Evaluation of purine-nucleoside degrading ability and in vivo uric acid lowering of Streptococcus thermophilus IDCC 2201, a novel antiuricemia strain.

This study evaluated 15 lactic acid bacteria with a focus on their ability to degrade inosine and hypo-xanthine-which are the intermediates in purine metabolism-for the management of hyperuricemia and gout. After a preliminary screening based on HPLC, Lactiplantibacillus plantarum CR1 and Lactiplantibacillus pentosus GZ1 were found to have the highest nucleoside degrading rates, and they were therefore selected for further characterization. S. thermophilus IDCC 2201, which possessed the hpt gene encoding hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and exhibited purine degradation, was also selected for further characterization. These three selected strains were examined in terms of their probiotic effect on lowering serum uric acid in a Sprague-Dawley (SD) rat model of potassium oxonate (PO)-induced hyperuricemia. Among these three strains, the level of serum uric acid was most reduced by S. thermophilus IDCC 2201 (p < 0.05). Further, analysis of the microbiome showed that administration of S. thermophlilus IDCC 2201 led to a significant difference in gut microbiota composition compared to that in the group administered with PO-induced hyperuricemia. Moreover, intestinal short-chain fatty acids (SCFAs) were found to be significantly increased. Altogether, the results of this work indicate that S. thermophilus IDCC 2201 lowers uric acid levels by degrading purine-nucleosides and also restores intestinal flora and SCFAs, ultimately suggesting that S. thermophilus IDCC 2201 is a promising candidate for use as an adjuvant treatment in patients with hyperuricemia.

Development and comparison of parallel reaction monitoring and data-independent acquisition methods for quantitative analysis of hydrophilic compounds in white tea.

In the present work, parallel reaction monitoring (PRM) and data-independent acquisition (DIA) methods were developed for the accurate quantitation of amino acids, alkaloids nucleosides and nucleotides in tea. The quality peaks were significantly enhanced by optimizing the LC elution procedure, HCD voltage, MS resolution, and scanning event. Both methods were validated with good liner linearity (0.004-200 µg/mL), LODs (0.001-0.309 µg/mL for PRM and 0.001-0.564 µg/mL for DIA). Applied to white tea sample, the contents of these hydrophilic compounds were range from 34,655.39 to 70,586.14 mg/kg, and caffeine (32,529.02 mg/kg) and theanine (5483.46 mg/kg) were determined as the most abundant ones. Based on the quantitation data set, the white tea samples from Puer, Lincang and Xishuangbanna were clearly discriminated using multivariate data analysis. The results of the present works show that PRM and DIA have great potential in quantitative analysis of multiple hydrophilic compounds in food samples.

Identification of potentially suitable areas for nucleosides of Pinellia Ternata (Thunb.) Breit using ecological niche modeling.

Pinellia ternata, a traditional Chinese medicine, is well-renowned for its effectiveness in treating sickness such as coughs with excessive phlegm, vomiting, and nausea. The nucleoside components of P. ternata have been shown to have antitumor activity. Identifying potential growth areas of high-quality P. ternata based on the content of five nucleoside components and the identification of climatic features suitable for the growth of P. ternata will help to conserve P. ternata resources with targeted bioactive compounds. Using high-performance liquid chromatography (HPLC), we determined five nucleoside components, uridine, guanosine, adenosine, inosine, and thymidine, at 27 sampling points of P. ternata collected from 21 municipalities of 11 provinces in China. We used ecological niche modeling to identify the major environmental factors associated with the high metabolite content of P. ternata, including precipitation of the warmest quarter, annual mean temperature, annual precipitation, and isothermality. Areas with high suitability for the five nucleosides were found in Hebei, Shandong, Shanxi, Gansu, Sichuan, Guizhou, and Hubei Provinces. Under the RCP 2.6, RCP 4.5, and RCP 8.5 scenarios, the areas with a suitable distribution decreased and some areas with high suitability became areas with low suitability. Overall, our findings advance our knowledge of the ecological impacts of climate change and provide a valuable reference for conserving and sustainably developing high-quality P. ternata resources in the future.

A Preliminary Survey of Transfer RNA Modifications and Modifying Enzymes of the Tropical Plant Cocos nucifera L.

The coconut (Cocos nucifera L.) is a commercial crop widely distributed among coastal tropical regions. It provides millions of farmers with food, fuel, cosmetics, folk medicine, and building materials. Among these, oil and palm sugar are representative extracts. However, this unique living species of Cocos has only been preliminarily studied at molecular levels. Benefiting from the genomic sequence data published in 2017 and 2021, we investigated the transfer RNA (tRNA) modifications and modifying enzymes of the coconut in this survey. An extraction method for the tRNA pool from coconut flesh was built. In total, 33 species of modified nucleosides and 66 homologous genes of modifying enzymes were confirmed using a nucleoside analysis using high-performance liquid chromatography combined with high-resolution mass spectrometry (HPLC-HRMS) and homologous protein sequence alignment. The positions of tRNA modifications, including pseudouridines, were preliminarily mapped using a oligonucleotide analysis, and the features of their modifying enzymes were summarized. Interestingly, we found that the gene encoding the modifying enzyme of 2'-O-ribosyladenosine at the 64th position of tRNA (Ar(p)64) was uniquely overexpressed under high-salinity stress. In contrast, most other tRNA-modifying enzymes were downregulated with mining transcriptomic sequencing data. According to previous physiological studies of Ar(p)64, the coconut appears to enhance the quality control of the translation process when subjected to high-salinity stress. We hope this survey can help advance research on tRNA modification and scientific studies of the coconut, as well as thinking of the safety and nutritional value of naturally modified nucleosides.

[Quality evaluation of Galli Gigerii Endothelium Corneum based on HPLC fingerprints and content determination of nucleosides].

Galli Gigerii Endothelium Corneum(GGEC), the dried gizzard membrane of Gallus gallus domesticus is a Chinese medicinal material commonly used for digestion. However, due to the particularity of texture and composition, its active ingre-dients have not been clarified so far, and there is also a lack of quality evaluation indicators. In this study, UPLC-Q-TOF-MS was used to analyze the chemical components from the water extract of GGEC, and ten nucleosides were identified for the first time. HPLC fingerprints of the water extracts of GGEC were established and the content of seven nucleosides was determined. The fingerprint similarities of 40 batches of GGEC samples ranged from 0.765 to 0.959, indicating that there were great differences among the GGEC products processed with different methods. In addition, SPSS 22.0 and SIMCA 14.1 were used for hierarchical cluster analysis(HCA) and principal component analysis(PCA) on the 19 common peaks of the HPLC fingerprints of GGEC, and the 40 batches of samples were divided into three categories: raw GGEC, fried GGEC and vinegar-processed GGEC. Eight differential components in GGEC were marked by orthogonal partial least squares discrimination analysis(OPLS-DA), two of which were adenine and thymine. The results of content determination showed that the total content of the seven nucleosides in raw GGEC, fried GGEC and vinegar-processed GGEC were 182.5-416.8, 205.3-368.7, and 194.2-283.0 µg·g~(-1), respectively. There were significant differences in the content of hypoxanthine, thymine and thymidine among the GGEC products processed with different methods(P<0.05), which were graded in the order of fried GGEC>vinegar-processed GGEC>raw GGEC. This suggested that the content of hypoxanthine, thymine and thymidine tended to increase during the frying process, and the variation range might be related to the degree of heat exposure. The established methods in this study were simple and reproducible, and could be used for qualitative and quantitative analysis of GGEC and its processed pro-ducts. This study also provided reference for the establishment of quality standards of GGEC with chemical components as control index.

Single-exonuclease nanocircuits reveal the RNA degradation dynamics of PNPase and demonstrate potential for RNA sequencing.

The degradation process of RNA is decisive in guaranteeing high-fidelity translation of genetic information in living organisms. However, visualizing the single-base degradation process in real time and deciphering the degradation mechanism at the single-enzyme level remain formidable challenges. Here, we present a reliable in-situ single-PNPase-molecule dynamic electrical detector based on silicon nanowire field-effect transistors with ultra-high temporal resolution. These devices are capable of realizing real-time and label-free monitoring of RNA analog degradation with single-base resolution, including RNA analog binding, single-nucleotide hydrolysis, and single-base movement. We discover a binding event of the enzyme (near the active site) with the nucleoside, offering a further understanding of the RNA degradation mechanism. Relying on systematic analyses of independent reads, approximately 80% accuracy in RNA nucleoside sequencing is achieved in a single testing process. This proof-of-concept sets up a Complementary Metal Oxide Semiconductor (CMOS)-compatible playground for the development of high-throughput detection technologies toward mechanistic exploration and single-molecule sequencing.

Xanthine dehydrogenase rewires metabolism and the survival of nutrient deprived lung adenocarcinoma cells by facilitating UPR and autophagic degradation.

Xanthine dehydrogenase (XDH) is the rate-limiting enzyme in purine catabolism by converting hypoxanthine to xanthine and xanthine to uric acid. The altered expression and activity of XDH are associated with the development and prognosis of multiple types of cancer, while its role in lung adenocarcinoma (LUAD) remains unknown. Herein, we demonstrated that XDH was highly expressed in LUAD and was significantly correlated with poor prognosis. Though inhibition of XDH displayed moderate effect on the viability of LUAD cells cultured in the complete medium, it significantly attenuated the survival of starved cells. Similar results were obtained in XDH-knockout cells. Nucleosides supplementation rescued the survival of starved LUAD cells upon XDH inhibition, while inhibition of purine nucleoside phosphorylase abrogated the process, indicating that nucleoside degradation is required for the XDH-mediated survival of LUAD cells. Accordingly, metabolic flux revealed that ribose derived from nucleoside fueled key carbon metabolic pathways to sustain the survival of starved LUAD cells. Mechanistically, down-regulation of XDH suppressed unfolded protein response (UPR) and autophagic flux in starved LUAD cells. Inhibition of XDH decreased the level of amino acids produced by autophagic degradation, which was accompanied with down-regulation of mTORC1 signaling. Supplementation of amino acids including glutamine or glutamate rescued the survival of starved LUAD cells upon knockout or inhibition of XDH. Finally, XDH inhibitors potentiated the anti-cancer activity of 2-deoxy-D-glucose that induced UPR and/or autophagy in vitro and in vivo. In summary, XDH plays a crucial role in the survival of starved LUAD cells and targeting XDH may improve the efficacy of drugs that induce UPR and autophagy in the therapy of LUAD.

Supplementary nucleosides improve the performance through enhanced enzyme activity, intestinal development and transporter genes in broiler chickens.

A biological experiment was carried out to evaluate dietary nucleoside supplementation on growth performance, digestive enzymes activities, immune response, and intestinal transporter genes expression in broiler chicken. A total of 720 newly hatched CARIBRO VISHAL broiler chicks were weighed and randomly divided into eight groups with nine replicates. The dietary treatments were as follows: Group I: diet without antibiotic supplement (control), group II: diet supplemented with antibiotic (positive control), groups III, IV and V: diet supplemented with combination of nucleosides at 0.5, 1.0 and 1.5 g/kg feed, respectively, for 14 days, groups VI, VII and VIII: diet supplemented with nucleosides at 0.5, 1.0 and 1.5 g/kg feed, respectively, for 21 days. The combination of nucleosides (equal proportion (1:1:1:1) adenosine, guanosine, cytosine, and uridine with 99% purity) were used in the study. Body weight was significantly higher in the birds fed diets containing antibiotics and 1.5 g/kg nucleosides fed groups. The supplementation had positive effect on the activity of amylase and lipase enzymes and the absorptive surface (villi length). It could be concluded that, the dietary supplementation of nucleosides improved the performance of broilers with better cellular and humoral immunity than control. The study further confirmed that nucleosides supplementation improved gut development and could be an alternative to antibiotic growth promoters in broiler production.

Chemical profiling and quantification of Yihuang decoction by high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and a diode array detector.

Yihuang decoction (YHD) is one of the most famous formulas in tradition Chinese medicine (TCM) and has been clinically used for treatment of vaginitis, pelvic inflammation and other gynecological diseases for hundreds of years. However, its chemical composition remains unclear. In this study, high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS) was employed for its chemical profiling investigation. As a result, 90 components were chemically defined, including 23 alkaloids, 14 organic acids, 3 phenylethanoid glycosides, 4 iridoid glycosides, 5 terpenoid lactones, 10 flavonoids, 8 nucleobases and nucleosides, 12 amino acids, and 11 other compounds. In addition, 8 representative compounds (acteoside, allantoin, berberine, 4-O-feruloylquinic acid, 5-O-feruloylquinic acid, gallic acid, geniposidic acid, and phellodendrine) were simultaneously determined in 10 batches of YHD samples by HPLC with a diode array detector (HPLC-DAD). For all the analytes, their calibration curves showed good linearity (R2 >0.9990) within the test ranges. RSDs of precision, repeatability and stability test were all below 3.50%. The overall recoveries ranged from 93.63% to 105.02%, with RSDs less than 3.50%. This study is supposed to exhibit a comprehensive chemical profiling of YHD and to provide some strong basis for quality control and even for action mechanism of this ancient classical prescription.

Nucleoside Triphosphate Diphosphohydrolase 1 Exhibits Enzymatic Activity toward Tenofovir Diphosphate.

Tenofovir (TFV; prescribed as TFV disoproxil fumarate and TFV alafenamide prodrugs) is currently used for HIV prevention and treatment. TFV must be phosphorylated twice into TFV-diphosphate (TFV-DP) to become pharmacologically active. Previously, we reported heterogeneity in TFV-DP distribution in colorectal tissue (a putative site of HIV infection) sections collected from research participants receiving a TFV-containing enema. This observed heterogeneity is likely multifactorial. Of note, TFV-DP is structurally similar to ATP. It is known that nucleotidases such as nucleoside triphosphate diphosphohydrolases (NTPDases) dephosphorylate ATP. Thus, it was hypothesized that NTPDase-mediated dephosphorylation plays a role in regulating TFV-DP levels in colorectal tissue. To test this hypothesis, recombinant NTPDase proteins (NTPDase 1, 3, 4, 5, 6, and 8) were incubated, individually, with TFV-DP to determine their abilities to dephosphorylate TFV-DP in vitro. Following incubations, TFV-DP dephosphorylation was determined using both malachite green phosphate assays and ultrahigh-performance liquid chromatography tandem mass spectrometry. From these, NTPDase 1 exhibited the highest activity toward TFV-DP. Further, enzyme kinetic analysis revealed Michaelis-Menten kinetics for NTPDase 1-mediated TFV-DP dephosphorylation. Next, immunoblot analyses were conducted to confirm the expression of NTPDase 1 protein in human colorectal tissue. Liquid chromatography coupled to mass spectrometry proteomics analysis was used to measure the relative abundance of NTPDases in human colorectal tissue among healthy adult individuals (n = 4). These analyses confirmed the high abundance of NTPDase 1 in human colorectal tissue. Taken together, results suggest that NTPDase 1 may contribute to the regulation of TFV-DP levels. The above data provide important insights into the dephosphorylation of TFV-DP. SIGNIFICANCE STATEMENT: Nucleoside triphosphate diphosphohydrolases (NTPDases) that are involved in enzymatic ATP dephosphorylation may contribute to tenofovir-diphosphate (TFV-DP) dephosphorylation, leading to its inactivation. In this study, the NTPDases responsible for TFV-DP dephosphorylation in vitro and their expression in human colorectal tissue were investigated. Through this work, it was demonstrated that NTPDase 1 has the highest activity toward TFV-DP dephosphorylation, and it was abundant in human colorectal tissue. Importantly, these studies will increase our understanding of TFV-DP disposition.

Quantitative multicomponent analysis of a single marker-based simultaneous determination and quality assessment of nucleoside analogs from Qi Zhi capsules.

Qi Zhi capsule (QZC) is approved by the State Drug Administration of China. The QZC consists of nine crude drugs, including astragalus, leeches, ground beetles, curcuma zedoary, hawthorn, semen cassiae, rhizoma sparganii, polygonum multiflorum, and peach kernel, of which leeches and ground beetles are Traditional Chinese Medicine of animal origin. Nucleosides are animal substances with pharmacological effects that are easy to extract and quantify. Different nucleoside analogs in distinct animal-based formulations can be used to characterize animal-based medicines. However, the quality control of a single indicator does not reflect the overall quality of Chinese medicine. Here, we developed a method to simultaneously determine the nucleoside analogs uracil, xanthine, hypoxanthine, uridine, guanine, and uric acid in QZCs using high-performance liquid chromatography. Hypoxanthine was used as an internal reference to determine relative correction factors for the other five components. The six components were determined in ten different batches of QZCs. There was no significant difference between the quantitative multicomponent analysis of a single marker and the external standard method. The relative standard deviation of total nucleosides analogs of 10 batches of samples was 7%. This method can be applied to simultaneously determine multiple active components in QZCs and other nucleoside analog drugs, enabling multi-indicator quality control.

Quality evaluation of Galli Gigerii Endothelium Corneum based on HPLC fingerprints and content determination of nucleosides / 中国中药杂志

Galli Gigerii Endothelium Corneum(GGEC), the dried gizzard membrane of Gallus gallus domesticus is a Chinese medicinal material commonly used for digestion. However, due to the particularity of texture and composition, its active ingre-dients have not been clarified so far, and there is also a lack of quality evaluation indicators. In this study, UPLC-Q-TOF-MS was used to analyze the chemical components from the water extract of GGEC, and ten nucleosides were identified for the first time. HPLC fingerprints of the water extracts of GGEC were established and the content of seven nucleosides was determined. The fingerprint similarities of 40 batches of GGEC samples ranged from 0.765 to 0.959, indicating that there were great differences among the GGEC products processed with different methods. In addition, SPSS 22.0 and SIMCA 14.1 were used for hierarchical cluster analysis(HCA) and principal component analysis(PCA) on the 19 common peaks of the HPLC fingerprints of GGEC, and the 40 batches of samples were divided into three categories: raw GGEC, fried GGEC and vinegar-processed GGEC. Eight differential components in GGEC were marked by orthogonal partial least squares discrimination analysis(OPLS-DA), two of which were adenine and thymine. The results of content determination showed that the total content of the seven nucleosides in raw GGEC, fried GGEC and vinegar-processed GGEC were 182.5-416.8, 205.3-368.7, and 194.2-283.0 μg·g~(-1), respectively. There were significant differences in the content of hypoxanthine, thymine and thymidine among the GGEC products processed with different methods(P<0.05), which were graded in the order of fried GGEC>vinegar-processed GGEC>raw GGEC. This suggested that the content of hypoxanthine, thymine and thymidine tended to increase during the frying process, and the variation range might be related to the degree of heat exposure. The established methods in this study were simple and reproducible, and could be used for qualitative and quantitative analysis of GGEC and its processed pro-ducts. This study also provided reference for the establishment of quality standards of GGEC with chemical components as control index.

Antimicrobial secondary metabolites from an endophytic fungus Aspergillus polyporicola.

Two new nucleoside derivatives, kipukasins O (1) and P (2), one new cyclohexenone derivative, arthropsadiol D (5), and one new natural product, (+)-2,5-dimethyl-3(2H)-benzofuranone (6), together with eleven known compounds (3, 4, 7-15), were obtained from the culture broth of the endophytic fungus Aspergillus polyporicola R2 isolated from the roots of Synsepalum dulcificum. Among them, the absolute configuration of compound 5 was determined by quantum chemical calculations of NMR chemical shifts and ECD spectrum. The antimicrobial activities of these compounds were evaluated. Compound 11 exhibited obvious inhibitory activity against MRSA, Staphylococcus aureus, Salmonella typhimurium, Botrytis cinerea, and Fusarium graminearum with MIC values of 4, 4, 4, 32, and 16 µg/mL, respectively. Compound 12 exhibited antibacterial activity against S. typhimurium and MRSA with MIC values of 4 and 16 µg/mL. Compound 6 exhibited antifungal activity against F. graminearum with MIC value of 32 µg/mL.

A review of traditional and current processing methods used to decrease the toxicity of the rhizome of Pinellia ternata in traditional Chinese medicine.

ETHNOPHARMACOLOGICAL RELEVANCE: The rhizome of Pinellia ternata (Thunb.) Breit, called Pinelliae Rhizoma (PR) and Banxia in Chinese, is a well-known traditional Chinese medicine (TCM) with the functions of "removing dampness-phlegm" and "downbear counterflow and check vomiting". PR has potential toxic effects that can be detoxified by Fuzhi processing (repeated processing using one or multiple adjuvants) with specific adjuvants. AIM OF THE STUDY: This paper aims to provide a summary of traditional and current processing methods used to detoxify PR. MATERIALS AND METHODS: The available references of the processing methods of PR from the classic books of Materia Medica, literature, online databases and masters or doctoral theses are collected and summarized. We also discussed the possible processing mechanisms of how we can achieve a safer and effective application of PR via these processing methods. RESULTS: PR cannot be administered orally before processing. PR contains nucleoside alkaloids, cerebrosides, fatty acids, lectin, polysaccharides, and calcium oxalate crystals. To date, although the active substances of PR are still unclear, the toxic components are almost completely clarified as needle-like calcium oxalate crystals (NCOCs) and lectin proteins. Furthermore, the toxic effects of PR include causing death in animals, inflammation, conjunctival irritation, pregnancy toxicity, teratogenicity, visceral toxicity, aphonia and vomiting. From ancient times to now, Fuzhi methods have remained the predominant method for PR processing, and the main adjuvants used are ginger juice, alum, licorice and lime. In addition, detoxification mechanisms are related to removing or damaging the NCOC and lectin in PR based on processing with adjuvants. Currently, Fuzhi processing has been greatly improved, and novel processing technologies with novel adjuvants have been used for PR processing. However, there are still some flaws in PR processing, which should be urgently solved in the future, and clarifying the characteristic bioactive compounds in PR corresponding to its function or effects is the most important step for PR processing. CONCLUSION: Our present paper reviewed the previous literature regarding all aspects of the processing of PR, and this paper will be helpful for achieving a safer and effective application of PR and its processed products and will also be beneficial for the further optimization of processing technology and clinical medication safety of PR.

High-dose adenosine versus saline-induced cardioplegic arrest in coronary artery bypass grafting: A randomized double-blind clinical feasibility trial.

BACKGROUND AND OBJECTIVE: In this clinical trial, we evaluated if a short-acting nucleoside, adenosine, as a high-dose bolus injection with blood cardioplegia induces faster arrest and provides better myocardial performance in patients after bypass surgery for coronary artery disease. METHODS: Forty-three patients scheduled for elective or urgent coronary artery bypass grafting were prospectively recruited in two-arm 1:1 randomized parallel groups to either receive 20 mg of adenosine (in 21 patients) or saline (in 22 patients) into the aortic root during the first potassium-enriched blood cardioplegia infusion. The main outcomes of the study were ventricular myocardial performance measured with cardiac index, right ventricular stroke work index, and left ventricular stroke work index at predefined time points and time to asystole after a single bolus injection of adenosine. Conventional myocardial biomarkers were compared between the two groups at predefined time points as secondary endpoints. Electrocardiographic data and other ad hoc clinical outcomes were compared between the groups. RESULTS: Compared with saline, adenosine reduced the time to asystole (68 (95% confidence interval (95% CI) = 37-100) versus 150 (95% CI = 100-210) seconds, p = 0.005). With myocardial performance, the results were inconclusive, since right ventricular stroke work index recovered better in the adenosine group (p = 0.008), but there were no significant overall differences in cardiac index and left ventricular stroke work index between the groups. Only the post-cardiopulmonary bypass cardiac index was better in the adenosine group (2.3 (95% CI = 2.2-2.5) versus 2.1 (95% CI = 1.9-2.2) L/min/m2, p = 0.016). There were no significant differences between the groups in cardiac biomarker values. CONCLUSIONS: A high dose adenosine bolus at the beginning of the first cardioplegia infusion resulted in significantly faster asystole in coronary artery bypass grafting patients but enhanced only partially the ventricular performance.EudraCT number: 2014-001382-26. https://www.clinicaltrialsregister.eu/ctr-search/trial/2014-001382-26/FI.

2-Selenouridine, a Modified Nucleoside of Bacterial tRNAs, Its Reactivity in the Presence of Oxidizing and Reducing Reagents.

The 5-substituted 2-selenouridines are natural components of the bacterial tRNA epitranscriptome. Because selenium-containing biomolecules are redox-active entities, the oxidation susceptibility of 2-selenouridine (Se2U) was studied in the presence of hydrogen peroxide under various conditions and compared with previously reported data for 2-thiouridine (S2U). It was found that Se2U is more susceptible to oxidation and converted in the first step to the corresponding diselenide (Se2U)2, an unstable intermediate that decomposes to uridine and selenium. The reversibility of the oxidized state of Se2U was demonstrated by the efficient reduction of (Se2U)2 to Se2U in the presence of common reducing agents. Thus, the 2-selenouridine component of tRNA may have antioxidant potential in cells because of its ability to react with both cellular ROS components and reducing agents. Interestingly, in the course of the reactions studied, we found that (Se2U)2 reacts with Se2U to form new 'oligomeric nucleosides' as linear and cyclic byproducts.

[Research progress on activities and mechanisms of anti-hepatitis B virus drugs].

Hepatitis B virus(HBV) is the pathogen causing hepatitis B, which is characterized by strong infectivity, high incidence, and widespread prevalence and has seriously threatened human health and affected their quality of life. Anti-HBV drugs in western medicine mainly include nucleosides(nucleic acids) and interferons, among which nucleosides(nucleic acids) are used more often. Due to the easy development of drug resistance, their therapeutic effects are not remarkable. Interferons can easily cause serious adverse reactions such as liver injury. Anti-HBV drugs in traditional Chinese medicine mainly include single Chinese herbs(Artemisiae Scopariae Herba, Artemisiae Annuae Herba, Salviae Miltiorrhizae Radix et Rhizoma, etc.) and Chinese herbal compounds(Yinchenhao Decoction, Xiaochaihu Decoction, Tiaogan Huaxian Pills, etc.), whose chemical compositions and action targets have not been fully identified. The combined medication is better than single medication, in that the former can improve drug resistance, make up each other's deficiencies, reduce adverse reactions, and prolong the action time. This study reviewed the anti-HBV activities and mechanisms of western drugs, Chinese herbs, and combined medications, in order to provide reference for the development and research of new anti-HBV drugs.

CPT1A-mediated fatty acid oxidation promotes cell proliferation via nucleoside metabolism in nasopharyngeal carcinoma.

As the first rate-limiting enzyme in fatty acid oxidation (FAO), CPT1 plays a significant role in metabolic adaptation in cancer pathogenesis. FAO provides an alternative energy supply for cancer cells and is required for cancer cell survival. Given the high proliferation rate of cancer cells, nucleotide synthesis gains prominence in rapidly proliferating cells. In the present study, we found that CPT1A is a determining factor for the abnormal activation of FAO in nasopharyngeal carcinoma (NPC) cells. CPT1A is highly expressed in NPC cells and biopsies. CPT1A dramatically affects the malignant phenotypes in NPC, including proliferation, anchorage-independent growth, and tumor formation ability in nude mice. Moreover, an increased level of CPT1A promotes core metabolic pathways to generate ATP, inducing equivalents and the main precursors for nucleotide biosynthesis. Knockdown of CPT1A markedly lowers the fraction of 13C-palmitate-derived carbons into pyrimidine. Periodic activation of CPT1A increases the content of nucleoside metabolic intermediates promoting cell cycle progression in NPC cells. Targeting CPT1A-mediated FAO hinders the cell cycle G1/S transition. Our work verified that CPT1A links FAO to cell cycle progression in NPC cellular proliferation, which supplements additional experimental evidence for developing a therapeutic mechanism based on manipulating lipid metabolism.

Succinate dehydrogenase/complex II is critical for metabolic and epigenetic regulation of T cell proliferation and inflammation.

Effective T cell-mediated immune responses require the proper allocation of metabolic resources to sustain growth, proliferation, and cytokine production. Epigenetic control of the genome also governs T cell transcriptome and T cell lineage commitment and maintenance. Cellular metabolic programs interact with epigenetic regulation by providing substrates for covalent modifications of chromatin. By using complementary genetic, epigenetic, and metabolic approaches, we revealed that tricarboxylic acid (TCA) cycle flux fueled biosynthetic processes while controlling the ratio of succinate/α-ketoglutarate (α-KG) to modulate the activities of dioxygenases that are critical for driving T cell inflammation. In contrast to cancer cells, where succinate dehydrogenase (SDH)/complex II inactivation drives cell transformation and growth, SDH/complex II deficiency in T cells caused proliferation and survival defects when the TCA cycle was truncated, blocking carbon flux to support nucleoside biosynthesis. Replenishing the intracellular nucleoside pool partially relieved the dependence of T cells on SDH/complex II for proliferation and survival. SDH deficiency induced a proinflammatory gene signature in T cells and promoted T helper 1 and T helper 17 lineage differentiation. An increasing succinate/α-KG ratio in SDH-deficient T cells promoted inflammation by changing the pattern of the transcriptional and chromatin accessibility signatures and consequentially increasing the expression of the transcription factor, PR domain zinc finger protein 1. Collectively, our studies revealed a role of SDH/complex II in allocating carbon resources for anabolic processes and epigenetic regulation in T cell proliferation and inflammation.

Pyrimidine inhibitors synergize with nucleoside analogues to block SARS-CoV-2.

The SARS-CoV-2 virus has infected more than 261 million people and has led to more than 5 million deaths in the past year and a half1 ( https://www.who.org/ ). Individuals with SARS-CoV-2 infection typically develop mild-to-severe flu-like symptoms, whereas infection of a subset of individuals leads to severe-to-fatal clinical outcomes2. Although vaccines have been rapidly developed to combat SARS-CoV-2, there has been a dearth of antiviral therapeutics. There is an urgent need for therapeutics, which has been amplified by the emerging threats of variants that may evade vaccines. Large-scale efforts are underway to identify antiviral drugs. Here we screened approximately 18,000 drugs for antiviral activity using live virus infection in human respiratory cells and validated 122 drugs with antiviral activity and selectivity against SARS-CoV-2. Among these candidates are 16 nucleoside analogues, the largest category of clinically used antivirals. This included the antivirals remdesivir and molnupiravir, which have been approved for use in COVID-19. RNA viruses rely on a high supply of nucleoside triphosphates from the host to efficiently replicate, and we identified a panel of host nucleoside biosynthesis inhibitors as antiviral. Moreover, we found that combining pyrimidine biosynthesis inhibitors with antiviral nucleoside analogues synergistically inhibits SARS-CoV-2 infection in vitro and in vivo against emerging strains of SARS-CoV-2, suggesting a clinical path forward.