bims-midhyp 2023-07-02 papers

bims-midhyp

Biomed News

on Mitochondrial dysfunction and hypoxia

Issue of 2023–07–02
twenty papers selected by
Alia Ablieh, Universität Heidelberg

Mitochondrial Damage and Hypertension: Another Dark Side of Sodium Excess.
The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.
The role of oxygen tension in cell fate and regenerative medicine: implications of hypoxia/hyperoxia and free radicals.
Pharmacological Modulation of Energy and Metabolic Pathways Protects Hearing in the Fus1/Tusc2 Knockout Model of Mitochondrial Dysfunction and Oxidative Stress.
The Multi-Faceted Nature of Renalase for Mitochondrial Dysfunction Improvement in Cardiac Disease.
Mitochondrial control of sleep.
Translation termination in human mitochondria - substrate specificity of mitochondrial release factors.
Aurora kinase A/AURKA functionally interacts with the mitochondrial ATP synthase to regulate energy metabolism and cell death.
Environmental and behavioral regulation of HIF-mitochondria crosstalk.
Mitochondria Quality Control and Male Fertility.
Hyperoxic exposure alters intracellular bioenergetics distribution in human pulmonary cells.
How does exercise affect energy metabolism? An in silico approach for cardiac muscle.
COX5A Alleviates Doxorubicin-Induced Cardiotoxicity by Suppressing Oxidative Stress, Mitochondrial Dysfunction and Cardiomyocyte Apoptosis.
Glycolysis Aids in Human Lens Epithelial Cells' Adaptation to Hypoxia.
Endothelial Cells and Mitochondria: Two Key Players in Liver Transplantation.
Fifty years of the mitochondrial pyruvate carrier: New insights into its structure, function, and inhibition.
Oxidative Stress Response Kinetics after 60 Minutes at Different Levels (10% or 15%) of Normobaric Hypoxia Exposure.
Metabolic orchestration of cell death by AMPK-mediated phosphorylation of RIPK1.
The Unfolded Protein Response Sensor IRE1 Regulates Activation of In Vitro Differentiated Type 1 Conventional DCs with Viral Stimuli.
Method of Monitoring 26S Proteasome in Cells Revealed the Crucial Role of PSMA3 C-Terminus in 26S Integrity.

Curr Nutr Rep. 2023 Jun 29.

Mitochondrial Damage and Hypertension: Another Dark Side of Sodium Excess.

Baris Afsar, Rengin Elsurer Afsar.

   PURPOSE OF REVIEW: Essential or primary hypertension (HT) is a worldwide health problem with no definitive cure. Although the exact pathogenesis of HT is not known, genetic factors, increased renin-angiotensin and sympathetic system activity, endothelial dysfunction, oxidative stress, and inflammation play a role in its development. Environmental factors such as sodium intake are also important for BP regulation, and excess sodium intake in the form of salt (NaCl, sodium chloride) increases blood pressure in salt-sensitive people. Excess salt intake increases extracellular volume, oxidative stress, inflammation, and endothelial dysfunction. Recent evidence suggests that increased salt intake also disturbs mitochondrial function both structurally and functionally which is important as mitochondrial dysfunction is associated with HT. In the current review, we have summarized the experimental and clinical data regarding the impact of salt intake on mitochondrial structure and function.
RECENT FINDINGS: Excess salt intake damage mitochondrial structure (e.g., shorter mitochondria with less cristae, increased mitochondrial fission, increased mitochondrial vacuolization). Functionally, high salt intake impairs mitochondrial oxidative phosphorylation and electron transport chain, ATP production, mitochondrial calcium homeostasis, mitochondrial membrane potential, and mitochondrial uncoupling protein function. Excess salt intake also increases mitochondrial oxidative stress and modifies Krebs cycle protein expressions. Studies have shown that high salt intake impairs mitochondrial structure and function. These maladaptive mitochondrial changes facilitate the development of HT especially in salt-sensitive individuals. High salt intake impairs many functional and structural components of mitochondria. These mitochondrial alterations along with increased salt intake promote the development of hypertension.

Keywords:  Blood pressure; Hypertension; Mitochondrial dysfunction; Salt; Sodium

DOI:  https://doi.org/10.1007/s13668-023-00486-9
Mol Biol Cell. 2023 Jun 28. mbcE23050205

The unfolded protein response of the endoplasmic reticulum supports mitochondrial biogenesis by buffering non-imported proteins.

Katharina Knöringer, Carina Groh, Lena Krämer, Kevin C Stein, Katja G Hansen, Jannik Zimmermann, Bruce Morgan, Johannes M Herrmann, Judith Frydman, Felix Boos.

Almost all mitochondrial proteins are synthesized in the cytosol and subsequently targeted to mitochondria. The accumulation of non-imported precursor proteins occurring upon mitochondrial dysfunction can challenge cellular protein homeostasis. Here we show that blocking protein translocation into mitochondria results in the accumulation of mitochondrial membrane proteins at the endoplasmic reticulum, thereby triggering the unfolded protein response (UPRER). Moreover, we find that mitochondrial membrane proteins are also routed to the ER under physiological conditions. The level of ER-resident mitochondrial precursors is enhanced by import defects as well as metabolic stimuli that increase the expression of mitochondrial proteins. Under such conditions, the UPRER is crucial to maintain protein homeostasis and cellular fitness. We propose the ER serves as a physiological buffer zone for those mitochondrial precursors that cannot be immediately imported into mitochondria while engaging the UPRER to adjust the ER proteostasis capacity to the extent of precursor accumulation.

DOI: https://doi.org/10.1091/mbc.E23-05-0205
Cell Tissue Bank. 2023 Jun 26.

The role of oxygen tension in cell fate and regenerative medicine: implications of hypoxia/hyperoxia and free radicals.

Mehdi Rasouli, Roya Fattahi, Ghader Nuoroozi, Zeinab Zarei-Behjani, Maliheh Yaghoobi, Zeinab Hajmohammadi, Simzar Hosseinzadeh.

  Oxygen pressure plays an integral role in regulating various aspects of cellular biology. Cell metabolism, proliferation, morphology, senescence, metastasis, and angiogenesis are some instances that are affected by different tensions of oxygen. Hyperoxia or high oxygen concentration, enforces the production of reactive oxygen species (ROS) that disturbs physiological homeostasis, and consequently, in the absence of antioxidants, cells and tissues are directed to an undesired fate. On the other side, hypoxia or low oxygen concentration, impacts cell metabolism and fate strongly through inducing changes in the expression level of specific genes. Thus, understanding the precise mechanism and the extent of the implication of oxygen tension and ROS in biological events is crucial to maintaining the desired cell and tissue function for application in regenerative medicine strategies. Herein, a comprehensive literature review has been performed to find out the impacts of oxygen tensions on the various behaviors of cells or tissues.

Keywords:  Angiogenesis; Cancer; Cell morphology; Cell proliferation; Oxygen; ROS; Senescence

DOI:  https://doi.org/10.1007/s10561-023-10099-9
Antioxidants (Basel). 2023 Jun 06. pii: 1225. [Epub ahead of print]12(6):

Pharmacological Modulation of Energy and Metabolic Pathways Protects Hearing in the Fus1/Tusc2 Knockout Model of Mitochondrial Dysfunction and Oxidative Stress.

Winston J T Tan, Joseph Santos-Sacchi, Jane Tonello, Anil Shanker, Alla V Ivanova.

  Tightly regulated and robust mitochondrial activities are critical for normal hearing. Previously, we demonstrated that Fus1/Tusc2 KO mice with mitochondrial dysfunction exhibit premature hearing loss. Molecular analysis of the cochlea revealed hyperactivation of the mTOR pathway, oxidative stress, and altered mitochondrial morphology and quantity, suggesting compromised energy sensing and production. Here, we investigated whether the pharmacological modulation of metabolic pathways using rapamycin (RAPA) or 2-deoxy-D-glucose (2-DG) supplementation can protect against hearing loss in female Fus1 KO mice. Additionally, we aimed to identify mitochondria- and Fus1/Tusc2-dependent molecular pathways and processes critical for hearing. We found that inhibiting mTOR or activating alternative mitochondrial energetic pathways to glycolysis protected hearing in the mice. Comparative gene expression analysis revealed the dysregulation of critical biological processes in the KO cochlea, including mitochondrial metabolism, neural and immune responses, and the cochlear hypothalamic-pituitary-adrenal axis signaling system. RAPA and 2-DG mostly normalized these processes, although some genes showed a drug-specific response or no response at all. Interestingly, both drugs resulted in a pronounced upregulation of critical hearing-related genes not altered in the non-treated KO cochlea, including cytoskeletal and motor proteins and calcium-linked transporters and voltage-gated channels. These findings suggest that the pharmacological modulation of mitochondrial metabolism and bioenergetics may restore and activate processes critical for hearing, thereby protecting against hearing loss.

Keywords:  2-DG; 2-deoxy-D-glucose; Fus1/Tusc2; Seahorse analysis; age-related hearing loss; cochlea; mitochondria; mitochondrial dysfunction; oxidative stress; rapamycin

DOI:  https://doi.org/10.3390/antiox12061225
Cells. 2023 06 12. pii: 1607. [Epub ahead of print]12(12):

The Multi-Faceted Nature of Renalase for Mitochondrial Dysfunction Improvement in Cardiac Disease.

Dijana Stojanovic, Miodrag Stojanovic, Jelena Milenkovic, Aleksandra Velickov, Aleksandra Ignjatovic, Maja Milojkovic.

  The cellular mechanisms and signaling network that guide the cardiac disease pathophysiology are inextricably intertwined, which explains the current scarcity of effective therapy and to date remains the greatest challenge in state-of-the-art cardiovascular medicine. Accordingly, a novel concept has emerged in which cardiomyocytes are the centerpiece of therapeutic targeting, with dysregulated mitochondria as a critical point of intervention. Mitochondrial dysfunction pluralism seeks a multi-faceted molecule, such as renalase, to simultaneously combat the pathophysiologic heterogeneity of mitochondria-induced cardiomyocyte injury. This review provides some original perspectives and, for the first time, discusses the functionality spectrum of renalase for mitochondrial dysfunction improvement within cardiac disease, including its ability to preserve mitochondrial integrity and dynamics by suppressing mitochondrial ΔΨm collapse; overall ATP content amelioration; a rise of mtDNA copy numbers; upregulation of mitochondrial genes involved in oxidative phosphorylation and cellular vitality promotion; mitochondrial fission inhibition; NAD+ supplementation; sirtuin upregulation; and anti-oxidant, anti-apoptotic, and anti-inflammatory traits. If verified that renalase, due to its multi-faceted nature, behaves like the "guardian of mitochondria" by thwarting pernicious mitochondrial dysfunction effects and exerting therapeutic potential to target mitochondrial abnormalities in failing hearts, it may provide large-scale benefits for cardiac disease patients, regardless of the underlying causes.

Keywords:  MAPK; NAD+; apoptosis; cardiac disease; mitochondrial dysfunction; oxidative stress; renalase; sirtuins

DOI:  https://doi.org/10.3390/cells12121607
Curr Opin Neurobiol. 2023 Jun 28. pii: S0959-4388(23)00058-2. [Epub ahead of print]81 102733

Mitochondrial control of sleep.

Celina Hartmann, Anissa Kempf.

  The function of sleep remains one of biology's biggest mysteries. A solution to this problem is likely to come from a better understanding of sleep homeostasis, and in particular of the cellular and molecular processes that sense sleep need and settle sleep debt. Here, we highlight recent work in the fruit fly showing that changes in the mitochondrial redox state of sleep-promoting neurons lie at the heart of a homeostatic sleep-regulatory mechanism. Since the function of homeostatically controlled behaviours is often linked to the regulated variable itself, these findings corroborate with the hypothesis that sleep serves a metabolic function.

Keywords:  Drosophila; Excitability; Metabolism; Mitochondria; OXPHOS; Oxidative phosphorylation; ROS; Reactive oxygen species; Redox state; Sleep; Sleep homeostasis; Sleep need

DOI:  https://doi.org/10.1016/j.conb.2023.102733
Biol Chem. 2023 Jun 29.

Translation termination in human mitochondria - substrate specificity of mitochondrial release factors.

Franziska Nadler, Ricarda Richter-Dennerlein.

  Mitochondria are the essential players in eukaryotic ATP production by oxidative phosphorylation, which relies on the maintenance and accurate expression of the mitochondrial genome. Even though the basic principles of translation are conserved due to the descendance from a bacterial ancestor, some deviations regarding translation factors as well as mRNA characteristics and the applied genetic code are present in human mitochondria. Together, these features are certain challenges during translation the mitochondrion has to handle. Here, we discuss the current knowledge regarding mitochondrial translation focusing on the termination process and the associated quality control mechanisms. We describe how mtRF1a resembles bacterial RF1 mechanistically and summarize in vitro and recent in vivo data leading to the conclusion of mtRF1a being the major mitochondrial release factor. On the other hand, we discuss the ongoing debate about the function of the second codon-dependent mitochondrial release factor mtRF1 regarding its role as a specialized termination factor. Finally, we link defects in mitochondrial translation termination to the activation of mitochondrial rescue mechanisms highlighting the importance of ribosome-associated quality control for sufficient respiratory function and therefore for human health.

Keywords:  COX1 translation; mitoribosome rescue; mitoribosome-associated quality control; mtRF1; mtRF1a; non-canonical stop codons

DOI:  https://doi.org/10.1515/hsz-2023-0127
Cell Death Discov. 2023 Jun 29. 9(1): 203

Aurora kinase A/AURKA functionally interacts with the mitochondrial ATP synthase to regulate energy metabolism and cell death.

Rakesh Kumar Sharma, Abderrahman Chafik, Giulia Bertolin.

Cancer cells often hijack metabolic pathways to obtain the energy required to sustain their proliferation. Understanding the molecular mechanisms underlying cancer cell metabolism is key to fine-tune the metabolic preference of specific tumors, and potentially offer new therapeutic strategies. Here, we show that the pharmacological inhibition of mitochondrial Complex V delays the cell cycle by arresting breast cancer cell models in the G0/G1 phase. Under these conditions, the abundance of the multifunctional protein Aurora kinase A/AURKA is specifically lowered. We then demonstrate that AURKA functionally interacts with the mitochondrial Complex V core subunits ATP5F1A and ATP5F1B. Altering the AURKA/ATP5F1A/ATP5F1B nexus is sufficient to trigger G0/G1 arrest, and this is accompanied by decreased glycolysis and mitochondrial respiration rates. Last, we discover that the roles of the AURKA/ATP5F1A/ATP5F1B nexus depend on the specific metabolic propensity of triple-negative breast cancer cell lines, where they correlate with cell fate. On one hand, the nexus induces G0/G1 arrest in cells relying on oxidative phosphorylation as the main source of energy. On the other hand, it allows to bypass cell cycle arrest and it triggers cell death in cells with a glycolytic metabolism. Altogether, we provide evidence that AURKA and mitochondrial Complex V subunits cooperate to maintain cell metabolism in breast cancer cells. Our work paves the way to novel anti-cancer therapies targeting the AURKA/ATP5F1A/ATP5F1B nexus to lower cancer cell metabolism and proliferation.

DOI: https://doi.org/10.1038/s41420-023-01501-2
Free Radic Biol Med. 2023 Jun 27. pii: S0891-5849(23)00502-6. [Epub ahead of print]

Environmental and behavioral regulation of HIF-mitochondria crosstalk.

Johannes Burtscher, Erich Hohenauer, Martin Burtscher, Grégoire P Millet, Margit Egg.

  Reduced oxygen availability (hypoxia) can lead to cell and organ damage. Therefore, aerobic species depend on efficient mechanisms to counteract detrimental consequences of hypoxia. Hypoxia inducible factors (HIFs) and mitochondria are integral components of the cellular response to hypoxia and coordinate both distinct and highly intertwined adaptations. This leads to reduced dependence on oxygen, improved oxygen supply, maintained energy provision by metabolic remodeling and tapping into alternative pathways and increased resilience to hypoxic injuries. On one hand, many pathologies are associated with hypoxia and hypoxia can drive disease progression, for example in many cancer and neurological diseases. But on the other hand, controlled induction of hypoxia responses via HIFs and mitochondria can elicit profound health benefits and increase resilience. To tackle pathological hypoxia conditions or to apply health-promoting hypoxia exposures efficiently, cellular and systemic responses to hypoxia need to be well understood. Here we first summarize the well-established link between HIFs and mitochondria in orchestrating hypoxia-induced adaptations and then outline major environmental and behavioral modulators of their interaction that remain poorly understood.

Keywords:  Altitude; Cellular stress; Circadian rhythm; Hypoxia inducible factors; Mitochondria; Physical activity

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.06.015
Biology (Basel). 2023 Jun 06. pii: 827. [Epub ahead of print]12(6):

Mitochondria Quality Control and Male Fertility.

José Costa, Patrícia C Braga, Irene Rebelo, Pedro F Oliveira, Marco G Alves.

  Mitochondria are pivotal to cellular homeostasis, performing vital functions such as bioenergetics, biosynthesis, and cell signalling. Proper maintenance of these processes is crucial to prevent disease development and ensure optimal cell function. Mitochondrial dynamics, including fission, fusion, biogenesis, mitophagy, and apoptosis, maintain mitochondrial quality control, which is essential for overall cell health. In male reproduction, mitochondria play a pivotal role in germ cell development and any defects in mitochondrial quality can have serious consequences on male fertility. Reactive oxygen species (ROS) also play a crucial role in sperm capacitation, but excessive ROS levels can trigger oxidative damage. Any imbalance between ROS and sperm quality control, caused by non-communicable diseases or environmental factors, can lead to an increase in oxidative stress, cell damage, and apoptosis, which in turn affect sperm concentration, quality, and motility. Therefore, assessing mitochondrial functionality and quality control is essential to gain valuable insights into male infertility. In sum, proper mitochondrial functionality is essential for overall health, and particularly important for male fertility. The assessment of mitochondrial functionality and quality control can provide crucial information for the study and management of male infertility and may lead to the development of new strategies for its management.

Keywords:  male fertility; mitochondrial quality control; non-communicable diseases; spermatozoa

DOI:  https://doi.org/10.3390/biology12060827
Life Sci. 2023 Jun 23. pii: S0024-3205(23)00515-5. [Epub ahead of print]328 121880

Hyperoxic exposure alters intracellular bioenergetics distribution in human pulmonary cells.

Tanvir Hossain, David M Eckmann.

   AIMS: Pulmonary oxygen toxicity is caused by exposure to a high fraction of inspired oxygen, which damages multiple cell types within the lung. The cellular basis for pulmonary oxygen toxicity includes mitochondrial dysfunction. The aim of this study was to identify the effects of hyperoxic exposure on mitochondrial bioenergetic and dynamic functions in pulmonary cells.
MAIN METHODS: Mitochondrial respiration, inner membrane potential, dynamics (including motility), and distribution of mitochondrial bioenergetic capacity in two intracellular regions were quantified using cultured human lung microvascular endothelial cells, human pulmonary artery endothelial cells and A549 cells. Hyperoxic (95 % O2) exposures lasted 24, 48 and 72 h, durations relevant to mechanical ventilation in intensive care settings.
KEY FINDINGS: Mitochondrial motility was altered following all hyperoxic exposures utilized in experiments. Inhomogeneities in inner membrane potential and respiration parameters were present in each cell type following hyperoxia. The partitioning of ATP-linked respiration was also hyperoxia-duration and cell type dependent. Hyperoxic exposure lasting 48 h or longer provoked the largest alterations in mitochondrial motility and the greatest decreases in ATP-linked respiration, with a suggestion of decreases in respiration complex protein levels.
SIGNIFICANCE: Hyperoxic exposures of different durations produce intracellular inhomogeneities in mitochondrial dynamics and bioenergetics in pulmonary cells. Oxygen therapy is utilized commonly in clinical care and can induce undesirable decrements in bioenergy function needed to maintain pulmonary cell function and viability. There may be adjunctive or prophylactic measures that can be employed during hyperoxic exposures to prevent the mitochondrial dysfunction that signals the presence of oxygen toxcity.

Keywords:  Bioenergetics; Hyperoxia; Inner membrane potential; Microscopy; Mitochondria; Motility; Perinuclear; Respiration

DOI:  https://doi.org/10.1016/j.lfs.2023.121880
Heliyon. 2023 Jun;9(6): e17164

How does exercise affect energy metabolism? An in silico approach for cardiac muscle.

Bahar Hazal Yalçınkaya, Seda Genc, Bayram Yılmaz, Mustafa Özilgen.

  We explored an in silico model of muscle energy metabolism and demonstrated its theoretical plausibility. Results indicate that energy metabolism triggered by activation can capture the muscle condition, rest, or exercise, and can respond accordingly adjusting the rates of their respiration and energy utilization for efficient use of the nutrients. Our study demonstrated during exercise higher respiratory activity causes a substantial increase in exergy release with an increase in exergy destruction, and entropy generation rate. The thermodynamic analysis showed that at the resting state when the exergy destruction rate was 0.66 W/kg and the respiratory metabolism energetic efficiency was 36% and exergetic efficiency was 32%; whereas, when the exergy destroyed was 1.24 W/kg, the energetic efficiency was 58% and exergetic efficiency was 50% during exercise. The efficiency results suggest the ability of the system to regulate itself in response to higher work demand and become more efficient in terms of converting energy coming from nutrients to useable energy when the circulating medium has sufficient energy precursor.

Keywords:  Entropy generation; Exergy destruction; Kinetic and thermodynamic analyses; Mitochondrial bioenergetics; Muscle work performance efficiency

DOI:  https://doi.org/10.1016/j.heliyon.2023.e17164
Int J Mol Sci. 2023 Jun 20. pii: 10400. [Epub ahead of print]24(12):

COX5A Alleviates Doxorubicin-Induced Cardiotoxicity by Suppressing Oxidative Stress, Mitochondrial Dysfunction and Cardiomyocyte Apoptosis.

Peipei Zhang, Hao Lu, Yuan Wu, Danbo Lu, Chenguang Li, Xiangdong Yang, Zhangwei Chen, Juying Qian, Junbo Ge.

  Doxorubicin (DOX) as a chemotherapeutic agent can cause mitochondrial dysfunction and heart failure. COX5A has been described as an important regulator of mitochondrial energy metabolism. We investigate the roles of COX5A in DOX-induced cardiomyopathy and explore the underlying mechanisms. C57BL/6J mice and H9c2 cardiomyoblasts were treated with DOX, and the COX5A expression was assessed. An adeno-associated virus serum type 9 (AAV9) and lenti-virus system were used to upregulate COX5A expression. Echocardiographic parameters, morphological and histological analyses, transmission electron microscope and immunofluorescence assays were used to assess cardiac and mitochondrial function. In a human study, we found that cardiac COX5A expression was dramatically decreased in patients with end-stage dilated cardiomyopathy (DCM) compared to the control group. COX5A was significantly downregulated following DOX stimulation in the heart of mice and H9c2 cells. Reduced cardiac function, decreased myocardium glucose uptake, mitochondrial morphology disturbance, reduced activity of mitochondrial cytochrome c oxidase (COX) and lowered ATP content were detected after DOX stimulation in mice, which could be significantly improved by overexpression of COX5A. Overexpression of COX5A effectively protected against DOX-induced oxidative stress, mitochondrial dysfunction and cardiomyocyte apoptosis in vivo and in vitro. Mechanistically, the phosphorylation of Akt (Thr308) and Akt (Ser473) were also decreased following DOX treatment, which could be reserved by the upregulation of COX5A. Furthermore, PI3K inhibitors abrogated the protection effects of COX5A against DOX-induced cardiotoxicity in H9c2 cells. Thus, we identified that PI3K/Akt signaling was responsible for the COX5A-mediated protective role in DOX-induced cardiomyopathy. These results demonstrated the protective effect of COX5A in mitochondrial dysfunction, oxidative stress, and cardiomyocyte apoptosis, providing a potential therapeutic target in DOX-induced cardiomyopathy.

Keywords:  COX5A; apoptosis; doxorubicin; mitochondrial dysfunction; oxidative stress

DOI:  https://doi.org/10.3390/ijms241210400
Antioxidants (Basel). 2023 Jun 19. pii: 1304. [Epub ahead of print]12(6):

Glycolysis Aids in Human Lens Epithelial Cells' Adaptation to Hypoxia.

Yuxin Huang, Xiyuan Ping, Yilei Cui, Hao Yang, Jing Bao, Qichuan Yin, Hailaiti Ailifeire, Xingchao Shentu.

  Hypoxic environments are known to trigger pathological damage in multiple cellular subtypes. Interestingly, the lens is a naturally hypoxic tissue, with glycolysis serving as its main source of energy. Hypoxia is essential for maintaining the long-term transparency of the lens in addition to avoiding nuclear cataracts. Herein, we explore the complex mechanisms by which lens epithelial cells adapt to hypoxic conditions while maintaining their normal growth and metabolic activity. Our data show that the glycolysis pathway is significantly upregulated during human lens epithelial (HLE) cells exposure to hypoxia. The inhibition of glycolysis under hypoxic conditions incited endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) production in HLE cells, leading to cellular apoptosis. After ATP was replenished, the damage to the cells was not completely recovered, and ER stress, ROS production, and cell apoptosis still occurred. These results suggest that glycolysis not only performs energy metabolism in the process of HLE cells adapting to hypoxia, but also helps them continuously resist cell apoptosis caused by ER stress and ROS production. Furthermore, our proteomic atlas provides possible rescue mechanisms for cellular damage caused by hypoxia.

Keywords:  apoptosis; endoplasmic reticulum (ER) stress; glycolysis; hypoxia; reactive oxygen species (ROS)

DOI:  https://doi.org/10.3390/antiox12061304
Int J Mol Sci. 2023 Jun 13. pii: 10091. [Epub ahead of print]24(12):

Endothelial Cells and Mitochondria: Two Key Players in Liver Transplantation.

Alessandro Parente, Mauricio Flores Carvalho, Andrea Schlegel.

  Building the inner layer of our blood vessels, the endothelium forms an important line communicating with deeper parenchymal cells in our organs. Previously considered passive, endothelial cells are increasingly recognized as key players in intercellular crosstalk, vascular homeostasis, and blood fluidity. Comparable to other cells, their metabolic function strongly depends on mitochondrial health, and the response to flow changes observed in endothelial cells is linked to their mitochondrial metabolism. Despite the direct impact of new dynamic preservation concepts in organ transplantation, the impact of different perfusion conditions on sinusoidal endothelial cells is not yet explored well enough. This article therefore describes the key role of liver sinusoidal endothelial cells (LSECs) together with their mitochondrial function in the context of liver transplantation. The currently available ex situ machine perfusion strategies are described with their effect on LSEC health. Specific perfusion conditions, including perfusion pressure, duration, and perfusate oxygenation are critically discussed considering the metabolic function and integrity of liver endothelial cells and their mitochondria.

Keywords:  endothelial cells; ischemia-reperfusion injury; machine perfusion; mitochondria; reactive oxygen species; shears stress

DOI:  https://doi.org/10.3390/ijms241210091
Acta Physiol (Oxf). 2023 Jun 27. e14016

Fifty years of the mitochondrial pyruvate carrier: New insights into its structure, function, and inhibition.

Sotiria Tavoulari, Maximilian Sichrovsky, Edmund R S Kunji.

  The mitochondrial pyruvate carrier (MPC) resides in the mitochondrial inner membrane, where it links cytosolic and mitochondrial metabolism by transporting pyruvate produced in glycolysis into the mitochondrial matrix. Due to its central metabolic role, it has been proposed as a potential drug target for diabetes, non-alcoholic fatty liver disease, neurodegeneration, and cancers relying on mitochondrial metabolism. Little is known about the structure and mechanism of MPC, as the proteins involved were only identified a decade ago and technical difficulties concerning their purification and stability have hindered progress in functional and structural analyses. The functional unit of MPC is a hetero-dimer comprising two small homologous membrane proteins, MPC1/MPC2 in humans, with the alternative complex MPC1L/MPC2 forming in the testis, but MPC proteins are found throughout the tree of life. The predicted topology of each protomer consists of an amphipathic helix followed by three transmembrane helices. An increasing number of inhibitors are being identified, expanding MPC pharmacology and providing insights into the inhibitory mechanism. Here, we provide critical insights on the composition, structure, and function of the complex and we summarize the different classes of small molecule inhibitors and their potential in therapeutics.

Keywords:  metabolism; mitochondria; pyruvate transport; small molecule inhibitors; transport mechanism

DOI:  https://doi.org/10.1111/apha.14016
Int J Mol Sci. 2023 Jun 15. pii: 10188. [Epub ahead of print]24(12):

Oxidative Stress Response Kinetics after 60 Minutes at Different Levels (10% or 15%) of Normobaric Hypoxia Exposure.

Clément Leveque, Simona Mrakic Sposta, Sigrid Theunissen, Peter Germonpré, Kate Lambrechts, Alessandra Vezzoli, Maristella Gussoni, Morgan Levenez, Pierre Lafère, François Guerrero, Costantino Balestra.

  In this study, the metabolic responses of hypoxic breathing for 1 h to inspired fractions of 10% and 15% oxygen were investigated. To this end, 14 healthy nonsmoking subjects (6 females and 8 males, age: 32.2 ± 13.3 years old (mean ± SD), height: 169.1 ± 9.9 cm, and weight: 61.6 ± 16.2 kg) volunteered for the study. Blood samples were taken before, and at 30 min, 2 h, 8 h, 24 h, and 48 h after a 1 h hypoxic exposure. The level of oxidative stress was evaluated by considering reactive oxygen species (ROS), nitric oxide metabolites (NOx), lipid peroxidation, and immune-inflammation by interleukin-6 (IL-6) and neopterin, while antioxidant systems were observed in terms of the total antioxidant capacity (TAC) and urates. Hypoxia abruptly and rapidly increased ROS, while TAC showed a U-shape pattern, with a nadir between 30 min and 2 h. The regulation of ROS and NOx could be explained by the antioxidant action of uric acid and creatinine. The kinetics of ROS allowed for the stimulation of the immune system translated by an increase in neopterin, IL-6, and NOx. This study provides insights into the mechanisms through which acute hypoxia affects various bodily functions and how the body sets up the protective mechanisms to maintain redox homeostasis in response to oxidative stress.

Keywords:  cellular reactions; decompression; human; human performance; hypoxia; oxygen biology; oxygen therapy

DOI:  https://doi.org/10.3390/ijms241210188
Science. 2023 Jun 30. 380(6652): 1372-1380

Metabolic orchestration of cell death by AMPK-mediated phosphorylation of RIPK1.

Tao Zhang, Daichao Xu, Elijah Trefts, Mingming Lv, Hiroyuki Inuzuka, Guobin Song, Min Liu, Jianlin Lu, Jianping Liu, Chen Chu, Min Wang, Huibing Wang, Huyan Meng, Hui Liu, Yuan Zhuang, Xingxing Xie, Fabin Dang, Dongxian Guan, Yuqin Men, Shuwen Jiang, Cong Jiang, Xiaoming Dai, Jing Liu, Zhen Wang, Peiqiang Yan, Jingchao Wang, Zhenbo Tu, Mrigya Babuta, Emily Erickson, Alissandra L Hillis, Christian C Dibble, John M Asara, Gyongy Szabo, Piotr Sicinski, Ji Miao, Yu-Ru Lee, Lifeng Pan, Reuben J Shaw, Junying Yuan, Wenyi Wei.

Adenosine monophosphate-activated protein kinase (AMPK) activity is stimulated to promote metabolic adaptation upon energy stress. However, sustained metabolic stress may cause cell death. The mechanisms by which AMPK dictates cell death are not fully understood. We report that metabolic stress promoted receptor-interacting protein kinase 1 (RIPK1) activation mediated by TRAIL receptors, whereas AMPK inhibited RIPK1 by phosphorylation at Ser415 to suppress energy stress-induced cell death. Inhibiting pS415-RIPK1 by Ampk deficiency or RIPK1 S415A mutation promoted RIPK1 activation. Furthermore, genetic inactivation of RIPK1 protected against ischemic injury in myeloid Ampkα1-deficient mice. Our studies reveal that AMPK phosphorylation of RIPK1 represents a crucial metabolic checkpoint, which dictates cell fate response to metabolic stress, and highlight a previously unappreciated role for the AMPK-RIPK1 axis in integrating metabolism, cell death, and inflammation.

DOI: https://doi.org/10.1126/science.abn1725
Int J Mol Sci. 2023 Jun 16. pii: 10205. [Epub ahead of print]24(12):

The Unfolded Protein Response Sensor IRE1 Regulates Activation of In Vitro Differentiated Type 1 Conventional DCs with Viral Stimuli.

Bernardita Medel, José Ignacio Bernales, Alonso Lira, Dominique Fernández, Takao Iwawaki, Pablo Vargas, Fabiola Osorio.

  Type 1 conventional dendritic cells (cDC1s) are leukocytes competent to coordinate antiviral immunity, and thus, the intracellular mechanisms controlling cDC1 function are a matter of intense research. The unfolded protein response (UPR) sensor IRE1 and its associated transcription factor XBP1s control relevant functional aspects in cDC1s including antigen cross-presentation and survival. However, most studies connecting IRE1 and cDC1 function are undertaken in vivo. Thus, the aim of this work is to elucidate whether IRE1 RNase activity can also be modeled in cDC1s differentiated in vitro and reveal the functional consequences of such activation in cells stimulated with viral components. Our data show that cultures of optimally differentiated cDC1s recapitulate several features of IRE1 activation noticed in in vivo counterparts and identify the viral analog Poly(I:C) as a potent UPR inducer in the lineage. In vitro differentiated cDC1s display constitutive IRE1 RNase activity and hyperactivate IRE1 RNase upon genetic deletion of XBP1s, which regulates production of the proinflammatory cytokines IL-12p40, TNF-α and IL-6, Ifna and Ifnb upon Poly(I:C) stimulation. Our results show that a strict regulation of the IRE1/XBP1s axis regulates cDC1 activation to viral agonists, expanding the scope of this UPR branch in potential DC-based therapies.

Keywords:  IRE1; cDC1s; dendritic cells; proinflammatory cytokines; unfolded protein response

DOI:  https://doi.org/10.3390/ijms241210205
Biomolecules. 2023 06 15. pii: 992. [Epub ahead of print]13(6):

Method of Monitoring 26S Proteasome in Cells Revealed the Crucial Role of PSMA3 C-Terminus in 26S Integrity.

Shirel Steinberger, Julia Adler, Yosef Shaul.

  Proteasomes critically regulate proteostasis via protein degradation. Proteasomes are multi-subunit complexes composed of the 20S proteolytic core particle (20S CP) that, in association with one or two 19S regulatory particles (19S RPs), generates the 26S proteasome, which is the major proteasomal complex in cells. Native gel protocols are used to investigate the 26S/20S ratio. However, a simple method for detecting these proteasome complexes in cells is missing. To this end, using CRISPR technology, we YFP-tagged the endogenous PSMB6 (β1) gene, a 20S CP subunit, and co-tagged endogenous PSMD6 (Rpn7), a 19S RP subunit, with the mScarlet fluorescent protein. We observed the colocalization of the YFP and mScarlet fluorescent proteins in the cells, with higher nuclear accumulation. Nuclear proteasomal granules are formed under osmotic stress, and all were positive for YFP and mScarlet. Previously, we have reported that PSMD1 knockdown, one of the 19 RP subunits, gives rise to a high level of "free" 20S CPs. Intriguingly, under this condition, the 20S-YFP remained nuclear, whereas the PSMD6-mScarlet was mostly in cytoplasm, demonstrating the distinct subcellular distribution of uncapped 20S CPs. Lately, we have shown that the PSMA3 (α7) C-terminus, a 20S CP subunit, binds multiple intrinsically disordered proteins (IDPs). Remarkably, the truncation of the PSMA3 C-terminus is phenotypically reminiscent of PSMD1 knockdown. These data suggest that the PSMA3 C-terminal region is critical for 26S proteasome integrity.

Keywords:  PSMA3 (α7); proteasome granules; proteasome subcellular localization; tagging 19S regulatory particle; tagging 20S proteasome

DOI:  https://doi.org/10.3390/biom13060992