Carbenoxolone-mediated cytotoxicity inhibits Vaccinia virus replication in a human keratinocyte cell line

Computational Study on Potential Novel Anti-Ebola Virus Protein VP35 Natural Compounds

Ebola virus (EBOV) is one of the most lethal pathogens that can infect humans. The Ebola viral protein VP35 (EBOV VP35) inhibits host IFN-α/β production by interfering with host immune responses to viral invasion and is thus considered as a plausible drug target. The aim of this study was to identify potential novel lead compounds against EBOV VP35 using computational techniques in drug discovery. The 3D structure of the EBOV VP35 with PDB ID: 3FKE was used for molecular docking studies. An integrated library of 7675 African natural product was pre-filtered using ADMET risk, with a threshold of 7 and, as a result, 1470 ligands were obtained for the downstream molecular docking using AutoDock Vina, after an energy minimization of the protein via GROMACS. Five known inhibitors, namely, amodiaquine, chloroquine, gossypetin, taxifolin and EGCG were used as standard control compounds for this study. The area under the curve (AUC) value, evaluating the docking protocol obtained from the receiver operating characteristic (ROC) curve, generated was 0.72, which was considered to be acceptable. The four identified potential lead compounds of NANPDB4048, NANPDB2412, ZINC000095486250 and NANPDB2476 had binding affinities of −8.2, −8.2, −8.1 and −8.0 kcal/mol, respectively, and were predicted to possess desirable antiviral activity including the inhibition of RNA synthesis and membrane permeability, with the probable activity (Pa) being greater than the probable inactivity (Pi) values. The predicted anti-EBOV inhibition efficiency values (IC₅₀), found using a random forest classifier, ranged from 3.35 to 11.99 μM, while the Ki values ranged from 0.97 to 1.37 μM. The compounds NANPDB4048 and NANPDB2412 had the lowest binding energy of −8.2 kcal/mol, implying a higher binding affinity to EBOV VP35 which was greater than those of the known inhibitors. The compounds were predicted to possess a low toxicity risk and to possess reasonably good pharmacological profiles. Molecular dynamics (MD) simulations of the protein–ligand complexes, lasting 50 ns, and molecular mechanisms Poisson-Boltzmann surface area (MM-PBSA) calculations corroborated the binding affinities of the identified compounds and identified novel critical interacting residues. The antiviral potential of the molecules could be confirmed experimentally, while the scaffolds could be optimized for the design of future novel anti-EBOV chemotherapeutics.

In silico and experimental studies of bovine serum albumin-encapsulated carbenoxolone nanoparticles with reduced cytotoxicity

Carbenoxolone (CBX) is a semi-synthetic plant derivative with pleiotropic pharmacological properties like anti-microbial and anti-inflammatory activities. Though approved for treatment of gastric ulcers, its use is limited due to adverse effects such as cytotoxicity. Bovine serum albumin (BSA) is a natural, non-toxic protein with high water-solubility and low immunogenicity, and is widely used as a nanocarrier for targeted drug delivery. In the present study, controlled release BSA-CBX nanoparticles (NPs) were synthesized by desolvation method to reduce drug cytotoxicity. These NPs showed desirable physicochemical properties such as particle size (∼240 nm), polydispersity index (0.08), zeta potential (-7.12 mV), drug encapsulation efficiency (72 %), and were stable for at least 3 months at room temperature. The drug was released from the BSA-CBX NPs in a biphasic manner in vitro following non-fickian diffusion. Computational analysis determined that the binding between BSA and CBX occurred through van der Waals forces, hydrophobic interactions, and hydrogen bonds with 93 % steric stability. Further, the cytotoxic assays demonstrated ∼1.8-4.9-fold reduction in cytotoxicity using three human cell lines (A549, MCF-7, and U-87). Subsequently, this novel CBX formulation with BSA as an efficient carrier can potentially be used for diverse biomedical applications.

Inhibition of medaka ovulation by gap junction blockers due to its disrupting effect on the transcriptional process of LH-induced Mmp15 expression

Using medaka, we found that in vitro follicle ovulation, but not germinal vesicle breakdown, was inhibited by three gap junction blockers, carbenoxolone, mefloquine, and flufenamic acid. The blockers specifically inhibited follicular expression of matrix metalloproteinase-15 mRNA and the protein (mmp15/Mmp15), a protease indispensable for medaka ovulation, indicating that gap junctional communication may be required for successful ovulation and mmp15/Mmp15 expression. Further experiments using carbenoxolone as the representative of the gap junction blockers showed that expression of nuclear progestin receptor (Pgr), a transcription factor required for mmp15 expression, was not affected by carbenoxolone treatment, but the formation of phosphorylated Pgr was considerably suppressed. Carbenoxolone treatment caused a decrease in the Pgr binding to the promoter region of mmp15. mRNA expression of cyclin-dependent protein kinase-9 (cdk9) and cyclin I (ccni), whose translation products are demonstrated to be involved in Pgr phosphorylation in the medaka ovulating follicles, was suppressed by carbenoxolone treatment. Transcripts of connexin 34.5 (cx34.5) and connexin 35.4 (cx35.4) were dominantly expressed in the follicle cells of ovulating follicles. The results indicate that gap junctional communication plays an important role in medaka ovulation.