Discovery of 2-(5-nitrothiazol-2-ylthio)benzo[d]thiazoles as novel c-Jun N-terminal kinase inhibitors

The Role of the Dysregulated JNK Signaling Pathway in the Pathogenesis of Human Diseases and Its Potential Therapeutic Strategies: A Comprehensive Review

JNK is named after c-Jun N-terminal kinase, as it is responsible for phosphorylating c-Jun. As a member of the mitogen-activated protein kinase (MAPK) family, JNK is also known as stress-activated kinase (SAPK) because it can be activated by extracellular stresses including growth factor, UV irradiation, and virus infection. Functionally, JNK regulates various cell behaviors such as cell differentiation, proliferation, survival, and metabolic reprogramming. Dysregulated JNK signaling contributes to several types of human diseases. Although the role of the JNK pathway in a single disease has been summarized in several previous publications, a comprehensive review of its role in multiple kinds of human diseases is missing. In this review, we begin by introducing the landmark discoveries, structures, tissue expression, and activation mechanisms of the JNK pathway. Next, we come to the focus of this work: a comprehensive summary of the role of the deregulated JNK pathway in multiple kinds of diseases. Beyond that, we also discuss the current strategies for targeting the JNK pathway for therapeutic intervention and summarize the application of JNK inhibitors as well as several challenges now faced. We expect that this review can provide a more comprehensive insight into the critical role of the JNK pathway in the pathogenesis of human diseases and hope that it also provides important clues for ameliorating disease conditions.

Exploring Thiazolopyridine AV25R: Unraveling of Biological Activities, Selective Anti-Cancer Properties and In Silico Target and Binding Prediction in Hematological Neoplasms

Thiazolopyridines are a highly relevant class of small molecules, which have previously shown a wide range of biological activities. Besides their anti-tubercular, anti-microbial and anti-viral activities, they also show anti-cancerogenic properties, and play a role as inhibitors of cancer-related proteins. Herein, the biological effects of the thiazolopyridine AV25R, a novel small molecule with unknown biological effects, were characterized. Screening of a set of lymphoma (SUP-T1, SU-DHL-4) and B- acute leukemia cell lines (RS4;11, SEM) revealed highly selective effects of AV25R. The selective anti-proliferative and metabolism-modulating effects were observed in vitro for the B-ALL cell line RS4;11. Further, we were able to detect severe morphological changes and the induction of apoptosis. Gene expression analysis identified a large number of differentially expressed genes after AV25R exposure and significant differentially regulated cancer-related signaling pathways, such as VEGFA-VEGFR2 signaling and the EGF/EGFR pathway. Structure-based pharmacophore screening approaches using in silico modeling identified potential biological AV25R targets. Our results indicate that AV25R binds with several proteins known to regulate cell proliferation and tumor progression, such as FECH, MAP11, EGFR, TGFBR1 and MDM2. The molecular docking analyses indicates that AV25R has a higher binding affinity compared to many of the experimentally validated small molecule inhibitors of these targets. Thus, here we present in vitro and in silico analyses which characterize, for the first time, the molecular acting mechanism of AV25R, including cellular and molecular biologic effects. Additionally, this predicted the target binding of the molecule, revealing a high affinity to cancer-related proteins and, thus, classified AVR25 for targeted intervention approaches.

Shikimate Kinase Inhibitors: An Update on Promising Strategy against Mycobacterium tuberculosis

Humanity has been battling with tuberculosis (TB) for a long period, and despite the availability of drugs well-known to act against the deadly microbe, the menace is still very far from reaching its end. Moreover, problems related to TB chemotherapy, such as lengthy treatment periods leading to poor patient compliance, increasing drug resistance, and association with another deadlier disease HIV-AIDS, make the situation alarming, thereby pressing the need for the discovery of new potent drugs urgently. Therefore, a drug target that is essential for survival and exclusive to M. tuberculosis presents a promising platform to explore novel molecules against the microorganism for better pathogen clearance with minimal toxicity. The shikimate pathway that leads to the synthesis of essential aromatic amino acids is one such attractive target. Shikimate kinase, the fifth enzyme of this pathway, converts shikimate to shikimate-3-phosphate by using ATP as a cosubstrate. Targeting shikimate kinase could be an effective strategy in light of its essentiality and absence of any homologue in mammals. This review discusses different strategies adopted for discovering novel compounds or scaffolds targeting M. tuberculosis shikimate kinase (MtSK) in vitro. The application of substrate analogues, their structure, and ligand-based approach for screening a library of anti-mycobacterial compounds, marine-derived molecules, and commercially available libraries have yielded promising MtSK inhibitors exhibiting micro-molar activities. To develop these leads into future drugs with minimum off-target effects on the host microenvironment, the molecules need to be structurally optimized for improved activities against enzymes and whole-cell organisms.

A review on synthetic chalcone derivatives as tubulin polymerisation inhibitors

Microtubules play an important role in the process of cell mitosis and can form a spindle in the mitotic prophase of the cell, which can pull chromosomes to the ends of the cell and then divide into two daughter cells to complete the process of mitosis. Tubulin inhibitors suppress cell proliferation by inhibiting microtubule dynamics and disrupting microtubule homeostasis. Thereby inducing a cell cycle arrest at the G2/M phase and interfering with the mitotic process. It has been found that a variety of chalcone derivatives can bind to microtubule proteins and disrupt the dynamic balance of microtubules, inhibit the proliferation of tumour cells, and exert anti-tumour effects. Consequently, a great number of studies have been conducted on chalcone derivatives targeting microtubule proteins. In this review, synthetic or natural chalcone microtubule inhibitors in recent years are described, along with their structure-activity relationship (SAR) for anticancer activity.

Design, Synthesis, Antibacterial Evaluation and Molecular Docking Studies of Some Newer Baenzothiazole Containing Aryl and Alkaryl Hydrazides

The alarming rise of bacterial resistance is occurring worldwide and endangering the efficacy of antibiotics. Therefore, development of new and efficient antibacterial agents remains paramount. In the present work, we designed and synthesized a series of N'-(1,3-benzothiazol-2-yl)-substituted aryl/aralkyl hydrazides C1-C27 and evaluated them in vitro for their antibacterial activity. Among all tested compounds, C10, C15, and C24 showed potent activity against Staphylococcus aureus ATCC 43300 (MRSA). Minimum bactericidal concentration studies of synthesized compounds are performed against selected bacterial strains. Time kill kinetics showed that the compounds C10 and C15 possess bactericidal activity against MRSA ATCC 43300, while compound C24 possess bactericidal activity against S. aureus NCIM 5022. In the extra-precision docking, compounds C1-C27 exhibited interactions mainly with the N-terminal and central domains of S. aureus GyrB catalytic pocket. Binding free energy (ΔGbind ) of compounds C1-C27/3U2K complexes were computed by MM-GBSA approach. Free energy components indicated Coulomb energy term as favorable for binding, while van der Waals and electrostatic solvation energy terms strongly disfavored the binding. ADMET properties of synthesized compounds C1-C27 are also computed.

Evaluation of 1,1-cyclopropylidene as a thioether isostere in the 4-thio-thienopyrimidine (TTP) series of antimalarials

The 4-(heteroarylthio)thieno[2,3-d]pyrimidine (TTP) series of antimalarials, represented by 1 and 17, potently inhibit proliferation of the 3D7 strain of P. falciparum (EC₅₀ 70-100 nM), but suffer from oxidative metabolism. The 1,1-cyclopropylidene isosteres 6 and 16 were designed to obviate this drawback. They were prepared by a short route that features a combined Peterson methylenation / cyclopropanation transformation of, e. g., ketone 7. Isosteres 6 and 16 possess significantly attenuated antimalarial potency relative to parents 1 and 17. This outcome can be rationalized based on the increased out-of-plane steric demands of the latter two. In support of this hypothesis, the relatively flat ketone 7 retains some of the potency of 1, even though it appears to be a comparatively inferior mimic with respect to electronics and bond lengths and angles. We also demonstrate crystallographically and computationally an apparent increase in the strength of the intramolecular sulfur hole interaction of 1 upon protonation.

JNK pathway signaling: a novel and smarter therapeutic targets for various biological diseases

JNK pathway regulates various physiological processes including inflammatory responses, cell differentiation, cell proliferation, cell death, cell survival and expression of proteins. Deregulation of JNK is linked with various diseases including neurodegenerative disease, autoimmune disease, diabetes, cancer, cardiac hypertrophy and asthma. Three distinct genes JNK1, JNK2 and JNK3 have been identified as regulator of JNK pathway. JNK1 and JNK2 have broad tissue distribution and play a potential role in insulin resistance, inflammation and cell signaling. JNK3 is predominantly found in the CNS neurons, making it an attractive target for neurodegenerative disorders. In this review, we summarize the evidence supporting JNK as a potent therapeutic target, and small molecules from various chemical classes as JNK inhibitors.

Galloyl benzamide-based compounds modulating tumour necrosis factor α-stimulated c-Jun N-terminal kinase and p38 mitogen-activated protein kinase signalling pathways

OBJECTIVES

The aim of this work is to investigate whether and how two newly synthesized 3,4,5-trimethoxygalloyl-containing compounds 1 and 3 interfere with the mitogen-activated protein kinase (MAPK) signalling pathways involved in several pathological events, ranging from inflammatory diseases to cancer.

METHODS

The effects on the phosphorylation of MAP kinases (c-Jun N-terminal kinases (JNKs), p38) and activation of nuclear factor-kappa B (NF-κB) pathways of 1 and its 1H-indazole-containing analogue 3, compared with those elicited by the known Adenosine Triphosphate (ATP)-competitive JNK inhibitor SP600125, were evaluated through Western blot analysis in murine fibroblasts NIH-3T3 and human endothelial cells EA.hy926 acutely treated with tumour necrosis factor-α (TNF-α). Their effects on cell viability were also assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay.

KEY FINDINGS

In cultured murine fibroblasts, 1 inhibited JNK signalling with a different mechanism from SP600125. It reduced c-Jun phosphorylation without altering phosphorylation levels of JNK protein. Compound 3, showing a profile similar to SP600125, inhibited JNK phosphorylation and partially inhibited p38 MAPK at 50 μm concentration. Compound 3 and SP600125 showed similar behaviour in both cell cultures. In contrast, compound 1 in EA.hy926 cells significantly interfered with JNK phosphorylation, did not decrease phosphorylation of c-Jun (Ser73), whereas significantly suppressed phosphorylation of p38 MAPK and reversed degradation of NF-κB signalling components.

CONCLUSIONS

3,4,5-Trimethoxygalloyl-based compounds 1 and 3, which did not show significant cell toxicity, modulate the TNF-α-induced activation of MAPK signalling, mainly inhibiting phosphorylation of JNK, c-Jun and p38 MAPK, in murine fibroblasts and human endothelial cells with different MAPK selectivity profiles. These compounds deserve future investigation in specific cell-based disease models and in-vivo pharmacology.

Identification and characterization of bi-thiazole-2,2'-diamines as kinase inhibitory scaffolds

Based on bioinformatics interrogation of the genome, >500 mammalian protein kinases can be clustered within seven different groups. Of these kinases, the mitogen-activated protein kinase (MAPK) family forms part of the CMGC group of serine/threonine kinases that includes extracellular signal regulated kinases (ERKs), cJun N-terminal kinases (JNKs), and p38 MAPKs. With the JNKs considered attractive targets in the treatment of pathologies including diabetes and stroke, efforts have been directed to the discovery of new JNK inhibitory molecules that can be further developed as new therapeutics. Capitalizing on our biochemical understanding of JNK, we performed in silico screens of commercially available chemical databases to identify JNK1-interacting compounds and tested their in vitro JNK inhibitory activity. With in vitro and cell culture studies, we showed that the compound, 4'-methyl-N(2)-3-pyridinyl-4,5'-bi-1,3-thiazole-2,2'-diamine (JNK Docking (JD) compound 123, but not the related compound (4'-methyl-N~2~-(6-methyl-2-pyridinyl)-4,5'-bi-1,3-thiazole-2,2'-diamine (JD124), inhibited JNK1 activity towards a range of substrates. Molecular docking, saturation transfer difference NMR experiments and enzyme kinetic analyses revealed both ATP- and substrate-competitive inhibition of JNK by JD123. In characterizing JD123 further, we noted its ATP-competitive inhibition of the related p38-γ MAPK, but not ERK1, ERK2, or p38-α, p38-β or p38-δ. Further screening of a broad panel of kinases using 10μM JD123, identified inhibition of kinases including protein kinase Bβ (PKBβ/Aktβ). Appropriately modified thiazole diamines, as typified by JD123, thus provide a new chemical scaffold for development of inhibitors for the JNK and p38-γ MAPKs as well as other kinases that are also potential therapeutic targets such as PKBβ/Aktβ.

Inhibition of JNK mitochondrial localization and signaling is protective against ischemia/reperfusion injury in rats

To build upon recent findings that mitochondrial JNK signaling is inhibited by selectively blocking the interaction between JNK and Sab, we utilized a cell-permeable peptide to demonstrate that ischemia/reperfusion (I/R) injury could be protected in vivo and that JNK mitochondrial signaling was the mechanism by which reactive oxygen species (ROS) generation, mitochondrial dysfunction, and cardiomyocyte cell death occur. We also demonstrated that 5 mg/kg SR-3306 (a selective JNK inhibitor) was able to protect against I/R injury, reducing infarct volume by 34% (p < 0.05) while also decreasing I/R-induced increases in the activity of creatine phosphokinase and creatine kinase-MB. TUNEL staining showed that the percent TUNEL positive nuclei in rat hearts increased 10-fold after I/R injury and that this was reduced 4-fold (p < 0.01) by SR-3306. These data suggest that blocking JNK mitochondrial translocation or JNK inhibition prevents ROS increases and mitochondrial dysfunction and may be an effective treatment for I/R-induced cardiomyocyte death.

Moderate correlations of in vitro versus in vivo pharmacokinetics questioning the need of early microsomal stability testing

BACKGROUND/AIMS

Putative in vitro-in vivo correlations of pharmacokinetic (PK) parameters are regarded as a prerequisite to filter hits derived from high-throughput screening (HTS) approaches for subsequent murine in vivo PK studies.

METHODS

In this study, we assessed stabilities in rat and human microsomes of 121 compounds from an early, academic drug discovery programme targeting the (pro)renin receptor and correlated the respective data with single-dose, in vivo PK parameters of 22 hits administered intravenously in rats.

RESULTS

After transformation of in vitro half-lives to predicted in vivo hepatic clearances, r(2) regarding in vitro-in vivo clearance correlations were 0.31 and 0.27 for the rat and human species, respectively.

CONCLUSIONS

Our data concerning structurally diverse real-world compounds indicate that microsomal stability testing is not a tool to triage early compounds for in vivo PK testing.

Medicinal significance of benzothiazole scaffold: an insight view

Heterocycles bearing nitrogen, sulphur and thiazole moieties constitute the core structure of a number of biologically interesting compounds. Benzothiazole, a group of xenobiotic compounds containing a benzene ring fused with a thiazole ring, are used worldwide for a variety of therapeutic applications. Benzothiazole and their heterocyclic derivatives represent an important class of compounds possessing a wide spectrum of biological activities. The myriad spectrum of medicinal properties associated with benzothiazole related drugs has encouraged the medicinal chemists to synthesize a large number of novel therapeutic agents. Several analogues containing benzothiazole ring system exhibit significant antitumour, antimicrobial, antidiabetic, anti-inflammatory, anticonvulsant, antiviral, antioxidant, antitubercular, antimalarial, antiasthmatic, anthelmintic, photosensitizing, diuretic, analgesic and other activities. This article is an attempt to present the research work reported in recent scientific literature on different pharmacological activities of benzothiazole compounds.

From in Silico Discovery to intra-Cellular Activity: Targeting JNK-Protein Interactions with Small Molecules

The JNK-JIP1 interaction represents an attractive target for the selective inhibition of JNK-mediated signaling. We report a virtual screening (VS) workflow, based on a combination of three-dimensional shape and electrostatic similarity to discover novel scaffolds for the development of non-ATP competitive inhibitors of JNK targeting the JNK-JIP interaction. Of 352 (0.13%) compounds selected from the NCI diversity set more than 22% registered as hits in a biochemical kinase assay. Several compounds discovered to inhibit JNK activity under standard kinase assay conditions also impeded JNK activity in HEK293 cells. These studies led to the discovery that the lignan (-)-zuonin A inhibits JNK-protein interactions with a selectivity of 100-fold over ERK2 and p38 MAPKα. These results demonstrate the utility of a virtual screening protocol to identify novel scaffolds for highly selective, cell-permeable inhibitors of JNK-protein interactions.

Computational insights for the discovery of non-ATP competitive inhibitors of MAP kinases

Due to their role in cellular signaling mitogen activated protein (MAP) kinases represent targets of pharmaceutical interest. However, the majority of known MAP kinase inhibitors compete with cellular ATP and target an ATP binding pocket that is highly conserved in the 500 plus representatives of the human protein kinase family. Here we review progress toward the development of non-ATP competitive MAP kinase inhibitors for the extracellular signal regulated kinases (ERK1/2), the c-jun N-terminal kinases (JNK1/2/3) and the p38 MAPKs (α, β, γ, and δ). Special emphasis is placed on the role of computational methods in the drug discovery process for MAP kinases. Topics include recent advances in X-ray crystallography theory that improve the MAP kinase structures essential to structurebased drug discovery, the use of molecular dynamics to understand the conformational heterogeneity of the activation loop and inhibitors discovered by virtual screening. The impact of an advanced polarizable force field such as AMOEBA used in conjunction with sophisticated kinetic and thermodynamic simulation methods is also discussed.

Biological activities of 2-mercaptobenzothiazole derivatives: a review

2-Mercaptobenzothiazoles are an important class of bioactive and industrially important organic compounds. These compounds are reported for their antimicrobial and antifungal activities, and are subsequently highlighted as a potent mechanism-based inhibitor of several enzymes like acyl coenzyme A cholesterol acyltransferase, monoamine oxidase, heat shock protein 90, cathepsin D, and c-Jun N-terminal kinases. These derivatives are also known to possess antitubercular, anti-inflammatory, antitumor, amoebic, antiparkinsonian, anthelmintic, antihypertensive, antihyperlipidemic, antiulcer, chemoprotective, and selective CCR3 receptor antagonist activity. This present review article focuses on the pharmacological profile of 2-mercaptobenzothiazoles with their potential activities.

Design and characterization of a potent and selective dual ATP- and substrate-competitive subnanomolar bidentate c-Jun N-terminal kinase (JNK) inhibitor

c-Jun N-terminal kinases (JNKs) represent valuable targets in the development of new therapies. Present on the surface of JNK is a binding pocket for substrates and the scaffolding protein JIP1 in close proximity to the ATP binding pocket. We propose that bidentate compounds linking the binding energies of weakly interacting ATP and substrate mimetics could result in potent and selective JNK inhibitors. We describe here a bidentate molecule, 19, designed against JNK. 19 inhibits JNK kinase activity (IC(50) = 18 nM; K(i) = 1.5 nM) and JNK/substrate association in a displacement assay (IC(50) = 46 nM; K(i) = 2 nM). Our data demonstrate that 19 targets for the ATP and substrate-binding sites on JNK concurrently. Finally, compound 19 successfully inhibits JNK in a variety of cell-based experiments, as well as in vivo where it is shown to protect against Jo-2 induced liver damage and improve glucose tolerance in diabetic mice.

High throughput screening of a library based on kinase inhibitor scaffolds against Mycobacterium tuberculosis H37Rv

Kinase targets are being pursued in a variety of diseases beyond cancer, including immune and metabolic as well as viral, parasitic, fungal and bacterial. In particular, there is a relatively recent interest in kinase and ATP-binding targets in Mycobacterium tuberculosis in order to identify inhibitors and potential drugs for essential proteins that are not targeted by current drug regimens. Herein, we report the high throughput screening results for a targeted library of approximately 26,000 compounds that was designed based on current kinase inhibitor scaffolds and known kinase binding sites. The phenotypic data presented herein may form the basis for selecting scaffolds/compounds for further enzymatic screens against specific kinase or other ATP-binding targets in Mycobacterium tuberculosis based on the apparent activity against the whole bacteria in vitro.

Characterization of a novel JNK (c-Jun N-terminal kinase) inhibitory peptide

An improved understanding of the roles of protein kinases in intracellular signalling and disease progression has driven significant advances in protein kinase inhibitor discovery. Peptide inhibitors that target the kinase protein substrate-binding site have continued to attract attention. In the present paper, we describe a novel JNK (c-Jun N-terminal kinase) inhibitory peptide PYC71N, which inhibits JNK activity in vitro towards a range of recombinant protein substrates including the transcription factors c-Jun, ATF2 (activating trancription factor 2) and Elk1, and the microtubule regulatory protein DCX (doublecortin). Analysis of cell culture studies confirmed the actions of a cell-permeable version of PYC71 to inhibit c-Jun phosphorylation during acute hyperosmotic stress. The analysis of the in vitro data for the kinetics of this inhibition indicated a substrate–inhibitor complex-mediated inhibition of JNK by PYC71N. Alanine-scanning replacement studies revealed the importance of two residues (PYC71N Phe9 or Phe11 within an FXF motif) for JNK inhibition. The importance of these residues was confirmed through interaction studies showing that each change decreased interaction of the peptide with c-Jun. Furthermore, PYC71N interacted with both non-phosphorylated (inactive) JNK1 and the substrate c-Jun, but did not recognize active JNK1. In contrast, a previously characterized JNK-inhibitory peptide TIJIP [truncated inhibitory region of JIP (JNK-interacting protein)], showed stronger interaction with active JNK1. Competition binding analysis confirmed that PYC71N inhibited the interaction of c-Jun with JNK1. Taken together, the results of the present study define novel properties of the PYC71N peptide as well as differences from the characterized TIJIP, and highlight the value of these peptides to probe the biochemistry of JNK-mediated substrate interactions and phosphorylation.