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McLaren AMR, Kawaja MD. Olfactory Dysfunction and Alzheimer's Disease: A Review. J Alzheimers Dis 2024; 99:811-827. [PMID: 38728185 DOI: 10.3233/jad-231377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
Alzheimer's disease is the most common cause of dementia, and it is one of the leading causes of death globally. Identification and validation of biomarkers that herald the onset and progression of Alzheimer's disease is of paramount importance for early reliable diagnosis and effective pharmacological therapy commencement. A substantial body of evidence has emerged demonstrating that olfactory dysfunction is a preclinical symptom of neurodegenerative diseases including Alzheimer's disease. While a correlation between olfactory dysfunction and Alzheimer's disease onset and progression in humans exists, the mechanism underlying this relationship remains unknown. The aim of this article is to review the current state of knowledge regarding the range of potential factors that may contribute to the development of Alzheimer's disease-related olfactory dysfunction. This review predominantly focuses on genetic mutations associated with Alzheimer's disease including amyloid-β protein precursor, presenilin 1 and 2, and apolipoprotein E mutations, that may (in varying ways) drive the cellular events that lead to and sustain olfactory dysfunction.
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Affiliation(s)
| | - Michael D Kawaja
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, ON, Canada
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, ON, Canada
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2
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GoodSmith MS, Wroblewski KE, Schumm LP, McClintock MK, Pinto JM. Association of APOE ε4 Status With Long-term Declines in Odor Sensitivity, Odor Identification, and Cognition in Older US Adults. Neurology 2023; 101:e1341-e1350. [PMID: 37495381 PMCID: PMC10558172 DOI: 10.1212/wnl.0000000000207659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 06/02/2023] [Indexed: 07/28/2023] Open
Abstract
BACKGROUND AND OBJECTIVES The APOE ε4 allele confers susceptibility to faster decline in odor identification and subsequently to Alzheimer disease (AD). Odor identification requires recognizing and naming odors and detecting them (odor sensitivity). Whether APOE ε4 is associated with decline of odor sensitivity and whether such decline serves as a harbinger of cognitive decline and AD remains unclear. We determined whether and when APOE ε4 affects decline in odor sensitivity, odor identification, and cognition in the National Social Life Health and Aging Project (NSHAP). METHODS We used data from NSHAP, a nationally representative survey study of home-dwelling US older adults. Olfaction was measured over time (odor identification in 2005, 2010, and 2015; odor sensitivity in 2010 and 2015; both using validated tests). Cognition was measured with a modified version of the Montreal Cognitive Assessment in 2010 and 2015. Genotyping was performed using DNA samples collected in 2010. Odor sensitivity and identification were compared among APOE ε4 carriers and noncarriers stratified by age. Relationships between APOE ε4, odor sensitivity, odor identification, and cognition were analyzed in cross-section using ordinal logistic regression and longitudinally using mixed-effects models adjusted for confounders. RESULTS Odor sensitivity was measured in 865 respondents, odor identification in 1,156 respondents, and cognition in 864 respondents; all these respondents had genetic data available. Odor sensitivity deficits in APOE ε4 carriers were apparent at ages 65-69 years, whereas odor identification deficits did not appear until ages 75-79 years. Subsequently, odor sensitivity did not decline more rapidly with aging in APOE ε4 carriers compared with that in noncarriers (carrier status and aging interaction: odds ratio [OR] 1.44, 95% CI 0.94-2.19, p = 0.092), whereas odor identification declined more rapidly in carriers (aging 10 years interaction: OR 0.26, 95% CI 0.13-0.52, p < 0.001). As expected, and in parallel to odor identification, cognition declined more rapidly in APOE ε4 carriers (interaction: OR 0.55, 95% CI 0.34-0.89, p = 0.015). DISCUSSION APOE ε4 affects decline of odor sensitivity earlier than odor identification or cognition. Thus, testing odor sensitivity may be useful to predict future impaired cognitive function. Identifying the mechanism underlying these relationships will elucidate the key role of olfaction in neurodegeneration during aging.
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Affiliation(s)
- Matthew S GoodSmith
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL.
| | - Kristen E Wroblewski
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - L Philip Schumm
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - Martha K McClintock
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
| | - Jayant M Pinto
- From the Internal Medicine-Pediatrics Residency Program (M.S.G.), Departments of Medicine and Pediatrics, Department of Public Health Sciences (K.E.W., L.P.S.), Department of Psychology and Institute for Mind and Biology (M.K.M.), and Section of Otolaryngology-Head and Neck Surgery (J.M.P.), Department of Surgery, The University of Chicago, IL
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3
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Jiang C, Chen Z, Wang X, Zhang Y, Guo X, Fan H, Huang D, He Y, Tang X, Ai Y, Liu Y, Yang H, Hao D. Curcumin-activated Olfactory Ensheathing Cells Improve Functional Recovery After Spinal Cord Injury by Modulating Microglia Polarization Through APOE/TREM2/NF-κB Signaling Pathway. J Neuroimmune Pharmacol 2023; 18:476-494. [PMID: 37658943 PMCID: PMC10577109 DOI: 10.1007/s11481-023-10081-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 08/02/2023] [Indexed: 09/05/2023]
Abstract
Transplantation of curcumin-activated olfactory ensheathing cells (aOECs) improved functional recovery in spinal cord injury (SCI) rats. Nevertheless, little is known considering the underlying mechanisms. At the present study, we investigated the promotion of regeneration and functional recovery after transplantation of aOECs into rats with SCI and the possible underlying molecular mechanisms. Primary OECs were prepared from the olfactory bulb of rats, followed by treatment with 1µM CCM at 7-10 days of culture, resulting in cell activation. Concomitantly, rat SCI model was developed to evaluate the effects of transplantation of aOECs in vivo. Subsequently, microglia were isolated, stimulated with 100 ng/mL lipopolysaccharide (LPS) for 24 h to polarize to M1 phenotype and treated by aOECs conditional medium (aOECs-CM) and OECs conditional medium (OECs-CM), respectively. Changes in the expression of pro-inflammatory and anti-inflammatory phenotypic markers expression were detected using western blotting and immunofluorescence staining, respectively. Finally, a series of molecular biological experiments including knock-down of triggering receptor expressed on myeloid cells 2 (TREM2) and analysis of the level of apolipoprotein E (APOE) expression were performed to investigate the underlying mechanism of involvement of CCM-activated OECs in modulating microglia polarization, leading to neural regeneration and function recovery. CCM-activated OECs effectively attenuated deleterious inflammation by regulating microglia polarization from the pro-inflammatory (M1) to anti-inflammatory (M2) phenotype in SCI rats and facilitated functional recovery after SCI. In addition, microglial polarization to M2 elicited by aOECs-CM in LPS-induced microglia was effectively reversed when TREM2 expression was downregulated. More importantly, the in vitro findings indicated that aOECs-CM potentiating LPS-induced microglial polarization to M2 was partially mediated by the TREM2/nuclear factor kappa beta (NF-κB) signaling pathway. Besides, the expression of APOE significantly increased in CCM-treated OECs. CCM-activated OECs could alleviate inflammation after SCI by switching microglial polarization from M1 to M2, which was likely mediated by the APOE/TREM2/NF-κB pathway, and thus ameliorated neurological function. Therefore, the present finding is of paramount significance to enrich the understanding of underlying molecular mechanism of aOECs-based therapy and provide a novel therapeutic approach for treatment of SCI.
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Affiliation(s)
- Chao Jiang
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Zhe Chen
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Xiaohui Wang
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Yongyuan Zhang
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Xinyu Guo
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
- Translational Medicine Center, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
| | - Hong Fan
- Translational Medicine Center, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Department of Neurology, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, 710004 China
| | - Dageng Huang
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Yuqing He
- Translational Medicine Center, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
| | - Xiangwen Tang
- Translational Medicine Center, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Basic Medical School Academy, Shaanxi University of Traditional Chinese Medicine, Xianyang, 712046 China
| | - Yixiang Ai
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Youjun Liu
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
| | - Hao Yang
- Translational Medicine Center, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
| | - Dingjun Hao
- Department of Spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Xi’an, 710054 China
- Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
- Department of spine Surgery, Hong Hui Hospital, Xi’an Jiaotong University, Shaanxi Key Laboratory of Spine Bionic Treatment, Xi’an, 710054 China
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Khan N, Alimova Y, Clark SJ, Vekaria H, Walsh AE, Williams HC, Hawk GS, Sullivan P, Johnson LA, McClintock TS. Human APOE ɛ3 and APOE ɛ4 Alleles Have Differential Effects on Mouse Olfactory Epithelium. J Alzheimers Dis 2021; 85:1481-1494. [PMID: 34958025 DOI: 10.3233/jad-215152] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Alzheimer's disease (AD) is a progressive age-dependent disorder whose risk is affected by genetic factors. Better models for investigating early effects of risk factors such as apolipoprotein E (APOE) genotype are needed. OBJECTIVE To determine whether APOE genotype produces neuropathologies in an AD-susceptible neural system, we compared effects of human APOE ɛ3 (E3) and APOE ɛ4 (E4) alleles on the mouse olfactory epithelium. METHODS RNA-Seq using the STAR aligner and DESeq2, immunohistochemistry for activated caspase-3 and phosphorylated histone H3, glucose uptake after oral gavage of 2-[1,2-3H (N)]-deoxy-D-glucose, and Seahorse Mito Stress tests on dissociated olfactory mucosal cells. RESULTS E3 and E4 olfactory mucosae show 121 differentially abundant mRNAs at age 6 months. These do not indicate differences in cell type proportions, but effects on 17 odorant receptor mRNAs suggest small differences in tissue development. Ten oxidoreductases mRNAs important for cellular metabolism and mitochondria are less abundant in E4 olfactory mucosae but this does not translate into differences in cellular respiration. E4 olfactory mucosae show lower glucose uptake, characteristic of AD susceptibility and consistent with greater expression of the glucose-sensitive gene, Asns. Olfactory sensory neuron apoptosis is unaffected at age 6 months but is greater in E4 mice at 10 months. CONCLUSION Effects of human APOE alleles on mouse olfactory epithelium phenotype are apparent in early adulthood, and neuronal loss begins to increase by middle age (10 months). The olfactory epithelium is an appropriate model for the ability of human APOE alleles to modulate age-dependent effects associated with the progression of AD.
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Affiliation(s)
- Naazneen Khan
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Yelena Alimova
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Sophie J Clark
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Hemendra Vekaria
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY, USA
| | - Adeline E Walsh
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Holden C Williams
- Department of Physiology, University of Kentucky, Lexington, KY, USA.,Sanders Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Gregory S Hawk
- Department of Statistics, University of Kentucky, Lexington, KY, USA
| | - Patrick Sullivan
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY, USA.,Department of Neuroscience, University of Kentucky, Lexington, KY, USA.,Lexington Veterans' Affairs Healthcare System, Lexington, KY, USA
| | - Lance A Johnson
- Department of Physiology, University of Kentucky, Lexington, KY, USA.,Sanders Brown Center on Aging, University of Kentucky, Lexington, KY, USA
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Tzeng WY, Figarella K, Garaschuk O. Olfactory impairment in men and mice related to aging and amyloid-induced pathology. Pflugers Arch 2021; 473:805-821. [PMID: 33608800 PMCID: PMC7895745 DOI: 10.1007/s00424-021-02527-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/07/2021] [Accepted: 01/28/2021] [Indexed: 12/31/2022]
Abstract
Olfaction, or the sense of smell, is one of the most ancient senses in men and mice, important for a large variety of innate and acquired behaviors. Clinical data reveal an early impairment of olfaction during normal aging and in the course of neurodegenerative diseases, but the underlying cellular/molecular mechanisms remain obscure. In the current review, we compare different aspects of the aging- and Alzheimer's disease related impairment of olfaction in men and mice, aiming at the identification of common morbidities and biomarkers, which can be analyzed in detail in the appropriate mouse models. We also identify common, often interdependent (patho)physiological pathways, including but not limited to extracellular amyloid depositions, neuroinflammation, ɛ4 allele of the apolipoprotein E, CNS insulin resistance, and the impairment of adult neurogenesis, to be targeted by basic and clinical research.
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Affiliation(s)
- Wen-Yu Tzeng
- Institute of Physiology, Department of Neurophysiology, Eberhard Karls University of Tübingen, Keplerstr. 15, 72074, Tübingen, Germany
| | - Katherine Figarella
- Institute of Physiology, Department of Neurophysiology, Eberhard Karls University of Tübingen, Keplerstr. 15, 72074, Tübingen, Germany
| | - Olga Garaschuk
- Institute of Physiology, Department of Neurophysiology, Eberhard Karls University of Tübingen, Keplerstr. 15, 72074, Tübingen, Germany.
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Olofsson JK. Olfaction and Aging: A Review of the Current State of Research and Future Directions. Iperception 2021; 12:20416695211020331. [PMID: 34249327 PMCID: PMC8239976 DOI: 10.1177/20416695211020331] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 04/21/2021] [Indexed: 11/16/2022] Open
Abstract
Olfaction, the sense of smell, is characterized by a notable age-dependency such that aging individuals are more likely to have poor olfactory abilities. These impairments are considered to be mostly irreversible and as having potentially profound effects on quality of life and food behavior, as well as constituting warning signs of mortality, cognitive dysfunction, and dementia. Here, we review the current state of research on aging and olfaction, focusing on five topics which we regard to be of particular relevance for the field: nutrition and health, cognition and dementia, mortality, environment and genetics, and training-based enhancement. Under each of these headlines, we provide a state-of-the-art overview and discuss gaps in our knowledge which might be filled by further research. Understanding how olfactory abilities are diminished in aging, and how they may be alleviated or recovered, involves a set of challenging tasks for researchers in the years to come.
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Affiliation(s)
- Jonas K. Olofsson
- Gösta Ekman Laboratory, Stockholm University, Stockholm, Sweden; Department of Psychology, Stockholm University, Stockholm, Sweden
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7
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Dibattista M, Pifferi S, Menini A, Reisert J. Alzheimer's Disease: What Can We Learn From the Peripheral Olfactory System? Front Neurosci 2020; 14:440. [PMID: 32508565 PMCID: PMC7248389 DOI: 10.3389/fnins.2020.00440] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 04/09/2020] [Indexed: 01/01/2023] Open
Abstract
The sense of smell has been shown to deteriorate in patients with some neurodegenerative disorders. In Parkinson's disease (PD) and Alzheimer's disease (AD), decreased ability to smell is associated with early disease stages. Thus, olfactory neurons in the nose and olfactory bulb (OB) may provide a window into brain physiology and pathophysiology to address the pathogenesis of neurodegenerative diseases. Because nasal olfactory receptor neurons regenerate throughout life, the olfactory system offers a broad variety of cellular mechanisms that could be altered in AD, including odorant receptor expression, neurogenesis and neurodegeneration in the olfactory epithelium, axonal targeting to the OB, and synaptogenesis and neurogenesis in the OB. This review focuses on pathophysiological changes in the periphery of the olfactory system during the progression of AD in mice, highlighting how the olfactory epithelium and the OB are particularly sensitive to changes in proteins and enzymes involved in AD pathogenesis. Evidence reviewed here in the context of the emergence of other typical pathological changes in AD suggests that olfactory impairments could be used to understand the molecular mechanisms involved in the early phases of the pathology.
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Affiliation(s)
- Michele Dibattista
- Department of Basic Medical Sciences, Neuroscience and Sensory Organs, University of Bari A. Moro, Bari, Italy
| | - Simone Pifferi
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy
| | - Anna Menini
- Neurobiology Group, SISSA, Scuola Internazionale Superiore di Studi Avanzati, Trieste, Italy
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Bathini P, Brai E, Auber LA. Olfactory dysfunction in the pathophysiological continuum of dementia. Ageing Res Rev 2019; 55:100956. [PMID: 31479764 DOI: 10.1016/j.arr.2019.100956] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 07/29/2019] [Accepted: 08/26/2019] [Indexed: 12/21/2022]
Abstract
Sensory capacities like smell, taste, hearing, vision decline with aging, but increasing evidence show that sensory dysfunctions are one of the early signs diagnosing the conversion from physiological to pathological brain state. Smell loss represents the best characterized sense in clinical practice and is considered as one of the first preclinical signs of Alzheimer's and Parkinson's disease, occurring a decade or more before the onset of cognitive and motor symptoms. Despite the numerous scientific reports and the adoption in clinical practice, the etiology of sensory damage as prodromal of dementia remains largely unexplored and more studies are needed to resolve the mechanisms underlying sensory network dysfunction. Although both cognitive and sensory domains are progressively affected, loss of sensory experience in early stages plays a major role in reducing the autonomy of demented people in their daily tasks or even possibly contributing to their cognitive decline. Interestingly, the chemosensory circuitry is devoid of a blood brain barrier, representing a vulnerable port of entry for neurotoxic species that can spread to the brain. Furthermore, the exposure of the olfactory system to the external environment make it more susceptible to mechanical injury and trauma, which can cause degenerative neuroinflammation. In this review, we will summarize several findings about chemosensory impairment signing the conversion from healthy to pathological brain aging and we will try to connect those observations to the promising research linking environmental influences to sporadic dementia. The scientific body of knowledge will support the use of chemosensory diagnostics in the presymptomatic stages of AD and other biomarkers with the scope of finding treatment strategies before the onset of the disease.
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Affiliation(s)
- Praveen Bathini
- Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Emanuele Brai
- VIB-KU Leuven Center for Brain & Disease Research, Laboratory for the Research of Neurodegenerative Diseases, Leuven, Belgium
| | - Lavinia Alberi Auber
- Department of Medicine, University of Fribourg, Fribourg, Switzerland; Swiss Integrative Center of Human Health, Fribourg, Switzerland.
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Misiak MM, Hipolito MS, Ressom HW, Obisesan TO, Manaye KF, Nwulia EA. Apo E4 Alleles and Impaired Olfaction as Predictors of Alzheimer's Disease. CLINICAL AND EXPERIMENTAL PSYCHOLOGY 2017; 3:169. [PMID: 29423459 PMCID: PMC5800509 DOI: 10.4172/2471-2701.1000169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Alzheimer's disease (AD) is the most common form of dementia that affects more than 5 million Americans. It is the only disease among the 10 causes of death that cannot be slowed or cured, thus raising the need for identification of early preclinical markers that could be the focus of preventative efforts. Although evidence is escalating that abnormalities in olfactory structure and function precede AD development and early cognitive impairments by one or more decades, the importance of olfaction is largely overlooked in AD, and such testing is not routinely performed in neurology clinics. Nevertheless, research using the olfactory model, has begun to advance our understanding of the preclinical pathophysiology of AD. Notably, an interesting series of studies is beginning to illuminate the relationship between Apolipoprotein E (ApoE) ε4 polymorphism and olfactory dysfunction and late-onset Alzheimer's disease. In this article, we reviewed present research on the significance of ApoE and olfaction to AD, summarized current studies on the associations and mechanisms of ApoE and olfactory dysfunction, and highlighted important gaps for future work to further advance the translational application of the olfactory paradigm to early, preclinical diagnosis and treatment of AD.
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Affiliation(s)
- Magdalena M Misiak
- Department of Psychiatry and Behavioral Sciences, Howard University, Washington DC, USA
- Department of Physiology, Howard University, Washington DC, USA
| | - MariaMananita S Hipolito
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA
| | - Habtom W Ressom
- Department of Medicine, Howard University, Washington DC, USA
| | | | | | - Evaristus A Nwulia
- Department of Psychiatry and Behavioral Sciences, Howard University, Washington DC, USA
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA
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Zhang J, Hao C, Jiang J, Feng Y, Chen X, Zheng Y, Liu J, Zhang Z, Long C, Yang L. The mechanisms underlying olfactory deficits in apolipoprotein E-deficient mice: focus on olfactory epithelium and olfactory bulb. Neurobiol Aging 2017; 62:20-33. [PMID: 29107844 DOI: 10.1016/j.neurobiolaging.2017.09.036] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 09/20/2017] [Accepted: 09/30/2017] [Indexed: 01/09/2023]
Abstract
Apolipoprotein E (ApoE) is highly expressed in the central nervous system including the olfactory epithelium (OE) and olfactory bulb (OB). ApoE induction is beneficial for Alzheimer's disease (AD) treatment, whereas ApoE deficiency results in impaired olfaction, but the timing and underlying molecular and cellular mechanisms of these effects remain unclear. Uncovering the mechanisms underlying olfactory dysfunction in ApoE-deficient mice might provide a potential avenue for the early diagnosis of AD. We used an ApoE knockout (ApoE-/-) mouse model and a cookie-finding test to reveal an olfactory deficit in 3- to 5-month-old, but not 1- to 2-month-old, ApoE-/- mice. Electrophysiological experiments indicated a significant decline in the electroolfactogram (EOG) amplitude, which was associated with an increase in rise time in ApoE-/- mice. Knockout mice also exhibited compromised olfactory adaptation, as well as a reduced number of mature olfactory sensory neurons in the OE. Local field potential recording in the OB showed that gamma oscillation power was enhanced, which might be attributed to an increase in GABAergic inhibition mediated by parvalbumin-expressing (PV) interneurons. This study demonstrates the critical involvement of ApoE in olfactory information processing in the OE and OB. ApoE deficiency results in olfaction deficits in mice as young as 3 months old, which has implications for AD pathogenesis.
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Affiliation(s)
- Jiajia Zhang
- School of Life Sciences, Guangzhou University, Guangzhou, China; School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Caiyuan Hao
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Jinxiang Jiang
- School of Psychology, South China Normal University, Guangzhou, China
| | - Yangjian Feng
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Xi Chen
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Ying Zheng
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Jiawei Liu
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Zhilin Zhang
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Cheng Long
- School of Life Sciences and Institute for Brain Research and Rehabilitation, South China Normal University, Guangzhou, China
| | - Li Yang
- School of Life Sciences, Guangzhou University, Guangzhou, China.
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11
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Josefsson M, Larsson M, Nordin S, Adolfsson R, Olofsson J. APOE-ɛ4 effects on longitudinal decline in olfactory and non-olfactory cognitive abilities in middle-aged and old adults. Sci Rep 2017; 7:1286. [PMID: 28455505 PMCID: PMC5430873 DOI: 10.1038/s41598-017-01508-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/28/2017] [Indexed: 11/29/2022] Open
Abstract
Characterizing aging-related decline trajectories in mental abilities, and relationships of the ɛ4 allele of the Apolipoprotein gene, helps to identify individuals at high risk for dementia. However, longitudinal changes in olfactory and non-olfactory cognitive abilities have not been investigated in relation to the ɛ4 allele. In the present study, participants from a large population-based study (657 middle-aged and 556 old) were tested over 10 years on their performance on an odor identification task and three non-olfactory cognitive tasks; MMSE, episodic memory, and semantic memory. Our key finding is that in middle-aged participants, odor identification declined twice as fast for ɛ4/4 homozygotes, compared to non-carriers. However, in old participants, the ɛ4/4 homozygotes showed an impaired odor identification ability, but they declined at a similar rate as the non-carriers. Furthermore, in old participants all assessments displayed aging-related declines, but exaggerated declines in ɛ4-carriers were found only in MMSE and episodic memory assessments. In sum, we present evidence that odor identification ability starts to decline already in middle-aged, and that carriers of ɛ4/4, who are at highest risk of developing dementia, decline twice as fast. Our results may have implications for use of odor identification assessment in detection of early-stage dementia.
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Affiliation(s)
- Maria Josefsson
- Centre for Demographic and Ageing Research, Umeå University, Umeå, Sweden.
| | - Maria Larsson
- Gösta Ekman Laboratory, Department of Psychology, Stockholm University, Stockholm, Sweden
| | - Steven Nordin
- Department of Psychology, Umeå University, Umeå, Sweden
| | - Rolf Adolfsson
- Department of Clinical Sciences, Psychiatry, Umeå University Hospital, Umeå, Sweden
| | - Jonas Olofsson
- Gösta Ekman Laboratory, Department of Psychology, Stockholm University, Stockholm, Sweden.,Swedish Collegium for Advanced Study, Uppsala, Sweden
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Olfactory memory in the old and very old: relations to episodic and semantic memory and APOE genotype. Neurobiol Aging 2015; 38:118-126. [PMID: 26827650 DOI: 10.1016/j.neurobiolaging.2015.11.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 10/16/2015] [Accepted: 11/21/2015] [Indexed: 01/10/2023]
Abstract
The neuroanatomical organization that underlies olfactory memory is different from that of other memory types. The present work examines olfactory memory in an elderly population-based sample (Swedish National Study on Aging and Care in Kungsholmen) aged 60-100 years (n = 2280). We used structural equation modeling to investigate whether olfactory memory in old age is best conceptualized as a distinct category, differentiated from episodic and semantic memory. Further, potential olfactory dedifferentiation and genetic associations (APOE) to olfactory function in late senescence were investigated. Results are in support of a 3-factor solution where olfactory memory, as indexed by episodic odor recognition and odor identification, is modeled separately from episodic and semantic memory for visual and verbal information. Increasing age was associated with poorer olfactory memory performance, and observed age-related deficits were further exacerbated for carriers of the APOE ε4 allele; these effects tended to be larger for olfactory memory compared to episodic and semantic memory pertaining to other sensory systems (vision, auditory). Finally, stronger correlations between olfactory and episodic memory, indicating dedifferentiation, were observed in the older age groups.
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13
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Dong J, Yang J, Tranah G, Franceschini N, Parimi N, Alkorta-Aranburu G, Xu Z, Alonso A, Cummings SR, Fornage M, Huang X, Kritchevsky S, Liu Y, London S, Niu L, Wilson RS, De Jager PL, Yu L, Singleton AB, Harris T, Mosley TH, Pinto JM, Bennett DA, Chen H. Genome-wide Meta-analysis on the Sense of Smell Among US Older Adults. Medicine (Baltimore) 2015; 94:e1892. [PMID: 26632684 PMCID: PMC5058953 DOI: 10.1097/md.0000000000001892] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 09/04/2015] [Accepted: 09/29/2015] [Indexed: 11/25/2022] Open
Abstract
Olfactory dysfunction is common among older adults and affects their safety, nutrition, quality of life, and mortality. More importantly, the decreased sense of smell is an early symptom of neurodegenerative diseases such as Parkinson disease (PD) and Alzheimer disease. However, the genetic determinants for the sense of smell have been poorly investigated. We here performed the first genome-wide meta-analysis on the sense of smell among 6252 US older adults of European descent from the Atherosclerosis Risk in Communities (ARIC) study, the Health, Aging, and Body Composition (Health ABC) study, and the Religious Orders Study and the Rush Memory and Aging Project (ROS/MAP). Genome-wide association study analysis was performed first by individual cohorts and then meta-analyzed using fixed-effect models with inverse variance weights. Although no SNPs reached genome-wide statistical significance, we identified 13 loci with suggestive evidence for an association with the sense of smell (Pmeta < 1 × 10). Of these, 2 SNPs at chromosome 17q21.31 (rs199443 in NSF, P = 3.02 × 10; and rs2732614 in KIAA1267-LRRC37A, P = 6.65 × 10) exhibited cis effects on the expression of microtubule-associated protein tau (MAPT, 17q21.31) in 447 frontal-cortex samples obtained postmortem and profiled by RNA-seq (P < 1 × 10). Gene-based and pathway-enrichment analyses further implicated MAPT in regulating the sense of smell in older adults. Similar results were obtained after excluding participants who reported a physician-diagnosed PD or use of PD medications. In conclusion, we provide preliminary evidence that the MAPT locus may play a role in regulating the sense of smell in older adults and therefore offer a potential genetic link between poor sense of smell and major neurodegenerative diseases.
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Affiliation(s)
- Jing Dong
- From the Epidemiology Branch (JD, ZX, SL, HC) and Biostatistics Branch (LN), National Institute of Environmental Health Sciences, Research Triangle Park, NC; Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, IL (JY, RSW, LY, DAB); California Pacific Medical Center Research Institute, San Francisco, CA (GT, NP, SC); Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC (NF); Department of Human Genetics, University of Chicago, Chicago, IL (GA-A); Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN (AA); Institute of Molecular Medicine and Human Genetics Center, University of Texas Health Science Center at Houston, Houston, TX (MF); Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, PA (XH); Sticht Center on Aging (SK) and Division of Public Health Sciences (YL), Wake Forest School of Medicine, Winston-Salem, NC; Program in Translational Neuro Psychiatric Genomics, Departments of Neurology and Psychiatry, Institute for the Neurosciences, Brigham and Women's Hospital; Harvard Medical School; Program in Medical and Population Genetics, Broad Institute, Boston, MA (PLD); Laboratory of Neurogenetics (ABS) and Laboratory of Epidemiology, Demography, and Biometry (TH), National Institute on Aging, Bethesda, MD; Division of Geriatrics, Department of Medicine, University of Mississippi Medical Center, Jackson, MS (THM); Section of Otolaryngology-Head and Neck Surgery, Department of Surgery, The University of Chicago Medicine and Biological Sciences, Chicago, IL (JMP); Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA (JY, LY, DAB); and Departments of Neurological Sciences and Behavioral Sciences, Rush University Medical Center, Chicago, IL, USA (RSW)
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14
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Huebbe P, Dose J, Schloesser A, Campbell G, Glüer CC, Gupta Y, Ibrahim S, Minihane AM, Baines JF, Nebel A, Rimbach G. Apolipoprotein E (APOE) genotype regulates body weight and fatty acid utilization-Studies in gene-targeted replacement mice. Mol Nutr Food Res 2014; 59:334-43. [DOI: 10.1002/mnfr.201400636] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 10/21/2014] [Accepted: 10/29/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Patricia Huebbe
- Institute of Human Nutrition and Food Science; University of Kiel; Kiel Germany
| | - Janina Dose
- Institute of Human Nutrition and Food Science; University of Kiel; Kiel Germany
| | - Anke Schloesser
- Institute of Human Nutrition and Food Science; University of Kiel; Kiel Germany
| | - Graeme Campbell
- Section Biomedical Imaging; Department of Diagnostic Radiology; University of Kiel; Kiel Germany
| | - Claus-Christian Glüer
- Section Biomedical Imaging; Department of Diagnostic Radiology; University of Kiel; Kiel Germany
| | - Yask Gupta
- Department of Dermatology; University of Lübeck; Lübeck Germany
| | - Saleh Ibrahim
- Department of Dermatology; University of Lübeck; Lübeck Germany
| | - Anne-Marie Minihane
- Department of Nutrition; Norwich Medical School; University of East Anglia; Norwich United Kingdom
| | - John F. Baines
- Institute for Experimental Medicine; University of Kiel; Kiel Germany
- Max Planck Institute for Evolutionary Biology; Plön Germany
| | - Almut Nebel
- Institute of Clinical Molecular Biology; University of Kiel; Kiel Germany
| | - Gerald Rimbach
- Institute of Human Nutrition and Food Science; University of Kiel; Kiel Germany
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15
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Hussain A, Luong M, Pooley A, Nathan BP. Isoform-specific effects of apoE on neurite outgrowth in olfactory epithelium culture. J Biomed Sci 2013; 20:49. [PMID: 23845000 PMCID: PMC3717083 DOI: 10.1186/1423-0127-20-49] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/08/2013] [Indexed: 11/10/2022] Open
Abstract
Background The apolipoprotein E4 (apoE4) genotype is a major risk factor for developing late-onset Alzheimer’s disease (AD). Inheritance of apoE4 is also associated with impairments in olfactory function in early stages of AD. In this project we examined the effects of the three common isoforms of human apoE (apoE2, apoE3, and apoE4) on neuronal differentiation and neurite outgrowth in explant cultures of mouse olfactory epithelium (OE). Results The OE cultures derived from apoE-deficient/knockout (KO) mice have significantly fewer neurons with shorter neurite outgrowth than cultures from wild-type (WT) mice. Treatment of the apoE KO culture with either purified human apoE2 or with human apoE3 significantly increased neurite outgrowth. In contrast, treatment with apoE4 did not have an effect on neurite outgrowth. The differential effects of human apoE isoforms on neurite outgrowth were abolished by blocking the low-density lipoprotein receptor-related protein (LRP) with lactoferrin and receptor-associated protein (RAP). Conclusion ApoE2 and apoE3 stimulate neurite outgrowth in OE cultures by interacting with the lipoprotein receptor, LRP. ApoE4, the isoform associated with AD, failed to promote neurite outgrowth, suggesting a potential mechanism whereby apoE4 may lead to olfactory dysfunction in AD patients.
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Affiliation(s)
- Aseem Hussain
- Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA
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16
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Nathan BP, Tonsor M, Struble RG. Long-term effects of estradiol replacement in the olfactory system. Exp Neurol 2012; 237:1-7. [PMID: 22691461 DOI: 10.1016/j.expneurol.2012.06.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 05/27/2012] [Accepted: 06/01/2012] [Indexed: 01/09/2023]
Abstract
Olfactory dysfunction often precedes other clinical symptoms in chronic neurodegenerative diseases like Alzheimer's disease and Parkinson's disease. Estrogen deficiency and apoE genotype are known risk factors in these diseases and these factors also affect olfaction. Therefore we examined the effects of estradiol replacement following ovariectomy on expression of apoE and markers of cell proliferation, neuronal maturation, synaptogenesis and reactive gliosis in the primary olfactory pathway of wild-type (WT) and apoE knockout (KO) mice. Estradiol replacement increased apoE staining in the olfactory nerve and glomerular layers. Estradiol increased astrocyte density and olfactory epithelium (OE) thickness regardless of the genotype. In addition estradiol treatment increased the number of mature neurons in the OE and glomerular synaptophysin in both genotypes, but the magnitude of increase was greater in the WT than in the KO mice. These data suggest that estrogen and apoE act synergistically to minimize the loss of mature sensory neurons and synapses following ovariectomy.
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Affiliation(s)
- Britto P Nathan
- Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA.
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17
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Nathan BP, Gairhe S, Nwosu I, Clark S, Struble RG. Reconstitution of the olfactory epithelium following injury in apoE-deficient mice. Exp Neurol 2010; 226:40-6. [PMID: 20696162 DOI: 10.1016/j.expneurol.2010.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 07/17/2010] [Accepted: 08/02/2010] [Indexed: 11/18/2022]
Abstract
ApoE, a protein component of lipoproteins, is extensively expressed in the primary olfactory pathway. Because apoE has been shown to play a vital role in nerve repair and remodeling, we hypothesized that apoE expression will increase in the injured olfactory epithelium (OE), and that apoE deficiency in apoE knockout (KO) mice will lead to delayed/incomplete reconstitution of the OE following injury. To directly test this hypothesis, we compared OE regeneration in wild-type (WT) and KO mice following injury induced by intranasal irrigation of Triton X-100. OE was collected at 0, 3, 7, 21, 42, and 56 days post lesion. The amount and distribution of apoE in the regenerating OE was measured by immunoblotting and immunohistochemistry. Rate of OE reconstitution in WT and KO mice was assessed by using three independent measures: (1) OE thickness was measured in cresyl-violet stained sections, (2) basal cell proliferation was determined by using bromodeoxyuridine (BrdU) staining, and (3) differentiation and maturation of olfactory sensory neurons were measured by immunoblotting and immunohistochemical analysis of growth associated protein (GAP) 43 and olfactory marker protein (OMP). The results revealed that apoE expression in the OE is highly regulated during the entire course of OE reconstitution post injury, and that apoE deficiency in apoE KO mice leads to delayed recovery of mature OMP(+) cells in the reconstituting OE. The data suggest that apoE production increases in the injured OE to facilitate maturation of olfactory sensory neurons.
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Affiliation(s)
- Britto P Nathan
- Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA.
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18
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Acute responses to estradiol replacement in the olfactory system of apoE-deficient and wild-type mice. Brain Res 2010; 1343:66-74. [PMID: 20447382 DOI: 10.1016/j.brainres.2010.04.070] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 04/23/2010] [Accepted: 04/26/2010] [Indexed: 01/16/2023]
Abstract
Epidemiological studies suggest that estrogen therapy protects against clinical expression of chronic neurological diseases. These beneficial effects of estrogen therapy are highly modified by apolipoprotein E (apoE) through an unknown mechanism. We examined the short-term effects of estradiol replacement in ovariectomized mice on apoE expression and markers for cell proliferation, reactive gliosis, neuronal maturation, and synaptogenesis in the primary olfactory pathway of wild-type (WT) and apoE knockout (KO) mice. Three days of estradiol replacement increased apoE expression in the olfactory nerve and in the glomerular layer. Estradiol treatment also increased cell proliferation, total cell numbers, number of mature neurons in the olfactory epithelium, and reactive astrocyte numbers in the olfactory bulb (OB) in both WT and KO mice. We also found that estradiol increased glomerular synaptophysin (Syn), but the magnitude of increase was potentiated by the presence of apoE. These data suggest that apoE may be necessary to elicit the complete effect of estradiol on Syn upregulation.
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Olofsson JK, Nordin S, Wiens S, Hedner M, Nilsson LG, Larsson M. Odor identification impairment in carriers of ApoE-ɛ4 is independent of clinical dementia. Neurobiol Aging 2010; 31:567-77. [DOI: 10.1016/j.neurobiolaging.2008.05.019] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 05/07/2008] [Accepted: 05/20/2008] [Indexed: 11/25/2022]
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20
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Olofsson JK, Rönnlund M, Nordin S, Nyberg L, Nilsson LG, Larsson M. Odor identification deficit as a predictor of five-year global cognitive change: interactive effects with age and ApoE-epsilon4. Behav Genet 2009; 39:496-503. [PMID: 19633944 DOI: 10.1007/s10519-009-9289-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 07/08/2009] [Indexed: 11/28/2022]
Abstract
Olfactory impairments are present in common neurodegenerative disorders and predict conversion to dementia in non-demented individuals with cognitive impairment. In cognitively intact elderly, evidence is sparse regarding the role of olfactory deficits in predicting cognitive impairment. The present study investigated predictors of 5-year prospective decline in the Mini-Mental State Examination (MMSE) in a large (n = 501), population-based sample of elderly (65-90 years) individuals. All participants were genotyped for the ApoE gene, assessed for health factors, and were non-demented at the baseline assessment. After partialling out the influences of demographic and health-factors at baseline and dementia at follow-up, poor odor identification ability in combination with older age and the ApoE-epsilon4 allele predicted larger prospective global cognitive decline. This effect could not be produced by a vocabulary test. In sum, the findings suggest that an olfactory deficit can dissociate between benign and malign global cognitive development in non-demented, very old epsilon4-carriers, who are at high risk of developing dementia.
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21
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Nwosu I, Gairhe S, Struble RG, Nathan BP. Impact of apoE deficiency during synaptic remodeling in the mouse olfactory bulb. Neurosci Lett 2008; 441:282-5. [PMID: 18621483 DOI: 10.1016/j.neulet.2008.05.117] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2008] [Revised: 05/26/2008] [Accepted: 05/31/2008] [Indexed: 11/27/2022]
Abstract
In this study we examined the role of apoE on the rate of synaptic recovery in the olfactory bulb (OB) following olfactory epithelium (OE) lesioning in mice. We used both immunoblotting and immunohistochemical techniques to compare the density of OB synaptophysin (Syn, a synaptic marker) in apoE-gene deficient/knockout (KO) mice and wild-type (WT) mice following OE lesion. We found that the whole bulb concentrations of Syn, measured by immunoblotting, declined sharply following injury in both WT and KO mice during the degenerative phase (3-7 days). After this initial decline, the Syn concentration gradually increased to normal levels by 56 days in WT mice. In contrast, Syn concentration in KO mice did not recover by day 56 when Syn density in WT was essentially normal. Glomerular Syn density, measured by immunohistochemistry, found a lower density in KO mice at all time points post-lesion. This lower concentration of whole bulb Syn parallels the slower recovery of glomerular area in KO mice. The data indicate that apoE deficiency in KO mice is associated with a delayed recovery of the glomerular area and a slower recovery in Syn concentration in the OB.
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Affiliation(s)
- Ikemefuna Nwosu
- Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, United States
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22
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Franssen EHP, de Bree FM, Verhaagen J. Olfactory ensheathing glia: Their contribution to primary olfactory nervous system regeneration and their regenerative potential following transplantation into the injured spinal cord. ACTA ACUST UNITED AC 2007; 56:236-58. [PMID: 17884174 DOI: 10.1016/j.brainresrev.2007.07.013] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Revised: 07/25/2007] [Accepted: 07/30/2007] [Indexed: 11/26/2022]
Abstract
Olfactory ensheathing glia (OEG) are a specialized type of glia that guide primary olfactory axons from the neuroepithelium in the nasal cavity to the brain. The primary olfactory system is able to regenerate after a lesion and OEG contribute to this process by providing a growth-supportive environment for newly formed axons. In the spinal cord, axons are not able to restore connections after an injury. The effects of OEG transplants on the regeneration of the injured spinal cord have been studied for over a decade. To date, of all the studies using only OEG as a transplant, 41 showed positive effects, while 13 studies showed limited or no effects. There are several contradictory reports on the migratory and axon growth-supporting properties of transplanted OEG. Hence, the regenerative potential of OEG has become the subject of intense discussion. In this review, we first provide an overview of the molecular and cellular characteristics of OEG in their natural environment, the primary olfactory nervous system. Second, their potential to stimulate regeneration in the injured spinal cord is discussed. OEG influence scar formation by their ability to interact with astrocytes, they are able to remyelinate axons and promote angiogenesis. The ability of OEG to interact with scar tissue cells is an important difference with Schwann cells and may be a unique characteristic of OEG. Because of these effects after transplantation and because of their role in primary olfactory system regeneration, the OEG can be considered as a source of neuroregeneration-promoting molecules. To identify these molecules, more insight into the molecular biology of OEG is required. We believe that genome-wide gene expression studies of OEG in their native environment, in culture and after transplantation will ultimately reveal unique combinations of molecules involved in the regeneration-promoting potential of OEG.
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Affiliation(s)
- Elske H P Franssen
- Netherlands Insitute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Meibergdreef 47, 1105 BA, Amsterdam, The Netherlands
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