Purine Compounds Research Articles

High Levels of Uric Acid Upregulate Endothelin Receptors: The Role of MAPK Pathways in an in vitro Study

IntroductionUric acid (UA) is the end product of purine compounds' metabolism. There is overwhelming evidence linking hyperuricemia (high levels of UA) and cerebrovascular diseases, but the effect of high levels of UA on cerebral vessels is not fully understood. The aim of this research is to clarify how UA affect the endothelin (ET) receptor in rat cerebral arteries and the related mechanism.Material and methodsIn an in vitro setting, segments of rat cerebral arteries (n=12) were exposed to high levels of UA, either alone or in conjunction with MAPK pathway inhibitors. ET agonists were used to induce contractions that were then measured with a myograph. ET receptor expression was measured using RT-PCR (n=6), Western Blot (n=3), or immunohistochemistry (n=3) to quantify mRNA and protein levels.ResultsThe study revealed that high levels of UA notably increase ETA and ETB receptor-induced contractions and boost the expression of ET receptors in cerebral arteries when compared to that are fresh or cultured alone, suggesting that UA enhances ETA and ETB receptors. Additionally, the up-regulation of ETB receptors induced by UA was inhibited by the p38 inhibitor SB203580, the JNK inhibitor SP600125, and the ERK1/2 inhibitor U0126. SB203580 significantly blocked the increase in ETA receptor-mediated contractions induced by UA and the upregulation of ETA receptor. Neither SP600125 nor U0126 had such effect.ConclusionsHigh levels of UA stimulate the up-regulation of ET receptors in rat cerebral arteries in vitro through MAPK pathways. This study may offer novel perspectives on hyperuricemia-associated cerebrovascular diseases.

ADVANCEMENTS IN UNDERSTANDING THE MOLECULAR MECHANISMS REGULATING URIC ACID METABOLISM IN THE INTESTINE

This review provides contemporary insights into the direct and indirect pathogenetic connections between purine compound metabolism and biochemical processes within the cells of the gastrointestinal system. A thorough analysis of recent publications from 2000 to 2024, sourced from databases including Scopus, PubMed, eLIIBRARY, and Google Scholar, was conducted. Uric acid serves as the end product of purine-containing compound catabolism. Its concentration is intricately regulated through the collaboration of the kidneys and gastrointestinal organs, namely the small intestine and liver. Gout, a chronic condition, emerges from the interplay between molecular genetic factors and external influences. Elevated levels of urates in the blood serum (hyperuricemia) and the deposition of sodium urate crystals in organs and tissues set off a cascade of inflammatory and fibrotic processes within mucosal, smooth muscle, parenchymal, and endothelial cells, including those within the gastrointestinal tract. Normally, a person excretes about 1.5 g of uric acid per day. Under physiological conditions, two-thirds of uric acid is excreted from the body by the kidneys, one-third through the intestines, and a small part is excreted with bile. The hypothesis that links the pathogenesis of hyperuricemia with “renal overload” suggests that the disease may develop as a result of impaired renal excretion with insufficient elimination of uric acid through the intestines. Part of uric acid transport systems actively works in hepatocytes and enterocytes, which determines its formation and clearance. Uric acid transporter proteins are divided into two categories: urate reabsorption transporters and urate excretion transporters, their expression is regulated by transcription factors, hormones and metabolites of intestinal microflora. The influence of intestinal microbiota on uric acid metabolism is related to its participation in purine metabolism, decomposition and elimination of uric acid with metabolites of intestinal flora and inhibition of gouty inflammation and is evaluated as a new therapeutic potential in gout and hyperuricemia, which allows to avoid kidney damage and urolithiasis.

Effect and mechanism of Yiqing decoction on hyperuricemia rats.

This study aimed to experimentally compare the uric acid-lowering effect and renal protection of Yiqing Fang in a rat model of hyperuricemia. Additionally, we used network pharmacology to predict the potential active components, targets, and pathways of Yiqing Fang. Male SD rats were randomly divided into control, model, Yiqing Fang, allopurinol, and probenecid groups. Serum creatinine (Scr), blood urea nitrogen (BUN), serum uric acid (UA), alanine transaminase (ALT), complete blood count, and urinary NAG enzyme levels were measured. Standard pathology and electron microscopy samples were prepared from the left kidney to observe renal pathological changes, renal fibrosis, and collagen III expression levels. In addition, we employed network pharmacology to investigate the molecular mechanisms and pathways of Yiqing Fang. The Yiqing Fang group showed significantly lower levels of Scr, BUN, UA, ALT, urinary NAG enzyme, complete blood count, and liver function tests compared to the model group (P < 0.05). Furthermore, both the Yiqing Fang and allopurinol groups exhibited significant reductions in renal pathological changes compared to the model group, along with decreased expression of collagen III. Network pharmacology analysis identified a total of 27 specific sites related to hyperuricemia. The main active components were predicted to include quercetin, berberine, beta-sitosterol, epimedin C, and dioscin. The primary target sites were predicted to include TNF, IL-6, IL-17, IL-1B, and VEGFA. Yiqing Fang may exert its effects through regulation of drug response, urate metabolism, purine compound absorption, inflammation response, lipopolysaccharide response, cytokine activity, and antioxidant activity. These effects may be mediated through signaling pathways such as IL-17, HIF-1, and AGE-RAGE. Yiqing Fang offers potential as a treatment for hyperuricemia due to its multiple active components, targeting of various sites, and engagement of multiple pathways.

Hyperuricemia, gout and digestive system pathology: common links of pathogenesis

The aim: to study and present scientists opinions on the direct and indirect clinical and pathogenetic purine compounds metabolism relationships with the digestive system physiological and pathological processes in normal uric acid levels conditions and in hyperuricemia and gout cases. Material and methods. A comprehensive analysis of available modern scientific official sources and regulatory documents for the last decade in the Scopus, PubMed.com, E-library databases. Conclusion. Based on the modern scientific literature data and numerous studies, we can say that there is a pathogenetic relationship between the level of uric acid and the digestive organs defeat.

Correlation between the bacterial community succession and purine compound changes during Huangjiu fermentation

Purine is mainly culprit of hyperuricemia (HUA) and gout, which is widely present in Huangjiu in the form of free bases. Bacterial succession plays an important role in quality control in Huangjiu. The correlation between the purine compound content and the bacterial communities during the fermentation process has not yet been evaluated. In this study, high-throughput sequencing (HTS) technology was used to monitor the bacterial community composition of Huangjiu at different fermentation stages. The correlation between the bacterial community and the contents of physicochemical properties and purine compounds were evaluated using the Spearman analysis method. The key enzymes of purine metabolism pathway in the microbial community were analyzed by bioinformatics using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). The results showed that the purine content in Huangjiu increased gradually in 0∼9d of fermentation (21.05–65.71 mg/L), and stabilized gradually in 12∼18d (65.63–69.55 mg/L), while the abundance of lactic acid bacteria (LAB) of bacterial microbial flora were increased (0∼9d) and then stabilized (12∼18d). Moreover, Lactobacillus acetotolerans and Lactobacillus helveticus were highly correlated positively with purine contents, while Limosilactobacillus fermentum and Lactiplantibacillus plantarum were correlated negatively. In addition, the dominant strains of bacteria were involved in the metabolism of purine, and the key enzymes for purine compound synthesis were more abundant than that for purine degradation. This study is helpful to scientifically understand the formation mechanism of purines, providing a basis for screening functional strains of purine degrading to accurately regulate purine level in Huangjiu.

Effect of the initial pH of the culture medium on the nutrient consumption pattern of Bifidobacterium animalis subsp. lactis Bb12 and the improvement of acid resistance by purine and pyrimidine compounds.

During fermentation, the accumulation of acidic products can induce media acidification, which restrains the growth of Bifidobacterium animalis subsp. lactis Bb12 (Bb12). This study investigated the nutrient consumption patterns of Bb12 under acid stress and effects of specific nutrients on the acid resistance of Bb12. Bb12 was cultured in chemically defined medium (CDM) at different initial pH values. Nutrient consumption patterns were analyzed in CDM at pH 5.3, 5.7, and 6.7. The patterns varied with pH: Asp+Asn had the highest consumption rate at pH 5.3 and 5.7, while Ala was predominant at pH 6.7. Regardless of the pH levels (5.3, 5.7, or 6.7), ascorbic acid, adenine, and Fe2+ were vitamins, nucleobases, and metal ions with the highest consumption rates, respectively. Nutrients whose consumption rates exceeded 50% were added individually in CDM at pH 5.3, 5.7, and 6.7. It was demonstrated that only some of them could promote the growth of Bb12. Mixed nutrients that could promote the growth of Bb12 were added to three different CDM. In CDM at pH 5.3, 5.7, and 6.7, it was found that the viable cell count of Bb12 was the highest after adding mixed nutrients, which were 8.87, 9.02, and 9.10 log CFU ml-1, respectively. The findings suggest that the initial pH of the culture medium affects the nutrient consumption patterns of Bb12. Specific nutrients can enhance the growth of Bb12 under acidic conditions and increase its acid resistance.

Inhibition of the Progression of Chronic Kidney Disease With Hyperuricemia

The final product of the catabolism of purine compounds in humans is uric acid (UA), which is a weak organic acid, over 98% of which is ionized into monosodium urate. UA is excreted by the kidneys, approximately 80-99% is reabsorbed in the proximal tubules of the kidneys. About 20% of UA is excreted through the intestine, where it is destroyed by microflora to carbon dioxide and water. The reference value of UA in blood plasma is 6.5-7 mg/dl in men and 6–6.5 mg/dl in women. The content of UA in the range of 360-400 μmol/l or 6-6.8 mg / dl increases the risk of crystallization under physiological conditions, and regardless of gender. UA levels greater than 7.0 mg/dl are associated with an increased risk of developing gout or nephrolithiasis. Hyperuricemia may occur due to increased production and / or decreased renal excretion of UA. Hyperuricemia is high in the general population and is associated with the development and progression of chronic kidney disease (CKD). Currently, allopurinol and febuxostat are used to correct hyperuricemia. The use of allopurinol should begin with a low dose (50-100 mg/day) and gradually titrate until the target level of UA in the blood is reached or until it is reached to the maximum. If necessary, the dose of allopurinol is increased by 100 mg every 2–4 weeks until the target serum UA level is reached. According to EULAR's recommendations for the treatment of gout, if the target level of UA cannot be achieved with an adequate dose of allopurinol, it should be replaced with febuxostat or uricosuric or a combination of febucostat with uricosuric. Febuxostat is also indicated for allopurinol intolerance. Febuxostat in doses of 80 and 120 mg/day was more effective than allopurinol at a dose of 300 mg/day. With CKD with mild or moderate renal failure, as well as in the elderly, it is not necessary to adjust the dose of febuxostat. The likelihood of reaching the target level of UA in the blood with reduced kidney function is higher in febuxostat. If the patient does not have serious cardiovascular diseases, the patient can be transferred to febuxostat, starting with a dose of 40 mg/day, and gradually titrated, especially in the case of CKD.

Identification of reaction sites and chlorinated products of purine bases and nucleosides during chlorination: a computational study.

Hypochlorous acid (HOCl) released from activated leukocytes plays a significant role in the human immune system, but is also implicated in numerous diseases due to its inappropriate production. Chlorinated nucleobases induce genetic changes that potentially enable and stimulate carcinogenesis, and thus have attracted considerable attention. However, their multiple halogenation sites pose challenges to identify them. As a good complement to experiments, quantum chemical computation was used to uncover chlorination sites and chlorinated products in this study. The results indicate that anion salt forms of all purine compounds play significant roles in chlorination except for adenosine. The kinetic reactivity order of all reaction sites in terms of the estimated apparent rate constant kobs-est (in M-1 s-1) is heterocyclic NH/N (102-107) > exocyclic NH2 (10-2-10) > heterocyclic C8 (10-5-10-1), but the order is reversed for thermodynamics. Combining kinetics and thermodynamics, the numerical simulation results show that N9 is the most reactive site for purine bases to form the main initial chlorinated product, while for purine nucleosides N1 and exocyclic N2/N6 are the most reactive sites to produce the main products controlled by kinetics and thermodynamics, respectively, and C8 is a possible site to generate the minor product. The formation mechanisms of biomarker 8-Cl- and 8-oxo-purine derivatives were also investigated. Additionally, the structure-kinetic reactivity relationship study reveals a good correlation between lg kobs-est and APT charge in all purine compounds compared to FED2 (HOMO), which proves again that the electrostatic interaction plays a key role. The results are helpful to further understand the reactivity of various reaction sites in aromatic compounds during chlorination.

Molecular mechanisms regulating uric acid metabolism in the human intestine, systematic literature review

This review presents recent data on direct and indirect pathogenetic relationships between metabolism of purine compounds and biochemical processes in cells of the digestive system. A comprehensive analysis of available modern publications for the period from 2000 to 2022 in the Scopus, PubMed, eLIIBRARY, and Google Scholar databases was performed. The hypothesis linking the pathogenesis of hyperuricemia to “renal overload” suggests that the disease may develop due to impaired renal excretion with insufficient excretion of uric acid (UA) via the intestine. Some of the UA transport systems work actively in hepatocytes and enterocytes, which determines their formation and excretion. UA transporter proteins are divided into two categories: urate reabsorption transporters and urate excretion transporters; their expression is regulated by transcription factors, hormones, and metabolites of the intestinal microflora. The influence of intestinal microbiota on UA metabolism is associated with its involvement in purine metabolism, degradation and excretion of UA together with metabolites of intestinal flora, and suppression of gout inflammation, and is evaluated as a new therapeutic potential for gout and hyperuricemia to prevent renal damage and urolithiasis.

Efficient removal of purine compounds from solutions via biomass carbons derived from pomelo peel

The high purine diet could result in the increase of the level of blood uric acid, causing serious health problems such as hyperuricemia, gout, nephropathy and cardiovascular diseases. To find out a safe, cheap and super adsorption material for removing purines in stomach or pretreating high-purine beverages, we used different tissues of pomelo peel to prepare biomass carbon by drying, chemical modification and carbonization and then applied it to remove purine compounds in strong acidic solution, beer and soybean milk. The characteristic analysis of pomelo-peel-derived carbons (PPCs) indicated that the preparation methods significantly affected the structures and adsorption capacities of PPCs. Compared with the biomass carbon derived from bamboo, PPCs exhibited higher adsorption capabilities for purine compounds in strong acidic solution (adsorption rates > 99% in 15min) and soybean milk (adsorption rates > 56% in 30min) but slightly lower adsorption capabilities in beer (adsorption rates > 52% in 30min). In addition, the adsorption capabilities of PPCs for purine compounds in beer and soybean milk were not obviously affected by temperatures. Therefore, PPCs are promising absorbents for applications in removing purine compounds from beverages to produce low-purine, healthier products for treating hyperuricemia. The strong adsorption capabilities of PPCs on purine compounds in strong acidic environment also provides a possibility of using the PPCs as food additives for removing purines in stomach for healthcare applications such as gout prevention after confirming their biosafety.

Screening and application of purine degrading Limosilactobacillus fermentum LF-1 from Huangjiu fermentation broth.

As the important building blocks of nucleic acids, purines are alkaloids and responsible for hyperuricemia and gout. The purine content in Huangjiu is higher, and mainly exists in the form of free bases, which is easier to be absorbed by human body. However, the currently available reports on purine in Huangjiu mainly focus on detection methods and content survey. No studies on the regulation of the purine content in Huangjiu have been reported. Eighty-four strains, with the degradation capacity of purine, were screened from the fermentation broth of Huangjiu. In detail, the isolated lactic acid bacteria (LAB) strain 75 # showed the strongest degradation ability of guanosine, inosine and four purines, which reduce their levels by 83.4% (guanosine), 97.4% (inosine), 95.1% (adenine), 95.0% (guanine), 94.9% (hypoxanthine) and 65.9% (xanthine), respectively. Subsequently, the LAB strain 75# was identified to be Limosilactobacillus fermentum by 16S rRNA gene sequencing, which was named as Limosilactobacillus fermentum LF-1 and applied to the fermentation of Huangjiu in the laboratory. Compared with the fermentation broth of Huangjiu without adding L. fermentum LF-1, the content of purine compounds in the fermentation broth inoculated with L. fermentum LF-1 was reduced by 64.7%. In addition, the fermented Huangjiu had richer flavor compounds, and the physicochemical indices were in accordance with the national standard of Chinese Huangjiu. The screened strain L. fermentum LF-1 may be a promising probiotic for the development of a novel that can efficiently degrade purine in Huangjiu. © 2023 Society of Chemical Industry.

Inborn Errors of Purine Salvage and Catabolism.

Cellular purine nucleotides derive mainly from de novo synthesis or nucleic acid turnover and, only marginally, from dietary intake. They are subjected to catabolism, eventually forming uric acid in humans, while bases and nucleosides may be converted back to nucleotides through the salvage pathways. Inborn errors of the purine salvage pathway and catabolism have been described by several researchers and are usually referred to as rare diseases. Since purine compounds play a fundamental role, it is not surprising that their dysmetabolism is accompanied by devastating symptoms. Nevertheless, some of these manifestations are unexpected and, so far, have no explanation or therapy. Herein, we describe several known inborn errors of purine metabolism, highlighting their unexplained pathological aspects. Our intent is to offer new points of view on this topic and suggest diagnostic tools that may possibly indicate to clinicians that the inborn errors of purine metabolism may not be very rare diseases after all.

Towards the Use of Adsorption Methods for the Removal of Purines from Beer.

Beer corresponds to a fermented alcoholic beverage composed of several components, including purine compounds. These molecules, when ingested by humans, can be catabolized into uric acid, contributing to uric acid’s level increase in serum, which may lead to hyperuricemia and gout. To assure a proper management of this disease, physicians recommend restrictive dietary measures, particularly by avoiding the consumption of beer. Therefore, it is of relevance to develop efficient methods to remove purine compounds from alcoholic beverages such as beer. In this review, we provide an introduction on fermented alcoholic beverages, with emphasis on beer, as well as its purine compounds and their role in uric acid metabolism in the human body in relation to hyperuricemia and gout development. The several reported enzymatic, biological and adsorption methods envisaging purine compounds’ removal are then reviewed. Some enzymatic and biological methods present drawbacks, which can be overcome by adsorption methods. Within adsorption methods, adsorbent materials, such as activated carbon or charcoal, have been reported and applied to beer or wort samples, showing an excellent capacity for adsorbing and removing purine compounds. Although the main topic of this review is on the removal of purine compounds from beer, other studies involving other matrices rather than beer or wort that are rich in purines are included, since they provide relevant clues on designing efficient removal processes. By ensuring the selective removal of purine compounds from this beverage, beer can be taken by hyperuricemic and gouty patients, avoiding restrictive dietary measures, while decreasing the related healthcare economic burden.

Screening and Evaluation of Purine-Nucleoside-Degrading Lactic Acid Bacteria Isolated from Winemaking Byproducts In Vitro and Their Uric Acid-Lowering Effects In Vivo

In Taiwan, adult hyperuricemia affects as many as 1 in 4 males and 1 in 6 females, who are predominantly young adults aged 19–45. In this study, lactic acid bacteria (LAB) with acid tolerance, bile salt tolerance and high affinity to intestinal cells were extracted from the side products of alcohol fermentation (distillers’ grains). These bacteria were evaluated for their ability to lower uric acid levels. Qualitative identification and quantitative analysis were performed using high-performance liquid chromatography (HPLC) on the purine-degrading enzymes to select purine-decomposing LAB for animal testing. When the final concentration of purine compounds reached 0.1% and 1%, seven strains of LAB showed potential in degrading purine compounds. HPLC was used to analyze their purine-degrading abilities, and the three best performing LAB strains, (107) 8–16, (107) tau 1–3, and (107) 6–10 were screened for further animal testing with Wistar rats. By the third week, the results showed that strain (107) 6–10 could prevent formation and reduce the levels of blood urea nitrogen (BUN) in yeast extract/potassium oxonate-induced hyperuricemia. The multi-strain lactic acid bacteria (MLAB) performed best for uric acid reduction in the serum and down regulated BUN. Yeast extract/potassium oxonate-induced hyperuricemia had no impact on serum creatinine, while LAB did not affect the creatinine concentration. In summary, MLAB not only protects kidney function but is also effective in regulating uric acid concentration in the body. Hence, MLAB can be used as a functional food supplement that prevents or aids the treatment of hyperuricemia in a rodent model.

Влияние пуринергической сигнальной системы на свойства клеток крови человека при старении организма

Adenosine triphosphate (ATP) molecules and nucleotide derivatives contribute to a wide range of cellular reactions through the activation of A2 and P2 purinergic receptors located on the cell surface. Almost any type of cells expresses such receptors, including red blood cells and white blood cells. The study of purinergic transmission of signals mediating calcium mobilization, actin polymerization, chemotaxis, release of mediators, tissue oxygenation, cell maturation, cytotoxicity, cell death and cell–cell interactions in dynamics at different stages of ontogenesis is an important issue in biology and medicine today. This paper aimed to explore the biophysical properties of blood cells during the activation of the purinergic signalling system in middle-aged people and older adults. To activate the elements of the purinergic signalling system, an in vitro model of mechanical stress was used. Blood samples were analysed using the methods of atomic force microscopy, namely, force spectroscopy and the Kelvin probe. When the purinergic signalling system is activated, an increase in ATP blood concentration is identified in the blood of both middle-aged people and older adults. In the blood of older adults, a smaller amount of ATP was recorded compared with the blood of middle-aged people, which can be due to changes in the expression of purinoreceptors on the surface of red blood cells at ageing. Erythrocytes and granulocytes in older adults are characterized by increased surface stiffness and potential upon activation of the purinergic signalling system, compared with cells of middle-aged people. In response to mechanical stress, lymphocyte membrane stiffness in older adults increases more significantly than in middle-aged people. Thus, the results indicate an important role of the ATP molecule and its derivatives in the regulation of functioning of blood cells through binding to receptors of the P2 family. Research on the changes in the biophysical properties of red blood cells and white blood cells at activation of the purinergic signalling system will allow us to identify new effects of purine compounds on intercellular interaction during ageing.

FTIR and FT-Raman spectra of 6-(dimethylamino)purine and its theoretical studies of anharmonic vibrational analysis using quantum chemical calculations

The present work explores the anharmonic vibrational and electronic spectral features of 6-(dimethylamino) purine (DMAP) compound with the help of the FTIR (4000−400 cm−1), FT-Raman (4000−50 cm−1) and UV–vis (600−180 nm) spectra as well as DFT calculations. Anharmonic frequencies on the structure of 6-dimethylaminopurine (DMAP) were computed using the generalized vibrational perturbation theory (GVPT2), vibrational self-consistence field (VSCF) theory and correlation-corrected vibrational self consistence field (PT2-VSCF) method in DFT/6−311 G(d,p) framework. The fully anharmonic frequencies calculated using different methods are in remarkable agreement with the experiments as reflected from RMSE and MAD values and show large improvement over the harmonic approximation. The magnitudes of coupling between pairs of normal modes were calculated using quartic force field (2MR-QFF) approximation. The interactions between pair of modes due to mode-mode coupling have significantly affected the vibrational frequencies. The effect of intermolecular interaction (N–H⋅⋅⋅⋅⋅N) on the geometrical parameters and vibrational frequencies were studied using comparison of results of the monomeric and dimeric structure of the titled molecule. The electronic spectra in the methanol, ethanol and water solvents have been analyzed using the TD-DFT approach and these are compared with the experiment. Furthermore, the associated nonlinear optical (NLO) properties, frontier molecular orbitals and molecular electrostatic potential (MEP) surface analysis have been studied.

Dielectric, Electrical Conductivity Behavior and Molecular Modeling of Some Pyrimidine and Purine Compounds

The dielectric and electrical conductivity measurements for biologically active nucleic acid compounds reveal semiconducting properties and small relaxation times. On the basis of electronic transition within molecules, two pathways for the conduction of electricity may be expected. The first conducting process occurring in the lower temperature region is attributed to n→π* transitions which require less energy to be performed. In the upper temperature region, conduction could be attributed to π→π* transitions which need more energy to participate in electronic conduction. The observed increment of conduction in the upper temperature region may be attributed to interactions between n→π* and π→π* transitions. Quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO) and the lowest unoccupied molecular orbital energy (ELUMO) were given using molecular modeling. Energy gap (ΔE) and parameters which give information about the reactive chemical behavior of compounds such as electronegativity (χ), chemical potential (µ), global hardness (η), softness (σ) and electrophilicity index (ω) were calculated.

Manipulation of Purine Metabolic Networks for Riboflavin Production in Bacillus subtilis.

Guanosine monophosphate, the precursor for riboflavin biosynthesis, can be converted to or generated from other purine compounds in purine metabolic networks. In this study, genes in these networks were manipulated in a riboflavin producer, Bacillus subtilis R, to test their contribution to riboflavin biosynthesis. Knocking out adenine phosphoribosyltransferase (apt), xanthine phosphoribosyltransferase (xpt), and adenine deaminase (adeC) increased the riboflavin production by 14.02, 6.78, and 41.50%, respectively, while other deletions in the salvage pathway, interconversion pathway, and nucleoside decomposition genes have no positive effects. The enhancement of riboflavin production in apt and adeC deletion mutants is dependent on the purine biosynthesis regulator PurR. Repression of ribonucleotide reductases (RNRs) led to a 13.12% increase of riboflavin production, which also increased in two RNR regulator mutants PerR and NrdR by 37.52 and 8.09%, respectively. The generation of deoxyribonucleoside competed for precursors with riboflavin biosynthesis, while other pathways do not contribute to the supply of precursors; nevertheless, they have regulatory effects.

A Selective and Sensitive Method for Simultaneous Quantification of Genotoxic Impurities in Penciclovir drug substance and its dosage forms using UPLC-MS/MS

A selective, rapid and sensitive method was developed for the determination of genotoxic impurities (2-Amino-6-chloro purine and Bromo compound) in Penciclovir drug substance using RPUPLC-MS/MS. The chromatographic separation was performed on Kromasil C8 column (150 mm x 4.6 mm, 5 μm) maintained at 45°C using 0.1%formic acids in water as buffer and acetonitrile through gradient programme. The flow rate was maintained at 0.5mL/min with an injection volume of 10 μL. For the quantification of genotoxic impurities, positive-electrospray ionisation (ESI) mode was selected. Penciclovir and its impurities were well separated within the shortest run time of 16min. The chromatographic method was developed, and the results of all validation parameters showed that the technique is well confined to the limits of ICH guidelines. The method has high sensitivity, and the limit of detection was found to be as low as 0.15 and 0.30 ppm for 2-Amino-6-chloro purine and Bromo compound. The recovery of 2-Amino-6-chloro purine and Bromo compound are found in the range of 80-120%. The linearity of peak area versus concentration was demonstrated in the range of LOQ - 150% level of impurities with a correlation coefficient of 0.9999. The method has proved too robust by introducing minuscule changes in the chromatographic parameters. The method was successfully validated and applied for Penciclovir drug substances and their dosage forms to determine the mentioned genotoxic impurities.

Association between hyperuricemia, gout, urate lowering therapy, and osteoarthritis: A protocol for a systematic review and meta-analysis.

Osteoarthritis (OA), a chronic and degenerative joint disease characterized by articular cartilage degeneration, sclerosis of subchondral bone, and osteophyte formation, is deemed a leading cause of activity limitation and disability among the elderly people. Serum uric acid (UA) is a terminal metabolite of purine compound, while hyperuricemia (HU) and UA crystals are recognized causes of gout. Several studies have investigated the correlations between HU, gout and OA, but the findings are inconclusive. We are also concerned whether the urate lowering therapy (ULT) can become a potential treatment for OA and intend to undertake this meta-analysis to clarify the related hypotheses. Systematic literature search will be conducted on PubMed, Embase, and Web of Science to identify relevant studies up to February 2020 using appropriate search strategies. All citations and abstracts retrieved from literature search will be assessed by two reviewers independently. The Newcastle-Ottawa Scale or the Cochrane risk of bias assessment tool will be used as appropriate to assess the quality and the risk of bias of the included studies. The heterogeneity and the publication bias of the studies will be investigated accordingly. We propose to undertake this meta-analysis as a feasible approach to clarify the associations between HU, gout or ULT, and OA. This meta-analysis will help to strengthen our knowledge of the pathogenesis of OA and promote the development of preventive or treatment strategies. PROSPERO registration number CRD42020168769.