bims-nenemi 2024-05-19 papers

bims-nenemi

Biomed News

on Neuroinflammation, neurodegeneration and mitochondria

Issue of 2024–05–19
eight papers selected by
Marco Tigano, Thomas Jefferson University

Oxidative stress induces release of mitochondrial DNA into the extracellular space in human placental villous trophoblast BeWo cells.
The integrated stress response promotes neural stem cell survival under conditions of mitochondrial dysfunction in neurodegeneration.
Single-cell mtDNA dynamics in tumors is driven by coregulation of nuclear and mitochondrial genomes.
Micronuclei induced by radiation, replication stress, or chromosome segregation errors do not activate cGAS-STING.
A novel MT-ATP6 variant associated with complicated ataxia in two unrelated Italian patients: case report and functional studies.
Mitochondrial F0F1-ATP synthase governs the induction of mitochondrial fission.
Residual OXPHOS is required to drive primary and metastatic lung tumours in an orthotopic breast cancer model.
Cardiolipin oxidized by ROS from complex II acts as a target of gasdermin D to drive mitochondrial pore and heart dysfunction in endotoxemia.

Am J Physiol Cell Physiol. 2024 May 13.

Oxidative stress induces release of mitochondrial DNA into the extracellular space in human placental villous trophoblast BeWo cells.

Jennifer J Gardner, Spencer C Cushen, Renee de Nazare Oliveira da Silva, Jessica L Bradshaw, Nataliia Hula, Isabelle K Gorham, Selina M Tucker, Zhengyang Zhou, Rebecca L Cunningham, Nicole R Phillips, Styliani Goulopoulou.

  Circulating cell-free mitochondrial DNA (ccf-mtDNA) is an indicator of cell death, inflammation, and oxidative stress. ccf-mtDNA differs in pregnancies with placental dysfunction from healthy pregnancies and the direction of this difference depends on gestational age and method of mtDNA quantification. Reactive oxygen species (ROS) trigger release of mtDNA from non-placental cells; yet it is unknown whether trophoblast cells release mtDNA in response to oxidative stress, a common feature of pregnancies with placental pathology. We hypothesized that oxidative stress would induce cell death and release of mtDNA from trophoblast cells. BeWo cells were treated with antimycin A (10-320 mM) or rotenone (0.2-50 mM) to induce oxidative stress. A multiplex real-time quantitative PCR (qPCR) assay was used to quantify mtDNA and nuclear DNA in membrane bound, non-membrane bound, and vesicular-bound forms in cell culture supernatants and cell lysates. Treatment with antimycin A increased ROS (p<0.0001), induced cell necrosis (p=0.0004) but not apoptosis (p=0.6471) and was positively associated with release of membrane-bound and non-membrane bound mtDNA (p<0.0001). Antimycin A increased mtDNA content in exosome-like extracellular vesicles (vesicular-bound form; p=0.0019) and reduced autophagy marker expression (LC3A/B, p=0.0002; p62, p<0.001). Rotenone treatment did not influence mtDNA release or cell death (p>0.05). Oxidative stress induces release of mtDNA into the extracellular space and causes non-apoptotic cell death and a reduction in autophagy markers in BeWo cells, an established in vitro model of human trophoblast cells. Intersection between autophagy and necrosis may mediate the release of mtDNA from the placenta in pregnancies exposed to oxidative stress.

Keywords:  mitochondrial DNA; placenta; pregnancy; reactive oxygen species; trophoblasts

DOI:  https://doi.org/10.1152/ajpcell.00091.2024
Aging Cell. 2024 May 16. e14165

The integrated stress response promotes neural stem cell survival under conditions of mitochondrial dysfunction in neurodegeneration.

Mohamed Ariff Iqbal, Maria Bilen, Yubing Liu, Vanessa Jabre, Bensun C Fong, Imane Chakroun, Smitha Paul, Jingwei Chen, Steven Wade, Michel Kanaan, Mary-Ellen Harper, Mireille Khacho, Ruth S Slack.

  Impaired mitochondrial function is a hallmark of aging and a major contributor to neurodegenerative diseases. We have shown that disrupted mitochondrial dynamics typically found in aging alters the fate of neural stem cells (NSCs) leading to impairments in learning and memory. At present, little is known regarding the mechanisms by which neural stem and progenitor cells survive and adapt to mitochondrial dysfunction. Using Opa1-inducible knockout as a model of aging and neurodegeneration, we identify a decline in neurogenesis due to impaired stem cell activation and progenitor proliferation, which can be rescued by the mitigation of oxidative stress through hypoxia. Through sc-RNA-seq, we identify the ATF4 pathway as a critical mechanism underlying cellular adaptation to metabolic stress. ATF4 knockdown in Opa1-deficient NSCs accelerates cell death, while the increased expression of ATF4 enhances proliferation and survival. Using a Slc7a11 mutant, an ATF4 target, we show that ATF4-mediated glutathione production plays a critical role in maintaining NSC survival and function under stress conditions. Together, we show that the activation of the integrated stress response (ISR) pathway enables NSCs to adapt to metabolic stress due to mitochondrial dysfunction and metabolic stress and may serve as a therapeutic target to enhance NSC survival and function in aging and neurodegeneration.

Keywords:  Hypoxia; Opa1; adult neurogenesis; intergrated stress response; metabolic adaptation; mitochondrial dynamics; neurodegeneration

DOI:  https://doi.org/10.1111/acel.14165
Nat Genet. 2024 May;56(5): 889-899

Single-cell mtDNA dynamics in tumors is driven by coregulation of nuclear and mitochondrial genomes.

Minsoo Kim, Alexander N Gorelick, Ignacio Vàzquez-García, Marc J Williams, Sohrab Salehi, Hongyu Shi, Adam C Weiner, Nick Ceglia, Tyler Funnell, Tricia Park, Sonia Boscenco, Ciara H O'Flanagan, Hui Jiang, Diljot Grewal, Cerise Tang, Nicole Rusk, Payam A Gammage, Andrew McPherson, Sam Aparicio, Sohrab P Shah, Ed Reznik.

The extent of cell-to-cell variation in tumor mitochondrial DNA (mtDNA) copy number and genotype, and the phenotypic and evolutionary consequences of such variation, are poorly characterized. Here we use amplification-free single-cell whole-genome sequencing (Direct Library Prep (DLP+)) to simultaneously assay mtDNA copy number and nuclear DNA (nuDNA) in 72,275 single cells derived from immortalized cell lines, patient-derived xenografts and primary human tumors. Cells typically contained thousands of mtDNA copies, but variation in mtDNA copy number was extensive and strongly associated with cell size. Pervasive whole-genome doubling events in nuDNA associated with stoichiometrically balanced adaptations in mtDNA copy number, implying that mtDNA-to-nuDNA ratio, rather than mtDNA copy number itself, mediated downstream phenotypes. Finally, multimodal analysis of DLP+ and single-cell RNA sequencing identified both somatic loss-of-function and germline noncoding variants in mtDNA linked to heteroplasmy-dependent changes in mtDNA copy number and mitochondrial transcription, revealing phenotypic adaptations to disrupted nuclear/mitochondrial balance.

DOI: https://doi.org/10.1038/s41588-024-01724-8
Mol Cell. 2024 May 09. pii: S1097-2765(24)00354-X. [Epub ahead of print]

Micronuclei induced by radiation, replication stress, or chromosome segregation errors do not activate cGAS-STING.

Tohru Takaki, Rhona Millar, Crispin T Hiley, Simon J Boulton.

  The cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a pivotal role in innate immune responses to viral infection and inhibition of autoimmunity. Recent studies have suggested that micronuclei formed by genotoxic stress can activate innate immune signaling via the cGAS-STING pathway. Here, we investigated cGAS localization, activation, and downstream signaling from micronuclei induced by ionizing radiation, replication stress, and chromosome segregation errors. Although cGAS localized to ruptured micronuclei via binding to self-DNA, we failed to observe cGAS activation; cGAMP production; downstream phosphorylation of STING, TBK1, or IRF3; nuclear accumulation of IRF3; or expression of interferon-stimulated genes. Failure to activate the cGAS-STING pathway was observed across primary and immortalized cell lines, which retained the ability to activate the cGAS-STING pathway in response to dsDNA or modified vaccinia virus infection. We provide evidence that micronuclei formed by genotoxic insults contain histone-bound self-DNA, which we show is inhibitory to cGAS activation in cells.

Keywords:  DNA damage; IRF3; STING; cGAS; chromosome missegregation; innate immune response; micronuclei; radiation; replication stress

DOI:  https://doi.org/10.1016/j.molcel.2024.04.017
Orphanet J Rare Dis. 2024 May 16. 19(1): 200

A novel MT-ATP6 variant associated with complicated ataxia in two unrelated Italian patients: case report and functional studies.

Daniele Sala, Silvia Marchet, Lorenzo Nanetti, Andrea Legati, Caterina Mariotti, Eleonora Lamantea, Daniele Ghezzi, Alessia Catania, Costanza Lamperti.

   BACKGROUND: MT-ATP6 is a mitochondrial gene which encodes for the intramembrane subunit 6 (or A) of the mitochondrial ATP synthase, also known asl complex V, which is involved in the last step of oxidative phosphorylation to produce cellular ATP through aerobic metabolism. Although classically associated with the NARP syndrome, recent evidence highlights an important role of MT-ATP6 pathogenic variants in complicated adult-onset ataxias.
METHODS: We describe two unrelated patients with adult-onset cerebellar ataxia associated with severe optic atrophy and mild cognitive impairment. Whole mitochondrial DNA sequencing was performed in both patients. We employed patients' primary fibroblasts and cytoplasmic hybrids (cybrids), generated from patients-derived cells, to assess the activity of respiratory chain complexes, oxygen consumption rate (OCR), ATP production and mitochondrial membrane potential.
RESULTS: In both patients, we identified the same novel m.8777 T > C variant in MT-ATP6 with variable heteroplasmy level in different tissues. We identifed an additional heteroplasmic novel variant in MT-ATP6, m.8879G > T, in the patients with the most severe phenotype. A significant reduction in complex V activity, OCR and ATP production was observed in cybrid clones homoplasmic for the m.8777 T > C variant, while no functional defect was detected in m.8879G > T homoplasmic clones. In addition, fibroblasts with high heteroplasmic levelsof m.8777 T > C variant showed hyperpolarization of mitochondrial membranes.
CONCLUSIONS: We describe a novel pathogenic mtDNA variant in MT-ATP6 associated with adult-onset ataxia, reinforcing the value of mtDNA screening within the diagnostic workflow of selected patients with late onset ataxias.

Keywords:   MT-ATP6 ; ATP synthase; Ataxia; Complex V; Cybrids; Mitochondria; OXPHOS; Oxygen consumption

DOI:  https://doi.org/10.1186/s13023-024-03212-y
iScience. 2024 May 17. 27(5): 109808

Mitochondrial F0F1-ATP synthase governs the induction of mitochondrial fission.

Charlène Lhuissier, Valérie Desquiret-Dumas, Anaïs Girona, Jennifer Alban, Justine Faure, Julien Cassereau, Philippe Codron, Guy Lenaers, Olivier R Baris, Naïg Gueguen, Arnaud Chevrollier.

  Mitochondrial dynamics is a process that balances fusion and fission events, the latter providing a mechanism for segregating dysfunctional mitochondria. Fission is controlled by the mitochondrial membrane potential (ΔΨm), optic atrophy 1 (OPA1) cleavage, and DRP1 recruitment. It is thought that this process is closely linked to the activity of the mitochondrial respiratory chain (MRC). However, we report here that MRC inhibition does not decrease ΔΨm nor increase fission, as evidenced by hyperconnected mitochondria. Conversely, blocking F0F1-ATP synthase activity induces fragmentation. We show that the F0F1-ATP synthase is sensing the inhibition of MRC activity by immediately promoting its reverse mode of action to hydrolyze matrix ATP and restoring ΔΨm, thus preventing fission. While this reverse mode is expected to be inhibited by the ATPase inhibitor ATPIF1, we show that this sensing is independent of this factor. We have unraveled an unexpected role of F0F1-ATP synthase in controlling the induction of fission by sensing and maintaining ΔΨm.

Keywords:  Biochemistry; Cell biology; Functional aspects of cell biology

DOI:  https://doi.org/10.1016/j.isci.2024.109808
Front Oncol. 2024 ;14 1362786

Residual OXPHOS is required to drive primary and metastatic lung tumours in an orthotopic breast cancer model.

Patries Herst, Georgia Carson, Danielle Lewthwaite, David Eccles, Alfonso Schmidt, Andrew Wilson, Carole Grasso, David O'Sullivan, Jiri Neuzil, Melanie McConnell, Michael Berridge.

   Background: Fast adaptation of glycolytic and mitochondrial energy pathways to changes in the tumour microenvironment is a hallmark of cancer. Purely glycolytic ρ0 tumour cells do not form primary tumours unless they acquire healthy mitochondria from their micro-environment. Here we explored the effects of severely compromised respiration on the metastatic capability of 4T1 mouse breast cancer cells.
Methods: 4T1 cell lines with different levels of respiratory capacity were generated; the Seahorse extracellular flux analyser was used to evaluate oxygen consumption rates, fluorescent confocal microscopy to assess the number of SYBR gold-stained mitochondrial DNA nucleoids, and the presence of the ATP5B protein in the cytoplasm and fluorescent in situ nuclear hybridization was used to establish ploidy. MinION nanopore RNA sequence analysis was used to compare mitochondrial DNA transcription between cell lines. Orthotopic injection was used to determine the ability of cells to metastasize to the lungs of female Balb/c mice.
Results: OXPHOS-deficient ATP5B-KO3.1 cells did not generate primary tumours. Severely OXPHOS compromised ρ0D5 cells generated both primary tumours and lung metastases. Cells generated from lung metastasis of both OXPHOS-competent and OXPHOS-compromised cells formed primary tumours but no metastases when re-injected into mice. OXPHOS-compromised cells significantly increased their mtDNA content, but this did not result in increased OXPHOS capacity, which was not due to decreased mtDNA transcription. Gene set enrichment analysis suggests that certain cells derived from lung metastases downregulate their epithelial-to-mesenchymal related pathways.
Conclusion: In summary, OXPHOS is required for tumorigenesis in this orthotopic mouse breast cancer model but even very low levels of OXPHOS are sufficient to generate both primary tumours and lung metastases.

Keywords:  breast cancer; glycolysis; intercellular mitochondrial transport; metastasis; orthotopic mouse model; oxidative phosphorylation

DOI:  https://doi.org/10.3389/fonc.2024.1362786
Cell Rep. 2024 May 15. pii: S2211-1247(24)00565-5. [Epub ahead of print]43(5): 114237

Cardiolipin oxidized by ROS from complex II acts as a target of gasdermin D to drive mitochondrial pore and heart dysfunction in endotoxemia.

Yan Tang, Junru Wu, Xuejing Sun, Shasha Tan, Wenbo Li, Siyu Yin, Lun Liu, Yuanyuan Chen, Yuanyuan Liu, Qian Tan, Youxiang Jiang, Wenjing Yang, Wei Huang, Chunyan Weng, Qing Wu, Yao Lu, Hong Yuan, Qingzhong Xiao, Alex F Chen, Qingbo Xu, Timothy R Billiar, Jingjing Cai.

  Cardiac dysfunction, an early complication of endotoxemia, is the major cause of death in intensive care units. No specific therapy is available at present for this cardiac dysfunction. Here, we show that the N-terminal gasdermin D (GSDMD-N) initiates mitochondrial apoptotic pore and cardiac dysfunction by directly interacting with cardiolipin oxidized by complex II-generated reactive oxygen species (ROS) during endotoxemia. Caspase-4/11 initiates GSDMD-N pores that are subsequently amplified by the upregulation and activation of NLRP3 inflammation through further generation of ROS. GSDMD-N pores form prior to BAX and VDAC1 apoptotic pores and further incorporate into BAX and VDAC1 oligomers within mitochondria membranes to exacerbate the apoptotic process. Our findings identify oxidized cardiolipin as the definitive target of GSDMD-N in mitochondria of cardiomyocytes during endotoxin-induced myocardial dysfunction (EIMD), and modulation of cardiolipin oxidation could be a therapeutic target early in the disease process to prevent EIMD.

Keywords:  CP: Immunology; cardiolipin; complex II; endotoxin-induced myocardial dysfunction; gasdermin D; mitochondria

DOI:  https://doi.org/10.1016/j.celrep.2024.114237