Role of host xanthine oxidase in infection due to enteropathogenic and Shiga-toxigenic Escherichia coli

Structural basis of transcriptional regulation by UrtR in response to uric acid

Uric acid (UA)-responsive transcriptional regulators (UrtRs), which belong to the multiple antibiotic resistance regulator (MarR) superfamily, transcriptionally coordinate virulence and metabolism in bacteria by modulating interactions with operator DNA in response to UA. To elucidate the transcriptional regulatory mechanism of UrtR, we structurally analyzed UrtR proteins, including PecS, MftR, and HucR, alone and in complex with UA or DNA. UrtR contains a dimerization domain (DD) and a winged helix-turn-helix domain (wHTHD) and forms a homodimer primarily via the DD, as observed for other MarR superfamily proteins. However, UrtRs are characterized by a unique N-terminal α-helix, which contributes to dimerization and UA recognition. In the absence of UA, the UrtR dimer symmetrically binds to the operator double-stranded DNA (dsDNA) by inserting its α4 recognition helix and β-stranded wing within the wHTHD into the major and minor grooves of dsDNA, respectively. Upon exposure to UA, UrtR accommodates UA in the intersubunit pocket between the DD and wHTHD. UA binding induces a conformational change in the major groove-binding core element of the UrtR wHTHD, generating a DNA binding-incompatible structure. This local allosteric mechanism of UrtR completely differs from that generally observed in other MarR superfamily members, in which the entire wHTHD undergoes effector-responsive global shifts.

Elucidating the role of gut microbiota dysbiosis in hyperuricemia and gout: Insights and therapeutic strategies

Hyperuricemia (HUA) is a condition associated with a high concentration of uric acid (UA) in the bloodstream and can cause gout and chronic kidney disease. The gut microbiota of patients with gout and HUA is significantly altered compared to that of healthy people. This article focused on the complex interconnection between alterations in the gut microbiota and the development of this disorder. Some studies have suggested that changes in the composition, diversity, and activity of microbes play a key role in establishing and progressing HUA and gout pathogenesis. Therefore, we discussed how the gut microbiota contributes to HUA through purine metabolism, UA excretion, and intestinal inflammatory responses. We examined specific changes in the composition of the gut microbiota associated with gout and HUA, highlighting key bacterial taxa and the metabolic pathways involved. Additionally, we discussed the effect of conventional gout treatments on the gut microbiota composition, along with emerging therapeutic approaches that target the gut microbiome, such as the use of probiotics and prebiotics. We also provided insights into a study regarding the gut microbiota as a possible novel therapeutic intervention for gout treatment and dysbiosis-related diagnosis.

Imperata cylindrica polysaccharide ameliorates intestinal dysbiosis and damage in hyperuricemic nephropathy

In this study, a combination of adenine and potassium oxonate was utilized to establish a hyperuricemic nephropathy (HN) mouse model, aiming to elucidate the effect through which Imperata Cylindrica polysaccharide (ICPC-a) ameliorates HN. In HN mice, an elevation in the abundance of Erysipelatoclostridium, Enterococcus, Prevotella, and Escherichia-Shigella was observed, whereas Lactobacillus and Bifidobacterium declined. Additionally, the systemic reductions in the levels of acetate, propionate, and butyrate, along with a significant increase in indole content, were noted. HN mice demonstrated intestinal barrier impairment, as evidenced by diminished mRNA expression of ZO-1, Occludin, and Claudin-1 and increased Mmp-9 levels. The pro-inflammatory factors IL-6, IL-17, TNF-α, IFN-γ, and COX-2 were overexpressed. Subsequent gavage intervention with ICPC-a markedly mitigated the inflammatory response and ameliorated colon tissue damage. ICPC-a effectively regulated the abundance of gut microbiota and their metabolites, including short-chain fatty acids (SCFAs), bile acids (BAs), and indole, promoting the correction of metabolic and gut microbiota imbalances in HN mice. These findings underscored the capacity of ICPC-a as a prebiotic to modulate gut microbiota and microbial metabolites, thereby exerting a multi-pathway and multi-targeted therapeutic effect on HN.

Effect of konjac glucomannan on gut microbiota from hyperuricemia subjects in vitro: fermentation characteristics and inhibitory xanthine oxidase activity

Background

The disorder of uric acid metabolism is closely associated with gut microbiota and short-chain fatty acids (SCFAs) dysregulation, but the biological mechanism is unclear, limiting the development of uric acid-lowering active polysaccharides. Konjac glucomannan (KGM) could attenuate metabolic disturbance of uric acid and modulate the gut microbiota. However, the relationship between uric acid metabolism and gut microbiota is still unknown.

Methods

In this study, The fecal samples were provided by healthy volunteers and hyperuricemia (HUA) patients. Fecal samples from healthy volunteers was regarded as the NOR group. Similarly, 10% HUA fecal suspension was named as the HUA group. Then, fecal supernatant was inoculated into a growth basal medium containing glucose or KGM, and healthy fecal samples were designated as the NOR-GLU and NOR-KGM groups, while HUA fecal samples were designated as the HUA-GLU and HUA-KGM groups. All samples were cultured in an anaerobic bag system. After fermentation for 24 h, the samples were collected for further analysis of composition of intestinal microbiota, SCFAs concentration and XOD enzyme activity.

Results

The results showed that KGM could be utilized and degraded by the gut microbiota from HUA subjects, and it could modulate the composition and structure of their HUA gut microbiota to more closely resemble that of a healthy group. In addition, KGM showed a superior modulated effect on HUA gut microbiota by increasing Megasphaera, Faecalibacterium, Lachnoclostridium, Lachnospiraceae, Anaerostipes, and Ruminococcus levels and decreasing Butyricicoccus, Eisenbergiella, and Enterococcus levels. Furthermore, the fermentation solution of KGM showed an inhibitory effect on xanthine oxidase (XOD) enzyme activity, which might be due to metabolites such as SCFAs.

Conclusion

In conclusion, the effect of KGM on hyperuricemia subjects was investigated based on the gut microbiota in vitro. In the present study. It was found that KGM could be metabolized into SCFAs by HUA gut microbiota. Furthermore, KGM could modulate the structure of HUA gut microbiota. At the genus level, KGM could decrease the relative abundances of Butyricicoccus, Eisenbergiella, and Enterococcus, while Lachnoclostridium and Lachnospiraceae in HUA gut microbiota were significantly increased by the addition of KGM. The metabolites of gut microbiota, such as SCFAs, might be responsible for the inhibition of XOD activity. Thus, KGM exhibited a superior probiotic function on the HUA gut microbiota, which is expected as a promising candidate for remodeling the HUA gut microbiota.

Food-derived bioactive peptides with anti-hyperuricemic activity: A comprehensive review

Hyperuricemia (HU) is a metabolic disorder caused by the overproduction or underexcretion of uric acid (UA) in the human body. Several approved drugs for the treatment of HU are available in the market; however, all these allopathic drugs exhibit multiple side effects. Therefore, the development of safe and effective anti-HU drugs is an urgent need. Natural compounds derived from foods and plants have the potential to decrease UA levels. Recently, food-derived bioactive peptides (FBPs) have gained attention as a functional ingredient owing to their biological activities. In the current review, we aim to explore the urate-lowering potential and the underlying mechanisms of FBPs. We found that FBPs mitigate HU by reducing blood UA levels through inhibiting key enzymes such as xanthine oxidase, increasing renal UA excretion, inhibiting renal UA reabsorption, increasing anti-oxidant activities, regulating inflammatory mediators, and addressing gut microbiota dysbiosis. In conclusion, FBPs exhibit strong potential to ameliorate HU.

Gut Microbiota and Metabolic Syndrome: Relationships and Opportunities for New Therapeutic Strategies

Since its discovery, numerous studies have shown the role of the microbiota in well-being and disease. The gut microbiota represents an essential factor that plays a multidirectional role that affects not just the gut but also other parts of the body, including the brain, endocrine system, humoral system, immune system, and metabolic pathways, as well as host-microbiome interactions. Through a comprehensive analysis of existing literature using the desktop research methodology, this review elucidates the mechanisms by which gut microbiota dysbiosis contributes to metabolic dysfunction, including obesity, dyslipidaemia, hypertension, atherosclerosis, hyperuricemia, and hyperglycaemia. Furthermore, it examines the bidirectional communication pathways between gut microbiota and host metabolism, highlighting the role of microbial-derived metabolites, immune modulation, and gut barrier integrity in shaping metabolic homeostasis. Importantly, the review identifies promising therapeutic strategies targeting the gut microbiota as potential interventions for metabolic syndrome, including probiotics, prebiotics, symbiotics, dietary modifications, and faecal microbiota transplantation. By delineating the bidirectional interactions between gut microbiota and metabolic syndrome, the review not only advances our understanding of disease pathophysiology but also underscores the potential for innovative microbiota-based interventions to mitigate the global burden of metabolic syndrome and its associated complications.

Emerging Roles of Xanthine Oxidoreductase in Chronic Kidney Disease

Xanthine Oxidoreductase (XOR) is a ubiquitous, essential enzyme responsible for the terminal steps of purine catabolism, ultimately producing uric acid that is eliminated by the kidneys. XOR is also a physiological source of superoxide ion, hydrogen peroxide, and nitric oxide, which can function as second messengers in the activation of various physiological pathways, as well as contribute to the development and the progression of chronic conditions including kidney diseases, which are increasing in prevalence worldwide. XOR activity can promote oxidative distress, endothelial dysfunction, and inflammation through the biological effects of reactive oxygen species; nitric oxide and uric acid are the major products of XOR activity. However, the complex relationship of these reactions in disease settings has long been debated, and the environmental influences and genetics remain largely unknown. In this review, we give an overview of the biochemistry, biology, environmental, and current clinical impact of XOR in the kidney. Finally, we highlight recent genetic studies linking XOR and risk for kidney disease, igniting enthusiasm for future biomarker development and novel therapeutic approaches targeting XOR.

Nutrition, gastrointestinal microorganisms and metabolites in mastitis occurrence and control

Mastitis affects almost all mammals including humans and dairy cows. In the dairy industry, bovine mastitis is a disease with a persistently high incidence, causing serious losses to the health of cows, the quality of dairy products, and the economy of dairy farms. Although local udder infection caused by the invasion of exogenous pathogens into the mammary gland was considered the main cause of mastitis, evidence has been established and continues to grow, showing that nutrition factors and gastrointestinal microbiome (GM) as well as their metabolites are also involved in the development of mammary inflammatory response. Suboptimal nutrition is recognized as a risk factor for increased susceptibility to mastitis in cattle, in particular the negative energy balance. The majority of data regarding nutrition and bovine mastitis involves micronutrients. In addition, the dysbiotic GM can directly trigger or aggravate mastitis through entero-mammary gland pathway. The decreased beneficial commensal bacteria, lowered bacterial diversity, and increased pathogens as well as proinflammatory metabolites are found in both the milk and gastrointestinal tract of mastitic dairy cows. This review discussed the relationship between the nutrition (energy and micronutrient levels) and mastitis, summarized the role of GM and metabolites in regulating mastitis. Meanwhile, several non-antibiotics strategies were provided for the prevention and alleviation of mastitis, including micronutrients, probiotics, short-chain fatty acids, high-fiber diet, inulin, and aryl hydrocarbon receptor.

Assessing the causal relationships of gut microbial genera with hyperuricemia and gout using two-sample Mendelian randomization

BACKGROUND AND AIMS

The causal relationship between gut microbiota and gout and hyperuricemia (HUA) has not been clarified. The objective of this research was to evaluate the potential causal effects of gut microbiota on HUA and gout using a two-sample Mendelian randomization (MR) approach.

METHODS AND RESULTS

Genetic instruments were selected using summary statistics from genome-wide association studies (GWASs) comprising a substantial number of individuals, including 18,473 participants for gut microbiome, 288,649 for serum urate (SU), and 763,813 for gout. Two-sample MR analyses were performed to determine the possible causal associations of gut microbial genera with the risk of HUA and gout using the inverse-variance weighted (IVW) method, and robustness of the results was confirmed by several sensitivity analyses. A reverse MR analysis was conducted on the bacterial taxa that were identified in forward MR analysis. Based on the results of MR analyses, Escherichia-Shigella (OR = 1.05; 95% CI, 1.01-1.08; P = 0.009) exhibited a positive association with SU levels, while Lachnospiraceae NC2004 group (OR = 0.95; 95% CI, 0.92-0.98; P = 0.001) and Family XIII AD3011 group (OR = 0.94; 95% CI, 0.90-0.99; P = 0.015) were associated with a reduced HUA risk. Moreover, Coprococcus 3 (OR = 1.17, 95% CI: 1.01-1.34, P = 0.031) was causally associated with a higher gout risk. In reverse MR analysis, no causal relationships were identified between these bacterial genera and HUA or gout.

CONCLUSION

This study provides evidence for a causal association between gut microbial genera and HUA or gout, and further investigations of the underlying mechanism are warranted.

The microbiota-gut-brain axis in Huntington's disease: pathogenic mechanisms and therapeutic targets

Huntington's disease (HD) is a currently incurable neurogenerative disorder and is typically characterized by progressive movement disorder (including chorea), cognitive deficits (culminating in dementia), psychiatric abnormalities (the most common of which is depression), and peripheral symptoms (including gastrointestinal dysfunction). There are currently no approved disease-modifying therapies available for HD, with death usually occurring approximately 10-25 years after onset, but some therapies hold promising potential. HD subjects are often burdened by chronic diarrhea, constipation, esophageal and gastric inflammation, and a susceptibility to diabetes. Our understanding of the microbiota-gut-brain axis in HD is in its infancy and growing evidence from preclinical and clinical studies suggests a role of gut microbial population imbalance (gut dysbiosis) in HD pathophysiology. The gut and the brain can communicate through the enteric nervous system, immune system, vagus nerve, and microbiota-derived-metabolites including short-chain fatty acids, bile acids, and branched-chain amino acids. This review summarizes supporting evidence demonstrating the alterations in bacterial and fungal composition that may be associated with HD. We focus on mechanisms through which gut dysbiosis may compromise brain and gut health, thus triggering neuroinflammatory responses, and further highlight outcomes of attempts to modulate the gut microbiota as promising therapeutic strategies for HD. Ultimately, we discuss the dearth of data and the need for more longitudinal and translational studies in this nascent field. We suggest future directions to improve our understanding of the association between gut microbes and the pathogenesis of HD, and other 'brain and body disorders'.

Whey Protein Peptide Pro-Glu-Trp Ameliorates Hyperuricemia by Enhancing Intestinal Uric Acid Excretion, Modulating the Gut Microbiota, and Protecting the Intestinal Barrier in Rats

Hyperuricemia (HUA) is a metabolic disorder characterized by an increase in the concentrations of uric acid (UA) in the bloodstream, intricately linked to the onset and progression of numerous chronic diseases. The tripeptide Pro-Glu-Trp (PEW) was identified as a xanthine oxidase (XOD) inhibitory peptide derived from whey protein, which was previously shown to mitigate HUA by suppressing UA synthesis and enhancing renal UA excretion. However, the effects of PEW on the intestinal UA excretion pathway remain unclear. This study investigated the impact of PEW on alleviating HUA in rats from the perspective of intestinal UA transport, gut microbiota, and intestinal barrier. The results indicated that PEW inhibited the XOD activity in the serum, jejunum, and ileum, ameliorated intestinal morphology changes and oxidative stress, and upregulated the expression of ABCG2 and GLUT9 in the small intestine. PEW reversed gut microbiota dysbiosis by decreasing the abundance of harmful bacteria (e.g., Bacteroides, Alloprevotella, and Desulfovibrio) and increasing the abundance of beneficial microbes (e.g., Muribaculaceae, Lactobacillus, and Ruminococcus) and elevated the concentration of short-chain fatty acids. PEW upregulated the expression of occludin and ZO-1 and decreased serum IL-1β, IL-6, and TNF-α levels. Our findings suggested that PEW supplementation ameliorated HUA by enhancing intestinal UA excretion, modulating the gut microbiota, and restoring the intestinal barrier function.

Role of Extracellular DNA in Bacterial Response to SOS-Inducing Drugs

The SOS response is a conserved stress response pathway that is triggered by DNA damage in the bacterial cell. Activation of this pathway can, in turn, cause the rapid appearance of new mutations, sometimes called hypermutation. We compared the ability of various SOS-inducing drugs to trigger the expression of RecA, cause hypermutation, and produce elongation of bacteria. During this study, we discovered that these SOS phenotypes were accompanied by the release of large amounts of DNA into the extracellular medium. The release of DNA was accompanied by a form of bacterial aggregation in which the bacteria became tightly enmeshed in DNA. We hypothesize that DNA release triggered by SOS-inducing drugs could promote the horizontal transfer of antibiotic resistance genes by transformation or by conjugation.

16S rRNA and Metagenomics Combined with UPLC-Q/TOF-MS Metabolomics Analysis Reveals the Potential Mechanism of Radix Astragali Against Hyperuricemia in Mice

Purpose

This study aimed to investigate the underlying treatment mechanism of Radix Astragali (RA) in hyperuricemia from the perspective of microbiota and metabolomics.

Methods

We used potassium oxyazinate (PO) to induce hyperuricemia mice, and we determined serum alanine aminotransferase/aspartate aminotransferase (ALT/AST), xanthine oxidase (XOD), creatinine (CRE), uric acid (UA), blood urea nitrogen (BUN) levels, liver XOD levels and assessed the kidney tissue histopathology. The therapeutic mechanism of RA in hyperuricemic mice was studied by 16S rRNA, metagenomic sequencing and metabolomics.

Results

Our research showed that RA has therapeutic effect in hyperuricemia mice, such as slow the weight loss, repair kidney damage, and downregulate serum UA, XOD, CRE, ALT/AST, BUN, and liver XOD levels. RA restored the disturbance structure of the microbiota in hyperuricemia mice by increasing the relative abundances of beneficial bacteria (Lactobacillaceae and Lactobacillus murine) but decreasing the relative abundances of pathogenic bacteria (Prevotellaceae, Rikenellaceae and Bacteroidaceae). Meanwhile, we found that RA directly regulated the metabolic pathway (such as linoleic acid metabolism and glycerophospholipid metabolism) and indirectly regulated bile acid metabolism by mediating microbiota to ameliorate metabolic disorders. Subsequently, there was a robust correlation between specific microbiota, metabolites and the disease index.

Conclusion

The ability of RA to protect mice against hyperuricemia is strongly linked to the microbiome-metabolite axis, which would provide evidence for RA as a medicine to prevent or treat hyperuricemia.

Microbiota as a new pathogenetic factor in the development of chronic hyperuricemia and gout. Part 2: gout therapy and the gut microbiota

The article presents current data on the effect of drugs for the treatment of gout on the composition and function of the intestinal microbiota. The potential possibilities of pre- and probiotics use for the prevention and complex therapy of gout are discussed, therapeutic effect may be associated with their impact on the uric acid synthesis and intestinal excretion, as well as with anti-inflammatory properties. The need for further research in this area is emphasized.

Effect of Bining decoction on gouty nephropathy: a network pharmacology analysis and preliminary validation of gut microbiota in a mouse model

Background

To use network pharmacology and gut microbiota sequencing to investigate the probable mechanism of Bining decoction (BN) in the treatment of gouty nephropathy (GN).

Methods

Firstly, the mechanism of therapeutic effects of BN on GN were collected by integrating network pharmacology. Secondly, the treatment effects of BN against GN in 30 Institute of Cancer Research (ICR) mice were evaluated by performing biochemical tests [uric acid, blood urea nitrogen, and creatinine (UA, BUN, and Cr)] and evaluating the renal weight index. Finally, 16S rRNA sequencing was utilized for elucidating the therapeutical effect of BN in GN.

Results

The results of gut microbiota sequencing analysis showed the abundance of Faecalibaculum, Romboutsia, Bifidobacterium, Bacteroides, Odoribacter, Lachnospiraceae NK4A136 group, unclassified_f__Lachnospiraceae, Roseburia, norank_f__Lachnospiraceae, Lactobacillus, Dubosiella, norank_f__Muribaculaceae, and Turicibacter in the BN group had a significant changed between-group comparisons. Using a network pharmacology-related database, 413 active components of BN were identified, as well as 1,085 GN-associated targets. The 118 targets of disease targets and component targets were mapped, of which the top 10 genes were selected. The Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that 157 pathways were enriched, which was partially consistent with the metabolic pathways of gut microbiota sequencing analysis.

Conclusions

Combining 16S rRNA gene sequencing and network pharmacology analysis, similar signaling pathways were followed: "Pathways in cancer" and "Adipocytokine signaling pathway". The results reveal that BN increases the abundance of Turicibacter, regulates the expression of JAK2 in the JAK/STAT pathway, increases the beneficial bacteria Turicibacter associated with intestinal butyric acid, which could enhance the intestinal barrier, and exert anti-inflammatory effects.

Disentangling the microbial ecological factors impacting honey bee susceptibility to Paenibacillus larvae infection

Paenibacillus larvae is a spore-forming bacterial entomopathogen and causal agent of the important honey bee larval disease, American foulbrood (AFB). Active infections by vegetative P. larvae are often deadly, highly transmissible, and incurable for colonies but, when dormant, the spore form of this pathogen can persist asymptomatically for years. Despite intensive investigation over the past century, this process has remained enigmatic. Here, we provide an up-to-date synthesis on the often overlooked microbiota factors involved in the spore-to-vegetative growth transition (corresponding with the onset of AFB disease symptoms) and offer a novel outlook on AFB pathogenesis by focusing on the 'collaborative' and 'competitive' interactions between P. larvae and other honey bee-adapted microorganisms. Furthermore, we discuss the health trade-offs associated with chronic antibiotic exposure and propose new avenues for the sustainable control of AFB via probiotic and microbiota management strategies.

The Global Regulator MftR Controls Virulence and Siderophore Production in Burkholderia thailandensis

Bacterial pathogens face iron limitation in a host environment. To overcome this challenge, they produce siderophores, small iron-chelating molecules.

Probiotics, bioactive compounds and dietary patterns for the effective management of hyperuricemia: a review

Hyperuricemia is closely linked with an increased risk of developing hypertension, diabetes, renal failure and other metabolic syndromes. Probiotics, bioactive compounds and dietary patterns are safe cost-efficient ways to control hyperuricemia, whereas comprehensive reviews of their anti-hyperuricemic mechanisms are limited. This review summarizes the roles of probiotics, bioactive compounds and dietary patterns in treating hyperuricemia and critically reviews the possible mechanisms by which these interventions exert their activities. The dietary patterns are closely related to the occurrence of hyperuricemia through the indirect action of gut microbiota or the direct effects of host purine metabolism. The Mediterranean and Dietary Approaches to Stop Hypertension diets help reduce serum uric acid concentrations and thus prevent hyperuricemia. Meanwhile, probiotics alleviate hyperuricemia by ways of absorbing purine, restoring gut microbiota dysbiosis and inhibiting xanthine oxidase (XO) activity. Bioactive compounds such as polyphenols, peptides and alkaloids exert various anti-hyperuricemic effects, by regulating urate transporters, blocking the active sites of XO and inhibiting the toll-like receptor 4/nuclear factor kappa B signaling pathway and NOD-, LRR- and pyrin domain-containing protein 3 signaling pathway. This review will assist people with hyperuricemia to adopt a healthy diet and contribute to the application of natural products with anti-hyperuricemic activity.

Gut microbiota remodeling: A promising therapeutic strategy to confront hyperuricemia and gout

The incidence of hyperuricemia (HUA) and gout continuously increases and has become a major public health problem. The gut microbiota, which colonizes the human intestine, has a mutually beneficial and symbiotic relationship with the host and plays a vital role in the host's metabolism and immune regulation. Structural changes or imbalance in the gut microbiota could cause metabolic disorders and participate in the synthesis of purine-metabolizing enzymes and the release of inflammatory cytokines, which is closely related to the occurrence and development of the metabolic immune disease HUA and gout. The gut microbiota as an entry point to explore the pathogenesis of HUA and gout has become a new research hotspot. This review summarizes the characteristics of the gut microbiota in patients with HUA and gout. Meanwhile, the influence of different dietary structures on the gut microbiota, the effect of the gut microbiota on purine and uric acid metabolism, and the internal relationship between the gut microbiota and metabolic endotoxemia/inflammatory factors are explored. Moreover, the intervention effects of probiotics, prebiotics, and fecal microbial transplantation on HUA and gout are also systematically reviewed to provide a gut flora solution for the prevention and treatment of related diseases.

Folic acid and zinc improve hyperuricemia by altering the gut microbiota of rats with high-purine diet-induced hyperuricemia

A high-purine diet can cause hyperuricemia and destroy the microbial composition of the gut microbiota. Both folic acid and zinc significantly reduce uric acid levels and alleviate hyperuricemia. However, whether the underlying mechanisms are associated with the regulation of the gut microbiota remain unknown. To explore alterations of the gut microbiota related to folic acid and zinc treatment in rats with hyperuricemia in our study. A hyperuricemic rat model was established with a high-purine diet. The effects of folic acid and zinc on uric acid levels were evaluated. Alterations of the gut microbiota related to hyperuricemia and the treatments were evaluated by sequencing using the Illumina MiSeq system. The results demonstrated that uric acid levels dropped observably, and the activities of adenosine deaminase (ADA) and xanthine oxidase (XOD) were downregulated after folic acid or zinc intervention. 16S rRNA gene sequencing-based gut microbiota analysis revealed that folic acid and zinc enhanced the abundance of probiotic bacteria and reduced that of pathogenic bacteria, thus improving intestinal barrier function. PICRUST analysis indicated that folic acid and zinc restored gut microbiota metabolism. These findings indicate that folic acid and zinc ameliorate hyperuricemia by inhibiting uric acid biosynthesis and stimulating uric acid excretion by modulating the gut microbiota. Thus, folic acid and zinc may be new and safe therapeutic agents to improve hyperuricemia.

The Interaction Between Dietary Fructose and Gut Microbiota in Hyperuricemia and Gout

With the worldwide epidemics of hyperuricemia and associated gout, the diseases with purine metabolic disorders have become a serious threat to human public health. Accumulating evidence has shown that they have been linked to increased consumption of fructose in humans, we hereby made a timely review on the roles of fructose intake and the gut microbiota in regulating purine metabolism, together with the potential mechanisms by which excessive fructose intake contributes to hyperuricemia and gout. To this end, we focus on the understanding of the interaction between a fructose-rich diet and the gut microbiota in hyperuricemia and gout to seek for safe, cheap, and side-effect-free clinical interventions. Furthermore, fructose intake recommendations for hyperuricemia and gout patients, as well as the variety of probiotics and prebiotics with uric acid-lowering effects targeting the intestinal tract are also summarized to provide reference and guidance for the further research.

The next generation beneficial actions of novel probiotics as potential therapeutic targets and prediction tool for metabolic diseases

The prevalence of metabolic disease has rising and affected over 1,000 million populations globally. Since the metabolic disease and its related complication are board, it has become the major health hazard of modern world. However, Long term medication of metabolic disease may cause serious side effects and risk for adverse health problems. Recently, emerging studies focus on exploring the mechanistic details of metabolic state in disease development and progression. Gut bacteria ecosystem was considered to play a pivotal role in regulating energy homeostasis and great associated with the development of metabolic disease. Accumulated evidences indicated that Akkermansia muciniphila, Faecalibacterium prausnitzii, and Roseburia hominis improve the balance of the microecology in the intestine of the host and have positive effects on enhancing nutrients absorption. Hence, the novel probiotics as therapeutic target to modify gut microbiota generally focus on improving microbiota dysbiosis, and offers new prospects for treating metabolic disease. In the present review, we discuss the significant roles and regulatory properties of specific bacterium in the context of intestinal microbial balance, explores the kinds of harmful/beneficial bacteria that were likely to act as indicator for metabolic disease. Further proposed a stepwise procedure in the basis of sequencing technology with that of innovative option to reestablish the microbial equilibrium and prevent metabolic disease.

Extracytoplasmic Function Sigma Factors Governing Production of the Primary Siderophores in Pathogenic Burkholderia Species

Bacteria respond to changing environments by modulating their gene expression programs. One of the mechanisms by which this may be accomplished is by substituting the primary σ factor with an alternative σ factor belonging to the family of extracytoplasmic function (ECF) σ factors. ECF σ factors are activated only in presence of specific signals, and they direct the RNA polymerase (RNAP) to transcribe a defined subset of genes. One condition, which may trigger the activation of an ECF σ factor, is iron limitation. To overcome iron starvation, bacteria produce and secrete siderophores, which chelate iron and facilitate its cellular uptake. In the genus Burkholderia, which includes several serious human pathogens, uptake of iron is critical for virulence, and expression of biosynthetic gene clusters encoding proteins involved in synthesis and transport of the primary siderophores are under control of an ECF σ factor. This review summarizes mechanisms involved in regulation of these gene clusters, including the role of global transcriptional regulators. Since siderophore-mediated iron acquisition is important for virulence, interference with this process constitutes a viable approach to the treatment of bacterial infections.

Fisetin Improves Hyperuricemia-Induced Chronic Kidney Disease via Regulating Gut Microbiota-Mediated Tryptophan Metabolism and Aryl Hydrocarbon Receptor Activation

The intestinal flora serves a critical role in the development of hyperuricemia-induced chronic kidney disease (CKD). We previously found that natural flavonol fisetin exhibited nephroprotective effects in hyperuricemic mice. However, the mechanism remains largely unknown. To investigate the underlying mechanism of fisetin, mice were fed with potassium oxonate and adenine to introduce hyperuricemia-induced CKD. Fisetin improved kidney function, ameliorated renal fibrosis, and restored enteric dysbacteriosis in hyperuricemia-induced CKD mice. Meanwhile, gut microbiota-derived tryptophan metabolites, especially l-kynurenine, showed correlations with nephroprotective profiles of fisetin. Additionally, the kidney expression of the aryl hydrocarbon receptor (AHR), an endogenous receptor of l-kynurenine, was enhanced in hyperuricemic mice and further reduced in fisetin-treated mice. Finally, in vitro results showed that inhibition of AHR activation attenuated l-kynurenine-induced fibrosis. These results highlighted that fisetin protected against hyperuricemia-induced CKD via modulating gut microbiota-mediated tryptophan metabolism and AHR activation.

Role of the SOS Response in the Generation of Antibiotic Resistance In Vivo

The SOS response to DNA damage is a conserved stress response in Gram-negative and Gram-positive bacteria. Although this pathway has been studied for years, its relevance is still not familiar to many working in the fields of clinical antibiotic resistance and stewardship. Under some conditions, the SOS response favors DNA repair and preserves the genetic integrity of the organism. On the other hand, the SOS response also includes induction of error-prone DNA polymerases, which can increase the rate of mutation, called the mutator phenotype or "hypermutation." As a result, mutations can occur in genes conferring antibiotic resistance, increasing the acquisition of resistance to antibiotics. Almost all of the work on the SOS response has been on bacteria exposed to stressors in vitro. In this study, we sought to quantitate the effects of SOS-inducing drugs in vivo, in comparison with the same drugs in vitro. We used a rabbit model of intestinal infection with enteropathogenic Escherichia coli strain E22. SOS-inducing drugs triggered the mutator phenotype response in vivo as well as in vitro. Exposure of E. coli strain E22 to ciprofloxacin or zidovudine, both of which induce the SOS response in vitro, resulted in increased antibiotic resistance to 3 antibiotics: rifampin, minocycline, and fosfomycin. Zinc was able to inhibit the SOS-induced emergence of antibiotic resistance in vivo, as previously observed in vitro. Our findings may have relevance in reducing the emergence of resistance to new antimicrobial drugs.

Bacillus Subtilis 29784 as a Feed Additive for Broilers Shifts the Intestinal Microbial Composition and Supports the Production of Hypoxanthine and Nicotinic Acid

The probiotic Bacillus subtilis strain 29784 (Bs29784) has been shown to improve performance in broilers. In this study, we used a metabolomic and 16S rRNA gene sequencing approach to evaluate effects of Bs29874 in the broiler intestine. Nicotinic acid and hypoxanthine were key metabolites that were produced by the strain in vitro and were also found in vivo to be increased in small intestinal content of broilers fed Bs29784 as dietary additive. Both metabolites have well-described anti-inflammatory effects in the intestine. Furthermore, Bs29784 supplementation to the feed significantly altered the ileal microbiome of 13-day-old broilers, thereby increasing the abundance of genus Bacillus, while decreasing genera and OTUs belonging to the Lactobacillaceae and Enterobacteriacae families. Moreover, Bs29784 did not change the cecal microbial community structure, but specifically enriched members of the family Clostridiales VadinBB60, as well as the butyrate-producing families Ruminococcaceae and Lachnospiraceae. The abundance of various OTUs and genera belonging to these families was significantly associated with nicotinic acid levels in the cecum, suggesting a possible cross-feeding between B. subtilis strain 29784 and these beneficial microbes. Taken together, the data indicate that Bs29784 exerts its described probiotic effects through a combined action of its metabolites on both the host and its microbiome.

Protective effects of Poria cocos and its components against cisplatin-induced intestinal injury

ETHNOPHARMACOLOGICAL RELEVANCE

Poria cocos (Schw.) Wolf (Poria) is a well-known traditional medicinal fungus. It has been considered to possess spleen-invigorating (Jianpi) effects in traditional Chinese medicine, and is used clinically to treat spleen deficiency (Pixu) with symptoms of intestinal disorders such as diarrhea, indigestion, mucositis and weight loss.

THE AIM OF THIS STUDY

To investigate the protective effects of Poria and its three component fractions (Water-soluble polysaccharides, WP; alkali-soluble polysaccharides, AP; triterpene acids, TA) on cisplatin-induced intestinal injury and explore the underlying mechanisms.

MATERIALS AND METHODS

C57BL/6 mice were treated with Poria powder (PP), WP, AP and TA by oral gavage respectively for 13 days, and intraperitoneally injected with 10 mg/kg of cisplatin on day 10 to conduct a cisplatin-induced intestinal injury model. Pathological changes of ileum and colon were examined using H&E staining. The composition of gut microbiota and the alteration of host metabolites were characterized by 16S rDNA amplicon sequencing and UPLC-QTOF-MS/MS based untargeted metabolomics analysis.

RESULTS

PP and WP attenuated the cisplatin-induced ileum and colon injury, and WP alleviated the weight loss and reversed the elevation of IL-2, IL-6 in serum. Both PP and WP could mitigate cisplatin-induced dysbiosis of gut microbiota, in particular PP and WP decreased the abundance of pathogenic bacteria including Proteobacteria, Cyanobacteria, Ruminococcaceae and Helicobacteraceae, while WP promoted the abundance of probiotics, such as Erysipelotrichaceae and Prevotellaceae. Moreover, WP attenuated the cisplatin-induced alteration of metabolic profiles. The levels of potential biomarkers, including xanthine, L-tyrosine, uridine, hypoxanthine, butyrylcarnitine, lysoPC (18:0), linoleic acid, (R)-3-hydroxybutyric acid, D-ribose, thiamine monophosphate, indolelactic acid and plamitic acid, showed significant correlations with intestinal flora.

CONCLUSIONS

PP and WP possess protective effects against cisplatin-induced intestinal injury via potentially regulating the gut microbiota and metabolic profiles.

Chicory ameliorates hyperuricemia via modulating gut microbiota and alleviating LPS/TLR4 axis in quail

BACKGROUND

High-purine diet can cause gut microbiota disorder, which is closely related to the occurrence of hyperuricemia (HUA). At the same time, the development of HUA is often accompanied by renal impairment. Chicory, a natural medicine, has a significant effect on lowering uric acid. However, whether its concrete mechanism is associated with the regulation of gut microbiota and renal damage is still unclear.

METHODS

Hyperuricemic quails induced by high-purine diet were used, and quails were divided into control (CON), model (MOD), and model plus high, middle, low doses of chicory. The uricosuric effect was evaluated by detecting the uric acid levels in serum and feces. Meanwhile, the morphology of intestine and kidney were observed by hematoxylin and eosin (HE) staining, and the expression of intestinal barrier junction proteins Occludin, Claudin-1 were detected by quantitative real-time polymerase chain reaction (qPCR) and western blotting. Furthermore, the latent mechanism was clarified by analyzing 16S rRNA amplicon of gut microbiota and measuring the changes of LPS/TLR4 axis inflammatory response of the kidney by western blotting and enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results showed that serum uric acid levels were significantly decreased, and the feces uric acid levels were noticeably increased after the intervention of chicory. In addition, chicory could repair the damage of intestinal mucosa and improve the permeability of intestinal barrier. Moreover, the 16S rRNA sequencing analysis uncovered that chicory restored gut microbiota by increasing the probiotics flora (Bifidobacterium, Erysipelotrichaceae) and reducing the pathogenic bacteria group (Helicobacteraceae). Furthermore, it was found that chicory reduced the LPS/TLR4 axis inflammatory response by down regulating the serum LPS and TLR4/NF-κB inflammatory pathway in kidney, thus promoting the excretion of uric acid in kidney.

CONCLUSION

Chicory intervention ameliorated HUA via modulating the imbalance of gut microbiota and suppressing LPS/TLR4 axis inflammatory reaction in quail model, which may be a promising candidate for hyperuricemia-relieving properties.

Dietary Vitamin E Intake Was Inversely Associated with Hyperuricemia in US Adults: NHANES 2009-2014

INTRODUCTION

Current evidence on the association between dietary vitamin E intake and hyperuricemia risk is limited and conflicting.

OBJECTIVE

The aim of the study was to assess the association of dietary vitamin E intake with hyperuricemia in US adults.

METHODS

We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey, 2009-2014. Dietary vitamin E intake was evaluated through two 24-h dietary recall interviews. Logistic regression and restricted cubic spline models were used to examine the association between dietary vitamin E intake and hyperuricemia.

RESULTS

Overall, 12,869 participants were included. The prevalence of hyperuricemia was 19.35%. After adjustment for age, gender, BMI, race, educational level, smoking status, alcohol consumption, physical activity, total daily energy intake, total cholesterol, protein intake, glomerular filtration rate, serum Cr, use of uric acid drugs, and drug abuse, the odds ratio (95% confidence interval) of hyperuricemia for the highest tertile of dietary vitamin E intake was 0.77 (0.63-0.96) compared with that of the lowest tertile. In men, dietary vitamin E intake and hyperuricemia were negatively correlated. In stratified analyses by age (20-39, 40-59, and ≥60 years), dietary vitamin E intake was inversely associated with hyperuricemia only among participants aged ≥60 years. Dose-response analyses showed that dietary vitamin E intake was inversely associated with hyperuricemia in a nonlinear manner.

CONCLUSION

Dietary vitamin E intake was negatively correlated with hyperuricemia in US adults, especially among males and participants aged ≥60 years.

Inflammatory response of uric acid produced by Porphyromonas gingivalis gingipains

Uric acid is a potential metabolite that serves as a danger-associated molecular pattern (DAMP) and induces inflammatory responses in sterile environments. Porphyromonas gingivalis is a keystone periodontopathogen, and its gingipain proteases play a critical role in the pathogenesis of periodontitis. In this study, we demonstrate that P. gingivalis gingipains play a role in THP-1 macrophage uric acid production by increasing the expression and activity of xanthine oxidoreductase (XOR). Uric acid sodium salt induces caspase-1 activation, cell death, and the expression of proinflammatory cytokines, including IL-1α, IL-6, and IL-8, in the human keratinocyte HOK-16B cell line. Our results suggest that gingipain-induced uric acid can mediate inflammation in periodontal tissue cells.

Mitochondria, the gut microbiome and ROS

In this review, we discuss the connections between mitochondria and the gut microbiome provided by reactive oxygen species (ROS). We examine the mitochondrion as an endosymbiotic organelle that is a hub for energy production, signaling, and cell homeostasis. Maintaining a diverse gut microbiome is generally associated with organismal fitness, intestinal health and resistance to environmental stress. In contrast, gut microbiome imbalance, termed dysbiosis, is linked to a reduction in organismal well-being. ROS are essential signaling molecules but can be damaging when present in excess. Increasing ROS levels have been shown to influence human health, homeostasis of gut cells, and the gastrointestinal microbial community's biodiversity. Reciprocally, gut microbes can affect ROS levels, mitochondrial homeostasis, and host health. We propose that mechanistic understanding of the suite of bi-directional interactions between mitochondria and the gut microbiome will facilitate innovative interdisciplinary studies examining evolutionary divergence and provide novel treatments and therapeutics for disease. GLOSS: In this review, we focus on the nexus between mitochondria and the gut microbiome provided by reactive oxygen species (ROS). Mitochondria are a cell organelle that is derived from an ancestral alpha-proteobacteria. They generate around 80% of the adenosine triphosphate that an organism needs to function and release a range of signaling molecules essential for cellular homeostasis. The gut microbiome is a suite of microorganisms that are commensal, symbiotic and pathogenic to their host. ROS are one predominant group of essential signaling molecules that can be harmful in excess. We suggest that the mitochondria- microbiome nexus is a frontier of research that has cross-disciplinary benefits in understanding genetic divergence and human well-being.

Coupling 16S rDNA Sequencing and Untargeted Mass Spectrometry for Milk Microbial Composition and Metabolites from Dairy Cows with Clinical and Subclinical Mastitis

The internal environment of the cow's udder directly affects the udder health and milk quality. 16S rDNA sequencing and liquid chromatography-mass spectrometry (LC-MS) methods were used to investigate the significant differences in milk microbial diversity and metabolites among cows that are healthy (H) and those suffering from subclinical mastitis (SM) and clinical mastitis (CM). Results uncovered more than 16 and 192 differently abundant microbiota at the phylum and genus levels, respectively, and 673 different levels of metabolites enriched in 20 pathways in milk among the 3 groups. This study revealed the positive relevance between Staphylococcus and Streptococcus and ceramide in milk from CM cows. Similarly, Acinetobacter and Corynebacterium were positively associated with testosterone glucuronide and 5-methyl-tetrahydrofolate, in milk from SM cows. On the basis of the combined analysis of microbiome and metabolome, this study indicated that, apart from the exogenous pathogens, some beneficial symbiotic bacteria, such as Dietzia, Aeromicrobium, Alistipes, and Sphingobacterium, rarely reported in milk have been found to be significantly reduced during mastitis.

The altered gut microbiota of high-purine-induced hyperuricemia rats and its correlation with hyperuricemia

Some studies on the hyperuricemia (HUA) have focused on intestinal bacteria. To better understand the correlation between gut microbiota and HUA, we established a HUA rat model with high-purine diet, and used 16S rRNA genes sequencing to analyze gut microbiota changes in HUA rats. To analyze the potential role played by gut microbiota in HUA, we altered the gut microbiota of HUA rats with antibiotics, and compared the degree of uric acid elevation between HUA and antibiotic-fed HUA rats (Ab+HUA). Finally, we established a recipient rat model, in which we transplanted fecal microbiota of HUA and normal rats into recipient rats. Three weeks later, we compared the uric acid content of recipient rats. As a result, the diversity and abundance of the gut microbiota had changed in HUA rats. The Ab-fed HUA rats had significantly lower uric acid content compared to the HUA rats, and gut microbiota from HUA rats increased uric acid content of recipient rats. The genera Vallitalea, Christensenella and Insolitispirillum may associate with HUA. Our findings highlight the association between gut microbiota and HUA, and the potential role played by gut microbiota in HUA. We hope that this finding will promote the isolation and culture of HUA-related bacteria and orient HUA-related studies from being correlational to mechanistic. These steps will therefore make it possible for us to treat HUA using gut microbiota as the target.

Novel probiotic approach to counter Paenibacillus larvae infection in honey bees

American foulbrood (AFB) is a highly virulent disease afflicting honey bees (Apis mellifera). The causative organism, Paenibacillus larvae, attacks honey bee brood and renders entire hives dysfunctional during active disease states, but more commonly resides in hives asymptomatically as inactive spores that elude even vigilant beekeepers. The mechanism of this pathogenic transition is not fully understood, and no cure exists for AFB. Here, we evaluated how hive supplementation with probiotic lactobacilli (delivered through a nutrient patty; BioPatty) affected colony resistance towards a naturally occurring AFB outbreak. Results demonstrated a significantly lower pathogen load and proteolytic activity of honey bee larvae from BioPatty-treated hives. Interestingly, a distinctive shift in the microbiota composition of adult nurse bees occurred irrespective of treatment group during the monitoring period, but only vehicle-supplemented nurse bees exhibited higher P. larvae loads. In vitro experiments utilizing laboratory-reared honey bee larvae showed Lactobacillus plantarum Lp39, Lactobacillus rhamnosus GR-1, and Lactobacillus kunkeei BR-1 (contained in the BioPatty) could reduce pathogen load, upregulate expression of key immune genes, and improve survival during P. larvae infection. These findings suggest the usage of a lactobacilli-containing hive supplement, which is practical and affordable for beekeepers, may be effective for reducing enzootic pathogen-related hive losses.

Abnormal metabolism of gut microbiota reveals the possible molecular mechanism of nephropathy induced by hyperuricemia

The progression of hyperuricemia disease is often accompanied by damage to renal function. However, there are few studies on hyperuricemia nephropathy, especially its association with intestinal flora. This study combines metabolomics and gut microbiota diversity analysis to explore metabolic changes using a rat model as well as the changes in intestinal flora composition. The results showed that amino acid metabolism was disturbed with serine, glutamate and glutamine being downregulated whilst glycine, hydroxyproline and alanine being upregulated. The combined glycine, serine and glutamate could predict hyperuricemia nephropathy with an area under the curve of 1.00. Imbalanced intestinal flora was also observed. Flavobacterium, Myroides, Corynebacterium, Alcaligenaceae, Oligella and other conditional pathogens increased significantly in the model group, while Blautia and Roseburia, the short-chain fatty acid producing bacteria, declined greatly. At phylum, family and genus levels, disordered nitrogen circulation in gut microbiota was detected. In the model group, the uric acid decomposition pathway was enhanced with reinforced urea liver-intestine circulation. The results implied that the intestinal flora play a vital role in the pathogenesis of hyperuricemia nephropathy. Hence, modulation of gut microbiota or targeting at metabolic enzymes, i.e., urease, could assist the treatment and prevention of this disease.

OHMI: the ontology of host-microbiome interactions

BACKGROUND

Host-microbiome interactions (HMIs) are critical for the modulation of biological processes and are associated with several diseases. Extensive HMI studies have generated large amounts of data. We propose that the logical representation of the knowledge derived from these data and the standardized representation of experimental variables and processes can foster integration of data and reproducibility of experiments and thereby further HMI knowledge discovery.

METHODS

Through a multi-institutional collaboration, a community-based Ontology of Host-Microbiome Interactions (OHMI) was developed following the Open Biological/Biomedical Ontologies (OBO) Foundry principles. As an OBO library ontology, OHMI leverages established ontologies to create logically structured representations of (1) microbiomes, microbial taxonomy, host species, host anatomical entities, and HMIs under different conditions and (2) associated study protocols and types of data analysis and experimental results.

RESULTS

Aligned with the Basic Formal Ontology, OHMI comprises over 1000 terms, including terms imported from more than 10 existing ontologies together with some 500 OHMI-specific terms. A specific OHMI design pattern was generated to represent typical host-microbiome interaction studies. As one major OHMI use case, drawing on data from over 50 peer-reviewed publications, we identified over 100 bacteria and fungi from the gut, oral cavity, skin, and airway that are associated with six rheumatic diseases including rheumatoid arthritis. Our ontological study identified new high-level microbiota taxonomical structures. Two microbiome-related competency questions were also designed and addressed. We were also able to use OHMI to represent statistically significant results identified from a large existing microbiome database data analysis.

CONCLUSION

OHMI represents entities and relations in the domain of HMIs. It supports shared knowledge representation, data and metadata standardization and integration, and can be used in formulation of advanced queries for purposes of data analysis.

Do Global Regulators Hold the Key to Production of Bacterial Secondary Metabolites?

The emergence of multiple antibiotic resistant bacteria has pushed the available pool of antibiotics to the brink. Bacterial secondary metabolites have long been a valuable resource in the development of antibiotics, and the genus Burkholderia has recently emerged as a source of novel compounds with antibacterial, antifungal, and anti-cancer activities. Genome mining has contributed to the identification of biosynthetic gene clusters, which encode enzymes that are responsible for synthesis of such secondary metabolites. Unfortunately, these large gene clusters generally remain silent or cryptic under normal laboratory settings, which creates a hurdle in identification and isolation of these compounds. Various strategies, such as changes in growth conditions and antibiotic stress, have been applied to elicit the expression of these cryptic gene clusters. Although a number of compounds have been isolated from different Burkholderia species, the mechanisms by which the corresponding gene clusters are regulated remain poorly understood. This review summarizes the activity of well characterized secondary metabolites from Burkholderia species and the role of local regulators in their synthesis, and it highlights recent evidence for the role of global regulators in controlling production of secondary metabolites. We suggest that targeting global regulators holds great promise for the awakening of cryptic gene clusters and for developing better strategies for discovery of novel antibiotics.

Redox Sensing by PecS from the Plant Pathogen Pectobacterium atrosepticum and Its Effect on Gene Expression and the Conformation of PecS-Bound Promoter DNA

The plant pathogen Pectobacterium atrosepticum encounters a stressful environment when it colonizes the plant apoplast. Chief among the stressors are the reactive oxygen species (ROS) that are produced by the host as a first line of defense. Bacterial transcription factors in turn use these signals as cues to upregulate expression of virulence-associated genes. We have previously shown that the transcription factor PecS from P. atrosepticum binds the promoters that drive expression of pecS and pecM, which encodes an efflux pump, to repress gene expression. We show here that addition of oxidant relieves repression in vivo and in vitro. While reduced PecS distorts promoter DNA on binding, oxidized PecS does not, as evidenced by DNaseI footprinting. PecS oxidation is reversible, as shown by an oxidant-dependent quenching of the intrinsic tryptophan fluorescence that is completely reversed upon addition of a reducing agent. Cysteine 45 positioned at the PecS dimer interface is the redox sensor. Reduced PecS-C45A causes less DNA distortion on binding compared to wild-type PecS; addition of an oxidant has no effect on binding, and PecS-C45A cannot repress gene expression. Our data suggest that reduced PecS distorts its cognate DNA on binding, perhaps inducing a conformation in which promoter elements are suboptimally aligned for RNA polymerase binding, resulting in transcriptional repression. In contrast, oxidized PecS binds promoter DNA such that RNA polymerase may successfully compete with PecS for binding, allowing gene expression. This mode of regulation would facilitate induction of the PecS regulon when the bacteria encounter host-derived ROS in the plant apoplast.

A role for Vibrio vulnificus PecS during hypoxia

The genus Vibrio includes serious human pathogens, and mollusks are a significant reservoir for species such as V. vulnificus. Vibrio species encode PecS, a member of the multiple antibiotic resistance regulator (MarR) family of transcription factors; pecS is divergently oriented to pecM, which encodes an efflux pump. We report here that Vibrio species feature frequent duplications of pecS-pecM genes, suggesting evolutionary pressures to respond to distinct environmental situations. The single V. vulnificus PecS binds two sites within the pecS-pecM intergenic region with K_d = 0.3 ± 0.1 nM, a binding that is attenuated by the ligands xanthine and urate, except when promoter DNA is saturated with PecS. A unique target is found in the intergenic region between genes encoding the nitric oxide sensing transcription factor, NsrR, and nod; the nod-encoded nitric oxide dioxygenase is important for preventing nitric oxide stress. Reporter gene assays show that PecS-mediated repression of gene expression can be relieved in presence of ligand. Since xanthine and urate are produced as part of the oxidative burst during host defenses and under molluscan hypoxia, we propose that these intermediates in the host purine degradation pathway function to promote bacterial survival during hypoxia and oxidative stress.

Emerging Role of Purine Metabolizing Enzymes in Brain Function and Tumors

The growing evidence of the involvement of purine compounds in signaling, of nucleotide imbalance in tumorigenesis, the discovery of purinosome and its regulation, cast new light on purine metabolism, indicating that well known biochemical pathways may still surprise. Adenosine deaminase is important not only to preserve functionality of immune system but also to ensure a correct development and function of central nervous system, probably because its activity regulates the extracellular concentration of adenosine and therefore its function in brain. A lot of work has been done on extracellular 5′-nucleotidase and its involvement in the purinergic signaling, but also intracellular nucleotidases, which regulate the purine nucleotide homeostasis, play unexpected roles, not only in tumorigenesis but also in brain function. Hypoxanthine guanine phosphoribosyl transferase (HPRT) appears to have a role in the purinosome formation and, therefore, in the regulation of purine synthesis rate during cell cycle with implications in brain development and tumors. The final product of purine catabolism, uric acid, also plays a recently highlighted novel role. In this review, we discuss the molecular mechanisms underlying the pathological manifestations of purine dysmetabolisms, focusing on the newly described/hypothesized roles of cytosolic 5′-nucleotidase II, adenosine kinase, adenosine deaminase, HPRT, and xanthine oxidase.

Proteomic Profiling of Burkholderia thailandensis During Host Infection Using Bio-Orthogonal Noncanonical Amino Acid Tagging (BONCAT)

Burkholderia pseudomallei and B. mallei are the causative agents of melioidosis and glanders, respectively, and are often fatal to humans and animals. Owing to the high fatality rate, potential for spread by aerosolization, and the lack of efficacious therapeutics, B. pseudomallei and B. mallei are considered biothreat agents of concern. In this study, we investigate the proteome of Burkholderia thailandensis, a closely related surrogate for the two more virulent Burkholderia species, during infection of host cells, and compare to that of B. thailandensis in culture. Studying the proteome of Burkholderia spp. during infection is expected to reveal molecular mechanisms of intracellular survival and host immune evasion; but proteomic profiling of Burkholderia during host infection is challenging. Proteomic analyses of host-associated bacteria are typically hindered by the overwhelming host protein content recovered from infected cultures. To address this problem, we have applied bio-orthogonal noncanonical amino acid tagging (BONCAT) to B. thailandensis, enabling the enrichment of newly expressed bacterial proteins from virtually any growth condition, including host cell infection. In this study, we show that B. thailandensis proteins were selectively labeled and efficiently enriched from infected host cells using BONCAT. We also demonstrate that this method can be used to label bacteria in situ by fluorescent tagging. Finally, we present a global proteomic profile of B. thailandensis as it infects host cells and a list of proteins that are differentially regulated in infection conditions as compared to bacterial monoculture. Among the identified proteins are quorum sensing regulated genes as well as homologs to previously identified virulence factors. This method provides a powerful tool to study the molecular processes during Burkholderia infection, a much-needed addition to the Burkholderia molecular toolbox.

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis

Many bacteria encode biosynthetic proteins that produce a vast array of natural products. These compounds are often synthesized during host invasion as they function as virulence factors. In addition, such secondary metabolites have yielded numerous molecular scaffolds with pharmaceutical and clinical importance. The gene clusters that encode proteins responsible for synthesis of these compounds are typically silenced or "cryptic" under laboratory growth conditions, hampering discovery of novel lead compounds. We report here that MftR is a global repressor of secondary metabolite synthesis in Burkholderia thailandensis and that urate functions as a physiologically relevant inducer of gene expression. Biosynthetic gene clusters under MftR control include those associated with production of the antimicrobial bactobolins, the iron siderophore malleobactin, and the virulence factor malleilactone. MftR also controls additional genes associated with survival in a host environment, such as genes encoding components of the type III secretion system (T3SS) and proteins linked to anaerobic respiration. This observation not only has implications for understanding activation of gene regulatory networks during host invasion, but it also paves the way for isolation of novel therapeutic leads.

Zinc blocks SOS-induced antibiotic resistance via inhibition of RecA in Escherichia coli

Zinc inhibits the virulence of diarrheagenic E. coli by inducing the envelope stress response and inhibiting the SOS response. The SOS response is triggered by damage to bacterial DNA. In Shiga-toxigenic E. coli, the SOS response strongly induces the production of Shiga toxins (Stx) and of the bacteriophages that encode the Stx genes. In E. coli, induction of the SOS response is accompanied by a higher mutation rate, called the mutator response, caused by a shift to error-prone DNA polymerases when DNA damage is too severe to be repaired by canonical DNA polymerases. Since zinc inhibited the other aspects of the SOS response, we hypothesized that zinc would also inhibit the mutator response, also known as hypermutation. We explored various different experimental paradigms to induce hypermutation triggered by the SOS response, and found that hypermutation was induced not just by classical inducers such as mitomycin C and the quinolone antibiotics, but also by antiviral drugs such as zidovudine and anti-cancer drugs such as 5-fluorouracil, 6-mercaptopurine, and azacytidine. Zinc salts inhibited the SOS response and the hypermutator phenomenon in E. coli as well as in Klebsiella pneumoniae, and was more effective in inhibiting the SOS response than other metals. We then attempted to determine the mechanism by which zinc, applied externally in the medium, inhibits hypermutation. Our results show that zinc interferes with the actions of RecA, and protects LexA from RecA-mediated cleavage, an early step in initiation of the SOS response. The SOS response may play a role in the development of antibiotic resistance and the effect of zinc suggests ways to prevent it.

[Effects of Clostridium butyricum on serum uric acid and inflammatory mediators in rats with hyperuricemia]

OBJECTIVE

To investigate the effects of intragastric administration of Clostridium butyricum in regulating serum uric acid, lipopolysaccharides (LPS), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in rats with hyperuricemia rats.

METHODS

Forty SD rats were randomized into 4 equal groups, namely the normal control group, hyperuricemia model group, benzbromarone (3 mg/kg daily) intervention group and live Clostridium butyricum group (1.5×10⁷ CFU/day). Except for those in the control group, the rats were subjected to intragastric administration of yeast extract and oteracil potassium once daily for 12 weeks to induce hyperuricemia with corresponding treatments. The changes in serum uric acid, lipopolysaccharides , IL-6 and TNF-α in each group were detected.

RESULTS

The serum level of uric acid was significantly higher in rats fed with high-purine diet than in the control rats (P<0.01), demonstrating the successful establishment of hyperuricemia models. In rats with hyperuricemia, serum uric acid level was positively correlated with the levels of LPS, IL-6 and TNF-α, and their serum levels decreased significantly and progressively with time in Benzbromarone group and Clostridium butyricum group. Benzbromarone was more effective in decreasing serum uric acid in the rats, while Clostridium butyricum produced a stronger effect in down-regulating the inflammatory mediators.

CONCLUSION

Chronic inflammatory reaction exists in rats with hyperuricemia. Intragastric administration of Clostridium butyricum can effectively decrease serum uric acid level and inhibit the inflammatory cytokines, and thus contributes to immune homeostasis in the intestines.

Combined Signature of the Fecal Microbiome and Metabolome in Patients with Gout

This study employed microbiome and metabolome analysis to explore the fecal signatures of gout patients. Fecal samples from 52 male individuals (26 healthy controls and 26 gout patients) were analyzed by ¹H NMR spectroscopy and Illumina Miseq sequencing. The signatures of microbiome showed being up-regulation of opportunistic pathogens, such as Bacteroides, Porphyromonadaceae Rhodococcus, Erysipelatoclostridium and Anaerolineaceae. The signatures of metabolome were some altered metabolites which may involve uric acid excretion, purine metabolism, and inflammatory responses. Meanwhile, the correlation between discrepant metabolites and microbial taxa indicated that they could be the combined signatures of gout. This study suggests that the combined analysis of the fecal microbiome and metabolome may effectively characterize diseases.

Aquaporin-3 mediates hydrogen peroxide-dependent responses to environmental stress in colonic epithelia

The colonic epithelium provides an essential barrier against the environment that is critical for protecting the body and controlling inflammation. In response to injury or gut microbes, colonic epithelial cells produce extracellular hydrogen peroxide (H₂O₂), which acts as a potent signaling molecule affecting barrier function and host defense. In humans, impaired regulation of H₂O₂ in the intestine has been associated with early-onset inflammatory bowel disease and colon cancer. Here, we show that signal transduction by H₂O₂ depends on entry into the cell by transit through aquaporin-3 (AQP3), a plasma membrane H₂O₂-conducting channel. In response to injury, AQP3-depleted colonic epithelial cells showed defective lamellipodia, focal adhesions, and repair after wounding, along with impaired H₂O₂ responses after exposure to the intestinal pathogen Citrobacter rodentium Correspondingly, AQP3^-/- mice showed impaired healing of superficial wounds in the colon and impaired mucosal innate immune responses against C. rodentium infection, manifested by reduced crypt hyperplasia, reduced epithelial expression of IL-6 and TNF-α, and impaired bacterial clearance. These results elucidate the signaling mechanism of extracellular H₂O₂ in the colonic epithelium and implicate AQP3 in innate immunity at mucosal surfaces.

Biological Activities of Uric Acid in Infection Due to Enteropathogenic and Shiga-Toxigenic Escherichia coli

In previous work, we identified xanthine oxidase (XO) as an important enzyme in the interaction between the host and enteropathogenic Escherichia coli(EPEC) and Shiga-toxigenic E. coli(STEC). Many of the biological effects of XO were due to the hydrogen peroxide produced by the enzyme. We wondered, however, if uric acid generated by XO also had biological effects in the gastrointestinal tract. Uric acid triggered inflammatory responses in the gut, including increased submucosal edema and release of extracellular DNA from host cells. While uric acid alone was unable to trigger a chloride secretory response in intestinal monolayers, it did potentiate the secretory response to cyclic AMP agonists. Uric acid crystals were formed in vivo in the lumen of the gut in response to EPEC and STEC infections. While trying to visualize uric acid crystals formed during EPEC and STEC infections, we noticed that uric acid crystals became enmeshed in the neutrophilic extracellular traps (NETs) produced from host cells in response to bacteria in cultured cell systems and in the intestine in vivo Uric acid levels in the gut lumen increased in response to exogenous DNA, and these increases were enhanced by the actions of DNase I. Interestingly, addition of DNase I reduced the numbers of EPEC bacteria recovered after a 20-h infection and protected against EPEC-induced histologic damage.

Animal Models of Enterohemorrhagic Escherichia coli Infection

The first major outbreaks caused by enterohemorrhagic Escherichia coli (EHEC) raised public and medical awareness of the risks associated with acquiring this potentially deadly infection. The widespread presence of these organisms in the environment, the severity of the clinical sequelae, and the lack of treatment options and effective preventive measures demand that we obtain a better understanding of how this group of organisms cause disease. Animal models allow study of the processes and factors that contribute to disease and, as such, form a valuable tool in the repertoire of infectious disease researchers. Yet despite more than 30 years of research, it seems that no single model host reproduces the full spectrum of clinical disease induced by EHEC in humans. In the first part of this review, a synopsis of what is known about EHEC infections is garnered from human outbreaks and biopsy specimens. The main features and limitations of EHEC infection models that are based on the three most commonly used species (pigs, rabbits, and mice) are described within a historical context. Recent advances are highlighted, and a brief overview of models based on other species is given. Finally, the impact of the host on moderating EHEC infection is considered in light of growing evidence for the need to consider the biology and virulence strategies of EHEC in the context of its niche within the intestine.