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Background: Autosomal recessive mutations in the glucocerebrosidase gene, Beta-glucocerebrosidase 1 (GBA1), cause the lysosomal storage disorder Gaucher's disease. Heterozygous carriers of most GBA1 mutations have dramatically increased Parkinson's disease (PD) risk, but the mechanisms and cells affected remain unknown. Glucocerebrosidase expression is relatively enriched in astrocytes, yet the impact of its mutation in these cells has not yet been addressed.Objectives: Emerging data supporting non-cell-autonomous mechanisms driving PD pathogenesis inspired the first characterization of GBA1-mutant astrocytes. In addition, we asked whether LRRK2, likewise linked to PD and enriched in astrocytes, intersected with GBA1 phenotypes.Methods: Using heterozygous and homozygous GBA1 D409V knockin mouse astrocytes, we conducted rigorous biochemical and image-based analyses of lysosomal function and morphology. We also examined basal and evoked cytokine response at the transcriptional and secretory levels.Results: The D409V knockin astrocytes manifested broad deficits in lysosomal morphology and function, as expected. This, however, is the first study to show dramatic defects in basal and TLR4-dependent cytokine production. Albeit to different extents, both the lysosomal dysfunction and inflammatory responses were normalized by inhibition of LRRK2 kinase activity, suggesting functional intracellular crosstalk between glucocerebrosidase and LRRK2 activities in astrocytes.Conclusions: These data demonstrate novel pathologic effects of a GBA1 mutation on inflammatory responses in astrocytes, indicating the likelihood of broader immunologic changes in GBA-PD patients. Our findings support the involvement of non-cell-autonomous mechanisms contributing to the pathogenesis of GBA1-linked PD and identify new opportunities to correct these changes with pharmacological intervention. © 2020 International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Background: Regulatory interactions between the gut and the brain are essential for energy homeostasis across systems. Current evidence indicates high‐fat, high‐carbohydrate diets (HFHC) impact Alzheimer's disease (AD) pathophysiology, however, the mechanisms underlying this association are poorly understood. We hypothesize that (1) Tumor Necrosis Factor (TNF) mediates metabolic inflammation in an obesogenic environment with impacts across the gut‐brain axis and (2) that HFHC interacts with an AD‐relevant genetic background to promote metabolic and immune dysregulation that accelerates pathological and behavioral dysfunction in an animal model of AD. Method: To investigate the effects of chronic systemic inflammation on AD‐associated pathology, 2‐month old female 5xFAD mice were fed HFHC or a control diets (CD) for 8 weeks. One month following dietary intervention, the brain‐permeant soluble TNF inhibitor XPro1595 or a brain‐impermeant pan (sol and membrane‐bound) TNF inhibitor Etanercept (Enbrel, Amgen‐Wyeth) or vehicle (saline) were dosed twice weekly for 4 weeks. Behavioral test were performed to assess cognitive parameters. Plasma, brain and gut were collected for evaluation of insulin impairment, metabolic and immune parameters. Cortical tissues were subjected to RNAseq analysis to determine gene pathways modified by interactions between diet, genotype, and TNF inhibition. Result: HFHC promoted metabolic syndrome features associated with increases in adiposity, body weight, and plasma glucose, cholesterol, leptin, and insulin. TNF inhibition did not rescue diet‐induced insulin increases, however XPro specifically reduced plasma glucose, while Enbrel increased HOMA‐IR in HFHC‐fed mice. HFHC diet increased circulating IL‐6, CXCL1, CXCL2 and CCL2 and TNF neutralization with either drug decreased IL‐6 in HFHC‐fed groups. In the colon, HFHC diet decreased CCL3 and TNF blockade increased colonic IL‐15 in HFHC‐fed mice. Ongoing behavioral assessment, cortical transcriptional analysis, and hippocampal protein profiles of insulin signaling and inflammatory markers will determine additional effects of TNF and HFHC in the 5XFAD animal model of AD. Conclusion: Collectively, these results suggest that TNF modulates systemic metabolic and inflammatory pathways induced by HFHC consumption and associated with neurodegeneration and neuroinflammation. Blocking soluble TNF decreases hyperglycemia triggered during diet‐induce obesity. Future studies focusing on the impact of TNF on energy homeostasis and inflammation will provide targets for new therapeutics against neurological disease. [ABSTRACT FROM AUTHOR]

Background: Gastrointestinal symptoms are common in Parkinson's disease and frequently precede the development of motor impairments. Intestinal inflammation has been proposed as a driver of disease pathology, and evaluation of inflammatory mediators in stool could possibly identify valuable early-stage biomarkers. We measured immune- and angiogenesis-related proteins in human stool to examine inflammatory profiles associated with Parkinson's disease.Methods: Stool samples and subjects' self-reported metadata were obtained from 156 individuals with Parkinson's disease and 110 without, including spouse and nonhousehold controls. Metadata were probed for disease-associated differences, and levels of 37 immune and angiogenesis factors in stool homogenates were measured by multiplexed immunoassay and compared across experimental groups.Results: Parkinson's disease patients reported greater incidence of intestinal disease and digestive problems than controls. Direct comparison of levels of stool analytes in patients and controls revealed elevated vascular endothelial growth factor receptor 1, interleukin-1α, and CXCL8 in patients' stool. Paired comparison of patients and spouses suggested higher levels of multiple factors in patients, but this was complicated by sex differences. Sex, body mass index, a history of smoking, and use of probiotics were found to strongly influence levels of stool analytes. Multivariate analysis accounting for these and other potential confounders confirmed elevated levels of interleukin-1α and CXCL8 and also revealed increased interleukin-1β and C-reactive protein in stool in Parkinson's disease. These differences were not dependent on subject age or disease duration.Conclusions: Levels of stool immune factors indicate that intestinal inflammation is present in patients with Parkinson's disease. © 2018 International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Background: Mutations in the progranulin gene (GRN) reduce levels of progranulin (PGRN) and granulins (GRNs) causing frontotemporal dementia (FTD), the most common form of early‐onset dementia. PGRN loss in neurons is associated with lysosome dysfunction resulting in diminished cathepsin protease activity. PGRN is also highly expressed in brain‐resident microglia and peripheral immune cells. Therefore, we asked if PGRN loss impacts immune cell profiles and communication in the gut‐brain axis during chronic systemic inflammation. Methods: We measured lysosomal‐associated proteases in microglia and peripheral immune cells using probes for cathepsin D and pan‐cysteine cathepsins; performed multiplexed RNA & digital spatial protein profiling analyses, immunohistochemistry, and deep‐immunophenotyping by flow cytometry on brain, spleen, and peripheral blood of Grn KO and Grn‐suffficient mice aged 3‐30 months. Furthermore, we exposed mice to experimental colitis to interrogate alterations in the gut‐brain axis. Results: Highest cathepsin D activity was found amongst Ly6C+, CD11b+ blood monocytes while pan‐cathepsin activity was highest in neutrophils and monocytes. In the spleen of aged Grn KO mice, T cell counts were reduced while Ly6C‐, CD68+ macrophages were increased compared to age‐matched Grn‐sufficient mice. In blood, aberrant T cell and monocyte activation markers in Grn KO mice were evident with minimal increases in inflammatory cytokines in plasma. Aged Grn KO mice exhibited decreased microglia (CD45int, CD11bhi) in the brain relative to Grn‐sufficient mice, with altered MHCII and CD68 expression. Additionally, CD4+ and CD8+ T cells were impacted in the brain of Grn KO mice compared to age‐matched Grn‐sufficient mice. PGRN loss was also associated with increased brain infiltration of activated peripheral monocytes and, interestingly, increased vulnerability to experimental colitis that was mitigated by loss of CCR2 function. Conclusions: These novel findings suggest that PGRN plays key regulatory functions in innate and adaptive immune cell populations, in central‐peripheral immune cell crosstalk and traffic to the CNS, and in regulating susceptibility to immune challenges that disrupt the gut‐brain signaling axis. Analysis of peripheral immune cells and colonic tissue from patients with Grn mutations or SNPs is ongoing and may shed light on the mechanisms by which GRN haploinsufficiency causes FTD. [ABSTRACT FROM AUTHOR]

Background: Sporadic Alzheimer's disease (AD) is a product of complex gene‐environment (GxE) interactions. Central‐peripheral immune cell crosstalk and traffic across the blood‐brain barrier (BBB) have been implicated in AD pathophysiology by recent studies that demonstrate a T‐cell signature in AD brain, gut dysbiosis in AD patients, and a significant epidemiological association between metabolic syndrome, obesity, and type‐2 diabetes with increased incidence of AD. Soluble tumor necrosis factor (sTNF), a known regulator of BBB and gut‐epithelial barrier permeability in chronic systemic inflammatory diseases that is increased in AD patient blood, was investigated as a regulator of immune cell traffic and AD‐like pathology in a mouse model of amyloid pathology subjected to an obesogenic diet. Method: To investigate the effects of chronic peripheral inflammation on neuroinflammation and AD‐associated pathology, 2‐month old female 5xFAD (Tg) or non‐Tg mice were fed a high‐fat high‐carbohydrate diet (HFHC) or a balanced control diet (CD) for 8 weeks. After 4 weeks of diet, BBB‐permeant XPro®1595 was given subcutaneously every third day to selectively inhibit sTNF signaling. Neuroimmunological, histological, biochemical, genomic, and transcriptomic analyses were used to analyze effects on blood and brain immune populations, BBB permeability, inflammatory gene and protein expression, and gut microbiome. Result: HFHC‐fed Tg mice showed decreased T cell numbers in the blood and increased Ly6C+ T cells in the brain as compared to Tg mice fed CD or non‐Tg HFHC‐fed mice. Tg mice fed HFHC diet displayed increased hippocampal TNF and ZO‐1 mRNA, modestly increased Aβ burden, and marked increases of Iba1+ cells. Analysis of gut microbiota revealed significant beta diversity genotype‐ and diet‐dependent differences between Tg and non‐Tg mice, synergy in GxE interactions, and the ability of XPro®1595 to reverse many of these features. Conclusion: Together, these data suggest that an obesogenic diet enhances BBB permeability, disrupts innate and adaptive immune cell populations in the blood, promotes gut dysbiosis, and enhanced traffic of immune cells to the CNS through sTNF‐dependent mechanisms. Clinical trials in patients with MCI/early AD are underway to investigate the ability of a weekly dose of XPro1595 to reduce underlying inflammation without immunosuppression via selective targeting of sTNF. [ABSTRACT FROM AUTHOR]

Background: Insulin resistance (IR) and systemic inflammation are risk factors for Alzheimer's disease (AD); however, the molecular and signaling mechanisms underlying this relationship are not well understood. Elevated plasma cytokine levels are associated with increased risk for both AD and IR. The cytokine tumor necrosis factor (TNF) is a major driver of inflammation and is implicated in IR and neurodegeneration. Here, we hypothesize that soluble TNF (solTNF) drives metabolic and immune alterations in the CNS and periphery that promote IR, thereby increasing the risk for AD pathologies. Method: To investigate this hypothesis, 2‐month old female 5xFAD mice were fed a high‐fat high‐carbohydrate diet (HFHC) or a control diet (CD) for 8 weeks. After 1 month, the brain‐permeant solTNF inhibitor XPro1595 or a brain‐impermeant pan (sol and membrane‐bound) TNF inhibitor Etanercept or saline were dosed twice weekly for 4 weeks. Plasma, adipose tissue, and gut were collected for evaluation of IR, metabolic and immune parameters. Molecular markers of insulin signaling, oxidative stress, mitochondrial impairment and inflammation were assessed in relevant brain regions (hippocampus, hypothalamus and cortex). Result: Our preliminary data demonstrate that HFHC‐fed 5XFAD mice exhibit increased body weight gain compared to CD groups. Ectopic lipid deposition, as measured by gonadal fat pad and liver volumes, was significantly increased, concurrent to anatomical indicators of intestinal inflammation, including shortened small intestine and colon. HFHC diet promoted systemic inflammation, as measured by increases in the classical pro‐inflammatory cytokines IL‐6 and TNF. Further, plasma LCN2, a downstream TNF inflammatory molecule associated with insulin insensitivity, hippocampal alterations, and previously observed to be increased in AD patients, was also significantly increased. Ongoing assessments of mRNA and protein expression of insulin signaling and inflammation in the hippocampus and cortex will determine additional effects of TNF in central insulin impairment and AD pathogenesis and will be presented and integrated into the overall findings. Conclusion: Together, these data suggest HFHC diet disrupts peripheral immune and metabolic parameters in the 5XFAD animal model of AD‐like pathology, thereby triggering neuroinflammation and insulin insensitivity, conditions which have been implicated in significantly increasing the risk for development of AD in humans. [ABSTRACT FROM AUTHOR]