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Nature Mar 2023Metabolic rewiring underlies the effector functions of macrophages, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable...
Metabolic rewiring underlies the effector functions of macrophages, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable isotope-assisted tracing, we show that an inflammatory aspartate-argininosuccinate shunt is induced following lipopolysaccharide stimulation. The shunt, supported by increased argininosuccinate synthase (ASS1) expression, also leads to increased cytosolic fumarate levels and fumarate-mediated protein succination. Pharmacological inhibition and genetic ablation of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) further increases intracellular fumarate levels. Mitochondrial respiration is also suppressed and mitochondrial membrane potential increased. RNA sequencing and proteomics analyses demonstrate that there are strong inflammatory effects resulting from FH inhibition. Notably, acute FH inhibition suppresses interleukin-10 expression, which leads to increased tumour necrosis factor secretion, an effect recapitulated by fumarate esters. Moreover, FH inhibition, but not fumarate esters, increases interferon-β production through mechanisms that are driven by mitochondrial RNA (mtRNA) release and activation of the RNA sensors TLR7, RIG-I and MDA5. This effect is recapitulated endogenously when FH is suppressed following prolonged lipopolysaccharide stimulation. Furthermore, cells from patients with systemic lupus erythematosus also exhibit FH suppression, which indicates a potential pathogenic role for this process in human disease. We therefore identify a protective role for FH in maintaining appropriate macrophage cytokine and interferon responses.
Topics: Humans; Argininosuccinate Synthase; Argininosuccinic Acid; Aspartic Acid; Cell Respiration; Cytosol; Fumarate Hydratase; Fumarates; Interferon-beta; Lipopolysaccharides; Lupus Erythematosus, Systemic; Macrophages; Membrane Potential, Mitochondrial; Metabolomics; Mitochondria; RNA, Mitochondrial
PubMed: 36890227
DOI: 10.1038/s41586-023-05720-6 -
Immunity Mar 2015Macrophage polarization involves a coordinated metabolic and transcriptional rewiring that is only partially understood. By using an integrated high-throughput...
Macrophage polarization involves a coordinated metabolic and transcriptional rewiring that is only partially understood. By using an integrated high-throughput transcriptional-metabolic profiling and analysis pipeline, we characterized systemic changes during murine macrophage M1 and M2 polarization. M2 polarization was found to activate glutamine catabolism and UDP-GlcNAc-associated modules. Correspondingly, glutamine deprivation or inhibition of N-glycosylation decreased M2 polarization and production of chemokine CCL22. In M1 macrophages, we identified a metabolic break at Idh, the enzyme that converts isocitrate to alpha-ketoglutarate, providing mechanistic explanation for TCA cycle fragmentation. (13)C-tracer studies suggested the presence of an active variant of the aspartate-arginosuccinate shunt that compensated for this break. Consistently, inhibition of aspartate-aminotransferase, a key enzyme of the shunt, inhibited nitric oxide and interleukin-6 production in M1 macrophages, while promoting mitochondrial respiration. This systems approach provides a highly integrated picture of the physiological modules supporting macrophage polarization, identifying potential pharmacologic control points for both macrophage phenotypes.
Topics: Animals; Argininosuccinic Acid; Aspartate Aminotransferase, Mitochondrial; Aspartic Acid; Chemokine CCL22; Citric Acid Cycle; Gene Expression Regulation; Gene Regulatory Networks; Glutamine; Glycosylation; Immunity, Innate; Interleukin-6; Isocitrate Dehydrogenase; Macrophages; Metabolic Networks and Pathways; Mice; Mitochondria; Nitric Oxide; Signal Transduction; Transcription, Genetic; Uridine Diphosphate N-Acetylglucosamine
PubMed: 25786174
DOI: 10.1016/j.immuni.2015.02.005 -
Genetics in Medicine : Official Journal... May 2012The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea... (Review)
Review
The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea cycle disorders (UCDs), a group of inborn errors of hepatic metabolism that often result in life-threatening hyperammonemia. Argininosuccinate lyase (ASL) catalyzes the fourth reaction in this cycle, resulting in the breakdown of argininosuccinic acid to arginine and fumarate. ASL deficiency (ASLD) is the second most common UCD, with a prevalence of ~1 in 70,000 live births. ASLD can manifest as either a severe neonatal-onset form with hyperammonemia within the first few days after birth or as a late-onset form with episodic hyperammonemia and/or long-term complications that include liver dysfunction, neurocognitive deficits, and hypertension. These long-term complications can occur in the absence of hyperammonemic episodes, implying that ASL has functions outside of its role in ureagenesis and the tissue-specific lack of ASL may be responsible for these manifestations. The biochemical diagnosis of ASLD is typically established with elevation of plasma citrulline together with elevated argininosuccinic acid in the plasma or urine. Molecular genetic testing of ASL and assay of ASL enzyme activity are helpful when the biochemical findings are equivocal. However, there is no correlation between the genotype or enzyme activity and clinical outcome. Treatment of acute metabolic decompensations with hyperammonemia involves discontinuing oral protein intake, supplementing oral intake with intravenous lipids and/or glucose, and use of intravenous arginine and nitrogen-scavenging therapy. Dietary restriction of protein and dietary supplementation with arginine are the mainstays in long-term management. Orthotopic liver transplantation (OLT) is best considered only in patients with recurrent hyperammonemia or metabolic decompensations resistant to conventional medical therapy.
Topics: Arginine; Argininosuccinate Lyase; Argininosuccinic Acid; Argininosuccinic Aciduria; Child, Preschool; Citrulline; Cognition Disorders; Diet, Protein-Restricted; Fumarates; Genetic Testing; Glucose; Humans; Hyperammonemia; Hypertension; Infant; Infant, Newborn; Lipids; Liver Diseases; Liver Transplantation; Neonatal Screening; Phenylbutyrates; Sodium Benzoate
PubMed: 22241104
DOI: 10.1038/gim.2011.1 -
American Journal of Medical Genetics.... Feb 2011The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea... (Review)
Review
The urea cycle consists of six consecutive enzymatic reactions that convert waste nitrogen into urea. Deficiencies of any of these enzymes of the cycle result in urea cycle disorders (UCD), a group of inborn errors of hepatic metabolism that often result in life threatening hyperammonemia. Argininosuccinate lyase (ASL) is a cytosolic enzyme which catalyzes the fourth reaction in the cycle and the first degradative step, that is, the breakdown of argininosuccinic acid to arginine and fumarate. Deficiency of ASL results in an accumulation of argininosuccinic acid in tissues, and excretion of argininosuccinic acid in urine leading to the condition argininosuccinic aciduria (ASA). ASA is an autosomal recessive disorder and is the second most common UCD. In addition to the accumulation of argininosuccinic acid, ASL deficiency results in decreased synthesis of arginine, a feature common to all UCDs except argininemia. Arginine is not only the precursor for the synthesis of urea and ornithine as part of the urea cycle but it is also the substrate for the synthesis of nitric oxide, polyamines, proline, glutamate, creatine, and agmatine. Hence, while ASL is the only enzyme in the body able to generate arginine, at least four enzymes use arginine as substrate: arginine decarboxylase, arginase, nitric oxide synthetase (NOS) and arginine/glycine aminotransferase. In the liver, the main function of ASL is ureagenesis, and hence, there is no net synthesis of arginine. In contrast, in most other tissues, its role is to generate arginine that is designated for the specific cell's needs. While patients with ASA share the acute clinical phenotype of hyperammonemia, encephalopathy, and respiratory alkalosis common to other UCD, they also present with unique chronic complications most probably caused by a combination of tissue specific deficiency of arginine and/or elevation of argininosuccinic acid. This review article summarizes the clinical characterization, biochemical, enzymatic, and molecular features of this disorder. Current treatment, prenatal diagnosis, diagnosis through the newborn screening as well as hypothesis driven future treatment modalities are discussed.
Topics: Arginase; Arginine; Argininosuccinate Lyase; Argininosuccinic Acid; Argininosuccinic Aciduria; Carboxy-Lyases; Humans; Hyperammonemia; Infant, Newborn; Liver Diseases; Neonatal Screening; Nitric Oxide Synthase; Ornithine; Urea Cycle Disorders, Inborn
PubMed: 21312326
DOI: 10.1002/ajmg.c.30289 -
Biomedicines Jun 2023Argininosuccinic aciduria (ASA) is a metabolic disorder caused by a deficiency in argininosuccinate lyase (ASL), which cleaves argininosuccinic acid to arginine and...
Argininosuccinic aciduria (ASA) is a metabolic disorder caused by a deficiency in argininosuccinate lyase (ASL), which cleaves argininosuccinic acid to arginine and fumarate in the urea cycle. ASL deficiency (ASLD) leads to hepatocyte dysfunction, hyperammonemia, encephalopathy, and respiratory alkalosis. Here we describe a novel therapeutic approach for treating ASA, based on nucleoside-modified messenger RNA (modRNA) formulated in lipid nanoparticles (LNP). To optimize ASL-encoding mRNA, we modified its cap, 5' and 3' untranslated regions, coding sequence, and the poly(A) tail. We tested multiple optimizations of the formulated mRNA in human cells and wild-type C57BL/6 mice. The ASL protein showed robust expression in vitro and in vivo and a favorable safety profile, with low cytokine and chemokine secretion even upon administration of increasing doses of ASL mRNA-LNP. In the ASL mouse model of ASLD, intravenous administration of the lead therapeutic candidate LNP-ASL CDS2 drastically improved the survival of the mice. When administered twice a week lower doses partially protected and 3 mg/kg LNP-ASL CDS2 fully protected the mice. These results demonstrate the considerable potential of LNP-formulated, modified ASL-encoding mRNA as an effective alternative to AAV-based approaches for the treatment of ASA.
PubMed: 37371829
DOI: 10.3390/biomedicines11061735 -
Journal of Inherited Metabolic Disease Nov 2019The urea cycle disorder (UCD) argininosuccinate lyase (ASL) deficiency, caused by a defective ASL enzyme, exhibits a wide range of phenotypes, from life-threatening... (Review)
Review
Argininosuccinate neurotoxicity and prevention by creatine in argininosuccinate lyase deficiency: An in vitro study in rat three-dimensional organotypic brain cell cultures.
The urea cycle disorder (UCD) argininosuccinate lyase (ASL) deficiency, caused by a defective ASL enzyme, exhibits a wide range of phenotypes, from life-threatening neonatal hyperammonemia to asymptomatic patients, with only the biochemical marker argininosuccinic acid (ASA) elevated in body fluids. Remarkably, even without ever suffering from hyperammonemia, patients often develop severe cognitive impairment and seizures. The goal of this study was to understand the effect on the known toxic metabolite ASA and the assumed toxic metabolite guanidinosuccinic acid (GSA) on developing brain cells, and to evaluate the potential role of creatine (Cr) supplementation, as it was described protective for brain cells exposed to ammonia. We used an in vitro model, in which we exposed three-dimensional (3D) organotypic rat brain cell cultures in aggregates to different combinations of the metabolites of interest at two time points (representing two different developmental stages). After harvest and cryopreservation of the cell cultures, the samples were analyzed mainly by metabolite analysis, immunohistochemistry, and western blotting. ASA and GSA were found toxic for astrocytes and neurons. This toxicity could be reverted in vitro by Cr. As well, an antiapoptotic effect of ASA was revealed, which could contribute to the neurotoxicity in ASL deficiency. Further studies in human ASL deficiency will be required to understand the biochemical situation in the brain of affected patients, and to investigate the impact of high or low arginine doses on brain Cr availability. In addition, clinical trials to evaluate the beneficial effect of Cr supplementation in ASL deficiency would be valuable.
Topics: Animals; Argininosuccinic Acid; Argininosuccinic Aciduria; Brain; Cells, Cultured; Creatine; Humans; Neurons; Neuroprotective Agents; Neurotoxicity Syndromes; Organ Culture Techniques; Rats; Tissue Scaffolds
PubMed: 30907007
DOI: 10.1002/jimd.12090 -
Journal of Inherited Metabolic Disease May 2017This UK-wide study defines the natural history of argininosuccinic aciduria and compares long-term neurological outcomes in patients presenting clinically or treated...
OBJECTIVES
This UK-wide study defines the natural history of argininosuccinic aciduria and compares long-term neurological outcomes in patients presenting clinically or treated prospectively from birth with ammonia-lowering drugs.
METHODS
Retrospective analysis of medical records prior to March 2013, then prospective analysis until December 2015. Blinded review of brain MRIs. ASL genotyping.
RESULTS
Fifty-six patients were defined as early-onset (n = 23) if symptomatic < 28 days of age, late-onset (n = 23) if symptomatic later, or selectively screened perinatally due to a familial proband (n = 10). The median follow-up was 12.4 years (range 0-53). Long-term outcomes in all groups showed a similar neurological phenotype including developmental delay (48/52), epilepsy (24/52), ataxia (9/52), myopathy-like symptoms (6/52) and abnormal neuroimaging (12/21). Neuroimaging findings included parenchymal infarcts (4/21), focal white matter hyperintensity (4/21), cortical or cerebral atrophy (4/21), nodular heterotopia (2/21) and reduced creatine levels in white matter (4/4). 4/21 adult patients went to mainstream school without the need of additional educational support and 1/21 lives independently. Early-onset patients had more severe involvement of visceral organs including liver, kidney and gut. All early-onset and half of late-onset patients presented with hyperammonaemia. Screened patients had normal ammonia at birth and received treatment preventing severe hyperammonaemia. ASL was sequenced (n = 19) and 20 mutations were found. Plasma argininosuccinate was higher in early-onset compared to late-onset patients.
CONCLUSIONS
Our study further defines the natural history of argininosuccinic aciduria and genotype-phenotype correlations. The neurological phenotype does not correlate with the severity of hyperammonaemia and plasma argininosuccinic acid levels. The disturbance in nitric oxide synthesis may be a contributor to the neurological disease. Clinical trials providing nitric oxide to the brain merit consideration.
Topics: Adolescent; Adult; Ammonia; Argininosuccinic Acid; Argininosuccinic Aciduria; Child; Child, Preschool; Female; Follow-Up Studies; Genotype; Humans; Hyperammonemia; Infant; Infant, Newborn; Male; Middle Aged; Mutation; Phenotype; Prospective Studies; Retrospective Studies; Young Adult
PubMed: 28251416
DOI: 10.1007/s10545-017-0022-x -
JIMD Reports 2017Argininosuccinic acid lyase (ASL) deficiency, caused by mutations in the ASL gene (OMIM: 608310) is a urea cycle disorder that has pleiotropic presentations. On the mild...
Argininosuccinic acid lyase (ASL) deficiency, caused by mutations in the ASL gene (OMIM: 608310) is a urea cycle disorder that has pleiotropic presentations. On the mild end, ASL deficiency can manifest as nonspecific neurocognitive abnormalities without readily identifiable signs to differentiate it from other causes of intellectual disability or learning disabilities. Dietary management and arginine supplementation, if initiated early, may ameliorate symptoms.Because of the nonspecific nature of the symptoms and the possibility for therapeutic management, ASL deficiency is part of the recommended uniform screening panel for newborn screening in the USA. We report here a case of ASL deficiency that was missed on newborn screening in the USA.The case reported here has two known pathogenic mutations - one with no residual activity and one with reported 10% residual activity. Review of this newborn screening results showed subtle elevation of citrulline, overlapping the normal range. These findings suggest that newborn screening may be missing other patients with ASL deficiency with at least one hypomorphic allele. This case was diagnosed incidentally, but in retrospect had symptoms best attributed in full or in part to his ASA deficiency, including protein aversion, developmental delay, and seizures. This case highlights the importance of considering ASL deficiency in patients with nonspecific abnormal neurocognitive signs, such as epilepsy and developmental delay, even when newborn screening was normal.
PubMed: 27515243
DOI: 10.1007/8904_2016_2