bims-celmim 2023-08-20 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2023–08–20
thirty-two papers selected by
Marc Segarra Mondejar, University of Cologne

Glutamine metabolism in diseases associated with mitochondrial dysfunction.
Interplay of energy metabolism and autophagy.
Monitoring Mitochondria Function in Ferroptosis.
Different levels of autophagy induced by transient serum starvation regulate metabolism and differentiation of porcine skeletal muscle satellite cells.
Lactate activates the mitochondrial electron transport chain independent of its metabolism.
MicroRNA-129-1-3p attenuates autophagy-dependent cell death by targeting MCU in granulosa cells of laying hens under H2O2-induced oxidative stress.
YAP governs cellular adaptation to perturbation of glutamine metabolism by regulating ATF4-mediated stress response.
Targeting BCAA metabolism to potentiate metformin's therapeutic efficacy in the treatment of diabetes in mice.
The diversified role of mitochondria in ferroptosis in cancer.
The mitophagy pathway and its implications in human diseases.
Mitochondria-related signaling pathways involved in breast cancer regulate ferroptosis.
Monitoring Lysosome Function in Ferroptosis.
Inhibition of ERK downregulates autophagy via mitigating mitochondrial fragmentation to protect SH-SY5Y cells from OGD/R injury.
Cardiovascular aging: the mitochondrial influence.
Muscle mitochondrial transplantation can rescue and maintain cellular homeostasis.
The emerging roles of MAPK-AMPK in ferroptosis regulatory network.
A cell-autonomous mechanism regulates BCAA catabolism in white adipocytes and systemic metabolic balance.
Novel targets of β-TrCP cooperatively accelerate carbohydrate and fatty acid consumption.
Endoplasmic reticulum stress induced by turbulence of mitochondrial fusion and fission was involved in stressed cardiomyocyte injury.
Acetyl-coenzyme A acetyltransferase 1 promotes brown adipogenesis by activating the AMPK-PGC1α signaling pathway.
BRD7 improves glucose homeostasis independent of IRS proteins.
Leucine suppresses glucagon secretion from pancreatic islets by directly modulating α -cell cAMP.
Regulation of autophagy in chick myotube cultures: Effect of uncoupling mitochondrial oxidative phosphorylation.
Activation of NLRP3 Inflammasome via Drp1 Overexpression in Kupffer Cells Aggravates Ischemia-reperfusion Injury in Hepatic Steatosis.
DNAJB3 attenuates ER stress through direct interaction with AKT.
URB597 exerts neuroprotective effects against transient brain ischemia injury in mice by regulating autophagic flux and necroptosis.
NLRX1: versatile functions of a mitochondrial NLR protein that controls mitophagy.
The role of candidate transport proteins in beta cell long-chain fatty acid uptake: where are we now?
NME3 binds to phosphatidic acid and mediates PLD6-induced mitochondrial tethering.
Sophoridine derivative 6j inhibits liver cancer cell proliferation via ATF3 mediated ferroptosis.
Hypoxia-induced PPFIA4 accelerates the progression of ovarian cancer through glucose metabolic reprogramming.
The potential role of glucose metabolism, lipid metabolism, and amino acid metabolism in the treatment of Parkinson's disease.

Mol Cell Neurosci. 2023 Aug 15. pii: S1044-7431(23)00081-7. [Epub ahead of print]126 103887

Glutamine metabolism in diseases associated with mitochondrial dysfunction.

Rebecca Bornstein, Michael T Mulholland, Margaret Sedensky, Phil Morgan, Simon C Johnson.

  Mitochondrial dysfunction can arise from genetic defects or environmental exposures and impact a wide range of biological processes. Among these are metabolic pathways involved in glutamine catabolism, anabolism, and glutamine-glutamate cycling. In recent years, altered glutamine metabolism has been found to play important roles in the pathologic consequences of mitochondrial dysfunction. Glutamine is a pleiotropic molecule, not only providing an alternate carbon source to glucose in certain conditions, but also playing unique roles in cellular communication in neurons and astrocytes. Glutamine consumption and catabolic flux can be significantly altered in settings of genetic mitochondrial defects or exposure to mitochondrial toxins, and alterations to glutamine metabolism appears to play a particularly significant role in neurodegenerative diseases. These include primary mitochondrial diseases like Leigh syndrome (subacute necrotizing encephalopathy) and MELAS (mitochondrial myopathy with encephalopathy, lactic acidosis, and stroke-like episodes), as well as complex age-related neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Pharmacologic interventions targeting glutamine metabolizing and catabolizing pathways appear to provide some benefits in cell and animal models of these diseases, indicating glutamine metabolism may be a clinically relevant target. In this review, we discuss glutamine metabolism, mitochondrial disease, the impact of mitochondrial dysfunction on glutamine metabolic processes, glutamine in neurodegeneration, and candidate targets for therapeutic intervention.

Keywords:  Glutamine toxicity; Mitochondrial disease; Neurodegenerative disease

DOI:  https://doi.org/10.1016/j.mcn.2023.103887
Autophagy. 2023 Aug 18. 1-11

Interplay of energy metabolism and autophagy.

Yuyao Feng, Ying Chen, Xiaoyong Wu, Junye Chen, Qingyan Zhou, Bao Liu, Liqin Zhang, Cong Yi.

  Macroautophagy/autophagy, is widely recognized for its crucial role in enabling cell survival and maintaining cellular energy homeostasis during starvation or energy stress. Its regulation is intricately linked to cellular energy status. In this review, covering yeast, mammals, and plants, we aim to provide a comprehensive overview of the understanding of the roles and mechanisms of carbon- or glucose-deprivation related autophagy, showing how cells effectively respond to such challenges for survival. Further investigation is needed to determine the specific degraded substrates by autophagy during glucose or energy deprivation and the diverse roles and mechanisms during varying durations of energy starvation.Abbreviations: ADP: adenosine diphosphate; AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATP: adenosine triphosphate; ER: endoplasmic reticulum; ESCRT: endosomal sorting complex required for transport; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GD: glucose deprivation; GFP: green fluorescent protein; GTPases: guanosine triphosphatases; HK2: hexokinase 2; K phaffii: Komagataella phaffii; LD: lipid droplet; MAP1LC3/LC3: microtubule-associated protein1 light chain 3; MAPK: mitogen-activated protein kinase; Mec1: mitosis entry checkpoint 1; MTOR: mechanistic target of rapamycin kinase; NAD (+): nicotinamide adenine dinucleotide; OGD: oxygen and glucose deprivation; PAS: phagophore assembly site; PCD: programmed cell death; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; ROS: reactive oxygen species; S. cerevisiae: Saccharomyces cerevisiae; SIRT1: sirtuin 1; Snf1: sucrose non-fermenting 1; STK11/LKB1: serine/threonine kinase 11; TFEB: transcription factor EB; TORC1: target of rapamycin complex 1; ULK1: unc-51 like kinase 1; Vps27: vacuolar protein sorting 27; Vps4: vacuolar protein sorting 4.

Keywords:  AMPK; Snf1; autophagy; carbon starvation; energy metabolism; glucose starvation

DOI:  https://doi.org/10.1080/15548627.2023.2247300
Methods Mol Biol. 2023 ;2712 103-115

Monitoring Mitochondria Function in Ferroptosis.

Fangquan Chen, Jiao Liu, Daolin Tang, Rui Kang.

  Ferroptosis is a type of regulated necrosis driven by uncontrolled membrane lipid peroxidation. Mitochondria, which are membrane-bound organelles present in almost all eukaryotic cells and play a central role in energy metabolism and various types of cell death, have a complicated role in ferroptosis. On one hand, mitochondrial-derived iron metabolism and reactive oxygen species (ROS) production may promote ferroptosis. On the other hand, mitochondria also possess a dihydroorotate dehydrogenase (DHODH)-dependent antioxidant system that detoxifies lipid peroxides. This chapter summarizes several methods, such as western blotting, immunofluorescence, cell viability assays, mitochondrial fluorescent probes, adenosine 5'-triphosphate (ATP) assay kits, mitochondrial respiration, and mitophagy tests, that may enable researchers to gain a deeper understanding of the dual role of mitochondria in ferroptosis.

Keywords:  Ferroptosis; Methods; Mitochondria

DOI:  https://doi.org/10.1007/978-1-0716-3433-2_10
Sci Rep. 2023 08 12. 13(1): 13153

Different levels of autophagy induced by transient serum starvation regulate metabolism and differentiation of porcine skeletal muscle satellite cells.

Yi Wang, Juan Gao, Bojun Fan, Yuemin Hu, Yuefei Yang, Yajie Wu, Feng Li, Huiming Ju.

This study aimed to investigate the effects of different levels of autophagy induced by transient serum starvation on the metabolism, lipid metabolism, and differentiation of porcine skeletal muscle satellite cells (SMSCs) to preliminary elucidate the role and function of autophagy in the regulatory network of skeletal muscle development. Different levels of autophagy were induced by controlling the serum concentration in the culture system for 24 h. Apoptosis, membrane potential, reactive oxygen species (ROS), ATP, and myogenic and lipogenic differentiation markers were monitored to determine if autophagy affected the metabolism and differentiation of SMSCs. Autophagy was induced in SMSCs via serum starvation (5%, 15%), as evidenced by decreased p62 and mTOR phosphorylation levels and increased LC3B lipidation and AMPK phosphorylation levels. Transmission electron microscopy revealed the presence of autophagosomes, and the rates of morphologically abnormal nuclei and mitochondria gradually increased with the decrease in serum concentration, the number of autophagic lysosomes also increased, indicating that 5% serum starvation induced severe autophagy, while 15% serum starvation induced mild autophagy. Compared with the control group and 15% serum-starved SMSCs, SMSCs undergoing 5% serum starvation had the highest intracellular ATP and ROS levels, the highest percentage of apoptotic cells, and the lowest membrane potential. The 15% serum-starved SMSCs had the highest membrane potential, but the percentage of apoptotic cells did not change significantly compared with the control group. The levels of the myogenic markers MyoD1 and MHC were significantly higher in 15% serum-starved SMSCs than in serum-sufficient SMSCs and the lowest in the 5% serum-starved SMSCs. The lipid contents (measured by Oil Red O staining and quantification of triglycerides) and lipogenic markers Peroxisome Proliferators-activated Receptors γ and Lipoprotein Lipase were also significantly higher in SMSCs undergoing 15% serum starvation than in the control group, and the lowest in the 5% serum-starved SMSCs. Different levels of starvation stress induce different levels of autophagy. Mild autophagy induced by moderate serum starvation promotes the metabolism and differentiation of SMSCs, while severe autophagy renders SMSCs more apoptotic, abnormal metabolism and suppresses SMSC differentiation into adipocytes or myocytes, and reduces lipid metabolisms. Our study suggests that autophagy plays a role in skeletal muscle development and may help design strategies for improving meat production traits in domestic pigs.

DOI: https://doi.org/10.1038/s41598-023-40350-y
bioRxiv. 2023 Aug 04. pii: 2023.08.02.551712. [Epub ahead of print]

Lactate activates the mitochondrial electron transport chain independent of its metabolism.

Xin Cai, Charles C Ng, Olivia Jones, Tak Shun Fung, Keunwoo Ryu, Dayi Li, Craig B Thompson.

Lactate has long been considered a cellular waste product. However, we found that as extracellular lactate accumulates, it also enters the mitochondrial matrix and stimulates mitochondrial electron transport chain (ETC) activity. The resulting increase in mitochondrial ATP synthesis suppresses glycolysis and increases the utilization of pyruvate and/or alternative respiratory substrates. The ability of lactate to increase oxidative phosphorylation does not depend on its metabolism. Both L- and D-lactate are effective at enhancing ETC activity and suppressing glycolysis. Furthermore, the selective induction of mitochondrial oxidative phosphorylation by unmetabolized D-lactate reversibly suppressed aerobic glycolysis in both cancer cell lines and proliferating primary cells in an ATP-dependent manner and enabled cell growth on respiratory-dependent bioenergetic substrates. In primary T cells, D-lactate enhanced cell proliferation and effector function. Together, these findings demonstrate that lactate is a critical regulator of the ability of mitochondrial oxidative phosphorylation to suppress glucose fermentation.

DOI: https://doi.org/10.1101/2023.08.02.551712
Poult Sci. 2023 Aug 03. pii: S0032-5791(23)00525-4. [Epub ahead of print]102(10): 103006

MicroRNA-129-1-3p attenuates autophagy-dependent cell death by targeting MCU in granulosa cells of laying hens under H2O2-induced oxidative stress.

Mingkun Zhu, Ming Yan, Jianfei Chen, Huaiyu Li, Yeshun Zhang.

  The present study aimed to investigate the mechanism of microRNA-129-1-3p (miR-129-1-3p) in regulating hydrogen peroxide (H2O2)-induced autophagic death of chicken granulosa cell by targeting mitochondrial calcium uniporter (MCU). The results indicated that the exposure of hens' ovaries to H2O2 resulted in a significant elevation in reactive oxygen species (ROS) levels, as well as the apoptosis of granulosa cells and follicular atresia. This was accompanied by an upregulation of glucose-regulated protein 75 (GRP75), voltage-dependent anion-selective channel 1 (VDAC1), MCU, mitochondria fission factor (MFF), microtubule-associated protein 1 light chain 3 (LC3) I, and LC3II expression, and a downregulation of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and mitofusin-2 (MFN2) expression. In hens' granulosa cells, a luciferase reporter assay confirmed that miR-129-1-3p directly regulates MCU. The induction of oxidative stress through H2O2 resulted in the activation of the permeability transition pore, an overload of calcium, depolarization of the mitochondrial membrane potential, dysfunction of mitochondria-associated endoplasmic reticulum membranes (MAMs), and ultimately, autophagic cell death. The overexpression of miR-129-1-3p effectively mitigated these H2O2-induced changes. Furthermore, miR-129-1-3p overexpression in granulosa cells prevented the alterations induced by H2O2 in the expression of key proteins that play crucial roles in maintaining the integrity of MAMs and regulating autophagy, such as GRP75, VDAC1, MFN2, PTEN-induced kinase 1 (Pink1), and parkin RBR E3 ubiquitin-protein ligase (Parkin). Together, these in vitro- and in vivo-based experiments suggest that miR-129-1-3p protects granulosa cells from oxidative stress-induced autophagic cell death by downregulating the MCU-mediated mitochondrial autophagy. miR-129-1-3p/MCU calcium signaling pathway may act as a new target to alleviate follicular atresia caused by oxidative stress in laying hens.

Keywords:  MCU; granulosa cell autophagy; laying hens; microRNA-129-1-3p; oxidative stress

DOI:  https://doi.org/10.1016/j.psj.2023.103006
Oncogene. 2023 Aug 17.

YAP governs cellular adaptation to perturbation of glutamine metabolism by regulating ATF4-mediated stress response.

Minjoong Kim, Sunsook Hwang, Byungjoo Kim, Seungmin Shin, Seungyeon Yang, Jihye Gwak, Seung Min Jeong.

Proliferating cells have metabolic dependence on glutamine to fuel anabolic pathways and to refill the mitochondrial carbon pool. The Hippo pathway is essential for coordinating cell survival and growth with nutrient availability, but no molecular connection to glutamine deprivation has been reported. Here, we identify a non-canonical role of YAP, a key effector of the Hippo pathway, in cellular adaptation to perturbation of glutamine metabolism. Whereas YAP is inhibited by nutrient scarcity, enabling cells to restrain proliferation and to maintain energy homeostasis, glutamine shortage induces a rapid YAP dephosphorylation and activation. Upon glutaminolysis inhibition, an increased reactive oxygen species production inhibits LATS kinase via RhoA, leading to YAP dephosphorylation. Activated YAP promotes transcriptional induction of ATF4 to induce the expression of genes involved in amino acid homeostasis, including Sestrin2. We found that YAP-mediated Sestrin2 induction is crucial for cell viability during glutamine deprivation by suppressing mTORC1. Thus, a critical relationship between YAP, ATF4, and mTORC1 is uncovered by our findings. Finally, our data indicate that targeting the Hippo-YAP pathway in combination with glutaminolysis inhibition may provide potential therapeutic approaches to treat tumors.

DOI: https://doi.org/10.1038/s41388-023-02811-6
Diabetologia. 2023 Aug 15.

Targeting BCAA metabolism to potentiate metformin's therapeutic efficacy in the treatment of diabetes in mice.

Xiaoyun Zhao, Xuejiao Zhang, Jingjing Pei, Yajin Liu, Wenyan Niu, Haipeng Sun.

   AIMS/HYPOTHESIS: An increasing body of evidence has shown that the catabolism of branched-chain amino acids (BCAAs; leucine, isoleucine and valine) is impaired in obese animals and humans, contributing to the development of insulin resistance and type 2 diabetes. Promoting BCAA catabolism benefits glycaemic control. It remains unclear whether BCAA catabolism plays a role in the therapeutic efficacy of currently used glucose-lowering drugs such as metformin.
METHODS: Mice were treated with vehicle or metformin (250 mg/kg per day) for more than 4 weeks to investigate the effects of metformin in vivo. In vitro, primary mouse hepatocytes and HepG2 cells were treated with 2 mmol/l metformin. The therapeutic efficacy of metformin in the treatment of type 2 diabetes was assessed in genetically obese (ob/ob) mice and high-fat-diet-induced obese (DIO) mice. Enhancing BCAA catabolism was achieved with a pharmacological agent, 3,6-dichlorobenzo[b]thiophene-2-carboxylic acid (BT2). The ob/ob mice were treated with a low-BCAA diet or intermittent protein restriction (IPR) to reduce BCAA nutritional intake.
RESULTS: Metformin unexpectedly inhibited the catabolism of BCAAs in obese mice, resulting in an elevation of BCAA abundance. AMP-activated protein kinase (AMPK) mediated the impact of metformin on BCAA catabolism in hepatocytes. Importantly, enhancing BCAA catabolism via a pharmacological agent BT2 significantly potentiated the glucose-lowering effect of metformin while decreasing circulating BCAA levels in ob/ob and DIO mice. Similar outcomes were achieved by a nutritional approach of reducing BCAA intake. IPR also effectively reduced the circulating BCAA abundance and enhanced metformin's glucose-lowering effect in ob/ob mice. BT2 and IPR treatments reduced the expression of fructose-1,6-bisphosphatase 1, a rate-limiting enzyme in gluconeogenesis, in the kidney but not liver, indicating the involvement of renal gluconeogenesis.
CONCLUSIONS/INTERPRETATION: Metformin self-limits its therapeutic efficacy in the treatment of type 2 diabetes by triggering the suppression of BCAA catabolism. Enhancing BCAA catabolism pharmacologically or reducing BCAA intake nutritionally potentiates the glucose-lowering effect of metformin. These data highlight the nutritional impact of protein on metformin's therapeutic efficacy and provide new strategies targeting BCAA metabolism to improve metformin's effects on the clinical outcome in diabetes.

Keywords:  Branched-chain amino acid; Diabetes mellitus; Metformin; Therapeutic efficacy

DOI:  https://doi.org/10.1007/s00125-023-05985-6
Cell Death Dis. 2023 08 14. 14(8): 519

The diversified role of mitochondria in ferroptosis in cancer.

Yu'e Liu, Shiping Lu, Lei-Lei Wu, Liang Yang, Lixue Yang, Jinghan Wang.

Ferroptosis is a form of regulated cell death induced by iron-dependent lipid peroxidation, and it has been studied extensively since its discovery in 2012. Induced by iron overload and ROS accumulation, ferroptosis is modulated by various cellular metabolic and signaling pathways. The GSH-GPX4 pathway, the FSP1-CoQ10 pathway, the GCH1-BH4 pathway, the DHODH-CoQH2 system and the sex hormones suppress ferroptosis. Mitochondrial iron metabolism regulates ferroptosis and mitochondria also undergo a morphological change during ferroptosis, these changes include increased membrane density and reduced mitochondrial cristae. Moreover, mitochondrial energy metabolism changes during ferroptosis, the increased oxidative phosphorylation and ATP production rates lead to a decrease in the glycolysis rate. In addition, excessive oxidative stress induces irreversible damage to mitochondria, diminishing organelle integrity. ROS production, mitochondrial membrane potential, mitochondrial fusion and fission, and mitophagy also function in ferroptosis. Notably, some ferroptosis inhibitors target mitochondria. Ferroptosis is a major mechanism for cell death associated with the progression of cancer. Metastasis-prone or metastatic cancer cells are more susceptible to ferroptosis. Inducing ferroptosis in tumor cells shows very promising potential for treating drug-resistant cancers. In this review, we present a brief retrospect of the discovery and the characteristics of ferroptosis, then we discuss the regulation of ferroptosis and highlight the unique role played by mitochondria in the ferroptosis of cancer cells. Furthermore, we explain how ferroptosis functions as a double-edged sword as well as novel therapies aimed at selectively manipulating cell death for cancer eradication.

DOI: https://doi.org/10.1038/s41419-023-06045-y
Signal Transduct Target Ther. 2023 08 16. 8(1): 304

The mitophagy pathway and its implications in human diseases.

Shouliang Wang, Haijiao Long, Lianjie Hou, Baorong Feng, Zihong Ma, Ying Wu, Yu Zeng, Jiahao Cai, Da-Wei Zhang, Guojun Zhao.

Mitochondria are dynamic organelles with multiple functions. They participate in necrotic cell death and programmed apoptotic, and are crucial for cell metabolism and survival. Mitophagy serves as a cytoprotective mechanism to remove superfluous or dysfunctional mitochondria and maintain mitochondrial fine-tuning numbers to balance intracellular homeostasis. Growing evidences show that mitophagy, as an acute tissue stress response, plays an important role in maintaining the health of the mitochondrial network. Since the timely removal of abnormal mitochondria is essential for cell survival, cells have evolved a variety of mitophagy pathways to ensure that mitophagy can be activated in time under various environments. A better understanding of the mechanism of mitophagy in various diseases is crucial for the treatment of diseases and therapeutic target design. In this review, we summarize the molecular mechanisms of mitophagy-mediated mitochondrial elimination, how mitophagy maintains mitochondrial homeostasis at the system levels and organ, and what alterations in mitophagy are related to the development of diseases, including neurological, cardiovascular, pulmonary, hepatic, renal disease, etc., in recent advances. Finally, we summarize the potential clinical applications and outline the conditions for mitophagy regulators to enter clinical trials. Research advances in signaling transduction of mitophagy will have an important role in developing new therapeutic strategies for precision medicine.

DOI: https://doi.org/10.1038/s41392-023-01503-7
Genes Dis. 2024 Jan;11(1): 358-366

Mitochondria-related signaling pathways involved in breast cancer regulate ferroptosis.

Xinrui Dong, Ye Li, Xiaonan Sheng, Weihang Zhou, Aijun Sun, Huijuan Dai.

  Ferroptosis is a novel form of regulated cell death characterized by iron-dependent excessive lipid peroxidation. The core organelle involved in ferroptosis is mitochondria. Mitochondria undergoing ferroptosis are distinct from normal mitochondria in terms of morphology, biochemistry, gene expression, and energy metabolism. An increasing number of studies have shown that mitochondria and their associated metabolic pathways mediate ferroptosis in the development and progression of breast cancer. In this review, we discuss the relevant research about ferroptosis in breast cancer and provide a comprehensive summary of mitochondrial regulation in ferroptosis from the perspective of lipid metabolism, oxidative phosphorylation, ion metabolism, glycometabolism, and nucleotide metabolism. We also summarize the application of mitochondrial metabolism-related pathways as ferroptosis treatment targets. Here we provide new insights into the relationship between mitochondria, ferroptosis, and breast cancer treatment.

Keywords:  Breast cancer; Cancer treatment; Ferroptosis; Lipid metabolism; Mitochondria; Oxidative phosphorylation

DOI:  https://doi.org/10.1016/j.gendis.2023.03.019
Methods Mol Biol. 2023 ;2712 91-102

Monitoring Lysosome Function in Ferroptosis.

Fangquan Chen, Rui Kang, Daolin Tang, Jiao Liu.

  Ferroptosis is a type of regulated cell death that occurs due to iron-induced membrane lipid peroxidation. Lysosomes, which are acidic, membrane-bound organelles containing various hydrolases, play a vital role in ferroptosis. They not only aid in the degradation of autophagic substrates, but also serve as signaling hubs in cell death. Specifically, lysosomes are involved in the induction and execution of ferroptosis through autophagy-mediated degradation of anti-ferroptotic proteins, lysosomal membrane permeability-mediated release of cathepsins, and iron-induced lysosomal membrane lipid peroxidation. Therefore, it is essential to have reliable methods for monitoring lysosomal functions, including lysosomal activity, pH, and membrane integrity, as well as iron accumulation and lipid peroxidation, to understand ferroptosis. This chapter introduces several protocols, such as western blotting, immunofluorescence, lysosomal probes, and lipid peroxidation assay kits, for monitoring the process of lysosome-related ferroptosis.

Keywords:  Autophagy; Cell death; Ferroptosis; Lysosome

DOI:  https://doi.org/10.1007/978-1-0716-3433-2_9
Cell Commun Signal. 2023 Aug 14. 21(1): 204

Inhibition of ERK downregulates autophagy via mitigating mitochondrial fragmentation to protect SH-SY5Y cells from OGD/R injury.

Zhang-Li Yuan, Yan-Zi Mo, De-Li Li, Lu Xie, Meng-Hua Chen.

   BACKGROUND: Cerebral ischemia-reperfusion injury (CIRI) is the main cause leading to high mortality and neurological disability in patients with cardiac arrest/cardiopulmonary resuscitation (CA/CPR). Our previous study found that extracellular signal-regulated kinase (ERK) activation, dynamin-related protein1 (Drp1)/Mitofusin2 (Mfn2)-dependent mitochondrial dynamics imbalance, and excessive autophagy were involved in the mechanism of nerve injury after CA/CPR. However, the specific pathological signaling pathway is still unknown. This study aimed to explore the molecular function changes of ERK-Drp1/Mfn2-autophagy signaling pathway in SH-SY5Y cell oxygen-glucose deprivation/reoxygenation (OGD/R) model, to further clarify the pathophysiological mechanism of CIRI, and to provide a new strategy for cerebral protection after CIRI.
METHODS: SH-SY5Y cells were pretreated with drugs 24 h before OGD/R. The Drp1 and Mfn2 knockdown were adopted small interfering RNAs. The overexpression of p-Drp1S616 and Mfn2 were used recombinant plasmids. The expression levels of mitochondrial dynamics proteins (p-Drp1, Drp1, Mfn2, Mfn1 and Opa1) and autophagy markers (LC3, Beclin1 and p62) were measured with the Western blotting. The mRNA levels after transfection were determined by PCR. Cell injury and viability were evaluated with released LDH activity and CCK8 assay kits. Mitochondria morphology and autophagosome were observed under transmission electron microscopy. Mitochondrial function was detected by the mitochondrial permeability transition pore assay kit. The co-expression of p-ERK, p-Drp1 and LC3 was assessed with multiple immunofluorescences. One-way analysis of variance followed by least significance difference post hoc analysis (for equal homogeneity) or Dunnett's T3 test (for unequal homogeneity) were used for statistical tests.
RESULTS: ERK inhibitor-PD98059 (PD) protects SH-SY5Y cells from OGD/R-induced injury; while ERK activator-TPA had the opposite effect. Similar to autophagy inhibitor 3-MA, PD downregulated autophagy to improve cell viability; while autophagy activator-rapamycin further aggravated cell death. PD and Drp1-knockdown synergistically attenuated OGD/R-induced Drp1 activation, mPTP opening and cell injury; overexpression of Drp1S616E or ablating Mfn2 partly abolished the protective effects of PD. Multiple immunofluorescences showed that p-ERK, p-Drp1 and LC3 were co-expressed.
CONCLUSION: Inhibition of ERK downregulates autophagy via reducing Drp1/Mfn2-dependent mitochondrial fragmentation to antagonize mitochondrial dysfunction and promotes cell survival in the SH-SY5Y cells OGD/R model. Video Abstract.

Keywords:  Autophagy; CIRI; Drp1; ERK; Mfn2; Mitochondrial dynamics; OGD/R

DOI:  https://doi.org/10.1186/s12964-023-01211-3
J Cardiovasc Aging. 2023 Jul;pii: 33. [Epub ahead of print]3(3):

Cardiovascular aging: the mitochondrial influence.

Shakti Sagar, Asa B Gustafsson.

  Age-associated cardiovascular disease is becoming progressively prevalent due to the increased lifespan of the population. However, the fundamental mechanisms underlying the aging process and the corresponding decline in tissue functions are still poorly understood. The heart has a very high energy demand and the cellular energy needed to sustain contraction is primarily generated by mitochondrial oxidative phosphorylation. Mitochondria are also involved in supporting various metabolic processes, as well as activation of the innate immune response and cell death pathways. Given the central role of mitochondria in energy metabolism and cell survival, the heart is highly susceptible to the effects of mitochondrial dysfunction. These key organelles have been implicated as underlying drivers of cardiac aging. Here, we review the evidence demonstrating the mitochondrial contribution to the cardiac aging process and disease susceptibility. We also discuss the potential mechanisms responsible for the age-related decline in mitochondrial function.

Keywords:  Aging; heart disease; mitochondria

DOI:  https://doi.org/10.20517/jca.2023.22
Am J Physiol Cell Physiol. 2023 Aug 14.

Muscle mitochondrial transplantation can rescue and maintain cellular homeostasis.

Debasmita Bhattacharya, Mikhaela B Slavin, David A Hood.

  Mitochondria control cellular functions through their metabolic role. Recent research that has gained considerable attention is their ability to transfer between cells. This has the potential of improving cellular functions in pathological or energy deficit conditions, but little is known about the role of mitochondrial transfer in sustaining cellular homeostasis. Few studies have investigated the potential of skeletal muscle as a source of healthy mitochondria that can be transferred to other cell types. Thus, we isolated intermyofibrillar mitochondria from murine skeletal muscle and incubated them with host cells. We observed dose- and time-dependent increases in mitochondrial incorporation into myoblasts. This resulted in elongated mitochondrial networks and an enhancement of bioenergetic profile of the host cells. Mitochondrial donation also rejuvenated the functional capacities of the myoblasts when respiration efficiency and lysosomal function were inhibited by complex I inhibitor rotenone and bafilomycin A, respectively. Mitochondrial transfer was accomplished via tunneling nanotubes, extracellular vesicles, gap junctions and by macropinocytosis internalization. Murine muscle mitochondria were also effectively transferred to human fibroblast cells having mitochondrial DNA mutations, resulting in augmented mitochondrial dynamics and metabolic functions. This improved cell function by diminishing ROS emission in the diseased cells. Our findings suggest that mitochondria from donor skeletal muscle can be integrated in both healthy and functionally compromised host cells leading to mitochondrial structural refinement and respiratory boost. This mitochondrial trafficking and bioenergetic reprogramming to maintain and revitalise tissue homeostasis could be a useful therapeutic strategy in treating diseases.

Keywords:  Lysosome; Mitochondrial DNA Defects; Mitochondrial Dynamics; Mitochondrial Transplantation; Oxygen Consumption

DOI:  https://doi.org/10.1152/ajpcell.00212.2023
Cell Commun Signal. 2023 Aug 14. 21(1): 200

The emerging roles of MAPK-AMPK in ferroptosis regulatory network.

Xinyue Wang, Xiao Tan, Jinping Zhang, Jiaping Wu, Hongjuan Shi.

  Ferroptosis, a newform of programmed cell death, driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes and is extremely dependent on iron ions, which is differs characteristics from traditional cell death has attracted greater attention. Based on the curiosity of this new form of regulated cell death, there has a tremendous progress in the field of mechanistic understanding of ferroptosis recent years. Ferroptosis is closely associated with the development of many diseases and involved in many diseases related signaling pathways. Not only a variety of oncoproteins and tumor suppressors can regulate ferroptosis, but multiple oncogenic signaling pathways can also have a regulatory effect on ferroptosis. Ferroptosis results in the accumulation of large amounts of lipid peroxides thus involving the onset of oxidative stress and energy stress responses. The MAPK pathway plays a critical role in oxidative stress and AMPK acts as a sensor of cellular energy and is involved in the regulation of the energy stress response. Moreover, activation of AMPK can induce the occurrence of autophagy-dependent ferroptosis and p53-activated ferroptosis. In recent years, there have been new advances in the study of molecular mechanisms related to the regulation of ferroptosis by both pathways. In this review, we will summarize the molecular mechanisms by which the MAPK-AMPK signaling pathway regulates ferroptosis. Meanwhile, we sorted out the mysterious relationship between MAPK and AMPK, described the crosstalk among ferroptosis and MAPK-AMPK signaling pathways, and summarized the relevant ferroptosis inducers targeting this regulatory network. This will provide a new field for future research on ferroptosis mechanisms and provide a new vision for cancer treatment strategies. Video Abstract.

Keywords:  AMPK; Autophagy; Ferroptosis; MAPK; p53

DOI:  https://doi.org/10.1186/s12964-023-01170-9
bioRxiv. 2023 Aug 01. pii: 2023.07.31.551146. [Epub ahead of print]

A cell-autonomous mechanism regulates BCAA catabolism in white adipocytes and systemic metabolic balance.

Ashley M Aguillard, Joyce Tzeng, Ismael Ferrer, Bjorn T Tam, Damaris N Lorenzo.

Elevated plasma branched-chain amino acids (BCAAs) are strongly associated with obesity, insulin resistance (IR), and diabetes in humans and rodent models. However, the mechanisms of BCAA dysregulation and its systemic, organ, and cell-specific implications in the development of obesity and IR are not well understood. To gain mechanistic insight into the causes and effects of plasma BCAA elevations, we leveraged mouse models with high circulating BCAA levels prior to the onset of obesity and IR. Young mice lacking ankyrin-B in white adipose tissue (WAT) or bearing an ankyrin-B variant that causes age-driven metabolic syndrome exhibit downregulation of BCAA catabolism selectively in WAT and excess plasma BCAAs. Using cellular assays, we demonstrated that ankyrin-B promotes the surface localization of the amino acid transporter Asct2 in white adipocytes, and its deficit impairs BCAA uptake. Excess BCAA supplementation worsened glucose tolerance and insulin sensitivity across genotypes. In contrast, BCAA overconsumption only increased adiposity in control mice, implicating WAT utilization of BCAAs in their obesogenic effects. These results shed light into the mechanistic underpinnings of metabolic syndrome caused by ankyrin-B deficits and provide new evidence of the relevance of WAT in the regulation of systemic BCAA levels, adiposity, and glucose homeostasis.
ARTICLE HIGHLIGHTS: Ankyrin-B deficits in adipose tissue result in elevated circulating BCAAs before the onset of obesity and insulin resistance.Ankyrin-B promotes the surface localization of the amino acid transporter Asct2 in white adipocytes and BCAA uptake.Excess BCAA supplementation worsens glucose tolerance and insulin sensitivity in ankyrin-B deficient mice.BCAA utilization by white adipose tissue is required for the obesogenic effects of BCAA overconsumption.

DOI: https://doi.org/10.1101/2023.07.31.551146
J Cell Physiol. 2023 Aug 16.

Novel targets of β-TrCP cooperatively accelerate carbohydrate and fatty acid consumption.

Hyun Jeong Joo, Matthew D'Alessandro, Gaeun Oh, Sora Han, Woo Jung Kim, Ga Eun Chung, Youjeong Jang, Jung Bok Lee, Choogon Lee, Young Yang.

  Cellular energy is primarily produced from glucose and fat through glycolysis and fatty acid oxidation (FAO) followed by the tricarboxylic acid cycle in mitochondria; energy homeostasis is carefully maintained via numerous feedback pathways. In this report, we uncovered a new master regulator of carbohydrate and lipid metabolism. When ubiquitin E3 ligase β-TrCP2 was inducibly knocked out in β-TrCP1 knockout adult mice, the resulting double knockout mice (DKO) lost fat mass rapidly. Biochemical analyses of the tissues and cells from β-TrCP2 KO and DKO mice revealed that glycolysis, FAO, and lipolysis were dramatically upregulated. The absence of β-TrCP2 increased the protein stability of metabolic rate-limiting enzymes including 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1A (CPT1A), and carnitine/acylcarnitine translocase (CACT). Our data suggest that β-TrCP is a potential regulator for total energy homeostasis by simultaneously controlling glucose and fatty acid metabolism and that targeting β-TrCP could be an effective strategy to treat obesity and other metabolic disorders.

Keywords:  E3 ligase; energy homeostasis; metabolism; obesity; ubiquitination; β-TrCP

DOI:  https://doi.org/10.1002/jcp.31095
J Cell Mol Med. 2023 Aug 18.

Endoplasmic reticulum stress induced by turbulence of mitochondrial fusion and fission was involved in stressed cardiomyocyte injury.

Shengnan Zhang, Yingmin Li, Weihao Zhu, Lihua Zhang, Lei Lei, Xiaofei Tian, Ke Chen, Weibo Shi, Bin Cong.

  Mitochondria are sensitive organelles that sense intrinsic and extrinsic stressors and maintain cellular physiological functions through the dynamic homeostasis of mitochondrial fusion and fission. Numerous pathological processes are associated with mitochondrial fusion and fission disorders. However, the molecular mechanism by which stress induces cardiac pathophysiological changes through destabilising mitochondrial fusion and fission is unclear. Therefore, this study aimed to investigate whether the endoplasmic reticulum stress signalling pathway initiated by the turbulence of mitochondrial fusion and fission under stressful circumstances is involved in cardiomyocyte damage. Based on the successful establishment of the classical stress rat model of restraint plus ice water swimming, we measured the content of serum lactate dehydrogenase. We used haematoxylin-eosin staining, special histochemical staining, RT-qPCR and western blotting to clarify the cardiac pathology, ultrastructural changes and expression patterns of mitochondrial fusion and fission marker proteins and endoplasmic reticulum stress signalling pathway proteins. The results indicated that mitochondrial fusion and fission markers and proteins of the endoplasmic reticulum stress JNK signalling pathway showed significant abnormal dynamic changes with the prolongation of stress, and stabilisation of mitochondrial fusion and fission using Mdivi-1 could effectively improve these abnormal expressions and ameliorate cardiomyocyte injury. These findings suggest that stress could contribute to pathological cardiac injury, closely linked to the endoplasmic reticulum stress JNK signalling pathway induced by mitochondrial fusion and fission turbulence.

Keywords:  endoplasmic reticulum stress; mitochondrial fission; mitochondrial fusion; myocardial injury; stress

DOI:  https://doi.org/10.1111/jcmm.17901
Biochim Biophys Acta Mol Cell Biol Lipids. 2023 Aug 13. pii: S1388-1981(23)00093-8. [Epub ahead of print] 159369

Acetyl-coenzyme A acetyltransferase 1 promotes brown adipogenesis by activating the AMPK-PGC1α signaling pathway.

Kaixiang Zhu, Ling Ni, Jianxiong Han, Zhongkang Yan, Yin Zhang, Feifei Wang, Lili Wang, Xingyuan Yang.

  Brown adipose tissue (BAT) is thermogenic, expressing high levels of uncoupling protein-1 to convert nutrient energy to heat energy, bypassing ATP synthesis. BAT is a promising therapeutic target for treatment of obesity and type 2 diabetes since it converts fatty acids into heat but mechanisms controlling brown adipogenesis remain unclear. Knockdown of acetyl-Coenzyme A acetyltransferase 1 (ACAT1) in C3H10T1/2 cells suppressed brown adipocyte maturation during the current study and ACAT1 overexpression promoted brown adipocyte maturation. The downstream target of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma coactivator-1-α (PGC1α), was involved in the action of ACAT1 on brown adipocyte maturation. ACAT1 overexpression enhanced AMPK phosphorylation and promoted PGC1α expression. It is suggested that ACAT1 promotes brown adipocyte maturation by activating the AMPK-PGC1α signaling pathway.

Keywords:  ACAT1; AMPK; Brown adipocytes; PGC1α; Palmitoylation

DOI:  https://doi.org/10.1016/j.bbalip.2023.159369
J Endocrinol. 2023 09 01. pii: e230119. [Epub ahead of print]258(3):

BRD7 improves glucose homeostasis independent of IRS proteins.

Yoo Kim, Junsik M Lee, Youngah Han, Rongya Tao, Morris F White, Renyan Liu, Sang Won Park.

  Bromodomain-containing protein 7 (BRD7) has emerged as a player in the regulation of glucose homeostasis. Hepatic BRD7 levels are decreased in obese mice, and the reinstatement of hepatic BRD7 in obese mice has been shown to establish euglycemia and improve glucose homeostasis. Of note, the upregulation of hepatic BRD7 levels activates the AKT cascade in response to insulin without enhancing the sensitivity of the insulin receptor (InsR)-insulin receptor substrate (IRS) axis. In this report, we provide evidence for the existence of an alternative insulin signaling pathway that operates independently of IRS proteins and demonstrate the involvement of BRD7 in this pathway. To investigate the involvement of BRD7 as a downstream component of InsR, we utilized liver-specific InsR knockout mice. Additionally, we employed liver-specific IRS1/2 knockout mice to examine the requirement of IRS1/2 for the action of BRD7. Our investigation of glucose metabolism parameters and insulin signaling unveiled the significance of InsR activation in mediating BRD7's effect on glucose homeostasis in the liver. Moreover, we identified an interaction between BRD7 and InsR. Notably, our findings indicate that IRS1/2 is not necessary for BRD7's regulation of glucose metabolism, particularly in the context of obesity. The upregulation of hepatic BRD7 significantly reduces blood glucose levels and restores glucose homeostasis in high-fat diet-challenged liver-specific IRS1/2 knockout mice. These findings highlight the presence of an alternative insulin signaling pathway that operates independently of IRS1/2 and offer novel insights into the mechanisms of a previously unknown insulin signaling in obesity.

Keywords:  BRD7; glucose metabolism; insulin receptor signaling; insulin receptor substrates

DOI:  https://doi.org/10.1530/JOE-23-0119
bioRxiv. 2023 Jul 31. pii: 2023.07.31.551113. [Epub ahead of print]

Leucine suppresses glucagon secretion from pancreatic islets by directly modulating α -cell cAMP.

Emily R Knuth, Hannah R Foster, Erli Jin, Matthew J Merrins.

Objective: Pancreatic islets are nutrient sensors that regulate organismal blood glucose homeostasis. Glucagon release from the pancreatic α-cell is important under fasted, fed, and hypoglycemic conditions, yet metabolic regulation of α-cells remains poorly understood. Here, we identified a previously unexplored role for physiological levels of leucine, which is classically regarded as a β-cell fuel, in the intrinsic regulation of α-cell glucagon release.
Methods: GcgCre ERT :CAMPER and GcgCre ERT :GCaMP6s mice were generated to perform dynamic, high-throughput functional measurements of α-cell cAMP and Ca 2+ within the intact islet. Islet perifusion assays were used for simultaneous, time-resolved measurements of glucagon and insulin release from mouse and human islets. The effects of leucine were compared with glucose and the mitochondrial fuels 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH, non-metabolized leucine analog that activates glutamate dehydrogenase), α-ketoisocaproate (KIC, leucine metabolite), and methyl-succinate (complex II fuel). CYN154806 (Sstr2 antagonist), diazoxide (K ATP activator, which prevents Ca 2+ -dependent exocytosis from α, β, and δ-cells), and dispersed α-cells were used to inhibit islet paracrine signaling and identify α-cell intrinsic effects.
Results: Mimicking the effect of glucose, leucine strongly suppressed amino acid-stimulated glucagon secretion. Mechanistically, leucine dose-dependently reduced α-cell cAMP at physiological concentrations, with an IC 50 of 57, 440, and 1162 μM at 2, 6, and 10 mM glucose, without affecting α-cell Ca 2+ . Leucine also reduced α-cell cAMP in islets treated with Sstr2 antagonist or diazoxide, as well as dispersed α-cells, indicating an α-cell intrinsic effect. The effect of leucine was matched by KIC and the glutamate dehydrogenase activator BCH, but not methyl-succinate, indicating a dependence on mitochondrial anaplerosis. Glucose, which stimulates anaplerosis via pyruvate carboxylase, had the same suppressive effect on α-cell cAMP but with lower potency. Similarly to mouse islets, leucine suppressed glucagon secretion from human islets under hypoglycemic conditions.
Conclusions: These findings highlight an important role for physiological levels of leucine in the metabolic regulation of α-cell cAMP and glucagon secretion. Leucine functions primarily through an α-cell intrinsic effect that is dependent on glutamate dehydrogenase, in addition to the well-established α-cell regulation by β/δ-cell paracrine signaling. Our results suggest that mitochondrial anaplerosis-cataplerosis facilitates the glucagonostatic effect of both leucine and glucose, which cooperatively suppress α-cell tone by reducing cAMP.
Highlights: Leucine inhibits glucagon secretion from mouse and human isletsLeucine suppresses α-cell cAMP via both direct and paracrine effectsAnaplerosis via glutamate dehydrogenase is sufficient to suppress α-cell cAMPLeucine suppresses α-cell cAMP and glucagon secretion more potently than glucose.

DOI: https://doi.org/10.1101/2023.07.31.551113
J Poult Sci. 2023 ;60 2023022

Regulation of autophagy in chick myotube cultures: Effect of uncoupling mitochondrial oxidative phosphorylation.

Kazuki Nakashima, Aiko Ishida.

  Abstracts: Skeletal muscles have a high demand for ATP, which is met largely through mitochondria oxidative phosphorylation. Autophagy is essential for the maintenance of skeletal muscle mass under catabolic conditions. This study investigated the effect of uncoupling mitochondrial oxidative phosphorylation on autophagy in chicken skeletal muscle. Chick myotubes were incubated with the mitochondrial uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP) at 25 μM for 3h. CCCP prevented the phosphorylation of p70 ribosomal S6 kinase 1 (Thr389), S6 ribosomal protein (Ser240/244), and eukaryotic translation initiation factor 4E-binding protein 1 (Thr37/46), which are the measures of the mechanistic target of rapamycin complex 1 (mTORC1) activity. CCCP significantly increased cytoplasmic and mitochondrial LC3-II content, which act as indices of index for autophagosome formation and mitophagy, respectively, but did not influence the expression of autophagy-related genes LC3B, GABARAPL1, and ATG12. Finally, surface sensing of translation method revealed that protein synthesis, a highly energy consuming process, was significantly decreased upon CCCP treatment. These results indicate that the uncoupling of mitochondrial oxidative phosphorylation stimulates autophagy and inhibits protein synthesis through mTORC1 signaling in chick myotube cultures.

Keywords:  autophagy; carbonyl cyanide m-chlorophenyl hydrazone (CCCP); chick myotubes; mitophagy; protein synthesis

DOI:  https://doi.org/10.2141/jpsa.2023022
J Clin Transl Hepatol. 2023 Oct 28. 11(5): 1069-1078

Activation of NLRP3 Inflammasome via Drp1 Overexpression in Kupffer Cells Aggravates Ischemia-reperfusion Injury in Hepatic Steatosis.

Lu Zhang, Mingfu Wang, Ran An, Jun Dai, Shujun Liu, Ming Chen, Haoran Ding.

   Background and Aims: Donors with fatty livers are considered to address the shortage of livers for transplantation, but those livers are particularly sensitive to ischemia-reperfusion injury (IRI), and an increased incidence of graft failure is observed. Kupffer cells account for 20-35% of liver nonparenchymal cells, and have been shown to participate in the process of IRI and inflammatory reactions of hepatic steatosis. NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) is an intracellular sensor activated by Kupffer cells to promote generation and participates in IRI. Dynamics-associated protein 1 (Drp1) is one of the main proteins regulating mitochondrial division and exacerbates IRI by affecting mitochondrial dynamics. The mechanism of interaction of Kupffer cells with Drp1 and NLRP3 to aggravate IRI has not been clarified.
Methods: A mouse model of hepatic steatosis was established by feeding the mice with a high-fat diet. In vitro experiments were performed using AML12 normal mouse liver cells and RAW264.7 mononuclear macrophage cells cultured in medium with palmitate and oleic acid. Western blotting and immunohistochemical (IHC) staining were used to detect the expression of NLRPP3 and Drp1 in IRI in the control and high-fat diet groups. The expression of F4/80+ cells during IRI in hepatic steatosis was verified by IHC staining, and the role of NLRPP3 and Drp1 in Kupffer-cell mediated IRI was investigated by targeting Drp-1 inhibition.
Results: Drp1 and NLRP3 expression was increased during IRI in hepatic steatosis, and the expression of Drp1 and NLRP3 were decreased after the elimination of Kupffer cells. That indicated Kupffer cells were involved in the process of IRI in hepatic steatosis through the action of Drp1 and NLRP3. After Drp1 inhibition, liver function was restored and NLRP3 expression level was reduced.
Conclusions: Kupffer cells aggravated IRI in hepatic steatosis via NLRP3 and Drp1. Drp1 inhibitors might be useful as specific therapeutics to alleviate IRI in hepatic steatosis and may have promise in case of liver donor shortage.

Keywords:  Drp1; Hepatic steatosis; Ischemia-reperfusion; Kupffer cells; NLRP3

DOI:  https://doi.org/10.14218/JCTH.2022.00109
PLoS One. 2023 ;18(8): e0290340

DNAJB3 attenuates ER stress through direct interaction with AKT.

Zeyaul Islam, Abdoulaye Diane, Namat Khattab, Mohammed Dehbi, Paul Thornalley, Prasanna R Kolatkar.

Metabolic stress involved in several dysregulation disorders such as type 2 diabetes mellitus (T2DM) results in down regulation of several heat shock proteins (HSPs) including DNAJB3. This down regulation of HSPs is associated with insulin resistance (IR) and interventions which induce the heat shock response (HSR) help to increase the insulin sensitivity. Metabolic stress leads to changes in signaling pathways through increased activation of both c-jun N-terminal kinase-1 (JNK1) and the inhibitor of κB inflammatory kinase (IKKβ) which in turn leads to inactivation of insulin receptor substrates 1 and 2 (IRS-1 and IRS-2). DNAJB3 interacts with both JNK1 and IKKβ kinases to mitigate metabolic stress. In addition DNAJB3 also activates the PI3K-PKB/AKT pathway through increased phosphorylation of AKT1 and its substrate AS160, a Rab GTPase-activating protein, which results in mobilization of GLUT4 transporter protein and improved glucose uptake. We show through pull down that AK T1 is an interacting partner of DNAJB3, further confirmed by isothermal titration calorimetry (ITC) which quantified the avidity of AKT1 for DNAJB3. The binding interface was identified by combining protein modelling with docking of the AKT1-DNAJB3 complex. DNAJB3 is localized in the cytoplasm and ER, where it interacts directly with AKT1 and mobilizes AS160 for glucose transport. Inhibition of AKT1 resulted in loss of GLUT4 translocation activity mediated by DNAJB3 and also abolished the protective effect of DNAJB3 on tunicamycin-induced ER stress. Taken together, our findings provide evidence for a direct protein-protein interaction between DNAJB3 and AKT1 upon which DNAJB3 alleviates ER stress and promotes GLUT4 translocation.

DOI: https://doi.org/10.1371/journal.pone.0290340
Eur J Pharmacol. 2023 Aug 10. pii: S0014-2999(23)00494-6. [Epub ahead of print] 175982

URB597 exerts neuroprotective effects against transient brain ischemia injury in mice by regulating autophagic flux and necroptosis.

Xiaoqian Yuan, Wenxuan Ye, Ling Chen, Doudou Luo, Li Zhou, Yan Qiu, Rengong Zhuo, Yun Zhao, Lu Peng, Lichao Yang, Xin Jin, Yu Zhou.

  Ischemic stroke is a leading cause of death and disability, and medical treatments for ischemic stroke are very limited. URB597 is a potent and selective inhibitor of fatty acid amide hydrolase (FAAH). However, the effect of URB597 on ischemic stroke and the underlying molecular mechanisms remain little known. In this study, focal cerebral ischemia was induced by transient middle cerebral artery occlusion in mice. Our results showed that URB597 dose-dependently improved neurological function and reduced brain infarct volume and brain edema 24 h after brain ischemia. The most effective dose was 1 mg/kg and the therapeutic time window was within 3 h after ischemic stroke. To further investigate the underlying mechanism, necroptosis and autophagy flux were detected by Western blot and/or immunofluorescence staining with or without chloroquine, an autophagic flux inhibitor. Our results showed that URB597 promoted autophagic flux and reduced neuronal necroptosis after brain ischemia and these effects could be abolished by chloroquine. In addition, we found that peroxisome proliferator-activated receptor α (PPARα) antagonist GW6471 partly abolished the effect of URB597 against brain ischemia and URB597 upregulated the expressions of PPARα. In conclusion, URB597 exerts a neuroprotective effect in a dose- and time-dependent manner, and this effect may be related to its restoration of autophagic flux and inhibition of neuronal necroptosis. PPARα is involved in the neuroprotective effect of URB597. This study provides novel evidence that URB597 may be a promising agent for the clinical treatment of ischemic stroke.

Keywords:  Autophagy flux; Cerebral ischemia; Necroptosis; Peroxisome proliferator-activated receptor α; URB597

DOI:  https://doi.org/10.1016/j.ejphar.2023.175982
Biomed J. 2023 Aug 11. pii: S2319-4170(23)00072-0. [Epub ahead of print] 100635

NLRX1: versatile functions of a mitochondrial NLR protein that controls mitophagy.

Paul Y Bi, Samuel A Killackey, Linus Schweizer, Stephen E Girardin.

NLRX1 is a member of the of the Nod-like receptor (NLR) family, and it represents a unique pattern recognition molecule (PRM) as it localizes to the mitochondrial matrix in resting conditions. Over the past fifteen years, NLRX1 has been proposed to regulate multiple cellular processes, including antiviral immunity, apoptosis, reactive oxygen species (ROS) generation and mitochondrial metabolism. Similarly, in vivo models have shown that NLRX1 was associated with the control of a number of diseases, including multiple sclerosis, colorectal cancer and ischemia-reperfusion injury. This apparent versatility in function hinted that a common and general overarching role for NLRX1 may exist. Recent evidence has suggested that NLRX1 controls mitophagy through the detection of a specific "danger signal", namely the defective import of proteins into mitochondria, or mitochondrial protein import stress (MPIS). In this review article, we propose that mitophagy regulation may represent the overarching process detected by NLRX1, which could in turn impact on a number of diseases if dysfunctional.

DOI: https://doi.org/10.1016/j.bj.2023.100635
Diabet Med. 2023 Aug 14. e15198

The role of candidate transport proteins in beta cell long-chain fatty acid uptake: where are we now?

Christina Clavelo-Farrow, Patricia Thomas.

  Type 2 diabetes (T2D) in humans is typically preceded by elevated levels of circulatory long-chain free fatty acids (LC-FFA). These excess LC-FFA are widely thought to be taken up by pancreatic beta cells, contributing to their dysfunction and death during the development of T2D; a process that has been termed lipotoxicity. Depending on their degree of saturation and carbon chain length, LC-FFA can exert different effects on pancreatic beta cells viability and function in vitro. Long-chain saturated fatty acids (LC-SFA) are thought to be toxic, whereas monounsaturated fatty acids are not and may even offer protection against the toxic effects of LC-SFAs. However, the mechanism of LC-FFA uptake into pancreatic beta cells is poorly understood, partly because it has been an understudied area of research. Determining how LC-FFA are taken up into beta cells is crucial for later formulation of therapies to prevent potential cellular overload of LC-FFA, thereby slowing the onset of T2D. In this work, we detail more than 40 years of literature investigating the role of membrane-associated transport proteins in LC-FFA uptake. By focusing on what is known in other cell types, we highlight where we can extrapolate our current understanding of protein-mediated transport to beta cells and uncover where further understanding is required.

Keywords:  Beta cells; candidate transport proteins; fatty acid uptake; lipotoxicity; long-chain fatty acids

DOI:  https://doi.org/10.1111/dme.15198
J Cell Biol. 2023 10 02. pii: e202301091. [Epub ahead of print]222(10):

NME3 binds to phosphatidic acid and mediates PLD6-induced mitochondrial tethering.

You-An Su, Hsin-Yi Chiu, Yu-Chen Chang, Chieh-Ju Sung, Chih-Wei Chen, Reika Tei, Xuang-Rong Huang, Shao-Chun Hsu, Shan-Shan Lin, Hsien-Chu Wang, Yu-Chun Lin, Jui-Cheng Hsu, Hermann Bauer, Yuxi Feng, Jeremy M Baskin, Zee-Fen Chang, Ya-Wen Liu.

Mitochondria are dynamic organelles regulated by fission and fusion processes. The fusion of membranes requires elaborative coordination of proteins and lipids and is particularly crucial for the function and quality control of mitochondria. Phosphatidic acid (PA) on the mitochondrial outer membrane generated by PLD6 facilitates the fusion of mitochondria. However, how PA promotes mitochondrial fusion remains unclear. Here, we show that a mitochondrial outer membrane protein, NME3, is required for PLD6-induced mitochondrial tethering or clustering. NME3 is enriched at the contact interface of two closely positioned mitochondria depending on PLD6, and NME3 binds directly to PA-exposed lipid packing defects via its N-terminal amphipathic helix. The PA binding function and hexamerization confer NME3 mitochondrial tethering activity. Importantly, nutrient starvation enhances the enrichment efficiency of NME3 at the mitochondrial contact interface, and the tethering ability of NME3 contributes to fusion efficiency. Together, our findings demonstrate NME3 as a tethering protein promoting selective fusion between PLD6-remodeled mitochondria for quality control.

DOI: https://doi.org/10.1083/jcb.202301091
Cell Death Discov. 2023 Aug 14. 9(1): 296

Sophoridine derivative 6j inhibits liver cancer cell proliferation via ATF3 mediated ferroptosis.

Kunpeng Tian, Jinrui Wei, Ru Wang, Mingming Wei, Fei Hou, Lichuan Wu.

Liver cancer is one of the most lethal malignancies with an annual death of over 830,000 cases. Although targeted therapeutic drugs have achieved certain clinical efficacy, only sorafenib and lenvatinib are currently marketed as first-line targeted drugs to treat patients with advanced liver cancer. Therefore, developing more drugs are urgently needed. Ferroptosis is an iron-dependent programmed cell death (PCD) distinct from known PCDs including apoptosis, necrosis, and autophagy. Targeting ferroptosis is recognized as a promising potential therapeutic modality for liver cancer. Activating transcription factor 3 (ATF3) is an important ferroptosis inducer and targeting ATF3 offers a potential means to cancer therapy. In the present study, we reported for the first time a sophoridine derivative 6j with promising anti-liver cancer effects in vitro and in vivo. Compound 6j could induce liver cancer cells ferroptosis by promoting the accumulation of intracellular Fe2+, reactive oxygen species (ROS), and MDA. Inhibition of ferroptosis by ferrostatin-1 alleviated 6j induced accumulation of Fe2+, ROS, and MDA and restored cell viability. Further study revealed that compound 6j upregulated the expression of ATF3 via ER stress and knockdown of ATF3 by RNA interference attenuated 6j induced ferroptosis and cell proliferation inhibition. This study would provide new insights for the design of ferroptosis inducers and the development of anti-liver cancer drugs.

DOI: https://doi.org/10.1038/s41420-023-01597-6
Med Oncol. 2023 Aug 18. 40(9): 272

Hypoxia-induced PPFIA4 accelerates the progression of ovarian cancer through glucose metabolic reprogramming.

Shu Tan, Hao Yu, Ye Xu, Yue Zhao, Ge Lou.

  Dysregulated glycolysis promotes growth and metastasis, which is one of the metabolic characteristics of ovarian cancer. Based on bioinformatics analysis, liprin-alpha-4 (PPFIA4) is a gene associated with hypoxia, and we aimed to investigate the potential mechanism of PPFIA4 during the reprogramming of glucose metabolism in ovarian cancer cells. Currently, the cell viability of ovarian cancer cells under the hypoxia treatment was evaluated by CCK-8 assay, and cell migration and invasion were measured by transwell assay and western blot. The effects of hypoxia treatment on glucose uptake, lactate production, extracellular acidification rate (ECAR), adenosine triphosphate (ATP), reactive oxygen species (ROS), Nicotinamide adenine dinucleotide phosphate (NADPH) and its oxidized form NADP + , and oxygen consumption rate (OCR) in ovarian cancer cells were examined. Then PPFIA4 was identified through bioinformatic analysis, and the regulatory effects of PPFIA4 on glucose metabolic reprogramming. Our data suggested that hypoxia enhanced the migration and invasion ability of ovarian cancer cells in vitro, and promoted the glucose metabolic reprogramming of ovarian cancer cells. Ovarian cancer cell viability, migration, and invasion were inhibited after PPFIA4 knockdown. Inhibition of PPFIA4 inhibited hypoxic-induced glucose metabolic reprogramming in ovarian cancer cells. In addition, PPFIA4 was found to bind to hypoxia-inducible factor 1alpha (HIF1A), and HIF1A prominently induced PPFIA4 expression. Collectively, HIF1A mediated upregulation of PPFIA4 and promoted reprogramming of glucose metabolism in ovarian cancer cells. Therefore, PPFIA4 may be a therapeutic target for ovarian cancer intervention.

Keywords:  Glycolysis; HIF1A; Hypoxia; Ovarian cancer; PPFIA4

DOI:  https://doi.org/10.1007/s12032-023-02144-0
CNS Neurosci Ther. 2023 Aug 14.

The potential role of glucose metabolism, lipid metabolism, and amino acid metabolism in the treatment of Parkinson's disease.

Hangzhen Li, Fancai Zeng, Cancan Huang, Qiqi Pu, Elizabeth Rosalind Thomas, Yan Chen, Xiang Li.

   PURPOSE OF REVIEW: Parkinson's disease (PD) is a common neurodegenerative disease, which can cause progressive deterioration of motor function causing muscle stiffness, tremor, and bradykinesia. In this review, we hope to describe approaches that can improve the life of PD patients through modifications of energy metabolism.
RECENT FINDINGS: The main pathological features of PD are the progressive loss of nigrostriatal dopaminergic neurons and the production of Lewy bodies. Abnormal aggregation of α-synuclein (α-Syn) leading to the formation of Lewy bodies is closely associated with neuronal dysfunction and degeneration. The main causes of PD are said to be mitochondrial damage, oxidative stress, inflammation, and abnormal protein aggregation. Presence of abnormal energy metabolism is another cause of PD. Many studies have found significant differences between neurodegenerative diseases and metabolic decompensation, which has become a biological hallmark of neurodegenerative diseases.
SUMMARY: In this review, we highlight the relationship between abnormal energy metabolism (Glucose metabolism, lipid metabolism, and amino acid metabolism) and PD. Improvement of key molecules in glucose metabolism, fat metabolism, and amino acid metabolism (e.g., glucose-6-phosphate dehydrogenase, triglycerides, and levodopa) might be potentially beneficial in PD. Some of these metabolic indicators may serve well during the diagnosis of PD. In addition, modulation of these metabolic pathways may be a potential target for the treatment and prevention of PD.

Keywords:  Parkinson's disease; amino acid metabolism; glucose metabolism; lipid metabolism

DOI:  https://doi.org/10.1111/cns.14411