Interactions of neurofibrosis and oligodendrogenesis following demyelination: Modulation by aging and exercise

The central nervous system does not undergo significant amounts of regeneration following injury. Despite this, cellular repair processes occur that help to limit the spread of injuries, maintain tissue integrity, and in some cases regenerate lost cells. Here I introduce central nervous system fibroblasts as regulators of regenerative processes in the central nervous system, and present aging and exercise as factors regulating fibroblasts and the lesioned environment. Fibroblasts are connective tissue cells that are found throughout the body. Under pathological conditions they contribute to tissue scarification by secreting excessive amounts of extracellular matrix that impairs regeneration. Fibroblasts in the central nervous system are normally found at the border regions in the meninges, perivascular space, and choroid plexus. In the injured central nervous system fibroblasts are elevated in the parenchyma and impair regenerative processes like axon regeneration. In this thesis I characterized the elevation of fibroblasts in the toxin induced lysolecithin model of central nervous system injury. One primary observation was the association of fibroblasts with microglia/macrophage responses, as well as the ability of macrophages to promote fibroblast migration in vitro. Central nervous system fibroblasts spatially obscured newly myelinating oligodendrocytes in lysolecithin lesions and inhibited the differentiation of oligodendrocyte progenitor cells in vitro. I explored the impact of age on the fibroblast response to lysolecithin injury. I found that age affected the proportion of the lysolecithin lesion occupied by fibroblasts, attenuated the immune response, and ablated the chemoattractant capacity of macrophages in vitro. Lastly, I described the changes that occur in the proteome of naïve and lysolecithin lesioned spinal cords and serum from exercising and sedentary mice. I also examined the effects of exercise on the young and middle-aged fibroblast response. I found that acute voluntary access to a running wheel resulted in significant protein changes related to metabolism, oxidative stress, and synaptic transmission. However, voluntary wheel running did not result in any changes to the fibroblast response in lysolecithin lesions in young and middle-aged mice. This thesis highlights the role of fibroblasts in central nervous system injuries, details the potential causes and outcomes of their elevation in the parenchyma, and also highlights the implications of aging and exercise for the fibroblast response and broader lysolecithin lesion environment

Niacin-mediated rejuvenation of macrophage/microglia enhances remyelination of the aging central nervous system

Abstract: Remyelination following CNS demyelination restores rapid signal propagation and protects axons; however, its efficiency declines with increasing age. Both intrinsic changes in the oligodendrocyte progenitor cell population and extrinsic factors in the lesion microenvironment of older subjects contribute to this decline. Microglia and monocyte-derived macrophages are critical for successful remyelination, releasing growth factors and clearing inhibitory myelin debris. Several studies have implicated delayed recruitment of macrophages/microglia into lesions as a key contributor to the decline in remyelination observed in older subjects. Here we show that the decreased expression of the scavenger receptor CD36 of aging mouse microglia and human microglia in culture underlies their reduced phagocytic activity. Overexpression of CD36 in cultured microglia rescues the deficit in phagocytosis of myelin debris. By screening for clinically approved agents that stimulate macrophages/microglia, we have found that niacin (vitamin B3) upregulates CD36 expression and enhances myelin phagocytosis by microglia in culture. This increase in myelin phagocytosis is mediated through the niacin receptor (hydroxycarboxylic acid receptor 2). Genetic fate mapping and multiphoton live imaging show that systemic treatment of 9–12-month-old demyelinated mice with therapeutically relevant doses of niacin promotes myelin debris clearance in lesions by both peripherally derived macrophages and microglia. This is accompanied by enhancement of oligodendrocyte progenitor cell numbers and by improved remyelination in the treated mice. Niacin represents a safe and translationally amenable regenerative therapy for chronic demyelinating diseases such as multiple sclerosis

Correction to: Niacin-mediated rejuvenation of macrophage/microglia enhances remyelination of the aging central nervous system.

The article Niacin‑mediated rejuvenation of macrophage/microglia enhances remyelination of the aging central nervous system, written by Khalil S. Rawji, Adam M.H. Young, Tanay Ghosh, Nathan J. Michaels, Reza Mirzaei, Janson Kappen, Kathleen L. Kolehmainen, Nima Alaeiilkhchi, Brian Lozinski, Manoj K. Mishra, Annie Pu, Weiwen Tang, Salma Zein, Deepak K. Kaushik, Michael B. Keough, Jason R. Plemel, Fiona Calvert, Andrew J. Knights, Daniel J. Gaffney, Wolfram Tetzlaff, Robin J. M. Franklin and V. Wee Yong, was originally published electronically on the publisher's internet

Effects of Crowding and Confinement on Enzyme Kinetics

Reverse micelles are formed by the aggregation of water inside of a bilayer formed by a surfactant in a non-polar solvent. The nanometer scale pool of water within the reverse micelles provides an environment to study the effects of confinement on enzymes as measured by changes in kinetics. The size of these reverse micelles is directly related to the ratio of water and surfactant. We and others have been studying the effects of crowding, the presence of large concentrations of solutes, on enzyme kinetics. What effect would it have on enzyme kinetics if these solutes were added to the confined environment of the reverse micelle? We have studied the effects of confinement on alpha-chymotrypsin in a system using dioctyl sulfosuccinate (AOT) as a surfactant, isooctane as the non-polar solvent, and N-succinyl-L-phenylalanine p-nitroanilide (SPN) as the substrate. Results will be analyzed within the Michaelis-Menten framework. * Indicates faculty mentor

Emerging role of galectin 3 in neuroinflammation and neurodegeneration

Neuroinflammation and neurodegeneration are key processes that mediate the development and progression of neurological diseases. However, the mechanisms modulating these processes in different diseases remain incompletely understood. Advances in single cell based multi-omic analyses have helped to identify distinct molecular signatures such as Lgals3 that is associated with neuroinflammation and neurodegeneration in the central nervous system (CNS). Lgals3 encodes galectin-3 (Gal3), a β-galactoside and glycan binding glycoprotein that is frequently upregulated by reactive microglia/macrophages in the CNS during various neurological diseases. While Gal3 has previously been associated with non-CNS inflammatory and fibrotic diseases, recent studies highlight Gal3 as a prominent regulator of inflammation and neuroaxonal damage in the CNS during diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. In this review, we summarize the pleiotropic functions of Gal3 and discuss evidence that demonstrates its detrimental role in neuroinflammation and neurodegeneration during different neurological diseases. We also consider the challenges of translating preclinical observations into targeting Gal3 in the human CNS

Pericytes as mediators of infiltration of macrophages in multiple sclerosis

Abstract Background Multiple sclerosis (MS) is a neurodegenerative condition of the central nervous system (CNS). It is associated with blood–brain barrier (BBB) breakdown and intravasation of leukocytes, particularly monocyte-derived macrophages, into the CNS. Pericytes are mural cells that are encased within the basement membrane of vasculature, and they contribute functionally to the neurovascular unit. These cells play an important role in maintaining BBB integrity and CNS homeostasis. However, the critical role of pericytes in mediating inflammation in MS or its models is unclear. Whether pericytes infiltrate into the CNS parenchyma in MS also needs clarification. Methods CNS samples from the experimental autoimmune encephalomyelitis (EAE) mouse model of MS were collected at different time points for immunohistochemical analysis of pericytes along the inflamed vasculature. These findings were validated using MS brain specimens, and further analysis of pericyte involvement in inflammation was carried out by culturing primary pericytes and macrophages. Multiplex ELISA, transmigration assay and real-time PCR were used to study the inflammatory potential of pericytes in cultures. Results We found that pericytes exhibit a heterogenous morphology, with notable elongation in the inflamed perivascular cuffs of EAE. This was manifested by a decrease in pericyte density but an increase in the coverage by pericytes along the vasculature. Chondroitin sulfate proteoglycans (CSPGs), a family of extracellular matrix proteins enriched within inflamed perivascular cuffs, elevated levels of pro-inflammatory chemokines/cytokines in pericytes in culture. Importantly, pericytes stimulated with CSPGs enhanced macrophage migration. We did not detect pericytes in the CNS parenchyma during EAE, and this was corroborated in MS brain samples. Conclusions Our data suggest that pericytes seek to restore the BBB through increased coverage, but that their exposure to CSPGs prompt their facilitation of macrophages to enter the CNS to elevate neuroinflammation in EAE and MS

Critical Media Literacy and Environmental Pedagogy: Children’s Books, Hip-Hop, Fake News and Hell

This panel consists of four presentations focusing on multiple literacies and their relationship to issues centering on critical environmental pedagogy and the global climate crisis. The presenters provide in-depth critical analysis of various forms of media from widely varying philosophical and theoretical perspectives. These various analyses help us formulate critical questions in unquestioning, authoritarian times. How are our understandings of the current global climate crisis influenced and developed through these various forms of media? The first presentation, The Power of Discourse: CML and The Tantrum that Saved the World. This research project uses both critical theory and Michel Foucault’s notion of power to analyze a new children’s picture book titled The Tantrum that Saved the World. Published in 2018 by World Saving Books, the e-version’s 64 colorfully illustrated pages tell of a little girl who stares down the climate crisis, channeling tantrum power into positive action. Equally important, the analysis brings media literacy into dialogue with discursive practices that cannot take hold in the absence of critical theory. The second presentation, Biased Coverage: How The Flint Water Crisis was Covered and Where We are Now. will focus on the media coverage immediately following the Flint water crisis and how it not only tapered off in the year that followed, but also was full of discriminatory, biased reporting and practices. Hip Hop and Climate Change the third presentation will focus on the texts and activist work of several hip-hop artists who are committed to eliminating oppressive conditions that are responsible for environmental degradation at today’s historical juncture. The final presentation, Hell: Critical Environmental Pedagogy through Popular Dystopic Films situates the critical analysis of popular fictional dystopic climate disaster films within the current historical dystopic-like milieu in which climate change is relegated to the status of hoax and the ways in which these films perpetuate the cultural hegemony (Gramsci, 1971) of the neo-liberal moment. Films such as The Day after Tomorrow and Hell are analyzed using a number of theoretical perspectives from Klein (2014) to Hedges (2015). Many documentaries have been produced on climate change but this presentation will focus on popular films. Brian Lozenski --Chair Derek Ford -- Discussan

Enhanced liver X receptor signalling reduces brain injury and promotes tissue regeneration following experimental intracerebral haemorrhage: roles of microglia/macrophages

Background Inflammation-exacerbated secondary brain injury and limited tissue regeneration are barriers to favourable prognosis after intracerebral haemorrhage (ICH). As a regulator of inflammation and lipid metabolism, Liver X receptor (LXR) has the potential to alter microglia/macrophage (M/M) phenotype, and assist tissue repair by promoting cholesterol efflux and recycling from phagocytes. To support potential clinical translation, the benefits of enhanced LXR signalling are examined in experimental ICH.Methods Collagenase-induced ICH mice were treated with the LXR agonist GW3965 or vehicle. Behavioural tests were conducted at multiple time points. Lesion and haematoma volume, and other brain parameters were assessed using multimodal MRI with T2-weighted, diffusion tensor imaging and dynamic contrast-enhanced MRI sequences. The fixed brain cryosections were stained and confocal microscopy was applied to detect LXR downstream genes, M/M phenotype, lipid/cholesterol-laden phagocytes, oligodendrocyte lineage cells and neural stem cells. Western blot and real-time qPCR were also used. CX3CR1CreER: Rosa26iDTR mice were employed for M/M-depletion experiments.Results GW3965 treatment reduced lesion volume and white matter injury, and promoted haematoma clearance. Treated mice upregulated LXR downstream genes including ABCA1 and Apolipoprotein E, and had reduced density of M/M that apparently shifted from proinflammatory interleukin-1β+ to Arginase1+CD206+ regulatory phenotype. Fewer cholesterol crystal or myelin debris-laden phagocytes were observed in GW3965 mice. LXR activation increased the number of Olig2+PDGFRα+ precursors and Olig2+CC1+ mature oligodendrocytes in perihaematomal regions, and elevated SOX2+ or nestin+ neural stem cells in lesion and subventricular zone. MRI results supported better lesion recovery by GW3965, and this was corroborated by return to pre-ICH values of functional rotarod activity. The therapeutic effects of GW3965 were abrogated by M/M depletion in CX3CR1CreER: Rosa26iDTR mice.Conclusions LXR agonism using GW3965 reduced brain injury, promoted beneficial properties of M/M and facilitated tissue repair correspondent with enhanced cholesterol recycling