1
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Mhatre-Winters I, Eid A, Han Y, Tieu K, Richardson JR. Sex and APOE Genotype Alter the Basal and Induced Inflammatory States of Primary Astrocytes from Humanized Targeted Replacement Mice. ASN Neuro 2023; 15:17590914221144549. [PMID: 36604975 PMCID: PMC9982390 DOI: 10.1177/17590914221144549] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Apolipoprotein E4 (APOE4) genotype and sex are significant risk factors for Alzheimer's disease (AD), with females demonstrating increased risk modulated by APOE genotype. APOE is predominantly expressed in astrocytes, however, there is a lack of comprehensive assessments of sex differences in astrocytes stratified by APOE genotype. Here, we examined the response of mixed-sex and sex-specific neonatal APOE3 and APOE4 primary mouse astrocytes (PMA) to a cytokine mix of IL1b, TNFa, and IFNg. Pro-inflammatory and anti-inflammatory cytokine profiles were assessed by qRT-PCR and Meso Scale Discovery multiplex assay. Mixed-sex APOE4 PMA were found to have higher basal messenger RNA expression of several pro-inflammatory cytokines including Il6, Tnfa, Il1b, Mcp1, Mip1a, and Nos2 compared to APOE3 PMA, which was accompanied by increased levels of these secreted cytokines. In sex-specific cultures, basal expression of Il1b, Il6, and Nos2 was 1.5 to 2.5 fold higher in APOE4 female PMA compared to APOE4 males, with both being higher than APOE3 PMA. Similar results were found for secreted levels of these cytokines. Together, these findings indicate that APOE4 genotype and female sex, contribute to a greater inflammatory response in primary astrocytes and these data may provide a framework for investigating the mechanisms contributing to genotype and sex differences in AD-related neuroinflammation.
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Affiliation(s)
- Isha Mhatre-Winters
- Department of Environmental Health Sciences, Robert Stempel College
of Public Health and Social Work, Florida International
University, Miami, FL, USA,Department of Neurosciences, School of Biomedical Sciences, Kent
State University, Kent, OH, USA
| | - Aseel Eid
- Department of Environmental Health Sciences, Robert Stempel College
of Public Health and Social Work, Florida International
University, Miami, FL, USA
| | - Yoonhee Han
- Department of Environmental Health Sciences, Robert Stempel College
of Public Health and Social Work, Florida International
University, Miami, FL, USA
| | - Kim Tieu
- Department of Environmental Health Sciences, Robert Stempel College
of Public Health and Social Work, Florida International
University, Miami, FL, USA
| | - Jason R. Richardson
- Department of Environmental Health Sciences, Robert Stempel College
of Public Health and Social Work, Florida International
University, Miami, FL, USA,Jason R. Richardson, Department of
Environmental Health Sciences, Robert Stempel College of Public Health and
Social Work, Florida International University, Miami, FL 33199-2156, USA.
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2
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Steele OG, Stuart AC, Minkley L, Shaw K, Bonnar O, Anderle S, Penn AC, Rusted J, Serpell L, Hall C, King S. A multi-hit hypothesis for an APOE4-dependent pathophysiological state. Eur J Neurosci 2022; 56:5476-5515. [PMID: 35510513 PMCID: PMC9796338 DOI: 10.1111/ejn.15685] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 03/31/2022] [Accepted: 04/25/2022] [Indexed: 01/01/2023]
Abstract
The APOE gene encoding the Apolipoprotein E protein is the single most significant genetic risk factor for late-onset Alzheimer's disease. The APOE4 genotype confers a significantly increased risk relative to the other two common genotypes APOE3 and APOE2. Intriguingly, APOE4 has been associated with neuropathological and cognitive deficits in the absence of Alzheimer's disease-related amyloid or tau pathology. Here, we review the extensive literature surrounding the impact of APOE genotype on central nervous system dysfunction, focussing on preclinical model systems and comparison of APOE3 and APOE4, given the low global prevalence of APOE2. A multi-hit hypothesis is proposed to explain how APOE4 shifts cerebral physiology towards pathophysiology through interconnected hits. These hits include the following: neurodegeneration, neurovascular dysfunction, neuroinflammation, oxidative stress, endosomal trafficking impairments, lipid and cellular metabolism disruption, impaired calcium homeostasis and altered transcriptional regulation. The hits, individually and in combination, leave the APOE4 brain in a vulnerable state where further cumulative insults will exacerbate degeneration and lead to cognitive deficits in the absence of Alzheimer's disease pathology and also a state in which such pathology may more easily take hold. We conclude that current evidence supports an APOE4 multi-hit hypothesis, which contributes to an APOE4 pathophysiological state. We highlight key areas where further study is required to elucidate the complex interplay between these individual mechanisms and downstream consequences, helping to frame the current landscape of existing APOE-centric literature.
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Affiliation(s)
| | | | - Lucy Minkley
- School of Life SciencesUniversity of SussexBrightonUK
| | - Kira Shaw
- School of Life SciencesUniversity of SussexBrightonUK
| | - Orla Bonnar
- School of Life SciencesUniversity of SussexBrightonUK
| | | | | | | | | | | | - Sarah King
- School of PsychologyUniversity of SussexBrightonUK
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3
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Lewandowski CT, Laham MS, Thatcher GR. Remembering your A, B, C's: Alzheimer's disease and ABCA1. Acta Pharm Sin B 2022; 12:995-1018. [PMID: 35530134 PMCID: PMC9072248 DOI: 10.1016/j.apsb.2022.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/27/2021] [Accepted: 01/07/2022] [Indexed: 12/24/2022] Open
Abstract
The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood–brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.
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4
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Kotredes KP, Oblak A, Pandey RS, Lin PBC, Garceau D, Williams H, Uyar A, O’Rourke R, O’Rourke S, Ingraham C, Bednarczyk D, Belanger M, Cope Z, Foley KE, Logsdon BA, Mangravite LM, Sukoff Rizzo SJ, Territo PR, Carter GW, Sasner M, Lamb BT, Howell GR. Uncovering Disease Mechanisms in a Novel Mouse Model Expressing Humanized APOEε4 and Trem2*R47H. Front Aging Neurosci 2021; 13:735524. [PMID: 34707490 PMCID: PMC8544520 DOI: 10.3389/fnagi.2021.735524] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/06/2021] [Indexed: 11/13/2022] Open
Abstract
Late-onset Alzheimer's disease (AD; LOAD) is the most common human neurodegenerative disease, however, the availability and efficacy of disease-modifying interventions is severely lacking. Despite exceptional efforts to understand disease progression via legacy amyloidogenic transgene mouse models, focus on disease translation with innovative mouse strains that better model the complexity of human AD is required to accelerate the development of future treatment modalities. LOAD within the human population is a polygenic and environmentally influenced disease with many risk factors acting in concert to produce disease processes parallel to those often muted by the early and aggressive aggregate formation in popular mouse strains. In addition to extracellular deposits of amyloid plaques and inclusions of the microtubule-associated protein tau, AD is also defined by synaptic/neuronal loss, vascular deficits, and neuroinflammation. These underlying processes need to be better defined, how the disease progresses with age, and compared to human-relevant outcomes. To create more translatable mouse models, MODEL-AD (Model Organism Development and Evaluation for Late-onset AD) groups are identifying and integrating disease-relevant, humanized gene sequences from public databases beginning with APOEε4 and Trem2*R47H, two of the most powerful risk factors present in human LOAD populations. Mice expressing endogenous, humanized APOEε4 and Trem2*R47H gene sequences were extensively aged and assayed using a multi-disciplined phenotyping approach associated with and relative to human AD pathology. Robust analytical pipelines measured behavioral, transcriptomic, metabolic, and neuropathological phenotypes in cross-sectional cohorts for progression of disease hallmarks at all life stages. In vivo PET/MRI neuroimaging revealed regional alterations in glycolytic metabolism and vascular perfusion. Transcriptional profiling by RNA-Seq of brain hemispheres identified sex and age as the main sources of variation between genotypes including age-specific enrichment of AD-related processes. Similarly, age was the strongest determinant of behavioral change. In the absence of mouse amyloid plaque formation, many of the hallmarks of AD were not observed in this strain. However, as a sensitized baseline model with many additional alleles and environmental modifications already appended, the dataset from this initial MODEL-AD strain serves an important role in establishing the individual effects and interaction between two strong genetic risk factors for LOAD in a mouse host.
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Affiliation(s)
| | - Adrian Oblak
- Stark Neurosciences Research Institute, School of Medicine, Indiana University Bloomington, Indianapolis, IN, United States
| | | | - Peter Bor-Chian Lin
- Stark Neurosciences Research Institute, School of Medicine, Indiana University Bloomington, Indianapolis, IN, United States
| | - Dylan Garceau
- The Jackson Laboratory, Bar Harbor, ME, United States
| | | | - Asli Uyar
- The Jackson Laboratory, Bar Harbor, ME, United States
| | - Rita O’Rourke
- The Jackson Laboratory, Bar Harbor, ME, United States
| | | | - Cynthia Ingraham
- Stark Neurosciences Research Institute, School of Medicine, Indiana University Bloomington, Indianapolis, IN, United States
| | | | | | - Zackary Cope
- Department of Medicine—Aging Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Kate E. Foley
- The Jackson Laboratory, Bar Harbor, ME, United States
| | | | | | - Stacey J. Sukoff Rizzo
- Department of Medicine—Aging Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Paul R. Territo
- Stark Neurosciences Research Institute, School of Medicine, Indiana University Bloomington, Indianapolis, IN, United States
| | | | | | - Bruce T. Lamb
- Stark Neurosciences Research Institute, School of Medicine, Indiana University Bloomington, Indianapolis, IN, United States
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5
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Montine TJ, Bukhari SA, White LR. Cognitive Impairment in Older Adults and Therapeutic Strategies. Pharmacol Rev 2021; 73:152-162. [PMID: 33298513 PMCID: PMC7736830 DOI: 10.1124/pharmrev.120.000031] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 10/12/2020] [Indexed: 12/12/2022] Open
Abstract
Cognitive impairment and its severe form dementia are increasingly prevalent in older adults and loom as a public health disaster unless effective interventions are developed. Cognitive impairment is a convergent trait caused by damage from an idiosyncratic mix of four prevalent diseases (Alzheimer disease; vascular brain injury; Lewy body diseases, such as Parkinson disease and dementia with Lewy bodies; and limbic-predominant age-related transactive response DNA-binding protein 43 encephalopathy) that is counterbalanced by individually varying resilience, which is comprised of reserve and compensation. Brain regional damage from each of these four prevalent diseases is generated by the net effect of injury and (mal)adaptive response and is accompanied by characteristic lesions. Existing therapeutics enhance resilience, whereas most agents under development target mechanisms of damage with only suppression of vascular brain injury yet to show therapeutic promise. We hope to anticipate future tailored interventions that target mechanisms of damage and thereby avert the oncoming surge of cognitive impairment and dementia in older adults. SIGNIFICANCE STATEMENT: Brain regional damage is generated by the net effect of injury and (mal)adaptive response. The extent to which signs and symptoms of such damage occur is influenced by an underlying resilience comprising reserve and compensation. Finding tailored interventions that target specific mechanisms of damage likely yields the most effective therapies.
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Affiliation(s)
- Thomas J Montine
- Department of Pathology, Stanford University, Stanford, California (T.J.M., S.A.B.) and Pacific Health Research and Education Institute, Honolulu, Hawaii (L.R.W.)
| | - Syed A Bukhari
- Department of Pathology, Stanford University, Stanford, California (T.J.M., S.A.B.) and Pacific Health Research and Education Institute, Honolulu, Hawaii (L.R.W.)
| | - Lon R White
- Department of Pathology, Stanford University, Stanford, California (T.J.M., S.A.B.) and Pacific Health Research and Education Institute, Honolulu, Hawaii (L.R.W.)
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6
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APOE in the normal brain. Neurobiol Dis 2020; 136:104724. [PMID: 31911114 DOI: 10.1016/j.nbd.2019.104724] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 12/19/2019] [Accepted: 12/31/2019] [Indexed: 12/25/2022] Open
Abstract
The APOE4 protein affects the primary neuropathological markers of Alzheimer's disease (AD): amyloid plaques, neurofibrillary tangles, and gliosis. These interactions have been investigated to understand the strong effect of APOE genotype on risk of AD. However, APOE genotype has strong effects on processes in normal brains, in the absence of the hallmarks of AD. We propose that CNS APOE is involved in processes in the normal brains that in later years apply specifically to processes of AD pathogenesis. We review the differences of the APOE protein found in the CNS compared to the plasma, including post-translational modifications (glycosylation, lipidation, multimer formation), focusing on ways that the common APOE isoforms differ from each other. We also review structural and functional studies of young human brains and control APOE knock-in mouse brains. These approaches demonstrate the effects of APOE genotype on microscopic neuron structure, gross brain structure, and behavior, primarily related to the hippocampal areas. By focusing on the effects of APOE genotype on normal brain function, approaches can be pursued to identify biomarkers of APOE dysfunction, to promote normal functions of the APOE4 isoform, and to prevent the accumulation of the pathologic hallmarks of AD with aging.
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7
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Higher soluble CD14 levels are associated with lower visuospatial memory performance in youth with HIV. AIDS 2019; 33:2363-2374. [PMID: 31764101 DOI: 10.1097/qad.0000000000002371] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVE HIV-associated neurocognitive disorders persist despite early antiretroviral therapy (ART) and optimal viral suppression. We examined the relationship between immunopathogenesis driven by various pathways of immune activation and discrete neurocognitive performance domains in youth with HIV (YWH). DESIGN Observational cross-sectional study. METHODS YWH, ages 20-28 years, enrolled in Adolescent Medicine Trials Network 071/101 were assessed for biomarkers of macrophage, lymphocyte activation, and vascular inflammation using ELISA/multiplex assays. Standardized neurocognitive tests were performed, and demographically adjusted z-scores were combined to form indices of attention, motor, executive function, verbal, and visuospatial memory. Cross-sectional analysis of the relationship between 18 plasma inflammatory biomarkers and each neurocognitive domain was performed. Linear regression models were fit for each combination of log-transformed biomarker value and neurocognitive domain score, and were adjusted for demographics, socioeconomic status, substance use, depression, CD4 T-cell count, HIV viral load, and ART status. RESULTS Study included 128 YWH [mean age 23.8 (SD 1.7) years, 86% men, 68% African American]. Verbal and visuospatial memory domains were most significantly impaired in the cohort (z = -1.59 and -1.0, respectively). Higher sCD14 was associated with impaired visuospatial memory, which remained robust after adjusting for other biomarkers, demographics, and HIV-associated covariates. Among biomarkers of vascular inflammation, sICAM-1 was negatively associated with verbal memory and attention, whereas sVCAM-1 was positively associated with executive function and visuospatial memory. Specific neurocognitive domains were not associated with sCD163, LPS, or CCL2 levels. CONCLUSION Impaired visuospatial memory in YWH is associated with immune activation, as reflected by higher sCD14.
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8
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Ben-Moshe H, Luz I, Liraz O, Boehm-Cagan A, Salomon-Zimri S, Michaelson D. ApoE4 Exacerbates Hippocampal Pathology Following Acute Brain Penetration Injury in Female Mice. J Mol Neurosci 2019; 70:32-44. [DOI: 10.1007/s12031-019-01397-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Accepted: 08/14/2019] [Indexed: 10/26/2022]
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9
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Newcombe EA, Camats-Perna J, Silva ML, Valmas N, Huat TJ, Medeiros R. Inflammation: the link between comorbidities, genetics, and Alzheimer's disease. J Neuroinflammation 2018; 15:276. [PMID: 30249283 PMCID: PMC6154824 DOI: 10.1186/s12974-018-1313-3] [Citation(s) in RCA: 333] [Impact Index Per Article: 55.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 09/11/2018] [Indexed: 12/21/2022] Open
Abstract
Alzheimer’s disease (AD) is a neurodegenerative disorder, most cases of which lack a clear causative event. This has made the disease difficult to characterize and, thus, diagnose. Although some cases are genetically linked, there are many diseases and lifestyle factors that can lead to an increased risk of developing AD, including traumatic brain injury, diabetes, hypertension, obesity, and other metabolic syndromes, in addition to aging. Identifying common factors and trends between these conditions could enhance our understanding of AD and lead to the development of more effective treatments. Although the immune system is one of the body’s key defense mechanisms, chronic inflammation has been increasingly linked with several age-related diseases. Moreover, it is now well accepted that chronic inflammation has an important role in the onset and progression of AD. In this review, the different inflammatory signals associated with AD and its risk factors will be outlined to demonstrate how chronic inflammation may be influencing individual susceptibility to AD. Our goal is to bring attention to potential shared signals presented by the immune system during different conditions that could lead to the development of successful treatments.
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Affiliation(s)
- Estella A Newcombe
- Neurula Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Building 79, Brisbane, 4072, QLD, Australia.
| | - Judith Camats-Perna
- Neurula Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Building 79, Brisbane, 4072, QLD, Australia
| | - Mallone L Silva
- Neurula Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Building 79, Brisbane, 4072, QLD, Australia
| | - Nicholas Valmas
- Queensland Brain Institute, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Tee Jong Huat
- Neurula Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Building 79, Brisbane, 4072, QLD, Australia.,Centre for Stem Cell Ageing and Regenerative Engineering, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Rodrigo Medeiros
- Neurula Laboratory, Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Building 79, Brisbane, 4072, QLD, Australia.
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10
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Di Lucente J, Nguyen HM, Wulff H, Jin LW, Maezawa I. The voltage-gated potassium channel Kv1.3 is required for microglial pro-inflammatory activation in vivo. Glia 2018; 66:1881-1895. [PMID: 30043400 DOI: 10.1002/glia.23457] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 04/26/2018] [Accepted: 05/02/2018] [Indexed: 11/09/2022]
Abstract
Microglia show a rich repertoire of activation patterns regulated by a complex ensemble of surface ion channels, receptors, and transporters. We and others have investigated whether microglia vary their K+ channel expression as a means to achieve functional diversity. However, most of the prior studies were conducted using in vitro models such as BV2 cells, primary microglia, or brain slices in culture, which may not accurately reflect microglia physiology in adult individuals. Here we employed an in vivo mouse model of selective innate immune activation by intracerebroventricular injection of lipopolysaccharides (ICV-LPS) to determine the role of the voltage-gated Kv1.3 channel in LPS-induced M1-like microglial activation. Using microglia acutely isolated from adult brains, we detected Kv1.3 and Kir2.1 currents, and found that ICV-LPS increased the current density and RNA expression of Kv1.3 but did not affect those of Kir2.1. Genetic knockout of Kv1.3 abolished LPS-induced microglial activation exemplified by Iba-1 immunoreactivity and expression of pro-inflammatory mediators such as IL-1β, TNF-α, IL-6, and iNOS. Moreover, Kv1.3 knockout mitigated the LPS-induced impairment of hippocampal long-term potentiation (hLTP), suggesting that Kv1.3 activity regulates pro-inflammatory microglial neurotoxicity. Pharmacological intervention using PAP-1, a small molecule that selectively blocks homotetrameric Kv1.3 channels, achieved anti-inflammatory and hLTP-recovery effects similar to Kv1.3 knockout. We conclude that Kv1.3 is required for microglial M1-like pro-inflammatory activation in vivo. A significant implication of our in vivo data is that Kv1.3 blockers could be therapeutic candidates for neurological diseases where microglia-mediated neurotoxicity is implicated in the pathogenesis.
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Affiliation(s)
- Jacopo Di Lucente
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
| | - Hai M Nguyen
- Department of Pharmacology, University of California, Davis, California
| | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California
| | - Lee-Way Jin
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
| | - Izumi Maezawa
- From the Department of Pathology and Laboratory Medicine and M.I.N.D. Institute, University of California Davis Medical Center, Sacramento, California
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11
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Aging and Apolipoprotein E in HIV Infection. J Neurovirol 2018; 24:529-548. [PMID: 29987582 PMCID: PMC6244718 DOI: 10.1007/s13365-018-0660-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/23/2018] [Accepted: 06/25/2018] [Indexed: 01/21/2023]
Abstract
With the implementation of increasingly effective antiretroviral therapy (ART) over the past three decades, individuals infected with HIV live a much longer life. HIV infection is no longer a terminal but rather a chronic disease. However, the lifespan of infected individuals remains shorter than that of their uninfected peers. Even with ART, HIV infection may potentiate “premature” aging. Organ-associated disease and systemic syndromes that occur in treated HIV-infection are like that of older, uninfected individuals. Brain aging may manifest as structural changes or neurocognitive impairment that are beyond the chronological age. The spectrum of neurological, cognitive, and motor deficiencies, currently described as HIV-associated neurocognitive disorders (HAND), may reflect earlier onset of mechanisms common to HIV infection and aging (accelerated aging). HAND could also reflect the neurological impact of HIV infection superimposed on comorbidities linked to age and chronic inflammation, leading to a higher prevalence of neurocognitive impairment across the age span (accentuated aging). In addition, apolipoprotein E (ApoE), one of the most influential host risk factors for developing Alzheimer’s disease, has been implicated in the development of HAND. But studies differ as to whether ApoE is relevant, and whether age and ApoE interact to impair brain function in the HIV-infected patient. What is clear is that HIV-infected individuals are living longer with HIV, and therefore factors related to aging and health need to be examined in the context of current, effective ART. This review addresses the recent evidence for the influence of aging and ApoE on HIV-associated neurocognitive impairment.
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12
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Dorey E, Bamji-Mirza M, Najem D, Li Y, Liu H, Callaghan D, Walker D, Lue LF, Stanimirovic D, Zhang W. Apolipoprotein E Isoforms Differentially Regulate Alzheimer's Disease and Amyloid-β-Induced Inflammatory Response in vivo and in vitro. J Alzheimers Dis 2018; 57:1265-1279. [PMID: 28372324 DOI: 10.3233/jad-160133] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neuroinflammation plays a critical role in neuronal dysfunction and death of Alzheimer's disease (AD). ApoE4 is a major risk factor of AD, while ApoE2 is neuroprotective. Little is known about the roles of ApoE isoforms in the neuroinflammation seen in AD. Their roles and mechanisms in Aβ-induced/neuroinflammation were investigated in this study using in vivo and in vitro models. Rat astrocytes were treated with lipid-poor recombinant hApoE and/or Aβ42. Mouse astrocyte lines-expressing lipidated hApoE were treated with Aβ42 and/or vitamin D receptor (VDR) agonist, 1α,25-dihydroxyvitamin D3. Cells and media were harvested for cytokine ELISA, RNA isolated for qRT-PCR, and nuclear protein for transcription factor (TF) arrays and EMSA. hApoE-transgenic and AD mice were mated to generate hApoE2/AD and hApoE4/AD mice. Mice were euthanized at 6 months of age. Brain tissues were collected for cytokine ELISA array, Aβ ELISA, immunoblotting, and immunohistochemistry. hApoE4/AD mice had significantly higher levels of inflammatory cytokines than hApoE2/AD mice. Lipidated hApoE4 significantly promoted inflammatory gene expression induced by Aβ42 but not recombinant hApoE4 in astrocytes as compared to controls. Lipidated hApoE3 provided a certain degree of protection against Aβ42-induced inflammatory response but not recombinant hApoE3 as compared to controls. Both lipidated and recombinant hApoE2 provided protection against Aβ42-induced inflammatory response compared to controls. TF array revealed that ApoE2 strongly activated VDR in Aβ42-treated astrocytes. Application of 1α,25-dihydroxyvitamin D3 completely inhibited Aβ-induced inflammatory gene expression in hApoE4-expressing astrocytes. The results suggest that ApoE4 promotes, but ApoE2 inhibits, AD/Aβ-induced neuroinflammation via VDR signaling. Targeting VDR signaling or active form of VD3 may relieve AD neuroinflammation or/and neurodegeneration.
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Affiliation(s)
- Evan Dorey
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Michelle Bamji-Mirza
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Dema Najem
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Yan Li
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Hong Liu
- Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Debbie Callaghan
- Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | | | - Lih-Fen Lue
- Banner Sun Health Research Institute, Sun City, AZ, USA
| | - Danica Stanimirovic
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
| | - Wandong Zhang
- Faculty of Medicine, University of Ottawa, Ottawa, Canada.,Human Health Therapeutics, National Research Council Canada, Ottawa, Canada
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13
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Griffioen K, Mattson MP, Okun E. Deficiency of Toll-like receptors 2, 3 or 4 extends life expectancy in Huntington's disease mice. Heliyon 2018; 4:e00508. [PMID: 29560427 PMCID: PMC5857515 DOI: 10.1016/j.heliyon.2018.e00508] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 11/30/2017] [Accepted: 01/08/2018] [Indexed: 01/05/2023] Open
Abstract
Huntington’s disease (HD), an autosomal dominant neurodegenerative disorder characterized by progressive striatal and cortical atrophy, has been strongly linked with neuroinflammation. Toll-like receptors, a family of innate immune receptors, are a major pathway for neuroinflammation with pleiotropic effects on neuronal plasticity and neurodevelopment. We assessed whether deficiency for TLRs 2, 3 or 4 affects life expectancy in the N171-82Q mouse model of HD. Our data indicate that homozygous TLRs 2 and 3 as well as heterozygous TLR4 deficiency significantly extends the life expectancy of HD mice. Our data suggest that multiple TLR pathways may be involved in the neuroinflammatory and degenerative processes during HD.
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Affiliation(s)
- Kathleen Griffioen
- Department of Biology and Chemistry, Liberty University, Lynchburg, VA, 24515, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, 21224, USA.,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Eitan Okun
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.,The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel.,The Paul Feder Laboratory on Alzheimer's Disease Research, Israel
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14
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Moser VA, Pike CJ. Obesity Accelerates Alzheimer-Related Pathology in APOE4 but not APOE3 Mice. eNeuro 2017; 4:ENEURO.0077-17.2017. [PMID: 28612048 PMCID: PMC5469027 DOI: 10.1523/eneuro.0077-17.2017] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/17/2017] [Accepted: 05/22/2017] [Indexed: 12/25/2022] Open
Abstract
Alzheimer's disease (AD) risk is modified by both genetic and environmental risk factors, which are believed to interact to cooperatively modify pathogenesis. Although numerous genetic and environmental risk factors for AD have been identified, relatively little is known about potential gene-environment interactions in regulating disease risk. The strongest genetic risk factor for late-onset AD is the ε4 allele of apolipoprotein E (APOE4). An important modifiable risk factor for AD is obesity, which has been shown to increase AD risk in humans and accelerate development of AD-related pathology in rodent models. Potential interactions between APOE4 and obesity are suggested by the literature but have not been thoroughly investigated. In the current study, we evaluated this relationship by studying the effects of diet-induced obesity (DIO) in the EFAD mouse model, which combines familial AD transgenes with human APOE3 or APOE4. Male E3FAD and E4FAD mice were maintained for 12 weeks on either a control diet or a Western diet high in saturated fat and sugars. We observed that metabolic outcomes of DIO were similar in E3FAD and E4FAD mice. Importantly, our data showed a significant interaction between diet and APOE genotype on AD-related outcomes in which Western diet was associated with robust increases in amyloid deposits, β-amyloid burden, and glial activation in E4FAD but not in E3FAD mice. These findings demonstrate an important gene-environment interaction in an AD mouse model that suggests that AD risk associated with obesity is strongly influenced by APOE genotype.
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Affiliation(s)
- V Alexandra Moser
- Neuroscience Graduate Program, Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089
| | - Christian J Pike
- Neuroscience Graduate Program, Leonard Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089
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15
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Postupna N, Latimer CS, Larson EB, Sherfield E, Paladin J, Shively CA, Jorgensen MJ, Andrews RN, Kaplan JR, Crane PK, Montine KS, Craft S, Keene CD, Montine TJ. Human Striatal Dopaminergic and Regional Serotonergic Synaptic Degeneration with Lewy Body Disease and Inheritance of APOE ε4. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:884-895. [PMID: 28212814 DOI: 10.1016/j.ajpath.2016.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 12/10/2016] [Accepted: 12/20/2016] [Indexed: 01/22/2023]
Abstract
Cognitive impairment in older individuals is a complex trait that in population-based studies most commonly derives from an individually varying mixture of Alzheimer disease, Lewy body disease, and vascular brain injury. We investigated the molecular composition of synaptic particles from three sources: consecutive rapid autopsy brains from the Adult Changes in Thought Study, a population-based cohort; four aged nonhuman primate brains optimally processed for molecular investigation; and targeted replacement transgenic mice homozygous for APOE ε4. Our major goal was to characterize the molecular composition of human synaptic particles in regions of striatum and prefrontal cortex. We performed flow cytometry to measure six markers of synaptic subtypes, as well as amyloid β 42 and paired helical filament tau. Our results showed selective degeneration of dopaminergic terminals throughout the striatum in individuals with Lewy body disease, and serotonergic degeneration in human ventromedial caudate nucleus from individuals with an APOE ε4 allele. Similar results were seen in mouse caudate nucleus homozygous for APOE ε4 via targeted replacement. Together, extension of these clinical, pathologic, and genetic associations from tissue to the synaptic compartment of cerebral cortex and striatum strongly supports our approach for accurately observing the molecular composition of human synapses by flow cytometry.
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Affiliation(s)
- Nadia Postupna
- Department of Pathology, University of Washington, Seattle, Washington
| | - Caitlin S Latimer
- Department of Pathology, University of Washington, Seattle, Washington
| | - Eric B Larson
- Group Health Research Institute, Seattle, Washington
| | - Emily Sherfield
- Department of Pathology, University of Washington, Seattle, Washington
| | - Julie Paladin
- Department of Pathology, University of Washington, Seattle, Washington
| | - Carol A Shively
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Matthew J Jorgensen
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Rachel N Andrews
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Jay R Kaplan
- Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Paul K Crane
- Department of Medicine, University of Washington, Seattle, Washington
| | | | - Suzanne Craft
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - C Dirk Keene
- Department of Pathology, University of Washington, Seattle, Washington
| | - Thomas J Montine
- Department of Pathology, University of Washington, Seattle, Washington.
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16
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Moser VA, Pike CJ. Obesity and sex interact in the regulation of Alzheimer's disease. Neurosci Biobehav Rev 2015; 67:102-18. [PMID: 26708713 DOI: 10.1016/j.neubiorev.2015.08.021] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 08/01/2015] [Accepted: 08/03/2015] [Indexed: 01/09/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder, for which a number of genetic, environmental, and lifestyle risk factors have been identified. A significant modifiable risk factor is obesity in mid-life. Interestingly, both obesity and AD exhibit sex differences and are regulated by sex steroid hormones. Accumulating evidence suggests interactions between obesity and sex in regulation of AD risk, although the pathways underlying this relationship are unclear. Inflammation and the E4 allele of apolipoprotein E have been identified as independent risk factors for AD and both interact with obesity and sex steroid hormones. We review the individual and cooperative effects of obesity and sex on development of AD and examine the potential contributions of apolipoprotein E, inflammation, and their interactions to this relationship.
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Affiliation(s)
- V Alexandra Moser
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA.
| | - Christian J Pike
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089, USA; Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089, USA.
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17
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Mhatre SD, Tsai CA, Rubin AJ, James ML, Andreasson KI. Microglial malfunction: the third rail in the development of Alzheimer's disease. Trends Neurosci 2015; 38:621-636. [PMID: 26442696 PMCID: PMC4670239 DOI: 10.1016/j.tins.2015.08.006] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 12/23/2022]
Abstract
Studies of Alzheimer's disease (AD) have predominantly focused on two major pathologies: amyloid-β (Aβ) and hyperphosphorylated tau. These misfolded proteins can accumulate asymptomatically in distinct regions over decades. However, significant Aβ accumulation can be seen in individuals who do not develop dementia, and tau pathology limited to the transentorhinal cortex, which can appear early in adulthood, is usually clinically silent. Thus, an interaction between these pathologies appears to be necessary to initiate and propel disease forward to widespread circuits. Recent multidisciplinary findings strongly suggest that the third factor required for disease progression is an aberrant microglial immune response. This response may initially be beneficial; however, a maladaptive microglial response eventually develops, fueling a feed-forward spread of tau and Aβ pathology.
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Affiliation(s)
- Siddhita D Mhatre
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA; Stanford Neurosciences Institute, Stanford, CA, USA
| | - Connie A Tsai
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA; Stanford Neurosciences Institute, Stanford, CA, USA; Neurosciences Graduate Program, Stanford University, Stanford, CA, USA
| | - Amanda J Rubin
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA; Stanford Neurosciences Institute, Stanford, CA, USA; Neurosciences Graduate Program, Stanford University, Stanford, CA, USA
| | - Michelle L James
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Katrin I Andreasson
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA; Stanford Neurosciences Institute, Stanford, CA, USA.
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18
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Gamba P, Testa G, Gargiulo S, Staurenghi E, Poli G, Leonarduzzi G. Oxidized cholesterol as the driving force behind the development of Alzheimer's disease. Front Aging Neurosci 2015; 7:119. [PMID: 26150787 PMCID: PMC4473000 DOI: 10.3389/fnagi.2015.00119] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 06/03/2015] [Indexed: 12/21/2022] Open
Abstract
Alzheimer’s disease (AD), the most common neurodegenerative disorder associated with dementia, is typified by the pathological accumulation of amyloid Aβ peptides and neurofibrillary tangles (NFT) within the brain. Considerable evidence indicates that many events contribute to AD progression, including oxidative stress, inflammation, and altered cholesterol metabolism. The brain’s high lipid content makes it particularly vulnerable to oxidative species, with the consequent enhancement of lipid peroxidation and cholesterol oxidation, and the subsequent formation of end products, mainly 4-hydroxynonenal and oxysterols, respectively from the two processes. The chronic inflammatory events observed in the AD brain include activation of microglia and astrocytes, together with enhancement of inflammatory molecule and free radical release. Along with glial cells, neurons themselves have been found to contribute to neuroinflammation in the AD brain, by serving as sources of inflammatory mediators. Oxidative stress is intimately associated with neuroinflammation, and a vicious circle has been found to connect oxidative stress and inflammation in AD. Alongside oxidative stress and inflammation, altered cholesterol metabolism and hypercholesterolemia also significantly contribute to neuronal damage and to progression of AD. Increasing evidence is now consolidating the hypothesis that oxidized cholesterol is the driving force behind the development of AD, and that oxysterols are the link connecting the disease to altered cholesterol metabolism in the brain and hypercholesterolemia; this is because of the ability of oxysterols, unlike cholesterol, to cross the blood brain barrier (BBB). The key role of oxysterols in AD pathogenesis has been strongly supported by research pointing to their involvement in modulating neuroinflammation, Aβ accumulation, and cell death. This review highlights the key role played by cholesterol and oxysterols in the brain in AD pathogenesis.
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Affiliation(s)
- Paola Gamba
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
| | - Gabriella Testa
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
| | - Simona Gargiulo
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
| | - Erica Staurenghi
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
| | - Giuseppe Poli
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
| | - Gabriella Leonarduzzi
- Department of Clinical and Biological Sciences, School of Medicine, University of Turin Orbassano, Torino, Italy
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19
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Tai LM, Ghura S, Koster KP, Liakaite V, Maienschein‐Cline M, Kanabar P, Collins N, Ben‐Aissa M, Lei AZ, Bahroos N, Green SJ, Hendrickson B, Van Eldik LJ, LaDu MJ. APOE-modulated Aβ-induced neuroinflammation in Alzheimer's disease: current landscape, novel data, and future perspective. J Neurochem 2015; 133:465-88. [PMID: 25689586 PMCID: PMC4400246 DOI: 10.1111/jnc.13072] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/10/2015] [Accepted: 02/11/2015] [Indexed: 01/12/2023]
Abstract
Chronic glial activation and neuroinflammation induced by the amyloid-β peptide (Aβ) contribute to Alzheimer's disease (AD) pathology. APOE4 is the greatest AD-genetic risk factor; increasing risk up to 12-fold compared to APOE3, with APOE4-specific neuroinflammation an important component of this risk. This editorial review discusses the role of APOE in inflammation and AD, via a literature review, presentation of novel data on Aβ-induced neuroinflammation, and discussion of future research directions. The complexity of chronic neuroinflammation, including multiple detrimental and beneficial effects occurring in a temporal and cell-specific manner, has resulted in conflicting functional data for virtually every inflammatory mediator. Defining a neuroinflammatory phenotype (NIP) is one way to address this issue, focusing on profiling the changes in inflammatory mediator expression during disease progression. Although many studies have shown that APOE4 induces a detrimental NIP in peripheral inflammation and Aβ-independent neuroinflammation, data for APOE-modulated Aβ-induced neuroinflammation are surprisingly limited. We present data supporting the hypothesis that impaired apoE4 function modulates Aβ-induced effects on inflammatory receptor signaling, including amplification of detrimental (toll-like receptor 4-p38α) and suppression of beneficial (IL-4R-nuclear receptor) pathways. To ultimately develop APOE genotype-specific therapeutics, it is critical that future studies define the dynamic NIP profile and pathways that underlie APOE-modulated chronic neuroinflammation. In this editorial review, we present data supporting the hypothesis that impaired apoE4 function modulates Aβ-induced effects on inflammatory receptor signaling, including amplification of detrimental (TLR4-p38α) and suppression of beneficial (IL-4R-nuclear receptor) pathways, resulting in an adverse NIP that causes neuronal dysfunction. NIP, Neuroinflammatory phenotype; P.I., pro-inflammatory; A.I., anti-inflammatory.
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Affiliation(s)
- Leon M. Tai
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
| | - Shivesh Ghura
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
| | - Kevin P. Koster
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
| | | | | | - Pinal Kanabar
- UIC Center for Research Informatics University of IllinoisChicagoIllinoisUSA
| | - Nicole Collins
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
| | - Manel Ben‐Aissa
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
| | - Arden Zhengdeng Lei
- UIC Center for Research Informatics University of IllinoisChicagoIllinoisUSA
| | - Neil Bahroos
- UIC Center for Research Informatics University of IllinoisChicagoIllinoisUSA
| | | | - Bill Hendrickson
- UIC Research Resources CenterUniversity of IllinoisChicagoIllinoisUSA
| | | | - Mary Jo LaDu
- Department of Anatomy and Cell BiologyUniversity of IllinoisChicagoIllinoisUSA
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20
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Li X, Montine KS, Keene CD, Montine TJ. Different mechanisms of apolipoprotein E isoform-dependent modulation of prostaglandin E2 production and triggering receptor expressed on myeloid cells 2 (TREM2) expression after innate immune activation of microglia. FASEB J 2015; 29:1754-62. [PMID: 25593125 DOI: 10.1096/fj.14-262683] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 12/15/2014] [Indexed: 01/14/2023]
Abstract
Several lines of evidence support immune response in brain as a mechanism of injury in Alzheimer disease (AD). Moreover, immune activation is heightened in apolipoprotein E (APOE) ε4 carriers; inhibitors of prostaglandin (PG) synthesis show a partially protective effect on AD risk from APOE ε4; and genetic variants in triggering receptor expressed on myeloid cells 2 (TREM2) are a rare but potent risk for AD. We tested the hypothesis that APOE ε4 inheritance modulates both the PGE2 pathway and TREM2 expression using primary murine microglia from targeted replacement (TR) APOE3/3 and APOE4/4 mice. Microglial cyclooxygenase-2, microsomal PGE synthase, and PGE2 expression were increased 2- to 25-fold in both genotypes by TLR activators; however, this induction was significantly (P < 0.01) greater in TR APOE4/4 microglia with TLR3 and TLR4 activators. Microglial TREM2 expression was reduced approximately 85% by all TLR activators; this reduction was approximately one-third greater in microglia from TR APOE4/4 mice. Importantly, both receptor-associated protein and a nuclear factor κ-light-chain-enhancer inhibitor blocked TR APOE4/4-dependent effects on the PGE2 pathway but not on TREM2 expression. These data demonstrate complementary, but mechanistically distinct, regulation of pro- and anti-inflammatory mediators in TR APOE4/4 murine microglia that yields a more proinflammatory state than with TR APOE3/3.
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Affiliation(s)
- Xianwu Li
- Department of Pathology, University of Washington, Seattle, Washington, USA
| | - Kathleen S Montine
- Department of Pathology, University of Washington, Seattle, Washington, USA
| | - C Dirk Keene
- Department of Pathology, University of Washington, Seattle, Washington, USA
| | - Thomas J Montine
- Department of Pathology, University of Washington, Seattle, Washington, USA
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21
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Apolipoprotein E, amyloid-beta, and neuroinflammation in Alzheimer's disease. Neurosci Bull 2014; 30:317-30. [PMID: 24652457 DOI: 10.1007/s12264-013-1422-z] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Accepted: 01/23/2014] [Indexed: 12/21/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by the accumulation and deposition of amyloid-beta (Aβ) peptides in the brain. Neuroinflammation occurs in the AD brain and plays a critical role in the neurodegenerative pathology. Particularly, Aβ evokes an inflammatory response that leads to synaptic dysfunction, neuronal death, and neurodegeneration. Apolipoprotein E (ApoE) proteins are involved in cholesterol transport, Aβ binding and clearance, and synaptic functions in the brain. The ApoE4 isoform is a key risk factor for AD, while the ApoE2 isoform has a neuroprotective effect. However, studies have reached different conclusions about the roles of the isoforms; some show that both ApoE3 and ApoE4 have anti-inflammatory effects, while others show that ApoE4 causes a predisposition to inflammation or promotes an inflammatory response following lipopolysaccharide treatment. These discrepancies may result from the differences in models, cell types, experimental conditions, and inflammatory stimuli used. Further, little was known about the role of ApoE isoforms in the Aβ-induced inflammatory response and in the neuroinflammation of AD. Our recent work showed that ApoE isoforms differentially regulate and modify the Aβ-induced inflammatory response in neural cells, with ApoE2 suppressing and ApoE4 promoting the response. In this article, we review the roles, mechanisms, and interrelations among Aβ, ApoE, and neuroinflammation in AD.
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22
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Okun E, Barak B, Saada-Madar R, Rothman SM, Griffioen KJ, Roberts N, Castro K, Mughal MR, Pita MA, Stranahan AM, Arumugam TV, Mattson MP. Evidence for a developmental role for TLR4 in learning and memory. PLoS One 2012; 7:e47522. [PMID: 23071817 PMCID: PMC3469493 DOI: 10.1371/journal.pone.0047522] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 09/12/2012] [Indexed: 01/08/2023] Open
Abstract
Toll-like receptors (TLRs) play essential roles in innate immunity and increasing evidence indicates that these receptors are expressed in neurons, astrocytes and microglia in the brain where they mediate responses to infection, stress and injury. Very little is known about the roles of TLRs in cognition. To test the hypothesis that TLR4 has a role in hippocampus-dependent spatial learning and memory, we used mice deficient for TLR4 and mice receiving chronic TLR4 antagonist infusion to the lateral ventricles in the brain. We found that developmental TLR4 deficiency enhances spatial reference memory acquisition and memory retention, impairs contextual fear-learning and enhances motor functions, traits that were correlated with CREB up-regulation in the hippocampus. TLR4 antagonist infusion into the cerebral ventricles of adult mice did not affect cognitive behavior, but instead affected anxiety responses. Our findings indicate a developmental role for TLR4 in shaping spatial reference memory, and fear learning and memory. Moreover, we show that central TLR4 inhibition using a TLR4 antagonist has no discernible physiological role in regulating spatial and contextual hippocampus-dependent cognitive behavior.
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Affiliation(s)
- Eitan Okun
- The Mina and Everard Goodman Faculty of Life Sciences, The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan, Israel.
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23
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Keene CD, Cudaback E, Li X, Montine KS, Montine TJ. Apolipoprotein E isoforms and regulation of the innate immune response in brain of patients with Alzheimer's disease. Curr Opin Neurobiol 2011; 21:920-8. [PMID: 21907569 DOI: 10.1016/j.conb.2011.08.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 08/05/2011] [Accepted: 08/15/2011] [Indexed: 02/08/2023]
Abstract
The largest genetic risk for late-onset Alzheimer's disease (AD) resides at the apolipoprotein E gene (APOE) locus, which has three common alleles (ɛ2, ɛ3, ɛ4) that encode three isoforms (apoE2, apoE3, apoE4). The very strong association of the APOE ɛ4 allele with AD risk and its role in the accumulation of amyloid β in brains of people and animal models solidify the biological relevance of apoE isoforms but do not provide mechanistic insight. The innate immune response is consistently observed in AD and is a likely contributor to neuronal injury and response to injury. Here we review emerging data showing that apoE isoform regulation of multiple facets of the innate immune response in the brain may alter AD not only through amyloid β-dependent mechanisms, but also through other, amyloid β-independent mechanisms.
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Affiliation(s)
- C Dirk Keene
- Department of Pathology, University of Washington, Seattle, WA, United States
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24
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Cudaback E, Li X, Montine KS, Montine TJ, Keene CD. Apolipoprotein E isoform-dependent microglia migration. FASEB J 2011; 25:2082-91. [PMID: 21385991 DOI: 10.1096/fj.10-176891] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Complement component C5a and ATP are potent effectors of microglial movement and are increased in diverse neurodegenerative diseases and at sites of injury. Apolipoprotein E (apoE) influences microglial function, and different human apoE isoforms confer variable risk for development of neurodegenerative disorders, especially Alzheimer's disease. The purpose of this investigation was to test the hypothesis that mouse apoE and human apoE isoforms influence microglial migration. Using primary wild-type and apoE-deficient microglia, we show that C5a- and ATP-stimulated chemotaxis are largely apoE-dependent processes with different molecular bases. Although the C5a-dependent chemotaxis of wild-type microglia was completely blocked by receptor-associated protein (RAP), suggesting apoE receptor involvement, ATP-stimulated migration was unaffected by RAP but was associated with differential ERK phosphorylation. Studies using primary microglia derived from targeted replacement mice "humanized" for the coding exons (protein isoform) of human ε2 (apoE2), ε3 (apoE3), or ε4 (apoE4) allele of APOE revealed that primary mouse microglia expressing apoE4 or apoE2 exhibited significantly reduced C5a- and ATP-stimulated migration compared with microglia expressing human apoE3. This study, for the first time, demonstrates apoE dependence and apoE isoform-specific modulation of microglial migration in response to distinct chemotactic stimuli commonly associated with neurodegenerative disease.
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Affiliation(s)
- Eiron Cudaback
- Department of Pathology, Neuropathology Division, University of Washington, Seattle, Washington, USA
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25
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Huebbe P, Lodge JK, Rimbach G. Implications of apolipoprotein E genotype on inflammation and vitamin E status. Mol Nutr Food Res 2010; 54:623-30. [PMID: 20183830 DOI: 10.1002/mnfr.200900398] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In Western societies the apolipoprotein E4 (apoE4) genotype is associated with increased morbidity and mortality and represents a significant risk factor for cardiovascular and Alzheimer's disease. In a recent study we observed significantly lower tissue alpha-tocopherol (alpha-TOH) concentrations in apoE4 compared with apoE3 mice. Furthermore, genes encoding for proteins involved in peripheral alpha-TOH transport and degradation were affected by the apoE genotype. Thus, the apoE4 genotype may be associated with lower vitamin E retention in peripheral tissues. This is possibly related to an altered lipoprotein metabolism including increased alpha-TOH retention in LDL, a decreased expression of lipoprotein receptors and impaired cellular vitamin E delivery system, and a greater intracellular degradation of tocopherols in the apoE4 genotype. An increasing number of studies in cultured cells, transgenic mice and human volunteers indicate a more pro-inflammatory state associated with the apoE4 allele. In apoE4 macrophages there is an enhanced transactivation of the key redox sensitive transcription factor NF-kappaB accompanied by a higher production of pro-inflammatory molecules (tumor necrosis factor alpha, interleukin 1beta, macrophage inflammatory protein 1-alpha) and a lower production of anti-inflammatory interleukin 10, as compared with apoE3 macrophages. Both tissue vitamin E retention and biomarkers of chronic inflammation may be affected by the apoE genotype.
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Affiliation(s)
- Patricia Huebbe
- Institute of Human Nutrition and Food Science, Christian-Albrechts-University, Kiel, Germany
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26
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Buchholz BM, Bauer AJ. Membrane TLR signaling mechanisms in the gastrointestinal tract during sepsis. Neurogastroenterol Motil 2010; 22:232-45. [PMID: 20377787 PMCID: PMC2951022 DOI: 10.1111/j.1365-2982.2009.01464.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Our bacterial residents are deadly Janus-faced indwellers that can lead to a sepsis-induced systemic inflammatory response syndrome and multiple organ failure. Over half of ICU patients suffer from infections and sepsis remains one of the top 10 causes of death worldwide. Severe ileus frequently accompanies sepsis setting up an insidious cycle of gut-derived microbial translocation and the copious intestinal production of potent systemic inflammatory mediators. Few therapeutic advances have occurred to prevent/treat the sequelae of sepsis. Here, we selectively review studies on cellular membrane-bound Toll-like receptor (TLR) mechanisms of ileus. Virtually, no data exist on Gram-positive/TLR2 signaling mechanisms of ileus; however, TLR2 is highly inducible by numerous inflammatory mediators and studies using clinically relevant scenarios of Gram-positive sepsis are needed. Specific Gram-negative/TLR4 signaling pathways are being elucidated using a 'reverse engineering' approach, which has revealed that endotoxin-induced ileus is dually mediated by classical leukocyte signaling and by a MyD88-dependent non-bone marrow-derived mechanism, but the specific roles of individual cell populations are still unknown. Like TLR2, little is also know of the role of flagellin/TLR5 signaling in ileus. But, much can be learned by understanding TLR signaling in other systems. Clearly, the use of polymicrobial models provides important clinical relevancy, but the simultaneous activation of virtually all pattern recognition receptors makes it impossible to discretely study specific pathways. We believe that the dissection of individual TLR pathways within the gastrointestinal tract, which can then be intelligently reassembled in a meaningful manner, will provide insight into treatments for sepsis.
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Affiliation(s)
- Bettina M. Buchholz
- Department of Medicine/Gastroenterology, University of Pittsburgh, Pittsburgh, PA, Department of Surgery, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
| | - Anthony J. Bauer
- Department of Medicine/Gastroenterology, University of Pittsburgh, Pittsburgh, PA
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27
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Bartzokis G. Alzheimer's disease as homeostatic responses to age-related myelin breakdown. Neurobiol Aging 2009; 32:1341-71. [PMID: 19775776 DOI: 10.1016/j.neurobiolaging.2009.08.007] [Citation(s) in RCA: 385] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 08/13/2009] [Accepted: 08/17/2009] [Indexed: 12/11/2022]
Abstract
The amyloid hypothesis (AH) of Alzheimer's disease (AD) posits that the fundamental cause of AD is the accumulation of the peptide amyloid beta (Aβ) in the brain. This hypothesis has been supported by observations that genetic defects in amyloid precursor protein (APP) and presenilin increase Aβ production and cause familial AD (FAD). The AH is widely accepted but does not account for important phenomena including recent failures of clinical trials to impact dementia in humans even after successfully reducing Aβ deposits. Herein, the AH is viewed from the broader overarching perspective of the myelin model of the human brain that focuses on functioning brain circuits and encompasses white matter and myelin in addition to neurons and synapses. The model proposes that the recently evolved and extensive myelination of the human brain underlies both our unique abilities and susceptibility to highly prevalent age-related neuropsychiatric disorders such as late onset AD (LOAD). It regards oligodendrocytes and the myelin they produce as being both critical for circuit function and uniquely vulnerable to damage. This perspective reframes key observations such as axonal transport disruptions, formation of axonal swellings/sphenoids and neuritic plaques, and proteinaceous deposits such as Aβ and tau as by-products of homeostatic myelin repair processes. It delineates empirically testable mechanisms of action for genes underlying FAD and LOAD and provides "upstream" treatment targets. Such interventions could potentially treat multiple degenerative brain disorders by mitigating the effects of aging and associated changes in iron, cholesterol, and free radicals on oligodendrocytes and their myelin.
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Affiliation(s)
- George Bartzokis
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Laskowitz DT, Vitek MP. Apolipoprotein E and neurological disease: therapeutic potential and pharmacogenomic interactions. Pharmacogenomics 2008; 8:959-69. [PMID: 17716229 DOI: 10.2217/14622416.8.8.959] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The apolipoprotein E (apoE) polymorphism is emerging as a uniquely important genetic modifier that affects functional outcome from both acute and chronic neurological injuries. Recent attention has focused on common denominator mechanisms by which apoE might affect brain injury and/or brain repair responses in clinically diverse diseases. Although endogenous apoE likely serves several adaptive functions in the injured CNS, there is growing evidence that its effect on modifying brain inflammatory responses and providing protection from excitotoxic injury may be central to its protective properties. A more complete understanding of the role that apoE plays in the injured brain has led to novel therapeutic strategies for both acute and chronic neurological disease.
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Affiliation(s)
- Daniel T Laskowitz
- Duke University Medical Center, Department of Medicine (Neurology), Box 2900, Durham, NC 27710, USA.
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Teter B. Life-span influences of apoE4 on CNS function. Neurobiol Aging 2007; 28:693-703; discussion 704-6. [PMID: 17045362 DOI: 10.1016/j.neurobiolaging.2006.06.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 06/22/2006] [Indexed: 11/20/2022]
Affiliation(s)
- Bruce Teter
- Department of Medicine SFVP, University of California, Los Angeles and Veteran's Administration-GLAHS, Sepulveda VA Medical Center, mc 151, 16111 Plummer St., Sepulveda, CA 91343, United States.
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