Targeting Wnt/ß-catenin signaling pathway in triple-negative breast cancer by benzylic organotrisulfides: Contribution of the released hydrogen sulfide towards potent anti-cancer activity.

The potent anti-cancer activity of naturally occurring organopolysulfides has attracted wide research attention over the last two decades. Sustained donation of hydrogen sulfide (H2S) from organopolysulfides is found to be beneficial for the treatment of several organ-specific cancers. In the present study, for the first time, the mechanism of action for the potent anti-cancer activity of bis(3,5-dimethoxybenzyl) trisulfide 4 against highly aggressive triple-negative breast cancer cells (MDA-MB-231) is described. Preliminary in vitro studies revealed potent anti-proliferative activity of the trisulfide 4 against triple-negative breast cancer cells with an IC50 value of 1.0 µM. Mechanistic studies reveal that the compound exhibited anti-cancer activity, primarily by targeting and suppressing the Wnt/ß-catenin signaling pathway. The inactivation of the ß-catenin level was associated with the cell cycle arrest in the G2/M phase and the significant down-regulation of downstream signaling genes such as Cyclin D1 and c-Myc expression. Several control experiments with analogous organosulfur compounds and the key enzyme inhibitors reveal that the presence of a trisulfide unit in the compound is crucial for the desired inactivation of ß-catenin expression, which is promoted by GSK-3ß-induced phosphorylation of ß-catenin and its proteasomal degradation. Moreover, the trisulfide unit or the released H2S induced down-regulation of the p53 expression with the possible S-sulfhydration process led to p53-independent up-regulation of p21 expression. Therefore, the key results of this study highlighting the potency of synthetic benzylic organotrisulfide and the released H2S towards the growth inhibition of triple-negative breast cancer via Wnt/ß-catenin signaling pathway would certainly be helpful for further studies and developing small-molecule anti-cancer therapeutics in future.

Stimuli-responsive prodrug of non-steroidal anti-inflammatory drug diclofenac: self-immolative drug release with turn-on near-infrared fluorescence.

Reactive oxygen species (ROS)-responsive near infrared (NIR) fluorogenic prodrug DCI-ROS is developed for the self-immolative release of diclofenac (DCF) with turn-on fluorescence. The non-toxic prodrug exhibited turn-on red fluorescence with endogenous ROS in cancer cells and inhibited COX-2 expression in the inflammation-induced macrophage cells. The prodrug strategy thus would be helpful for the controlled fluorogenic delivery of DCF for inflammatory diseases.

Thioredoxin reductase-triggered fluorogenic donor of hydrogen sulfide: a model study with a symmetrical organopolysulfide probe with turn-on near-infrared fluorescent emission.

We describe herein the rational development of an organopolysulfide-based fluorogenic donor of hydrogen sulfide (H2S) DCI-PS, which can be activated by the antioxidant selenoenzyme thioredoxin reductase (TrxR) with concomitant release of the dicyanoisophorone-based near-infrared (NIR) fluorophore. Along with the polysulfide probe DCI-PS capable of releasing the NIR fluorophore and H2S, the corresponding disulfide-probe DCI-DS was also rationally designed and synthesized, which releases the fluorophore without donating H2S. Detailed spectroscopic and kinetic studies in an aqueous medium revealed significantly higher reactivity of the probes towards DTT (for TrxR activity) over the well-known cellular abundant biothiol GSH. Mechanistically, the nucleophilic attack at the disulfide/polysulfide linkage by the thiol/selenol group of the bio-analytes leads to the self-immolative cyclization process with the release of the turn-on fluorophore with/without H2S. Considering the overexpression of mammalian TrxR in cancer cells, the turn-on fluorogenic H2S donation process from the cellular non-toxic DCI-PS was validated in a representative breast cancer cell line (MDA-MB-231) for the sustained donation of H2S with concomitant release of the red-emitting NIR fluorophore. The TrxR-triggered fluorescence turn-on process in DCI-PS was further supported by the significant inhibition of the fluorogenic process in the presence of TrxR-selective small-molecule inhibitors and by the significant binding affinity predicted by the protein-ligand docking study. Results with the antioxidant enzyme-triggered intracellular sustained donation of H2S with concomitant fluorescence turn-on will certainly find wider biomedical applications in the near future, particularly in H2S-mediated therapeutics in disease states.

Venetoclax: a promising repurposed drug against SARS-CoV-2 main protease.

Global health care emergency caused by a new coronavirus (severe acute respiratory syndrome coronavirus 2 or SARS-CoV-2) demands urgent need to repurpose the approved pharmaceutical drugs. Main protease, Mpro of SARS-CoV-2 draws significant attention as a drug target. Herein, we have screened FDA approved organosulfur drugs (till 2016) and our laboratory synthesized organosulfur and organoselenium compounds (L1-L306) against Mpro-apo using docking followed by classical MD simulations. Additionally, a series of compounds (L307-L364) were chosen from previous experimental studies, which were reported to exhibit inhibitory potentials towards Mpro. We found several organosulfur drugs, particularly Venetoclax (FDA approved organosulfur drug for Leukemia) to be a high-affinity binders to the Mpro of SARS-CoV-2. The results reveal that organosulfur compounds including Venetoclax preferentially bind (non-covalently) to the non-catalytic pocket of the protein located in the dimer interface. We found that the ligand binding is primarily favoured by ligand-protein van der Waals interaction and penalized by desolvation effect. Interestingly, Venetoclax binding alters the local flexibility of Mpro and exerts pronounced effect in the C-terminal as well as two loop regions (Loop-A and Loop-B) that play important roles in catalysis. These findings highlighted the importance of drug repurposing and explored the non-catalytic pockets of Mpro in combating COVID-19 infection in addition to the importance of catalytic binding pocket of the protein.Communicated by Ramaswamy H. Sarma.

Benzimidazole- and Imidazole-Fused Selenazolium and Selenazinium Selenocyanates: Ionic Organoselenium Compounds with Efficient Peroxide Scavenging Activities.

Three new classes of ionic organoselenium compounds containing cationic benzimidazolium and imidazolium ring systems with selenocyanates as counterions are described. The cyclization of N,N'-disubstituted benzimidazolium and imidazolium bromides having N-(CH2)2-Br and N-(CH2)3-Br groups in the presence of potassium selenocyanate (KSeCN) led to formation of the corresponding selenazolium selenocyanates (21a, 21b, 22a, and 22b) and selenazinium selenocyanates (21c, 21d, 22c, and 22d). However, the open-chain selenocyanates with additional selenocyanate counterions (21e, 21f, 22e, and 22f) were formed from the N,N'-disubstituted benzimidazolium and imidazolium bromides having N-(CH2)6-Br groups. Mechanistic studies were carried out to understand the feasibility of such cyclization processes in the presence of KSeCN. The compounds were studied further for their potencies to catalytically reduce H2O2 in the presence of thiols. Interestingly, the cyclic selenazolium (21a, 21b, 22a, and 22b) and selenazinium compounds (21c, 21d, 22c, and 22d) exhibited significantly higher antioxidant activities than the corresponding acyclic selenocyanates (21f, 22e, and 22f). Selected compounds (22d and 22e) were further evaluated for their potencies in modulating the intracellular level of reactive oxygen species (ROS) in a representative macrophage cell line (RAW 264.7). Owing to the cationic nature of compounds, they may target and scavenge mitochondrial ROS in the cellular medium.

The biothiol-triggered organotrisulfide-based self-immolative fluorogenic donors of hydrogen sulfide enable lysosomal trafficking.

Biothiol-reactive organotrisulfide-based self-immolative fluorogenic donors of H2S are rationally designed for the efficient monitoring of intracellular and lysosomal trafficking of H2S with a concomitant turn-on fluorescence. The non-toxic nature of the donors with a sustained release of H2S will certainly be helpful for their biomedical applications in the future.

Novel Approach to Generate a Self-Deliverable Ru(II)-Based Anticancer Agent in the Self-Reacting Confined Gel Space.

Finding the most effective method for cancer treatment is one of the thought-provoking tasks. Drug delivery by collapsing of metallogel to the cancer cell is an appealing way out. Cancer cells have an acidic environment due to excessive accumulation of lactic acid. In this work, the novel G5 gelator with a strategically free carboxylic acid arm has been designed and fabricated and characterized by several spectroscopic and microscopic techniques. These experiments suggest the formation of an ordered supramolecular gel with clover-leaf-like morphology. Mechanical properties from rheological measurements suggest the viscoelastic nature of the gel. Furthermore, we have obtained crystals of G5 from the pure dimethyl sulfoxide solution, whereas gelation gets induced by addition of water. This G5 gelator loses its gelation capability once the carboxylate is esterified by layering with methanol, which furnished the crystals of Me-G5' (G5' = G5-H). Further, the G5 gelator is used for the formation of ruthenium metallogel. Interestingly, we obtained the monomeric species [Ru(G5')(η6-p-cymene)Cl] [Ru(II)G5] only in confined gel space upon addition of a [Ru2(η6-p-cymene)2Cl4] dimer to G5. The Ru(II)G5 metallogel has an inherent anticancer property with an IC50 value of 10.53 µM for the A549 cancer cell line. Treatment of the Ru(II)G5 metallogel by lactic acid for mimicking the acidic environment of the malignant cell results in collapsing of the gel by releasing the ruthenium metal ion. This released ruthenium ion binds with the lactic acid derivative making the gelator G5 free and producing a new compound Ru(II)L, which has also shown the anticancer property. The molecular docking study revealed that the released G5 could interact with a monocarboxylate transporter to disrupt the lactate transport chain, which might induce apoptosis.

Trisulfides over disulfides: highly selective synthetic strategies, anti-proliferative activities and sustained H2S release profiles.

Temperature- and solvent-induced selective synthesis of trisulfides and disulfides is demonstrated. A remarkable selectivity was achieved using Na2S as a sulfur-transfer agent under mild, greener, catalyst-free and additive-free conditions. This study reveals trisulfides as a better model than disulfides in general for a sustained release of H2S and potent anti-cancer activities.

Potent anti-proliferative activities of organochalcogenocyanates towards breast cancer.

The pharmacological importance, particularly the anti-cancer and chemopreventive potentials, of organochalcogen compounds has attracted wide research attention recently. Herein we describe the synthesis of a series of organochalcogenocyanates that have one or more selenocyanate or thiocyanate units in a single molecule. The anti-proliferative activity of these organochalcogenocyanates in different breast cancer cells shows that selenocyanates exhibit much higher anti-proliferative activities than thiocyanates in general. Our study reveals that the activity of benzyl selenocyanate (1, BSC) could be significantly enhanced by 4-nitro substitution (12), which was more selective towards triple-negative breast cancer cells (MDA-MB-231) over other ER+ breast cancer cells (MCF-7 and T-47D). Furthermore, to the best of our knowledge, this is the first report on the synthesis of compounds having more than two selenocyanate units with promising anti-proliferative activities. Our studies further indicate that the apoptotic activities of selenocyanates are associated with modulation of cellular morphology and cell cycle arrest at S-phase. Selenocyanates also inhibited cellular migration and exhibited weak antioxidant activities. An effective binding interaction of compound 12 with serum albumin indicates its feasible transport in the bloodstream for its enhanced anti-cancer properties. Mechanistic studies by western blot analysis demonstrate that benzylic selenocyanates exhibit anti-proliferative activities by modulating key cellular proteins such as Survivin, Bcl-2 and COX-2; this was further supported by molecular docking studies. The results of this study would be helpful in designing suitable chemotherapeutic and chemopreventive drugs in the future.

Ruthenium(ii) arene NSAID complexes: inhibition of cyclooxygenase and antiproliferative activity against cancer cell lines.

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of molecules which have been found to be active against cancer cells with chemopreventive properties by targeting cyclooxygenase (COX-1 and COX-2) and lipoxygenase (LOX), commonly upregulated (particularly COX-2) in malignant tumors. Arene ruthenium(ii) complexes with a pseudo-octahedral coordination environment containing different ancillary ligands have shown remarkable activity against primary and metastatic tumors as reported earlier. This work describes the synthesis of four novel ruthenium(ii)-arene complexes viz. [Ru(η6-p-cymene)(nap)Cl] 1 [Hnap = naproxen or (S)-2-(6-methoxy-2-naphthyl)propionic acid], [Ru(η6-p-cymene)(diclo)Cl] 2 [Hdiclo = diclofenac or 2-[(2,6-dichlorophenyl)amino] benzeneacetic acid, [Ru(η6-p-cymene)(ibu)Cl] 3 [Hibu = ibuprofen or 2-(4-isobutylphenyl)propanoic acid] and [Ru(η6-p-cymene)(asp)Cl] 4 [Hasp = aspirin or 2-acetoxy benzoic acid] using different NSAIDs as chelating ligands. Complexes 1-3 have shown promising antiproliferative activity against three different cell lines with GI50 (concentration of drug causing 50% inhibition of cell growth) values comparable to adriamycin. At the concentration of 50 µM, complex 3 is more effective in the inhibition of cyclooxygenase and lipooxygenase enzymes, followed by complex 2 and complex 1 in comparison to their respective free NSAID ligands indicating a possible correlation between the inhibition of COX and/or LOX and anticancer properties. Molecular docking studies with COX-2 reveal that complexes 1 and 2 having naproxen and diclofenac ligands exhibit stronger interactions with COX-2 than their respective free NSAIDs and these results are in good agreement with their relative experimentally observed COX inhibition as well as anti-proliferative activities.

Atom based 3D-QSAR studies on 2,4-dioxopyrimidine-1-carboxamide analogs: Validation of experimental inhibitory potencies towards acid ceramidase.

Ceramide (Cer), the central lipid molecule in sphingolipid biosynthesis and degradation, which plays a key role in sphingolipid signaling, induces cell differentiation and apoptosis. Cellular degradation of ceramide to sphingosine is catalyzed by a family of ceramidases (CDases). Pharmacological inhibition of ceramidases and more particularly, acid ceramidase (aCDase) is suggestive of a chemotherapeutic approach as it increases the cellular concentration of ceramide inducing apoptosis. In the present report, we have utilized atom-based 3D-QSAR method to analyze the structural aspects on a series of 2,4-dioxopyrimidine-1-carboxamide (carmofur) derivatives as potent inhibitors of aCDase. In this approach the experimental dataset was divided into training (83%) and test (17%) sets and the best model was chosen based on randomized trial distributions consisting of five compounds in a test set with a wide range of activity profile and superior values of statistical parameters such as Q(2) and R(2) values. The reported experimental results by Piomelli and co-workers on the inhibition of aCDase by the carmofur derivatives were correlated using robust 3D-QSAR as well as docking methods. With careful structure-activity correlation studies the carmofur analogs were classified into four sub-categories (Set 1-4) to understand the effect of each structural features separately. This approach led us to short-list most active carmofur derivatives such as compounds 26, 30 and 32 with the incorporation of more than one structural features in a single molecule. However, the inhibition potency might further be enhanced by designing compound 33 upon the incorporation of all features in a single compound. Compound 33 that was missing in the experimental study by Piomelli and co-workers (J. Med. Chem. 2013, 56, 3518), could be identified using 3D-QSAR studies. Moreover, the importance of structural features in lead inhibitors such as 26, 30 and 32 along with 33 was further justified by their efficient molecular interactions at the active site of homology modeled protein human N-acyl ethanolamine hydrolyzing acid amidase (hNAAA) as evidenced by molecular docking study. Furthermore, efficient molecular interaction of some representative inhibitors with hNAAA led to the understanding that hNAAA could be a possible alternative of aCDase for developing potent inhibitors.

New avenue in the treatment of temporal lobe epilepsy by classical anti-epileptics: A hypothetical establishment of executioner Caspase 3 inactivation by molecular modeling.

Patients with temporal lobe epilepsy (TLE) are prescribed first-line antiepileptic drugs and surgery to the management of this disorder. Unfortunately, the surgical treatment has been shown to be beneficial for the selected patients but fails to provide a seizure-free outcome in 20-30% of TLE patients. In our present study, we investigate the possibilities of marketed antiepileptic drugs in a different manner to improve the present situation in TLE. Molecular docking simulation study and various open source computational tools were used to perform the study. AutoDock 4.2 MGL tools, Pymol visualize tools, Patch dock server, and Swarm Dock servers (protein-protein docking) were used to perform the molecular modeling. FTsite and computed atlas of surface topography of protein open source server were used to understand the pocket and ligand binding information respectively. Toxtree application was used to determine the toxicity profile of the drug by Cramers rule. The obtained molecular docking models (Caspase 3, Procaspase 8, and Fas-associated death domain [FADD]) with selected compounds (Clonazepam, Clobazepam, and Retigabine) showed promising trio blocking event of FADD, Caspase 3, and Procaspase 8 (-6.66 kcal, -8.1 kcal, 6.46 kcal) by Clonazepam respectively. Protein-protein interaction study (Swarm Dock, Patch Dock server) indicated promising results that helped to establish our hypothesis. Toxtree showed a quantitative structure toxicity relationship report that helps to clarify the toxicity of the selected compounds. Clonazepam showed a trio inhibition property that may lead to develop a new era of the new generation benzodiazepine prototype drugs in the future. Filtered compounds will further process for higher in vitro, in vivo models for better understanding of the mechanism.

Natural polyphenols down-regulate universal stress protein in Mycobacterium tuberculosis: An in-silico approach.

Universal stress protein (USP) is a novel target to overcome the tuberculosis resistance. Our present study enlightens the possibilities of some natural polyphenols as an antioxidant for USP. The study has shown some molecular simulations of some selected natural antioxidants with USP. We have considered USP (Rv1636) strain for homology modeling and the selected template was taken for the docking study. Curcumin, catechin, reservetrol has shown ARG 136 (1.8Å) hydrogen bonding and two ionic bonding with carboxyl group of curcumin with LEU 130 (3.3Å) and ASN 144 (3.4Å) respectively. INH was taken for the standard molecule to perform molecular simulation. It showed poor binding interaction with the target, that is, -5.18 kcal, and two hydrogen bonding with SER 140 (1.887Å), ARG 147 (2.064Å) respectively. The study indicates possible new generation curcumin analogue for future therapy to down-regulate USP.