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Tombini M, Sicari M, Pellegrino G, Ursini F, Insardá P, Di Lazzaro V. Nutritional Status of Patients with Alzheimer's Disease and Their Caregivers. J Alzheimers Dis 2018; 54:1619-1627. [PMID: 27636839 DOI: 10.3233/jad-160261] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Malnutrition is one of the most important conditions that negatively affects the health of elder people, particularly in patients with dementia. OBJECTIVE To provide an assessment of nutritional status of patients affected by Alzheimer's disease (AD) living at home and of their caregivers by means of Mini Nutritional Assessment (MNA), and to explore the influence of different factors on nutrition. METHODS 90 patients affected by AD living at home and 90 age- and sex-matched caregivers were enrolled. Patients and caregivers, coming from an urban-rural fringe of Southern Italy, were assessed using full MNA, Mini-Mental State Examination, Geriatric Depression Scale- short form, Activity of Daily Living, and Instrumental Activities of Daily Living scales. RESULTS Malnutrition was found with high prevalence in patients affected by AD of different severity (more than 95% of patients were malnourished or at risk of malnutrition), and associated with reduced functional status. An altered nutrition was also recognized with high rate in the group of caregivers (23.3% were malnourished and 41.1% at risk of malnutrition) and the worse nutritional condition was correlated with higher age and lower functional and cognitive status and education. A positive correlation between MNA score of AD patients and caregivers was found. CONCLUSION Corrective measures should be taken in order to early identify nutritional deficiencies and risk of malnutrition observed with high rate in both groups of AD patients and their caregivers; in these subjects a nutrition education program and intervention policies are mandatory to restore nutritional status.
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Affiliation(s)
- Mario Tombini
- Department of Medicine, Unit of Neurology, Neurophysiology, Neurobiology, Campus Bio-Medico University, Rome, Italy
| | - Maura Sicari
- Centro Nutrizione Clinica e Umana, Reggio Calabria, Italy
| | - Giovanni Pellegrino
- Department of Medicine, Unit of Neurology, Neurophysiology, Neurobiology, Campus Bio-Medico University, Rome, Italy.,Multimodal Functional Imaging Laboratory, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Francesca Ursini
- Department of Medicine, Unit of Neurology, Neurophysiology, Neurobiology, Campus Bio-Medico University, Rome, Italy
| | | | - Vincenzo Di Lazzaro
- Department of Medicine, Unit of Neurology, Neurophysiology, Neurobiology, Campus Bio-Medico University, Rome, Italy
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Jakubík J, El-Fakahany EE. Allosteric Modulation of Muscarinic Acetylcholine Receptors. Pharmaceuticals (Basel) 2010; 3:2838-2860. [PMID: 27713379 PMCID: PMC4034100 DOI: 10.3390/ph3092838] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 08/17/2010] [Accepted: 08/18/2010] [Indexed: 11/16/2022] Open
Abstract
An allosteric modulator is a ligand that binds to an allosteric site on the receptor and changes receptor conformation to produce increase (positive cooperativity) or decrease (negative cooperativity) in the binding or action of an orthosteric agonist (e.g., acetylcholine). Since the identification of gallamine as the first allosteric modulator of muscarinic receptors in 1976, this unique mode of receptor modulation has been intensively studied by many groups. This review summarizes over 30 years of research on the molecular mechanisms of allosteric interactions of drugs with the receptor and for new allosteric modulators of muscarinic receptors with potential therapeutic use. Identification of positive modulators of acetylcholine binding and function that enhance neurotransmission and the discovery of highly selective allosteric modulators are mile-stones on the way to novel therapeutic agents for the treatment of schizophrenia, Alzheimer’s disease and other disorders involving impaired cognitive function.
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Affiliation(s)
- Jan Jakubík
- Institute of Physiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 00 Praha, Czech Republic.
| | - Esam E El-Fakahany
- Division of Neuroscience Research in Psychiatry, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
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Nicolas A, Nourhashemi LF, Lanzmann‐Petithory D, Vellas B. Nutrition and Cognitive Function. ACTA ACUST UNITED AC 2008. [DOI: 10.1046/j.1523-5408.2001.00137.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Anne‐Sophie Nicolas
- Hôpital La Grave‐Casselardit, Toulouse
- Groupe Danone, Unité Recherche Nutrition,
Le Plessis‐Robinson, France
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4
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Joseph JA, Shukitt-Hale B, Casadesus G, Fisher D. Oxidative Stress and Inflammation in Brain Aging: Nutritional Considerations. Neurochem Res 2005; 30:927-35. [PMID: 16187227 DOI: 10.1007/s11064-005-6967-4] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2005] [Indexed: 10/25/2022]
Abstract
Aging can be defined as the condition where stressors are not counteracted by protective functions, leading to a dysregulation in development. These changes can be translated into decrements in neuronal functioning accompanied by behavioral declines, such as decreases in motor and cognitive performance, in both humans and animals. When coupled with genetic alterations, the ultimate expression of these changes is seen in diseases such as Alzheimer disease (AD). This association will be discussed in the last section of this chapter. In this review we will describe motor and cognitive deficits in behavior due to aging, and show how these deficits are related to increased vulnerability to oxidative stress, inflammation or signaling. Importantly, using muscarinic receptors as examples, we will also try to show that the sensitivity to these insults may be differentially expressed among neurotransmitter receptor subtypes.
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Affiliation(s)
- J A Joseph
- USDA-ARS, Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA.
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5
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Jhoo JH, Kim HC, Nabeshima T, Yamada K, Shin EJ, Jhoo WK, Kim W, Kang KS, Jo SA, Woo JI. Beta-amyloid (1-42)-induced learning and memory deficits in mice: involvement of oxidative burdens in the hippocampus and cerebral cortex. Behav Brain Res 2005; 155:185-96. [PMID: 15364477 DOI: 10.1016/j.bbr.2004.04.012] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Revised: 04/13/2004] [Accepted: 04/13/2004] [Indexed: 10/26/2022]
Abstract
We have demonstrated that oxidative stress is involved, at least in part, in beta-amyloid protein (Abeta)-induced neurotoxicity in vivo [Eur. J. Neurosci. 1999;11:83-90; Neuroscience 2003;119:399-419]. However, mechanistic links between oxidative stress and memory loss in response to Abeta remain elusive. In the present study, we examined whether oxidative stress contributes to the memory deficits induced by intracerebroventricular injection of Abeta (1-42) in mice. Abeta (1-42)-induced memory impairments were observed, as measured by the water maze and passive avoidance tests, although these impairments were not found in Abeta (40-1)-treated mice. Treatment with antioxidant alpha-tocopherol significantly prevented memory impairment induced by Abeta (1-42). Increased activities of the cytosolic Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and mitochondrial Mn-superoxide dismutase (Mn-SOD) were observed in the hippocampus and cerebral cortex of Abeta (1-42)-treated animals, as compared with Abeta (40-1)-treated mice. The induction of Cu,Zn-SOD was more pronounced than that of Mn-SOD after Abeta (1-42) insult. However, the concomitant induction of glutathione peroxidase (GPX) in response to significant increases in SOD activity was not seen in animals treated with Abeta (1-42). Furthermore, glutathione reductase (GRX) activity was only increased at 2h after Abeta (1-42) injection. Production of malondialdehyde (lipid peroxidation) and protein carbonyl (protein oxidation) remained elevated at 10 days post-Abeta (1-42), but the antioxidant alpha-tocopherol significantly prevented these oxidative stresses. Therefore, our results suggest that the oxidative stress contributes to the Abeta (1-42)-induced learning and memory deficits in mice.
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Affiliation(s)
- Jin Hyeong Jhoo
- Department of Psychiatry, Pundang Jesaeng Hospital, Daejin Medical Center, Seongnam, South Korea
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6
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Joseph JA, Fisher DR, Carey A, Szprengiel A. The M3 muscarinic receptor i3 domain confers oxidative stress protection on calcium regulation in transfected COS-7 cells. Aging Cell 2004; 3:263-71. [PMID: 15379850 DOI: 10.1111/j.1474-9728.2004.00123.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Evidence suggests that muscarinic receptors (MAChRs) are involved in various aspects of neuronal and vascular functioning, and that there is selective oxidative stress sensitivity (OSS) among MAChR subtypes. COS-7 cells transfected with M1, M2 and M4 subtypes show greater OSS than the M1 and M3 subtypes, as seen by the decreased ability of cells to extrude or sequester calcium (Ca(2+)) following exposure to dopamine (DA) or A beta 25-35, and depolarization by oxotremorine. We sought to determine which receptor domain may be responsible for the differential vulnerability to OS between 'OS-sensitive' (M1) and 'non-sensitive' (M3) subtypes. Comparison of the amino acid sequences of each receptor has shown that the third cytoplasmic loop (i3 loop) is the domain with the most variability between the two subtypes. Therefore, mutations were made by either deleting or exchanging the i3 loop of M1 and M3 receptors. Experiments revealed that deletions of the i3 loop increased DA sensitivity (a lower percentage of cells showing recovery of [Ca(2+)](i) following depolarization) in both receptors. Chimerics of M1 in which the i3 loop of the M3 was exchanged with the i3 loop of the M1 (M1M3i3) showed that DA sensitivity was reduced (a greater percentage of cells showing increases in calcium clearance) following depolarization. The M3 chimerics containing the M1 i3 loop (M3M1i3) offered no protection against DA-induced decrements in calcium buffering. Results suggest that the longer i3 loop of the M3 may decrease OSS, possibly playing a role in targeting antioxidants to specific receptor sites that impart OSS.
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7
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Kim HC, Yamada K, Nitta A, Olariu A, Tran MH, Mizuno M, Nakajima A, Nagai T, Kamei H, Jhoo WK, Im DH, Shin EJ, Hjelle OP, Ottersen OP, Park SC, Kato K, Mirault ME, Nabeshima T. Immunocytochemical evidence that amyloid beta (1-42) impairs endogenous antioxidant systems in vivo. Neuroscience 2003; 119:399-419. [PMID: 12770555 DOI: 10.1016/s0306-4522(02)00993-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Amyloid beta, the major constituent of the senile plaques in the brains of patients with Alzheimer's disease, is cytotoxic to neurons and has a central role in the pathogenesis of the disease. We have previously demonstrated that potent antioxidants idebenone and alpha-tocopherol prevent learning and memory impairment in rats which received a continuous intracerebroventricular infusion of amyloid beta, suggesting a role for oxidative stress in amyloid beta-induced learning and memory impairment. To test the hypothesis, in the present study, we investigated alterations in the immunoreactivity of endogenous antioxidant systems such as mitochondrial Mn-superoxide dismutase, glutathione, glutathione peroxidase and glutathione-S-transferase following the continuous intracerebroventricular infusion of amyloid beta for 2 weeks. The infusion of amyloid beta (1-42) resulted in a significant reduction of the immunoreactivity of these antioxidant substances in such brain areas as the hippocampus, parietal cortex, piriform cortex, substantia nigra and thalamus although the same treatment with amyloid beta (40-1) had little effect. The alterations induced by amyloid beta (1-42) were not uniform, but rather specific for each immunoreactive substance in a brain region-dependent manner. These results demonstrate a cytological effect of oxidative stress induced by amyloid beta (1-42) infusion. Furthermore, our findings may indicate a heterogeneous susceptibility to the oxidative stress produced by amyloid beta.
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Affiliation(s)
- H-C Kim
- Department of Pharmacy, College of Pharmacy, Kangwon National University, Korea Institute of Drug Abuse, Chunchon 200-701, South Korea
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Shor-Posner G, Lecusay R, Morales G, Campa A, Miguez-Burbano MJ. Neuroprotection in HIV-positive drug users: implications for antioxidant therapy. J Acquir Immune Defic Syndr 2002; 31 Suppl 2:S84-8. [PMID: 12394787 DOI: 10.1097/00126334-200210012-00009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Impaired neuroprotection resulting from oxidative stress has been implicated in neurodegeneration in a number of pathologic conditions of the brain, including both subcortical and cortical type dementias. Production of excessive oxidative stress, moreover, can lead to elevated levels of certain proinflammatory cytokines that are considered to be contributing factors to neuronal injury and are evident in HIV-related dementia as well as in other neurodegenerative conditions. Inhibitors of oxidative damage could thus be promising therapeutic agents for preventing progressive nerve cell death and slowing the advance of neurodegenerative disease. The potential of antioxidant therapy to provide neuroprotection is substantiated by studies demonstrating reduced oxidative stress with supplementation and lower risk for cognitive impairment with higher plasma antioxidant levels.
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Affiliation(s)
- Gail Shor-Posner
- Department of Psychiatry, University of Miami School of Medicine, Florida, USA
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9
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Fawcett JR, Bordayo EZ, Jackson K, Liu H, Peterson J, Svitak A, Frey WH. Inactivation of the human brain muscarinic acetylcholine receptor by oxidative damage catalyzed by a low molecular weight endogenous inhibitor from Alzheimer's brain is prevented by pyrophosphate analogs, bioflavonoids and other antioxidants. Brain Res 2002; 950:10-20. [PMID: 12231224 DOI: 10.1016/s0006-8993(02)02981-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Oxidative stress has been implicated as a contributing factor to neurodegeneration in Alzheimer's disease. An endogenous, low molecular weight (LMW) inhibitor from Alzheimer's brain inactivates the human brain muscarinic acetylcholine receptor (mAChR). The inhibitor prevents agonist and antagonist binding to the mAChR as assessed by radioligand binding studies. The LMW endogenous inhibitor, which has components with molecular weights between 100 and 1000 Da, requires dissolved oxygen and glutathione. Prevention of inactivation of the mAChR with peroxidase suggests that the LMW endogenous inhibitor generates peroxide. Heme, previously shown to be present in the LMW endogenous inhibitor, also inactivates the mAChR in the presence of peroxide. Free radical damage to the muscarinic receptor by the endogenous inhibitor can be prevented through the use of naturally occurring antioxidants including bilirubin, biliverdin, carnosol, myricetin and quericetin. In addition, pyrophosphate, imidodiphosphate, bisphosphonates and related compounds also protect the muscarinic receptor from free radical damage. Inactivation of the mAChR by the LMW endogenous inhibitor is likely to be a factor in the continual decline of Alzheimer's patients, even those taking acetylcholinesterase inhibitors. Natural antioxidants and pyrophosphate analogs may improve the effectiveness of acetylcholinesterase inhibitors and prove useful in the treatment and prevention of Alzheimer's disease since the muscarinic acetylcholine receptor is required for memory, and decreased cholinergic function is a critical deficit in Alzheimer's disease.
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Affiliation(s)
- John R Fawcett
- The Alzheimer's Research Center, HealthPartners Research Foundation, Regions Hospital, 640 Jackson Street, St. Paul, MN 55101-2595, USA
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10
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Abstract
As the number of older people is growing rapidly worldwide and the fact that elderly people are also apparently living longer, dementia, the most common cause of cognitive impairment is getting to be a greater public health problem. Nutrition plays a role in the ageing process, but there is still a lack of knowledge about nutrition-related risk factors in cognitive impairment. Research in this area has been intensive during the last decade, and results indicate that subclinical deficiency in essential nutrients (antioxidants such as vitamins C, E and beta-carotene, vitamin B(12), vitamin B(6), folate) and nutrition-related disorders, as hypercholesterolaemia, hypertriacylglycerolaemia, hypertension, and diabetes could be some of the nutrition-related risk factors, which can be present for a long time before cognitive impairment becomes evident. Large-scale clinical trials in high-risk populations are needed to determine whether lowering blood homocysteine levels reduces the risk of cognitive impairment and may delay the clinical onset of dementia and perhaps of Alzheimer's disease. A curative treatment of cognitive impairment, especially Alzheimer's disease, is currently impossible. Actual drug therapy, if started early enough, may slow down the progression of the disease. Longitudinal studies are required in order to establish the possible link of nutrient intake--nutritional status with cognitive impairment, and if it is possible, in fact, to inhibit or delay the onset of dementia.
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Affiliation(s)
- M González-Gross
- Institut für Ernährungswissenschaft, Abteilung Pathophysiologie der Ernährung, Rheinische Friedrich-Wilhelms-Universität, D-53115 Bonn, Germany.
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Nourhashémi F, Ousset PJ, Guyonnet S, Andrieu S, Rolland Y, Adoue D, Vellas B, Albarède JL. [Alzheimer's disease: from pathology to preventive methods?]. Rev Med Interne 2000; 21:524-32. [PMID: 10909152 DOI: 10.1016/s0248-8663(00)89228-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Sporadic Alzheimer's disease is the most frequent form of dementia and appears to be associated with increasing age and certain genetic and environmental factors. Some studies have recently been published on potential protective factors. CURRENT KNOWLEDGE AND KEY POINTS Several genes appear to be involved; one of the most common is the ApoE4 allele on chromosome 19. The physiopathology is not elucidated, but recent studies have shown a protective effect for NSAIDs, estrogen, nutritional factors (vitamins E, B6 and B12) as well as some biochemical amino acids (homocysteine). FUTURE PROSPECTS AND PROJECTS Interventional studies are now in progress and some preventive approaches will soon be available.
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Affiliation(s)
- F Nourhashémi
- Service de médecine interne et de gérontologie clinique, hôpital Purpan-Casselardit, CHU, Toulouse, France
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12
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Abstract
Glutathione is an important antioxidant that is involved in numerous cellular activities. gamma-Glutamylcysteine synthetase (gammaGCS) is a key regulatory enzyme in the synthesis of glutathione. It is a heterodimeric zinc metalloprotein that belongs to a unique class of proteins that gain activity due to formation of a reversible disulfide bond. The two subunits of gammaGCS exhibit differential and coordinate transcription regulation. In addition, the subunits are regulated at the posttranscriptional and posttranslational levels. These various levels of regulation allow numerous stimuli to induce or inhibit activity.
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Affiliation(s)
- S R Soltaninassab
- Department of Radiation Oncology, Vanderbilt University School of Medicine and Vanderbilt-Ingram Cancer Center, Nashville, TN 37232, USA
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Nourhashemi F, Gillette-Guyonnet S, Andrieu S, Ghisolfi A, Ousset PJ, Grandjean H, Grand A, Pous J, Vellas B, Albarede JL. Alzheimer disease: protective factors. Am J Clin Nutr 2000; 71:643S-649S. [PMID: 10681273 DOI: 10.1093/ajcn/71.2.643s] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Approximately 6-8% of all persons aged >65 y have Alzheimer disease and the prevalence of the disease is increasing. Any intervention strategy aimed at decreasing risks or delaying the onset of the disease will therefore have a substantial effect on health care costs. Nutrition seems to be one of the factors that may play a protective role in Alzheimer disease. Many studies suggest that oxidative stress and the accumulation of free radicals are involved in the pathophysiology of the disease. Several studies have shown the existence of a correlation between cognitive skills and the serum concentrations of folate, vitamin B-12, vitamin B-6, and, more recently, homocysteine. However, nutritional factors have to be studied not alone but with the other factors related to Alzheimer disease: genetics, estrogen, antiinflammatory drug use, and socioeconomic variables. The objective of this article was to review recent studies in this field.
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Affiliation(s)
- F Nourhashemi
- Department of Internal Medicine and Clinical Gerontology, University Hospital, Toulouse, France
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Lagalwar S, Bordayo EZ, Hoffmann KL, Fawcett JR, Frey WH. Anandamides inhibit binding to the muscarinic acetylcholine receptor. J Mol Neurosci 1999; 13:55-61. [PMID: 10691292 DOI: 10.1385/jmn:13:1-2:55] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Loss of memory and cholinergic transmission are associated with both Alzheimer's disease (AD) and marijuana use. The human brain muscarinic acetylcholine receptor (mAChR), which is involved in memory function and is inhibited by arachidonic acid, is also inhibited by anandamides. Two agonists of the cannabinoid receptor derived from arachidonic acid, anandamide (AEA) and R-methanandamide, inhibit ligand binding to the mAChR. Binding of the mAChR antagonist [3H]quinuclidinyl benzilate ([3H]QNB) is inhibited up to 89% by AEA (half-maximal inhibition at 50 microM). Binding of the more polar antagonist [N-methyl-3H]scopolamine ([3H]NMS) is inhibited by AEA up to 76% (half-maximal inhibition at 44 microM). R-methanandamide inhibits more than 90% of both [3H]QNB binding (I50 = 34 microM) and [3H]NMS binding (I50 = 15 microM) to the mAChR. Both AEA and R-methanandamide stimulate mAChR binding of the agonist [3H]oxotremorine-M at low concentrations (25-75 microM), but significantly inhibit agonist binding at higher concentrations (I50 = 150 microM). The cannabinoid antagonist SR141716A did not alter AEA or R-methanandamide inhibition of [3H]NMS binding to the mAChR, even at concentrations as high as 1 microM. Further, the cannabinoid agonist WIN 55212-2 does not alter antagonist binding to the mAChR. This demonstrates that mAChR inhibition by the anandamides is not mediated by the cannabinoid receptor. Since AEA and R-methanandamide are structurally similar to arachidonic acid, they may interact with the mAChR in a similar manner to inhibit receptor function.
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Affiliation(s)
- S Lagalwar
- Department of Neurology, Alzheimer's Research Center, HealthPartners, Regions Hospital, St. Paul, MN 55101-2595, USA
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Kjome JR, Swenson KA, Johnson MN, Bordayo EZ, Anderson LE, Klevan LC, Fraticelli AI, Aldrich SL, Fawcett JR, Venters HD, Ala TA, Frey WH. Inhibition of antagonist and agonist binding to the human brain muscarinic receptor by arachidonic acid. J Mol Neurosci 1998; 10:209-17. [PMID: 9770643 DOI: 10.1007/bf02761775] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Arachidonic acid (AA) inhibits the binding of [3H]quinclidinyl benzilate ([3H]QNB) to the human brain muscarinic cholinergic receptor (mAChR). AA inhibits at lower concentrations in the absence of glutathione (I50 = 15 microM) than in the presence of glutathione (I50 = 42 microM). Inhibition of mAChR binding shows specificity for AA and is reduced with loss of one or more double bonds or with either a decrease or increase in the length of the fatty acid chain. Metabolism of AA by the lipoxygenase, epoxygenase, or fatty acid cyclooxygenase pathways is not required for the inhibitory activity of AA on mAChR binding. Inhibition of [3H]QNB binding by AA is reversible. While decreasing Bmax, AA increased the apparent KD for [3H]QNB and for the more polar antagonist [3H]NMS. In addition, AA inhibits binding of the agonist [3H]oxotremorine-M (I50 = 60 microM) and is the first mediator of mAChR action to be shown to reversibly inhibit mAChR binding. The feedback inhibition of the mAChR by AA may serve a homeostatic function similar to the reuptake and hydrolysis of acetylcholine following cholinergic nerve transmission.
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Affiliation(s)
- J R Kjome
- Department of Neurology, Alzheimer's Treatment and Research Center, HealthPartners, Regions Hospital, St. Paul, MN 55101-2595, USA
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Venters HD, Bonilla LE, Jensen T, Garner HP, Bordayo EZ, Najarian MM, Ala TA, Mason RP, Frey WH. Heme from Alzheimer's brain inhibits muscarinic receptor binding via thiyl radical generation. Brain Res 1997; 764:93-100. [PMID: 9295197 DOI: 10.1016/s0006-8993(97)00425-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An endogenous inhibitor (< 3500 Da) of antagonist binding to the muscarinic acetylcholine receptor (mAChR) has been reported to be elevated 3-fold in Alzheimer's disease (AD) brain. This endogenous inhibitor was found to require the presence of reducing agents such as reduced glutathione (GSH) for optimal activity. In the presence of GSH, the inhibitor was shown to generate thiyl radicals which irreversibly inhibited the mAChR. We now report that the inhibitor contains free heme, a well-established source of oxidative stress capable of generating free radicals and causing neurotoxicity. While FeSO4, microperoxidase and hemin all inhibited antagonist binding to the mAChR, only hemin shared the inhibitor's requirement for GSH. Both the free radical scavengers Trolox and Mn2+, and the metal chelator, EDTA, blocked the activity of the endogenous AD inhibitor and of hemin. Heme oxygenase-1 (HO-1) markedly reduced the activity of both the endogenous AD inhibitor and hemin, indicating that the endogenous inhibitor contains heme. Mass spectrometric analysis confirmed the presence of free heme and heme fragments in fractions of the endogenous AD inhibitor. The antioxidants estrogen, vitamin E and vitamin C all protected the mAChR from irreversible inhibition by the endogenous inhibitor or hemin. These antioxidants may function to protect the integrity of the mAChR in vivo and may have therapeutic potential in AD where free heme could be a source of oxidative stress.
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Affiliation(s)
- H D Venters
- Department of Neurology, The Alzheimer's Treatment and Research Center, Health Partners/St. Paul Ramsey Medical Center, MN 55101-2595, USA
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17
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Affiliation(s)
- R Lethem
- Department of Psychiatry, Whittington Hospital, London, UK
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