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Item4-Ethylguaiacol Modulates Neuroinflammation and Promotes Heme Oxygenase-1 Expression to Ameliorate Brain Injury in Ischemic Stroke(Frontiers, 2022-07) Weng, Wen-Tsan; Kuo, Ping-Chang; Scofield, Barbara A.; Paraiso, Hallel C.; Brown, Dennis A.; Yu, I-Chen; Yen, Jui-Hung; Microbiology and Immunology, School of MedicineIschemic stroke is caused by a sudden reduction in cerebral blood flow that subsequently induces a complex cascade of pathophysiological responses, leading to brain inflammation and irreversible infarction. 4-ethylguaiacol (4-EG) is reported to suppress inflammatory immune responses. However, whether 4-EG exerts anti-inflammatory effects in ischemic stroke remains unexplored. We evaluated the therapeutic potential of 4-EG and examined the cellular and molecular mechanisms underlying the protective effects of 4-EG in ischemic stroke. The effect of 4-EG in ischemic stroke was determined by using a transient middle cerebral artery occlusion (MCAO) animal model followed by exploring the infarct size, neurological deficits, microglia activation, inflammatory cytokine production, blood–brain barrier (BBB) disruption, brain endothelial cell adhesion molecule expression, and microglial heme oxygenase-1 (HO-1) expression. Nrf2-/- and HO-1 inhibitor ZnPP-treated mice were also subjected to MCAO to evaluate the role of the Nrf2/HO-1 pathway in 4-EG-mediated protection in ischemic stroke. We found that 4-EG attenuated infarct size and neurological deficits, and lessened BBB disruption in ischemic stroke. Further investigation revealed that 4-EG suppressed microglial activation, peripheral inflammatory immune cell infiltration, and brain endothelial cell adhesion molecule upregulation in the ischemic brain. Finally, we identified that the protective effect of 4-EG in ischemic stroke was abolished in Nrf2-/– and ZnPP-treated MCAO mice. Our results identified that 4-EG confers protection against ischemic stroke and reveal that the protective effect of 4-EG in ischemic stroke is mediated through the induction of the Nrf2/HO1 pathway. Thus, our findings suggest that 4-EG could be developed as a novel therapeutic agent for the treatment of ischemic stroke. ItemChlorpyrifos Oxon Primes Microglia: Enhanced LPS-Induced TNFα Production(Office of the Vice Chancellor for Research, 2016-04-08) Kouame, Elaine; Brookins, Savannah; Jayaraj, Richard L.; Taetzsch, Thomas; Mumaw, Christy; Block, Michelle L.Microglia, the resident innate immune cells of the brain, respond to various environmental stimuli, including factors from surrounding tissue and from systemic inputs. These stimuli impact microglial function in both health and disease. Increasing evidence implicates microglia and neuroinflammation in Gulf War illness (GWI) pathology. Gulf War illness is an untreatable chronic multi symptomatic disorder that affects about 30% of Gulf War veterans. It has been proposed that “multiple hits” from exposure to various environmental neurotoxicants such as Chlorpyrifos (CPF), an organophosphate pesticide, combined with low inflammation may initiate exaggerated and persistent central nervous system (CNS) pathology to drive GWI. CPF oxon, an active metabolite of CPF, is associated with deleterious CNS effects, but the role of microglia behind this phenomenon is not fully understood.To investigate the effects of CPF oxon on microglia, we assessed microglial ROS, pro-inflammatory cytokine factors, and NF-κB p50 DNA binding activity in the presence of CPF oxon. HAPI microglia cells were treated with CPF oxon (1μM-1nM), which resulted in a dose dependent increase in H2O2 production at 3 hours and elevated superoxide at 30 minutes. CPF oxon failed to initiate TNFα and nitric oxide from microglia cultures. However, CPF oxon significantly decreased NF-κB p50 binding to DNA in microglia, a key redox signaling mechanism linked to microglial priming. Consistent with this premise, pre-treatment with CPF oxon (0.5μM) amplified LPSinduced TNFα production in microglia and neuron-glia cultures. Moreover, when CPF oxon and LPS challenged cells were pre-treated with DPI, a NOX2 inhibitor, we found a significant reduction in TNFα response when compared to non-treated cells, supporting that NOX2 may regulate CPF oxon priming in microglia. These data suggest that CPF oxon may induce ROS production in microglia to reprogram these cells to become more sensitive to pro-inflammatory stimuli (priming). ItemDithiolethione ACDT suppresses neuroinflammation and ameliorates disease severity in experimental autoimmune encephalomyelitis(Elsevier, 2018) Kuo, Ping-Chang; Brown, Dennis A.; Scofield, Barbara A.; Paraiso, Hallel C.; Wang, Pei-Yu; Yu, I-Chen; Yen, Jui-Hung; Microbiology and Immunology, School of MedicineMultiple sclerosis (MS) is an autoimmune disorder characterized by the central nervous system (CNS) infiltration of myelin-specific pathogenic T cells followed by brain inflammation in association with demyelination. Similarly, experimental autoimmune encephalomyelitis (EAE), the animal model of MS, also exhibits increased CNS infiltration of pathogenic T cells, including Th1 and Th17, leading to detrimental effects of neuroinflammation and demyelination. We previously reported that 3H-1,2-dithiole-3-thione (D3T), the structurally-simplest of the sulfur-containing dithiolethiones, exerted a promising therapeutic effect in EAE. In the current study we report that 5-Amino-3-thioxo-3H-(1,2)dithiole-4-carboxylic acid ethyl ester (ACDT), a substituted derivative of D3T, exhibits anti-inflammatory properties in EAE. ACDT, administered post immunization, delayed disease onset and reduced disease severity in chronic C57BL/6 EAE, and ACDT, administered during disease remission, suppressed disease relapse in relapsing-remitting SJL/J EAE. Further analysis of the cellular and molecular mechanisms underlying the protective effects of ACDT in EAE revealed that ACDT inhibited pathogenic T cell infiltration, suppressed microglia activation, repressed neurotoxic A1 astrocyte generation, lessened blood-brain barrier disruption, and diminished MMP3/9 production in the CNS of EAE. In summary, we demonstrate that ACDT suppresses neuroinflammation and ameliorates disease severity in EAE through multiple cellular mechanisms. Our findings suggest the potential of developing ACDT as a novel therapeutic agent for the treatment of MS/EAE. ItemGWAS of longitudinal amyloid accumulation on 18F-florbetapir PET in Alzheimer’s disease implicates microglial activation gene IL1RAP.(Oxford UP, 2015-10) Ramanan, Vijay K.; Risacher, Shannon L.; Nho, Kwangsik; Kim, Sungeun; Shen, Li; McDonald, Brenna C.; Yoder, Karmen K.; Hutchins, Gary D.; West, John D.; Tallman, Eileen F.; Gao, Sujuan; Foroud, Tatiana M.; Farlow, Martin R.; De Jager, Philip L.; Bennett, David A.; Aisen, Paul S.; Petersen, Ronald C.; Jack, Clifford R.; Toga, Arthur W.; Green, Robert C.; Jagust, William J.; Weiner, Michael W.; Saykin, Andrew J.; Department of Medical and Molecular Genetics, IU School of MedicineIn a genome-wide study, Ramanan et al. discover an association between the microglial activation gene IL1RAP and higher rates of amyloid plaque accumulation as measured by PET in prodromal Alzheimer’s disease. Activated microglia may be crucial in amyloid clearance, and targeting the interleukin-1/IL1RAP pathway may be a potential therapeutic approach. ItemHX600, a synthetic agonist for RXR-Nurr1 heterodimer complex, prevents ischemia-induced neuronal damage(Elsevier, 2018-10) Loppi, S.; Kolosowska, N.; Kärkkäinen, O.; Korhonen, P.; Huuskonen, M.; Grubman, A.; Dhungana, H.; Wojciechowski, S.; Pomeshchik, Y.; Giordano, M.; Kagechika, H.; White, A.; Auriola, S.; Koistinaho, J.; Landreth, Gary E.; Hanhineva, K.; Kanninen, K.; Malm, T.; Anatomy and Cell Biology, School of MedicineIschemic stroke is amongst the leading causes of death and disabilities. The available treatments are suitable for only a fraction of patients and thus novel therapies are urgently needed. Blockage of one of the cerebral arteries leads to massive and persisting inflammatory reaction contributing to the nearby neuronal damage. Targeting the detrimental pathways of neuroinflammation has been suggested to be beneficial in conditions of ischemic stroke. Nuclear receptor 4A-family (NR4A) member Nurr1 has been shown to be a potent modulator of harmful inflammatory reactions, yet the role of Nurr1 in cerebral stroke remains unknown. Here we show for the first time that an agonist for the dimeric transcription factor Nurr1/retinoid X receptor (RXR), HX600, reduces microglia expressed proinflammatory mediators and prevents inflammation induced neuronal death in in vitro co-culture model of neurons and microglia. Importantly, HX600 was protective in a mouse model of permanent middle cerebral artery occlusion and alleviated the stroke induced motor deficits. Along with the anti-inflammatory capacity of HX600 in vitro, treatment of ischemic mice with HX600 reduced ischemia induced Iba-1, p38 and TREM2 immunoreactivities, protected endogenous microglia from ischemia induced death and prevented leukocyte infiltration. These anti-inflammatory functions were associated with reduced levels of brain lysophosphatidylcholines (lysoPCs) and acylcarnitines, metabolites related to proinflammatory events. These data demonstrate that HX600 driven Nurr1 activation is beneficial in ischemic stroke and propose that targeting Nurr1 is a novel candidate for conditions involving neuroinflammatory component. ItemThe Role of TGF-B Activated Kinase (TAK1) in Retinal Development and Inflammation(2021-08) Carrillo, Casandra; Belecky-Adams, Teri; Baucum, A.J.; Berbari, NicolasTransforming growth factor β-activated kinase 1 (TAK1), a hub kinase at the convergence of multiple signaling pathways, is critical to the development of the central nervous system and has been found to play a role in cell death and apoptosis. TAK1 may have the potential to elucidate mechanisms of cell cycle and neurodegeneration. The Belecky-Adams laboratory has aimed to study TAK1 and its potential roles in cell cycle by studying its role in chick retinal development as well as its possible implication in the progression of diabetic retinopathy (DR). Chapter 3 includes studies that explore TAK1 in a study in chick retinal development and TAK1 in in vitro studies in retinal microglia. Using the embryonic chick, immunohistochemistry for the activated form of TAK1 (pTAK1) showed localization of pTAK1 in differentiated and progenitor cells of the retina. Using an inhibitor or TAK1 activite, (5Z)-7-Oxozeaenol, in chick eye development showed an increase in progenitor cells and a decrease in differentiated cells. This study in chick suggests TAK1 may be a critical player in the regulation of the cell cycle during retinal development. Results from experimentation in chick led to studying the potential role of TAK1 in inflammation and neurodegeneration. TAK1 has previously been implicated in cell death and apoptosis suggesting that TAK1 may be a critical player in inflammatory pathways. TAK1 has been implicated in the regulation of inflammatory factors in different parts of the CNS but has not yet been studied specifically in retina or in specific retinal cells. Chapter 2 includes studies from the Belecky-Adams laboratory of in vitro work with retinal microglia. Retinal microglia were treated with activators and the translocation to the nucleus of a downstream factor of TAK1 was determined: NF-kB. Treatment of retinal microglia in the presence of activators with TAKinib, an inhibitor of TAK1 activation, revealed that TAK1 inhibition reduces the activation of downstream NF-kB. Together this data suggests that TAK1 may be implicated in various systems of the body and further studies on its mechanisms may help elucidate potential therapeutic roles of the kinase. ItemTREM2 is required for microglial instruction of astrocytic synaptic engulfment in neurodevelopment(Wiley, 2019) Jay, Taylor R.; von Saucken, Victoria E.; Muñoz, Braulio; Codocedo, Juan F.; Atwood, Brady K.; Lamb, Bruce T.; Landreth, Gary E.; Anatomy and Cell Biology, School of MedicineVariants in the microglial receptor TREM2 confer risk for multiple neurodegenerative diseases. However, it remains unknown how this receptor functions on microglia to modulate these diverse neuropathologies. To understand the role of TREM2 on microglia more generally, we investigated changes in microglial function in Trem2−/− mice. We found that loss of TREM2 impairs normal neurodevelopment, resulting in reduced synapse number across the cortex and hippocampus in 1-month-old mice. This reduction in synapse number was not due directly to alterations in interactions between microglia and synapses. Rather, TREM2 was required for microglia to limit synaptic engulfment by astrocytes during development. While these changes were largely normalized later in adulthood, high fat diet administration was sufficient to reinitiate TREM2-dependent modulation of synapse loss. Together, this identifies a novel role for microglia in instructing synaptic pruning by astrocytes to broadly regulate appropriate synaptic refinement, and suggests novel candidate mechanisms for how TREM2 and microglia could influence synaptic loss in brain injury and disease.