Synthesis and structure-activity relationship analysis of 2-substituted-1,2,4-triazolo[1,5-a]pyrimidin-7-ones and their 6-carboxylate derivatives as xanthine oxidase inhibitors.

Hyperuricemia is characterised by high blood levels of uric acid, and it can degenerate into gout when monosodium urate crystals precipitate in joints and other tissues. Uric acid is produced during the catabolism of xanthine by the enzyme xanthine oxidase (XO), which is the primary therapeutic target in gout treatment. Current XO inhibitors approved to treat gout, such as allopurinol and febuxostat, suffer from serious adverse effects, creating the need for new drug molecules. Three libraries comprising 75 purine analogues were designed using a 1,2,4-triazolo[1,5-a]pyrimidine scaffold, synthesised and tested in vitro as potential XO inhibitors. The screening identified that 23 compounds exhibited better inhibitory activity than allopurinol, with 2-(4-isopropoxyphenyl)-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxylic acid being 23 times more potent. Enzyme kinetics studies and molecular docking simulations were performed on the most active compounds to identify the mechanism of action and intermolecular interactions between the active site of XO and the inhibitors. The most potent compounds exhibited a mix-type inhibition mechanism and were predicted to interact with the same amino acid residues as allopurinol. These novel purine analogues are promising hits for further new lead development among purine-like drug XO inhibitors with therapeutic potential in the treatment of hyperuricemia and associated diseases.

Bacterial Purine Nucleoside Phosphorylases from Mesophilic and Thermophilic Sources: Characterization of Their Interaction with Natural Nucleosides and Modified Arabinofuranoside Analogues.

The enzymatic synthesis of nucleoside derivatives is an important alternative to multi-step chemical methods traditionally used for this purpose. Despite several undeniable advantages of the enzymatic approach, there are a number of factors limiting its application, such as the limited substrate specificity of enzymes, the need to work at fairly low concentrations, and the physicochemical properties of substrates-for example, low solubility. This research conducted by our group is dedicated to the advantages and limitations of using purine nucleoside phosphorylases (PNPs), the main enzymes for the metabolic reutilization of purines, in the synthesis of modified nucleoside analogues. In our work, the substrate specificity of PNP from various bacterial sources (mesophilic and thermophilic) was studied, and the effect of substrate, increased temperature, and the presence of organic solvents on the conversion rate was investigated.

Chemical genetic analysis of enoxolone inhibition of C. difficile toxin production reveals adenine deaminase and ATP synthase as anti-virulence targets.

Toxins TcdA and TcdB are the main virulence factors of Clostridioides difficile, a leading cause of hospital-acquired diarrhea. Despite their importance, there is a significant knowledge gap of druggable targets for inhibiting toxin production. To address this, we screened non-antibiotic phytochemicals to identify potential chemical genetic probes to discover anti-virulence drug targets. This led to the identification of 18ß-glycyrrhetinic acid (enoxolone), a licorice metabolite, as an inhibitor of TcdA and TcdB biosynthesis. Using affinity-based proteomics, potential targets were identified as ATP synthase subunit alpha (AtpA) and adenine deaminase (Ade, which catalyzes conversion of adenine to hypoxanthine in the purine salvage pathway). To validate these targets, a multi-faceted approach was adopted. Gene silencing of ade and atpA inhibited toxin biosynthesis, while SPR and ITC molecular interaction analyses revealed direct binding of enoxolone to Ade. Metabolomics demonstrated enoxolone induced the accumulation of adenosine, while depleting hypoxanthine and ATP in C. difficile. Transcriptomics further revealed enoxolone dysregulated phosphate uptake genes, which correlated with reduced cellular phosphate levels. These findings suggest that enoxolone's cellular action is multi-targeted. Accordingly, supplementation with both hypoxanthine and triethyl phosphate (TEP), a phosphate source, was required to fully restore toxin production in the presence of enoxolone. In conclusion, through the characterization of enoxolone, we identified promising anti-virulence targets that interfere with nucleotide salvage and ATP synthesis, which may also block toxin biosynthesis.

Evolution of the biochemistry underpinning purine alkaloid metabolism in plants.

Purine alkaloids are naturally occurring nitrogenous methylated derivatives of purine nucleotide degradation products, having essential roles in medicine, food and various other aspects of our daily lives. They are generated through convergent evolution in different plant species. The pivotal reaction steps within the purine alkaloid metabolic pathways have been largely elucidated, and the convergent evolution of purine alkaloids has been substantiated through bioinformatic, biochemical and other research perspectives within S-adenosyl-ʟ-methionine-dependent N-methyltransferases. Currently, the biological and ecological roles of purine alkaloids, further refinement of the purine alkaloid metabolic pathways and the investigation of purine alkaloid adaptive evolutionary mechanisms continue to attract widespread research interest. The exploration of the purine alkaloid metabolic pathways also enhances our comprehension of the biochemical mechanism, providing insights into inter-species interactions and adaptive evolution and offering potential value in drug development and agricultural applications. Here, we review the progress of research in the distribution, metabolic pathway elucidation and regulation, evolutionary mechanism and ecological roles of purine alkaloids in plants. The opportunities and challenges involved in elucidating the biochemical basis and evolutionary mechanisms of the purine alkaloid metabolic pathways, as well as other research aspects, are also discussed. This article is part of the theme issue 'The evolution of plant meta-bolism'.

HIF-1α-HPRT1 axis promotes tumorigenesis and gefitinib resistance by enhancing purine metabolism in EGFR-mutant lung adenocarcinoma.

BACKGROUND: The mutations of oncogenic epidermal growth factor receptor (EGFR) is an important cause of lung adenocarcinoma (LUAD) malignance. It has been knowm that metabolic reprogramming is an important hallmark of malignant tumors, and purine metabolism is a key metabolic pathway for tumor progression and drug resistance, but its relationship with the EGFR-mutant LUAD is unclear. METHODS: Metabolic reprogramming was studied through capillary electrophoresis-time of flight mass spectrometry (CE-TOF/MS)-based metabolic profiling analysis. Cell proliferation in vitro was evaluated by EdU staining and cell cycle assay. Tumorigenicity in vivo was tested by subcutaneous tumor formation experiment in nude mice. The binding of hypoxia-inducible factor-1 alpha (HIF-1α) and hypoxanthine phosphoribosyltransferase 1 (HPRT1) was detected by DNA pull­down assay and Chromatin immunoprecipitation (ChIP) assays. HIF-1α, HPRT1, DNA damage and cell apoptosis related genes were examined by western blot. In addition, RNA sequencing, mass spectrometry and bioinformatics analysis were performed. RESULTS: We found that mutated EGFR (muEGFR) upregulates HPRT1 to promote purine metabolism and tumorigenesis of EGFR-mutant LUAD. Mechanistically, muEGFR increases HIF-1α expression through protein stability. Meanwhile, up-regulated HIF-1α bound to the promoter of HPRT1 and transcriptionally activates HPRT1 expression, enhancing purine metabolism to maintain rapid tumor cell proliferation in EGFR-mutant LUAD. Further, gefitinib inhibited the synthesis of purine nucleotides, and HPRT1 inhibition increased the sensitivity of gefitinib to EGFR-mutant LUAD. CONCLUSIONS: Our study reveals that muEGFR-HIF-1α-HPRT1 axis plays a key role in EGFR-mutant LUAD and provides a new strategy-inhibiting purine metabolism for treating EGFR-mutant LUAD.

Effect of low-purine diet on the serum uric acid of gout patients in different clinical subtypes: a prospective cohort study.

BACKGROUND: The pathogenic causes of primary gout include urate overproduction and/or renal or extra-renal urate underexcretion. The aim of this study was to evaluate the association of gout subtypes with the response to low-purine diet (LPD). METHODS: This is a single-center prospective clinical study. Gout patients visiting from 2019 to 2022, from Shandong Gout Clinic Center at the Affiliated Hospital of Qingdao University, China, assigned to three groups according to clinical subtypes, were enrolled and all treated with 2-week low-purine diet. General characteristics, serum uric acid (sUA) and other clinical biochemical variables before and after the diet were evaluated. RESULTS: A total of 626 gout patients (age 41.20 ± 13.41 years, male 98.0%) were included. Of these, 69 (11.0%) were overproduction type, 428 (68.37%) were underexcretion type, and 129 (20.61%) were combined type. Overall, there was a substantial decrease in sUA after a 2-week LPD (p < 0.001). In addition, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), serum alanine aminotransferase (ALT), serum aspartate aminotransferase (AST), serum triglycerides (TG), serum total cholesterol (TC), blood urea nitrogen (BUN) and serum creatinine (Scr) levels were lower than those at baseline (p < 0.05). On the other hand, there were significant differences in the reduction of sUA among different types, the rank order being overproduction type (- 88.81 ± 63.01 µmol/L) > combined type (- 65.22 ± 44.13 µmol/L) > underexcretion type (- 57.32 ± 61.19 µmol/L). After adjusting for age, BMI and baseline sUA and eGFR, there were still significant differences in the decline of serum uric acid among different types. Higher baseline sUA (95%CI - 0.285, - 0.191; p < 0.001) and BUN (95%CI - 6.751, - 0.602; p < 0.001) were correlated with greater decrease of sUA. CONCLUSIONS: Our findings support the protective role of low-purine diet on sUA levels in gout patients, especially overproduction type. Furthermore, LPD could exert a beneficial effect on gout patients' blood pressure, BMI, blood lipid, BUN and Scr levels. Trial registration Registered with ChiCTR, No. ChiCTR1900022981 at 06/05/2019.

Dose rate dependent genotoxic and metabolic effects predict onset of impaired development and mortality in Atlantic salmon (S. salar) embryos exposed to chronic gamma radiation.

Release of radionuclides to the environment from either nuclear weapon and fuel cycles or from naturally occurring radionuclides (NORM) may cause long term contamination of aquatic ecosystems and chronic exposure of living organisms to ionizing radiation, which in turn could lead to adverse effects compromising the sustainability of populations. To address the effects of chronic ionizing radiation on the development of fish, Atlantic salmon embryos were exposed from fertilization until hatching (88 days, 550 day-degree) to dose rates from 1 to 30 mGy·h-1 gamma radiation (60Co). The lowest adopted dose rate was similar to the highest doses measured in some water bodies right after the Chernobyl accident (1 mGy·h-1), however, well above current environmentally realistic scenarios (20 µGy·h-1), or the threshold assumed for significant effects on fish population (40 µGy·h-1). Dose dependent effects were observed on survival, hatching, morbidity, DNA damage, antioxidant defenses, and metabolic status. Histopathological analysis showed dose rate dependent impairment of eye and brain tissues development and establishment of epidermal mucus cell layers accompanied by increased DNA damage at doses ≥1.3 Gy (dose rates ≥1 mGy·h-1). At ≥32.8 Gy (dose rates ≥20 mGy·h-1) deformities and developmental growth defects resulted in respective 46 and 95 % pre-hatch mortality. The 10 mGy·h-1 exposure (≥ 12 Gy total dose) caused significantly increased DNA damage, impaired eye development, and both premature and delayed hatching, while no deformities or effect on survival were observed. We observed a dose rate dependent reduction from dose rate ≥ 20 mGy·h-1 (≥ 27 Gy total dose) on antioxidant SOD, catalase and glutathione reductase enzyme activities. The reduction of antioxidant enzyme activities was in line with observed developmental delay and disturbance to time of hatching. Metabolomic profiles showed a clear shift at dose rates ≥10 mGy·h-1 (≥ 12 Gy total dose) in pathways related to oxidative stress, detoxification, DNA damage and repair. Due to gamma radiation exposure, a switch of central metabolism from glycolysis, citric acid cycle and lactate production towards pentose phosphate pathway indicated a rewiring mechanism for increased production of reductive equivalents to maintain redox homeostasis at the expense of energy output and thus embryonic development.

Untargeted metabolomics analysis of the urinary metabolic signature of acute and chronic gout.

BACKGROUND: Gout is a common kind of inflammatory arthritis with metabolic disorders. However, the detailed pathogenesis of gout is complex and not fully clear. We investigated the urine metabolic profiling of gout patients by ultra-performance liquid chromatograph quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). METHOD: Urine metabolites were extracted from 26 acute gout patients, 31 chronic gout patients, and 32 healthy controls. Metabolite extracts were analyzed by UPLC-Q-TOF-MS for untargeted metabolomics. The peak area of creatinine was used to correct the content variations of urine samples for the semi-quantitative analysis. The value of variable importance in the projection (VIP) was obtained through the orthogonal partial least squares-discrimination analysis (OPLS-DA), and several differential metabolites were screened out. RESULTS: The potential metabolic markers of gout in different stages were found based on the t-test. Finally, 18 different metabolites were identified through Human Metabolome Database (HMDB) and Targeted-MS/MS. The receiver operating characteristic (ROC) curve results revealed that all the screened biomarkers exerted high accuracy and diagnostic value. Pathway analysis indicated that the significantly different metabolites were mainly involved in purine metabolism and amino acid metabolism. CONCLUSION: The identified potential biomarkers are mainly involved in purine metabolism and amino acid metabolism, which leads us to further explore the pathogenesis of gout. This will lead us to further explore the pathogenesis of gout and provide the basis and ideas for the prevention and treatment of gout.

Simultaneous determination of canonical purine metabolism using a newly developed HILIC-MS/MS in cultured cells.

Purine metabolism acts as the core role in human metabolic network. It offers purine metabolites as raw material for building blocks in cell survival and proliferation. Purine metabolites are the most abundant metabolic substrates in organisms. There are few reports to simultaneously quantify canonical purine metabolism in cells. A novel hydrophilic interaction liquid chromatography coupled with mass spectrometry (HILIC-MS/MS) method was developed to simultaneously determine purines profile in biological samples. Chromatographic separation was achieved using a HILIC (Waters Xbridge™ Amide) column. Different optimizing chromatographic conditions and mass spectrometric parameters were tested in order to provide the best separation and the lowest limit of quantification (LLOQ) values for targeted metabolites. The validation was evaluated according to the Food and Drug Administration guidelines. The limit of determination (LOD) and the LOQ values were in the range of 0.02-8.33 ng mL-1 and 0.1-24.5 ng mL-1, respectively. All calibration curves displayed good linear relationship of with excellent correlation coefficient (r) ranging from 0.9943 to 0.9999. Both intra-day and inter-day variability were below 15 %, respectively. Trueness, expressed as relative error, was always within ±15 %. In addition, no derivatization procedure and ion-pair reagents are in need. The innovated approach demonstrates high sensitivity, strong specificity, and good repeatability, making it suitable for absolute quantitative studies of canonical purine metabolism in cultured cells.

Deciphering the Impact of Nucleosides and Nucleotides on Copper Ion and Dopamine Coordination Dynamics.

The mode of coordination of copper(II) ions with dopamine (DA, L) in the binary, as well as ternary systems with Ado, AMP, ADP, and ATP (L') as second ligands, was studied with the use of experimental-potentiometric and spectroscopic (VIS, EPR, NMR, IR)-methods and computational-molecular modeling and DFT-studies. In the Cu(II)/DA system, depending on the pH value, the active centers of the ligand involved in the coordination with copper(II) ions changed from nitrogen and oxygen atoms (CuH(DA)3+, Cu(DA)2+), via nitrogen atoms (CuH2(DA)24+), to oxygen atoms at strongly alkaline pH (Cu(DA)22+). The introduction of L' into this system changed the mode of interaction of dopamine from oxygen atoms to the nitrogen atom in the hydroxocomplexes formed at high pH values. In the ternary systems, the ML'-L (non-covalent interaction) and ML'HxL, ML'L, and ML'L(OH)x species were found. In the Cu(II)/DA/AMP or ATP systems, mixed forms were formed up to a pH of around 9.0; above this pH, only Cu(II)/DA complexes occurred. In contrast to systems with AMP and ATP, ternary species with Ado and ADP occurred in the whole pH range at a high concentration, and moreover, binary complexes of Cu(II) ions with dopamine did not form in the detectable concentration.

Novel purine derivatives as selective CDK2 inhibitors with potential anticancer activities: Design, synthesis and biological evaluation.

Purine analogues were discovered to be inhibitors of CDK2, suggesting a potential therapeutic scaffold. This paper addresses the design, synthesis, and anticancer evaluation of purine analogues as kinase inhibitors. In the early stages of the investigation, the designed compounds demonstrated a promising docking score and greater protein-ligand stability in MD simulation than the standard, indicating a higher affinity against CDK2. Thus, we synthesised new purine analogues under simple and optimised reaction conditions. Among the studies under NCI-60, 5g and 5i were the most effective, with a percentage GI of 98.09 and 90 against OVCAR-4 and SNB-75, respectively, at a dose of 10 µM. Additionally, 5g and 5i demonstrated 7.80-fold and 1.54-fold greater cytotoxicity against PA-1 and MCF-7, with IC50s of 1.08 µM and 3.54 µM, respectively, compared to seliciclib (8.43 µM and 5.46 µM). In addition, 5g and 5i showed selective cytotoxicity against PA-1 and MCF-7 than normal cells, with selectivity indexes of 26.40 and 15.45, respectively, as compared to the standard (SI=3.83 and 5.91). In the kinase selectivity assay, both compounds demonstrated greater affinity against CDK2 than other kinases, with IC50 of 0.21 µM and 0.59 µM, in contrast to the standard (IC50 = 0.63 µM). Furthermore, 5g confirmed kinase inhibition in the western blot by lowering CDK2, cyclin A2, and other downstream substrates. Moreover, it triggered cell death by apoptosis and cell cycle arrest in G2/M. Taken together, 5g merits further investigation in PKPD research to discover a potential therapeutic candidate against cancer.

In situ chemoproteomic profiling reveals itaconate inhibits de novo purine biosynthesis in pathogens.

Itaconate serves as an immune-specific metabolite that regulates gene transcription and metabolism in both host and pathogens. S-itaconation is a post-translational modification that regulates immune response; however, its antimicrobial mechanism under the physiological condition remains unclear. Here, we apply a bioorthogonal itaconate probe to perform global profiling of S-itaconation in living pathogens, including S. Typhimurium, S. aureus, and P. aeruginosa. Some functional enzymes are covalently modified by itaconate, including those involved in the de novo purine biosynthesis pathway. Further biochemical studies demonstrate that itaconate suppresses this specific pathway to limit Salmonella growth by inhibiting the initiator purF to lower de novo purine biosynthesis and simultaneously targeting the guaABC cluster to block the salvage route. Our chemoproteomic study provides a global portrait of S-itaconation in multiple pathogens and offers a valuable resource for finding susceptible targets to combat drug-resistant pathogens in the future.

Discovery of a potent, Highly selective, and In vivo anti-inflammatory Efficacious, P2Y6R antagonist with a novel quinoline-pyrazole scaffold.

The P2Y6 receptor (P2Y6R), as a crucial member of the purine family, is a potential therapeutic target for the treatment of intestinal inflammation, tracheal inflammation and diabetes. We first discovered the hit compound (5a, IC50 = 168.5 nM against P2Y6R) through our in-house library screening. Then, further medicinal chemistry efforts were made to optimize compound 5a, and a potent P2Y6R antagonist (5 ab) with better antagonistic activity (IC50 = 19.6 nM) was obtained. The molecular docking, CETSA, SPR and pull-down results indicated that compound 5 ab displayed strong binding to P2Y6R. Also, compound 5 ab possessed high selectivity and satisfying oral bioactivity and pharmacokinetic profiles. In experiments with LPS-induced acute lung injury in mice, after treatment with compound 5 ab, the level of inflammatory factors IL-6, TNF-α and IL-ß were considerably decreased, the infiltration of immune cells was decreased. Further exploration revealed that 5 ab inhibited the expression and release of chemokines in lung tissue, suppressing the activation of the NLRP3 inflammasome. Compound 5 ab had certain anti-inflammatory abilities in vivo and in vitro. These results demonstrate that compound 5 ab is a potential P2Y6R antagonist and is worthy of further study.

Harnessing nucleotide metabolism and immunity in cancer: a tumour microenvironment perspective.

The tumour microenvironment (TME) is a dynamic nexus where cancer cell metabolism and the immune system intricately converge, with nucleotide metabolism (NM) playing a pivotal role. This review explores the critical function of NM in cancer cell proliferation and its profound influence on the TME and immune landscape. NM is essential for DNA and RNA synthesis and is markedly upregulated in cancer cells to meet the demands of rapid growth. This metabolic rewiring fuels cancer progression, but also shapes the TME, impacting the function and viability of immune cells. The altered nucleotide milieu in the TME can suppress immune response, aiding cancer cell evasion from immune surveillance. Drug discoveries in the field of NM have revealed different therapeutic strategies, including inhibitors of nucleotide synthesis and drugs targeting salvage pathways, which are discussed thoroughly in this review. Furthermore, the emerging strategy of combining NM-targeted therapies with immunotherapies is emphasised, particularly their effect on sensitising tumours to immune checkpoint inhibitors and enhancing overall treatment efficacy. The Human Genome Project paved the way for personalised medicine, countering the established 'one size fits all' approach to cancer treatment. Advances in understanding the TME and NM have spurred interest in personalised therapeutic strategies. This review highlights the potential of leveraging individual tumour metabolic profiles to guide treatment selection, aiming to optimise efficacy and minimise adverse effects. The strategic importance of targeting NM in cancer therapy and its synergistic potential with immunotherapies offers a path towards more effective and personalised cancer treatments.

Empowering probiotics with high xanthine transport for effective hyperuricemia management.

Hyperuricemia, a prevalent metabolic disorder, poses a susceptibility to various complications. The conventional pharmacotherapeutic approaches for hyperuricemia often entail notable adverse effects, posing substantial clinical challenges. Hence, the imperative lies in the development of novel, safe and effective strategies for preventing and treating hyperuricemia. Here, we developed a probiotic Escherichia coli Nissle 1917 strain, designated as YES301, which contains a rationally designed xanthine importer XanQ, enabling efficient uptake of xanthine and hypoxanthine, consequently leading to reduced serum uric acid concentrations and amelioration of renal impairments in a murine model of hyperuricemia. Importantly, YES301 exhibited a therapeutic efficacy comparable to allopurinol, a conventional uric acid-lowering agent, and manifesting fewer adverse effects and enhanced biosafety. These findings highlight the promising potential of engineered probiotics in the management of hyperuricemia through reducing intestinal purine levels.

circE2F1-encoded peptide inhibits circadian machinery essential for nucleotide biosynthesis and tumor progression via repressing SPIB/E2F1 axis.

Circadian clock dominates a variety of biological activities, while its roles and regulatory mechanisms in neuroblastoma (NB), a pediatric extracranial malignancy, still remain largely elusive. Herein, through comprehensive analyses of public datasets, E2F transcription factor 1 (E2F1) and its circular RNA (circE2F1)-encoded 99-amino acid peptide (E2F1-99aa) were identified as vital regulators of circadian machinery essential for purine and pyrimidine biosynthesis during NB progression. Mechanistically, through interaction with Spi-B transcription factor (SPIB), E2F1 was transactivated to up-regulate circadian machinery genes (CRY1 and TIMELESS), resulting in relief of CLOCK/BMAL1-repressed transcription of enzymes (DHODH, PAICS, or PPAT) essential for de novo purine and pyrimidine biosynthesis. The biogenesis of circE2F1 was repressed by eukaryotic translation initiation factor 4A3 (EIF4A3), while E2F1-99aa or its truncated peptide competitively bound to SPIB, leading to decrease in SPIB-E2F1 interaction, circadian machinery and nucleotide biosynthetic gene expression, purine or pyrimidine biosynthesis, tumorigenesis, and aggresiveness of NB cells. In clinical NB cases, high EIF4A3, E2F1 or SPIB expression was correlated with low survival possibility of patients, while lower circE2F1 or E2F1-99aa levels were associated with advanced stages and tumor progression. These results indicate that circE2F1-encoded peptide inhibits circadian machinery essential for nucleotide biosynthesis and tumor progression via repressing SPIB/E2F1 axis.

Bacterial cross-feeding can promote gene retention by lowering gene expression costs.

Gene loss is expected in microbial communities when the benefit of obtaining a biosynthetic precursor from a neighbor via cross-feeding outweighs the cost of retaining a biosynthetic gene. However, gene cost primarily comes from expression, and many biosynthetic genes are only expressed when needed. Thus, one can conversely expect cross-feeding to repress biosynthetic gene expression and promote gene retention by lowering gene cost. Here we examined long-term bacterial cocultures pairing Escherichia coli and Rhodopseudomonas palustris for evidence of gene loss or retention in response to cross-feeding of non-essential adenine. Although R. palustris continued to externalize adenine in long-term cultures, E. coli did not accumulate mutations in purine synthesis genes, even after 700 generations. E. coli purine synthesis gene expression was low in coculture, suggesting that gene repression removed selective pressure for gene loss. In support of this explanation, R. palustris also had low transcript levels for iron-scavenging siderophore genes in coculture, likely because E. coli facilitated iron acquisition by R. palustris. R. palustris siderophore gene mutations were correspondingly rare in long-term cocultures but were prevalent in monocultures where transcript levels were high. Our data suggests that cross-feeding does not always drive gene loss, but can instead promote gene retention by repressing costly expression.

Engaging natural regulatory myeloid cells to restrict T-cell hyperactivation-induced liver inflammation via extracellular vesicle-mediated purine metabolism regulation.

Rationale: Dysregulated T-cell immune response-mediated inflammation plays critical roles in the pathology of diverse liver diseases, but the underlying mechanism of liver immune homeostasis control and the specific therapies for limiting T-cell overactivation remain unclear. Methods: The metabolic changes in concanavalin A (ConA) mice and autoimmune hepatitis (AIH) patients and their associations with liver injury were analyzed. The expression of purine catabolism nucleases (e.g., CD39 and CD73) on liver cells and immune cells was assessed. The effects of MCregs and their extracellular vesicles (EVs) on CD4+ T-cell overactivation and the underlying mechanism were also explored. Results: Our findings revealed significant alterations in purine metabolism in ConA mice and AIH patients, which correlated with liver injury severity and therapeutic response. CD39 and CD73 were markedly upregulated on CD11b+Gr-1+ MCs under liver injury conditions. The naturally expanded CD39+CD73+Gr-1highCD11b+ MCreg subset during early liver injury effectively suppressed CD4+ T-cell hyperactivation and liver injury both in vitro and in vivo. Mechanistically, MCregs released CD73high EVs, which converted extracellular AMP to immunosuppressive metabolites (e.g., adenosine and inosine), activating the cAMP pathway and inhibiting glycolysis and cytokine secretion in activated CD4+ T cells. Conclusions: This study provides insights into the mechanism controlling immune homeostasis during the early liver injury phase and highlights that MCreg or MCreg-EV therapy may be a specific strategy for preventing diverse liver diseases induced by T-cell overactivation.

Adipocyte-secreted PRELP promotes adipocyte differentiation and adipose tissue fibrosis by binding with p75NTR to activate FAK/MAPK signaling.

Adipocyte-secreted factors intricately regulate adipose tissue function, and the underlying molecular mechanisms are only partially understood. However, the function of PRELP, which is a key component of the extracellular matrix (ECM) in adipocytes, remains largely unknown. In this study, we demonstrate that PRELP was upregulated in both obese humans and mice, which exhibited a positive correlation with metabolic disorders. PRELP knockout could resist HFD-induced obesity and inhibit adipocyte differentiation. PRELP knockout improved glucose tolerance, insulin sensitivity and alleviated adipose tissue fibrosis. Mechanistically, PRELP was secreted into the ECM and bound to the extracellular domain of its receptor p75NTR in adipocytes, which further activated the FAK/MAPK (JNK, p38 MAPK, ERK1/2) signaling pathway, promoting adipocyte differentiation and exacerbating adipocyte fibrosis. Adipocyte PRELP plays a pivotal role in regulating obesity and adipose tissue fibrosis through an autocrine manner, and PRELP may be a therapeutic target for obesity and its related metabolic disorders.

Pentachlorophenol Exposure Delays the Recovery of Colitis in Association With Altered Gut Microbiota and Purine Metabolism.

Pentachlorophenol (PCP) was used widely as preservative and biocide and has been banned due to with various harmful effects, such as carcinogenicity and teratogenicity. However, the effects of PCP on colitis induced by dextrose sodium sulfate (DSS) remain largely unknown. Serum metabolomics and gut microbiota were investigated to elucidate the underlying mechanisms. Exposure to 20 µg/L PCP aggravated DSS-induced body weight loss, colon shortening, severe histological injuries, and upregulation of TNFα, iNOS, IL-1ß, and IL-6. Serum metabolomics showed that both DSS and PCP could significantly disrupted tryptophan metabolism in normal mice. Interestingly, PCP exposure intensified the disturbance in purine metabolism but not tryptophan metabolism caused by DSS. Quantitative analysis of tryptophan and metabolites further confirmed that PCP exposure significantly increased the serum contents of serotonin, adenine, guanine, guanosine, inosine monophosphate (IMP), inosine, and hypoxanthine in DSS-treated mice. The overall gut microbial community was significantly modified by PCP and DSS treatment alone. Rikenellaceae_RC9_Gut_group, Colidextribacter, and Desulfovibrio were more abundant in colitis mice following PCP exposure. Further integrative analysis of differential bacteria and purine metabolites highlighted a significant correlation between Desulfovibrio and several purine metabolites, including guanine, guanosine, hypoxanthine, IMP, and inosine. Adenosine ribonucleotides de novo biosynthesis, inosine-5'-phosphate biosynthesis I, and urate biosynthesis/inosine 5'-phosphate degradation pathways were depleted in colitis mice upon PCP treatment. Taken together, PCP exposure delayed the recovery of colitis induced by DSS in association with altered gut microbiota and serum metabolites, which were enriched in tryptophan and purine metabolism.