cytokines. Mechanisms related to prebiotic-induced changes in gut microbiota (shot-gun sequencing) and their metabolic by-products (volatile organic compounds) and de novo lipogenesis (using deuterium incorporation) will also be investigated. Discussion There are currently no medications or surgical procedures approved for the treatment of NAFLD and weight loss via lifestyle modification remains the cornerstone of current care recommendations. Given that prebiotics target multiple metabolic impairments associated with NAFLD, investigating their ability to modulate the gut microbiota and hepatic health in patients with NAFLD is warranted.
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    Gut-derived Danger Signals Contribute to Hepatocellular Injury and Inflammation during Non-alcoholic Fatty Liver Disease
    (2016) Reid, Danielle; Eksteen, Bertus; Reimer, Raylene; Madsen, Karen; von der Weid, Pierre-Yves; Beck, Paul; McKay, Derek; Jenne, Craig
    Non-alcoholic fatty liver disease (NAFLD) has become the leading liver disease in North America. Associated with the obesity epidemic, it is estimated that NAFLD currently affects over seven million Canadians. In certain cases, individuals with NAFLD may develop a progressive, inflammatory liver disease known as non-alcoholic steatohepatitis (NASH) that may lead to cirrhosis or hepatocellular carcinoma. Currently, the etiology of NASH remains unclear and there are no treatment strategies available beyond intensive dietary and lifestyle modification. The goal of this dissertation was to examine if the activation of liver-resident macrophages, Kupffer cells, by gut-derived metabolites contributes to the release of pro-inflammatory mediators and the recruitment of effector immune cells to promote inflammation and hepatocellular damage in experimental NASH. We found that Kupffer cells are critical for initiating inflammation during NASH while the absence of KCs limits the recruitment of leukocytes into the liver and protects against inflammation. Moreover, we identified unique transcriptional differences in resident and recruited macrophage populations that reflect the dynamic changes we characterized in Kupffer cells and infiltrating monocyte-derived macrophages during NASH. It has been suggested that compromised gut barrier function associated with obesity may result in the translocation of microbial by-products into the liver and contribute to hepatocellular injury and inflammation observed in NASH. We strengthen this link between the gut and the liver through the identification of novel, gut-derived volatile organic compounds (VOCs) in portal circulation in mice with NASH that have the potential to directly disrupt cellular processes in KCs and result in the secretion of proinflammatory cytokines. Once in the liver, microbial by-products such as VOCs may be detected by KCs through innate pattern recognition receptors such as the NLRP3 inflammasome, lead to the activation of KCs and contribute to inflammation in the liver. We found that the expression of the NLRP3 inflammasome within KCs has a dual proinflammatory and protective role during the development of experimental steatohepatitis. These studies provide evidence that gut-liver crosstalk influencing the activation of Kupffer cells is central in the development of experimental NASH and should be a major target for the development of novel treatment strategies.
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    Innate and Adaptive Cell Populations Driving Inflammation in Dry Eye Disease
    (2018-08-12) Reyes, José L.; Vannan, Danielle T.; Eksteen, Bertus; Avelar, Imelda Juárez; Rodríguez, Tonathiu; González, Marisol Ibet; Mendoza, Alicia Vázquez
    Dry eye disease (DED) is the most common ocular disease and affects millions of individuals worldwide. DED encompasses a heterogeneous group of diseases that can be generally divided into two forms including aqueous-deficient and evaporative DED. Evidence suggests that these conditions arise from either failure of lacrimal gland secretion or low tear film quality. In its secondary form, DED is often associated with autoimmune diseases such as Sjögren’s syndrome and rheumatoid arthritis. Current treatment strategies for DED are limited to anti-inflammatory medications that target the immune system as the source of deleterious inflammation and tissue injury. However, there is a lack of understanding of the underlying pathogenesis of DED, and subsequently, there are very few effective treatment strategies. The gap in our knowledge of the etiology of primary DED is in part because the majority of research in DED focused on secondary autoimmune causes. This review focuses on what is currently understood about the contribution of innate and adaptive immune cell populations in the pathogenesis of DED and highlights the need to continue investigating the central role of immunity driving DED.
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    Molecular Mechanisms and Functional Role of Hepatic Invariant Natural Killer T cell Recruitment Following Sterile Injury in the Liver
    (2017) Liew, Pei; Kubes, Paul; Mody, Christopher; Eksteen, Bertus; Mallevaey, Thierry; Senger, Donna
    After traumatic injury, the body must return to homeostasis as quickly as possible through initial destruction of injured cells and clearance of debris (inflammation) followed by a critical switch towards vascular and tissue reconstruction (non-inflammatory restitution). While many different immune cells are known to infiltrate a site of injury for specific effector functions, it is reasonable to hypothesize that some cells function as directors of inflammation whereupon sensing the degree of injury, these cells orchestrate the local immune response towards a restitution phase by affecting the local cytokine milieu. This progression could be defective in non-resolving sterile injuries where a failure to transition to repair or a persistence of inflammation leads to chronic inflammation. Invariant Natural Killer T (iNKT) cells are innate lymphocytes that prominently regulate inflammation due to their rapid release of pivotal cytokines during pathological states, which can then differentially impact the downstream immune response and disease outcome. In this thesis, using intravital microscopy, we observed that patrolling iNKT cells in the liver were initially selectively repelled from a site of hepatic injury but were subsequently strategically arrested via self-antigens and cytokines, circumscribing the injured site at exactly the location where monocytes co-localized and hepatocytes proliferated. iNKT cell activation signals were temporally- and spatially-regulated as self-antigen presentation via CD1d occurred first before being closely followed by cytokine signaling. Additionally, both activation signals were located adjacent to the injury and not further away. Activation of iNKT cells through these two mechanisms resulted in the production of IL-4 but not IFN-γ which promoted increased hepatocyte proliferation, monocyte transition (from classical to tissue repair monocytes) and improved healing. Disruption of any of these mechanisms led to a delay of wound healing. We show that self-antigens, beyond the known role in iNKT cell development, were fundamental for monocyte transition, appropriate collagen deposition and hepatocyte proliferation. Hepatic iNKT cells were instrumental in directing and modulating the transformation from inflammation to tissue restitution after sterile injury in the liver for essential timely wound repair.
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    The Role of B-cells in Regulating Pulmonary Neutrophils in vivo
    (2018-01-17) Kim, Jung Hwan; Yipp, Bryan; Kubes, Paul; Patel, Kamala; Eksteen, Bertus
    Neutrophils, the major innate immune cell, are short-lived and typically considered as pro-inflammatory. As such, its pre-dominant role is to clear infections via the release of cytotoxic granules and phagocytosis. The production of neutrophils is regulated in the bone marrow, which generates about 1011 neutrophils per day in humans. Newly produced neutrophils circulate and transit through all organs receiving blood flow, seeking out infections and inflammatory signals. During homeostasis, neutrophils age overtime and are thought to be cleared from the system by macrophages in lymphoid organs. However, despite t extensive research, a complete life-cycle of neutrophils, including the aging process and regulation of neutrophil clearance, remains poorly understood. Interestingly, the pulmonary vasculature contains a significant amount of retained neutrophils that are higher concentration than their circulating counterpart. These marginated neutrophils were described to be retained within the pulmonary vasculature via CXCR4, a marker that is up-regulated on aged neutrophils. Therefore, we hypothesized that margination of neutrophils in the lung might represent a key intermediate step in the regulation and elimination of neutrophils. In this body of work, we discovered lung neutrophils display an aged phenotype where they express a higher level of CD18 and CXCR4 than the peripheral pool. Interestingly, these aged neutrophils bind pulmonary circulating B-cells via CD18. Moreover, such intercellular interaction between the two cells induces apoptosis in neutrophils that also depends on CD18, leading to the removal of subsequent apoptotic neutrophils by macrophages. B-cell depletion resulted in neutrophil inflammation leading to interstitial lung disease (ILD), and was attenuated by B-cell adoptive transfer or neutrophil depletion. During a model of rheumatoid arthritis (RA), B-cell sufficient animals were protected from neutrophil pulmonary inflammation; however, CD19-deficient mice, which have defective B-cell populations and response regulation, developed lung neutrophilic inflammation in addition to arthritis. Thus, we have defined a new regulatory role of B-cells to control neutrophils in pulmonary capillaries and found that the lung is a key site for neutrophil life-cycle.