Synthesis and Biological Evaluation of Prodrugs For Nitroreductase Based 4-β-Amino-4'-Demethylepipodophyllotoxin As Potential Anticancer Agents

A series of prodrugs for nitroreductase based 4-β-amino-4'- Demethylepipodophyllotoxin as potential anticancer agents were synthesized, and their antiproliferative activities in vitro showed compounds 2b (IC50=0.77, 0.83 and 1.19 μM) and 2d (IC50=0.98, 0.91 and 1.58 μM) were greatly selectively toxic to tumor cells A-549, HeLa and HepG2, respectively, and lower damage to normal WI-38 cells in comparison with positive agent Etoposide and Demethylepipodophyllotoxin, and induced cell cycle arrest in the G2/M phase with a concomitant decrease in the population of G1 phase in HeLa cells, which were accompanied by apoptosis. Furthermore, Molecular docking model showed that compounds 2b and 2d appeared to form stable bonds with NTR 1DS7. Taken together, these conjugates have the potential to be developed as anti-tumor drugs.

Crystal structure of human METTL6, the m3C methyltransferase

In tRNA, the epigenetic m3C modification at position 32 in the anticodon loop is highly conserved in eukaryotes, which maintains the folding and basepairing functions of the anticodon. However, the responsible enzymes METTL2 and METTL6 were identified only in recent years. The loss of human METTL6 (hMETTL6) affects the translational process and proteostasis in cells, while in mESCs cells, it leads to defective pluripotency potential. Despite its important functions, the catalytic mechanism of the C32 methylation by this enzyme is poorly understood. Here we present the 1.9 Å high-resolution crystal structure of hMETTL6 bound by SAH. The key residues interacting with the ligand were identified and their roles were confirmed by ITC. We generated a docking model for the hMETTL6-SAH-CMP ternary complex. Interestingly, the CMP molecule binds into a cavity in a positive patch with the base ring pointing to the inside, suggesting a flipped-base mechanism for methylation. We further generated a model for the quaternary complex with tRNASer as a component, which reasonably explained the biochemical behaviors of hMETTL6. Taken together, our crystallographic and biochemical studies provide important insight into the molecular recognition mechanism by METTL6 and may aid in the METTL-based rational drug design in the future.

Computer-aided structural optimization, synthesis, evaluation of the antimicrobial and cytotoxic activity of some pyrazoline derivatives

Introduction: In the last few decades, pyrazoline-based substances have emerged as potential antimicrobial and anticancer candidates. In concern with antimicrobial activity, this study aims to build a docking model to predict the structure of potential 2-pyrazoline derivatives. The cytotoxicity of some compounds was also evaluated to get insight into the structure–anticancer activity relationship of the 2-pyrazoline derivatives. Methods: Docking models were built on virtual FabH enzymes using FlexX platform with 2-pyrazoline derivatives served as test sets. Afterward, derivatives with high docking scores were chemically synthesized and evaluated for antibacterial activity using the agar dilution method. Furthermore, MTT assay was used to assess the cytotoxicity of these compounds. Results: The docking score and the in vitro minimum inhibitory concentration (MIC) value on Staphylococcus aureus (S. aureus) bacteria strongly correlate with an R-square value of 0.6751 (p < 0.0001). Four 2 pyrazoline derivatives were synthesized and evaluated for antimicrobial activity. Their MIC values on S. aureus range between 4 and 16 μg/mL, consistent with ones predicted by the docking model. Apropos cytotoxic properties, a series of 2-pyrazolines exhibit a moderate activity on HepG2, RD, and MDA-MB-231. The most active compound, HP10, has the IC50 values on these cell lines. which are 26.62 μM, 17.74 μM, 14.47 μM, respectively. Conclusion: Our research built a docking model on the virtual S. aureus FabH enzyme with high potential in predicting antibacterial activities of different 2-pyrazoline derivatives. Moreover, our cytotoxicity results provided data for further studies on the anticancer activity of these promising derivatives.

GABAA Receptor Subunit Composition Drives Its Sensitivity to the Insecticide Fipronil

Fipronil (FPN) is a worldwide-used neurotoxic insecticide, targeting, and blocking GABAA receptors (GABAARs). Beyond its efficiency on insect GABAARs, FPN causes neurotoxic effects in humans and mammals. Here, we investigated the mode of action of FPN on mammalian α6-containing GABAARs to understand its inhibitory effects on GABA-induced currents, as a function of the synaptic or extrasynaptic localization of GABAARs. We characterized the effects of FPN by electrophysiology using Xenopus oocytes which were microtransplanted with cerebellum membranes or injected with α6β3, α6β3γ2S (synaptic), and α6β3δ (extrasynaptic) cDNAs. At micromolar concentrations, FPN dose-dependently inhibited cerebellar GABA currents. FPN acts as a non-competitive antagonist on ternary receptors. Surprisingly, the inhibition of GABA-induced currents was partial for extra-synaptic (α6β3δ) and binary (α6β3) receptors, while synaptic α6β3γ2S receptors were fully blocked, indicating that the complementary γ or δ subunit participates in FPN-GABAAR interaction. FPN unexpectedly behaved as a positive modulator on β3 homopentamers. These data show that FPN action is driven by the subunit composition of GABAARs—highlighting the role of the complementary subunit—and thus their localization within a physiological synapse. We built a docking model of FPN on GABAARs, which reveals two putative binding sites. This is consistent with a double binding mode of FPN on GABAARs, possibly one being of high affinity and the other of low affinity. Physiologically, the γ/δ subunit incorporation drives its inhibitory level and has important significance for its toxicity on the mammalian nervous system, especially in acute exposure.

Synthesis of an Adamantyl Derivative and their Theoretical Interaction with both COX-1 and COX-2 Enzymes

Various drugs have been used to treat pain; nevertheless, several drugs can produce side effects such as bronchospasm, thinning, and angioedema. In the search for new therapeutic alternatives, some drugs have been elaborated using different reagents that are difficult to handle and require special conditions such as different pH and higher temperatures. Therefore, this research aimed to prepare an adamantyl derivative (compound 4) from 1-Adamantyl bromomethyl ketone using some chemical strategies. Besides, a theoretical evaluation of the interaction of compound 4 with both cyclooxygenase enzymes (COX-1 and COX-2) was evaluated using either 4cox or 5jw1 proteins as theoretical models. In addition, both indomethacin and celecoxib drugs were used as controls in a docking model. The results showed that compound 4 has a higher affinity by both 4cox and 5jw1 proteins surface compared with either indomethacin or celecoxib drugs. In conclusion, these data suggest that 4 could be a good candidate for pain treatment.

Screening and Identification of a Novel Anti-tuberculosis Compound That Targets Deoxyuridine 5′-Triphosphate Nucleotidohydrolase

Tuberculosis (TB) is still a threat to humans worldwide. The rise of drug-resistant TB strains has escalated the need for developing effective anti-TB agents. Deoxyuridine 5′-triphosphate nucleotidohydrolase (dUTPase) is essential for thymidylate biosynthesis to maintain the DNA integrity. In Mycobacterium tuberculosis, dUTPase provides the sole source for thymidylate biosynthesis, which also has the specific five-residue loop and the binding pockets absent in human dUTPase. Therefore, dUTPase has been regarded as a promising anti-TB drug target. Herein, we used a luminescence-based dUTPase assay to search for the inhibitors target M. tuberculosis dUTPase (Mt-dUTPase) and identified compound F0414 as a potent Mt-dUTPase inhibitor with an IC50 of 0.80 ± 0.09 μM. F0414 exhibited anti-TB activity with low cytotoxicity. Molecular docking model and site-directed mutation experiments revealed that P79 was the key residue in the interaction of Mt-dUTPase and F0414. Moreover, F0414 was shown to have stronger binding with Mt-dUTPase than with Mt-P79A-dUTPase by surface plasmon resonance (SPR) detection. Interestingly, F0414 exhibited insensitivity and weak directly binding on human dUTPase compared with that on Mt-dUTPase. All the results highlight that F0414 is the first compound reported to have anti-TB activity by inhibiting Mt-dUTPase, which indicates the potential application in anti-TB therapy.

Alpha-Glucosidase Inhibitory Assay-Screened Isolation and Molecular Docking Model from Bauhinia pulla Active Compounds

The aim of this research was to establish the constituents of Bauhinia pulla as anti-diabetic agents. A phytochemistry analysis was conducted by chromatographic and spectroscopic techniques. The alpha-glucosidase inhibitory assay screening resulted in the isolation of eight known compounds of quercetin, quercitrin, luteolin, 5-deoxyluteolin, 4-methyl ether isoliquiritigenin, 3,2′,4′-trihydroxy-4-methoxychalcone, stigmasterol and β-sitosterol. Ethanol leaf extracts showed potential effects, which led to a strong inhibitory activity of isolated quercetin at 138.95 µg/mL and 5.41 µg/mL of IC50, respectively. The docking confirmed that flavonoids and chalcones had the same potential binding sites and responsibilities for their activity. This study was the first report of Bauhinia pulla chemical constituents and its alpha-glucosidase inhibition.

Quality Assessment of Protein Docking Models Based on Graph Neural Network

Protein docking provides a structural basis for the design of drugs and vaccines. Among the processes of protein docking, quality assessment (QA) is utilized to pick near-native models from numerous protein docking candidate conformations, and it directly determines the final docking results. Although extensive efforts have been made to improve QA accuracy, it is still the bottleneck of current protein docking systems. In this paper, we presented a Deep Graph Attention Neural Network (DGANN) to evaluate and rank protein docking candidate models. DGANN learns inter-residue physio-chemical properties and structural fitness across the two protein monomers in a docking model and generates their probabilities of near-native models. On the ZDOCK decoy benchmark, our DGANN outperformed the ranking provided by ZDOCK in terms of ranking good models into the top selections. Furthermore, we conducted comparative experiments on an independent testing dataset, and the results also demonstrated the superiority and generalization of our proposed method.

Effects of nicotinic acetylcholine receptor-activating alkaloids on anxiety-like behavior in zebrafish

Alkaloids are a structurally complex group of natural products that have a diverse range of biological activities and significant therapeutic applications. In this study, we examined the acute, anxiolytic-like effects of nicotinic acetylcholine receptor (nAChR)-activating alkaloids with reported neuropharmacological effects but whose effects on anxiety are less well understood. Because α4β2 nAChRs can regulate anxiety, we first demonstrated the functional activities of alkaloids on these receptors in vitro. Their effects on anxiety-like behavior in zebrafish were then examined using the zebrafish novel tank test (NTT). The NTT is a relatively high-throughput behavioral paradigm that takes advantage of the natural tendency of fish to dive down when stressed or anxious. We report for the first time that cotinine, anatabine, and methylanatabine may suppress this anxiety-driven zebrafish behavior after a single 20-min treatment. Effective concentrations of these alkaloids were well above the concentrations naturally found in plants and the concentrations needed to induce anxiolytic-like effect by nicotine. These alkaloids showed good receptor interactions at the α4β2 nAChR agonist site as demonstrated by in vitro binding and in silico docking model, although somewhat weaker than that for nicotine. Minimal or no significant effect of other compounds may have been due to low bioavailability of these compounds in the brain, which is supported by the in silico prediction of blood–brain barrier permeability. Taken together, our findings indicate that nicotine, although not risk-free, is the most potent anxiolytic-like alkaloid tested in this study, and other natural alkaloids may regulate anxiety as well.