A colorimetric assay adapted to fragment screening revealing aurones and chalcones as new arginase inhibitors.

Arginase, a difficult-to-target metalloenzyme, is implicated in a wide range of diseases, including cancer, infectious, and cardiovascular diseases. Despite the medical need, existing inhibitors have limited structural diversity, consisting predominantly of amino acids and their derivatives. The search for innovative arginase inhibitors has now extended to screening approaches. Due to the small and narrow active site of arginase, screening must meet the criteria of fragment-based screening. However, the limited binding capacity of fragments requires working at high concentrations, which increases the risk of interference and false positives. In this study, we investigated three colorimetric assays and selected one based on interference for screening under these challenging conditions. The subsequent adaptation and application to the screening a library of metal chelator fragments resulted in the identification of four compounds with moderate activity. The synthesis and evaluation of a series of compounds from one of the hits led to compound 21a with an IC50 value of 91.1 µM close to the reference compound piceatannol. Finally, molecular modelling supports the potential binding of aurones and chalcones to the active site of arginase, suggesting them as new candidates for the development of novel arginase inhibitors.

Comparison of a selective STAT3 inhibitor with a dual STAT3/STAT1 inhibitor using a dextran sulfate sodium murine colitis model: new insight into the debate on selectivity.

Background: Recent advances in the treatment of inflammatory bowel disease include antitumor necrosis factor antibodies and the Janus kinase inhibitor tofacitinib, approved for ulcerative colitis. Janus kinase recruits signal transducers and activators of transcriptions (STAT), which are promising targets in inflammatory bowel diseases. However few inhibitors have been evaluated, and their selectivity with respect to STAT1 and STAT3 remains controversial. Here, we investigated the therapeutic potential of a selective inhibitor vs. a non-selective, closely related compound, in a dextran sulfate sodium (DSS) murine colitis model. Methods: Thirty Swiss/CD-1 male mice were used in this study. They were divided into a healthy control group, a colitis-DSS control group, a compound (cpd) 23-treated group, a cpd 46-treated group and an icariin-treated group. For the coadministration experiment with rutin, the cpd 46-treated group and the icariin-treated group were replaced by the oral rutin-treated group and the coadministration rutin/cpd 23-treated group. The effect of the tested inhibitors was also assessed by quantification of proinflammatory markers. Results: The selective inhibitor had a significantly greater effect than the dual inhibitor on the disease activity index. We also noticed in curative treatment a significant decrease in the most abundant proinflammatory biomarker present in neutrophilic granulocytes, myeloperoxidase and on proinflammatory cytokines, including tumor necrosis factor-α, interferon-γ, interleukins -6 and -23, with a mild synergy with rutin, the glycoside of quercetin. Conclusion: The current study shows how STAT3 selective inhibitors can exert a significant therapeutic effect in the treatment of experimental DSS-colitis.

Arginase inhibitory activities of chemical constituents from Macaranga hurifolia Beille leaves.

The methanolic extract of the leaves of Macaranga hurifolia Beille showed arginase inhibitory activity (40% at 100 µg/mL) and was then fractionated to obtain nine polyphenolic compounds. Their structures were elucidated on the basis of NMR spectroscopic data, and by comparison with data previously reported in the literature, as gallic acid (1), 3,4-dihydroxybenzoic acid (2), chlorogenic acid, (3), corilagin (4), cynaroside (5), cosmosiin (6), hyperoside (7) isoquercitrin (8) and guajaverin (9). These compounds have been evaluated as arginase inhibitors. Compounds 4, 7, 8 and 9 showed varying arginase inhibitory activities with IC50 values ranging from 102 to 302 µM. All the isolated compounds were previously identified in this species but their activities on arginase are reported here for the first time.

An Update on Arginase Inhibitors and Inhibitory Assays.

Arginase, which converts arginine into ornithine and urea, is a promising therapeutic target. Arginase is involved in cardiovascular diseases, parasitic infections and through a critical role in immunity, in some cancers. There is a need to develop effective arginase inhibitors and therefore efforts to identify and optimize new inhibitors are increasing. Several methods of evaluating arginase activity are available, but few directly measure the product. Radiometric assays need to separate urea and dying reactions require acidic conditions and sometimes heating. Hence, there are a variety of different approaches available, and each approach has its own limits and benefits. In this review, we provide an update on arginase inhibitors, followed by a discussion on available arginase assays and alternative methods, focusing on the intrinsic biases and parameters that are likely to impact results.

Cinnamides Target Leishmania amazonensis Arginase Selectively.

Caffeic acid and related natural compounds were previously described as Leishmania amazonensis arginase (L-ARG) inhibitors, and against the whole parasite in vitro. In this study, we tested cinnamides that were previously synthesized to target human arginase. The compound caffeic acid phenethyl amide (CAPA), a weak inhibitor of human arginase (IC50 = 60.3 ± 7.8 µM) was found to have 9-fold more potency against L-ARG (IC50 = 6.9 ± 0.7 µM). The other compounds that did not inhibit human arginase were characterized as L-ARG, showing an IC50 between 1.3-17.8 µM, and where the most active was compound 15 (IC50 = 1.3 ± 0.1 µM). All compounds were also tested against L. amazonensis promastigotes, and only the compound CAPA showed an inhibitory activity (IC50 = 80 µM). In addition, in an attempt to gain an insight into the mechanism of competitive L-ARG inhibitors, and their selectivity over mammalian enzymes, we performed an extensive computational investigation, to provide the basis for the selective inhibition of L-ARG for this series of compounds. In conclusion, our results indicated that the compounds based on cinnamoyl or 3,4-hydroxy cinnamoyl moiety could be a promising starting point for the design of potential antileishmanial drugs based on selective L-ARG inhibitors.

Arginase inhibitory properties of flavonoid compounds from the leaves of Mulberry (Morus alba, Moraceae).

OBJECTIVES: We aimed to isolate and identify bioactive molecules from Morus alba (Moraceae) leaves having arginase inhibitory activity towards the combat of clinical outcomes related to endothelial dysfunction. METHOD: Extraction and isolation were carried out by successive macerations, prepurification by using a Solid Phase Extraction (SPE) and separation using preparative PLC. The structures of the isolated components were established and confirmed by spectroscopic analyses, including the ESI-HRMS and NMR spectroscopic investigations. Biological evaluation was performed by using an in vitro assay with liver bovine purified arginase and by an ex vivo aortic ring study. KEY FINDINGS: We demonstrated that a phenolic extract from the leaves of M. alba possesses mammalian arginase inhibitory capacities. Investigation of the chemical constituents of its leaves results in the isolation and identification of ten compounds investigated in vitro for their arginase inhibitory capacities. Four compounds showed significant inhibition of arginase, with percentage inhibition ranging from 54% to 83% at 100 µm. In isolated rat aortic rings incubated with NO synthase inhibitor, Luteolin-7-diglucoside compound (2) was able to increase acetylcholine-induced relaxation. CONCLUSIONS: These results demonstrated the attractive ability of M. alba to be a potential source for the discovery of new active products on vascular system.

Cyperaceae Species Are Potential Sources of Natural Mammalian Arginase Inhibitors with Positive Effects on Vascular Function.

The inhibition of arginase is of substantial interest for the treatment of various diseases of public health interest including cardiovascular diseases. Using an ex vivo experiment on rat aortic rings and an in vitro assay with liver bovine purified arginase, it was demonstrated that several polyphenolic extracts from Cyperus and Carex species possess vasorelaxant properties and mammalian arginase inhibitory capacities. Phytochemical studies performed on these species led to the identification of eight compounds, including monomers, dimers, trimers, and tetramers of resveratrol. The potential of these stilbenes as inhibitors of mammalian arginase was assessed. Five compounds, scirpusin B (5), ε-viniferin (4), cyperusphenol B (6), carexinol A (7), and the new compound virgatanol (1), showed significant inhibition of arginase, with percentage inhibition ranging from 70% to 95% at 100 µg/mL and IC50 values between 12.2 and 182.1 µM, confirming that these stilbenes may be useful for the development of new pharmaceutical products.

Arginase Inhibitors: A Rational Approach Over One Century.

Arginase (EC 3.5.3.1) is the bimanganese enzyme that converts L-arginine into ornithine and urea. This enzyme was discovered more than a century ago and early α-amino acids were identified as weak inhibitors. It was only during the 90s, after nitric oxide (NO) was reported as one of the most important biological mediators and when tight interrelation of arginase and NO synthase was found, that the development of arginase inhibitors was accelerated. The regulation of arginase activity by the N-hydroxy-L-arginine (3, NOHA) intermediate of the NO synthesis was the starting point of the N-hydroxy-nor-arginine (21, nor-NOHA) that proved to be the first micromolar inhibitor. The previously known manganese and arginase binding by borate inspired the 2(S)-amino-6-boronohexanoic acid (39, ABH) and S-(2-boronoethyl)-L-cysteine (40, BEC) now both considered as reference compounds in arginase inhibition. The high-resolution crystal structure of arginase and molecular modeling has rendered possible the recent design of (53) the strongest α,α-disubstituted derivatives of ABH. Simultaneously, traditional medicinal plants have contributed as a source of molecular diversity to the discovery of arginase inhibitors. This rational, step-by-step approach serves as guide in the present review where emphasis is placed on structure activity relationships. Highlights exhaustive review on arginase inhibitors highlight is made on rational approach to conception and structure activity relationships evaluation model is systematically mentioned with results.

Carbon nanotubes as gene carriers: Focus on internalization pathways related to functionalization and properties.

Carbon nanotubes represent promising transporters for delivery of DNA and other biomolecules into living cells. Various methods of CNTs surface functionalization have been developed. These are essential to improve CNTs dispersibility and permit their interactions with biological structures that broaden their use in advanced biomedical applications. The present review discusses the different single walled carbon nanotubes and multiwalled carbon nanotubes functionalization methods, leading to the formation of optimized and functionalized-CNT complexes with DNA. F-CNTs are recognized as efficient and promising gene carriers. Emphasis is then placed on the processes used by f-CNTs/DNA complexes to cross cell membranes. Energy independent pathways and uptake mechanisms dependent on energy, such as endocytosis or phagocytosis, are reported by many studies, and if these mechanisms seem contradictory at first sight, a detailed review of the literature illustrates that they are rather complementary. Preferential use of one or the other depends on the DNA and CNTs chemical nature and physical parameters, experimental procedures and cell types. STATEMENT OF SIGNIFICANCE: Efficient non-viral gene delivery is desirable, yet challenging. CNTs appear as a promising solution to penetrate into cells and successfully deliver DNA. Moreover, the field of use of CNTs as gene carrier is large and is currently growing. This critical review summarizes the development and evaluation of CNTs as intracellular gene delivery system and provides an overview of functionalized CNTs/DNA cellular uptake mechanisms, depending on several parameters of CNTs/DNA complexes.

Cinnamide Derivatives as Mammalian Arginase Inhibitors: Synthesis, Biological Evaluation and Molecular Docking.

Arginases are enzymes that are involved in many human diseases and have been targeted for new treatments. Here a series of cinnamides was designed, synthesized and evaluated in vitro and in silico for their inhibitory activity against mammalian arginase. Using a microassay on purified liver bovine arginase (b-ARG I), (E)-N-(2-phenylethyl)-3,4-dihydroxycinnamide, also named caffeic acid phenylamide (CAPA), was shown to be slightly more active than our natural reference inhibitor, chlorogenic acid (IC50 = 6.9 ± 1.3 and 10.6 ± 1.6 µM, respectively) but it remained less active that the synthetic reference inhibitor Nω-hydroxy-nor-l-arginine nor-NOHA (IC50 = 1.7 ± 0.2 µM). Enzyme kinetic studies showed that CAPA was a competitive inhibitor of arginase with Ki = 5.5 ± 1 µM. Whereas the activity of nor-NOHA was retained (IC50 = 5.7 ± 0.6 µM) using a human recombinant arginase I (h-ARG I), CAPA showed poorer activity (IC50 = 60.3 ± 7.8 µM). However, our study revealed that the cinnamoyl moiety and catechol function were important for inhibitory activity. Docking results on h-ARG I demonstrated that the caffeoyl moiety could penetrate into the active-site pocket of the enzyme, and the catechol function might interact with the cofactor Mn2+ and several crucial amino acid residues involved in the hydrolysis mechanism of arginase. The results of this study suggest that 3,4-dihydroxycinnamides are worth being considered as potential mammalian arginase inhibitors, and could be useful for further research on the development of new arginase inhibitors.

Selective Inhibition of STAT3 with Respect to STAT1: Insights from Molecular Dynamics and Ensemble Docking Simulations.

STAT3 protein, which is known to be involved in cancer development, is a promising target for anticancer therapy. Successful inhibitors of STAT3 should not affect an activity of closely related protein STAT1, which makes their development challenging. The mechanisms of selectivity of several existing STAT3 inhibitors are not clear. In this work, we studied molecular mechanisms of selectivity of 13 experimentally tested STAT3 inhibitors by means of extensive molecular dynamics and ensemble docking simulations. It is shown that all studied inhibitors bind to the large part of the protein surface in an unspecific statistical manner. The binding to the dimerization interface of the SH2 domain, which is usually considered as the main target region, is not energetically preferable. Binding in this region is remarkably similar for STAT1 and STAT3 proteins and cannot explain experimentally observed selectivity toward STAT3. We propose a new mechanism of selectivity called "selectivity by distraction" for existing STAT3 inhibitors. This mechanism is based on equilibrium statistical partitioning of inhibitor molecules between protein domains. The unspecific binding of inhibitors to the DNA-binding and the coil-coil domains is stronger in STAT1 in comparison to STAT3 while the energies of their binding to SH2 domains are comparable. This "distracts" inhibitor molecules from the SH2 domain of STAT1 and leads to higher effective concentration of inhibitors in the vicinity of the SH2 domain of STAT3.

Nanovectorization of DNA Through Cells Using Protamine Complexation.

Carbon nanotubes (CNT) are currently used as a promising family of nanovectors able to deliver different types of therapeutic molecules. Several applications dealing with CNT used as drug nanocarriers have been developed since their ability to penetrate into the cells has been proved. CNT can thus load several active molecules to various cells. In this paper, we will use molecular dynamic simulation to describe theoretically the potential of CNT to transport and deliver DNA through the formation of protamine-DNA-CNT complex.

Novel aminotetrazole derivatives as selective STAT3 non-peptide inhibitors.

The development of inhibitors blocking STAT3 transcriptional activity is a promising therapeutic approach against cancer and inflammatory diseases. In this context, the selectivity of inhibitors against the STAT1 transcription factor is crucial as STAT3 and STAT1 play opposite roles in the apoptosis of tumor cells and polarization of the immune response. A structure-based virtual screening followed by a luciferase-containing promoter assay on STAT3 and STAT1 signaling were used to identify a selective STAT3 inhibitor. An important role of the aminotetrazole group in modulating STAT3 and STAT1 inhibitory activities has been established. Optimization of the hit compound leads to 23. This compound inhibits growth and survival of cells with STAT3 signaling pathway while displaying a minimal effect on STAT1 signaling. Moreover, it prevents lymphocyte T polarization into Th17 and Treg without affecting their differentiation into Th1 lymphocyte.

Nanovectorization of TRAIL with single wall carbon nanotubes enhances tumor cell killing.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL or Apo2L) is a member of the tumor necrosis factor (TNF) superfamily. This type II transmembrane protein is able to bound specifically to cancer cell receptors (i.e., TRAIL-R1 (or DR4) and TRAIL-R2 (or DR5)) and to induce apoptosis without being toxic for healthy cells. Because membrane-bound TRAIL induces stronger receptor aggregation and apoptosis than soluble TRAIL, we proposed here to vectorize TRAIL using single-walled carbon nanotubes (SWCNTs) to mimic membrane TRAIL. Owing to their exceptional and revolutional properties, carbon nanotubes, especially SWCNTs, are used in a wide range of physical or, now, medical applications. Indeed due to their high mechanical resistance, their high flexibility and their hydrophobicity, SWCNTs are known to rapidly diffuse in an aqueous medium such as blood, opening the way of development of new drug nanovectors (or nanocarriers). Our TRAIL-based SWCNTs nanovectors proved to be more efficient than TRAIL alone death receptors in triggering cancer cell killing. These NPTs increased TRAIL pro-apoptotic potential by nearly 20-fold in different Human tumor cell lines including colorectal, nonsmall cell lung cancer, or hepatocarcinomas. We provide thus a proof-of-concept that TRAIL nanovector derivatives based on SWCNT may be useful to future nanomedicine therapies.

Donepezil-ferulic acid hybrids as anti-Alzheimer drugs.

BACKGROUND: Due to the complex nature of Alzheimer's disease, there is a renewed and growing search for multitarget drugs. RESULTS: Donepezil-ferulic acid hybrids (DFAHs) were prepared by the one-pot Ugi-4CR in low-to-moderate yields. DFAHs are potent antioxidant agents, showing oxygen radical absorbance capacity values in the range 4.80-8.71 trolox equivalents, quite higher compared with those recorded for ferulic acid and melatonin. From the ChEs inhibition studies, we conclude that DFAH 8, bearing an ethylene linker, and DFAH 12, bearing a propylene linker, both substituted with a melatonin motif, are the most potent inhibitors, in the nanomolar range. CONCLUSION: We have identified DFAH 8 as a very potent antioxidant, and totally selective equineButyrylCholinEsterase (eqBuChE) inhibitor.

Novel tacrine-grafted Ugi adducts as multipotent anti-Alzheimer drugs: a synthetic renewal in tacrine-ferulic acid hybrids.

Herein we describe the design, multicomponent synthesis, and biological, molecular modeling and ADMET studies, as well as in vitro PAMPA-blood-brain barrier (BBB) analysis of new tacrine-ferulic acid hybrids (TFAHs). We identified (E)-3-(hydroxy-3-methoxyphenyl)-N-{8[(7-methoxy-1,2,3,4-tetrahydroacridin-9-yl)amino]octyl}-N-[2-(naphthalen-2-ylamino)2-oxoethyl]acrylamide (TFAH 10 n) as a particularly interesting multipotent compound that shows moderate and completely selective inhibition of human butyrylcholinesterase (IC50 =68.2 nM), strong antioxidant activity (4.29 equiv trolox in an oxygen radical absorbance capacity (ORAC) assay), and good ß-amyloid (Aß) anti-aggregation properties (65.6 % at 1:1 ratio); moreover, it is able to permeate central nervous system (CNS) tissues, as determined by PAMPA-BBB assay. Notably, even when tested at very high concentrations, TFAH 10 n easily surpasses the other TFAHs in hepatotoxicity profiling (59.4 % cell viability at 1000 µM), affording good neuroprotection against toxic insults such as Aß1-40 , Aß1-42 , H2 O2 , and oligomycin A/rotenone on SH-SY5Y cells, at 1 µM. The results reported herein support the development of new multipotent TFAH derivatives as potential drugs for the treatment of Alzheimer's disease.

Quinolone-benzylpiperidine derivatives as novel acetylcholinesterase inhibitor and antioxidant hybrids for Alzheimer disease.

Design, synthesis and evaluation of new acetylcholinesterase inhibitors by combining quinolinecarboxamide to a benzylpiperidine moiety are described. Then, a series of hybrids have been developed by introducing radical scavengers. Molecular modeling was performed and structure activity relationships are discussed. Among the series, most potent compounds show effective AchE inhibitions, high selectivities over butyrylcholinesterase and high radical scavenging activities. On the basis of this work, the ability of quinolone derivatives to serve in the design of N-benzylpiperidine linked multipotent molecules for the treatment of Alzheimer Disease has been established.

First domino radical cyclisation/Smiles rearrangement combination.

An unprecedented domino radical cyclisation-Smiles rearrangement process affording 3-(2'-aryl-N-methyl acetamido)indolin-2-ones is presented. Experimental rationalisation of this approach and description of an unexpected tricyclic core are also handled.