Browsing by Author "Block, Michelle L."
Now showing 1 - 10 of 17
Results Per Page
Sort Options
Item Aberrant Neural Activity in Cortico-Striatal-Limbic Circuitry Underlies Behavioral Deficits in a Mouse Model of Neurofibromatosis Type 1(2022-05) Drozd, Hayley Paulina; McKinzie, David L.; Clapp, D. Wade; Shekhar, Anantha; Lukkes, Jodi L.; Lapish, Christopher L.; Block, Michelle L.Nearly 18% of children are diagnosed with developmental disabilities. Autism spectrum disorders (ASDs) and attention deficit hyperactivity disorder (ADHD) are increasingly common developmental disabilities, but neither is well understood. ADHD and ASD are both prevalent in the genetic disorder Neurofibromatosis type 1 (NF1) which impairs the Ras-MAPK/ERK pathway through mutation of the neurofibromin gene (NF1+/−). More broadly, syndromic forms of developmental disorders are often caused by mutations of proteins in pathways interconnected with Ras including TSC1/2, FMR1, and SynGAP. Of NF1 patients, around 30-50% are diagnosed with ASDs and more than 60% with ADHD. These studies are the first to show that male mice haploinsufficient for the Nf1 gene (Nf1+/−) exhibit deficits in behavioral inhibition in multiple contexts, a key feature of ADHD. They exhibit hyperactivity and impulsivity in an open field, delay discounting task, and cliff avoidance reaction test, rescuable through treatment with the clinically effective ADHD drug, guanfacine (α2A adrenergic receptor agonist). Previous experiments in our lab identified social deficits including deficits in consolidation of social memory. Using optogenetics and awake behaving electrode recordings, we explored the role of the cortico-striatal-limbic circuitry in impulsivity and in social deficits in male Nf1+/− mice. Manipulation of the prefrontal cortex, nucleus accumbens, or basolateral amygdala through optogenetics rescued social deficits. These studies are the first to record brain activity in a preclinical model of NF1 during impulsive behavior, finding broad spectrum changes across slow, delta, theta, and gamma oscillatory frequencies and decreased synchrony of the prefrontal cortex and nucleus accumbens during a delay discounting task. Overall, Nf1+/− male mice with deletion of a single NF1 gene recapitulate cognitive phenotypes of NF1 patients and are a useful model system to identify alterations in neural circuitry associated with ASD and ADHD.Item Aspergillus versicolor Inhalation Triggers Neuroimmune, Glial, and Neuropeptide Transcriptional Changes(Sage, 2021) Ladd, Thatcher B.; Johnson, James A., Jr.; Mumaw, Christen L.; Greve, Hendrik J.; Xuei, Xiaoling; Simpson, Ed; Barnes, Mark A.; Green, Brett J.; Croston, Tara L.; Ahmed, Chandrama; Lemons, Angela; Beezhold, Donald H.; Block, Michelle L.; Medical and Molecular Genetics, School of MedicineIncreasing evidence associates indoor fungal exposure with deleterious central nervous system (CNS) health, such as cognitive and emotional deficits in children and adults, but the specific mechanisms by which it might impact the brain are poorly understood. Mice were exposed to filtered air, heat-inactivated Aspergillus versicolor (3 × 105 spores), or viable A. versicolor (3 × 105 spores) via nose-only inhalation exposure 2 times per week for 1, 2, or 4 weeks. Analysis of cortex, midbrain, olfactory bulb, and cerebellum tissue from mice exposed to viable A. versicolor spores for 1, 2, and 4 weeks revealed significantly elevated pro-inflammatory (Tnf and Il1b) and glial activity (Gdnf and Cxc3r1) gene expression in several brain regions when compared to filtered air control, with the most consistent and pronounced neuroimmune response 48H following the 4-week exposure in the midbrain and frontal lobe. Bulk RNA-seq analysis of the midbrain tissue confirmed that 4 weeks of A. versicolor exposure resulted in significant transcriptional enrichment of several biological pathways compared to the filtered air control, including neuroinflammation, glial cell activation, and regulation of postsynaptic organization. Upregulation of Drd1, Penk, and Pdyn mRNA expression was confirmed in the 4-week A. versicolor exposed midbrain tissue, highlighting that gene expression important for neurotransmission was affected by repeated A. versicolor inhalation exposure. Taken together, these findings indicate that the brain can detect and respond to A. versicolor inhalation exposure with changes in neuroimmune and neurotransmission gene expression, providing much needed insight into how inhaled fungal exposures can affect CNS responses and regulate neuroimmune homeostasis.Item Atypical microglial response to biodiesel exhaust in healthy and hypertensive rats(Elsevier, 2017-03) Mumaw, Christen L.; Surace, Michael; Levesque, Shannon; Kodavanti, Urmila P.; Kodavanti, Prasada Rao S.; Royland, Joyce E.; Block, Michelle L.; Anatomy and Cell Biology, School of MedicineAccumulating evidence suggests a deleterious role for urban air pollution in central nervous system (CNS) diseases and neurodevelopmental disorders. Microglia, the resident innate immune cells and sentinels in the brain, are a common source of neuroinflammation and are implicated in how air pollution may exert CNS effects. While renewable energy, such as soy-based biofuel, is of increasing public interest, there is little information on how soy biofuel may affect the brain. To address this, male spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats were exposed to 100% Soy Biodiesel Exhaust (100SBDE; 0, 50, 150 and 500 μg/m3) by inhalation for 4 h/day for 4 weeks (5 days/week). IBA-1 staining of microglia in the substantia nigra revealed significant changes in morphology with 100SBDE exposure in rats from both genotypes, where the SHR were less sensitive. Further analysis failed to show consistent changes in pro-inflammatory cytokine expression, nitrated protein, and arginase1 expression in brain tissue from either rat strain exposed to 100SBDE. CX3CR1 and fractalkine mRNA expression were lower in the striatum of all 100SBDE exposed rats, but greater SBDE exposure was required for loss of fractalkine expression in the SHR. Together, these data support that month-long 100SBDE exposure impacts the basal ganglia with changes in microglia morphology, an impaired fractalkine axis, and an atypical activation response without traditional markers of M1 or M2 activation, where the SHR may be less sensitive to these effects.Item Chlorpyrifos 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).Item Circulating HMGB1 is elevated in veterans with Gulf War Illness and triggers the persistent pro-inflammatory microglia phenotype in male C57Bl/6J mice(Springer Nature, 2021-07-12) Garza-Lombó, Carla; Thang, Morrent; Greve, Hendrik J.; Mumaw, Christen L.; Messenger, Evan J.; Ahmed, Chandrama; Quinn, Emily; Sullivan, Kimberly; Block, Michelle L.; Pharmacology and Toxicology, School of MedicineGulf War Illness (GWI) is a chronic, multi-symptom peripheral and CNS condition with persistent microglial dysregulation, but the mechanisms driving the continuous neuroimmune pathology are poorly understood. The alarmin HMGB1 is an autocrine and paracrine pro-inflammatory signal, but the role of circulating HMGB1 in persistent neuroinflammation and GWI remains largely unknown. Using the LPS model of the persistent microglial pro-inflammatory response, male C57Bl/6J mice injected with LPS (5 mg/kg IP) exhibited persistent changes in microglia morphology and elevated pro-inflammatory markers in the hippocampus, cortex, and midbrain 7 days after LPS injection, while the peripheral immune response had resolved. Ex vivo serum analysis revealed an augmented pro-inflammatory response to LPS when microglia cells were cultured with the 7-day LPS serum, indicating the presence of bioactive circulating factors that prime the microglial pro-inflammatory response. Elevated circulating HMGB1 levels were identified in the mouse serum 7 days after LPS administration and in the serum of veterans with GWI. Tail vein injection of rHMGB1 in male C57Bl/6 J mice elevated TNFα mRNA levels in the liver, hippocampus, and cortex, demonstrating HMGB1-induced peripheral and CNS effects. Microglia isolated at 7 days after LPS injection revealed a unique transcriptional profile of 17 genes when compared to the acute 3 H LPS response, 6 of which were also upregulated in the midbrain by rHMGB1, highlighting a distinct signature of the persistent pro-inflammatory microglia phenotype. These findings indicate that circulating HMGB1 is elevated in GWI, regulates the microglial neuroimmune response, and drives chronic neuroinflammation that persists long after the initial instigating peripheral stimulus.Item Diesel exhaust impairs TREM2 to dysregulate neuroinflammation(BMC, 2020-11-22) Greve, Hendrik J.; Mumaw, Christen L.; Messenger, Evan J.; Kodavanti, Prasada R. S.; Royland, Joyce L.; Kodavanti, Urmila P.; Block, Michelle L.; Pharmacology and Toxicology, School of MedicineBACKGROUND: Air pollution has been linked to neurodegenerative diseases, including Alzheimer's disease (AD), and the underlying neuroimmune mechanisms remain poorly understood. TREM2 is a myeloid cell membrane receptor that is a key regulator of disease-associated microglia (DAM) cells, where loss-of-function TREM2 mutations are associated with an increased risk of AD. At present, the basic function of TREM2 in neuroinflammation is a point of controversy. Further, the impact of air pollution on TREM2 and the DAM phenotype is largely unknown. Using diesel exhaust (DE) as a model of urban air pollution exposure, we sought to address its impact on TREM2 expression, the DAM phenotype, the association of microglia with the neurovasculature, and the role of TREM2 in DE-induced neuroinflammation. METHODS: WYK rats were exposed for 4 weeks to DE (0, 50, 150, 500 μg/m3) by inhalation. DE particles (DEP) were administered intratracheally once (600 μg/mouse) or 8 times (100 μg/mouse) across 28 days to male mice (Trem2+/+, Trem2-/-, PHOX+/+, and PHOX-/-). RESULTS: Rats exposed to DE exhibited inverted-U patterns of Trem2 mRNA expression in the hippocampus and frontal cortex, while TREM2 protein was globally diminished, indicating impaired TREM2 expression. Analysis of DAM markers Cx3Cr1, Lyz2, and Lpl in the frontal cortex and hippocampus showed inverted-U patterns of expression as well, supporting dysregulation of the DAM phenotype. Further, microglial-vessel association decreased with DE inhalation in a dose-dependent manner. Mechanistically, intratracheal administration of DEP increased Tnf (TNFα), Ncf1 (p47PHOX), and Ncf2 (p67PHOX) mRNA expression in only Trem2+/+ mice, where Il1b (IL-1β) expression was elevated in only Trem2-/- mice, emphasizing an important role for TREM2 in DEP-induced neuroinflammation. CONCLUSIONS: Collectively, these findings reveal a novel role for TREM2 in how air pollution regulates neuroinflammation and provides much needed insight into the potential mechanisms linking urban air pollution to AD.Item Identifying the Neural Circuit That Regulates Social Familiarity Induced Anxiolysis (SoFiA)(2020-06) Majumdar, Sreeparna; Cummins, Theodore R.; Truitt, William A.; Block, Michelle L.; Johnson, Phillip L.; Engleman, Eric A.Mental health is crucially linked to social behavior. A crucial aspect of healthy social behavior involves learning to adapt emotional responses to social cues, for example learning to suppress anxiety through social familiarity, or social familiarity induced anxiolysis (SoFiA). SoFiA is well documented; however, the neural mechanisms of SoFiA are unclear. SoFiA is modeled in rats by employing a social interaction habituation (SI-hab) protocol. Using SI-hab protocol it has been determined that SoFiA represents social safety learning, which requires both anxiogenic stimulus (Anx) and social familiarity (SF) during training sessions (5-6 daily SI sessions), and SoFiA expression is dependent on infralimbic cortex (IL). Based on these findings we hypothesize that Anx and SF are processed by unique neural systems, and repeated convergence of these signals interact within IL to induce plasticity, resulting in social safety learning and anxiolysis. Following SoFiA expression, rats were either sacrificed 30 minutes {for gene expression or Neural Activity Regulated Gene (NARG) analysis} or perfused 90 minutes (for cFos immunoreactivity analysis) after SI session on social training day 5. This led to gaining insights into regions of brain involved in SoFiA response as well as the underlying molecular mechanisms. We identified amygdala, specifically the central amygdala (CeA), basomedial amygdala (BMA) and basolateral amygdala (BLA) as potential candidate regions in SoFiA response. Next, we investigated the role of IL and its efferent pathways in SoFiA expression using inhibitory DREADDs and intersectional chemogenetics to inhibit IL projection neurons and/or axons. We identified that specific projection neurons within the IL are pivotal for SoFiA expression, and that within these projections, the ones that specifically projected to the amygdala are most crucial for expression of SoFiA.Item Immunoregulation of the central response to peripheral nerve injury: motoneuron survival and relevance to ALS(2017-04) Setter, Deborah Olmstead; Jones, Kathryn J.; Block, Michelle L.; Sanders, Virginia M.; Sengelaub, Dale R.; Xu, Xiao-MingFacial nerve axotomy (FNA) in immunodeficient mice causes significantly more facial motoneuron (FMN) loss relative to wild type (WT), indicating that the immune system is neuroprotective. Further studies reveal that both CD4+ T cells and interleukin 10 (IL-10) act centrally to promote neuronal survival after injury. This study first investigated the roles of IL-10 and CD4+ T cells in neuroprotection after axotomy. CD4+ T cell-mediated neuroprotection requires centrally-produced IL-10, but the source of IL-10 is unknown. Using FNA on IL-10 reporter mice, immunohistochemistry was employed to identify the IL-10 source. Unexpectedly, axotomy induced astrocyte production of IL-10. To test if microglia- or astrocyte-specific IL-10 is needed for neuroprotection, cell-specific conditional knockout mice were generated. Neither knockout scenario affected FMN survival after FNA, suggesting that coordinated IL-10 production by both glia contributes to neuroprotection. The effect of immune status on the post-FNA molecular response was studied to characterize CD4+ T cell-mediated neuroprotection. In the recombinase-activating gene2 knockout (RAG-2-/-) mouse model of immunodeficiency, glial microenvironment responses were significantly impaired. Reconstitution with CD4+ T cells restored glial activation to normal levels. Motoneuron regeneration responses remained unaffected by immune status. These findings indicate that CD4+ T cell-mediated neuroprotection after injury occurs indirectly via microenvironment regulation. Immunodysregulation is evident in amyotrophic lateral sclerosis (ALS), and FMN survival after FNA is worse in the mutant superoxide dismutase (mSOD1) mouse model of ALS. Further experiments reveal that mSOD1 CD4+ T cells are neuroprotective in RAG-2-/- mice, whereas mSOD1 whole splenocytes (WS) are not. The third aim examined if the mSOD1 WS environment inhibits mSOD1 CD4+ T cell glial regulation after axotomy. Unexpectedly, both treatments were equally effective in promoting glial activation. Instead, mSOD1 WS treatment induced a motoneuron-specific death mechanism prevalent in ALS. In conclusion, the peripheral immune system regulates the central glial microenvironment utilizing IL-10 to promote neuronal survival after axotomy. Astrocytes, specifically, may be responsible for transducing peripheral immune signals into microenvironment regulation. Additionally, the immune system in ALS may directly participate in disease pathology.Item Loss of NF-κB p50 function synergistically augments microglial priming in the middle-aged brain(BMC, 2019-03-12) Taetzsch, Thomas; Benusa, Savannah; Levesque, Shannon; Mumaw, Christen L.; Block, Michelle L.; Anatomy and Cell Biology, School of MedicineBACKGROUND: While NF-κB p50 function is impaired in central nervous system disease, aging in non-CNS tissues, and response to reactive oxygen species, the role of NF-κB p50 in aging-associated microglial pro-inflammatory priming is poorly understood. METHODS: Male NF-κB p50+/+ and NF-κB p50-/- mice at three different ages (1.5-3.0 month old, 8.0-11.0 month old, and 16.0-18.0 month old) were treated with LPS (5 mg/kg, IP) to trigger peripheral inflammation, where circulating cytokines, neuroinflammation, microglia morphology, and NF-κB p50/p65 function in brain tissue were determined 3 h later. RESULTS: Peripheral LPS injection in 9-month-old C57BL/6 mice resulted in lower NF-κB p50 DNA binding of nuclear extracts from the whole brain, when compared to 3-week-old C57BL/6 mice, revealing differences in LPS-induced NF-κB p50 activity in the brain across the mouse lifespan. To examine the consequences of loss NF-κB p50 function with aging, NF-κB p50+/+ and NF-κB p50-/- mice of three different age groups (1.5-3.0 month old, 8.0-11.0 month old, and 16.0-18.0 month old) were injected with LPS (5 mg/kg, IP). NF-κB p50-/- mice showed markedly elevated circulating, midbrain, and microglial TNFα when compared to NF-κB p50+/+ mice at all ages. Notably, the 16.0-18.0-month-old (middle aged) NF-κB p50-/- mice exhibited synergistically augmented LPS-induced serum and midbrain TNFα when compared to the younger (1.5-3.0 month old, young adult) NF-κB p50-/- mice. The 16.0-18.0-month-old LPS-treated NF-κB p50-/- mice also had the highest midbrain IL-1β expression, largest number of microglia with changes in morphology, and greatest elevation of pro-inflammatory factors in isolated adult microglia. Interestingly, aging NF-κB p50-/- mice exhibited decreased brain NF-κB p65 expression and activity. CONCLUSIONS: These findings support that loss of NF-κB p50 function and aging in middle-aged mice may interact to excessively augment peripheral/microglial pro-inflammatory responses and point to a novel neuroinflammation signaling mechanism independent the NF-κB p50/p65 transcription factor in this process.Item Microglial priming through the lung-brain axis: the role of air pollution-induced circulating factors(Federation of American Societies for Experimental Biology, 2016-05) Mumaw, Christen L.; Levesque, Shannon; McGraw, Constance; Robertson, Sarah; Lucas, Selita; Stafflinger, Jillian E.; Campen, Matthew J.; Hall, Pamela; Norenberg, Jeffrey P.; Anderson, Tamara; Lund, Amie K.; McDonald, Jacob D.; Ottens, Andrew K.; Block, Michelle L.; Anatomy and Cell Biology, School of MedicineAir pollution is implicated in neurodegenerative disease risk and progression and in microglial activation, but the mechanisms are unknown. In this study, microglia remained activated 24 h after ozone (O3) exposure in rats, suggesting a persistent signal from lung to brain. Ex vivo analysis of serum from O3-treated rats revealed an augmented microglial proinflammatory response and β-amyloid 42 (Aβ42) neurotoxicity independent of traditional circulating cytokines, where macrophage-1 antigen-mediated microglia proinflammatory priming. Aged mice exhibited reduced pulmonary immune profiles and the most pronounced neuroinflammation and microglial activation in response to mixed vehicle emissions. Consistent with this premise, cluster of differentiation 36 (CD36)(-/-) mice exhibited impaired pulmonary immune responses concurrent with augmented neuroinflammation and microglial activation in response to O3 Further, aging glia were more sensitive to the proinflammatory effects of O3 serum. Together, these findings outline the lung-brain axis, where air pollutant exposures result in circulating, cytokine-independent signals present in serum that elevate the brain proinflammatory milieu, which is linked to the pulmonary response and is further augmented with age.