bims-midneu 2021-05-09 papers

bims-midneu

Biomed News

on Mitochondrial dysfunction in neurodegeneration

Issue of 2021–05–09
23 papers selected by
Radha Desai, Merck Sharp & Dohme Corp.

Distinct fission signatures predict mitochondrial degradation or biogenesis.
Upregulation of brain cholesterol levels inhibits mitophagy in Alzheimer disease.
Drp1-dependent peptide reverse mitochondrial fragmentation, a homeostatic response in Friedreich ataxia.
Prohibitin depletion extends lifespan of a TORC2/SGK-1 mutant through autophagy and the mitochondrial UPR.
Neuroinflammatory Mechanisms of Mitochondrial Dysfunction and Neurodegeneration in Glaucoma.
DNA polymerase gamma mutations that impair holoenzyme stability cause catalytic subunit depletion.
Adaptation of mitochondrial network dynamics and velocity of mitochondrial movement to chronic stress present in fibroblasts derived from patients with sporadic form of Alzheimer's disease.
Ablation of dynamin-related protein 1 promotes diabetes-induced synaptic injury in the hippocampus.
Gain of PITRM1 peptidase in cortical neurons affords protection of mitochondrial and synaptic function in an advanced age mouse model of Alzheimer's disease.
Bi-allelic KARS1 pathogenic variants affecting functions of cytosolic and mitochondrial isoforms are associated with a progressive and multi-system disease.
Nicotinamide provides neuroprotection in glaucoma by protecting against mitochondrial and metabolic dysfunction.
FSHR-1/GPCR Regulates the Mitochondrial Unfolded Protein Response in Caenorhabditis elegans.
Role of mTOR-Regulated Autophagy in Synaptic Plasticity Related Proteins Downregulation and the Reference Memory Deficits Induced by Anesthesia/Surgery in Aged Mice.
Molecular Mechanisms Underlying TDP-43 Pathology in Cellular and Animal Models of ALS and FTLD.
Attenuation of inhibitory PAS domain protein-induced cell death by synthetic peptides derived from Mcl-1 transmenbrane domain.
Integration of Mass Spectrometry Imaging and Machine Learning Visualizes Region-Specific Age-Induced and Drug-Target Metabolic Perturbations in the Brain.
CRISPR/dCas9-Mediated Parkin Inhibition Impairs Mitophagy and Aggravates Apoptosis of Rat Nucleus Pulposus Cells Under Oxidative Stress.
Brain MRS correlates with mitochondrial dysfunction biomarkers in MELAS-associated mtDNA mutations.
Mendelian neurodegenerative disease genes involved in autophagy.
Fluorescent probe for early mitochondrial voltage dynamics.
Electroacupuncture at GV20‑GB7 regulates mitophagy to protect against neurological deficits following intracerebral hemorrhage via inhibition of apoptosis.
Impact of mitochondrial aldehyde dehydrogenase 2 on cognitive impairment in the AD model mouse.
Regulatory mechanisms of mitochondrial BKCa channels.

Nature. 2021 May 05.

Distinct fission signatures predict mitochondrial degradation or biogenesis.

Tatjana Kleele, Timo Rey, Julius Winter, Sofia Zaganelli, Dora Mahecic, Hélène Perreten Lambert, Francesco Paolo Ruberto, Mohamed Nemir, Timothy Wai, Thierry Pedrazzini, Suliana Manley.

Mitochondrial fission is a highly regulated process that, when disrupted, can alter metabolism, proliferation and apoptosis1-3. Dysregulation has been linked to neurodegeneration3,4, cardiovascular disease3 and cancer5. Key components of the fission machinery include the endoplasmic reticulum6 and actin7, which initiate constriction before dynamin-related protein 1 (DRP1)8 binds to the outer mitochondrial membrane via adaptor proteins9-11, to drive scission12. In the mitochondrial life cycle, fission enables both biogenesis of new mitochondria and clearance of dysfunctional mitochondria through mitophagy1,13. Current models of fission regulation cannot explain how those dual fates are decided. However, uncovering fate determinants is challenging, as fission is unpredictable, and mitochondrial morphology is heterogeneous, with ultrastructural features that are below the diffraction limit. Here, we used live-cell structured illumination microscopy to capture mitochondrial dynamics. By analysing hundreds of fissions in African green monkey Cos-7 cells and mouse cardiomyocytes, we discovered two functionally and mechanistically distinct types of fission. Division at the periphery enables damaged material to be shed into smaller mitochondria destined for mitophagy, whereas division at the midzone leads to the proliferation of mitochondria. Both types are mediated by DRP1, but endoplasmic reticulum- and actin-mediated pre-constriction and the adaptor MFF govern only midzone fission. Peripheral fission is preceded by lysosomal contact and is regulated by the mitochondrial outer membrane protein FIS1. These distinct molecular mechanisms explain how cells independently regulate fission, leading to distinct mitochondrial fates.

DOI: https://doi.org/10.1038/s41586-021-03510-6
Autophagy. 2021 May 04. 1-3

Upregulation of brain cholesterol levels inhibits mitophagy in Alzheimer disease.

Vicente Roca-Agujetas, Cristina de Dios, Xenia Abadin, Anna Colell.

  Mitochondrial dysfunction is behind several neurodegenerative diseases, including Alzheimer disease (AD). Accumulation of damaged mitochondria is already observed at the early stages of AD and has been linked to impaired mitophagy, but the mechanisms underlying this alteration are still not fully known. In our recent study, we show that intracellular cholesterol enrichment can downregulate amyloid beta (Aβ)-induced mitophagy. Mitochondrial glutathione depletion resulting from high cholesterol levels promotes PINK1 (PTEN induced kinase 1)-mediated mitophagosome formation; however, mitophagy flux is ultimately disrupted, most likely due to fusion deficiency of endosomes-lysosomes caused by cholesterol. Meanwhile, in APP-PSEN1-SREBF2 mice, an AD mouse model that overexpresses the cholesterol-related transcription factor SREBF2, cholesterol accumulation prompts an oxidative- and age-dependent cytosolic aggregation of the mitophagy adaptor OPTN (optineurin), which prevents mitophagosome formation despite enhanced PINK1-PRKN/parkin signaling. Hippocampal neurons from postmortem brain of AD individuals reproduce the progressive accumulation of OPTN in aggresome-like structures accompanied by high levels of mitochondrial cholesterol in advanced stages of the disease. Overall, these data provide new insights into the impairment of the PINK1-PRKN mitophagy pathway in AD and suggest the combination of mitophagy inducers with strategies focused on restoring the cholesterol homeostasis and mitochondrial redox balance as a potential disease-modifying therapy for AD.

Keywords:  Alzheimer disease; Mitophagy; PINK1; aggresomes; autophagy; cholesterol; optineurin; parkin

DOI:  https://doi.org/10.1080/15548627.2021.1920814
Pharmacol Res Perspect. 2021 May;9(3): e00755

Drp1-dependent peptide reverse mitochondrial fragmentation, a homeostatic response in Friedreich ataxia.

Joseph Johnson, Elizabeth Mercado-Ayón, Elisia Clark, David Lynch, Hong Lin.

  Friedreich ataxia is an autosomal recessive, neurodegenerative disease characterized by the deficiency of the iron-sulfur cluster assembly protein frataxin. Loss of this protein impairs mitochondrial function. Mitochondria alter their morphology in response to various stresses; however, such alterations to morphology may be homeostatic or maladaptive depending upon the tissue and disease state. Numerous neurodegenerative diseases exhibit excessive mitochondrial fragmentation, and reversing this phenotype improves bioenergetics for diseases in which mitochondrial dysfunction is a secondary feature of the disease. This paper demonstrates that frataxin deficiency causes excessive mitochondrial fragmentation that is dependent upon Drp1 activity in Friedreich ataxia cellular models. Drp1 inhibition by the small peptide TAT-P110 reverses mitochondrial fragmentation but also decreases ATP levels in frataxin-knockdown fibroblasts and FRDA patient fibroblasts, suggesting that fragmentation may provide a homeostatic pathway for maintaining cellular ATP levels. The cardiolipin-stabilizing compound SS-31 similarly reverses fragmentation through a Drp1-dependent mechanism, but it does not affect ATP levels. The combination of TAT-P110 and SS-31 does not affect FRDA patient fibroblasts differently from SS-31 alone, suggesting that the two drugs act through the same pathway but differ in their ability to alter mitochondrial homeostasis. In approaching potential therapeutic strategies for FRDA, an important criterion for compounds that improve bioenergetics should be to do so without impairing the homeostatic response of mitochondrial fragmentation.

Keywords:  ATP; Drp1; Drp1-dependent small peptides; Friedreich ataxia; frataxin; mitochondrial fragmentation; mitochondrial homeostasis

DOI:  https://doi.org/10.1002/prp2.755
Aging Cell. 2021 May 03. e13359

Prohibitin depletion extends lifespan of a TORC2/SGK-1 mutant through autophagy and the mitochondrial UPR.

Patricia de la Cruz-Ruiz, Blanca Hernando-Rodríguez, Mercedes M Pérez-Jiménez, María Jesús Rodríguez-Palero, Manuel D Martínez-Bueno, Antoni Pla, Roxani Gatsi, Marta Artal-Sanz.

  Mitochondrial prohibitins (PHB) are highly conserved proteins with a peculiar effect on lifespan. While PHB depletion shortens lifespan of wild-type animals, it enhances longevity of a plethora of metabolically compromised mutants, including target of rapamycin complex 2 (TORC2) mutants sgk-1 and rict-1. Here, we show that sgk-1 mutants have impaired mitochondrial homeostasis, lipogenesis and yolk formation, plausibly due to alterations in membrane lipid and sterol homeostasis. Remarkably, all these features are suppressed by PHB depletion. Our analysis shows the requirement of SRBP1/SBP-1 for the lifespan extension of sgk-1 mutants and the further extension conferred by PHB depletion. Moreover, although the mitochondrial unfolded protein response (UPRmt ) and autophagy are induced in sgk-1 mutants and upon PHB depletion, they are dispensable for lifespan. However, the enhanced longevity caused by PHB depletion in sgk-1 mutants requires both, the UPRmt and autophagy, but not mitophagy. We hypothesize that UPRmt induction upon PHB depletion extends lifespan of sgk-1 mutants through autophagy and probably modulation of lipid metabolism.

Keywords:  SGK-1; UPRmt; autophagy; lipogenesis; mitochondria; prohibitin

DOI:  https://doi.org/10.1111/acel.13359
J Ophthalmol. 2021 ;2021 4581909

Neuroinflammatory Mechanisms of Mitochondrial Dysfunction and Neurodegeneration in Glaucoma.

Joao N Duarte.

The exact mechanism of retinal ganglion cell loss in the pathogenesis of glaucoma is yet to be understood. Mitochondrial damage-associated molecular patterns (DAMPs) resulting from mitochondrial dysfunction have been linked to Leber's hereditary optic neuropathy and autosomal dominant optic atrophy, as well as to brain neurodegenerative diseases. Recent evidence shows that, in conditions where mitochondria are damaged, a sustained inflammatory response and downstream pathological inflammation may ensue. Mitochondrial damage has been linked to the accumulation of age-related mitochondrial DNA mutations and mitochondrial dysfunction, possibly through aberrant reactive oxygen species production and defective mitophagy. The present review focuses on how mitochondrial dysfunction may overwhelm the ability of neurons and glial cells to adequately maintain homeostasis and how mitochondria-derived DAMPs trigger the immune system and induce neurodegeneration.

DOI: https://doi.org/10.1155/2021/4581909
Nucleic Acids Res. 2021 May 06. pii: gkab282. [Epub ahead of print]

DNA polymerase gamma mutations that impair holoenzyme stability cause catalytic subunit depletion.

Pedro Silva-Pinheiro, Carlos Pardo-Hernández, Aurelio Reyes, Lisa Tilokani, Anup Mishra, Raffaele Cerutti, Shuaifeng Li, Dieu-Hien Rozsivalova, Sebastian Valenzuela, Sukru A Dogan, Bradley Peter, Patricio Fernández-Silva, Aleksandra Trifunovic, Julien Prudent, Michal Minczuk, Laurence Bindoff, Bertil Macao, Massimo Zeviani, Maria Falkenberg, Carlo Viscomi.

Mutations in POLG, encoding POLγA, the catalytic subunit of the mitochondrial DNA polymerase, cause a spectrum of disorders characterized by mtDNA instability. However, the molecular pathogenesis of POLG-related diseases is poorly understood and efficient treatments are missing. Here, we generate the PolgA449T/A449T mouse model, which reproduces the A467T change, the most common human recessive mutation of POLG. We show that the mouse A449T mutation impairs DNA binding and mtDNA synthesis activities of POLγ, leading to a stalling phenotype. Most importantly, the A449T mutation also strongly impairs interactions with POLγB, the accessory subunit of the POLγ holoenzyme. This allows the free POLγA to become a substrate for LONP1 protease degradation, leading to dramatically reduced levels of POLγA in A449T mouse tissues. Therefore, in addition to its role as a processivity factor, POLγB acts to stabilize POLγA and to prevent LONP1-dependent degradation. Notably, we validated this mechanism for other disease-associated mutations affecting the interaction between the two POLγ subunits. We suggest that targeting POLγA turnover can be exploited as a target for the development of future therapies.

DOI: https://doi.org/10.1093/nar/gkab282
FASEB J. 2021 Jun;35(6): e21586

Adaptation of mitochondrial network dynamics and velocity of mitochondrial movement to chronic stress present in fibroblasts derived from patients with sporadic form of Alzheimer's disease.

Karolina Drabik, Karolina Piecyk, Artur Wolny, Lidia Szulc-Dąbrowska, Grażyna Dębska-Vielhaber, Stefan Vielhaber, Jerzy Duszyński, Dominika Malińska, Joanna Szczepanowska.

  Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. Only 10% of all cases are familial form, the remaining 90% are sporadic form with unknown genetic background. The etiology of sporadic AD is still not fully understood. Pathogenesis and pathobiology of this disease are limited due to the limited number of experimental models. We used primary culture of fibroblasts derived from patients diagnosed with sporadic form of AD for investigation of dynamic properties of mitochondria, including fission-fusion process and localization of mitochondria within the cell. We observed differences in mitochondrial network organization with decreased mitochondrial transport velocity, and a drop in the frequency of fusion-fission events. These studies show how mitochondrial dynamics adapt to the conditions of long-term mitochondrial stress that prevails in cells of sporadic form of AD.

Keywords:  Alzheimer’s disease; fibroblasts; mitochondrial dynamics

DOI:  https://doi.org/10.1096/fj.202001978RR
Cell Death Dis. 2021 May 05. 12(5): 445

Ablation of dynamin-related protein 1 promotes diabetes-induced synaptic injury in the hippocampus.

Gyeongah Park, Jong Youl Lee, Hye Min Han, Hyeong Seok An, Zhen Jin, Eun Ae Jeong, Kyung Eun Kim, Hyun Joo Shin, Jaewoong Lee, Dawon Kang, Hyun Joon Kim, Yong Chul Bae, Gu Seob Roh.

Dynamin-related protein 1 (Drp1)-mediated mitochondrial dysfunction is associated with synaptic injury in the diabetic brain. However, the dysfunctional mitochondria by Drp1 deletion in the diabetic brain are poorly understood. Here, we investigated the effects of neuron-specific Drp1 deletion on synaptic damage and mitophagy in the hippocampus of a high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice. HFD/STZ-induced diabetic mice exhibited metabolic disturbances and synaptic damages. Floxed Drp1 mice were crossed with Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα)-Cre mice, to generate neuron-specific Drp1 knockout (Drp1cKO) mice, which showed marked mitochondrial swelling and dendritic spine loss in hippocampal neurons. In particular, diabetic Drp1cKO mice exhibited an increase in dendritic spine loss and higher levels of oxidative stress and neuroinflammation compared with diabetic wild-type (WT) mice. Diabetic WT mice generally displayed increased Drp1-induced small mitochondrial morphology in hippocampal neurons, but large mitochondria were prominently observed in diabetic Drp1cKO mice. The levels of microtubule-associated protein 1 light-chain 3 and lysosomal-associated membrane protein 1 proteins were significantly increased in the hippocampus of diabetic Drp1cKO mice compared with diabetic WT mice. The inhibition of Drp1 adversely promotes synaptic injury and neurodegeneration in the diabetic brain. The findings suggest that the exploratory mechanisms behind Drp1-mediated mitochondrial dysfunction could provide a possible therapeutic target for diabetic brain complications.

DOI: https://doi.org/10.1038/s41419-021-03723-7
Aging Cell. 2021 May 05. e13368

Gain of PITRM1 peptidase in cortical neurons affords protection of mitochondrial and synaptic function in an advanced age mouse model of Alzheimer's disease.

Fang Du, Qing Yu, Shijun Yan, Zhihua Zhang, Jhansi Rani Vangavaragu, Doris Chen, Shi Fang Yan, Shirley ShiDu Yan.

  Mitochondrial dysfunction is one of the early pathological features of Alzheimer's disease (AD). Accumulation of cerebral and mitochondrial Aβ links to mitochondrial and synaptic toxicity. We have previously demonstrated the mechanism by which presequence peptidase (PITRM1)-mediated clearance of mitochondrial Aβ contributes to mitochondrial and cerebral amyloid pathology and mitochondrial and synaptic stress in adult transgenic AD mice overexpressing Aβ up to 12 months old. Here, we investigate the effect of PITRM1 in an advanced age AD mouse model (up to 19-24 months) to address the fundamental unexplored question of whether restoration/gain of PITRM1 function protects against mitochondrial and synaptic dysfunction associated with Aβ accumulation and whether this protection is maintained even at later ages featuring profound amyloid pathology and synaptic failure. Using newly developed aged PITRM1/Aβ-producing AD mice, we first uncovered reduction in PITRM1 expression in AD-affected cortex of AD mice at 19-24 months of age. Increasing neuronal PITRM1 activity/expression re-established mitochondrial respiration, suppressed reactive oxygen species, improved synaptic function, and reduced loss of synapses even at advanced ages (up to 19-24 months). Notably, loss of PITRM1 proteolytic activity resulted in Aβ accumulation and failure to rescue mitochondrial and synaptic function, suggesting that PITRM1 activity is required for the degradation and clearance of mitochondrial Aβ and Aβ deposition. These data indicate that augmenting PITRM1 function results in persistent life-long protection against Aβ toxicity in an AD mouse model. Therefore, augmenting PITRM1 function may enhance Aβ clearance in mitochondria, thereby maintaining mitochondrial integrity and ultimately slowing the progression of AD.

Keywords:  amyloid pathology; mitochondria-related proinflammation; mitochondrial Aβ clearance; mitochondrial proteolysis; synaptic rescue

DOI:  https://doi.org/10.1111/acel.13368
Hum Mutat. 2021 May 03.

Bi-allelic KARS1 pathogenic variants affecting functions of cytosolic and mitochondrial isoforms are associated with a progressive and multi-system disease.

Telethon Undiagnosed Diseases Program

  KARS1 encodes a lysyl-transfer RNA synthetase (LysRS) that links lysine to its cognate tRNA. Two different KARS1 isoforms exert functional effects in cytosol and mitochondria. Bi-allelic pathogenic variants in KARS1 have been associated to sensorineural hearing and visual loss, neuropathy, seizures, and leukodystrophy. We report the clinical, biochemical and neuroradiological features of nine individuals with KARS1-related disorder carrying 12 different variants with nine of them being novel. The consequences of these variants on the cytosol and/or mitochondrial LysRS were functionally validated in yeast mutants. Most cases presented with severe neurological features including congenital and progressive microcephaly, seizures, developmental delay/intellectual disability, and cerebral atrophy. Oculo-motor dysfunction and immuno-hematological problems were present in six and three cases, respectively. A yeast growth defect of variable severity was detected for most variants on both cytosolic and mitochondrial isoforms. The detrimental effects of two variants on yeast growth were partially rescued by lysine supplementation. Congenital progressive microcephaly, oculo-motor dysfunction and immuno-hematological problems are emerging phenotypes in KARS1-related disorders. The data in yeast emphasize the role of both mitochondrial and cytosolic isoforms in the pathogenesis of KARS1-related disorder and supports the therapeutic potential of lysine supplementation at least in a subset of patients. This article is protected by copyright. All rights reserved.

Keywords:  KARS; KARS1; LysRS; Lysyl-transfer RNA synthetase; mitochondrial disease

DOI:  https://doi.org/10.1002/humu.24210
Redox Biol. 2021 Apr 24. pii: S2213-2317(21)00136-1. [Epub ahead of print]43 101988

Nicotinamide provides neuroprotection in glaucoma by protecting against mitochondrial and metabolic dysfunction.

James R Tribble, Amin Otmani, Shanshan Sun, Sevannah A Ellis, Gloria Cimaglia, Rupali Vohra, Melissa Jöe, Emma Lardner, Abinaya P Venkataraman, Alberto Domínguez-Vicent, Eirini Kokkali, Seungsoo Rho, Gauti Jóhannesson, Robert W Burgess, Peter G Fuerst, Rune Brautaset, Miriam Kolko, James E Morgan, Jonathan G Crowston, Marcela Votruba, Pete A Williams.

  Nicotinamide adenine dinucleotide (NAD) is a REDOX cofactor and metabolite essential for neuronal survival. Glaucoma is a common neurodegenerative disease in which neuronal levels of NAD decline. We assess the effects of nicotinamide (a precursor to NAD) on retinal ganglion cells (the affected neuron in glaucoma) in normal physiological conditions and across a range of glaucoma relevant insults including mitochondrial stress and axon degenerative insults. We demonstrate retinal ganglion cell somal, axonal, and dendritic neuroprotection by nicotinamide in rodent models which represent isolated ocular hypertensive, axon degenerative, and mitochondrial degenerative insults. We performed metabolomics enriched for small molecular weight metabolites for the retina, optic nerve, and superior colliculus which demonstrates that ocular hypertension induces widespread metabolic disruption, including consistent changes to α-ketoglutaric acid, creatine/creatinine, homocysteine, and glycerophosphocholine. This metabolic disruption is prevented by nicotinamide. Nicotinamide provides further neuroprotective effects by increasing oxidative phosphorylation, buffering and preventing metabolic stress, and increasing mitochondrial size and motility whilst simultaneously dampening action potential firing frequency. These data support continued determination of the utility of long-term nicotinamide treatment as a neuroprotective therapy for human glaucoma.

Keywords:  Glaucoma; Metabolism; Metabolomics; Mitochondria; Nicotinamide; Retina; Retinal ganglion cell

DOI:  https://doi.org/10.1016/j.redox.2021.101988
Genetics. 2020 Feb 01. 214(2): 409-418

FSHR-1/GPCR Regulates the Mitochondrial Unfolded Protein Response in Caenorhabditis elegans.

Sungjin Kim, Derek Sieburth.

  The mitochondrial unfolded protein response (UPRmt) is an evolutionarily conserved adaptive response that functions to maintain mitochondrial homeostasis following mitochondrial damage. In Caenorhabditis elegans, the nervous system plays a central role in responding to mitochondrial stress by releasing endocrine signals that act upon distal tissues to activate the UPRmt. The mechanisms by which mitochondrial stress is sensed by neurons and transmitted to distal tissues are not fully understood. Here, we identify a role for the conserved follicle-stimulating hormone G protein-coupled receptor, FSHR-1, in promoting UPRmt activation. Genetic deficiency of fshr-1 severely attenuates UPRmt activation and organism-wide survival in response to mitochondrial stress. FSHR-1 functions in a common genetic pathway with SPHK-1/sphingosine kinase to promote UPRmt activation, and FSHR-1 regulates the mitochondrial association of SPHK-1 in the intestine. Through tissue-specific rescue assays, we show that FSHR-1 functions in neurons to activate the UPRmt, to promote mitochondrial association of SPHK-1 in the intestine, and to promote organism-wide survival in response to mitochondrial stress. We propose that FSHR-1 functions cell nonautonomously in neurons to activate UPRmt upstream of SPHK-1 signaling in the intestine.

Keywords:  FSHR-1; UPRmt; paraquat; sphingosine kinase

DOI:  https://doi.org/10.1534/genetics.119.302947
Front Aging Neurosci. 2021 ;13 628541

Role of mTOR-Regulated Autophagy in Synaptic Plasticity Related Proteins Downregulation and the Reference Memory Deficits Induced by Anesthesia/Surgery in Aged Mice.

Sunan Gao, Siyu Zhang, Hongmei Zhou, Xiaoyan Tao, Yunjian Ni, Daqing Pei, Shuai Kang, Weiwei Yan, Jian Lu.

  Postoperative cognitive dysfunction increases mortality and morbidity in perioperative patients and has become a major concern for patients and caregivers. Previous studies demonstrated that synaptic plasticity is closely related to cognitive function, anesthesia and surgery inhibit synaptic function. In central nervous system, autophagy is vital to synaptic plasticity, homeostasis of synapticproteins, synapse elimination, spine pruning, proper axon guidance, and when dysregulated, is associated with behavioral and memory functions disorders. The mammalian target of rapamycin (mTOR) negatively regulates the process of autophagy. This study aimed to explore whether rapamycin can ameliorate anesthesia/surgery-induced cognitive deficits by inhibiting mTOR, activating autophagy and rising synaptic plasticity-related proteins in the hippocampus. Aged C57BL/6J mice were used to establish POCD models with exploratory laparotomy under isoflurane anesthesia. The Morris Water Maze (MWM) was used to measure reference memory after anesthesia and surgery. The levels of mTOR phosphorylation (p-mTOR), Beclin-1 and LC3-II were examined on postoperative days 1, 3 and 7 by western blotting. The levels of synaptophysin (SYN) and postsynaptic density protein 95 (PSD-95) in the hippocampus were also examined by western blotting. Here we showed that anesthesia/surgery impaired reference memory and induced the activation of mTOR, decreased the expression of autophagy-related proteins such as Beclin-1 and LC3-II. A corresponding decline in the expression of neuronal/synaptic, plasticity-related proteins such as SYN and PSD-95 was also observed. Pretreating mice with rapamycin inhibited the activation of mTOR and restored autophagy function, also increased the expression of SYN and PSD-95. Furthermore, anesthesia/surgery-induced learning and memory deficits were also reversed by rapamycin pretreatment. In conclusion, anesthesia/surgery induced mTOR hyperactivation and autophagy impairments, and then reduced the levels of SYN and PSD-95 in the hippocampus. An mTOR inhibitor, rapamycin, ameliorated anesthesia/surgery-related cognitive impairments by inhibiting the mTOR activity, inducing activation of autophagy, enhancing SYN and PSD-95 expression.

Keywords:  aged; mTOR; postoperative cognitive dysfunction; rapamycin; synaptic plasticity

DOI:  https://doi.org/10.3389/fnagi.2021.628541
Int J Mol Sci. 2021 Apr 29. pii: 4705. [Epub ahead of print]22(9):

Molecular Mechanisms Underlying TDP-43 Pathology in Cellular and Animal Models of ALS and FTLD.

Alistair Wood, Yuval Gurfinkel, Nicole Polain, Wesley Lamont, Sarah Lyn Rea.

  Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are neurodegenerative disorders that exist on a disease spectrum due to pathological, clinical and genetic overlap. In up to 97% of ALS cases and ~50% of FTLD cases, the primary pathological protein observed in affected tissues is TDP-43, which is hyperphosphorylated, ubiquitinated and cleaved. The TDP-43 is observed in aggregates that are abnormally located in the cytoplasm. The pathogenicity of TDP-43 cytoplasmic aggregates may be linked with both a loss of nuclear function and a gain of toxic functions. The cellular processes involved in ALS and FTLD disease pathogenesis include changes to RNA splicing, abnormal stress granules, mitochondrial dysfunction, impairments to axonal transport and autophagy, abnormal neuromuscular junctions, endoplasmic reticulum stress and the subsequent induction of the unfolded protein response. Here, we review and discuss the evidence for alterations to these processes that have been reported in cellular and animal models of TDP-43 proteinopathy.

Keywords:  RNA metabolism; TARDBP/TDP-43; amyotrophic lateral sclerosis; frontotemporal lobar degeneration; mitochondrial dysfunction; proteinopathy; proteostasis

DOI:  https://doi.org/10.3390/ijms22094705
Cell Death Discov. 2021 May 04. 7(1): 92

Attenuation of inhibitory PAS domain protein-induced cell death by synthetic peptides derived from Mcl-1 transmenbrane domain.

Shuya Kasai, Ken-Ichi Yasumoto, Kazuhiro Sogawa.

Expression of Inhibitory PAS domain protein (IPAS) induces apoptosis by inhibiting the anti-apoptotic activity of mitochondrial pro-survival proteins including Bcl-xL and Mcl-1 through direct binding. Analysis to examine the IPAS-binding region in Bcl-xL demonstrated that the C-terminal transmembrane (TM) domain is indispensable for the specific binding. A chimeric protein composed of the TM domain of Mcl-1 fused to the C-terminus of Citrine also exhibited a binding affinity to IPAS, and markedly attenuated apoptosis caused by the overexpression of Cerulean-IPAS in SH-SY5Y cells. HIV-1 TAT cell-penetrating peptide-conjugated synthetic peptides that cover whole or parts of the Mcl-1 TM domain showed anti-apoptotic activity in the CoCl2-induced cell death in PC12 cells. Administration of these highly effective anti-apoptotic peptides to mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that produces a reliable mouse model of Parkinson's disease (PD) decreased neuronal cell loss in the substantia nigra pars compacta. Therefore, the peptides may be considered promising therapeutic agents for neurodegenerative disorders such as PD and stroke.

DOI: https://doi.org/10.1038/s41420-021-00475-3
ACS Chem Neurosci. 2021 May 03.

Integration of Mass Spectrometry Imaging and Machine Learning Visualizes Region-Specific Age-Induced and Drug-Target Metabolic Perturbations in the Brain.

Theodosia Vallianatou, Reza Shariatgorji, Anna Nilsson, Maria Karlgren, Heather Hulme, Elva Fridjonsdottir, Per Svenningsson, Per E Andrén.

  Detailed metabolic imaging of specific brain regions in early aging may expose pathophysiological mechanisms and indicate effective neuropharmacological targets in the onset of cognitive decline. Comprehensive imaging of brain aging and drug-target effects is restricted using conventional methodology. We simultaneously visualized multiple metabolic alterations induced by normal aging in specific regions of mouse brains by integrating Fourier-transform ion cyclotron resonance mass spectrometry imaging and combined supervised and unsupervised machine learning models. We examined the interplay between aging and the response to tacrine-induced acetylcholinesterase inhibition, a well-characterized therapeutic treatment against dementia. The dipeptide carnosine (β-alanyl-l-histidine) and the vitamin α-tocopherol were significantly elevated by aging in different brain regions. l-Carnitine and acetylcholine metabolism were found to be major pathways affected by aging and tacrine administration in a brain region-specific manner, indicating altered mitochondrial function and neurotransmission. The highly interconnected hippocampus and retrosplenial cortex displayed different age-induced alterations in lipids and acylcarnitines, reflecting diverse region-specific metabolic effects. The subregional differences observed in the hippocampal formation of several lipid metabolites demonstrate the unique potential of the technique compared to standard mass spectrometry approaches. An age-induced increase of endogenous antioxidants, such as α-tocopherol, in the hippocampus was detected, suggesting an augmentation of neuroprotective mechanisms in early aging. Our comprehensive imaging approach visualized heterogeneous age-induced metabolic perturbations in mitochondrial function, neurotransmission, and lipid signaling, not always attenuated by acetylcholinesterase inhibition.

Keywords:  Acetylcholine; aging; brain metabolomics; lipids; mass spectrometry imaging; tacrine

DOI:  https://doi.org/10.1021/acschemneuro.1c00103
Front Mol Biosci. 2021 ;8 674632

CRISPR/dCas9-Mediated Parkin Inhibition Impairs Mitophagy and Aggravates Apoptosis of Rat Nucleus Pulposus Cells Under Oxidative Stress.

Tao Lan, Yu-Chen Zheng, Ning-Dao Li, Xiao-Sheng Chen, Zhe Shen, Bin Yan.

   Objective: The aim of this study is to explore the role of Parkin in intervertebral disk degeneration (IDD) and its mitophagy regulation mechanism.
Study design and methods: Rat nucleus pulposus (NP) cells were stimulated with hydrogen peroxide (H2O2) to a mimic pathological condition. Apoptosis and mitophagy were assessed by Western blot, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and immunofluorescence staining. The CRISPR-dCas9-KRAB system was used to silence the expression of Parkin.
Result: In this study, we found that Parkin was downregulated in rat NP cells under oxidative stress. In addition, treatment with H2O2 resulted in mitochondrial dysfunction, autophagy inhibition, and a significant increase in the rate of apoptosis of NP cells. Meanwhile, mitophagy inhibition enhanced H2O2-induced apoptosis. Furthermore, repression of Parkin significantly attenuated mitophagy and exacerbated apoptosis.
Conclusion: These results suggested that Parkin may play a protective role in alleviating the apoptosis of NP cells via mitophagy, and that targeting Parkin may provide a promising therapeutic strategy for the prevention of IDD.

Keywords:  CRISPR/dCas9; IDD; Parkin; apoptosis; mitophagy

DOI:  https://doi.org/10.3389/fmolb.2021.674632
Ann Clin Transl Neurol. 2021 May 05.

Brain MRS correlates with mitochondrial dysfunction biomarkers in MELAS-associated mtDNA mutations.

Laura L Gramegna, Stefania Evangelisti, Lidia Di Vito, Chiara La Morgia, Alessandra Maresca, Leonardo Caporali, Giulia Amore, Lia Talozzi, Claudio Bianchini, Claudia Testa, David N Manners, Irene Cortesi, Maria L Valentino, Rocco Liguori, Valerio Carelli, Caterina Tonon, Raffaele Lodi.

OBJECTIVE: The purpose of this study was to investigate correlations between brain proton magnetic resonance spectroscopy (1 H-MRS) findings with serum biomarkers and heteroplasmy of mitochondrial DNA (mtDNA) mutations. This study enrolled patients carrying mtDNA mutations associated with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS), and MELAS-Spectrum Syndrome (MSS).
METHODS: Consecutive patients carrying mtDNA mutations associated with MELAS and MSS were recruited and their serum concentrations of lactate, alanine, and heteroplasmic mtDNA mutant load were evaluated. The brain protocol included single-voxel 1 H-MRS (1.5T) in the medial parieto-occipital cortex (MPOC), left cerebellar hemisphere, parieto-occipital white matter (POWM), and lateral ventricles. Relative metabolite concentrations of N-acetyl-aspartate (NAA), choline (Cho), and myo-inositol (mI) were estimated relative to creatine (Cr), using LCModel 6.3.
RESULTS: Six patients with MELAS (age 28 ± 13 years, 3 [50%] female) and 17 with MSS (age 45 ± 11 years, 7 [41%] female) and 39 sex- and age-matched healthy controls (HC) were enrolled. These patients demonstrated a lower NAA/Cr ratio in MPOC compared to HC (p = 0.006), which inversely correlated with serum lactate (p = 0.021, rho = -0.68) and muscle mtDNA heteroplasmy (p < 0.001, rho = -0.80). Similarly, in the cerebellum patients had lower NAA/Cr (p < 0.001), Cho/Cr (p = 0.002), and NAA/mI (p = 0.001) ratios, which negatively correlated with mtDNA blood heteroplasmy (p = 0.001, rho = -0.81) and with alanine (p = 0.050, rho = -0.67). Ventricular lactate was present in 78.3% (18/23) of patients, correlating with serum lactate (p = 0.024, rho = 0.58).
CONCLUSION: Correlations were found between the peripheral and biochemical markers of mitochondrial dysfunction and brain in vivo markers of neurodegeneration, supporting the use of both biomarkers as signatures of MELAS and MSS disease, to evaluate the efficacy of potential treatments.

DOI: https://doi.org/10.1002/acn3.51329
Cell Discov. 2020 May 05. 6(1): 24

Mendelian neurodegenerative disease genes involved in autophagy.

Eleanna Stamatakou, Lidia Wróbel, Sandra Malmgren Hill, Claudia Puri, Sung Min Son, Motoki Fujimaki, Ye Zhu, Farah Siddiqi, Marian Fernandez-Estevez, Marco M Manni, So Jung Park, Julien Villeneuve, David Chaim Rubinsztein.

The lysosomal degradation pathway of macroautophagy (herein referred to as autophagy) plays a crucial role in cellular physiology by regulating the removal of unwanted cargoes such as protein aggregates and damaged organelles. Over the last five decades, significant progress has been made in understanding the molecular mechanisms that regulate autophagy and its roles in human physiology and diseases. These advances, together with discoveries in human genetics linking autophagy-related gene mutations to specific diseases, provide a better understanding of the mechanisms by which autophagy-dependent pathways can be potentially targeted for treating human diseases. Here, we review mutations that have been identified in genes involved in autophagy and their associations with neurodegenerative diseases.

DOI: https://doi.org/10.1038/s41421-020-0158-y
Chem Commun (Camb). 2021 May 06.

Fluorescent probe for early mitochondrial voltage dynamics.

Cinthia Hernández-Juárez, Ricardo Flores-Cruz, Arturo Jiménez-Sánchez.

Mitochondrial voltage dynamics plays a crucial role in cell healthy and disease. Here, a new fluorescent probe to monitor mitochondrial early voltage variations is described. The slowly permeant probe is retained in mitochondria during measurements to avoid interferences from natural membrane potential by incorporating an hydrolizable ester function. Voltage, local polarity, pH parameters and transmembrane dynamics were found to be deeply correlated opening a approach in mitochondrial sensing.

DOI: https://doi.org/10.1039/d1cc01944a
Mol Med Rep. 2021 Jul;pii: 492. [Epub ahead of print]24(1):

Electroacupuncture at GV20‑GB7 regulates mitophagy to protect against neurological deficits following intracerebral hemorrhage via inhibition of apoptosis.

Ruiqiao Guan, Zhihao Li, Xiaohong Dai, Wei Zou, Xueping Yu, Hao Liu, Qiuxin Chen, Wei Teng, Peng Liu, Xiaoying Liu, Shanshan Dong.

  The acupuncture penetrating line of Baihui (GV20) to Qubin (GB7) spans the parietal, frontal and temporal lobes. The present study aimed to elucidate the mechanism by which electroacupuncture (EA) at GV20‑GB7 regulates mitophagy in intracerebral hemorrhage (ICH) and whether it serves a neuroprotective role. A whole blood‑induced ICH model was used. Mitophagy‑regulating proteins, including BCL/adenovirus E1B 19 kDa‑interacting protein 3 (BNIP3), PTEN‑induced putative kinase 1 (PINK1), Parkin and apoptosis‑associated proteins were detected by western blotting; autophagy following ICH was evaluated by immunofluorescent techniques; morphological characteristics of mitophagy were observed using transmission electron microscopy; and TUNEL assay was performed to determine the number of apoptotic cells. Immunohistochemistry was used to detect p53 expression. The protective role of EA (GV20‑GB7) via enhanced mitophagy and suppressed apoptosis in ICH was further confirmed by decreased modified neurological severity score. The results showed that EA (GV20‑GB7) treatment upregulated mitochondrial autophagy following ICH and inhibited apoptotic cell death. The mechanism underlying EA (GV20‑GB7) treatment may involve inhibition of p53, an overlapping protein of autophagy and apoptosis. EA (GV20‑GB7) treatment decreased neurobehavioral deficits following ICH but pretreatment with 3‑methyladenine counteracted the beneficial effects of EA (GV20‑GB7) treatment. In conclusion, EA (GV20‑GB7) improved recovery from ICH by regulating the balance between mitophagy and apoptosis.

Keywords:  apoptosis; autophagy; electroacupuncture; intracerebral hemorrhage; mitophagy

DOI:  https://doi.org/10.3892/mmr.2021.12131
Acta Biochim Biophys Sin (Shanghai). 2021 May 06. pii: gmab057. [Epub ahead of print]

Impact of mitochondrial aldehyde dehydrogenase 2 on cognitive impairment in the AD model mouse.

Ying Yang, Wei Chen, Xiaoming Wang, Wei Ge.

  Alzheimer's disease (AD) is one of the major life-threatening diseases for the elderly because neither pathogenesis nor effective treatment is available. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) has been shown to reduce the cell-damaging aldehydes in response to reactive oxygen species (ROS). However, whether it plays a role in AD remains elusive. In the present study, we found that ALDH2 overexpression significantly improved the cognitive function of the AD mouse. Behavioral analyses of ALDH2-overexpressing APP/PS1 AD mice showed that the learning and cognitive abilities were significantly higher in these mice than in the control group APP/PS1 mice. Further open-field behavior experiments showed the same results. At the cellular level, ALDH2 protects nerve cells. HT22 cells were challenged with Aβ to establish an AD cell model, in the presence or absence of the ALDH2 activator Alda-1 and ALDH2 inhibitor Daidzin. Incubation with 50 μM Aβ for 24 h significantly reduced HT22 cell survival and cell viability, the effects of which were attenuated by the ALDH2 activator Alda-1 (50 μM). Aβ challenge promoted apoptosis and upregulated caspase3 level but suppressed Bcl-2 level, and the upregulated caspase3 level was reversed by the ALDH-2 agonist Alda-1. Aβ-induced clonal ball abnormal was reversed by Alda-1. Aβ altered the mitochondria geometry evidenced by vacuolar degeneration and membrane rupture, whereas Alda-1 changed the Aβ-induced mitochondria geometry anomalies. Moreover, superoxide anion and toxic 4-hydroxy-nonanal (4-HNE) and ROS increased by Aβ challenge were reversed by Alda-1. Meanwhile, Aβ-induced ATP reduction was reversed by Alda-1. Taken together, ALDH2 overexpression significantly improves the cognitive function of the AD mice. Furthermore, our results suggested that ALDH2 protects against Aβ hippocampal neuronal toxicity possibly through alleviating toxic aldehydes and ROS, as well as increasing ATP production to preserve mitochondrial integrity and reduce neuronal apoptosis.

Keywords:  Alzheimer’s disease (AD); mitochondrial aldehyde dehydrogenase 2 (ALDH2); β-amyloid (Aβ)

DOI:  https://doi.org/10.1093/abbs/gmab057
Channels (Austin). 2021 Dec;15(1): 424-437

Regulatory mechanisms of mitochondrial BKCa channels.

Ana L González-Cota, Carmen Santana-Calvo, Rocío Servín-Vences, Gerardo Orta, Enrique Balderas.

  The mitochondrial BKCa channel (mitoBKCa) is a splice variant of plasma membrane BKCa (Maxi-K, BKCa, Slo1, KCa1.1). While a high-resolution structure of mitoBKCa is not available yet, functional and structural studies of the plasma membrane BKCa have provided important clues on the gating of the channel by voltage and Ca2+, as well as the interaction with auxiliary subunits. To date, we know that the control of expression of mitoBKCa, targeting and voltage-sensitivity strongly depends on its association with its regulatory β1-subunit, which overall participate in the control of mitochondrial Ca2+-overload in cardiac myocytes. Moreover, novel regulatory mechanisms of mitoBKCa such as β-subunits and amyloid-β have recently been proposed. However, major basic questions including how the regulatory BKCa-β1-subunit reaches mitochondria and the mechanism through which amyloid-β impairs mitoBKCa channel function remain to be addressed.

Keywords:  BKca channels; DEC sequence; Maxi-K channels; Mitochondria; amyloid beta; beta subunits; genetic origin

DOI:  https://doi.org/10.1080/19336950.2021.1919463