Synthesis, molecular docking and inhibition studies of novel 3-N-aryl substituted-2-heteroarylchromones targeting microtubule affinity regulating kinase 4 inhibitors

Column Chromatography-Free Synthesis of Spirooxindole and Spiroindanone-Based Naphthalimides as Potent c-MYC G4 Stabilizers and HSA Binders for Elevating Anticancer Potential

G-quadruplex (G4) DNA plays a pivotal regulatory role in fundamental biological processes, integral for governing cellular functions such as replication, transcription, and repair in living cells. Within cancer cells, G4 DNA exerts an impact on the expression of crucial genes such as c-MYC, effectively repressing its activity when structured within its promoter region. Therefore, employing molecular scaffolds to target these structures offers an attractive strategy for altering their functions. In our pursuit of potent and selective G-quadruplex binders, herein we report a series of spironaphthalimide-pyrrolidine analogues that demonstrate the ability to stabilize c-MYC G4 formation and subsequently inhibit c-MYC expression. These analogues are evaluated for their anticancer activity against 60 human cancer cell lines at 10 μM. The most potent analogues 8j and 21c underwent additional testing at five dose concentrations (10-4-10-8 M) where low MG-MID GI50 values are observed for both the analogues 8j (9.98 μM) and 21c (2.49 μM). To correlate with the antiproliferative activity, the mechanism is explored in vitro by performing Pu27 DNA binding studies through multispectroscopic techniques, and the results are compared with Pu22, human telomere, and calf thymus DNA. Additionally, insights from molecular docking suggested stacking over the G-tetrad of G4 structures of both analogues, with quantum mechanical studies further reinforcing the rationale for the stability of this quadruplex secondary structure. The analogues are also evaluated for their binding affinity to human serum albumin, revealing their robust capability to effectively bind and potentially facilitate targeted delivery to specific sites. Amidst the abundance of G4s across the human genome, the above findings underscore the significance of spiro analogues, with potent multitargeting anticancer attributes, marking a transformative leap forward in G4-ligand innovation, promising frontiers in the quest for effective anticancer modalities.

Selective Recognition of Oncogene Promoter C-Myc G-Quadruplex: Design, Synthesis, and In Vitro Evaluation of Naphthalimide and Imidazo[1,2-a]pyrazines for Their Anticancer Activity

c-Myc is a transcription factor that is overexpressed in most human cancers. Despite its challenging nature, we have developed a series of naphthalimide-imidazopyrazine conjugates to target c-Myc. The library of synthesized derivatives was tested for their anticancer activity against a nine-panel of cancer cell lines. Compound 8eb showed excellent cytotoxicity against all the tested cancer cell lines, with the range of growth inhibition from -98.79% to 96.62% at a single-dose concentration of 10-5 M. Further, 8eb was employed for a 5-dose assay against the same cancer cell lines, which showed efficacy at varying concentrations with an MG-MID GI50 value of 2.61 μM. Biophysical studies were performed to explore the interaction of 8eb with c-Myc Pu27 over ct-DNA, oncogene promotor Pu22, and human telomere, with a binding constant value of 1.3 × 107 M-1. Additionally, experiments were performed to get insights into the interaction mechanism between 8eb and the c-Myc oncogene promoter. A molecular docking study unveiled the stacking of the compound with G4 DNA through groove binding, where very few reports are available, with a favorable binding energy of -9.2 kcal/mol. Moreover, the pharmacokinetic study and HOMO-LUMO energy gap analysis underscored the potency of the active candidate. The compound's binding ability toward HSA was also assessed, where results suggested effective binding of the compound to HSA, revealing its potential for easy delivery to the target site. The above findings suggested that these newly synthesized candidates with potent anticancer activity offer a promising avenue as G4 DNA c-Myc stabilizers.

In Vitro Cytotoxicity and Mechanistic Investigation of Quinazolin-4(1H)-One Linked Coumarin as a Potent Anticancer Agent

Quinazolinone-coumarin conjugates synthesized through Late-Stage Functionalization approach are evaluated for their in vitro biological activity for 60 human cancer cell lines representing nine different cancer types. Among the synthesized compounds, eight displayed significant growth inhibitory activity across a spectrum of cancer types, with compound 23 demonstrating particularly notable cytotoxicity. Further investigation involved a five-dose assay of compound 23 against NCI-60 cancer cell lines, revealing its efficacy at different concentrations. Additionally, binding studies elucidated its interaction with Human Serum Albumin (HSA) and DNA. The results indicated a strong binding affinity of 23 with HSA, evidenced by a high binding constant (2.26 × 105 M-1). Moreover, its interaction with DNA occurred via intercalation, specifically between the base pairs of DNA strands, with a binding constant of 5.51 × 104 M-1. This suggests that compound 23 has the ability to bind to both DNA and transport proteins, making it a promising pharmacophore with potential therapeutic applications.

Design, synthesis, molecular docking and anti-proliferative activity of novel phenothiazine containing imidazo[1,2-a]pyridine derivatives against MARK4 protein

A series of novel phenothiazine-containing imidazo[1,2-a]pyridine derivatives were designed and synthesized under metal-free conditions in excellent yield. These derivatives were effectively transformed further into N-alkyl, sulfoxide, and sulfone derivatives. Derivatives were deployed against human microtubule affinity regulating kinase (MARK4), some molecules play crucial roles in cell-cycle progression such as G1/S transition and regulator of microtubule dynamics. Hence, molecules have shown excellent MARK4 inhibitory potential. Molecules with excellent IC50 values were selected for further studies such as ligand interactions using fluorescence quenching experiments for the binding constant. The highest binding constant was calculated as K = 0.79 × 105 and K = 0.1 × 107 for compounds 6a and 6h, respectively. Molecular docking, cell cytotoxicity, mitochondrial reactive oxygen species measurement and oxidative DNA damage were also studied to understand the mechanism of action of the molecules on cancer cells. It was found that the designed and synthesized compounds played anti-cancer roles by binding and inhibiting MARK4 protein.

Exploring the promising potential of noscapine for cancer and neurodegenerative disease therapy through inhibition of integrin-linked kinase-1

Integrin-linked kinase (ILK), a β1-integrin cytoplasmic domain interacting protein, supports multi-protein complex formation. ILK-1 is involved in neurodegenerative diseases by promoting neuro-inflammation. On the other hand, its overexpression induces epithelial-mesenchymal transition (EMT), which is a major hallmark of cancer and activates various factors associated with a tumorigenic phenotype. Thus, ILK-1 is considered as an attractive therapeutic target. We investigated the binding affinity and ILK-1 inhibitory potential of noscapine (NP) using spectroscopic and docking approaches followed by enzyme inhibition activity. A strong binding affinity of NP was measured for the ILK-1 with estimated Ksv (M-1) values of 1.9 × 105, 3.6 × 105, and 4.0 × 105 and ∆G0 values (kcal/mol) -6.19554, -7.8557 and -8.51976 at 298 K, 303 K, and 305 K, respectively. NP binds to ILK-1 with a docking score of -6.6 kcal/mol and forms strong interactions with active-site pocket residues (Lys220, Arg323, and Asp339). The binding constant for the interaction of NP to ILK-1 was 1.04 × 105 M-1, suggesting strong affinity and excellent ILK-1 inhibitory potential (IC50 of ∼5.23μM). Conformational dynamics of ILK-1 were also studied in the presence of NP. We propose that NP presumably inhibits ILK-1-mediated phosphorylation of various downstream signalling pathways that are involved in cancer cell survival and neuroinflammation.

In Vitro and In Silico Analysis of the Bindings between Legacy and Novel Per- and Polyfluoroalkyl Substances and Human Serum Albumin

Per- and polyfluoroalkyl substances (PFASs) are emerging contaminants of concern that can enter the human body through a variety of pathways and thereby cause harmful effects. Exposure of pregnant women to PFASs could even affect both the mother and the child. Human serum albumin (HSA) is considered to be the primary transport protein for a variety of substances in body fluids. It can be bound to different contaminants and might result in possible effects on human health. Yet, few studies are available on the binding affinity of legacy PFASs and their novel alternatives to HSA. In this study, the binding mechanisms of HSA to both legacy PFASs and their novel alternatives were investigated using fluorescence spectroscopy, together with further molecular docking. The results show that all the target PFASs were statically quenched against HSA with binding ratios of 1:1. The binding constants of long-chain PFASs and novel alternatives of perfluoroalkanesulfonic acids (PFSAs) were greater than 102, whereas those of short-chain PFASs alternatives and novel alternatives of perfluorocarboxylic acids (PFCAs) were less than 102. In general, the binding affinities of PFCAs on HSA were less than that of PFSAs, while the binding affinities of short-chain PFASs alternatives on HSA were smaller than those of long-chain PFASs and their novel alternatives. Therefore, bindings to HSA could be considered as an important influencing factor for the bioaccumulation of legacy and novel PFASs in the human body.

Tauopathy in AD: Therapeutic Potential of MARK-4

Alzheimer's disease (AD) is one of the leading causes of cognitive decline, which leads to dementia and poses significant challenges for its therapy. The reason is primarily the ineffective available treatments targeting the underlying pathology of AD. It is a neurodegenerative disease that is mainly characterised by the various molecular pathways contributing to its complex pathology, including extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs), oxidative stress, and neuroinflammation. One of the crucial features is the hyperphosphorylation of tau proteins, which is facilitated by microtubule affinity-regulating kinase-4 (MARK-4). The kinase plays a crucial role in the disease development by modifying microtubule integrity, leading to neuronal dysfunction and death. MARK-4 is thus a druggable target and has a pivotal role in AD. Amongst MARK-4 inhibitors, 16 compounds demonstrate significant capacity in molecular docking studies, showing high binding affinity to MARK-4 and promising potential for tau inhibition. Further, in-vitro investigations provide evidence of their neuroprotective properties. The present review mainly focuses on the role of MARK-4 and its potential inhibitors used in treating AD, which have been thoroughly investigated in silico and in vitro..

Mechanistic insights into MARK4 inhibition by galantamine toward therapeutic targeting of Alzheimer's disease

Introduction: Hyperphosphorylation of tau is an important event in Alzheimer's disease (AD) pathogenesis, leading to the generation of "neurofibrillary tangles," a histopathological hallmark associated with the onset of AD and related tauopathies. Microtubule-affinity regulating kinase 4 (MARK4) is an evolutionarily conserved Ser-Thr (S/T) kinase that phosphorylates tau and microtubule-associated proteins, thus playing a critical role in AD pathology. The uncontrolled neuronal migration is attributed to overexpressed MARK4, leading to disruption in microtubule dynamics. Inhibiting MARK4 is an attractive strategy in AD therapeutics. Methods: Molecular docking was performed to see the interactions between MARK4 and galantamine (GLT). Furthermore, 250 ns molecular dynamic studies were performed to investigate the stability and conformational dynamics of the MARK4-GLT complex. We performed fluorescence binding and isothermal titration calorimetry studies to measure the binding affinity between GLT and MARK4. Finally, an enzyme inhibition assay was performed to measure the MARK4 activity in the presence and absence of GLT. Results: We showed that GLT, an acetylcholinesterase inhibitor, binds to the active site cavity of MARK4 with an appreciable binding affinity. Molecular dynamic simulation for 250 ns demonstrated the stability and conformational dynamics of the MARK4-GLT complex. Fluorescence binding and isothermal titration calorimetry studies suggested a strong binding affinity. We further show that GLT inhibits the kinase activity of MARK4 significantly (IC50 = 5.87 µM). Conclusion: These results suggest that GLT is a potential inhibitor of MARK4 and could be a promising therapeutic target for AD. GLT's inhibition of MARK4 provides newer insights into the mechanism of GLT's action, which is already used to improve cognition in AD patients.

D3CARP: a comprehensive platform with multiple-conformation based docking, ligand similarity search and deep learning approaches for target prediction and virtual screening

Resource- and time-consuming biological experiments are unavoidable in traditional drug discovery, which have directly driven the evolution of various computational algorithms and tools for drug-target interaction (DTI) prediction. For improving the prediction reliability, a comprehensive platform is highly expected as some previously reported webservers are small in scale, single-method, or even out of service. In this study, we integrated the multiple-conformation based docking, 2D/3D ligand similarity search and deep learning approaches to construct a comprehensive webserver, namely D3CARP, for target prediction and virtual screening. Specifically, 9352 conformations with positive control of 1970 targets were used for molecular docking, and approximately 2 million target-ligand pairs were used for 2D/3D ligand similarity search and deep learning. Besides, the positive compounds were added as references, and related diseases of therapeutic targets were annotated for further disease-based DTI study. The accuracies of the molecular docking and deep learning approaches were 0.44 and 0.89, respectively. And the average accuracy of five ligand similarity searches was 0.94. The strengths of D3CARP encompass the support for multiple computational methods, ensemble docking, utilization of positive controls as references, cross-validation of predicted outcomes, diverse disease types, and broad applicability in drug discovery. The D3CARP is freely accessible at https://www.d3pharma.com/D3CARP/index.php.

Membrane-active substituted triazines as antibacterial agents against Staphylococcus aureus with potential for low drug resistance and broad activity

A library of new naphthalimide-triazine analogues was synthesized as broad-spectrum antibacterial agents to overcome drug resistance. Bioactivity assay reveals that derivative 8e, with benzylamine in its structure, exhibits strong antibacterial properties against multi-drug resistance Staphylococcus aureus at a concentration of 1.56 μg/ml. It was also found to be better than chloromycin and amoxicillin. The active compound 8e efficiently inhibits the development of drug resistance within 11 passages. In addition, compound 8e inhibits the formation of biofilms in S. aureus and acts rapidly in bactericidal efficacy. Furthermore, mechanistic studies reveal that compound 8e effectively destroys the cytoplasmic membrane of bacteria, leading to leakage of intercellular protein content and loss in metabolic activity. Compound 8e binds to HSA readily with a binding constant of 1.32 × 10⁵ M^-1, indicating that the compound could be delivered to the target site effectively. Compound 8e can also form a supramolecular complex with DNA to obstruct DNA replications. These results suggest that analogue 8e could be further developed as a potential antibacterial agent. Furthermore, the cytotoxicity of all the synthesized compounds was evaluated against 60 human cancer cell lines to test their potential for anticancer agents.

Interaction of polystyrene nanoplastics with human fibrinogen

Nanoplastics are an emerging environmental contaminant that can penetrate biological barriers to enter the bloodstream and risk human health. In this context, nanoplastics are likely to interact with proteins in the blood to possibly affect protein structure and function and consequently induce biological effects. Here we report that polystyrene (PS), PS-NH₂, and PS-COOH nanoplastics disrupt the structure of human fibrinogen (HF) in a dose-dependent manner, as revealed by UV-vis and fluorescence spectroscopy. All three nanoplastics interacted with HF in a similar way, with PS-NH₂ having the greatest effect on HF structure. Furthermore, fibrinogen polymerization experiments demonstrated that nanoplastics have the potential to promote blood coagulation, with PS-NH₂ again having a stronger effect. Collectively, these results provide insights into the interactions occurring between nanoplastics and HF, the likely transport and fate of nanoplastics in organisms, and their potential pathophysiological consequences.

Microtubule-affinity regulating kinase 4: A potential drug target for cancer therapy

The human genome encodes more than 500 protein kinases that work by transferring the γ-phosphate group from ATP to serine, threonine, or tyrosine (Ser/Thr/Tyr) residues. Various kinases are associated with the onset of cancer and its further progression. The recent advancements in developing small-molecule kinase inhibitors to treat different cancer types have shown noticeable results in clinical therapies. Microtubule-affinity regulating kinase 4 (MARK-4) is a Ser/Thr protein kinase that relates structurally to AMPK/Snf1 subfamily of the CaMK kinases. The protein kinase modulates major signalling pathways such as NF-κB, mTOR and the Hippo-signalling pathway. MARK4 is associated with various cancer types due to its important role in regulating microtubule dynamics and subsequent cell division. Aberrant expression of MARK4 is linked with several pathologies such as cancer, Alzheimer's disease, obesity, etc. This review provides detailed information on structural aspects of MARK4 and its role in various signalling pathways related to cancer. Several therapeutic molecules were designed to inhibit the MARK4 activity from controlling associated diseases. The review further highlights kinase-targeted drug discovery and development in oncology and cancer therapies. Finally, we summarize the latest findings regarding the role of MARK4 in cancer, diabetes, and neurodegenerative disease path to provide a solid rationale for future investigation and therapeutic intervention.

Multitargeting the Action of 5-HT6 Serotonin Receptor Ligands by Additional Modulation of Kinases in the Search for a New Therapy for Alzheimer's Disease: Can It Work from a Molecular Point of View?

In view of the unsatisfactory treatment of cognitive disorders, in particular Alzheimer’s disease (AD), the aim of this review was to perform a computer-aided analysis of the state of the art that will help in the search for innovative polypharmacology-based therapeutic approaches to fight against AD. Apart from 20-year unrenewed cholinesterase- or NMDA-based AD therapy, the hope of effectively treating Alzheimer’s disease has been placed on serotonin 5-HT₆ receptor (5-HT₆R), due to its proven, both for agonists and antagonists, beneficial procognitive effects in animal models; however, research into this treatment has so far not been successfully translated to human patients. Recent lines of evidence strongly emphasize the role of kinases, in particular microtubule affinity-regulating kinase 4 (MARK4), Rho-associated coiled-coil-containing protein kinase I/II (ROCKI/II) and cyclin-dependent kinase 5 (CDK5) in the etiology of AD, pointing to the therapeutic potential of their inhibitors not only against the symptoms, but also the causes of this disease. Thus, finding a drug that acts simultaneously on both 5-HT₆R and one of those kinases will provide a potential breakthrough in AD treatment. The pharmacophore- and docking-based comprehensive literature analysis performed herein serves to answer the question of whether the design of these kind of dual agents is possible, and the conclusions turned out to be highly promising.

Photoredox-Catalyzed Cascade of o-Hydroxyarylenaminones to Access 3-Aminated Chromones

Reported herein is a photoredox-catalyzed amination of o-hydroxyarylenaminones with tert-butyl ((perfluoropyridin-4-yl)oxy)carbamate, a versatile amidyl-radical precursor developed in our laboratory. This work establishes a new cascade pathway for the assembly of a range of 3-aminochromones under mild conditions. Downstream transformations of the obtained 3-aminochromones to construct diverse amino pyrimidines greatly broaden the applications of this photocatalyzed protocol.

Synthesis and photobiological applications of naphthalimide-benzothiazole conjugates: cytotoxicity and topoisomerase IIα inhibition

Conjugates of naphthalimide, benzothiazole, and indole moieties are synthesized that show excellent cytotoxicity against A549 (lung), MCF7 (breast), and HeLa (cervix) cancer cell lines with IC₅₀ values in the range of 0.14–8.59 μM. Compounds 12 and 13 substituted with ethanolamine and propargyl groups reveal potent cytotoxicity towards A549 cancer cells with IC₅₀ values of 140 and 310 nM, respectively. These compounds are further evaluated as potent inhibitors of human type IIα topoisomerase. These conjugates also reveal strong interaction towards human serum albumin (HSA) with binding constant values of 1.75 × 10⁵ M⁻¹ and 1.88 × 10⁵ M⁻¹, respectively, and formation of the stable complex at ground state with static quenching. Docking studies also confirm the effective interactions between conjugates and topoisomerase.

Conjugates of naphthalimide, benzothiazole, and indole moieties are synthesized that show excellent cytotoxicity against A549 (lung), MCF7 (breast), and HeLa (cervix) cancer cell lines with IC₅₀ values in the range of 0.14–8.59 μM.

Myricetin inhibits breast and lung cancer cells proliferation via inhibiting MARK4

Identifying novel molecules as potential kinase inhibitors are gaining significant attention globally. The present study suggests Myricetin as a potential inhibitor of microtubule-affinity regulating kinase (MARK4), adding another molecule to the existing list of anticancer therapeutics. MARK4 regulates initial cell division steps and is a potent druggable target for various cancers. Structure-based docking with 100 ns molecular dynamics simulation depicted activity of Myricetin in the active site pocket of MARK4 and the formation of a stable complex. The fluorescence-based assay showed excellent affinity of Myricetin to MARK4 guided by static and dynamic quenching. Moreover, the assessment of enthalpy change (∆H) and entropy change (∆S) delineated electrostatic interactions as a dominant force in the MARK4-myricetin interaction. Isothermal titration calorimetric measurements revealed spontaneous binding of Myricetin with MARK4. Further, the kinase assay depicted significant inhibition of MARK4 by Myricetin with IC₅₀  = 3.11 µM. Additionally, cell proliferation studies established that Myricetin significantly inhibited the cancer cells (MCF-7 and A549) proliferation, and inducing apoptosis. This study provides a solid rationale for developing Myricetin as a promising anticancer molecule in the MARK4 mediated malignancies.

SET8 mitigates hepatic ischemia/reperfusion injury in mice by suppressing MARK4/NLRP3 inflammasome pathway

AIMS

Hepatic ischemia/reperfusion (I/R) injury is a critical factor affecting the prognosis of liver surgery. The aim of this study is to explore the effects of SET8 on hepatic I/R injury and the putative mechanisms.

MAIN METHODS

The expression of SET8 and MARK4 in I/R group and sham group were detected both in vivo and in vitro. In addition, mouse and RAW 264.7 cells were transfected with MARK4 siRNA and SET8 siRNA knockdown of MARK4 and SET8, respectively. The expression of SET8, MARK4 and NLRP3-associated proteins were detected after different treatments. The pathology of liver and the serologic detection were detected after different treatments.

KEY FINDINGS

Our present study identified SET domain-containing protein 8 (SET8) as an efficient protein, which can negatively regulate hepatic I/R-mediated inflammatory response and ameliorate hepatic I/R injury by suppressing microtubule affinity-regulating kinase 4 (MARK4)/ NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway. The data showed that MARK4 deficiency inhibited hypoxia/reoxygenation (H/R)-induced NLRP3 inflammasome activation, while SET8 deficiency showed the opposite effect. We further demonstrated that SET8 restrained NLRP3 inflammasome activation by inhibiting MARK4. Moreover, we verified SET8 made protective effect on hepatic I/R injury.

SIGNIFICANCE

SET8 plays an essential role in hepatic ischemia/reperfusion injury in mice by suppressing MARK4/NLRP3 inflammasome pathway. Our results may offer a new strategy to mitigate hepatic I/R injury.

Targeting Tau Hyperphosphorylation via Kinase Inhibition: Strategy to Address Alzheimer's Disease

Microtubule-associated protein tau is involved in the tubulin binding leading to microtubule stabilization in neuronal cells which is essential for stabilization of neuron cytoskeleton. The regulation of tau activity is accommodated by several kinases which phosphorylate tau protein on specific sites. In pathological conditions, abnormal activity of tau kinases such as glycogen synthase kinase-3 β (GSK3β), cyclin-dependent kinase 5 (CDK5), c-Jun N-terminal kinases (JNKs), extracellular signal-regulated kinase 1 and 2 (ERK1/2) and microtubule affinity regulating kinase (MARK) lead to tau hyperphosphorylation. Hyperphosphorylation of tau protein leads to aggregation of tau into paired helical filaments like structures which are major constituents of neurofibrillary tangles, a hallmark of Alzheimer's disease. In this review, we discuss various tau protein kinases and their association with tau hyperphosphorylation. We also discuss various strategies and the advancements made in the area of Alzheimer's disease drug development by designing effective and specific inhibitors for such kinases using traditional in vitro/in vivo methods and state of the art in silico techniques.

Copper(I) and silver(I) complexes of anthraldehyde thiosemicarbazone: synthesis, structure elucidation, in vitro anti-tuberculosis/cytotoxic activity and interactions with DNA/HSA

A reaction of copper(i) halides (X = I, Br, Cl) and silver(i) halides with 9-anthraldehyde thiosemicarbazone (9-Hanttsc, H1L) and triphenylphosphine produced halogen-bridged dinuclear complexes, [M2(μ2-X)2(η1-S-9-Hanttsc)2(Ph3P)2] (M = Cu, X = Cl, 1; Br, 2; I, 3; M = Ag, X = Cl, 4; Br, 5). A similar reaction of 9-anthraldehyde-N1-methyl thiosemicarbazone (9-Hanttsc-N1-Me, H2L) with Ph3P and silver(i) halides yielded sulfur-bridged dimers, [Ag2X2(μ2-S-9-Hanttsc-N1-Me)2(Ph3P)2] (X = Cl, 9; Br, 10), however with copper(i) halides insoluble compounds were formed, which upon the addition of one extra mole of Ph3P gave mononuclear complexes of the formula [CuX(η1-S-9-Hanttsc-N1-Me)(Ph3P)2] (X = Cl, 6; Br, 7; I, 8). All of the complexes have been characterized by elemental analysis, NMR (1H, 13C) spectroscopy and single crystal X-ray crystallography (2, 5, 6, and 9). Both the ligands (H1L and H2L) and their complexes (1-10) were tested for their anti-tubercular and anticancer activities. The interactions of the ligands and their complexes (copper and silver) with calf thymus DNA (ct-DNA) and human serum albumin (HSA) were examined through UV-visible and fluorescence spectroscopy. Results showed that copper complex 2 displayed strong interactions with ct-DNA and HSA having binding constant values of 6.66 × 104 M-1 and 3.28 × 104 M-1, respectively, followed by silver complex 10 which gave binding constant values of 4.60 × 104 M-1 and 3.06 × 104 M-1, respectively. All of the complexes also showed good interactions with DNA in docking studies.

Emerging role of protein kinases in diabetes mellitus: From mechanism to therapy

Diabetes mellitus has emerged as a severe burden on the medical health system across the globe. Presently, around 422 million people are suffering from diabetes which is speculated to be expanded to about 600 million by 2035. Patients with type 2 diabetes are at increased risk of developing detrimental metabolic and cardiovascular complications. The scientific understanding of this chronic disease and its underlying root cause is not yet fully unraveled. Protein kinases are well known to regulate almost every cellular process through phosphorylation of target protein in diverse signaling pathways. The important role of several protein kinases including AMP-activated protein kinase, IκB kinase and protein kinase C have been well demonstrated in various animal models. They modulate glucose tolerance, inflammation and insulin resistance in the cells via acting on diverse downstream targets and signaling pathways. Thus, modulating the activity of potential human kinases which are significantly involved in diabetes by targeting with small molecule inhibitors could be an attractive therapeutic strategy to tackle diabetes. In this chapter, we have discussed the potential role of protein kinases in glucose metabolism and insulin sensitivity, and in the pathogenesis of diabetes mellitus. Furthermore, the small molecules reported in the literature that can be potentially used for the treatment of diabetes have been discussed in detail.

Inhibiting CDK6 Activity by Quercetin Is an Attractive Strategy for Cancer Therapy

Cyclin-dependent kinase 6 (CDK6) is a potential drug target that plays an important role in the progression of different types of cancers. We performed in silico and in vitro screening of different natural compounds and found that quercetin has a high binding affinity for the CDK6 and inhibits its activity with an IC50 = 5.89 μM. Molecular docking and a 200 ns whole atom simulation of the CDK6-quercetin complex provide insights into the binding mechanism and stability of the complex. Binding parameters ascertained by fluorescence and isothermal titration calorimetry studies revealed a binding constant in the range of 107 M-1 of quercetin to the CDK6. Thermodynamic parameters associated with the formation of the CDK6-quercetin complex suggested an electrostatic interaction-driven process. The cell-based protein expression studies in the breast (MCF-7) and lung (A549) cancer cells revealed that the treatment of quercetin decreases the expression of CDK6. Quercetin also decreases the viability and colony formation potential of selected cancer cells. Moreover, quercetin induces apoptosis, by decreasing the production of reactive oxygen species and CDK6 expression. Both in silico and in vitro studies highlight the significance of quercetin for the development of anticancer leads in terms of CDK6 inhibitors.

Design and Development of Small-Molecule Arylaldoxime/5-Nitroimidazole Hybrids as Potent Inhibitors of MARK4: A Promising Approach for Target-Based Cancer Therapy

Microtubule affinity-regulating kinase 4 (MARK4), a member of the serine/threonine kinase family, is an emerging therapeutic target in anticancer drug discovery paradigm due to its involvement in regulation of microtubule dynamics, cell cycle regulation, and cancer progression. Therefore, to identify the novel chemical architecture for the design and development of novel MARK4 inhibitors with concomitant radical scavenging property, a series of small-molecule arylaldoxime/5-nitroimidazole conjugates were designed and synthesized via multistep chemical reactions following the pharmacophoric hybridization approach. Compound 4h was identified as a promising MARK4 inhibitor with high selectivity toward MARK4 inhibition as compared to the panel of screened 30 kinases pertaining to the serine/threonine family, which was validated by molecular docking and fluorescence binding studies. The comprehensive cell-based examination divulged the promising apoptotic, antiproliferative, and antioxidant potential for the chemotype 4h. The compound 4h was endowed with the K _a value of 3.6 × 10³ M^-1 for human serum albumin, which reflects its remarkable transportation and delivery properties to the target site via blood. The present study impedes that in the future, such compounds may stand as optimized pharmacological lead candidates in drug discovery for targeting cancer via MARK4 inhibition with a remarkable anticancer profile.

Spectroscopy and molecular docking approach for investigation on the binding of nocodazole to human serum albumin

The interaction between nocodazole (Nz) and human serum albumin (HSA) under controlled physiological condition (pH 7.4) is examined using absorption, emission, fluorescence lifetime (FLT) and circular dichroism (CD) spectroscopic techniques. The binding constant (order of 10⁵ M^-1) from UV-vis and fluorescence spectroscopy reveals a strong interaction between Nz and HSA. Fluorescence quenching study shows that Nz binds with HSA through static quenching process. It is induced by formation of Nz-HSA complex because the Stern-Volmer quenching constant is inversely correlated with the temperature which is further verified by time-resolved fluorescence spectroscopy. The thermodynamic parameters at different temperatures indicate that the binding process is spontaneous where hydrogen bonding interactions and Van der Waals forces play major roles during the interaction between Nz and HSA. By means of spectroscopy and molecular modeling, we have discovered and interpreted the alteration of the secondary structure of HSA by Nz complexation. Synchronous, three-dimensional fluorescence and CD spectroscopic results reveal that the addition of Nz to HSA affects changes in the micro-environment and conformation of HSA. According to Förster Resonance Energy Transfer (FRET), the binding distance (r) between Nz and residue of HSA is <8 nm with excellent energy efficiency. The docking study suggests that nocodazole binds at Domain IIA in the hydrophobic pocket of human serum albumin.

Structural and biochemical investigation of MARK4 inhibitory potential of cholic acid: Towards therapeutic implications in neurodegenerative diseases

Microtubule affinity regulating kinase (MARK4) is considered as a potential drug target for diabetes, cancer, and neurodegenerative diseases. Since the role of MARK4 in the phosphorylation of tau protein and subsequently Alzheimer's disease has been established, therefore, we have investigated the binding affinity and MARK4 inhibitory potential of cholic acid (CHA) using both computational and spectroscopic methods. Molecular docking suggested a strong binding of CHA to the functionally important residues of MARK4. We further performed 500 ns molecular dynamics simulation which suggested the MARK4-CHA system was quite stable throughout the simulation trajectory. CHA potential binds to the MARK4 with a binding constant (K) of 10⁷ M^-1 at 288 K. Further, MARK4 activity was inhibited by CHA with an IC₅₀ = 5.5 μM. Further insights into the thermodynamic parameters suggested that MARK4-CHA complex formation is driven by both electrostatic and van der Waals interactions. Overall study provides a rationale to use CHA in the drug development via MARK4 inhibition, towards possible therapeutic implications in neurodegenerative diseases.

MARK4 Inhibited by AChE Inhibitors, Donepezil and Rivastigmine Tartrate: Insights into Alzheimer's Disease Therapy

Microtubule affinity-regulating kinase (MARK4) plays a key role in Alzheimer’s disease (AD) development as its overexpression is directly linked to increased tau phosphorylation. MARK4 is a potential drug target of AD and is thus its structural features are employed in the development of new therapeutic molecules. Donepezil (DP) and rivastigmine tartrate (RT) are acetylcholinesterase (AChE) inhibitors and are used to treat symptomatic patients of mild to moderate AD. In keeping with the therapeutic implications of DP and RT in AD, we performed binding studies of these drugs with the MARK4. Both DP and RT bound to MARK4 with a binding constant (K) of 10⁷ M⁻¹. The temperature dependency of binding parameters revealed MARK−DP complex to be guided by static mode while MARK−RT complex to be guided by both static and dynamic quenching. Both drugs inhibited MARK4 with IC₅₀ values of 5.3 μM (DP) and 6.74 μM (RT). The evaluation of associated enthalpy change (ΔH) and entropy change (ΔS) implied the complex formation to be driven by hydrogen bonding making it seemingly strong and specific. Isothermal titration calorimetry further advocated a spontaneous binding. In vitro observations were further complemented by the calculation of binding free energy by molecular docking and interactions with the functionally-important residues of the active site pocket of MARK4. This study signifies the implications of AChE inhibitors, RT, and DP in Alzheimer’s therapy targeting MARK4.

Synthesis of naphthalimide-phenanthro[9,10-d]imidazole derivatives: In vitro evaluation, binding interaction with DNA and topoisomerase inhibition

The synthesis and characterization of a series of naphthalimide and phenanthro[9,10-d]imidazole conjugate is described. These compounds are evaluated in vitro for their cytotoxicity towards 60 human cancer cell lines. Derivative 16 shows excellent cytotoxic activity against these cancer cell lines with the range of growth inhibition from -55.78 to 94.53. The most potent derivative (ethylpiperazine, 16) is further studied to evaluate the interaction with ct-DNA using absorption and emission spectroscopy as well as DNA viscosity measurement. The DNA binding studies indicate that compound 16 is significantly interacted with DNA through groove binding having binding constant value of 7.81 × 10⁴ M^-1 alongwith partial intercalation between the base pairs of DNA strands. Further, topoisomerase inhibition study suggests that compound 16 is induced apoptosis and inhibits human topoisomerase (Topo-IIα) as a possible intracellular target. Molecular docking study of compound 16 with ct-DNA shows good docking score.

PCC0208017, a novel small-molecule inhibitor of MARK3/MARK4, suppresses glioma progression in vitro and in vivo

Gliomas are the most common primary intracranial neoplasms among all brain malignancies, and the microtubule affinity regulating kinases (MARKs) have become potential drug targets for glioma. Here, we report a novel dual small-molecule inhibitor of MARK3 and MARK4, designated as PCC0208017. In vitro, PCC0208017 strongly inhibited kinase activity against MARK3 and MARK4, and strongly reduced proliferation in three glioma cell lines. This compound attenuated glioma cell migration, glioma cell invasion, and angiogenesis. Molecular mechanism studies revealed that PCC0208017 decreased the phosphorylation of Tau, disrupted microtubule dynamics, and induced a G2/M phase cell cycle arrest. In an in vivo glioma model, PCC0208017 showed robust anti-tumor activity, blood–brain barrier permeability, and a good oral pharmacokinetic profile. Molecular docking studies showed that PCC0208017 exhibited high binding affinity to MARK3 and MARK4. Taken together, our study describes for the first time that PCC0208017, a novel MARK3/MARK4 inhibitor, might be a promising lead compound for treatment of glioma.

Targets and pathways involved in the antitumor activity of citral and its stereo-isomers

This review provides a comprehensive analysis of the anticancer potential of the natural product citral (CIT) found in many plants and essential oils, and extensively used in the food and cosmetic industry. CIT is composed of two stereoisomers, the trans-isomer geranial being a more potent anticancer compound than the cis-isomer neral. CIT inhibits cancer cell proliferation and induces cancer cell apoptosis. Its pluri-factorial mechanism of anticancer activity is essentially based on three pillars: (i) a drug-induced accumulation of reactive oxygen species in cancer cells leading to an oxidative burst and DNA damages, (ii) a colchicine-like inhibition of tubulin polymerization and promotion of microtubule depolymerization, associated with an inhibition of the microtubule affinity-regulating kinase MARK4, and (iii) a potent inhibition of the aldehyde dehydrogenase isoform ALDH1A3 which is associated with cancer stem cell proliferation and chemoresistance. This unique combination of targets and pathways confers a significant anticancer potential. However, the intrinsic potency of CIT is limited, mainly because the drug is not very stable and has a low bioavailability and it does not present a high selectivity for cancer cells versus non-tumor cells. Stable formulations of CIT, using cyclodextrins, biodegradable polymers, or various nano-structured particles have been designed to enhance the bioavailability, to increase the effective doses window and to promote the anticancer activity. The lack of tumor cell selectivity is more problematic and limits the use of the drug in cancer therapy. Nevertheless, CIT offers interesting perspectives to design more potent analogues and drug combinations with a reinforced antitumor potential.

Discovery of 4-(2-(dimethylamino)ethoxy)benzohydrazide derivatives as prospective microtubule affinity regulating kinase 4 inhibitors

Microtubule affinity regulating kinase 4 (MARK4) is a Ser/Thr kinase, considered as a potential drug target for cancer, diabetes and neurodegenerative diseases. Due to its significant role in the development and progression of cancer, different in-house libraries of synthesized small molecules were screened to identify potential MARK4 inhibitors. A small library of hydrazone compounds showed a considerable binding affinity to MARK4. The selected compounds were further scrutinized using an enzyme inhibition assay and finally two hydrazone derivatives (H4 and H19) were selected that show excellent inhibition (nM range). These compounds have a strong binding affinity for MARK4 and moderate binding with human serum albumin. Anticancer studies were performed on MCF-7 and A549 cells, suggesting H4 and H19 selectively inhibit the growth of cancer cells. The IC₅₀ value of compound H4 and H19 was found to be 27.39 μM and 34.37 μM for MCF-7 cells, while for A549 cells it was 45.24 μM and 61.50 μM, respectively. These compounds inhibited the colonogenic potential of cancer cells and induced apoptosis. Overall findings reflect that hydrazones/hydrazone derivatives could be exploited as potential lead molecules for developing effective anticancer therapies via targeting MARK4.

Inhibition studies of MARK4 with selected hydrazone derivatives.

Identification of morpholine based hydroxylamine analogues: selective inhibitors of MARK4/Par-1d causing cancer cell death through apoptosis

Interaction of compound32with various active site residues of MARK4.

Differential Expression of MARK4 Protein and Related Perturbations in Females with Ovulatory PCOS

Background:

Ovulatory PCOS (OPCOS) is the mildest form of the polycystic ovarian syndrome among all four determined phenotypes. Though the females with OPCOS are ovulating, hyperandrogenism and polycystic ovarian morphology increase the susceptibility of cardiovascular diseases, insulin resistance, hyperlipidemia and metabolic syndrome in these females.

Objectives:

The aim of the study was to identify the significance associated with OPCOS phenotype through serum proteomic profiling of OPCOS females and normal age-matched healthy ovulating females.

Methods:

One and two-dimensional gel-based proteomic approaches were adopted to fractionate the complex serum proteome. Differential protein profiles generated were analyzed with PD-QUEST Software. Protein spots differing in intensity by >2-fold were selected and identified further by MALDI-TOF MS. Validation of identified protein was carried out by Biolayer Interferometry.

Results:

One and two-dimensional gel profiles revealed a differential expression pattern of proteins. 10 selected spots were identified as GMP synthase [glutamine hydrolyzing], zinc finger protein 518A, pericentriolar material 1 protein, BCLAF1 and THRAP3 family member 3, MAP/microtubule affinityregulating kinase 4, H/ACA ribonucleoprotein complex subunit 1, Melanoma-associated antigen B3 and Zinc finger protein 658B. Expression of MAP/microtubule affinity-regulating kinase 4 (MARK4) was found to be downregulated in OPCOS females as compared to controls on validation.

Conclusion:

Reduced expression of MARK4 protein in OPCOS increases the associated risk of hyperlipidemia, hyperandrogenism and metabolic syndrome, thus the protein holds strong candidature as a drug target for the syndrome.

Identification of α-Mangostin as a Potential Inhibitor of Microtubule Affinity Regulating Kinase 4

Microtubule affinity regulating kinase 4 (MARK4) is a potential drug target for neuronal disorders and several types of cancers. Filtration of naturally occurring compound libraries using high-throughput screening and enzyme assay suggest α-mangostin is a potential inhibitor of MARK4. Structure-based docking and 100 ns molecular dynamics simulation revealed that the binding of α-mangostin stabilizes the MARK4 structure. Enzyme inhibition and binding studies showed that α-mangostin inhibited MARK4 in the submicromolar range with IC₅₀ = 1.47 μM and binding constant (K_a) 5.2 × 10⁷ M^-1. Cell-based studies suggested that α-mangostin inhibited the cell viability (MCF-7 and HepG2), induced apoptosis, arrested the cell cycle in the G0/G1 phase, and reduced tau-phosphorylation. This study implicates MARK4 as a new target of α-mangostin, adding an additional lead molecule to the anticancer repertoire.

Effective synthesis of benzimidazoles-imidazo[1,2-a]pyrazine conjugates: A comparative study of mono-and bis-benzimidazoles for antitumor activity

A novel series of 6-substituted-8-(1-cyclohexyl-1H-benzo[d]imidazole-6-yl)imidazo[1,2-a]pyrazine and 6-substituted-8-(1-benzyl-1H-benzo[d]imidazole-6-yl)imidazo[1,2-a]pyrazine is first time synthesized and screen in vitro biological activity for 60 human cancer cell lines representing nine different cancer types. Derivatives 10 and 36 show antitumor activity for all tested cell lines, display comparable full panel mean-graph midpoint growth inhibition (MG_MID GI₅₀) values of 2.10 and 2.23 μM, respectively. Furthermore, these derivatives show strong binding interactions with DNA and bovine serum albumin (BSA), studied through absorption, emission, and circular dichroism techniques. These spectroscopic studies reveal that imidazo[1,2-a]pyrazine-benzimidazoles 10 and 36, intercalate with ct-DNA as a leading interaction for fundamental biologically significant effects, with monobenzimidazole show better activity than bisbenzimidazole. These experiments have confirmed that the imidazo[1,2-a]pyrazine and benzimidazole moieties are efficient pharmacophores to trigger binding to DNA. These compounds have also interacted with bovine serum albumin protein that demonstrating high values of binding constant.

Discovery of Coumarin as Microtubule Affinity-Regulating Kinase 4 Inhibitor That Sensitize Hepatocellular Carcinoma to Paclitaxel

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide. Nowadays, pharmacological therapy for HCC is in urgent needs. Paclitaxel is an effective drug against diverse solid tumors, but commonly resisted in HCC patients. We recently have disclosed that microtubule affinity-regulating kinase 4 (MARK4) increases the microtubule dynamics and confers paclitaxel resistance in HCC, suggesting MARK4 as an attractive target to overcome paclitaxel resistance. Herein, we synthesized and identified coumarin derivatives 50 as a novel MARK4 inhibitor. Biological evaluation indicated compound 50 directly interacted with MARK4 and inhibited its activity in vitro, suppressed cell viability and induced apoptosis of HCC cells in a MARK4-dependent manner. Importantly, compound 50 significantly increased the drug response of paclitaxel treatment to HCC cells, providing a promise strategy to HCC treatment and broadening the application of paclitaxel in cancer therapy.

Hesperidin-CAMKIV interaction and its impact on cell proliferation and apoptosis in the human hepatic carcinoma and neuroblastoma cells

Calcium/calmodulin-dependent protein kinase IV (CAMKIV) is a key regulatory molecule of cell signaling, and thereby controls its growth and proliferation, including expression of certain genes. The overexpression of CAMKIV is directly associated with the development of different types of cancers. Hesperidin is abundantly found in citrus fruits and exhibits wide range of pharmacological activities including anti-inflammatory, antibacterial and anticancerous effects. We have investigated binding mechanism of hesperidin with the CAMKIV using molecular docking methods followed by fluorescence quenching and isothermal titration calorimetric assays. An appreciable binding affinity of hesperidin was observed with CAMKIV during fluorescence quenching and isothermal titration calorimetric studies. Efficacy of hesperidin to inhibit the growth of human hepatic carcinoma (HepG2) and neuroblastoma (SH-SY5Y) cancer cell lines were investigated. Hesperidin has significantly reduced the proliferation of HepG2 and SH-SY5Y cells and induces apoptosis by activating the caspase-3-dependent intrinsic pathway through the upregulation of proapoptotic Bax protein. Hesperidin treatment reduces the mitochondrial membrane potential of HepG2 and SH-SY5Y cells. All these observations clearly anticipated hesperidin a potent inhibitor of CAMKIV which may be further exploited a newer therapeutic approach for the management of different cancer types.

Probing the Inhibition of Microtubule Affinity Regulating Kinase 4 by N-Substituted Acridones

Microtubule affinity regulating kinase 4 (MARK4) becomes a unique anti-cancer drug target as its overexpression is responsible for different types of cancers. In quest of novel, effective MARK4 inhibitors, some acridone derivatives were synthesized, characterized and evaluated for inhibitory activity against human MARK4. Among all the synthesized compounds, three (7b, 7d and 7f) were found to have better binding affinity and enzyme inhibition activity in µM range as shown by fluorescence binding, ITC and kinase assays. Here we used functional assays of selected potential lead molecules with commercially available panel of 26 kinases of same family. A distinctive kinase selectivity profile was observed for each compound. The selective compounds were identified with submicromolar cellular activity against MARK4. Furthermore, in vitro antitumor evaluation against cancerous cells (MCF-7 and HepG2) revealed that compounds 7b, 7d and 7f inhibit cell proliferation and predominantly induce apoptosis in MCF-7 cells, with IC50 values of 5.2 ± 1.2 μM, 6.3 ± 1.2 μM, and 5.8 ± 1.4 μM respectively. In addition, these compounds significantly upsurge the oxidative stress in cancerous cells. Our observations support our approach for the synthesis of effective inhibitors against MARK4 that can be taken forward for the development of novel anticancer molecules targeting MARK4.