ABSTRACT
INTRODUCTION: At the Alzheimer's Association's APOE and Immunity virtual conference, held in October 2021, leading neuroscience experts shared recent research advances on and inspiring insights into the various roles that both the apolipoprotein E gene (APOE) and facets of immunity play in neurodegenerative diseases, including Alzheimer's disease and other dementias. METHODS: The meeting brought together more than 1200 registered attendees from 62 different countries, representing the realms of academia and industry. RESULTS: During the 4-day meeting, presenters illuminated aspects of the cross-talk between APOE and immunity, with a focus on the roles of microglia, triggering receptor expressed on myeloid cells 2 (TREM2), and components of inflammation (e.g., tumor necrosis factor α [TNFα]). DISCUSSION: This manuscript emphasizes the importance of diversity in current and future research and presents an integrated view of innate immune functions in Alzheimer's disease as well as related promising directions in drug development.
Subject(s)
Alzheimer Disease , Humans , Alzheimer Disease/pathology , Microglia/pathology , Inflammation , Apolipoproteins E/geneticsABSTRACT
Inflammation has been linked to the development of nonmotor symptoms in Parkinson's disease (PD), which greatly impact patients' quality of life and can often precede motor symptoms. Suitable animal models are critical for our understanding of the mechanisms underlying disease and the associated prodromal disturbances. The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkey model is commonly seen as a "gold standard" model that closely mimics the clinical motor symptoms and the nigrostriatal dopaminergic loss of PD, however MPTP toxicity extends to other nondopaminergic regions. Yet, there are limited reports monitoring the MPTP-induced progressive central and peripheral inflammation as well as other nonmotor symptoms such as gastrointestinal function and microbiota. We report 5 cases of progressive parkinsonism in non-human primates to gain a broader understanding of MPTP-induced central and peripheral inflammatory dysfunction to understand the potential role of inflammation in prodromal/pre-motor features of PD-like degeneration. We measured inflammatory proteins in plasma and CSF and performed [18F]FEPPA PET scans to evaluate translocator proteins (TSPO) or microglial activation. Monkeys were also evaluated for working memory and executive function using various behavior tasks and for gastrointestinal hyperpermeability and microbiota composition. Additionally, monkeys were treated with a novel TNF inhibitor XPro1595 (10 mg/kg, n = 3) or vehicle (n = 2) every three days starting 11 weeks after the initiation of MPTP to determine whether XPro1595 would alter inflammation and microglial behavior in a progressive model of PD. The case studies revealed that earlier and robust [18F]FEPPA PET signals resulted in earlier and more severe parkinsonism, which was seen in male cases compared to female cases. Potential other sex differences were observed in circulating inflammation, microbiota diversity and their metabolites. Additional studies with larger group sizes of both sexes would enable confirmation and extension of these findings. If these findings reflect potential differences in humans, these sex differences have significant implications for therapeutic development of inflammatory targets in the clinic.
Subject(s)
Disease Models, Animal , Gastrointestinal Microbiome , Inflammation/metabolism , Macaca mulatta , Microglia/metabolism , Parkinsonian Disorders/physiopathology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine , Anilides , Animals , Behavior, Animal , Cognition/physiology , Disease Progression , Fatty Acids, Volatile/metabolism , Female , Magnetic Resonance Imaging , Male , Microglia/drug effects , Microglia/pathology , Neurotoxins , Parkinsonian Disorders/diagnostic imaging , Parkinsonian Disorders/metabolism , Parkinsonian Disorders/microbiology , Positron-Emission Tomography , Pyridines , Tumor Necrosis Factor Inhibitors/pharmacology , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
Physical and psychosocial maltreatment experienced before the age of 18, termed early life adversity (ELA), affects an estimated 39% of the world's population, and has long-term detrimental health and psychological outcomes. While adult phenotypes vary following ELA, inflammation and altered stress responsivity are pervasive. Cytokines, most notably tumor necrosis factor (TNF), are elevated in adults with a history of ELA. While soluble TNF (solTNF) drives chronic inflammatory disease, transmembrane TNF facilitates innate immunity. Here, we test whether solTNF mediates the behavioral and molecular outcomes of adolescent psychological stress by administering a brain permeable, selective inhibitor of solTNF, XPro1595. Male and female C57BL/6 mice were exposed to an aggressive rat through a perforated translucent ball ('predatory stress') or transported to an empty room for 30â¯min for 30â¯days starting on postnatal day 34. Mice were given XPro1595 or vehicle treatment across the last 15â¯days. Social interaction, sucrose preference, and plasma inflammation were measured at 2 and 4â¯weeks, and open field behavior, adiposity, and neuroinflammation were measured at 4â¯weeks. Chronic adolescent stress resulted in increased peripheral inflammation and dysregulated neuroinflammation in adulthood in a sex-specific manner. Abnormal social and open field behavior, fat pad weight, and fecal boli deposition were noted after 30â¯days; solTNF antagonism ameliorated the effects of stress. Together, these data support our hypothesis, and suggest that targeting solTNF with XPro1595 may improve quality of life for individuals with a history of adolescent stress.
Subject(s)
Adiposity , Inflammation , Sex Factors , Stress, Psychological , Tumor Necrosis Factor-alpha , Animals , Female , Male , Mice , Adiposity/drug effects , Age Factors , Inflammation/etiology , Inflammation/metabolism , Mice, Inbred C57BL , Models, Animal , Obesity/etiology , Obesity/physiopathology , Tumor Necrosis Factor-alpha/antagonists & inhibitorsABSTRACT
BACKGROUND: Efforts to identify fluid biomarkers of Parkinson's disease (PD) have intensified in the last decade. As the role of inflammation in PD pathophysiology becomes increasingly recognized, investigators aim to define inflammatory signatures to help elucidate underlying mechanisms of disease pathogenesis and aid in identification of patients with inflammatory endophenotypes that could benefit from immunomodulatory interventions. However, discordant results in the literature and a lack of information regarding the stability of inflammatory factors over a 24-h period have hampered progress. METHODS: Here, we measured inflammatory proteins in serum and CSF of a small cohort of PD (n = 12) and age-matched healthy control (HC) subjects (n = 6) at 11 time points across 24 h to (1) identify potential diurnal variation, (2) reveal differences in PD vs HC, and (3) to correlate with CSF levels of amyloid ß (Aß) and α-synuclein in an effort to generate data-driven hypotheses regarding candidate biomarkers of PD. RESULTS: Despite significant variability in other factors, a repeated measures two-way analysis of variance by time and disease state for each analyte revealed that serum IFNγ, TNF, and neutrophil gelatinase-associated lipocalin (NGAL) were stable across 24 h and different between HC and PD. Regression analysis revealed that C-reactive protein (CRP) was the only factor with a strong linear relationship between CSF and serum. PD and HC subjects showed significantly different relationships between CSF Aß proteins and α-synuclein and specific inflammatory factors, and CSF IFNγ and serum IL-8 positively correlated with clinical measures of PD. Finally, linear discriminant analysis revealed that serum TNF and CSF α-synuclein discriminated between PD and HC with a minimum of 82% sensitivity and 83% specificity. CONCLUSIONS: Our findings identify a panel of inflammatory factors in serum and CSF that can be reliably measured, distinguish between PD and HC, and monitor inflammation as disease progresses or in response to interventional therapies. This panel may aid in generating hypotheses and feasible experimental designs towards identifying biomarkers of neurodegenerative disease by focusing on analytes that remain stable regardless of time of sample collection.
Subject(s)
Inflammation Mediators/blood , Inflammation Mediators/cerebrospinal fluid , Parkinson Disease/blood , Parkinson Disease/cerebrospinal fluid , alpha-Synuclein/blood , alpha-Synuclein/cerebrospinal fluid , Biomarkers/blood , Biomarkers/cerebrospinal fluid , Female , Humans , Male , Parkinson Disease/diagnosis , Severity of Illness IndexABSTRACT
The mechanisms underlying the association between chronic psychological stress, development of metabolic syndrome (MetS), and behavioral impairment in obesity are poorly understood. The aim of the present study was to assess the effects of mild chronic psychological stress on metabolic, inflammatory, and behavioral profiles in a mouse model of diet-induced obesity. We hypothesized that (1) high-fat high-fructose diet (HFHF) and psychological stress would synergize to mediate the impact of inflammation on the central nervous system in the presence of behavioral dysfunction, and that (2) HFHF and stress interactions would impact insulin and lipid metabolism. C57Bl/6 male mice underwent a combination of HFHF and two weeks of chronic psychological stress. MetS-related conditions were assessed using untargeted plasma metabolomics, and structural and immune changes in the gut and liver were evaluated. Inflammation was measured in plasma, liver, gut, and brain. Our results show a complex interplay of diet and stress on gut alterations, energetic homeostasis, lipid metabolism, and plasma insulin levels. Psychological stress and HFHF diet promoted changes in intestinal tight junctions proteins and increases in insulin resistance and plasma cholesterol, and impacted the RNA expression of inflammatory factors in the hippocampus. Stress promoted an adaptive anti-inflammatory profile in the hippocampus that was abolished by diet treatment. HFHF increased hippocampal and hepatic Lcn2 mRNA expression as well as LCN2 plasma levels. Behavioral changes were associated with HFHF and stress. Collectively, these results suggest that diet and stress as pervasive factors exacerbate MetS-related conditions through an inflammatory mechanism that ultimately can impact behavior. This rodent model may prove useful for identification of possible biomarkers and therapeutic targets to treat metabolic syndrome and mood disorders.
Subject(s)
Behavior, Animal/drug effects , Diet, High-Fat/adverse effects , Fructose/adverse effects , Gene Regulatory Networks/drug effects , Inflammation/genetics , Metabolism/genetics , Stress, Psychological/physiopathology , Stress, Psychological/psychology , Animals , Body Weight , Brain Chemistry/genetics , Energy Metabolism/drug effects , Gastrointestinal Tract/metabolism , Lipid Metabolism/drug effects , Lipocalin-2/biosynthesis , Lipocalin-2/genetics , Liver/metabolism , Male , Mice , Mice, Inbred C57BL , Social BehaviorABSTRACT
Dopamine (DA) replacement therapy with L-DOPA continues to be the primary treatment of Parkinson's disease; however, long-term therapy is accompanied by L-DOPA-induced dyskinesias (LID). Several experimental and clinical studies have established that Propranolol, a ß-adrenergic receptor antagonist, reduces LID without affecting L-DOPA's efficacy. However, the exact mechanisms underlying these effects remain to be elucidated. The aim of this study was to evaluate the anti-dyskinetic profile of Propranolol against a panel of DA replacement strategies, as well as elucidate the underlying neurochemical mechanisms. Results indicated that Propranolol, in a dose-dependent manner, reduced LID, without affecting motor performance. Propranolol failed to alter dyskinesia produced by the D1 receptor agonist, SKF81297 (0.08 mg/kg, sc), or the D2 receptor agonist, Quinpirole (0.05 mg/kg, sc). These findings suggested a pre-synaptic mechanism for Propranolol's anti-dyskinetic effects, possibly through modulating L-DOPA-mediated DA efflux. To evaluate this possibility, microdialysis studies were carried out in the DA-lesioned striatum of dyskinetic rats and results indicated that co-administration of Propranolol (20 mg/kg, ip) was able to attenuate L-DOPA- (6 mg/kg, sc) induced DA efflux. Therefore, Propranolol's anti-dyskinetic properties appear to be mediated via attenuation of L-DOPA-induced extraphysiological efflux of DA.
Subject(s)
Adrenergic beta-Antagonists/pharmacology , Dopamine/metabolism , Dyskinesia, Drug-Induced/prevention & control , Parkinsonian Disorders/metabolism , Propranolol/pharmacology , Animals , Antiparkinson Agents/adverse effects , Chromatography, High Pressure Liquid , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Dyskinesia, Drug-Induced/metabolism , Levodopa/adverse effects , Male , Microdialysis , Motor Activity/drug effects , Rats , Rats, Sprague-DawleyABSTRACT
BACKGROUND: There is ample evidence that psychological stress adversely affects many diseases. Recent evidence has shown that intense stressors can increase inflammation within the brain, a known mediator of many diseases. However, long-term outcomes of chronic psychological stressors that elicit a neuroinflammatory response remain unknown. METHODS: To address this, we have modified previously described models of rat/mouse predatory stress (PS) to increase the intensity of the interaction. We postulated that these modifications would enhance the predator-prey experience and increase neuroinflammation and behavioral dysfunction in prey animals. In addition, another group of mice were subjected to a modified version of chronic unpredictable stress (CUS), an often-used model of chronic stress that utilizes a combination of stressors that include physical, psychological, chemical, and other. The CUS model has been shown to exacerbate a number of inflammatory-related diseases via an unknown mechanism. Using these two models we sought to determine: 1) whether chronic PS or CUS modulated the inflammatory response as a proposed mechanism by which behavioral deficits might be mediated, and 2) whether chronic exposure to a pure psychological stressor (PS) leads to deficits similar to those produced by a CUS model containing psychological and physical stressors. Finally, to determine whether acute PS has neuroinflammatory consequences, adult mice were examined at various time-points after PS for changes in inflammation. RESULTS: Adolescent mice subjected to chronic PS had increased basal expression of inflammation within the midbrain. CUS and chronic PS mice also had an impaired inflammatory response to a subsequent lipopolysaccharide challenge and PS mice displayed increased anxiety- and depressive-like behaviors following chronic stress. Finally, adult mice subjected to acute predatory stress had increased gene expression of inflammatory factors. CONCLUSION: Our results demonstrate that predatory stress, an ethologically relevant stressor, can elicit changes in neuroinflammation and behavior. The predatory stress model may be useful in elucidating mechanisms by which psychological stress modulates diseases with an inflammatory component.
Subject(s)
Aging , Encephalitis/etiology , Polysaccharides/adverse effects , Stress, Psychological/complications , Analysis of Variance , Animals , Brain/metabolism , Corticosterone/blood , Cytokines/genetics , Cytokines/metabolism , Disease Models, Animal , Encephalitis/blood , Encephalitis/pathology , Food Preferences/drug effects , Food Preferences/physiology , Gene Expression Regulation/drug effects , Gene Expression Regulation/physiology , Hindlimb Suspension/methods , Male , Mice , Mice, Inbred C57BL , RNA, Messenger/metabolism , Rats , Sucrose/administration & dosage , Sweetening Agents/administration & dosageABSTRACT
Generally speaking, inflammation as a key piece to the Parkinson's disease (PD) puzzle is a relatively new concept. Acceptance of this concept has gained ground as studies by various researchers have demonstrated the potential of mitigating nigral cell death by curtailing inflammation in animal models of PD. We propose that the significance of inflammation in PD pathology may extend beyond the nigrostriatal region. In the current review, we present an argument for this based on the Braak staging and discuss how inflammation might contribute to the development of non-motor PD symptoms.
Subject(s)
Parkinson Disease/physiopathology , Animals , Dopamine/metabolism , Humans , Inflammation/etiology , Inflammation/physiopathology , Nerve Degeneration/physiopathology , Parkinson Disease/complications , Parkinson Disease/pathology , Sleep/physiologyABSTRACT
Parkinson's disease (PD) is a progressive neurodegenerative disorder typified by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). Recent evidence indicates that neuroinflammation may play a critical role in the pathogenesis of PD, particularly tumor necrosis factor (TNF). We have previously shown that soluble TNF (solTNF) is required to mediate robust degeneration induced by 6-hydroxydopamine (6-OHDA) or lipopolysaccharide. What remains unknown is whether TNF inhibition can attenuate the delayed and progressive phase of neurodegeneration. To test this, rats were injected in the SNpc with lentivirus encoding dominant-negative TNF (lenti-DN-TNF) 2 weeks after receiving a 6-OHDA lesion. Remarkably, when examined 5 weeks after the initial 6-OHDA lesion, no further loss of nigral DA neurons was observed. Lenti-DN-TNF also attenuated microglial activation. Together, these data suggest that TNF is likely a critical mediator of nigral DA neuron death during the delayed and progressive phase of neurodegeneration, and that microglia may be the principal cell type involved. These promising findings provide compelling reasons to perform DN-TNF gene transfer studies in nonhuman primates with the long-term goal of using it in the clinic to prevent the delayed and progressive degeneration of DA neurons that gives rise to motor symptoms in PD.
Subject(s)
Dopamine/metabolism , Genetic Therapy/methods , Neurons/pathology , Parkinson Disease/pathology , Parkinson Disease/therapy , Substantia Nigra/pathology , Tumor Necrosis Factor-alpha/genetics , Animals , Astrocytes/metabolism , Astrocytes/pathology , Cell Death/genetics , Disease Models, Animal , Female , Gene Transfer Techniques , Genetic Vectors/administration & dosage , Genetic Vectors/genetics , Humans , Lentivirus/genetics , Microglia/metabolism , Microglia/pathology , Neurons/metabolism , Oxidopamine , Parkinson Disease/genetics , Parkinson Disease/metabolism , Rats , Rats, Sprague-Dawley , Substantia Nigra/metabolism , Tumor Necrosis Factor-alpha/biosynthesisABSTRACT
Chronic dopamine replacement therapy in Parkinson's disease (PD) leads to deleterious motor sequelae known as L-DOPA-induced dyskinesia (LID). No known therapeutic can eliminate LID, but preliminary evidence suggests that dl-1-isopropylamino-3-(1-naphthyloxy)-2-propanol [(±)propranolol], a nonselective ß-adrenergic receptor (ßAR) antagonist, may reduce LID. The present study used the rat unilateral 6-hydroxydopamine model of PD to characterize and localize the efficacy of (±)propranolol as an adjunct to therapy with L-DOPA. We first determined whether (±)propranolol was capable of reducing the development and expression of LID without impairing motor performance ON and OFF L-DOPA. Coincident to this investigation, we used reverse-transcription polymerase chain reaction techniques to analyze the effects of chronic (±)propranolol on markers of striatal activity known to be involved in LID. To determine whether (±)propranolol reduces LID through ßAR blockade, we subsequently examined each enantiomer separately because only the (-)enantiomer has significant ßAR affinity. We next investigated the effects of a localized striatal ßAR blockade on LID by cannulating the region and microinfusing (±)propranolol before systemic L-DOPA injections. Results showed that a dose range of (±)propranolol reduced LID without deleteriously affecting motor activity. Pharmacologically, only (-)propranolol had anti-LID properties indicating ßAR-specific effects. Aberrant striatal signaling associated with LID was normalized with (±)propranolol cotreatment, and intrastriatal (±)propranolol was acutely able to reduce LID. This research confirms previous work suggesting that (±)propranolol reduces LID through ßAR antagonism and presents novel evidence indicating a potential striatal locus of pharmacological action.
Subject(s)
Adrenergic beta-Antagonists/pharmacology , Antiparkinson Agents/toxicity , Dyskinesia, Drug-Induced/drug therapy , Levodopa/toxicity , Motor Activity/drug effects , Parkinsonian Disorders/drug therapy , Animals , Benzoxazines , Corpus Striatum/drug effects , Disease Models, Animal , Dose-Response Relationship, Drug , Dyskinesia, Drug-Induced/diagnosis , Dyskinesia, Drug-Induced/metabolism , Male , Medial Forebrain Bundle/drug effects , Molecular Targeted Therapy , Oxazines , Oxidopamine/administration & dosage , Rats , Rats, Sprague-Dawley , Receptors, Adrenergic, beta , Time FactorsABSTRACT
Clinical and experimental studies implicate the use of serotonin (5-HT)1A receptor agonists for the reduction of L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia (LID). Although raphe nuclei likely play a role in these antidyskinetic effects, an unexplored population of striatal 5-HT1A receptors (5-HT1AR) may also contribute. To better characterize this mechanism, L-DOPA-primed hemiparkinsonian rats received the 5-HT1AR agonist +/-8-OH-DPAT (0, 0.1, 1.0 mg/kg, i.p.) with or without cotreatment with the 5-HT1AR antagonist WAY100635 (0.5 mg/kg, i.p.) 5 min after L-DOPA, after which abnormal involuntary movements (AIMs), rotations, and forelimb akinesia were quantified. To establish the effects of 5-HT1AR stimulation on L-DOPA-induced c-fos and preprodynorphin (PPD) mRNA within the dopamine-depleted striatum, immunohistochemistry and real-time reverse transcription polymerase chain reaction, respectively, were used. Finally, to determine the contribution of striatal 5-HT1AR to these effects, L-DOPA-primed hemiparkinsonian rats received bilateral intrastriatal microinfusions of +/-8-OH-DPAT (0, 5, or 10 microg/side), WAY100635 (5 microg/side), or both (10 microg + 5 microg/side) 5 min after L-DOPA, after which AIMs and rotations were examined. Systemic +/-8-OH-DPAT dose- and receptor-dependently attenuated L-DOPA-mediated AIMs and improved forelimb akinesia. Striatal c-fos immunoreactivity and PPD mRNA ipsilateral to the lesion were strongly induced by L-DOPA, while +/-8-OH-DPAT suppressed these effects. Finally, intrastriatal infusions of +/-8-OH-DPAT reduced AIMs while coinfusion of WAY100635 reversed its antidyskinetic effect. Collectively, these results support the hypothesis that the cellular and behavioral properties of 5-HT1AR agonists are conveyed in part via a population of functional 5-HT1AR within the striatum.
Subject(s)
Antiparkinson Agents/therapeutic use , Corpus Striatum/drug effects , Levodopa/therapeutic use , Parkinsonian Disorders/drug therapy , Receptor, Serotonin, 5-HT1A/metabolism , 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology , Animals , Dynorphins/metabolism , Dyskinesia, Drug-Induced/drug therapy , Dyskinesia, Drug-Induced/metabolism , Levodopa/adverse effects , Male , Motor Activity/drug effects , Oxidopamine , Parkinsonian Disorders/chemically induced , Parkinsonian Disorders/metabolism , Piperazines/pharmacology , Protein Precursors/metabolism , Proto-Oncogene Proteins c-fos/metabolism , Pyridines/pharmacology , RNA, Messenger/metabolism , Rats , Rats, Sprague-Dawley , Serotonin 5-HT1 Receptor Agonists , Serotonin 5-HT1 Receptor Antagonists , Serotonin Antagonists/pharmacology , Serotonin Receptor Agonists/pharmacologyABSTRACT
Convergent evidence indicates that in later stages of Parkinson's disease raphestriatal serotonin neurons compensate for the loss of nigrostriatal dopamine neurons by converting and releasing dopamine derived from exogenous administration of the pharmacotherapeutic L-3,4-dihydroxyphenyl-L-alanine (L-dopa). Because the serotonin system is not equipped with dopamine autoregulatory mechanisms, it has been postulated that raphe-mediated striatal dopamine release may fluctuate dramatically. These fluctuations may portend the development of abnormal involuntary movements called L-dopa-induced dyskinesia (LID). As such, it has been hypothesized that reducing the activity of raphestriatal neurons could dampen supraphysiological stimulation of striatal dopamine receptors thereby alleviating LID. To directly address this, the current study employed the rodent model of LID to investigate the contribution of the rostral raphe nuclei (RRN) in the development, expression and treatment of LID. In the first study, dual serotonin/dopamine selective lesions of the RRN and medial forebrain bundle, respectively, verified that the RRN are essential for the development of LID. In a direct investigation into the neuroanatomical specificity of these effects, microinfusions of +/-8-OH-DPAT into the intact dorsal raphe nucleus dose-dependently attenuated the expression of LID without affecting the antiparkinsonian efficacy of L-dopa. These current findings reveal the integral contribution of the RRN in the development and expression of LID and implicate a prominent role for dorsal raphe 5-HT1AR in the efficacious properties of 5-HT1AR agonists.
Subject(s)
Dyskinesia, Drug-Induced/physiopathology , Raphe Nuclei/physiopathology , Receptor, Serotonin, 5-HT1A/metabolism , 3,4-Dihydroxyphenylacetic Acid/metabolism , Animals , Corpus Striatum/metabolism , Dopamine/metabolism , Hydroxyindoleacetic Acid/metabolism , Levodopa , Male , Medial Forebrain Bundle/drug effects , Medial Forebrain Bundle/physiopathology , Motor Activity/drug effects , Neurons/drug effects , Neurons/metabolism , Raphe Nuclei/drug effects , Rats , Rats, Sprague-Dawley , Serotonin/metabolism , Serotonin Agents/pharmacologyABSTRACT
Recent work from our laboratory and others has shown that certain stressors increase expression of the pro-inflammatory cytokine interleukin-1beta (IL-1) in the hypothalamus. The first goal of the following studies was to assess the impact of acute stress on other key inflammatory factors, including both cytokines and cell surface markers for immune-derived cells resident to the CNS in adult male Sprague Dawley rats exposed to intermittent footshock (80 shocks, 90 s variable ITI, 5 s each). While scattered changes in IL-6 and GFAP were observed in the hippocampus and cortex, we found the hypothalamus to be exquisitely sensitive to the effects of footshock. At the level of the hypothalamus, mRNA for IL-1 and CD14 were significantly increased, while at the same time CD200R mRNA was significantly decreased. A subsequent experiment demonstrated that propranolol (20mg/kg i.p.) blocked the increase in IL-1 and CD14 mRNA observed in the hypothalamus, while the decrease in CD200R was unaffected by propranolol. Interestingly, inhibition of glucocorticoid synthesis via injection of metyrapone (50mg/kg s.c.) plus aminoglutethimide (100mg/kg s.c.) increased basal IL-1 mRNA and augmented IL-1 and CD14 expression provoked by footshock. Injection of minocycline, a putative microglial inhibitor, blocked the IL-1 response to footshock, while CD14 and CD200R were unaffected. Together, these gene expression changes (i) provide compelling evidence that stress may provoke neuroinflammatory changes that extend well beyond isolated changes in a single cytokine; (ii) suggest opposing roles for classic stress-responsive factors (norepinephrine and corticosterone) in the modulation of stress-related neuroinflammation; (iii) indicate microglia within the hypothalamus may be key players in stress-related neuroinflammation; and (iv) provide a potential mechanism (increased CD14) by which acute stress primes reactivity to later immune challenge.
Subject(s)
Hypothalamus/physiology , Interleukin-1/genetics , Lipopolysaccharide Receptors/genetics , Microglia/physiology , Neurons/physiology , Stress, Physiological/genetics , Adrenergic beta-Antagonists/pharmacology , Analysis of Variance , Animals , Cerebral Cortex/drug effects , Cerebral Cortex/physiology , Corticosterone/blood , Electroshock , Enzyme Inhibitors/pharmacology , Gene Expression , Hippocampus/drug effects , Hippocampus/physiology , Hypothalamus/drug effects , Interleukin-1/immunology , Lipopolysaccharide Receptors/immunology , Male , Metyrapone/pharmacology , Microglia/drug effects , Minocycline/pharmacology , Propranolol/pharmacology , RNA, Messenger/physiology , Radioimmunoassay , Rats , Rats, Sprague-Dawley , Receptors, Adrenergic, beta/physiology , Reverse Transcriptase Polymerase Chain Reaction , Stress, Physiological/immunologyABSTRACT
BACKGROUND: Insulin impairment and inflammation are two features common to type 2 diabetes and Alzheimer's disease; however, the molecular and signaling interactions underlying this relationship are not well understood. Mounting evidence point to the associations between the disruption of metabolite processing in insulin impairment and neurodegenerative conditions such as Alzheimer's. Although the brain depends partially on metabolites processed in the periphery, to date, little is known about how soluble tumor necrosis factor signaling (solTNF) impacts integrated peripheral immune and metabolic feedback signals in states of energy overload and insulin insensitivity. METHODS: C57Bl/6J mice were fed a high-fat high-carbohydrate diet (HFHC) for 14 weeks. The brain-permeant biologic XPro1595® was used to block solTNF-dependent pathways. Metabolic and immune alterations were evaluated in the gut, liver, and brain. Behavioral tests were performed. Untargeted metabolomics was carried out in the plasma and liver. RESULTS: HFHC diet promotes central insulin impairment and dysregulation of immune-modulatory gene expressed in the brain. Alteration of metabolites associated with type 2 diabetes and Alzheimer's such as butanoate, glutamate, biopterin, branched-chain amino acids, purines, and proteoglycan metabolism was observed in HFHC-fed mice. solTNF inhibition ameliorates hepatic metabolic disturbances and hepatic and intestinal lipocalin-2 levels, and decreases insulin impairment in the brain and behavioral deficits associated with HFHC diet. CONCLUSIONS: Our novel findings suggest that HFHC diet impacts central insulin signaling and immune-metabolic interactions in a solTNF-dependent manner to increase the risk for neurodegenerative conditions. Our novel findings indicate that selective solTNF neutralization can ameliorate peripheral and central diet-induced insulin impairment and identify lipocalin-2 as a potential target for therapeutic intervention to target inflammation and insulin disturbances in obesogenic environments. Collectively, our findings identify solTNF as a potential target for therapeutic intervention in inflammatory states and insulin disturbances in obesogenic environments to lower risk for AD.
Subject(s)
Alzheimer Disease/physiopathology , Diabetes Mellitus, Type 2/physiopathology , Metabolic Syndrome/physiopathology , Obesity/physiopathology , Tumor Necrosis Factor-alpha/antagonists & inhibitors , Analysis of Variance , Animals , Diet, Carbohydrate Loading , Male , Mice, Inbred C57BL , Risk Factors , Signal Transduction/physiology , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Convergent evidence suggests that serotonin 5-HT1A receptor (5-HT1AR) agonists reduce l-DOPA-induced dyskinesia by auto-regulating aberrant release of l-DOPA-derived dopamine (DA) from raphestriatal neurons. However, recent findings indicate that 5-HT1AR stimulation also modifies D1 receptor (D1R)-mediated dyskinesia and rotations implicating a previously unexplored extra-raphe mechanism. In order to characterize the contribution of the striatum to these effects, rats with medial forebrain bundle DA lesions were tested for abnormal involuntary movements (AIMs) and rotations following striatal microinfusions of the 5-HT1AR agonist +/-8-OH-DPAT and systemic D1R agonist treatment with SKF81297. Additional rats with multi-site striatal DA lesions were tested for motor disability following systemic or intrastriatal +/-8-OH-DPAT with or without systemic SKF81297. In rats with medial forebrain bundle lesions, striatal infusions of +/-8-OH-DPAT dose-dependently reduced AIMs while conversely increasing rotations. In rats with striatal lesions, +/-8-OH-DPAT alone, both systemic and intrastriatal administration, optimally reversed motor disability. Collectively, these results support an important functional interaction between 5-HT1AR and D1R in the striatum with implications for the improved treatment of Parkinson's disease.
Subject(s)
Corpus Striatum/metabolism , Dyskinesia, Drug-Induced/metabolism , Functional Laterality/physiology , Movement Disorders/metabolism , Parkinson Disease , Receptor, Serotonin, 5-HT1A/metabolism , Receptors, Dopamine D1/metabolism , 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology , Adrenergic Agents/toxicity , Animals , Benzazepines/pharmacology , Biogenic Monoamines/metabolism , Brain Chemistry/drug effects , Chromatography, High Pressure Liquid/methods , Corpus Striatum/drug effects , Desipramine/pharmacology , Disease Models, Animal , Dopamine Agonists/pharmacology , Enzyme Inhibitors/pharmacology , Functional Laterality/drug effects , Male , Movement Disorders/drug therapy , Movement Disorders/etiology , Oxidopamine/toxicity , Parkinson Disease/complications , Parkinson Disease/drug therapy , Parkinson Disease/pathology , Piperazines/pharmacology , Psychomotor Performance/drug effects , Pyridines/pharmacology , Rats , Rats, Sprague-Dawley , Serotonin Antagonists/pharmacology , Serotonin Receptor Agonists/pharmacology , Time FactorsABSTRACT
Recent findings from our laboratory and others indicate that exposure to stress can increase expression of the pro-inflammatory cytokine interleukin-1 (IL-1). In a series of studies examining this response, we observed pronounced differences in baseline levels of hypothalamic IL-1 of pair-housed rats. We hypothesized that these pair-wise differences might be a result of prolonged social stress associated with dominance/submissiveness, and that the submissive animal would show heightened baseline levels of IL-1. In order to test this hypothesis, we utilized a food competition paradigm (access to cheerios) to assess dominance within a dyad prior to the assessment of hypothalamic IL-1 levels. Based on the results of this test, clear dominance hierarchies were observed in approximately 50% of the dyads, a ratio comparable to what has been reported previously. More importantly, this dominant/submissive categorization could be used to predict pair-wise differences in hypothalamic IL-1 with greater than 90% accuracy. Specifically, the submissive rat in each dyad (determined a priori) consistently evinced hypothalamic IL-1 levels that were nearly double that of its dominant cage mate. Further studies demonstrated that submissive rats showed a more rapid and pronounced hyperthermic response to novel environment stress relative to dominant rats. Interestingly, social status had no effect on corticosterone reactivity, even when the nature and intensity of the stressor was varied. Finally, maintenance of a clear dominance hierarchy obfuscated hypothalamic IL-1 responses to footshock exposure, with the most robust increases in hypothalamic IL-1 provoked by footshock being observed in pairs where there was no clear dominance hierarchy. Together, these findings suggest that social status can have a significant impact on stress reactivity and neuroimmune consequences of stressor exposure even in the unperturbed home cage environment.
Subject(s)
Hypothalamus/immunology , Hypothalamus/metabolism , Interleukin-1/metabolism , Social Dominance , Stress, Psychological/immunology , Acute Disease , Animals , Corticosterone/blood , Electroshock , Feeding Behavior/physiology , Fever/immunology , Fever/metabolism , Male , Predictive Value of Tests , Rats , Rats, Sprague-Dawley , Stress, Psychological/metabolism , Testosterone/bloodABSTRACT
The noradrenergic system plays an integral role in the stress response and modulates expression of proinflammatory cytokines. Recent work from our laboratory and others has shown that certain stressors increase the expression of the proinflammatory cytokine interleukin-1beta (IL-1beta) in the hypothalamus and spleen. One goal of the following studies was to assess the role of norepinephrine in stress-elicited increases in IL-1beta. To do this, adult male Sprague-Dawley rats were injected with propranolol (20 mg/kg i.p.) or desipramine (20 mg/kg s.c.) and exposed to 80 inescapable footshocks (2.0 mA, 90 s variable ITI, 5 s each). We found that propranolol blocked the IL-1beta response to footshock in both the hypothalamus and the spleen, while the noradrenergic reuptake inhibitor desipramine significantly augmented the footshock-induced IL-1beta response in both of these sites. Our second goal was to determine whether these effects would also be blocked by administration of a putative microglial inhibitor (minocycline). Minocycline (40 mg/kg i.p.) completely reversed the footshock-induced increase in hypothalamic IL-1beta but had no effect on the IL-1beta response in the spleen. Moreover, lack of an effect of minocycline on conditioned fear responding suggests that the effect of this drug cannot be explained by nonspecific sedative properties produced by the drug. Together, these data suggest that NE powerfully modulates the hypothalamic and splenic IL-1beta response to stress, and that microglia may be a primary cellular source of central IL-1beta in response to footshock.
Subject(s)
Hypothalamus/metabolism , Interleukin-1/metabolism , Microglia/metabolism , Norepinephrine/metabolism , Spleen/metabolism , Stress, Psychological/physiopathology , Adrenergic Uptake Inhibitors/pharmacology , Animals , Anti-Anxiety Agents/pharmacology , Anti-Bacterial Agents/pharmacology , Desipramine/pharmacology , Hypothalamus/drug effects , Male , Microglia/drug effects , Minocycline/pharmacology , Propranolol/pharmacology , Rats , Rats, Sprague-Dawley , Spleen/drug effectsABSTRACT
Exposure to stressors such as footshock, tailshock, and immobilization have been shown to induce hypothalamic IL-1 production, while other stressors such as restraint, maternal separation, social isolation, and predator exposure have no effect on hypothalamic IL-1 levels. This disparity of findings has led to considerable controversy regarding the ability of stressors to induce hypothalamic IL-1 expression. Thus, the goal of the following experiments was to examine hypothalamic IL-1 responses in adult male Sprague-Dawley rats following exposure to a diverse set of stressors. Our data indicate that exposure to 2h of restraint in a Plexiglas tube, glucoprivic challenge induced by administration of 2-deoxyglucose (2-DG), or insulin-induced hypoglycemia all fail to alter hypothalamic IL-1 levels despite robust activation of the pituitary-adrenal response. However, when restraint was administered on an orbital shaker or in combination with insulin-induced hypoglycemia, robust increases in hypothalamic IL-1 were observed. No effects of glucoprivic (2-DG) challenge were observed when combined with restraint, indicating some specificity in the hypothalamic IL-1 response to stress. We also provide a preliminary validation of the ELISA detection method for IL-1, showing that (a) Western blot analyses confirmed strong immunopositive banding at the apparent molecular weight of both mature IL-1beta and the IL-1beta prohormone, and (b) footshock led to a two-fold increase in mRNA for IL-1 in the hypothalamus as detected by RT-PCR. These data provide novel insight into the characteristics of a stressor that may be necessary for the observation of stress-induced increases in hypothalamic IL-1.
Subject(s)
Gene Expression Regulation , Hypothalamus/metabolism , Interleukin-1/metabolism , Stress, Physiological/metabolism , Analysis of Variance , Animals , Antimetabolites/toxicity , Blood Glucose/metabolism , Blotting, Western/methods , Corticosterone/blood , Deoxyglucose/toxicity , Dose-Response Relationship, Drug , Electroshock/adverse effects , Food Deprivation , Gene Expression Regulation/drug effects , Gene Expression Regulation/physiology , Interleukin-1/genetics , Lipopolysaccharides/toxicity , Male , RNA, Messenger/biosynthesis , Radioimmunoassay/methods , Rats , Restraint, Physical/methods , Reverse Transcriptase Polymerase Chain Reaction/methods , Spleen/metabolism , Stress, Physiological/etiology , Time FactorsABSTRACT
Psychological stress can have devastating and lasting effects on a variety of behaviors, especially those associated with mental illnesses such as anxiety and depression. Animal models of chronic stress are frequently used to elucidate the mechanisms underlying the relationship between stress and mental health disorders and to develop improved treatment options. The current study expands upon a novel chronic stress paradigm for mice: predatory stress. The predatory stress model incorporates the natural predator-prey relationship that exists among rats and mice and allows for greater interaction between the animals, in turn increasing the extent of the stressful experience. In this study, we evaluated the behavioral effects of exposure to 15 days of predatory stress on an array of behavioral indices. Up to 2 weeks after the end of stress, adult male mice showed an increase of anxiety-like behaviors as measured by the open field and social interaction tests. Animals also expressed an increase in depressive-like behavior in the sucrose preference test. Notably, performance on the novel object recognition task, a memory test, improved after predatory stress. Taken as a whole, our results indicate that 15 exposures to this innovative predatory stress paradigm are sufficient to elicit robust anxiety-like behaviors with evidence of co-morbid depressive-like behavior, as well as changes in cognitive behavior in male mice.
Subject(s)
Anxiety/etiology , Depression/etiology , Predatory Behavior , Stress, Psychological/complications , Animals , Anxiety/complications , Depression/complications , Disease Models, Animal , Exploratory Behavior/physiology , Food Preferences , Interpersonal Relations , Male , Maze Learning , Mice , Mice, Inbred C57BL , Sucrose/administration & dosage , Sweetening Agents/administration & dosage , Time FactorsABSTRACT
Quantitative MRI of neuromelanin (NM) containing structures (referred to as NM-MRI) in the brainstem, namely the locus coeruleus (LC) and substantia nigra (SN), may assist with the early detection of Parkinson's disease (PD) and Alzheimer's disease (AD) as well as differential diagnosis in the early disease stages. In this study, two gradient echo (GRE) sequences with magnetization transfer contrast (MTC) preparation pulses were developed to simultaneously image the LC and SN. This has been a challenge with NM-MRI techniques used in previous studies due to the relatively high specific absorption rate (SAR) induced by these techniques. In addition, a semi-automated quantitative analysis scheme was applied to estimate volumes and contrast-to-noise ratios (CNR) of the LC and SN based on segmentation of both structures. Compared to a T1-weighted turbo spin echo (TSE) sequence typically used for simultaneous imaging of the LC and SN, the two GRE-MTC sequences exhibited improved performance in terms of higher sensitivity (in CNR) in imaging the SN and lower SAR during the scans. A multiple-measurement protocol was adopted as well so that motion degraded measurements could be removed and artifacts associated with motion could be corrected. The present approach has demonstrated advantages in image acquisition (lower SAR and higher sensitivity), image pre-processing (with motion correction) and quantitative image analysis (segmentation-based estimation of volume and CNR) when compared with existing NM-MRI approaches. This approach has potential for detection and monitoring of neurodegeneration in LC and SN in disease states including AD and PD.