Search

Background: The development of organ fibrosis after injury requires activation of transforming growth factor β(1) which regulates the transcription of profibrotic genes. The systemic administration of a proteasomal inhibitor has been reported to prevent the development of fibrosis in the liver, kidney and bone marrow. It is hypothesised that proteasomal inhibition would prevent lung and skin fibrosis after injury by inhibiting TGF-β(1)-mediated transcription.Methods: Bortezomib, a small molecule proteasome inhibitor in widespread clinical use, was administered to mice beginning 7 days after the intratracheal or intradermal administration of bleomycin and lung and skin fibrosis was measured after 21 or 40 days, respectively. To examine the mechanism of this protection, bortezomib was administered to primary normal lung fibroblasts and primary lung and skin fibroblasts obtained from patients with idiopathic pulmonary fibrosis and scleroderma, respectively.Results: Bortezomib promoted normal repair and prevented lung and skin fibrosis when administered beginning 7 days after the initiation of bleomycin. In primary human lung fibroblasts from normal individuals and patients with idiopathic pulmonary fibrosis and in skin fibroblasts from a patient with scleroderma, bortezomib inhibited TGF-β(1)-mediated target gene expression by inhibiting transcription induced by activated Smads. An increase in the abundance and activity of the nuclear hormone receptor PPARγ, a repressor of Smad-mediated transcription, contributed to this response.Conclusions: Proteasomal inhibition prevents lung and skin fibrosis after injury in part by increasing the abundance and activity of PPARγ. Proteasomal inhibition may offer a novel therapeutic alternative in patients with dysregulated tissue repair and fibrosis. [ABSTRACT FROM AUTHOR]

Rationale: Diabetic patients have a lower incidence of acute respiratory distress syndrome (ARDS), and those who develop ARDS are less likely to die. The mechanisms that underlie this protection are unknown.Objectives: To determine whether leptin resistance, a feature of diabetes, prevents fibroproliferation after lung injury.Methods: We examined lung injury and fibroproliferation after the intratracheal instillation of bleomycin in wild-type and leptin-resistant (db/db) diabetic mice. We examined the effect of leptin on transforming growth factor (TGF)-β(1)-mediated transcription in primary normal human lung fibroblasts. Bronchoalveolar lavage fluid (BAL) samples from patients with ARDS and ventilated control subjects were obtained for measurement of leptin and active TGF-β(1) levels.Measurements and Main Results: Diabetic mice (db/db) were resistant to lung fibrosis. The db/db mice had higher levels of peroxisome proliferator-activated receptor-γ (PPARγ), an inhibitor of the transcriptional response to TGF-β(1), a cytokine critical in the pathogenesis of fibroproliferative ARDS. In normal human lung fibroblasts, leptin augmented the transcription of profibrotic genes in response to TGF-β(1) through a mechanism that required PPARγ. In patients with ARDS, BAL leptin levels were elevated and correlated with TGF-β(1) levels. Overall, there was no significant relationship between BAL leptin levels and clinical outcomes; however, in nonobese patients, higher BAL leptin levels were associated with fewer intensive care unit- and ventilator-free days and higher mortality.Conclusions: Leptin signaling is required for bleomycin-induced lung fibrosis. Leptin augments TGF-β(1) signaling in lung fibroblasts by inhibiting PPARγ. These findings provide a mechanism for the observed protection against ARDS observed in diabetic patients. [ABSTRACT FROM AUTHOR]

Objective: Myofibroblasts express [alpha]-smooth muscle actin ([alpha]SMA), are important in tissue repair, and are present in the early phase of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). We wished to determine whether bronchoalveolar lavage fluid (BALF) from ALI/ARDS patients can induce myofibroblast differentiation and if this induction is associated with outcome.Design: A single-center cohort study enrolling patients between 2002 and 2005.Setting: Medical intensive care unit of a tertiary care medical center.Patients: Adult patients meeting the American-European Consensus Conference definition of ALI/ARDS.Interventions: BALF was collected from ALI/ARDS patients within 48 hrs of intubation and incubated with normal human lung fibroblasts in vitro, and [alpha]SMA expression was assessed by reverse transcription polymerase chain reaction. BALF was also collected and tested from negative control patients. ALI/ARDS patients were followed for 28 days or death.Measurements and Main Results: Thirty-one lung injury and 11 negative control patients were enrolled from 2002 to 2005. ALI/ARDS BALF demonstrated potent [alpha]SMA induction with a mean value 92% greater than negative controls (34.5% +/- 7.6% vs. 18% +/- 2.4% of maximal transforming growth factor [TGF]-[beta]1 [5 ng/mL], p < .02). The specific TGF-[beta]1 receptor inhibitor SB431542 reduced ALI/ARDS BALF-stimulated [alpha]SMA induction by 52% (p < .005). There was no correlation between ALI/ARDS BALF-induced [alpha]SMA and procollagen 3 induction (r = -.08, p = .66). The odds ratio for survival was 6.75 (1.15-39.80) times higher for ALI/ARDS patients with [alpha]SMA induction between 15% and 75% of maximal TGF-[beta]1 induction (5 ng/mL) than outside this range.Conclusions: ALI/ARDS BALF-induced myofibroblast differentiation is partially attributable to TGF-[beta]1. Procollagen 3 and [alpha]SMA are regulated by distinct mechanisms in ALI/ARDS and there may be an optimal level of myofibroblast induction that is associated with better outcome. [ABSTRACT FROM AUTHOR]

Background: Pathological accumulation of aggregated α-synuclein (aSYN) is a common feature of Parkinson's disease (PD). However, the mechanisms by which intracellular aSYN pathology contributes to dysfunction and degeneration of neurons in the brain are still unclear. A potentially relevant target of aSYN is the mitochondrion. To test this hypothesis, genetic and physiological methods were used to monitor mitochondrial function in substantia nigra pars compacta (SNc) dopaminergic and pedunculopontine nucleus (PPN) cholinergic neurons after stereotaxic injection of aSYN pre-formed fibrils (PFFs) into the mouse brain., Methods: aSYN PFFs were stereotaxically injected into the SNc or PPN of mice. Twelve weeks later, mice were studied using a combination of approaches, including immunocytochemical analysis, cell-type specific transcriptomic profiling, electron microscopy, electrophysiology and two-photon-laser-scanning microscopy of genetically encoded sensors for bioenergetic and redox status., Results: In addition to inducing a significant neuronal loss, SNc injection of PFFs induced the formation of intracellular, phosphorylated aSYN aggregates selectively in dopaminergic neurons. In these neurons, PFF-exposure decreased mitochondrial gene expression, reduced the number of mitochondria, increased oxidant stress, and profoundly disrupted mitochondrial adenosine triphosphate production. Consistent with an aSYN-induced bioenergetic deficit, the autonomous spiking of dopaminergic neurons slowed or stopped. PFFs also up-regulated lysosomal gene expression and increased lysosomal abundance, leading to the formation of Lewy-like inclusions. Similar changes were observed in PPN cholinergic neurons following aSYN PFF exposure., Conclusions: Taken together, our findings suggest that disruption of mitochondrial function, and the subsequent bioenergetic deficit, is a proximal step in the cascade of events induced by aSYN pathology leading to dysfunction and degeneration of neurons at-risk in PD., (© 2024. The Author(s).)

Fueled by technological and conceptual advancements over the past two decades, research in cancer metabolism has begun to answer questions dating back to the time of Otto Warburg. But, as with most fields, new discoveries lead to new questions. This review outlines the emerging challenges that we predict will drive the next few decades of cancer metabolism research. These include developing a more realistic understanding of how metabolic activities are compartmentalized within cells, tissues, and organs; how metabolic preferences in tumors evolve during cancer progression from nascent, premalignant lesions to advanced, metastatic disease; and, most importantly, how we can best translate basic observations from preclinical models into novel therapies that benefit patients with cancer. With modern tools and an incredible amount of talent focusing on these problems, the upcoming decades should bring transformative discoveries., (Copyright © 2024 Cold Spring Harbor Laboratory Press; all rights reserved.)

TP53 tumor suppressor is frequently altered in lethal, castration-resistant prostate cancer (CRPC). However, to date there are no effective treatments that specifically target TP53 alterations. Using transcriptomic and metabolomic analyses, we have shown here that TP53-altered prostate cancer exhibits an increased dependency on asparagine (Asn) and overexpresses Asn synthetase (ASNS), the enzyme catalyzing the synthesis of Asn. Mechanistically, the loss or mutation of TP53 transcriptionally activated ASNS expression, directly and via mTORC1-mediated ATF4 induction, driving de novo Asn biosynthesis to support CRPC growth. TP53-altered CRPC cells were sensitive to Asn restriction by knockdown of ASNS or L-asparaginase treatment to deplete the intracellular and extracellular sources of Asn, respectively, and cell viability was rescued by Asn addition. Notably, pharmacological inhibition of intracellular Asn biosynthesis using a glutaminase inhibitor and depletion of extracellular Asn with L-asparaginase significantly reduced Asn production and effectively impaired CRPC growth. This study highlights the significance of ASNS-mediated metabolic adaptation as a synthetic vulnerability in CRPC with TP53 alterations, providing a rationale for targeting Asn production to treat these lethal prostate cancers. Significance: TP53-mutated castration-resistant prostate cancer is dependent on asparagine biosynthesis due to upregulation of ASNS and can be therapeutically targeted by approaches that deplete intracellular and extracellular asparagine., (©2024 American Association for Cancer Research.)

Lymphocyte activation gene 3 (Lag3) is an inhibitory co-receptor expressed on activated T cells and has been proposed to regulate regulatory T (Treg) cell function. However, its precise modality and mechanisms remain elusive. We generated Treg cell-specific Lag3-mutant mouse models and found that Lag3 was essential for Treg cell control of autoimmunity. RNA sequencing analysis revealed that Lag3 mutation altered genes associated with metabolic processes, especially Myc target genes. Myc expression in Lag3-mutant Treg cells was increased to the level seen in conventional T helper (Th)1-type effector cells and directly correlated with their metabolic profiles and in vivo suppressive functions. The phosphatidylinositol 3-kinase (PI3K)-Akt-Rictor pathway was activated in Lag3-mutant Treg cells, and inhibiting PI3K, Rictor, or lactate dehydrogenase A (Ldha), a key Myc target enzyme converting pyruvate to lactate, was sufficient to restore normal metabolism and suppressive function in Lag3-mutant Treg cells. These findings indicate that Lag3 supports Treg cell suppression partly by tuning Myc-dependent metabolic programming., Competing Interests: Declaration of interests J.C. is a founder and shareholder in Moonlight Bio., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Vasodilation in response to low oxygen (O 2 ) tension (hypoxic vasodilation) is an essential homeostatic response of systemic arteries that facilitates O 2 supply to tissues according to demand. However, how blood vessels react to O 2 deficiency is not well understood. A common belief is that arterial myocytes are O 2 -sensitive. Supporting this concept, it has been shown that the activity of myocyte L-type Ca 2+ channels, the main ion channels responsible for vascular contractility, is reversibly inhibited by hypoxia, although the underlying molecular mechanisms have remained elusive. Here, we show that genetic or pharmacological disruption of mitochondrial electron transport selectively abolishes O 2 modulation of Ca 2+ channels and hypoxic vasodilation. Mitochondria function as O 2 sensors and effectors that signal myocyte Ca 2+ channels due to constitutive Hif1α-mediated expression of specific electron transport subunit isoforms. These findings reveal the acute O 2 -sensing mechanisms of vascular cells and may guide new developments in vascular pharmacology., (© 2024. The Author(s).)

Microglia are necessary for central nervous system (CNS) function during development and play roles in ageing, Alzheimer's disease and the response to demyelinating injury 1-5 . The mitochondrial respiratory chain (RC) is necessary for conventional T cell proliferation 6 and macrophage-dependent immune responses 7-10 . However, whether mitochondrial RC is essential for microglia proliferation or function is not known. We conditionally deleted the mitochondrial complex III subunit Uqcrfs1 (Rieske iron-sulfur polypeptide 1) in the microglia of adult mice to assess the requirement of microglial RC for survival, proliferation and adult CNS function in vivo. Notably, mitochondrial RC function was not required for survival or proliferation of microglia in vivo. RNA sequencing analysis showed that loss of RC function in microglia caused changes in gene expression distinct from aged or disease-associated microglia. Microglia-specific loss of mitochondrial RC function is not sufficient to induce cognitive decline. Amyloid-β plaque coverage decreased and microglial interaction with amyloid-β plaques increased in the hippocampus of 5xFAD mice with mitochondrial RC-deficient microglia. Microglia-specific loss of mitochondrial RC function did impair remyelination following an acute, reversible demyelinating event. Thus, mitochondrial respiration in microglia is dispensable for proliferation but is essential to maintain a proper response to CNS demyelinating injury., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Abstract: Chromosomal translocation (4;14), an adverse prognostic factor in multiple myeloma (MM), drives overexpression of the histone methyltransferase nuclear receptor binding SET domain protein 2 (NSD2). A genome-wide CRISPR screen in MM cells identified adenylate kinase 2 (AK2), an enzyme critical for high-energy phosphate transfer from the mitochondria, as an NSD2-driven vulnerability. AK2 suppression in t(4;14) MM cells decreased nicotinamide adenine dinucleotide phosphate (NADP[H]) critical for conversion of ribonucleotides to deoxyribonucleosides, leading to replication stress, DNA damage, and apoptosis. Driving a large genome-wide increase in chromatin methylation, NSD2 overexpression depletes S-adenosylmethionine, compromising the synthesis of creatine from its precursor, guanidinoacetate. Creatine supplementation restored NADP(H) levels, reduced DNA damage, and rescued AK2-deficient t(4;14) MM cells. As the creatine phosphate shuttle constitutes an alternative means for mitochondrial high-energy phosphate transport, these results indicate that NSD2-driven creatine depletion underlies the hypersensitivity of t(4;14) MM cells to AK2 loss. Furthermore, AK2 depletion in t(4;14) cells impaired protein folding in the endoplasmic reticulum, consistent with impaired use of mitochondrial adenosine triphosphate (ATP). Accordingly, AK2 suppression increased the sensitivity of MM cells to proteasome inhibition. These findings delineate a novel mechanism in which aberrant transfer of carbon to the epigenome creates a metabolic vulnerability, with direct therapeutic implications for t(4;14) MM., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

The circadian clock orchestrates vital physiological processes such as metabolism, immune function, and tissue regeneration, aligning them with the optimal time of day. This study identifies an intricate interplay between the circadian clock within muscle stem cells (SCs) and their capacity to modulate the immune microenvironment during muscle regeneration. We uncover that the SC clock provokes time of day-dependent induction of inflammatory response genes following injury, particularly those related to neutrophil activity and chemotaxis. These responses are driven by rhythms of cytosolic regeneration of the signaling metabolite NAD+. We demonstrate that genetically enhancing cytosolic NAD+ regeneration in SCs is sufficient to induce robust inflammatory responses that significantly influence muscle regeneration. Furthermore, using mononuclear single-cell sequencing of the regenerating muscle niche, we uncover a key role for the cytokine CCL2 in mediating SC-neutrophil crosstalk in a time of day-dependent manner. Our findings highlight a crucial intersection between SC metabolic shifts and immune responses within the muscle microenvironment, dictated by the circadian rhythms, and underscore the potential for targeting circadian and metabolic pathways to enhance tissue regeneration.

Newborn mammalian cardiomyocytes quickly transition from a fetal to an adult phenotype that utilizes mitochondrial oxidative phosphorylation but loses mitotic capacity. We tested whether forced reversal of adult cardiomyocytes back to a fetal glycolytic phenotype would restore proliferative capacity. We deleted Uqcrfs1 (mitochondrial Rieske iron-sulfur protein, RISP) in hearts of adult mice. As RISP protein decreased, heart mitochondrial function declined, and glucose utilization increased. Simultaneously, the hearts underwent hyperplastic remodeling during which cardiomyocyte number doubled without cellular hypertrophy. Cellular energy supply was preserved, AMPK activation was absent, and mTOR activation was evident. In ischemic hearts with RISP deletion, new cardiomyocytes migrated into the infarcted region, suggesting the potential for therapeutic cardiac regeneration. RNA sequencing revealed upregulation of genes associated with cardiac development and proliferation. Metabolomic analysis revealed a decrease in α-ketoglutarate (required for TET-mediated demethylation) and an increase in S-adenosylmethionine (required for methyltransferase activity). Analysis revealed an increase in methylated CpGs near gene transcriptional start sites. Genes that were both differentially expressed and differentially methylated were linked to upregulated cardiac developmental pathways. We conclude that decreased mitochondrial function and increased glucose utilization can restore mitotic capacity in adult cardiomyocytes, resulting in the generation of new heart cells, potentially through the modification of substrates that regulate epigenetic modification of genes required for proliferation.

The release of paused RNA polymerase II (RNAPII) from promoter-proximal regions is tightly controlled to ensure proper regulation of gene expression. The elongation factor PTEF-b is known to release paused RNAPII via phosphorylation of the RNAPII C-terminal domain by its cyclin-dependent kinase component, CDK9. However, the signal and stress-specific roles of the various RNAPII-associated macromolecular complexes containing PTEF-b/CDK9 are not yet clear. Here, we identify and characterize the CDK9 complex required for transcriptional response to hypoxia. Contrary to previous reports, our data indicate that a CDK9 complex containing BRD4 but not AFF1/4 is essential for this hypoxic stress response. We demonstrate that BRD4 bromodomains (BET) are dispensable for the release of paused RNAPII at hypoxia-activated genes and that BET inhibition by JQ1 is insufficient to impair hypoxic gene response. Mechanistically, we demonstrate that the C-terminal region of BRD4 is required for Polymerase-Associated Factor-1 Complex (PAF1C) recruitment to establish an elongation-competent RNAPII complex at hypoxia-responsive genes. PAF1C disruption using a small-molecule inhibitor (iPAF1C) impairs hypoxia-induced, BRD4-mediated RNAPII release. Together, our results provide insight into potentially targetable mechanisms that control the hypoxia-responsive transcriptional elongation., Competing Interests: Competing interests statement:The authors declare no competing interest.

Cellular purines, particularly adenosine 5'-triphosphate (ATP), fuel many metabolic reactions, but less is known about the direct effects of pyrimidines on cellular metabolism. We found that pyrimidines, but not purines, maintain pyruvate oxidation and the tricarboxylic citric acid (TCA) cycle by regulating pyruvate dehydrogenase (PDH) activity. PDH activity requires sufficient substrates and cofactors, including thiamine pyrophosphate (TPP). Depletion of cellular pyrimidines decreased TPP synthesis, a reaction carried out by TPP kinase 1 (TPK1), which reportedly uses ATP to phosphorylate thiamine (vitamin B1). We found that uridine 5'-triphosphate (UTP) acts as the preferred substrate for TPK1, enabling cellular TPP synthesis, PDH activity, TCA-cycle activity, lipogenesis, and adipocyte differentiation. Thus, UTP is required for vitamin B1 utilization to maintain pyruvate oxidation and lipogenesis.

Antitumor responses of CD8+ T cells are tightly regulated by distinct metabolic fitness. High levels of glutathione (GSH) are observed in the majority of tumors, contributing to cancer progression and treatment resistance in part by preventing glutathione peroxidase 4-dependent (GPX4-dependent) ferroptosis. Here, we show the necessity of adenosine A2A receptor (A2AR) signaling and the GSH/GPX4 axis in orchestrating metabolic fitness and survival of functionally competent CD8+ T cells. Activated CD8+ T cells treated ex vivo with simultaneous inhibition of A2AR and lipid peroxidation acquire a superior capacity to proliferate and persist in vivo, demonstrating a translatable means to prevent ferroptosis in adoptive cell therapy. Additionally, we identify a particular cluster of intratumoral CD8+ T cells expressing a putative gene signature of GSH metabolism (GMGS) in association with clinical response and survival across several human cancers. Our study addresses a key role of GSH/GPX4 and adenosinergic pathways in fine-tuning the metabolic fitness of antitumor CD8+ T cells.

Mature oligodendrocytes (OLG) are the myelin-forming cells of the central nervous system. Recent work has shown a dynamic role for these cells in the plasticity of neural circuits, leading to a renewed interest in voltage-sensitive currents in OLG. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and their respective current (I h ) were recently identified in mature OLG and shown to play a role in regulating myelin length. Here we provide a biochemical and electrophysiological characterization of HCN channels in cells of the oligodendrocyte lineage. We observed that mice with a nonsense mutation in the Hcn2 gene ( Hcn2 ap/ap ) have less white matter than their wild type counterparts with fewer OLG and fewer oligodendrocyte progenitor cells (OPCs). Hcn2 ap/ap mice have severe motor impairments, although these deficits were not observed in mice with HCN2 conditionally eliminated only in oligodendrocytes ( Cnp cre /+ ; Hcn2 F/F ). However, Cnp cre /+ ; Hcn2 F/F mice develop motor impairments more rapidly in response to experimental autoimmune encephalomyelitis (EAE). We conclude that HCN2 channels in OLG may play a role in regulating metabolism., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lyman, Han, Robinson, Weinberg, Fisher, Heuermann, Lyman, Kim, Ludwig, Chandel, Does, Miller and Chetkovich.)

Mutations in genes that affect mitochondrial function cause primary mitochondrial diseases. Mitochondrial diseases are highly heterogeneous and even patients with the same mitochondrial disease can exhibit broad phenotypic heterogeneity, which is poorly understood. Mutations in subunits of mitochondrial respiratory complex I cause complex I deficiency, which can result in severe neurological symptoms and death in infancy. However, some complex I deficiency patients present with much milder symptoms. The most common nuclear gene mutated in complex I deficiency is the highly conserved core subunit NDUFS1. To model the phenotypic heterogeneity in complex I deficiency, we used RNAi lines targeting the Drosophila NDUFS1 homolog ND-75 with different efficiencies. Strong knockdown of ND-75 in Drosophila neurons resulted in severe behavioural phenotypes, reduced lifespan, altered mitochondrial morphology, reduced endoplasmic reticulum (ER)-mitochondria contacts and activation of the unfolded protein response (UPR). By contrast, weak ND-75 knockdown caused much milder behavioural phenotypes and changes in mitochondrial morphology. Moreover, weak ND-75 did not alter ER-mitochondria contacts or activate the UPR. Weak and strong ND-75 knockdown resulted in overlapping but distinct transcriptional responses in the brain, with weak knockdown specifically affecting proteosome activity and immune response genes. Metabolism was also differentially affected by weak and strong ND-75 knockdown including gamma-aminobutyric acid (GABA) levels, which may contribute to neuronal dysfunction in ND-75 knockdown flies. Several metabolic processes were only affected by strong ND-75 knockdown including the pentose phosphate pathway and the metabolite 2-hydroxyglutarate (2-HG), suggesting 2-HG as a candidate biomarker of severe neurological mitochondrial disease. Thus, our Drosophila model provides the means to dissect the mechanisms underlying phenotypic heterogeneity in mitochondrial disease., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Glioblastoma (GBM) is a malignancy dominated by the infiltration of tumor-associated myeloid cells (TAMCs). Examination of TAMC metabolic phenotypes in mouse models and patients with GBM identified the de novo creatine metabolic pathway as a hallmark of TAMCs. Multi-omics analyses revealed that TAMCs surround the hypoxic peri-necrotic regions of GBM and express the creatine metabolic enzyme glycine amidinotransferase (GATM). Conversely, GBM cells located within these same regions are uniquely specific in expressing the creatine transporter (SLC6A8). We hypothesized that TAMCs provide creatine to tumors, promoting GBM progression. Isotopic tracing demonstrated that TAMC-secreted creatine is taken up by tumor cells. Creatine supplementation protected tumors from hypoxia-induced stress, which was abrogated with genetic ablation or pharmacologic inhibition of SLC6A8. Lastly, inhibition of creatine transport using the clinically relevant compound, RGX-202-01, blunted tumor growth and enhanced radiation therapy in vivo. This work highlights that myeloid-to-tumor transfer of creatine promotes tumor growth in the hypoxic niche., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Poxviruses are unusual DNA viruses that replicate in the cytoplasm. To do so, they encode approximately 100 immunomodulatory proteins that counteract cytosolic nucleic acid sensors such as cGAMP synthase (cGAS) along with several other antiviral response pathways. Yet most of these immunomodulators are expressed very early in infection while many are variable host range determinants, and significant gaps remain in our understanding of poxvirus sensing and evasion strategies. Here, we show that after infection is established, subsequent progression of the viral lifecycle is sensed through specific changes to mitochondria that coordinate distinct aspects of the antiviral response. Unlike other viruses that cause extensive mitochondrial damage, poxviruses sustain key mitochondrial functions including membrane potential and respiration while reducing reactive oxygen species that drive inflammation. However, poxvirus replication induces mitochondrial hyperfusion that independently controls the release of mitochondrial DNA (mtDNA) to prime nucleic acid sensors and enables an increase in glycolysis that is necessary to support interferon stimulated gene (ISG) production. To counter this, the poxvirus F17 protein localizes to mitochondria and dysregulates mTOR to simultaneously destabilize cGAS and block increases in glycolysis. Our findings reveal how the poxvirus F17 protein disarms specific mitochondrially orchestrated responses to later stages of poxvirus replication., (© 2023. The Author(s).)

Apolipoprotein E (ApoE) is recognized for its pleiotropic properties that suppress inflammation. We report that ApoE serves as a metabolic rheostat that regulates microRNA control of glycolytic and mitochondrial activity in myeloid cells and hematopoietic stem and progenitor cells (HSPCs). ApoE expression in myeloid cells increases microRNA-146a, which reduces nuclear factor κB (NF-κB)-driven GLUT1 expression and glycolytic activity. In contrast, ApoE expression reduces microRNA-142a, which increases carnitine palmitoyltransferase 1a (CPT1A) expression, fatty acid oxidation, and oxidative phosphorylation. Improved mitochondrial metabolism by ApoE expression causes an enrichment of tricarboxylic acid (TCA) cycle metabolites and nicotinamide adenine dinucleotide (NAD + ) in macrophages. The study of mice with conditional ApoE expression supports the capacity of ApoE to foster microRNA-controlled immunometabolism. Modulation of microRNA-146a and -142a in the hematopoietic system of hyperlipidemic mice using RNA mimics and antagonists, respectively, improves mitochondrial metabolism, which suppresses inflammation and hematopoiesis. Our findings unveil microRNA regulatory circuits, controlled by ApoE, that exert metabolic control over hematopoiesis and inflammation in hyperlipidemia., Competing Interests: Declaration of interests The authors declare no competing interests., (Published by Elsevier Inc.)

Over the past decade or two, targeting metabolism has been effective in the treatment of many diseases and disorders, particularly cancer. In a metabolism focus issue in Cell Chemical Biology, this Voices piece asks researchers from a range of backgrounds: what are some major challenges and opportunities facing the field in the coming years?, Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023. Published by Elsevier Ltd.)

Alveolar epithelial type 1 (AT1) cells are necessary to transfer oxygen and carbon dioxide between the blood and air. Alveolar epithelial type 2 (AT2) cells serve as a partially committed stem cell population, producing AT1 cells during postnatal alveolar development and repair after influenza A and SARS-CoV-2 pneumonia 1-6 . Little is known about the metabolic regulation of the fate of lung epithelial cells. Here we report that deleting the mitochondrial electron transport chain complex I subunit Ndufs2 in lung epithelial cells during mouse gestation led to death during postnatal alveolar development. Affected mice displayed hypertrophic cells with AT2 and AT1 cell features, known as transitional cells. Mammalian mitochondrial complex I, comprising 45 subunits, regenerates NAD + and pumps protons. Conditional expression of yeast NADH dehydrogenase (NDI1) protein that regenerates NAD + without proton pumping 7,8 was sufficient to correct abnormal alveolar development and avert lethality. Single-cell RNA sequencing revealed enrichment of integrated stress response (ISR) genes in transitional cells. Administering an ISR inhibitor 9,10 or NAD + precursor reduced ISR gene signatures in epithelial cells and partially rescued lethality in the absence of mitochondrial complex I function. Notably, lung epithelial-specific loss of mitochondrial electron transport chain complex II subunit Sdhd, which maintains NAD + regeneration, did not trigger high ISR activation or lethality. These findings highlight an unanticipated requirement for mitochondrial complex I-dependent NAD + regeneration in directing cell fate during postnatal alveolar development by preventing pathological ISR induction., (© 2023. The Author(s).)

Histone H4 lysine 16 acetylation (H4K16ac), governed by the histone acetyltransferase MOF, orchestrates gene expression regulation and chromatin interaction. However, the roles of MOF and H4K16ac in controlling cellular function and regulating mammalian tissue development remain unclear. Here we show that conditional deletion of Mof in the skin, but not Kansl1, causes severe defects in the self-renewal of basal epithelial progenitors, epidermal differentiation, and hair follicle growth, resulting in barrier defects and perinatal lethality. MOF-regulated genes are highly enriched for essential functions in the mitochondria and cilia. Genetic deletion of Uqcrq, an essential subunit for the electron transport chain (ETC) Complex III, in the skin, recapitulates the defects in epidermal differentiation and hair follicle growth observed in MOF knockout mouse. Together, this study reveals the requirement of MOF-mediated epigenetic mechanism for regulating mitochondrial and ciliary gene expression and underscores the important function of the MOF/ETC axis for mammalian skin development., (© 2023. The Author(s).)

Mammalian retinal metabolism favors aerobic glycolysis. However, the role of glycolytic metabolism in retinal morphogenesis remains unknown. We report that aerobic glycolysis is necessary for the early stages of retinal development. Taking advantage of an unbiased approach that combines the use of eye organoids and single-cell RNA sequencing, we identify specific glucose transporters and glycolytic genes in retinal progenitors. Next, we determine that the optic vesicle territory of mouse embryos displays elevated levels of glycolytic activity. At the functional level, we show that removal of Glucose transporter 1 and Lactate dehydrogenase A gene activity from developing retinal progenitors arrests eye morphogenesis. Surprisingly, we uncover that lactate-mediated upregulation of key eye-field transcription factors is controlled by the epigenetic modification of histone H3 acetylation through histone deacetylase activity. Our results identify an unexpected bioenergetic independent role of lactate as a signaling molecule necessary for mammalian eye morphogenesis., (© 2023. The Author(s).)

Mutations in subunits of the mitochondrial NADH dehydrogenase cause mitochondrial complex I deficiency, a group of severe neurological diseases that can result in death in infancy. The pathogenesis of complex I deficiency remain poorly understood, and as a result there are currently no available treatments. To better understand the underlying mechanisms, we modelled complex I deficiency in Drosophila using knockdown of the mitochondrial complex I subunit ND-75 (NDUFS1) specifically in neurons. Neuronal complex I deficiency causes locomotor defects, seizures and reduced lifespan. At the cellular level, complex I deficiency does not affect ATP levels but leads to mitochondrial morphology defects, reduced endoplasmic reticulum-mitochondria contacts and activation of the endoplasmic reticulum unfolded protein response (UPR) in neurons. Multi-omic analysis shows that complex I deficiency dramatically perturbs mitochondrial metabolism in the brain. We find that expression of the yeast non-proton translocating NADH dehydrogenase NDI1, which reinstates mitochondrial NADH oxidation but not ATP production, restores levels of several key metabolites in the brain in complex I deficiency. Remarkably, NDI1 expression also reinstates endoplasmic reticulum-mitochondria contacts, prevents UPR activation and rescues the behavioural and lifespan phenotypes caused by complex I deficiency. Together, these data show that metabolic disruption due to loss of neuronal NADH dehydrogenase activity cause UPR activation and drive pathogenesis in complex I deficiency., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Granat et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Epigenetic status-altering mutations in chromatin-modifying enzymes are a feature of human diseases, including many cancers. However, the functional outcomes and cellular dependencies arising from these mutations remain unresolved. In this study, we investigated cellular dependencies, or vulnerabilities, that arise when enhancer function is compromised by loss of the frequently mutated COMPASS family members MLL3 and MLL4. CRISPR dropout screens in MLL3/4-depleted mouse embryonic stem cells (mESCs) revealed synthetic lethality upon suppression of purine and pyrimidine nucleotide synthesis pathways. Consistently, we observed a shift in metabolic activity toward increased purine synthesis in MLL3/4-KO mESCs. These cells also exhibited enhanced sensitivity to the purine synthesis inhibitor lometrexol, which induced a unique gene expression signature. RNA-Seq identified the top MLL3/4 target genes coinciding with suppression of purine metabolism, and tandem mass tag proteomic profiling further confirmed upregulation of purine synthesis in MLL3/4-KO cells. Mechanistically, we demonstrated that compensation by MLL1/COMPASS was underlying these effects. Finally, we demonstrated that tumors with MLL3 and/or MLL4 mutations were highly sensitive to lometrexol in vitro and in vivo, both in culture and in animal models of cancer. Our results depicted a targetable metabolic dependency arising from epigenetic factor deficiency, providing molecular insight to inform therapy for cancers with epigenetic alterations secondary to MLL3/4 COMPASS dysfunction.

Octopamine is a well-established invertebrate neurotransmitter involved in fight or flight responses. In mammals, its function was replaced by epinephrine. Nevertheless, it is present at trace amounts and can modulate the release of monoamine neurotransmitters by a yet unidentified mechanism. Here, through a multidisciplinary approach utilizing in vitro and in vivo models of α-synucleinopathy, we uncovered an unprecedented role for octopamine in driving the conversion from toxic to neuroprotective astrocytes in the cerebral cortex by fostering aerobic glycolysis. Physiological levels of neuron-derived octopamine act on astrocytes via a trace amine-associated receptor 1-Orai1-Ca 2+ -calcineurin-mediated signaling pathway to stimulate lactate secretion. Lactate uptake in neurons via the monocarboxylase transporter 2-calcineurin-dependent pathway increases ATP and prevents neurodegeneration. Pathological increases of octopamine caused by α-synuclein halt lactate production in astrocytes and short-circuits the metabolic communication to neurons. Our work provides a unique function of octopamine as a modulator of astrocyte metabolism and subsequent neuroprotection with implications to α-synucleinopathies.

Mitochondria have emerged as signaling organelles with roles beyond their well-established function in generating ATP and metabolites for macromolecule synthesis. Healthy mitochondria integrate various physiologic inputs and communicate signals that control cell function or fate as well as adaptation to stress. Dysregulation of these mitochondrial signaling networks are linked to pathology. Here we outline a few modes of signaling between the mitochondrion and the cytoplasm. To view this SnapShot, open or download the PDF., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In vitro studies have associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, whereas pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfill their homeostatic activities are incompletely understood. Here, we identified OXPHOS as the highest discriminating process among TMFs from different organs in homeostasis by analysis of RNA-seq data in both humans and mice. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell-cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), thus preventing insulin resistance and hepatosteatosis. Hence, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Targeting KRAS-mutated non-small-cell lung cancer (NSCLC) remains clinically challenging. Here we show that loss of function of Miz1 inhibits lung tumorigenesis in a mouse model of oncogenic KRAS-driven lung cancer. In vitro, knockout or silencing of Miz1 decreases cell proliferation, clonogenicity, migration, invasion, or anchorage-independent growth in mutant (MT) KRAS murine or human NSCLC cells but has unremarkable impact on non-tumorigenic cells or wild-type (WT) KRAS human NSCLC cells. RNA-sequencing reveals Protocadherin-10 (Pcdh10) as the top upregulated gene by Miz1 knockout in MT KRAS murine lung tumor cells. Chromatin immunoprecipitation shows Miz1 binding on the Pcdh10 promoter in MT KRAS lung tumor cells but not non-tumorigenic cells. Importantly, silencing of Pcdh10 rescues cell proliferation and clonogenicity in Miz1 knockout/knockdown MT KRAS murine or human tumor cells, and rescues allograft tumor growth of Miz1 knockout tumor cells in vivo. Miz1 is upregulated in MT KRAS lung tumor tissues compared with adjacent non-involved tissues in mice. Consistent with this, Miz1 is upregulated while Pcdh10 is downregulated in human lung adenocarcinomas (LUAD) compared with normal tissues, and high Miz1 levels or low Pcdh10 levels are associated with poor survival in lung cancer patients. Furthermore, the Miz1 signature is associated with worse survival in MT but not WT KRAS LUAD, and Pcdh10 is downregulated in MT compared to WT KRAS LUAD. Taken together, our studies implicate the Miz1/Pcdh10 axis in oncogenic KRAS-driven lung tumorigenesis., Competing Interests: Declaration of competing interest The authors declare no potential conflicts of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Mitochondria and peroxisomes are dynamic signaling organelles that constantly undergo fission, driven by the large GTPase dynamin-related protein 1 (DRP1; encoded by DNM1L). Patients with de novo heterozygous missense mutations in DNM1L present with encephalopathy due to defective mitochondrial and peroxisomal fission (EMPF1) - a devastating neurodevelopmental disease with no effective treatment. To interrogate the mechanisms by which DRP1 mutations cause cellular dysfunction, we used human-derived fibroblasts from patients who present with EMPF1. In addition to elongated mitochondrial morphology and lack of fission, patient cells display lower coupling efficiency, increased proton leak and upregulation of glycolysis. Mitochondrial hyperfusion also results in aberrant cristae structure and hyperpolarized mitochondrial membrane potential. Peroxisomes show a severely elongated morphology in patient cells, which is associated with reduced respiration when cells are reliant on fatty acid oxidation. Metabolomic analyses revealed impaired methionine cycle and synthesis of pyrimidine nucleotides. Our study provides insight into the role of mitochondrial dynamics in cristae maintenance and the metabolic capacity of the cell, as well as the disease mechanism underlying EMPF1., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Glioblastoma (GBM) is a primary tumor of the brain defined by its uniform lethality and resistance to conventional therapies. There have been considerable efforts to untangle the metabolic underpinnings of this disease to find novel therapeutic avenues for treatment. An emerging focus in this field is fatty acid (FA) metabolism, which is critical for numerous diverse biological processes involved in GBM pathogenesis. These processes can be classified into four broad fates: anabolism, catabolism, regulation of ferroptosis, and the generation of signaling molecules. Each fate provides a unique perspective by which we can inspect GBM biology and gives us a road map to understanding this complicated field. This Review discusses the basic, translational, and clinical insights into each of these fates to provide a contemporary understanding of FA biology in GBM. It is clear, based on the literature, that there are far more questions than answers in the field of FA metabolism in GBM, and substantial efforts should be made to untangle these complex processes in this intractable disease.

Timely crop water stress detection can help precision irrigation management and minimize yield loss. A two-year study was conducted on non-invasive winter wheat water stress monitoring using state-of-the-art computer vision and thermal-RGB imagery inputs. Field treatment plots were irrigated using two irrigation systems (flood and sprinkler) at four rates (100, 75, 50, and 25% of crop evapotranspiration [ET c ]). A total of 3200 images under different treatments were captured at critical growth stages, that is, 20, 35, 70, 95, and 108 days after sowing using a custom-developed thermal-RGB imaging system. Crop and soil response measurements of canopy temperature (T c ), relative water content (RWC), soil moisture content (SMC), and relative humidity (RH) were significantly affected by the irrigation treatments showing the lowest T c (22.5 ± 2 °C), and highest RWC (90%) and SMC (25.7 ± 2.2%) for 100% ET c , and highest T c (28 ± 3 °C), and lowest RWC (74%) and SMC (20.5 ± 3.1%) for 25% ET c . The RGB and thermal imagery were then used as inputs to feature-extraction-based deep learning models (AlexNet, GoogLeNet, Inception V3, MobileNet V2, ResNet50) while, RWC, SMC, T c , and RH were the inputs to function-approximation models (Artificial Neural Network (ANN), Kernel Nearest Neighbor (KNN), Logistic Regression (LR), Support Vector Machine (SVM) and Long Short-Term Memory (DL-LSTM)) to classify stressed/non-stressed crops. Among the feature extraction-based models, ResNet50 outperformed other models showing a discriminant accuracy of 96.9% with RGB and 98.4% with thermal imagery inputs. Overall, classification accuracy was higher for thermal imagery compared to RGB imagery inputs. The DL-LSTM had the highest discriminant accuracy of 96.7% and less error among the function approximation-based models for classifying stress/non-stress. The study suggests that computer vision coupled with thermal-RGB imagery can be instrumental in high-throughput mitigation and management of crop water stress.

Aging is among the most important risk factors for morbidity and mortality. To contribute toward a molecular understanding of aging, we analyzed age-resolved transcriptomic data from multiple studies. Here, we show that transcript length alone explains most transcriptional changes observed with aging in mice and humans. We present three lines of evidence supporting the biological importance of the uncovered transcriptome imbalance. First, in vertebrates the length association primarily displays a lower relative abundance of long transcripts in aging. Second, eight antiaging interventions of the Interventions Testing Program of the National Institute on Aging can counter this length association. Third, we find that in humans and mice the genes with the longest transcripts enrich for genes reported to extend lifespan, whereas those with the shortest transcripts enrich for genes reported to shorten lifespan. Our study opens fundamental questions on aging and the organization of transcriptomes., (© 2022. The Author(s).)

Leigh syndrome (LS) is a rare, inherited neurometabolic disorder that presents with bilateral brain lesions caused by defects in the mitochondrial respiratory chain and associated nuclear-encoded proteins. We generated human induced pluripotent stem cells (iPSCs) from three LS patient-derived fibroblast lines. Using whole-exome and mitochondrial sequencing, we identified unreported mutations in pyruvate dehydrogenase (GM0372, PDH; GM13411, MT-ATP6/PDH) and dihydrolipoyl dehydrogenase (GM01503, DLD). These LS patient-derived iPSC lines were viable and capable of differentiating into progenitor populations, but we identified several abnormalities in three-dimensional differentiation models of brain development. LS patient-derived cerebral organoids showed defects in neural epithelial bud generation, size and cortical architecture at 100 days. The double mutant MT-ATP6/PDH line produced organoid neural precursor cells with abnormal mitochondrial morphology, characterized by fragmentation and disorganization, and showed an increased generation of astrocytes. These studies aim to provide a comprehensive phenotypic characterization of available patient-derived cell lines that can be used to study Leigh syndrome., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)