Aging is associated with cognitive decline in various domains, including memory. The age-related increase in systemic inflammation has been identified as a potential mechanism contributing to these memory impairments. Specifically, elevated inflammation may impair neurotrophic factor production and function, which is important for maintaining brain health. Physical activity has been identified as a potential strategy for preventing or delaying memory decline, given its ability to reduce inflammation and stimulate neurotrophic factor expression. The present study investigated the relationship between cardiorespiratory fitness, a proxy for habitual physical activity, and memory in older adults. Inflammation and neurotrophic factors were examined as potential mechanisms mediating this relationship. Sixty-five community dwelling older adults (Mage = 70.6 ± 4.0) completed the Rockport 1-mile walk test to predict their cardiorespiratory fitness, as well as the Mnemonic Similarity Task to assess memory. Serum samples were collected to examine inflammatory markers, including interleukin-6 (IL-6), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP), as well as neurotrophic factors, including brain derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1). No relationship was found between cardiorespiratory fitness and memory (p > .05). However, older adults with greater cardiorespiratory fitness had lower levels of IL-6 (p < .01) and TNF-α (p < .01) and trended towards higher levels of BDNF (p = .078). Furthermore, IL-6 was negatively correlated with IGF-1 (p < .01), suggesting higher inflammation may impair IGF-1 production. Contrary to our hypotheses, sequential mediation analyses revealed no indirect effect of inflammatory markers and neurotrophic factors on the relationship between cardiorespiratory fitness and memory. Our results suggest that cardiorespiratory fitness may promote favourable changes in inflammatory markers and neurotrophic factors, which—given previous literature—could help to support brain health with advancing age. More research is needed to further examine the relationship between cardiorespiratory fitness and memory. / Thesis / Master of Science (MSc)

Immune responses during lung infections must be tightly regulated in order to permit pathogen eradication while maintaining organ function. Although mechanisms involve complex networks of cytokines, the interferon (IFN) response has been shown to be an important driver of lung inflammation. Type I IFNs consist of a group of structurally similar cytokines that are produced during virus infection and are an integral part in regulating the immune response. However, in response to certain stimuli, type I IFNs have also been found to be central in the initiation of lung inflammatory responses by inducing the recruitment and activation of immune cells and thus may contribute to disease severity. Another cytokine that has been associated with chronic lung inflammation is the gp130 cytokine, Oncostatin M. Transient pulmonary overexpression of Oncostatin M by Adenovirus vector (AdOSM) induces lung inflammation biased toward Th2 cytokines associated with eosinophilia and alternatively activated (AA/M2) macrophage accumulation. Here we demonstrated that C57Bl/6 mice deficient of the type I interferon receptor (IFNAR1-/-), were less responsive against a suboptimal dose of AdOSM at day 7 post infection compared to AdOSM-treated wild-type. We observed a significant reduction in OSM mRNA and protein levels in AdOSM-treated IFNAR1-/- mice, compared to treated wild-type, which resulted in significant attenuation in OSM-induced inflammatory cell infiltration, epithelial hyperplasia, and alveolar wall thickening. Furthermore, IL-6 overexpression (as a comparator gp130 cytokine), induced lymphocyte accumulation in IFNAR1-/- mice, but at significantly lower levels than AdIL-6-treated wild-type. These results demonstrate that cross talk between IFNAR and gp130 cytokine signaling were required for maximal AdOSM- and AdIL-6-mediated pulmonary inflammation. We also observed that IFNAR1 deficiency directly and negatively regulated OSM-mediated responses in vitro. OSM-induced pSTAT3 levels were consistently lower in murine and human IFNAR1-deficient fibroblasts, compared to OSM-stimulated wild-type cells. This was associated with diminished OSM-induced IL-6 and MCP-1 production from IFNAR1-/- fibroblasts. Furthermore, we found that the combination of OSM and IFN-α led to increased IL-6 production from C57Bl/6 and BALB/c-derived Mouse Lung Fibroblasts (MLFs) then when either cytokine was used alone suggesting that these two cytokines can work in concert. Our findings are the first to suggest that IFNAR signaling participates in OSM-mediated responses in vitro and is required for maximal AdOSM-induced pulmonary inflammation in vivo. / Thesis / Master of Science (MSc)

Chronic systemic inflammation increases with age and is associated with late life diseases (e.g. sarcopenia, and frailty) but the mechanisms causing systemic inflammation are largely unknown. Our laboratory has shown that the aged microbiome increases intestinal permeability which allows bacterial products into the circulation, thus causing systemic inflammation. We do not, however, know which microbes drive this phenomenon and ultimately impact healthy or unhealthy aging. To determine the degree to which frailty, sarcopenia, and systemic inflammation can be accelerated or exacerbated via the microbiome, we colonized germfree (recipient) mice with ‘young’ (≤6 months) or ‘old’ (≥ 18 months) microbiota from specific pathogen free mice. Initially, we investigated the impact of recipient age by colonizing young and old germfree mice. Differences in sarcopenia and cellular inflammation were driven by recipient age, not microbiota age, after 6 weeks of colonization, while frailty decreased in old mice colonized with young microbiota. To further investigate the impact of the microbiota in aging, we colonized middle-aged (10-14 month) germfree mice and assessed them 6 weeks and 6 months post colonization. The aged microbiota drove an increase in frailty after 6 months of colonization. To understand the differences between young and old microbial compositions we quantified short-chain fatty acids and sequenced 16S rRNA from fecal pellets of young and old mice. We used frailty, sarcopenia, and cellular inflammation data to identify relationships with short-chain fatty acids and the microbial community. We have identified specific microbes that correlate with age, frailty, sarcopenia, and cellular inflammation from Lachnospiraceae, Akkermansiaceae and Rikenellaceae families. By understanding the role of the microbiome in healthy and unhealthy aging we can develop therapeutics to combat chronic systemic inflammation and prevent and/or reverse poor health outcomes. / Thesis / Master of Science (MSc)

The present studies were conducted to determine the effects of obesity on insulin resistance, inflammatory state and risk for laminitis, and the effectiveness of exercise training to reduce obesity and insulin resistance in equids. Practical methods of assessing adiposity were developed and verified, including a condition scoring system for neck crest adiposity and morphometric measurements for generalized (girth:height) and localized (neck circumference:height) adiposity. Evaluation of 74 and 57 pony mares in March of two consecutive years resulted in the identification of predictive tests for incipient pasture-associated laminitis, including hyperinsulinemia (> 32 mU/L), hyperleptinemia (> 7.3 ng/mL), and generalized (body condition score ≥ 7) and localized (cresty neck score ≥ 4) obesity. Induction of obesity in 13 Arabian geldings by 4 months of overfeeding resulted in compensated insulin resistance (minimal model analysis) with hyperinsulinemia and hyperleptinemia. Although lipid concentrations (nonesterified fatty acids and triglyceride) decreased on a high concentrate diet, they did not differ before and after weight gain. The resulting obesity-induced insulin resistance was accompanied by an increase in chemokine (monocyte chemoattractant protein [MCP]-1, MCP-2, interleukin [IL]-8) but not inflammatory cytokine (tumor necrosis factor [TNF]α, IL-1β, IL-6) mRNA expression in subcutaneous adipose tissue. Additionally, there was a decrease in plasma TNFα protein concentration with weight gain. By using 12 of the obese, insulin resistant Arabian geldings (8 exercised, 4 control) it was demonstrated that 8 weeks of moderate intensity exercise training reduced adiposity (4% reduction in body weight, 35% reduction in fat mass) without affecting glucose and insulin dynamics or plasma hormone and lipid concentrations. Collectively, these studies demonstrate the impact obesity has on metabolism and risk for laminitis in equids, and that exercise training may provide an effective countermeasure for the reduction of obesity. / Ph. D.

Monocytes are dynamic innate immune cells that respond differently based upon the dose and duration of an infection. While super low dose endotoxin is found in chronic inflammatory diseases such as atherosclerosis, exposure to high dose endotoxin leads to sepsis. However, clear characterization of monocytes and the underlying mechanisms in these disease conditions is lacking. To elucidate the missing information, we conducted two different projects. In the first project, we investigated the role of super low dose endotoxin in polarizing monocytes to a prolonged low-grade inflammatory state with no resolution, disrupting homeostasis. This low grade inflammatory phenotype was confirmed by sustained induction of inflammatory mediators CD40 and CD11a. In addition, low grade inflammatory monocytes influence neighboring T cells by suppressing T cell regulatory functions. Mechanistically, we showed that the non-resolving inflammatory phenotypes in monocytes is dependent on non-traditional TLR4 adaptor called TRAM. In the second project, we focused on the effects of high dose endotoxin on monocyte phenotypes. We reported that high dose endotoxin give rise to a mix of both immunosuppressive and pathogenic inflammatory monocytes, leading to monocyte exhaustion. While thorough research is conducted to study the immunosuppressive monocytes and underlying long term effects, role of pathogenic inflammatory monocytes is not well addressed. Monocyte exhaustion leads to elevated levels of CD38, an inflammatory mediator, elevated ROS levels, depleted NAD+ and mitochondrial respiration. STAT1 and KLF4 are critical transcription factors in sustaining exhausted phenotypes. Indeed, TRAM adaptor molecule also mediates this exhaustion as TRAM deletion restores monocyte health. Taken together, our work defines novel monocyte phenotypes and mechanism in super-low dose or high dose endotoxin environments. / Doctor of Philosophy / Healthy inflammatory response is represented by initial induction of inflammatory cells in the site of infection and pathogen clearance, followed by resolution of inflammation and damage repair. This balance between inflammation and resolution maintains immune homeostasis. Imbalances in this homeostasis can be a cause or effect of various disease conditions such as atherosclerosis and sepsis, for example. Despite rigorous research, these diseases are still prevalent and treatments are still lacking. It is essential to investigate inflammatory responses at a cellular level and understand how an immune cell responds to a given pathogen. Depending upon the intensity, dose and duration of a pathogen can dictate immune cell functions. Recent discoveries, including the research in our lab have reported that super low dose bacterial endotoxin exacerbates atherosclerosis. Mouse monocytes (innate immune cells) treated with super low dose endotoxin continuously induce mild but sustained inflammatory molecules but are unable to exhibit resolving mediators to dampen the inflammation and hence, monocyte homeostasis is disrupted. Homeostatic imbalance is also in seen in sepsis, when monocytes exposed to high dose bacterial endotoxin. Due to a repetitive exposure to high dose endotoxin, monocytes are unable to respond accurately, where they simultaneously exhibit inflammatory and anti-inflammatory mediators but in a dysregulated manner.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13610号 / 論医博第2320号 / 新制||医||1073(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 川口 義弥, 教授 伊達 洋至, 教授 長船 健二 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Inflammation can be initiated by an innate immune sensor, followed by activation of a signal mediator, resulting in control of immune response by a signal regulator. Mammalian nucleotide-binding oligomerization domain protein 1 (Nod1) and Nod2 initiate host innate immune response by recognition of specific bacterial molecules, resulting in the production of pro-inflammatory cytokines, chemokines, and anti-microbial peptides. A candidate sequence of chicken Nod1 (ChNod1) was identified with no current evidence of ChNod2. Stimulation of transiently overexpressed ChNod1 and its mutants with mammalian Nod-specific ligands was not conclusive of the function of ChNod1 most likely due to self-activation of ChNod1. In vitro studies showed no significant difference in expression of Nod1, its signaling molecules and pro-inflammatory cytokines in stimulated chicken mononuclear cells with synthetic ligands for mammalian Nod1 or Nod2. A signal mediator, macrophage migration inhibitory factor (MIF) inhibits the random migration of macrophages. Chemotaxis assay using recombinant ChMIF (rChMIF) revealed a substantial decrease in migration of macrophages. qRT-PCR analysis revealed that the presence of rChMIF enhanced levels of IL-1β and iNOS during monocytes stimulation with LPS. Additionally, Con A-stimulated lymphocytes exhibited enhanced IFN-γ and IL-2 transcripts in the presence of rChMIF. IL-22, which may act as a signal regulator, is an important effector of activated Th1 and Th17 as well as natural killer cells during inflammation. Recombinant ChIL-22 alone did not have an impact on chicken embryo kidney epithelial cells (CKECs); however, co-stimulation of CKECs with LPS and rChIL-22 enhanced the production of pro-inflammatory cytokines and anti-microbial peptides. Furthermore, rChIL-22 alone stimulated acute phase reactants in chicken embryo liver cells. These effects of rChIL-22 were abolished by addition of rChIL22 binding protein. Taken together, these results indicate an important role of ChIL-22 on epithelial cells and hepatocytes during inflammation. In this project, we identified and characterized the avian inflammatory mediators ChNod1, ChMIF, and ChIL-22. Studying each of their biological function in avian inflammation, especially under pathogenic challenges in epithelial tissues will provide a foundation for understanding the role of these inflammatory mediators in mucosal immunity. / Ph. D.