bims-cesemi Biomed News
on Cellular senescence and mitochondria
Issue of 2024–11–24
sixteen papers selected by
Julio Cesar Cardenas, Universidad Mayor



  1. Biochem Biophys Res Commun. 2024 Nov 12. pii: S0006-291X(24)01526-2. [Epub ahead of print]739 150990
      The multifunctional promyelocytic leukemia protein (PML) is involved in the regulation of various cellular processes in both physiological and pathological conditions. Specifically, PML is one of the inositol-1,4,5-trisphosphate receptors (IP3Rs) activity regulators and can influence Ca2+ transport from the endoplasmic reticulum (ER) to mitochondria. In this work, the effects of PML knockout on calcium homeostasis in the cytosol, ER, and mitochondria of HeLa cells were studied upon stimulation with histamine, which induces Ca2+ mobilization from the ER via IP3Rs. We utilized calcium indicators with different subcellular localizations, including synthetic dyes Fura-2 (cytosolic), Xrhod-5F (mitochondrial), and protein sensor R-CEPIAer (ER), as well as mitochondrial potential-sensitive probes Rh123 and TMRM. Our results show that PML knockout induced changes in HeLa cell and mitochondrial morphology, slightly decreased basal and integral Ca2+ levels, enhanced mitochondrial Ca2+ uptake from the cytoplasm, and maintained residual mitochondrial potential after depolarization. Additionally, it reduced the Ca2+ pool in ER membranes not associated with histamine receptor activation and, consequently, IP3Rs. These findings suggest that changes in calcium ion transport due to PML knockout in HeLa cells affect mitochondrial activity.
    Keywords:  Endoplasmic reticulum; Fluorescence microscopy; Intracellular calcium; Mitochondria; Mitochondria-associated membranes (MAMs)
    DOI:  https://doi.org/10.1016/j.bbrc.2024.150990
  2. J Biochem. 2024 Nov 16. pii: mvae079. [Epub ahead of print]
      Cellular senescence is an irreversible cell cycle arrest induced by stresses such as telomere shortening and oncogene activation. It acts as a tumor suppressor mechanism that prevents the proliferation of potentially tumorigenic cells. Paradoxically, senescent stromal cells that arise in the tumor microenvironment have been shown to promote tumor progression. In addition, senescent cells that accumulate in vivo over time are thought to contribute to aging and age-related diseases. These deleterious effects of senescent cells involve the secretion of bioactive molecules such as inflammatory cytokines and chemokines, a phenomenon known as the senescence-associated secretory phenotype (SASP). While the role of cellular senescence in vivo is becoming increasingly clear, the intracellular signaling pathways that induce the expression of senescent phenotypes are not fully understood. In this review, we outline senescence-associated signaling pathways and their relevance to cancer and aging.
    Keywords:  SASP; aging; cancer; cellular senescence; stress signaling
    DOI:  https://doi.org/10.1093/jb/mvae079
  3. Free Radic Biol Med. 2024 Nov 16. pii: S0891-5849(24)01018-9. [Epub ahead of print]226 237-250
       INTRODUCTION: Skeletal muscle mitochondrial dysfunction is a key characteristic of aging muscle and contributes to age related diseases such as sarcopenia, frailty, and type 2 diabetes. Mitochondrial oxidative stress has been implicated as a driving factor in these age-related diseases, however whether it is a cause, or a consequence of mitochondrial dysfunction remains to be determined. The development of flexible genetic models is an important tool to test the mechanistic role of mitochondrial oxidative stress on skeletal muscle metabolic dysfunction. We characterize a new model of inducible and reversible mitochondrial redox stress using a tetracycline controlled skeletal muscle specific short hairpin RNA targeted to superoxide dismutase 2 (iSOD2).
    METHODS: iSOD2 KD and control (CON) animals were administered doxycycline for 3- or 12- weeks and followed for up to 24 weeks and mitochondrial respiration and muscle contraction were measured to define the time course of SOD2 KD and muscle functional changes and recovery.
    RESULTS: Maximum knockdown of SOD2 protein occurred by 6 weeks and recovered by 24 weeks after DOX treatment. Mitochondrial aconitase activity and maximum mitochondrial respiration declined in KD muscle by 12 weeks and recovered by 24 weeks. There were no significant differences in antioxidant or mitochondrial biogenesis genes between groups. Twelve-week KD showed a small, but significant decrease in muscle fatigue resistance. The primary phenotype was reduced metabolic flexibility characterized by impaired pyruvate driven respiration when other substrates are present. The pyruvate dehydrogenase kinase inhibitor dichloroacetate partially restored pyruvate driven respiration, while the thiol reductant DTT did not.
    CONCLUSION: We use a model of inducible and reversible skeletal muscle SOD2 knockdown to demonstrate that elevated matrix superoxide reversibly impairs mitochondrial substrate flexibility characterized by impaired pyruvate oxidation. Despite the bioenergetic effect, the limited change in gene expression suggests that the elevated redox stress in this model is confined to the mitochondrial matrix.
    Keywords:  Inducible SOD2 knockdown; Metabolic inflexibility; Mitochondrial oxidative stress; Mitochondrial respiration; Pyruvate oxidation; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.10.310
  4. J Cell Sci. 2024 Nov 21. pii: jcs.261844. [Epub ahead of print]
      Therapy-induced senescence (TIS) in Glioblastoma (GBM) residual disease and escape from TIS account for resistance and recurrence, but the mechanism of TIS manifestation remains obscure. Here, we demonstrate that replication stress (RS) is critical for the induction of TIS in residual cells by employing an in-vitro GBM therapy-resistance cellular model. Interestingly, we found a 'bi-phasic' mode of DNA damage after radiation treatment and revealed that the second phase of DNA damage arises majorly in the S-phase of residual cells due to RS. Mechanistically, we show that persistent phosphorylated ATR is a safeguard for radiation resilience, while the other canonical RS molecules remain unaltered during the second phase of DNA damage. Importantly, RS precedes the induction of senescence, and ATR inhibition results in TIS reduction, leading to apoptosis. Moreover, ATR inhibition sensitized PARP-1 inhibitor-induced enhanced TIS-mediated resistance, leading to cell death. Our study demonstrates the crucial role of RS in TIS induction and maintenance in GBM residual cells, and targeting ATR alone or in combination with a PARPi will be an effective strategy to eliminate TIS for better treatment outcomes.
    Keywords:  ATR; Biphasic DNA damage response; Glioblastoma; Replication stress; Therapy resistance; Therapy-induced senescence
    DOI:  https://doi.org/10.1242/jcs.261844
  5. Cell Calcium. 2024 Nov 16. pii: S0143-4160(24)00129-5. [Epub ahead of print]124 102971
      In a comment to our recent publication, Nicholls question our results and interpretation based on theoretical arguments that reveal a profound misunderstanding of our publication.
    Keywords:  Antiporters; Membrane potential; Mitochondria; Sodium proton exchange
    DOI:  https://doi.org/10.1016/j.ceca.2024.102971
  6. Transl Med Commun. 2024 ;pii: 21. [Epub ahead of print]9(1):
       Background: Many tumors contain hypoxic microenvironments caused by inefficient tumor vascularization. Hypoxic tumors have been shown to resist conventional cancer therapies. Hypoxic cancer cells rely on glucose to meet their energetic and anabolic needs to fuel uncontrolled proliferation and metastasis. This glucose dependency is linked to a metabolic shift in response to hypoxic conditions.
    Methods: To leverage the glucose dependency of hypoxic tumor cells, we assessed the effects of a mild reduction in systemic glucose by controlling both dietary carbohydrates with a ketogenic diet and endogenous glucose production by using metformin on two mouse models of triple-negative breast cancer (TNBC).
    Results: Here, we showed that animals with TNBC treated with the combination regimen of ketogenic diet and metformin (a) had their tumor burden lowered by two-thirds, (b) displayed 38% slower tumor growth, and (c) showed 36% longer latency, compared to the animals treated with a ketogenic diet or metformin alone. As a result, lowering systemic glucose by this combined dietary and pharmacologic approach improved overall survival in our mouse TNBC models by 31 days, approximately equivalent to 3 years of life extension in human terms.
    Conclusion: This preclinical study demonstrates that reducing systemic glucose by combining a ketogenic diet and metformin significantly inhibits tumor proliferation and increases overall survival. Our findings suggest a possible treatment for a broad range of hypoxic and glycolytic tumor types that can augment existing treatment options to improve patient outcomes.
    Keywords:  Glycolytic tumor; Hypoxic tumor; Ketogenic diet; Metformin; Systemic glucose limitation
    DOI:  https://doi.org/10.1186/s41231-024-00178-8
  7. Trends Biochem Sci. 2024 Nov 21. pii: S0968-0004(24)00254-8. [Epub ahead of print]
      Oxidative phosphorylation (OxPhos) is the energy-transfer process that generates most of our ATP, fueled by proton and electrical gradients across the inner mitochondrial membrane. A new surprising finding by Hernansanz-Agustín et al. demonstrates that between one-third and half of this gradient is attributable to Na+, transported in exchange for protons within complex I.
    Keywords:  complex I; ion transport; mitochondria; oxidative phosphorylation; sodium–proton exchange
    DOI:  https://doi.org/10.1016/j.tibs.2024.11.002
  8. J Exp Med. 2025 01 06. pii: e20220979. [Epub ahead of print]222(1):
      The importance of calcium (Ca2+) as a second messenger in T cell signaling is exemplified by genetic deficiencies of STIM1 and ORAI1, which abolish store-operated Ca2+ entry (SOCE) resulting in combined immunodeficiency (CID). We report five unrelated patients with de novo missense variants in ITPR3, encoding a subunit of the inositol 1,4,5-trisphosphate receptor (IP3R), which forms a Ca2+ channel in the endoplasmic reticulum (ER) membrane responsible for the release of ER Ca2+ required to trigger SOCE, and for Ca2+ transfer to other organelles. The patients presented with CID, abnormal T cell Ca2+ homeostasis, incompletely penetrant ectodermal dysplasia, and multisystem disease. Their predominant T cell immunodeficiency is characterized by significant T cell lymphopenia, defects in late stages of thymic T cell development, and impaired function of peripheral T cells, including inadequate NF-κB- and NFAT-mediated, proliferative, and metabolic responses to activation. Pathogenicity is not due to haploinsufficiency, rather ITPR3 protein variants interfere with IP3R channel function leading to depletion of ER Ca2+ stores and blunted SOCE in T cells.
    DOI:  https://doi.org/10.1084/jem.20220979
  9. Aging (Albany NY). 2024 Nov 18. null
      Aging of the epidermis partially occurs as a consequence of epidermal cell senescence, a non-proliferative state in which cells remain metabolically active and acquire changes in their secretome. We previously reported that senescent normal human epidermal keratinocytes (NHEKs) have two opposite outcomes: either cell death by excess of autophagic activity or escape from senescence to give rise to post-senescence neoplastic emerging (PSNE) cells. In this study, we investigated the role of PTGS2, the inducible enzyme of the prostaglandin biosynthesis pathway, in the onset of NHEK senescence and in the switch from senescence to pre-transformation. We provide evidence that the PTGS2/PGE2/EP4 pathway plays a critical role in NHEK senescence as well as in senescence escape. We show that treating proliferating NHEKs with prostaglandin E2 (PGE2) or with an agonist of one of its receptors, EP4, induced the establishment of the senescent phenotype, according to several markers including the senescence-associated β-galactosidase activity. Conversely, treating already senescent NHEKs with an antagonist of EP4, or knocking-down PTGS2 by siRNA resulted in the decrease of the percentage of senescence-associated β-galactosidase-positive cells. We also demonstrate that the PSNE frequency was significantly decreased upon PTGS2 silencing by siRNA, pharmacological PTGS2 inhibition, or treatment by an EP4 antagonist, while on the contrary treatments with PGE2 or EP4 agonist increased the PSNE frequency. These results indicate that the PTGS2/PGE2/EP4 pathway is required to induce and maintain the senescent phenotype of NHEKs, and that PGE2 level is a potential determinant of the initial steps of the age-related oncogenic process.
    Keywords:  EP receptors; PTGS2; keratinocyte; neoplastic transformation; prostaglandins; senescence
    DOI:  https://doi.org/10.18632/aging.206149
  10. bioRxiv. 2024 Nov 03. pii: 2024.10.31.621317. [Epub ahead of print]
      Cancer cells are exposed to diverse metabolites in the tumor microenvironment that are used to support the synthesis of nucleotides, amino acids, and lipids needed for rapid cell proliferation 1-3 . Recent work has shown that ketone bodies such as β-hydroxybutyrate (β-OHB), which are elevated in circulation under fasting conditions or low glycemic diets, can serve as an alternative fuel that is metabolized in the mitochondria to provide acetyl-CoA for the tricarboxylic acid (TCA) cycle in some tumors 4-7 . Here, we discover a non-canonical route for β-OHB metabolism, in which β-OHB can bypass the TCA cycle to generate cytosolic acetyl-CoA for de novo fatty acid synthesis in cancer cells. We show that β-OHB-derived acetoacetate in the mitochondria can be shunted into the cytosol, where acetoacetyl-CoA synthetase (AACS) and thiolase convert it into acetyl-CoA for fatty acid synthesis. This alternative metabolic routing of β-OHB allows it to avoid oxidation in the mitochondria and net contribute to anabolic biosynthetic processes. In cancer cells, β-OHB is used for fatty acid synthesis to support cell proliferation under lipid-limited conditions in vitro and contributes to tumor growth under lipid-limited conditions induced by a calorie-restricted diet in vivo . Together, these data demonstrate that β-OHB is preferentially used for fatty acid synthesis in cancer cells to support tumor growth.
    DOI:  https://doi.org/10.1101/2024.10.31.621317
  11. Nature. 2024 Nov 20.
      Glioblastoma is incurable and in urgent need of improved therapeutics1. Here we identify a small compound, gliocidin, that kills glioblastoma cells while sparing non-tumour replicative cells. Gliocidin activity targets a de novo purine synthesis vulnerability in glioblastoma through indirect inhibition of inosine monophosphate dehydrogenase 2 (IMPDH2). IMPDH2 blockade reduces intracellular guanine nucleotide levels, causing nucleotide imbalance, replication stress and tumour cell death2. Gliocidin is a prodrug that is anabolized into its tumoricidal metabolite, gliocidin-adenine dinucleotide (GAD), by the enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) of the NAD+ salvage pathway. The cryo-electron microscopy structure of GAD together with IMPDH2 demonstrates its entry, deformation and blockade of the NAD+ pocket3. In vivo, gliocidin penetrates the blood-brain barrier and extends the survival of mice with orthotopic glioblastoma. The DNA alkylating agent temozolomide induces Nmnat1 expression, causing synergistic tumour cell killing and additional survival benefit in orthotopic patient-derived xenograft models. This study brings gliocidin to light as a prodrug with the potential to improve the survival of patients with glioblastoma.
    DOI:  https://doi.org/10.1038/s41586-024-08224-z
  12. Antioxid Redox Signal. 2024 Nov 22.
      Significance: Cellular senescence is a critical process underlying aging and is associated with age-related diseases such as Alzheimer's disease. Lipids are implicated in cellular senescence. Fatty acids, particularly eicosanoids, have been associated with various forms of senescence and inflammation, and the associated reactive oxygen species production has been proposed as a therapeutic target for mitigating senescence. When overactivated, calcium-dependent phospholipase A2 (cPLA2) catalyzes the conversion of arachidonic acid into eicosanoids such as leukotrienes and prostaglandins. Recent Advances: With a growing understanding of the importance of lipids as mediators and modulators of senescence, cPLA2 has emerged as a compelling drug target. cPLA2 overactivation plays a significant role in several pathways associated with senescence, including neuroinflammation and oxidative stress. Critical Issues: Previous cPLA2 inhibitors have shown potential in ameliorating inflammation and oxidative stress, but the dominant hurdles in the central nervous system-targeting drug discovery are specificity and blood-brain barrier penetrance. Future Directions: With the need for more effective drugs against neurological diseases, we emphasize the significance of discovering new brain-penetrant, potent, and specific cPLA2 inhibitors. We discuss how the recently developed Virtual Synthon Hierarchical Enumeration Screening, an iterative synthon-based approach for fast structure-based virtual screening of billions of compounds, provides an efficient exploration of large chemical spaces for the discovery of brain-penetrant cPLA2 small-molecule inhibitors. Antioxid. Redox Signal. 00, 000-000.
    Keywords:  calcium-dependent phospholipase A2 (cPLA2); cellular senescence; eicosanoids; inflammation; oxidative stress; small-molecule screening
    DOI:  https://doi.org/10.1089/ars.2024.0794
  13. Commun Biol. 2024 Nov 21. 7(1): 1551
      Many aging clocks have recently been developed to predict health outcomes and deconvolve heterogeneity in aging. However, existing clocks are limited by technical constraints, such as low spatial resolution, long processing time, sample destruction, and a bias towards specific aging phenotypes. Therefore, here we present a non-destructive, label-free and subcellular resolution approach for quantifying aging through optically resolving age-dependent changes to the biophysical properties of NAD(P)H in mitochondria through fluorescence lifetime imaging (FLIM) of endogenous NAD(P)H fluorescence. We uncover age-dependent changes to mitochondrial NAD(P)H across tissues in C. elegans that are associated with a decline in physiological function and construct non-destructive, label-free and cellular resolution models for prediction of age, which we refer to as "mito-NAD(P)H age clocks." Mito-NAD(P)H age clocks can resolve heterogeneity in the rate of aging across individuals and predict remaining lifespan. Moreover, we spatiotemporally resolve age-dependent changes to mitochondria across and within tissues, revealing multiple modes of asynchrony in aging and show that longevity is associated with a ubiquitous attenuation of these changes. Our data present a high-resolution view of mitochondrial NAD(P)H across aging, providing insights that broaden our understanding of how mitochondria change during aging and approaches which expand the toolkit to quantify aging.
    DOI:  https://doi.org/10.1038/s42003-024-07243-w
  14. Cancer Metab. 2024 Nov 19. 12(1): 35
       BACKGROUND: Glioblastoma is an aggressive cancer that originates from abnormal cell growth in the brain and requires metabolic reprogramming to support tumor growth. Metabolic reprogramming involves the upregulation of various metabolic pathways. Although the activation of specific metabolic pathways in glioblastoma cell lines has been documented, the comprehensive profile of metabolic reprogramming and the role of each pathway in glioblastoma tissues in patients remain elusive.
    METHODS: We analyzed 38 glioblastoma tissues. As a test set, we examined 20 tissues from Kyushu University Hospital, focusing on proteins related to several metabolic pathways, including glycolysis, the one-carbon cycle, glutaminolysis, and the mitochondrial tricarboxylic acid cycle. Subsequently, we analyzed an additional 18 glioblastoma tissues from Kagoshima University Hospital as a validation set. We also validated our findings using six cell lines, including U87, LN229, U373, T98G, and two patient-derived cells.
    RESULTS: The levels of mitochondria-related proteins (COX1, COX2, and DRP1) were correlated with each other and with glutaminolysis-related proteins (GLDH and GLS1). Conversely, their expression was inversely correlated with that of glycolytic proteins. Notably, inhibiting the glutaminolysis pathway in cell lines with high GLDH and GLS1 expression proved effective in suppressing tumor growth.
    CONCLUSIONS: Our findings confirm that glioblastoma tissues can be categorized into glycolytic-dominant and mitochondrial-dominant types, as previously reported. The mitochondrial-dominant type is also glutaminolysis-dominant. Therefore, inhibiting the glutaminolysis pathway may be an effective treatment for mitochondrial-dominant glioblastoma.
    Keywords:  Glioblastoma; Glutaminolysis; Metabolic changes; Mitochondria
    DOI:  https://doi.org/10.1186/s40170-024-00364-0
  15. Biomed Pharmacother. 2024 Nov 19. pii: S0753-3322(24)01576-2. [Epub ahead of print]181 117690
      Diverse agents targeting (macro)autophagy, a critical metabolic stress response in cancer cells, have been proposed for cancer therapy. In previous studies, we showed that NNC-55-0396 (NNC) induces glioblastoma cell death by activating the Unfolded Protein Response (UPR) of ER stress and increasing cytosolic Ca2+ levels. Here, we report that NNC affects both ends of the autophagy process, causing extensive cytoplasmic vacuolation. Our results show that: (1) NNC induces autophagy downstream of UPR and Ca2+ signaling pathways, thus silencing IRE1α/JNK1 or inhibiting Ca2+/IP3R signaling prevents NNC-induced vacuolation. (2) Silencing ATG5 delays cell death, indicating that autophagy induction plays a role in NNC's cytotoxic effects. (3) NNC and other Ca2+-mobilizing agents transcriptionally upregulate p62/SQSTM1, an autophagosome cargo receptor, highlighting a role for this protein in the response to NNC. (4) Studies using tandem fluorescent-tagged LC3 and electron microscopy, however, further reveal that NNC blocks late-stage autophagy that leads to enlarged degradative compartments accumulating ubiquitin-tagged cargoes. (5) Finally, NNC impedes pro-cathepsin-B processing, an effect that is reversed with a weak acid co-treatment, suggesting that lysosomal dysfunction due to increased intraluminal pH is the underlying cause of the autophagy blockade. Together, these findings underscore a multi-level dysregulation of autophagy that contributes to NNC's anti-tumoral effects.
    Keywords:  Calcium; UPR; autophagy; cell death; glioblastoma; tetralines
    DOI:  https://doi.org/10.1016/j.biopha.2024.117690
  16. Clin Transl Med. 2024 Nov;14(11): e70030
      Glioblastoma, the most frequent primary malignant brain tumour in adults, is characterised by profound yet dynamic hypoxia and nutrient depletion. To sustain survival and proliferation, tumour cells are compelled to acquire metabolic plasticity with the induction of adaptive metabolic programs. Here, we interrogated the pathways necessary to enable processing of nutrients other than glucose. We employed genetic approaches (stable/inducible overexpression, CRISPR/Cas9 knockout), pharmacological interventions with a novel inhibitor of AMP-activated protein kinase (AMPK) in glioblastoma cell culture systems and a proteomic approach to investigate mechanisms of metabolic plasticity. Moreover, a spatially resolved multiomic analysis was employed to correlate the gene expression pattern of PGC-1α with the local metabolic and genetic architecture in human glioblastoma tissue sections. A switch from glucose to alternative nutrients triggered an activation of AMPK, which in turn activated PGC-1α-dependent adaptive programs promoting mitochondrial metabolism. This sensor-effector mechanism was essential for metabolic plasticity with both functional AMPK and PGC-1α necessary for survival and growth of cells under nonglucose nutrient sources. In human glioblastoma tissue specimens, PGC-1α-expression correlated with nonhypoxic tumour niches defining a specific metabolic compartment. Our findings reveal a cell-intrinsic nutrient sensing and switching mechanism. The exposure to alternative fuels triggers a starvation signal that subsequently is passed on via AMPK and PGC-1α to induce adaptive programs necessary for broader spectrum nutrient metabolism. The integration of spatially resolved transcriptomic data confirms the relevance of PGC-1α especially in nonhypoxic tumour regions. Thus, the AMPK-PGC-1α axis is a candidate for therapeutic inhibition in glioblastoma. KEY POINTS/HIGHLIGHTS: AMPK activation induces PGC-1α expression in glioblastoma during nutrient scarcity. PGC-1α enables metabolic plasticity by facilitating metabolism of alternative nutrients in glioblastoma. PGC-1α expression is inversely correlated with hypoxic tumour regions in human glioblastomas.
    Keywords:  AMP‐activated protein kinase; PGC‐1α; PPARGC1A; glioblastoma; hypoxia; metabolic plasticity; tumour microenvironment
    DOI:  https://doi.org/10.1002/ctm2.70030