Lobeline: A multifunctional alkaloid modulates cholinergic and glutamatergic activities.

Developing drugs for Alzheimer's disease (AD) is an extremely challenging task due to its devastating pathology. Previous studies have indicated that natural compounds play a crucial role as lead molecules in the development of drugs. Even though, there are remarkable technological advancements in the isolation and synthesis of natural compounds, the targets for many of them are still unknown. In the present study, lobeline, a piperidine alkaloid has been identified as a cholinesterase inhibitor through chemical similarity assisted target fishing method. The structural similarities between lobeline and donepezil, a known acetylcholinesterase (AChE) inhibitor encouraged us to hypothesize that lobeline may also exhibit AChE inhibitory properties. It was further confirmed by in silico, in vitro and biophysical studies that lobeline could inhibit cholinesterase. The binding profiles indicated that lobeline has a higher affinity for AChE than BChE. Since excitotoxicity is one of the major pathological events associated with AD progression, we also investigated the neuroprotective potential of lobeline against glutamate mediated excitotoxicity in rat primary cortical neurons. The cell based NMDA receptor (NMDAR) assay with lobeline suggested that neuroprotective potential of lobeline is mediated through the blockade of NMDAR activity.

A multidimensional computational exploration of congenital myasthenic syndrome causing mutations in human choline acetyltransferase.

Missense mutations of human choline acetyltransferase (CHAT) are mainly associated with congenital myasthenic syndrome (CMS). To date, several pathogenic mutations have been reported, but due to the rarity and genetic complexity of CMS and difficult genotype-phenotype correlations, the CHAT mutations, and their consequences are underexplored. In this study, we systematically sift through the available genetic data in search of previously unreported pathogenic mutations and use a dynamic in silico model to provide structural explanations for the pathogenicity of the reported deleterious and undetermined variants. Through rigorous multiparameter analyses, we conclude that mutations can affect CHAT through a variety of different mechanisms: by disrupting the secondary structure, by perturbing the P-loop through long-range allosteric interactions, by disrupting the domain connecting loop, and by affecting the phosphorylation process. This study provides the first dynamic look at how mutations affect the structure and catalytic activity in CHAT and highlights the need for further genomic research to better understand the pathology of CHAT.

Crystal structure of phospholipase A2 in complex with 1-naphthaleneacetic acid.

Phospholipase A2 (PLA2 ) is one of the rate limiting enzymes involved in the production of arachidonic acid, a potent inflammatory mediator. PLA2 is widely distributed all over the animal kingdom. It is also seen in inflammatory exudation and venoms of different organisms. The studies demonstrated that PLA2 inhibitors have broad spectrum activities that they can either be used against inflammation or envenomation. In this study, the inhibitory activity of 1-napthaleneacetic acid (NAA) against porcine pancreatic PLA2 has been explained through isothermal titration calorimetry and enzyme kinetics studies. The atomic level of interactions of NAA with PLA2 was also studied using X-ray crystallography. Apart from these findings, the theoretical binding affinities and mode of interactions of two naphthalene-based NSAIDs such as naproxen (NAP) and nabumetone (NAB) were studied through molecular modeling. The studies proved that the selected ligands are binding at the doorway of the active site cleft and hindering the substrate entry to the active site. The study brings out a potential scaffold for the designing of broad spectrum PLA2 inhibitors which can be used for inflammation or envenomation. © 2018 IUBMB Life, 70(10):995-1001, 2018.

2D finger-printing and molecular docking studies identified potent mosquito repellents targeting odorant binding protein 1.

Personal protection measures against the mosquitoes like the use of repellents constitute valuable tools in the effort to prevent the transmission of vector-borne diseases. Therefore, the discovery of novel repellent molecules which will be effective at lower concentrations and provide a longer duration of protection remains an urgent need. Mosquito Odorant-Binding Proteins (OBPs) involved in the initial steps of the olfactory signal transduction cascade have been recognized not only as passive carriers of odors and pheromones but also as the first molecular filter to discriminate semiochemicals, hence serving as molecular targets for the design of novel pest control agents. Among the three-dimensional structures of mosquito OBPs solved in the last decades, the OBP1 complexes with known repellents have been widely used as reference structures in docking analysis and molecular dynamics simulation studies for the structure-based discovery of new molecules with repellent activity. Herein, ten compounds known to be active against mosquitoes and/or displaying a binding affinity for Anopheles gambiae AgamOBP1 were used as queries in an in silico screening of over 96 million chemical samples in order to detect molecules with structural similarity. Further filtering of the acquired hits on the basis of toxicity, vapor pressure, and commercial availability resulted in 120 unique molecules that were subjected to molecular docking studies against OBP1. For seventeen potential OBP1-binders, the free energy of binding (FEB) and mode of interaction with the protein were further estimated by molecular docking simulations leading to the selection of eight molecules exhibiting the highest similarity with their parental compounds and favorable energy values. The in vitro determination of their binding affinity to AgamOBP1 and the evaluation of their repellent activity against female Aedes albopictus mosquitoes revealed that our combined ligand similarity screening and OBP1 structure-based molecular docking successfully detected three molecules with enhanced repellent properties. A novel DEET-like repellent with lower volatility (8.55 × 10-4 mmHg) but a higher binding affinity for OBP1 than DEET (1.35 × 10-3 mmHg). A highly active repellent molecule that is predicted to bind to the secondary Icaridin (sIC)-binding site of OBP1 with higher affinity than to the DEET-site and, therefore, represents a new scaffold to be exploited for the discovery of binders targeting multiple OBP sites. Finally, a third potent repellent exhibiting a high degree of volatility was found to be a strong DEET-site binder of OBP1 that could be used in slow-release formulations.

Targeting LIF/LIFR signaling in cancer.

Leukemia inhibitory factor (LIF), and its receptor (LIFR), are commonly over-expressed in many solid cancers and recent studies have implicated LIF/LIFR axis as a promising clinical target for cancer therapy. LIF/LIFR activate oncogenic signaling pathways including JAK/STAT3 as immediate effectors and MAPK, AKT, mTOR further downstream. LIF/LIFR signaling plays a key role in tumor growth, progression, metastasis, stemness and therapy resistance. Many solid cancers show overexpression of LIF and autocrine stimulation of the LIF/LIFR axis; these are associated with a poorer relapse-free survival. LIF/LIFR signaling also plays a role in modulating multiple immune cell types present in tumor micro environment (TME). Recently, two targeted agents that target LIF (humanized anti-LIF antibody, MSC-1) and LIFR inhibitor (EC359) were under development. Both agents showed effectivity in preclinical models and clinical trials using MSC-1 antibody are in progress. This article reviews the significance of LIF/LIFR pathways and inhibitors that disrupt this process for the treatment of cancer.

Exploring the binding mode of PQ912 against secretory glutaminyl cyclase through systematic exploitation of conformational ensembles.

Secretory glutaminyl cyclase (sQC) plays an important role in the formation of the pyroglutamate-amyloid beta (pGlu-Aß) peptide, one of the most abundant variants of Aß found in the Alzheimer's disease (AD) brain. This post-translationally modified pGlu-Aß possesses high toxicity and rapid aggregation propensity when compared to the wild-type Aß (WT-Aß). Since pGlu-Aß acts as seed for WT-Aß, the inhibition of sQC limits the formation of pGlu-Aß and reduces the overall load of Aß plaques in the AD brain. PQ912 is a potent inhibitor of sQC and has been enrolled in phase 2b clinical trial of the AD drug development pipeline; however, the binding mode of PQ912 against sQC is not elucidated yet. Understanding the binding mode of PQ912 is important as it helps in the discovery against AD where sQC as a target. To explore the binding mode of PQ912, we employed ensemble docking towards 9 sQC structures that differ either in active site geometry or in the bound ligands. Further pose clustering and binding energy calculations yielded three possible binding modes for PQ912. Finally, all atom molecular dynamics simulations determined the most energetically favorable binding mode for PQ912, in the active site of sQC, which is similar to that of LSB-09, a recently reported sQC inhibitor containing benzimidazole-6-carboxamide moiety.

EC313-a tissue selective SPRM reduces the growth and proliferation of uterine fibroids in a human uterine fibroid tissue xenograft model.

Uterine fibroids (UFs) are associated with irregular or excessive uterine bleeding, pelvic pain or pressure, or infertility. Ovarian steroid hormones support the growth and maintenance of UFs. Ulipristal acetate (UPA) a selective progesterone receptor (PR) modulator (SPRM) reduce the size of UFs, inhibit ovulation and lead to amenorrhea. Recent liver toxicity concerns with UPA, diminished enthusiasm for its use and reinstate the critical need for a safe, efficacious SPRM to treat UFs. In the current study, we evaluated the efficacy of new SPRM, EC313, for the treatment for UFs using a NOD-SCID mouse model. EC313 treatment resulted in a dose-dependent reduction in the fibroid xenograft weight (p < 0.01). Estradiol (E2) induced proliferation was blocked significantly in EC313-treated xenograft fibroids (p < 0.0001). Uterine weight was reduced by EC313 treatment compared to UPA treatment. ER and PR were reduced in EC313-treated groups compared to controls (p < 0.001) and UPA treatments (p < 0.01). UF specific desmin and collagen were markedly reduced with EC313 treatment. The partial PR agonism and no signs of unopposed estrogenicity makes EC313 a candidate for the long-term treatment for UFs. Docking studies have provided a structure based explanation for the SPRM activity of EC313.

EC359: A First-in-Class Small-Molecule Inhibitor for Targeting Oncogenic LIFR Signaling in Triple-Negative Breast Cancer.

Leukemia inhibitory factor receptor (LIFR) and its ligand LIF play a critical role in cancer progression, metastasis, stem cell maintenance, and therapy resistance. Here, we describe a rationally designed first-in-class inhibitor of LIFR, EC359, which directly interacts with LIFR to effectively block LIF/LIFR interactions. EC359 treatment exhibits antiproliferative effects, reduces invasiveness and stemness, and promotes apoptosis in triple-negative breast cancer (TNBC) cell lines. The activity of EC359 is dependent on LIF and LIFR expression, and treatment with EC359 attenuated the activation of LIF/LIFR-driven pathways, including STAT3, mTOR, and AKT. Concomitantly, EC359 was also effective in blocking signaling by other LIFR ligands (CTF1, CNTF, and OSM) that interact at LIF/LIFR interface. EC359 significantly reduced tumor progression in TNBC xenografts and patient-derived xenografts (PDX), and reduced proliferation in patient-derived primary TNBC explants. EC359 exhibits distinct pharmacologic advantages, including oral bioavailability, and in vivo stability. Collectively, these data support EC359 as a novel targeted therapeutic that inhibits LIFR oncogenic signaling.See related commentary by Shi et al., p. 1337.

Derivatives form better lipoxygenase inhibitors than piperine: in vitro and in silico study.

Piperine is a secondary metabolite of black pepper. Its uses in medicine were already studied. However, its derivatives have not gained considerable attention. In the presented study, the Lipoxygenase (LOX) inhibitory activity of piperine and its derivatives, piperonylic acid, piperic acid, and piperonal have been assessed and compared by enzyme kinetics, ITC and molecular modeling experiments. The presented investigations expressed that all the studied compounds inhibited LOX by binding at its active site. The IC(50) values of these compounds were deduced from the kinetics data and found to be 85.79, 43.065, 45.17, and 50.78 µm for piperine, piperonylic acid, piperic acid, and piperonal, respectively. The binding free energies obtained from ITC experiments were -7.47, -8.33, -8.09, and -7.86 kcal/mol for piperine, piperonylic acid, piperic acid, and piperonal, respectively. Similarly, the glide scores obtained for piperine, piperonylic acid, piperic acid, and piperonal were -7.28, -10.32, -10.72, and -9.57 kcal/mol, respectively. The results of ITC and molecular modeling experiments suggested that piperonylic acid and piperonal exhibit stronger binding at the active site than piperine does. From the presented studies, it could be concluded that derivatives of piperine may be of higher significance than piperine for certain medicinal applications, implicating (Ayurvedic) fermented herbal drugs with piperine in them.

A lectin from Spatholobus parviflorus inhibits Aspergillus flavus α-amylase: enzyme kinetics and thermodynamic studies.

Aspergillus flavus is a commonly found fungal pathogen which produces structurally related and highly toxic secondary metabolites, aflatoxins. It has been proposed that α-amylase inhibitors may limit the ability of the fungus to produce aflatoxins. Hence, this enzyme is a potent target for the development of antifungal agents. In this study, it was found that Spatholobus parviflorus seed lectin (SPL) can inhibit the growth of A. flavus with a MIC value of 1.5 mg/mL. The enzyme kinetics, molecular modeling and isothermal titration calorimetric studies suggest that SPL can inhibit α-amylase with Ki value of 0.0042 mm. Hence, it is suggested that the antifungal activity of SPL might be partly due to its ability to inhibit the enzyme α-amylase.

An isoquinoline alkaloid, berberine, can inhibit fungal alpha amylase: enzyme kinetic and molecular modeling studies.

Aspergillus flavus is a commonly found fungal pathogen, which produces aflatoxins, highly toxic and hepatocarcinogenic natural compounds. Inhibition of fungal alpha amylase activity has been found to limit the ability of the fungus to produce aflatoxins. Berberine, an isoquinoline alkaloid commonly found in many medicinal plants, was identified to inhibit the growth of A. flavus. The amount of berberine required to inhibit the fungal mycelial growth was determined. The compound was also found to inhibit the alpha amylase from the A. flavus. The binding affinity of the compound toward alpha amylase and the enzyme inhibitory activity have been determined by enzyme kinetic studies and Isothermal Titration Calorimetric analysis. Molecular modeling and docking studies were carried out to understand the enzyme-ligand interactions.

Binding to PLA2 may contribute to the anti-inflammatory activity of catechol.

Inhibiting PLA(2) activity should, in theory, be an effective approach to control the inflammation. Several naturally occurring polyphenolic compounds have been reported as inhibitors of PLA(2) . Among the naturally occurring polyphenols, catechol (1,2-dihydroxybenzene) possesses anti-inflammatory activity. Catechol can inhibit cyclooxygenase and lipo-oxygenase. By means of enzyme kinetic study, it was revealed that catechol can inhibit PLA(2) also. Crystal structure showed that catechol binds to PLA(2) at the opening of the active site cleft. This might stop the entry of substrate into the active site. Hence, catechol can be used as a lead compound for the development of novel anti-inflammatory drugs with PLA(2) as the target.

Anti-inflammatory property of n-hexadecanoic acid: structural evidence and kinetic assessment.

Ester bond hydrolysis of membrane phospholipids by Phospholipase A(2) and consequent release of fatty acids are the initiating steps of inflammation. It is proposed in this study that the inhibition of phospholipase A(2) is one of the ways to control inflammation. Investigations are carried out to identify the mode of inhibition of phospholipase A(2) by the n-hexadecanoic acid. It may help in designing of specific inhibitors of phospholipase A(2) as anti-inflammatory agents. The enzyme kinetics study proved that n-hexadecanoic acid inhibits phospholipase A(2) in a competitive manner. It was identified from the crystal structure at 2.5 Å resolution that the position of n-hexadecanoic acid is in the active site of the phospholipase A(2). The binding constant and binding energy have also been calculated using Isothermal Titration Calorimetry. Also, the binding energy of n-hexadecanoic acid to phospholipase A(2) was calculated by in silico method and compared with known inhibitors. It may be concluded from the structural and kinetics studies that the fatty acid, n-hexadecanoic acid, is an inhibitor of phospholipase A(2), hence, an anti-inflammatory compound. The inferences from the present study validate the rigorous use of medicated oils rich in n-hexadecanoic acid for the treatment of rheumatic symptoms in the traditional medical system of India, Ayurveda.