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Sobel RA, Albertelli M, Hinojoza JR, Eaton MJ, Grimes KV, Rubenstein E. Azetidine-2-Carboxylic Acid-Induced Oligodendrogliopathy: Relevance to the Pathogenesis of Multiple Sclerosis. J Neuropathol Exp Neurol 2022; 81:414-433. [PMID: 35521963 PMCID: PMC9123080 DOI: 10.1093/jnen/nlac028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The naturally occurring imino acid azetidine-2-carboxylic acid (Aze) is consumed by humans and can be misincorporated in place of proline in myelin basic protein (MBP) in vitro. To determine Aze effects on the mammalian CNS in vivo, adult CD1 mice were given Aze orally or intraperitoneally. Clinical signs reminiscent of MBP-mutant mice occurred with 600 mg/kg Aze exposure. Aze induced oligodendrocyte (OL) nucleomegaly and nucleoplasm clearing, dilated endoplasmic reticulum, cytoplasmic vacuolation, abnormal mitochondria, and Aze dose-dependent apoptosis. Immunohistochemistry demonstrated myelin blistering and nuclear translocation of unfolded protein response (UPR)/proinflammatory molecules (ATF3, ATF4, ATF6, eIF2α, GADD153, NFκB, PERK, XBP1), MHC I expression, and MBP cytoplasmic aggregation in OL. There were scattered microglial nodules in CNS white matter (WM); other CNS cells appeared unaffected. Mice given Aze in utero and postnatally showed more marked effects than their dams. These OL, myelin, and microglial alterations are found in normal-appearing WM (NAWM) in multiple sclerosis (MS) patients. Thus, Aze induces a distinct oligodendrogliopathy in mice that recapitulates MS NAWM pathology without leukocyte infiltration. Because myelin proteins are relatively stable throughout life, we hypothesize that Aze misincorporation in myelin proteins during myelinogenesis in humans results in a progressive UPR that may be a primary process in MS pathogenesis.
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Affiliation(s)
- Raymond A Sobel
- From the Laboratory Service, Veterans Affairs Health Care System, Palo Alto, California, USA.,Department of Pathology, Stanford University School of Medicine, Stanford, California, USA
| | - Megan Albertelli
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California, USA
| | - Julian R Hinojoza
- From the Laboratory Service, Veterans Affairs Health Care System, Palo Alto, California, USA.,Department of Pathology, Stanford University School of Medicine, Stanford, California, USA
| | - Mary Jane Eaton
- From the Laboratory Service, Veterans Affairs Health Care System, Palo Alto, California, USA.,Department of Pathology, Stanford University School of Medicine, Stanford, California, USA
| | - Kevin V Grimes
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California, USA
| | - Edward Rubenstein
- Department of Medicine, Stanford University School of Medicine, Stanford, California, USA
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The Type 2 Diabetes Factor Methylglyoxal Mediates Axon Initial Segment Shortening and Alters Neuronal Function at the Cellular and Network Levels. eNeuro 2021; 8:ENEURO.0201-21.2021. [PMID: 34531281 PMCID: PMC8496204 DOI: 10.1523/eneuro.0201-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/23/2021] [Accepted: 09/07/2021] [Indexed: 02/02/2023] Open
Abstract
Recent evidence suggests that alteration of axon initial segment (AIS) geometry (i.e., length or location along the axon) contributes to CNS dysfunction in neurological diseases. For example, AIS length is shorter in the prefrontal cortex of type 2 diabetic mice with cognitive impairment. To determine the key type 2 diabetes-related factor that produces AIS shortening we modified levels of insulin, glucose, or the reactive glucose metabolite methylglyoxal in cultures of dissociated cortices from male and female mice and quantified AIS geometry using immunofluorescent imaging of the AIS proteins AnkyrinG and βIV spectrin. Neither insulin nor glucose modification altered AIS length. Exposure to 100 but not 1 or 10 μm methylglyoxal for 24 h resulted in accumulation of the methylglyoxal-derived advanced glycation end-product hydroimidazolone and produced reversible AIS shortening without cell death. Methylglyoxal-evoked AIS shortening occurred in both excitatory and putative inhibitory neuron populations and in the presence of tetrodotoxin (TTX). In single-cell recordings resting membrane potential was depolarized at 0.5-3 h and returned to normal at 24 h. In multielectrode array (MEA) recordings methylglyoxal produced an immediate ∼300% increase in spiking and bursting rates that returned to normal within 2 min, followed by a ∼20% reduction of network activity at 0.5-3 h and restoration of activity to baseline levels at 24 h. AIS length was unchanged at 0.5-3 h despite the presence of depolarization and network activity reduction. Nevertheless, these results suggest that methylglyoxal could be a key mediator of AIS shortening and disruptor of neuronal function during type 2 diabetes.
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Yermakov LM, Griggs RB, Drouet DE, Sugimoto C, Williams MT, Vorhees CV, Susuki K. Impairment of cognitive flexibility in type 2 diabetic db/db mice. Behav Brain Res 2019; 371:111978. [PMID: 31141724 PMCID: PMC6579681 DOI: 10.1016/j.bbr.2019.111978] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 05/23/2019] [Accepted: 05/24/2019] [Indexed: 01/05/2023]
Abstract
Impaired executive function is a major peril for patients with type 2 diabetes, reducing quality of life and ability for diabetes management. Despite the significance of this impairment, few animal models of type 2 diabetes examine domains of executive function such as cognitive flexibility or working memory. Here, we evaluated these executive function domains in db/db mice, an established model of type 2 diabetes, at 10 and 24 weeks of age. The db/db mice showed impaired cognitive flexibility in the Morris water maze reversal phase. However, the db/db mice did not show apparent working memory disturbance in the spatial working memory version of the Morris water maze or in the radial water maze. We also examined axon initial segments (AIS) and nodes of Ranvier, key axonal domains for action potential initiation and propagation. AIS were significantly shortened in medial prefrontal cortex and hippocampus of 26-week-old db/db mice compared with controls, similar to our previous findings in 10-week-old mice. Nodes of Ranvier in corpus callosum, previously shown to be unchanged at 10 weeks, were elongated at 26 weeks, suggesting an important role for this domain in disease progression. Together, the findings help establish db/db mice as a model of impaired cognitive flexibility in type 2 diabetes and advance our understanding of its pathophysiology.
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Affiliation(s)
- Leonid M Yermakov
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
| | - Ryan B Griggs
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
| | - Domenica E Drouet
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA
| | - Chiho Sugimoto
- Department of Pediatrics, University of Cincinnati College of Medicine and Division of Neurology, Cincinnati Children's Research Foundation, Cincinnati, OH 45229, USA
| | - Michael T Williams
- Department of Pediatrics, University of Cincinnati College of Medicine and Division of Neurology, Cincinnati Children's Research Foundation, Cincinnati, OH 45229, USA
| | - Charles V Vorhees
- Department of Pediatrics, University of Cincinnati College of Medicine and Division of Neurology, Cincinnati Children's Research Foundation, Cincinnati, OH 45229, USA
| | - Keiichiro Susuki
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45435, USA.
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