Urease inhibitors as potential drugs for gastric and urinary tract infections: a patent review

Successful treatment of encrusted cystitis: A case report and review of literature

BACKGROUND

Encrusted cystitis (EC) is a chronic inflammation of the bladder associated with mucosal encrustations. Early diagnosis and optimal treatment are not well established. Here, we report a case of EC successfully treated with com-bination therapy.

CASE SUMMARY

A 27-year-old man presented with frequency, urgency, dysuria, gross hematuria and suprapubic pain for 2 mo. He was diagnosed with EC based on characteristic calcifications of the bladder wall (most of them were struvite), cystoscopy and histopathological examination. He was cured after combined therapy of elimination of encrustations, bladder instillation of hyaluronic acid and injection of botulinum-A neurotoxin into bladder submucosal tissue.

CONCLUSION

Bladder instillation of hyaluronic acid and injection of botulinum-A neurotoxin into the bladder submucosal tissue can be used for treatment of EC.

Natural therapeutics for urinary tract infections-a review

Background

The recurrence of the urinary tract infections (UTI), following the antibiotic treatments suggests the pathogen’s resistance to conventional antibiotics. This calls for the exploration of an alternative therapy.

Main body

The anti-uropathogenic and bactericidal activity of many plant extracts was reported by many researchers, which involves only preliminary antibacterial studies using different basic techniques like disk diffusion, agar well diffusion, or minimum inhibitory concentration (MIC) of the crude plant extracts, but reports on the specific action of the phytoconstituents against uropathogens are limited. Vaccinium macrocarpon Aiton (cranberry) is the best-studied home remedy for UTI. Some evidences suggest that proanthocyanins present in cranberry, prevent bacteria from adhering to the walls of the urinary tract, subsequently blocking the further steps of uropathogenesis. Probiotics such as Lactobacillus and Bifidobacterium are beneficial microorganisms that may act by the competitive exclusion principle to defend against infections in the urogenital tracts. Reports on potential vaccine agents and antibodies targeting the different toxins and effecter proteins are still obscure except uropathogenic E. coli.

Conclusion

This review highlights some of the medicinal herbs used by aborigines to prevent or treat acute or chronic urinary tract infections, botanicals with established urobactericidal activity, clinical trials undertaken to compare the efficacy of cranberry products in UTI prevention, and other natural therapeutics reported for UTI.

Novel thiobarbiturates as potent urease inhibitors with potential antibacterial activity: Design, synthesis, radiolabeling and biodistribution study

Urease enzyme is a virulence factor that helps in colonization and maintenance of highly pathogenic bacteria in human. Hence, the inhibition of urease enzymes is well-established to be a promising approach for preventing deleterious effects of ureolytic bacterial infections. In this work, novel thiobarbiturate derivatives were synthesized and evaluated for their urease inhibitory activity. All tested compounds effectively inhibited the activity of urease enzyme. Compounds 1, 2a, 2b, 4 and 9 displayed remarkable anti-urease activity (IC₅₀ = 8.21-16.95 μM) superior to that of thiourea reference standard (IC₅₀ = 20.04 μM). Moreover, compounds 3a, 3g, 5 and 8 were equipotent to thiourea. Among the tested compounds, morpholine derivative 4 (IC₅₀ = 8.21 µM) was the most potent one, showing 2.5 folds the activity of thiourea. In addition, the antibacterial activity of the synthesized compounds was estimated against both standard strains and clinical isolates of urease producing bacteria. Compound 4 explored the highest potency exceeding that of cephalexin reference drug. Moreover, biodistribution study using radiolabeling approach revealed a remarked uptake of ^99mTc-compound 4 into infection induced in mice. Furthermore, a molecular docking analysis revealed proper orientation of title compounds into the urease active site rationalizing their potent anti-urease activity.

A Novel Urease Inhibitor of Ruminal Microbiota Screened through Molecular Docking

Inhibition of the urease activity of ruminal microbiota is not only beneficial for increasing dietary and endogenic urea-N utilization efficiency in ruminants but also might be applicable for the preservation of nitrogen fertilizer in soil and treatment of gastrointestinal and urinary tract infections caused by ureolytic bacteria. To discover urease inhibitors to efficiently target ruminal microbiota, the identified ruminal microbial metagenomic urease gene was used to construct a homology model to virtually screen urease inhibitors from the ChemDiv database by molecular docking. The GMQE and QMEAN values of the homology model were 0.85 and −0.37, respectively, indicating a good model quality. The inhibition effect of the screened urease inhibitor for ruminal urea degradation was assessed by ruminal microbial fermentation in vitro. The toxic effect of the candidate inhibitor was performed using gut Caco-2 cells in vitro. The results showed that compound 3-[1-[(aminocarbonyl)amino]-5-(4-methoxyphenyl)-1H-pyrrol-2-yl] propanoic acid (ChemDiv_ID: 6238-0047, IC₅₀ = 65.86 μM) was found to be the most effective urease inhibitor among the candidate compounds. Compound 6238-0047 significantly lowered the amount of urea degradation and ammonia production in ruminal microbial fermentation. The 24 h degradation rate of compound 6238-0047 in ruminal microbial fermentation was 3.32%–16.00%. In addition, compound 6238-0047 (10–100 μM) had no significant adverse effect on the cell viability of Caco-2 cells. Molecular docking showed that compound 6238-0047 could interact with Asp359 in the active site and Cys318 in the flap region by the hydrogen bond and Pi-Alkyl interaction, respectively. Compound 6238-0047 could be used as a novel inhibitor for decreasing the urease activity of ruminal microbiota.

Insights into the Design of Inhibitors of the Urease Enzyme - A Major Target for the Treatment of Helicobacter pylori Infections

Expressed by a variety of plants, fungi and bacteria, the urease enzyme is directly associated with the virulence factor of many bacteria, including Helicobacter pylori, a gram-negative bacterium related to several gastrointestinal diseases and responsible for one of the most frequent bacterial infections throughout the world. The Helicobacter pylori Urease (HPU) is a nickel-dependent metalloenzyme expressed in response to the environmental stress caused by the acidic pH of the stomach. The enzyme promotes the increase of gastric pH through acid neutralization by the products of urea hydrolysis, then critically contributing to the colonization and pathogenesis of the microorganism. At the same time, standard treatments for Helicobacter pylori infections have limitations such as the increasing bacterial resistance to the antibiotics used in the clinical practice. As a strategy for the development of novel treatments, urease inhibitors have proved to be promising, with a wide range of chemical compounds, including natural, synthetic and semisynthetic products to be researched and potentially developed as new drugs. In this context, this review highlights the advances in the field of HPU inhibition, presenting and discussing the basis for the research of new molecules aiming at the identification of more efficient therapeutic entities.

Identification of novel bacterial urease inhibitors through molecular shape and structure based virtual screening approaches

The enzyme urease is an essential colonizing factor of the notorious carcinogenic pathogen Helicobacter pylori (H. pylori), conferring acid resistance to the bacterium. Recently, antibiotic resistant strains have emerged globally with little to no alternative treatment available. In this study we propose novel urease inhibitors capable of controlling infection by H. pylori and other pathogenic bacteria. We employed hierarchal computational approaches to screen new urease inhibitors from commercial chemical databases followed by in vitro anti-urease assays. Initially ROCS shape-based screening was performed using o-chloro-hippurohydroxamic acid followed by molecular docking studies. Out of 1.83 million compounds, 1700 compounds were retrieved based on having a ROCS Tanimoto combo score in the range of values from 1.216 to 1.679. These compounds were further screened using molecular docking simulations and the 100 top ranked compounds were selected based on their Glide score. After structural classification of the top ranked compounds, eight compounds were selected and purchased for biological assays. The plausible binding modes of the most active compounds were also confirmed using molecular dynamics (MD) simulations. Compounds 1, 2 and 3 demonstrated good urease inhibitory properties (IC₅₀ = 0.32, 0.68 and 0.42 μM) compared to the other compounds. Enzyme kinetic studies revealed that compounds 1 and 3 are competitive inhibitors while 2 is a mixed type inhibitor of the urease enzyme. Cell based urease inhibition and MTT assay showed that these compounds blocked H. pylori urease activity, affecting bacterial growth and acid tolerance.

The enzyme urease is an essential colonizing factor of the notorious carcinogenic pathogen Helicobacter pylori (H. pylori), conferring acid resistance to the bacterium.

Synthesis, Biological Evaluation and Molecular Docking of Deferasirox and Substituted 1,2,4-Triazole Derivatives as Novel Potent Urease Inhibitors: Proposing Repositioning Candidate

A series of new deferasirox derivatives were synthesized through the reaction of monosubstituted hydrazides with 2-(2-hydroxyphenyl)-4H-benzo[e][1,3]oxazin-4-one. For the first time, deferasirox and some of its derivatives were evaluated for their in vitro inhibitory activity against Jack bean urease. The potencies of the members of this class of compounds are higher than that of acetohydroxamic acid. Two compounds, bearing tetrazole and hydrazine derivatives (bioisoester of carboxylate group), represented the most potent urease inhibitory activity with IC₅₀ values of 1.268 and 3.254 μm, respectively. In silico docking studies were performed to delineate possible binding modes of the compounds with the enzyme, urease. Docking analysis suggests that the synthesized compounds were anchored well in the catalytic site and extending to the entrance of binding pocket and thus restrict the mobility of the flap by interacting with its crucial amino acid residues, CME592 and His593. The overall results of urease inhibition have shown that these target compounds can be further optimized and developed as a lead skeleton for the discovery of novel urease inhibitors.

Insight into the inhibitory effects of Zanthoxylum nitidum against Helicobacter pylori urease and jack bean urease: Kinetics and mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum nitidum (Roxb.) DC. is a traditional Chinese medicine characterised by anti-inflammatory and anti-Helicobacter pylori, which is widely used to treat H. pylori-induced gastric disease in China. However, the underlying mechanism related to its anti-H. pylori activity remains unclear. Urease plays a crucial role in the colonisation and survival of H. pylori.

AIM OF THE STUDY

The root aqueous extract of Z. nitidum against H. pylori urease (HPU) and jack bean urease (JBU) was investigated to illuminate the inhibitory potency, kinetics and potential mechanism.

MATERIALS AND METHODS

Z. nitidum components were determined by UPLC. The enzyme inhibitory effects of Z. nitidum were examined using modified spectrophotometric Berthelot (phenol-hypochlorite) method. Urease inhibition kinetics were determined by Lineweaver-Burk plots. Sulfhydryl group reagents and Ni²⁺-binding inhibitors were used in the mechanism study. Moreover, the molecular docking technique was used to investigate the binding conformations of the main compounds of Z. nitidum on Urease.

RESULTS

According to UPLC results, the major components of Z. nitidum were magnoflorine, sanguinarine, nitidine chloride, chelerythrine, skimmianine and L-Sesamin. Z. nitidum has higher enzyme inhibitory activity on HPU (IC₅₀ = 1.29 ± 0.10 mg/mL) than on JBU (IC₅₀ = 2.04 ± 0.27 mg/mL). Enzyme inhibitory kinetic analysis revealed that the type of Z. nitidum inhibition against HPU was a slow-binding and mixed-type, whereas a slow-binding and non-competitive type inhibited JBU. Further mechanism study indicated that the active site of sulfhydryl group might be the target of inhibition by Z. nitidum. The molecular docking study indicated that the above six main components of Z. nitidum exhibited stronger affinity to HPU than to JBU through interacting with the key amino acid residues located on the mobile flap or interacting with the active site Ni²⁺. Results indicated that these components are potential active ingredients directed against urease.

CONCLUSIONS

Z. nitidum inactivated urease in a concentration-dependent manner through slow-binding inhibition and binding to the urease active site sulfhydryl group. Our investigation might provide experimental evidence for the traditional application of Z. nitidum in the treatment of H. pylori-associated gastric disorders.

Hydrazine clubbed 1,3-thiazoles as potent urease inhibitors: design, synthesis and molecular docking studies

Synthesis of a novel series of hydrazine clubbed 1,3-thiazoles (5a-m) has been described by reacting hydrazine-1-carbothioamides (3a-k) with α-chloro- or bromo-acetophenones (4a-d) in refluxing ethanol in good to excellent yields (65-86%). Structural confirmation was based upon spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, FT-IR and mass spectrometry. The biological application of these motifs has been demonstrated in terms of their strong urease inhibition activity. The results of in vitro study revealed that all the compounds are the potent inhibitors of urease. The IC₅₀ (ranging in between 110 and 440 nM) values were higher as compared to that of standard, i.e., thiourea (IC₅₀ = 490 ± 10 nM). The synthesized compounds were docked at the active sites of the Jack bean urease enzyme in order to explore the possible binding interactions of enzyme-ligand complexes; the results reinforced the in vitro biological activity results.

Crystal engineering of exemestane to obtain a co-crystal with enhanced urease inhibition activity

Co-crystallization is a phenomenon widely employed to enhance the physio-chemical and biological properties of active pharmaceutical ingredients (APIs). Exemestane, or 6-methyl-ideneandrosta-1,4-diene-3,17-dione, is an anabolic steroid used as an irreversible steroidal aromatase inhibitor, which is in clinical use to treat breast cancer. The present study deals with the synthesis of co-crystals of exemestane with thio-urea by liquid-assisted grinding. The purity and homogeneity of the exemestane-thio-urea (1:1) co-crystal were confirmed by single-crystal X-ray diffraction followed by thermal stability analysis on the basis of differential scanning calorimetry and thermogravimetric analysis. Detailed geometric analysis of the co-crystal demonstrated that a 1:1 co-crystal stoichiometry is sustained by N-H⋯O hydrogen bonding between the amine (NH2) groups of thio-urea and the carbonyl group of exemestane. The synthesized co-crystal exhibited potent urease inhibition activity in vitro (IC50 = 3.86 ± 0.31 µg ml-1) compared with the API (exemestane), which was found to be inactive, and the co-former (thio-urea) (IC50 = 21.0 ± 1.25 µg ml-1), which is also an established tested standard for urease inhibition assays in vitro. The promising results of the present study highlight the significance of co-crystallization as a crystal engineering tool to improve the efficacy of pharmaceutical ingredients. Furthermore, the role of various hydrogen bonds in the crystal stability is successfully analysed quantitatively using Hirshfeld surface analysis.

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

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In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.

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The present review with 411 references, in which we focused on the literature data published mainly from 2011 to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different molecular targets and their potential use as drugs to treat various types of diseases. Reference was also made to substantial literature data acquired before 2011 in this burgeoning research area.

Comparative Genomics of Antibiotic-Resistant Uropathogens Implicates Three Routes for Recurrence of Urinary Tract Infections

The rise of antimicrobial resistance in uropathogens has complicated the management of urinary tract infections (UTIs), particularly in patients who are afflicted by recurrent episodes of UTIs. Antimicrobial-resistant (AR) uropathogens persistently colonizing individuals at asymptomatic time points have been implicated in the pathophysiology of UTIs. The dynamics of uropathogen persistence following the resolution of symptomatic disease are, however, mostly unclear. To further our understanding, we determined longitudinal AR uropathogen carriage and clonal persistence of uropathogenic Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae isolates in the intestinal and urinary tracts of patients affected by recurrent and nonrecurrent UTIs. Clonal tracking of isolates in consecutively collected urine and fecal specimens indicated repeated transmission of uropathogens between the urinary tract and their intestinal reservoir. Our results further implicate three independent routes of recurrence of UTIs: (i) following an intestinal bloom of uropathogenic bacteria and subsequent bladder colonization, (ii) reinfection of the urinary tract from an external source, and (iii) bacterial persistence within the urinary tract. Taken together, our observation of clonal persistence following UTIs and uropathogen transmission between the intestinal and urinary tracts warrants further investigations into the connection between the intestinal microbiome and recurrent UTIs.IMPORTANCE The increasing antimicrobial resistance of uropathogens is challenging the continued efficacy of empiric antibiotic therapy for UTIs, which are among the most frequent bacterial infections worldwide. It has been suggested that drug-resistant uropathogens could persist in the intestine after the resolution of UTI and cause recurrences following periurethral contamination. A better understanding of the transmission dynamics between the intestinal and urinary tracts, combined with phenotypic characterization of the uropathogen populations in both habitats, could inform prudent therapies designed to overcome the rising resistance of uropathogens. Here, we integrate genomic surveillance with clinical microbiology to show that drug-resistant clones persist within and are readily transmitted between the intestinal and urinary tracts of patients affected by recurrent and nonrecurrent UTIs. Thus, our results advocate for understanding persistent intestinal uropathogen colonization as part of the pathophysiology of UTIs, particularly in patients affected by recurrent episodes of symptomatic disease.

Synthesis, Antioxidant and Antiurease Activities of Some New 5,6- dichloro-2-(4-fluorobenzyl)-1H-benzimidazole Derivatives Containing Furan, Oxadiazole, Triazole and Thiadiazole Moieties

Background:

Benzimidazoles and its derivatives have been attracting interest for many years because of their biological activities. Benzimidazoles containing different heterocyclic moieties have wide range of biological activities such as antimicrobial, antioxidant, anticancer, antiviral, etc.

Methods:

In this study, some benzimidazole derivatives containing furan, oxadiazole, triazole and thiadiazole moieties have been synthesized and then evaluated for their antioxidant and antiurease activities.

Results:

The results showed that all the tested benzimidazoles indicated remarkable urease inhibitory potentials with IC50 values ranging between 0.303±0.03 to 0.591±0.08 µM.

Conclusion:

In conclusion, synthesized benzimidazole derivatives showed good antioxidant and antiurease activities. Heterocyclic groups on benzimidazole nucleus enhance the activities.

Contribution of Resveratrol in the Development of Novel Urease Inhibitors: Synthesis, Biological Evaluation and Molecular Docking Studies

Aims and Objective:

A new library of resveratrol derivatives was designed and synthesized in excellent yield via two-step reaction utilizing Vilsmeier reaction as the first step and subsequent addition of substituted aromatic amine in the second step.

Methods:

Synthesized compounds were investigated for their antioxidant as well as for in vitro inhibition activity against jack bean urease enzyme. Compounds R3b and R4 with IC50 value 18.85±0.15 and 21.60±0.19µM against urease enzyme and 6.01±0.07 and 7.52±0.14µM in vitro- DPPH free radical scavenging activity have emerged as most active molecules from the selected library. Molecular simulation studies were also carried out for determining the interaction detail of newly synthesized compounds within a protein pocket.

Results and Conclusion:

Newly synthesized compounds were found to possess better docking score (-5.941 to -6.894) and binding energy (-46.854 to -56.455) as compared to the parent resveratrol (-5.45 and -20.155) which revealed that the newly synthesized compounds bind in a better way as compared to the parent molecule

Utility of anthranilic acid and diethylacetylenedicarboxylate for the synthesis of nitrogenous organo/organometallic compounds as urease inhibitors

Fumarate diester 3 was synthesized upon reacting anthranilic acid with diethylacetylenedicarboxylate. Compound 3 was reacted with different nucleophiles in mild reaction conditions. Selected reaction routes that afforded products 6, 9, 10, 11, and 12 were explained. The estimated mechanism for the reaction of 3 with ethylenediamine to afford 9 was proved by X-ray single-crystal and retro-synthetic reaction. Acetyl anthranilic acid was utilized with zinc and copper to afford the organometallic compounds 14a and 14b, respectively. Three single crystals were afforded for 3, 9 and the organocopper complex 14b. Target compounds were screened for their inhibitory potential against urease enzyme. Most compounds were more potent than thiourea as standard inhibitor, considering that oxopiperazine 9 exhibited double the activity: IC₅₀ = 8.16 ± 0.65 µM (thiourea IC₅₀ = 20.04 ± 0.33 µM). Docking studies were in agreement with the in vitro enzyme assay.

A patent update on therapeutic applications of urease inhibitors (2012-2018)

INTRODUCTION

Urease is a nickel-containing metalloenzyme that is commonly found in different bacteria, plants, algae, and fungi and mediates the growth of many pathogenic bacteria in the acidic environment of the stomach. Despite the large number of molecules known to have excellent urease inhibitory activity, there is an alarming lack of urease inhibitor drugs on the market.

AREAS COVERED

This review aims to provide a comprehensive overview of the different types of molecules patented as potent urease inhibitors from the year 2012 to 2018.

EXPERT OPINION

Urease is an important target to treat urease-related bacterial infections manifesting as gastric ulcers, urinary tract infections, and kidney stones. Although many different molecules as inhibitors of urease have been reported, only a few have advanced to clinical trials. The development of new effective urease inhibitors demands new suitable lead molecules. This review covers the patents on urease inhibitors in recent years (2012-2018) with a hope to bring into focus the issue and need for availability of new urease inhibitors on the market.

Investigation on the effect of alkyl chain linked mono-thioureas as Jack bean urease inhibitors, SAR, pharmacokinetics ADMET parameters and molecular docking studies

The increasing resistance of pathogens to common antibiotics, as well as the need to control urease activity to improve the yield of soil nitrogen fertilization in agricultural applications, has stimulated the development of novel classes of molecules that target urease as an enzyme. In this context, the newly developed compounds on the basis of 1-heptanoyl-3-arylthiourea family were evaluated for Jack bean urease enzyme inhibition activity to validate their role as potent inhibitors of this enzyme. 1-Heptanoyl-3-arylthioureas were obtained in excellent yield and characterized through spectral and elemental analysis. All the compounds displayed remarkable potency against urease inhibition as compared to thiourea standard. It was found that novel compounds fulfill the criteria of drug-likeness by obeying Lipinski's rule of five. Particularly compound 4a and 4c can serve as lead molecules in 4D (drug designing discovery and development). Kinetic mechanism and molecular docking studies also carried out to delineate the mode of inhibition and binding affinity of the molecules.

Systems Approaches for Unveiling the Mechanism of Action of Bismuth Drugs: New Medicinal Applications beyond Helicobacter Pylori Infection

Metallodrugs have been widely used as diagnostic and therapeutic agents. Understanding their mechanisms of action may lead to advances in rational drug design. However, to achieve this, diversified approaches are required because of the complexity of metal-biomolecule interactions. Bismuth drugs in combination with antibiotics as a quadruple therapy show excellent success rates in the eradication of Helicobacter pylori, even for antibiotic-resistant strains, and in fact, they have been used in the clinic for decades for the treatment of infection. Understanding the mechanism of action of bismuth drugs may extend their medicinal application beyond the treatment of H. pylori infection. This Account describes several general strategies for mechanistic studies of metallodrugs, including system pharmacology and metalloproteomics approaches. The application of these approaches is exemplified using bismuth drugs. Through a system pharmacology approach, we showed that glutathione- and multidrug-resistance-associated protein 1-mediated self-propelled disposal of bismuth in human cells might explain the selective toxicity of bismuth drugs to H. pylori but not the human host. The development of metalloproteomics has enabled extensive studies of the putative protein targets of metallodrugs with a dynamic range of affinity. Continuous-flow GE-ICP-MS allows simultaneous monitoring of metals and their associated proteins with relatively high affinity on a proteome-wide scale. The fluorescence approach relies on unique M ⁿ⁺-NTA-based fluorescence probes and is particularly applicable for mining those proteins that bind to metals/metallodrugs weakly or transiently. Integration of these methods with quantitative proteomics makes it possible to maximum coverage of bismuth-associated proteins, and the sustained efficacy of bismuth drugs lies in their ability to disrupt multiple biological pathways through binding and functional perturbation of key enzymes. The knowledge acquired by mechanistic studies of bismuth drugs led to the discovery of UreG as a new target for the development of urease inhibitors. The ability of Bi(III) to inhibit metallo-β-lactamase (MBL) activity through displacement of the Zn(II) cofactor renders bismuth drugs new potential as broad-spectrum inhibitors of MBLs. Therefore, bismuth drugs could be repurposed together with clinically used antibiotics as a cotherapy to cope with the current antimicrobial resistance crisis. We anticipate that the methodologies described in this Account are generally applicable for understanding the (patho)physiological roles of metals/metallodrugs. Our mechanism-guided discovery of new druggable targets as well as new medicinal applications of bismuth drugs will inspire researchers in relevant fields to engage in the rational design of drugs and reuse of existing drugs, eventually leading to the development of new effective therapeutics.

Synthesis of terpenoid oxo derivatives with antiureolytic activity

Urease is an important virulence factor for a variety of pathogenic bacteria strains such as Helicobacter pylori, which colonizes human gastric mucosa, and Proteus sp., responsible for urinary tract infections. Specific inhibition of urease activity could be a promising adjuvant strategy for eradication of these pathogens. Due to the interesting antiureolytic activity of carvone and the scant information regarding the inhibitory properties of corresponding monoterpenes, we decided to study selected monoterpenic ketones and their oxygen derivatives. Several monoterpenes and their terpenoid oxygen derivatives were evaluated in vitro against Sporosarcina pasteurii urease. The most effective inhibitors-derivatives of β-cyclocitral (ester 10 and bromolactone 14)-were described with [Formula: see text] of 46.7 µM and 45.8 µM, respectively. Active inhibitors of native urease were tested against H. pylori and Proteus mirabilis whole cells. Here, the most active inhibitor, 14, was characterized with IC₅₀ values of 0.32 mM and 0.61 mM for P. mirabilis and H. pylori, respectively. The antibacterial activity of a few tested inhibitors was also observed. Compound 14 limited the growth of E. coli ([Formula: see text]= 250 μg/mL). Interestingly, 10 was the only compound that was effective against both Gram-negative and Gram-positive bacteria. It had a [Formula: see text] of 150 μg/mL against E. coli and S. aureus. In the presented study a group of novel antiureolytic compounds was characterised. Besides carvone stereoisomers, these are the only terpenoid urease inhibitors described so far.

Recent advances in design of new urease inhibitors: A review

Urease is a nickel-dependent metalloenzyme found in plants, some bacteria, and fungi. Bacterial enzyme is of special importance since it has been demonstrated as a potent virulence factor for some species. Especially it is central to Helicobacter pylori metabolism and virulence being necessary for its colonization of the gastric mucosa, and is a potent immunogen that elicits a vigorous immune response. Therefore, it is not surprising that efforts to design, synthesize and evaluate of new inhibitors of urease are and active field of medicinal chemistry. In this paper recent advances on this field are reviewed.

Ureases: Historical aspects, catalytic, and non-catalytic properties - A review

Urease (urea amidohydrolase, EC 3.5.1.5) is a nickel-containing enzyme produced by plants, fungi, and bacteria that catalyzes the hydrolysis of urea into ammonia and carbamate. Urease is of historical importance in Biochemistry as it was the first enzyme ever to be crystallized (1926). Finding nickel in urease's active site (1975) was the first indication of a biological role for this metal. In this review, historical and structural features, kinetics aspects, activation of the metallocenter and inhibitors of the urea hydrolyzing activity of ureases are discussed. The review also deals with the non-enzymatic biological properties, whose discovery 40 years ago started a new chapter in the study of ureases. Well recognized as virulence factors due to the production of ammonia and alkalinization in diseases by urease-positive microorganisms, ureases have pro-inflammatory, endocytosis-inducing and neurotoxic activities that do not require ureolysis. Particularly relevant in plants, ureases exert insecticidal and fungitoxic effects. Data on the jack bean urease and on jaburetox, a recombinant urease-derived peptide, have indicated that interactions with cell membrane lipids may be the basis of the non-enzymatic biological properties of ureases. Altogether, with this review we wanted to invite the readers to take a second look at ureases, very versatile proteins that happen also to catalyze the breakdown of urea into ammonia and carbamate.

Targeting Helicobacter pylori urease activity and maturation: In-cell high-throughput approach for drug discovery

BACKGROUND

Helicobacter pylori is a bacterium strongly associated with gastric cancer. It thrives in the acidic environment of the gastric niche of large portions of the human population using a unique adaptive mechanism that involves the catalytic activity of the nickel-dependent enzyme urease. Targeting urease represents a key strategy for drug design and H. pylori eradication.

METHOD

Here, we describe a novel method to screen, directly in the cellular environment, urease inhibitors. A ureolytic Escherichia coli strain was engineered by cloning the entire urease operon in an expression plasmid and used to test in-cell urease inhibition with a high-throughput colorimetric assay. A two-plasmid system was further developed to evaluate the ability of small peptides to block the protein interactions that lead to urease maturation.

RESULTS

The developed assay is a robust cellular model to test, directly in the cell environment, urease inhibitors. The efficacy of a co-expressed peptide to affect the interaction between UreF and UreD, two accessory proteins necessary for urease activation, was observed. This event involves a process that occurs through folding upon binding, pointing to the importance of intrinsically disordered hot spots in protein interfaces.

CONCLUSIONS

The developed system allows the concomitant screening of a large number of drug candidates that interfere with the urease activity both at the level of the enzyme catalysis and maturation.

GENERAL SIGNIFICANCE

As inhibition of urease has the potential of being a global antibacterial strategy for a large number of infections, this work paves the way for the development of new candidates for antibacterial drugs.

Research progress in urinary tract infection and its therapeutic drugs

Objective

The objective of this study was to understand the pathological mechanism and therapeutic progress in the study of urinary tract infections to provide references for clinical diagnosis and identification and development of therapeutic drugs.

Methods

We summarized the types, pathological mechanisms, and therapeutic drugs for urinary tract infections on the basis of recent publications on these infections, both domestic and abroad.

Results and conclusions

Urinary tract infection is mainly caused by pathogenic bacterial infection and treated by targeting bacterial adhesion, bacterial toxin, protease, urease, and siderophores, as well as using pili as vaccines and small-molecule drugs. Vaccines that target bacterial adhesion can block well the interaction between pathogens and the body, thereby reducing the incidence of urinary tract infections. The clinical efficacy of vaccines targeting bacterial toxins and proteases needs further evaluation. Vaccines targeting iron carriers retard disease progression and attenuate bacterial colonization. Urease-targeted small-molecule drugs exhibit certain curative effects and serious side effects. Small pili-targeted drugs can prevent and treat urinary tract infections by blocking the colonization and invasion of pathogens in animal models of urinary tract infections on the bladder. Adhesive FimH antibodies have entered Phase I clinical trials. However, pilicides, mannosides, and vaccines that target pili, iron carriers, and other virulence factors are still in the experimental or preclinical stages of research.

Metallochaperone UreG serves as a new target for design of urease inhibitor: A novel strategy for development of antimicrobials

Urease as a potential target of antimicrobial drugs has received considerable attention given its versatile roles in microbial infection. Development of effective urease inhibitors, however, is a significant challenge due to the deeply buried active site and highly specific substrate of a bacterial urease. Conventionally, urease inhibitors are designed by either targeting the active site or mimicking substrate of urease, which is not efficient. Up to now, only one effective inhibitor—acetohydroxamic acid (AHA)—is clinically available, but it has adverse side effects. Herein, we demonstrate that a clinically used drug, colloidal bismuth subcitrate, utilizes an unusual way to inhibit urease activity, i.e., disruption of urease maturation process via functional perturbation of a metallochaperone, UreG. Similar phenomena were also observed in various pathogenic bacteria, suggesting that UreG may serve as a general target for design of new types of urease inhibitors. Using Helicobacter pylori UreG as a showcase, by virtual screening combined with experimental validation, we show that two compounds targeting UreG also efficiently inhibited urease activity with inhibitory concentration (IC)₅₀ values of micromolar level, resulting in attenuated virulence of the pathogen. We further demonstrate the efficacy of the compounds in a mammalian cell infection model. This study opens up a new opportunity for the design of more effective urease inhibitors and clearly indicates that metallochaperones involved in the maturation of important microbial metalloenzymes serve as new targets for devising a new type of antimicrobial drugs.

Urease, a metalloenzyme that catalyzes the hydrolysis of urea, plays important roles in the survival and virulence of many microbial pathogens, and has long been considered an important drug target for the development of novel antimicrobials. However, its deeply buried active site and highly specific substrate of bacterial urease make it very challenging to design effective urease inhibitors by conventional approaches. In this study, we reveal that a bismuth-based drug (colloidal bismuth subcitrate) inhibits urease activity in an unusual way. This drug binds the urease accessary protein UreG and inhibits its GTPase activity, thus perturbing nickel insertion into the apo-urease, a process called urease maturation. UreG is therefore proposed as an alternative target for the development of urease inhibitors. Using H. pylori UreG as an example, combined with virtual screening and experimental validation, we further show that several small molecules that bind and functionally disrupt UreG could indeed inhibit urease activity in bacteria and in a cell infection model and possess potent antimicrobial activity. In summary, we discovered metallochaperone UreG as a new target for the design of urease inhibitors. Such a strategy should have a broad application in the development of metalloenzyme inhibitors.

Urease-aided calcium carbonate mineralization for engineering applications: A review

Inducing calcium carbonate precipitation is another important function of urease in nature. The process takes advantage of the supply of carbonate ions derived from urea hydrolysis and of an increase in pH generated by the reaction, effects that in the presence of Ca²⁺ ions lead to the precipitation of CaCO₃. Further to its importance in nature, if performed in a biomimetic manner, the urease-aided CaCO₃ mineralization offers enormous potential in innovative engineering applications as an eco-friendly technique operative under mild conditions, to be used for remediation and cementation/deposition in field applications in situ. These include among others, the strengthening and consolidation of soil/sand, the protection and restoration of stone and concrete structures, conservation of stone cultural heritage materials, cleaning waste- and groundwater of toxic metals and radionuclides, and plugging geological formations for the enhancement of oil recovery and geologic CO₂ sequestration. In view of the potential of this newly emerging interdisciplinary branch of engineering, this article presents the principles of urease-aided calcium carbonate mineralization apposed to other biomineralization processes, and reviews the advantages and limitations of the technique compared to the conventional techniques presently in use. Further, it presents areas of its existing and potential applications, notably in geotechnical, construction and environmental engineering, and its future perspectives.

Biological Evaluation and Molecular Docking of Protocatechuic Acid from Hibiscus sabdariffa L. as a Potent Urease Inhibitor by an ESI-MS Based Method

Studies on enzyme inhibition remain a crucial area in drug discovery since these studies have led to the discoveries of new lead compounds useful in the treatment of several diseases. In this study, protocatechuic acid (PCA), an active compound from Hibiscus sabdariffa L. has been evaluated for its inhibitory properties against jack bean urease (JBU) as well as its possible toxic effect on human gastric epithelial cells (GES-1). Anti-urease activity was evaluated by an Electrospray Ionization-Mass Spectrometry (ESI-MS) based method, while cytotoxicity was assayed by the MTT method. PCA exerted notable anti-JBU activity compared with that of acetohydroxamic acid (AHA), with IC50 values of 1.7 and 3.2 µM, respectively. PCA did not show any significant cytotoxic effect on (GES-1) cells at concentrations ranging from 1.12 to 3.12 µM. Molecular docking study revealed high spontaneous binding ability of PCA to the active site of urease. Additionally, the anti-urease activity was found to be related to the presence of hydroxyl moieties of PCA. This study presents PCA as a natural urease inhibitor, which could be used safely in the treatment of diseases caused by urease-producing bacteria.

Sulfonamide-Linked Ciprofloxacin, Sulfadiazine and Amantadine Derivatives as a Novel Class of Inhibitors of Jack Bean Urease; Synthesis, Kinetic Mechanism and Molecular Docking

Sulfonamide derivatives serve as an important building blocks in the drug design discovery and development (4D) process. Ciprofloxacin-, sulfadiazine- and amantadine-based sulfonamides were synthesized as potent inhibitors of jack bean urease and free radical scavengers. Molecular diversity was explored and electronic factors were also examined. All 24 synthesized compounds exhibited excellent potential against urease enzyme. Compound 3e (IC₅₀ = 0.081 ± 0.003 µM), 6a (IC₅₀ = 0.0022 ± 0.0002 µM), 9e (IC₅₀ = 0.0250 ± 0.0007 µM) and 12d (IC₅₀ = 0.0266 ± 0.0021 µM) were found to be the lead compounds compared to standard (thiourea, IC₅₀ = 17.814 ± 0.096 µM). Molecular docking studies were performed to delineate the binding affinity of the molecules and a kinetic mechanism of enzyme inhibition was propounded. Compounds 3e, 6a and 12d exhibited a mixed type of inhibition, while derivative 9e revealed a non-competitive mode of inhibition. Compounds 12a, 12b, 12d, 12e and 12f showed excellent radical scavenging potency in comparison to the reference drug vitamin C.

Aminophosphinates against Helicobacter pylori ureolysis-Biochemical and whole-cell inhibition characteristics

Urease is an important virulence factor from Helicobacter pylori that enables bacterial colonization of human gastric mucosa. Specific inhibition of urease activity can be regarded as a promising adjuvant strategy for eradication of this pathogen. A group of organophosphorus inhibitors of urease, namely, aminophosphinic acid and aminophosphonic acid derivatives, were evaluated in vitro against H. pylori urease. The kinetic characteristics of recombinant enzyme activity demonstrated a competitive reversible mode of inhibition with K_i values ranging from 0.294 to 878 μM. N-n-Hexylaminomethyl-P-aminomethylphosphinic acid and N-methylaminomethyl-P-hydroxymethylphosphinic acid were the most effective inhibitors (K_i = 0.294 μM and 1.032 μM, respectively, compared to K_i = 23 μM for the established urease inhibitor acetohydroxamic acid).

The biological relevance of the inhibitors was verified in vitro against a ureolytically active Escherichia coli Rosetta host that expressed H. pylori urease and against a reference strain, H. pylori J99 (CagA⁺/VacA⁺). The majority of the studied compounds exhibited urease-inhibiting activity in these whole-cell systems. Bis(N-methylaminomethyl)phosphinic acid was found to be the most effective inhibitor in the susceptibility profile studies of H. pylori J99. The cytotoxicity of nine structurally varied inhibitors was evaluated against four normal human cell lines and was found to be negligible.

Hibiscus sabdariffa L. and Its Bioactive Constituents Exhibit Antiviral Activity against HSV-2 and Anti-enzymatic Properties against Urease by an ESI-MS Based Assay

For decades, Hibiscus sabdariffa L. and its phytochemicals have been shown to possess a wide range of pharmacologic properties. In this study, aqueous extract of Hibiscus sabdariffa (AEHS) and its bioactive constituent protocatechuic acid (PCA), have been evaluated in vitro for their antiviral activity against HSV-2 clinical isolates and anti-enzymatic activity against urease. Antiherpetic activity was evaluated by the titer reduction assay in infected Vero cells, and cytotoxicity was evaluated by the neutral red dye-uptake method. Anti-urease activity was determined by a developed Electrospray Ionization-Mass Spectrometry (ESI-MS)-based assay. PCA showed potent anti-HSV-2 activity compared with that of acyclovir, with EC₅₀ values of 0.92 and 1.43 µg∙mL⁻¹, respectively, and selectivity indices > 217 and > 140, respectively. For the first time, AEHS was shown to exert anti-urease inhibition activity, with an IC₅₀ value of 82.4 µg∙mL⁻¹. This, combined with its safety, could facilitate its use in practical applications as a natural urease inhibitor. Our results present Hibiscus sabdariffa L. and its bioactive compound PCA as potential therapeutic agents in the treatment of HSV-2 infection and the treatment of diseases caused by urease-producing bacteria.

Epiberberine, a natural protoberberine alkaloid, inhibits urease of Helicobacter pylori and jack bean: Susceptibility and mechanism

In our previous study, Rhizoma Coptidis extract was found to exert more potent inhibitory effect than its major component berberine towards urease from Helicobacter pylori (HPU) and jack bean (JBU). In continuation of our work, the present study was designed to further comparatively investigate the urease inhibitory activities of five major protoberberine alkaloids in Rhizoma Coptidis, namely berberine, palmatine, coptisine, epiberberine, jateorhizine to identify the bioactive constituent, and illuminate the potential mechanism of action. Results indicated that the five protoberberine alkaloids acted as concentration-dependent inactivators of urease with IC₅₀ values ranging between 3.0 and 5087μM for HPU and 2.3->10,000μM for JBU, respectively. Notably, epiberberine (EB) was found to be the most potent inhibitor against both ureases with IC₅₀ values of 3.0±0.01μM for HPU and 2.3±0.01μM for JBU, which was more effective than the standard urease inhibitor, acetohydroxamic acid (83±0.01μM for HPU and 22±0.01μM for JBU, respectively). Further kinetic analysis revealed that the type of EB inhibition against HPU was slow-binding and uncompetitive, with K_i of 10.6±0.01μM, while slow-binding and competitive against JBU with K_i of 4.6±0.01μM. Addition of thiol reagents, such as l-cysteine, glutathione and dithiothreitol, significantly abolished the inhibition, while Ni²⁺ competitive inhibitors, boric acid and sodium fluoride, synergetically inhibited urease with EB, indicating the obligatory role of the active site sulfhydryl group for the inhibition. In addition, binding of EB with the urease proved to be reversible, as about 65% and 90% enzymatic activity of HPU and JBU, respectively, could be restored by dithiothreitol application. These findings highlighted the potential role of Rhizoma Coptidis protoberberine alkaloids, especially EB, as a lead urease inhibitor in the treatment of diseases associated with ureolytic bacteria. Thus, EB had good potential for further development into a promising therapeutic approach for the treatment of urease-related diseases.

The Development of Urease Inhibitors: What Opportunities Exist for Better Treatment of Helicobacter pylori Infection in Children?

Stomach infection with Helicobacter pylori (H. pylori) causes severe gastroduodenal diseases in a large number of patients worldwide. The H. pylori infection breaks up in early childhood, persists lifelong if not treated, and is associated with chronic gastritis and an increased risk of peptic ulcers and gastric cancer. In recent years, the problem of drug-resistant strains has become a global concern that makes the treatment more complicated and the infection persistent at higher levels when the antibiotic treatment is stopped. Such problems have led to the development of new strategies to eradicate an H. pylori infection. Currently, one of the most important strategies for the treatment of H. pylori infection is the use of urease inhibitors. Despite the fact that large numbers of molecules have been shown to exert potent inhibitory activity against H. pylori urease, most of them were prevented from being used in vivo and in clinical trials due to their hydrolytic instability, toxicity, and appearance of undesirable side effects. Therefore, it is crucial to focus attention on the available opportunities for the development of urease inhibitors with suitable pharmacokinetics, high hydrolytic stability, and free toxicological profiles. In this commentary, we aim to afford an outline on the current status of the use of urease inhibitors in the treatment of an H. pylori infection, and to discuss the possibility of their development as effective drugs in clinical trials.