Ornithine Decarboxylase 1 Research Articles

Impact of polyamine supplementation on GnRH expression, folliculogenesis, and puberty onset in young mice

BackgroundThe hypothalamic-pituitary-gonadal (HPG) axis is pivotal in regulating reproductive functions, with gonadotropin-releasing hormone (GnRH) acting as a central regulator. Recently, polyamines have been shown to regulate the HPG axis, including GnRH expression and ovarian biology in old and adult rodents. The present study firstly highlights the age-specific variation in the polyamine and their corresponding biosynthetic enzymes in the ovary during aging, and further, the study focuses on the effect of polyamines, putrescine, and agmatine, in young female mice. Method and resultImmunofluorescence analysis revealed age-related differences in the expression of ornithine decarboxylase 1 (ODC1), spermine (SPM), and spermidine (SPD) in the ovaries, with adult mice exhibiting significantly higher expression levels compared to young and old mice. Likewise, qPCR analysis showed the mRNA levels of Odc1, Spermidine synthase (Srm), and Spermine synthase (Sms) show a significant increase in adult ovaries, which is then followed by a significant decline in old age. Histological examination demonstrated morphological alterations in the ovaries with age, including decreased follicle numbers and increased stromal cells in old mice. Furthermore, treatment with putrescine, a polyamine, in young mice resulted in larger ovaries and increased follicle numbers compared to controls. Additionally, serum levels of gonadotropin-releasing hormone (GnRH) and progesterone (P4) were measured, showing elevated levels in polyamine-treated mice. GnRH mRNA expression also increased significantly. Gene expression analysis revealed upregulation of genes associated with folliculogenesis such as Fshr, Bmp15, Gdf9, Amh, Star, Hsdb3, and Plaur in the ovaries and onset of puberty such as Tac2, and Kiss1, and a decrease in Mkrn3 in the hypothalamus of polyamine-treated mice. ConclusionThis study investigates the effect of polyamines in young immature female mice, shedding light on their role in upregulating GnRH, and enhancing folliculogenesis. Overall, these findings suggest that polyamines play a crucial role in ovarian aging and HPG axis regulation, offering potential therapeutics to reinstate fertility in reproductively challenged individuals.

Ame-miR-1-3p of bee venom reduced cell viability through the AZIN1/OAZ1-ODC1-polyamines pathway and enhanced the defense ability of honeybee (Apis mellifera L.).

Bee venom serves as an essential defensive weapon for bees and also finds application as a medicinal drug. MicroRNAs (miRNAs) serve as critical regulators and have been demonstrated to perform a variety of biological functions. However, the presence of miRNAs in bee venom needs to be confirmed. Therefore, we conducted small RNA sequencing and identified 158 known miRNAs, 15 conserved miRNAs and 4 novel miRNAs. It is noteworthy that ame-miR-1-3p, the most abundant among them, accounted for over a quarter of all miRNA reads. To validate the function of ame-miR-1-3p, we screened 28 candidate target genes using transcriptome sequencing and three target gene prediction software (miRanda, PITA and TargetScan) for ame-miR-1-3p. Subsequently, we employed real-time quantitative reverse transcription PCR (qRT-PCR), Western blot and other technologies to confirm that ame-miR-1-3p inhibits the relative expression of antizyme inhibitor 1 (AZIN1) by targeting the 3' untranslated region (UTR) of AZIN1. This, in turn, caused ODC antizyme 1 (OAZ1) to bind to ornithine decarboxylase 1 (ODC1) and mark ODC1 for proteolytic destruction. The reduction in functional ODC1 ultimately resulted in a decrease in polyamine biosynthesis. Furthermore, we determined that ame-miR-1-3p accelerates cell death through the AZIN1/OAZ1-ODC1-polyamines pathway. Our studies demonstrate that ame-miR-1-3p diminishes cell viability and it may collaborate with sPLA2 to enhance the defence capabilities of honeybees (Apis mellifera L.). Collectively, these data further elucidate the defence mechanism of bee venom and expand the potential applications of bee venom in medical treatment.

Abstract PO5-27-09: Pharmacological eIF4E inhibition suppresses anti-tumor activity in ER+ breast cancer

Abstract Elevated levels of eukaryotic initiation factor 4E (eIF4E) are found in a broad range of cancers, including breast, and have been associated with aggressive, drug resistant tumors. Furthermore, elevated eIF4E activity is sufficient to cause transformation in various cancers, while inhibition suppresses tumor growth. eIF4E, the main regulator and rate limiting factor of protein synthesis, is the downstream integrator of several important oncogenic signaling pathways (PI3K/AKT/mTOR, Ras/Raf/MEK, and Myc). Activation of eIF4E results in increased protein levels of key proliferation and metabolism proteins such as Cyclin D1 (CCND1) and Ornithine Decarboxylase 1 (ODC1), as well as an overall increase in cellular synthesis machinery, causing cellular growth and proliferation. Here, we describe the development and characterization of novel, potent, and selective eIF4E inhibitors. Compounds from this chemical series have nanomolar activity in multiple biochemical and biophysical m7G cap-competition assays as well as potent inhibition of translation in cellular and biochemical assays. In cells, these compounds rapidly and reversibly decrease protein levels of several oncogenes, including CCND1, leading to a G1 cell cycle arrest. We demonstrate that eIF4E inhibitors cause growth inhibition in a variety of breast cancer cell lines, including ER+ breast cancer. These inhibitors also inhibit growth of breast cancer lines with acquired resistance to Palbociclib with the same potency as the parental cell lines. Additionally, eIF4E inhibition shows an increased sensitivity in resistant cell lines when combined with standard of care (SOC), including Palbociclib. Select analogs from the series demonstrate favorable ADMET/PK properties with good oral bioavailability and low safety risk. Lastly, these compounds have demonstrated near complete tumor growth inhibition in non-breast cancer in vivo models. Ongoing experiments will address in vivo efficacy in ER+ breast cancer in both monotherapy and in combination with SOC. Citation Format: Matthew Friedersdorf, Devon Blake, Sarah Thompson, Krista Marran, Jessica Sorrentino. Pharmacological eIF4E inhibition suppresses anti-tumor activity in ER+ breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-27-09.

Pirin Promotes the Progression of Non-Small-Cell Lung Cancer by Increasing ODC1 to Suppress Autophagy.

Non-small-cell lung cancer (NSCLC), a common malignant tumor, requires deeper pathogenesis investigation. Autophagy is an evolutionarily conserved lysosomal degradation process that is frequently blocked during cancer progression. It is an urgent need to determine the novel autophagy-associated regulators in NSCLC. Here, we found that pirin was upregulated in NSCLC, and its expression was positively correlated with poor prognosis. Overexpression of pirin inhibited autophagy and promoted NSCLC proliferation. We then performed data-independent acquisition-based quantitative proteomics to identify the differentially expressed proteins (DEPs) in pirin-overexpression (OE) or pirin-knockdown (KD) cells. Among the pirin-regulated DEPs, ornithine decarboxylase 1 (ODC1) was downregulated in pirin-KD cells while upregulated along with pirin overexpression. ODC1 depletion reversed the pirin-induced autophagy inhibition and pro-proliferation effect in A549 and H460 cells. Immunohistochemistry showed that ODC1 was highly expressed in NSCLC cancer tissues and positively related with pirin. Notably, NSCLC patients with pirinhigh/ODC1high had a higher risk in terms of overall survival. In summary, we identified pirin and ODC1 as a novel cluster of prognostic biomarkers for NSCLC and highlighted the potential oncogenic role of the pirin/ODC1/autophagy axis in this cancer type. Targeting this pathway represents a possible therapeutic approach to treat NSCLC.

Combined untargeted metabolomics and network pharmacology approaches to reveal the therapeutic role of withanolide B in psoriasis

Psoriasis is a refractory inflammatory skin disorder in which keratinocyte hyperproliferation is a crucial pathogenic factor. Up to now, it is commonly acknowledged that psoriasis has a tight connection with metabolic disorders. Withanolides from Datura metel L. (DML) have been proved to possess anti-inflammatory and anti-proliferative properties in multiple diseases including psoriasis. Withanolide B (WB) is one of the abundant molecular components in DML. However, existing experimental studies regarding the potential effects and mechanisms of WB on psoriasis still remain lacking. Present study aimed to integrate network pharmacology and untargeted metabolomics strategies to investigate the therapeutic effects and mechanisms of WB on metabolic disorders in psoriasis. In our study, we observed that WB might effectively improve the symptoms of psoriasis and alleviate the epidermal hyperplasia in imiquimod (IMQ)-induced psoriasis-like mice. Both network pharmacology and untargeted metabolomics results suggested that arachidonic acid metabolism and arginine and proline metabolism pathways were linked to the treatment of psoriasis with WB. Meanwhile, we also found that WB may affect the expression of regulated enzymes 5-lipoxygenase (5-LOX), 12-LOX, ornithine decarboxylase 1 (ODC1) and arginase 1 (ARG1) in the arachidonic acid metabolism and arginine and proline metabolism pathways. In summary, this paper showed the potential metabolic mechanisms of WB against psoriasis and suggested that WB would have greater potential in psoriasis treatment.

Polyamine-mediated ferroptosis amplification acts as a targetable vulnerability in cancer

Targeting ferroptosis, an iron-dependent form of regulated cell death triggered by the lethal overload of lipid peroxides, in cancer therapy is impeded by our limited understanding of the intersection of tumour’s metabolic feature and ferroptosis vulnerability. In the present study, arginine is identified as a ferroptotic promoter using a metabolites library. This effect is mainly achieved through arginine’s conversion to polyamines, which exerts their potent ferroptosis-promoting property in an H2O2-dependent manner. Notably, the expression of ornithine decarboxylase 1 (ODC1), the critical enzyme catalysing polyamine synthesis, is significantly activated by the ferroptosis signal——iron overload——through WNT/MYC signalling, as well as the subsequent elevated polyamine synthesis, thus forming a ferroptosis-iron overload-WNT/MYC-ODC1-polyamine-H2O2 positive feedback loop that amplifies ferroptosis. Meanwhile, we notice that ferroptotic cells release enhanced polyamine-containing extracellular vesicles into the microenvironment, thereby further sensitizing neighbouring cells to ferroptosis and accelerating the “spread” of ferroptosis in the tumour region. Besides, polyamine supplementation also sensitizes cancer cells or xenograft tumours to radiotherapy or chemotherapy through inducing ferroptosis. Considering that cancer cells are often characterized by elevated intracellular polyamine pools, our results indicate that polyamine metabolism exposes a targetable vulnerability to ferroptosis and represents an exciting opportunity for therapeutic strategies for cancer.

Elevated expression of HIGD1A drives hepatocellular carcinoma progression by regulating polyamine metabolism through c-Myc–ODC1 nexus

BackgroundHypoxia contributes to cancer progression through various molecular mechanisms and hepatocellular carcinoma (HCC) is one of the most hypoxic malignancies. Hypoxia-inducible gene domain protein-1a (HIGD1A) is typically induced via epigenetic regulation and promotes tumor cell survival during hypoxia. However, the role of HIGD1A in HCC remains unknown.MethodsHIGD1A expression was determined in 24 pairs of human HCC samples and para-tumorous tissues. Loss-of-function experiments were conducted both in vivo and in vitro to explore the role of HIGD1A in HCC proliferation and metastasis.ResultsIncreased HIGD1A expression was found in HCC tissues and cell lines, which was induced by hypoxia or low-glucose condition. Moreover, HIGD1A knockdown in HCC cells arrested the cell cycle at the G2/M phase and promoted hypoxia-induced cell apoptosis, resulting in great inhibition of cell proliferation, migration, and invasion, as well as tumor xenograft formation. Interestingly, these anti-tumor effects were not observed in normal hepatocyte cell line L02. Further, HIGD1A knockdown suppressed the expression of ornithine decarboxylase 1 (ODC1), a rate-limiting enzyme of polyamine metabolism under c-Myc regulation. HIGD1A was found to bind with the c-Myc promoter region, and its knockdown decreased the levels of polyamine metabolites. Consistently, the inhibitory effect on HCC phenotype by HIGD1A silencing could be reversed by overexpression of c-Myc or supplementation of polyamines.ConclusionsOur results demonstrated that HIGD1A activated c-Myc–ODC1 nexus to regulate polyamine synthesis and to promote HCC survival and malignant phenotype, implying that HIGD1A might represent a novel therapeutic target for HCC.

Long-term inhibition of ODC1 in APP/PS1 mice rescues amyloid pathology and switches astrocytes from a reactive to active state

Alzheimer’s disease (AD) is characterized by the loss of memory due to aggregation of misphosphorylated tau and amyloid beta (Aβ) plaques in the brain, elevated release of inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and reactive oxygen species from astrocytes, and subsequent neurodegeneration. Recently, it was found that enzyme Ornithine Decarboxylase 1 (ODC1) acts as a bridge between the astrocytic urea cycle and the putrescine-to-GABA conversion pathway in the brain of AD mouse models as well as human patients. In this study, we show that the long-term knockdown of astrocytic Odc1 in APP/PS1 animals was sufficient to completely clear Aβ plaques in the hippocampus while simultaneously switching the astrocytes from a detrimental reactive state to a regenerative active state, characterized by proBDNF expression. Our experiments also reveal an effect of astrocytic ODC1 inhibition on the expression of genes involved in synapse pruning and organization, histone modification, apoptotic signaling and protein processing. These genes are previously known to be associated with astrocytic activation and together create a neuroregeneration-supportive environment in the brain. By inhibiting ODC1 for a long period of 3 months in AD mice, we demonstrate that the beneficial amyloid-clearing process of astrocytes can be completely segregated from the systemically harmful astrocytic response to insult. Our study reports an almost complete clearance of Aβ plaques by controlling an endogenous degradation process, which also modifies the astrocytic state to create a regeneration-supportive environment in the brain. These findings present the potential of modulating astrocytic clearance of Aβ as a powerful therapeutic strategy against AD.

Mechanistic exploration of Yiqi Liangxue Shengji prescription on restenosis after balloon injury by integrating metabolomics with network pharmacology

Context Yiqi Liangxue Shengji prescription (YQLXSJ) is a traditional Chinese medicine (TCM) formula that has long been used for treatment after percutaneous coronary intervention (PCI). Objective To investigate the putative pharmacological mechanism of YQLXSJ on restenosis through an integrated approach utilizing metabolomics and network pharmacology. Materials and methods Forty male Sprague–Dawley rats were divided into sham, model, YQLXSJ, and positive groups. YQLXSJ group received the treatment of YQLXSJ (6 g/kg/d, i.g.) and the positive group was treated with atorvastatin (2 mg/kg/d, i.g.). After 4 weeks, the improvement in intimal hyperplasia was evaluated by ultrasound, H&E staining, and immunofluorescence. UPLC–MS/MS technology was utilized to screen the differential metabolites. Network pharmacology was conducted using TCMSP, GeneCards, and Metascape, etc., in combination with metabolomics. Eventually, the core targets were acquired and validated. Results Compared to models, YQLXSJ exhibited decreased intima-media thickness on ultrasound (0.23 ± 0.02 mm vs. 0.20 ± 0.01 mm, p < 0.01) and reduced intima thickness by H&E (30.12 ± 6.05 μm vs. 14.32 ± 1.37 μm, p < 0.01). We identified 18 differential metabolites and 5 core targets such as inducible nitric oxide synthase (NOS2), endothelial nitric oxide synthase (NOS3), vascular endothelial growth factor-A (VEGFA), ornithine decarboxylase-1 (ODC1) and group IIA secretory phospholipase A2 (PLA2G2A). These targets were further confirmed by molecular docking and ELISA. Discussion and conclusions This study confirms the effects of YQLXSJ on restenosis and reveals some biomarkers. TCM has great potential in the prevention and treatment of restenosis by improving metabolic disorders.

Bachmann-Bupp syndrome and treatment.

Bachmann-Bupp syndrome (BABS) is a neurodevelopmental disorder characterized by developmental delay, hypotonia, and varying forms of non-congenital alopecia. The condition is caused by 3'-end mutations of the ornithine decarboxylase 1 (ODC1) gene, which produce carboxy (C)-terminally truncated variants of ODC, a pyridoxal 5'-phosphate-dependent enzyme. C-terminal truncation of ODC prevents its ubiquitin-independent proteasomal degradation and leads to cellular accumulation of ODC enzyme that remains catalytically active. ODC is the first rate-limiting enzyme that converts ornithine to putrescine in the polyamine pathway. Polyamines (putrescine, spermidine, spermine) are aliphatic molecules found in all forms of life and are important during embryogenesis, organogenesis, and tumorigenesis. BABS is an ultra-rare condition with few reported cases, but it serves as a convincing example for drug repurposing therapy. α-Difluoromethylornithine (DFMO, also known as eflornithine) is an ODC inhibitor with a strong safety profile in pediatric use for neuroblastoma and other cancers as well as West African sleeping sickness (trypanosomiasis). Patients with BABS have been treated with DFMO and have shown improvement in hair growth, muscle tone, and development.

Polyamine catabolism is concentrated in tumor-associated histiocytes in diffuse large B-cell lymphoma and classic Hodgkin lymphoma

Polyamines are cationic molecules necessary for cell survival, growth, and replication [1–5]. Polyamines come in a variety of structural forms and are principally regulated by two enzymes, spermine/spermidine acetyltransferase-1 (SAT1) and ornithine decarboxylase-1 (ODC1). SAT1 targets the polyamines spermidine and spermine for degradation via acetylation, while ODC1 is involved in converting the polyamine precursor molecule to more complex polyamines [6–8]. Polyamines and their regulatory enzymes have been implicated in tumor metastasis [9,10] and in crosstalk between oncogenes [11–13] in numerous types of cancer, but their role has never been evaluated in B-cell malignancies. In this study, we examine the expression of SAT1 in diffuse large B-cell lymphoma (DLBCL) and classic Hodgkin lymphoma (HL). We found that SAT1 is expressed in all examined cases of DLBCL (n = 15) and HL (n = 5), though the levels of expression across cases vary. We also note that SAT1 expression appears to be concentrated in tumor-associated histiocytes, rather than tumor cells in both DLBCL and HL. We propose that these findings indicate that the polyamine catabolic enzyme, SAT1, plays an unappreciated role in the pathogenesis of B-cell neoplasms.

Triptolide attenuates irritable bowel syndrome via inhibiting ODC1

BackgroundIrritable bowel syndrome (IBS) is a chronic disorder of the gut-brain axis with significant morbidity. Triptolide, an active compound extracted from Tripterygium wilfordii Hook F (TwHF), has been widely used as a major medicinal herb in the treatment of inflammatory disease.MethodsThe chronic-acute combined stress (CAS) stimulation was used to establish IBS rat model. The model rats were then gavaged with triptolide. Forced swimming, marble-burying, fecal weight and abdominal withdrawal reflex (AWR) score were recorded. Pathologic changes in the ileal and colonic tissues were validated by hematoxylin and eosin staining. The inflammatory cytokines and Ornithine Decarboxylase-1 (ODC1) in the ileal and colonic tissues were performed by ELISA and WB.ResultsTriptolide didn’t have antidepressant- and antianxiety- effects in rats caused by CAS, but decreased fecal weight and AWR score. In addition, Triptolide reduced the release of IL-1, IL-6, and TNF-α and the expression of ODC1 in the ileum and colon.ConclusionThe therapeutic efficacy of triptolide for IBS induced by CAS was revealed in this study, which may be related to the reduction of ODC1.

Microbiota engage a HDAC3 rheostat to shape ILC3 metabolism and function in the gut

Abstract Group 3 innate lymphoid cells (ILC3s) respond to microbial colonization of the intestine to coordinate tissue health. This process involves interpretation of host- or microbial-derived signals that must be tightly regulated to preserve immunologic homeostasis. Here we examine a key epigenomic regulator that is responsive to microbial-derived factors, histone deacetylase 3 (HDAC3), and find that lineage-specific deletion results in reduced ILC3s and increased susceptibility to intestinal damage. In contrast, the lineage-specific deletion of an essential corepressor, NCOR1, results in elevated ILC3s and enhanced protection from intestinal damage. This indicates that HDAC3 mediates both a supportive deacetylase-independent role and a repressive deacetylase-dependent role in ILC3s. To explore genes promoted by HDAC3, we performed RNA sequencing and found that HDAC3 deficient ILC3s exhibit impaired transcription of genes involved in polyamine synthesis including the polyamine rate limiting enzyme ornithine decarboxylase 1 (ODC1) and spermine oxidase (SMOX). At steady state, ILC3s uniquely express high levels of ODC1 and SMOX compared to other lymphocytes, and transcription of these genes is influenced by IL-23 and the presence of the microbiota. Overall, this indicates that HDAC3 is a rheostat of ILC3 functionality in the intestine, with the hypothesis that HDAC3/NCOR1 limit tissue protective ILC3 responses, and NCOR1 independent HDAC3-mediated transcription of polyamine synthesis genes promotes ILC3 tissue protective responses. Supported by NIDDK National Research Service Award (NRSA) T32 Diversity Administrative Supplement (NOT-DK-21-016), R01AI143842, R01AI123368, R01AI145989, U01AI095608, R21CA249274, R01AI162936, R01CA274534 and the NIAID Mucosal Immunology Studies Team (MIST), an Investigators in the Pathogenesis of Infectious Disease Award from the Burroughs Wellcome Fund, Linda and Glenn Greenberg, the Dalton Family Foundation, and the Roberts Institute for Research in IBD. G.F.S. is a CRI Lloyd J. Old STAR.

Polyamine metabolism impacts T cell dysfunction in the oral mucosa of people living with HIV

Metabolic changes in immune cells contribute to both physiological and pathophysiological outcomes of immune reactions. Here, by comparing protein expression, transcriptome, and salivary metabolome profiles of uninfected and HIV+ individuals, we found perturbations of polyamine metabolism in the oral mucosa of HIV+ patients. Mechanistic studies using an in vitro human tonsil organoid infection model revealed that HIV infection of T cells also resulted in increased polyamine synthesis, which was dependent on the activities of caspase-1, IL-1β, and ornithine decarboxylase-1. HIV-1 also led to a heightened expression of polyamine synthesis intermediates including ornithine decarboxylase-1 as well as an elevated dysfunctional regulatory T cell (TregDys)/T helper 17 (Th17) cell ratios. Blockade of caspase-1 and polyamine synthesis intermediates reversed the TregDys phenotype showing the direct role of polyamine pathway in altering T cell functions during HIV-1 infection. Lastly, oral mucosal TregDys/Th17 ratios and CD4 hyperactivation positively correlated with salivary putrescine levels, which were found to be elevated in the saliva of HIV+ patients. Thus, by revealing the role of aberrantly increased polyamine synthesis during HIV infection, our study unveils a mechanism by which chronic viral infections could drive distinct T cell effector programs and Treg dysfunction.

Gasdermin D Deficiency in Vascular Smooth Muscle Cells Ameliorates Abdominal Aortic Aneurysm Through Reducing Putrescine Synthesis.

Abdominal aortic aneurysm (AAA) is a common vascular disease associated with significant phenotypic alterations in vascular smooth muscle cells (VSMCs). Gasdermin D (GSDMD) is a pore-forming effector of pyroptosis. In this study, the role of VSMC-specific GSDMD in the phenotypic alteration of VSMCs and AAA formation is determined. Single-cell transcriptome analyses reveal Gsdmd upregulation in aortic VSMCs in angiotensin (Ang) II-induced AAA. VSMC-specific Gsdmd deletion ameliorates Ang II-induced AAA in apolipoprotein E (ApoE)-/- mice. Using untargeted metabolomic analysis, it is found that putrescine is significantly reduced in the plasma and aortic tissues of VSMC-specific GSDMD deficient mice. High putrescine levels trigger a pro-inflammatory phenotype in VSMCs and increase susceptibility to Ang II-induced AAA formation in mice. In a population-based study, a high level of putrescine in plasma is associated with the risk of AAA (p < 2.2 × 10-16 ), consistent with the animal data. Mechanistically, GSDMD enhances endoplasmic reticulum stress-C/EBP homologous protein (CHOP) signaling, which in turn promotes the expression of ornithine decarboxylase 1 (ODC1), the enzyme responsible for increased putrescine levels. Treatment with the ODC1 inhibitor, difluoromethylornithine, reduces AAA formation in Ang II-infused ApoE-/- mice. The findings suggest that putrescine is a potential biomarker and target for AAA treatment.

Circular RNA circ_0003028 regulates cell development through modulating miR-498/ornithine decarboxylase 1 axis in hepatocellular carcinoma.

Circular RNA has been revealed to participate in multiple biological functions and contribute to various diseases' progression. This study aims to clarify the role of circ_0003028 and its potential molecular mechanism in hepatocellular carcinoma (HCC). The levels of circ_0003028, miR-498, and ornithine decarboxylase 1 (ODC1) mRNA were examined by quantitative real-time PCR. The cell proliferation ability was detected via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, colony formation, and 5-ethynyl-2'-deoxyuridine assays. The apoptotic rate was evaluated through flow cytometry. The migration and invasion capacity was tested by using wound healing assay and transwell assay. The protein levels of E-cadherin, N-cadherin, and vimentin were measured by western blot assay. The ceRNA regulatory mechanism of circ_0003028 was observed via dual-luciferase reporter and RNA pull-down assays. The mice xenograft models were constructed to confirm the oncogenicity of circ_0003028 in HCC in vivo . Circ_0003028 and ODC1 were upregulated, whereas miR-498 was downregulated in HCC tissues and cells. Circ_0003028 knockdown inhibited cell proliferation and metastasis, and promoted apoptosis. MiR-498 was a direct target of circ_0003028, and inhibition of miR-498 reversed the inhibitory effect of circ_0003028 silencing on HCC progression. Moreover, ODC1 was a direct target of miR-498 and ODC1 overexpression abated the anticancer roles of miR-498 in HCC. Additionally, circ_0003028 regulated ODC1 expression by sponging miR-498. Finally, we found that circ_0003028 could induce epithelial-mesenchymal transition of HCC cells by exosome pathway. In brief, the results demonstrated that circ_0003028 exerted tumourigenicity roles via miR-498/ODC1 signaling axis, providing a promising biomarker and therapeutic target for HCC.

LACC1 bridges NOS2 and polyamine metabolism in inflammatory macrophages.

The mammalian immune system uses various pattern recognition receptors to recognize invaders and host damage and transmits this information to downstream immunometabolic signalling outcomes. Laccase domain-containing 1 (LACC1) protein is an enzyme highly expressed in inflammatory macrophages and serves a central regulatory role in multiple inflammatory diseases such as inflammatory bowel diseases, arthritis and clearance of microbial infection1-4. However, the biochemical roles required for LACC1 functions remain largely undefined. Here we elucidated a shared biochemical function of LACC1 in mice and humans, converting L-citrulline to L-ornithine (L-Orn) and isocyanic acid and serving as a bridge between proinflammatory nitric oxide synthase (NOS2) and polyamine immunometabolism. We validated the genetic and mechanistic connections among NOS2, LACC1 and ornithine decarboxylase 1 (ODC1) in mouse models and bone marrow-derived macrophages infected by Salmonella enterica Typhimurium. Strikingly, LACC1 phenotypes required upstream NOS2 and downstream ODC1, and Lacc1-/- chemical complementation with its product L-Orn significantly restored wild-type activities. Our findings illuminate a previously unidentified pathway in inflammatory macrophages, explain why its deficiency may contribute to human inflammatory diseases and suggest that L-Orn could serve as a nutraceutical to ameliorate LACC1-associated immunological dysfunctions such as arthritis or inflammatory bowel disease.

Advanced pathway engineering for phototrophic putrescine production

SummaryThe polyamine putrescine (1,4‐diaminobutane) contributes to cellular fitness in most organisms, where it is derived from the amino acids ornithine or arginine. In the chemical industry, putrescine serves as a versatile building block for polyamide synthesis. The green microalga Chlamydomonas reinhardtii accumulates relatively high putrescine amounts, which, together with recent advances in genetic engineering, enables the generation of a powerful green cell factory to promote sustainable biotechnology for base chemical production. Here, we report a systematic investigation of the native putrescine metabolism in C. reinhardtii, leading to the first CO2‐based bio‐production of putrescine, by employing modern synthetic biology and metabolic engineering strategies. A CRISPR/Cas9‐based knockout of key enzymes of the polyamine biosynthesis pathway identified ornithine decarboxylase 1 (ODC1) as a gatekeeper for putrescine accumulation and demonstrated that the arginine decarboxylase (ADC) route is likely inactive and that amine oxidase 2 (AMX2) is mainly responsible for putrescine degradation in C. reinhardtii. A 4.5‐fold increase in cellular putrescine levels was achieved by engineered overexpression of potent candidate ornithine decarboxylases (ODCs). We identified unexpected substrate promiscuity in two bacterial ODCs, which exhibited co‐production of cadaverine and 4‐aminobutanol. Final pathway engineering included overexpression of recombinant arginases for improved substrate availability as well as functional knockout of putrescine degradation, which resulted in a 10‐fold increase in cellular putrescine titres and yielded 200 mg/L in phototrophic high cell density cultivations after 10 days.

Arginine Regulates Zygotic Genome Activation in Porcine Embryos Under Nutrition Restriction.

Arginine has a positive effect on pre-implantation development in pigs. However, the exact mechanism by which arginine promotes embryonic development is undefined. Here, single-cell RNA sequencing technology was applied to porcine in vivo pre-implantation embryos from the zygote to morula stage, it was found that that the expression of arginine metabolism-related genes clearly changed from the 2-cell stage to the 4-cell stage, when zygotic genome activation (ZGA) occurs in porcine embryos. Further analysis showed that arginine metabolism-related genes are significantly correlated with key ZGA genes. To determine the function of arginine in porcine embryos during ZGA, the in vitro fertilization embryos were cultured in PZM-3 medium (0.12 mM arginine, Control group), a modified PZM-3 medium (0 mM arginine, Block group) and a modified PZM-3 medium supplemented with arginine (0.12 mM arginine, Block + Arg group). The results showed that the 4-cell arrest rate was significantly increased in the Block group compared to the Control group (P < 0.05). The 4-cell arrest rate in the Block + Arg group was significantly decreased than that in the Block group (P < 0.05). Meanwhile, the expression of ZGA marker genes and SIRT1 protein in 4-cell embryos was significantly decreased in the Block group compared to the Control group, and their expression was significantly increased in the Block + Arg group. In addition, we observed that the glutathione (GSH), ATP levels, and lipid droplet contents were significantly increased, and the reactive oxygen species (ROS) level was decreased in the Block + Arg group compared to the Block group. Compared with Control group, spermine content in culture medium and the mRNA expression of ornithine decarboxylase1 (ODC1) of embryos in the Block group were significantly decreased (P < 0.05), and those in the Block + Arg group were significantly increased compared with the Block group (P < 0.05). Moreover, when difluoromethylornithine (an inhibitor of ODC1) was added to the modified PZM-3 medium supplemented with arginine, the effect of arginine on ZGA was inhibited. In summary, our findings demonstrated that arginine may regulate ZGA under nutrition restriction in porcine embryos by promoting polyamine synthesis.

Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimer’s disease

Alzheimer's disease (AD) is one of the foremost neurodegenerative diseases, characterized by beta-amyloid (Aβ) plaques and significant progressive memory loss. In AD, astrocytes are proposed to take up and clear Aβ plaques. However, how Aβ induces pathogenesis and memory impairment in AD remains elusive. We reportthat normal astrocytes show non-cyclic urea metabolism, whereas Aβ-treated astrocytes show switched-on urea cycle with upregulated enzymes and accumulated entering-metabolite aspartate, starting-substrate ammonia, end-product urea, and side-product putrescine. Gene silencing of astrocytic ornithine decarboxylase-1 (ODC1), facilitating ornithine-to-putrescine conversion, boosts urea cycle and eliminates aberrant putrescine and its toxic byproducts ammonia and H2O2 and its end product GABA to recover from reactive astrogliosis and memory impairment in AD. Our findings implicate that astrocytic urea cycle exerts opposing roles of beneficial Aβ detoxification and detrimental memory impairment in AD. We propose ODC1 inhibition as a promising therapeutic strategy for AD to facilitate removal of toxic molecules and prevent memory loss.