Discovery of novel propargylamine-modified 4-aminoalkyl imidazole substituted pyrimidinylthiourea derivatives as multifunctional agents for the treatment of Alzheimer's disease

Innovative pathological network-based multitarget approaches for Alzheimer's disease treatment

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and is a major health threat globally. Its prevalence is forecasted to exponentially increase during the next 30 years due to the global aging population. Currently, approved drugs are merely symptomatic, being ineffective in delaying or blocking the relentless disease advance. Intensive AD research describes this disease as a highly complex multifactorial disease. Disclosure of novel pathological pathways and their interconnections has had a major impact on medicinal chemistry drug development for AD over the last two decades. The complex network of pathological events involved in the onset of the disease has prompted the development of multitarget drugs. These chemical entities combine pharmacological activities toward two or more drug targets of interest. These multitarget-directed ligands are proposed to modify different nodes in the pathological network aiming to delay or even stop disease progression. Here, we review the multitarget drug development strategy for AD during the last decade.

Reactive oxygen species in biological systems: Pathways, associated diseases, and potential inhibitors-A review

Reactive oxygen species (ROS) are produced under normal physiological conditions and may have beneficial and harmful effects on biological systems. ROS are involved in many physiological processes such as differentiation, proliferation, necrosis, autophagy, and apoptosis by acting as signaling molecules or regulators of transcription factors. In this case, maintaining proper cellular ROS levels is known as redox homeostasis. Oxidative stress occurs because of the imbalance between the production of ROS and antioxidant defenses. Sources of ROS include the mitochondria, auto-oxidation of glucose, and enzymatic pathways such as nicotinamide adenine dinucleotide phosphate reduced (NAD[P]H) oxidase. The possible ROS pathways are NF-κB, MAPKs, PI3K-Akt, and the Keap1-Nrf2-ARE signaling pathway. This review covers the literature pertaining to the possible ROS pathways and strategies to inhibit them. Additionally, this review summarizes the literature related to finding ROS inhibitors.

Latest advances in dual inhibitors of acetylcholinesterase and monoamine oxidase B against Alzheimer's disease

Alzheimer's disease (AD) is a progressive brain disease characterised by progressive memory loss and cognition impairment, ultimately leading to death. There are three FDA-approved acetylcholinesterase inhibitors (donepezil, rivastigmine, and galantamine, AChEIs) for the symptomatic treatment of AD. Monoamine oxidase B (MAO-B) has been considered to contribute to pathologies of AD. Therefore, we reviewed the dual inhibitors of acetylcholinesterase (AChE) and MAO-B developed in the last five years. In this review, these dual-target inhibitors were classified into six groups according to the basic parent structure, including chalcone, coumarin, chromone, benzo-fused five-membered ring, imine and hydrazine, and other scaffolds. Their design strategies, structure-activity relationships (SARs), and molecular docking studies with AChE and MAO-B were analysed and discussed, giving valuable insights for the subsequent development of AChE and MAO-B dual inhibitors. Challenges in the development of balanced and potent AChE and MAO-B dual inhibitors were noted, and corresponding solutions were provided.

Construction of Graphene Quantum Dot-based Dissolving Microneedle Patches for the Treatment of Bacterial Keratitis

Bacterial keratitis (BK) is an ophthalmic infection caused by bacteria and poses a risk of blindness. Numerous drugs have been used to treat BK, the majority suffered from limited effect owing to their backward antimicrobial and delivery efficacy. Herein, we evaluated the antibacterial effect of a cationic carbon-based nanomaterial, i.e., imidazole-modified graphene quantum dots (IMZ-GQDs), which exhibits disinfection rates of >90% against three typical Gram-positive strains within 3 h owing to the loss of membrane integrity and decline in membrane potential. For ocular application, we further developed IMZ-GQDs-loaded dissolving microneedle patches (IMZ-GQDs MNs) via a typical two-step micromolding method. IMZ-GQDs MNs showed sufficient dissolution and penetration for intrastromal delivery in vitro and successfully overcome the rabbit corneal epithelial layer in vivo. The excellent biocompatibility of IMZ-GQDs MNs was demonstrated both in cell and animal models, and they exhibited low cytotoxicity, low invasiveness and low ocular irritation. The topical application of IMZ-GQDs MNs has the benefits of both high antibacterial activity and effective drug delivery, thereby leading to the resolution of Staphylococcus aureus-induced BK in rabbits in 7 days. Therefore, IMZ-GQDs MNs is a promising approach for BK treatment, which is safe and efficient.

Discovery of novel 5-(2-hydroxyphenyl)-2-phthalide-3(3H)-pyrazolones as balanced multifunctional agents against Alzheimer's disease

Based on previous work, a series of novel 5-(2-hydroxyphenyl)-2-phthalide-3(3H)-pyrazolones derivatives were identified as potential multifunctional therapeutic agents for Alzheimer's disease. Biological evaluation exhibited that these derivatives had great performance against MAO-B, Aβ_1-42 aggregation, oxidative stress and metal ion dyshomeostasis. Among them, 10x was selected as the optimal agent for its excellent MAO-B inhibitory activity (IC₅₀ = 0.41 μM, SI > 24.4), good antioxidant activity (1.16 Trolox equivalent) and anti-Aβ aggregation activity (56.03% and 57.51% for inhibition of self- and Cu²⁺-induced Aβ_1-42 aggregation; 81.91% and 82.40% for disaggregation of self- and Cu²⁺-induced Aβ_1-42 fibrils at 25.0 μM). Besides, 10x also exhibited obvious metal-ion chelating ability, anti-neuroinflammation (NO, TNF-α), neuroprotective activity and BBB permeability. More importantly, in vivo behavioral assessment demonstrated 10x could remarkably improve the memory and cognitive impairment in Aβ_1-42 induced AD mice model. Overall, these test results indicated 10x could serve as a balanced multifunctional anti-AD agent and deserved further research.

Propargylamine: an important moiety in drug discovery

Propargylamine is a chemical moiety whose properties have made it a widely distributed group within the fields of medicinal chemistry and chemical biology. Its particular reactivity has traditionally popularized the preparation of propargylamine derivatives using a large variety of synthetic strategies, which have facilitated the access to these compounds for the study of their biomedical potential. This review comprehensively covers and analyzes the applications that propargylamine-based derivatives have achieved in the drug discovery field, both from a medicinal chemistry perspective and from a chemical biology-oriented approach. The principal therapeutic fields where propargylamine-based compounds have made an impact are identified, and a discussion of their influence and growing potential is included.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

Inhibitory potential of nitrogen, oxygen and sulfur containing heterocyclic scaffolds against acetylcholinesterase and butyrylcholinesterase

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure-activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010-2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

HDAC1/MAO-B dual inhibitors against Alzheimer's disease: Design, synthesis and biological evaluation of N-propargylamine-hydroxamic acid/o-aminobenzamide hybrids

A series of N-propargylamine-hydroxamic acid/o-aminobenzamide hybrids inhibitors combining the typical pharmacophores of hydroxamic acid/o-aminobenzamide and propargylamine were designed and synthesized as HDAC1/MAO-B dual inhibitors for the treatment of Alzheimer's disease. Most of the hybrids displayed moderate to good MAO-B inhibitory activities. Among them, Hybrid If exhibited the most potent activity against MAO-B and HDAC1 (MAO-B, IC₅₀ = 99.0 nM; HDAC1, IC₅₀ = 21.4 nM) and excellent MAO selectively (MAO-A, IC₅₀ = 9923.0 nM; SI = 100.2). Moreover, compound If significantly reversed Aβ1-42-induced PC12 cell damage and decreased the production of intracellular ROS, exhibiting favorable antioxidant activity. More importantly, hybrid If instantly penetrated the BBB and accumulated in brain tissue as well as markedly ameliorated cognitive dysfunction in a Morris water maze ICR mice model. In summary, HDAC1/MAO-B dual inhibitor If is a promising potential agent for the therapy of Alzheimer's disease.

Development of novel 2-aminoalkyl-6-(2-hydroxyphenyl)pyridazin-3(2H)-one derivatives as balanced multifunctional agents against Alzheimer's disease

Based on multitarget-directed ligands approach, through two rounds of screening, a series of 2-aminoalkyl-6-(2-hydroxyphenyl)pyridazin-3(2H)-one derivatives were designed, synthesized and evaluated as innovative multifunctional agents against Alzheimer's disease. In vitro biological assays indicated that most of the hybrids were endowed with great AChE inhibitory activity, excellent antioxidant activity and moderate Aβ_1-42 aggregation inhibition. Taken both efficacy and balance into account, 12a was identified as the optimal multifunctional ligand with significant inhibition of AChE (EeAChE, IC₅₀ = 0.20 μM; HuAChE, IC₅₀ = 37.02 nM) and anti-Aβ activity (IC₅₀ = 1.92 μM for self-induced Aβ_1-42 aggregation; IC₅₀ = 1.80 μM for disaggregation of Aβ_1-42 fibrils; IC₅₀ = 2.18 μM for Cu²⁺-induced Aβ_1-42 aggregation; IC₅₀ = 1.17 μM for disaggregation of Cu²⁺-induced Aβ_1-42 fibrils; 81.7% for HuAChE-induced Aβ_1-40 aggregation). Moreover, it was equipped with the potential to serve as antioxidant (3.03 Trolox equivalents), metals chelator and anti-neuroinflammation agent for synergetic treatment. Finally, in vivo study demonstrated that 12a, with suitable BBB permeability (log BB = -0.61), could efficaciously ameliorate cognitive dysfunction on scopolamine-treated mice by regulating cholinergic system and oxidative stress simultaneously. Altogether, these results highlight the potential of 12a as an innovative balanced multifunctional candidate for Alzheimer's disease treatment.

Design, synthesis, biological activity, molecular docking, and molecular dynamics of novel benzimidazole derivatives as potential AChE/MAO-B dual inhibitors

To develop new acetylcholinesterase (AChE)-monoamine oxidase-B (MAO-B) dual inhibitors against Alzheimer's disease, the benzimidazole ring, which has a propargyl side chain with previously proven selective MAO-B inhibitory activity, was used as the main structure. Moreover, like donepezil, it was thought that the enzyme AChE would provide π-π interactions with the peripheral anionic side in this structure. Piperazine derivatives were chosen for the cationic active site. The synthesis of the compounds was carried out in five steps. The structures of the compounds were determined using ¹ H-NMR (nuclear magnetic resonance), ¹³ C-NMR, and high-resolution mass spectrometry spectroscopic methods. First, the in vitro AChE, butyrylcholinesterase (BChE), MAO-A, and MAO-B inhibitory potentials of the obtained compounds were investigated. As a result of activity tests, compounds 5b, 5e, 5g, and 5h showed inhibitory activity against AChE; compounds 5e and 5g showed inhibitory activity against MAO-B. None of the compounds showed inhibitory activity against BChE or MAO-A. Compounds 5e and 5g showed dual inhibition. Among these compounds, compound 5g had inhibition potential similar to that of donepezil and selegiline. For compound 5g, further kinetic studies and Aβ-plaque inhibitory potentials were investigated using in vitro methods. Molecular docking studies were performed using both AChE and hMAO-B crystals to elucidate the compound's interactions with the enzyme active site. The binding modes of the compound on AChE were fully elucidated by molecular dynamics studies.

The molecular mechanism, targets, and novel molecules in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurological illness that causes dementia mainly in the elderly. The challenging obstacles related to AD has freaked global healthcare system to encourage scientists in developing novel therapeutic startegies to overcome with the fatal disease. The current treatment therapy of AD provides only symptomatic relief and to some extent disease-modifying effects. The current approach for AD treatment involves designing of cholinergic inhibitors, Aβ disaggregation inducing agents, tau inhibitors and several antioxidants. Hence, extensive research on AD therapy urgently requires a deep understanding of its pathophysiology and exploration of various chemical scaffolds to design and develop a potential drug candidate for the treatment. Various issues linked between disease and therapy need to be considered such as BBB penetration capability, clinical failure and multifaceted pathophisiology requires a proper attention to develop a lead candidate. This review article covers all probable mechanisms including one of the recent areas for investigation i.e., lipid dyshomeostasis, pathogenic involvement of P. gingivalis and neurovascular dysfunction, recently reported molecules and drugs under clinical investigations and approved by FDA for AD treatment. Our summarized information on AD will attract the researchers to understand and explore current status and structural modifications of the recently reported heterocyclic derivatives in drug development for AD therapy.

Ultrasound assisted synthesis of hybrid quinoline-imidazole derivatives: a green synthetic approach

A green, straightforward and efficient study for obtaining hybrid quinoline-imidazole derivatives under ultrasound (US) irradiation as well as under conventional thermal heating (TH) has been presented. The reaction pathway involves only two steps: the N-alkylation of imidazole ring and a Huisgen [3 + 2] dipolar cycloaddition reaction of ylides to dimethyl acetylenedicarboxylate (DMAD). For both types of reactions, a green workup procedure under US irradiation has been presented. Under US irradiation, the N-alkylation of nitrogen atoms from the imidazole nucleus has outstanding benefits in terms of reaction time, energy consumption and yields, and can thereby be considered an environmentally friendly method. Forty new hybrid quinoline-imidazole compounds have been synthesized: 18 salts, 8 dihydro-benzopyrrolo imidazolo quinoline, 9 benzopyrrolo-imidazolo quinoline and 5 dihydro-pyrroloquinoxaline quinoline cycloadducts.

Choline Chloride-Based DES as Solvents/Catalysts/Chemical Donors in Pharmaceutical Synthesis

DES are mixtures of two or more compounds, able to form liquids upon mixing, with lower freezing points when compared to the individual constituents (eutectic mixtures). This attitude is due to the specific hydrogen-bond interactions network between the components of the mixture. A notable characteristic of DES is the possibility to develop tailor-made mixtures by changing the components ratios or a limited water dilution, for special applications, making them attractive for pharmaceutical purposes. In this review, we focused our attention on application of ChCl-based DES in the synthesis of pharmaceutical compounds. In this context, these eutectic mixtures can be used as solvents, solvents/catalysts, or as chemical donors and we explored some representative examples in recent literature of such applications.

Structural exploration of multifunctional monoamine oxidase B inhibitors as potential drug candidates against Alzheimer's disease

AD is one of the most typical neurodegenerative disorders that suffer many seniors worldwide. Recently, MAO inhibitors have received increasing attention not only for their roles involved in monoamine neurotransmitters metabolism and oxidative stress but also for their additional neuroprotective and neurorescue effects against AD. The curiosity in MAO inhibitors is reviving, and novel MAO-B inhibitors recently developed with ancillary activities (e.g., Aβ aggregation and AChE inhibition, anti-ROS and chelating activities) have been proposed as multitarget drugs foreshadowing a positive outlook for the treatment of AD. The current review describes the recent development of the design, synthesis, and screening of multifunctional ligands based on MAO-B inhibition for AD therapy. Structure-activity relationships and rational design strategies of the synthetic or natural product derivatives (chalcones, coumarins, chromones, and homoisoflavonoids) are discussed.

Multi-Target-Directed Ligands as an Effective Strategy for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurological disorder, and multiple pathological factors are believed to be involved in the genesis and progression of the disease. A number of hypotheses, including Acetylcholinesterase, Monoamine oxidase, β-Amyloid, Tau protein, etc., have been proposed for the initiation and progression of the disease. At present, acetylcholine esterase inhibitors and memantine (NMDAR antagonist) are the only approved therapies for the symptomatic management of AD. Most of these single-target drugs have miserably failed in the treatment or halting the progression of the disease. Multi-factorial diseases like AD require complex treatment strategies that involve simultaneous modulation of a network of interacting targets. Since the last few years, Multi-Target-Directed Ligands (MTDLs) strategy, drugs that can simultaneously hit multiple targets, is being explored as an effective therapeutic approach for the treatment of AD. In the current review article, the authors have briefly described various pathogenic pathways associated with AD. The importance of Multi-Target-Directed Ligands and their design strategies in recently reported articles have been discussed in detail. Potent leads are identified through various structure-activity relationship studies, and their drug-like characteristics are described. Recently developed promising compounds have been summarized in the article. Some of these MTDLs with balanced activity profiles against different targets have the potential to be developed as drug candidates for the treatment of AD.

Small-Molecule Inhibitors of Reactive Oxygen Species Production

Reactive oxygen species (ROS) are involved in physiological cellular processes including differentiation, proliferation, and apoptosis by acting as signaling molecules or regulators of transcription factors. The maintenance of appropriate cellular ROS levels is termed redox homeostasis, a balance between their production and neutralization. High concentrations of ROS may contribute to severe pathological events including cancer, neurodegenerative, and cardiovascular diseases. In recent years, approaches to target the sources of ROS production directly in order to develop tool compounds or potential therapeutics have been explored. Herein, we briefly outline the major sources of cellular ROS production and comprehensively review the targeting of these by small-molecule inhibitors. We critically assess the value of ROS inhibitors with different mechanisms-of-action, including their potency, mode-of-action, known off-target effects, and clinical or preclinical status, while suggesting future avenues of research in the field.

Alzheimer's Disease: Related Targets, Synthesis of Available Drugs, Bioactive Compounds Under Development and Promising Results Obtained from Multi-target Approaches

We describe herein the therapeutic targets involved in Alzheimer's disease as well as the available drugs and their synthetic routes. Bioactive compounds under development are also exploited to illustrate some recent research advances on the medicinal chemistry of Alzheimer's disease, including structure-activity relationships for some targets. The importance of multi-target approaches, including some examples from our research projects, guides new perspectives in search of more effective drug candidates. This review comprises the period between 2001 and early 2020.

Sulfur-containing therapeutics in the treatment of Alzheimer's disease

Sulfur is widely existent in natural products and synthetic organic compounds as organosulfur, which are often associated with a multitude of biological activities. OBenzothiazole, in which benzene ring is fused to the 4,5-positions of the thiazolerganosulfur compounds continue to garner increasing amounts of attention in the field of medicinal chemistry, especially in the development of therapeutic agents for Alzheimer's disease (AD). AD is a fatal neurodegenerative disease and the primary cause of age-related dementia posing severe societal and economic burdens. Unfortunately, there is no cure for AD. A lot of research has been conducted on sulfur-containing compounds in the context of AD due to their innate antioxidant potential and some are currently being evaluated in clinical trials. In this review, we have described emerging trends in the field, particularly the concept of multi-targeting and formulation of disease-modifying strategies. SAR, pharmacological targets, in vitro/vivo ADMET, efficacy in AD animal models, and applications in clinical trials of such sulfur compounds have also been discussed. This article provides a comprehensive review of organosulfur-based AD therapeutic agents and provides insights into their future development.

A comprehensive review of monoamine oxidase inhibitors as Anti-Alzheimer's disease agents: A review

Monoamine oxidases (MAO-A and MAO-B) are mammalian flavoenzyme, which catalyze the oxidative deamination of several neurotransmitters like norepinephrine, dopamine, tyramine, serotonin, and some other amines. The oxidative deamination produces several harmful side products like ammonia, peroxides, and aldehydes during the biochemical reaction. The concentration of biochemical neurotransmitter alteration in the brain by MAO is directly related with several neurological disorders like Alzheimer's disease and Parkinson's disease (PD). Activated MAO also contributes to the amyloid beta (Aβ) aggregation by two successive cleft β-secretase and γ-secretase of amyloid precursor protein (APP). Additionally, activated MAO is also involved in aggregation of neurofibrillary tangles and cognitive destruction through the cholinergic neuronal damage and disorder of the cholinergic system. MAO inhibition has general anti-Alzheimer's disease effect as a consequence of oxidative stress reduction prompted by MAO enzymes. In this review, we outlined and addressed recent understanding on MAO enzymes such as their structure, physiological function, catalytic mechanism, and possible therapeutic goals in AD. In addition, it also highlights the current development and discovery of potential MAO inhibitors (MAOIs) from various chemical scaffolds.

Perspectives for New and More Efficient Multifunctional Ligands for Alzheimer's Disease Therapy

Despite tremendous research efforts at every level, globally, there is still a lack of effective drugs for the treatment of Alzheimer's disease (AD). The biochemical mechanisms of this devastating neurodegenerative disease are not yet clearly understood. This review analyses the relevance of multiple ligands in drug discovery for AD as a versatile toolbox for a polypharmacological approach to AD. Herein, we highlight major targets associated with AD, ranging from acetylcholine esterase (AChE), beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1), glycogen synthase kinase 3 beta (GSK-3β), N-methyl-d-aspartate (NMDA) receptor, monoamine oxidases (MAOs), metal ions in the brain, 5-hydroxytryptamine (5-HT) receptors, the third subtype of histamine receptor (H3 receptor), to phosphodiesterases (PDEs), along with a summary of their respective relationship to the disease network. In addition, a multitarget strategy for AD is presented, based on reported milestones in this area and the recent progress that has been achieved with multitargeted-directed ligands (MTDLs). Finally, the latest publications referencing the enlarged panel of new biological targets for AD related to the microglia are highlighted. However, the question of how to find meaningful combinations of targets for an MTDLs approach remains unanswered.

Multitarget Therapeutic Strategies for Alzheimer's Disease: Review on Emerging Target Combinations

Neurodegenerative diseases represent nowadays one of the major health problems. Despite the efforts made to unveil the mechanism leading to neurodegeneration, it is still not entirely clear what triggers this phenomenon and what allows its progression. Nevertheless, it is accepted that neurodegeneration is a consequence of several detrimental processes, such as protein aggregation, oxidative stress, and neuroinflammation, finally resulting in the loss of neuronal functions. Starting from these evidences, there has been a wide search for novel agents able to address more than a single event at the same time, the so-called multitarget-directed ligands (MTDLs). These compounds originated from the combination of different pharmacophoric elements which endowed them with the ability to interfere with different enzymatic and/or receptor systems, or to exert neuroprotective effects by modulating proteins and metal homeostasis. MTDLs have been the focus of the latest strategies to discover a new treatment for Alzheimer's disease (AD), which is considered the most common form of dementia characterized by neurodegeneration and cognitive dysfunctions. This review is aimed at collecting the latest and most interesting target combinations for the treatment of AD, with a detailed discussion on new agents with favorable in vitro properties and on optimized structures that have already been assessed in vivo in animal models of dementia.

Treatment of Brain Edema by Wogonoside Is Associated with Inhibition of Neuronal Apoptosis and SIRT1 Activation in Rats

Background

Brain edema and neuronal apoptosis are closely associated with loss of neurological function and death in rats with subarachnoid hemorrhage (SAH). The present study investigated the effect of wogonoside on brain edema induced by SAH in rats and studied the mechanism involved.

Material/Methods

The rats were intra-gastrically administered 10, 20, 50, 100, 150 and 200 mg/kg doses of wogonoside 24 h prior to SAH induction. Western blotting was used to assess levels of pro-apoptotic protein, SIRT1, ZO-1, and p53 protein expression. Apoptotic nuclei were detected using immunofluorescence and TUNEL staining.

Results

Wogonoside treatment significantly suppressed edema formation in SAH-induced rats. Pre-treatment with wogonoside exhibited an inhibitory effect on SAH-induced extravascular Evans blue staining in rats. The expression of ZO-1, Occludin, and Claudin-5 proteins was increased by wogonoside in the SAH-induced rats. The inhibitory effect of SAH was completely reversed in the rats treated with the 200 mg/kg dose of wogonoside. The expression of SIRT1 protein was upregulated, and p53 and AC-p53 were downregulated by wogonoside in SAH rats. Wogonoside treatment significantly reduced SAH-mediated promotion of Bax, Puma, Noxa, Bid, and cleaved Caspase-3 expression. In the SAH-induced rats, pre-treatment with wogonoside reduced the TUNEL-positive cell count.

Conclusions

The present study demonstrated that wogonoside prevents brain edema development and apoptosis of neurons in rats by promoting SIRT1 expression and suppression of p53 activation. Therefore, wogonoside has therapeutic potential for the treatment of edema and needs to be investigated further to completely define the mechanism involved.

Hydroxypyridinone-Coumarin Inhibits the Proliferation of MHCC97 and HepG2 Human Hepatocellular Carcinoma Cells and Down-Regulates the Phosphoinositide-3 Kinase Pathway

Background

Worldwide, hepatocellular carcinoma (HCC) is one of the most commonly diagnosed malignant diseases and is the third leading cause of cancer-related death. This study aimed to investigate the effect of hydroxypyridinone-coumarin (HPC) on MHCC97 and HepG2 human HCC cells and the mechanisms involved.

Material/Methods

MHCC97 and HepG2 human HCC cells were cultured in vitro. An MTT cytotoxicity assay was used to assess cell viability and proliferation, with and without treatment with HPC. Cell autophagosomes were labeled with GFP-LC3 using confocal fluorescence microscopy. Western blot was used to measure protein expression.

Results

HPC significantly reduced the cell proliferation rate in a concentration-dependent manner, with 2 μM of HPC resulting in a reduced proliferation rate of MHCC97 cells (by 36%) and HepG2 cells (by 29%) (P<0.02). HPC significantly reduced autophagy in MHCC97 and HepG2 cells. Western blot showed that treatment with HPC significant upregulated Atg5, beclin-1, LC3-phosphatidylethanolamine conjugate (LC3-II), and Atg-3, reduced p62 and Akt protein expression, and induced phosphorylation of ERK1/2. GFP-LC3B labeling in MHCC97 and HepG2 cells was increased following HPC treatment.

Conclusions

HPC induced autophagy and inhibited the proliferation of MHCC97 and HepG2 HCC cells in vitro and involved activation of ERK1/2 and down-regulation of the Akt pathway.

Treatment of Alzheimer's disease with framework nucleic acids

OBJECTIVES

To provide a new research direction for nerve regeneration and strategy for Alzheimer's disease treatment, tetrahedral DNA nanostructures (TDNs)-novel tetrahedral framework nucleic acid molecule nanoparticles (tFNA) that can inhibit the apoptosis of nerve cells are employed in the experiment.

MATERIALS AND METHODS

To verify the successful preparation of TDNs, the morphology of TDNs was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The expression of apoptosis-related genes and proteins was investigated by confocal microscope, flow cytometry, PCR and Western blot to detect the impact of TDNs on the Alzheimer's model. And finally, Morris water maze experiment was used to test behavioural changes and Nissl stain was detected to observe the morphology and quantity of neurons in the hippocampus. Immunofluorescence stain was used to observe the Aβ stain, and TUNEL dyeing was utilized to observe neuronal apoptosis.

RESULTS

In vitro and in vivo experiments confirm that TDNs, in a specific concentration range, have no toxic or side effects on nerve cells, can effectively inhibit apoptosis in an Alzheimer's disease cell model and effectively improve memory and learning ability in a rat model of Alzheimer's disease.

CONCLUSIONS

These findings suggest that TDNs may be a promising drug for the treatment of Alzheimer's disease.

Calycosin and 8-O-methylretusin isolated from Maackia amurensis as potent and selective reversible inhibitors of human monoamine oxidase-B

Nineteen compounds were isolated from the stems of Maackia amurensis by activity-guided screening for new human monoamine oxidase-B (hMAO-B) inhibitors. Among the compounds isolated, flavonoids calycosin (5) and 8-O-methylretusin (6) were found to potently and selectively inhibit hMAO-B (IC₅₀ = 0.24 and 0.23 μM, respectively) but not hMAO-A with high selectivity index (SI) values (SI = 293.8 and 81.3, respectively). In addition, 5 and 6 reversibly and competitively inhibited hMAO-B with K_i values of 0.057 and 0.054 μM, respectively. A pterocarpan (-)-medicarpin (18) was also observed to strongly inhibit hMAO-B (IC₅₀ = 0.30 μM). Most of the compounds weakly inhibited AChE, except isolupalbigenin (13) (IC₅₀ = 20.6 μM), which suggested 13 be considered a potential dual function inhibitor of MAO-B and AChE. Molecular docking simulation revealed that the binding affinities of 5 and 6 for hMAO-B (both -9.3 kcal/mol) were higher than those for hMAO-A (-7.4 and -7.2 kcal/mol, respectively). Compound 5 was found to interact by hydrogen bonding with hMAO-B at Cys172 residue (distance: 3.250 Å); no hydrogen bonding was predicted between 5 and hMAO-A. These findings suggest that compounds 5 and 6 be considered novel potent, selective, and reversible hMAO-B inhibitors and candidates for the treatment of neurological disorders.

Ferulic Acid Induces Apoptosis of HeLa and Caski Cervical Carcinoma Cells by Down-Regulating the Phosphatidylinositol 3-Kinase (PI3K)/Akt Signaling Pathway

Background

Ferulic acid is an antioxidant phenolic compound derived from plants, which has effects on cancer cells. This study aimed to investigate the effects of ferulic acid on HeLa and Caski human cervical carcinoma cells and the molecular mechanisms involved.

Material/Methods

HeLa and Caski human cervical carcinoma cells were grown in culture and treated with increasing doses of ferulic acid. The MTT assay was used to evaluate cell viability. Flow cytometry was performed with 4′,6-diamidino-2-phenylindole (DAPI) and Annexin V staining for cell apoptosis. The expression of myeloid leukemia cell differentiation-1 (Mcl-1) protein and MCL-1 mRNA were determined by Western blot and reverse transcription-polymerase chain reaction (RT-PCR).

Results

Ferulic acid significantly reduced HeLa and Caski cell viability in the concentration range of 4–20 μM (P<0.05). Ferulic acid treatment promoted DNA condensation and significantly increased apoptosis in Caski cells (P<0.05). Ferulic acid treatment resulted in the activation of pro-caspase-3, pro-caspase-8, pro-caspase-9, and PARP. The MTT assay showed that ferulic acid did not reduce the viability of Caski cells treated with the caspase inhibitor, z-VAD-fmk. Ferulic acid reduced the levels of Bcl-2 and Mcl-1, and increased the levels of Bax and reactive oxygen species (ROS). In Caski cells, Akt and PI3K phosphorylation were reduced by ferulic acid in a concentration-dependent manner.

Conclusions

The effects of ferulic acid were dose-dependent and resulted in cell cytotoxicity and apoptosis of HeLa and Caski cells, and the PI3K/Akt signaling pathway was down-regulated in Caski cells.

Development of a telescoped synthesis of 4-(1H)-cyanoimidazole core accelerated by orthogonal reaction monitoring

Telescoped synthesis enabled by reaction monitoring.

Propargylamine-derived multi-target directed ligands for Alzheimer's disease therapy

Current options for the treatment of Alzheimeŕs disease have been restricted to prescription of acetylcholinesterase inhibitors or N-methyl-d-aspartate receptor antagonist, memantine. Propargylamine-derived multi-target directed ligands, such as ladostigil, M30, ASS234 and contilisant, involve different pathways. Apart from acting as inhibitors of both cholinesterases and monoamine oxidases, they show improvement of cognitive impairment, antioxidant activities, enhancement of iron-chelating activities, protect against tau hyperphosphorylation, block metal-associated oxidative stress, regulate APP and Aβ expression processing by the non-amyloidogenic α-secretase pathway, suppress mitochondrial permeability transition pore opening, and coordinate protein kinase C signaling and Bcl-2 family proteins. Other hybrid propargylamine derivatives are also reported.

Inhibition of Colon Cancer Cell Growth by Imidazole Through Activation of Apoptotic Pathway

Background

This study aimed to investigate the inhibitory effect of imidazole on colon cancer cell proliferation and understand the mechanism involved.

Material/Methods

MTT assay and flow cytometry using Hoechst 33258 staining were used to assess cell proliferation and morphology, respectively. Changes in protein expression was determined by western blotting assay. The reactive oxygen species (ROS) production in DLD-1 cells was analyzed by flow cytometry using DCFH-DA (2′,7′-dichlorofluorescein diacetate) stain.

Results

DLD-1 and HCT-116 cell viability was suppressed by imidazole in a concentration-based manner. At the concentration of 36 μM, imidazole reduced DLD-1 and HCT-116 cell viability to 22% and 28%, respectively. Treatment with imidazole led to chromatin material condensation, detaching of cells, and apoptotic nuclei. In imidazole treated cells, the G1/G0 phase cell proportion increased, whereas in the S and G2/M phases the cell proportion decreased. Imidazole treatment of DLD-1 cells markedly promoted activation of caspase-3, caspase-8, and caspase-9. The level of cleaved PARP1 was also upregulated in DLD-1 cells with imidazole treatment. Treatment of DLD-1 cells with imidazole suppressed Bcl-2 and promoted Bax, p53, and cytc expression. The Akt activation was suppressed by imidazole treatment in DLD-1 cells. ROS generation in DLD-1 cells was enhanced markedly by treatment with imidazole.

Conclusions

The present study demonstrated that imidazole inhibited colon cancer cell viability through activation of apoptosis and cell cycle arrest by increasing the generation of ROS, caspase activation, and apoptotic protein expression. Therefore, imidazole can act as a therapeutic molecule for the treatment of colon cancer.

Discovery of Simplified Sampangine Derivatives with Potent Antifungal Activities against Cryptococcal Meningitis

Cryptococcal meningitis (CM) is associated with high morbidity and mortality. Current antifungal drug therapy for CM has the following challenges: limited efficacy, significant side effects, emerging drug resistance, and unavailability in highly needed countries. There is an urgent need to develop novel CM therapeutic agents with a new mode of action. On the basis of the antifungal natural product sampangine, herein, novel simplified isoxazole derivatives were identified to possess excellent inhibitory activity against Cryptococcus neoformans (C. neoformans). Particularly, compound 9a was highly active (the minimum inhibitory concentration of 80% inhibition, MIC₈₀ = 0.031 μg/mL) and significantly inhibited biofilm formation, melanin, and urease production of C. neoformans. 9a had good blood-brain barrier (BBB) permeability and effectively reduced the brain fungal burden in a murine model of cryptococcosis. The antifungal mechanism of compound 9a was preliminarily investigated by transmission electron microscopy and flow cytometry. It was able to cause necrocytosis of C. neoformans cells and cell cycle arrest in the G1/S phase. Isoxazole compound 9a represents a promising lead compound for the development of novel CM therapeutic agents.

Recent Developments in Metal-Based Drugs and Chelating Agents for Neurodegenerative Diseases Treatments

The brain has a unique biological complexity and is responsible for important functions in the human body, such as the command of cognitive and motor functions. Disruptive disorders that affect this organ, e.g. neurodegenerative diseases (NDDs), can lead to permanent damage, impairing the patients' quality of life and even causing death. In spite of their clinical diversity, these NDDs share common characteristics, such as the accumulation of specific proteins in the cells, the compromise of the metal ion homeostasis in the brain, among others. Despite considerable advances in understanding the mechanisms of these diseases and advances in the development of treatments, these disorders remain uncured. Considering the diversity of mechanisms that act in NDDs, a wide range of compounds have been developed to act by different means. Thus, promising compounds with contrasting properties, such as chelating agents and metal-based drugs have been proposed to act on different molecular targets as well as to contribute to the same goal, which is the treatment of NDDs. This review seeks to discuss the different roles and recent developments of metal-based drugs, such as metal complexes and metal chelating agents as a proposal for the treatment of NDDs.

Discovery of Carboline Derivatives as Potent Antifungal Agents for the Treatment of Cryptococcal Meningitis

Clinical treatment of cryptococcal meningitis (CM) remains a significant challenge because of the lack of effective and safe drug therapies. Developing novel CM therapeutic agents with novel chemical scaffolds and new modes of action is of great importance. Herein, new β-hexahydrocarboline derivatives are shown to possess potent anticryptococcal activities. In particular, compound A4 showed potent in vitro and in vivo anticryptococcal activity with good metabolic stability and blood-brain barrier permeability. Compound A4 was orally active and could significantly reduce brain fungal burdens in a murine model of CM. Moreover, compound A4 could inhibit several virulence factors of Cryptococcus neoformans and might act by a new mode of action. Preliminary mechanistic studies revealed that compound A4 induced DNA double-stranded breaks and cell cycle arrest at the G2 phase by acting on the Cdc25c/CDK1/cyclin B pathway. Taken together, β-hexahydrocarboline A4 represents a promising lead compound for the development of next-generation CM therapeutic agents.

Reconsideration of Anticholinesterase Therapeutic Strategies against Alzheimer's Disease

Alzheimer's disease (AD) is well-known as a severe neurodegeneration disease involving complicated etiologies, and cholinesterase inhibition remain the prevailing mode of clinical intervention in AD management. Although most clinically applied cholinesterase inhibitors (ChEIs) achieve limited clinical outcomes, research on the central cholinergic system is still thriving. Recently, an impressive amount of knowledge regarding novel acetylcholinesterase functions, as well as the close association between the central cholinergic system and other key elements for AD pathogenesis, has accumulated, highlighting that this field still has great potential for future drug development. In contrast to the overwhelmingly disappointing clinical therapeutic effects of various disease-modifying drug candidates, interesting evidence has continued to emerge over the past 20 years from the wealth of preclinical and clinical data on the usage of ChEIs, indicating underestimated clinical benefits due to physician ambivalence, a lack of persistent treatment, and inappropriate medication times or doses. Here we pinpoint several topics fit for future attention, focusing on the updated cholinergic hypothesis, especially the pleiotropic relationships with key pathogenetic signaling pathways and functions in AD, as well as possible novel therapeutic strategies, including novel ChEIs and cholinesterase inhibition-based innovative multifunctional therapeutic candidates. We intend to strengthen the future value of the precise application of cholinergic drugs, especially novel ChEIs, as a cornerstone pharmacological approach to AD treatment, either alone or in combination with other targets, to relieve symptoms and to modify disease progression.

Rational Design of Novel Selective Dual-Target Inhibitors of Acetylcholinesterase and Monoamine Oxidase B as Potential Anti-Alzheimer's Disease Agents

Multifunctional agents aiming at cholinesterases (ChEs) and monoamine oxidases (MAOs) are promising therapy for Alzheimer's disease (AD). Herein, a series of novel propargylamine-modified pyrimidinylthiourea derivatives (1-4) were designed and synthesized as dual inhibitors of ChEs and MAOs with other functions against AD. Most of these derivatives inhibited ChEs and MAOs with IC₅₀ values in the micro- or nanomolar ranges. Compound 1c displayed the dual functional profile of targeting the AChE (IC₅₀ = 0.032 ± 0.007 μM) and MAO-B (IC₅₀ = 2.117 ± 0.061 μM), along with the improved blood-brain barrier (BBB) permeability, antioxidant ability, and good copper chelating property in vitro. Animal studies showed that compound 1c·HCl could inhibit the cerebral AChE/MAO-B activities and alleviate scopolamine-induced cognitive impairment in mice. Combined with good oral bioavailability ( F = 45.55%), these findings demonstrated that compound 1c may be a potent brain permeable multifunctional candidate for the treatment of AD.

Multitarget therapeutic strategies for Alzheimer's disease

Neurodegenerative diseases such as Alzheimer’s, Huntington’s and Parkinson’s diseases have multifaceted nature because of the different factors contributing to their progression. The complex nature of neurodegenerative diseases has developed a pressing need to design multitarget-directed ligands to address the complementary pathways involved in these diseases. The major enzyme targets for development of therapeutics for Alzheimer’s disease are cholinesterase and β-secretase enzymes. In this review, we discuss recent advances in profiling single target inhibitors based on these enzymes to multitarget-directed ligands as potential therapeutics for this devastating disease. In addition, therapeutics based on iron chelation strategy are discussed as well.

New amyloid beta-disaggregating agents: synthesis, pharmacological evaluation, crystal structure and molecular docking of N-(4-((7-chloroquinolin-4-yl)oxy)-3-ethoxybenzyl)amines

In the journey towards the development of potent multi-targeted ligands for the treatment of Alzheimer's disease, a series of Aβ aggregation inhibitors having quinoline scaffold were designed utilizing computational biology tools, synthesized and characterized by various spectral techniques including single-crystal X-ray crystallography. Organic syntheses relying upon convergent synthetic routes were employed. Investigations via ThT fluorescence assay, electron microscopy and transmission electron microscopy revealed the synthesized derivatives to exhibit Aβ self-aggregation inhibition. Molecules 5g and 5a showed the highest inhibitory potential, 53.73% and 53.63% at 50 μM respectively; higher than the standard Aβ disaggregating agent, curcumin. Molecules 5g and 5a disaggregated AChE-induced (58.26%, 47.36%) Aβ aggregation more than two fold more than the standard drug-donepezil (23.66%) and inhibited Cu2+-induced Aβ aggregation. A docking study significantly showed their interaction with key residues of Aβ and the results were in accordance with the study. Besides, these compounds also exhibited potential antioxidant activity (5a, 2.7240 Trolox equivalent by ORAC assay) and metal chelating property. Furthermore, the stoichiometric ratio of Cu (ii)-5a and Cu(ii)-5g complexes were found by Job's method (0.5 : 1 for 5a and 0.8 : 1 for 5g). In silico ADMET profiling showed these derivatives to have drug like properties with very low toxicity effects in the pharmacokinetic study. Overall, these results displayed a multi-activity profile with promising Aβ aggregation inhibition and antioxidation and metal chelation activity that could be helpful for developing new multifunctional agents against Alzheimer's disease.

Design of Diarylheptanoid Derivatives as Dual Inhibitors Against Class IIa Histone Deacetylase and β-amyloid Aggregation

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with multiple etiologies. Beta-amyloid (Aβ) self-aggregation and overexpression of class IIa histone deacetylases (HDACs) are strongly implicated with AD pathogenesis. In this study, a series of novel diarylheptanoid derivatives were designed, synthesized and evaluated for use as dual Aβ self-aggregation and class IIa HDAC inhibitors. Among these compounds, 4j, 5c, and 5e displayed effective inhibitions for Aβ self-aggregation, HDAC5 activity and HDAC7 activity with IC₅₀ values of <10 μM. The compounds contain three common features: (1) a catechol or pyrogallol moiety, (2) a carbonyl linker and (3) an aromatic ring that can function as an HDAC cap and create hydrophobic interactions with Aβ_1-42. Furthermore, compounds 4j, 5c, and 5e showed no significant cytotoxicity to human neuroblastoma SH-SY5Y cells and also exhibited neuroprotective effect against H₂O₂-induced toxicity. Overall, these promising in vitro data highlighted compounds 4j, 5c, and 5e as lead compounds that are worthy for further investigation.