bims-smemid 2023-07-30 papers

on Stress metabolism in mitochondrial dysfunction

Issue of 2023–07–30
ten papers selected by
Deepti Mudartha, The International Institute of Molecular Mechanisms and Machines

3-hydroxykynurenine is a ROS-inducing cytotoxic tryptophan metabolite that disrupts the TCA cycle.
Complex II Biology in Aging, Health, and Disease.
Assembly of mitochondrial succinate dehydrogenase in human health and disease.
Human IP3 receptor triple knockout stem cells remain pluripotent despite altered mitochondrial metabolism.
Remodelling of the Mitochondrial Bioenergetic Pathways in Human Cultured Fibroblasts with Carbohydrates.
Rev1 deficiency induces a metabolic shift in MEFs that can be manipulated by the NAD+ precursor nicotinamide riboside.
Mechanism of PGC-1α-mediated mitochondrial biogenesis in cerebral ischemia-reperfusion injury.
Metabolites of Life: Phosphate.
Bypassing mitochondrial defects rescues Huntington's phenotypes in Drosophila.
Metabolomics Analysis Reveals Altered Metabolic Pathways and Response to Doxorubicin in Drug-Resistant Triple-Negative Breast Cancer Cells.

bioRxiv. 2023 Jul 10. pii: 2023.07.10.548411. [Epub ahead of print]

3-hydroxykynurenine is a ROS-inducing cytotoxic tryptophan metabolite that disrupts the TCA cycle.

Jane L Buchanan, Adam J Rauckhorst, Eric B Taylor.

Tryptophan is an essential amino acid that is extensively characterized as a regulator of cellular function through its metabolism by indoleamine 2,3-deoxygenase (IDO) into the kynurenine pathway. However, despite decades of research on tryptophan metabolism, the metabolic regulatory roles of it and its metabolites are not well understood. To address this, we performed an activity metabolomics screen of tryptophan and most of its known metabolites in cell culture. We discovered that treatment of human colon cancer cells (HCT116) with 3-hydroxykynurenine (3-HK), a metabolite of kynurenine, potently disrupted TCA cycle function. Citrate and aconitate levels were increased, while isocitrate and all downstream TCA metabolites were decreased, suggesting decreased aconitase function. We hypothesized that 3HK or one of its metabolites increased reactive oxygen species (ROS) and inhibited aconitase activity. Accordingly, we observed almost complete depletion of reduced glutathione and a decrease in total glutathione levels. We observed a dose-dependent decrease in cell viability after 48 hours of 3HK treatment. These data suggest that raising the intracellular levels of 3HK could be sufficient to induce ROS-mediated apoptosis. We modulated the intracellular levels of 3HK by combined induction of IDO and knockdown of kynureninase (KYNU) in HCT116 cells. Cell viability decreased significantly after 48 hours of KYNU knockdown compared to controls, which was accompanied by increased ROS production and Annexin V staining revealing apoptosis. Finally, we identify xanthommatin production from 3-HK as a candidate radical-producing, cytotoxic mechanism. Our work indicates that KYNU may be a target for disrupting tryptophan metabolism. Interestingly, many cancers exhibit overexpression of IDO, providing a cancer-specific metabolic vulnerability that could be exploited by KYNU inhibition.

DOI: https://doi.org/10.1101/2023.07.10.548411
Antioxidants (Basel). 2023 Jul 24. pii: 1477. [Epub ahead of print]12(7):

Complex II Biology in Aging, Health, and Disease.

Eric Goetzman, Zhenwei Gong, Bob Zhang, Radhika Muzumdar.

  Aging is associated with a decline in mitochondrial function which may contribute to age-related diseases such as neurodegeneration, cancer, and cardiovascular diseases. Recently, mitochondrial Complex II has emerged as an important player in the aging process. Mitochondrial Complex II converts succinate to fumarate and plays an essential role in both the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC). The dysfunction of Complex II not only limits mitochondrial energy production; it may also promote oxidative stress, contributing, over time, to cellular damage, aging, and disease. Intriguingly, succinate, the substrate for Complex II which accumulates during mitochondrial dysfunction, has been shown to have widespread effects as a signaling molecule. Here, we review recent advances related to understanding the function of Complex II, succinate signaling, and their combined roles in aging and aging-related diseases.

Keywords:  Complex II; aging; reactive oxygen species; succinate dehydrogenase

DOI:  https://doi.org/10.3390/antiox12071477
Free Radic Biol Med. 2023 Jul 23. pii: S0891-5849(23)00552-X. [Epub ahead of print]

Assembly of mitochondrial succinate dehydrogenase in human health and disease.

Ke Cao, Jie Xu, Wenli Cao, Xueqiang Wang, Weiqiang Lv, Mengqi Zeng, Xuan Zou, Jiankang Liu, Zhihui Feng.

  Mitochondrial succinate dehydrogenase (SDH), also known as electron transport chain (ETC) Complex II, is the only enzyme complex engaged in both oxidative phosphorylation and the tricarboxylic acid (TCA) cycle. SDH has received increasing attention due to its crucial role in regulating mitochondrial metabolism and human health. Despite having the fewest subunits among the four ETC complexes, functional SDH is formed via a sequential and well-coordinated assembly of subunits. Along with the discovery of subunit-specific assembly factors, the dynamic involvement of the SDH assembly process in a broad range of diseases has been revealed. Recently, we reported that perturbation of SDH assembly in different tissues leads to interesting and distinct pathophysiological changes in mice, indicating a need to understand the intricate SDH assembly process in human health and diseases. Thus, in this review, we summarize recent findings on SDH pathogenesis with respect to disease and a focus on SDH assembly.

Keywords:  Mitochondria; Succinate dehydrogenase; Succinate dehydrogenase assembly factors; Tricarboxylic acid cycle

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.07.023
Cell Calcium. 2023 Jul 17. pii: S0143-4160(23)00093-3. [Epub ahead of print]114 102782

Human IP3 receptor triple knockout stem cells remain pluripotent despite altered mitochondrial metabolism.

Julius Rönkkö, Yago Rodriguez, Tiina Rasila, Rubén Torregrosa-Muñumer, Jana Pennonen, Jouni Kvist, Emilia Kuuluvainen, Ludo Van Den Bosch, Ville Hietakangas, Geert Bultynck, Henna Tyynismaa, Emil Ylikallio.

  Inositol 1,4,5-trisphosphate receptors (IP3Rs) are ER Ca2+-release channels that control a broad set of cellular processes. Animal models lacking IP3Rs in different combinations display severe developmental phenotypes. Given the importance of IP3Rs in human diseases, we investigated their role in human induced pluripotent stem cells (hiPSC) by developing single IP3R and triple IP3R knockouts (TKO). Genome edited TKO-hiPSC lacking all three IP3R isoforms, IP3R1, IP3R2, IP3R3, failed to generate Ca2+ signals in response to agonists activating GPCRs, but retained stemness and pluripotency. Steady state metabolite profiling and flux analysis of TKO-hiPSC indicated distinct alterations in tricarboxylic acid cycle metabolites consistent with a deficiency in their pyruvate utilization via pyruvate dehydrogenase, shifting towards pyruvate carboxylase pathway. These results demonstrate that IP3Rs are not essential for hiPSC identity and pluripotency but regulate mitochondrial metabolism. This set of knockout hiPSC is a valuable resource for investigating IP3Rs in human cell types of interest.

Keywords:  Ca(2+) signaling; IP(3)R1; IP(3)R2; IP(3)R3; Induced pluripotent stem cells; Inositol 1,4,5-trisphosphate receptors; Mitochondria; TCA; iPSC

DOI:  https://doi.org/10.1016/j.ceca.2023.102782
Biology (Basel). 2023 Jul 14. pii: 1002. [Epub ahead of print]12(7):

Remodelling of the Mitochondrial Bioenergetic Pathways in Human Cultured Fibroblasts with Carbohydrates.

Margherita Protasoni, Jan-Willem Taanman.

  Mitochondrial oxidative phosphorylation defects underlie many neurological and neuromuscular diseases. Patients' primary dermal fibroblasts are one of the most commonly used in vitro models to study mitochondrial pathologies. However, fibroblasts tend to rely more on glycolysis than oxidative phosphorylation for their energy when cultivated in standard high-glucose medium, rendering it difficult to expose mitochondrial dysfunctions. This study aimed to systematically investigate to which extent the use of galactose- or fructose-based medium switches the fibroblasts' energy metabolism to a more oxidative state. Highly proliferative cells depend more on glycolysis than less proliferative cells. Therefore, we investigated two primary dermal fibroblast cultures from healthy subjects: a highly proliferative neonatal culture and a slower-growing adult culture. Cells were cultured with 25 mM glucose, galactose or fructose, and 4 mM glutamine as carbon sources. Compared to glucose, both galactose and fructose reduce the cellular proliferation rate, but the galactose-induced drop in proliferation is much more profound than the one observed in cells cultivated in fructose. Both galactose and fructose result in a modest increase in mitochondrial content, including mitochondrial DNA, and a disproportionate increase in protein levels, assembly, and activity of the oxidative phosphorylation enzyme complexes. Galactose- and fructose-based media induce a switch of the prevalent biochemical pathway in cultured fibroblasts, enhancing aerobic metabolism when compared to glucose-based medium. While both galactose and fructose stimulate oxidative phosphorylation to a comparable degree, galactose decreases the cellular proliferation rate more than fructose, suggesting that a fructose-based medium is a better choice when studying partial oxidative phosphorylation defects in patients' fibroblasts.

Keywords:  fructose; galactose; glucose; mitochondria; mitochondrial DNA; mitochondrial respiration; oxidative phosphorylation

DOI:  https://doi.org/10.3390/biology12071002
Heliyon. 2023 Jun;9(6): e17392

Rev1 deficiency induces a metabolic shift in MEFs that can be manipulated by the NAD+ precursor nicotinamide riboside.

Sharath Anugula, Zhiquan Li, Yuan Li, Alexander Hendriksen, Peter Bjarn Christensen, Lin Wang, Jonathan M Monk, Niels de Wind, Vilhelm A Bohr, Claus Desler, Robert K Naviaux, Lene Juel Rasmussen.

  Replication stress, caused by Rev1 deficiency, is associated with mitochondrial dysfunction, and metabolic stress. However, the overall metabolic alterations and possible interventions to rescue the deficits due to Rev1 loss remain unclear. Here, we report that loss of Rev1 leads to intense changes in metabolites and that this can be manipulated by NAD + supplementation. Autophagy decreases in Rev1-/- mouse embryonic fibroblasts (MEFs) and can be restored by supplementing the NAD+ precursor nicotinamide riboside (NR). The abnormal mitochondrial morphology in Rev1-/- MEFs can be partially reversed by NR supplementation, which also protects the mitochondrial cristae from rotenone-induced degeneration. In nematodes rev-1 deficiency causes sensitivity to oxidative stress but this cannot be rescued by NR supplementation. In conclusion, Rev1 deficiency leads to metabolic dysregulation of especially lipid and nucleotide metabolism, impaired autophagy, and mitochondrial anomalies, and all of these phenotypes can be improved by NR replenishment in MEFs.

Keywords:  Autophagy; Healthspan; Mitochondria; NAD+; Nicotinamide riboside; Replication stress; Rev1

DOI:  https://doi.org/10.1016/j.heliyon.2023.e17392
Front Mol Neurosci. 2023 ;16 1224964

Mechanism of PGC-1α-mediated mitochondrial biogenesis in cerebral ischemia-reperfusion injury.

Ying Yuan, Yuan Tian, Hui Jiang, Luo-Yang Cai, Jie Song, Rui Peng, Xiao-Ming Zhang.

  Cerebral ischemia-reperfusion injury (CIRI) is a series of cascade reactions that occur after blood flow recanalization in the ischemic zone in patients with cerebral infarction, causing an imbalance in intracellular homeostasis through multiple pathologies such as increased oxygen free radicals, inflammatory response, calcium overload, and impaired energy metabolism, leading to mitochondrial dysfunction and ultimately apoptosis. Rescue of reversibly damaged neurons in the ischemic hemispheric zone is the key to saving brain infarction and reducing neurological deficits. Complex and active neurological functions are highly dependent on an adequate energy supply from mitochondria. Mitochondrial biogenesis (MB), a process that generates new functional mitochondria and restores normal mitochondrial function by replacing damaged mitochondria, is a major mechanism for maintaining intra-mitochondrial homeostasis and is involved in mitochondrial quality control to ameliorate mitochondrial dysfunction and thus protects against CIRI. The main regulator of MB is peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), which improves mitochondrial function to protect against CIRI by activating its downstream nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) to promote mitochondrial genome replication and transcription. This paper provides a theoretical reference for the treatment of neurological impairment caused by CIRI by discussing the mechanisms of mitochondrial biogenesis during cerebral ischemia-reperfusion injury.

Keywords:  PGC-1α; apoptosis; cerebral ischemia–reperfusion injury; mitochondria; mitochondrial biogenesis

DOI:  https://doi.org/10.3389/fnmol.2023.1224964
Metabolites. 2023 Jul 19. pii: 860. [Epub ahead of print]13(7):

Metabolites of Life: Phosphate.

Janusz Wiesław Błaszczyk.

  The process of aging and escalating the failure of all body organs has become the center of interest in contemporary science and medicine. The leading role of phosphate-calcium tandem deficiency as a pacemaker of metabolic senescence has emerged recently. Most of the phosphates in the human body are stored in the bones, which seem to play a pivotal role in all metabolic and energetic processes. Bone metabolism combines physical activity with adaptive changes in the internal environment of the body, which is necessary for its survival. Phosphate-calcium signaling is the primary mechanism for controlling homeostasis and its recovery after exercise-induced disorders. Phosphates play an important role in the regulation of energy metabolism both by regulating postprandial glucose storage in the muscles and in the liver, as well as the distribution and adaptation of energy metabolites to the needs of the brain and skeletal muscles. The bone-driven energy metabolism is of decisive importance for maintaining all vital functions of the body organs, including their proper functioning and integrated interplay. The phosphate-calcium tandem contributes to the development and proper functioning of the organism, whereas energy dysmetabolism is the main cause of aging and the final termination of life.

Keywords:  aging; bone; energy metabolism; life cycle; phosphate

DOI:  https://doi.org/10.3390/metabo13070860
Neurobiol Dis. 2023 Jul 24. pii: S0969-9961(23)00251-6. [Epub ahead of print] 106236

Bypassing mitochondrial defects rescues Huntington's phenotypes in Drosophila.

Susanna Campesan, Ivana Del Popolo, Kyriaki Marcou, Anna Straatman-Iwanowska, Mariaelena Repici, Kalina V Boytcheva, Victoria E Cotton, Natalie Allcock, Ezio Rosato, Charalambos P Kyriacou, Flaviano Giorgini.

  Huntington's disease (HD) is a fatal neurodegenerative disease with limited treatment options. Human and animal studies have suggested that metabolic and mitochondrial dysfunctions contribute to HD pathogenesis. Here, we use high-resolution respirometry to uncover defective mitochondrial oxidative phosphorylation and electron transfer capacity when a mutant huntingtin fragment is targeted to neurons or muscles in Drosophila and find that enhancing mitochondrial function can ameliorate these defects. In particular, we find that co-expression of parkin, an E3 ubiquitin ligase critical for mitochondrial dynamics and homeostasis, produces significant enhancement of mitochondrial respiration when expressed either in neurons or muscles, resulting in significant rescue of neurodegeneration, viability and longevity in HD model flies. Targeting mutant HTT to muscles results in larger mitochondria and higher mitochondrial mass, while co-expression of parkin increases mitochondrial fission and decreases mass. Furthermore, directly addressing HD-mediated defects in the fly's mitochondrial electron transport system, by rerouting electrons to either bypass mitochondrial complex I or complexes III-IV, significantly increases mitochondrial respiration and results in a striking rescue of all phenotypes arising from neuronal mutant huntingtin expression. These observations suggest that bypassing impaired mitochondrial respiratory complexes in HD may have therapeutic potential for the treatment of this devastating disorder.

Keywords:  Huntingtin; Huntington's disease; Mitochondrial dysfunction; Neurodegeneration; Parkin

DOI:  https://doi.org/10.1016/j.nbd.2023.106236
Metabolites. 2023 Jul 20. pii: 865. [Epub ahead of print]13(7):

Metabolomics Analysis Reveals Altered Metabolic Pathways and Response to Doxorubicin in Drug-Resistant Triple-Negative Breast Cancer Cells.

Blake R Rushing, Sabrina Molina, Susan Sumner.

  This study aimed to investigate metabolic changes following the acquisition of resistance to doxorubicin in the triple-negative breast cancer (TNBC) cell line MDA-MB-231. Two drug-resistant cell lines, DOX-RES-50 and DOX-RES-100, were generated by treating MDA-MB-231 cells with doxorubicin for 24 h and allowing them to recover for six weeks. Both drug-resistant cell lines demonstrated an increase in doxorubicin IC50 values, indicating acquired drug resistance. Metabolomics analysis showed clear separation between the parental MDA-MB-231 cell line and the drug-resistant cell lines. Pathway analysis revealed that arginine and proline metabolism, glutathione metabolism, and beta-alanine metabolism were significantly perturbed in the drug-resistant cell lines compared to the parental cell line. After matching signals to an in-house library of reference standards, significant decreases in short- and medium-chain acylcarnitines and significant increases in long-chain acylcarnitines, 5-oxoproline, and 7-ketodeoxycholic acid were observed in the resistant cell lines as compared to the parental MDA-MB-231 cell line. In addition to baseline metabolic differences, we also investigated differences in metabolic responses in resistant cell lines upon a second exposure at multiple concentrations. Results indicate that whereas the parental MDA-MB-231 cell line had many metabolites that responded to doxorubicin in a dose-dependent manner, the two resistant cell lines lost a dose-dependent response for the majority of these metabolites. The study's findings provide insight into how metabolism is altered during the acquisition of resistance in TNBC cells and how the metabolic response to doxorubicin changes upon repeated treatment. This information can potentially identify novel targets to prevent or reverse multi-drug resistance in TNBC, and also demonstrate the usefulness of metabolomics technology in identifying new mechanisms of drug resistance in cancer and potential drug targets.

Keywords:  chemotherapy; doxorubicin; drug resistance; metabolomics; triple-negative breast cancer

DOI:  https://doi.org/10.3390/metabo13070865