bims-nenemi Biomed News
on Neuroinflammation, neurodegeneration and mitochondria
Issue of 2023–08–27
eleven papers selected by
Marco Tigano, Thomas Jefferson University



  1. bioRxiv. 2023 Apr 12. pii: 2023.04.12.536613. [Epub ahead of print]
      Senescence is a state of indefinite cell cycle arrest associated with aging, cancer, and age-related diseases. Here, using label-based mass spectrometry, ribosome profiling and nanopore direct RNA sequencing, we explore the coordinated interaction of translational and transcriptional programs of human cellular senescence. We find that translational deregulation and a corresponding maladaptive integrated stress response (ISR) is a hallmark of senescence that desensitizes senescent cells to stress. We show that senescent cells maintain high levels of eIF2α phosphorylation, typical of ISR activation, but translationally repress the stress response transcription factor 4 (ATF4) by ineffective bypass of the inhibitory upstream open reading frames. Surprisingly, ATF4 translation remains inhibited even after acute proteotoxic and amino acid starvation stressors, resulting in a highly diminished stress response. Furthermore, absent a response, stress exacerbates the senescence secretory phenotype and inflammatory pathways thus acting as a possible mechanistic link to disease. Our results reveal a novel mechanism that senescent cells exploit to evade an adaptive stress response and remain viable.
    DOI:  https://doi.org/10.1101/2023.04.12.536613
  2. bioRxiv. 2023 Aug 08. pii: 2023.07.20.549924. [Epub ahead of print]
      The nervous system plays a critical role in maintaining whole-organism homeostasis; neurons experiencing mitochondrial stress can coordinate the induction of protective cellular pathways, such as the mitochondrial unfolded protein response (UPR MT ), between tissues. However, these studies largely ignored non-neuronal cells of the nervous system. Here, we found that UPR MT activation in four, astrocyte-like glial cells in the nematode, C. elegans , can promote protein homeostasis by alleviating protein aggregation in neurons. Surprisingly, we find that glial cells utilize small clear vesicles (SCVs) to signal to neurons, which then relay the signal to the periphery using dense-core vesicles (DCVs). This work underlines the importance of glia in establishing and regulating protein homeostasis within the nervous system, which can then impact neuron-mediated effects in organismal homeostasis and longevity.
    One-Sentence Summary: Glial cells sense mitochondrial stress and signal a beneficial stress signal to promote neuronal health and longevity.
    DOI:  https://doi.org/10.1101/2023.07.20.549924
  3. Signal Transduct Target Ther. 2023 Aug 23. 8(1): 311
      As key organelles involved in cellular metabolism, mitochondria frequently undergo adaptive changes in morphology, components and functions in response to various environmental stresses and cellular demands. Previous studies of mitochondria research have gradually evolved, from focusing on morphological change analysis to systematic multiomics, thereby revealing the mitochondrial variation between cells or within the mitochondrial population within a single cell. The phenomenon of mitochondrial variation features is defined as mitochondrial heterogeneity. Moreover, mitochondrial heterogeneity has been reported to influence a variety of physiological processes, including tissue homeostasis, tissue repair, immunoregulation, and tumor progression. Here, we comprehensively review the mitochondrial heterogeneity in different tissues under pathological states, involving variant features of mitochondrial DNA, RNA, protein and lipid components. Then, the mechanisms that contribute to mitochondrial heterogeneity are also summarized, such as the mutation of the mitochondrial genome and the import of mitochondrial proteins that result in the heterogeneity of mitochondrial DNA and protein components. Additionally, multiple perspectives are investigated to better comprehend the mysteries of mitochondrial heterogeneity between cells. Finally, we summarize the prospective mitochondrial heterogeneity-targeting therapies in terms of alleviating mitochondrial oxidative damage, reducing mitochondrial carbon stress and enhancing mitochondrial biogenesis to relieve various pathological conditions. The possibility of recent technological advances in targeted mitochondrial gene editing is also discussed.
    DOI:  https://doi.org/10.1038/s41392-023-01546-w
  4. Immunohorizons. 2023 Aug 01. 7(8): 587-599
      Activated B cells experience metabolic changes that require mitochondrial remodeling, in a process incompletely defined. In this study, we report that mitochondrial antiviral signaling protein (MAVS) is involved in BCR-initiated cellular proliferation and prolonged survival. MAVS is well known as a mitochondrial-tethered signaling adaptor with a central role in viral RNA-sensing pathways that induce type I IFN. The role of MAVS downstream of BCR stimulation was recognized in absence of IFN, indicative of a path for MAVS activation that is independent of viral infection. Mitochondria of BCR-activated MAVS-deficient mouse B cells exhibited a damaged phenotype including disrupted mitochondrial morphology, excess mitophagy, and the temporal progressive blunting of mitochondrial oxidative capacity with mitochondrial hyperpolarization and cell death. Costimulation of MAVS-deficient B cells with anti-CD40, in addition to BCR stimulation, partially corrected the mitochondrial structural defects and functionality. Our data reveal a (to our knowledge) previously unrecognized role of MAVS in controlling the metabolic fitness of B cells, most noticeable in the absence of costimulatory help.
    DOI:  https://doi.org/10.4049/immunohorizons.2300038
  5. DNA (Basel). 2022 Dec;2(4): 264-278
      DNA-Protein cross-links (DPCs) are cytotoxic DNA lesions with a protein covalently bound to the DNA. Although much has been learned about the formation, repair, and biological consequences of DPCs in the nucleus, little is known regarding mitochondrial DPCs. This is due in part to the lack of robust and specific methods to measure mitochondrial DPCs. Herein, we reported an enzyme-linked immunosorbent assay (ELISA)-based method for detecting mitochondrial DPCs formed between DNA and mitochondrial transcription factor A (TFAM) in cultured human cells. To optimize the purification and detection workflow, we prepared model TFAM-DPCs via Schiff base chemistry using recombinant human TFAM and a DNA substrate containing an abasic (AP) lesion. We optimized the isolation of TFAM-DPCs using commercial silica gel-based columns to achieve a high recovery yield for DPCs. We evaluated the microplate, DNA-coating solution, and HRP substrate for specific and sensitive detection of TFAM-DPCs. Additionally, we optimized the mtDNA isolation procedure to eliminate almost all nuclear DNA contaminants. For proof of concept, we detected the different levels of TFAM-DPCs in mtDNA from HEK293 cells under different biological conditions. The method is based on commercially available materials and can be amended to detect other types of DPCs in mitochondria.
    Keywords:  DNA damage; DNA lesions; DNA repair; abasic sites; mitochondrial DNA (mtDNA); mitochondrial transcription factor A (TFAM); protein DNA adducts
    DOI:  https://doi.org/10.3390/dna2040019
  6. Cell Death Dis. 2023 Aug 26. 14(8): 561
      Cellular stress responses including the unfolded protein response (UPR) decide over the fate of an individual cell to ensure survival of the entire organism. During physiologic UPR counter-regulation, protective proteins are upregulated to prevent cell death. A similar strategy induces resistance to UPR in cancer. Therefore, we hypothesized that blocking protein synthesis following induction of UPR substantially enhances drug-induced apoptosis of malignant cells. In line, upregulation of the chaperone BiP was prevented by simultaneous arrest of protein synthesis in B cell malignancies. Cytotoxicity by immunotoxins-approved inhibitors of protein synthesis-was synergistically enhanced in combination with UPR-inducers in seven distinct hematologic and three solid tumor entities in vitro. Synergistic cell death depended on mitochondrial outer membrane permeabilization via BAK/BAX, which correlated with synergistic, IRE1α-dependent reduction of BID, accompanied by an additive fall of MCL-1. The strong synergy was reproduced in vivo against xenograft mouse models of mantle cell lymphoma, Burkitt's lymphoma, and patient-derived acute lymphoblastic leukemia. In contrast, synergy was absent in blood cells of healthy donors suggesting a tumor-specific vulnerability. Together, these data support clinical evaluation of blocking stress response counter-regulation using inhibitors of protein synthesis as a novel therapeutic strategy.
    DOI:  https://doi.org/10.1038/s41419-023-06055-w
  7. Cells. 2023 Aug 08. pii: 2017. [Epub ahead of print]12(16):
      Optic atrophy-1 (OPA1) plays a crucial role in the regulation of mitochondria fusion and participates in maintaining the structural integrity of mitochondrial cristae. Here we elucidate the role of OPA1 cleavage induced by calcium swelling in the presence of Myls22 (an OPA1 GTPase activity inhibitor) and TPEN (an OMA1 inhibitor). The rate of ADP-stimulated respiration was found diminished by both inhibitors, and they did not prevent Ca2+-induced mitochondrial respiratory dysfunction, membrane depolarization, or swelling. L-OPA1 cleavage was stimulated at state 3 respiration; therefore, our data suggest that L-OPA1 cleavage produces S-OPA1 to maintain mitochondrial bioenergetics in response to stress.
    Keywords:  OPA1; calcium retention capacity; heart mitochondria; membrane potential; mitochondrial respiration; mitochondrial swelling
    DOI:  https://doi.org/10.3390/cells12162017
  8. Inflammation. 2023 Aug 24.
      Hypoxia inducible factor-1α (HIF-1α) is a crucial therapeutic target in various diseases, including cancer and fibrosis. We previously demonstrated that transfection with double-stranded RNA (dsRNA), including polyI:C and the dsRNA genome of mammalian orthoreovirus, resulted in significant reduction in HIF-1α protein levels in cultured cells; however, it remained to be elucidated how dsRNA induced down-regulation of HIF-1α protein levels. In this study, we examined the mechanism of dsRNA-mediated down-regulation of HIF-1α protein levels. We found that among the various cellular factors involved in dsRNA-mediated innate immunity, knockdown and knockout of protein kinase R (PKR) significantly restored HIF-1α protein levels in dsRNA-transfected cells, indicating that PKR was involved in dsRNA-mediated down-regulation of HIF-1α. Proteasome inhibitors significantly restored the HIF-1α protein levels in dsRNA-transfected cells. Ubiquitination levels of HIF-1α were increased by transfection with dsRNA. These findings indicated that degradation of HIF-1α in a ubiquitin-proteasome pathway was promoted in a PKR-dependent manner following dsRNA transfection. Expression of not only HIF-1α but also several proteins, including CDK4 and HER2, was down-regulated following dsRNA transfection. These data provide important clues for elucidation of the mechanism of dsRNA-mediated cellular toxicity, as well as for therapeutic application of dsRNA.
    Keywords:  Double-stranded RNA; HIF-1α; PKR; Proteasome; Ubiquitin
    DOI:  https://doi.org/10.1007/s10753-023-01881-8
  9. bioRxiv. 2023 Aug 09. pii: 2023.08.09.552495. [Epub ahead of print]
      Cardiovascular disease continues to take more human lives than all cancer combined, prompting the need for improved research models and treatment options. Despite a significant progress in development of mature heart-on-a-chip models of fibrosis and cardiomyopathies starting from induced pluripotent stem cells (iPSCs), human cell-based models of myocardial inflammation are lacking. Here, we bioengineered a vascularized heart-on-a-chip system with circulating immune cells to model SARS-CoV-2-induced acute myocarditis. Briefly, we observed hallmarks of COVID-19-induced myocardial inflammation in the heart-on-a-chip model, as the presence of immune cells augmented the expression levels of proinflammatory cytokines, triggered progressive impairment of contractile function and altered intracellular calcium transient activities. An elevation of circulating cell-free mitochondrial DNA (ccf-mtDNA) was measured first in the in vitro heart-on-a-chip model and then validated in COVID-19 patients with low left ventricular ejection fraction (LVEF), demonstrating that mitochondrial damage is an important pathophysiological hallmark of inflammation induced cardiac dysfunction. Leveraging this platform in the context of SARS-CoV-2 induced myocardial inflammation, we established that administration of human umbilical vein-derived EVs effectively rescued the contractile deficit, normalized intracellular calcium handling, elevated the contraction force and reduced the ccf- mtDNA and chemokine release via TLR-NF-kB signaling axis.
    DOI:  https://doi.org/10.1101/2023.08.09.552495
  10. Redox Biol. 2023 Aug 18. pii: S2213-2317(23)00258-6. [Epub ahead of print]66 102857
      Radiation-induced intestinal injury (RIII), a common gastrointestinal complication caused by radiotherapy on pelvic, abdominal and retroperitoneal tumors, seriously affects the life quality of patients and may result in termination of radiotherapy. At present, the pathogenesis of RIII has not been fully understood. Herein, we demonstrated that ferroptosis played a critical role in RIII occurrence. The RNA sequencing analysis strongly hinted ferroptosis was involved in RIII mice. In line with this, the levels of 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), markers of lipid peroxidation, remarkably increased in RIII mice. And the ferroptosis inhibitor, Ferrostatin-1 (Fer-1), improved the mice survival and alleviated intestinal fibrosis in vivo. Moreover, our results revealed that arachidonic acid (AA) enhanced ferroptosis in cultured intestinal epithelial cells (IECs) and organoids in vitro after irradiation, and AA gavage aggravated RIII in mice. Mechanistic studies revealed the level of ACSL4 protein significantly increased in mouse jejunums and IECs after irradiation. Radiation-induced ferroptosis in IECs was also prevented following ACSL4 knockdown or with the function inhibitor of ACSL4. Furthermore, we found that transcription of ACSL4 induced by irradiation was regulated by STAT1/IRF1 axis, and AMPK activation triggered by AA negatively regulated radiation-induced ferroptosis. Taken together, our results suggest that ferroptosis mediates RIII and reducing dietary AA intake as well as targeting the STAT1-IRF1-ACSL4 axis or AMPK may be the potential approaches to alleviate RIII.
    Keywords:  ACSL4; Arachidonic acid; Ferroptosis; Lipid peroxidation; Radiation-induced intestinal injury
    DOI:  https://doi.org/10.1016/j.redox.2023.102857
  11. Cell Rep. 2023 Aug 20. pii: S2211-1247(23)01025-2. [Epub ahead of print]42(8): 113014
      CXCL9 expression is a strong predictor of response to immune checkpoint blockade therapy. Accordingly, we sought to develop therapeutic strategies to enhance the expression of CXCL9 and augment antitumor immunity. To perform whole-genome CRISPR-Cas9 screening for regulators of CXCL9 expression, a CXCL9-GFP reporter line is generated using a CRISPR knockin strategy. This approach finds that IRF1 limits CXCL9 expression in both tumor cells and primary myeloid cells through induction of SOCS1, which subsequently limits STAT1 signaling. Thus, we identify a subset of STAT1-dependent genes that do not require IRF1 for their transcription, including CXCL9. Targeting of either IRF1 or SOCS1 potently enhances CXCL9 expression by intratumoral macrophages, which is further enhanced in the context of immune checkpoint blockade therapy. We hence show a non-canonical role for IRF1 in limiting the expression of a subset of STAT1-dependent genes through induction of SOCS1.
    Keywords:  CP: Cancer; CRISPR-Cas9; Cxcl10; Cxcl9; DCs; Irf1; Socs1; cancer; immunotherapy; macrophages
    DOI:  https://doi.org/10.1016/j.celrep.2023.113014