Polyamine metabolism is a central determinant of helper T cell lineage fidelity

Oleic acid regulates CD4+ T cells differentiation by targeting ODC1-mediated STAT5A phosphorylation in Vogt-Koyanagi-Harada disease

BACKGROUND

Vogt-Koyanagi-Harada (VKH) is a multisystemic autoimmune disorder characterized by bilateral panuveitis frequently accompanied by neurologic manifestations. While metabolic dysregulation is increasingly recognized in the context of autoimmune diseases, the role of specific metabolites in VKH disease remains unexplored.

METHODS

Non-targeted and targeted metabolomics analysis, phospho-antibody array, proteome microarray, surface plasmon resonance, and molecular simulation were used to identify molecular target of OA.

RESULTS

We investigated metabolic profile of VKH disease and found that oleic acid (OA) was enriched in this disease. A series of functional assays showed that OA could exacerbate experimental autoimmune uveitis (EAU) in association with increased frequency of Th1 and Th17 cells and decreased proportion of Treg cells in vitro. However, the specific molecular target of OA remains elusive. Through proteome microarrays, molecular simulations and surface plasmon resonance assays, Ornithine decarboxylase 1 (ODC1) was identified as target protein of OA. OA could bind to ODC1, increase ODC1 protein expression in both a time- and concentration-dependent manner and promote subsequently putrescine production. Phospho-antibody array analysis revealed that OA inhibited phosphorylation of STAT5A (Y694) in CD4+T cells, leading to imbalance of Th1/Th17 and Treg cells and decreased transcription of IL-10. OA upregulated ODC1 protein and putrescine levels through binding to LYS-78, inhibited phosphorylation of STAT5A protein and subsequently decreased binding of STAT5A at IL-10 promoter.

CONCLUSION

These results reveals that OA could be a crucial metabolite for modulation of CD4+T cell differentiation and that ODC1-mediated phosphorylation and transcriptional activity of STAT5A contributes to development of VKH disease progression, highlighting ODC1 as a novel therapeutic target in VKH disease.

TIGIT deficiency promotes autoreactive CD4+ T-cell responses through a metabolic‒epigenetic mechanism in autoimmune myositis

Polymyositis (PM) is a systemic autoimmune disease characterized by muscular inflammatory infiltrates and degeneration. T-cell immunoreceptor with Ig and ITIM domains (TIGIT) contributes to immune tolerance by inhibiting T cell-mediated autoimmunity. Here, we show that a reduced expression of TIGIT in CD4+ T cells from patients with PM promotes these cells' differentiation into Th1 and Th17 cells, which could be rescued by TIGIT overexpression. Knockout of TIGIT enhances muscle inflammation in a mouse model of experimental autoimmune myositis. Mechanistically, we find that TIGIT deficiency enhances CD28-mediated PI3K/AKT/mTOR co-stimulatory pathway, which promotes glucose oxidation, citrate production, and increased cytosolic acetyl-CoA levels, ultimately inducing epigenetic reprogramming via histone acetylation. Importantly, pharmacological inhibition of histone acetylation suppresses the differentiation of Th1 and Th17 cells, alleviating muscle inflammation. Thus, our findings reveal a mechanism by which TIGIT directly affects the differentiation of Th1 and Th17 T cells through metabolic‒epigenetic reprogramming, with important implications for treating systemic autoimmune diseases.

Cohabitation facilitates microbiome shifts that promote isoflavone transformation to ameliorate liver injury

Acetaminophen overuse is a leading cause of acute liver injury (ALI). Although ALI is linked to inter-individual differences in microbiome composition, the mechanisms remain unclear. We demonstrate that horizontal transmission of gut microbiota between male and female mice impacts ALI and identify Rikenellamicrofusus-mediated isoflavone transformation as determinants of ALI severity. R. microfusus increases upon cohabitation with bacterial β-galactosidase enhancing intestinal absorption of isoflavone biochanin-A (Bio-A). R. microfusus mono-colonization reduced ALI severity following acetaminophen overdose. Genetic or chemical-mediated inhibition of β-galactosidase blocked Bio-A release and negated the hepatoprotective effects of R. microfusus. Bio-A directly binds to pyruvate carboxylase (PC) and propionyl-CoA carboxylase subunit alpha (PCCA), augmenting the tricarboxylic acid cycle and promoting protective glutathione synthesis in hepatocytes. Additionally, immunohistochemical analysis revealed reduced hepatic PC and PCCA expression in liver failure (LF) patients. These findings highlight the impacts of microbiome composition on ALI and the ability of microbial isoflavone absorption to mitigate ALI severity.

Native nucleosomes intrinsically encode genome organization principles

The eukaryotic genome is packed into nucleosomes of 147 base pairs around a histone core and is organized into euchromatin and heterochromatin, corresponding to the A and B compartments, respectively1,2. Here we investigated whether individual nucleosomes contain sufficient information for 3D genomic organization into compartments, for example, in their biophysical properties. We purified native mononucleosomes to high monodispersity and used physiological concentrations of polyamines to determine their condensability. The chromosomal regions known to partition into A compartments have low condensability and those for B compartments have high condensability. Chromatin polymer simulations using condensability as the only input, without any trans factors, reproduced the A/B compartments. Condensability is also strongly anticorrelated with gene expression, particularly near the promoters and in a cell type-dependent manner. Therefore, mononucleosomes have biophysical properties associated with genes being on or off. Comparisons with genetic and epigenetic features indicate that nucleosome condensability is an emergent property, providing a natural axis on which to project the high-dimensional cellular chromatin state. Analysis using various condensing agents or histone modifications and mutations indicates that the genome organization principle encoded into nucleosomes is mostly electrostatic in nature. Polyamine depletion in mouse T cells, resulting from either knocking out or inhibiting ornithine decarboxylase, results in hyperpolarized condensability, indicating that when cells cannot rely on polyamines to translate the biophysical properties of nucleosomes to 3D genome organization, they accentuate condensability contrast, which may explain the dysfunction observed with polyamine deficiency3-5.

Polyamine metabolism in prostate cancer

PURPOSE OF REVIEW

Normal and malignant prostate engage in high rates of de novo polyamine synthesis. This review considers how polyamine metabolism regulates prostate cancer initiation and progression.

RECENT FINDINGS

The androgen receptor (AR) establishes a metabolic program to drive robust polyamine synthesis in the normal prostate. Upon malignant transformation, this AR-driven metabolic program persists and is optimized for oncogenesis by the proto-oncogene MYC and/or alterations to PI3K signaling. A deeper understanding of the function of polyamines in prostate cancer may be obtained by considering their function in the normal prostate.

SUMMARY

Recent findings support ongoing research into the role of polyamines in driving prostate cancer initiation and progression and suggest targeting polyamine metabolism remains a promising therapeutic strategy for prevention and treatment of prostate cancer.

Identification of Immune Characteristics of 2 Subtypes of Breast Cancer by Combining Polyamine Metabolism-related Genes to Help With Immunotherapy

This project aims to explore the clustering value of polyamine metabolism-related genes (PMRGs) in breast cancer (BC) to assist treatment. ConsensusClusterPlus R package was employed to cluster BC patients based on the expression of PMRGs. Using the edgeR R package, we analyzed differentially expressed genes (DEGs) of different molecular clusters. Core genes were screened and enriched by the PPI network. Univariate COX was applied to determine genes tightly linked with survival. ConsensusClusterPlus R package was employed to cluster PMRGs. Differences in immune infiltration and expression of immune checkpoints between 2 subgroups were analyzed. Response to immunotherapy was assessed based on the expression level of immunophenoscore (IPS). Drug sensitivity of different PMRG clusters was assessed by pRRophitic R package. We clustered BC patients into 2 different subtypes with different survival rates and biological functions based on the expression of 16 PMRGs. Application of univariate COX analysis identified genes greatly associated with survival and divided BC patients into 2 different PMRG clusters. Patients in the 2 clusters exhibited differences in overall survival rate and immune cell infiltration levels, with multiple immune cells displaying higher immune levels in PMRG cluster 2. PMRG cluster 2 demonstrated higher expression of HLA and IC as well as IPS. Cluster 1 exhibited higher sensitivity to (5Z)-7-Oxozeaenol, 5-Fluorouracil, and 681640, while cluster 2 exhibited higher sensitivity to A-443654 and A-770041. We identified 2 clusters of PMRG with significant differences in the immune microenvironment in BC and predicted potential drugs, aiming to find new directions for clinical treatment of BC.

Phenotyping the Chemical Communications of the Intestinal Microbiota and the Host: Secondary Bile Acids as Postbiotics

The current definition of a postbiotic is a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host". Postbiotics can be mainly classified as metabolites, derived from intestinal bacterial fermentation, or structural components, as intrinsic constituents of the microbial cell. Secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) are bacterial metabolites generated by the enzymatic modifications of primary bile acids by microbial enzymes. Secondary bile acids function as receptor ligands modulating the activity of a family of bile-acid-regulated receptors (BARRs), including GPBAR1, Vitamin D (VDR) receptor and RORγT expressed by various cell types within the entire human body. Secondary bile acids integrate the definition of postbiotics, exerting potential beneficial effects on human health given their ability to regulate multiple biological processes such as glucose metabolism, energy expenditure and inflammation/immunity. Although there is evidence that bile acids might be harmful to the intestine, most of this evidence does not account for intestinal dysbiosis. This review examines this novel conceptual framework of secondary bile acids as postbiotics and how these mediators participate in maintaining host health.

A noncanonical role of SAT1 enables anchorage independence and peritoneal metastasis in ovarian cancer

Anchorage-independent survival of ovarian tumor cells in ascites is the initial and critical step for peritoneal metastasis. How ovarian tumor cells achieve anchorage independence remains unclear. Here we show that a noncanonical role of spermidine/spermine N1-acetyltransferase 1 (SAT1) dictates anchorage-independent cell survival and potentiates metastatic dissemination in ovarian cancer. SAT1-high cancer cells are prevalent in ascitic tumors, and high SAT1 expression in primary tumors is linked to increased peritoneal metastasis rates in ovarian cancer patients. Mechanistically, SAT1 noncanonically acetylates H3K27 domains in multiple mitosis-regulating genes, increasing their transcriptional levels and protecting disseminating cells from aberrant mitosis and mitotic cell death. Notably, the acetylation of H3K27 by SAT1 depends on the reductive carboxylation of glutamine to supply acetyl-CoA in the nucleus. SAT1 inhibition with the small-molecule inhibitor ginkgolide B attenuates the metastatic tumor burden in mouse models. We conclude that SAT1 inhibition is a promising therapeutic strategy for metastatic ovarian cancer.

The roles of arginases and arginine in immunity

Arginase activity and arginine metabolism in immune cells have important consequences for health and disease. Their dysregulation is commonly observed in cancer, autoimmune disorders and infectious diseases. Following the initial description of a role for arginase in the dysfunction of T cells mounting an antitumour response, numerous studies have broadened our understanding of the regulation and expression of arginases and their integration with other metabolic pathways. Here, we highlight the differences in arginase compartmentalization and storage between humans and rodents that should be taken into consideration when assessing the effects of arginase activity. We detail the roles of arginases, arginine and its metabolites in immune cells and their effects in the context of cancer, autoimmunity and infectious disease. Finally, we explore potential therapeutic strategies targeting arginases and arginine.

Spermine attenuates TGF-β-induced EMT by downregulating fibronectin

Epithelial-mesenchymal transition (EMT) is a highly dynamic cellular process that occurs in development, tissue repair, and cancer metastasis. As a master EMT inducer, transforming growth factor-beta (TGF-β) can activate the EMT program by regulating the expression of key EMT-related genes and triggering other required cellular changes. However, it is unclear whether cell metabolism is involved in TGF-β-induced EMT. Here, we characterized early metabolic changes in response to transient TGF-β stimulation in HaCaT cells and discovered that TGF-β signaling significantly reduces the intracellular polyamine pool. Exogenous addition of spermine, but not other polyamines, attenuates TGF-β-induced EMT. Mechanistically, spermine downregulates the extracellular matrix protein fibronectin. Furthermore, we found that TGF-β activates extracellular signal-regulated kinase to enhance the expression of spermine oxidase, which is responsible for the reduced spermine concentration. This action of TGF-β on EMT via the polyamine metabolism provides new insights into the mechanisms underlying EMT and might be exploited as a way to target the EMT program for therapy.

Polyamine-Depleting Hydrogen-Bond Organic Frameworks Unleash Dendritic Cell and T Cell Vigor for Targeted CRISPR/Cas-Assisted Cancer Immunotherapy

Polyamines have tantalized cancer researchers as a potential means to rein in the rampant growth of cancer cells. However, clinical trials in recent decades have disappointed in delivering notable progress. Herein, a microfluidic-assisted synthetic hydrogen-bond organic framework (HOF) as a polyamine-depleting nanoplatforms designed to unleash the vigor of both dendritic cells (DCs) and T cells for precision cancer immunotherapy is reported. Upon internalization by tumor cells, the loaded plasma amine oxidase (PAO) in HOF efficiently depletes polyamines, remolding the tumor microenvironment and alleviating T-cell immunosuppression. This process also generates acrolein and H2O2, triggering CRISPR-assisted neoantigen generation. Specifically, Acrolein induces carbonyl stress, increasing mutational burdens. Simultaneously, HOF leverages the energy from the bis[2,4,5-trichloro-6-(pentyloxycarbonyl)phenyl] oxalate (CPPO)-H2O2 reaction for CRET-triggered singlet oxygen production, leading to thioether bond cleavage and release CRISPR-Cas9. Once released, CRISPR-Cas9 knocks out the DNA mismatch repair (MMR)-related MLH1 gene, further elevating mutational burdens and generating neoantigens, ideal targets for DCs. This dual-action strategy not only corrects T-cell immunosuppression but also enhances DC efficacy, presenting a powerful approach for tumor immunotherapy.

Spermidine restricts neonatal inflammation via metabolic shaping of polymorphonuclear myeloid-derived suppressor cells

Newborns exhibit a heightened vulnerability to inflammatory disorders due to their underdeveloped immune system, yet the underlying mechanisms remain poorly understood. Here we report that plasma spermidine is correlated with the maturity of human newborns and reduced risk of inflammation. Administration of spermidine led to the remission of neonatal inflammation in mice. Mechanistic studies revealed that spermidine enhanced the generation of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) via downstream eIF5A hypusination. Genetic deficiency or pharmacological inhibition of deoxyhypusine synthase (DHPS), a key enzyme of hypusinated eIF5A (eIF5AHyp), diminished the immunosuppressive activity of PMN-MDSCs, leading to aggravated neonatal inflammation. The eIF5AHyp pathway was found to enhance the immunosuppressive function via histone acetylation-mediated epigenetic transcription of immunosuppressive signatures in PMN-MDSCs. These findings demonstrate the spermidine-eIF5AHyp metabolic axis as a master switch to restrict neonatal inflammation.

The role of colonic microbiota amino acid metabolism in gut health regulation

The human gut microbiota plays a critical role in maintaining host homeostasis through metabolic activities. Among these, amino acid (AA) metabolism by the microbiota in the large intestine is highly heterogeneous and relevant to host health. Despite increasing interest, microbial AA metabolism remains relatively unexplored. This review highlights recent advances in colonic microbial AA metabolism, including auxotrophies, AA synthesis, and dissimilatory AA metabolites, and their implications in gut health, focusing on major gastrointestinal diseases including colorectal cancer, inflammatory bowel disease, and irritable bowel syndrome.

The tumor microenvironment is an ecosystem sustained by metabolic interactions

Cancer-associated fibroblasts (CAFs) and immune cells make up two major components of the tumor microenvironment (TME), contributing to an ecosystem that can either support or restrain cancer progression. Metabolism is a key regulator of the TME, providing a means for cells to communicate with and influence each other, modulating tumor progression and anti-tumor immunity. Cells of the TME can metabolically interact directly through metabolite secretion and consumption or by influencing other aspects of the TME that, in turn, stimulate metabolic rewiring in target cells. Recent advances in understanding the subtypes and plasticity of cells in the TME both open up new avenues and create challenges for metabolically targeting the TME to hamper tumor growth and improve response to therapy. This perspective explores ways in which the CAF and immune components of the TME could metabolically influence each other, based on current knowledge of their metabolic states, interactions, and subpopulations.

Immunogenic shift of arginine metabolism triggers systemic metabolic and immunological reprogramming to suppress HER2 + breast cancer

BACKGROUND

Arginine metabolism in tumors is often shunted into the pathway producing pro-tumor and immune suppressive polyamines (PAs), while downmodulating the alternative nitric oxide (NO) synthesis pathway. Aiming to correct arginine metabolism in tumors, arginine deprivation therapy and inhibitors of PA synthesis have been developed. Despite some therapeutic advantages, these approaches have often yielded severe side effects, making it necessary to explore an alternative strategy. We previously reported that supplementing sepiapterin (SEP), the endogenous precursor of tetrahydrobiopterin (BH4, the essential NO synthase cofactor), could correct arginine metabolism in tumor cells and tumor-associated macrophages (TAMs) and induce their metabolic and phenotypic reprogramming. We saw that oral SEP treatment effectively suppressed the growth of HER2-positive mammary tumors in animals. SEP also has no reported dose-dependent toxicity in clinical trials for metabolic disorders. In the present study, we tested our hypothesis that a long-term administration of SEP to individuals susceptible to HER2-positive mammary tumor would protect them against tumor occurrence.

METHODS

We administered SEP, in comparison to control DMSO, to MMTV-neu mice susceptible to HER2-positive mammary tumors for 8 months starting at their pre-pubertal stage. We monitored tumor onsets to determine the rate of tumor-free survival. After 8 months of treatment, we grouped animals into DMSO treatment with or without tumors and SEP treatment with or without tumors. We analyzed blood metabolites, PBMC, and bone marrow of DMSO vs. SEP treated animals.

RESULTS

We found that a long-term use of SEP in animals susceptible to HER2-positive mammary tumors effectively suppressed tumor occurrence. These SEP-treated animals had undergone reprogramming of the systemic metabolism and immunity, elevating total T cell counts in the circulation and bone marrow. Given that bone marrow-resident T cells are mostly memory T cells, it is plausible that chronic SEP treatment promoted memory T cell formation, leading to a potent tumor prevention.

CONCLUSIONS

These findings suggest the possible roles of the SEP/BH4/NO axis in promoting memory T cell formation and its potential therapeutic utility for preventing HER2-positive breast cancer.

Crohn's Disease-associated variant in laccase domain containing 1 (LACC1) modulates T cell gene expression, metabolism and T cell function

Genome wide association studies (GWAS) identify many risks for Crohn's disease (CD), including a site near the metabolism gene laccase domain containing 1 (LACC1). We previously found this site near LACC1 was associated with decreased LACC1 expression in T lymphocytes, yet the mechanism affecting gene expression and its links to T cell function and inflammatory disease were unknown. Here we identify variants in the promoter region that influence transcription of LACC1. Direct association of disease-risk variants with lower LACC1 pre-mRNA in human CD4+ T cells is confirmed by comparing transcripts from each allele from donors heterozygous for the LACC1 CD-risk allele. Using gene editing, we validate the function of this promoter region in LACC1 expression in T cells. Human CD4+ T cells with LACC1 gene knockdown show altered metabolism, including reduced oxygen consumption rate, and reduced in vitro regulatory T cell differentiation. Therefore, our study provides a mechanism linking these specific LACC1 variants to colitis by attributing promoter region variants to changes in T cell metabolism and function.

Conversion of T Effector Cells Into T Regulatory Cells in Type 1 Diabetes/Latent Autoimmune Diabetes of Adults by Inhibiting eIF5A and Notch Pathways

Background

The generation of functionally active, stable T regulatory cells (Tregs) is a crucial target of type 1 diabetes (T1D) immunotherapy. This study investigated therapeutic intervention for T1D/Latent autoimmune diabetes in adults (LADA), wherein the diabetogenic proinflammatory Treg (intermediate) cell subset was characterized and driven to a Treg phenotype (CD4+CD25+FOXP3+). This involved simultaneous inhibition of the eukaryotic initiation factor 5a (eIF5a) and Notch pathways using GC7 (N1-Guanyl-1,7-diaminoheptane) and Anti-DLL4 (Delta-like-ligand-4).

Methods

Peripheral blood from patients with T1D/LADA and healthy adults (n=7 each) was used to isolate the CD4+CD25- T cell population and CD4 deficient peripheral blood mononuclear cells (PBMCs). Cells were subjected to GAD65+GC7+anti-DLL4 treatment for seven days and compared with conventional anti-CD3/CD28/CD137 stimulation for conversion into the Tregs. Newly plasticized Tregs were assessed for their suppressive potential against freshly isolated autologous T responder cells. In addition, live, dead, and apoptotic cell counts were performed to evaluate the adverse effects of immunomodulatory treatment on immune cells. The data was analyzed with GraphPad Prism using 1- or 2-way ANOVA and a Student's t-test.

Results

A unique population of proinflammatory cytokines expressing intermediate Tregs (CD4+CD25-IFNg+IL17+FOXP3+) was characterized in T1D/LADA patients and found significantly increased compared to age-matched healthy adults. Simultaneous inhibition of eIF5a and Notch pathways could induce Treg phenotype in Treg-deficient CD4+ T cells and CD4 deficient PBMCs from T1D/LADA patients. GAD65+GC7+anti-DLL4 treatment plasticized Tregs withstanding a proinflammatory milieu mimicking T1D/LADA, and the plasticized Tregs exhibited a stable and suppressive functional phenotype. Furthermore, GAD65+GC7+anti-DLL4 treatment had no adverse effects on immune cells.The present approach is a multipronged approach involving the inhibition of eIF5a and Notch pathways that addresses the upregulation of immune tolerance, differentiation, and proliferation of cytotoxic T cells and alleviates β-cell dysfunction. Additionally, this treatment strategy could also be leveraged to boost Treg generation following islet transplantation or as a combinational therapy along with adoptive cell transfer.

The polyamine-regulating enzyme SSAT1 impairs tissue regulatory T cell function in chronic cutaneous inflammation

Regulatory T (Treg) cells are a critical immune component guarding against excessive inflammation. Treg cell dysfunction can lead to chronic inflammatory diseases with current therapies aimed at inhibiting effector T cells rather than rescuing Treg cell function. We utilized single-cell RNAsequencing data from patients with chronic inflammation to identify SAT1, the gene encoding spermidine/spermine N1-acetyltransferase (SSAT), as a driver of skin-resident Treg cell dysfunction. CRISPRa-driven SAT1 expression in human skin-derived Treg cells impaired their suppressive function and induced a pro-inflammatory phenotype. During cutaneous type-17 inflammation, keratinocyte 4-1BBL induces SAT1 on Treg cells. In a mouse model of psoriasis, pharmacological inhibition of SSAT rescued Treg cell number and function. Together, these data show that SAT1 expression has severe functional consequences on Treg cells and suggest a therapeutic target to treat chronic inflammatory disease.

Breastmilk polyamines modify gut gene expression in children at three months of age

BACKGROUND & AIMS

Breastmilk is one of the main sources of exogenous polyamines for newborns and contains higher polyamine content than infant formulas. Polyamines are involved in gut maturation and immune system regulation in animals, although the underlying mechanisms are not fully understood. We quantified polyamines in human mature breastmilk and evaluate their effects on intestinal gene expression in babies at three months of age.

METHODS

Polyamines were quantified in mature milk of 195 women from the prospective Mediterranean NELA birth cohort (Murcia, Spain) at 3 months postpartum. Maternal dietary intake was assessed by food frequency questionnaires. Intestinal gene expression was analysed in babies receiving breastmilk, with high (>p50, n = 25) or low (

RESULTS

Spermidine and spermine were the most prevalent polyamines in breastmilk at 3 months postpartum, while levels of putrescine were lower. Maternal dietary intake of polyamines was not associated with polyamine concentration in breastmilk and there were no differences in the polyamine content between allergic and non-allergic mothers. Microarray analyses of exfoliated gut cells revealed that cell localization and immune system were the most significant biological processes affected by high vs low polyamines in breastmilk. There were 15 differentially expressed genes, 3 up-regulated and 12 down-regulated, in high compared to low polyamine groups. Among the up-regulated genes were tumour necrosis factor alpha-induced protein 6 (TNFAIP6) and interleukin 8; while other immune system-related genes, such as integral membrane protein 2C, lymphocyte antigen 6 complex, transmembrane protein 179B were down-regulated.

CONCLUSIONS

Mature breastmilk presents spermidine and spermine as the most prevalent polyamines. Babies receiving milk with higher polyamine levels showed differences in the expression of genes associated with cell localization and immune system processes.

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Key Words

• Breastmilk
• Exfoliome
• Gene expression
• Intestine
• Polyamines
• Transcriptome

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MESH Headings

• Humans
• Female
• Polyamines/analysis
• Infant
• Milk, Human/chemistry
• Prospective Studies
• Spermidine/analysis
• Adult
• Spain
• Spermine/analysis
• Putrescine/analysis
• Male
• Gene Expression

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Affiliation(s)

María Sánchez-Campillo Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain
Antonio Gázquez Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain; Maternal and Child Health and Development Research Network (RICORS-SAMID), Institute of Health Carlos III, Madrid, Spain
María T Pastor-Fajardo Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Pediatrics, Hospital General Universitario de Elche, Alicante, Spain
María J López-Andreo Biology Molecular Section (ACTI), University of Murcia, Murcia, Spain
Adrián Pérez-Andrés Department of Physiology, University of Murcia, Murcia, Spain
Carmen Martínez-Graciá Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Food Science and Technology Department, Faculty of Veterinary, University of Murcia, Murcia, Spain
Jesús Vioque Health and Biomedical Research Institute of Alicante, University Miguel Hernandez (ISABIAL-UMH), Alicante, Spain; CIBER Epidemiology and Public Health (CIBERESP), Madrid, Spain
Virginia Pérez-Fernández Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Sociosanitary Sciences, Faculty of Medicine, University of Murcia, Murcia, Spain
Luís García-Marcos Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Network of Asthma and Adverse and Allergic Reactions (ARADyAL), Madrid, Spain; Pediatric Allergy and Pulmonology Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain
Elvira Larqué Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain; Maternal and Child Health and Development Research Network (RICORS-SAMID), Institute of Health Carlos III, Madrid, Spain.

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Effects of temperature to the liver transcriptome in the hybrid puffer fish (Takifugu rubripes ♀ × Takifugu obscurus ♂)

Water temperature exerts a crucial impact on the growth and development of fish. Hybrids may integrate the superior traits of their parents, thereby leading to higher economic benefits. Takifugu rubripes and T. obscurus are two important economic species in Asia. Here, to investigated the effect of temperature on the hybrid puffer larvae (T. rubripes ♀ × T. obscurus ♂), the larvae (0.79 ± 0.02 cm in body length) were treated to three temperatures: 15 °C (T15), 20 °C (T20), and 25 °C (T25) for 45 days. At the end of the study, the body length and weight were measured, the survival rate was calculated, and liver transcriptome analysis was performed on liver tissues. The hybrid puffer larvae in the T25 group showed a significant increase in average body length and body weight compared to the T15 and T20 groups (P < 0.05). 1292, 329, and 1927 differentially expressed genes (DEGs) were identified in T15 vs. T20, T20 vs. T25, and T15 vs. T25 groups, respectively. KEGG enrichment analyses showed that DEGs were primarily involved in the citrate cycle (TCA cycle), PPAR signaling, glycine, serine and threonine metabolism, and protein digestion and absorption pathways. These results indicated that temperature affects metabolism, signal transduction and protein digestion and absorption in hybrid puffer fish. In addition, twelve DEGs were randomly selected for RNA-seq validation, and the transcriptome results were consistent with the qPCR validation results, illustrating the accuracy of transcriptome sequencing. These findings deepen our understanding of the complex molecular mechanism of the response of hybrid puffer fish to temperature changes and contribute to the development of hybrid puffer fish breeding.

Arginine: at the crossroads of nitrogen metabolism

L-arginine is the most nitrogen-rich amino acid, acting as a key precursor for the synthesis of nitrogen-containing metabolites and an essential intermediate in the clearance of excess nitrogen. Arginine's side chain possesses a guanidino group which has unique biochemical properties, and plays a primary role in nitrogen excretion (urea), cellular signaling (nitric oxide) and energy buffering (phosphocreatine). The post-translational modification of protein-incorporated arginine by guanidino-group methylation also contributes to epigenetic gene control. Most human cells do not synthesize sufficient arginine to meet demand and are dependent on exogenous arginine. Thus, dietary arginine plays an important role in maintaining health, particularly upon physiologic stress. How cells adapt to changes in extracellular arginine availability is unclear, mostly because nearly all tissue culture media are supplemented with supraphysiologic levels of arginine. Evidence is emerging that arginine-deficiency can influence disease progression. Here, we review new insights into the importance of arginine as a metabolite, emphasizing the central role of mitochondria in arginine synthesis/catabolism and the recent discovery that arginine can act as a signaling molecule regulating gene expression and organelle dynamics.

Spermine synthase engages in macrophages M2 polarization to sabotage antitumor immunity in hepatocellular carcinoma

Disturbances in tumor cell metabolism reshape the tumor microenvironment (TME) and impair antitumor immunity, but the implicit mechanisms remain elusive. Here, we found that spermine synthase (SMS) was significantly upregulated in tumor cells, which correlated positively with the immunosuppressive microenvironment and predicted poor survival in hepatocellular carcinoma (HCC) patients. Via "subcutaneous" and "orthotopic" HCC syngeneic mouse models and a series of in vitro coculture experiments, we identified elevated SMS levels in HCC cells played a role in immune escape mainly through its metabolic product spermine, which induced M2 polarization of tumor-associated macrophages (TAMs) and subsequently corresponded with a decreased antitumor functionality of CD8+ T cells. Mechanistically, we discovered that spermine reprogrammed TAMs mainly by activating the PI3K-Akt-mTOR-S6K signaling pathway. Spermine inhibition in combination with immune checkpoint blockade effectively diminished tumor burden in vivo. Our results expand the understanding of the critical role of metabolites in regulating cancer progression and antitumor immunity and open new avenues for developing novel therapeutic strategies against HCC.

Type 2 immunity in allergic diseases

Significant advancements have been made in understanding the cellular and molecular mechanisms of type 2 immunity in allergic diseases such as asthma, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis (EoE), food and drug allergies, and atopic dermatitis (AD). Type 2 immunity has evolved to protect against parasitic diseases and toxins, plays a role in the expulsion of parasites and larvae from inner tissues to the lumen and outside the body, maintains microbe-rich skin and mucosal epithelial barriers and counterbalances the type 1 immune response and its destructive effects. During the development of a type 2 immune response, an innate immune response initiates starting from epithelial cells and innate lymphoid cells (ILCs), including dendritic cells and macrophages, and translates to adaptive T and B-cell immunity, particularly IgE antibody production. Eosinophils, mast cells and basophils have effects on effector functions. Cytokines from ILC2s and CD4+ helper type 2 (Th2) cells, CD8 + T cells, and NK-T cells, along with myeloid cells, including IL-4, IL-5, IL-9, and IL-13, initiate and sustain allergic inflammation via T cell cells, eosinophils, and ILC2s; promote IgE class switching; and open the epithelial barrier. Epithelial cell activation, alarmin release and barrier dysfunction are key in the development of not only allergic diseases but also many other systemic diseases. Recent biologics targeting the pathways and effector functions of IL4/IL13, IL-5, and IgE have shown promising results for almost all ages, although some patients with severe allergic diseases do not respond to these therapies, highlighting the unmet need for a more detailed and personalized approach.

Maternal supplementation spermidine during gestation improves placental angiogenesis and reproductive performance of high prolific sows

Spermidine (SPD) is a widely recognized polyamine compound found in mammalian cells and plays a key role in various cellular processes. We propose that SPD may enhance placental vascular development in pregnant sows, leading to increased birth weight of piglets. Six hundred and nine sows at 60 days of gestation were randomly assigned into a basal diet (CON group), basal diet supplemented 10 mg/kg of SPD (SPD1 group), and basal diet supplemented 20 mg/kg of SPD (SPD2 group), respectively. Compared with the CON, SPD1 significantly increased the average number of healthy piglets per litter and the placental efficiency (P < .05), while the average number of mummified fetus per litter and the percentage of weak piglets significantly decreased (P < .05). In the plasma metabolomics, SPD content in plasma of sows (P = .075) and umbilical cord plasma of piglets (P = .078) had an increasing trend in response to SPD1. Furthermore, SPD1 increased the expression of the vascular endothelial cell marker protein, platelet endothelial cell adhesionmolecule-1 (PECAM-1/CD31) and the density of placental stromal vessels (P < .05). Moreover, as compared to CON, SPD2 significantly decreased the average number of mummified fetus per litter (P < .05), while the placental efficiency and the expression of amino acid transporter solute carrier (SLC) family 7, member7 (SLC7A7) and glucose transporters SLC2A2) and SLC5A4 in placental tissue significantly increased (P < .05). These results suggest that maternal supplementation of SPD during pregnancy increased healthy litter number, and promoted placental tissue development. Our findings provide evidence that maternal SPD has the potential to improve the production performance of sows.

How the early life microbiome shapes immune programming in childhood asthma and allergies

Despite advances in our understanding of their diagnosis and treatment, pediatric allergies impose substantial burdens on affected children, families, and healthcare systems. Further, the prevalence of allergic diseases has dramatically increased over the past half-century, leading to additional concerns and concerted efforts to identify the origins, potential predictors and preventions, and therapies of allergic diseases. Together with the increase in allergic diseases, changes in lifestyle and early-life environmental influences have corresponded with changes in colonization patterns of the infant gut microbiome. The gut microbiome plays a key role in developing the immune system, thus greatly influencing the development of allergic disease. In this review, we specifically highlight the importance of the proper maturation and composition of the gut microbiome as an essential step in healthy child development or disease progression. By exploring the intertwined development of the immune system and microbiome across pediatric allergic diseases, we provide insights into potential novel strategies for their prevention and management.

Targeting SMOX Preserves Optic Nerve Myelin, Axonal Integrity, and Visual Function in Multiple Sclerosis

Multiple sclerosis (MS) is a highly disabling chronic neurological condition affecting young adults. Inflammation, demyelination, and axonal damage are key pathological features of MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Our previous work demonstrated that inhibiting spermine oxidase (SMOX) with MDL72527, a selective irreversible pharmacological inhibitor, significantly reduced clinical symptoms, retinal ganglion cell (RGC) loss, and optic nerve inflammation in EAE mice. The present study explored the broader therapeutic potential of SMOX inhibition, focusing on myelin preservation, axonal integrity, and visual function in the EAE model. Electron microscopy of optic nerve cross-sections showed significant preservation of myelin thickness and axonal integrity due to SMOX inhibition. The quantitative assessment showed that g-ratio and axon count metrics were significantly improved in MDL72527-treated EAE mice compared to their vehicle-treated counterparts. Immunofluorescence studies confirmed these findings, showing increased preservation of myelin and axonal proteins in MDL72527-treated EAE mice compared to the vehicle-treated group. Functional assessment studies (Electroretinography) demonstrated significant improvement in RGC function and axonal conduction in EAE mice treated with MDL72527. Furthermore, SMOX inhibition downregulated the expression of galectin3 (Gal3), a mediator of neuroinflammation, indicating Gal3's role in SMOX-mediated neuroprotection. This study provides compelling evidence for the potential of SMOX inhibition as a therapeutic strategy in multiple sclerosis and other demyelinating disorders.

The Associations of Dietary Polyamines with Incident Type 2 Diabetes Mellitus: A Large Prospective Cohort Study

OBJECTIVES

This study aimed to analyze the associations between dietary polyamine intake and incident T2DM.

METHODS

This prospective analysis included 168,137 participants from the UK Biobank who did not have T2DM at baseline. Dietary polyamines were calculated based on portion sizes of food items and a nutrient database. Incident T2DM was defined by hospital admissions with ICD10 codes E11-E14. Cox proportional hazard regression models and restricted cubic splines were used to examine the associations between dietary polyamine intake and incident T2DM.

RESULTS

During a median follow-up of 11.2 years (IQR, 11.8-13.2), 4422 (2.6%) participants developed T2DM. The average (SD) daily dietary intake was 10.5 (11.8) mg/day for spermidine, 4.3 (2.1) mg/day for spermine, and 12.7 (6.9) mg/day for putrescine. Compared to quintile 1, the multivariable-adjusted hazard ratios (95% CI) for quintiles 2-5 of dietary spermidine were 0.87 (0.79 to 0.96), 0.87 (0.79 to 0.96), 0.91 (0.82 to 0.99), and 0.96 (0.88 to 1.06); for dietary spermine, they were 1.01 (0.91 to 1.11), 1.03 (0.93 to 1.13), 1.07 (0.97 to 1.18), and 1.11 (1.01 to 1.23); and for dietary putrescine, they were 0.84 (0.76 to 0.92), 0.83 (0.79 to 0.91), 0.82 (0.74 to 0.90), and 0.87 (0.80 to 0.96).

CONCLUSIONS

Higher dietary spermidine and putrescine were associated with a lower risk of T2DM, while higher dietary spermine appeared to be associated with a higher risk of T2DM. These findings suggest optimal levels of dietary polyamine intake and indicate that polyamines may be promising targets for nutritional interventions in the prevention and management of T2DM.

Gut microbiota as a modulator of type 1 diabetes: A molecular perspective

Type 1 diabetes (T1D) is defined as an autoimmune metabolic disorder, characterized by destruction of pancreatic β-cells and high blood sugar levels. If left untreated, T1D results in severe health complications, including cardiovascular and kidney disease, as well as nerve damage, with ultimately grave consequences. Besides the role of genetic and certain environmental factors in T1D development, in the last decade, one new player emerged to affect T1D pathology as well, and that is a gut microbiota. Dysbiosis of gut bacteria can contribute to T1D by gut barrier disruption and the activation of autoimmune response, leading to the destruction of insulin producing cells, causing the development and aggravation of T1D symptoms. The relationship between gut microbiota and diabetes is complex and varies between individuals and additional research is needed to fully understand the effects of gut microbiome alternations in T1D pathogenesis. Therefore, the goal of this review is to understand the current knowledge in underlying molecular mechanism of gut microbiota effects, which leads to the new approaches for further studies in the prevention and treatment of T1D.

Androgen receptor drives polyamine synthesis creating a vulnerability for prostate cancer

Supraphysiological androgen (SPA) treatment can paradoxically restrict growth of castration-resistant prostate cancer with high androgen receptor (AR) activity, which is the basis for use of Bipolar Androgen Therapy (BAT) for patients with this disease. While androgens are widely appreciated to enhance anabolic metabolism, how SPA-mediated metabolic changes alter prostate cancer progression and therapy response is unknown. Here, we report that SPA markedly increased intracellular and secreted polyamines in prostate cancer models. This occurred through AR binding at enhancer sites upstream of the ODC1 promoter to increase abundance of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine synthesis, and de novo synthesis of polyamines from arginine. SPA-stimulated polyamines enhance prostate cancer fitness, as dCas9-KRAB-mediated inhibition of AR regulation of ODC1 or direct ODC inhibition by difluoromethylornithine (DFMO) increased efficacy of SPA. Mechanistically, this occurred in part due to increased activity of S-adenosylmethionine decarboxylase 1 (AMD1), which was stimulated both by AR and by loss of negative feedback by polyamines, leading to depletion of its substrate S-adenosylmethionine and global protein methylation. These data provided the rationale for a clinical trial testing the safety and efficacy of BAT in combination with DFMO for patients with metastatic castration-resistant prostate cancer. Pharmacodynamic studies of this drug combination in the first five patients on trial indicated that the drug combination resulted in effective polyamine depletion in plasma. Thus, the AR potently stimulates polyamine synthesis, which constitutes a vulnerability in prostate cancer treated with SPA that can be targeted therapeutically.

Solute Transporter OCTN1/Slc22a4 Affects Disease Severity and Response to Infliximab in Experimental Colitis: Role of Gut Microbiota and Immune Modulation

BACKGROUND

Inflammatory bowel diseases are chronic disabling conditions with a complex and multifactorial etiology, still incompletely understood. OCTN1, an organic cation transporter, could have a role in modulating the inflammatory response, and some genetic polymorphisms of this molecule have been associated with increased risk of inflammatory bowel diseases. Until now, limited information exists on its potential in predicting/modulating patient's response to therapies. The aim of this study was to evaluate the role of OCTN1 in modifying gut microbiota and mucosal immunity in response to infliximab therapy in murine colitis.

METHODS

A dextran sodium sulphate model of colitis was used to assess the clinical efficacy of infliximab administered intravenously in ocnt1 gene knockout mice and their C57BL/6 controls. Stool, colon, and mesenteric lymph node samples were collected to evaluate differences in gut microbiota composition, histology, and T cell populations, respectively.

RESULTS

Octn1 -/- influences the microbiota profile and is associated with a worse dysbiosis in mice with colitis. Infliximab treatment attenuates colitis-associated dysbiosis, with an increase of bacterial richness and evenness in both strains. In comparison with wild type, octn1-/- mice have milder disease and a higher baseline percentage of Treg, Tmemory, Th2 and Th17 cells.

CONCLUSIONS

Our data support the murine model to study OCTN1 genetic contribution to inflammatory bowel diseases. This could be the first step towards the recognition of this membrane transporter as a biomarker in inflammatory conditions and a predictor of response to therapies.

Metabolic adaptations of ILC2 and Th2 cells in type 2 immunity

Type 2 immune responses play a crucial role in host defense against parasitic infections but can also promote the development of allergies and asthma. This response is orchestrated primarily by group 2 innate lymphoid cells (ILC2) and helper type 2 (Th2) cells, both of which undergo substantial metabolic reprogramming as they transition from resting to activated states. Understanding these metabolic adaptations not only provides insights into the fundamental biology of ILC2 and Th2 cells but also opens up potential therapeutic avenues for the identification of novel metabolic targets that can extend the current treatment regimens for diseases in which type 2 immune responses play pivotal roles. By integrating recent findings, this review underscores the significance of cellular metabolism in orchestrating immune functions and highlights future directions for research in this evolving field.

Metabolic footprint and logic through the T cell life cycle

A simple definition of life is a system that can self-replicate (proliferation) and self-sustain (metabolism). At the cellular level, metabolism has evolved to drive proliferation, which requires energy and building blocks to duplicate cellular biomass before division. T lymphocytes (or T cells) are required for adaptive immune responses, protecting us against invading and malignant agents capable of hyper-replication. To gain a competitive advantage over these agents, activated T cells can duplicate their biomass and divide into two daughter cells in as short as 2-6 hours, considered the fastest cell division among all cell types in vertebrates. Thus, the primary task of cellular metabolism has evolved to commit available resources to drive T cell hyperproliferation. Beyond that, the T cell life cycle involves an ordered series of fate-determining events that drive cells to transition between discrete cell states. At the life stages not involved in hyperproliferation, T cells engage metabolic programs that are more flexible to sustain viability and maintenance and sometimes are fine-tuned to support specific cellular activities. Here, we focus on the central carbon metabolism, which is most relevant to cell proliferation. We provide examples of how the changes in the central carbon metabolism may or may not change the fate of T cells and further explore a few conceptual frameworks, such as metabolic flexibility, the Goldilocks Principle, overflow metabolism, and effector-signaling metabolites, in the context of T cell fate transitions.

Tumor cell-derived spermidine promotes a protumorigenic immune microenvironment in glioblastoma via CD8+ T cell inhibition

The glioblastoma (GBM) microenvironment is enriched in immunosuppressive factors that potently interfere with the function of cytotoxic T lymphocytes. Cancer cells can directly affect the immune system, but the mechanisms driving these interactions are not completely clear. Here, we demonstrate that the polyamine metabolite spermidine (SPD) was elevated in the GBM tumor microenvironment. Exogenous administration of SPD drove tumor aggressiveness in an immune-dependent manner in preclinical mouse models via reduction of CD8+ T cell frequency and reduced cytotoxic function. Knockdown of ornithine decarboxylase, the rate-limiting enzyme in SPD synthesis, did not affect cancer cell growth in vitro but did result in extended survival. Furthermore, patients with GBM with a more favorable outcome had a significant reduction in SPD compared with patients with a poor prognosis. Our results demonstrate that SPD functions as a cancer cell-derived metabolite that drives tumor progression by reducing CD8+ T cell numbers and function.

Genetically encoded fluorescent reporter for polyamines

Polyamines are abundant and evolutionarily conserved metabolites that are essential for life. Dietary polyamine supplementation extends life-span and health-span. Dysregulation of polyamine homeostasis is linked to Parkinson's disease and cancer, driving interest in therapeutically targeting this pathway. However, measuring cellular polyamine levels, which vary across cell types and states, remains challenging. We introduce a first-in-class genetically encoded polyamine reporter for real-time measurement of polyamine concentrations in single living cells. This reporter utilizes the polyamine-responsive ribosomal frameshift motif from the OAZ1 gene. We demonstrate broad applicability of this approach and reveal dynamic changes in polyamine levels in response to genetic and pharmacological perturbations. Using this reporter, we conducted a genome-wide CRISPR screen and uncovered an unexpected link between mitochondrial respiration and polyamine import, which are both risk factors for Parkinson's disease. By offering a new lens to examine polyamine biology, this reporter may advance our understanding of these ubiquitous metabolites and accelerate therapy development.

The microbiome diversifies N-acyl lipid pools - including short-chain fatty acid-derived compounds

N-acyl lipids are important mediators of several biological processes including immune function and stress response. To enhance the detection of N-acyl lipids with untargeted mass spectrometry-based metabolomics, we created a reference spectral library retrieving N-acyl lipid patterns from 2,700 public datasets, identifying 851 N-acyl lipids that were detected 356,542 times. 777 are not documented in lipid structural databases, with 18% of these derived from short-chain fatty acids and found in the digestive tract and other organs. Their levels varied with diet, microbial colonization, and in people living with diabetes. We used the library to link microbial N-acyl lipids, including histamine and polyamine conjugates, to HIV status and cognitive impairment. This resource will enhance the annotation of these compounds in future studies to further the understanding of their roles in health and disease and highlight the value of large-scale untargeted metabolomics data for metabolite discovery.

Novel deoxyhypusine synthase (DHPS) inhibitors target hypusination-induced vasculogenic mimicry (VM) against malignant melanoma

Vasculogenic mimicry (VM) contributes factor to the poor prognosis of malignant melanoma. Developing deoxyhypusine synthase (DHPS) inhibitors against melanoma VM is clinically essential. In this study, we optimized and synthesized a series of compounds based on the candidate structure, and the hit compound 7k was identified through enzyme assay and cell viability inhibition screening. Both inside and outside the cell, 7k's ability to target DHPS and its high affinity were demonstrated. Molecular dynamics and point mutation indicated that mutations of K329 or V129 in DHPS abolish 7k's inhibitory activity. Using PCR arrays, solid-state antibody microarrays, and angiogenesis assays investigated 7k's impact on melanoma cells to reveal that DHPS regulates melanoma VM by promoting FGFR2 and c-KIT expression. Surprisingly, 7k was discovered to inhibit MC1R-mediated melanin synthesis in the zebrafish. Pharmacokinetic evaluations demonstrated 7k's favorable properties, and xenograft models evidenced its notable anti-melanoma efficacy, achieving a TGI of 73 %. These results highlighted DHPS as key in melanoma VM formation and confirmed 7k's potential as a novel anti-melanoma agent.

Macrophages and T cells in metabolic disorder-associated cancers

Cancer and metabolic disorders have emerged as major global health challenges, reaching epidemic levels in recent decades. Often viewed as separate issues, metabolic disorders are shown by mounting evidence to heighten cancer risk and incidence. The intricacies underlying this connection are still being unraveled and encompass a complex interplay between metabolites, cancer cells and immune cells within the tumour microenvironment (TME). Here, we outline the interplay between metabolic and immune cell dysfunction in the context of three highly prevalent metabolic disorders, namely obesity; two associated liver diseases, metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH); and type 2 diabetes. We focus primarily on macrophages and T cells, the critical roles of which in dictating inflammatory response and immune surveillance in metabolic disorder-associated cancers are widely reported. Moreover, considering the ever-increasing number of patients prescribed with metabolism disorder-altering drugs and diets in recent years, we discuss how these therapies modulate systemic and local immune phenotypes, consequently impacting cancer malignancy. Collectively, unraveling the determinants of metabolic disorder-associated immune landscape and their role in fuelling cancer malignancy will provide a framework essential to therapeutically address these highly prevalent diseases.

Immunogenic shift of arginine metabolism triggers systemic metabolic and immunological reprogramming to prevent HER2+ breast cancer

Arginine metabolism in tumors is often shunted into the pathway producing pro-tumor and immune suppressive polyamines (PAs), while downmodulating the alternative nitric oxide (NO) synthesis pathway. Aiming to correct arginine metabolism in tumors, arginine deprivation therapy and inhibitors of PA synthesis have been developed. Despite some therapeutic advantages, these approaches have often yielded severe side effects, making it necessary to explore an alternative strategy. We previously reported that supplementing SEP, the endogenous precursor of BH4 (the essential NO synthase cofactor), could correct arginine metabolism in tumor cells and tumor-associated macrophages (TAMs) and induce their metabolic and phenotypic reprogramming. We saw that oral SEP treatment effectively suppressed the growth of HER2-positive mammary tumors in animals. SEP also has no reported dose-dependent toxicity in clinical trials for metabolic disorders. In the present study, we report that a long-term use of SEP in animals susceptible to HER2-positive mammary tumors effectively prevented tumor occurrence. These SEP-treated animals had undergone reprogramming of the systemic metabolism and immunity, elevating total T cell counts in the circulation and bone marrow. Given that bone marrow-resident T cells are mostly memory T cells, it is plausible that chronic SEP treatment promoted memory T cell formation, leading to a potent tumor prevention. These findings suggest the possible roles of the SEP/BH4/NO axis in promoting memory T cell formation and its potential therapeutic utility for preventing HER2-positive breast cancer.

Genetically encoded fluorescent sensors for visualizing polyamine levels, uptake, and distribution

Polyamines are abundant and physiologically essential biomolecules that play a role in numerous processes, but are disrupted in diseases such as cancer, and cardiovascular and neurological disorders. Despite their importance, measuring free polyamine concentrations and monitoring their metabolism and uptake in cells in real-time remains impossible due to the lack of appropriate biosensors. Here we engineered, characterized, and validated the first genetically encoded biosensors for polyamines, named iPASnFRs. We demonstrate the utility of iPASnFR for detecting polyamine import into mammalian cells, to the cytoplasm, mitochondria, and the nucleus. We demonstrate that these sensors are useful to probe the activity of polyamine transporters and to uncover biochemical pathways underlying the distribution of polyamines amongst organelles. The sensors powered a high-throughput small molecule compound library screen, revealing multiple compounds in different chemical classes that strongly modulate cellular polyamine levels. These sensors will be powerful tools to investigate the complex interplay between polyamine uptake and metabolic pathways, address open questions about their role in health and disease, and enable screening for therapeutic polyamine modulators.

Androgen signaling restricts glutaminolysis to drive sex-specific Th17 metabolism in allergic airway inflammation

Female individuals have an increased prevalence of many Th17 cell-mediated diseases, including asthma. Androgen signaling decreases Th17 cell-mediated airway inflammation, and Th17 cells rely on glutaminolysis. However, it remains unclear whether androgen receptor (AR) signaling modifies glutamine metabolism to suppress Th17 cell-mediated airway inflammation. We show that Th17 cells from male humans and mice had decreased glutaminolysis compared with female individuals, and that AR signaling attenuated Th17 cell mitochondrial respiration and glutaminolysis in mice. Using allergen-induced airway inflammation mouse models, we determined that females had a selective reliance upon glutaminolysis for Th17-mediated airway inflammation, and that AR signaling attenuated glutamine uptake in CD4+ T cells by reducing expression of glutamine transporters. In patients with asthma, circulating Th17 cells from men had minimal reliance upon glutamine uptake compared to Th17 cells from women. AR signaling thus attenuates glutaminolysis, demonstrating sex-specific metabolic regulation of Th17 cells with implications for Th17 or glutaminolysis targeted therapeutics.

Polyamine Anabolism Promotes Chemotherapy-Induced Breast Cancer Stem Cell Enrichment

Breast cancer patients may initially benefit from cytotoxic chemotherapy but experience treatment resistance and relapse. Chemoresistant breast cancer stem cells (BCSCs) play a pivotal role in cancer recurrence and metastasis, however, identification and eradication of BCSC population in patients are challenging. Here, an mRNA-based BCSC signature is developed using machine learning strategy to evaluate cancer stemness in primary breast cancer patient samples. Using the BCSC signature, a critical role of polyamine anabolism in the regulation of chemotherapy-induced BCSC enrichment, is elucidated. Mechanistically, two key polyamine anabolic enzymes, ODC1 and SRM, are directly activated by transcription factor HIF-1 in response to chemotherapy. Genetic inhibition of HIF-1-controlled polyamine anabolism blocks chemotherapy-induced BCSC enrichment in vitro and in xenograft mice. A novel specific HIF-1 inhibitor britannin is identified through a natural compound library screening, and demonstrate that coadministration of britannin efficiently inhibits chemotherapy-induced HIF-1 transcriptional activity, ODC1 and SRM expression, polyamine levels, and BCSC enrichment in vitro and in xenograft and autochthonous mouse models. The findings demonstrate the key role of polyamine anabolism in BCSC regulation and provide a new strategy for breast cancer treatment.

Deoxyhypusine synthase deficiency syndrome zebrafish model: aberrant morphology, epileptiform activity, and reduced arborization of inhibitory interneurons

DHPS deficiency syndrome is an ultra-rare neurodevelopmental disorder (NDD) which results from biallelic mutations in the gene encoding the enzyme deoxyhypusine synthase (DHPS). DHPS is essential to synthesize hypusine, a rare amino acid formed by post-translational modification of a conserved lysine in eukaryotic initiation factor 5 A (eIF5A). DHPS deficiency syndrome causes epilepsy, cognitive and motor impairments, and mild facial dysmorphology. In mice, a brain-specific genetic deletion of Dhps at birth impairs eIF5AHYP-dependent mRNA translation. This alters expression of proteins required for neuronal development and function, and phenotypically models features of human DHPS deficiency. We studied the role of DHPS in early brain development using a zebrafish loss-of-function model generated by knockdown of dhps expression with an antisense morpholino oligomer (MO) targeting the exon 2/intron 2 (E2I2) splice site of the dhps pre-mRNA. dhps knockdown embryos exhibited dose-dependent developmental delay and dysmorphology, including microcephaly, axis truncation, and body curvature. In dhps knockdown larvae, electrophysiological analysis showed increased epileptiform activity, and confocal microscopy analysis revealed reduced arborisation of GABAergic neurons. Our findings confirm that hypusination of eIF5A by DHPS is needed for early brain development, and zebrafish with an antisense knockdown of dhps model features of DHPS deficiency syndrome.

Polyamine Pathway Inhibitor DENSPM Suppresses Lipid Metabolism in Pheochromocytoma Cell Line

Pheochromocytomas (PCCs) are tumors arising from chromaffin cells in the adrenal medulla, and paragangliomas (PGLs) are tumors derived from extra-adrenal sympathetic or parasympathetic paraganglia; these tumors are collectively referred to as PPGL cancer. Treatment for PPGL primarily involves surgical removal of the tumor, and only limited options are available for treatment of the disease once it becomes metastatic. Human carriers of the heterozygous mutations in the succinate dehydrogenase subunit B (SDHB) gene are susceptible to the development of PPGL. A physiologically relevant PCC patient-derived cell line hPheo1 was developed, and SDHB_KD cells carrying a stable short hairpin knockdown of SDHB were derived from it. An untargeted metabolomic approach uncovered an overactive polyamine pathway in the SDHB_KD cells that was subsequently fully validated in a large set of human SDHB-mutant PPGL tumor samples. We previously reported that treatment with the polyamine metabolism inhibitor N1,N11-diethylnorspermine (DENSPM) drastically inhibited growth of these PCC-derived cells in culture as well as in xenograft mouse models. Here we explored the mechanisms underlying DENSPM action in hPheo1 and SDHB_KD cells. Specifically, by performing an RNAseq analysis, we have identified gene expression changes associated with DENSPM treatment that broadly interfere with all aspects of lipid metabolism, including fatty acid (FA) synthesis, desaturation, and import/uptake. Furthermore, by performing an untargeted lipidomic liquid chromatography-mass spectrometry (LC/MS)-based analysis we uncovered specific groups of lipids that are dramatically reduced as a result of DENSPM treatment. Specifically, the bulk of plasmanyl ether lipid species that have been recently reported as the major determinants of cancer cell fate are notably decreased. In summary, this work suggests an intersection between active polyamine and lipid pathways in PCC cells.

Spermidine-eIF5A axis is essential for muscle stem cell activation via translational control

Adult skeletal muscle stem cells, also known satellite cells (SCs), are quiescent and activate in response to injury. However, the activation mechanisms of quiescent SCs (QSCs) remain largely unknown. Here, we investigated the metabolic regulation of SC activation by identifying regulatory metabolites that promote SC activation. Using targeted metabolomics, we found that spermidine acts as a regulatory metabolite to promote SC activation and muscle regeneration in mice. Mechanistically, spermidine activates SCs via generating hypusinated eIF5A. Using SC-specific eIF5A-knockout (KO) and Myod-KO mice, we further found that eIF5A is required for spermidine-mediated SC activation by controlling MyoD translation. More significantly, depletion of eIF5A in SCs results in impaired muscle regeneration in mice. Together, the findings of our study define a novel mechanism that is essential for SC activation and acts via spermidine-eIF5A-mediated MyoD translation. Our findings suggest that the spermidine-eIF5A axis represents a promising pharmacological target in efforts to activate endogenous SCs for the treatment of muscular disease.

Inflammation primes the murine kidney for recovery by activating AZIN1 adenosine-to-inosine editing

The progression of kidney disease varies among individuals, but a general methodology to quantify disease timelines is lacking. Particularly challenging is the task of determining the potential for recovery from acute kidney injury following various insults. Here, we report that quantitation of post-transcriptional adenosine-to-inosine (A-to-I) RNA editing offers a distinct genome-wide signature, enabling the delineation of disease trajectories in the kidney. A well-defined murine model of endotoxemia permitted the identification of the origin and extent of A-to-I editing, along with temporally discrete signatures of double-stranded RNA stress and adenosine deaminase isoform switching. We found that A-to-I editing of antizyme inhibitor 1 (AZIN1), a positive regulator of polyamine biosynthesis, serves as a particularly useful temporal landmark during endotoxemia. Our data indicate that AZIN1 A-to-I editing, triggered by preceding inflammation, primes the kidney and activates endogenous recovery mechanisms. By comparing genetically modified human cell lines and mice locked in either A-to-I-edited or uneditable states, we uncovered that AZIN1 A-to-I editing not only enhances polyamine biosynthesis but also engages glycolysis and nicotinamide biosynthesis to drive the recovery phenotype. Our findings implicate that quantifying AZIN1 A-to-I editing could potentially identify individuals who have transitioned to an endogenous recovery phase. This phase would reflect their past inflammation and indicate their potential for future recovery.

Aryl Hydrocarbon Receptor Knockout Accelerates PanIN Formation and Fibro-Inflammation in a Mutant Kras -Driven Pancreatic Cancer Model

OBJECTIVES

The pathogenesis of pancreas cancer (PDAC) remains poorly understood, hindering efforts to develop a more effective therapy for PDAC. Recent discoveries show the aryl hydrocarbon receptor (AHR) plays a crucial role in the development of several cancers and can be targeted for therapeutic effect. However, its involvement in the pathogenesis of PDAC remains unclear. To address this gap, we evaluated the role of AHR in the development of PDAC precancerous lesions in vivo .

MATERIALS AND METHODS

We created a global AHR-null, mutant Kras -driven PDAC mouse model (A -/- KC) and evaluated the changes in PDAC precursor lesion formation (PanIN-1, 2, and 3) and associated fibro-inflammation between KC and A -/- KC at 5 months of age. We then examined the changes in the immune microenvironment followed by single-cell RNA-sequencing analysis to evaluate concomitant transcriptomic changes.

RESULTS

We identified a significant increase in PanIN-1 lesion formation and PanIN-1 associated fibro-inflammatory infiltrate in A -/- KC versus KC mice. This was associated with significant changes in the adaptive immune system, particularly a decrease in the CD4+/CD8+ T-cell ratio, as well as a decrease in the T-regulatory/Th17 T-cell ratio suggesting unregulated inflammation.

CONCLUSIONS

These findings show the loss of AHR results in heightened Kras -induced PanIN formation, through modulation of immune cells within the pancreatic tumor microenvironment.

Short-term post-fast refeeding enhances intestinal stemness via polyamines

For over a century, fasting regimens have improved health, lifespan and tissue regeneration in diverse organisms, including humans1-6. However, how fasting and post-fast refeeding affect adult stem cells and tumour formation has yet to be explored in depth. Here we demonstrate that post-fast refeeding increases intestinal stem cell (ISC) proliferation and tumour formation; post-fast refeeding augments the regenerative capacity of Lgr5+ ISCs, and loss of the tumour suppressor gene Apc in post-fast-refed ISCs leads to a higher tumour incidence in the small intestine and colon than in the fasted or ad libitum-fed states, demonstrating that post-fast refeeding is a distinct state. Mechanistically, we discovered that robust mTORC1 induction in post-fast-refed ISCs increases protein synthesis via polyamine metabolism to drive these changes, as inhibition of mTORC1, polyamine metabolite production or protein synthesis abrogates the regenerative or tumorigenic effects of post-fast refeeding. Given our findings, fast-refeeding cycles must be carefully considered and tested when planning diet-based strategies for regeneration without increasing cancer risk, as post-fast refeeding leads to a burst in stem-cell-driven regeneration and tumorigenicity.

DHPS-Mediated Hypusination Regulates METTL3 Self-m6A-Methylation Modification to Promote Melanoma Proliferation and the Development of Novel Inhibitors

Discovering new treatments for melanoma will benefit human health. The mechanism by which deoxyhypusine synthase (DHPS) promotes melanoma development remains elucidated. Multi-omics studies have revealed that DHPS regulates m6A modification and maintains mRNA stability in melanoma cells. Mechanistically, DHPS activates the hypusination of eukaryotic translation initiation factor 5A (eIF5A) to assist METTL3 localizing on its mRNA for m6A modification, then promoting METTL3 expression. Structure-based design, synthesis, and activity screening yielded the hit compound GL-1 as a DHPS inhibitor. Notably, GL-1 directly inhibits DHPS binding to eIF5A, whereas GC-7 cannot. Based on the clarification of the mode of action of GL-1 on DHPS, it is found that GL-1 can promote the accumulation of intracellular Cu2+ to induce apoptosis, and antibody microarray analysis shows that GL-1 inhibits the expression of several cytokines. GL-1 shows promising antitumor activity with good bioavailability in a xenograft tumor model. These findings clarify the molecular mechanisms by which DHPS regulates melanoma proliferation and demonstrate the potential of GL-1 for clinical melanoma therapy.

Metabolic regulation of mRNA splicing

Alternative mRNA splicing enables the diversification of the proteome from a static genome and confers plasticity and adaptiveness on cells. Although this is often explored in development, where hard-wired programs drive the differentiation and specialization, alternative mRNA splicing also offers a way for cells to react to sudden changes in outside stimuli such as small-molecule metabolites. Fluctuations in metabolite levels and availability in particular convey crucial information to which cells react and adapt. We summarize and highlight findings surrounding the metabolic regulation of mRNA splicing. We discuss the principles underlying the biochemistry and biophysical properties of mRNA splicing, and propose how these could intersect with metabolite levels. Further, we present examples in which metabolites directly influence RNA-binding proteins and splicing factors. We also discuss the interplay between alternative mRNA splicing and metabolite-responsive signaling pathways. We hope to inspire future research to obtain a holistic picture of alternative mRNA splicing in response to metabolic cues.

P53-dependent hypusination of eIF5A affects mitochondrial translation and senescence immune surveillance

Cellular senescence is characterized by a permanent growth arrest and is associated with tissue aging and cancer. Senescent cells secrete a number of different cytokines referred to as the senescence-associated secretory phenotype (SASP), which impacts the surrounding tissue and immune response. Here, we find that senescent cells exhibit higher rates of protein synthesis compared to proliferating cells and identify eIF5A as a crucial regulator of this process. Polyamine metabolism and hypusination of eIF5A play a pivotal role in sustaining elevated levels of protein synthesis in senescent cells. Mechanistically, we identify a p53-dependent program in senescent cells that maintains hypusination levels of eIF5A. Finally, we demonstrate that functional eIF5A is required for synthesizing mitochondrial ribosomal proteins and monitoring the immune clearance of premalignant senescent cells in vivo. Our findings establish an important role of protein synthesis during cellular senescence and suggest a link between eIF5A, polyamine metabolism, and senescence immune surveillance.