Isozyme-Specific Ligands for O-acetylserine sulfhydrylase, a Novel Antibiotic Target

Conceived and designed the experiments: FS PC BC ES AM. Performed the experiments: FS RS ES PF SR. Analyzed the data: FS BC ES PF GEK PFC AM. Contributed reagents/materials/analysis tools: PC PB GC. Wrote the paper: FS GEK BC AM.The last step of cysteine biosynthesis in bacteria and plants is catalyzed by O-acetylserine sulfhydrylase. In bacteria, two isozymes, O-acetylserine sulfhydrylase-A and O-acetylserine sulfhydrylase-B, have been identified that share similar binding sites, although the respective specific functions are still debated. O-acetylserine sulfhydrylase plays a key role in the adaptation of bacteria to the host environment, in the defense mechanisms to oxidative stress and in antibiotic resistance. Because mammals synthesize cysteine from methionine and lack O-acetylserine sulfhydrylase, the enzyme is a potential target for antimicrobials. With this aim, we first identified potential inhibitors of the two isozymes via a ligand- and structure-based in silico screening of a subset of the ZINC library using FLAP. The binding affinities of the most promising candidates were measured in vitro on purified O-acetylserine sulfhydrylase-A and O-acetylserine sulfhydrylase-B from Salmonella typhimurium by a direct method that exploits the change in the cofactor fluorescence. Two molecules were identified with dissociation constants of 3.7 and 33 µM for O-acetylserine sulfhydrylase-A and O-acetylserine sulfhydrylase-B, respectively. Because GRID analysis of the two isoenzymes indicates the presence of a few common pharmacophoric features, cross binding titrations were carried out. It was found that the best binder for O-acetylserine sulfhydrylase-B exhibits a dissociation constant of 29 µM for O-acetylserine sulfhydrylase-A, thus displaying a limited selectivity, whereas the best binder for O-acetylserine sulfhydrylase-A exhibits a dissociation constant of 50 µM for O-acetylserine sulfhydrylase-B and is thus 8-fold selective towards the former isozyme. Therefore, isoform-specific and isoform-independent ligands allow to either selectively target the isozyme that predominantly supports bacteria during infection and long-term survival or to completely block bacterial cysteine biosynthesis.Yeshttp://www.plosone.org/static/editorial#pee

Research Letter—Outcomes of Outpatient Native Kidney Biopsies at the McGill University Health Center: A Quality Assurance Audit

Background: Percutaneous kidney biopsies are essential for diagnosis and management of kidney diseases. However, post-procedural bleeding is a significant risk associated with biopsies. At the McGill University Health Center, the 2 main hospitals, the Royal Victoria Hospital and the Montreal General Hospital, have different observation protocols for outpatient native kidney biopsies. Currently, patients are admitted for a 24-hour inpatient observation at the Montreal General Hospital, whereas patients biopsied at the Royal Victoria Hospital are discharged after 6 to 8 hours of observation at the end of the day. Most Canadian centers do not admit patients for an overnight observation, and it was unclear why this practice continued at the Montreal General Hospital. Objective: Our objective was to determine the incidence of complications post-renal biopsy over the past 5 years at both hospital sites, and compare them to each other, as well as to established rates in the available literature. Design: This assessment was designed as a quality assurance audit. Setting: This audit was conducted from a local registry of renal biopsies performed at the McGill University Health Center between January 2015 to January 2020. Patients: We included all adult patients (between the ages 18 and 80) with outpatient native kidney biopsies performed at the McGill University Health Center between 2015 and 2020. Measurements: We collected the included patients’ baseline demographics and risk factors at the time of biopsy, including age, BMI, creatinine, estimated glomerular filtration rate, pre- and post-biopsy hemoglobin, platelet, urea, coagulation profile, blood pressure, kidney side/size as well as needle size, and number of passes made. Methods: We compared the incidence of both minor and major bleeding complications at the Montreal General and the Royal Victoria Hospital. Variables that were measured included hemoglobin before and after biopsy, incidence of minor bleeding complications (defined by hematomas and gross hematuria), and incidence of major complications (defined by post-biopsy bleeding requiring either transfusions or another procedure to stop the bleeding), as well as the incidence of admissions post-biopsy. Results: The incidence of major complications was 2.87% over 5 years (5/174 patients), which is comparable with that reported in the literature. Our transfusion incidence was 1.72% (3/174 patients) and our embolization incidence was 2.3% (4/174 patients) over the 5 study years. Our total number of major events was low and the patients who had major events had significant risk factors for bleeding. All events occurred within 6 hours of observation. Limitations: This was a retrospective study with a low event number. Additionally, since the events included only those recorded at the McGill University Health Center, it is possible that the events of interest may have occurred at other hospital sites without the author’s knowledge. Conclusions: Based on the results of this audit, all major bleeding events occurred within 6 hours of a percutaneous kidney biopsy, suggesting that patients should be monitored for 6 to 8 hours following biopsy. The next step after this quality assurance audit is a quality improvement project and a cost-effectiveness analysis to assess whether post-biopsy practices should be amended at the McGill University Health Center

Sodium-glucose co-transporter 2 inhibitors in patients with chronic kidney disease

Diabetes drives an increasing burden of cardiovascular and renal disease worldwide, motivating the search for new hypoglycemic agents that confer cardiac and renal protective effects. Although initially developed as hypoglycemic agents, sodium-glucose co-transporter 2 (SGLT-2) inhibitors have since been studied in patients with and without diabetes for the management of heart failure and chronic kidney disease. A growing body of evidence supports the efficacy and safety of SGLT-2 inhibitors in patients with chronic kidney disease (CKD), based on complex mechanisms of action that extend far beyond glucosuria and that confer beneficial effects on cardiovascular and renal hemodynamics, fibrosis, inflammation, and end-organ protection. This review focuses on the pharmacology and pathophysiology of SGLT-2 inhibitors in patients with CKD, as well as their cardiovascular and renal effects in this population. We are focusing on the five agents that have been tested in cardiovascular outcome trials and that have been approved either in Europe or in North America: empagliflozin, dapagliflozin, canagliflozin, ertugliglozin, and sotagliflozin

Role of a Probiotic Strain in the Modulation of Gut Microbiota and Cytokines in Inflammatory Bowel Disease

Human gut is one of the major niches for anaerobes which play diverse functional role in host physiology and development. Gut microbiota maintains a homeostasis and dysbiosis may contribute in pathogenesis of different diseases including inflammatory bowel disease (IBD). Probiotic intervention is an established approach to maintain microbial homeostasis for the prevention and treatment of different diseases. The efficacy of probiotic strain Bacillus clausii UBBC-07 has been demonstrated and established in various diseases but its efficacy in IBD is under reported. To assess the effect of Bacillus clausii UBBC-07 in IBD patients, a randomized controlled study was conducted. Patients were randomly allocated to either placebo or probiotic B clausii UBBC-07 for four weeks along with the standard medical treatment (SMT). Enrolled patients were evaluated before and after intervention for GI survival of the given probiotic, change in GI microbiota, change in serum cytokines, serotonin and dopamine, symptoms of disease, physical, behavioral and psychological parameters. B clausii UBBC-07 showed good survival in IBD patients in the treatment group (p <0.01) without any reported adverse event. Metagenomic analysis showed that the given probiotic strain was able to modulate the gut microbiota in treated group. Phylum Firmicutes was increased and phylum Bacteriodetes was decreased in the probiotic treated group. A significant increase was observed in the abundance of bacterial genera Lactobacillus, Bifidobacterium and Faecalibacterium in the probiotic treated group (p<0.01) as compared to placebo group. These results indicated the given probiotic strain was able to modulate that gut microbiota in probiotic treated group. Significant increase was observed in IL-10 (p <0.05) and variable decrease in the secretion of IL-1β, TNF- α, IL-6, IL -17 and IL -23 in probiotic treated group. Change in the concentration of serum dopamine and serotonin in the treatment group was not significant as compared to placebo group. In the treatment group a significant decrease in the symptoms of IBD and improvement in the psychological parameter to various degrees was noted. These results indicated that probiotic strain B clausii UBBC-07 affected the gut microbiota and cytokine secretion and shown efficacy in IBD patients

GRID MIFs calculated for OASS-A and OASS-B.

<p>Red, blue and green contours identify the hydrogen bond acceptor, hydrogen bond donor and hydrophobic MIFs, respectively, calculated for OASS-A (pink cartoons) towards OASS-B (cyan cartoons). In <b>Panel B</b> compounds <b>1</b> and <b>13</b> are shown in ball and stick.</p

List of compounds tested against both OASS-A and OASS-B.

<p>List of compounds tested against both OASS-A and OASS-B.</p

List of compounds selected from virtual screening and tested against OASS-B.

*<p>due to the strong emission at 500 nm for excitation at 412 nm, this compound was assayed at concentrations lower than 100 µM and no binding was observed.</p

LigPlot of the wild type tetrapeptide ligand in the active site of <i>Haemophilus influenzae</i> OASS.

<p>The interactions between the Asn-Leu-Asn-Ile tetrapeptide and the active site residues of <i>H. influenzae</i> OASS-A (PDB code: 1Y7L) are reported. The figure was drawn with LigPlot program version 4.5.3 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0077558#pone.0077558-Laskowski1" target="_blank">[124]</a>.</p

Compounds selected by SBVS/LBVS-docking procedures for OASS-A and OASS-B.

<p>Compounds selected by SBVS/LBVS-docking procedures for OASS-A and OASS-B.</p