Proteus mirabilis Urease: Unsuspected Non-Enzymatic Properties Relevant to Pathogenicity

Is bismuth(III) able to inhibit the activity of urease? Puzzling results in the quest for soluble urease complexes for agrochemical and medicinal applications

Bismuth(III) complexes have been reported to act as inhibitors of the enzyme urease, ubiquitously present in soils and implicated in the pathogenesis of several microorganisms. The general insolubility of Bi(III) complexes in water at neutral pH, however, is an obstacle to their utilization. In our quest to improve the solubility of Bi(III) complexes, we selected a compound reported to inhibit urease, namely [Bi(HEDTA)]·2H2O, and co-crystallized it with (i) racemic DL-histidine to obtain the conglomerate [Bi2(HEDTA)2(μ-D-His)2]·6H2O + [Bi2(HEDTA)2(μ-L-His)2]·6H2O, (ii) enantiopure L-histidine to yield [Bi2(HEDTA)2(μ-L-His)2]·6H2O, and (iii) cytosine to obtain [Bi(HEDTA)]·Cyt·2H2O. All compounds, synthesised by mechanochemical methods and by slurry, were characterized in the solid state by calorimetric (DSC and TGA) and spectroscopic (IR) methods, and their structures were determined using powder X-ray diffraction (PXRD) data. All compounds show an appreciable solubility in water, with values ranging from 6.8 mg mL-1 for the starting compound [Bi(HEDTA)]·2H2O to 36 mg mL-1 for [Bi2(HEDTA)2(μ-L-His)2]·6H2O. The three synthesized compounds as well as [Bi(HEDTA)]·2H2O were then tested for inhibition activity against urease. Surprisingly, no enzymatic inhibition was observed during in vitro assays using Canavalia ensiformis urease and in vivo assays using cultures of Helicobacter pylori, raising questions on the efficacy of Bi(III) compounds to counteract the negative effects of urease activity in the agro-environment and in human health.

In vitro antibacterial and antioxidant activity of flavonoids from the roots of Tephrosia vogelii: a combined experimental and computational study

Tephrosia vogelii is a traditional medicinal plant used to treat hypertension, diarrhea and urinary disorders. Silica gel chromatographic separation of CH2Cl2/MeOH (1:1) roots extract of T. vogelii afforded seven compounds namely; β-sitosterol (1a), stigmasterol (1b), 6a, 12a-dehydro-deguelin (2), tephrosin (3), maackiain (4), obovatin (5) and 6-oxo, 6a, 12a-dehydro-deguelin (6). GC-MS analysis of essential oils from the root of T. vogelii displayed a total of 17 compounds of which cis-nerolidol (41.7 %) and cadinol (19.7 %) were the major constituents. CH2Cl2/MeOH (1:1) extract, MeOH extract, maackiain (4) and obovatin (5) showed moderate inhibitory activity against Pseudomonas aeruginosa with MIC value of 0.5, 0.66, 0.83 and 0.83 mg/mL, respectively, compared to ciprofloxacin (MIC of 0.078 μg/mL). 6a, 12a-dihydro-deguelin (2), and 6-oxo, 6a, 12a-dehydro-deguelin (6) displayed significant activity against S. epidermis with MIC values of 0.66 mg/mL. Tephrosin (3) and maackiain (4) also showed moderate antibacterial activity against Staphylococcus aureus and Proteus mirabilis with MIC values of 0.83 and 0.5 mg/mL, respectively, compared to ciprofloxacin (0.312 μg/mL). The radical scavenging activity results indicated that tephrosin (3), obovatin (5) and 6-oxo, 6a, 12a-dehydro-deguelin (6) showed potent DPPH scavenging activity with IC50 values of 10.97, 10.43 and 10.73 μg/mL, respectively, compared to ascorbic acid (IC50 of 5.83 μg/mL). The docking prediction results revealed that 6a, 12a-dehydro-deguelin (2) displayed the best binding energy of -8.1 kcal/mol towards pyruvate kinase of S. aureus (PDB ID: 3T07) and -7.9 kcal/mol towards P. mirabilis urease (PDB ID: 1E9Y) and DNA gyrase B of Escherichia coli (PDB: 4F86) receptors compared to ciprofloxacin (-7.2 to -8.0 kcal/mol). Maackiain (4) and obovatin (5) displayed the minimum binding energy of -7.9 and -8.2 kcal/mol towards the LasR protein of P. aeruginosa (PDB: ID 2UV) and S. epidermidis FtsZ (PDB: ID 4M8I), respectively. The SwissADME drug-likeness and Pro Tox II toxicity prediction results indicated that compounds (2-6) obeyed Lipinski's rule of five with 0 violations and none of them were found to be hepatotoxic, mutagenic, and cytotoxic, respectively. The in vitro assessment results supported by the in silico analysis revealed that crude extracts and isolated compounds showed promising antibacterial and antioxidant activity, which proves the therapeutic potential of the roots of T. vogelii.

One enzyme, many faces: urease is also canatoxin

Ureases catalyze the hydrolysis of urea into carbamate and ammonia. Well-conserved proteins, most plant ureases are hexamers of a single chain subunit, like the most abundant isoform of the jack bean (Canavalia ensiformis) urease (JBU). Canatoxin (CNTX) was originally isolated from these seeds as a neurotoxic protein, and later characterized as an isoform of JBU with lower molecular mass and enzyme activity. Inactive CNTX oligomers form upon storage and stabilization of CNTX was achieved by treatment with low concentration of formaldehyde, avoiding its oligomerization. Here, nano-LC-MS/MS-based peptide analysis of CNTX revealed 804 amino acids identical to those of JBU's sequence (840 amino acids). De novo sequencing of CNTX revealed 15 different peptides containing substitution of amino acid residues, denoting CNTX as a product of a paralog gene of JBU. The MS/MS analysis of formaldehyde-treated CNTX showed that amino acid residues located at the trimer-trimer interface of JBU's hexamer were modified. The data confirmed that CNTX is an isoform of JBU and elucidated that stabilization by formaldehyde treatment occurs by modification of amino acids at the protein's surface that prevents the formation of the hexamer and of higher molecular mass inactive aggregates. HIGHLIGHTSCanatoxin (CNTX) is an isoform of jack bean urease (JBU, hexamer of 90 kDa chains)MS/MS sequencing of CNTX showed 804 amino acids identical in JBU (840 residues)Formaldehyde treatment of CNTX stabilizes its toxicity and avoids oligomerizationModified amino acid residues in CNTX are at the trimer-trimer interface of JBUCommunicated by Ramaswamy H. Sarma.

Advances in the study of the effects of gut microflora on microglia in Alzheimer's disease

Alzheimer's disease (AD) is a central nervous system (CNS) degenerative disorder, is caused by various factors including β-amyloid toxicity, hyperphosphorylation of tau protein, oxidative stress, and others. The dysfunction of microglia has been associated with the onset and advancement of different neurodevelopmental and neurodegenerative disorders, such as AD. The gut of mammals harbors a vast and complex population of microorganisms, commonly referred to as the microbiota. There's a growing recognition that these gut microbes are intrinsically intertwined with mammalian physiology. Through the circulation of metabolites, they establish metabolic symbiosis, enhance immune function, and establish communication with different remote cells, including those in the brain. The gut microbiome plays a crucial part in influencing the development and performance of microglia, as indicated by recent preclinical studies. Dysbiosis of the intestinal flora leads to alterations in the microglia transcriptome that regulate the interconversion of microglia subtypes. This conversation explores recent research that clarifies how gut bacteria, their byproducts, and harmful elements affect the activation and characteristics of microglia. This understanding opens doors to innovative microbial-based therapeutic strategies for early identification and treatment goals in AD.

N-acetylcysteine prevents catheter occlusion and inflammation in catheter associated-urinary tract infections by suppressing urease activity

Introduction

Proteus mirabilis is a key pathobiont in catheter-associated urinary tract infections (CA-UTIs), which is well known to form crystalline biofilms that occlude catheters. Urease activity alkylates urine through the release of ammonia, consequentially resulting in higher levels of Mg2+ and Ca2+ and formation of crystals. In this study, we showed that N-acetyl cysteine (NAC), a thiol antioxidant, is a potent urease inhibitor that prevents crystalline biofilm formation.

Methods

To quantify urease activity, Berthelot's method was done on bacterial extracts treated with NAC. We also used an in vitro catheterised glass bladder model to study the effect of NAC treatment on catheter occlusion and biofilm encrustation in P. mirabilis infections. Inductively-coupled plasma mass spectrometry (ICP-MS) was performed on catheter samples to decipher elemental profiles.

Results

NAC inhibits urease activity of clinical P. mirabilis isolates at concentrations as low as 1 mM, independent of bacterial killing. The study also showed that NAC is bacteriostatic on P. mirabilis, and inhibited biofilm formation and catheter occlusion in an in vitro. A significant 4-8log10 reduction in viable bacteria was observed in catheters infected in this model. Additionally, biofilms in NAC treated catheters displayed a depletion of calcium, magnesium, or phosphates (>10 fold reduction), thus confirming the absence of any urease activity in the presence of NAC. Interestingly, we also showed that not only is NAC anti-inflammatory in bladder epithelial cells (BECs), but that it mutes its inflammatory response to urease and P. mirabilis infection by reducing the production of IL-6, IL-8 and IL-1b.

Discussion

Using biochemical, microbiological and immunological techniques, this study displays the functionality of NAC in preventing catheter occlusion by inhibiting urease activity. The study also highlights NAC as a strong anti-inflammatory antibiofilm agent that can target both bacterial and host factors in the treatment of CA-UTIs.

Could the Urease of the Gut Bacterium Proteus mirabilis Play a Role in the Altered Gut-Brain Talk Associated with Parkinson's Disease?

Intestinal dysbiosis seems to play a role in neurodegenerative pathologies. Parkinson's disease (PD) patients have an altered gut microbiota. Moreover, mice treated orally with the gut microbe Proteus mirabilis developed Parkinson's-like symptoms. Here, the possible involvement of P. mirabilis urease (PMU) and its B subunit (PmUreβ) in the pathogenesis of PD was assessed. Purified proteins were given to mice intraperitoneally (20 μg/animal/day) for one week. Behavioral tests were conducted, and brain homogenates of the treated animals were subjected to immunoassays. After treatment with PMU, the levels of TNF-α and IL-1β were measured in Caco2 cells and cellular permeability was assayed in Hek 293. The proteins were incubated in vitro with α-synuclein and examined via transmission electron microscopy. Our results showed that PMU treatment induced depressive-like behavior in mice. No motor deficits were observed. The brain homogenates had an increased content of caspase-9, while the levels of α-synuclein and tyrosine hydroxylase decreased. PMU increased the pro-inflammatory cytokines and altered the cellular permeability in cultured cells. The urease, but not the PmUreβ, altered the morphology of α-synuclein aggregates in vitro, forming fragmented aggregates. We concluded that PMU promotes pro-inflammatory effects in cultured cells. In vivo, PMU induces neuroinflammation and a depressive-like phenotype compatible with the first stages of PD development.

Design, Synthesis, Characterization and Computational Studies of Mannich Bases Oxadiazole Derivatives as New Class of Jack Bean Urease Inhibitors

Mannich bases consisting of 1,3,4-oxadiazole-2-thione (3 a-3 l) bearing various substituents were synthesized and found potent jack bean urease inhibitors. The prepared compounds showed significantly good inhibitory activities with IC50 values from 9.45±0.05 to 267.42±0.23 μM. The compound 3 k containing 4-chlorophenyl (-R) and 4-hydroxyphenyl (-R') was most active with IC50 9.45±0.05 μM followed by 3 e (IC50 22.52±0.15 μM) in which -R was phenyl and -R' was isopropyl group. However, when both -R and -R' were either 4-chlorophenyl groups (3 l) or only -R' was 4-nitrophenyl (3 i), both compounds were found inactive. The detailed binding affinities of the produced compounds with protein were explored through molecular docking and data-supported in-vitro enzyme inhibition profiles. Drug likeness was confirmed by in silico ADME investigations and molecular orbital analysis (HOMO-LUMO) and electrostatic potential maps were got from DFT calculations. ESP maps exposed that there are two potential binding sites with the most positive and most negative parts.

Helicobacter pylori Urease: Potential Contributions to Alzheimer’s Disease

Alzheimer’s disease (AD) causes dementia and memory loss in the elderly. Deposits of beta-amyloid peptide and hyperphosphorylated tau protein are present in a brain with AD. A filtrate of Helicobacter pylori’s culture was previously found to induce hyperphosphorylation of tau in vivo, suggesting that bacterial exotoxins could permeate the blood–brain barrier and directly induce tau’s phosphorylation. H. pylori, which infects ~60% of the world population and causes gastritis and gastric cancer, produces a pro-inflammatory urease (HPU). Here, the neurotoxic potential of HPU was investigated in cultured cells and in rats. SH-SY5Y neuroblastoma cells exposed to HPU (50–300 nM) produced reactive oxygen species (ROS) and had an increased [Ca²⁺]i. HPU-treated BV-2 microglial cells produced ROS, cytokines IL-1β and TNF-α, and showed reduced viability. Rats received daily i.p., HPU (5 µg) for 7 days. Hyperphosphorylation of tau at Ser199, Thr205 and Ser396 sites, with no alterations in total tau or GSK-3β levels, and overexpression of Iba1, a marker of microglial activation, were seen in hippocampal homogenates. HPU was not detected in the brain homogenates. Behavioral tests were performed to assess cognitive impairments. Our findings support previous data suggesting an association between infection by H. pylori and tauopathies such as AD, possibly mediated by its urease.