bims-medebr 2023-12-31 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2023–12–31
twelve papers selected by
Regina F. Fernández, Johns Hopkins University

Cholesterol redistribution triggered by CYP46A1 gene therapy improves major hallmarks of Niemann-Pick type C disease but is not sufficient to halt neurodegeneration.
Inhibition of lipid synthesis by the HIV integrase strand transfer inhibitor elvitegravir in primary rat oligodendrocyte cultures.
Phospholipase Modulation of Synaptic Membrane Landscape: Driving Force Behind Memory Formation?
Protein N-myristoylation plays a critical role in the mitochondrial localization of human mitochondrial complex I accessory subunit NDUFB7.
Increased neurotoxicity of high-density lipoprotein secreted from murine reactive astrocytes deficient in a peroxisomal very-long-chain fatty acid transporter Abcd1.
Hippocampal metabolic profile during epileptogenesis in the pilocarpine model of epilepsy.
Astrocytes control hippocampal synaptic plasticity through the vesicular-dependent release of D-serine.
Datasets assessing lipid-content in optically cleared brains.
The role of lysine acetylation in the function of mitochondrial ribosomal protein L12.
Glymphatic dysfunction coincides with lower GABA levels and sleep disturbances in succinic semialdehyde dehydrogenase deficiency.
Regulation of respiratory complex I assembly by FMN cofactor targeting.
Opto-Lipidomics of Tissues.

Biochim Biophys Acta Mol Basis Dis. 2023 Dec 22. pii: S0925-4439(23)00359-9. [Epub ahead of print] 166993

Cholesterol redistribution triggered by CYP46A1 gene therapy improves major hallmarks of Niemann-Pick type C disease but is not sufficient to halt neurodegeneration.

Maria João Nunes, Andreia Neves Carvalho, Joana Reis, Daniela Costa, Miguel Moutinho, Joana Mateus, Rita Mendes de Almeida, Sara Brito, Daniela Risso, Sofia Nunes, Margarida Castro-Caldas, Maria João Gama, Cecília M P Rodrigues, Sara Xapelli, Maria José Diógenes, Nathalie Cartier, Farah Chali, Françoise Piguet, Elsa Rodrigues.

  Cholesterol 24-hydroxylase (CYP46A1) is an exclusively neuronal cytochrome P450 enzyme responsible for converting cholesterol into 24S-hydroxycholesterol, which serves as the primary pathway for eliminating cholesterol in the brain. We and others have shown that increased activity of CYP46A1 leads to reduced levels of cholesterol and has a positive effect on cognition. Therefore, we hypothesized that CYP46A1 could be a potential therapeutic target in Niemann-Pick type C (NPC) disease, a rare and fatal neurodegenerative disorder, characterized by cholesterol accumulation in endolysosomal compartments. Herein, we show that CYP46A1 ectopic expression, in cellular models of NPC and in Npc1tm(I1061T) mice by adeno-associated virus-mediated gene therapy improved NPC disease phenotype. Amelioration in functional, biochemical, molecular and neuropathological hallmarks of NPC disease were characterized. In vivo, CYP46A1 expression partially prevented weight loss and hepatomegaly, corrected the expression levels of genes involved in cholesterol homeostasis, and promoted a redistribution of brain cholesterol accumulated in late endosomes/lysosomes. Moreover, concomitant with the amelioration of cholesterol metabolism dysregulation, CYP46A1 attenuated microgliosis and lysosomal dysfunction in mouse cerebellum, favoring a pro-resolving phenotype. In vivo CYP46A1 ectopic expression improves important features of NPC disease and may represent a valid therapeutic approach to be used concomitantly with other drugs. However, promoting cholesterol redistribution does not appear to be enough to prevent Purkinje neuronal death in the cerebellum. This indicates that cholesterol buildup in neurons might not be the main cause of neurodegeneration in this human lipidosis.

Keywords:  Brain cholesterol metabolism; CYP46A1; Gene therapy; Neurodegeneration; Niemann pick type C disorders

DOI:  https://doi.org/10.1016/j.bbadis.2023.166993
Front Mol Neurosci. 2023 ;16 1323431

Inhibition of lipid synthesis by the HIV integrase strand transfer inhibitor elvitegravir in primary rat oligodendrocyte cultures.

Hubert Monnerie, Micah Romer, Lindsay M Roth, Caela Long, John S Millar, Kelly L Jordan-Sciutto, Judith B Grinspan.

  Combined antiretroviral therapy (cART) has greatly decreased mortality and morbidity among persons with HIV; however, neurologic impairments remain prevalent, in particular HIV-associated neurocognitive disorders (HANDs). White matter damage persists in cART-treated persons with HIV and may contribute to neurocognitive dysfunction as the lipid-rich myelin membrane of oligodendrocytes is essential for efficient nerve conduction. Because of the importance of lipids to proper myelination, we examined the regulation of lipid synthesis in oligodendrocyte cultures exposed to the integrase strand transfer inhibitor elvitegravir (EVG), which is administered to persons with HIV as part of their initial regimen. We show that protein levels of genes involved in the fatty acid pathway were reduced, which correlated with greatly diminished de novo levels of fatty acid synthesis. In addition, major regulators of cellular lipid metabolism, the sterol regulatory element-binding proteins (SREBP) 1 and 2, were strikingly altered following exposure to EVG. Impaired oligodendrocyte differentiation manifested as a marked reduction in mature oligodendrocytes. Interestingly, most of these deleterious effects could be prevented by adding serum albumin, a clinically approved neuroprotectant. These new findings, together with our previous study, strengthen the possibility that antiretroviral therapy, at least partially through lipid dysregulation, may contribute to the persistence of white matter changes observed in persons with HIV and that some antiretrovirals may be preferable as life-long therapy.

Keywords:  HIV; Hand; SREBP; cART; myelin; oligodendrocyte

DOI:  https://doi.org/10.3389/fnmol.2023.1323431
Cold Spring Harb Perspect Biol. 2023 Dec 27. pii: a041405. [Epub ahead of print]

Phospholipase Modulation of Synaptic Membrane Landscape: Driving Force Behind Memory Formation?

Tristan P Wallis, Frédéric A Meunier.

The synapse is the communication unit of the brain, linking billions of neurons through trillions of synaptic connections. The lipid landscape of the synaptic membrane underpins neurotransmitter release through the exocytic fusion of neurotransmitter-containing vesicles, endocytic recycling of these synaptic vesicles, and the postsynaptic response following binding of the neurotransmitter to specialized receptors. How the connected brain can learn and acquire memories through synaptic plasticity is unresolved. Phospholipases, and especially the phospholipase A1 isoform DDHD2, have recently been shown to play a critical role in memory acquisition through the generation of saturated free fatty acids such as myristic and palmitic acids. This emerging synaptic plasticity pathway suggests that phospholipases cannot only respond to synaptic activity by altering the phospholipid landscape but also contribute to the establishment of long-term memories in our brain.

DOI: https://doi.org/10.1101/cshperspect.a041405
Sci Rep. 2023 12 27. 13(1): 22991

Protein N-myristoylation plays a critical role in the mitochondrial localization of human mitochondrial complex I accessory subunit NDUFB7.

Haruna Harada, Koko Moriya, Hirotsugu Kobuchi, Naotada Ishihara, Toshihiko Utsumi.

The present study examined human N-myristoylated proteins that specifically localize to mitochondria among the 1,705 human genes listed in MitoProteome, a mitochondrial protein database. We herein employed a strategy utilizing cellular metabolic labeling with a bioorthogonal myristic acid analog in transfected COS-1 cells established in our previous studies. Four proteins, DMAC1, HCCS, NDUFB7, and PLGRKT, were identified as N-myristoylated proteins that specifically localize to mitochondria. Among these proteins, DMAC1 and NDUFB7 play critical roles in the assembly of complex I of the mitochondrial respiratory chain. DMAC1 functions as an assembly factor, and NDUFB7 is an accessory subunit of complex I. An analysis of the intracellular localization of non-myristoylatable G2A mutants revealed that protein N-myristoylation occurring on NDUFB7 was important for the mitochondrial localization of this protein. Furthermore, an analysis of the role of the CHCH domain in NDUFB7 using Cys to Ser mutants revealed that it was essential for the mitochondrial localization of NDUFB7. Therefore, the present results showed that NDUFB7, a vital component of human mitochondrial complex I, was N-myristoylated, and protein N-myrisotylation and the CHCH domain were both indispensable for the specific targeting and localization of NDUFB7 to mitochondria.

DOI: https://doi.org/10.1038/s41598-023-50390-z
J Inherit Metab Dis. 2023 Dec 25.

Increased neurotoxicity of high-density lipoprotein secreted from murine reactive astrocytes deficient in a peroxisomal very-long-chain fatty acid transporter Abcd1.

Naoki Fujitani, Tomoya Akashi, Masayoshi Saito, Masashi Morita, Takanori So, Kozo Oka.

  X-linked adrenoleukodystrophy (X-ALD) is a genetic neurodegenerative disorder caused by pathogenic variants in ABCD1, resulting in the accumulation of very-long-chain fatty acids (VLCFAs) in tissues. The etiology of X-ALD is unclear. Activated astrocytes play a pathological role in X-ALD. Recently, reactive astrocytes have been shown to induce neuronal cell death via saturated lipids in high-density lipoprotein (HDL), although how HDL from reactive astrocytes exhibits neurotoxic effects has yet to be determined. In this study, we obtained astrocytes from wild-type and Abcd1-deficient mice. HDL was purified from the culture supernatant of astrocytes, and the effect of HDL on neurons was evaluated in vitro. To our knowledge, this study shows for the first time that HDL obtained from Abcd1-deficient reactive astrocytes induces a significantly higher level of lactate dehydrogenase (LDH) release, a marker of cell damage, from mouse primary cortical neurons as compared to HDL from wild-type reactive astrocytes. Notably, HDL from Abcd1-deficient astrocytes contained significantly high amounts of VLCFA-containing phosphatidylcholine (PC) and LysoPC. Activation of Abcd1-deficient astrocytes led to the production of HDL containing decreased amounts of PC with arachidonic acid in sn-2 acyl moieties and increased amounts of LysoPC, presumably through cytosolic phospholipase A2 α upregulation. These results suggest that compositional changes in PC and LysoPC in HDL, due to Abcd1 deficiency and astrocyte activation, may contribute to neuronal damage. Our findings provide novel insights into central nervous system pathology in X-ALD.

Keywords:  adrenoleukodystrophy; high-density lipoprotein; lysophosphatidylcholine; neurotoxicity; reactive astrocyte; very-long-chain fatty acid

DOI:  https://doi.org/10.1002/jimd.12703
Biomed Chromatogr. 2023 Dec 28. e5820

Hippocampal metabolic profile during epileptogenesis in the pilocarpine model of epilepsy.

Letícia Meier, Estevan Bruginski, Joseane Righes Marafiga, Letícia Barbieri Caus, Mayara Vendramin Pasquetti, Maria Elisa Calcagnotto, Francinete Ramos Campos.

  Temporal lobe epilepsy (TLE) is a common form of refractory epilepsy in adulthood. The metabolic profile of epileptogenesis is still poorly investigated. Elucidation of such a metabolic profile using animal models of epilepsy could help identify new metabolites and pathways involved in the mechanisms of epileptogenesis process. In this study, we evaluated the metabolic profile during the epileptogenesis periods. Using a pilocarpine model of epilepsy, we analyzed the global metabolic profile of hippocampal extracts by untargeted metabolomics based on ultra-performance liquid chromatography-high-resolution mass spectrometry, at three time points (3 h, 1 week, and 2 weeks) after status epilepticus (SE) induction. We demonstrated that epileptogenesis periods presented different hippocampal metabolic profiles, including alterations of metabolic pathways of amino acids and lipid metabolism. Six putative metabolites (tryptophan, N-acetylornithine, N-acetyl-L-aspartate, glutamine, adenosine, and cholesterol) showed significant different levels during epileptogenesis compared to their respective controls. These putative metabolites could be associated with the imbalance of neurotransmitters, mitochondrial dysfunction, and cell loss observed during both epileptogenesis and epilepsy. With these findings, we provided an overview of hippocampal metabolic profiles during different stages of epileptogenesis that could help investigate pathways and respective metabolites as predictive tools in epilepsy.

Keywords:  UPLC-HRMS; epileptogenesis; metabolic profile; pilocarpine model; temporal lobe epilepsy; untargeted metabolomics

DOI:  https://doi.org/10.1002/bmc.5820
Front Cell Neurosci. 2023 ;17 1282841

Astrocytes control hippocampal synaptic plasticity through the vesicular-dependent release of D-serine.

Daniela Sofia Abreu, Joana I Gomes, Filipa F Ribeiro, Maria J Diógenes, Ana M Sebastião, Sandra H Vaz.

  Astrocytes, the most abundant glial cells in the central nervous system (CNS), sense synaptic activity and respond through the release of gliotransmitters, a process mediated by intracellular Ca2+ level changes and SNARE-dependent mechanisms. Ionotropic N-methyl-D-aspartate (NMDA) receptors, which are activated by glutamate along with D-serine or glycine, play a crucial role in learning, memory, and synaptic plasticity. However, the precise impact of astrocyte-released D-serine on neuronal modulation remains insufficiently characterized. To address this, we have used the dominant negative SNARE (dnSNARE) mouse model, which selectively inhibits SNARE-dependent exocytosis from astrocytes. We recorded field excitatory postsynaptic potentials (fEPSPs) in CA3-CA1 synapses within hippocampal slices obtained from dnSNARE mice and wild-type (Wt) littermates. Our results demonstrate that hippocampal θ-burst long-term potentiation (LTP), a critical form of synaptic plasticity, is impaired in hippocampal slices from dnSNARE mice. Notably, this LTP impairment was rescued upon incubation with D-serine. To further investigate the involvement of astrocytes in D-serine-mediated mechanisms of LTP maintenance, we perfused hippocampal slices with L-serine - a substrate used by both neurons and astrocytes for D-serine production. The enhancement in LTP observed in dnSNARE mice was exclusively associated with D-serine presence, with no effects evident in the presence of L-serine. Additionally, both D- and L-serine reduced basal synaptic strength in the hippocampal slices of both Wt and dnSNARE mice. These results provide compelling evidence that distinct processes underlie the modulation of basal synaptic transmission and LTP through D-serine. Our findings underscore the pivotal contribution of astrocytes in D-serine-mediated processes that govern LTP establishment and basal transmission. This study not only provides essential insights into the intricate interplay between neurons and astrocytes but also emphasizes their collective role in shaping hippocampal synaptic function.

Keywords:  astrocyte; d-serine; gliotransmission; synaptic plasticity; tripartite synapse

DOI:  https://doi.org/10.3389/fncel.2023.1282841
Data Brief. 2024 Feb;52 109795

Datasets assessing lipid-content in optically cleared brains.

Shimrit Oz, Galit Saar, Shunit Olszakier, Ronit Heinrich, Mykhail O Kompanets, Shai Berlin.

  Multi-modal imaging, by light-microscopy (LM) and Magnetic Resonance Imaging (MRI), holds promise for examining the brain across various resolutions and scales. While MRI acquires images in three dimensions, acquisition of intact whole-brain by LM requires a process of tissue clearing that renders the brain transparent. Removal of lipids (delipidation) is a critical step in the tissue clearing process, and was previsouly suggested to be the cause for absence of MRI contrast in cleared brains. Yet, the association between MRI contrast, delipidation and the different clearing techniques is debatable. Here, we provide datasets concerning lipid-content in cleared brain tissues obtained by various approaches. Fixed mouse and rat brains were cleared by CLARITY, Scale, uDISCO and ECi clearing techniques. Lipid-content was assessed at various intermediate steps of the different clearing methods, as well as at the end of the processes. Methods employed included whole brain MRI acquisition, Oil Red O (ORO)- and carbocyanine DiI-staining of cryosections, and DiI-washout assay from brain slices. MRI contrast-to-noise ratio, staining intensities and integrity of tissue were systematically analyzed. We demonstrate that lipid electrophoresis, an essential step of the CLARITY approach, engenders progressive reduction in MRI contrast in non-cleared (PFA-fixed) control brains, as well as strongly reduces contrast from uDISCO and ECi-cleared brains. ORO minimally stained CLARITY-cleared brains, however efficiently labelled uDISCO and ECi-cleared brains. Conversely, and in contrast to ORO-staining, DiI equally stained control, CLARITY, ECi and uDISCO-cleared brains. Both ORO- and DiI-staining demonstrated impairment in brain tissue integrity following CLARITY, but less so in uDISCO and ECi brains. DiI-washout assay demonstrated that each of the solvents employed along the process of uDISCO and ECi are highly delipidating, as well as the SDS-electrophoresis employed during CLARITY clearing. However, Scale treatment preserved most of the DiI dye. These data emphasize the variability in lipid assessment of cleared tissues by common techniques, and may help to resolve the contribution of lipids in brain MRI contrast.

Keywords:  Fluorescent probe; Histochemistry; Imaging; Lipids; MRI; Tissue-clearing

DOI:  https://doi.org/10.1016/j.dib.2023.109795
Proteins. 2023 Dec 25.

The role of lysine acetylation in the function of mitochondrial ribosomal protein L12.

Katelynn V Paluch, Karlie R Platz, Emma J Rudisel, Ryan R Erdmann, Taylor R Laurin, Kristin E Dittenhafer-Reed.

  Mitochondria play a central role in energy production and cellular metabolism. Mitochondria contain their own small genome (mitochondrial DNA, mtDNA) that carries the genetic instructions for proteins required for ATP synthesis. The mitochondrial proteome, including the mitochondrial transcriptional machinery, is subject to post-translational modifications (PTMs), including acetylation and phosphorylation. We set out to determine whether PTMs of proteins associated with mtDNA may provide a potential mechanism for the regulation of mitochondrial gene expression. Here, we focus on mitochondrial ribosomal protein L12 (MRPL12), which is thought to stabilize mitochondrial RNA polymerase (POLRMT) and promote transcription. Numerous acetylation sites of MRPL12 were identified by mass spectrometry. We employed amino acid mimics of the acetylated (lysine to glutamine mutants) and deacetylated (lysine to arginine mutants) versions of MRPL12 to interrogate the role of lysine acetylation in transcription initiation in vitro and mitochondrial gene expression in HeLa cells. MRPL12 acetyl and deacetyl protein mimics were purified and assessed for their ability to impact mtDNA promoter binding of POLRMT. We analyzed mtDNA content and mitochondrial transcript levels in HeLa cells upon overexpression of acetyl and deacetyl mimics of MRPL12. Our results suggest that MRPL12 single-site acetyl mimics do not change the mtDNA promoter binding ability of POLRMT or mtDNA content in HeLa cells. Individual acetyl mimics may have modest effects on mitochondrial transcript levels. We found that the mitochondrial deacetylase, Sirtuin 3, is capable of deacetylating MRPL12 in vitro, suggesting a potential role for dynamic acetylation controlling MRPL12 function in a role outside of the regulation of gene expression.

Keywords:  acetylation; mitochondrial DNA; mitochondrial genome; mitochondrial proteins; post-translational protein modification; transcription

DOI:  https://doi.org/10.1002/prot.26654
J Sleep Res. 2023 Dec 26. e14105

Glymphatic dysfunction coincides with lower GABA levels and sleep disturbances in succinic semialdehyde dehydrogenase deficiency.

Itay Tokatly Latzer, Edward Yang, Onur Afacan, Erland Arning, Alexander Rotenberg, Henry H C Lee, Jean-Baptiste Roullet, Phillip L Pearl.

  Succinic semialdehyde dehydrogenase deficiency (SSADHD) is an inherited metabolic disorder of γ-aminobutyrate (GABA) catabolism. Cerebral waste clearance along glymphatic perivascular spaces depends on aquaporin 4 (AQP4) water channels, the function of which was shown to be influenced by GABA. Sleep disturbances are associated independently with SSADHD and glymphatic dysfunction. This study aimed to determine whether indices of the hyperGABAergic state characteristic of SSADHD coincide with glymphatic dysfunction and sleep disturbances and to explicate the modulatory effect that GABA may have on the glymphatic system. The study included 42 individuals (21 with SSADHD; 21 healthy controls) who underwent brain MRIs and magnetic resonance spectroscopy (MRS) for assessment of glymphatic dysfunction and cortical GABA, plasma GABA measurements, and circadian clock gene expression. The SSADHD subjects responded to an additional Children's Sleep Habits Questionnaire (CSHQ). Compared with the control group, SSADHD subjects did not differ in sex and age but had a higher severity of enlarged perivascular spaces in the centrum semiovale (p < 0.001), basal ganglia (p = 0.01), and midbrain (p = 0.001), as well as a higher MRS-derived GABA/NAA peak (p < 0.001). Within the SSADHD group, the severity of glymphatic dysfunction was specific for a lower MRS-derived GABA/NAA (p = 0.04) and lower plasma GABA (p = 0.004). Additionally, the degree of their glymphatic dysfunction correlated with the CSHQ-estimated sleep disturbances scores (R = 5.18, p = 0.03). In the control group, EPVS burden did not correlate with age or cerebral and plasma GABA values. The modulatory effect that GABA may exert on the glymphatic system has therapeutic implications for sleep-related disorders and neurodegenerative conditions associated with glymphatic dysfunction.

Keywords:  4-hydroxybutyric aciduria; ALDH5A1; gamma-aminobutyric acid; perivascular; sleep

DOI:  https://doi.org/10.1111/jsr.14105
Redox Biol. 2023 Dec 20. pii: S2213-2317(23)00402-0. [Epub ahead of print]69 103001

Regulation of respiratory complex I assembly by FMN cofactor targeting.

Andrea Curtabbi, Adela Guarás, José Luis Cabrera-Alarcón, Maribel Rivero, Enrique Calvo, Marina Rosa-Moreno, Jesús Vázquez, Milagros Medina, José Antonio Enríquez.

  Respiratory complex I plays a crucial role in the mitochondrial electron transport chain and shows promise as a therapeutic target for various human diseases. While most studies focus on inhibiting complex I at the Q-site, little is known about inhibitors targeting other sites within the complex. In this study, we demonstrate that diphenyleneiodonium (DPI), a N-site inhibitor, uniquely affects the stability of complex I by reacting with its flavin cofactor FMN. Treatment with DPI blocks the final stage of complex I assembly, leading to the complete and reversible degradation of complex I in different cellular models. Growing cells in medium lacking the FMN precursor riboflavin or knocking out the mitochondrial flavin carrier gene SLC25A32 results in a similar complex I degradation. Overall, our findings establish a direct connection between mitochondrial flavin homeostasis and complex I stability and assembly, paving the way for novel pharmacological strategies to regulate respiratory complex I.

Keywords:  DPI; FMN; OXPHOS; Respiratory complex I

DOI:  https://doi.org/10.1016/j.redox.2023.103001
Adv Sci (Weinh). 2023 Dec 25. e2302962

Opto-Lipidomics of Tissues.

Magnus Jensen, Shiyue Liu, Elzbieta Stepula, Davide Martella, Anahid A Birjandi, Keith Farrell-Dillon, Ka Lung Andrew Chan, Maddy Parsons, Ciro Chiappini, Sarah J Chapple, Giovanni E Mann, Tom Vercauteren, Vincenzo Abbate, Mads S Bergholt.

  Lipid metabolism and signaling play pivotal functions in biology and disease development. Despite this, currently available optical techniques are limited in their ability to directly visualize the lipidome in tissues. In this study, opto-lipidomics, a new approach to optical molecular tissue imaging is introduced. The capability of vibrational Raman spectroscopy is expanded to identify individual lipids in complex tissue matrices through correlation with desorption electrospray ionization (DESI) - mass spectrometry (MS) imaging in an integrated instrument. A computational pipeline of inter-modality analysis is established to infer lipidomic information from optical vibrational spectra. Opto-lipidomic imaging of transient cerebral ischemia-reperfusion injury in a murine model of ischemic stroke demonstrates the visualization and identification of lipids in disease with high molecular specificity using Raman scattered light. Furthermore, opto-lipidomics in a handheld fiber-optic Raman probe is deployed and demonstrates real-time classification of bulk brain tissues based on specific lipid abundances. Opto-lipidomics opens a host of new opportunities to study lipid biomarkers for diagnostics, prognostics, and novel therapeutic targets.

Keywords:  Raman spectroscopy; lipidomics; mass spectrometry

DOI:  https://doi.org/10.1002/advs.202302962