Structural-based virtual screening and identification of novel potent antimicrobial compounds against YsxC of Staphylococcus aureus

Human UDP-glucuronosyltransferase 1As catalyze aristolochic acid D O-glucuronidation to form a lesser nephrotoxic glucuronide

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acids (AAs) are naturally occurring nitro phenanthrene carboxylic acids primarily found in plants of the Aristolochiaceae family. Aristolochic acid D (AAD) is a major constituent in the roots and rhizomes of the Chinese herb Xixin (the roots and rhizomes of Asarum heterotropoides F. Schmidt), which is a key material for preparing a suite of marketed Chinese medicines. Structurally, AAD is nearly identical to the nephrotoxic aristolochic acid I (AAI), with an additional phenolic group at the C-6 site. Although the nephrotoxicity and metabolic pathways of AAI have been well-investigated, the metabolic pathway(s) of AAD in humans and the influence of AAD metabolism on its nephrotoxicity has not been investigated yet.

AIM OF THE STUDY

To identify the major metabolites of AAD in human tissues and to characterize AAD O-glucuronidation kinetics in different enzyme sources, as well as to explore the influence of AAD O-glucuronidation on its nephrotoxicity.

MATERIALS AND METHODS

The O-glucuronide of AAD was biosynthesized and its chemical structure was fully characterized by both 1H-NMR and 13C-NMR. Reaction phenotyping assays, chemical inhibition assays, and enzyme kinetics analyses were conducted to assess the crucial enzymes involved in AAD O-glucuronidation in humans. Docking simulations were performed to mimic the catalytic conformations of AAD in human UDP-glucuronosyltransferases (UGTs), while the predicted binding energies and distances between the deprotonated C-6 phenolic group of AAD and the glucuronyl moiety of UDPGA in each tested human UGT isoenzyme were measured. The mitochondrial membrane potentials (MMP) and reactive oxygen species (ROS) levels in HK-2 cells treated with either AAI, or AAD, or AAD O-glucuronide were tested, to elucidate the impact of O-glucuronidation on the nephrotoxicity of AAD.

RESULTS

AAD could be rapidly metabolized in human liver and intestinal microsomes (HLM and HIM, respectively) to form a mono-glucuronide, which was purified and fully characterized as AAD-6-O-β-D-glucuronide (AADG) by NMR. UGT1A1 was the predominant enzyme responsible for AAD-6-O-glucuronidation, while UGT1A9 contributed to a lesser extent. AAD-6-O-glucuronidation in HLM, HIM, UGT1A1 and UGT1A9 followed Michaelis-Menten kinetics, with the Km values of 4.27 μM, 9.05 μM, 3.87 μM, and 7.00 μM, respectively. Docking simulations suggested that AAD was accessible to the catalytic cavity of UGT1A1 or UGT1A9 and formed catalytic conformations. Further investigations showed that both AAI and AAD could trigger the elevated intracellular ROS levels and induce mitochondrial dysfunction and in HK-2 cells, but AADG was hardly to trigger ROS accumulation and mitochondrial dysfunction.

CONCLUSION

Collectively, UGT1A-catalyzed AAD 6-O-glucuronidation represents a crucial detoxification pathway of this naturally occurring AAI analogs in humans, which is very different from that of AAI.

Identification of novel CA IX inhibitor: Pharmacophore modeling, docking, DFT, and dynamic simulation

Human Carbonic anhydrase IX (hCA IX) is found to be an essential biomarker for the treatment of hypoxic tumors in both the early and metastatic stages of cancer. Due to its active function in maintaining pH levels and overexpression in hypoxic conditions, hCA IX inhibitors can be a potential candidate specifically designed to target cancer development at various stages. In search of selective hCA IX inhibitors, we developed a pharmacophore model from the existing natural product inhibitors with IC50 values less than 50 nm. The identified hit molecules were then investigated on protein-ligand interactions using molecular docking experiments followed by molecular dynamics simulations. Among the zinc database 186 hits with an RMSD value less than 1 were obtained, indicating good contact with key residues HIS94, HIS96, HIS119, THR199, and ZN301 required for optimum activity. The top three compounds were subjected to molecular dynamics simulations for 100 ns to know the protein-ligand complex stability. Based on the obtained MD simulation results, binding free energies are calculated. Density Functional Theory (DFT) studies confirmed the energy variation between the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO). The current study has led to the discovery of lead compounds that show considerable promise as hCA IX inhibitors and suggests that three compounds with special molecular features are more likely to be better-inhibiting hCA IX. Compound S35, characterized by a higher stability margin and a smaller energy gap in quantum studies, is an ideal candidate for selective inhibition of CA IX.

3D computer modeling of inhibitors targeting the MCF-7 breast cancer cell line

This study focused on developing new inhibitors for the MCF-7 cell line to contribute to our understanding of breast cancer biology and various experimental techniques. 3D QSAR modeling was used to design new tetrahydrobenzo[4, 5]thieno[2, 3-d]pyrimidine derivatives with good characteristics. Two robust 3D-QSAR models were developed, and their predictive capacities were confirmed through high correlations [CoMFA (Q2 = 0.62, R 2 = 0.90) and CoMSIA (Q2 = 0.71, R 2 = 0.88)] via external validations (R2 ext = 0.90 and R2 ext = 0.91, respectively). These successful evaluations confirm the potential of the models to provide reliable predictions. Six candidate inhibitors were discovered, and two new inhibitors were developed in silico using computational methods. The ADME-Tox properties and pharmacokinetic characteristics of the new derivatives were evaluated carefully. The interactions between the new tetrahydrobenzo[4, 5]thieno[2, 3-d]pyrimidine derivatives and the protein ERα (PDB code: 4XO6) were highlighted by molecular docking. Additionally, MM/GBSA calculations and molecular dynamics simulations provided interesting information on the binding stabilities between the complexes. The pharmaceutical characteristics, interactions with protein, and stabilities of the inhibitors were examined using various methods, including molecular docking and molecular dynamics simulations over 100 ns, binding free energy calculations, and ADME-Tox predictions, and compared with the FDA-approved drug capivasertib. The findings indicate that the inhibitors exhibit significant binding affinities, robust stabilities, and desirable pharmaceutical characteristics. These newly developed compounds, which act as inhibitors to mitigate breast cancer, therefore possess considerable potential as prospective drug candidates.

Molecular modeling and simulation approaches to characterize potential molecular targets for burdock inulin to instigate protection against autoimmune diseases

In the current study, we utilized molecular modeling and simulation approaches to define putative potential molecular targets for Burdock Inulin, including inflammatory proteins such as iNOS, COX-2, TNF-alpha, IL-6, and IL-1β. Molecular docking results revealed potential interactions and good binding affinity for these targets; however, IL-1β, COX-2, and iNOS were identified as the best targets for Inulin. Molecular simulation-based stability assessment demonstrated that inulin could primarily target iNOS and may also supplementarily target COX-2 and IL-1β during DSS-induced colitis to reduce the role of these inflammatory mechanisms. Furthermore, residual flexibility, hydrogen bonding, and structural packing were reported with uniform trajectories, showing no significant perturbation throughout the simulation. The protein motions within the simulation trajectories were clustered using principal component analysis (PCA). The IL-1β-Inulin complex, approximately 70% of the total motion was attributed to the first three eigenvectors, while the remaining motion was contributed by the remaining eigenvectors. In contrast, for the COX2-Inulin complex, 75% of the total motion was attributed to the eigenvectors. Furthermore, in the iNOS-Inulin complex, the first three eigenvectors contributed to 60% of the total motion. Furthermore, the iNOS-Inulin complex contributed 60% to the total motion through the first three eigenvectors. To explore thermodynamically favorable changes upon mutation, motion mode analysis was carried out. The Free Energy Landscape (FEL) results demonstrated that the IL-1β-Inulin achieved a single conformation with the lowest energy, while COX2-Inulin and iNOS-Inulin exhibited two lowest-energy conformations each. IL-1β-Inulin and COX2-Inulin displayed total binding free energies of - 27.76 kcal/mol and - 37.78 kcal/mol, respectively, while iNOS-Inulin demonstrated the best binding free energy results at - 45.89 kcal/mol. This indicates a stronger pharmacological potential of iNOS than the other two complexes. Thus, further experiments are needed to use inulin to target iNOS and reduce DSS-induced colitis and other autoimmune diseases.

Structural insight into the binding mode of cefotaxime and meropenem to TEM-1, SHV-1, KPC-2, and Amp-C type beta-lactamases

Antimicrobial resistance is an emerging threat to public health around the world. The study employs computational and biophysical methods to investigate the properties of cefotaxime and meropenem's binding to various beta-lactamases like TEM-1, SHV-1, KPC-2, and Amp-C. The enzyme kinetics of purified proteins revealed an increase in Michaelis constant (Km) value in the presence of meropenem and cefotaxime, indicating a decrease in enzyme affinity for nitrocefin. Proteins interact with meropenem/cefotaxime, causing quenching through complex formation. All proteins have one binding site, and binding constant (Kb) values are 104, indicating strong interaction. The study found that meropenem and cefotaxime had high fitness scores for Amp-C, KPC-2,TEM-1 and SHV-1, with binding energy ranging from -7.4 to -7.8, and hydrogen bonds between them. Molecular Dynamic simulation of protein-ligand complexes revealed cefotaxime-binding proteins have slightly lower Root Mean Square Deviation(RMSD) than meropenem-binding proteins, indicating stable association antibiotics with these proteins.

Anticholinesterase activities of novel isoindolin-1,3-dione-based acetohydrazide derivatives: design, synthesis, biological evaluation, molecular dynamic study

In pursuit of developing novel cholinesterase (ChE) inhibitors through molecular hybridization theory, a novel series of isoindolin-1,3-dione-based acetohydrazides (compounds 8a-h) was designed, synthesized, and evaluated as possible acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. In vitro results revealed IC50 values ranging from 0.11 ± 0.05 to 0.86 ± 0.02 µM against AChE and 5.7 ± 0.2 to 30.2 ± 2.8 µM against BChE. A kinetic study was conducted on the most potent compound, 8a, to ascertain its mode of inhibition, revealing its competitive mode against AChE. Furthermore, the binding interaction modes of the most active compound within the AChE active site was elucidated. Molecular dynamics simulations of compound 8a were performed to assess the stability of the 8a-AChE complex. In silico pharmacokinetic predictions for the most potent compounds indicated their potential as promising lead structure for the development of new anti-Alzheimer's disease (anti-AD) agents.

Iso-mukaadial acetate and ursolic acid acetate bind to Plasmodium Falciparum heat shock protein 70: towards targeting parasite protein folding pathway

Plasmodium falciparum is the most lethal malaria parasite. P. falciparum Hsp70 (PfHsp70) is an essential molecular chaperone (facilitates protein folding) and is deemed a prospective antimalarial drug target. The present study investigates the binding capabilities of select plant derivatives, iso-mukaadial acetate (IMA) and ursolic acid acetate (UAA), against P. falciparum using an in silico docking approach. The interaction between the ligands and PfHsp70 was evaluated using plasmon resonance (SPR) analysis. Molecular docking, binding free energy analysis and molecular dynamics simulations were conducted towards understanding the mechanisms by which the compounds bind to PfHsp70. The molecular docking results revealed ligand flexibilities, conformations and positions of key amino acid residues and protein-ligand interactions as crucial factors accounting for selective inhibition of Hsp70. The simulation results also suggest protein-ligand van der Waals forces as the driving force guiding the interaction of these compounds with PfHsp70. Of the two compounds, UAA and IMA bound to PfHsp70 within the micromolar range based on surface plasmon resonance (SPR) based binding assay. Our findings pave way for future rational design of new selective compounds targeting PfHsp70.

In silico investigation of cholesterol-lowering drugs to find potential inhibitors of dehydrosqualene synthase in Staphylococcus aureus

Staphylococcus aureus is a lethal pathogen that can cause various bacterial infections. This study targets the CrtM enzyme of S. aureus, which is crucial for synthesizing golden carotenoid pigment: staphyloxanthin, which provides anti-oxidant activity to this bacterium for combating antimicrobial resistance inside the host cell. The present investigation quests for human SQS inhibitors against the CrtM enzyme by employing structure-based drug design approaches including induced fit docking (IFD), molecular dynamic (MD) simulations, and binding free energy calculations. Depending upon the docking scores, two compounds, lapaquistat acetate and squalestatin analog 20, were identified as the lead molecules exhibit higher affinity toward the CrtM enzyme. These docked complexes were further subjected to 100 ns MD simulation and several thermodynamics parameters were analyzed. Further, the binding free energies (ΔG) were calculated for each simulated protein-ligand complex to study the stability of molecular contacts using the MM-GBSA approach. Pre-ADMET analysis was conducted for systematic evaluation of physicochemical and medicinal chemistry properties of these compounds. The above study suggested that lapaquistat acetate and squalestatin analog 20 can be selected as potential lead candidates with promising binding affinity for the S. aureus CrtM enzyme. This study might provide insights into the discovery of potential drug candidates for S. aureus with a high therapeutic index.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03862-y.

Mechanisms Involved in Therapeutic Effects of Scutellaria baicalensis Georgi in Oral Squamous Cell Carcinoma Based on Systems Biology and Structural Bioinformatics Approaches

Objective

Oral squamous cell carcinoma (OSCC) is the most frequent oral cancer, constituting more than 90% of all oral carcinomas. The 5-year survival rate of OSCC patients is not satisfactory, and therefore, there is an urgent need for new practical therapeutic approaches besides the current therapies to overcome OSCC. Scutellaria baicalensis Georgi (SBG) is a plant of the family Lamiaceae with several pharmaceutical properties such as antioxidant, anti-inflammatory, and anticancer effects. Previous studies have demonstrated the curative effects of SBG in OSCC.

Methods

A systems biology approach was conducted to identify differentially expressed miRNAs (DEMs) in OSCC patients with a dismal prognosis compared to OSCC patients with a favorable prognosis. A protein interaction map (PIM) was built based on DEMs targets, and the hub genes within the PIM were indicated. Subsequently, the prognostic role of the hubs was studied using Kaplan-Meier curves. Next, the binding affinity of SBG's main components, including baicalein, wogonin, oroxylin-A, salvigenin, and norwogonin, to the prognostic markers in OSCC was evaluated using molecular docking analysis.

Results

Survival analysis showed that overexpression of CAV1, SERPINE1, ACTB, SMAD3, HMGA2, MYC, EIF2S1, HSPA4, HSPA5, and IL6 was significantly related to a poor prognosis in OSCC. Besides, molecular docking analysis demonstrated the ΔGbinding and inhibition constant values between SBG's main components and SERPINE1, ACTB, HMGA2, EIF2S1, HSPA4, and HSPA5 were as <-8.00 kcal/mol and nanomolar concentration, respectively. The most salient binding affinity was observed between wogonin and SERPINE1 with a criterion of ΔGbinding < -10.02 kcal/mol.

Conclusion

The present results unraveled potential mechanisms involved in therapeutic effects of SBG in OSCC based on systems biology and structural bioinformatics analyses.

Structural Insights into the Catalytic Activity of Cyclobacterium marinum N-Acetylglucosamine Deacetylase

N-Acetylglucosamine deacetylase from Cyclobacterium marinum (CmCBDA) is a highly effective and selective biocatalyst for the production of d-glucosamine (GlcN) from N-acetylglucosamine (GlcNAc). However, the underlying catalytic mechanism remains elusive. Here, we show that CmCBDA is a metalloenzyme with a preference for Ni2+ over Mn2+. Crystal structures of CmCBDA in complex with Ni2+ and Mn2+ revealed slight remodeling of the CmCBDA active site by the metal ions. We also demonstrate that CmCBDA exists as a mixture of homodimers and monomers in solution, and dimerization is indispensable for catalytic activity. A mutagenesis analysis also indicated that the active site residues Asp22, His72, and His143 as well as the residues involved in dimerization, Pro52, Trp53, and Tyr55, are essential for catalytic activity. Furthermore, a mutation on the protein surface, Lys219Glu, resulted in a 2.3-fold improvement in the deacetylation activity toward GlcNAc. Mechanistic insights obtained here may facilitate the development of CmCBDA variants with higher activities.

Ginkgolide B attenuates cerebral ischemia-reperfusion injury via inhibition of ferroptosis through disrupting NCOA4-FTH1 interaction

ETHNOPHARMACOLOGICAL RELEVANCE

Cerebral ischemia/reperfusion (I/R) injury is a major cause of neuronal damage and death. Ginkgolide B (GB) has been shown to exhibit neuroprotective effects in various brain injury models.

AIM OF STUDY

The aim of study was to investigate the potential role of GB in protecting against cerebral I/R injury and explore the underlying mechanisms.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were exposed to transient middle cerebral artery occlusion (tMCAO) followed by reperfusion in order to trigger cerebral I/R injury. The rats were treated with different doses of GB, vehicle control or positive drug. Neurological function, infarct volume, and levels of ferroptosis markers were evaluated. In vitro experiments were performed using OGD/R-induced PC12 cells to further investigate the effects of GB on ferroptosis and its mechanisms. In addition, molecular docking, and microscale thermophoresis (MST) assay were conducted to explore the combination of GB and NCOA4.

RESULTS

Reduced infarct volume and enhanced neurological function were signs of dose-dependent protection from cerebral I/R injury by GB therapy. Additionally, GB treatment had an impact on the levels of oxidative stress and ferroptosis markers, including reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and Fe2+ in the cerebral environment during IR injury. Moreover, relevant ferroptosis key factors such as ACSL4, GPX4, FTH1, and NCOA4 can be regulated by GB. In OGD/R-induced PC12 cells, GB protected against ferroptosis by inhibiting autophagy and disrupting the interaction of NCOA4-FTH1.

CONCLUSION

Our findings suggest that GB may protect against cerebral I/R injury by inhibiting ferroptosis through disrupting NCOA4-FTH1 interaction. GB has potential therapeutic applications for cerebral I/R injury, and further investigation of the underlying mechanisms and clinical trials are warranted.

Induction of apoptotic cell death of cholangiocarcinoma cells by tiliacorinine from Tiliacora triandra: A mechanistic insight

BACKGROUND

Cholangiocarcinoma (CCA) exhibits poor response to the present chemotherapeutic agents and frequently develops drug resistance. Finding novel anticancer drugs might enhance patient outcomes. Tiliacorinine, a bisbenzylisoquinoline alkaloid from the Thai medicinal plant Tiliacora triandra, effectively induced apoptosis of human CCA cell lines and inhibited tumor growth in mice. Here, we elucidate further the molecular mechanisms underlining the cytotoxicity of tiliacorinine and its implication in overcoming gemcitabine-resistance of CCA cells.

METHODS

Cytotoxicity of tiliacorinine against CCA cell lines was assessed using MTT assay. The molecular signaling was determined using Western blot analysis. Molecular docking simulations were applied to predict the binding affinity and orientation of tiliacorinine to the possible binding site(s) of the target proteins.

RESULTS

Tiliacorinine induced apoptotic cell death of CCA cells in a dose- and time-dependent manner. Tiliacorinine significantly suppressed the expression of anti-apoptotic proteins, Bcl-xL and XIAP; activated apoptotic machinery proteins, caspase-3, caspase-9, and PARP; and decreased the levels of pAkt and pSTAT3. EGF/EGFR activation model and molecular docking simulations revealed EGFR, Akt, and STAT3 as potent targets of tiliacorinine. Molecular docking simulations indicated a strong binding affinity of tiliacorinine to the ATP-binding pockets of EGFR, PI3K, Akt, JAK2, and SH2 domain of STAT3. Tiliacorinine could synergize with gemcitabine and restore the cytotoxicity of gemcitabine against gemcitabine-resistant CCA cells.

CONCLUSION

Tiliacorinine effectively induced apoptosis via binding and blocking the actions of EGFR, Akt, and STAT3.

GENERAL SIGNIFICANCE

Tiliacorinine is a novel multi-kinase inhibitor and possibly a potent anti-cancer agent, in cancers with high activation of EGFR.

Lignin-ultrasound method: Enhancement of antimicrobial capacity of MoS2-containing films

To improve the antimicrobial ability of MoS2-containing films, we used lignin and triple-frequency ultrasound for liquid-phase exfoliation (LPE) to obtain MoS2 nanosheets. Photoresponsive antimicrobial films with MoS2 nanosheets, lignin, polyvinyl alcohol and deep eutectic solvents were subsequently prepared. Lignin functionalized the MoS2 nanosheets by chemically linking with S in MoS2 and significantly improved the exfoliation efficiency. Tri-frequency ultrasound produces beneficial effects on the LPE process by creating a more homogeneous sound field and a stronger degree of cavitation. The concentration of MoS2 nanosheets in the exfoliating solution could reach 1.713 mg/mL under the effect of lignin-ultrasound. The antimicrobial ability of the films was analyzed, and the colony-forming units of E. coli and S. aureus could be reduced from 7 × 106 to 1 × 106 cfu/mL under the irradiation of infrared. The lignin in the film undergoes depolymerization and demethoxylation under the irradiation of infrared to have a more phenolic hydroxyl structure, which confers the growth inhibition ability of the films for bacteria that cannot be in close contact with the film. The method we used has some significance for the preparation of MoS2 nanosheets, and composite films prepared from MoS2, and lignin can be used in food packaging, wound antimicrobials, and other fields.

Ab initio and comparative 3D modeling of FAM222A-encoded protein and target-driven-based virtual screening for the identification of novel therapeutics against Alzheimer's disease

The complex nature of Alzheimer's disease (AD) makes it difficult to understand the exact molecular processes leading to neuron death. However, two molecular factors - the production of amyloid-beta plaques and tau tangles - are considered to be linked to AD. A genetic marker for brain atrophy, FAM222A, has been identified by the unique cross-phenotype meta-analysis of genetics imaging and the molecular features show an interaction between the protein aggregatin encoded by FAM222A and amyloid beta (Aβ)-peptide (1-42) via its N-terminal Aβ binding domain, thus increasing Aβ aggregation. Function of Aggregatin protein is unclear, and its 3D structure has not been investigated in experimental analysis, so far. Hence, in the present study, first time in literature, 3D models of FAM222A-encoded Aggregatin were systematically constructed by applying diverse homology modeling approaches and they were used as target structures at the virtual screening of FDA-approved drugs and drugs currently under research in clinical trials. Then, the identified hit molecules were chosen for further molecular dynamics (MD) simulations and post-MD analyses. Our integrated ligand-based and protein-driven-based virtual screening results show that Cefpiramide, Diniprofylline, Fostriecin, and Droperidol may target Aggregatin.

Potential inhibitors of FemC to combat Staphylococcus aureus: virtual screening, molecular docking, dynamics simulation, and MM-PBSA analysis

FemC is a methicillin resistance factor involved in the alterations of peptidoglycan and glutamine synthesis in Staphylococcus aureus. To identify the potent antibacterial agents, antibacterial molecules were screened against the predicted and validated FemC model. Based on docking scores, presence of essential interactions with active site residues of FemC, pharmacokinetic, and ADMET properties, six candidates were shortlisted and subjected to molecular dynamics to evaluate the stability of FemC-ligand complexes. Further, per residue decomposition analysis and Molecular Mechanics/Poisson-Boltzmann Surface Area (MMPBSA) analysis confirmed that S15, M16, S17, R31, R43, Q47, K48 and R49 of FemC played a vital role in the formation of lower energy stable FemC-inhibitor(s) complexes. Therefore, in the present study, the reported six molecules (Z317461228, Z92241701, Z30923155, Z30202349, Z2609517102 and Z92470167) may pave the path to design the scaffold of novel potent antimicrobials against S. aureus.Communicated by Ramaswamy H. Sarma.

Structure-Based In Silico Screening of Marine Phlorotannins for Potential Walrus Calicivirus Inhibitor

A new calicivirus isolated from a walrus was reported in 2004. Since unknown marine mammalian zoonotic viruses could pose great risks to human health, this study aimed to develop therapeutic countermeasures to quell any potential outbreak of a pandemic caused by this virus. We first generated a 3D model of the walrus calicivirus capsid protein and identified compounds from marine natural products, especially phlorotannins, as potential walrus calicivirus inhibitors. A 3D model of the target protein was generated using homology modeling based on two publicly available template sequences. The sequence of the capsid protein exhibited 31.3% identity and 42.7% similarity with the reference templates. The accuracy and reliability of the predicted residues were validated via Ramachandran plotting. Molecular docking simulations were performed between the capsid protein 3D model and 17 phlorotannins. Among them, five phlorotannins demonstrated markedly stable docking profiles; in particular, 2,7-phloroglucinol-6,6-bieckol showed favorable structural integrity and stability during molecular dynamics simulations. The results indicate that the phlorotannins are promising walrus calicivirus inhibitors. Overall, the study findings showcase the rapid turnaround of in silico-based drug discovery approaches, providing useful insights for developing potential therapies against novel pathogenic viruses, especially when the 3D structures of the viruses remain experimentally unknown.

Compound effect and mechanism of oxidative damage induced by nanoplastics and benzo [a] pyrene

Nanoplastics and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soil environments. In order to objectively evaluate the toxic interaction between polystyrene nanoplastics (PS NPs) and benzo [a] pyrene (BaP), oxidative damage at the level of earthworm cells and biomacromolecules was investigated by experiments combined with molecular dynamics simulation. Studies on cells reveal that PS NPs and BaP had synergistic toxicity when it came to causing oxidative stress. Cellular reactive oxygen species (ROS) levels under combined pollutant exposure were 24% and 19% higher, respectively than when PS NPs and BaP were exposed alone (compared to the blank group). In addition, BaP and PS NPs inhibited the ability of CAT to decompose H2O2 by affecting the structure of the proximal amino acid Tyr 357 in the active center of CAT, which exacerbated oxidative stress to a certain extent. Therefore, the synergistic toxic effect of BaP and PS NPs is due to the mutual complement of the two to the induction of protein structural looseness, and the strengthening of the stability of the conjugate (CAT-BaP-PS) under the weak interaction. This work provides a new perspective and approach on how to talk about the toxicity of combined pollutants.

Preparation and characterization of porous membranes of glucomannan and silver decorated cellulose nanocrystals for application as biomaterial

Bacterial infection usually represents a threat in medical wound care, due to the increase in treatment complexity and the risk of antibiotic resistance. For presenting interesting characteristics for the use as biomaterial, natural polymers have been explored for this application. Among them, a promising candidate is the konjac glucomannan (KGM) with outstanding biocompatibility and biodegradability but lack of antibacterial activity. In this study, KGM was combined with silver decorated cellulose nanocrystals (CNC-Ag) to prepare membranes by using a recent reported casting-freezing method. The results highlight the potential anti-adhesive activity of the new materials against Staphylococcus aureus upon contact, without the burst release of silver nanoparticles. Furthermore, the incorporation of CNC enhanced the thermal stability of these membranes while preserving the favorable mechanical properties of the KGM-based material. These findings highlight a straightforward approach to enhance the antibacterial properties of natural polymers, which can be effectively useful in medical devices like wound dressings that typically lack such properties.

The inhibitory mechanism of echinacoside against Staphylococcus aureus Ser/Thr phosphatase Stp1 by virtual screening and molecular modeling

CONTEXT

Stp1 is a new potential target closely related to the pathogenicity of Staphylococcus aureus (S. aureus). In this study, effective Stp1 inhibitors were screened via virtual screening and enzyme activity experiments, and the inhibition mechanism was analyzed using molecular dynamics simulation.

METHODS

AutoDock Vina 4.0 software was used for virtual screening. The molecular structures of Stp1 and ligands were obtained from the RCSB Protein Data Bank and Zinc database, respectively. The molecular dynamics simulation used the Gromacs 4.5.5 software package with the Amberff99sb force field and TIP3P water model. AutoDock Tools was used to add polar hydrogen atoms to Stp1 and distribute part of the charge generated by Kollman's combined atoms. The binding free energies were calculated using the Amber 10 package.

RESULTS

The theoretical calculation results are consistent with the experimental results. We found that echinacoside (ECH) substantially inhibits the hydrolytic activity of Stp1. ECH competes with the substrate by binding to the active center of Stp1, resulting in a decrease in Stp1 activity. In addition, Met39, Gly41, Asp120, Asn162, and Ile163 were identified to play key roles in the binding of Stp1 to ECH. The benzene ring of ECH also plays an important role in complex binding. These findings provide a robust foundation for the development of innovative anti-infection drugs.

Promising antibacterials for LLM of Staphylococcus aureus using virtual screening, molecular docking, dynamics, and MMPBSA

In S. aureus, lipophilic membrane (LLM) protein is a methicillin resistance factor and is an essential role in peptidoglycan metabolism. The virtual screening of antibacterial molecules against the model of LLM was performed to identify the potent antibacterial molecules. Molecular docking results of pharmacokinetic filtered molecules illustrated that five molecules had higher binding affinities than tunicamycin (TUM) and were stabled via non-covalent interactions (hydrogen bond and hydrophobic interactions) at the active site of LLM. Further, molecular dynamics results revealed that binding of identified antibacterial molecules with LLM resulted in stable LLM-inhibitor(s) complexes. Molecular Mechanics/Position-Boltzmann Surface Area (MMPBSA) analysis showed that LLM-inhibitor(s) complexes had high binding affinities in the range of -213.49 ± 2.24 to -227.42 ± 3.05 kJ/mol. The amino acid residues decomposition analysis confirmed that identified antibacterial molecules bound at the active site (Asn148, Leu149, Asp151, Asp208, His269, His271, and His272) of LLM. Noticeably, the current study found five antibacterial molecules (BDE 27575101, BDE 33638168, BDE 33672484, LAS 51502073, and BDE 25098678) were highly potent than TUM and even than earlier reported molecules. Therefore, here reported antibacterial molecules may be used directly or developed to inhibit LLM of S. aureus.Communicated by Ramaswamy H. Sarma.

Application of CRISPR-Cas system in the diagnosis and therapy of ESKAPE infections

Antimicrobial-resistant ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. ESKAPE pathogens are the most common opportunistic pathogens in nosocomial infections, and a considerable number of their clinical isolates are not susceptible to conventional antimicrobial therapy. Therefore, innovative therapeutic strategies that can effectively deal with ESKAPE pathogens will bring huge social and economic benefits and ease the suffering of tens of thousands of patients. Among these strategies, CRISPR (clustered regularly interspaced short palindromic repeats) system has received extra attention due to its high specificity. Regrettably, there is currently no direct CRISPR-system-based anti-infective treatment. This paper reviews the applications of CRISPR-Cas system in the study of ESKAPE pathogens, aiming to provide directions for the research of ideal new drugs and provide a reference for solving a series of problems caused by multidrug-resistant bacteria (MDR) in the post-antibiotic era. However, most research is still far from clinical application.

Exploring and targeting potential druggable antimicrobial resistance targets ArgS, SecY, and MurA in Staphylococcus sciuri with TCM inhibitors through a subtractive genomics strategy

Staphylococcus sciuri (also currently Mammaliicoccus sciuri) are anaerobic facultative and non-motile bacteria that cause significant human pathogenesis such as endocarditis, wound infections, peritonitis, UTI, and septic shock. Methicillin-resistant S. sciuri (MRSS) strains also infects animals that include healthy broilers, cattle, dogs, and pigs. The emergence of MRSS strains thereby poses a serious health threat and thrives the scientific community towards novel treatment options. Herein, we investigated the druggable genome of S. sciuri by employing subtractive genomics that resulted in seven genes/proteins where only three of them were predicted as final targets. Further mining the literature showed that the ArgS (WP_058610923), SecY (WP_058611897), and MurA (WP_058612677) are involved in the multi-drug resistance phenomenon. After constructing and verifying the 3D protein homology models, a screening process was carried out using a library of Traditional Chinese Medicine compounds (consisting of 36,043 compounds). The molecular docking and simulation studies revealed the physicochemical stability parameters of the docked TCM inhibitors in the druggable cavities of each protein target by identifying their druggability potential and maximum hydrogen bonding interactions. The simulated receptor-ligand complexes showed the conformational changes and stability index of the secondary structure elements. The root mean square deviation (RMSD) graph showed fluctuations due to structural changes in the helix-coil-helix and beta-turn-beta changes at specific points where the pattern of the RMSD and root mean square fluctuation (RMSF) (< 1.0 Å) support any major domain shifts within the structural framework of the protein-ligand complex and placement of ligand was well complemented within the binding site. The β-factor values demonstrated instability at few points while the radius of gyration for structural compactness as a time function for the 100-ns simulation of protein-ligand complexes showed favorable average values and denoted the stability of all complexes. It is assumed that such findings might facilitate researchers to robustly discover and develop effective therapeutics against S. sciuri alongside other enteric infections.

An integrated computational approach towards novel drugs discovery against polyketide synthase 13 thioesterase domain of Mycobacterium tuberculosis

The acquired drug resistance by Mycobacterium tuberculosis (M. tuberculosis) to antibiotics urges the need for developing novel anti-M. tuberculosis drugs that possess novel mechanism of action. Since traditional drug discovery is a labor-intensive and costly process, computer aided drug design is highly appreciated tool as it speeds up and lower the cost of drug development process. Herein, Asinex antibacterial compounds were virtually screened against thioesterase domain of Polyketide synthase 13, a unique enzyme that forms α-alkyl β-ketoesters as a direct precursor of mycolic acids which are essential components of the lipid-rich cell wall of M. tuberculosis. The study identified three drug-like compounds as the most promising leads; BBB_26582140, BBD_30878599 and BBC_29956160 with binding energy value of - 11.25 kcal/mol, - 9.87 kcal/mol and - 9.33 kcal/mol, respectively. The control molecule binding energy score is -9.25 kcal/mol. Also, the docked complexes were dynamically stable with maximum root mean square deviation (RMSD) value of 3 Å. Similarly, the MM-GB\PBSA method revealed highly stable complexes with mean energy values < - 75 kcal/mol for all three systems. The net binding energy scores are validated by WaterSwap and entropy energy analysis. Furthermore, The in silico druglike and pharmacokinetic investigation revealed that the compounds could be suitable candidates for additional experimentations. In summary, the study findings are significant, and the compounds may be used in experimental validation pipeline to develop potential drugs against drug-resistant tuberculosis.

Design, Molecular Modeling, MD Simulations, Essential Dynamics, ADMET, DFT, Synthesis, Anti-proliferative, and Apoptotic Evaluations of a New Anti-VEGFR-2 Nicotinamide Analogue

OBJECTIVES

This study aims to design and evaluate (in silico and in vitro) a new nicotinamide derivative as an inhibitor of VEGFR-2, a major mediator of angiogenesis Methods: The following in silico studies were performed; DFT calculations, molecular modelling, MD simulations, MM-GBSA, PLIP, and PCAT studies. The compound's in silico (ADMET) analysis was also conducted. Subsequently, the compound ((E)-N-(4-(1-(2-(4-(4-Chlorobenzamido)benzoyl)hydrazono)ethyl) phenyl)nicotinamide) was successfully synthesized and designated as compound X. In vitro, VEGFR-2 inhibition and cytotoxicity of compound X against HCT-116 and A549 cancer cell lines and normal Vero cell lines were conducted. Apoptosis induction and migration assay of HCT-116 cell lines after treatment with compound X were also evaluated.

RESULTS

DFT calculations assigned stability and reactivity of compound X. Molecular docking and MD simulations indicated its excellent binding against VEGFR-2. Furthermore, MM-GBSA analysis, PLIP experiments, and PCAT studies confirmed compound X's correct binding with optimal dynamics and energy. ADMET analysis expressed its general likeness and safety. The in vitro assays demonstrated that compound X effectively inhibited VEGFR-2, with an IC50 value of 0.319 ± 0.013 μM and displayed cytotoxicity against HCT-116 and A549 cancer cell lines, with IC50 values of 57.93 and 78.82 μM, respectively. Importantly, compound X exhibited minimal toxicity towards the non-cancerous Vero cell lines, (IC50 = 164.12 μM). Additionally, compound X significantly induced apoptosis of HCT-116 cell lines and inhibited their potential to migrate and heal.

CONCLUSION

In summary, the presented study has identified compound X as a promising candidate for the development of a novel apoptotic lead anticancer drug.

Molecular modeling, simulation and docking of Rv1250 protein from Mycobacterium tuberculosis

Computational prediction and protein structure modeling have come to the aid of various biological problems in determining the structure of proteins. These technologies have revolutionized the biological world of research, allowing scientists and researchers to gain insights into their biological questions and design experimental research much more efficiently. Pathogenic Mycobacterium spp. is known to stay alive within the macrophages of its host. Mycobacterium tuberculosis is an acid-fast bacterium that is the most common cause of tuberculosis and is considered to be the main cause of resistance of tuberculosis as a leading health issue. The genome of Mycobacterium tuberculosis contains more than 4,000 genes, of which the majority are of unknown function. An attempt has been made to computationally model and dock one of its proteins, Rv1250 (MTV006.22), which is considered as an apparent drug-transporter, integral membrane protein, and member of major facilitator superfamily (MFS). The most widely used techniques, i.e., homology modeling, molecular docking, and molecular dynamics (MD) simulation in the field of structural bioinformatics, have been used in the present work to study the behavior of Rv1250 protein from M. tuberculosis. The structure of unknown TB protein, i.e., Rv1250 was retrived using homology modeling with the help of I-TASSER server. Further, one of the sites responsible for infection was identified and docking was done by using the specific Isoniazid ligand which is an inhibitor of this protein. Finally, the stability of protein model and analysis of stable and static interaction between protein and ligand molecular dynamic simulation was performed at 100 ns The designing of novel Rv1250 enzyme inhibitors is likely achievable with the use of proposed predicted model, which could be helpful in preventing the pathogenesis caused by M. tuberculosis. Finally, the MD simulation was done to evaluate the stability of the ligand for the specific protein.

Promising antivirals for PLpro of SARS-CoV-2 using virtual screening, molecular docking, dynamics, and MMPBSA

The recent pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (COVID-19) is a viral respiratory disease that has been spread all over the globe. Therefore, it is an urgent requirement to identify and develop drugs for this contagious infection. The papain-like protease (PLpro) of SARS-CoV-2 performs critical functions in virus replication and immune evasion, making it an enticing therapeutic target. SARS-CoV-2 and SARS-CoV PLpro proteases have significant similarities, and an inhibitor discovered for SARS-CoV PLpro is an exciting first step toward therapeutic development. Here, a set of antiviral molecules were screened at the catalytic and S-binding allosteric sites of papain-like protease (PLpro). Molecular docking results suggested that five molecules (44560613, 136277567, S5652, SC75741, and S3833) had good binding affinities at both sites of PLpro. Molecular dynamics analysis like root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg), solvent accessible surface area (SASA), and hydrogen bond results showed that identified molecules with PLpro tend to form stable PLpro-inhibitor(s) complexes. Molecular Mechanics/Position-Boltzmann Surface Area (MMPBSA) analysis confirmed that antiviral molecules bound PLpro complex had lower energy (-184.72 ± 7.81 to -215.67 ± 6.73 kJ/mol) complexes. Noticeably, computational approaches revealed promising antivirals candidates for PLpro, which may be further tested by biochemical and cell-based assays to assess their potential for SARS-CoV-2.Communicated by Ramaswamy H. Sarma.