bims-mepmim 2024-02-04 papers

bims-mepmim

Biomed News

on Metabolites in pathological microenvironments and immunometabolism

Issue of 2024‒02‒04
28 papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

Neutral ceramidase regulates breast cancer progression by metabolic programming of TREM2-associated macrophages.
Obesity causes mitochondrial fragmentation and dysfunction in white adipocytes due to RalA activation.
A structure-function analysis of hepatocyte arginase 2 reveals mitochondrial ureahydrolysis as a determinant of glucose oxidation.
Activation of GPR3-β-arrestin2-PKM2 pathway in Kupffer cells stimulates glycolysis and inhibits obesity and liver pathogenesis.
Adrenal Abcg1 controls cholesterol flux and steroidogenesis.
Folate depletion induces erythroid differentiation through perturbation of de novo purine synthesis.
Decreased pyruvate dehydrogenase activity in Tafazzin-deficient cells is caused by dysregulation of pyruvate dehydrogenase phosphatase 1 (PDP1).
Reversal of Pulmonary Hypertension in a Human-Like Model: Therapeutic Targeting of Endothelial DHFR.
ACOD1 deficiency offers protection in a mouse model of diet-induced obesity by maintaining a healthy gut microbiota.
Cancer-associated fibroblasts contributed to hepatocellular carcinoma recurrence and metastasis via CD36-mediated fatty-acid metabolic reprogramming.
Itaconate stabilizes CPT1a to enhance lipid utilization during inflammation.
The B-cell subsets contribute to myocardial protection by inducing neutrophil apoptosis after ischemia and reperfusion.
A universal metabolite repair enzyme removes a strong inhibitor of the TCA cycle.
Discoveries of GPR39 as an evolutionarily conserved receptor for bile acids and of its involvement in biliary acute pancreatitis.
In-vivo tracking of deuterium metabolism in mouse organs using LC-MS/MS.
Human alveolar macrophages display marked hypo-responsiveness to IFN-γ in both proteomic and gene expression analysis.
AP-1γ2 is an adaptor protein 1 variant required for endosome-to-Golgi trafficking of the mannose-6-P receptor (CI-MPR) and ATP7B copper transporter.
7-Dehydrocholesterol is an endogenous suppressor of ferroptosis.
Myeloid and lymphoid expression of C9orf72 regulates IL-17A signaling in mice.
Microbiota-derived butyrate restricts tuft cell differentiation via histone deacetylase 3 to modulate intestinal type 2 immunity.
Photoswitchable PROTACs for Reversible and Spatiotemporal Regulation of NAMPT and NAD.
Low-input lipidomics reveals lipid metabolism remodelling during early mammalian embryo development.
Lactate utilization enables metabolic escape to confer resistance to BET inhibition in acute myeloid leukemia.
Farnesoid X receptor agonist tropifexor detoxifies ammonia by regulating the glutamine metabolism and urea cycles in cholestatic livers.
The mitochondrial biliverdin exporter ABCB10 in hepatocytes mitigates neutrophilic inflammation in alcoholic hepatitis.
Upregulated Selenoprotein I during LPS-induced B cell activation promotes lipidomic changes and is required for effective differentiation into IgM secreting plasma B cells.
The BCKDK inhibitor BT2 is a chemical uncoupler that lowers mitochondrial ROS production and de novo lipogenesis.
Mitochondrial DNA mutations drive aerobic glycolysis to enhance checkpoint blockade response in melanoma.

Nat Commun. 2024 Feb 01. 15(1): 966

Neutral ceramidase regulates breast cancer progression by metabolic programming of TREM2-associated macrophages.

Rui Sun, Chao Lei, Zhishan Xu, Xuemei Gu, Liu Huang, Liang Chen, Yi Tan, Min Peng, Kavitha Yaddanapudi, Leah Siskind, Maiying Kong, Robert Mitchell, Jun Yan, Zhongbin Deng.

The tumor microenvironment is reprogrammed by cancer cells and participates in all stages of tumor progression. Neutral ceramidase is a key regulator of ceramide, the central intermediate in sphingolipid metabolism. The contribution of neutral ceramidase to the reprogramming of the tumor microenvironment is not well understood. Here, we find that deletion of neutral ceramidase in multiple breast cancer models in female mice accelerates tumor growth. Our result show that Ly6C+CD39+ tumor-infiltrating CD8 T cells are enriched in the tumor microenvironment and display an exhausted phenotype. Deletion of myeloid neutral ceramidase in vivo and in vitro induces exhaustion in tumor-infiltrating Ly6C+CD39+CD8+ T cells. Mechanistically, myeloid neutral ceramidase is required for the generation of lipid droplets and for the induction of lipolysis, which generate fatty acids for fatty-acid oxidation and orchestrate macrophage metabolism. Metabolite ceramide leads to reprogramming of macrophages toward immune suppressive TREM2+ tumor associated macrophages, which promote CD8 T cells exhaustion.

DOI: https://doi.org/10.1038/s41467-024-45084-7
Nat Metab. 2024 Jan 29.

Obesity causes mitochondrial fragmentation and dysfunction in white adipocytes due to RalA activation.

Wenmin Xia, Preethi Veeragandham, Yu Cao, Yayun Xu, Torrey E Rhyne, Jiaxin Qian, Chao-Wei Hung, Peng Zhao, Ying Jones, Hui Gao, Christopher Liddle, Ruth T Yu, Michael Downes, Ronald M Evans, Mikael Rydén, Martin Wabitsch, Zichen Wang, Hiroyuki Hakozaki, Johannes Schöneberg, Shannon M Reilly, Jianfeng Huang, Alan R Saltiel.

Mitochondrial dysfunction is a characteristic trait of human and rodent obesity, insulin resistance and fatty liver disease. Here we show that high-fat diet (HFD) feeding causes mitochondrial fragmentation in inguinal white adipocytes from male mice, leading to reduced oxidative capacity by a process dependent on the small GTPase RalA. RalA expression and activity are increased in white adipocytes after HFD. Targeted deletion of RalA in white adipocytes prevents fragmentation of mitochondria and diminishes HFD-induced weight gain by increasing fatty acid oxidation. Mechanistically, RalA increases fission in adipocytes by reversing the inhibitory Ser637 phosphorylation of the fission protein Drp1, leading to more mitochondrial fragmentation. Adipose tissue expression of the human homolog of Drp1, DNM1L, is positively correlated with obesity and insulin resistance. Thus, chronic activation of RalA plays a key role in repressing energy expenditure in obese adipose tissue by shifting the balance of mitochondrial dynamics toward excessive fission, contributing to weight gain and metabolic dysfunction.

DOI: https://doi.org/10.1038/s42255-024-00978-0
Cell Mol Gastroenterol Hepatol. 2024 Jan 25. pii: S2352-345X(24)00015-8. [Epub ahead of print]

A structure-function analysis of hepatocyte arginase 2 reveals mitochondrial ureahydrolysis as a determinant of glucose oxidation.

Yiming Zhang, Jiameng Sun, Henry D Wasserman, Joshua A Adams, Cassandra B Higgins, Shannon C Kelly, Louise Lantier, Brian J DeBosch.

  Restoring hepatic and peripheral insulin sensitivity is critical to prevent or reverse metabolic syndrome and type 2 diabetes. Glucose homeostasis comprises in part the complex regulation of hepatic glucose production, and insulin-mediated glucose uptake and oxidation in peripheral tissues. We previously identified hepatocyte arginase 2 (Arg2) as an inducible ureahydrolase that improves glucose homeostasis and enhances glucose oxidation in multiple obese, insulin resistant models. We therefore examined structure-function determinants through which hepatocyte Arg2 governs systemic insulin action and glucose oxidation. To do this, we generated mice expressing wild-type murine Arg2, enzymatically inactive Arg2 (Arg2H160F) and Arg2 lacking its putative mitochondrial targeting sequence (Arg2Δ1-22). We expressed these hepatocyte-specific constructs in obese, diabetic (db/db) mice, and performed genetic complementation analyses in hepatocyte-specific Arg2-deficent (Arg2LKO) mice. We show that Arg2 attenuates hepatic steatosis, independent of mitochondrial localization or ureahydrolase activity, and that enzymatic arginase activity is dispensable for Arg2 to augment total body energy expenditure. In contrast, mitochondrial localization and ureahydrolase activity were required for Arg2-mediated reductions in fasting glucose and insulin resistance indices. Mechanistically, Arg2Δ1-22 and Arg2H160F failed to suppress glucose appearance during hyperinsulinemic-euglycemic clamping. Quantification of heavy-isotope-labeled glucose oxidation further revealed that mistargeting or ablating Arg2 enzymatic function abrogates Arg2-induced peripheral glucose oxidation. We conclude that the metabolic effects of Arg2 extend beyond its enzymatic activity, yet hepatocyte mitochondrial ureahydrolysis drives hepatic and peripheral oxidative metabolism. The data define a structure-based mechanism mediating hepatocyte Arg2 function, and nominate hepatocyte mitochondrial ureahydrolysis as a key determinant of glucose oxidative capacity in mammals.

Keywords:  GLUT; Urea cycle; arginase; diabetes; energy metabolism; glucose transport; insulin resistance; metabolic dysfunction-associated steatotic liver disease; mitochondria; obesity; oxidation; proteomics; thermogenesis

DOI:  https://doi.org/10.1016/j.jcmgh.2024.01.016
Nat Commun. 2024 Jan 27. 15(1): 807

Activation of GPR3-β-arrestin2-PKM2 pathway in Kupffer cells stimulates glycolysis and inhibits obesity and liver pathogenesis.

Ting Dong, Guangan Hu, Zhongqi Fan, Huirui Wang, Yinghui Gao, Sisi Wang, Hao Xu, Michael B Yaffe, Matthew G Vander Heiden, Guoyue Lv, Jianzhu Chen.

Kupffer cells are liver resident macrophages and play critical role in fatty liver disease, yet the underlying mechanisms remain unclear. Here, we show that activation of G-protein coupled receptor 3 (GPR3) in Kupffer cells stimulates glycolysis and protects mice from obesity and fatty liver disease. GPR3 activation induces a rapid increase in glycolysis via formation of complexes between β-arrestin2 and key glycolytic enzymes as well as sustained increase in glycolysis through transcription of glycolytic genes. In mice, GPR3 activation in Kupffer cells results in enhanced glycolysis, reduced inflammation and inhibition of high-fat diet induced obesity and liver pathogenesis. In human fatty liver biopsies, GPR3 activation increases expression of glycolytic genes and reduces expression of inflammatory genes in a population of disease-associated macrophages. These findings identify GPR3 activation as a pivotal mechanism for metabolic reprogramming of Kupffer cells and as a potential approach for treating fatty liver disease.

DOI: https://doi.org/10.1038/s41467-024-45167-5
Endocrinology. 2024 Feb 01. pii: bqae014. [Epub ahead of print]

Adrenal Abcg1 controls cholesterol flux and steroidogenesis.

Jani Liimatta, Evelyn Curschellas, Emre Murat Altinkilic, Rawda Naamneh Elzenaty, Philipp Augsburger, Therina du Toit, Clarissa D Voegel, David T Breault, Christa E Flück, Emanuele Pignatti.

  Cholesterol is the precursor of all steroids, but how cholesterol flux is controlled in steroidogenic tissues is poorly understood. The cholesterol exporter ABCG1 is an essential component of the reverse cholesterol pathway and its global inactivation results in neutral lipid redistribution to tissue macrophages. The function of ABCG1 in steroidogenic tissues, however, has not been explored. To model this, we inactivated Abcg1 in the mouse adrenal cortex, which led to an adrenal-specific increase in transcripts involved in cholesterol uptake and de novo synthesis. Abcg1 inactivation did not affect adrenal cholesterol content, zonation, or serum lipid profile. Instead, we observed a moderate increase in corticosterone production that was not recapitulated by the inactivation of the functionally similar cholesterol exporter Abca1. Altogether, our data imply that Abcg1 controls cholesterol uptake and biosynthesis and regulates glucocorticoid production in the adrenal cortex, introducing the possibility that ABCG1 variants may account for physiological or subclinical variation in stress response.

Keywords:  Abcg1; adrenal cortex; cholesterol; glucocorticoids; steroids

DOI:  https://doi.org/10.1210/endocr/bqae014
Sci Adv. 2024 Feb 02. 10(5): eadj9479

Folate depletion induces erythroid differentiation through perturbation of de novo purine synthesis.

Adam G Maynard, Nancy K Pohl, Annabel P Mueller, Boryana Petrova, Alan Y L Wong, Peng Wang, Andrew J Culhane, Jeannette R Brook, Leah M Hirsch, Ngoc Hoang, Orville Kirkland, Tatum Braun, Sarah Ducamp, Mark D Fleming, Hojun Li, Naama Kanarek.

Folate, an essential vitamin, is a one-carbon acceptor and donor in key metabolic reactions. Erythroid cells harbor a unique sensitivity to folate deprivation, as revealed by the primary pathological manifestation of nutritional folate deprivation: megaloblastic anemia. To study this metabolic sensitivity, we applied mild folate depletion to human and mouse erythroid cell lines and primary murine erythroid progenitors. We show that folate depletion induces early blockade of purine synthesis and accumulation of the purine synthesis intermediate and signaling molecule, 5'-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR), followed by enhanced heme metabolism, hemoglobin synthesis, and erythroid differentiation. This is phenocopied by inhibition of folate metabolism using the inhibitor SHIN1, and by AICAR supplementation. Mechanistically, the metabolically driven differentiation is independent of mechanistic target of rapamycin complex 1 (mTORC1) and adenosine 5'-monophosphate-activated protein kinase (AMPK) and is instead mediated by protein kinase C. Our findings suggest that folate deprivation-induced premature differentiation of erythroid progenitor cells is a molecular etiology to folate deficiency-induced anemia.

DOI: https://doi.org/10.1126/sciadv.adj9479
J Biol Chem. 2024 Jan 30. pii: S0021-9258(24)00073-5. [Epub ahead of print] 105697

Decreased pyruvate dehydrogenase activity in Tafazzin-deficient cells is caused by dysregulation of pyruvate dehydrogenase phosphatase 1 (PDP1).

Zhuqing Liang, Tyler Ralph-Epps, Michael W Schmidtke, Vikalp Kumar, Miriam L Greenberg.

Cardiolipin (CL), the signature lipid of the mitochondrial inner membrane, is critical for maintaining optimal mitochondrial function and bioenergetics. Disruption of CL metabolism, caused by mutations in the CL remodeling enzyme TAFAZZIN, results in the rare and life-threatening disorder Barth syndrome (BTHS). While the clinical manifestations of BTHS, such as dilated cardiomyopathy and skeletal myopathy, point to defects in mitochondrial bioenergetics, the disorder is also characterized by broad metabolic dysregulation, including abnormal levels of metabolites associated with the tricarboxylic acid (TCA) cycle. In line with this, recent studies have identified inhibition of pyruvate dehydrogenase (PDH), the gatekeeper enzyme for TCA cycle carbon influx, as a key deficiency in various BTHS model systems. However, the molecular mechanisms linking aberrant CL remodeling, particularly the primary, direct consequence of reduced tetralinoleoyl-CL (TLCL) levels, to PDH activity deficiency are not yet understood. This knowledge gap has limited our understanding of lipid-mediated metabolic regulation in BTHS and hindered the development of effective treatment strategies. In the current study, we provide evidence that remodeled TLCL promotes PDH function by directly binding to and enhancing the activity of PDH phosphatase 1 (PDP1). This is supported by our findings that TLCL uniquely activates PDH in a dose-dependent manner, TLCL binds to PDP1 in vitro, TLCL-mediated PDH activation is attenuated in the presence of phosphatase inhibitor, and PDP1 activity is decreased in Tafazzin-knockout (TAZ-KO) C2C12 myoblasts. Additionally, we observed decreased mitochondrial calcium levels in TAZ-KO cells, which may affect the calcium-sensitive activity of PDP1. Treating TAZ-KO cells with calcium lactate (CaLac) increases mitochondrial calcium and restores PDH activity and mitochondrial oxygen consumption rate. Based on our findings, we conclude that reduced mitochondrial calcium levels and decreased binding of PDP1 to TLCL contribute to decreased PDP1 activity in TAZ-KO cells.

DOI: https://doi.org/10.1016/j.jbc.2024.105697
Circ Res. 2024 Feb 01.

Reversal of Pulmonary Hypertension in a Human-Like Model: Therapeutic Targeting of Endothelial DHFR.

Priya Murugesan, Yixuan Zhang, Yuanli Huang, Nobel Chengong Zong, Ji Youn Youn, Wenhui Chen, Chen Wang, Joseph Loscalzo, Hua Cai.

  BACKGROUND: Pulmonary hypertension (PH) is a progressive disorder characterized by remodeling of the pulmonary vasculature and elevated mean pulmonary arterial pressure, resulting in right heart failure.METHODS: Here, we show that direct targeting of the endothelium to eNOS (endothelial nitric oxide synthase) with DAHP (2,4-diamino 6-hydroxypyrimidine; an inhibitor of GTP cyclohydrolase 1, the rate-limiting synthetic enzyme for the critical eNOS cofactor tetrahydrobiopterin) induces human-like, time-dependent progression of PH phenotypes in mice.
RESULTS: Critical phenotypic features include elevation in mean pulmonary arterial pressure, right ventricular systolic blood pressure, and right ventricular/(LV+S) ratio; extensive vascular remodeling of pulmonary arterioles with increased medial thickness/perivascular collagen deposition and increased expression of PCNA (proliferative cell nuclear antigen) and alpha-actin; increased total and mitochondrial superoxide production, reduced tetrahydrobiopterin, and nitric oxide bioavailabilities; and formation of an array of human-like vascular lesions. Intriguingly, novel in-house generated endothelial-specific dihydrofolate reductase (DHFR) transgenic mice were completely protected from the pathophysiological and molecular features of PH upon DAHP treatment or hypoxia. Furthermore, DHFR overexpression with a pCMV-DHFR plasmid transfection in mice after initiation of DAHP treatment completely reversed PH phenotypes. DHFR knockout mice spontaneously developed PH at baseline and had no additional deterioration in response to hypoxia, indicating an intrinsic role of DHFR deficiency in causing PH. RNA-sequencing experiments indicated great similarity in gene regulation profiles between the DAHP model and patients with human PH.
CONCLUSIONS: Taken together, these results establish a novel human-like murine model of PH that has long been lacking in the field, which can be broadly used for future mechanistic and translational studies. These data also indicate that targeting endothelial DHFR deficiency represents a novel and robust therapeutic strategy for the treatment of PH.

Keywords:  fibrinolytic agents; hypertension, pulmonary; hypoxia; tetrahydrobiopterin; vasodilation

DOI:  https://doi.org/10.1161/CIRCRESAHA.123.323090
Cell Death Dis. 2024 Feb 01. 15(2): 105

ACOD1 deficiency offers protection in a mouse model of diet-induced obesity by maintaining a healthy gut microbiota.

Tanja Eberhart, Federico Uchenna Stanley, Luisa Ricci, Tiziana Chirico, Roberto Ferrarese, Sofia Sisti, Alessandra Scagliola, Andreina Baj, Sylvia Badurek, Andreas Sommer, Rachel Culp-Hill, Monika Dzieciatkowska, Engy Shokry, David Sumpton, Angelo D'Alessandro, Nicola Clementi, Nicasio Mancini, Simone Cardaci.

Aconitate decarboxylase 1 (ACOD1) is the enzyme synthesizing itaconate, an immuno-regulatory metabolite tuning host-pathogen interactions. Such functions are achieved by affecting metabolic pathways regulating inflammation and microbe survival. However, at the whole-body level, metabolic roles of itaconate remain largely unresolved. By using multiomics-integrated approaches, here we show that ACOD1 responds to high-fat diet consumption in mice by promoting gut microbiota alterations supporting metabolic disease. Genetic disruption of itaconate biosynthesis protects mice against obesity, alterations in glucose homeostasis and liver metabolic dysfunctions by decreasing meta-inflammatory responses to dietary lipid overload. Mechanistically, fecal metagenomics and microbiota transplantation experiments demonstrate such effects are dependent on an amelioration of the intestinal ecosystem composition, skewed by high-fat diet feeding towards obesogenic phenotype. In particular, unbiased fecal microbiota profiling and axenic culture experiments point towards a primary role for itaconate in inhibiting growth of Bacteroidaceae and Bacteroides, family and genus of Bacteroidetes phylum, the major gut microbial taxon associated with metabolic health. Specularly to the effects imposed by Acod1 deficiency on fecal microbiota, oral itaconate consumption enhances diet-induced gut dysbiosis and associated obesogenic responses in mice. Unveiling an unrecognized role of itaconate, either endogenously produced or exogenously administered, in supporting microbiota alterations underlying diet-induced obesity in mice, our study points ACOD1 as a target against inflammatory consequences of overnutrition.

DOI: https://doi.org/10.1038/s41419-024-06483-2
Exp Cell Res. 2024 Jan 30. pii: S0014-4827(24)00037-5. [Epub ahead of print] 113947

Cancer-associated fibroblasts contributed to hepatocellular carcinoma recurrence and metastasis via CD36-mediated fatty-acid metabolic reprogramming.

Han Wang, Fangming Liu, Xiaoling Wu, Guiqi Zhu, Zheng Tang, Weifeng Qu, Qianfu Zhao, Run Huang, Mengxin Tian, Yuan Fang, Xifei Jiang, Chenyang Tao, Jun Gao, Weiren Liu, Jian Zhou, Jia Fan, Duojiao Wu, Yinghong Shi.

  Cancer-associated fibroblasts (CAFs) are the main components in the tumor microenvironment. Tumors activate fibroblasts from quiescent state into activated state by secreting cytokines, and activated CAFs may in turn promote tumor progression and metastasis. Therefore, studies targeting CAFs could enrich the therapeutic options for tumor treatment. In this study, we demonstrate that the content of lipid droplets and the expression of autophagosomes were higher in CAFs than in peri-tumor fibroblasts (PTFs), which was inhibited by 5-(tetradecyloxy)-2-furoic acid(TOFA). The expression of CD36 in CAFs was higher than that in PTFs at both mRNA and protein levels. Inhibition of CD36 activity using either the CD36 inhibitor SSO or siRNA had a significant negative impact on the proliferation and migration abilities of CAFs, which was associated with reduced levels of relevant activated genes (α-SMA, FAP, Vimentin) and cytokines (IL-6, TGF-β and VEGF-α). SSO also inhibited HCC growth and tumorigenesis in nude mice orthotopically implanted with CAFs and HCC cells. Our data further show that CD36+CAFs affected the expression of PD-1 in CTLs leading to CTL exhaustion, and that patients with high CD36 expression in CAFs were correlated with shorter overall survival (OS). Together, our data demonstrate that CAFs were active in lipid metabolism with increased lipid content and lipophagy activity. CD36 may play a key role in the regulation of the biological behaviors of CAFs, which may influence the proliferation and migration of tumor cells by reprograming the lipid metabolism in tumor cells. Thus, CD36 could be an effective therapeutic target for the treatment of HCC.

Keywords:  CD36; Cancer-associated fibroblasts; Hepatocellular carcinoma; T cell exhaustion

DOI:  https://doi.org/10.1016/j.yexcr.2024.113947
Elife. 2024 Feb 02. pii: RP92420. [Epub ahead of print]12

Itaconate stabilizes CPT1a to enhance lipid utilization during inflammation.

Rabina Mainali, Nancy Buechler, Cristian Otero, Laken Edwards, Chia-Chi Key, Cristina Furdui, Matthew A Quinn.

  One primary metabolic manifestation of inflammation is the diversion of cis-aconitate within the tricarboxylic acid (TCA) cycle to synthesize the immunometabolite itaconate. Itaconate is well established to possess immunomodulatory and metabolic effects within myeloid cells and lymphocytes, however, its effects in other organ systems during sepsis remain less clear. Utilizing Acod1 knockout mice that are deficient in synthesizing itaconate, we aimed to understand the metabolic role of itaconate in the liver and systemically during sepsis. We find itaconate aids in lipid metabolism during sepsis. Specifically, Acod1 KO mice develop a heightened level of hepatic steatosis when induced with polymicrobial sepsis. Proteomics analysis reveals enhanced expression of enzymes involved in fatty acid oxidation in following 4-octyl itaconate (4-OI) treatment in vitro. Downstream analysis reveals itaconate stabilizes the expression of the mitochondrial fatty acid uptake enzyme CPT1a, mediated by its hypoubiquitination. Chemoproteomic analysis revealed itaconate interacts with proteins involved in protein ubiquitination as a potential mechanism underlying its stabilizing effect on CPT1a. From a systemic perspective, we find itaconate deficiency triggers a hypothermic response following endotoxin stimulation, potentially mediated by brown adipose tissue (BAT) dysfunction. Finally, by use of metabolic cage studies, we demonstrate Acod1 KO mice rely more heavily on carbohydrates versus fatty acid sources for systemic fuel utilization in response to endotoxin treatment. Our data reveal a novel metabolic role of itaconate in modulating fatty acid oxidation during polymicrobial sepsis.

Keywords:  fatty acid oxidation; immunology; inflammation; itaconate; mouse

DOI:  https://doi.org/10.7554/eLife.92420
JCI Insight. 2024 Jan 30. pii: e167201. [Epub ahead of print]

The B-cell subsets contribute to myocardial protection by inducing neutrophil apoptosis after ischemia and reperfusion.

Fangyang Huang, Jialiang Zhang, Hao Zhou, Tianyi Qu, Yan Wang, Kexin Jiang, Yutong Liu, Yuan Ning Xu, Mao Chen, Li Chen.

  A robust sterile inflammation underlies myocardial ischemia and reperfusion injury (MIRI). Several subsets of B-cells possess the immune-regulatory capacity that limits tissue damage, yet the role of B-cells in MIRI remains elusive. Here, we sought to elucidate the contribution of B-cells to the MIRI by transient ligation of the left anterior descending in the B-cell depleted or deficient mice. Following ischemia and reperfusion (I/R), regulatory B-cells are rapidly recruited to the heart. B-cell-depleted or deficient mice exhibited exacerbated tissue damage, adverse cardiac remodeling, and an augmented inflammatory response after I/R. Rescue and chimeric experiments indicated that the cardioprotective effect of B-cells was not solely dependent on IL10. Coculture experiments demonstrated that B-cells induced neutrophil apoptosis through contact-dependent interaction, subsequently promoting reparative macrophage polarization by facilitating the phagocytosis of neutrophils by macrophages. The in-vivo cardioprotective effect of B-cells was absent in absence of neutrophils after I/R. Mechanistically, ligand-receptor imputation identified FCER2A as a potential mediator of interactions between B-cells and neutrophils. Blocking FCER2A on B-cells resulted in a reduction in the percentage of apoptotic neutrophils, contributing to the deterioration of cardiac remodeling. Our findings unveil a potential cardioprotective role of B-cells in myocardial I/R through mechanisms involving FCER2A, neutrophil, and macrophage.

Keywords:  Apoptosis; Cardiology; Cardiovascular disease; Immunology; Innate immunity

DOI:  https://doi.org/10.1172/jci.insight.167201
Nat Commun. 2024 Jan 29. 15(1): 846

A universal metabolite repair enzyme removes a strong inhibitor of the TCA cycle.

Anthony J Zmuda, Xiaojun Kang, Katie B Wissbroecker, Katrina Freund Saxhaug, Kyle C Costa, Adrian D Hegeman, Thomas D Niehaus.

A prevalent side-reaction of succinate dehydrogenase oxidizes malate to enol-oxaloacetate (OAA), a metabolically inactive form of OAA that is a strong inhibitor of succinate dehydrogenase. We purified from cow heart mitochondria an enzyme (OAT1) with OAA tautomerase (OAT) activity that converts enol-OAA to the physiological keto-OAA form, and determined that it belongs to the highly conserved and previously uncharacterized Fumarylacetoacetate_hydrolase_domain-containing protein family. From all three domains of life, heterologously expressed proteins were shown to have strong OAT activity, and ablating the OAT1 homolog caused significant growth defects. In Escherichia coli, expression of succinate dehydrogenase was necessary for OAT1-associated growth defects to occur, and ablating OAT1 caused a significant increase in acetate and other metabolites associated with anaerobic respiration. OAT1 increased the succinate dehydrogenase reaction rate by 35% in in vitro assays with physiological concentrations of both succinate and malate. Our results suggest that OAT1 is a universal metabolite repair enzyme that is required to maximize aerobic respiration efficiency by preventing succinate dehydrogenase inhibition.

DOI: https://doi.org/10.1038/s41467-024-45134-0
Sci Adv. 2024 Feb 02. 10(5): eadj0146

Discoveries of GPR39 as an evolutionarily conserved receptor for bile acids and of its involvement in biliary acute pancreatitis.

Zhentao Zi, Yi Rao.

Acute pancreatitis (AP) is one of the most common gastrointestinal diseases. Bile acids (BAs) were proposed to be a cause of AP nearly 170 years ago, though the underlying mechanisms remain unclear. Here, we report that two G protein-coupled receptors, GPR39 and GHSR, mediated cellular responses to BAs. Our results revealed GPR39 as an evolutionarily conserved receptor for BAs, particularly 3-O-sulfated lithocholic acids. In cultured cell lines, GPR39 is sufficient for BA-induced Ca2+ elevation. In pancreatic acinar cells, GPR39 mediated BA-induced Ca2+ elevation and necrosis. Furthermore, AP induced by BAs was significantly reduced in GPR39 knockout mice. Our findings provide in vitro and in vivo evidence demonstrating that GPR39 is necessary and sufficient to mediate BA signaling, highlighting its involvement in biliary AP pathogenesis, and suggesting it as a promising therapeutic target for biliary AP.

DOI: https://doi.org/10.1126/sciadv.adj0146
J Chromatogr A. 2024 Jan 28. pii: S0021-9673(24)00064-5. [Epub ahead of print]1717 464691

In-vivo tracking of deuterium metabolism in mouse organs using LC-MS/MS.

Siva Swapna Kasarla, Vera Flocke, Nay Min Thaw Saw, Antonia Fecke, Albert Sickmann, Matthias Gunzer, Ulrich Flögel, Prasad Phapale.

  Mass spectrometry-based metabolomics with stable isotope labeling (SIL) is an established tool for sensitive and precise analyses of tissue metabolism, its flux, and pathway activities in diverse models of physiology and disease. Despite the simplicity and broad applicability of deuterium (2H)-labeled precursors for tracing metabolic pathways with minimal biological perturbations, they are rarely employed in LC-MS/MS-guided metabolomics. In this study, we have developed a LC-MS/MS-guided workflow to trace deuterium metabolism in mouse organs following 2H7 -glucose infusion. The workflow includes isotopically labeled glucose infusion, mouse organ isolation and metabolite extraction, zwitterion-based hydrophilic interaction liquid chromatography (HILIC) coupled to high-resolution tandem mass spectrometry, targeted data acquisition for sensitive detection of deuterated metabolites, a spectral library of over 400 metabolite standards, and multivariate data analysis with pathway mapping. The optimized method was validated for matrix effects, normalization, and quantification to provide both tissue metabolomics and tracking the in-vivo metabolic fate of deuterated glucose through key metabolic pathways. We quantified more than 100 metabolites in five major mouse organ tissues (liver, kidney, brain, brown adipose tissue, and heart). Furthermore, we mapped isotopologues of deuterated metabolites from glycolysis, tricarboxylic acid (TCA) cycle, and amino acid pathways, which are significant for studying both health and various diseases. This study will open new avenues in LC-MS based analysis of 2H-labeled tissue metabolism research in animal models and clinical settings.

Keywords:  Deuterium tracing; LC-MS; Metabolic flux; Metabolomics; Tissue metabolism

DOI:  https://doi.org/10.1016/j.chroma.2024.464691
PLoS One. 2024 ;19(2): e0295312

Human alveolar macrophages display marked hypo-responsiveness to IFN-γ in both proteomic and gene expression analysis.

Bonnie A Thiel, Kathleen C Lundberg, Daniela Schlatzer, Jessica Jarvela, Qing Li, Rachel Shaw, Scott M Reba, Shane Fletcher, Sara E Beckloff, Mark R Chance, W Henry Boom, Richard F Silver, Gurkan Bebek.

Alveolar macrophages (AM) perform a primary defense mechanism in the lung through phagocytosis of inhaled particles and microorganisms. AM are known to be relatively immunosuppressive consistent with the aim to limit alveolar inflammation and maintain effective gas exchange in the face of these constant challenges. How AM respond to T cell derived cytokine signals, which are critical to the defense against inhaled pathogens, is less well understood. For example, successful containment of Mycobacterium tuberculosis (Mtb) in lung macrophages is highly dependent on IFN-γ secreted by Th-1 lymphocytes, however, the proteomic IFN-γ response profile in AM remains mostly unknown. In this study, we measured IFN-γ induced protein abundance changes in human AM and autologous blood monocytes (MN). AM cells were activated by IFN-γ stimulation resulting in STAT1 phosphorylation and production of MIG/CXCL9 chemokine. However, the global proteomic response to IFN-γ in AM was dramatically limited in comparison to that of MN (9 AM vs 89 MN differentially abundant proteins). AM hypo-responsiveness was not explained by reduced JAK-STAT1 signaling nor increased SOCS1 expression. These findings suggest that AM have a tightly regulated response to IFN-γ which may prevent excessive pulmonary inflammation but may also provide a niche for the initial survival and growth of Mtb and other intracellular pathogens in the lung.

DOI: https://doi.org/10.1371/journal.pone.0295312
J Biol Chem. 2024 Jan 31. pii: S0021-9258(24)00076-0. [Epub ahead of print] 105700

AP-1γ2 is an adaptor protein 1 variant required for endosome-to-Golgi trafficking of the mannose-6-P receptor (CI-MPR) and ATP7B copper transporter.

Lucas Alves Tavares, Roger Luiz Rodrigues, Cristina Santos da Costa, Jonas Alburqueque Nascimento, Julianne Vargas de Carvalho, Andreia Nogueira de Carvalho, Gonzalo Mardones, Luis L P daSilva.

  Selective retrograde transport from endosomes back to the trans-Golgi network (TGN) is important for maintaining protein homeostasis, recycling receptors, and returning molecules that were transported to wrong compartments. Two important transmembrane proteins directed to this pathway are the Cation-Independent Mannose-6-phosphate receptor (CI-MPR) and the ATP7B copper transporter. Among CI-MPR functions is the delivery of acid hydrolases to lysosomes, while ATP7B facilitates the transport of cytosolic copper ions into organelles or the extracellular space. Precise subcellular localization of CI-MPR and ATP7B is essential for proper functioning of these proteins. This study shows that both CI-MPR and ATP7B interact with a variant of the clathrin adaptor 1 (AP-1) complex that contains a specific isoform of the γ-adaptin subunit called γ2. Through synchronized anterograde trafficking and cell-surface uptake assays, we demonstrated that AP-1γ2 is dispensable for ATP7B and CI-MPR exit from the TGN, while being critically required for ATP7B and CI-MPR retrieval from endosomes to the TGN. Moreover, AP-1γ2 depletion leads to retention of endocytosed CI-MPR in endosomes enriched in retromer complex subunits. These data underscore the importance of AP-1γ2 as a key component in the sorting and trafficking machinery of CI-MPR and ATP7B, highlighting its essential role in the transport of proteins from endosomes.

Keywords:  AP-1γ2; ATP7B; CI-MPR; clathrin; receptor recycling; retrograde transport

DOI:  https://doi.org/10.1016/j.jbc.2024.105700
Nature. 2024 Jan 31.

7-Dehydrocholesterol is an endogenous suppressor of ferroptosis.

Florencio Porto Freitas, Hamed Alborzinia, Ancély Ferreira Dos Santos, Palina Nepachalovich, Lohans Pedrera, Omkar Zilka, Alex Inague, Corinna Klein, Nesrine Aroua, Kamini Kaushal, Bettina Kast, Svenja M Lorenz, Viktoria Kunz, Helene Nehring, Thamara N Xavier da Silva, Zhiyi Chen, Sena Atici, Sebastian G Doll, Emily L Schaefer, Ifedapo Ekpo, Werner Schmitz, Aline Horling, Peter Imming, Sayuri Miyamoto, Ann M Wehman, Thiago C Genaro-Mattos, Karoly Mirnics, Lokender Kumar, Judith Klein-Seetharaman, Svenja Meierjohann, Isabel Weigand, Matthias Kroiss, Georg W Bornkamm, Fernando Gomes, Luis Eduardo Soares Netto, Manjima B Sathian, David B Konrad, Douglas F Covey, Bernhard Michalke, Kurt Bommert, Ralf C Bargou, Ana Garcia-Saez, Derek A Pratt, Maria Fedorova, Andreas Trumpp, Marcus Conrad, José Pedro Friedmann Angeli.

Ferroptosis is a form of cell death that has received considerable attention not only as a means to eradicate defined tumour entities but also because it provides unforeseen insights into the metabolic adaptation that tumours exploit to counteract phospholipid oxidation1,2. Here, we identify proferroptotic activity of 7-dehydrocholesterol reductase (DHCR7) and an unexpected prosurvival function of its substrate, 7-dehydrocholesterol (7-DHC). Although previous studies suggested that high concentrations of 7-DHC are cytotoxic to developing neurons by favouring lipid peroxidation3, we now show that 7-DHC accumulation confers a robust prosurvival function in cancer cells. Because of its far superior reactivity towards peroxyl radicals, 7-DHC effectively shields (phospho)lipids from autoxidation and subsequent fragmentation. We provide validation in neuroblastoma and Burkitt's lymphoma xenografts where we demonstrate that the accumulation of 7-DHC is capable of inducing a shift towards a ferroptosis-resistant state in these tumours ultimately resulting in a more aggressive phenotype. Conclusively, our findings provide compelling evidence of a yet-unrecognized antiferroptotic activity of 7-DHC as a cell-intrinsic mechanism that could be exploited by cancer cells to escape ferroptosis.

DOI: https://doi.org/10.1038/s41586-023-06878-9
Sci Transl Med. 2024 Jan 31. 16(732): eadg7895

Myeloid and lymphoid expression of C9orf72 regulates IL-17A signaling in mice.

Francesco Limone, Alexander Couto, Jin-Yuan Wang, Yingying Zhang, Blake McCourt, Cerianne Huang, Adina Minkin, Marghi Jani, Sarah McNeer, James Keaney, Gaëlle Gillet, Rodrigo Lopez Gonzalez, Wendy A Goodman, Irena Kadiu, Kevin Eggan, Aaron Burberry.

A mutation in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Patients with ALS or FTD often develop autoimmunity and inflammation that precedes or coincides with the onset of neurological symptoms, but the underlying mechanisms are poorly understood. Here, we knocked out murine C9orf72 in seven hematopoietic progenitor compartments by conditional mutagenesis and found that myeloid lineage C9orf72 prevents splenomegaly, loss of tolerance, and premature mortality. Furthermore, we demonstrated that C9orf72 plays a role in lymphoid cells to prevent interleukin-17A (IL-17A) production and neutrophilia. Mass cytometry identified early and sustained elevation of the costimulatory molecule CD80 expressed on C9orf72-deficient mouse macrophages, monocytes, and microglia. Enrichment of CD80 was similarly observed in human spinal cord microglia from patients with C9ORF72-mediated ALS compared with non-ALS controls. Single-cell RNA sequencing of murine spinal cord, brain cortex, and spleen demonstrated coordinated induction of gene modules related to antigen processing and presentation and antiviral immunity in C9orf72-deficient endothelial cells, microglia, and macrophages. Mechanistically, C9ORF72 repressed the trafficking of CD80 to the cell surface in response to Toll-like receptor agonists, interferon-γ, and IL-17A. Deletion of Il17a in C9orf72-deficient mice prevented CD80 enrichment in the spinal cord, reduced neutrophilia, and reduced gut T helper type 17 cells. Last, systemic delivery of an IL-17A neutralizing antibody augmented motor performance and suppressed neuroinflammation in C9orf72-deficient mice. Altogether, we show that C9orf72 orchestrates myeloid costimulatory potency and provide support for IL-17A as a therapeutic target for neuroinflammation associated with ALS or FTD.

DOI: https://doi.org/10.1126/scitranslmed.adg7895
Immunity. 2024 Jan 24. pii: S1074-7613(24)00027-X. [Epub ahead of print]

Microbiota-derived butyrate restricts tuft cell differentiation via histone deacetylase 3 to modulate intestinal type 2 immunity.

Emily M Eshleman, Taylor Rice, Crystal Potter, Amanda Waddell, Seika Hashimoto-Hill, Vivienne Woo, Sydney Field, Laura Engleman, Hee-Woong Lim, Michael A Schumacher, Mark R Frey, Lee A Denson, Fred D Finkelman, Theresa Alenghat.

  Tuft cells in mucosal tissues are key regulators of type 2 immunity. Here, we examined the impact of the microbiota on tuft cell biology in the intestine. Succinate induction of tuft cells and type 2 innate lymphoid cells was elevated with loss of gut microbiota. Colonization with butyrate-producing bacteria or treatment with butyrate suppressed this effect and reduced intestinal histone deacetylase activity. Epithelial-intrinsic deletion of the epigenetic-modifying enzyme histone deacetylase 3 (HDAC3) inhibited tuft cell expansion in vivo and impaired type 2 immune responses during helminth infection. Butyrate restricted stem cell differentiation into tuft cells, and inhibition of HDAC3 in adult mice and human intestinal organoids blocked tuft cell expansion. Collectively, these data define a HDAC3 mechanism in stem cells for tuft cell differentiation that is dampened by a commensal metabolite, revealing a pathway whereby the microbiota calibrate intestinal type 2 immunity.

Keywords:  HDAC3; butyrate; development; epigenetics; intestine; microbiota; organoid; stem cell; tuft cell; type 2 immunity

DOI:  https://doi.org/10.1016/j.immuni.2024.01.002
Angew Chem Int Ed Engl. 2024 Jan 28. e202315997

Photoswitchable PROTACs for Reversible and Spatiotemporal Regulation of NAMPT and NAD.

Junfei Cheng, Jing Zhang, Shipeng He, Minyong Li, Guoqiang Dong, Chunquan Sheng.

  Nicotinamide adenine dinucleotide (NAD+) serves as an essential coenzyme for DNA synthesis and has diverse biological functions. Nicotinamide phosphoribosyltransferase (NAMPT) is the key rate-limiting enzyme involved in NAD+ biosynthesis in mammals. Herein, the first chemical tool for optical control of NAMPT and NAD+ in biological systems was developed using the photoswitchable proteolysis-targeting chimeras (PS-PROTACs) strategy. NAMPT activator and dimethylpyrazolazobenzene photoswitch was innovatively used to design highly efficient PS-PROTACs, enabling up- and down- reversible regulation of NAMPT and NAD+ in a light-dependent manner and reduced the toxicity associated with inhibitor-based PS-PROTACs. Interestingly, the PS-PROTAC could be activated under the 620 nm irradiation, realizing in vivo optical manipulation of antitumor activity, NAMPT and NAD+.

Keywords:  Activator; NAD+; NAMPT; Photoswitchable PROTAC; Visible Light

DOI:  https://doi.org/10.1002/anie.202315997
Nat Cell Biol. 2024 Feb 01.

Low-input lipidomics reveals lipid metabolism remodelling during early mammalian embryo development.

Ling Zhang, Jing Zhao, Sin Man Lam, Lang Chen, Yingzhuo Gao, Wenjie Wang, Yuyan Xu, Tianyu Tan, Hua Yu, Min Zhang, Xufeng Liao, Mengchen Wu, Tianyun Zhang, Jie Huang, Bowen Li, Quan D Zhou, Ning Shen, Hyeon Jeong Lee, Cunqi Ye, Da Li, Guanghou Shui, Jin Zhang.

Lipids are indispensable for energy storage, membrane structure and cell signalling. However, dynamic changes in various categories of endogenous lipids in mammalian early embryonic development have not been systematically characterized. Here we comprehensively investigated the dynamic lipid landscape during mouse and human early embryo development. Lipid signatures of different developmental stages are distinct, particularly for the phospholipid classes. We highlight that the high degree of phospholipid unsaturation is a conserved feature as embryos develop to the blastocyst stage. Moreover, we show that lipid desaturases such as SCD1 are required for in vitro blastocyst development and blastocyst implantation. One of the mechanisms is through the regulation of unsaturated fatty-acid-mediated fluidity of the plasma membrane and apical proteins and the establishment of apical-basal polarity during development of the eight-cell embryo to the blastocyst. Overall, our study provides an invaluable resource about the remodelling of the endogenous lipidome in mammalian preimplantation embryo development and mechanistic insights into the regulation of embryogenesis and implantation by lipid unsaturation.

DOI: https://doi.org/10.1038/s41556-023-01341-3
Cancer Res. 2024 Jan 29.

Lactate utilization enables metabolic escape to confer resistance to BET inhibition in acute myeloid leukemia.

Andrew J Monteith, Haley E Ramsey, Alexander J Silver, Donovan Brown, Dalton Greenwood, Brianna N Smith, Ashley D Wise, Juan Liu, Sarah D Olmstead, Jackson Watke, Maria P Arrate, Agnieszka E Gorska, Londa Fuller, Jason W Locasale, Matthew C Stubbs, Jeffrey C Rathmell, Michael R Savona.

Impairing the BET-family co-activator BRD4 with small molecule inhibitors (BETi) showed encouraging pre-clinical activity in treating acute myeloid leukemia (AML). However, dose-limiting toxicities and limited clinical activity dampened the enthusiasm for BETi as a single agent. BETi resistance in AML myeloblasts was found to correlate with maintaining mitochondrial respiration, suggesting that identifying the metabolic pathway sustaining mitochondrial integrity could help develop approaches to improve BETi efficacy. Herein, we demonstrated that mitochondria-associated lactate dehydrogenase allows AML myeloblasts to utilize lactate as a metabolic bypass to fuel mitochondrial respiration and maintain cellular viability. Pharmacologically and genetically impairing lactate utilization rendered resistant myeloblasts susceptible to BET inhibition. Low-dose combinations of BETi and oxamate, a lactate dehydrogenase inhibitor, reduced in vivo expansion of BETi-resistant AML in cell line and patient-derived murine models. These results elucidate how AML myeloblasts metabolically adapt to BETi by consuming lactate and demonstrate that combining BETi with inhibitors of lactate utilization may be useful in AML treatment.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-0291
Eur J Pharmacol. 2024 Jan 28. pii: S0014-2999(24)00022-0. [Epub ahead of print]966 176334

Farnesoid X receptor agonist tropifexor detoxifies ammonia by regulating the glutamine metabolism and urea cycles in cholestatic livers.

Yongtao Xiao, Weipeng Wang, Shicheng Peng, Ying Lu, Jun Du, Wei Cai.

  Hyperammonemia refers to elevated levels of ammonia in the blood, which is an important pathological feature of liver cirrhosis and hepatic failure. Preclinical studies suggest tropifexor (TXR), a novel non-bile acid agonist of Farnesoid X Receptor (FXR), has shown promising effects on reducing hepatic steatosis, inflammation, and fibrosis. This study evaluates the impact of TXR on hyperammonemia in a piglet model of cholestasis. We here observed blood ammonia significantly elevated in patients with biliary atresia (BA) and was positively correlated with liver injury. Targeted metabolomics and immunblotting showed glutamine metabolism and urea cycles were impaired in BA patients. Next, we observed that TXR potently suppresses bile duct ligation (BDL)-induced injuries in liver and brain with improving the glutamine metabolism and urea cycles. Within the liver, TXR enhances glutamine metabolism and urea cycles by up-regulation of key regulatory enzymes, including glutamine synthetase (GS), carbamoyl-phosphate synthetase 1 (CPS1), argininosuccinate synthetase (ASS1), argininosuccinate lyase (ASL), and arginase 1 (ARG1). In primary mice hepatocytes, TXR detoxified ammonia via increasing ureagenesis. Mechanically, TXR activating FXR to increase express enzymes that regulating ureagenesis and glutamine synthesis through a transcriptional approach. Together, these results suggest that TXR may have therapeutic implications for hyperammonemic conditions in cholestatic livers.

Keywords:  Ammonia; Cholestasis; FXR; Glutamine metabolism; Urea cycles

DOI:  https://doi.org/10.1016/j.ejphar.2024.176334
Redox Biol. 2024 Jan 24. pii: S2213-2317(24)00028-4. [Epub ahead of print]70 103052

The mitochondrial biliverdin exporter ABCB10 in hepatocytes mitigates neutrophilic inflammation in alcoholic hepatitis.

Vincent Gutierrez, Doyeon Kim-Vasquez, Michael Shum, Qihong Yang, Dante Dikeman, Stan G Louie, Orian S Shirihai, Hidekazu Tsukamoto, Marc Liesa.

Acute liver failure caused by alcoholic hepatitis (AH) is only effectively treated with liver transplantation. Livers of patients with AH show a unique molecular signature characterized by defective hepatocellular redox metabolism, concurrent to hepatic infiltration of neutrophils that express myeloperoxidase (MPO) and form neutrophil extracellular traps (NETs). Exacerbated NET formation and MPO activity contribute to liver damage in mice with AH and predicts poor prognosis in AH patients. The identification of pathways that maladaptively exacerbate neutrophilic activity in liver could inform of novel therapeutic approaches to treat AH. Whether the redox defects of hepatocytes in AH directly exacerbate neutrophilic inflammation and NET formation is unclear. Here we identify that the protein content of the mitochondrial biliverdin exporter ABCB10, which increases hepatocyte-autonomous synthesis of the ROS-scavenger bilirubin, is decreased in livers from humans and mice with AH. Increasing ABCB10 expression selectively in hepatocytes of mice with AH is sufficient to decrease MPO gene expression and histone H3 citrullination, a specific marker of NET formation. These anti-inflammatory effects can be explained by ABCB10 function reducing ROS-mediated actions in liver. Accordingly, ABCB10 gain-of-function selectively increased the mitochondrial GSH/GSSG ratio and decreased hepatic 4-HNE protein adducts, without elevating mitochondrial fat expenditure capacity, nor mitigating steatosis and hepatocyte death. Thus, our study supports that ABCB10 function regulating ROS-mediated actions within surviving hepatocytes mitigates the maladaptive activation of infiltrated neutrophils in AH. Consequently, ABCB10 gain-of-function in human hepatocytes could potentially decrease acute liver failure by decreasing the inflammatory flare caused by excessive neutrophil activity.

DOI: https://doi.org/10.1016/j.redox.2024.103052
J Leukoc Biol. 2024 Jan 30. pii: qiae024. [Epub ahead of print]

Upregulated Selenoprotein I during LPS-induced B cell activation promotes lipidomic changes and is required for effective differentiation into IgM secreting plasma B cells.

Chi Ma, FuKun W Hoffmann, Ashley E Shay, Imhoi Koo, Kathy A Green, William R Green, Peter R Hoffmann.

  The mechanisms driving metabolic reprogramming during B cell activation are unclear, particularly roles for enzymatic pathways involved in lipid remodeling. We found that murine B cell activation with lipopolysaccharide (LPS) led to a 1.6-fold increase in total lipids that included higher levels of phosphatidylethanolamine (PE) and plasmenyl PE. Selenoprotein I (SELENOI) is an[62] ethanolamine phospholipid transferase involved in the synthesis of both PE and plasmenyl PE, and SELENOI expression was also upregulated during activation. Selenoi knockout (KO) B cells exhibited decreased levels of plasmenyl PE, which plays an important antioxidant role. Lipid peroxidation was measured and found to increase ∼2-fold in KO versus WT B cells. Cell death was not impacted by KO in LPS-treated B cells and proliferation was only slightly reduced, but differentiation into CD138 + Blimp-1+ plasma B cells was decreased ∼2-fold. This led to examination of B cell receptors important for differentiation that recognize the ligand B cell activating factor (BAFF), and levels of the transmembrane activator and calcium-modulator and cytophilin ligand interactor (TACI; CD267) were significantly decreased on KO B cells compared to WT controls. Vaccination with ovalbumin (OVA)/adjuvant led to decreased OVA-specific IgM levels in sera of KO mice compared to WT mice. Real-time PCR analyses revealed a decreased switch from surface to secreted IgM in spleens of KO mice induced by vaccination or LP-BM5 retrovirus infection. Overall, these findings detail the lipidomic response of B cells to LPS activation and reveal the importance of upregulated SELENOI for promoting differentiation into IgM secreting plasma B cells.

Keywords:  IgM; antibody; ethanolamine phospholipid transferase; phosphatidylethanolamine; plasma B cell

DOI:  https://doi.org/10.1093/jleuko/qiae024
J Biol Chem. 2024 Jan 30. pii: S0021-9258(24)00078-4. [Epub ahead of print] 105702

The BCKDK inhibitor BT2 is a chemical uncoupler that lowers mitochondrial ROS production and de novo lipogenesis.

Aracely Acevedo, Anthony E Jones, Bezawit T Danna, Rory Turner, Katrina P Montales, Cristiane Benincá, Karen Reue, Orian S Shirihai, Linsey Stiles, Martina Wallace, Yibin Wang, Ambre M Bertholet, Ajit S Divakaruni.

  Elevated levels of branched chain amino acids (BCAAs) and branched-chain α-ketoacids (BCKAs) are associated with cardiovascular and metabolic disease, but the molecular mechanisms underlying a putative causal relationship remain unclear. The branched-chain ketoacid dehydrogenase kinase (BCKDK) inhibitor BT2 is often used in preclinical models to increase BCAA oxidation and restore steady-state BCAA and BCKA levels. BT2 administration is protective in various rodent models of heart failure and metabolic disease, but confoundingly, targeted ablation of Bckdk in specific tissues does not reproduce the beneficial effects conferred by pharmacologic inhibition. Here we demonstrate that BT2, a lipophilic weak acid, can act as a mitochondrial uncoupler. Measurements of oxygen consumption, mitochondrial membrane potential, and patch-clamp electrophysiology show BT2 increases proton conductance across the mitochondrial inner membrane independently of its inhibitory effect on BCKDK. BT2 is roughly six-fold less potent than the prototypical uncoupler 2,4-dinitrophenol (DNP), and phenocopies DNP in lowering de novo lipogenesis and mitochondrial superoxide production. The data suggest the therapeutic efficacy of BT2 may be attributable to the well-documented effects of mitochondrial uncoupling in alleviating cardiovascular and metabolic disease.

Keywords:  BT2; ROS production; branched-chain amino acids; cardiometabolic disease; chemical uncoupling; mitochondria

DOI:  https://doi.org/10.1016/j.jbc.2024.105702
Nat Cancer. 2024 Jan 29.

Mitochondrial DNA mutations drive aerobic glycolysis to enhance checkpoint blockade response in melanoma.

Mahnoor Mahmood, Eric Minwei Liu, Amy L Shergold, Elisabetta Tolla, Jacqueline Tait-Mulder, Alejandro Huerta-Uribe, Engy Shokry, Alex L Young, Sergio Lilla, Minsoo Kim, Tricia Park, Sonia Boscenco, Javier L Manchon, Crístina Rodríguez-Antona, Rowan C Walters, Roger J Springett, James N Blaza, Louise Mitchell, Karen Blyth, Sara Zanivan, David Sumpton, Edward W Roberts, Ed Reznik, Payam A Gammage.

The mitochondrial genome (mtDNA) encodes essential machinery for oxidative phosphorylation and metabolic homeostasis. Tumor mtDNA is among the most somatically mutated regions of the cancer genome, but whether these mutations impact tumor biology is debated. We engineered truncating mutations of the mtDNA-encoded complex I gene, Mt-Nd5, into several murine models of melanoma. These mutations promoted a Warburg-like metabolic shift that reshaped tumor microenvironments in both mice and humans, consistently eliciting an anti-tumor immune response characterized by loss of resident neutrophils. Tumors bearing mtDNA mutations were sensitized to checkpoint blockade in a neutrophil-dependent manner, with induction of redox imbalance being sufficient to induce this effect in mtDNA wild-type tumors. Patient lesions bearing >50% mtDNA mutation heteroplasmy demonstrated a response rate to checkpoint blockade that was improved by ~2.5-fold over mtDNA wild-type cancer. These data nominate mtDNA mutations as functional regulators of cancer metabolism and tumor biology, with potential for therapeutic exploitation and treatment stratification.

DOI: https://doi.org/10.1038/s43018-023-00721-w